Calculations of selective Si epitaxial growth

Abstract

Dichlorosilane (DCS) is widely used in the semiconductor industry for selective epitaxial growth (SEG) of Si. Si SEG currently requires high temperatures, on the order of 800 °C; multiple approaches have been attempted to deposit Si at lower temperature, but no viable alternatives have been found. This failure is attributed to a poor understanding of the mechanisms and the underlying factors that determine Si growth. In this study, we investigate Si SEG using DCS and HCl on a crystalline silicon (c-Si) surface as compared to on SiO2 using density functional theory. Our calculations of Si SEG reaction mechanisms illustrate three factors that contribute to selectivity. First is that surface passivation by Cl does not limit SEG growth on c-Si while it hinders nucleation on the SiO2 surface. Second is that amorphous growth at nucleation sites on the SiO2 surface is slower than epitaxial growth on c-Si. Third is that the low entropic cost of epitaxial growth on c-Si is important for selectivity. The mechanistic understanding from this investigation suggests that future searches for low-temperature SEG of Si could focus on SiH2R2 like precursors.