Review on Methods for Trench MOSFET Gate Oxide Reliability and Switching Speed Improvement

Abstract

In high density vertical trenched power double-diffused metal oxide semiconductor (DMOS), the trench width (CD) continually shrinks as driven by market for low cost and longer battery lifetime. Subsequently, this imposes technical challenges to keep high breakdown voltage without affecting other performances such as gate charge and on-state resistance. This paper discusses some of the technical challenges faced and suggested solutions. The various methods to improve the trench oxide uniformity and trench corner profile are also presented through experimental data. Different methods to thicken the trench bottom oxide to reduce gate-to-drain capacitance (Cgd) and eliminate the oxide weak points are introduced. This paper also reviews advanced industrial developments to increase the device switching speed as well as breakdown voltage.