Fabrication methods based on wet etching process for the realization of silicon MEMS structures with new shapes

In this paper, fabrication methods are developed in order to realize the silicon microelectromechanical systems components with new shapes in {100} Si wafers. Fabrication process utilizes wet etching with a single step of photolithography. The silicon etching is carried out in complementary metal oxide semiconductor process compatible pure and surfactant Triton-X-100 [C(14)H(22)O(C(2)H(4)O] (n) , n = 9-10) added tetramethylammonium hydroxide (TMAH) solutions. The fabricated structures are divided in two categories: fixed and freestanding. The fixed structures are realized in single oxidized silicon wafers, while freestanding are formed in silicon nitride-based silicon on insulator (SOI) wafers. The SOI wafers are prepared by bonding the oxidized and the nitride deposited wafers, followed by thinning and chemical mechanical polishing processes. The etching results such as {100} and {110}Si etch rates, undercutting at rounded concave and sharp convex corners and etched surface morphologies are measured in both pure and Triton added TMAH solutions. Different concentrations of TMAH are used to optimize the etching conditions for desired etched profiles.