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

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', V_s. The evolution of V_s depth profiles is controlled by an exchange with another (mobile) kind of vacancy that is likely to be a 'Watkins vacancy', V_w, first observed at cryogenic temperatures. At low T the conversion of V_s into V_w 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 V_s. The total vacancy community includes, beside V_s and V_w, also a fast vacancy V_f that is responsible for the vacancy contribution into self-diffusion at high T. In RTA experiments, the V_f species seems to be completely annihilated by self-interstitials which leaves only two other vacancy species, V_s and V_w. [ABSTRACT FROM AUTHOR]