Abstract
A thermal flow sensor has been fabricated and characterized, consisting of a center resistive heater surrounded by two upstream and one downstream temperature sensing resistors. The heater and temperature sensing resistors are fabricated from nitrogen-doped(n-type) polycrystalline silicon carbide(poly-SiC) deposited by LPCVD(low pressure chemical vapor deposition) on LPCVD silicon nitride films on a Si substrate. Cavities were etched into the Si substrate from the front side to create suspended silicon nitride membranes carrying the poly-SiC elements. One upstream sensor is located <TEX>$50{\mu}m$</TEX> from the heater and has a sensitivity of <TEX>$0.73{\Omega}$</TEX>/sccm with <TEX>${\sim}15\;ms$</TEX> rise time in a dynamic range of 1000 sccm. N-type poly-SiC has a linear negative temperature coefficient and a TCR(temperature coefficient of resistance) of <TEX>$-1.24{\times}10^{-3}/^{\circ}C$</TEX> from room temperature to <TEX>$100^{\circ}C$</TEX>.
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