Undercut Compensation for Xenon Difluoride Etching of Polysilicon Thin-films

This paper presents a new undercut compensation etch technique that provides better control over lateral undercutting of polysilicon thin-films using xenon difluoride (XeF₂) vapour as the etchant. A significant reduction in the lateral undercutting of polysilicon thin-films was achieved by placing silicon etch buffers beside polysilicon etch samples during the XeF₂ etch process. This technique extends XeF₂´s etching capability to include fine geometry patterning of polysilicon films to be used as MEMS structural layers.