Measuring Vacancy Diffusivity and Vacancy Assisted Clustering by Nitridation Enhanced Diffusion of Sb IN Si(100) Doping Superlattices

Abstract

An investigation of the properties of Si native point defects was undertaken using low temperature annealing of molecular beam epitaxially grown Sb and B doping superlattice structures. The superlattice structures, consisting of 10 nm B or Sb doping spikes separated by 100 nm, were annealed in NH 3 at 810°C, 860°C, and 910°C. During thermal nitridation under these annealing conditions, we observed enhanced Sb diffusivity caused by the injection of vacancies, and retarded B diffusivity, resulting from the depletion of interstitials. Since the diffusivities of Sb and B are proportional to the vacancy and interstitial concentrations respectivity, spatially resolved diffusivity measurements permit effective point defect diffusivities to be inferred. From the spatial decay length of the Sb diffusion enhancement, lower limits for the effective vacancy diffusivity were obtained (limited by possible vacancy trapping). Evidence of vacancy assisted Sb clustering during NH 3 anneals is also presented.