Geometry Dependence of Poly-Si Oxidation and Its Application to Self-align, Maskless Process for Nano-scale Vertical CMOS Structures

摘要

Geometry dependent thermal oxidation rates of silicon/polysilicon on concave and convex surfaces are complex and need a better understanding. The complexity is a result of several competing effects, namely, volume expansion stress, area effects, stress from etch damage, and crystal orientation. In this paper we present a systematic study to decouple these effects using both experimental test structures and simulations. Among other things, the result of this work directly impacts CMOS gate stack processing on vertical MOSFETs. In addition, we use the differential oxidation rate understanding to describe a novel technique for self-aligned maskless process. We apply this to create a process for vertical CMOS structure, which is capable of self-aligning and resolving very small features without photolithography.