Thermal compensation for aluminum nitride Lamb wave resonators operating at high temperature

Thermal compensation for aluminum nitride (AlN) Lamb wave resonators operating at high temperature is experimentally demonstrated in this study. By adding a compensating layer of silicon dioxide (SiO₂), the turnover temperature can be designed for high temperature operation by varying the normalized AlN thickness (h_AlN/λ) and the normalized SiO2 thickness (h_SiO2/λ) in the AlN/SiO₂ composite stack. With different designs of h_AlN/λ and h_SiO2/λ, the Lamb wave resonators were well temperature-compensated at 214°C, 430°C, and 542°C, respectively. Furthermore, several testing cycles in the full temperature range from 25°C to 700°C were taken to demonstrate the repeatability of the frequency characteristics. This thermal compensation technology is promising for future applications to piezoelectric resonators, filters, and sensors at high temperature.