Retarded boron and phosphorus diffusion in silicon nanopillars due to stress induced vacancy injection

Abstract

Phosphorus and boron diffusion in silicon at temperatures between 900 and 1050 °C was studied both in bulk and nanostructured samples by means of scanning spreading resistance microscopy. The dopant diffusion from highly doped silicon substrates into 300–1200 nm diameter natural silicon nanopillars is clearly retarded compared to dopant diffusion in the bulk material. A three-dimensional solution of Fick’s equation enables a better understanding of dopant diffusion processes in silicon nanostructures, including all participating point defects. The observed decrease of diffusivity by 20%–50% can be explained by the injection of vacancies at the sidewalls of the pillar. The results do not provide any evidence on a possible change in point defect properties or fundamental diffusion processes in silicon nanostructures with respect to bulk silicon.