A method for thinning SOI films having improved thickness uniformity

摘要

A method of thinning SOI films for providing ultra-thin active device regions having excellent thickness uniformity and further having self-aligned isolation regions between the active device regions is disclosed. A substrate (16) having an isolation layer (14) formed thereon and further having a single crystal silicon (12) layer formed upon the isolation layer is first provided. A thermal oxide layer (18) is grown upon the silicon layer, patterned in desired regions corresponding to polish stop regions positioned between predetermined active device regions, and etched. The underlying silicon layer (12) is thereafter etched according to the patterned thermal oxide layer (18) with a high selectivity etch, thereby creating grooves (22) in the silicon layer.Optionally, a thin buffer oxide layer (26) is grown upon side wall edges. A layer (28) of an insulative polish stop material is then blanket deposited. A polysilicon layer (30) is then deposited upon the polish stop material to further completely fill the grooves and then is planarized down to the top polish stop material. The top polish stop material and the oxide layer are then etched away. Lastly, by chemical-mechanical polishing, the silicon, sidewall polish stop material, and polysilicon are thinned down to the bottom polish stop material, whereby active device regions (32) having uniform thickness corresponding to the thickness of the bottom polish stop material are created between insulating regions (40).