An in situ study of silicon and silicon-dioxide surfaces by contact angle measurement and ellipsometry

Successful preparation of silicon surfaces prior to microelectronic device processing is fundamental to production of high quality devices. Cleaning and passivation are the crucial elements of this preparation. Thermal oxidation of Si to SiO{dollar}sb2{dollar} is uniquely effective at passivation, creating a nearly perfect interface between the Si substrate and the SiO{dollar}sb2{dollar} film. In spite of the fact that many successful cleaning procedures for silicon exist, quantification of these procedures has been rather scarce. In addition it is shown in this work that the use of varied pre-oxidation cleaning treatments can significantly alter the kinetics of subsequent thermal oxidation of silicon. For these reasons two highly surface sensitive techniques, ellipsometry and contact angle measurement, are used to study the effect of chemical cleaning treatments on silicon surfaces. The unique feature of the work is the performance of the analysis in the actual cleaning environment, that is, in liquid phase ambients. It is felt that a better understanding of cleaning solution-semiconductor surface interactions can be gained by observing the surfaces actually in the cleaning ambients. Through the use of specially designed quartz sample cells, both ellipsometric and contact angle measurements are carried out in the presence of various solutions enabling in situ analyses of Si and SiO{dollar}sb2{dollar} surfaces in the cleaning environment. The etch of SiO{dollar}sb2{dollar} by dilute aqueous HF is monitored both by ellipsometry and contact angle measurement and the combined experimental results indicate the existence of a residual fluorocarbon layer on the Si surface immediately following complete etch of SiO{dollar}sb2{dollar} from a Si substrate by HF.