High aspect ratio microstructure fabrication using SU-8 resist

The SU-8 series is a negative, epoxy-type, near-UV photoresist. It has good light sensitivity and can be structured to more than 2mm in thickness by UV exposure. It's very suitable for the application in MEMS, UV-LIGA, ultra-film(1.2). Fast prototyped from the SU-8 microstructure is a very simple way to manufacture high aspect ratio micromechanical components. The cost of this process is much lower than that of the LIGA process. We adopted electroplating method to prototype SU-8. So metallic film needed to be sputtered on the surface of the silicon wafer. In order to study the adhesive strength between different metallic films and the SU-8, we prepared four substrates with Cu, NiFe, Au, and Ti film respectively. We found the Ti film has the strongest adhesive strength with the resist. When the film is FeNi, we should decrease the exposure duration to obtain good adhesive strength, due to the strong refection of the film.