Boron Diffusion into Silicon Using Elemental Boron

Boron diffusion into silicon has been investigated by a closed tube method using elemental boron as the source. Amount of the source, source temperature, and diffusion temperature are the main parameters controlling the surface concentration. It is presumably boron oxide formed by oxidation of the source boron that actually contributes to boron transfer in a closed tube system. The diffusion coefficient of boron in silicon is given by D=5.1exp (-85,000/R T), and its concentration dependence is examined. The masking effect of silicon oxide against boron diffusion is also examined on the basis of the two boundary diffusion model. The diffusion coefficient of boron in silicon oxide is smaller than that in silicon by three orders of magnitude, and the activation energy of the diffusion is about 36 kcal, which is less than a half of that reported previously.