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SOI for MEMS, NEMS, sensors and more at IEDM ’14 (Part 3 of 3 in ASN’s IEDM coverage)

iedm_logoImportant SOI-based developments in MEMS, NEMS (like MEMS but N for nano), sensors and energy harvesting shared the spotlight with advanced CMOS and future devices at IEDM 2014 (15-17 December in San Francisco). IEDM is the world’s showcase for the most important applied research breakthroughs in transistors and electronics technology.

Here in Part 3, we’ll cover these remaining areas. (In Part 1 of ASN’s IEDM coverage, we had a rundown of the top papers on FD-SOI and SOI-FinFETs. Part 2 looked at papers covering future device architectures leveraging SOI.)

Summaries culled from the abstracts follow.

Sensors

4.2: Three-Dimensional Integrated CMOS Image Sensors with Pixel-Parallel A/D Converters Fabricated by Direct Bonding of SOI Layers

M. Gotoet al (NHK Research Labs, U Tokyo)

This illustration (a) shows a schematic diagram of the 3D integrated CMOS image sensor; (b) shows a conceptual diagram of the image sensor pixel; (c) is a cross-sectional scanning electron microscope image of a bonded CMOS image sensor pixel with no voids observed at the bonded interface and with the upper layer thinned to 6.5 µm; and (d) is a photograph of the bonded CMOS image sensor array, where 60-µm-square photodiodes (PD) are stacked on inverters.(NHK paper 4.2 at IEDM '14)

This illustration (a) shows a schematic diagram of the 3D integrated CMOS image sensor; (b) shows a conceptual diagram of the image sensor pixel; (c) is a cross-sectional scanning electron microscope image of a bonded CMOS image sensor pixel with no voids observed at the bonded interface and with the upper layer thinned to 6.5 µm; and (d) is a photograph of the bonded CMOS image sensor array, where 60-µm-square photodiodes (PD) are stacked on inverters.(NHK paper 4.2 at IEDM ’14)

The resolutions and frame rates of CMOS image sensors have increased greatly to meet demands for higher-definition video systems, but their design may soon be obsolete. That’s because photodetectors and signal processors lie in the same plane, on the substrate, and many pixels must time-share a signal processor. That makes it difficult to improve signal processing speed. NHK researchers developed a 3D parallel-processing architecture they call “pixel-parallel” processing, where each pixel has its own signal processor. Photodetectors and signal processors are built in different vertically stacked layers. The signal from each pixel is vertically transferred and processed in individual stacks.

3D stacking doesn’t degrade spatial resolution, so both high resolution and a high frame rate are achieved. 3D stacked image sensors have been reported previously, but they either didn’t have a signal processor in each stack or they used TSV/microbump technology, reducing resolution. NHK discusses how photodiode and inverter layers were bonded with damascened gold electrodes to provide each pixel with analog-to-digital conversion and a pulse frequency output. A 64-pixel prototype sensor was built, which successfully captured video images and had a wide dynamic range of >80 dB, with the potential to be increased to >100dB.

 

4.5: Experimental Demonstration of a Stacked SOI Multiband Charged-Coupled Device

C.-E. Chang et al (Stanford, SLAC)

Multiband light absorption and charge extraction in a stacked SOI multiband CCD are experimentally demonstrated for the first time. This proof of concept is a key step in the realization of the technology which promises multiple-fold efficiency improvements in color imaging over current filter- and prism-based approaches.

 

15.4: A Semiconductor Bio-electrical Platform with Addressable Thermal Control for Accelerated Bioassay Development

T.-T. Chen et al (TSMC, U Illinois),

In this work, the researchres introduce a bioelectrical platform consisting of field effect transistor (FET) bio-sensors, temperature sensors, heaters, peripheral analog amplifiers and digital controllers, fabricated by a 0.18μm SOI-CMOS process technology. The bio-sensor, formed by a sub-micron FET with a high-k dielectric sensing film, exhibits near-Nernst sensitivity (56-59 mV/pH) for ionic detection. There were also 128×128 arrays tested by monitoring changes in enzyme reactions and DNA hybridization. The electrical current changes correlated to changes in pH reaching -1.387μA/pH with 0.32μA standard variation. The detection of urine level via an enzyme(urease)-catalyzed reaction has been demonstrated to a 99.9% linearity with 0.1μL sample volume. And the detection of HBV DNA was also conducted to a 400mV equivalent surface potential change between 1 μM matched and mismatched DNA. As a proof of concept, they demonstrated the capabilities of the device in terms of detections of enzymatic reaction and immobilization of bio-entities.  The proposed highly integrated devices have the potential to largely expand its applications to all the heat-mediated bioassays, particularly with 1-2 order faster thermal response within only 0.5% thermal coupling and smaller volume samples. This work presents an array device consisting of multiple cutting-edge semiconductor components to assist the development of electrical bio assays for medical applications.

 

NEMS & MEMS

22.1: Nanosystems Monolithically Integrated with CMOS: Emerging Applications and Technologies

J. Arcamone et al (U Grenoble, Leti, Minatec),

This paper reviews the last major realizations in the field of monolithic integration of NEMS with CMOS. This integration scheme drastically improves the efficiency of the electrical detection of the NEMS motion. It also represents a compulsory milestone to practically implement breakthrough applications of NEMS, such as mass spectrometry, that require large capture cross section (VLSI-arrayed NEMS) and individual addressing (co-integration of NEMS arrays with CMOS electronic loop).

 

22.2: A Self-sustained Nanomechanical Thermal-piezoresistive Oscillator with Ultra-Low Power Consumption

K.-H. Li et al (National Tsing Hua U)

This work demonstrates wing-type thermal-piezoresistive oscillators operating at about 840 kHz under vacuum with ultralow power consumption of only 70 µW for the first time. The thermally-actuated piezoresistively-sensed (i.e., thermalpiezoresistive) resonator can achieve self-sustained oscillation using a sufficient dc bias current through its thermal beams without additional electronic circuits. By using proper control of silicon etching (ICP) recipe, the submicron cross-sectional dimension of the thermal beams can be easily and reproducibly fabricated in one process step.

 

22.4: High Performance Polysilicon Nanowire NEMS for CMOS Embedded Nanosensors

I. Ouerghiet al (Leti)

The researchers present for the first time sub-100nm poly-Silicon nanowire (poly-Si NW) based NEMS resonators for low-cost co-integrated mass sensors on CMOS featuring excellent performance when compared to crystalline silicon. In particular, comparable quality factors (130 in the air, 3900 in vacuum) and frequency stabilities are demonstrated when compared to crystalline Si. The minimum measured Allan deviation of 7×10-7 leads to a mass resolution detection down to 100 zg (100×10-2 g). Several poly-Si textures are compared and the impact on performances is studied (quality factor, gauge factor, Allan variances, noise, temperature dependence (TCR)). Moreover a novel method for in-line NW gauges factor (GF) extraction is proposed and used.

 

22.5: Integration of RF MEMS Resonators and Phononic Crystals for High Frequency Applications with Frequency-selective Heat Management and Efficient Power Handling

H. Campanella et al (A*STAR, National U Singapore)

A radio frequency micro electromechanical system (RFMEMS) Lamb-wave resonator made of aluminum nitride (AlN) that is integrated with AlN phononic crystal arrays to provide frequency-selective heat management, improved power handling capability, and more efficient electromechanical coupling at ultra high frequency (UHF) bands. RFMEMS+PnC integration is scalable to microwave bands.

 

22.6: A Monolithic 9 Degree of Freedom (DOF) Capacitive Inertial MEMS Platform

I. E. Ocak et al  (IME, A*STAR Singapore)

A 9 degree of freedom inertial MEMS platform, integrating 3 axis gyroscopes, accelerometers, and magnetometers on the same substrate is presented. This method reduces the assembly cost and removes the need for magnetic material deposition and axis misalignment calibration. Platform is demonstrated by comparing fabricated sensor performances with simulation results.

 

15.6: MEMS Tunable Laser Using Photonic Integrated Circuits

M. Ren et al (Nanyang Technological University, A*STAR)

This paper reports a monolithic MEMS tunable laser using silicon photonic integrated circuit, formed in a ring cavity. In particular, all the necessary optical functions in a ring laser system, including beam splitting/combining, isolating, coupling, are realized using the planar passive waveguide structures. Benefited from the high light-confinement capability of silicon waveguides, this design avoids beam divergence in free-space medium as suffered by conventional MEMS tunable lasers, and thus guarantees superior performance. The proposed laser demonstrates large tuning range (55.5 nm),excellent single-mode properties (50 dB side-mode-suppression ratio (SMSR) and 130 kHz linewdith), compact size (3mm × 2mm), and single-chip integration without other separated optical elements.

 

Energy Harvesting

8.4: A High Efficiency Frequency Pre-defined Flow-driven Energy Harvester Dominated by On-chip Modified Helmholtz Resonating Cavity

X.J. Mu et al (A*STAR)

The researchers present a novel flow-driven energy harvester with its frequency dominated by on-chip modified Helmholtz Resonating Cavity (HRC). This device harvests pneumatic kinetic energy efficiently and demonstrates a power density of 117.6 μW/cm2, peak to peak voltage of 5 V, and charging of a 1 μF capacitor in 200 ms.

8.5: Fabrication of Integrated Micrometer Platform for Thermoelectric Measurements

M. Haras et al  (IEMN, ST)

Preliminary simulations of lateral thermo-generators showed that silicon’s harvesting capabilities, through a significant thermal conductivity reduction, could compete with conventional thermoelectric materials, offering additional: CMOS compatibility; harmlessness and cost efficiency. The researchers report the fabrication and characterization of integrated platforms showing a threefold reduction of thermal conductivity in 70nm thick membranes.

 

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This has been the 3rd post in a 3-part series. Part 1 (click here to  read it) of ASN’s IEDM ’14 coverage gave a rundown of the top FD-SOI and SOI-FinFET papers.  Part 2 (click here to  read it) looked at papers covering SOI-based future device architectures.

 

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SOI-based future device structures at IEDM ’14 (Part 2 of 3 in ASN’s IEDM coverage)

iedm_logoBeyond FD-SOI and FinFETs, important SOI-based developments in advanced device architectures including nanowires (NW), gate all around (GAA) and other FET structures shared the spotlight at IEDM 2014 (15-17 December in San Francisco). IEDM is the world’s showcase for the most important applied research breakthroughs in transistors and electronics technology.

Here in Part 2 of ASN’s IEDM coverage, we’ll cover future device architectures. In Part 1, we had a rundown of the top SOI-based advanced CMOS papers. In Part 3 we’ll look at MEMS, NEMS, sensors and more.

Summaries culled from the abstracts follow.

16.2: Dual-Channel CMOS Co-Integration with Si Channel NFET and Strained-SiGe Channel PFET in Nanowire Device Architecture Featuring 15nm Gate Length

P. Nguyen et al (Leti, ST, Soitec)

 

Omega-gate CMOS nanowire transistors, with a diameter of 12nm and gate length of 15nm. The NFETs have a silicon channel while the PFETs have a SiGe channel. The germanium (Ge) content is estimated to be 30%. (Courtesy: Leti, ST, Soitec at IEDM 14, Paper 16.2)

Omega-gate CMOS nanowire transistors, with a diameter of 12nm and gate length of 15nm. The NFETs have a silicon channel while the PFETs have a SiGe channel. The germanium (Ge) content is estimated to be 30%. (Courtesy: Leti, ST, Soitec at IEDM
14, Paper 16.2)

The researchers have fabricated the first hybrid channel omega-gate CMOS nanowire (NW) with strained SiGe-channel (cSiGe) p-FETs and Si-channel n-FET. An optimized process flow based on the Ge enrichment technique results in a +135% hole mobility enhancement at long gate lengths compared to Si. Effectiveness of cSiGe channel is also evidenced for ultra-scaled p-FET NW (LG=15 nm) with +90% ION current improvement. [110]-oriented NW is shown to be the best candidate to improve drive current under compressive strain. In this work, the strain is measured by using precession electron diffraction with a 1nm spatial resolution. Furthermore, they show that hybrid integration reduces the delay of CMOS ring oscillator (FO=3) by 50% at VDD=0.9V. Finally, they demonstrate the most aggressively scaled hybrid CMOS NWs reported to date with NW width and gate length down to 7nm and 11nm, while maintaining high drive current (687µA/µm for p-FET and 647µA/µm for n-FET) with low leakage current and excellent short-channel-control (DIBL<50mV/V).

 

20.5: Study of the Piezoresistive Properties of NMOS and PMOS Omega-Gate SOI Nanowire Transistors: Scalability Effects and High Stress Level

J. Pelloux-Prayer et al (Leti, Soitec, Tokyo Tech)

The researchers present a comprehensive study of piezoresistive properties of aggressively scaled MOSFET devices. For the first time, the evolution of the piezoresistive coefficients with scaled dimensions is presented (gate length down to 20nm and channel width down to 8nm), and from the low to high stress regime (above 1GPa). They show that the downscaling of geometrical parameters doesn’t allow the use of the conventional definition of piezoresistivity tensor elements. The obtained results give a comprehensive insight on strain engineering ability in aggressively scaled CMOS technology.

 

20.3: Direct Observation of Self-heating in III-V Gate-all-around Nanowire MOSFETs

S.H. Shin et al (Purdue U)

Multi-gate devices, such as, FinFET, Gate-all-around transistors (GAA-FET) improve 3D electrostatic control of the channel, but the corresponding increase in self-heating may compromise both performance and reliability. Although the self-heating effect (SHE) of FinFET appears significant, but tolerable, the same may not be true for GAA geometry, especially in quasi-ballistic regime where hot spots and non-classical heat-dissipation pathways may lead to localized damage. The existing reports of the SHE on the SOI, FinFET or GAA-FET have so far relied either on indirect electrical measurements with inherent temporal delays, or on optical infra-red (λ>1.5μm ) imaging that cannot resolve deep submicron features. As a result, it has so far been impossible to resolve the spatio-temporal features of SHE fully. In this paper, the researchers develop an ultra-fast, high resolution thermo-reflectance (TR) imaging technique to (i) directly observe the local temperature rise of GAA-FET with different number of nanowires (NW)(ii) characterize/interpret the time constants of heating and cooling through high resolution transient measurements, (iii) identify critical paths for heat dissipation, and (iv) detect in-situ time-dependent breakdown of individual NW.

