Study on Influence of O2 Concentration in Wafer Cleaning Ambient for Smoothness of Silicon (110) Surface Appearing at Sidewall of Three-Dimensional Transistors

Abstract

We investigated the influence of O2 concentration in ultra pure water (UPW) on the Si(110) surface roughness during the immersion of Si into UPW. The suppressing of O2 concentration in UPW is very effective to suppress the increase of microroughness of Si(110) surface. The O2 concentration in UPW can be controlled by the ambient O2 concentration. Si(110) surface cannot be roughened when the O2 concentration is suppressed to less than 100 ppm in ambient (4 ppb in UPW) and the immersion time is less than 1 hour. It can be expected that the Si(110) surface flatness is maintained, and this surface is mainly used for the channel of FinFET. Furthermore, we demonstrated that the O2 concentration in a prototype 200-mm single-wafer cleaning chamber can be decreased to less than 100 ppm within 1 minute by an N2 purge of 200 l/min.