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Thin chips speed up computing

A stack of silicon chip processors

Traditional silicon chip processsors have hit their limits(Source: iStockphoto)


The team, based at the University of California, Berkeley, set out to solve several problems limiting the operating capacities of the current generation of silicon 'chips', such as heat build-up and quantum mechanical effects.

According to new research published last week in the journal Nature, the trick to getting around the silicon impasse is to combine silicon technology with something a little more exotic - in this case, indium arsenide.

"The problem is that right now you're generating so much heat from the chip. You're putting a lot of power in and a lot of energy is being dissipated as heat and the chips get heated up," says Professsor Ali Javey, one of the paper's authors.

"We can't really push today's chips to their limits because the chip will actually fry. So by lowering the power needed to run the individual transistors that could have a drastic improvement in the performance of the circuits as well."

Chip manufacturers have been able to skirt around the issue of quantum effects and heat by adding more processor cores, rather than increasing transistor densities - most modern PCs use multiple cores to increase processing power.

Javey says the process he has been working on involves growing a single crystalline layer of indium arsenide onto a gallium antimonide wafer, also one crystalline layer thick.

"After this we pattern the indium arsenide layer and etch away the sacrificial layer. This causes the indium oxide layer to be almost freestanding. Then we basically transfer the indium arsenide structures from the source wafer to a silicon dioxide substrate," he says. "So now we have a layer of single crystalline indium arsenide, which is a high electron mobility material, on top of a silicon substrate."

Javey says there has been a lot of interest in the process.

More power from less energy

"Compound semiconductors including indium arsenide on silicon substrates are generally better semiconductors when it comes to how fast electrons move in these materials," he says. "That means that you can actually make faster electronics using these materials, you can make lower power electronic devices that operate on low voltages."

And that means less energy lost as heat.

Professor Andrew Dzurak, director of the Semiconductor Nanofabrication Facility at the University of New South Wales, says the work at Berkeley is "very cool", and could go a long way to overcoming some of the limitations currently facing chip manufacturers.

But Dzurak says that one of the issues facing alternative materials such as indium arsenide is the heavy investment in existing materials and intellectual effort.

He also stresses that these semiconductor wafers are only likely to be a stopgap measure.

"The only problem is that even if you did use these new materials and really squeezed out the performance, you're still going to hit those fundamental limits that are now being approached in silicon, it's just that we'll hit these problems a decade or so later."
