Fabrication of a PMMA Torsional Micromirror Device Based on Hot Embossing Process

This paper reports the fabrication of a PMMA torsional micromirror device using hot embossing and ultra-precision machining. The mirror is operated based on electrostatic vertical comb-drive actuators. The fabrication process is described as followings. First, two-stepped silicon mold is fabricated from silicon wafer by photolithography and ICP-RIE. Next, the micromirror device structures are formed on PMMA by hot embossing method. The comb-drive actuator has finger width and gap between fingers are both 5 um, and device thickness is about 60 um. The PMMA layer that remained after hot embossing is removed by ultra-precision cutting method to release the movable parts. The maximum surface roughness of the mirror after released by ultra-precision cutting is 87 nm (Rz). Finally, the device is coated with a gold layer to create the electrical conductivity for comb finger of the actuator. PMMA torsional micromirror comb-drive actuator has been fabricated, and the device was tested successfully.