High sensitivity MEMS ultrasound arrays by lateral ferroelectric polarization

摘要

This paper discusses the design of advanced micromachined ferroelectric ultrasound transducers for use at 3 MHz. 16×16 arrays of resonant monomorph sensors have been constructed, with sol-gel PZT as the active ferroelectric layer deposited on insulating layers of ZrO{sub}2 and SiO{sub}2. A novel in-plane polarization of the PZT is used to maximize sensitivity, while trading off reduced output capacitance to match the CMOS buffer electronics. This results in about 30 dB improved sensitivity compared to conventional polarizing across the thickness of the PZT layer. Fluid-filled through wafer holes are used as an acoustic matching network to achieve resonance at both 1 and 3 MHz. A lumped element equivalent circuit model is presented, as well as Finite Element Analysis results. Performance predictions for projector efficiency and receive response are given. Test results are presented including transmit response, receive sensitivity, and frequency response.