Experimental determination of Al1-xScxN thin film thermo-electro-acoustic properties up to 140°C by using SAW resonators

1 µm thick sputtered Al1-xScxN films were used to fabricate SAW resonators with 2-20 µm wavelength and the frequency response was measured in the range of 20 °C to 140 °C. Extracted phase velocity dispersion curve was in good agreement with the simulated dispersion curve by FEM model. Moreover, for each investigated temperature, the corresponding phase velocity shift dispersion curves as a function of normalized thickness were shown in detail for each resonator layer (Si substrate, AlScN piezoelectric layer, and Pt electrode), and the independent thermal influence of the Si, AlScN, and Pt were evaluated. The temperature coefficients of frequency (TCF) of Al1-xScxN (x = 0, 0.14, 0.32) layer was calculated independently and compared with the combined TCFs of the resonators.