Selective electroless silver plating of three dimensional SU-8 microstructures on silicon for metamaterials applications

We report a method for selective silver coating of SU-8 structures on Si substrates by treating the sample with radio frequency plasma prior to electroless plating. Silver films with high conductivity of9 x 10 super(-8) Omega .m and lowsurface roughness of 9 nm have been obtained. When combined with two-photon lithography, this process can be utilized for three-dimensional metamaterials applications. Unlike previous work on selective coating, our process can coat directly on SU-8 photoresist that is widely used for two-photon lithography and does not require any resin modification.