Patent ID: 6967170

Claim:
A method of forming silicon nitride spacers, comprising: forming a silicon dioxide layer proximate a transistor gate assembly; forming a silicon nitride layer over the transistor gate assembly and over the silicon dioxide layer; first plasma etching the silicon nitride, the first plasma etching comprising a first center-to-edge uniformity across a surface of a substrate supporting the gate assembly and comprising a first selectivity for the silicon nitride relative to the silicon oxide; second plasma etching the silicon nitride, the second plasma etching comprising a second center-to-edge uniformity across the surface and comprising a second selectivity for the silicon nitride relative to the silicon oxide, the second center-to-edge uniformity being less than the first center-to-edge uniformity, the second selectivity being greater than the first selectivity, the first and second plasma etchings patterning the silicon nitride into spacers proximate the transistor gate; and cleaning a component of the silicon nitride from at least one sidewall of a reaction chamber containing the substrate between the first plasma etching and the second plasma etching.