Elimination of oxynitride (ONO) etch residue and polysilicon stringers through isolation of floating gates on adjacent bitlines by polysilicon oxidation

摘要

A method for fabricating a first memory cell and a second memory cell electrically isolated from each other. A first polysilicon (poly I) layer is formed on an oxide coated substrate. A masking layer is deposited or grown on the poly I layer, and at least a portion of the masking layer is etched so as to pattern the first memory cell and the second memory cell and an unmasked portion therebetween. The unmasked portion of the poly I layer is transformed into an insulator via thermal oxidation such that the insulator electrically isolates a floating gate of the first memory cell from a floating gate of the second memory cell. An interpoly dielectric layer and a second polysilicon (poly II) layer is formed over the poly I layer and insulator substantially free of abrupt changes in step height.