 

9.6: In-situ Doped and Tensilely Stained Ge Junctionless Gate-all-around nFETs on SOI Featuring Ion = 828µA/µm, Ion/Ioff ~ 1×105, DIBL= 16-54 mV/V, and 1.4X External Strain Enhancement

I-H. Wong et al (Taiwan U)

In-situ CVD doping and laser annealing can reach [P] and tensile strain as high as 2×1020 cm-3 and 0.37%. Junctionless Ge gate-all-around nFETs with 9 nm-Wfin and 0.8 nm-EOT achieves the record high Ion of 828 µA/µm. The Ion enhancement of ~40% is achieved under the tensile strain of 0.25%.

 

27.6: Flexible High-performance Nonvolatile Memory by Transferring GAA Silicon Nanowire SONOS onto a Plastic Substrate

J.-M. Choi et al (KAIST, NASA)

Flexible nonvolatile memory is demonstrated with excellent memory properties comparable to the traditional wafer-based rigid type of memory. This  achievement is realized through the transfer of an ultrathin film consisting of single crystalline silicon nanowire (SiNW) gate-all-around (GAA) SONOS memory devices onto a plastic substrate from a host silicon wafer.

13.2: High Ion/Ioff Ge-source Ultrathin Body Strained-SOI Tunnel FETs – Impact of Channel Strain, MOS Interfaces and Back Gate on the Electrical Properties

M. Kim et al (U Tokyo)

The researchers demonstrated Ge/strained-Si hetero-junction TFETs with in-situ B doped Ge. The increase in channel strain and optimization of PMA have successfully realized high performance of steep SSmin below 30 mV/dec and large Ion/Ioff ratio over 3×107.

13.3: Comprehensive Performance Re-assessment of TFETs with a Novel Design by Gate and Source Engineering from Device/Circuit Perspective

Q. Huang et al (Peking U)

In this paper, a novel TFET design, called Pocket-mSTFET, is proposed and experimentally demonstrated by evaluating the performance from device metrics to circuit implementation for low-power SoC applications. For the first time, from a circuit design perspective, TFETs performance in terms of ION, IOFF, subthreshold slope (SS), output behavior, capacitance, delay, noise and gain are experimentally benchmarked and also compared with MOSFET. By gate and source engineering without area penalty, the compatibly-fabricated Pocket-mSTFET on SOI substrate shows superior performance with the minimum SS of 29mV/dec at 300K, high ION (~20μA/μm) and large ION/IOFF ratio (~108) at 0.6V. Circuit-level implementation based on Pocket-mSTFET also shows significant improvement on energy efficiency and power reduction at VDD of 0.4V, which indicates great potential of this TFET design for low-power digital and analog applications.

13.4: A Schottky-Barrier Silicon FinFET with 6.0 mV/dec Subthreshold Slope over 5 Decades of Current

J. Zhang et al (EPFL)

The researchers demonstrate a steep subthreshold slope silicon FinFET with Schottky source/drain. The device shows a minimal SS of 3.4 mV/dec and an average SS of 6.0 mV/dec over 5 decades of current swing. Ultra-low leakage floor of 0.06 pA/μm is also achieved with high Ion/Ioff ratio of 107.

 

26.2: Thin-Film Heterojunction Field-Effect Transistors for Ultimate Voltage Scaling and Low-Temperature Large-Area Fabrication of Active-Matrix Backplanes

B. Hekmatshoar et al (IBM)

Heterojunction field-effect thin-film transistors with crystalline Si channels and gate regions comprised of hydrogenated amorphous silicon or organic materials are demonstrated. The HJFET devices are processed at 200ºC and room temperature, respectively; and exhibit operation voltages below 1V, subthreshold slopes of 70-100mV/dec and off currents as low as 25 fA/um.

 

26.7 Performance Enhancement of a Novel P-type Junctionless Transistor Using a Hybrid Poly-Si Fin Channel for 3D IC Applications

Y.-C. Cheng et al (National Tsing Hua U, National Chiao Tung U)

The hybrid fin poly-Si channel junctionless field-effect transistors (FET) are fabricated first. This novel devices show stable temperature/reliability characteristics, and excellent electrical performances in terms of steep SS (64mV/dec), high Ion/Ioff (>107) and small DIBL (3mV/V). The devices are highly promising for future further scaling and 3D stacked ICs applications.

 

35.1: A Physics-based Compact Model for FETs from Diffusive to Ballistic Carrier Transport Regimes

S. Rakhejaet al (MIT, Purdue U)

The virtual source (VS) model provides a simple, physical description of transistors that operate in the quasi-ballistic regime. Through comparisons to measured data, key device parameters can be extracted. The VS model suffers from three limitations: i) it is restricted to short channels, ii) the transition between linear and saturation regions is treated empirically, and iii) the injection velocity cannot be predicted, it must be extracted by fitting the model to measured data. This paper discusses a new model, which uses only a few physical parameters and is fully consistent with the VS model. The new model: i) describes both short and long channel devices, ii) provides a description of the current at any drain voltage without empirical fitting, and iii) predicts the injection velocity (device on-current). The accuracy of the model is demonstrated by comparison with measured data for III-V HEMTs and ETSOI Si MOSFETs.

 

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This is the 2nd post in a 3-part series. Part 1 (click here to  read it) of ASN’s IEDM ’14 coverage gave a rundown of the top FD-SOI and SOI-FinFET papers.  Part 3 (click here to read it) covers SOI-based MEMS, NEMS, sensors and more.

 

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10nm FD-SOI, SOI FinFETs at IEDM ’14 (Part 1 of 3 in ASN’s IEDM coverage)

iedm_logoFD-SOI at 10nm (and other nodes) as well as SOI FinFETs shared the spotlight at IEDM 2014 (15-17 December in San Francisco), the world’s showcase for the most important applied research breakthroughs in transistors and electronics technology.

There were about 40 SOI-based papers presented at IEDM. Here in Part 1 of ASN’s IEDM coverage, we have a rundown of the top SOI-based advanced CMOS papers. In Part 2, we’ll cover papers on future device architectures. In Part 3 we’ll look at the papers on MEMS, NEMS, sensors and more.

Summaries culled from the abstracts follow.

 

The FD-SOI Papers

9.1: FD-SOI CMOS Devices Featuring Dual Strained Channel and Thin BOX Extendable to the 10nm Node.

Q. Liu et al (STMicroelectronics, CEA-LETI, IBM, Soitec)

In their IEDM ‘14 paper 9.1 on 10nm FD-SOI, ST, IBM, Leti and Soitec reported a low-temperature process that was developed to form a defect-free SiGe channel from the strained SOI starting substrate. (Image courtesy: ST et al, IEDM 2014)

In their IEDM ‘14 paper 9.1 on 10nm FD-SOI, ST, IBM, Leti and Soitec reported a low-temperature process that was developed to form a defect-free SiGe channel from the strained SOI starting substrate. (Image courtesy: ST et al, IEDM 2014)

In this work, researchers from STMicroelectronics and the IBM Technology Development Alliance demonstrate the successful implementation of strained FDSOI devices with LG, spacer & BOX dimensions scaled to 10nm feature sizes.

Two additional enabling elements for scaling FD-SOI devices to the 10nm node are reported: advanced strain techniques for performance improvement, and reduced BOX thickness for better SCE & higher body factor. The researchers also report the first demonstration of strain reversal in strained SOI by the incorporation of SiGe in a short-channel PFET device. With regard to performance, at 0.75V the devices achieved a competitive effective drive current of 340 µA/µm for NFET at Ioff=1 nA/um (the highest performing FD-SOI NFET ever reported), and with a fully compressively strained 30% SiGe-on-insulator (SGOI) channel on a thin (20nm) BOX substrate, PFET effective drive current was 260 µA/µm at Ioff=1 nA/um. Competitive sub-threshold slope and DIBL are also reported.

 

[13] and [14] are Intel papers on 22nm bulk FinFET. [15] is TSMC on 16nm bulk FinFET. [9] is Leti et al on 14nm FD-SOI. “This work” pertains to the 10nm FD-SOI process presented by ST et al at IEDM ‘14. (Courtesy: ST et al, IEDM 2014)

[13] and [14] are Intel papers on 22nm bulk FinFET. [15] is TSMC on 16nm bulk FinFET. [9] is Leti et al on 14nm FD-SOI. “This work” pertains to the 10nm FD-SOI process presented by ST et al at IEDM ‘14.
(Courtesy: ST et al, IEDM 2014)

7.2: A Mobility Enhancement Strategy for sub-14nm Power-efficient FDSOI Technologies

B. De Salvo et al. (Leti, ST, IMEP, IBM, Soitec)

This paper presents an original multi-level evaluation methodology for stress engineering device design of next-generation power-efficient devices. Ring oscillator simulations showed that a dynamic power gain of 50% could be achieved while maintaining circuit frequency performance thanks to the use of efficient mobility boosters. Thus a clear scaling path to achieve high-mobility, power-efficient sub-14nm FDSOI technologies has been identified.

 

3.4: Single-P-Well SRAM Dynamic Characterization with Back-Bias Adjustment for Optimized Wide-Voltage Range SRAM Operation in 28nm UTBB FD-SOI

O. Thomas et al (UC Berkeley, ST)

This paper demonstrates the 28nm ultra-thin body and buried oxide (UTBB) FD-SOI high-density (0.120µm²) single pwell (SPW) bitcell architecture for the design of low-power wide voltage range systems enabled by back-bias adjustment. A 410mV minimum operating voltage and less than 310mV data retention voltage with less than 100fA/bitcell are measured in a 140kb programmable dynamic SRAM. Improved bitcell read access time and write-ability through back-bias are demonstrated with less than 5% of stand-by power overhead.

 

27.5: New Insights on Bottom Layer Thermal Stability and Laser Annealing Promises for High Performance 3D Monolithic Integration

C. Fenouillet-Beranger et al (Leti, ST, LASSE)

For the first time the maximum thermal budget of in-situ doped source/drain state-of-the-art FD-SOI bottom MOSFET transistors is quantified to ensure transistors stability in Monolithic 3D (M3D) integration. Thanks to silicide stability improvement, the top MOSFET temperature could be relaxed up to 500°C. Laser anneal is then considered as a promising candidate for junctions activation. Thanks to in-depth morphological and electrical characterizations, it shows very promising results for high performance Monolithic 3D integration.

 

9.2 Future Challenges and opportunities for Heterogeneous process technology. Toward the thin films, Zero intrinsic Variabiliiy devices, Zero power Era (Invited)

S. Deleonibus et al (Leti)

By 2025, 25 % of the World Gross Domestic Product will depend on the development of Information and Communication Technologies . Less greedy device, interconnect, computing technologies and architectures are essential to aim at x1000 less power consumption.

IBM’s SOI-FinFET, eDRAM and 3D Papers

32.1: Electrical Characterization of FinFET with Fins Formed by Directed Self Assembly at 29 nm Fin Pitch Using a Self-Aligned Fin Customization Scheme

H. Tsai et al (IBM)

These drawings illustrate the process flow for forming groups of SOI fins using the directed self-assembly technique. (IBM at IEDM ’14, paper 32.1)

These drawings illustrate the process flow for forming groups of SOI fins using the directed self-assembly technique. (IBM at IEDM ’14, paper 32.1)

High density fin formation is one of the most critical processes in the FinFET device fabrication flow. Given that a typical device is composed of an ensemble of fins, each fin must be nearly identical to avoid performance degradation arising from geometric variation. Thus, techniques for fin patterning must demonstrate the ability to form fins with a high degree of structural precision. In this paper, IBM researchers present the use of directed self-assembly using block copolymers (BCP) and 193nm immersion (193i) lithography as a suitable way to make the fins of FinFETs for beyond the 10 nm node.

(a) Shows groups of two fins formed by the process, while (b) is a cross-sectional image of a larger group of fins. (IBM at IEDM ’14, paper 32.1)

(a) Shows groups of two fins formed by the process, while (b) is a cross-sectional image of a larger group of fins. (IBM at IEDM ’14, paper 32.1)

 

Essentially, a topographic template pattern was created on a chemically neutral surface. Confinement of the BCP between the sidewalls of the template provides an ordering force that drives the pattern into registry with the surface topography. Electrical data produced from fins with a 29-nm pitch patterned with this approach showed good uniformity, with no signs of gross variation in critical dimensions.

Fabrication of FinFET devices using the self-assembly process (a) before customization; (b) after customization; (c) after gate patterning; and (d) after spacer formation and epitaxial Si growth. (IBM at IEDM ’14, paper 32.1)

Fabrication of FinFET devices using the self-assembly process (a) before customization; (b) after customization; (c) after gate patterning; and (d) after spacer formation and epitaxial Si growth. (IBM at IEDM ’14, paper 32.1)

 

3.8 High Performance 14nm SOI FinFET CMOS Technology with 0.0174μm2 embedded DRAM and 15 Levels of Cu Metallization (Late News)

C-H. Lin et al (IBM)

The IBM team presents a fully integrated 14nm CMOS technology featuring FinFET architecture on an SOI substrate for a diverse set of SoC applications including high-performance server microprocessors and low-power ASICs. A unique dual workfunction process optimizes the threshold voltages of both NMOS and PMOS transistors without any mobility degradation in the channel and without reliance on problematic approaches like heavy doping or Lgate modulation to create Vt differentiation. The IBM technology features what may be the smallest, densest embedded DRAM memory ever demonstrated (a cell size of just 0.0174µm2) for high-speed performance in a fully integrated process flow. Because the technology is envisioned for use in SoC applications ranging from video game consoles to enterprise-level corporate data centers, the IBM design also features a record 15 levels of copper interconnect to give circuit designers more freedom than ever before to distribute power and clock signals efficiently across an entire SoC chip, which may be as large as 600mm2.

The SOI FinFET’s excellent subthreshold behavior allows gate length scaling to the sub 20nm regime and superior low Vdd operation. This leads to a substantial (>35%) performance gain for Vdd ~0.8V compared to the HP 22nm planar predecessor technology. At the same time, the exceptional FE/BE reliability enables high Vdd (>1.1V) operation essential to the high single thread performance for processors intended for ‘scale-up’ enterprise systems. A hierarchical BEOL with 15 levels of copper interconnect delivers both high performance wire-ability as well as effective power supply and clock distribution for very large >600mm2 SoCs.

