Methods of forming silicon nitride spacers, and methods of forming dielectric sidewall spacers

The invention includes a method of patterning a material over a semiconductive substrate, comprising: a) forming a layer of first material against a second material and over the substrate, the substrate comprising a surface having a center and an edge; b) first etching the first material in a reaction chamber, the first etching comprising a first center-to-edge uniformity across the surface of the wafer and comprising a first selectivity for the first material relative to the second material; c) second etching the first material in the reaction chamber, the second etching comprising a second selectivity for the first material relative to the second material, the second center-to-edge uniformity being less than the first center-to-edge uniformity, the second selectivity being greater than the first selectivity; and d) cleaning a component of the first material from at least one sidewall of the reaction chamber between the first and second etchings.