Design And Fabrication Of SIO2 Micromechanical Structures Inside Anisotropically Etched Cavity

Abstract

In the present work, we report a novel process for fabricating suspended silicon dioxide micro-structures inside the anisotropically etched cavity formed in (100) silicon wafers. Using this new process, the moving parts are "recessed" in the substrate which can be packaged and handled easily compared to non-recessed structures. In the fabrication process, spin coated liquid photoresist is used. There is a common problem of thinning of photoresist on convex edges of the cavity during photolithography steps. As a result, silicon dioxide is etched away from these edges. During subsequent anisotropic etching of silicon to release the microstructures, the unprotected convex edges are also etched resulting in failure of the process. To overcome this problem, two different methods are used. In the first method, high viscosity positive photoresist (Shipley STR-1045) is used and the multiple coatings are carried out to cover the convex edges adequately. This protects the oxide on convex edges in buffered hydrofluo...