Patent ID: 6703315
Filing Date: 2004-03-09
Classification: H01L

Abstract:
A method of forming a shallow trench within a trench capacitor structure, said method comprising:providing a trench capacitor structure comprising (a) a silicon substrate having an upper and a lower surface; (b) first and second trenches extending from said upper surface into said silicon substrate; (c) first and second oxide regions lining at least portions of said first and second trenches; and (d) first and second polysilicon regions at least partially filling said oxide lined first and second trenches; and forming a shallow trench from an upper surface of said structure, said shallow trench having a substantially flat trench bottom that forms an interface with portions of said silicon substrate, said first oxide region, said second oxide region, said first polysilicon region and said second polysilicon region, said shallow trench being formed by a process comprising (a) a first plasma etching step having an oxide:silicon:polysilicon selectivity of >1:1:1 and (b) a second plasma etching step having an oxide:silicon:polysilicon selectivity of <1:1:1.