THE SIO2-SI3N4 INTERFACE, .1. NATURE OF THE INTERPHASE

Recent reports in the literature have suggested that Si2N2O forms in t he oxidation of Si3N4 as a buffer suboxide below the silica crust, and that equilibrium between SiO2 and Si3N4 requires the presence of this buffer. Here we report the examination of SiO2/Si3N4 boundaries of di fferent genesis, by a variety of techniques, all of which failed to de tect Si2N2O. What was found in each case is a graded suboxide whose co mposition merges seamlessly with the higher oxide above and the Si3N4 below. Part I presents the results of compositional depth profiling ac ross the suboxide. In Part II a model is proposed to explain how O-2 d iffusion in the graded suboxide limits Si3N4 oxidation kinetics.