Numerical simulation and fabrication of microscale, multilevel, tapered mold inserts using UV-Lithographie, Galvanoformung, Abformung (LIGA) technology

Techniques for economic fabrication of high-aspect-ratio microscale structures (HARMS) are being investigated intensely. Microdevices employing metal-based HARMS are of particular interest for mechanical, electro-mechanical, and chemical applications. In many applications, HARMS with two or more heights are needed. Fabrication of these multi-level HARMS by compression molding requires two-level or multi-level mold inserts. In addition, tapered mold inserts would help achieving easy insert-part separation. This paper reports a process for fabricating two-level tapered mold inserts by combining UV-lithography of SU-8 resist, one-step metal electrodeposition, polish and level, followed by SU-8 resist removal. Without tilting and rotation during the lithography step, tapered plating molds are obtained by employing characteristics of UV-lithography and resist development. The SU-8 removal method used does not reduce the strength of the electrodeposited mold insert. Efficacy of our approach is demonstrated with a two-level mold insert prototype.