Methods for improving within-wafer uniformity of gate oxide

摘要

Novel methods for improving the within-wafer uniformity of a gate oxide layer on a semiconductor wafer substrate. According to a first embodiment, a gate oxide layer is formed on a wafer using conventional oxidation parameters and equipment. Next, the edge-thick gate oxide layer is nitridated using a center-thick plasma nitridation profile to enhance uniformity in thickness of the gate oxide layer between the center region and the edge or peripheral regions of the wafer. According to a second embodiment, the wafer substrate is first nitridated and then oxidized to form the gate oxide layer. The nitrogen incorporated into the wafer surface during the nitridation step retards oxidation of the wafer at the wafer edge to enhance uniformity in thickness of the gate oxide layer between the center region and the edge or peripheral regions of the wafer.