High frequency piezoelectric micromachined ultrasonic transducers for imaging applications

Abstract

Methods for fabricating high frequency ultrasound transducer and array based on piezoelectric films and MEMS technology are presented in this paper. Piezoelectric PZT films up to 30 μm-thick deposited on silicon substrate have been prepared by a modified sol-gel process. The raw materials included lead acetate trihydrate and zirconium n-propoxide and titanate isoproxide. The sol-gel PZT solutions were prepared using above materials and 2-methoxyethanol as the solvent. Spin-coated films were annealed at 750 ^oC by a rapid thermal annealing (RTA) process. Thicker PZT films were fabricated by repeating this process and using a modified PZT composite solution. The high frequency single element transducers actuated by the PZT films were fabricated and pulse-echo measurement results show the transducers had a broad bandwidth and high central frequencies. The beam profile of one 103 MHz transducer was measured using a 8 μm diameter wire and a lateral resolution of 33 μm was observed. A micromachined process to fabricate high frequency linear array will be also presented.