Ultra-thin gate oxide formation using an n2o plasma

Abstract

A fabrication process for semiconductor devices is disclosed for forming ultra-thin gate oxides, whereby a silicon substrate is subjected to an N,O plasma to form the ultra-thin gate oxide. According to one embodiment, the silicon substrate is heated in a deposition chamber and the N,O plasma is created by applying RF power to a showerhead from which the N,O is dispensed. By reacting an N,O plasma directly with the silicon substrate it is possible to achieve gate oxides with thicknesses less than 20 Å and relative uniformities of less than 1% standard deviation. The oxide growth rate resulting from the presently disclosed N,O plasma treatment is much slower than other known oxide formation techniques. One advantage of the disclosed N,O plasma treatment over thermal oxidation lies in the predictability of oxide growth thickness resulting from reaction with N,O plasma versus the strong variation in oxide formation rates exhibited by thermal oxidation. Following gate oxide formation, a high temperature anneal may be performed, preferably in an RTA apparatus. By combining the N,O plasma treatment with an RTA process, the disclosed method is believed to offer a controllable and reproducible method for fabricating highly uniform, ultra-thin gate oxides, having low trapping state densities.