Massive replication of polymeric high-aspect-ratio microstructures using PDMS casting

Abstract

This paper presents a rapid replication technique for polydimethylsiloxane (PDMS) high aspect ratio microstructures (HARMs) and a pattern transfer technique for replication of metallic HARMs on other substrates (such as circuit containing substrates) using such replicated PDMS HARMs. A high aspect ratio metallic micromold insert, featuring a variety of test microstructures made of electroplated nickel, has been fabricated by the standard deep X-ray lithography (DXRL) process. Mixed pre-polymer PDMS with a curing agent has been cast onto the metallic micromold insert test patterns to create replicated polymeric HARMs. The replicated PDMS HARMs could be used to massively reproduce high aspect ratio metallic microstructures on other substrates using a pattern transfer technique. In order to demonstrate the concept, an experiment has been carried out to attach the replicated PDMS HARMs onto a silicon substrate which has pre-deposited photoresist and metallic seed layer. Electrodeposition has been carried out through the attached PDMS HARMs mold followed by the subsequent removal of the PDMS, resulting in high aspect ratio metallic microstructures on the silicon substrate. This technique could be used to massively reproduce metallic HARMs on circuit containing substrates to create 3-D integrated MEMS devices.