Patent ID: 8110464

Claim:
A method of protecting an SOI layer during deep trench etch, comprising: commencing with an SOI layer atop a BOX layer which is atop an underlying substrate into which a deep trench will be formed; disposing an oxide layer atop the SOI layer; disposing a nitride layer atop the oxide layer; disposing a hard mask layer atop the nitride layer; forming an initial trench extending through the SOI layer, resulting in an opening in the SOI layer having an inner periphery; pulling back the SOI layer, via a timed ammonium hydroxide etch, thereby forming an opening in the SOI layer; forming a protective oxide structure on the opening in the SOI layer, wherein the protective oxide structure is bounded by the BOX layer and the oxide layer; and extending the initial trench into the substrate to form a deep trench via a reactive ion etch; and removing the hard mask layer.