 

16.1: First Demonstration of High-Ge-Content Strained-Si1-xGex (x=0.5) on Insulator PMOS FinFETs with High Hole Mobility and Aggressively Scaled Fin Dimensions and Gate Lengths for High-Performance Applications

P. Hashemi et al (IBM)

Strained SiGe FinFETs are a promising PMOS technology for the 10nm technology node and beyond, due to their excellent electrostatics and built-in uniaxial compression. Yet while SiGe FinFETs with moderate germanium (Ge) content have been characterized, little data exists on FinFETs with high Ge  content. And, what little data does exist is mostly focused on relaxed or strained pure Ge. For the first time anywhere, IBM detailed CMOS-compatible, low-power and high-performance SiGe PMOS FinFETs with more than 50% Ge content. The devices feature ultra-narrow fin widths – down to 3.3 nm – which provide excellent short-channel control for low-power applications.  Using a Si-cap-free passivation process, they report SS=68mV/dec and μeff=390±12 cm2/Vs at Ninv=1e13 cm-2, outperforming the state-of-the-art relaxed Ge FinFETs. They demonstrated the highest performance ever reported (Ion=0.42mA/µm and Ioff=100nA/µm) for sub-20nm PMOS FinFETs at 0.5 V.

 

19.4: 0.026µm2 High Performance Embedded DRAM in 22nm Technology for Server and SOC Applications

C. Pei et al (IBM)

This paper presents the industry’s smallest eDRAM based on IBM’s 22nm (partially depleted) SOI technology, which has been recently leveraged for IBM’s 12-core 649mm2 Server Processor POWER8™. It summarizes the n-band resistance innovations, and reports for the first time the asymmetric embedded stressor, cavity implant and through gate implant employed in 22nm eDRAM technology. The fully integrated 256Mb product array has demonstrated capability of 1.4ns cycle time, which is significantly faster than any other embedded DRAM.

 

14.6: Through Silicon Via (TSV) Effects on Devices in Close Proximity– the Role of Mobile Ion Penetration – Characterization and Mitigation

C. Kothandaraman et al (IBM)

The research team identified and studied a new interaction between TSV processes and devices in close proximity, different from mechanical stress. Detailed characterization via Triangular Voltage Sweep (TVS) and SIMS shows the role of mobile ion penetration from BEOL layers. They then presented an improved process, confirmed in test structures and DRAM.

 

RF-SOI

18.4: Technology Pathfinders for Low Cost and Highly Integrated RF Front End Modules

C. Raynaud (Leti)

This paper highlights the challenges related to the increasing number of modes (GSM, WCDMA, LTE) and frequency bands in mobile devices. It describes the technology pathfinders to get cheaper highly integrated multimode multi–band RF Front End modules.

 

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This is the 1st post in a 3-part series. Part 2 (click here to  read it) of ASN’s IEDM ’14 coverage looks at papers covering SOI-based future device architectures.  Part 3 (click here to read it) covers SOI-based MEMS, NEMS, sensors and more.

ByAdministrator

The SOI Papers at VLSI ’14 (Part 2):

Last week we posted Part 1 of our round-up of SOI papers at the VLSI Symposia – which included the paper showing that 14nm FD-SOI should match the performance of 14nm bulk FinFETs. (If you missed Part 1, covering the three big 14nm FD-SOI and 10nm FinFET papers, click here to read it now.)

This post here gives you the abstracts of all the other papers we couldn’t fit into Part 1.  (Note that as of this posting date, the papers are not yet available on the IEEE Xplore site – but they should be shortly.)

There are in fact two symposia under the VLSI umbrella: one on technology and one on circuits. We’ll cover both here. Read on!

 

(More!) SOI Highlights from the Symposium on VLSI Technology

4.2: III-V Single Structure CMOS by Using Ultrathin Body InAs/GaSb-OI Channels on Si, M. Yokoyama et al. (U. Tokyo, NTT)

The authors propose and demonstrate the operation of single structure III-V CMOS transistors by using metal S/D ultrathin body (UTB) InAs/GaSb-on-insulator (-OI) channels on Si wafers. It is found that the CMOS operation of the InAs/GaSb-OI channel is realized by using ultrathin InAs layers, because of the quantum confinement of the InAs channel and the tight gate control. The quantum well (QW) InAs/GaSb-OI on Si structures are fabricated by using direct wafer bonding (DWB). They experimentally demonstrate both n-and p-MOSFET operation for an identical InAs/GaSb-OI transistor by choosing the appropriate thickness of InAs and GaSb channel layers. The channel mobilities of both InAs n- and GaSb p-MOSFET are found to exceed those of Si MOSFETs.

 

4.4:  High Performance InGaAs-On-Insulator MOSFETs on Si by Novel Direct Wafer Bonding Technology Applicable to Large Wafer Size Si, S. Kim et al. (U. Tokyo, IntelliEPI)

The authors present the first demonstration of InGaAs-on-insulator (-OI) MOSFETs with wafer size scalability up to Si wafer size of 300 mm and larger by a direct wafer bonding (DWB) process using InGaAs channels grown on Si donor substrates with III-V buffer layers instead of InP donor substrates. It is found that this DWB process can provide the high quality InGaAs thin films on Si. The fabricated InGaAs-OI MOSFETs have exhibited the high electron mobility of 1700 cm2/Vs and large mobility enhancement factor of 3× against Si MOSFETs.

 

6.1: Simple Gate Metal Anneal (SIGMA) Stack for FinFET Replacement Metal Gate Toward 14nm and Beyond, T. Ando et al. (IBM)

The authors demonstrate a Simple Gate Metal Anneal (SIGMA) stack for FinFET Replacement Metal Gate technology with a 14nm design rule. The SIGMA stack uses only thin TiN layers as workfunction (WF)-setting metals for CMOS integration. The SIGMA stack provides 100x PBTI lifetime improvement via band alignment engineering. Moreover, the SIGMA stack enables 9nm more gate length (Lg) scaling compared to the conventional stack with matched gate resistance due to absence of high resistivity WF-setting metal and more room for W in the gate trench. This gate stack solution opens up pathways for aggressive Lg scaling toward the 14nm node and beyond.

 

8.1: First Demonstration of Strained SiGe Nanowires TFETs with ION Beyond 700μA/μm, A. Villalon et al. (CEA-LETI, U.Udine, IMEP-LAHC, Soitec)

The authors presented for the first time high performance Nanowire (NW) Tunnel FETs (TFET) obtained with a CMOS-compatible process flow featuring compressively strained Si1-xGex (x=0, 0.2, 0.25) nanowires, Si0.7Ge0.3 Source and Drain and High-K/Metal gate. Nanowire architecture strongly improves electrostatics, while low bandgap channel (SiGe) provides increased band-to-band tunnel (BTBT) current to tackle low ON current challenges. They analyzed the impact of these improvements on TFETs and compare them to MOSFET ones. Nanowire width scaling effects on TFET devices were also investigated, showing a 1/W3 dependence of ON current ION per wire. The fabricated devices exhibit higher Ion than any previously reported TFET, with values up to 760μA/μm and average subthreshold slopes (SS) of less than 80mV/dec.

8.2: Band-to-Band Tunneling Current Enhancement Utilizing Isoelectronic Trap and its Application to TFETs, T. Mori et al. (AIST)

The authors proposed a new ON current boosting technology for TFETs utilizing an isoelectronic trap (IET), which is formed by introducing electrically inactive impurities. They  demonstrated tunneling current enhancement by 735 times in Si-based diodes and 11 times enhancement in SOI-TFETs owing to non-thermal tunneling component by the Al-N isoelectronic impurity complex. The IET technology would be a breakthrough for ON current enhancement by a few orders in magnitude in indirect-transition semiconductors such as Si and SiGe.

 

9.1: Ge CMOS: Breakthroughs of nFETs (I max=714 mA/mm, gmax=590 mS/mm) by Recessed Channel and S/D, H. Wu et al. (Purdue U.)

The authors report on a new approach to realize the Ge CMOS technology based on the recessed channel and source/drain (S/D). Both junctionless (JL) nFETs and pFETs are integrated on a common GeOI substrate. The recessed S/D process greatly improves the Ge n-contacts. A record high maximum drain current (Imax) of 714 mA/mm and trans-conductance (gmax) of 590 mS/mm, high Ion/Ioff ratio of 1×105 are archived at channel length (Lch) of 60 nm on the nFETs. Scalability studies on Ge nFETs are conducted sub-100 nm region down to 25 nm for the first time. Considering the Fermi level pining near the valence band edge of Ge, a novel hybrid CMOS structure with the inversion-mode (IM) Ge pFET and the accumulation-mode (JAM) Ge nFET is proposed.

 

13.4: Lowest Variability SOI FinFETs Having Multiple Vt by Back-Biasing, T. Matsukawa et al. (AIST)

FinFETs with an amorphous metal gate (MG) are fabricated on silicon-on-thin-buried-oxide (SOTB) wafers for realizing both low variability and tunable threshold voltage (Vt) necessary for multiple Vt solution. The FinFETs with an amorphous TaSiN MG record the lowest on-state drain cur-rent (Ion) variability (0.37 %μm) in comparison to bulk and SOI planar MOSFETs thanks to the suppressed variability of Vt (AVt=1.32 mVμm), drain induced barrier lowering (DIBL) and trans-conductance (Gm). Back-biasing through the SOTB provides excellent Vt controllability keeping the low Vt variability in contrast to Vt tuning by fin channel doping.

 

13.6: Demonstration of Ultimate CMOS based on 3D Stacked InGaAs-OI/SGOI Wire Channel MOSFETs with Independent Back Gate (Late News), T. Irisawa et al. (GNC-AIST)

An ultimate CMOS structure composed of high mobility wire channel InGaAs-OI nMOSFETs and SGOI pMOSFETs has been successfully fabricated by means of sequential 3D integration. Well behaved CMOS inverters and first demonstration of InGaAs/SiGe (Ge) dual channel CMOS ring oscillators are reported. The 21-stage CMOS ring oscillator operation was achieved at Vdd as low as 0.37 V with the help of adaptive back gate bias, VBG control.

 

17.3: Ultralow-Voltage Design and Technology of Silicon-on-Thin-Buried-Oxide (SOTB) CMOS for Highly Energy Efficient Electronics in IoT Era (Invited), S. Kamohara et al. (Low-power Electronics Association & Project, U. Electro-Communications, Keio U, Shibaura IT, Kyoto IT, U.Tokyo)

Ultralow-voltage (ULV) operation of CMOS circuits is effective for significantly reducing the power consumption of the circuits. Although operation at the minimum energy point (MEP) is effective, its slow operating speed has been an obstacle. The silicon-on-thin-buried-oxide (SOTB) CMOS is a strong candidate for ultralow-power (ULP) electronics because of its small variability and back-bias control. These advantages of SOTB CMOS enable power and performance optimization with adaptive Vth control at ULV and can achieve ULP operation with acceptably high speed and low leakage. In this paper, the authors describe their recent results on the ULV operation of the CPU, SRAM, ring oscillator, and, other lcircuits. Their 32-bit RISC CPU chip, named “Perpetuum Mobile,” has a record low energy consumption of 13.4 pJ when operating at 0.35 V and 14 MHz. Perpetuum-Mobile micro-controllers are expected to be a core building block in a huge number of electronic devices in the internet-of-things (IoT) era.

 

18.1: Direct Measurement of the Dynamic Variability of 0.120μm2 SRAM Cells in 28nm FD-SOI Technology, J. El Husseini et al. (CEA-Leti, STMicroelectronics)

The authors presented a new characterization technique successfully used to measure the dynamic variability of SRAMs at the bitcell level. This effective method easily replaces heavy simulations based on measures at transistors level. (It’s worth noting that this could save characterization/modeling costs and improve the accuracy of modeling.)  Moreover, an analytical model was proposed to explain the SRAM cell variability results. Using this model, the read failure probability after 10 years of working at operating conditions is estimated and is shown to be barely impacted by this BTI-induced variability in this FD-SOI technology.

 

18.2: Ultra-Low Voltage (0.1V) Operation of Vth Self-Adjusting MOSFET and SRAM Cell, A. Ueda et al. (U. Tokyo)

A Vth self-adjusting MOSFET consisting of floating gate is proposed and the ultra-low voltage operation of the Vth self-adjustment and SRAM cell at as low as 0.1V is successfully demonstrated.  In this device, Vth automatically decreases at on-state and increases at off-state, resulting in high Ion/Ioff ratio as well as stable SRAM operation at low Vdd. The minimum operation voltage at 0.1V is experimentally demonstrated in 6T SRAM cell with Vth self-adjusting nFETs and pFETs.

 

18.3: Systematic Study of RTN in Nanowire Transistor and Enhanced RTN by Hot Carrier Injection and Negative Bias Temperature Instability, K. Ota et al. (Toshiba)

The authors experimentally study the random telegraph noise (RTN) in nanowire transistor (NW Tr.) with various NW widths (W), lengths (L), and heights (H). Time components of RTN such as time to capture and emission are independent of NW size, while threshold voltage fluctuation by RTN was inversely proportional to the one-half power of circumference corresponding to the conventional carrier number fluctuations regardless of the side surface orientation. Hot carrier injection (HCI) and negative bias temperature instability (NBTI) induced additional carrier traps leading to the increase in the number of observed RTN. Moreover, threshold voltage fluctuation is enhanced by HCI and NBTI and increase of threshold voltage fluctuation becomes severer in narrower W.

 

SOI Highlights from the Symposium on VLSI Circuits

C19.4: A 110mW, 0.04mm2, 11GS/s 9-bit interleaved DAC in 28nm FDSOI with >50dB SFDR across Nyquist. E. Olieman et al. (U.Twente)

The authors presented an innovative nine-bit interleaved DAC (digital-to-analog converter) implemented in a 28nm FD-SOI technology. It uses two-time interleaving to suppress the effects of the main error mechanism of current-steering DACs. In addition, its clock timing can be tuned by back gate bias voltage. The DAC features an 11 GS/s sampling rate while occupying only 0.04mm2 and consuming only 110mW at a 1.0V supply voltage.

 

UTwenteC194VLSI14lowres

(Courtesy: VLSI Symposia)

A nine-bit interleaved digital-to-analog converter (DAC) from the University of Twente uses two-time interleaving to suppress the effects of the main error mechanism of current-steering DACs. The low-power device features an 11 GS/s sampling rate and occupies only 0.04mm2. From A 110mW, 0.04mm2, 11GS/s 9-bit interleaved DAC in 28nm FDSOI with >50dB SFDR across Nyquist, E. Olieman et al. (University of Twente)

 

 

C6.4: A Monolithically-Integrated Optical Transmitter and Receiver in a Zero-Change 45nm SOI Process, M. Georgas et al . (MIT, U.Colorado/Boulder)

An optical transmitter and receiver with monolithically-integrated photonic devices and circuits are demonstrated together for the first time in a commercial 45nm SOI process, without any process changes. The transmitter features an interleaved-junction carrier-depletion ring modulator and operates at 3.5Gb/s with an 8dB extinction ratio and combined circuit and device energy cost of 70fJ/bit. The optical receiver connects to an integrated SiGe detector designed for 1180nm wavelength and performs at 2.5Gb/s with 15μA sensitivity and energy cost of 220fJ/bit.

