How do computers get faster?
Aerogels are substances so porous that they contain more air than solid material. Used as insulators in computer chips, they could more than double their speed. Scientists at Semiconductor Research Corp. Center for Advanced Interconnect Science and Technology (CAIST) at Rensselaer Polytechnic Institute are engaged in detailed investigations of aerogels and their manufacturing processes. In addition, they use computer models to make predictions about their potential performance and product properties.
At the IEEE International Electron Devices Meeting on December 10, 1997, Texas Instruments presented a successful combination of copper wire and xerogel. According to company representatives, this combination, combined with a new design, could produce computer chips that are about 10 times faster than today's models.
By using good insulators-materials with a low dielectric constant-designers are able to place interconnects very close together on a chip without slowing down the signals passing through. At the moment silicon dioxide is mainly used in the chips. This has a dielectric constant of about 4. If the constant could be reduced to about 2, it would at least double the speed of a computer. In their investigations, CAIST scientists deal with polymers whose corresponding value is around 2.5. The dielectric constant of air, as the ideal insulator, is taken as 1.0. But chips can't be held together with air. The CAIST researchers are now trying to solve this problem with aerogels.
CAIST's Joel Plawsky, Peter Wayner Jr. and William Gill have succeeded in developing highly porous silicon films that are 65 to 90 percent air and have a dielectric constant between 2.3 and 1.4. The scientists have proven that they can control both the porosity and the thickness of the film. It also doesn't appear to have any issues with water absorption or heat sensitivity during use.
Numerous technical questions still need to be clarified. According to Plawsky, however, the new material can probably be used industrially within the next five years.
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