Nickel and copper electroplating of proton beam micromachined SU-8 resist

Proton beam micromachining (PBM) has been shown to be a powerful technique to produce three-dimensional (3D) high-aspect-ratio microstructures (Watt et al., 2000). Potential commercial applications of PBM, which is a fast direct write technique, will become feasible if the fabrication of metallic molds or stamps is realised. Metallic components can be produced by electroplating a master from a microstructure produced in resist. The production of high-aspect-ratio metallic stamps and molds requires a lithographic technique capable of producing smooth and near 90° sidewalls and a one to one conversion of a resist structure to a metallic microstructure. PBM is the only technique capable of producing high-aspect-ratio microstructures with sub-micron details via a direct write process. In PBM, SU-8 (Lorenz et al., 1997) resist structures are produced by exposing the SU-8 resist with a focused MeV proton beam followed by chemical development and a subsequent electroplating step using Ni or Cu. The data presented shows that PBM can successfully produce high-aspect-ratio, sub-micron sized smooth metallic structures with near 90° sidewall profiles.