The influence of impurities on the growth of helium-induced cavities in silicon

The effects of implanted oxygen, carbon, nitrogen, and self-damage on the growth of helium-induced cavities in silicon during high-temperature annealing have been studied. Impurities and helium were implanted into silicon at room temperature. Annealing at temperatures above 1000 K converts small He-filled bubbles into larger empty voids. The mean void size after annealing for 30 min at 1173 K was significantly reduced by the presence of all three implanted impurities. In extreme cases, the mean void radius is reduced from 10 nm, for a pure He implant, to 2.8 nm in a C pre-implanted sample. On the other hand, self-ion damage, unless at or near the level sufficient to cause amorphization, does not significantly affect cavity growth during annealing. We speculate that the presence of impurities significantly reduces the movement of voids by pinning them to dislocations or impurity aggregates or by chemical reactions at the void surfaces.