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8
Impurities in Silicon Wafers
8.1 Effect of Intentional and Unintentional Impurities
and Their Influence on Silicon Devices
There are two types of impurities in silicon wafers. Any nonsilicon atoms are considered
impurities. Some of them are added intentionally, whereas others are present despite the
best efforts to drive them away from the silicon lattice. As was discussed earlier, the sili-
con lattice is not very dense, and its lling factor is much less when compared to other
close-packed structures, so there is a lot of scope to occupy the interstitial positions in
the lattice. This accommodative property of silicon traps many metall ...