Robots for hire
Self-healing systems are nothing new. Memory has been rerouting traffic when cells go bad for decades. But generally this kind of technology is there when you buy it.

Researchers at Cornell are taking the idea of a self-repairing system one step further. They’re experimenting with robots that can fix things where it’s dangerous for people to go—like on the sides of skyscrapers or in space.

One of the prototype machines is a robot that can assemble and disassemble trusses—the supports in roofs and bridges—and which includes reflectivity sensors to identify where it is on a structure. The result is that it can maneuver without explicit commands from the person controlling the robot.

Why send a person to a dangerous place when you can send a machine? Real machines don’t eat quiche.

The darker side of matter
Neutrinos, those little particles that have been linked to everything from Einstein to dark matter, apparently come in different flavors. In fact, they blend together and morph, which UC Berkeley researchers believe explains why there isn’t an abundance of antimatter.

It appears that neutrinos and antineutrinos oscillate differently. Exactly how this will play out in the commercial world is unknown. Researchers aren’t even sure how it will evolve on the pure research side, because these little particles are so small and difficult to measure–their mass actually fluctuates–that we’re just now beginning to even detect them. But the more this progresses, the more interesting this whole field will become–and the more it will shed light on bigger particles that are in use commercially.

A cyclindrical antineutrino detector. Source: UC Berkeley.

–Ed Sperling

By David Lammers
Intel Corp. dropped a rock into the pond of transistor technology when it announced its 22nm tri-gate technology in San Francisco earlier this month. The ripples continue to move out from that event, with impacts on IDMs, foundries, and fabless semiconductor companies being closely studied.

Now that Intel has come out of the closet with its tri-gate technology, “the foundry customers are all going to ask, ‘When am I going to get a FinFET? What does it look like?’” said one source, who asked not to be identified.

What they may find is a transistor that is rather difficult to build, at least for the companies that lack the resources to make the jump from planar to vertical structures. “Intel’s competitors will all be taking that thing (the tri-gate device) apart. They will learn from it. They will catch up, but it is not automatic and takes time. Intel has shown its technology leadership, but of course they have to invest an enormous amount of money to stay ahead and the competitors have to spend a much smaller amount to copy,” the source said.

Opinions differ on how quickly finFETs will enter the SoC space. At the Intel tri-gate rollout, Intel architecture general manager Dadi Perlmutter said Intel’s goal is to achieve “parity,” rolling out MPUs and SoC products on the latest technology at the same time. The lag is declining node by node, he said.

Planar vs. FinFET

Analyst Nathan Brookwood, sees Intel introducing tri-gate-based, 22nm, Atom-based SoCs for smartphones and tablets in the fourth quarter of 2012. Those “Silvermont” SoCs would be supplanted in 2014 by the 14nm-based “Airmont” SoCs. If that scenario proves accurate, Intel will be on the market with Atom-based and MPU products at the same time in 2014.

If Intel meets its target, and if TSMC rolls its finFET technology in 2015 at the 14nm node, at least two companies would be on vertical transistors for SoCs. There is speculation that TSMC might pursue a planar transistor for low-cost applications at the 14nm generation, using finFETs for the high-performance graphics MPUs, FPGAs, and others. And some believe that Intel will be more active in the foundry space, partly as a way to monetize the estimated $2 billion it took to develop the 22nm tri-gate technology.

Dean Freeman, a manufacturing technology analyst at Gartner Inc., said Intel’s tri-gate technology is impressive. “However, the SOI group won’t give up any ground.” The SOI consortium is working closely with ARM to demonstrate lower power consumption, at 1 to 2 GHz performance, for smart phones. But Freeman said most of those smartphone chips are produced on bulk wafers today, and they will be reluctant to spend much on the additional wafer cost represented by UTB-SOI wafers. Even AMD has switched to bulk (non-SOI) technology for its low-cost Fusion products, he noted.

On the other hand, Freeman said the vertical devices require a big change in the design tools, and a complete redesign of a company’s proprietary intellectual property. “Not all devices need 3D. Tri-gate will be used for Intel’s X86 products, and IBM will go 3D for its high-performance devices. Some high-performance ASSPs might need 3D as well. I am not certain about the ARM devices,” he said.

