What's old is new again


SSMC fab, SingaporeYesterday, Singapore-based foundry SSMC celebrated its tenth anniversary of silicon manufacture with the news that it was to spend $30m — split roughly 50/50 between R&D and manufacturing — to extend the fab’s lifetime. The investment is meant to keep SSMC’s 200mm production lines relevant in a business now dominated by plants that process larger wafers and which should be more cost-effective.

“We are putting in place a vision that ensures SSMC is in a good position for the next decade or two,” said CEO Jagadish CV.

Jointly owned by NXP Semiconductor and Taiwanese foundry TSMC, SSMC was one the last big 200mm digital logic-oriented fabs to be constructed, opening just ahead of the dot-com crash. It produced the first yielding silicon in October 2000, so barely turned in a quarter’s worth of production wafers before the slump.

After the recovery, 300mm production with 0.13µm copper processes had pretty much taken over from 200mm, which because of the decisions made by production-equipment makers, were stuck on 0.15µm and larger linewidths and aluminium metal interconnect.

Rather than throw in the towel, SSMC changed direction, concentrating on ‘ABCD’ products — analogue, bipolar, CMOS and DMOS. Basically, stuff that wasn’t the standard CMOS turned out by 300mm fabs owned by TSMC and others.

“Many of the products they produce are not linewidth-driven, such as lighting control. All of them require high voltages and high-voltage circuits don’t scale well, so there is no advantage in moving to 40nm,” said René Penning de Vries, senior vice president and CTO of NXP.

But the company did not just stick with the 0.18µm processes that were available when the fab opened in 2000. By pushing the equipment SSMC had, the foundry was able to introduce a 0.14µm process in the first half of the decade. This has gradually expanded from being a 5V-maximum technology to one that can handle voltages up to 100V.

The big shrink
By the end of the year, SSMC expects to have a 0.11µm process running — using pretty much the same equipment the company has used for its other operations — and is looking at introducing ultralow leakage variants, similar to the 180ULL process for 0.18µm linewidths that TSMC launched recently.

“We have even been challenged to do 90nm, not using techniques such as immersion lithography but using the same toolset. Those types of opportunity do exist,” said Jagadish.

The extension to 0.11µm is thanks to the same techniques that have helped make it possible to draw features as small as 40nm using light that has a wavelength four or five times larger.

“For many, many years, people have declared litho to be dead. But it continues,” said Richard Thurston, vice president and general counsel of TSMC, and a director of SSMC. “The same thing has happened here.”

Why do this when there are 300mm fabs out there with similar processes? For a customer like Geoff Lees, general manager of NXP’s microcontroller division, manufacturing on 200mm makes more sense for microcontroller production on a cost-per-die basis.

“The economics of 300mm tend to drive a different strategy,” said Lees, talking late last year about his plans for the microcontroller business.

Production on 200mm lines makes it easier to produce a wider range of peripherals and memory options for 32bit microcontrollers, which, individually, tend to be medium-volume products because they go into industrial and automotive systems. Move to 300mm, and you have to strip out a lot of the variety or eat the die cost of producing large memory arrays and then simply fuse half of it out to produce the ‘cheaper’ low-end versions.

Although there is potential to extend the process roadmap to 90nm at SSMC, the main focus will be on applications such as automotive and lighting, where the demand is for higher voltages. In MCUs, 90nm makes it possible to reduce the size of on-chip memory which can reach into the megabytes on 32bit designs. However, Lees cautions that circuits such as power management units don’t scale well and make it hard to churn out low-end, low-memory devices on 90nm because of the relative size of the power unit and other analogue peripherals.

“It’s hard to get a tiny die at 90nm,” said Lees.

Lights and fast cars
By concentrating on automotive and lighting, Jagadish hopes to extend the operational life of SSMC out as far as 2025. At the moment, 6 per cent of SSMC’s wafers go into automotive. “The board has set a direction for that to go to 20 per cent,” he said.

“The other applications we are looking at are in the low-energy market, such as fluorescent lighting,” said Jagadish. “We are looking at cornering a niche: making silicon for CCFL control with one-chip solutions that we can offer to the lighting manufacturers.”

“This ‘more than Moore’ aspect very much distinguishes SSMC from many of the 8in fabs out there,” said Thurston, who pointed to changes in the chipmaking economy that are putting a new focus on older process technologies.

“Scalability is the key issue. If Moore’s Law had plenty of room to run, then you would go the newer generations more readily. But Moore’s Law is hitting the wall and companies are discovering that scalability doesn’t necessarily matter,” Thurston added. “We are seeing a resurgence in ‘mainstream’ business. We are seeing that, with each of these older generations, starting with 0.18µm, applications in RF or automotive can get a lot more of our technology and IP.

“We have these aging fabs. Let’s make them more profitable and give our engineers more than a 300mm roadmap.”

De Vries added: “The base tecnhology is available. It’s now about building upon this base technology. We see it as very much application driven. Many things are changing and they often require dedicated solutions, with the ability to sense the ambient environment or improve the efficiency of solar cells.”

LED centre
TSMC is not just reworking its older 200mm fabs. The company held the groundbreaking ceremony for a new fab and research centre in Hsinchu that will concentrate on LED lighting and solar cells. The company is spending NT$5.5bn ($170m) to build phase one of the lighting research centre. It’s a move that will see TSMC expand from being a front-end foundry to a supplier of packaged lighting products.

The unit is headed by Rick Tsai, president of new business, who up to last year was CEO of TSMC before chairman Morris Chang stepped in to take up the reins of the company’s core business.

Tsai said at the groundbreaking: “We will enter the market next year by offering LED light sources and light engines.”

The LED fab will be built in two phases. In phase one, equipment will start moving in during the fourth quarter of 2010 with plans to go to full production as early as the first quarter of 2011. TSMC will decide whether to press ahead with phase two based on the results of the first phase.

$170m buys a reasonable amount of production in the older process technologies used for LED production but is a tiny fraction of TSMC’s overall planned capital spend for 2010 of close to $5bn — most of that money will go into 40nm and 28nm capacity expansion on 300mm lines. But lighting by itself could be a huge market as production costs come down and device lifetimes improve.

The key question is whether, for markets such as lighting, because the volumes could be so huge, manufacturers will move to 300mm production over time even for these ‘older’ technologies to get the benefits of scale or trade lower capital spending for higher production cost to get very high long-term return on capital employed (ROCE) scores.