Author Archives: sdavis

IEDM 2014 Preview

By Dick James, Chipworks

Later this month, the good and the great of the electron device world will make their usual pilgrimage to San Francisco for the 2014 IEEE International Electron Devices Meeting.  To quote the conference web front page, IEDM is “the world’s pre-eminent forum for reporting technological breakthroughs in the areas of semiconductor and electronic device technology, design, manufacturing, physics, and modeling. IEDM is the flagship conference for nanometer-scale CMOS transistor technology, advanced memory, displays, sensors, MEMS devices, novel quantum and nano-scale devices and phenomenology, optoelectronics, devices for power and energy harvesting, high-speed devices, as well as process technology and device modeling and simulation. The conference scope not only encompasses devices in silicon, compound and organic semiconductors, but also in emerging material systems. IEDM is truly an international conference, with strong representation from speakers from around the globe.”

That’s a pretty broad range of topics, but from my perspective at Chipworks, focused on the analysis of chips that have made it to production, it’s the conference where companies strut their technology, and post some of the research that may make it into real product in the next few years.

In the last few days I’ve gone through the advance program, and here’s my look at what’s coming up, in more or less chronological order.  As usual there are overlapping sessions with interesting papers in parallel slots, but we’ll take the decision as to which to attend on the conference floor.

Saturday/Sunday

Again this year the conference starts on the Saturday afternoon, with a set of six 90-minute tutorials on a range of leading-edge topics:

The first three are from 2.45 – 4.15, and the remainder from 4.30 – 6.00.  This year I hope to make it to my old friend Wilfried Vandervorst’s session on characterisation, and possibly the other imec tutorial on memories at 4.30.

Wilfried gave an impressive talk at the imec symposium at Semicon West, and this time he has an hour and a half instead of 45 minutes, so hopefully a good bit more detail on what we can see, now that we are counting atoms in transistor analysis.

On Sunday December 14th, we start with the short courses, Challenges of 7nm CMOS Technologies” and “3D System Integration Technology. Last year the short course was “Challenges of 10nm and 7nm CMOS Technologies”, so I guess we’ve moved on a bit; though I still need convincing that the 10-nm process architectures are locked down as yet.

Hidenobu Fukutome of Samsung has organised the former, and we have some impressive speakers – Greg Yeric, Senior Principal Design Engineer of ARM, (Circuit application requirements), Peide Ye, Purdue University (Device challenges), Guido Groeseneken, KU Leuven & imec, (Reliability challenges), Eric Karl, Intel, (On-die memory challenges), and Tsutomu Tezuka, Advanced LSI Technology Laboratory, Toshiba (Process and integration challenges). With 14-nm product on the market now, we need to look ahead, so this is appropriate – on the Intel clock, 7-nm is only four – five years away!

It now seems that 10-nm will be silicon-based, so we’ll see what the guys predict for 7-nm; new channel materials, nanowire transistors, and how will they integrate into a manufacturable process? What will be the effects on the performance of the basic logic blocks? What will device reliability be like with the potential new materials/structures? Hopefully we’ll find out here!

Eric Beyne of imec has set up the other short course; 3D is a very hot topic these days, both finFET and die stacking – here we are talking about die stacking.

Denis Dutoit of Cea-Leti looks at 3D System Design – Challenges for 3D Integration; I have the distinct impression that the manufacturing technology is in place, but design and test still have a way to go.

Next up is Kangwook Lee, Tohoku U, on Enabling Technologies: TSV Technology; again TSV technology is being promoted as here by both foundries and OSATs, and some products such as the Xilinx 2.5D FPGAs are out there, and stacked memories such as the Hybrid Memory Cube are sampling.

After lunch we have 3D evangelist extraordinaire Subu Iyer from IBM, talking about Enabling technologies: 3D integration for the Memory subsystem. IBM has been embedding DRAM into their products for several generations now, and as noted above, we are starting to see 3D-packaged memory come on to the market.

Wafer-to-wafer bonding is an essential part of 3D stacking, and that’s the topic of James Lu from Rensselaer Polytechnic. The last session is on 3D Reliability and Impact of 3D Integration on Devices, with Kristof Croes of imec discussing the device effects of the additional processing needed to make a 3D stack.

So some good solid stuff – although the courses make a long Sunday, from 9 a.m. to 5.30 p.m., but it’s worth sticking around to the end.

Sunday evening has some extra sessions; Sematech is holding a session on “Materials & Technologies for Beyond CMOS” at an as-yet unnamed location; and Leti will host a workshop on their “vision for silicon nano-technologies in the next 10 years” from 5.30 – 8.30 pm at the Nikko Hotel, across the street from the Hilton.

Monday

Monday morning we have the plenary session, with three pertinent talks on the challenges of contemporary electronics:

  • SiC MOSFET Development for Industrial Markets, John Palmour, Cree Inc. – broadening the range of uses for silicon carbide?
  • Are 3D atomic printers around the corner? Enrico Prati, CNR IMM (Italy’s Institute for Microelectronics and Microsystems) – now that 3D printers are becoming consumer goods, can we push the idea into the atomic scale? That sounds like the potential for everything from drugs design to the ultimate version of Moore’s law..
  • Research into ADAS with Driving Intelligence for Future Innovation, Hideo Inoue, Toyota – Automated Driver Assistance Systems; moving towards the self-driving car?

After lunch we have seven parallel sessions coming up!

Session 2 is a focus session on power devices, with a kick-off paper by John Baliga of NCSU, on the Social Impact of Power Semiconductor Devices (2.1). John invented the IGBT in his time at GE back in the 80’s, and claims that the technology has reduced global carbon dioxide emissions by 75 trillion pounds over the last 30 years. He speculates that this can only increase with the introduction of new power devices. Papers 2.32.5 and 2.7 look like reviews of high-power switch technologies, and Si-, SiC and GaN-based power devices, respectively, while 2.2 and 2.6 look at specific SiC JFET and GaN HEMT devices.

Session 3 is the hot Advanced CMOS Technology group of papers with late news additions by Intel (3.7) and IBM (3.8), both on 14-nm finFET technologies, which even triggered their own press release.

The Intel finFET (note – not trigate!) device features “a novel subfin doping technique” to minimise fin doping and leakage under the fins, and air-gaps in two metallisation levels. This is the first use of air-gaps in a production logic part that I know of; we’ve seen them in memory chips for a while. Intel had a persuasive paper on this at the 2010 IITC conference [1], and I was wondering if we would see implementation at this node.

If you hunt hard in Intel’s August 14-nm announcement, you can find the air-gaps in the M5 level:

Intel airgaps1

 

And we did find them in the M5 and M7 levels, but I will leave any detailed comment until a later blog. The IITC paper [1] speaks of using a mask step to define specific air-gap locations, and we can confirm that masking has indeed been used to define specific locations.

Now that we are analysing the Intel part, it would be remiss of me not to show an early shot of the fins, and they are clearly different from the 22-nm variety. There has been an obvious reduction in the width of the fin from its initial etched dimension, and it is tempting from this image to say that the NMOS fin is wider than the PMOS, but again more thorough discussion will have to wait.

Intel fins

IBM’s finFET is on SOI (of course, this is IBM!) and has a “unique dual workfunction process” which allows multi-Vt versions of both NMOS and PMOS, and claims sub-20 nm gate lengths. The process also includes fifteen metal layers and the latest version of their e-DRAM technology.

With all the Intel/IBM hype, I have become out of order here, because paper 3.1 from TSMC discloses what looks like their 16FF+ 16-nm finFET technology, advanced from the 16FF reported last year. A 15% speed boost and 30% power reduction is claimed, or 40% speed gain and 60% power saving compared to the 20-nm process.

Gossip in the industry has it that 16FF was not advanced enough for TSMC’s customers, so they did some transistor engineering and cranked up the performance; 16FF is not even mentioned on the website these days, and 16FF+ is now in risk production, with endorsements by Avago, Freescale, LG Electronics, MediaTek, Nvidia, Renesas and Xilinx, .

It will be interesting to see if any of the dimensions have changed from the 48 nm fin pitch and 90 nm contacted gate pitch announced last year. The metal stack is stated to be the same as the 20-nm planar process with a 1x pitch of 64 nm.

Paper 3.2 is from Avago, discussing Analog Circuit and Device Interaction in High-Speed SerDes Design in 16nm FinFet Process, and Renesas presents 3.3, on 16-nm 6T SRAM macros, both presumably TSMC’s process. 3.4 again looks at SRAM, but this time on STMicroelectronics’ 28-nm UTBB FDSOI process.

Next up is a couple of academic papers (3.5 & 3.6), discussing a 28-nm integrated RF power amplifier, and a 3D-stacked light harvester on a “epi-like Ge/Si monolithic 3D-IC with low-power logic/NVM circuits”.

3.7 and 3.8 are the Intel and IBM papers, and 3.9 is another late-news paper, from STMicroelectronics, but a change of pace from the finFETs – a 55-nm SiGe BiCMOS technology this time.

And by now it’s 5pm, the end of an intense afternoon!

In session 4, we take a look at Display and Imaging Systems. STMicroelectronics starts us off discussing MOS Capacitor Deep Trench Isolation for CMOS Image Sensors (4.1) in a joint talk with CNRS and CEA-LETI.

Goto 4.2

 

One of the goals in image sensors has to be integrating the A/D converters on each pixel, instead of at the edge of the pixel array, and 3D stacking comes to images sensors in paper 4.2 from NHK and U Tokyo; in which SOI wafers are direct bonded so as to provide each pixel with A/D conversion.

However, we won’t be seeing this in a phone anytime soon, as it is a proof-of-concept with 60-µm square pixels, as opposed to the 1-2 µm pixel pitch in most phone cameras.

NHK (jointly with Panasonic and U Hyogo) has another stacked sensor in 4.3, this time a selenium photodiode stacked on CMOS circuitry.

The remaining four papers are academic, covering far-infrared (4.4), a stacked SOI multi-band CCD (4.5), an embedded CCD in CMOS (4.6), and the display paper is 4.7, a solid-state incandescent device.

Session 5 covers Nano Device Technology – 2D Devices, a research session; 5.5 is a review of Nanophotonics with two-dimensional atomic crystals; the other papers all cover graphene devices (5.3, 5.4 and 5.6), black phosphorus (5.2), and molybdenum disulphide and tungsten diselenide (5.1, 5.7).

