Ultra Temperature-Stable Bulk-Acoustic-Wave Resonators with SiO 2 Compensation Layer

This paper describes temperature compensated bulk acoustic-wave resonators (BAR) with temperature coefficient of frequency (TCF) less than 1 ppm/degC 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 Al/ZnO/Al/SiO
₂
on a surface micromachined cantilever that is released by XeF
₂
vapor etching and high-overtone acoustic resonator (HBAR) composed of an Al/ZnO/Al resonator on a bulk micromachined SiO
₂
/Si/SiO
₂
supporting substrate.