SU-8 thick photoresist processing as a functional material for MEMS applications

The use of SU-8 high aspect ratio, thick, photoresist as a functional material for MEMS applications is described in this paper. SU-8 processing is developed to implement low-stress SU-8 structures as permanent and functional material incorporated with silicon-on-insulator technologies. Silicon micromachined cantilevers were fabricated with SU-8 structures on the cantilevers as added masses. Separation of material function can be achieved in this way. Silicon provides excellent mechanical properties, while SU-8 is used as extra mass to adjust the mechanical behaviour. The resonance behaviour of the cantilever structure with SU-8 is characterized through measurement, simulation and calculation, and the strength of the SU-8 material for this purpose is evaluated. The results show that SU-8 is well suited as a permanent material in mechanically active MEMS devices, and several applications are suggested. 3D MEMS architectures can also be achieved in this manner.