Resistive RAM is discussed in session 6. CEA-Leti has three papers in the afternoon,  (6.1, 6.3, 6.5) The first (joint with Altis Semi) looks at oxygen vacancies in doped oxide/Cu-based conductive bridge RAM (CBRAM), improving the Cu filament formation in the resistive layer; 6.3 is an invited paper that takes a higher level view of CBRAM and OxRAM devices in two different applications; and 6.5 is a detailed examination of CBRAM operation.

Micron and Sony get together to build a 27-nm 16Gb Cu-ReRAM part in 6.2, with a 1T 6F2 cell – definitely some DRAM technology showing up here, in the buried wordlines:

6.2 Zhurak

 

TSMC and National Tsing Hua U have a 28-nm BEOL RRAM in 6.4; Stanford U looks at thickness limits in HfO-based RRAM in 6.6; Crossbar (6.7) discusses crossbar RRAM arrays; and imec/KU Leuven finishes the session with a paper on a TiN/Si/TiN selection device for RRAM switching elements (6.8).

Modeling Simulation of Extremely Scaled Group IV and III-V FETs is the topic in session 7, looking way ahead.

In paper 7.1, imec and Synopsys look at the stress effects of 3D stacking on 7-nm devices(!); 7.2 examines mobility enhancement in sub-14nm FDSOI, by the CEA-Leti/STMicroelectronics/IMEP/IBM/SOITEC FDSOI crew; and transient electrothermal effects in nanoscale FETS are considered in 7.3., from Osaka U and Kobe U, and JST-CREST.

Victor Moroz (Synopsys) does a comparative analysis of 7-nm finFETs in different materials in 7.4 – this might be a follow-up of his talk at Semicon West back in July, in which he concluded that silicon is still the best channel material, at least for low-power mobile devices.

Samsung and Udine U also look at different material nFinFETs (7.5, 7.6), and Peking U discusses III-V ultra-thin body pMOSFETs in the last paper of the session (7.7).

NEMS (Nanoelectromechanical Systems) and Energy Harvesters are dealt with in Session 8 – six academic papers, ranging from graphene and Mo disulphide atomic-scale layers that vibrate at RF frequencies (8.1), to photoelectric hydrolysis on MIS photocathodes (8.6).

For those interested in energy storage, Intel have fabricated porous silicon capacitors (8.2) that can potentially be integrated on-die or onto solar cells, taking advantage of the extreme conformal deposition capabilities of atomic-layer deposition (ALD). The image below shows a top-down view of the porous silicon before and after ALD TiN deposition; the wall of the pore walls get thicker, but the pore structure doesn’t change. Capacitances of up to 3 milliFarads/cm2 are claimed.

8.2 Fig 5_Gardner

 

Then in the evening we have the conference reception at 6.30, through until 8 pm.

Tuesday

In the morning we have another seven parallel sessions, starting with session 9 on Advanced CMOS Devices for 10nm Node and Beyond, so another one I will definitely be targeting.

The first paper (9.1, from IBM/STMicroelectronics/SOITEC/CEA-Leti) is about strained 10-nm FDSOI devices, incorporating “a fully compressively strained 30% SiGe-on-insulator (SGOI) channel PFET on a thin (20nm) BOX substrate”; they also report ‘strain reversal’ in a PFET – is that so much strain that it reduces mobility? In their workshops at last year’s IEDM and Semicon West, CEA-Leti have been showing a roadmap that jumps from 28-nm to 14-nm and then 10-nm nodes – this looks like the first showing of the 10-nm technology.

That is followed (9.2) by an invited talk from Simon Deleonibus of CEA-Leti on how process technologies can move us towards the zero-power era(?).

Purdue U claims the First Experimental Demonstration of Ge CMOS Circuits (9.3) on a GeOI substrate, while TSMC details InAlP-capped Ge nFETs on Si and Ge substrates (9.4), and Ge n-finFETs on Si (9.5). Still in germanium, National Taiwan U talks Ge nanowire nFETs on SOI (9.6).

The last paper of the session (9.7) is from AIST in Japan on tunnel finFETS in a CMOS process.

Session 10 is a focus session on Novel Imagers and Specialty Imaging Applications, starting with an invited talk by Jiaju Ma (10.1) from the Thayer School of Engineering at Dartmouth, on the Quanta image sensor; as near as I can make out, this type of sensor scans the pixel array so fast that it effectively reads individual photoelectrons, and the image is formed by integrating x, y, and time.

Paper 10.2 from TU Delft discusses single-photon avalanche diodes (SPADs), which have enabled solid state range finding, fluorescence lifetime imaging, and time-of-flight positron emission tomography. The topic of 10.3 (Ritsumeikan U, TU Delft, Osaka U) is high-speed image sensors, aiming for one giga-frame per second!

Another invited talk is by Siemens (10.4), about organic photodetector imaging, and next  imec details a CMOS-compatible approach to hyper- and multispectral imaging (10.5).

In a different spin, Annette Grot of Pacific Biosciences (10.6) will discuss how high-resolution, low-noise and high-speed image sensors have enabled large amounts of DNA to be sequenced quickly and at reduced cost; and how further advances will keep on pushing productivity and cost reduction.

For the final talk, we go from chip-scale to huge – the large scale hybrid pixel detector systems used at the Large Hadron Collider experiments at CERN (10.8).

Session 11 is the second group of talks about power and compound semi technologies, this time on High Voltage and RF Devices. Five of the six papers are on GaN devices, and one (11.2) describes a diamond MOSFET good up to 400C. We have a new acronym in there – a SLCFET (Super-Lattice Castellated Field Effect Transistor), with a 3D castellated gate structure (11.5) – that should make for a couple of interesting slides!

Circuit/Device Variability and Integrated Passives Performance is the focus of session 12; the middle papers, 12.3 and 12.4 are the passives talks, on Ultra-High-Q Air-Core Slab Inductors (IBM), and Above CMOS Integrated High Quality Inductors for wireless power transmission (HONG Kong UST). The other discussions range from finFET simulations (12.1 and 12.2) through MTJs for random number generation (12.5), noise suppression by using dynamic threshold voltage MOSFETs (12.6), and finally a consideration by ARM of poly pitch co-optimization in standard cells below 28-nm (12.7).

We look ahead to TFETs and other Steep-Swing Devices in session 13. The first paper (UCal Berkeley, Toshiba) discusses a nano-mechanical relay (13.1), which inherently has zero off-state leakage and perfectly abrupt ON/OFF switching behavior, but also serious manufacturing challenges. 13.2 and 13.3 are TFET talks, the 13.4 topic is a Schottky-barrier Si FinFET, and 13.5 and 13.6 review piezoelectric negative differential capacitance effects and devices.

Advanced Memories and TSV are the subjects of session 14; the first four papers are more resistive RAM, from imec (14.1 and 14.2), Politecnico di Milano/Micron (14.3) and Politecnico di Milano/Adesto (14.4). Adesto is the only company I know actually selling CBRAM parts, although we haven’t had a chance to look at them yet.

14.5 is a follow-up paper looking at noise in Samsung’s V-NAND flash [2], and 14.6 is also a follow-up from IBM on mobile ion penetration from BEOL layers close to TSVs. IBM’s TSV process uses MEOL connection to the TSVs [3], so it’s feasible that there could be some cross-contamination. Tohoku U contributes the last discussion (14.7), testing polyimide TSV liners as a way of reducing the stress in the adjacent silicon.

More sensors and MEMS papers in session 15; the first three are from Tsinghua U, about different applications of graphene MEMS (15.2 also from Berkeley), and TSMC/U Illinois contribute 15.4, on an integrated 180-nm SOI-CMOS biosensor.

A*STAR in Singapore author the final two papers, but on very different topics. 15.5 is an optical biosensor with Ge photodetectors built in to the back end, and 15.6 details a MEMS-tunable laser combined with a photonic IC.

The speaker at the conference lunch will be T.J. Rodgers, founder, President and CEO of Cypress Semiconductor, a well-known voice in the business for decades. Given the recent news of the merger between Cypress and Spansion, he could be an illuminating speaker!

Session 16 focuses on Ge and SiGe Transistors, starting with an IBM/GLOBALFOUNDRIES report (16.1) on strained SiGe-OI finFETs with 50% Ge and fin width of 3.3 nm and gate length of ~16 nm; clearly aimed at the 10-nm node.

16.2 Fig4(combined)_Barraud-c

 

Looking a bit further into the future, CEA-Leti/STMicroelectronics/SOITEC (16.2) examine omega-gate CMOS nanowires, with strained SiGe-channel p-FETs and Si-channel n-FETs, integrated into a SOI-CMOS process. From the look of the pictures below they are using a gate-first approach, so there is still some life in that technology.

16.3 is another nanowire paper from National Tsing Hua U, this time with dopant-free Ge junctionless nanowire non-volatile memories as well as Si nanowire FETs; and 16.4 is a study of Ge quantum-well finFETs fabricated on a 300mm bulk Si substrate, from Penn and N. Carolina SUs with TSMC and Kurt Lesker Co.

Imec tries out replacement metal gates on Ge n-finFETs with raised NiSiGe source/drains in 16.5; AIST examines poly-Ge-OI junctionless p- and n-finFETs, fabbed by flash annealing in 16.6; and Purdue U (16.7) reports on GeOI CMOS devices with recessed S/D.

Session 17 looks at Trapping Mechanisms in AlGaN/GaN Transistors; definitely at the academic end of the scale for me, although the last paper, CMOS-Compatible GaN-on-Si Field-Effect Transistors for High Voltage Power Applications, by TSMC, seems a bit out of place (17.6).

Session 18 is the second one on circuit/device interaction, this time considering Analog and Mixed Signal Circuits. Xilinx studies the interaction between devices and analog circuits used in high-speed transceivers in both planar and FinFet processes in 18.1. Part of this will be using the TSMC 16-nm finFET process, we’ll see if it adds anything to their paper in session 3.

Broadcom looks at mismatch in HKMG transistors related to the layout, and finds sensitivity to top metal routing, in 18.2. GLOBALFOUNDRIES (18.3) looks at Analog and I/O Scaling in 10nm SoC Technology and Beyond; is it better to take an increasing proportion of the die for hard-to-shrink analog, or go with TSVs and multiple dies?

