Multiple structural forms of a vacancy in silicon as evidenced by vacancy profiles produced by rapid thermal annealing

Abstract

Vacancy depth profiles installed by rapid thermal annealing can be monitored either by Pt diffusion or through vacancy‐assisted oxygen precipitation. The features of these profiles clearly show that the vacancy species manifested in these experiments is a “slow vacancy”, Vs. The evolution of Vs depth profiles is controlled by an exchange with another (mobile) kind of vacancy that is likely to be a “Watkins vacancy”, Vw, first observed at cryogenic temperatures. At low T the conversion of Vs into Vw is slow and practically irreversible. At higher T the two species coexist in an equilibrium ratio and diffuse as one entity with an averaged diffusivity. This model provides a good fit to the RTA‐installed depth profiles of Vs. The total vacancy community includes, beside Vs and Vw, also a fast vacancy Vf that is responsible for the vacancy contribution into self‐diffusion at high T. In RTA experiments, the Vf species seems to be completely annihilated by self‐interstitials which leaves only two other vacancy species, Vs and Vw.