Oxygen Diffusion in Silicon: The Influence of Hydrogen

Abstract

Oxygen is incorporated at concentration levels of order 10¹⁸ cm^-3 in single crystals of silicon grown using the Czochralski method. These silicon wafers are extensively used in device applications. During thermal processing, depending on the processing parameters, the oxygen atoms aggregate to form clusters of various sizes and also Si0₂ precipitates [1]. The precipitation of oxygen leads to the formation of extended defects in the silicon wafer, improving its mechanical properties and also “gettering” impurities from the the bulk. The rate-limiting step in oxygen aggregation is the diffusion of oxygen through the bulk of the material. Thus, there has been extensive investigation of the diffusion of oxygen in silicon, using a range of experimental techniques [2]. In this article, we will summarize recent theoretical results [3] which have allowed us to resolve many outstanding puzzles about oxygen diffusion and give a comprehensive account of the underlying atomistic processes. In addition, we report hitherto unpublished results on the effects of H on O diffusion.