A method for fabricating a semiconductor product includes applying a photo-resist layer to a substrate, the photo-resist layer including a higher acid concentration at an upper portion of the photo-resist layer than at a lower portion of the photo-resist layer. The method also includes exposing the photo-resist layer to a light source through a mask including a feature, the photo-resist layer including a floating, diffusing acid that will diffuse into a region of the photo-resist layer affected by the feature while not diffusing into a feature formed by the mask.