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More Good FD-SOI News from DATE Conference – ST, Leti, Mentor, CMP

At the recent DATE Conference in Grenoble (DATE is like DAC, but in Europe, alternating yearly between Grenoble and Dresden), STMicroelectronics, CEA-Leti & Mentor Graphics joined forces for a FD-SOI presentation organized by CMP and sponsored by Mentor.

Here are some of the highlights (the complete presentations are all available from the CMP website).

FD-SOI: From Successful Collaborative R&D to Successful Silicon Results

Presented by Philippe Magarshack, Technology R&D Group Vice-President and Central CAD GM at STMicroelectronics – Download pdf

  • In this general overview of their ultra-thin body & BoX approach (UTBB), he said that the process technology is very simple, with 12-15% fewer steps
  • Starting at 28nm, they see at least 3 generations
  • They’ve finalized things with GlobalFoundries
  • It’s particularly good for low-power and analog designers
  • For analog, it’s a whole new playing field, with “wonderful properties” for circuit design techniques (6x better gain, no pocket implants…)


Design Infrastructure to Support Advanced FD-SOI Below 20nm

Presented by Jean-Marc Talbot, Senior Director of Engineering Analog & Mixed Signal at Mentor Graphics Grenoble R&D Center – Download pdf

  • Mentor did some awesome work on ST’s FD-SOI project.  The challenge was moving from the models (which were done by Leti) to robust circuit simulators in under two years – which they did.
  • ST had existing characterization tools that Mentor integrated tightly for FD-SOI and did specific tuning for the SPICE engine, resulting in a 5x speed-up in characterization!
  • “The design infrastructure to support FD-SOI technology is up and running,” he concluded.

Mentor FDSOI slide 19

Roadmap Towards 10nm FD-SOI Node

Presented by Laurent Malier, CEO of CEA-LetiDownload pdf

  • Leti has silicon layers down to 3.5nm
  • For boosting pFETs with SiGe, they’re seeing better results with FDSOI than bulk FinFETs.

The advantages of back-biasing increase as you shrink the SOI layers, so it will get even better with each node!

  • The path to 10nm FD-SOI is already defined. “We are really confident in the roadmap,” he said.
  • At 10nm all the benefits remain. Models for 10nm will be available Q1 ’14, and the design kits in Q3 ’14.
  • Leti is working with Mentor, with ST in Crolles (near Grenoble) and with IBM in NY on optimization.

LETI FDSOI slide 17

A few other notables from the DATE conference:

  • In a “Testimonial” session, ST Advanced I/O design engineer Hubert Degoirat talked about designing high-speed I/O Interfaces in 28nm FDSOI. They used MunEDA’s WiCkeD analysis and optimization tools (which he said were very user-friendly). This let them do things like reduce the propagation delay of a voltage comparator by about 35%.
  • At the CMP booth, Technical Director Kholdoun Torki said that requests for the 28nm FD-SOI PDK are coming in fast and furious. As you may recall reading in a previous blog, CMP is offering multi-project wafer runs of ST’s 28nm FD-SOI technology on Soitec wafers with Leti models. It’s the same ARM-core based technology that GF will be rolling out in high-volume. As of today, CMP’s gotten requests from over 50 institutions across the globe.

Go Ahead – Take 28nm FD-SOI Out for a Test Drive

CMP is offering multi-project wafer runs of ST’s 28nm FD-SOI technology on Soitec wafers with Leti models. It’s the same technology that GF will be rolling out in high-volume next year. This article details how it works, and what it includes.

What would a port to 28nm FD-SOI do for your design? A recent announcement by CMP, STMicroelectronics and Soitec invites you to find out. Specifically, ST’s CMOS 28nm Fully Depleted Silicon-On-Insulator (FD-SOI) process – which uses innovative silicon substrates from Soitec and incorporates robust, compact models from Leti – is now available for prototyping to universities, research labs and design companies through the silicon brokerage services provided by CMP (Circuits Multi Projets®). ST is releasing this process technology to third parties as it nears completion of its first commercial FD-SOI wafersWhat you can get from CMP is the same process technology that will be available to all at GlobalFoundries in high-volume next year.