CEA-Leti has a pathfinding paper (18.4) reviewing RF front-end modules (FEMs) in the light of the increasing number of modes (GSM, WCDMA, LTE, etc) and frequency bands in mobile devices. There are now more than 40 bands worldwide, so we see multiple FEMs in the worldphones we take apart, and keeping costs down while enhancing capability is one of the understated challenges in the industry.

There is more RF from Mediatek in 18.5, this time examining Digitally-Intensive RF Transceivers in Highly Scaled CMOS; apparently, these days embedded intelligence is needed on-chip to reduce the sensitivity of circuit performance to device characteristics.

The last paper in the session (18.6) is from Keio U, discussing circuit/device interaction in the 3D context of inductive coupling between dies.

Session 19 is the third memory session, this time on MRAM, DRAM and NAND; the first three talks are focused on STT-MRAM, from imec (19.1), Hanyang U/Samsung (19.2), and LEAP (19.3). Then IBM updates on their embedded DRAM (19.4), now at the 22-nm node in their latest Power8 processor (which, being IBM, is ~650 sq. mm!).

TSMC discusses a new Self-Aligned Nitride non-volatile memory cell in 19.5, and Macronix updates us on their BE-SONOS charge-trapping NAND flash (19.6) in the last paper of the session.

Characterization and Reliability of Advanced Devices is the subject of Session 20; papers 20.1, 20.3, and 20.5 all deal with nanowire characterization; imec has two studies, on HKMG InGaAs finFETs (20.2), and ESD diodes in Si finFETS (20.4); and finally two invited reliability presentations, by Jim Stathis of IBM (20.6) and Tony Oates of TSMC (20.7), on what the challenges are in their field as we move beyond 14/16 nm.

Session 21 is a group of five papers discussing Atomistic Modeling of Device Interfaces and Materials, the first being a multi-national study of hole traps in p-MOSFETs (21.1); I had not realized that such traps had similar characteristics in different oxide dielectrics, whether it be silicon or high-k; and it appears that hydroxyl (-OH) groups could be the cause.

The next three talks (21.2, 21.3, 21.4) are also dielectric and interface studies, as is the last, but 21.5 is focused on HfO and HfAlO-based RRAM.

We go back to MEMS in session 22, actually NEMS as well, as in 22.1, which is a review of integrating NEMS with CMOS (U Grenoble Alpes, CEA-Leti, MINATEC), and 22.4, another CEA-Leti talk on polySi nanowire sensors. Tsing-hua U has two papers also, 22.2 on a nanomechanical thermal-piezoresistive oscillator, and 22.3 on CMOS-MEMS Oscillators. The final two presentations are from A*STAR, about integrating RF MEMS resonators and phononic crystals (22.5), and a 9 degree of freedom capacitive sensor.

That brings us to the end of the afternoon, and Applied Materials is hosting a panel on “The Transistor Revolution” in the Nikko Ballroom in the Nikko Hotel. In parallel Coventor is hosting an event “Survivor, Variation in the 3D Era“ in the Carmel Room, also at the Nikko Hotel. They both usually cater us well, so once we’re sated from the hospitality we can wander back to the Hilton for the conference evening panel:

“60 Years of IEDM and Counting: Did we push silicon based devices for integrated electronics to the ultimate and what does the future hold?”

Usually there are two panels, having one avoids conflicts this year; and there are some distinguished panelists – Krishna Saraswat from Stanford University, with two colleagues, Yoshio Nishi and Philip Wong, Chenming Hu (UCal Berkeley), Hiroshi Iwai Tokyo Institute of Technology), Jesus del Alamo (MIT), and Kurt Petersen, co-founder of six MEMS companies, and a member of the Band of Angels.

Wednesday

Wednesday morning has sessions 25 – 31; S25 on III-V for Logic; MIT has two papers, on InGaAs Quantum-Well MOSFETs (25.1), and InGaAs/InAs heterojunction single nanowire vertical tunnel FETs (25.5).

25.2 is an invited review of “High-Performance III-V Devices for Future Logic Applications”, by Dae-Hyun Kim of GLOBALFOUNDRIES; 25.3, by IBM, is more high-performance self-aligned InGaAs-channel MOSFETs; 25.4 (UCal, Santa Barbera) is also InGaAs, but with InP Recessed Source/Drain Spacers; and 25.6 discusses an InAlN/AlN/GaN triple T-shape fin-HEMT (Nanyang TU, Ohio State U, Institute of Materials Research and Engineering).

S26 covers Thin Film Transistors for Display and Large Area Electronic Applications. Imec demonstrates an ultra-low power organic 8 bit transponder chip in 26.1, followed by IBM with heterojunction field-effect thin-film transistors (TFTs) with crystalline Si channels, and gate regions comprised of hydrogenated amorphous silicon or organic materials (26.2).

CBRITE is next up (26.3), on High Performance Metal Oxide TFTs, then a change of pace to carbon nanotubes with sputtered and spray-coated.

26.5 Fig 3 lSi on paper large_Trifunovic

 

Metal oxides to form complementary inverters, from the Swiss Federal Institute of Technology, Imperial College London, and U Würzburg (26.4).

Believe it or not, Delft U has worked out a way to put silicon TFTs on paper or other soft substrates:

“The Delft team made the devices by casting a quantity of liquid polysilane onto a substrate, and forming a thin film from it by “doctor-blading,” or skimming it with a blade. High-performance polysilicon channel regions then were formed by laser annealing, using short pulses of coherent light to selectively crystallize the disordered film. The maximum temperature required was only 150ºC, making the TFTs suitable for paper and plastic substrates such as PET and PEN.” (26.5)

Tsing Hua U finishes up the session with the last two papers – a study of “Ultra-Thin Body (2.4nm) Poly-Si Junctionless Thin Film Transistors with a Trench Structure”, claimed to be useful for displays and 3DICs; and more poly-Si channel junctionless  FETs, but this time with a poly fin (26.6, 26.7).

Hybrid and 3D Integration is the topic of Session 27; TSMC starts off with a review paper about wafer-level system integration technologies (27.1), followed by Nikon, demonstrating their precision-aligning Cu-Cu bonding system for 3DICs (27.2); then TSMC adds high-k metal-insulator-metal capacitors to their CoWoS interposers (27.3).

Stanford U pushes the boundaries in paper 27.4 by integrating traditional silicon-FETs with RRAM and carbon nanotube-FETs, to form four vertically-stacked circuit layers (logic layer followed by two memory layers followed by a logic layer).

27.6 Fig1_Choi

 

CEA-Leti has been working on monolithic 3D integration for a while, and here they consider the thermal budget of the bottom layers (27.5). The last paper has KAIST transferring SOI silicon nanowire SONOS memory onto a plastic substrate, after thinning down to the buried oxide (27.6).

We have more emerging memory papers in session 28, together with a couple on heterogeneous integration. Toshiba starts the session discussing high density STT-MRAM for cache memory (28.1), using MTJs embedded in the back-end stack. Tohoku U and NEC look at hybrid MTJ/CMOS logic in 28.2 to make ultra-low-power logic LSI, and Rambus investigates surge current control in RRAM arrays in 28.3.

Paper 28.4 is a CEA-Leti (et al.) study of pattern recognition using convolutional neural networks made from HfO2 based OxRAM devices as binary synapses. National Chiao Tung U is also researching synaptic use of RRAM for neuromorphic computation in 28.5.

Tohoku U returns with a 3-D stacked multicore processor module made from a 4-layer 3-D stacked multicore processor chip and a 2-layer 3-D stacked cache memory chip (28.6), and using backside TSVs to enable multichip-on-wafer 3D integration. Below is an X-ray tomograph of the TSV stacks, the processor on the left and the memory on the right:

28.6 Figure17_LKW_Tohoku

In 28.7, Penn State U et al. demonstrate coupled hybrid vanadium dioxide FET oscillators in a platform for associative computing, claiming ~20x power reduction compared with CMOS; and the last paper from UCal Berkeley (28.8) integrates NEMS into a CMOS back-end stack for ultra-low power applications.

Session 29 continues the memory theme, discussing PCM and Neural Networks, and kicked off (29.1) by Micron Italy (et al.) looking into different GeSbTe PCM cell architectures.

29.2 Fig1

 

29.2 is from the Japanese LEAP consortium, describing a new type of PCM, “topological-switching random-access memory,” (TRAM). It differs from conventional PCM in that the latter works by the rapid heating of a chalcogenide material, which shifts it between its crystalline and amorphous states; whereas TRAM stores data by movement of germanium atoms within a GeTe/SbTe crystal superlattice:

The authors claim up to 20x reduction in programming energy, achieving a set/reset current as low as 55 µA.

We have an invited paper in 29.3, “Phase Change Memory and its Intended Applications”, by Chung Lam of IBM, followed by a statistical study of PCM to optimize memory capacity (29.4, UCal Berkeley et al.). We get back to PCM-based neural networks in 29.5, again from IBM, and Politecnico di Milano/Micron look at PCM set-transition energies (square vs triangular pulse) in 29.6.

IBM again takes the podium in 29.7, examining access devices for crossbar resistive memories, and they are a co-author with Macronix and National Tsing Hua U in the last paper, detailing a PCM recovery method – apparently a local anneal can be done on-chip to recover the phase-change properties if they degrade due to too many cycles (29.8).

Simulation of Novel Materials and Devices for FETs are considered in session 30; Toyota Tech Institute, Osaka U, and U Tsukuba (30.1) show that random dopant fluctuation in the source region causes a noticeable variability in the on-current of Si nanowire transistors, and its impact is found to be much larger than that of random telegraph noise (RTN).

30.2 is a review of Tunnel-FETs for future low-power technology nodes, by imec; 30.3 (U Florida) simulates Mo-disulphide-WTelluride vertical tunneling transistors; 30.4 (ETH Zurich) is another Mo-disulphide transistor study, as is 30.5, but also evaluates W-diselenide (UCal Santa Barbara); and the session finishes with a simulation of a (B-N) co-doped graphene TFET by Hong Kong UST/NanoAcademic Technologies (30.6).

