Annealing effects on transition region at Si-SiO₂ interface

Annealing effects on transition regions at the Si-SiO₂ interface for thin oxide films have been investigated. Thin oxide films with thickness less than 100Å were prepared by the following methods: (1) dry oxidation, (2) dry oxidation and subsequent annealing in an argon atmosphere, and (3) thinning of thick oxide films formed by dry oxidation. The values of barrier height for electrons at the Si-SiO₂ interface have been evaluated from Fowler-Nordheim plots. The values for the samples prepared by (2) and (3) were larger than that by (1). The increase of the barrier height is attributed to the decrease of transition regions induced by annealing or oxidation for long periods. XPS and growth rate measurements were also performed for ultra thin dioxide films formed at low temperature of 600 °C. The results show that the transition regions, containing suboxides, are formed in the initial stage of oxidation. On the basis of these observations, a model of the decrease of transition regions is proposed.