ByAdministrator

The SOI Papers at VLSI ’14 (Part 1): Breakthroughs in 14nm FD-SOI, 10nm SOI-FinFETs

The VLSI Symposia – one on technology and one on circuits – are among the most influential in the semiconductor industry. Three hugely important papers were presented – one on 14nm FD-SOI and two on 10nm SOI FinFETs – at the most recent symposia in Honolulu (9-13 June 2014). In fact, three out of four papers in the Highlights Sessions covered SOI devices for the 10 and 14nm nodes.

There were so many great SOI-based papers that we’re going to cover this conference in two posts.  This post covers the three big 14nm FD-SOI and 10nm FinFET papers. Summaries and abstracts of all the others will be covered in Part 2 (click here to read Part 2).  Please note that as of this posting date, the papers are not yet available from the IEEE Xplore site – but they should be shortly.

Read on!

Top SOI Highlights from the Symposium on VLSI Technology

2.3: 14-nm FDSOI Platform Technology for High-Speed and Energy-Efficient Applications. O. Weber et al. (STMicroelectronics, CEA-LETI, IBM)

This is the big paper we’ve been waiting for – the one that indicates 14nm FD-SOI should match the performance of 14nm bulk FinFETs. We still don’t have a side-by-side FD-SOI v. bulk FinFET comparison, as there is scant data at comparable leakage on bulk FinFETs at 14nm publicly available with which to compare. But based on what they’ve been seeing and some extrapolation, the FD-SOI  technology developers see the figures presented in this paper as a big win.  We’ve already seen hints of this in a recent ASN piece (click here to see that one) showing 14nm FD-SOI matching 14nm bulk for performance and coming in at a much lower cost.  Now in terms of performance, here’s the VLSI paper detailing the FD-SOI side of the story.

The authors confirm a scaling path for FD-SOI technology down to 14nm, using strain-engineered FD-SOI transistors. Compared to 28-nm FDSOI, this work provides an 0.55x area reduction from scaling and delivers a 30% speed boost at the same power, or a 55% power reduction at the same speed, due to an increase in drive current and low gate-to-drain capacitance. Using forward back-bias, an additional 40% dynamic power reduction for ring oscillators is experimentally demonstrated. Moreover, a full single-port SRAM is described, including a 0.081 μm2 high-density bitcell and two 0.090 μm2 bitcell designs used to address high-performance and low-leakage/low Vmin requirements.

Paper-T2.3-14nm-FDSOI-Technology-for-High-Speed-and-Energy-Efficient-Applications

(Courtesy: VLSI Symposia)

 

TEM of an FD-SOI nMOS transistor, showing gate-to-drain capacitance components and experimental values. From 14-nm FDSOI Platform Technology for High-Speed and Energy-Efficient Applications (O. Weber et al., STMicroelectronics, CEA-LETI & IBM)

 

 

 

 

 

2.2: A 10nm Platform Technology for Low Power and High Performance Application Featuring FINFET Devices with Multi Workfunction Gate Stack on Bulk and SOI.  K.-I. Seo et al.  (Samsung, IBM, ST, GF, UMC)

This paper covers the first-ever demonstration of FinFET technology suitable for 10-nm CMOS manufacturing. Targeting low-power and high-performance, it offers the tightest contacted poly pitch (64 nm) and metallization pitch (48 nm) ever reported on both bulk and SOI substrates. A 0.053 μm2 SRAM bit-cell – and this part was on SOI –  was reported with a low corresponding static noise margin of 140 mV at 0.75 V.  The team developed intensive multi-patterning technology and various self-aligned processes with 193i lithography to overcome optical patterning limits. A multi-workfunction gate stack provides Vt tunability without the variability degradation channel dopants induce.

Paper-T2.2-A-10nm-Platform-Technology-for-Low-Power-and-High-Performance-Applications-Featuring-FINFET-Devices-with-Multi-Workfunction-Gate-Stack-on-Bulk-and-SOI

(Courtesy: VLSI Symposia)

 

Projected scaling trend, featuring the tightest contacted poly pitch (CPP=64 nm) and metallization pitch (Mx=48 nm) ever reported, on both bulk and SOI substrates. From A 10nm Platform Technology for Low Power and High Performance Application Featuring FINFET Devices with Multi Workfunction Gate Stack on Bulk and SOI, by K.-I. Seo et al.  (Samsung, IBM, ST GF, UMC)

 

 

 

 

2.4: Strained Si1-xGex-on-Insulator PMOS FinFETs with Excellent Sub-Threshold Leakage, Extremely-High Short-Channel Performance and Source Injection Velocity for 10nm Node and Beyond, P. Hashemi et al. (IBM, GlobalFoundries, MIT)

The authors demonstrated high performance (HP) s-SiGe pMOS pMOSsfinFETs with Ion/Ieff of ~1.05/0.52mA/μm and ~1.3/0.71mA/μm at Ioff=100nA/μm at VDD=0.8 and 1V, extremely high intrinsic performance and source injection velocity. Compared to earlier work, an optimized process flow and a novel interface passivation scheme, result in ~30% mobility enhancement and dramatic sub-threshold-swing reduction to 65mV/dec. They also demonstrate the most aggressively scaled s-SiGe finFET reported to date, with WFIN~8nm and L G~15nm, while maintaining high current drive and low leakage. With their very low GIDL-limited ID, min and more manufacturing-friendly process compared to high-Ge content SiGe devices, as well as impressive Ion~0.42mA/μm at Ioff =100nA/μm and gm, int as high as 2.4mS/μm at VDD=0.5V, s-SiGe FinFETs are strong candidates for future HP and low-power applications.

VLSI_2.4

(Courtesy: VLSI Symposia)

 

TEM images of the most aggressively scaled SiGe FinFET reported to date with a fin width of ~8nm and gate length of ~15nm. From Strained Si1-xGex-on-Insulator PMOS FinFETs with Excellent Sub-Threshold Leakage, Extremely-High Short-Channel Performance and Source Injection Velocity for 10nm Node and Beyond, P. Hashemi et al. (IBM, GlobalFoundries, MIT)

 

 

 

Rump Sessions

There were also two rump sessions held during the conference, which were co-chaired by Soitec CTO Carlos Mazure. The SOI ecosystem was well-represented, the rooms were packed and the debate lively.

Rump Session 1: Who gives up on scaling first: device and process technology engineers, circuit designers, or company executives?  Which scaling ends first – memory, or logic? Panelists: M. Bohr, Intel; M. Cao, TSMC; J. Chen, Nvidia; S-H Lee, Hynix; T-J King Liu, UC Berkeley; K. Nii, Renesas: R. Shrivastava, Sandisk; H. Jaouen, STMicroelectronics; E. Terzioglu, Qualcomm

The take-away here is that the majority of panelists and attendees see company executives giving up on scaling in the face of rising costs.

Rump Session 2: 450 mm, EUV, III-V, 3D; All in 7nm? Are you serious?!  Panelists:  W. Arnold, ASML;
 R. Gottscho, Lam Research; K. Hasserjian, AMAT; S. Iyer, IBM;
 C. Maleville, Soitec; A. Steegen, IMEC

The general consensus was that 3D integration is needed and will be adopted at the 7nm node due to delays and the high cost of the EUV and III-V, and the lack of 450mm wafer supply and support.

ByAdministrator

IEDM ’13 (Part 2): More SOI and Advanced Substrate Papers

SOI and other advanced substrates were the basis for dozens of excellent papers at IEDM ’13.  Last week we covered the FD-SOI papers (click here if you missed that piece). In this post, we’ll cover the other major SOI et al papers – including those on FinFETs, RF and various advanced devices.

Brief summaries, culled from the program (and some of the actual papers) follow.

 

SOI-FinFETS

9.4 2nd Generation Dual-Channel Optimization with cSiGe for 22nm HP Technology and Beyond (IBM)

This paper about performance boosters is applicable to all flavors of SOI-based devices, including FinFET, planar FD-SOI and partially-depleted SOI. At 22nm for high-performance (HP), IBM is still doing the traditional partially-depleted (PD) SOI. At 14nm, when they go to SOI-FinFETs, one of the channel stressors to boost performance is Silicon-Germanium (cSiGe). To better understand the physics, layout effects and impact of cSiGe on device performance, IBM leveraged their 22nm HP technology to do a comprehensive study. They got a 20% performance boost and 10% Short Channel Effect (SCE) improvement, and showed that this 2nd generation high-performance dual-channel process can be integrated into a manufacturable and yieldable technology, thereby providing a solid platform for introduction of SiGe FinFet technology.

 

13.5 Comprehensive study of effective current variability and MOSFET parameter correlations in 14nm multi-Fin SOI FINFETs  (GlobalFoundries, IBM)

SOI FINFETs are very attractive because of their added immunity to Vt variability due to undoped channels. However, circuit level performance also depends on the effective current (Ieff) variability. According to the advance program, “A first time rigorous experimental study of effective current (Ieff) variability in high-volume manufacturable (HVM) 14nm Silicon-On-Insulator (SOI) FINFETs is reported which identifies, threshold voltage (Vtlin), external resistance (Rext), and channel trans-conductance (Gm) as three independent sources of variation. The variability in Gm, Vtlin (AVT=1.4(n)/0.7(p) mV-μm), and Ieff exhibit a linear Pelgrom fit indicating local variations, along with non-zero intercept which suggests the presence of global variations at the wafer level. Relative contribution of Gm to Ieff variability is dominant in FINFETs with small number of fins (Nfin); however, both Gm and Rext variations dominate in large Nfin devices. Relative contribution of Vtlin remains almost independent of Nfin. Both n and p FINFETs show the above mentioned trends.”

 

20.5 Heated Ion Implantation Technology for Highly Reliable Metal-gate/High-k CMOS SOI FinFETs (AIST, Nissin Ion Equipment)

In this paper, the researchers thoroughly investigated the impact of the heated ion implantation (I/I) technology on HK/MG SOI FinFET performance and reliability, which it turns out is excellent. They demonstrated that “…the heated I/I brings perfect crystallization after annealing even in ultrathin Si channel. For the first time, it was found that the heated I/I dramatically improves the characteristics such as Ion-Ioff, Vth variability, and bias temperature instability (BTI) for both nMOS and pMOS FinFETs in comparison with conventional room temperature I/I.”

 

26.2:  Advantage of (001)/<100> oriented Channel to Biaxial and Uniaxial Strained Ge-on-Insulator pMOSFETs with NiGe S/D (AIST)

In this paper about boosters in fully-depleted planar SOI and GeOI based devices, the researchers “compared current drivability between (001)/<100> and (001)/<110> strained Ge-on-insulator pMOSFETs under biaxial and uniaxial stress.” They experimentally demonstrated for the first time that in short channel (Lg < 100 nm) devices, <100> channels exhibit higher drive current than <110> channels under both the biaxial- and the uniaxial stress, in spite of the disadvantage in mobility, although this is not the case with longer channel devices. The advantage is attributable to higher drift velocity in high electric field along the direction and becomes more significant for shorter Lg devices. The strained-Ge (001)/<100> channel MOSFET have a potential to serve as pFET of ultimately scaled future CMOS.

 

33.1 Simulation Based Transistor-SRAM Co-Design in the Presence of Statistical Variability and Reliability (Invited) (U. Glasgow, GSS, IBM)

With ever-reducing design cycles and time-to-market, design teams need early delivery of a reliable PDK before mature silicon data becomes available. This paper shows that the GSS ‘atomistic’ simulator GARAND used in this study provides accurate prediction of transistor characteristics, performance and variability at the early stages of new technology development and can serve as a reliable source for PDK development of emerging technologies, such as SOI FinFET.  Specifically, the authors report on, “…a systematic simulation study of the impact of process and statistical variability and reliability on SRAM cell design in a 14nm technology node SOI FinFET transistors. A comprehensive statistical compact modeling strategy is developed for early delivery of a reliable PDK, which enables TCAD- based transistor-SRAM co-design and path finding for emerging technology nodes.” 

 

RF-SOI

1.3: Smart Mobile SoC Driving the Semiconductor Industry: Technology Trend, Challenges and Opportunities (Qualcomm)

In this plenary presentation, Geoffry Yeap, VP of Technology at Qualcomm gave a perspective on state of the art mobile SoCs and RF/analog technologies for RF SOCs. The challenge, he said in his paper, is “…lower power for days of active use”. He cited the backgate for asymmetric gate operation and dynamic Vt control, noting that FinFETs lack an easy way to access the back gates. “This is especially crucial when Vdd continues to scale lower to a point that there is just not sufficient (Vg-Vt) to yield meaningful drive current,” he continued. While he sees FD-SOI “very attractive”, he is concerned about the ecosystem, capacity and starting wafer price.

With respect to RF-SOI, the summary of his talk in the program stated, “Cost/power reduction and unique product capability are enabled by RF front end integration of power amplifiers, antenna switches/tuners and power envelope tracker through a cost-effective RF-SOI instead of the traditional GaAs.”

 

Advanced Devices

Post-FinFETs, one of the next-generation device architectures being heavily investigated now is  gate-all-around (GAA). While FinFETs have gate material on three sides, in GAA devices the gate completely surrounds the channel. A popular fabrication technique is to build them around a nanowire, often on an SOI substrate.

4.4 Demonstration of Improved Transient Response of Inverters with Steep Slope Strained Si NW TFETs by Reduction of TAT with Pulsed I-V and NW Scaling  (Forschungszentrum Jülich, U. Udine, Soitec)

This is a paper about a strained Si (sSi) nanowire array Tunnel FETs (TFETs). The researchers demonstrated that scaled gate all around (GAA) strained Si (sSi) nanowire array (NW) Tunnel FETs (TFETs) allow steep slope switching with remarkable high ION due to optimized tunneling junctions. Very steep tunneling junctions have been achieved by implantations into silicide (IIS) and dopant segregation (DS) with epitaxial Ni(AlxSi1-x)2 source and drain. The low temperature and pulse measurements demonstrate steep slope TFETs with very high I60 as TAT is suppressed. GAA NW TFETs seem less vulnerable to trap assisted tunneling (TAT). Time response analysis of complementary-TFET inverters demonstrated experimentally for the first time that device scaling and improved electrostatics yields to faster time response.

