Fabrication of three-dimensional microstructure by nickel plating and photolithography

A combination of plating technology and photolithography has long been applied for the preparation of minute metallic structures, for example the metal stamper for replication of master discs. This replication technique exhibits a highly precise traceability even with shapes in submicrometre order. Microelectro mechanical systems (MEMS) are expected to progress and the field requires minute metal components. In particular, three-dimensional metal components are greatly in demand. In the conventional process, however, a two-dimensional developed image of thick photoresist is formed to increase the height of the structure. In other words, it allows industry to merely form so called '2.5-dimensional (pseudo 3D) structure'. Consequently, it is difficult and/or impossible to fabricate a metal structure with variation in the horizontal direction such as overhangs. Recently, the formation method of multilayered photoresist moulds has been reported. This technique enables the formation of the stacked photoresist mould having a structure formed with different images for the 1st and 2nd layers. In this study, formation of a micrometallic structure by combination of the double layered photoresist mould and plating method is reported.