Process optimization of optical lithography of SU-8 photoresist

On the basis of UV-LIGA technique, we used SU-8 photoresist to fabricate high aspect ratio microstructures, the highest aspect ratio of which was 20. The influences of wavelength of exposing source and exposing dose on the resist microstructures was investigated. A non-line rule of microstructures' dimension change according to the exposing dose was found. The rule was explained from a number of reacting molecules and the space structure of polymer generated by the molecules. In light of the rule, a new method of eliminating the T-top of SU-8 microstructures was proposed.