High-Surface-Quality and Wider-Modulation-Range Continuous Face-Sheet Micro Deformable Mirror Based on SOI
A new type of continuous face-sheet micro deformable mirror was designed and fabricated based on SOI (Silicon-on-Insulator) technology for high optical efficiency applications in adaptive optics system. SOI provided a Silicon-Insulator-Silicon structure, and the insulator-layer of the three-layer structure was taken as etch-stop layer in deep silicon etching, which made the suspended bulk silicon membrane obtained easily. And the reflective face did not suffer etch-step due to the protection of insulator-layer. The mirror was composed of 5-um-thick and 10-mm-diameter flexible bulk silicon membrane, and actuated by 69 electrostatic actuators which evaporated on glass substrate. SOI and glass wafer were bonded together by anodic bonding, forming a separation gap of 15um between the mirror face and electrostatic pad, which offered a maximum effectual displacement of 5um by considering the pull-in effect. Fabrication process was introduced in detail. Bulk silicon micromachining was employed, methods mainly include Inductivity Coupled Plasma (ICP) etching and Si/Glass anodic bonding technique.
L. Tian et al., "High-Surface-Quality and Wider-Modulation-Range Continuous Face-Sheet Micro Deformable Mirror Based on SOI", Advanced Materials Research, Vols. 60-61, pp. 185-188, 2009