Strained Silicon Increases Chip Speeds by 35%
Peter Singer, Editor-in-Chief -- Semiconductor International, 7/1/2001
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The new technology takes advantage of the natural tendency for atoms inside compounds to align with one another. When silicon is deposited on top of a substrate with atoms spaced farther apart — in this case, silicon germanium — IBM scientists are able to strain, or stretch the silicon by taking advantage of the natural tendency of atoms inside different crystals to align with one another (Fig. 1). In the strained silicon, electrons experience less resistance and flow up to 70% faster, which can lead to chips that are up to 35% faster — without having to shrink the size of transistors. In practice, the Si/SiGe layer is used directly beneath the gate (Fig. 2).
"Just as important as finding ways to improve the performance of silicon is getting these breakthroughs out of the labs and into the marketplace quickly," said Bijan Davari, vice president of semiconductor development, IBM Microelectronics. "Strained silicon, combined with our prior advances in copper, silicon on insulator, silicon germanium and low-k materials, will allow us to maintain our one- to two-year lead in semiconductor technologies over the rest of the industry."
| 1. When silicon is put on top of silicon germanium, the atoms in the silicon stretch, or "strain" to align with the atoms in the silicon germanium. (Source: IBM) |
| 2. The image on the left shows electrons flowing through a current silicon chip. On the right is an image of electrons flowing through "strained silicon." The electrons flow up to 70% faster through strained silicon because there is less resistance, resulting in chip speed increases of up to 35%. (Source: IBM) |
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