Reaction of atomic hydrogen with crystalline silicon

Abstract

The kinetics of the gas-solid reaction of crystalline silicon, Si(111), and atomic hydrogen (thermally generated in a tungsten oven) have been studied by the modulated molecular beam mass spectrometric technique. Volatile silicon tetrahydride, SiH 4, and recombined molecular hydrogen were the only reaction products detected from ambient temperature to 1000 K. At room temperature the majority of the incident H atoms recombined on the Si surface and was re-emitted as H 2; part of it diffused into the Si lattice; and a small fraction (~3%) reacted to produce SiH 4. The etch rate increased with beam intensity but decreased with increasing temperature. The proposed mechanism involves saturation of the surface dangling bonds by H atoms, formation of SiH and SiH 2 surface complexes, and reaction of the latter with a weakly-bound mobile overlayer of H atoms. Rate constants characterizing the elementary steps of the mechanism were determined by fitting the model to the data.