Polycrystalline silicon carbide for surface micromachining

Polycrystalline silicon carbide (poly-SiC) films have been deposited on polysilicon-coated, 4-inch silicon wafers in an atmospheric pressure chemical vapor deposition (APCVD) reactor using parameters similar to those developed by our group for single crystal SiC growth. With highly-oriented (110) polysilicon films as substrates, poly-SiC films of the same preferred crystalline orientation have been grown. Characterization of the substrate before and after deposition by X-ray diffraction (XRD) reveals that the orientation of the polysilicon substrate changes from predominantly (110) before SiC deposition to a mixture of (110) and (111) during the high-temperature (e.g., 1300°C) film growth. This change has no affect on the overlying poly-SiC film. Surface profilometry and scanning electron microscopy (SEM) are used to characterize the surface of the deposited films. Lateral resonant devices are surface-micromachined from the poly-SiC films using a single mask process. Devices with lateral dimensions of up to 500 μm and free of residual-stress-induced deformations have been successfully fabricated. These microactuators exhibit actuation voltages as low as 30 V and resonant frequencies in the 20-60 kHz range