Setting the Emissivity of an Imaging Bolometer in the Surface Temperature Profile Measurement of SiC-Based MEMS Heaters

The proper usage of a bandwidth-limited imaging bolometer for the measurement of the lateral temperature profile of microstructures in Silicon-Carbide (SiC) is analyzed. The SiC spectral emissivity, ϵSiC(λ), has a dip at λ∼12μm, which is in the band of a typical commercially available instrument and complicates the selection of the value of the equivalent emissivity, ϵeq,SiC, in the instrument settings. The impact is analyzed by deduction using simulation, and by experimental validation. Membranes of 3C-SiC of 1000 μm diameter and 3 μm thickness have been fabricated on Si wafers, with integrated poly-SiC resistors for both membrane heating and on-membrane temperature measurement for calibration purposes. The optimum setting was found as ϵeq,SiC = 0.705 ± 0.025 by deduction and as ϵeq,SiC = 0.66 ± 0.06 by experimental validation in the temperature range 120 °C to 400 °C. The apparent temperature coefficient of emissivity, TCE< 2 × 10−4 °C−1 is due to the shift of the Wien peak wavelength relative to the instrument’s sensitivity band.