Si self-diffusivity using isotopically pure ³⁰Si epitaxial layers

In order to understand the properties of point defects in Si, it is important to clarify temperature dependence of Si intrinsic self-diffusion coefficient over a wide temperature range. In this work, we used highly isotopically enriched ³⁰ Si epi-layers as a diffusion source to bulk and epi-layers Si and evaluated self-diffusion ³⁰Si epi-layers were grown on each CZ-Si substrate and non-doped epi-layer grown on CZ-Si substrate using low pressure CVD with ³⁰SiH₄. Diffusion was performed in resistance furnaces under pure Ar (99.9%) atmosphere at temperature between 867 and 1300°C. After annealing, the concentrations of the respective Si isotopes were measured with SIMS. Diffusion coefficients of ³⁰Si (called Si self-diffusivity, D^SD) were determined using numerical fitting process with ³⁰Si SIMS profiles. We found no major differences in self-diffusivity between in bulk Si and epi-layers Si. It was shown that within 867-1300°C range, D^SD can be described by an Arrhenius equation with one single activation enthalpy, D^SD = 14 exp (-4.37 eV/kT). The present result is in good agreement with that of Bracht et al.