Universal Concept for Fabricating Low Residual Stress PZT Film-Based PMUT on Silicon Wafer Using Bottom-Up Method

A novel bottom-up scheme for fabricating low residual stressed piezoelectric micromachined ultrasonic transducers (PMUTs) on a silicon wafer is first proposed worldwide. We successfully integrated the hydrothermal lead zirconium titanate (PZT) film on foil into the silicon wafer with micromachined thru-holes by SU8 photoresist adhesive bonding. The photolithography, metal deposition, etching, and wire bonding processes are then executed on the "PZT film on silicon wafer" to complete the PMUT. The proof-of-concept PMUT is demonstrated, with the fundamental resonant frequency of 648 kHz and 12 kHz bandwidth operated in the air when driven with a sinusoidal wave of 10 V
peak-to-peak
. The proposed bottom-up scheme opens doors to a bright feature for fabricating the PMUTs with versatile designs and circuit integration.