Posted: January 8, 2008

New technology aims to cool hot chips

(Nanowerk News) In the semiconductor industry, being "hot" isn't a good thing.
Heat bedevils semiconductor engineers, who have in recent years seen their quest to build ever-faster chips frustrated by the ravages of excess heat. At the same time, they are under pressure to better control heat amid rising electricity costs for cooling electronics, demand for longer battery life in mobile devices and an ascendant green movement.
Now a small Durham, N.C.-based company called Nextreme Inc. says it has found a way to make chips "cool" again. The company, a spinoff of research institute RTI International, has developed a technology it says can lower temperatures in only the specific areas of chips that get too hot, allowing for more cost-efficient cooling than has been possible before. It says the technology is easier for semiconductor manufacturers to implement than other approaches because it can be integrated into current manufacturing processes.
"Heat's a system killer, and it's actually become one of the biggest problems, especially in small devices. This could be a way to fix that," says Rob Enderle, principal analyst at Enderle Group of San Jose, Calif.
"We've solved it," says Paul Magill, Nextreme's vice president of marketing and business development, of the heat problem. "This is a world-changing idea that doesn't require the world to change."
Nextreme unveiled its product in October and has been providing engineering samples to potential customers. It hasn't signed any licensing deals yet, but Magill says the company is in "in-depth discussions with virtually every major semi manufacturer in the U.S.," and is near a deal with a major packaging house to demonstrate the technology.
One prospective customer is Princeton Lightwave Inc., an optical-semiconductor company in Cranbury, N.J., that thinks Nextreme's technology could allow it to ensure its optics remain cool and perform optimally even when surrounding electronics heat up.
If the technology works as advertised, something Princeton Lightwave hasn't firmly established yet, "then the implications are obviously huge," says Sabbir Rangwala, vice president of product development. "I think this is quite revolutionary."
Nextreme is taking on a central conundrum for the chip industry: Improving processor performance produces heat, and heat hurts performance.
Engineers had long boosted chip capabilities, while reducing manufacturing costs, by shrinking chip features and running the circuitry faster. That, however, increased electricity leakage, which manifested as heat. The heat began hurting chip performance and, if too hot for too long, caused its fine circuitry and transistors to break apart, hurting reliability.
To complicate matters further, the problem comes largely from "hot spots," which form in places where blocks of transistors are squished together to speed up circuitry. And a lack of uniform temperature across a chip also drags on performance.
The heat problem has led chip giants like Intel Corp. and Advanced Micro Devices Inc. to abandon efforts to further speed up their processors and, instead, to put multiple processors, or cores, on a chip. Nextreme says its technology could make multi-core processors unnecessary.
Intel declined to comment on Nextreme's technology, though the start-up's chief technology officer is a former Intel senior scientist.
AMD also had no comment on Nextreme and highlighted its efforts to improve energy efficiency, including its participation in a number of green initiatives and improvements to its processors.
Without better energy efficiency or cooling, multi-core processors may not prove a solution for long. That is because each core usually has hot spots, says Avram Bar-Cohen, a professor of mechanical engineering at the University of Maryland who specializes in thermal management.
'You're at risk of the same hot spot being multiplied by the number of cores," he says. "The challenge is 'How do we remove these hot spots?'"
Up to now, cooling just the hot spots, and not the entire chip, has been difficult, though that would conserve resources. For instance, if the kitchen is hot, it is better to cool just that room than to turn up the air conditioning for the whole home.
Nextreme says it can do this. Using nanotechnology, it found a way to apply thermal material called bismuth telluride only in the places that get too hot. It puts a thin film of the material into copper pillar bumps, which are an increasingly popular method for attaching chips to their packages. The bumps themselves aid the cause of cooling, but the thermal material also conducts heat away from the hot spot. Nextreme says it can reduce temperatures by as much as 60 degrees Celsius, though hot spots typically only need 5 to 15 degrees of cooling.
"It brings thermal-management capabilities down to the core of the processor," says Nextreme's Magill. "What we're talking about is: Stop cooling everything, and start cooling only what needs to be cooled."
Source: The Associated Press
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