Using oxide sidewall taper to improve breakdown voltage in planar junction of DMOS devices by a simple process

Argon ion implantation was used to create a damaged surface layer on field oxide. Subsequent oxide etching created a tapered oxide transition from thin oxide to thick field oxide. This structure effectively improves the breakdown voltage of the planar junction of a DMOS device which makes use of a poly field plate to enhance the breakdown voltage. The process is simple, reproducible and introduces no new mask steps.