Vacancy Species Produced by Rapid Thermal Annealing of Silicon Wafers

Abstract

Rapid thermal annealing (RTA) of Czochralski silicon wafers at around 1260°C installs a depth profile of some vacancy species. Subsequent oxygen precipitation in such wafers is vacancy-assisted. The data on RTA-installed vacancy profiles - and the corresponding precipitate density profiles - suggest that there is a slow-diffusing vacancy species (Vs) along with two fast-diffusing species: a Watkins vacancy (Vw) manifested in irradiation experiments and fast vacancy (Vf) responsible for the high-T vacancy contribution into self-diffusion. The Vs species are lost during cooling stage of RTA, and the loss seems to occur by conversion of Vs into Vf followed by a quick out-diffusion of Vf. A model based on this scenario provides a good fit to the reported profiles of oxide precipitate density in RTA wafers for different values of TRTA and different cooling rates.