The last focus session is session 31, Sensors, MEMS, and BioMEMS. It opens with a display of bio-MEMS for handling single molecules, including silicon nano tweezers, arrays of micro chambers, and chips with linear bio molecular motors (31.1, U Tokyo). The specific application is the use of MEMS technology on the molecular scale to conduct studies of DNA degradation and protein mutation related to Alzheimer’s disease. MEMS tweezers were used to trap bundles of DNA molecules to study them for stiffness and viscosity, which are markers of DNA degradation.  Here we have an electron microscope image of a DNA molecular bundle between the tips:

31.1 fig2_Fujita

 

Next up, U Bologna/U Southampton research the use of AC nanowire sensing that can capture both magnitude and phase information of the device response (31.2); 31.3 is a review of “MEMS for Cell Mechanobiology” (Stanford U); and 31.4 is also a review, of “Organic Electrochemical Transistors for BioMEMS Applications”, from Ecole Nationale Supérieure des Mines.

U Cincinnati (et al.) follows, with a tempting look at a “novel multimodality lab-on-a-tube smart catheter”, which can accurately track multiple parameters in an injured brain (31.5); 31.6 (Ritsumeikan U) shows off another medical device, an all polymer pneumatic balloon actuator, fabricated from polymers such as polyimide and polydimethylsiloxane that we are familiar with in the chip business. Paper 31.7 from MC10 completes the session by demonstrating examples of skin-based systems that incorporate physiological sensors and actuators configured in stretchable formats.

After the morning sessions, the IEDM Entrepreneurs Lunch is back for a third year, featuring a presentation by Kathryn Kranen, Former President and CEO of Jasper Design Automation.

Also at lunchtime ASM is hosting their regular IEDM seminar (Wednesday this year, instead of the Monday as of last year) on “14nm & Beyond – Fins all Around”, at the Nikko Hotel across the street from the Hilton. There’s no website, so interested parties should contact Rosanne de Vries, by replying to rosanne.de.vries@asm.com. And there’s a bit of self-promotion here, since I’m one of the guest speakers!

32.1 FIG6-HR_Tsai

 

We are back to Process and Manufacturing Technology in S32 after lunch, with a focus on Advanced Process Modules. IBM details some of its work on finFETs formed by Directed Self Assembly (DSA) in 32.1, achieving 29 nm fin pitch, and maybe giving us more evidence that EUV may never happen..

In 32.2 Samsung discusses their 10-nm interconnect strategy; judging by the abstract, we might be moving to Cu+Ru liner by the time we get to 10 nm. An imec/Micron/Hynix joint paper (32.3) reveals a new front-end scheme (gate and diffusion replacement), which allows high-thermal budget processes for applications such as control logic for memory (e.g. DRAM periphery).

Paper 32.4 is from Albany CNSE and its sponsors, examining the contact resistivity on n+ InGaAs fin sidewall surfaces; U Tokyo discusses oxygen effects in Ge MOSFETs in 32.5; 32.6 is a review of ion implantation techniques and capabilities by Applied Materials, from doping to materials engineering; and 32.7 covers “A Novel Junctionless FinFET Structure with Sub-5nm Shell Doping Profile by Molecular Monolayer Doping and Microwave Annealing”. The lead authors are from National Nano Device Laboratories, National Chiao Tung U, and National Cheng Kung U, but Michael Current and Evans Analytical are also involved, so at the least there should be some interesting analytical data included.

Session 33 has Exploratory Devices as the subject, inevitably academic in nature – Carnegie Mellon starts off (33.1) showing a four-terminal spintronic device, followed by Tohoku U, investigating 1x-nm perpendicular-anisotropy CoFeB-MgO based MTJs (33.2). Then we have a two-sided graphene oxide doped silicon oxide based RRAM (33.3) from National Sun Yat-Sen U, Peking U, and Stanford U; and a new material raises its head in (33.4) – iodostannane, basically tin activated with iodine, in a new kind of transistor, the topological-insulator field-effect transistor.

National Nano Device Laboratories, et al., present CMOS-compatible Mo-disulphide 3DFETs in 33.5, and Stanford U end the session with a review of carbon nanotube transistors.

Reliability: BTI, HCI and Breakdown are dealt with in session 34. A SMIC-sponsored work on NBTI in HKMG is covered in 34.1, co-authored by Peking U, Liverpool John Moores U, and UCal Berkeley. Liverpool John Moores U and imec look at NBTI of Ge pMOSFETs (34.2), and AIST has researched PBTI in n-fin-TFETs in 34.3; imec is back in 34.4, reviewing BTI reliability in “beyond-silicon devices”; and 34.5 covers RTN in both SiON and HKMG devices, by Peking U and SMIC.

Samsung (34.6) studies hot carrier induced dynamic variation in nano-scaled SiON/Poly, HK/MG and finFET devices, and the final paper of the session is from IBM and SRDC, discussing breakdown mechanisms in dielectric BEOL stacks (34.7).

The last session (numerically), session 35, covers Compact Modeling of devices. MIT and Purdue U get together to present a new model for FETs, which uses only a few physical parameters and is consistent with the virtual source model (35.1). They demonstrate its accuracy by comparison with measured data for III-V HEMTs and ETSOI Si MOSFETs.

NXP/UFRGS have a new noise (RTN/LFN) model for MOSFETS in 35.2, followed by IBM discussing several width dependent transistor current characteristics (35.3). We jump to TSVs in 35.4, with a CEA-Leti (et al.) study of thermal dissipation in 3D ICs and an associated model; IMECAS presents a surface potential-based compact model for a-IGZO TFTs in RFID applications in 35.5; and Purdue U/GLOBALFOUNDRIES model MTJs in 35.6.

Chronologically the last papers are due at 4.05 pm – by then a lot of attendees will have headed for home, especially since this year’s conference is so close to the Christmas break.

I will definitely be suffering from information overload and becoming brain-numb, but with 218 papers and an average of six parallel sessions at any one time, plus the offsite events, that’s not really surprising. On the other hand, where else do we go to get all this amazing stuff?

Time to unwind, maybe do a little holiday shopping, and go for an indulgent meal.

References:

[1]     H.J. Yoo et al., “Demonstration of a reliable high-performance and yielding Air gap interconnect process”, IITC 2010, pp. 1-3

[2]     J. Jang, et al., “Vertical Cell Array using TCAT (Terabit Cell Array Transistor) Technology for Ultra High density NAND Flash Memory” VLSI 2009, pp.192-193

[3]     M. G. Farooq et al., “3D Copper TSV Integration, Testing and Reliability”, IEDM 2011, pp.143-146

 

Intel’s 14nm Parts are Finally Here!

By Dick James, Chipworks

Earlier last week, a couple of laptops arrived from Japan using the Core M version of Intel’s Broadwell processor. Straight into the lab, and within a few hours the first sight of the die structure, confirming that it is indeed the 14nm technology.

The first image below is an image of a die that was given a bevel polish, so that we can look at the transistors in plan view. It’s a bit fuzzy, due to the high magnification, and construction we have going on next door; but we have measured ten contacted gate pitches as you can see, and that looks pretty close to the 70nm that was announced by Intel back in August.

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Intel Aug 11_14 slide 16

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On another part of the bevel we can see the fins, and here we have counted 20 pitches (third image above). Which agrees with the 42nm pitch in the Intel webcast. So far, so good!

If we look at the cross-section (fourth image), Intel has stayed with their thick top metal that they have been using since the 65-nm node, which means that we have to squint awfully hard to see THIRTEEN layers of metal, and a MIM-cap layer under the top metal.

10_General_Structure_168232-c-a_branded

A look at the edge seal (fifth image), which doesn’t have the top metal or the MIM-cap, makes it easier to count twelve layers. We are used to seeing twelve-plus metal layers in IBM chips (their 22nm Power8 has fifteen!), but Intel has been using nine for the last few generations, going up to eleven in the Baytrail SoC chip.

06_Inner_Die_Seal_168232-c-a_branded

Intel quoted 52 nm interconnect pitch, but we see 54nm (sixth image). Although that is within measurement error, and we may not have sectioned the most tightly packed part of the die.

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As yet we don’t have any detailed TEM imaging to look at the transistors or fins in close-up, so we can’t verify if the fins have vertical walls or not, as shown by Intel (seventh image).

Intel Aug 11_14 slide 22

The cross-section seems to show that essentially the 14nm process is a shrink of the 22nm technology, with the modified fins; the gate metallisation looks similar to the 22nm, with tungsten gate fill as in the earlier process. (As an aside, this will make it the fourth generation replacement metal gate process – this technology has legs!)

Intel and IBM are giving late news papers at IEDM in December, and apparently there are air gaps in the back-end dielectric stack – we have not found those yet. We have confirmed the SRAM cell size in the cache memory is ~0.058 µm2.

Our analysis is ongoing, and we look forward to some great images!

The Second Shoe Drops – Now We Have the Samsung V-NAND Flash

By Dick James, Senior Technology Analyst, Chipworks

Two weeks ago, we posted about the TSMC 20nm product that we had in-house; now after waiting for a year since Samsung’s announcement of V-NAND production, we have that in the lab and can start to see what it looks like.

The vertical flash was first released in an enterprise solid-state drive (SSD) last year, in 960 GB and 480 GB versions, but with no model number, so essentially for sampling only to established customers. Then in May this year they announced a second-generation V-NAND SSD, with a stack of 32 cell layers.

However, on July 1 at this year’s Samsung SSD Global Summit they unveiled the SSD 850 Pro, aimed at high-end PCs and workstations, and said to be available in July. Of course we immediately put out feelers and got some on pre-order.  They showed up last week and we have the first few images.

First, though, let’s think about what the changes are from the conventional planar NAND. Samsung posted a slick video which gives a summary of the technology. The first thing to note is that we have gone from the ETOX floating-gate charge storage that we have seen in the last umpteen generations of flash, to charge-trap storage (CTF – Charge Trap Flash) in which the charge is stored on a silicon nitride layer (otherwise known as a SONOS cell – Si/SiO/SiN/SiO/Si).

The SONOS stack is then oriented vertically, using a polysilicon cylinder as the substrate silicon, and wrapping the other layers around the central cylinder.

