Fabrication of thick electroforming micro mould using a KMPR negative tone photoresist

The microfabrication of thick electroforming micro moulds using a KMPR negative tone photoresist has been investigated. SU-8 resist is currently the most widely used thick resist for electroforming masking, but difficulties in removing crosslinked SU-8 have considerably limited its applications in microelectroforming applications. KMPR resist is a complement to SU-8 in providing electroforming moulds. A considerable advantage of KMPR compared to SU-8 is that it can easily be removed after completion of electroforming using commercially available chemical removers. In the characterization of KMPR for making microelectroforming moulds, an optimized double spin lithography process using an UV mask aligner has been developed. The process enables the KMPR moulds to have dimensional accuracy and sidewall verticality comparable to those of SU-8. Structures of 180 mu m in thickness and aspect ratio of 18:1 have been fabricated repeatedly in experiments. Microelectroforming was conducted in the KMPR moulds and the results show excellent geometry. The KMPR moulds were easily stripped without damaging the metal components or leaving residues around the metal structures. KMPR resist was also successfully stripped from confined areas, such as nickel channels of 180 mu m thickness and 40 mu m width.