Fabrication of a polymeric tapered HARMs array utilizing a low-cost nickel electroplated mold insert

A simple low-cost technique has been developed to fabricate a mold insert for replicating polymeric tapered high aspect ratio microstructures. A backside exposure technique is used to first obtain a tapered sidewall structure as an electroplating mold in SU-8 photoresist on a glass wafer. Nickel electroplating is utilized to form the mold insert. The lowest average surface roughness of the nickel mold insert on the side that interfaces with the glass wafer during electroplating is measured to be 7.02 nm. A novel technique involving use of titanium putty is introduced here to reduce cost and effort required to fabricate the mold insert. Replication of tapered microstructures in polymeric materials utilizing the fabricated mold insert is demonstrated here in polydimethylsiloxane by a direct molding process and in polymethyl methacrylate by hot embossing. The fabrication details for the mold insert are described. Advantages and disadvantages of the use of titanium putty for achieving superior metal surface finish are given.