Gary Patton, an IBM vice president who manages the Fishkill Alliance including Samsung, Toshiba, STMicro, and GlobalFoundries, said the alliance is developing several different transistors for the 14nm node. IBM will continue to develop an SOI technology with finFET transistors, adding its on-chip SOI-based embedded DRAM technology. Other members of the alliance need a bulk FinFET, and others, including STMicroelectronics, are pursuing a planar UTB-SOI approach (which IBM refers to as Extremely Thin (ET)-SOI) using back-gate biasing underneath the planar channel to boost performance or reduce power consumption.

“ET-SOI with a back-bias operation is pretty comparable with finFETs for certain applications. FinFETs are pretty complex, and ST Micro is pretty confident in ET-SOI,” Patton said during a brief interview at the Advanced Semiconductor Manufacturing Conference, held in Saratoga Springs, N.Y., this month. Patton said members of the Fishkill Alliance and IBM Albany will give three papers at the upcoming VLSI Symposium, planned for early June, on SOI finFETs, bulk finFETs and ET-SOI.

“FinFETs have some performance advantages, but Intel and others will have to show that they can control the tolerances, including at the source and drain regions. On the other hand, ET-SOI appears to have some resistance problems, so we’ll have to see how it plays out,” Patton said.

Freeman said the Fishkill Alliance has been a huge success, but warned that the shift to a tri-gate transistor “does give Intel a crack at the mobile device market, as the power consumption is very good.”

The Gartner analyst added, “What IBM needs to look out for is an Intel alliance forming. You already have Toshiba and Samsung working with Intel on some transistor technology, so there could be some cracks forming. There is the possibility of two camps, but Intel is so protective of its IP it will be interesting to see how this plays out.”

Chenming Hu, who led a UC Berkeley team that did much of the early work on both finFETs and UTB-SOI a dozen years ago, said he believes for finFETs and UTB-SOI technology will be deployed. Manufacturing finFETs, with the need for a very thin fin at close tolerances, is challenging for all but the largest companies such as Intel and TSMC.

“If the interface with the design team is close, and the resources are large enough, the lure of finFETs is that they can be scaled. But it does take investments. UTB-SOI does not take as much technology development investment,” Hu said.

UC Berkeley's Hu

“I remain steadfast in my belief that both FinFETs and UTB-SOI will be going to manufacturing,” Hu said. “I expect both to go into production. The very large companies, such as Intel and TSMC, will have the resources to go to FinFETs. Some other companies may go to UTB-SOI. ST Microelectronics is probably the closest to using UTB-SOI. FinFETs may be more versatile in performance and power. On the other hand, FinFETs take a lot more development resources, in terms of the manufacturing control, the layouts, and the libraries. In FinFETs, the gate widths are discrete, rather than continuous. And the thickness of the fin needs to be scaled, along with the gate length.”

Scott Thompson, a professor at the University of Florida, said the manufacturing challenges of finFETs may provide Intel with a five-year lead, or longer.

“Developing a complex technology like tri-gate requires significant investment in silicon resources and manpower—development teams of perhaps more than 1,000 people. The complexities for development mean that hundreds of thousands of wafers have to be run to solve the issues. The tri-gate development is at least an order of magnitude more complex than strained silicon at 90nm, or HKMG at 45nm. That is why it took Intel eight years to implement, and why I don’t think anyone else will have in market for more than five years,” said Thompson, who spent two decades in technology development at Intel’s technology and manufacturing group at Hillsboro, Ore.

Manufacturing perfect fins over billions or trillions transistors is quite a challenge, Thompson said, adding that “it can be done in a fab that runs a single process, with equipment and settings that are kept constant. The manufacturing flow has unique advantages for high-end processors but does have problems supporting several key features needed for SOCs: multiple threshold voltages, and thin and thick oxides in support of analog.”

By Ed Sperling
UC Berkeley’s Jan Rabaey talks about taking the same tools and methodologies we’ve developed in the chip world and expanding them to the outside world. This is like moving from nanometers to kilometers, where proximity effects may include your neighbor’s dog. Synopsys’ Karen Bartleson and Yvette Huygen share the credit for this really interesting conversation.

Cadence’s Richard Goering follows a discussion involving Broadcom and Cyclic Design about assertion challenges and solutions. Considering the amount of time assertions can save on the back time, grab all you can on this subject.

Mentor’s Colin Walls says the real benefit of USB 3.0 is speed. That’s no surprise, but what is surprising is how tricky—and potentially expensive—the implementation will be. I/O Silver!

Semico’s Joanne Itow says wafer demand will grow in 2011 and that the impact of the Japanese earthquake was temporary. Despite what you may have heard, good news is still news.

