Patent ID: 7122439
Filing Date: 2006-10-17
Classification: H01L

Abstract:
1. A method, comprising: (a) providing a substrate; (b) forming a trench in said substrate, said trench having sidewalls and a bottom, said trench having an upper region adjacent to a top surface of said substrate and a lower region adjacent to said bottom of said trench, said upper region abutting said lower region; (c) forming a protective layer on said sidewalls and said bottom of said trench, said protective layer comprises a outer layer of silicon nitride on a layer of polysilicon on an inner layer of silicon nitride on a layer of silicon oxide, said layer of silicon oxide in direct physical contact with said sidewalls of said trench; (d) removing said protective layer from said sidewalls in said lower region of said trench and from said bottom of said trench; (e) oxidizing a layer of said substrate exposed in step (d) on said sidewalls in said lower region of said trench and on said bottom of said trench; and (f) removing said layer of said substrate oxidized in step (e) from said lower region of said trench.