Abstract: A method of forming a mask from a metal layer deposited upon a substrate patterned for exposure of a workpiece to radiation of a specific range of wavelengths with the substrate being transparent to the radiation comprises the following steps. Form the metal layer superjacent to the substrate. Form a photoresist layer superjacent to the metal layer. Expose the photoresist layer to a pattern. Develop the photoresist to Form a photoresist mask with an opening therethrough. Bake the photoresist mask, the metal layer and the substrate. Perform a descum operation. Perform an isotropic etching of the metal layer through the opening in the mask. Perform an after etching inspection measurement. Strip the photoresist mask. Perform an after stripping inspection measurement. The isotropic etching is performed with a wet etchant. The descum operation is performed with a dry plasma process including oxygen and nitrogen gases and an inert gas selected from argon and helium.