High-Q and low TCF HBAR based on LiTaO3 substrate

This work presents a comparison between three different High-overtone Bulk Acoustic Resonators based on different materials. Furthermore, the goal of this work is to realize a High-overtone Bulk Acoustic Resonators presented a temperature coefficient of frequency less than 10 ppm over a wide range of temperature around a turnover temperature, and a Q.f product higher than 5×10¹³ Hz. After a discussion about the choice of materials to achieve such resonator and the description of our microfabrication, three High-overtone Bulk Acoustic Resonators based on a Lithium of Niobate, Quartz, Lithium of Tantalate, AlN and Sapphire materials are compared in term of the temperature coefficient of frequency, the Q.f product and the phase noise. The new HBAR exhibits a Q.f product around 3.7×10¹³ Hz, a turnover around 55°C with a parabolic shape and a temperature coefficient of frequency around +/-4 ppm/K.