Synopsys’ Michael Franzi isn’t impressed with his buddy’s new speaker system. We’re not exactly sure why this is relevant to design engineers, but it’s an interesting rant.

Cadence’s Tom Anderson is back with part two of his dissertation on assertions—this one focused on an approach taken by NextOp Software. It’s always good to wake up to how the real world uses EDA tools. It also makes it easier to sleep at night knowing that they really do use them.

XtremeEDA’s Neil Johnson looks at what UVM needs to succeed. This is a meaty list, broken into bite-size pieces. Jerky, anyone?

Synopsys’ Eric Huang has some fun with numbers about Apple’s mobile market share. So is the iPad the new phone format for people over 40 who can’t read the text on their smartphone?

Mentor’s Thomas Bollaert examines the fundamentals of high-level synthesis in the second of a series. The focus on this one is loop unrolling and pipelining.  Here’s the link to part one, as well.

With all the talk about cloud-based EDA, Synopsys’ David Hsu looks at Amazon’s recent outage. Yes, the company will learn from the outage. But that doesn’t mean there won’t be another one.

By Cheryl Ajluni

At the 46th Design Automation Conference in San Francisco last month, attention turned to a discussion of how to extend the momentum of Moore’s Law into the next decade. One plausible solution, according to Philippe Magarshack, the general manager of Central CAD & Design Solutions at STMicroelectronics, is 3D stacking for complex System-on-Chips (SoCs).

The concept of 3D stacking or integration technology is not new. In fact, 3D stacking of dies has been successfully demonstrated and is currently being commercially employed in some embedded domains (e.g., stacking DRAM memory on CPU cores). A recent 3D IC report from Yole Développement suggests that by 2012, the number of 3D IC-processed wafers could surpass 10 million units, driven in part by handset, wireless and computing applications. Given the intense interest and work going into developing 3D integration technology, this prediction seems just about right—assuming, of course, that a few challenges can first be met.

Exploring the third dimension

Very simply put, 3D integration consists of stacking integrated circuits and connecting them vertically so that they behave as a single device. A 3D chip is therefore just a stack of multiple device layers with direct vertical interconnects tunneling through them. So what’s the big deal about 3D integration?

Today’s semiconductor chips face extreme pressure to achieve increased performance, while reducing their size and accommodating lots of new functionality. When these factors coalesce in traditional 2D chips, longer interconnects result. In SoCs, longer interconnects translate into reduced speed and increased power consumption.

A key benefit of 3D integration is that it can reduce the length of interconnects. Additionally, it provides higher transistor density, faster interconnects and heterogeneous technology integration, with potentially lower power, cost and faster time-to-market. As Matt Nowak, director of engineering in the VLSI technology group of Qualcomm’s CDMA technology division, pointed out in a DAC 2008 presentation, the 3D approach “achieves extremely high densities, allowing us to use heterogeneous technologies and reduce form factor. The key is that it enables the use of new differentiating technologies to build new architectures that cannot be built in existing technologies.”

Eyeing recent developments

Up to this point, most efforts in 3D integration have focused on developing different fabrication techniques for stacking multiple device layers and forming the vertical interconnects. Much of the work has been done through collaborations with academia, industry organizations and government-sponsored laboratories around the world. One of the key technologies to come out of this research is a next-generation interconnect technology known as Through-Silicon Via (TSV). The TSV is a vertical electrical connection that passes completely through a silicon wafer or die to produce multilevel chips with an optimum combination of cost, functionality, performance, and power consumption. By using TSV technology, 3D ICs can pack greater functionality into a smaller footprint and realize shorter critical electrical paths, resulting in faster operation.

Some of the other developments to come out of ongoing 3D integration research were recently recognized at the Electronic Components and Technology Conference. Sandia National Laboratories presented details of its W TSV process, which is said to provide a suitably low-resistance metal with a coefficient of thermal expansion close to Si, a via fill that is conformal, and can be readily integrated into IC fabrication. IMEC introduced a novel process for die-to-wafer bonding (using Cu-Cu bonds) of its 3D SIC technology and a scalable TSV technology for 3D wafer-level packaging. Its TSV technology is designed for 3D structures where interconnects are fabricated after standard CMOS processing.

SEMATECH also is focusing its 3D research on TSV technology, particularly for implementation. The industry organization is actively working to bring together partners from across industry—chipmakers, equipment and materials suppliers, assembly and packaging service companies—to make 3D TSV suitable for high-volume manufacturing (Figure 1).

