Reverse dopant redistribution during the initial stages of the oxidation of heavily doped silicon in dry oxygen

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Abstract
The oxidation of heavily phosphorus-doped (100) and (111) silicon in the 800–1000 °C range in dry oxygen was studied in the thin-film regime using in situ ellipsometry. The oxide growth kinetics indicate that, in the initial stages of oxidation, phosphorus piles up at the Si-SiO2 interface, resulting in a decrease in the surface concentration of electrically active phosphorus and an oxidation rate similar to that of lightly doped silicon. As the oxide grows, the surface concentration of electrically active phosphorus reaches and exceeds its bulk value, and the SiO2 growth rate gradually becomes similar to that of heavily doped silicon in the thick-film regime. An empirical model is introduced to account for the influence of this reverse dopant redistribution on SiO2 growth kinetics in the thin-film regime.