Method for thinning soi films having improved thickness uniformity

Abstract

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 having an isolation layer formed thereon and further having a single crystal silicon layer formed upon the isolation layer is first provided. A thermal oxide layer is grown upon the silicon layer, patterned in desired regions corresponding to polish stop regions positioned between predetermined active device regions, and etched. The silicon layer is thereafter etched according to the patterned thermal oxide layer with a high selectivity etch, thereby creating grooves in the silicon layer. An insulative polish stop material is then deposited upon the thermal oxide, silicon, and isolation layers, the polish stop material forming top, sidewall, and bottom polish stop material thereon, respectively, partially filling the grooves, and further wherein the bottom polish stop material comprises a prescribed thickness. Polysilicon is 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 have uniform thickness corresponding to the thickness of the bottom polish stop material.