Fabrication of 3D photoresist microstructures for the polymer vertical comb drive

Thick photoresist has been widely used to construct the microstructures in many micro-system applications, such as micro channels and micro molds for the electroplated metals in UV-LIGA process. Here, a simple process by combing double-side and multi-partial exposure techniques is proposed to fabricate the suspended 3D photoresist microstructures with uneven thickness. Since the development depth is determined via the control of development, exposure, and soft bake time. Experimental results indicate that longer soft bake time can achieve stable development depth under different development and exposure time. The 3D microstructures and the polymer vertical comb drive (VCD) made of thick photoresist AZ9260 (R) are fabricated here to demonstrate the proposed process. The experimental results show that the electrical conduction of the VCD can be completed by means of the Cu sputtering on the structure surface, and the electrical isolation is achieved via the undercut design.