Polymer microlens replication by Nanoimprint Lithography using proton beam fabricated Ni stamp

It is essential to have a simplified and a rapid method for fabricating micro/nano structures in different kinds of polymeric materials. Though it is possible to fabricate arrays of microlens directly by P beam writing (PBW), it is restricted to a few types of resist materials. Therefore we have fabricated a Ni electroplated metallic stamp comprising of arrays of inverse/negative features of microlenses. The metallic stamp of about 500 μm thick is made on a silicon wafer coated with 10 μm thick polymethylglutarimide (PMGI) resist and the desired structures are written by PBW followed by thermal reflow and Ni electroplating. An array of microlenses is imprinted on a polycarbonate (PC) substrate by the Nanoimprint Lithography (NIL) technique and the replicated microlenses featuring various numerical apertures, diameters and pitches are characterized.