IBA study of the growth mechanisms of very thin silicon oxide films: the effect of wafer cleaning

Abstract

The growth mechanisms of very thin silicon oxide films formed during rapid thermal oxidation were studied using ion beam analysis and 18O isotopic tracing methods. In this paper we report on the effects of different cleaning procedures of silicon wafers prior to oxidation in dry oxygen (16O2 followed by 18O2) on the growth mechanisms and kinetics. Typical oxide thicknesses ranging from 0.2 to 10 nm were studied. The 18O and 16O isotopic profiles were determined by ion beam analysis methods, namely: the 18O(p, α)15N narrow resonance at 151 keV, and the 18O(p, α)15N and the 16O(d, p)17O reactions associated with step-by-step chemical dissolution. The profiles could be related to current theories on the initial stages of thermal growth of silicon oxide layers allowing us to draw some conclusions regarding the role of surface cleaning of the silicon wafers on the formation of silicon fragments in the volume of the very thin oxide layer. The influence of rapid thermal processing parameters like temperature, time and oxygen partial pressure on the growth mechanisms were also studied and discussed here.