MEMS flow sensors with silicon-carbide erosion resistant coating

This paper presents an application of a non-planar polycrystalline silicon carbide (poly-SiC) coating for a MEMS capacitive flow sensor to enhance its erosive wear resistance. The device is fabricated on Silicon-On-Insulator wafers with 100 micrometer device layer using only three photo-lithographic mask layers. The whole device is coated in non-planar poly-SiC using a low pressure chemical vapor deposition (LPCVD) method. Experimental testing with an air flow at atmospheric pressure shows that the output capacitance follows a quadratic function of the gas velocity, as was predicted from preliminary calculations. Erosion testing using sandblasting equipment shows superior erosive resistance of the sensor with poly-SiC coating compared to the one without poly-SiC coating.