 

IBM_IEDMBangsaruntip20.2Fig.4

(image courtesy: IBM, IEEE/IEDM)

20.2 Density Scaling with Gate-All-Around Silicon Nanowire MOSFETs for the 10 nm Node and Beyond (IBM)

Record Silicon Nanowire MOSFETs: IBM researchers described a silicon nanowire (SiNW)-based MOSFET fabrication process that produced gate-all-around (GAA) SiNW devices at sizes compatible with the scaling needs of 10-nm CMOS technology. They built a range of GAA SiNW MOSFETs, some of which featured an incredible 30-nm SiNW pitch (the spacing between adjacent nanowires) with a gate pitch of 60 nm. Devices with a 90-nm gate pitch demonstrated the highest performance ever reported for a SiNW device at a gate pitch below 100 nm— peak/saturation current of 400/976 µA/µm, respectively, at 1 V. Although this work focused on NFETs, the researchers say the same fabrication techniques can be used to produce PFETs as well, opening the door to a potential ultra-dense, high-performance CMOS technology.

 

 

26.4 FDSOI Nanowires: An Opportunity for Hybrid Circuit with Field Effect and Single Electron Transistors (Invited) (Leti)

This paper is about nanowires and single electron transistors (SET).  As indicated in the  program, “When FDSOI nanowires width is scaled down to 5nm, the nanowires can encounter a dramatic transition to single electron transistor characteristics. This enables the first room temperature demonstration of hybrid SET-FET circuits thus paving the way for new logic paradigms based on SETs. Further scaling would rely on deterministic dopant positioning. We have also shown that Si based electron pumps using tunable barriers based on FETs are promising candidates to realize the quantum definition of the Ampere.”

 

26.6 Asymmetrically Strained High Performance Germanium Gate-All-Around Nanowire p-FETs Featuring 3.5 nm Wire Width and Contractable Phase Change Liner Stressor (Ge2Sb2Te5) (National U. Singapore, Soitec)

In this paper about GAA and nanowires, the researchers report “…the first demonstration of germanium (Ge) GAA nanowire (NW) p-FETs integrated with a contractable liner stressor. High performance GAA NW p-FET featuring the smallest wire width WNW of ~3.5 nm was fabricated. Peak intrinsic Gm of 581 μS/μm and SS of 125 mV/dec was demonstrated. When the Ge NW p-FETs were integrated with the phase change material Ge2Sb2Te5 (GST) as a liner stressor, the high asymmetric strain was induced in the channel to boost the hole mobility, leading to ~95% intrinsic Gm,lin and ~34% Gm,sat enhancement. Strain and mobility simulations show good scalability of GST liner stressor and great potential for hole mobility enhancement.”

 

III-V, More Than Moore and Other Interesting Topics

28.5 More than Moore: III-V Devices and Si CMOS Get It Together (Invited) (Raytheon)

This is continuation of a major ongoing III-V and CMOS  integration project that Raytheon et al wrote about in ASN five years ago (see article here).  As noted in the IEDM program, the authors “…summarize results on the successful integration of III-V electronic devices with Si CMOS on a common silicon substrate using a fabrication process similar to SiGe BiCMOS. The heterogeneous integration of III-V devices with Si CMOS enables a new class of high performance, ‘digitally assisted’, mixed signal and RF ICs.

 

31.1 Technology Downscaling Worsening Radiation Effects in Bulk: SOI to the Rescue (Invited) (ST)

In this paper, the authors explore the reliability issues faced by the next generation of devices.  As they note in the description of the paper in the program, “Extrinsic atmospheric radiations are today as important to IC reliability as intrinsic failure modes. More and more industry segments are impacted. Sub-40nm downscaling has a profound impact on the Soft Error Rate (SER) of BULK technologies. The enhanced resilience of latest SOI technologies will fortunately help leveraging existing robust design solutions.”

 

13.3 A Multi-Wavelength 3D-Compatible Silicon Photonics Platform on 300mm SOI Wafers for 25Gb/s Applications (ST, Luxtera)

Luxtera’s work on Silicon Photonics and now products based on integrated optical communications has been covered here at ASN for years. In this paper Luxtera and ST (which now is Luxtera’s manufacturing partner) present a low-cost 300mm Silicon Photonics platform for 25Gb/s application compatible with 3D integration and featuring competitive optical passive and active performance. This platform aims at industrialization and offering to system designers a wide choice of electronic IC, targeting markets applications in the field of Active optical cables, optical Modules, Backplanes and Silicon  Photonics Interposer.

 

Irisawa (2.2) Fig.9

The graph above shows the high electron mobility of Triangular MOSFETs with InGaAs Channels. (Image courtesy: AIST, IEEE/IEDM) 

 

2.2. High Electron Mobility Triangular InGaAs-OI nMOSFETs with (111)B Side Surfaces Formed by MOVPE Growth on Narrow Fin Structures (AIST, Sumitomo, Tokyo Institute of Technology)

InGaAs is a promising channel material for high-performance, ultra-low-power n-MOSFETs because of its high electron mobility, but multiple-gate architectures are required to make the most of it, because multiple gates offer better control of electrostatics. In addition, it is difficult to integrate highly crystalline InGaAs with silicon, so having multiple gates offers the opportunity to take advantage of the optimum crystal facet of the material for integration. A research team led by Japan’s AIST built triangular InGaAs-on-insulator nMOSFETs with smooth side surfaces along the <111>B crystal facet and with bottom widths as narrow as 30 nm, using a metalorganic vapor phase epitaxy (MOVPE) growth technique. The devices demonstrated a high on-current of 930 μA/μm at a 300-nm gate length, showing they have great potential for ultra-low power and high performance CMOS applications.

 

16.4. High performance sub-20-nm-channel-length extremely-thin body InAs-on-insulator Tri-gate MOSFETs with high short channel effect immunity and Vth tenability (Sumitomo, Tokyo Institute of Technology)

This III-V paper investigates the effects of vertical scaling and the tri-gate structure on electrical properties of extremely-thin-body (ETB) InAs-on-insulator (-OI) MOSFETs. “It was found that Tbody scaling provides better SCEs control, whereas Tbody scaling causes μfluctuation reduction. To achieve better SCEs control, Tchannel scaling is more favorable than Tbuffer scaling, indicating QW channel structure with MOS interface buffer is essential in InAs-OI MOSFETs. Also, the Tri-gate ETB InAs-OI MOSFETs shows significant improvement of short channel effects (SCEs) control with small effective mobility (μeff) reduction. As a result, we have successfully fabricated sub-20-nm-Lch InAs-OI MOSFETs with good electrostatic with S.S. of 84 mV/dec, DIBL of 22 mV/V, and high transconductance (Gm) of 1.64 mS/μm. Furthermore, we have demonstrated wide-range threshold voltage (Vth) tunability in Tri-gate InAs-OI MOSFETs through back bias voltage (VB) control. These results strongly suggest that the Tri-gate ETB III-V-OI structure is very promising scaled devices on the Si platform to simultaneously satisfy high performance high SCE immunity and Vth tunability.”

11.1 A Flexible Ultra-Thin-Body SOI Single-Photon Avalanche Diode (TU Delft)

This is a paper on flexible electronics for display and imaging systems. “The world’s first flexible ultra-thin-body SOI single-photon avalanche diode (SPAD) is reported by device layer transfer to plastic with peak PDP at 11%, DCR around 20kHz and negligible after pulsing and cross-talk. It compares favorably with CMOS SPADs while it can operate both in FSI and BSI with 10mm bend diameter,” say the researchers.

 

11.7 Local Transfer of Single-Crystalline Silicon (100) Layer by Meniscus Force and Its Application to High-Performance MOSFET Fabrication on Glass Substrate (Hiroshima U.)

In this is a paper on flexible electronics for display and imaging systems, the researchers “…propose a novel low-temperature local layer transfer technique using meniscus force. Local transfer of the thermally-oxidized SOI layer to glass was carried out without any problem. The n-channel MOSFET fabricated on glass using the SOI layer showed very high mobility of 742 cm2V-1s-1, low threshold voltage of 1.5 V.  These results suggest that the proposed (meniscus force-mediated layer transfer) technique (MLT) and MOSFET fabrication process opens up a new field of silicon applications that is independent of scaling.”

 

Note: the papers themselves are typically available through the IEEE Xplore Digital Libary within a few months of the conference.

 

Special thanks to Mariam Sadaka and Bich-Yen Nguyen of Soitec for their help and guidance in compiling this post.

ByAdministrator

The FD-SOI Papers at IEDM ’13

FD-SOI was a hot topic at this year’s IEEE International Electron Devices Meeting (IEDM) (www.ieee-iedm.org), the world’s showcase for the most important applied research breakthroughs in transistors and electronics technology.

The FD-SOI papers featured high performance, low leakage, ultra-low power (0.4V),  excellent variability, reliability and scalability down to the 10 nm node using thin SOI and thin BOX substrate. Performance boosters using high mobility materials such as thin strain Si, Ge, and III-V on-Insulator were also presented.

Brief summaries of the FD-SOI papers, culled from the Advance Program (and some of the actual papers) follow.

9.2 High Performance UTBB FDSOI Devices Featuring 20nm Gate Length for 14nm Node and Beyond (STMicroelectronics, Leti, IBM, Renesas, Soitec, GlobalFoundries) 

This was the big paper reporting on ST’s flavor of high-performance FD-SOI (UTBB, which stands for ultra-thin-body-and-box) with 20nm gatelength, which target the 14nm node. In addition to excellent results, the paper demonstrated that  “…FD-SOI reliability is superior to Bulk devices.”

ST_IEDM13table1
[8] C. Auth, et al, VLSI, p.131, 2012 [9] C.-H. Jan, et al, IEDM, p.44, 2012

 

Specifically, the alliance reports, for the first time, on high performance UTBB FD-SOI devices with a gate length (LG) of 20nm and BOX thickness (TBOX) of 25nm, featuring dual channel FETs (Si channel NFET and compressively strained SiGe channel PFET). Competitive effective current (Ieff) reaches 630μA/μm and 670μA/μm for NFET and PFET, respectively, at off current (Ioff) of 100nA/μm and Vdd of 0.9V.

Excellent electrostatics are obtained, demonstrating the scalability of these devices to14nm and beyond. Very low AVt (1.3mV•μm) of channel SiGe (cSiGe) PFET devices is reported for the first time. BTI was improved >20% vs a comparable bulk device. The paper concludes with evidence of continued scalability to 10nm 

ST_IEDM13_Fig4

and below.

The effective current (Ieff), as a function of Ioff, is shown in Fig. 4. At Vdd=0.9V, NFET/PFET Ieff reach 630/670μA/μm at Ioff=100nA/μm, respectively. They are the best performing FDSOI CMOS devices reported so far, featuring non-strained Si channel NFET and strained SiGe channel PFET.”

7.3 Innovative ESD protections for UTBB FD-SOI Technology (STMicroelectronics, IMEP-LAHC)

ESD (electrostatic discharge) protection is often cited as a challenge in FD-SOI, and the ESD devices are typically put into a “hybrid” section of the chip, where the top silicon and insulator are etched away exposing the “bulk” silicon base wafer. In this paper, however, the ST-IMEP team presented FD-SOI ESD protection devices that achieve “remarkable performance in terms of leakage current and triggering control.” They demonstrate “ultra-low leakage current below 0.1 pA/μm and adjustable triggering (1.1V < Vt1 < 2.6V) capability. These devices rely on gate-controlled injection barriers and match the 28nm UTBB-FDSOI ESD design window by triggering before the nominal breakdown voltage of digital core MOS transistors.”

 

7.4 Comparison of Self-Heating Effect (SHE) in Short-Channel Bulk and Ultra-Thin BOX SOI MOSFETs: Impacts of Doped Well, Ambient Temperature, and SOI/BOX Thicknesses on SHE (Keio University, AIST)

This paper refutes those who say that the self-heating effect (SHE) is a bigger concern for SOI-based devices than bulk. The researchers investigated and compared bulk and SOI FETs including 6-nm ultra-thin (UT) BOX devices. They clarified, for the first time, that SHE is not negligible in bulk FETs, mainly due  to a decrease in the thermal conductivity of the more heavily doped well.  They found that the channel temperature of 6-nm UT BOX SOI FETs is close to that of bulk FETs at a chip temperature under operations. They then proposed a thermal-aware FD-SOI device design structure based on evaluated BOX/SOI thickness dependences of SHE. They concluded that SHEs in UTBB FETs with raised S/D and/or contact pitch scaling could be comparable to bulk FETs in deeply scaled nodes.

 

20.3 Gate-Last Integration on Planar FDSOI MOSFET: Impact of Mechanical Boosters and Channel Orientations  (Leti, ST)

This paper presents the industry’s first “gate last” (GL) results for FD-SOI, with ultra-thin silicon body (3-5nm) and BOX (25nm).  The team successfully fabricated transistors down to the 15nm gate length, with metal-last on high-k first (TiN/HfSiON). They thoroughly characterized the gate stack (reliability, work-function tuning on Equivalent Oxide Thickness EOT=0.85nm) and transport (hole mobility, Raccess) for different surface and channel orientations. They report excellent Ion, p=1020μA/μm at Ioff, p=100nA/μm at Vdd=0.9V supply voltage for <110> pMOS channel on (001) surface with in-situ boron doped SiGe Raised Source and Drain (RSD) and compressive CESL. They cite the high efficiency of the strain transfer into the ultra-thin channel (-1.5%), as evidenced by physical strain measurements by dark field holography.

 

12.4 UTSOI2: A Complete Physical Compact Model for UTBB and Independent Double Gate MOSFETs (ST, Leti)

Compact models of transistors and other elementary devices are used to predict the behavior of a design. As such, they are embedded in simulations like SPICE that designers run before actual manufacturing. In this paper, ST and Leti researchers presented a complete physical compact model called UTSOI2, which is dedicated to Ultra-Thin Body and Box FD-SOI technology, and is able to describe accurately independent double gate operation for sub-20nm nodes. It meets standard Quality and Robustness tests for circuit design applications.

12.5 Mobility in High-K Metal Gate UTBB-FDSOI Devices: From NEGF to TCAD Perspectives (Invited) (ST, Leti, U. Udine, Synopsys, Laboratoire Hubert Curien & Institut d’Optique, IBM)

This paper reviews important theoretical and experimental aspects of both electrostatics and channel mobility in High-K Metal Gate UTBB-FDSOI MOSFETs. With an eye toward optimization, the team presents a simulation chain, including advanced quantum solvers, and semi-empirical Technology Computer Assisted Design (TCAD) tools.

