Acceleration Factors for the Decomposition of Thermally Grown SiO₂ Films

Abstract

Thermal SiO2 films on Si subjected to high temperature heat-treatments in O2-free ambients are unstable because Si supplied from the substrate reacts with SiO2 to form volatile SiO. The SiO2 decomposition process occurs nonuniformly at the interface and results in the growth of voids in the oxide where the SiO2 is completely removed. The formation of these voids was investigated for poly-Si oxides and oxides grown on crystalline Si substrates. The crystalline Si received special treatments before and after oxidation, which included preoxidation annealing, ion implantation of Ar or Si, Cu diffusion, and Ar sputtering of the surface. The results suggest that the SiO2 decomposition is initiated at crystalline defects in the substrate where the SiO production is locally enhanced. The growth of the voids is influenced by preoxidation annealing of the Si substrates. Metal impurities, especially Cu, do not increase the decomposition rate by a catalytic mechanism, but they may cause a secondary effect when precipitated at crystalline defects prior to oxidation. © 1987, The Electrochemical Society, Inc. All rights reserved.