Fig. 1  Cell structure transition from planar to V-NAND stack

Fig. 1 Cell structure transition from planar to V-NAND stack

 

The wordlines (control gates) become a horizontal layer, and the bitlines are connected to the top of the polySi cylinder; the select gates are formed by the top and bottom conductive layers [1]. Samsung describes the use of a tungsten replacement metal gate [1], and 24 wordline layers plus 2 dummy wordlines and two select gates for a total of 28 layers [2].

Fig. 2  Schematic of  V-NAND cell stack

Fig. 2 Schematic of V-NAND cell stack

 

We also see in Fig.2 a “blocking layer” in between the metal gate and the SiN, which at least implies the use of a high-k dielectric instead of an oxide layer for the capacitative coupling layer, as used in their CTF parts from 2006.

One of the many challenges using a vertical stack such as the V-NAND is etching through a stack of many dissimilar layers, to etch the holes for the polySi cylinder channels,  the slots through the stack to separate the wordlines, and the vias down to the wordlines (etching holes down to a staircase of extended wordlines). In fact, the whole stack is a big etching problem – see Fig.3.

Fig. 3  Schematic of etching steps in V-NAND stack

Fig. 3 Schematic of etching steps in V-NAND stack

 

Now that we have the production part, Samsung have clearly solved those problems. Let’s take a first look at what’s inside. Fig. 4 is a photo of the die, and Fig. 5 shows the die mark – the “A” on the end denoting the second-generation product. Interestingly, the “DG” in the part number normally denotes a 128-Gb die, but this part is actually ~86 Gb, since we have twelve flash dies in our 128-GB solid-state drive.

Fig.4 Die photo of  Samsung K9ADGD8S0A V-NAND flash device

Fig.4 Die photo of Samsung K9ADGD8S0A V-NAND flash device

The part described in the ISSCC paper [2] was an actual 128-Gb device, with a chip size of ~133 sq. mm. Our 86-Gb die has shrunk to ~85 sq.mm., slightly increasing the bit density from 0.96 to 0.99 Gb/sq.mm.

 

Fig. 5  Die mark

Fig. 5 Die mark

When we cross-section the chip, the staircase shown in Fig. 3 shows up nicely:

Fig. 6  SEM cross-section of Samsung V-NAND stack

Fig. 6 SEM cross-section of Samsung V-NAND stack

In this first shot, we don’t appear to have sectioned through any of the vias to the wordline layers; the vertical features appear to be polySi cylinders drilled into the outer edges of the stack. If we look closer at the edge of the array, that does appear to be the case (Fig. 7).

Fig. 7  Edge of V-NAND flash array

Fig. 7 Edge of V-NAND flash array

On the left side of the image we can see the array proper. SEM images can always be confusing, but it appears that the polySi bitline cylinders are staggered, and the slots between wordlines are filled with tungsten to contact the substrate for the lower select transistors. Fig. 8 shows things in a little more detail, and we can clearly see that the bitline contacts are staggered. We can also see that there are 38 layers in the stack; 32 wordlines, plus four dummy wordlines, plus the select transistors at top and bottom.

Fig. 8  Close-up image of V-NAND flash array

Fig. 8 Close-up image of V-NAND flash array

At the moment, that’s as far as we’ve got; we don’t yet have any materials analysis, but my guess is that the three interconnect layers are tungsten, copper and aluminum, as in a lot of other Samsung memory chips.

We will of course being preparing a report on this seminal part, so for more details contact Chipworks, or keep an eye on my Twitter account, @ChipworksDick.  Once the dust has settled, I hope to get into a bit more detail in a future blog in a few months time.

[1] J. Jang et al., “Vertical Cell Array using TCAT (Terabit Cell Array Transistor) Technology for Ultra High Density NAND Flash Memory“, Dig. Symp. VLSI Tech., pp. 192-193, June 2009

[2] K-T Park et al., “Three-Dimensional 128Gb MLC Vertical NAND Flash-Memory with 24-WL Stacked Layers and 50MB/sHigh-Speed Programming“, Proc. ISSCC, pp. 334-335, Feb. 2014

TSMC 20nm Arrives – The First Shoe Drops

By Dick James, Senior Technology Analyst, Chipworks

For us at Chipworks interested in leading edge processes, 2014 so far has been the year of waiting for parts and processes that have been announced, but not shown up in the world of commercial production. It will surprise no-one in the business that they are Intel’s 14-nm, the 20-nm products from any of the big three foundries (in particular TSMC), and vertical NAND (in particular Samsung, since they are the first claiming shipment).

There are of course other products that we are anticipating such as the latest SDRAM, STT or resistive RAM, and anything with TSVs, but they are lower-key and will not get the same attention from the majority of our customers.

So now the first shoe has dropped (must check where that metaphor came from!), and we have a TSMC-fabbed 20-nm part in-house. It is in the lab at the moment, and we are waiting for the analysis results.

It will be interesting to see what changes TSMC has made from the 28-nm process; in general, I expect mostly a shrink of the latter process, with no change to the materials of the high-k stack, though maybe to the sequence. At 28-nm the high- k was put down first, before the dummy poly gate, and it makes sense to move that deposition to after poly gate removal. That way, the high-k layer does not have to suffer the poly formation and source-drain engineering process steps, saving it from quite a bit of thermal processing.

Below is an illustration of a NMOS transistor from a Qualcomm Snapdragon 800, fabricated in the TSMC 28HPM process. The slight indent at the bottom of the metal stack (indicated by the arrow), above the high-k layers, indicates that the high-k was formed before the polysilicon deposition and the subsequent source/drain engineering.

Fig. 1: NMOS Transistor in Qualcomm Snapdragon 800

Fig. 1: NMOS Transistor in Qualcomm Snapdragon 800

The dark line at the perimeter of the metal gate is the tantalum-based barrier layer between the Ti-Al work-function doping layer and the TiAlN work-function layer, and is the first layer formed after the dummy poly removal. Intel used this sequence for their 45-nm process, but modified it at the 32-nm node to deposit the high-k stack after poly removal (high-k last – see below).

Fig. 2 Intel 32-nm NMOS Transistor

Fig. 2 Intel 32-nm NMOS Transistor

You can see that Intel also adopted raised source/drains, with stacking faults to apply tensile stress; we will see if TSMC does the same in their second generation gate-last HKMG process. They could also change the gate fill metal, since in a smaller gate it may be difficult to use the PVD Ti/Al/Cu from the 28nm sequence.

Fig. 3 PMOS Transistor in Qualcomm Snapdragon 800

Fig. 3 PMOS Transistor in Qualcomm Snapdragon 800

When it comes to PMOS, I also expect a high-k last version of the 28-nm gate structure, with the latest version of e-SiGe source/drains, likely with a sigma-cavity etch to the (111) planes. We already have raised source/drains, and the Ge content is ~50%, so not much opportunity for change there.

As for the back-end, presumably there will be a reduction in the k-value of the low-k dielectric, and maybe some thinning of the barrier layer in the metal trenches, both of which are trends that progress relatively slowly by comparison with the front-end.

Back in May, Applied Materials announced a cobalt CVD system aimed at improving copper fill and electro-migration performance. I wouldn’t have expected to see this in use yet, but at Semicon I heard that over 90 of these systems have already been shipped, so there is at least a possibility that we’ll see cobalt in our 20-nm metallization.

All pure speculation, but as a blogger and analyst, I’m paid to speculate!

As for “the first shoe drop”, it’s a variant on “waiting for the other shoe to drop“; apparently it’s a reference to cheap apartment housing where tenants would hear their neighbours above taking off and dropping their first shoes on to the floor; and then wait for the second shoes to drop.

Intel’s e-DRAM Shows Up In The Wild

When Intel launched their Haswell series chips last June, they stated that the high-end systems would have embedded DRAM, as a separate chip in the package; and they gave a paper at the VLSI Technology Symposium [1] that month, and another at IEDM [2].

It took us a while to track down a couple of laptops with the requisite Haswell version, but we did and now we have a few images that show it’s a very different structure from the other e-DRAMs that we’ve seen.

IBM has been using e-DRAM for years, and in all of their products since the 45nm node. They have progressed their trench DRAM technology to the 22nm node [3], though we have yet to see that in production.

Embedded DRAM in IBM Power 7+ (32-nm)

Embedded DRAM in IBM Power 7+ (32-nm) (Click to view full screen)

TSMC and Renesas have also used e-DRAM in the chips they make for the gaming systems, the Microsoft Xbox and the Nintendo Wii. They use a more conventional form of memory stack with polysilicon wine-glass-shaped capacitors. TSMC uses a cell-under-bit stack where the bitline is above the capacitors, and Renesas a cell-over-bit (COB) structure with the bitline below.

Embedded DRAM in Microsoft Xbox GPU fabbed by TSMC (65-nm)

Embedded DRAM in Microsoft Xbox GPU fabbed by TSMC (65-nm) (Click to view full screen)

Intel also uses a COB stack, but they build a MIM capacitor in the metal-dielectric stack using a cavity formed in the lower metal level dielectrics. The part is fabbed in Intel’s 9-metal, 22nm process:

Embedded DRAM in Nintendo Wii U GPU fabbed by Renesas (45nm)

Embedded DRAM in Nintendo Wii U GPU fabbed by Renesas (45nm) (Click to view full screen)

When we zoom in and look at the edge of the capacitor array, we can see that the M2 – M4 stack has been used to form the mould for the capacitors.

General structure of Intel’s 22-nm embedded DRAM part from Haswell package

General structure of Intel’s 22-nm embedded DRAM part from Haswell package (Click to view full screen)

Looking a little closer, we can see the wordline transistors on the tri-gate fin, with passing wordlines at the end of each fin. Two capacitors contact each fin, and the bitline contact is in the centre of the fin.

Intel’s 22-nm embedded DRAM stack

Intel’s 22-nm embedded DRAM stack (Click to view full screen)

We can see some structure in the capacitors, but at the moment we have not done any materials analysis.  A beveled sample lets us view the plan-view:

Plan-view image of the Intel 22-nm embedded DRAM capacitors

Plan-view image of the Intel 22-nm embedded DRAM capacitors (Click to view full screen)

The capacitors are clearly rectangular, but again in the SEM we cannot see any detailed structure. We’ll have to wait for further analysis with the TEM for that!