 

33.2 Suppression of Die-to-Die Delay Variability of Silicon on Thin Buried Oxide (SOTB) CMOS Circuits by Balanced P/N Drivability Control with Back-Bias for Ultralow-Voltage (0.4 V) Operation (LEAP, U. Tokyo)

SOTB is what Hitachi calls its flavor of FD-SOI.  The researchers point out that small-variability transistors like SOTB are effective for reducing the operation voltage (Vdd). This paper proposes the balanced n/p drivability for reducing the die-to-die delay variation by back bias for various circuits. Excellent delay variability reduction by this n/p balanced control is demonstrated at ultra-low Vdd of 0.4 V.

 

2.8: Co-Integration of InGaAs n- and SiGe p-MOSFETs into Digital CMOS Circuits Using Hybrid Dual-Channel ETXOI Substrate (IBM)

ETSOI is IBM’s flavor of FD-SOI, and this paper is about FD-SOI devices using high mobility material for boosting performance. The presenters “demonstrate for the first time on the same wafer and on the same device level a dense co-integration of co-planar nano-scaled SiGe p-FETs and InGaAs n-FETs UTBB FETs. This result is based on hybrid substrates containing extremely-thin SiGe and InGaAs layers on insulators (ETXOI) using double bonding.” They showed a) that it could be done; b) it’s viable hybrid high-mobility dual-channel CMOS; c) it still supports back-biasing for Vt tuning.

 

5.2 Surface Roughness Limited Mobility Modeling in Ultra-Thin SOI and Quantum Well III-V MOSFETs  (DIEGM – U. Udine)

As with the IBM paper (2.8) above, this paper is about FD-SOI devices using high mobility material for boosting performance. The abstract explains, “This paper presents a new model for surface roughness mobility accounting for the wave-function oxide penetration and can naturally deal with Hetero-Structure. Calibration with experiments in Si MOSFETs results in a r.m.s. value of the SR spectrum in close agreement with AFM and TEM measurements.” The simulated μSR in III-V UTB MOSFETs shows a weaker degradation at small channel thickness (Tw) than predicted by the T6w law observed in UTB Si MOSFETs.

Please stay tuned for a subsequent ASN post that will cover the meeting’s SOI-FinFET, RF-SOI and advanced device papers.  (The papers themselves are typically available through the IEEE Xplore Digital Libary within a few months of the conference.)

ByAdele Hars

Fully-Depleted SOI (and more) at VLSI (Kyoto): some knock-your-socks-off papers

Look for some breakthrough FD-SOI and other excellent SOI-based papers coming out of the 2013 Symposia on VLSI Technology and Circuits in Kyoto (June 10-14).

By way of explanation, VSLI comprises two symposia: one on Technology; one on Circuits. However, papers that are relevant to both are presented in “Jumbo Joint Focus” sessions.

Here’s a quick preview.

Papers in the Jumbo-Joint Focus Sessions

JJ2-3: FDSOI Process/Design full solutions for Ultra Low Leakage, High Speed and Low Voltage SRAMs, R. Ranica et al., STMicroelectronics & CEA-LETI

In this paper from STMicroelectronics and CEA-LETI, six Transistor SRAM (6T- SRAM) cells for High Density (0.120 µm2), High Current (0.152 µm2) and Low Voltage (0.197µm2) purposes are fabricated with 28 nm node FDSOI technology for the first time. Starting from a direct porting of bulk planar CMOS design, the improvement in read current Iread has been confirmed up to +50% (@Vdd=1.0V) & +200% (@ Vdd=0.6 V), respectively, compared with 28 nm Low-Power (LP) CMOS technology. Additionally, -100mV minimum operating voltage (Vmin) reduction has been demonstrated with 28 nm FDSOI technology. Alternative flip-well and single well architecture provides further speed and Vmin improvement, down to 0.42V on 1Mb 0.197µm2 . Ultimate stand-by leakage below 1pA on 0.120 µm2 bitcell at Vdd=0.6V is finally reached by taking the full benefits of the back bias capability of FDSOI.

Cross-sectional and plain view of FDSOI SRAM cells for High Density (0.120 µm2), High Current (0.152 µm2) and Low Voltage(0.197µm2).

JJ1-8: First Demonstration of a Full 28nm High-k/Metal Gate Circuit Transfer from Bulk to UTBB FDSOI Technology Through Hybrid Integration, D. Golanski et al, ST Microelectronics and CEA-LETI

For the first time a full hybrid integration scheme is proposed, allowing a full circuit design transfer from 28nm Bulk CMOS high-k/metal gate onto UTBB FDSOI with minimum design effort. As the performance of FDSOI logic and SRAM devices have already been reported, this paper highlights the original way to integrate ESD devices, variable MOS capacitors and vertical bipolar transistor within the frame of our hybrid technology. Competitive ESD performance for the same footprint is achieved through hybrid MOSFETS snap-back voltage reduction, obtained by implant engineering. In addition, we demonstrate that the performance of Silicon Controlled Rectifier (SCR) and ESD diodes are matched vs Bulk technology while maintaining the performance of FDSOI devices and without any additional masks.

JJ1-9: 2.6GHz Ultra-Wide Voltage Range Energy Efficient Dual A9 in 28nm UTBB FD-SOI, D. Jacquet et al. STMicroelectronics

This paper presents the implementation details and silicon results of a 2.6GHz dual-core ARM Cortex A9 manufactured in a 28nm Ultra-Thin Body and BOX FD-SOI technology. The implementation is based on a fully synthesizable standard design flow, and the design exploits the great flexibility provided by FD-SOI technology, notably a wide Dynamic Voltage and Frequency Scaling (DVFS) range, from 0.6V to 1.2V, and forward body bias (FBB) techniques up to 1.3V bias voltage, thus enabling an extremely energy efficient implementation.
(Note: ST has indicated that 2.6GHz voltage range in the title dates from the time the paper was submitted earlier this year; the actual presentation will show a more extended range.)

JJ2-1 (Invited): Fully-Depleted Planar Technologies and Static RAM, T. Hook et al, IBM, STMicroelectronics, LETI

Key elements of FDSOI (Fully Depleted Silicon on Insulator) technology as applied to SRAMs are described.Thick- and thin-Bottom Oxide (BOX) variants are discussed.

JJ2-4: Ultralow-Voltage Operation of Silicon-on-Thin-BOX (SOTB) 2Mbit SRAM Down to 0.37 V Utilizing Adaptive Back Bias, Y. Yamamoto et al, Low-power Electronics Association & Project (LEAP), The University of Tokyo

We demonstrated record 0.37 V minimum operation voltage (Vmin) of 2Mbit Silicon-on-Thin-Buried-oxide (SOTB) 6T-SRAM. Thanks to small variability of SOTB (AVT~1.2-1.3 mVμm) and adaptive body biasing (ABB), Vmin was lowered down to ~0.4 V regardless of temperature. Both fast access time and small standby leakage were achieved by ABB.
(Note: SOTB is a flavor of planar FD-SOI.)

In the Circuits Symposia

Paper T2-2: High Performance Si1-xGex Channel on Insulator Trigate PFETs Featuring an Implant- Free Process and Aggressively-Scaled Fin and Gate Dimensions, P. Hasemi et al., IBM & GlobalFoundries.

The adoption of advanced high-mobility Silicon Germanium (SiGe) channel materials with aggressively scaled Tri-gate pFETs on insulator is reported for the first time. SiGe is widely known as a suitable channel material for p-type MOS device, thanks to its higher hole mobility than that in conventional silicon material. In this paper, IBM and GlobalFoundries report a SiGe channel Tri-gate pFET with aggressively scaled Fin width (Wfin) and Gate length(Lg) dimensions, which is fabricated using SiGe on insulator substrate. Excellent electrostatic control down to Lg= 18 nm and Wfin< 18 nm has been reported. Using an optimized implant-free raised source/drain process, on-current Ion = 1.1 mA/µm at off-leakage current Ioff = 100 nA/µm and supply voltage Vdd= 1.0 V has been achieved.

(a) Cross-section TEM images across SiGe fin with Hfin = 17 nm and Wfin = 10.0, 13.5 and 18.0 nm. (b) Cross-section TEM image of a single-fin with Gate length less than 20 nm.

(a) Cross-section TEM images across SiGe fin with Hfin = 17 nm and Wfin = 10.0, 13.5 and 18.0 nm.
(b) Cross-section TEM image of a single-fin with Gate length less than 20 nm.

15-4: A 28GHz Hybrid PLL in 32nm SOI CMOS, M. Ferriss et al, IBM

A hybrid PLL is introduced, which features a simple switched resistor analog proportional path filter in parallel with a highly digital integral path. The integral path control scheme for the LC-tank VCO includes a novel linearly scaled capacitor bank configuration. At 28 GHz the RMS jitter is 199fs (1MHz to 1GHz), phase noise is -110dBc/Hz at 10MHz offset. The 140μmx160μm 32μm SOI CMOS PLL locks from 23.8 to 30.2 GHz, and draws 31mA from a 1V supply.

21-1: A 35mW 8 b 8.8 GS/s SAR ADC with Low-Power Capacitive Reference Buffers in 32 nm Digital SOI CMOS, L. Kull et al, IBM, EPFL

An asynchronous 8x interleaved redundant SAR ADC achieving 8.8GS/s at 35mW and 1V supply is presented. The ADC features pass-gate selection clocking scheme for time skew minimization and per-channel gain control based on low-power reference voltage buffers. Gain control of each sub-ADC is based on a fine-grain, robust R-3R ladder. The sub-ADC stacks the capacitive SAR DAC with the reference capacitor to reduce the area and enhance the settling speed. The speed and area optimized sub-ADC as well as a short tracking window of 1/8 period enable a low input capacitance and therefore render an input buffer unnecessary. The ADC achieves 38.5dB SNDR and 58fJ/conversion-step with a core chip area of 0.025mm2in 32nm CMOS SOI technology.

21-3: An 8.5mW 5GS/s 6b Flash ADC with Dynamic Offset Calibration in 32nm CMOS SOI, V.H.-C. Chen and L. Pileggi, Carnegie Mellon University

This paper describes a 5GS/s 6bit flash ADC fabricated in a 32nm CMOS SOI. The randomness of process mismatch is exploited to compensate for dynamic offset errors of comparators that occur during high speed operation. Utilizing the proposed calibration, comparators are designed with near-minimum size transistors and built-in reference levels. The ADC achieves an SNDR of 30.9dB at Nyquist and consumes 8.5mW with an FoM of 59.4fJ/conv-step.

In the Technology Symposia

5-3: Optimal Device Architecture and Hetero-Integration Scheme for III-V CMOS, Z. Yuan et al, Stanford University, Applied Materials, Sematech, Texas State University

Low density-of-states (DOS) of carriers and higher dielectric constants in III-Vs warrants transistor architecture with better electrostatics than conventional FinFETs. Additionally, the integration of III-V FinFETs on 300mm silicon wafers is a key technological challenge due to the large lattice-mismatch between III-Vs and silicon. This paper presents a statistical variability study of III-V and Si FinFETs, from which SOI-FinFET architecture is recommended for III-Vs. The co-integration of InAs-OI NMOS and GaSb-OI PMOS on silicon is proposed for its excellent carrier transport and favorable band-lineup. Such hetero-integration is demonstrated on silicon substrate using rapid-melt-growth technique.

10-1: Benefits of Segmented Si/SiGe p-Channel MOSFETs for Analog/RF Applications, N. Xu et al, University of California, Applied Materials, Soitec

Segmented-channel Si and SiGe P-MOSFETs (SegFETs) are compared against control devices fabricated using the same process but starting with non-corrugated substrates, with respect to key analog/RF performance metrics. SegFETs are found to have significant benefits due to their enhanced electrostatic integrity, lower series resistance and greater mobility enhancement, and hence show promise for future System-on-Chip applications.

14.5: 64nm Pitch Interconnects: Optimized for Designability, Manufacturability and Extendibility, C. Goldberg et al, STMicroelectronics, Samsung Electronics, GlobalFoundries, IBM

In this paper, we present a 64nm pitch integration and materials strategy to enable aggressive groundrules and extendibility for multi-node insertions. Exploitation of brightfield entitlements at trench and via lithography enables tight via and bi-directional trench pitch. Setting the same mask metal spacing equal to CPP maximized density scaling and speed of standard cell automation by avoiding cell abutment conflicts. A Self-Aligned-Via (SAV) approach was exploited for single pattern via extendibility, enabling via placement at CPP with a single mask. Yield ramp rate, groundrule validation, and reliability qualification were each accelerated by early brightfield adoption for trench and via, producing a robust cross-module process window. The resulting groundrules and process module have been plugged in to multiple technology nodes without re-development needed (e.g. 20LPM, 14nm FINFET, 14FDSOI, 10nm P&R levels). Scaling, performance, and reliability requirements are achieved across a spectrum of low power-high performance applications.

15-1: Innovative Through-Si 3D Lithography for Ultimate Self-Aligned Planar Double-Gate and Gate-All-Around Nanowire Transistors, R. Coquand et al, STMicroelectronics, CEA-LETI, IMEP-LAHC

This paper reports the first electrical results of self-aligned multigate devices based on an innovative 3D-lithography process. HSQ resist exposition through the Silicon channel allows the formation of self-aligned trenches in a single step. Planar Double-Gate (DG) and Gate-All-Around Silicon Nanowire (GAA Si NW) transistors are fabricated with conformal SiO2-Poly-Si gate stack and the first electrical results obtained with this technique are presented. The good nMOS performances (ION of 1mA per μm at VT+0.7V) with excellent electrostatics (SS down to 62mV per dec and DIBL below 10mV per V at LG 80nm) are paving the way to the ultimate CMOS architecture. To meet all requirements of lowpower SoCs, we also demonstrate the feasibility of fabricating such devices with High-K Metal-Gate (HK-MG) stack and their possible co-integration with FDSOI structures.

15-3: Scaling of Ω-Gate SOI Nanowire N- and P-FET Down to 10nm Gate Length: Size- and Orientation-Dependent Strain Effects, S. Barraud et al, CEA-LETI, CEA-INAC, STMicroelectronics, IMEP-LAHC

High-performance strained Silicon-On-Insulator nanowires with gate width and length scaled down to 10nm are presented. For the first time, effectiveness of sSOI substrates is demonstrated for ultra-scaled N-FET NW (LG=10nm) with an outstanding ION current and an excellent electrostatic immunity (DIBL=82mV/V). P-FET NW performance enhancement is achieved using in-situ etching and selective epitaxial growth of boron-doped SiGe for the formation of recessed Sources/ Drains (S/D). We show an ION improvement up to +100% induced by recessed SiGe S/D for LG=13nm P-FET NW. Finally, size- and orientation-dependent strain impact on short channel performances is discussed. <110> Si NWs provide the best opportunities for strain engineering.

