Patent ID: 6897120

Claim:
A method of forming integrated circuitry comprising: forming a layer of oxide material over a semiconductor substrate; forming a silicon nitride layer over the layer of oxide material; forming a patterned photoresist comprising masking layer over the silicon nitride layer, the patterned masking layer comprising mask openings therethrough; and etching an opening through the silicon nitride layer, through the layer of oxide material and into a semiconductive material of the semiconductor substrate, the etching occurring through the mask openings substantially selectively to the photoresist comprising layer using a single etching chemistry produced by generating a plasma from a processing gas consisting of ammonia and at least one fluorocarbon selected from the group consisting of CF 4 , C 4 F 8 , C 4 F 8 , C 2 F 6 , C 3 F 8 , C 6 F 8 , and chlorofluorocarbons, the etching being conducted under etching conditions effective to substantially anisotropically etch the silicon nitride comprising layer, the etching chemistry comprising a volumetric ratio of all fluorocarbon to the ammonia of from 40:1 to 20:1 and providing increased selectivity to the photoresist comprising masking layer than would otherwise occur using identical etching chemistry and identical etching conditions without any ammonia.