Nitrogen Effects on the Integrity of Silicon Dioxide Grown on Polycrystalline Silicon

Abstract

In this paper, we describe a simple technique to achieve a thin nitrided polyoxide film, only requiring an extra nitrogen implantation to be compatible with the floating gate nonvolatile memory process. The integrity of polyoxides is improved by using the through-silicon-gate nitrogen implantation. Nitridation can be achieved by implanting nitrogen into polysilicon gate followed by a high temperature annealing to drive the nitrogen atoms across the polysilicon, through the polyoxide, and to incorporate nitrogen at the polyoxide/polysilicon interface. The nitrogen-rich layer formed during the driven-in process not only strengthens the polyoxide structure but also improves the polyoxide quality. Improvements of electrical characteristics such as a low leakage current, a low electron trapping, and a high breakdown field for both positive and negative biases have been observed.