title: Fabrication and characterization of piezoelectric micromachined ultrasonic transducers with thick composite PZT films.
abstract: Ferroelectric microelectromechanical systems (MEMS) has been a growing area of research in past decades, in which ferroelectric films are combined with silicon technology for a variety of applications, such as piezo-electric micromachined ultrasonic transducers (pMUTs), which represent a new approach to ultrasound detection and generation. For ultrasound-radiating applications, thicker PZT films are preferred because generative force and response speed of the diaphragm-type transducers increase with increasing film thickness. However, integration of 4- to 20-microm thick PZT films on silicon wafer, either the deposition or the patterning, is still a bottleneck in the micromachining process. This paper reports on a diaphragm-type pMUT. A composite coating technique based on chemical solution deposition and high-energy ball milled powder has been used to fabricate thick PZT films. Micromachining of the pMUTs using such thick films has been investigated. The fabricated pMUT with crack-free PZT films up to 7-microm thick was evaluated as an ultrasonic transmitter. The generated sound pressure level of up to 120 dB indicates that the fabricated pMUT has very good ultrasound-radiating performance and, therefore, can be used to compose pMUT arrays for generating ultrasound beam with high directivity in numerous applications. The pMUT arrays also have been demonstrated.
authors.affiliation: Microelectronics Centre, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798. ezhwang@ntu.edu.sg
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Wang
authors.forename: Weiguang
authors.initials: W
authors.lastname: Zhu
authors.forename: Hong
authors.initials: H
authors.lastname: Zhu
authors.forename: Jianmin
authors.initials: J
authors.lastname: Miao
authors.forename: Chen
authors.initials: C
authors.lastname: Chao
authors.forename: Changlei
authors.initials: C
authors.lastname: Zhao
authors.forename: Ooi Kiang
authors.initials: OK
authors.lastname: Tan
mesh_terms: D017076:Computer-Aided Design; D025802:Electric Capacitance; D004582:Electronics, Medical; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007854:Lead / Q000737:chemistry* / Q000528:radiation effects; D008567:Membranes, Artificial; D008904:Miniaturization; D014025:Titanium / Q000737:chemistry* / Q000528:radiation effects; D014159:Transducers; D014463:Ultrasonography / Q000295:instrumentation* / Q000379:methods; D015040:Zirconium / Q000737:chemistry* / Q000528:radiation effects
chemical_list: D008567:Membranes, Artificial; C065536:lead titanate zirconate; D007854:Lead; D015040:Zirconium; D014025:Titanium