Intel claims a cell capacitance of more than 13 fF and a cell size of 0.029 sq. microns, so about a third of their 22-nm SRAM cell area of ~0.09 sq. microns, and a little larger than the IBM equivalent of 0.026 sq. microns. The wordline transistors are low-leakage trigate transistors with an enlarged contacted gate pitch of 108 nm (the minimum CGP is 90 nm).

In the Haswell usage the die is used as a 128 MB L4 cache, with a die size of ~79 sq. mm, co-packaged with the CPU.

Intel Haswell CPU with co-packaged eDRAM

Intel Haswell CPU with co-packaged eDRAM (Click to view full screen)

Intel got out of the commodity DRAM business almost thirty years ago; it will be interesting to see where they take their new entry, though not likely into competition with the big three suppliers. Their “Knights Landing” high-performance computing (HPC) platform is reported to use 16 GB of eDRAM, which will take the equivalent of 128 of these chips, so perhaps the future is in HPC and gaming systems such as the one we bought to get the part.

References

[1] R. Brain et al., A 22nm High Performance Embedded DRAM SoC Technology Featuring Tri-gate Transistors and MIMCAP COB, Proc VLSI Symp 2013, pp. 16-17.

[2] Y. Wang et al., Retention Time Optimization for eDRAM in 22nm Tri-Gate CMOS Technology, Proc IEDM 2013, pp. 240-243.

[3] S. Narasimha et al., 22nm High-Performance SOI Technology Featuring Dual-Embedded Stressors, Epi-Plate High-K Deep-Trench Embedded DRAM and Self-Aligned Via 15LM BEOL, Proc. IEDM 2012 pp. 52-55.

IEDM 2013 Preview

Next week, the researchers and practitioners of the electron device world will be gathering in Washington D.C. for the 2013 IEEE International Electron Devices Meeting.  To quote the conference web front page, “IEDM is the flagship conference for nanometer-scale CMOS transistor technology, advanced memory, displays, sensors, MEMS devices, novel quantum and nano-scale devices and phenomenology, optoelectronics, devices for power and energy harvesting, high-speed devices, as well as process technology and device modeling and simulation. The conference scope not only encompasses devices in silicon, compound and organic semiconductors, but also in emerging material systems.”

From my perspective at Chipworks, focused on chips that have made it to production, it’s the conference where companies strut their technology, and post some of the research that may make it into real product in the next few years.

In the last few days I’ve gone through the advance program, and here’s my pick of what I want to try and get to, in more or less chronological order.  As usual there are overlapping sessions with interesting papers in parallel slots, but we’ll take the decision as to which to attend on the conference floor.

For the second year the conference starts on the Saturday afternoon, with a set of six 90-minute tutorials on a range of leading-edge topics:

  • Nano Electronics – The use of Low-Dimensional Systems for Device Applications, Joerg Appenzeller,Purdue University
  • Interface Properties for SiC and GaN MOS Devices, T. Paul Chow, Rensselaer Polytechnic Institute
  • Energy Harvesting for Self-Powered Electronic Systems, Rob van Schaijk R&D Manager Sensors &Energy Harvesters, Holst Centre / IMEC
  • Tunnel FETs – Beating the 60 mV/Decade Limit, Erik Lind, EIT, Lund University
  • Atomic-Scale Modeling and Simulations for Nanoelectronics, Sumeet C. Pandey and Roy Meade,Emerging Memory Group, Process R&D, Micron Technology Inc.
  • 3D Chip Stacking, Mukta Farooq, Systems & Technology Group, IBM

The first three are from 2.45 – 4.15, and the remainder from 4.30 – 6.00.  I won’t make it to any of them; dedicated nerd I may be, but I want at least some of my weekend!

On Sunday December 4th, we start with the short courses, “Challenges of 10nm and 7nm CMOS Technologies” and “Beyond CMOS: Emerging Materials and Devices.

Aaron Thean of IMEC has organised the former, and we have some impressive speakers – Frederic Boeuf, ST Microelectronics, (Device Challenges and Opportunities for 10nm and Below CMOS Nodes), Zsolt Tokei, also of IMEC, (Challenges of 10nm & 7nm Advanced Interconnect), Andy Wei, GLOBALFOUNDRIES, (Process Integration Challenges in 10nm CMOS Technology), Paul Franzon, NCSU, (Manufacturing, Design, and Test of 2.5D- and 3D-Stacked ICs), and Mark Neisser, Sematech (Lithography Challenges and EUV Readiness for 10nm and Beyond). With 14-nm product expected to hit the market next year, we need to look ahead, so this is appropriate  – on the Intel clock, 10-nm is only two – three years away!

I’m now telling folks to think about the end of silicon, at least as we know it, since my brain will not wrap around the idea of 10- and 7-nm gates, and 10-nm gates are only 30 – 40 atoms across, depending on orientation! There’s lots of talk about integrating high-mobility materials onto silicon (imec had an announcement about InGaAs finFETs only a few weeks ago), so this course will help put that into context and cover off how the transistors fit into the rest of the stack.

Tom Theis of SRC has set up the other short course; now that we are reaching the end of silicon transistors, where do we go beyond CMOS?

Ken Uchida of Keio University reprises some of the first course with a session on Extending the FET; then Adrian M. Ionescu from the Ecole Polytechnique Federale de Lausanne discusses Tunnel FETs to give insights into perhaps the best known low-voltage device.

Nanomagnetic Devices are reviewed by Rolf Allenspach from IBM Zurich Research Labs, looking at the material properties and challenges, and some example devices.

All of these futuristic devices have to be compared to each other to see which ones have practical potential, so Dmitri Nikonov of Intel covers off Performance Benchmarking Methodology for Emerging Devices, looking at the rigorous methodology developed by the SRC’s Nanoelectronics Research Initiative, with some comparative results.

The final talk is on Emerging Devices for Quantum Computing by Michelle Simmons from the University of New South Wales, showing the device requirements for a practical quantum computer, then a quick survey of exploratory devices, and a closer look at one or two promising device concepts.

So some good solid stuff – although the courses make a long Sunday, from 9 a.m. to 5.30 p.m., but it’s worth sticking around to the end.

For the first time I can remember the Sunday evening has some extra sessions; Sematech is hosting a session on “Beyond CMOS” at the Fairfax at Embassy Row, from 5:30 – 8:35; and Leti will host a workshop on “Latest Advances in Cost-effective and Power-efficient Technologies for the Future of the Semiconductor Industry” from 6 – 9 pm at the Churchill Hotel, across the street from the Hilton.

Monday morning we have the plenary session, with three pertinent talks on the challenges of contemporary electronics:

  • Graphene Future Emerging Technology, by Andrea Ferrari, from the University of Cambridge – given the developments in this field in the last few years, it’s time to look ahead and try and create a roadmap for this potentially disruptive technology, so this should be illuminating;
  • Heterogeneous 3D Integration – Technology Enabler Toward Future Super-Chips, Mitsumasa Koyanagi, Tohoku University – we are already seeing a form of heterogeneous integration in RF front-end modules (but at the package level), and with Luxtera’s optical interface chips, but this talk will describe the higher levels of integration being researched at Tohoku U and elsewhere.
  • Smart Mobile SoC Driving the Semiconductor Industry: Technology Trend, Challenges and Opportunities, Geoffrey Yeap, Qualcomm. As VP of Technology, Geoffrey Yeap has been at the heart of the mobile revolution, and helped push the company into the top ten; so this should be an interesting review of the last few years of mobile chip developments, and the challenges of squeezing more and more functionality onto ICs, for more and more RF bands, and in ever thinner phones.

At lunchtime ASM is hosting their regular IEDM seminar (Monday this year, instead of the Wednesday as in previous years) on Integrating High Mobility Materials, again at the Churchill Hotel.

After lunch we have seven parallel sessions coming up! Session 2 gets straight into the way-ahead material with papers on germanium & III-V CMOS devices, although we seem to be moving away from R towards D in the R&D spectrum; for example, paper 2.8 from IBM builds InGaAs n- and SiGe p-MOSFETs on hybrid substrates formed by direct wafer bonding of SiGe and InGaAs layers.

Session 3 details MRAM and NAND flash memories, starting with an invited talk by AIST on Future Prospects of MRAM Technologies (3.1), and the session ends with papers from Hynix and Macronix, the former on a 1x-nm multi-level cell NAND flash (3.6), and the latter on a dual-channel 3D NAND flash (3.7).

In session 4, we have the more futuristic topic of Steep Slope Devices, including papers from imec (4.2) and Intel (4.3) on tunnel FETs.

Now that we are into the finFET era, there is an interesting simulation paper in session 5; Analysis of Dopant Diffusion and Defects in Fin Structure (5.7), a joint paper by Panasonic and imec.

Session 6 focuses on Power Devices, with an indication that TSMC is getting into the business; they have a joint paper with Honk Kong UST on interface traps in Al2O3/AlGaN/GaN MIS devices (6.3). Mitsubishi is giving an invited talk on high voltage and large current SiC power devices (6.5), and we get back to MOS with a joint paper on the operating limits of LDMOS from NXP and U Twente.

The first two papers in session 7 discuss the reliability degradation caused by TSVs and 3D stacking, as measured by DRAM retention time; it appears that if wafers are thinned to 30 microns or less the DRAM performance drops off significantly due to stresses caused by the TSVs and microbumps (7.1, 7.2).

This year’s IEDM has focus sessions, and session 8 is the first, on Sensors and Microsystems for Biomedical Applications, with seven invited talks on different aspects of biosensors and biomedical devices.

Then in the evening we have the conference reception at 6:30, through until 8 pm.

Tuesday morning we have another seven parallel sessions, starting with session 9 on Advanced CMOS Technology, so one I will definitely be targeting. The first paper (9.1) is TSMC’s launch of their 16-nm finFET process, with a claimed doubling of logic density over their 28-nm process, with more than 35% speed gain or over 55% power reduction, and a 0.07 sq. micron 6T SRAM cell size.

 Screen Shot 2013-12-06 at 10.28.55 AM

Comparison of TSMC 16-nm finFET performance with 28-nm HKMG planar process (Source: TSMC, IEDM)

 

That is followed (9.2) by the competing 20-nm FDSOI process from the ISDA Alliance (IBM, STMicroelectronics, Renesas, GLOBALFOUNDRIES, SOITEC, and CEA-LETI).