The CMP multi-project wafer service allows organizations to obtain small quantities of advanced ICs – typically from a few dozen (for a prototype, say) to over a hundred thousand units (for low-volume production). CMP is a non-profit, non-sponsored organization created in 1981, with a long history of offering SOI and other advanced processes. It offers industrial quality process lines – with industrial-level, stable yields. Headquartered in Grenoble, France, CMP has over 1000 clients in 70 countries.

The cost of ST’s 28nm FD-SOI CMOS process at CMP has been fixed at 18,000 €/mm2, with a minimum of 1mm2.  At this point in scaling, that gets you about two million gates – about eight million transistors.  So the pricing is very aggressive for an advanced technology node – and it comes down if you get more than 3mm2, and even more if you get >15mm2, Kholdoun Torki, CMP Technical Director explained to ASN.

Dr. Torki was kind enough to elaborate a bit on the particulars for us. Here’s what he says. The ST design kit contains a full-custom part, and standard-cells and I/O libraries with digital design-flows supported under Cadence Encounter and Synopsys Physical Compiler. The design-kit is from ST Front-End Manufacturing and Technology, Crolles. CMP delivers this design-kit under NDA.

Devices are supported for UTSOI (ultra-thin SOI) models, which were developed by and are the property of Leti.

The UTSOI model is available under Eldo from Mentor and Hspice from Synopsys. It is also expected to be available for Spectre (Cadence) and for Golden Gate and ADS (Agilent) within the next few months.

CMP provides the first level support (installation, and general questions on the use of the kit). Multi-Projects Wafer runs are organized at ST Crolles. For low volume production, a quote is issued on a case-by-case basis, on request.

The ST 28nm FD-SOI offering has a true 28nm BEOL metallization with .1µ metal pitch, says Dr. Torki.

CMP also has offered the Leti 20nm FD-SOI R&D process since 2010. (In fact for those looking even further ahead, Leti has predictive model cards down to 11nm.) It is expected the 20nm FD-SOI process from ST, incorporating strategic technology from Leti, will be available from CMP towards the end of next year, although the exact date has not yet been fixed.

How it works

In Multi-Project Wafer runs, costs are shared (and reduced) because the reticle area is shared across customers. CMP offers one-stop shopping, including:

  • NDA processing
  • the design-kits linking CAD and processes, and related support
  • Design submission, checking, and final database to the Fab
  • Wafer sawing and Packaging
  • Export license processing
  • Chip delivery

Because reticles are shared across multiple designs, CMP customers benefit from very attractive pricing. (Courtesy: CMP)

Last year (2011), CMP handled 273 circuits, including prototypes, low-volume production runs and industrial applications.

For organizations like the 77 customers in 23 countries using 28nm bulk CMOS through CMP’s program, migrating from 28nm CMOS bulk to 28nm FD-SOI will be seamless, says Dr. Torki. There are no disruptions in process or design. There are the same layer numbers and names, so they can load a bulk design directly into an FD-SOI design environment. They use the common design-rules platform (ISDA alliance design-rules), and bulk devices can be co-integrated with FD-SOI devices as needed.

These are real, leading edge chips and circuits we’re talking about. Here’s what you get:

  • 28nm HK/MG FD-SOI with ultra-thin BOX and ground plane
  • 10 Cu metal layers: (6 thin + 2 medium + 2 thick)
  • Triple Well (Deep N-Well allows the P-Well to be isolated from the substrate)
  • Single IO oxide + Single core oxide.
  • Double VT: 1.0V Low Vt transistors (LVT) + 1.0V super Regular Vt transistors (RVT)
  • Low Leakage (high density) SRAM using LP core oxide
  • IO supply voltage: 1.8 V using the IO oxide.
  • Ultra Low k inter-level dielectric
  • 0.10µ metal pitch
  • Self-aligned silicided drain, source and gate
  • Poly and active resistors: Silicide protection over active areas for ESD protection
  • CMP for enhanced planarization (on STI, Contacts, Metals and vias).

FD-SOI Transistor (Courtesy: ST)

The 28nm FD-SOI standard-cells, IO cells and related IP are all from ST. The CORE cells Libraries include:

  • CORE_LL: Low Power LVT
  • CORE_LR: Low Power RVT
  • CLOCK (LL and LR): Buffer cells and the same for clock tree synthesis
  • PR: Place and route filler cells.

