Selective metallization of cured SU-8 microstructures using electroless plating method

In this paper, we report a research work on the fabrication and selective metallization of high aspect ratio cured SU-8 polymer microstructures on silicon substrate using UV lithography technology and selective electroless plating method. Electroless plating of metal films on both the top and sidewall surfaces of microstructures was achieved while the silicon substrate was not coated. The details of the successfully developed procedures are presented, including the surface modification of cured SU-8 microstructures and the electroless plating of gold and copper. The surface modification was realized through attaching Au colloidal film to amine group, that forms a seed layer on cured SU-8 polymer for electroless plating of copper after the polymer surfaces were exposed under large UV irradiation. Experiments demonstrated that UV exposure dosage and illumination direction are two of the most dominant parameters in the selective electroless plating process. The approach can also be easily adapted to electroplating other metals with different electroless plating baths in theory.