Patent ID: 6479352
Filing Date: 2002-11-12
Classification: H01L

Abstract:
A method of forming a high voltage MOSFET comprising the steps of:providing a substrate of a first conductivity type; depositing an epitaxial layer on the substrate, said epitaxial layer having a first conductivity type; forming first and second body regions in the epitaxial layer to define a drift region therebetween, said body regions having a second conductivity type; forming first and second source regions of the first conductivity type in the first and second body regions, respectively; and forming a plurality of trenches in said drift region of the epitaxial layer; filling said trenches with a material having a dopant of the second conductivity type, said trenches extending toward the substrate from the first and second body regions; diffusing at least a portion of said dopant from said trenches into portions of the epitaxial layer adjacent the trenches; measuring a breakdown voltage in said epitaxial layer; comparing the measured breakdown voltage to a predetermined relationship between breakdown voltage and diffusion time to determine a remaining diffusion time to achieve a prescribed breakdown voltage; and performing an additional diffusion step for said remaining diffusion time.