Fabrication of High Aspect Ratio SU-8 Microstructures on Piezoelectric Transducers

A methodology to fabricate high aspect ratio (HAR) SU-8 micro structures on piezoelectric and metallic substrates is presented. In this work, several fabrication trials were carried out to optimize the SU-8 fabrication process. The fabrication recipe mentioned in the SU-8 (Microchem, USA) datasheet is employed for the initial fabrication trials. The SU-8 structures (micropillars) fabricated during these trials resulted in poor bonding with the surface of piezoelectric substrate. In the later trials a thin film of OmniCoat (Microchem, USA) is coated over the substrate before coating the SU-8 film to improve the adhesion quality of the SU-8 micropillars to the substrate. The fabrication methodology used during the trails and results on the quality of the fabricated HAR SU-8 pillars are discussed in the paper.