Paper 9.3 takes us into the world of 3D-IC with a paper on layered ultrathin-body (UTB) circuits stacked on 300nm-thick interlayer dielectric (ILD) layers.

 

 Screen Shot 2013-12-06 at 10.29.32 AM

TEM image of 3D-layered UTB chip (Source: NNDL/Stanford/NTHU/UC Berkely, IEDM)

Amorphous silicon layers were deposited and crystallized with laser pulses, then planarized with low-temperature CMP to thin the layers, allowing formation of ultrathin, ultraflat devices.

IBM takes the next slot (9.4) with what looks like an update on their 22-nm gate-first process debuted last year (paper 3.3 last year), discussing 2nd Generation Dual-Channel Optimization with cSiGe for 22nm HP Technology and Beyond.

Intel also gives an update, this time on their eDRAM technology disclosed at the VLSI Symposium in June (Retention Time Optimization for eDRAM in 22nm Tri-Gate CMOS Technology, 9.5).

 Screen Shot 2013-12-06 at 10.30.16 AM

Details from Intel eDRAM paper at 2013 VLSI Technology Symposium

 

The session finishes up with a paper on embedded flash in a 55nm process from Fujitsu (9.6), and one on SRAM-like local interconnect structures for 20nm middle-of-line metallization from GLOBALFOUNDRIES; they claim that this helps them “achieve industry’s most optimum 20nm technology offerings.”

So I guess from the above I will be in session 9 all morning, so I will have to give session 10 on RRAM and FERAM a miss, even though there is interesting progress in the field, including 28nm RRAM in a paper (10.3) co-authored by TSMC.

Session 11 is focused on Flexible Electronics, a look into the future, but not too far away, judging by some of the talks.

Session 12 is the first on Modeling and Simulation, focusing on Technology CAD, with a few topics that catch my eye; paper 12.2 on Alloy Scattering in SiGe Channel from Samsung; Mobility in High-K Metal Gate UTBB-FDSOI Devices, an invited talk (12.5) from STMicroelectronics; Threshold Behavior of the Drift Region: the Missing Piece in LDMOS Modeling (12.7), from NXP; and Copper Through Silicon Via Induced Keep Out Zone for 10nm Node Bulk FinFET CMOS  Technology (12.8), a joint paper from imec and Synopsys.

It seems that session 13 is a bit of a catch-all session on Advanced Manufacturing, since it includes invited papers on 3D memory (13.1) from Micron, GaN-on-Si from Toshiba (13.2), photonics on SOI by Luxtera and STMicroelectronics (13.3), TSMC’s take on glass interposers (13.4) and 450mm (13.7), and III-V growth on 300mm wafers from Aixtron (13.6).

Next we have another bio-session, BioMEMS and BioSensors, including two DNA analysis-on-chip papers (14.1 & 14.3). The last parallel session of the morning is session 15, on Reliability of BEOL and FEOL Devices, and it now seems that graphene and nanotubes have been around long enough that we have an invited talk on their reliability (15.1).

The speaker at the conference lunch will be David Luebke, Senior Director of Research at Nvidia, on the topic, The Current State-of-the-Art and Advances in Visual/GPU Computing.

Session 16 in the afternoon is about III-V Logic, looking ahead to when silicon can no longer provide the performance needed.

Session 17 is another focus session, this time on Analog and Mixed Signal Circuit/Device Interactions. We have a series of invited talks on the impact of nanometer scaling and finFETS on analog design and performance, RF technology, and a look at terahertz RF in CMOS, all of which catch my interest.

We are back to Sensors, Resonators, and Microsystems in session 18, and Nanosheet and Nanotube Technology in session 19, and it seems that molybdenum disulphide is now taking attention away from graphene since there are a couple of papers on that topic.

Session 20 is another multi-topic group of papers, on Fully Depleted Planar, 3D Ge Device Technology and RRAM Memory processing. We have TSMC and GloFo/Samsung/imec talking Ge finFETs (20.1 & 20.4), Si nanowires from IBM (20.2), and gate-last FDSOI from STMicroelectronics and CEA-LETI (20.3); two papers on doping finFETS by AIST/Nissin and AMAT/GloFo/Hynix (20.5 & 20.6); and to finish the session two RRAM talks by Macronix/National TsingHua U and Stanford U (20.7 & 20.8). The last paper uses block copolymer self-assembly lithography to get the device down to less than 12nm.

Memory Characterization and Reliability is the subject of Session 21, mostly of resistive memories; Session 22 is another Modeling and Simulation group of papers, this time on Innovative Devices, mainly resistive memories.

That brings us to the end of the afternoon, and now we have a dilemma – three offsite events – IEDM is getting popular with the industry! Applied Materials is hosting a panel on “3D NAND Is a Reality – What’s Next?” at the Omni Shoreham Hotel from 5 – 7.30 pm; Coventor is also hosting a panel at the Churchill Hotel, from 5:30 – 8:30, on “Insights from the Experts on Advanced Technology Development”; and Synopsys is having a TCAD reception, again at the Churchill, from 6 – 8 pm.

Once we’re sated from the hospitality, we can wander back to the Hilton and try and stay awake for the conference evening panels:

“Is there life beyond conventional CMOS?” moderated by Jeff Welser of IBM – now becoming a perennial question! The panelists are An Chen (GLOBALFOUNDRIES), Tetsuo Endoh (Tohoku University), Marc Heyns (IMEC Fellow), Mark Rodwell (UC Santa Barbara), Alan Seabaugh (Notre Dame), and Ian Young (Intel).

And:

“Will Voltage Scaling in CMOS Technology Come to an END?” with Kevin Zhang of Intel as moderator. Panelists for this session are Rob Aitken (ARM), Kelin Kuhn (Intel), Sreedhar Natarajan (TSMC), Tak Ning (IBM), Ann Steegen (imec), and Nobuyuki Sugii ( LEAP).

Wednesday morning has sessions 25 – 30; S25 on Advanced 3D Packaging and Emerging Memory Systems; TSMC is detailing an Array Antenna Integrated Fan-out Wafer Level Packaging (25.1), and Maxim is giving an invited talk on 3D Heterogeneous Integration for Analog, as the first two papers.

S26 covers Ge Channel and Nanowire Devices, obviously looking ahead, but catching my interest are A Group IV Solution for 7nm FinFET CMOS (26.3), from Synopsys/Stanford, and A Practical Si Nanowire Technology… (26.5) from Samsung.

Session 27 – Display and Imaging Devices has three papers on thin-film transistors for displays, and three imaging talks; Sony describes a Three-dimensional .. 1.20 μm Pixel Back-Illuminated CMOS Image Sensor (27.4), and Infineon has a novel Trench Gate Photo Cell (27.6) which could find use as the ambient light sensor that we see in so many mobile phones.

We have more III-V and TFET papers in session 28, but including an invited talk from Raydeon (More than Moore: III-V Devices and Si CMOS Get It Together – 28.5) on integrating III-V devices with Si CMOS on a common silicon substrate, which should be interesting in these days of 3D.

Session 29 has a couple of interesting papers on BEOL from Renesas and Samsung (29.1 & 29.2), and Hitachi/ASET discusses Fabricating 3D Integrated CMOS Devices by Using Wafer Stacking and Via-last TSV Technologies (29.5).

Conductive Bridge and Phase Change RAM papers make up session 30; the first two are CBRAM, and the rest PCM. Micron discusses Interface Engineering for Thermal Disturb Immune Phase Change Memory Technology in paper 30.4.

After the morning sessions, the IEDM Entrepreneurs Lunch is back for a second year, with Steve Nasiri, founder of Invensense, and now angel investor and mentor at Nasiri Ventures LLC, as guest speaker.

We are back to Characterization, Reliability, and Yield in S31 after lunch, with a focus on Device Variation and Noise. STMicroelectronics is giving an invited presentation on the Growing Impact of Atmospheric Radiations on sub-65nm CMOS BULK/FDSOI Technologies (31.1), we have two papers on SRAM, and the last three discuss random telegraph noise in MOSFETs, resistive RAM, and HEMTs, respectively.

Session 32 is the third Modeling and Simulation session, this time on Modeling Beyond CMOS Devices, Interconnects and GaN HEMT – getting a bit esoteric for my focus, unfortunately – but then with all the parallel sessions we have to miss some of them.

The last session (numerically), session 33, covers Circuit/Device Variability and Reliability. Asen Asenov of University of Glasgow/Gold Standard Simulations has a joint paper with IBM on Simulation Based Transistor-SRAM Co-Design in the Presence of Statistical Variability and Reliability (33.1), detailing the impact of process and statistical variability and reliability on SRAM cell design in 14nm technology node SOI FinFET transistors; with Intel’s 14nm due next year we might get some insights, though time will tell if they have moved to SOI trigate transistors from the bulk material that they currently use at 22nm.

By the end, I’m usually suffering from information overload and becoming brain-numb, but with 215 papers and an average of six parallel sessions at any one time, plus the offsite events, that’s not really surprising. On the other hand, where else do we go to get all this amazing stuff?

GLOBALFOUNDRIES to make Apple chips in New York fab?

I normally don’t have the time to follow local press, but occasionally Google Alerts pops up with something quite interesting. In this case, the Albany Times Union from Albany, New York had an intriguing headline that supports some of the gossip around Apple’s fabrication plans for their A-series processor chips, up to now fabbed by Samsung.

At least in the short term, and from a technology point of view, this makes a lot more sense than Apple’s much-vaunted switch to TSMC, since GLOBALFOUNDRIES (as part of the Common Platform alliance with Samsung) uses a gate-first HKMG process rather than TSMC’s gate-last strategy. In fact, a couple of years ago GLOBALFOUNDRIES and Samsung announced that they were synchronizing their fabs so that customers could transfer products from one foundry to the other without the pain of redesign.

At the 20-nm node it might be different story, since all the foundries will be using gate-last processes; I can see TSMC picking up some of the business then, and there are persistent rumours of Apple trial lots going through TSMC.

It also makes sense that GLOBALFOUNDRIES would make a pitch for the Apple work, since they are hungry for customers, and if they can get in at the 28-nm node they will be well positioned for 20-nm products in the next A-chip generations. Apple business would also help fill the potential second fab for which they have obtained outline planning permission in the Luther Forest Technology Campus.

