Low-temperature diffusion of dopant atoms in silicon during interfacial silicide formation

Abstract

It has been recently reported that the formation of transition-metal silicides induces a strong enhancement of dopant diffusion in silicon at low temperatures (\ensuremath{\sim}250\ifmmode^\circ\else\textdegree\fi{}C). However, the mechanism which is responsible for the enhanced diffusion has not been addressed. We have undertaken a systematic study to clarify the mechanism. Our results show that diffusion enhancement occurs only as a result of advancing silicide-silicon interfaces. We also find that diffusion enhancement is a unique feature of the interfacial formation of near-noble-metal silicides, but not refractory-metal silicides. By correlating these observations with the interstitial diffusion of near-noble-metal atoms in silicon, we propose that during silicide formation a large number of point defects is generated in the silicon near the silicide-silicon interface, and that these point defects are responsible for the enhanced diffusivity of substitutional dopants at low temperatures.