Temperature compensation of thin AlN film resonators utilizing the lowest order symmetric lamb mode

Micromachined thin film plate acoustic wave resonators (FPAR) utilizing the lowest order symmetric Lamb wave (S0) propagating in highly textured 2 mum thick Aluminum Nitride (AlN) membranes have been successfully demonstrated. However, a notable drawback of the proposed devices is their non-zero temperature coefficient of frequency (TCF) which lies in the range -20 ppm/K to -25 ppm/K. In this work temperature compensation of thin AlN film Lamb wave resonators is studied and demonstrated. Temperature compensation, while retaining at the same time the device electromechanical coupling, is experimentally demonstrated. The zero TCF Lamb wave resonators are fabricated onto composite AlN/SiO₂ membranes. Q factors of around 1400 have been measured at a frequency of around 755 MHz.