A method for etching a poly-granular metal-based film includes providing a flow of a background gas in a plasma etching chamber containing a semiconductor structure including the poly-granular metal-based film formed over a substrate with a mask patterned over the poly-granular metal-based film. The method also includes applying a source power to generate a background plasma from the background gas, and providing a flow of a modifying gas while maintaining the flow of the background gas to generate a modifying plasma that produces a surface modification region with a substantially uniform depth in the top surface of the poly-granular metal-based film exposed by the mask. The method further includes stopping the flow of the modifying gas while maintaining the flow of the background gas, and applying a biasing power to the substrate to remove the surface modification region.