17-2 (Late News): Experimental Analysis and Modeling of Self Heating Effect in Dielectric Isolated Planar and Fin Devices, S. Lee et al, IBM

Field Effect Transistors on SOI offer inherent capacitance and process advantages. The flow of heat generated at the drain junction may be impeded by dielectric isolation but an assessment must also account for conduction of heat through the gate stack and through the device contacts, and its impact on device characteristics should be captured by the scalable model to enable accurate circuit design. A quantitative comparison to 45nm planar SOI shows that while the scaled FinFET on dielectric devices show higher normalized thermal resistance, as expected from device scaling, the characteristic time constant for self heating is still well below the operating frequency of typical logic circuits, hence resulting in negligible self heating effect. For cases where the self heating becomes a factor, e.g., in high-speed I/O circuits, the same design methods can be applied for both planar and FinFET devices on dielectric isolation.

ByGianni PRATA

IEDM 11: The SOI Papers

IEDMHeld every December, the IEEE International Electron Devices Meeting (IEDM) (www.ieee-iedm.org) presents the best applied research in electronics from corporate, university and government labs around the world. Brief descriptions of the IEDM 2011 papers with research related to SOI and some other advanced substrates follows. The full program is available at: http://www.his.com/~iedm/program/11advprg.pdf The papers themselves are now available through the IEEE Xplore Digital Libary. Links are embedded in the titles here.

Session 4, Paper 1

Architecting Advanced Technologies for 14nm and Beyond with 3D FinFET Transistors for the Future SoC Applications (Invited)

A. Keshavarzi, D. Somasekhar, M. Rashed, S. Ahmed, K. Maitra, R. Miller, A. Knorr, Jin Cho, R. Augur, S. Banna, C-H. Shaw, A. Halliyal,U. Schroeder, A. Wei, J. Egley, K. Korablev, S. Luning, M-R. Lin, S. Venkatesan, S. Kengeri, G. Bartlett (GlobalFoundries).

This paper focuses on circuit and device interactions for architecting the advanced technologies for 14nm and beyond using 3D fully depleted FinFET transistors for the future SoC applications, citing various challenges & potential solutions. It notes that FinFETs can be fabricated on bulk or SOI wafers, however there is trade-off of ease of isolation, less RDF, Fin height control, and lower Cj vs wafer cost. While Bulk FinFETs provide more strain engineering capability, the authors note that strained SOI substrate showed elevated mobility due to induced uniaxial strain. (They cite a June ’11 paper entitled Aggressively Scaled Strained-Silicon-on-Insulator Undoped-Body High-k/Metal-Gate nFinFETs for High-Performance Logic Applications (IEEE Electron Device Letters, K. Maitra et al) which found that Strained SOI (SSOI) FinFETs exhibit drive currents suitable for high-performance logic technology, and that there is a ~ 15% mobility-induced ION enhancement with SSOI relative to SOI nFinFETs at ultrashort gate lengths.) They also note that that FinFETs will have good SER performance for better system reliability due to the device being segmented and even more isolated when deployed on SOI substrate.

Session 5, Paper 4

Statistical Variability and Reliability in Nanoscale FinFETs

Xingsheng Wang, Andrew R. Brown1, Binjie Cheng and Asen Asenov (University of Glasgow)

The comprehensive full-scale simulation study of statistical variability and reliability in the emerging and scaled 3D FinFETs on SOI substrate with gate-lengths of 20nm, 14nm and 10nm and low channel doping is presented. All major sources of statistical variability are investigated, along with interface trapped charges associated with N/PBTI.

Session 5, Paper 6

Self-Heating Induced Feedback Effect on Drain Current Mismatch and its Modeling

J.J.-Y. Kuo, P. Su (National Chiao Tung U)

A self-heating induced feedback (SHFE) effect on the drain current mismatch has been reported and modeled. The accuracy of the new model has been verified with experimental data. This effect needs to be considered when one-to-one comparisons between SOI and bulk devices regarding the variability are made. By 3-D atomistic electro-thermal simulations. The authors show that the SOI FinFET device exhibits smaller drain current variation than the bulk FinFET counterpart due to the SHFE.

Session 5, Paper 7

Transistor Matching and Silicon Thickness Variation in ETSOI Technology

Terence B. Hook*, Maud VinetO, Richard Murphy*, Shom Ponoth* Laurent GrenouilletO (*IBM Microelectronics, OLETI)

This paper examines transistor threshold voltage matching as a function of silicon thickness variation in ETSOI (Extremely Thin Silicon On Insulator) transistors. By analyzing AFM data, threshold voltage, and electrical silicon thickness data the authors show the behavior is not random, but has a strong dependence on distance, a weak dependence on area, and is amenable to improvement through process optimization. Adjacent transistors are very closely matched

Session 7, Paper 3

Advances, Challenges and Opportunities in 3D CMOS Sequential Integration (Invited)

P. Batude, M. Vinet, B. Previtali, C. Tabone, C. Xu, B. Sklenard, P. Coudrain*, S. Bobba*, H. Ben Jamaa, P-E. Gaillardon, A. Pouydebasque, O. Thomas, C. Le Royer, J.-M. Hartmann, L. Sanchez, L. Baud, V. Carron, L. Clavelier, G. DeMicheli**, S. Deleonibus, O. Faynot, T. Poiroux (CEA-LETI, Minatec, *STMicroelectronics, **EPFL)

3D sequential integration enables the full use of the third dimension thanks to its high alignment performance. In this paper, the authors address the major challenges of 3D sequential: in particular, the control of molecular bonding allows them to obtain pristine quality top active layer. With the help of Solid Phase Epitaxy, they can match the performance of top FET, processed at low temperature (600°C), with the bottom FET devices. Finally, the development of a stable salicide enables bottom performance to be retained after top FET processing. They conclude that overcoming of these major technological issues offers a wide range of applications. Partitioning at the transistor scale 3D sequential integration enables both increasing density and performance without resorting to aggressive scaling. Its key technological enablers are molecular bonding and a low temperature top FET process which leads to the design of 3D transistors matching the targets of advanced nodes thanks to low access resistance, salicide, scaled EOT, optimized threshold voltage and mobility boosters.

Session 14, Paper 1

A Novel Silicon-On-Quartz (SOQ) Device for Optical Mobile Applications

T. Nagata, H. Kanemaru, M. Ikegami, Y. Nagatomo*, R. Nakamura**, M. Handa**, K. Uchibori** (OKI Semiconductor Miyazaki Co., Ltd, *OKI Semiconductor Co., Ltd, **Citizen Finetech Iyota)

The authors explain that silicon on quartz (SOQ) technology is a great and promising technique for next generation mobile displays, enabling smaller and lighter liquid crystal displays for cell phones, near-eye displays, pico-projectors and view finders. And the technique can lead to fabricate SOQ device with high mobility and high reliability. The authors have successfully realized excellent optical transparent LCOS panels by combining a novel SOQ device with excellent panel technology. Mass production has begun.

Session 15, Paper 2

Improving the Energy/Power Constraint for Technology Optimization

(D.J. Frank, L. Chang, W. Haensch (IBM T.J. Watson Research Center)

Consideration of energy and power constraints is critical in establishing roadmap projections for future generations of CMOS technology. The authors introduce a new optimization constraint, energy x power density, which better reflects actual design goals and compromises, and use it to evaluate technology scaling trends, highlighting differences from conventional expectations about scaling.

Session 15, Paper 5

Assessment of Fully-Depleted Planar CMOS for Low Power Complete Circuit Operation

Z. Ren, S. Mehta, J. Cai*, S. Wu, Y. Zhu*, T. Kanarsky, S. Kanakasabapathy, L.F. Edge, R. Zhang, P. Lindo, J. Koshy, K. Tabakman, P. Kulkarni, V. Sardesai, K. Cheng, A. Khakifirooz, B. Doris, H. Bu, D.-G. Park (IBM SRDC, *IBM T.J. Watson Research Center)

In this paper, the authors present results and discuss issues related to implementation of large scale circuits in extremely thin (ET) SOI CMOS for low power applications. They have demonstrated that they can fabricate low power (LP) CMOS with centered Vts and good Vt uniformity across wafer and wafer to wafer. Using this CMOS, they have fabricated low leakage and high performance ring oscillators (with delay ~20% faster than the standard 28 nm LP bulk). They have also obtained perfect 2.25M SRAM arrays, functioning down to Vdd of 0.5V, and have shown that a 10-level BEOL process has minimal impact on device stability.

Session 16, Paper 3

Complementary Thin-base Symmetric Lateral Bipolar Transistors on SOI

J. Cai, T.H. Ning, C. D’Emic, K.K. Chan, W.E. Haensch, D.-G. Park (IBM T.J. Watson Research Center)

The authors present NPN and PNP thin-base symmetric lateral bipolar transistors on SOI, a bipolar device architecture that will naturally integrate into an existing CMOS process flow without adding the complexity of vertical scaling present in the conventional high performance bipolar technologies. It overcomes the problems associated with conventional bipolar transistors including performance degradation at high current density and slow switching speed in saturation and fabricated samples show immunity to base-push-out effect. Primary applications for low voltage and memory applications are discussed. Modeling results show possibilities for high frequency analogy/mixed signal applications with fMAX >1THz as well as for digital applications at supply voltage of 0.5V with current lithography capability and SOI thickness of 20 nm.

Session 16, Paper 4

Experimental Evidence of Increased Deformation Potential at MOS Interface and its Impact on Characteristics of ETSOI FETs

T. Ohashi, T. Takahashi, N. Beppu, S. Oda, K. Uchida (Tokyo Institute of Technology)

The authors propose a new physical model of deformation potential (Dac, which determines the strength of electron-phonon scattering) in MOS structures. It is proposed and demonstrated that Dac increases sharply at Si/SiO2 interfaces within a range of a few nanometers. Since SOI has two Si/SiO2 interfaces, Dac effectively increases in ETSOI because of the contributions from both the interfaces. The increased Dac results in mobility degradation in ETSOI; whereas it contributes to an increase in stress-induced mobility enhancement in thinner SOI devices. They conclude that this finding is indispensable for designing nanoscale 3D FETs.

Session 16, Paper 5

First Demonstration of Ultrathin Body c-SiGe Channel FDSOI pMOSFETs Combined with SiGe(:B) RSD: Drastic Improvement of Electrostatics (Vth, p tuning, DIBL) and Transport (µ0, Isat) Properties Down to 23nm Gate Length

C. Le Royer, A. Villalon, M. Cassé, D. Cooper, J. Mazurier, B. Prévitali, C. Tabone, P. Perreau, J.-M. Hartmann, P. Scheiblin, F. Allain, F. Andrieu, O. Weber, P. Batude, O. Faynot, T. Poiroux (CEA-LETI, Minatec)

The authors present the first successful integration of ultrathin (3.2nm) c-SiGe20% layers in Fully Depleted (FD) SOI pMOSFETs combined with SiGe30%(:B) RSD. c-Si0.8Ge0.2/SOI channels shift the threshold voltage by +120mV (with excellent variability) without SCE or DIBL degradation. Moreover the fabricated devices exhibit excellent variability performance and significant gain in Access resistance (-60%), transconductance and Isat (+170% & +220% @ L=23nm).

Session 18, Paper 1

Impact of TDDB in MG/HK Devices on Circuit Functionality in Advanced CMOS Technologies

A. Kerber, D. Lipp, M. Trentzsch, B.P. Linder*, E. Cartier* (GLOBALFOUNDRIES, IBM Research Division*)

The impact of time-dependent dielectric breakdown (TDDB) in MG/HK devices on SOI CMOS circuit functionality is examined using a novel fast PCI card based characterization setup. Detailed information on the role of the driver resistance on circuit failure is provided. By comparing breakdown in circuits with TDDB characteristics in discrete devices, it is shown that soft breakdown in cross-coupled inverter circuits is well correlated with soft breakdown in discrete devices. However, in all cases studied, it is observed that immediate circuit failure during high voltage stress is prevented by the resistance of the driver element. Implications of these findings on circuit lifetime assessment are discussed.

Session 18, Paper 6

Low Frequency Noise Variability in High-k/metal Gate Stack 28nm bulk and FD-SOI CMOS Transistors

E.G. Ioannidis, S. Haendler, A. Bajolet, T. Pahron, N. Planes, F. Arnaud, R.A. Bianchi, M. Haond, D. Golanski, J. Rosa, C. Fenouillet-Beranger, P. Perreau**, C.A. Dimitriadis***, G. Ghibaudo* (STMicroelectronics,*IMEP LAHC, **CEA-LETI, Minatec, ***Aristotele University of Thessaloniki)

The authors present the first thorough investigation of low frequency noise (LFN) and statistical noise variability in high-k/metal gate stack 28nm bulk and FD-SOI CMOS transistors. The results clearly indicate that the LFN variability of 28nm FD-SOI CMOS technology is improved as compared to previous 45nm and 32nm bulk CMOS technologies. Moreover, 28nm FD-SOI technology provides even better LFN variability (factor 2). Finally, circuit simulations have shown that the LFN variability has a serious impact on the SRAM cell operation.

Session 25, Paper 3

Chip-level Power-Performance Optimization Through Thermally-Driven Across-Chip Variation (ACV) Reduction

X. Yu, O. Gluschenkov, N.D. Zamdmer, J. Deng, B.A. Goplen*, H.S. Landis*, R. Logan, J.A. Culp, Y. Liang, M. Cai, W.-h. Lee, N. Rovedo, F.D. Tamweber, D.M. Lea, B.J. Greene, D.K. Slisher, A.I. Chou, H. Trombley*, S.V. Deshpande, W.K. Henson, A.C. Mocuta, K. Rim (IBM SRDC, *IBM Systems and Technology Group)

The authors note that standby leakage power has become increasingly important in semiconductor chip product design. Precise prediction of total chip leakage is of critical importance, but is very challenging to achieve. In this paper, the authors explore the quantitative connection between leakage uplift and ACV in depth at the chip product level, and demonstrate a product power-performance optimization in 32nm SOI by reducing product ACV with a process improvement. They propose a metric to capture the impact of ACV on chip-level leakage to quantitatively predict product-level leakage power using basic FET parameters, together with random and systematic intra-die variation. They demonstrated in hardware the means of monitoring components of variation, and applied these measurements to dramatically reduce product-level leakage with an improved thermal annealing process.

