Large-area molded silicon nitride torsion mirrors

We have developed a simple process for silicon nitride structures with increased out-of-plane stiffness. The essential elements of this process are molded vertical features that provide the desired stiffness, and a post-release substrate etch that allows for a large air gap without elevators or pop-up mechanisms usually associated with surface micromachined structures requiring large range of motion. Our process is a hybrid incorporating features of molded thin film micromachining coupled with a deep substrate etch typical of bulk micromachining. This paper describes large mirrors up to 400 /spl mu/m diameter that are well suited for beam pointing applications such as optical switching.