A method for evaluating acoustic Bragg reflector by ultrasonic microscope

Bragg reflector in solidly mounted resonators (SMR) is usually evaluated by comparing entire impedance properties of SMR with the properties of free standing FBAR. Therefore, we cannot obtain piezoelectric layer and Bragg reflector separatory. We here present a experimental method for evaluating acoustic properties of Bragg reflectors using pulse-echo method in the GHz ranges. High quality Sc
0.40
Al
0.60
N film transducers with acoustic conversion loss of 5.4 dB and fractional band width of 106% were employed. Ta
2
O
5
/SiO
2
Bragg reflectors were prepared as a test sample. As a result, the experimentally extracted mechanical properties of Bragg reflector showed good agreement with theoretical prediction simulated by Mason's equivalent circuit model.