High overtone bulk acoustic resonators for high temperature sensing applications

High overtone Bulk Acoustic Resonators have been developed for radio-frequency application such as oscillator stabilization, but also as an alternative to surface acoustic wave resonator for sensor development. In the present work, the possibility to operate such devices at temperature up to 800°C is investigated experimentally. Devices built using Aluminum Nitride deposited on Silicon with Platinum electrodes have been manufactured and resonance frequencies near the 434-MHz centered ISM band have been characterized from room conditions to 800°C. Although the exposition to such a temperature yields changes in the device response, it turns out that the operation is partly reversible and that these HBARs could operate without major defects for several tens of hours at such regimes. The development of wireless temperature sensors on this base then reveals accessible.