Figure 1. In contrast to the 2D-SoC or 3D System-in-Package, 3D TSVs offer a cost-effective way to achieve high density and performance, while also being able to integrate non-CMOS products with CMOS. The SEMATECH 3D project is based on cost modeling to assure products will be both manufacturable and affordable.

Help: tool support needed!

While ongoing research and development is absolutely critical to the success of 3D integration, perhaps one of the greatest challenges it faces is tool support in terms of design techniques and methodologies. Without it, engineers have virtually no efficient way to exploit the technology’s benefits. Tool support is especially critical when it comes to 3D integration because vertical stacking tends to increase thermal resistances, further exacerbating temperature-induced problems that can negatively affect system reliability, performance and leakage power. The use of 3D also will significantly complicate the typical design flow.

The key, of course, lies in creating a standardized design environment and methodology for physical design of 3D chips that could support a range of different tools. Having the tools integrated in one place would make it easier for designers to explore and make architectural decisions and then, to hand those decisions off to next stages in the design process.

3D IC integration is still in its infancy and, as a result, tools developed today for one specific application (e.g., stacked memory) may not be suitable for heterogeneous integration tomorrow. Nevertheless, there are some tools available now, with more in development. Some of these tools include:

3D PathFinding

Javelin Design Automation. 3D PathFinding provides a detailed 3D flow for accurate performance/power/cost estimates that can be used for rapid design exploration and optimization of 3D stacked ICs. Developed in collaboration with IMEC and Qualcomm, the solution extends Javelin’s existing PathFinding methodology and j360 Silicon PathFinder physical design prototype platform to support virtual chip design (Figure 2).

Figure 2. Javelin’s 3D PathFinding solution allows the designer to assess the impact of various 3D interconnect strategies throughout the IC design and fabrication process, in a matter of just a few hours or days. Silicon process engineers can use it to fine-tune their technology to the system architecture specifications.

MAX-3D, R3Integrator, R3CAD, and R3Artist; R3Logic

These tools, developed through work conducted as part of research programs sponsored by the Defense Advanced Research Projects Agency (DARPA), enable 3D IC design and analysis (Figure 3). MAX-3D is a 3D mask layout tool whose technology file includes all properties of stacking process, wafer orientations, bond materials, via electrical/material properties, and also incorporates 2D foundry design kits. R3Integrator is used for die/interposer/package co-design with TSVs. R3CAD is a java-based, multi-platform tool for 3D design research and prototype study and R3Artist is an embedded 3D layout editor (Figure 3).

R3Logic is currently collaborating with STMicroelectronics and CEA-LETI to develop a full 3D design flow for 3D heterogeneous system and system-in-package design.

Figure 3. R3Artist features single and multiple wafer technologies, integrated material properties database and solid model extraction, including dielectric layers.

3DCACTI

3DCACTI estimates the optimum access times and power dissipation of a cache using 3D IC technology for a given number of active device layers and by partitioning device layers for various technology nodes. Based on the estimation, it searches for the optimized configuration that provides the best delay, power and area efficiency trade-off according to the cost function for a given number of different 3D partitions.

3D Magic and PR3D, Massachusetts Institute of Technology

3D Magic is a comprehensive layout methodology for 3D circuit-layout editing and extraction with MAGIC, an open source layout editor developed by UC Berkeley. PR3D is a placement and routing tool for standard cell design in 3D. Both tools were developed through MIT’s Interconnect Focus Center Research Program. MIT also developed SysRel (System-Level IC Reliability) for assessing the interconnect reliability of 3D ICs from a thermal-aware perspective at the circuit-layout level.

Conclusion

With the pressure on traditional 2D chips mounting, 3D integration has begun to establish itself as a viable means of breathing more life into Moore’s Law. It certainly touches on all the hot buttons in the industry today, namely low power, cost and time-to-market. The challenge will be in ensuring that these benefits are realized in a timely and efficient manner. 3D-specific design tools and methodologies are coming to meet this challenge head on. In the meantime, the tools available now and the groundwork for future tools and methodologies being laid by industry organizations, academia and commercial companies alike, will go along way in ensuring 3D integration plays a critical role in the future of the semiconductor industry.

David Patterson, Professor of Computer Science at UC Berkeley, presented his views to the Naval Postgraduate School about the prospects for multicore programming success. This video was excerpted from his presentation.