A new surface rounding technique for deep submicron CMOS transistor

Abstract

The effect of oxidation temperature on corner founding has been studied. As the temperature increases, the curvature of corners becomes larger. This effect improves the subthreshold behaviour and eliminates the "early turn on" effect. However, the bottom edges form a sharp convex curve which will lead to poor reliability behaviour. Hence, a new surface patterning technique using a novel etching process has been developed and is demonstrated in this paper to be able to achieve a rounded silicon channel. Unlike the thermal oxidation where corner rounding only takes place at the edges, this proposed method uses a two-stage etch process to round the entire silicon surface without compromising the bottom edges.