A mushroom-shaped convex poly-Si structure for preventing z-directional stiction of an SOI-MEMS device

This paper describes a novel convex poly-Si structure capable of preventing a silicon-on-insulator micro-electromechanical- systems (SOI-MEMS) structure that is movable in the z-direction from sticking to a supporting substrate. This structure is referred to as a poly-Si mushroom-shaped structure (pSiMS) because the structure has a convex shape that resembles a pileus of a mushroom. A pSiMS with a height of 0.6 μm and a diameter of 2.8 μm was fabricated on doubly clamped and cantilever beams by the formation of a mold and by refilling the mold with poly-Si. We performed a stiction test and succeeded in preventing 2-mm-long beams from sticking by forming pSiMSs. The test results demonstrated the effectiveness of the pSiMS.