Novel fabrication process for a monolithic PMMA torsion mirror and vertical comb actuator

Abstract

This paper presents a novel fabrication process for monolithic PMMA (polymethylmethacrylate) vertical comb-drive actuators utilizing hot embossing, surface-activated direct bonding and elliptical vibration cutting. The robustness and capability of the method are demonstrated through the fabrication of sophisticated PMMA freestanding microstructures, such as a rotation mirror device integrated with vertical comb actuators. The fabrication process consists of silicon mold fabrication by deep-RIE, PMMA microstructure formation by hot embossing, PMMA–PMMA direct bonding by surface activation, releasing or removal of a PMMA layer remaining after hot embossing by elliptical vibration cutting, and finally, metallization by sputtering to form electrodes. An efficient technique to protect the PMMA microstructures during the release process using reinforcement material is applied. A monolithic PMMA torsion mirror driven by a vertical comb actuator has been fabricated successfully.