Abstract
LIGA process, which combines deep lithography, electroforming and polymer micromolding techniques, can be used in developing MEMS (micro electro mechanical systems) devices or systems such as micro actuators, micro heat exchangers, micro pumps, micro mixers, micro sensors and micro optical systems. The goal of this study aimed at developing the thick film resists and the needed process techniques for laser-LIGA and UV-LIGA processes.The study can be divided into two parts. In Part I, some polymeric materials including PMMA, Poly(MMA-co-MAA), commercial photoresist SU-8 and organic soluble polyimides were prepared and studied as laser-LIGA thick film resists. The results show that PMMA, Poly(MMA-co-MAA), PI-6 and PI-7 are good candidates for laser-LIGA thick film resists. The poor capability of linewidth definition and difficulties of stripping after well crosslinked limit the application of commercial photoresist SU-8 in laser-LIGA process. However, by taking the advantage of photosensitivity of SU-8, a process combining excimer laser processing and photolithography techniques was developed for fabricating embedded microchannels.In Part II of this study, a novel positive-tone thick photoresist combining bulk polymerization method, casting technique and chemically amplified concept was developed for UV-LIGA process successfully. At present, the ring-shape microstructures with 150 mm tall and 15 mm wide have been realized and the calculated aspect ratio is 10.