A method for providing etch selectivity in substrate processing is disclosed. More particularly, a plasma treatment is provided to a plurality of exposed structures comprised of varying materials. The plasma treatment will preferentially enhance the etch selectivity between at least two of the exposed structures. In one embodiment, the plurality of exposed structures are utilized as part of a multi-patterning substrate process. In one embodiment, the exposed structures may comprise an organic planarization layer and a spin-on-metal layer. The plasma treatment may comprise a plasma formed using nitrogen and hydrogen gasses and the emission of vacuum ultra-violet (VUV) wavelength radiation from such a plasma.