UV-LIGA fabrication of microscale two-level mold inserts for MEMS applications

Techniques for fabricating high-aspect-ratio microscale structures (HARMS) are being investigated for wide-ranging applications. Microdevices employing metal-based HARMS are of particular interest for mechanical, electro-mechanical, and chemical applications. In many applications, HARMS with two or several distinct heights are necessary, the fabrication of which necessitates two-level or multi-level mold inserts. In addition, tapered mold inserts would help achieving easy insert-part separation. Here we report a process for fabricating two-level, tapered mold inserts by combining UV-lithography on SU-8 resist, one-step metal electrodeposition, polish and level, and SU-8 resist removal. Without tilt and rotation during the lithography process, tapered SU-8 plating molds are obtained by employing light diffraction during lithography and proper development procedures. The SU-8 resist removal process does not reduce its strength. Efficacy of this approach is demonstrated with a two-level insert prototype suitable for fabricating micro heat exchanger parts by compression micromolding.