Design and Fabrication of Piezoelectric Micromachined Ultrasound Transducer (pMUT) with Partially-Etched ZnO Film.

Junhong Li,Wei Ren,Chenghao Wang,Guoxiang Fan

doi:10.3390/s17061381

Abstract

A square piezoelectric composite diaphragm was analyzed by the finite element method to enhance the sensitivity of a piezoelectric micromachined ultrasound transducer (pMUT). The structures of electrode and piezoelectric film were optimized and a centric electrode was designed to avoid the counteraction of stress in the centre and edges. In order to further improve the sensitivity; a pMUT with partially-etched piezoelectric film was adopted. The receive and transmit sensitivities of the pMUT were analyzed in details. The receive sensitivity of pMUT with partially-etched ZnO film is 3.3 dB or 6.8 dB higher than those with a centric and whole electrode, respectively; and the amplitude of a partially-etched ZnO film pMUT under a certain voltage is 5.5 dB and 30 dB higher than those with centric and whole electrode separately. Two pMUT-based ZnO films were fabricated by micromachining technology and their receive and transmit sensitivities were tested. The ZnO films deposited by direct current (DC) magnetron sputtering exhibit a densely packed structure with columnar crystallites. The test results show that the structure of the square diaphragm with partially-etched piezoelectric layer can significantly improve the transducer sensitivity. The receive sensitivity and transmit sensitivity are −238.35 dB (ref. 1 V/μPa) and 150.42 dB (ref. 1 μPa/V); respectively.

Highlights

Micromachined ultrasound transducers (MUTs) have been extensively developed
The MUTs work on either electrostatic or piezoelectric principles, and they can be be classified as capacitive MUTs and piezoelectric MUTs
In order to improve the properties of piezoelectric micromachined ultrasound transducer (pMUT), Belgacem studied the influence of centred and ring top electrode on the coupling factor of pMUT with a circular piezoelectric composite diaphragm released by the expensive deep reactive

Summary

Introduction

Micromachined ultrasound transducers (MUTs) have been extensively developed. Arrays with high element density, small element size and high resonant frequency are easy to realize by MUT [1,2,3]. The piezoelectric film and structure of pMUT are two important factors that affect the sensitivity. Thethis vibration diaphragms of pMUTs include was removed of outside theinclude electrode this can films improve the coupling factor [28].and. The working process of pMUTs involves theory analysis of square composite diaphragms difficult to be carried out by of the analytical methods. The piezoelectric working process of pMUTs involvesisthe transmission and reception transmission and reception of sound waves, the receive and transmit sensitivity of pMUTs analytical methods. The working process of pMUTs involves the transmission and reception of need sound waves, the receive and transmit sensitivity of pMUTs need to be analyzed. Sensitivities of pMUTs pMUTs withdesigned partially-etched and whole films were tested and process.

Finite

Microfabrication of pMUT

Results and Discussion

13. Receive

Conclusions