There are two ways to double the number of transistors on a computer chip: Either make the chip twice as big – not an option for small electronic devices – or halve the size of the transistors.
This second option is what Gordon Moore, founder of Intel Corp., was referring to in a paper he wrote in 1965 when he enacted what quickly became known as Moore’s Law, that the number of transistors on a chip of a given size would double every two years.
After a half-century, there’s been concern that the law will soon expire because the current chemical mix used to lay out the chip’s circuit patterns is approaching its limit for miniaturization. That chemical mix is called photoresist, or simply resist.
So Intel has teamed up with the Lawrence Berkeley Laboratory of the U.S. Department of Energy (DOE) to design a wholly new version of resist that can keep shrinking transistors, making them faster and saving energy, which is especially important for small, battery-powered devices.
Their paper published in the journal Nanotechnology says the resist developed by the Berkeley Lab and DOE is a combination of two previous versions of resist and has the properties needed to further miniaturize microprocessors, including mechanical stability and improved sensitivity to light.
Here, in brief, is how microprocessors are made: A clean silicon wafer is coated with a layer of photoresist, then ultraviolet light beamed through a kind of stencil projects an image of a circuit pattern onto the wafer, chemically altering the resist where the stencil allows light to reach the coated silicon.
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The wafer is then rinsed in a solution that washes away unwanted resist and leaves only the resist that channels wires and transistors. The process is repeated until the wafer has all the components it needs.
But the ultraviolet light used to delineate circuit patterns on today’s chips has wavelengths of up to 193 nanometers, or billionths of a meter. The use of this light is closing in on its limit for miniaturization, so the team from Intel and the Berkeley Lab decided to use what’s known as extreme ultraviolet light (EUV), with a much shorter wavelength of 13.5 nanometers.
So the researchers investigated two forms of resist, one that has good mechanical stability but requires long and expensive exposure to EUV light, and a second that’s less mechanically stable but is requires less exposure to EUV light. By combining the two forms of resist the researchers wound up with a resist that had the desirable properties of both and lacked their undesirable qualities.
Now all that’s left to do is develop a way to mass-produce the new chips. The team reports that this shouldn’t be a problem. Chips are expected to be ready for market as soon as 2017 – plenty of time to maintain the validity of Moore’s Law.
By Andy Tully of Oilprice.com
Andy Tully is a veteran news reporter who is now the news editor for Oilprice.com