The IO cells Libraries include:

  • Digital
  • Analog
  • Flip-Chip bumps
  • ESD

You can find more details at the CMP website, or from the paper Dr. Torki presented at the 2012 SOI Conference.

So this represents a real opportunity.  Universities, often doing important research for industrial partners, have long known the value of using services like CMP’s. But with this latest ST-CMP-Soitec announcement, the fabless world can do more than kick the tires – they can take 28nm FD-SOI for a real test drive.

FD-SOI promises an extremely cost-effective, performance-enhanced, power-miser of a chip.  Wouldn’t you like to give it a try?

ST White Paper Excerpts: Planar Fully-Depleted Silicon Technology to Design Competitive SOCs at 28nm and Beyond

STMicroelectronics recently issued a major white paper detailing the choice of FD-SOI for consumer SOCs at 28nm and beyond. This article excerpts some of the highlights.

From “Planar Fully-Depleted Silicon Technology to Design Competitive SOC at 28nm and Beyond” (White paper by STMicroelectronics and Soitec):

“ FD-SOI Executive Summary

Planar FD is a promising technology for modern mobile and consumer multimedia chips. It combines high performance and low power consumption, complemented by an excellent responsiveness to power management design techniques. The fabrication process is comparatively simple and is a low-risk evolution from conventional planar bulk CMOS – and there is little disruption at the design level, too.

At 28nm, we find that planar FD more than matches the peak performance of “G”-type technology, at the cost and complexity of a low-power type technology, with better power efficiency across use cases than any of the conventional bulk CMOS flavors.

Looking further, for 20nm and 14nm, we believe planar FD will be extremely competitive with respect to alternative approaches in terms of performance and power, while being both simpler and more suited to low-power design techniques. In short, a better choice for the type of SOC we offer.

Planar fully depleted silicon technology will be ready as early as 2012 to compete in the forthcoming superphones era and in many other consumer segments. ”

Having identified that conventional planar bulk CMOS would not meet all the requirements of mobile and consumer multimedia System-on-Chip (SOC) ICs in the coming years, STMicroelectronics assessed alternative options. It is possible to propose a 28nm planar FD solution available as a second generation shortly after readiness of traditional 28nm on bulk silicon, with better time-to-market than waiting for availability of the 20nm node. It is also an excellent learning step to prepare a 20nm planar FD process. Our evaluations show that 20nm planar FD has also a very competitive potential performance-wise vs. FinFET for System-on-Chip applications.

ST Technology Overview

Figure 1: ST’s planar FD device structure features (notional perspective, notional cross-section, TEM cross-section):

  • Immunity to Short Channel Effects and variability (no channel doping, so no Random Doping Fluctuations / RDF)

  • For the 28nm node, the selected BOX thickness is 25nm.

  • Ultra-thin BOX advantages include:

    – further improved electrostatic control and relaxed thinness requirement of the top silicon,

    – enables back-biasing through the BOX,

    – enables the implantation, during the fabrication process, of heavily doped “ground planes” or “back-planes” under the BOX, for improved electrostatics and/or VT adjustment and/or best-efficiency of back-bias,

    – brings the ability, during the fabrication process, to locally remove the top silicon and BOX to reach the base bulk silicon and co-integrate a few (non geometry-critical) devices on Bulk with devices on SOI – with a small step height between an SOI zone and a Bulk zone, compatible with lithography tools.

  • BOX offers total dielectric isolation of the very thin active layer and naturally ultra-shallow junctions, leading to lower source/drain capacitance, lower leakage and latch-up immunity.

Planar FD technology allows several methods for setting the threshold voltage VT, including engineering the gate stack work function, trimming the gate length and other process engineering techniques. Thanks to this, STMicroelectronics’ 28FDSOI technology is capable of offering 3 VTs (HVT, RVT, LVT), as in traditional bulk CMOS technologies.

Circuit-Level Benchmarking

To assess how the improved planar FD-SOI transistor characteristics translate at the circuit level, STMicroelectronics has benchmarked a number of representative IP blocks, including an ARM Cortex-A9 CPU core. To that aim, we have extracted logic critical paths with associated RC parasitics from placed-and-routed designs and have re-characterized them by swapping 28nm traditional bulk CMOS transistor SPICE models with 28nm planar FD SPICE models.

