Chemical Vapor‐Deposited Boron Nitride Film on Silicon as a Boron Diffusion Source

Abstract

CVD‐BN films deposited onto silicon have been investigated as a diffusion source. The concentration ratio of boron to nitrogen in the as‐deposited BN film could be controlled in the range from 1.4 to 2.5 by changing the depositing temperature with the ratio of . The boron concentration at the silicon surface depends mainly on the concentration ratio and remains constant during the heat‐treatment for diffusion, but decreases with diffusion temperature. The concentration ratio of boron nitride to excess boron in the film has been empirically formulated in the Boltzmann form as a function of the deposition temperature. The boron surface concentration has also been described in the Boltzmann form, in terms of the diffusion temperature and the concentration ratio . The excess boron atoms in the BN film cause boron diffusion into the silicon. The activation energy for excess boron diffusion in the BN film is approximately proportional to the concentration ratio .