Double-sided MEMS mirror for L-switching matrix

SOI wafers are finding increasing applications in MEMS devices. The device Si, buried oxide, and handle Si layers provide mechanical and structural properties to create more complex 3D free standing structures. This paper presents the fabrication process of double-sided mirror by using surface and bulk micromachining of SOI wafers. Silicon nitride thin firms are deposited on device layer of SOI to provide torsion bar material of the mirror. Device layer provides single crystal Si mechanical reinforcement to counteract the stress associated with silicon nitride. The underlying buried oxide acts as an etch-stop layer during DRIE of the Si handle layer and sacrificial layer for releasing the torsion bars. The dimensions of the mirror are 250um by 500um suspended by two torsion bars that are 350um by 6um by 0.4um.