With test chips in our 28nm planar FD technology becoming available, we are demonstrating that

the models predict well the silicon behavior. We are therefore confident that the benchmarks presented below are reliable and will be matched by SOC implementations.

The benchmarks compare the merits at the 28nm node of ST’s planar FD technology (“28FD”) with a state-of-the-art Low-Power technology (“28LP”) and a more performance-oriented, state-of-art General Purpose technology (“28G”). They are all based on evaluation of an ARM Cortex-A9 core. The analysis focuses on the higher end of the range of operating frequencies found in a SOC, since modern mobile and consumer multimedia demand high performance from their master CPU (for example, a Cortex-A9 or the forthcoming A15).

Performance at nominal Vdd : best speed/leakage trade-off: 28FD consistently outperforms both 28LP and 28G (Figure 2).

Figure 2: Best operating frequency for any class of leakage (TT process, 85C)

speed/leakage ratio maintained at reduced Vdd : reducing Vdd is a very good way to save dynamic power. It is therefore realistic to envisage building 28FD chips that match 28G or 28LP performance at a fraction of the power consumption.

Leading-edge performance across the full Vdd range: 28FD exhibits outstanding performance at all practical Vdd values. In particular, when maximum circuit speed is sought, only the low- and ultra-low-VT flavors of 28G compare with 28FD LVT; however they are much leakier and more limited in terms of, e.g., Vdd overdrive they can withstand without reliability concerns.

Best Power Efficiency Across Use Cases: the 28FD technology is power-efficient across the full Vdd and target frequency range (Figure 3). Contrary to G-type technology, with 28FD a given logic circuit that is power-efficient with Vdd set to reach a certain operating frequency (say, 2GHz range) remains efficient with Vdd set for a different target frequency range (e.g., sub-1.5GHz).

Figure 3: Power efficiency across all use cases (TT process, WC temp)

Focus on SRAM: 
The bitcells proposed in 28FD technology have very competitive cell current (Icell) vs. standby current ratio, which is representative of the performance/leakage power trade-off for SRAM arrays (Figure 4). This is true for all bit cells flavors: high-density and low-leakage oriented, or high-speed oriented. The footprint of the 4 bitcells proposed in 28FD is the same as that of the 4 bitcells proposed in 28LP.

Figure 4: SRAM memory bit cells performance/leakage. The power supply of 28FD SRAM arrays can be lowered by 100mV from nominal and still match the performance of 28LP SRAM arrays operated at nominal Vdd, while offering a 2x to 5x reduction in leakage power.

Commonalities with 28nm LP Bulk

STMicroelectronics’ strategy when developing the 28nm planar FD technology has been to reuse as much as possible the 28nm low-power bulk CMOS process.

Overall, the Back-End is 100% identical to the traditional 28nm bulk low-power CMOS process, and the Front-End of Line (FEOL) is 80% common with that same process.

The planar FD process saves about 10% of the steps required to fabricate the chips on the wafers. This approximately offsets the cost overhead of the starting wafers. As a result, the 28nm planar FD technology matches the cost of a conventional low-power technology while delivering extremely competitive performance.

Design Considerations

Designing on planar FD requires specific extraction deck and SPICE models. Apart from that, the design flows, methodologies and tools do not need any adaptation that would be specific to planar FD (Figure 5).

Figure 5: ST’s SOC implementation flow outline

Models: SPICE compact models have been developed for accurately representing planar FD transistors. The model we use is now integrated in all major commercially available simulators, such as Mentor’s ELDO, Synopsys’ HSPICE and XA or Cadence’ SPECTRE. A model card has been extracted for all transistors and other devices available in our 28nm planar FD technology.

Flow and Design Platform: With adequate SPICE models integrated in the PDK, the design flow is identical to that used with conventional 28nm Bulk CMOS technology. We have developed a full design platform for SOC, re-using work done for 28nm Bulk. It consists of standard cell libraries (multi-channel and multi-VT) with power management elements (power switches, level shifters etc.), embedded memories, analog foundation IP (such as PLLs and the likes) and specialty IP (Antifuse etc.).

A design platform developed for bulk CMOS technology can be ported to planar FD by re-characterization using planar FD SPICE models, which we have done for a variety of back-biasing conditions. Only a limited number of critical IPs need to be tuned or redesigned: Analog IP, IOs, Fuse.