When it comes to the processes, the 28-nm samples that we have seen from GloFo and Samsung are remarkably similar; this is a SEM cross-section of the transistors and first-level metal in the Rockchip RK3188 that Ajit Manocha announced at Semicon West:

Rockchip RK3188_branded 1
Now let’s look at a similar section out of a Samsung Exynos 5410 app’s processor:

Samsung Exynos 5410_branded 2

There may be some very subtle differences that show up in very detailed analysis, but essentially they look pretty close; the fab synchronizing looks good to me!

So the Times Union report may be just a blog rumour, but given the apparent compatibility of the two processes, it has the whiff of authenticity, and we may see A7s out of New York State in the not too distant future.

Now, if we get one into Chipworks, can we tell the difference?

Apple A7 uses Samsung’s 28nm process

Last week, we started tearing down the Apple iPhone 5S. There has been much speculation that Apple would be moving their processor chips over to TSMC, but I think that we can now decisively say that this has not occurred – they have migrated to 28nm, but still at Samsung.

Apple's A7 Processor Die Image (click to view full screen.)

Apple’s A7 Processor Die Image (click to view full screen.)

Earlier in the day last Friday we established from the look of the die that the A7 was manufactured by Samsung. In the meantime our guys have been grafting away in the lab, and came to the “boring” conclusion that the chip looked exactly the same as the last one.

The devil is in the details, however, and we have to do some measurements to see the difference.

Below is a SEM image of a cross-section of a group of transistors in the A6 (APL0598) chip, fabbed in the Samsung 32nm high-k-metal gate (HKMG) process.  For convenience we have measured ten, so the dimension of the contacted gate pitch is 123nm.

SEM Cross-Section of Apple A6 (APL0598) Die (click to view full screen)

SEM Cross-Section of Apple A6 (APL0598) Die (click to view full screen)

Now if we look at a similar image of the A7 (APL0698) below, and we see that the contacted gate pitch is 114nm. So, even allowing for measurement error (we figure +/- 5%), we’re pretty sure that we see a shrink, and that the A7 is made on the same process as the new Samsung Exynos 5410, the 28nm HKMG process.

SEM Cross-Section of Apple A7 (APL0698) Die (click to view full screen.)

SEM Cross-Section of Apple A7 (APL0698) Die (click to view full screen.)

That doesn’t sound much, a mere 4 nm, but again if you do the math and remember  that we’re talking area shrink, not linear dimensions, then 28^2 divided by 32^2 (784/1024) comes out at about 77 percent of the area for the equivalent functionality. Or, given that the A7 is 102 mm^2 compared with 97 mm^2 for the A6, more functions in a slightly bigger area.

Below is a delayered sample of the A7, but we have yet to identify what that functionality is, something that we will be doing in the next few weeks.

Transistor-Level Image of the Apple A7 (click to view full screen)

Transistor-Level Image of the Apple A7 (click to view full screen)

 

 

 

Qualcomm Snapdragon 800 and Rockchip RK3188 – Battle of the Foundries!

The Snapdragon 800 (Qualcomm MSM8974) is Qualcomm’s leading-edge, low-power, mobile phone app’s processor with built-in 3G/4G LTE modem, using the latest Krait 400 CPU rated at 2.3 GHz and their 450 MHz Adreno 330 GPU. It was launched at this year’s CES International with this rather slick commercial.

Significantly, it is fabricated using the TSMC 28HPM (28-nm, High-Performance Mobile) process, which extends TSMC’s high-k, metal gate (HKMG) processing into the mobile space. Before this, all Qualcomm’s mobile chips were made with the TSMC 28LP polysilicon gate/SiON process; and to our knowledge, this is the first volume production part using 28HPM.

The 28HPM process sees a shrink in minimum gate lengths and SRAM cell size when compared with the 28HP process, and the inclusion of embedded SiGe source/drains for PMOS strain, which was not part of 28HPL.

 

TSMC 28HPM PMOS transistor

TSMC claims the technology can provide better speed than 28HP while giving similar leakage power to 28LP. The wide performance/leakage coverage apparently makes 28HPM ideal for applications from networking, tablet, to mobile consumer products.

 

 

The Rockchip RK3188 is targeted on tablets rather than phones, but it uses the GLOBALFOUNDRIES’ 28SLP (Super Low Power) process, their equivalent to TSMC’s 28HPM, aimed at mobile products. It is again a quad-core part, this time with ARM A9 CPUs running at 1.6 GHz, and quad-core ARM Mali GPUs rated at 600 MHz.

 

Rockchip RK3188 floorplan showing some of the major functional blocks

Rockchip has squeezed the functionality into ~25 sq. mm, less than a quarter of the size of the Qualcomm chip; not least because the A9 cores are noticeably smaller than the Qualcomm-designed Krait cores based on the ARM architecture, and of course there is no LTE.

GLOBALFOUNDRIES is obviously happy to have won the Rockchip business – their CEO Ajit Manocha specifically mentioned the partnership in his keynote talk at Semicon West:

 

 

The 28SLP process differs in a basic way from the TSMC 28HPM – GloFo is using their version of the Common Platform (GLOBALFOUNDRIES, IBM, Samsung) 28-nm process, which is a ‘gate first’ variety, i.e. a polysilicon gate is used with a HKMG stack at its base, doped to form NMOS and PMOS transistors. TSMC’s ‘gate last’ process uses a sacrificial polysilicon gate for all the processing up to the end of the source/drain processing, then the polysilicon is removed and replaced with distinct HKMG stacks which are tuned for NMOS and PMOS.

Like the other Common Platform HKMG processes, a SiGe channel is used in the PMOS transistors, though with GloFo’s own spin – none of these processes are the same from the different vendors.

Compared with the older 32-nm HKMG process used for AMD processors, the Rockchip uses bulk silicon, not SOI, and gate lengths, contacted gate pitches and SRAM cell size are shrunk, but in the same ballpark as TSMC’s process. There is no dual-stress liner or embedded SiGe source/drains to enhance PMOS performance, but this product is rated at 1.8GHz rather than TSMC/Qualcomm’s 2.3 GHz.

 

GLOBALFOUNDRIES 28SLP PMOS transistor

So we have two processes targeted at similar spaces, but with very different takes on how to do it. TSMC and Qualcomm are following the industry norm, supplying chips to a US company from Taiwan, and GLOBALFOUNDRIES and Rockchip have reversed the trend, supplying chips to China from the West, and it’s tempting to speculate they are from the Malta fab in New York.

A Dispatch from SEMICON West – Applied Materials Launches Epi System Focused on NMOS Strain

Flying in to SFO on July 7, I must have been one of many attendees delayed by the after-effects of the Asiana Airlines crash there the day before. In my case it was only an hour or so (i.e. as normal), but we couldn’t avoid seeing the remains of the aircraft as we landed. Despite the fact that the plane was burnt out, I couldn’t help being impressed that the main body of the plane had survived the impact, and of course all but two of the passengers survived – and they were outside the plane.

By coincidence I flew through Heathrow a week after another 777 did a belly-flop there a few years ago, and again I was impressed at the strength of the airframe – an engine had been ripped off a wing but otherwise it was pretty well intact – and fortunately in that case there was no fire, and no fatalities.

That’s hardly relevant to SEMICON West of course, but it’s hard not to get involved when we get that close to the statistics of travel accidents, be they road, rail or air.

Anyway – back to the show – or at least the pre-show events. Applied Materials (AMAT) had an analyst day on Monday, and in the morning they invited a few of us to some product launches. The one that caught my eye and ear was a new epi system focused on NMOS epitaxial source/drains to create channel strain, since that has been mooted as a next step for several years now, but not shown up in a production context.

The theory is that if you can get carbon and phosphorus to replace silicon atoms in the crystalline structure, because they are smaller than silicon, they will generate tensile stress in the crystal lattice. When it is deposited in cavities etched in source/drains the stress is applied to the channel. (Putting the larger germanium atoms in the lattice has the opposite effect, and creates compressive stress, an effect used since the 90nm node.)

 

Schematic of e-SiGe in PMOS (left), and e-Si:CP in NMOS (right) source/drains

The problem (as I understand it) has been that the carbon does not like staying in such substitutional positions, and it will abandon them as soon as it sees anneal temperatures, thus losing the stress effect. Phosphorus is happy to be substitutional, and has of course been used as a n-type dopant for decades, so I suspect the problem there is simply getting the concentration to a level sufficient to stress the lattice.

So on Monday AMAT launched the Applied Centura RP Epi system with an NMOS transistor application. To quote: “This capability supports the industry’s move to extend epi deposition from PMOS transistors to NMOS transistors at the 20nm node, enabling chipmakers to build faster devices and deliver next-generation mobile computing power.”

 

 

The Applied folks seem confident that once the epi is formed, the carbon can be kept stable and capable of applying the strain at the end of the manufacturing process. I quizzed them as to how this is done and apparently the keys are the quality of the clean after cavity etch (i.e. AMAT’s Siconi dry clean), plus millisecond annealing to minimize the thermal budget.

There is plenty of literature documenting the effect; at last year’s IEDM conference, IBM announced their 22nm server process, which uses embedded strain for both N- and P-MOS[1]. Together with nitride stress, they claim a 10 percent performance increase over the 32nm equivalent. I also asked the speaker there about the carbon stability, and he confirmed that they regard it as a manufacturable process.

Cross-section of NFET showing embedded Si:C Source/Drain Stressor [1]

It seems the time of e-Si:CP NMOS is here. Applied certainly hopes so: they estimate the available market at over $500M and expanding, and that revenue has doubled over the last five years, and they have more than 80 percent share. They see an incremental $250M in revenue from epi systems by 2016.

I’ve been waiting for epi-strained NMOS for the last couple of process generations, and had almost been convinced that it wouldn’t happen. Now we have to watch for it when we get the next 20nm parts!

[1] S. Narasimha et al., “22nm High-Performance SOI Technology Featuring Dual-Embedded Stressors, Epi- Plate High-K Deep-Trench Embedded DRAM and Self-Aligned Via 15LM BEOL”, IEDM 2012, pp 52 – 55.