AlScN-on-SiC Diaphragm Multimode Micromechanical Resonators for High-Temperature Sensing Applications

We demonstrate circular diaphragm multimode micromechanical resonators made of heterostructure thin film of aluminum scandium nitride (AlScN) sputtered on cubic silicon carbide (3C-SiC). We systematically characterize the multimode resonators from room temperature up to 600ºC high-temperature environment. We observe clear consistency in resonances measured in heating up and cooling down processes, validating that the AlScN/SiC diaphragm resonators can operate robustly in high-temperature environment up to 600°C without observable degradation. Raman spectroscopy results indicate that the turning points of the peak positions of the longitudinal optical (LO) phonon modes of both 3C-SiC and AlScN occur in almost the same temperature region where the turning point of temperature coefficient of resonance frequency (TCf) is observed. We calibrate the device temperature by measuring Raman peak of the silicon (Si) substrate of the chip, yielding a crystal lattice temperature of 410ºC at the heater setting temperature being 600ºC. The heating efficiency can be improved by clamping the chip using a clip or jig with lower thermal conductivity.