At the SOC level, migrating an existing design from bulk to planar FD represents an effort comparable to half-node migration. It brings very worthwhile benefits at reasonable efforts.

All techniques used in low-power designs are applicable to planar FD. Those that can be enhanced with planar FD include: multi-VT, power switches, reverse and forward body bias, and voltage scaling.

Back-biasing consists of applying a voltage just under the BOX of target transistors. Doing so changes the electrostatic control of the transistors and shifts their threshold voltage VT, to either get more drive current (hence higher performance) at the expense of increased leakage current (forward back-bias, FBB) or cut leakage current at the expense of reduced performance. While back-bias in planar FD is somewhat similar to body-bias that can be implemented in bulk CMOS technology, it offers a number of key advantages in terms of level and efficiency of the bias that can be applied.  Back-biasing can be utilized in a dynamic way, on a block-by-block basis. It can be used to boost performance during the limited periods of time when maximum peak performance is required from that block. It can also be used to cut leakage during the periods of time when limited performance is not an issue. In other words, back-bias offers a new and efficient knob on the speed/power trade-off.


28nm: We expect to sign-off designs breaking the 2GHz barrier under worst-case conditions, in a power-efficient and cost-efficient way. For lower performance targets, there is also the opportunity to design ultra-low-power chips that can fulfill their functional specifications using a very low Vdd, for example in the 0.6-0.8V range. The Process Design Kit (PDK) is available, targeting the technology to be open for risk production by mid-2012.

20nm: We intend to scale our planar FD technology to 20nm, introducing a number of improvements to continue pushing the performance and retain a low power consumption. The objective is to bring up a solution that will improve on what mobile-optimized planar bulk CMOS will achieve, and will be extremely competitive vs. potential FinFET-based approaches for SOC – while keeping a simple and cost-efficient approach. The design rules will be compatible with 20nm bulk CMOS. This technology will bridge the gap to 14nm and provide an interesting alternative to the cost and complexity of introducing Extreme-UV and FinFET structures. Evaluation SPICE models are available, and full PDK is scheduled by end of 2012, with risk production for 13Q3.

14nm: Based on the assessments we have performed, we are confident that the planar FD technology is shrinkable to 14nm. Silicon and buried oxide thickness will need to be reduced to within limits that wafer manufacturers and CMOS process technology can handle.

Bulk logic designs for mobile apps port directly to FD-SOI

Bulk logic designs can be ported directly to FD-SOI for high-performing, low-power mobile apps.

Fully-depleted (FD)-SOI is a potential alternative to BULK 20nm. But what sort of the impact will that have on the design flow? The short answer is: very little.

Designs for low-power mobile applications in 28nm bulk benefit significantly in terms of increased performance and decreased power when ported to 20/22nm fully-depleted (FD)-SOI. From the designer’s perspective, the port is essentially direct – really no different from any standard port to a smaller geometry.

Interconnects, routing and RC parasitics are identical. Logic, memories, low- and high-voltage I/O and analog parts are handle in the same way as on bulk. Where there are differences, they are more at the device/process level, and do not pose any particular challenges to the designer at this point. This includes SPICE models, antenna effect, ESD protection, I/O and analog, and back-gate bias.

Synopsys Cadence Magma
Synthesis Design Compiler RTL Compiler Talus Design
Place & route IC Compiler SoCE Nanoroute Talus
Timing analysis PrimeTime (NLDM, CCS) ETS (NLDM, ECSM) Talus (NLDM, CCS)
Power analysis PTPX, PrimeRail (NLDM, CCS) EPS, VoltageStorm Talus
Signal integrity PTSI CeltIC Talus
DFT Tetramax
Verification Formality Conformal

ARM uses standard packages from the leading EDA vendors in SOI ASIC design

20nm FD-SOI v. 28nm Bulk

To get some clear figures on power and performance, ARM recently ported a Cortex-M0 from 28nm bulk to 20nm FD-SOI.  We used the Cortex M0 implementation flow that was proven in 22nm SOI. This included:

