Tag Archive U.Tokyo

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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.

 

~ ~ ~

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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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.

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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.)

ByGianni PRATA

Breakthroughs at the IEDM

The IEEE’s International Electron Devices Meeting (IEDM) is the world’s showcase for the most important applied research breakthroughs in transistors and electronics technology.

Here are a few highlights from some of the papers that presented advances in SOI-based devices and architectures at the most recent meeting (December 2008, San Francisco). Read More