The influences of residual stress on the frequency of ultrasonic transducers with composite membrane structure

초록

Arrayed ultrasonic sensors based on the piezoelectric thin Film (lead-zirconate-titanate : Pb (Zr0.52Ti0.48)O-3) having composite membrane structure are fabricated. Different thermal and elastic characteristics of each layer generate the residual stress during the high temperature deposition processes, accomplished diaphragm is consequently bowing. We present the membrane deflection effects originated from the residual stress on the resonant frequencies of the sensor chips. The resonant frequencies (f(r)) measured of each sensor structures are located in the range of 87.6 similar to 111 kHz, these are larger 30 similar to 40 kHz than the resultant frequencies of FEM. Tile primary factors off, deviations from the ideal FEM results are the membrane deflections, and the influence of stiffness variations are not so large on that. Membrane deflections have the effect of total thickness increase which sensitively change the f(r) to the positive direction. Stress generations of the membrane are also numerically predicted for considering the effect of stiffness variations on the f(r).

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