Observation of inverse U-shaped profiles after platinum diffusion in silicon

Abstract

Inverse U-shaped profiles of platinum in silicon were obtained after diffusion at 700 °C. Deep level transient spectroscopy was used to determine the platinum concentrations in various depths of the samples. In the bulk, a higher concentration of platinum was found than at the surface. Therefore, these platinum profiles are called ‘‘inverse U-shaped profiles.’’ These diffusion profiles can be described by the Frank–Turnbull mechanism, assuming that the initial concentration of vacancies is higher than their equilibrium concentration. Therefore, the observation of inverse U-shaped profiles after platinum diffusion may serve as the evidence that diffusion processes, which involve vacancies, are determined in the bulk by the initial vacancy concentration and not by the vacancy equilibrium concentration at temperatures of ∼850 °C and below.