Selective electro-less plating of SU-8 microstructures fabricated using two-photon polymerization

In this paper, we report a method for fabricating an array of 3D silver-coated polymer microstructures. The process involves three dimensional nanolithography using two-photon polymerization of SU-8 photoresist that has been spin coated onto a silicon substrate. The resulting polymer structures are selectively coated with silver using an electroless silver nitrate plating solution. We utilize a radio frequency plasma pretreatment process to modify the surface of the polymeric microstructures prior to electroless silver plating. Optimization of this pretreatment process allows us to selectively silver plate the polymer structures whilst leaving the silicon substrate uncoated. This technique opens up the possibility of fabricating true three dimensional metallic nanostructures for metamaterials and plasmonics applications.