Method of forming a laterally-varying charge profile in silicon carbide

Abstract

A method of forming a laterally-varying charge profile in a silicon carbide substrate includes the steps of forming a silicon nitride layer on a polysilicon layer formed on the silicon carbide substrate, and patterning the silicon nitride layer to provide a plurality of silicon nitrite layer segments which are spaced apart in the lateral direction and which are provided with openings therebetween which are of varying widths. The polysilicon layer is oxidized using the layer segments as an oxidation mask to form a silicon dioxide layer of varying thickness from the polysilicon layer and to form a polysilicon layer portion therebeneath of varying thickness. The silicon dioxide layer and silicon nitride layer segments are removed, and a dopant is ion implanted into the silicon carbide substrate using the polysilicon layer portion of varying thickness as an implantation mask to form a laterally-varying charge profile in the silicon carbide substrate. This method provides an effective and commercially-feasible technique for forming various high-power lateral semiconductor devices, including MOSFET, JFET, diode and IGBT structures, with excellent high-temperature and high-power operating characteristics.