Process of continuous membrane micro-deformable mirror based on SOI wafer

Silicon on insulator (SOI) provides a three-layer structure of Si/SiO₂/Si, and makes it possible to achieve continuous membrane micro-deformable mirror based on deep reactive ion etching (DRIE). By using the SiO₂ as the self-stop layer of dry etching, a single crystal silicon reflective mirror membrane can be readily realized with uniform and precisely controlled thickness. A process based on DRIE and anodic bonding of SOI wafer/Pyrex 7740 glass was presented, and a micro-deformable mirror with 69 actuators was fabricated and tested. The micro-deformable mirror, with an aperture of 10 mm, exhibits a working range of 4.25 μm, a PV flatness of 1.2 μm and a RMS roughness of 193 nm.