Patent ID: 6825097
Filing Date: 2004-11-30
Classification: H01L

Abstract:
A method of forming an isolation trench in a silicon substrate having a device layer above an insulating layer (SOI), comprising the steps of:etching a trench with substantially vertical sides and bottom corners in said SOI substrate; growing a first liner of thermal oxide having a first liner thickness on said vertical sides and a second thickness, smaller than said first thickness, in said bottom corners, whereby said aperture has a greater width at the bottom; depositing a preliminary liner of oxide of moderate conformality on said first liner on said sides and in said bottom corners, said preliminary liner being thicker in said bottom corners and, together with said first liner, leaving an aperture within said trench having substantially vertical sides; and depositing an oxide fill layer filling said aperture and extending outside said trench; whereby the material filling said isolation trench at an intermediate level comprises at least three types of oxideâ€”said first liner of thermal oxide adjacent to said vertical sides, said preliminary liner abutting said first liner and said oxide fill layer abutting said preliminary liner.