Low-Temperature Formation of Thin-Gate SiO2 Films by the Ultrahigh-Vacuum Chemical Vapor Deposition with Reduced Subcutaneous Oxidation Using Remote-Plasma-Activated Oxygen and Si2H6

Abstract

We have investigated the growth condition dependence on the properties of SiO2 films by remote-plasma-enhanced chemical vapor deposition (RPECVD) in an ultrahigh vacuum system with remote-plasma-activated oxygen and Si2H6. During the RPECVD, subcutaneous oxidation of the Si substrate was not negligible, which degraded the controllability of the film thickness and the electrical properties. The amount of the active oxygen species that dominates the reactions of subcutaneous oxidation was considered to be significantly reduced with increasing O2 flow rate, while that of “pure” CVD remained unchanged. As a result, precise control of the RPECVD SiO2 thickness with reduced subcutaneous oxidation has been achieved by setting the O2 flow rate to the maximum and by using higher Si2H6 flow rates. The characteristics of the SiO2 films obtained using optimized RPECVD conditions at temperatures lower than 600°C without a postannealing process have been demonstrated to be comparable to those of thermally grown films.