Ultra temperature-stable bulk-acoustic-wave resonators with SiO2 compensation layer

This paper describes temperature compensated bulk acoustic-wave resonators (BAR) with temperature coefficient of frequency (TCF) less than 1 ppm/degrees C at above 3 GHz. The temperature compensation is produced from the unique physical property of silicon dioxide's positive TCF, unlike most other materials that have negative TCF. Two types of resonators have been explored: film bulk acoustic resonator (FBAR) composed of A1/ZnO/A1/SiO2 on a surface micromachined cantilever that is released by XeF2 vapor etching and high-overtone acoustic resonator (HBAR) composed of an A1/Zn0/A1 resonator on a bulk micromachined SiO2/Si/SiO2 supporting substrate.