Etching methods, methods of removing portions of material, and methods of forming silicon nitride spacers

In one embodiment, the invention includes a method of removing at least a portion of a material from a substrate. The method includes providing a substrate in a reaction chamber, the substrate having a material supported thereover, and first etching the material while the substrate is in the reaction chamber. The method also includes, after the first etching, cleaning a component from at least one sidewall of the reaction chamber while the substrate remains therein; the component comprising a species that is present in the material. The cleaning includes exposing the sidewall and substrate to conditions which substantially selectively remove the component from the sidewall while not removing the material from the substrate, and not etching any other materials supported by the substrate. After the cleaning, the method includes second etching the material while the substrate is in the reaction chamber.