Abstract: Methods are described for removing a material from a substrate by dissolving an etchant into a solvent to form a solution; and exposing the substrate to the solution so that the etchant in the solution removes material from the substrate; wherein during the exposure the solution is maintained in a supercritical or near-supercritical phase. The described methods can include additional steps, such as exposing a precursor of the material to a reagent to form the material, and depositing a second material onto the substrate after removing the material from the substrate.