Method of preventing polysilicon stringers during formation of a stacked double polysilicon structure by using dielectric sidewall spacers

Claim 1

A process of forming a stacked polysilicon structure on an underlying material, the process comprising the steps of: forming a first layer of polysilicon on the material; anisotropically etching the first layer of polysilicon to form a first polysilicon region having substantially vertical sidewalls; forming a dielectric spacer layer on the structure resulting from the foregoing steps; etching the dielectric spacer layer in a two-step etch module to form dielectric sidewall spacers on the substantially vertical sidewalls of the first polysilicon region, the two-step etch module including an initial anisotropic dry etch that removes a substantial thickness of the dielectric spacer layer while leaving a remaining portion of the dielectric spacer layer and a wet etch that removes the remaining portion of the dielectric spacer layer, whereby an upper surface of the first polysilicon region is exposed; forming a layer of interpolysilicon dielectric material on the exposed upper surface of the first polysilicon region; forming a second layer of polysilicon on the structure resulting from the above-recited steps; and anisotropically etching the second layer of polysilicon to form a second polysilicon region over the first polysilicon region but separated therefrom by interpolysilicon dielectric material.