Session 25, Paper 5

Drain Current Variability and MOSFET Parameters Correlations in Planar FDSOI Technology

J. Mazurier, O. Weber, F. Andrieu, O. Rozeau, M-A. Jaud, F. Allain, L. Tosti, L. Brévard, P. Perreau, C. Fenouillet-Beranger, F.A. Khaja*, B. Colombeau*, G. De Cock, G. Ghibaudo**, M. Belleville, O. Faynot, T. Poiroux (CEA-LETI, Minatec, *Varian Semiconductor Equipment Associates, **IMEP-LAHC, Minatec)

The authors present for the first time an extensive experimental study of the statistical variability of the drain current in 6nm thin undoped SOI MOSFETs. ID variations are found to be highly correlated with both threshold voltage and ON-state resistance fluctuations. Taking into account such correlations is of great interest for an accurate definition of spice model corners, and for optimizing FD-SOI technology. They also evidence the main technological sources of ID fluctuation.

Session 29, Paper 3

VLSI Silicon Multi-Gas Analyzer Coupling Gas Chromatography and NEMS Detectors

A. Niel, V. Gouttenoire, M. Petitjean, N. David, R. Barattin, M. Matheron, F. Ricoul, T. Bordy, H. Blanc, J. Ruellan, D. Mercier, N. Pereira-Rodrigues, G. Costa, V. Agache, S. Hentz, JC Gabriel, F. Baleras, C. Marcoux, T. Ernst, L. Duraffourg, E. Colinet, A. Andreucci, E. Ollier, P. Puget, J. Arcamone, E.B. Myers*, M.L. Roukes* (CEA-LETI, Minatec, *California Institute of Technology)

This work demonstrates for the first time VLSI-compatible nano/microfabricated, high-performance, portable multi-gas analyzers associating gas chromatography and Nano-Electro-Mechanical Systems (NEMS) detectors. The system presented in this paper features state-of-the-art experimental results in terms of limit of GC-mediated gas detection, and provides unique advantages in terms of compactness and portability. The fabrication process is straightforward and fully compatible with CMOS front-end processes: resonators are fabricated on the 160nm thick top silicon layer of 200mm SOI wafers (with a 400nm thick buried silicon oxide). NEMS are defined by two successive deep-UV (DUV) and e-beam lithography (eBL) steps with the same resist. The results of this work pave the way for the industrialization of ultra-miniaturized multi-gas analyzers.

Session 32, Paper 4

Comprehensive Analysis of UTB GeOI Logic Circuits and 6T SRAM Cells Considering Variability and Temperature Sensitivity

V.P.-H. Hu, M.-L. Fan, P. Su, C.-T.Chuang (National Chiao Tung University)

A comprehensive analysis of leakage-delay, stability and variability of GeOI logic circuits and SRAM cells with respect to the SOI counterparts is presented. The UTB GeOI circuits show better power-performance than the bulk Ge-channel circuits, and preserve the leakage reduction property of stacking devices. For equal Ion design, the GeOI SRAM cells exhibit better µRSNM/σRSNM and smaller cell leakage variation.

Session 34, Paper 6

Thermal-Aware Device Design of Nanoscale Bulk/SOI FinFETs: Suppression of Operation Temperature and Its Variability

T. Takahashi, N. Beppu, K. Chen, S. Oda, K. Uchida (Tokyo Institute of Technology)

The self-heating effects of Bulk/SOI FinFETs are systematically investigated in terms of thermal resistance, for the first time. For the Bulk FinFETs, it is clarified that a) Bulk FinFETs have significantly lower thermal resistance, b)doping density fluctuation causes fluctuation in operation temperature, and c) the thermal variability can be suppressed by the extension length scaling. For the SOI FinFETs, it is demonstrated that the influence of interface thermal resistance is larger due to the relatively larger heat flow to the gate electrode.

Session 34, Paper 7

Hardware-assisted 3D TCAD for Predictive Capacitance Extraction in 32nm SOI SRAMs

A. Bhoj, R. Joshi, S. Polonsky, R. Kanj, S. Saroop*, Y. Tan*, N.K. Jha** (IBM Research, *IBM, **Princeton University)

A comprehensive process/layout-independent TCAD flow is applied to FEOL/BEOL analysis/design of 32nm SOI SRAMs using, for the first time, iterative 3D TCAD capacitance extraction assisted by hardware data. Using the flow, FEOL junction capacitance is identified as the dominant factor affecting total bitline capacitance variation. Leveraging hardware data, the method is able to effectively predict other key capacitances (e.g., wordline) of generic layouts in the same process, thereby reducing the silicon footprint (cost) for test structures during early phases of technology development.

Session 34, Paper 8

Compact Capacitance and Capacitive Coupling-Noise Modeling of Through-Oxide Vias in FDSOI Based Ultra-High Density 3-D ICs

C. Xu, K. Banerjee (University of California)

The authors explain that Fully-Depleted SOI (FDSOI) technology boosts the opportunity to make 3-D ICs with ultra-high integration density, due to the short and tiny Through-Oxide Vias (TOVs), which are made after removing the entire silicon under the buried-oxide layer (using the BOX as an etch-stop). The work presentented in this paper develops for the first time compact physical models for the capacitance of the TOV and the coupling capacitance between TOV and active region in presence of periodical power lines. The models agree well with a 3D capacitance solver. The models are further used to analyze the threshold voltage variation in FDSOI MOSFETs. The results show that TOVs in FDSOI have larger Z11 (indicating higher performance), and that the impact of TOV in FDSOI on Vth variation is less (more) at high (low) frequencies, as compared to TSV in bulk-CMOS based 3-D ICs. These results provide important insights to TOV/TSV design and optimization in emerging 3-D ICs.

ByGianni PRATA

ISSCC 2011

Website: http://isscc.org
20-24 February 2011, San Francisco, CA

ISSCC – the International Solid-State Circuits Conference – is the flagship conference of the Solid-State Circuits Society. It is widely considered the premier forum for presenting advances in solid-state circuits and systems-on-a-chip.

Here is a round-up of this year’s major SOI-based papers.

Session 4: Enterprise Processors & Components

#4.1:  A 5.2Ghz Microprocessor Chip for the IBM zEnterpriseTM System

J. Warnock, Y. Chan, W. Huott, S. Carey, M. Fee, H. Wen, M. Saccamango, F. Malgioglio, P. Meaney, D. Plass, Y-H. Chan, M. Mayo, G. Mayer, L. Sigal, D. Rude, R. Averill, M. Wood, T. Strach, H. Smith, B. Curran, E. Schwarz, L. Eisen, D. Malone, S. Weitzel, P-K. Mak, T. McPherson, C. Webb (IBM)

With this paper, IBM demonstrated the first commercial processor breaking the 5GHz speed  barrier.  The microprocessor chip for the IBM zEnterprise 196 system, it is implemented in 45nm SOI. It contains 4 processor cores running at 5.2GHz, and includes an on-chip high-speed 24MB shared DRAM L3 cache. The IBM team used a comprehensive design approach combining detailed power modeling and reduction techniques, with programmable timing control and a number of high-performance process-technology features in order to achieve this speed breakthrough within the available power envelope.

#4.2: Dynamic Hit Logic With Embedded 8Kb SRAM in 45nm SOI for the zEnterpriseTM Processor

A. R. Pelella, Y. H. Chan, B. Balakrishnan, P. Patel, D. Rodko, R. E. Serton (IBM)

This paper describes dynamic hit logic with an embedded 8Kbit SRAM. The 14b hit logic uses a search-for-a-hit scheme with programmable launch and reset clocks. Array BIST provides both the hit logic and SRAM with full at-speed test coverage. The SRAM (1R/1W) uses 45nm SOI 6T cell with domino hierarchical dual-read bitlines.

#4.5:  Design Solutions for the Bulldozer 32nm SOI 2-core Processor Module in an 8-Core CPU

T. Fischer, S. Arekapudi, E. Busta, C. Dietz, M. Golden, S. Hilker, A. Horiuchi, K. A. Hurd, D. Johnson, H. McIntyre, S. Naffziger, J. Vinh, J. White, K. Wilcox (AMD)

This paper describes the new “Bulldozer” 2-core CPU module that contains 213M transistors in an11-metal layer 32nm high-k metal-gate SOI CMOS process. In addition to the micro-architecture improvements, the components, such as the L1 and L2 caches, the integer unit and the Floating Point unit, are designed to achieve higher frequency, lower power consumption, and lower gate counts per cycle than the 45nm AMD core while maintaining IPC (Instructions per Cycles). It achieves over 3.5GHz in an area (including 2MB L2 cache) of 30.9mm2.

#4.6:  40-Entry Unified Out-of-Order Scheduler and Integer Execution Unit for the AMD Bulldozer x86-64 Core

M. Golden, S. Arekapudi, J. Vinh (AMD)

This paper presents a 40-instruction out-of-order scheduler that issues four operations per cycle and supports single-cycle operation wakeup. The integer execution unit supports single-cycle bypass between four functional units. Critical paths are implemented without exotic circuit techniques or heavy reliance on full-custom design. Architectural choices minimize power consumption.


Session 8: Wireline Architectures and Circuits for Next Generation Wireline Transceivers

#8.8: A 14Gb/s High-Swing Thin-Oxide Device SST TX in 45nm CMOS SOI

C. Menolfi, T. Toifl, M. Rueegg, M. Braendli, P. Buchmann, M. Kossel, T. Morf (IBM, Miromico)

The IBM/Zurich R&D team presented a 14Gb/s high-swing source-series-terminated (SST) TX that features up to twice the signaling amplitude of a conventional SST design. The 4-tap FFE TX is based on a high-voltage, thin-oxide device SST output driver stage whose pull-up and pull-down switches are driven from separate, split supply pre-drivers. Implemented in 45nm CMOS SOI, the circuit consumes 85.5mW at 14Gb/s from a nominal supply of 1V and an output driver supply of 2V.


Session 12: Design In Emerging Technologies

#12.4:  A 3.9ns 8.9mW 4×4 Silicon Photonic Switch Hybrid Integrated with CMOS Driver

A. Rylyakov, C. Schow, B. Lee, W. Green, J. Van Campenhout, M. Yang, F. Doany, S. Assefa, C. Jahnes, J. Kash, Y. Vlasov (IBM)

A monolithic 4×4 silicon photonic router, composed of 6 2×2 2mW 3.9ns 300×50µm2 Mach-Zehnder interferometer switches, is flip-chip bonded with a custom 90nm bulk CMOS driver, routing 3×40Gb/s WDM data with BER <10-12, less than -10dB cross-talk and 7dB loss. The size of the micro-assembly is 1×2×2mm3.


Session 14:  High-Performance Embedded Memory

#14.1: A 64Mb SRAM in 32nm High-k Metal-Gate SOI Technology with 0.7v Operation Enabled by Stability, Write-Ability and Read-Ability Enhancements

H. Pilo, I. Arsovski1, K. Batson, G. Braceras, J. Gabric, R. Houle, S. Lamphier, F. Pavlik, A. Seferagic, L-Y. Chen, S-B. Ko, C. Radens (IBM)

This paper described the first 32nm embedded SRAM SOI implementation that enables low-power operation down to 0.7V.  The SRAM features a 0.154µm2 bitcell. A 0.7V VDDMIN operation is enabled by three assist features. Stability is improved by a bitline regulation scheme that reduces charge injection into the bitcell. Enhancements to the write path include an increase of 40% of bitline boost voltage. Finally, a bitcell-tracking delay circuit improves both performance and yield across the process space.

#14.2: A 4R2W Register File for a 2.3Ghz Wire-Speed PowerTM Processor With Double-Pumped Write Operation

G. S. Ditlow, R. K. Montoye, S. N. Storino, S. M. Dance, S. Ehrenreich, B. M. Fleischer, T. W. Fox, K. M. Holmes, J. Mihara, Y. Nakamura, S. Onishi, R. Shearer, D. Wendel, L. Chang (IBM)

IBM introduces architectural techniques to significantly improve the area, power, and performance of multi-ported register file arrays. A 144×78b macro for a 45nm SOI-CMOS 2.3GHz POWER™ processor is presented with double-pumped write ports that are operated twice in a single cycle and replicated read ports that are combined from duplicate data copies. A compact 2R1W memory cell is thus leveraged to perform a 4R2W function with near 2× area and read power reduction, low 190ps read latency, and fast error correction. The macro operates at up to 2.76GHz at a supply voltage of 0.9V.

#14.3: An 8MB Level-3 Cache in 32nm SOI With Column-Select Aliasing

D. Weiss, M. Dreesen, M. Ciraula, C. Henrion, C. Helt, R. Freese, T. Miles, A. Karegar, R. Schreiber, B. Schneller, J. Wuu (AMD)

This paper presents the design of the 8MB level-3 cache in 32nm SOI-CMOS for AMD’s next-generation Bulldozer architecture that operates above 2.4GHz at 1.1V. Area efficiency is improved by the use of a column-select aliasing technique, in which column select wires are shared between odd and even pairs for reads and writes, while leakage power is minimized by supply gating and floating bitlines. An efficient redundancy scheme is also implemented using centralized redundancy blocks instead of storing all redundant data in the data macro itself.


Session 19:  Energy-Efficient Digital Low-Power Digital Techniques

#19.3: Comparison of 65nm LP Bulk and LP PD-SOI With Adaptive Power Gate Body Bias for an LDPC Codec

J. Le Coz, P. Flatresse, S. Engels, A. Valentian, M. Belleville, C. Raynaud, D. Croain, P. Urard (STMicroelectronics, CEA-LETI-MINATEC)

This paper compares a 65nm LP PD-SOI technology combined with an enhanced power gate device utilizing automatic adaptive body bias, to a standard LP CMOS bulk implementation, demonstrating an 802.11n LDPC codec. The authors show how a low resistivity produced with forward body bias of the power switch, combined with PD-SOI can reduce leakage current by 52.4% vs. bulk and increase the frequency by 20% at 1.2V, while decreasing power by 30% at 360MHz.


Session 25:  Wireline CDRs and Equalization Techniques

#25.6: A 15Gb/s 0.5mw/Gb/s 2-Tap DFE Receiver With Far-End Crosstalk Cancellation

M. Honarvar Nazari, A. Emami-Neyestanak (CalTech)

In this paper, a 2-tap DFE receiver is implemented in a 45nm SOI technology. High data rate and low power dissipation is achieved using a switched-capacitor S/H/summer front-end, which enables FEXT cancellation with 33µW/Gb/s/lane power overhead. It equalizes 15Gb/s data over a link with >14dB loss and dissipates 7.5mW from a 1.2V supply.

20-24 February 2011, San Francisco, CA