A method of fabricating workpieces includes one or more layers on a substrate that are masked with an ion implantation mask comprising two or more layers. The mask layers include a first mask layer closer to the substrate, and a second mask layer on the first mask layer. The method also comprises ion implanting one or more of the layers on the substrate. Ion implantation may form portions with altered physical properties from the layers under the mask. The portions may form a plurality of non-magnetic regions corresponding to apertures in the mask.