  • synthesis, place and route, and the same reduced set of standard cells for 20nm FDSOI and 28nm bulk
  • parasitics extraction for interconnects from the routed 22nm SOI M0 core (22nm SOI Back-End Of Line (BEOL) is considered to be the most representative of current bulk/FD-SOI 20nm BEOL)
  • characterization of 20nm FDSOI and 28nm bulk standard cells (typical process corner and room temperature)
  • different voltages to create the corresponding .lib files that would be used for timing and power analysis of the M0 core: 0.7, 0.8, 0.9 and 1V
  • timings and power were compared for the routed M0 core based on 20nm FD-SOI and 28nm bulk characterizations (.lib).
ARM, 2011 IEEE SOI Conference

Source: ARM, 2011 IEEE SOI Conference

In any next-node port, you typically expect to get a 25% improvement in performance, but in porting from 28nm bulk to 20nm FD-SOI, FD-SOI boosted the improvement far beyond the expected 25%. At a Vdd (supply voltage) of 1.0V, we saw a 40% improvement in performance. At 0.9V, we saw 66%. For Vdd of 0.8, we saw an 80% improvement. And for Vdd of 0.7, we saw an improvement of 125%.

Power is consistently reduced by 30%, and leakage holds steady.

Remember, this is a straight port, which gives us a baseline figure. There are several powerful process and design optimization techniques that can boost those numbers even higher without significantly increasing the complication factor.

Existing design, tremendous results

The conclusions we have drawn are that:

  • a standard bulk ASIC design flow can be used for FDSOI – don’t expect any change
  • an existing bulk logic design can be directly ported to FDSOI
  • you just need to check the timing closure – there is no timing variability (this is not PD-SOI)

FD-SOI should give tremendous advantages in terms of both power and performance. These low-voltage, high-performance chips are perfect for low-power applications, with the undoped channel in the low voltage SRAM resulting in higher margins. For some applications, RF features will also be improved if designers choose high-resistivity substrates.

FD-SOI is all a designer needs for high-performing, low-power mobile applications. And happily from the designer’s point of view, FD-SOI is as simple as designing in bulk.


This article was adapted from “FDSOI Design Portability from BULK at 20nm Node”, which was presented at the 2011 IEEE SOI Conference.

Calibre Adapts Easily to SOI

How tools from Mentor keep SOI transparent for design; flexible and robust for tapeout.

The Mentor Graphics Calibre® nm Platform is built to provide maximum flexibility for designers and tapeout managers employing multiple technologies in their overall IC portfolio.

Although SOI requires substantially different and somewhat more complex design rules compared to bulk CMOS, they can be coded in a straightforward manner using the Calibre user-friendly rule definition language and rule writer interface. Customers can simply augment their bulk CMOS rule decks by adding specific rules for SOI. Read More

Partners In Design: Standard Tools Simplify Rad-Hard SOI Design

Honeywell has worked with the top EDA tool vendors to develop the SOI process design kits (PDKs) needed by both in-house designers and foundry customers. Rick Veres, Honeywell EDA Manager, explains.

ASIC Design With Pilot Flow

For digital rad-hard ASIC design, we worked with Synopsys to adapt the Pilot Design Environment to our process. The environment supports their entire RTL to GDSII flow, including all their synthesis tools, place and route, insertion and so forth—the standard industry flow. Our SOI cell libraries are all radhard optimized for commercial, military or satellite applications.

Analog, Mixed Signal, RF and High Temp

Honeywell provides mixed signal/analog SOI devices and cells to support a broad range of customer’s mixed mode ASICs. The design environment maintains all the digital capabilities while supplying analog cells and SRAM for true mixed signal ASICs. The design flow and associated Design Kits are supported for Cadence mixed signal tools.

For RFIC design and simulation, Honeywell’s SOI fab processes are supported by Cadence (Tality) PDKs, including RF Spectre.

For high temperature SOI CMOS, the Cadence PDK full-custom development library supports Cadence schematic capture, simulation, layout and verification tools.

Calibre for Physical Verification

Mentor Graphics has been very instrumental in helping us develop our SOI capability in their Calibre tool. We use Calibre to verify designs before we run them in the fab. There are some nuances that a user doesn’t see, that as a developer we do. For example, we have twice as many rules we have to implement and check in SOI versus standard bulk. But the complexity is all on the developer side. The user just runs it—it’s transparent to them. Mentor Graphics has done some significant and impressive work for us.