Optimization of electrode size for aluminum-nitride matrix ultrasonic transducers in the frequency range above 200 MHz

Yangjie Wei; Thomas Herzog; Henning Heuer

doi:10.1016/j.ultras.2012.10.018

Optimization of electrode size for aluminum-nitride matrix ultrasonic transducers in the frequency range above 200 MHz

Ultrasonics. 2013 Mar;53(3):739-44. doi: 10.1016/j.ultras.2012.10.018. Epub 2012 Nov 19.

Authors

Yangjie Wei¹, Thomas Herzog, Henning Heuer

Affiliation

¹ Graduate School of Chinese Academy of Science, State Key Laboratory of Robotics, Shenyang Institute of Automation, CAS, Shenyang, China. weiyangjie@sia.cn

PMID: 23218910
DOI: 10.1016/j.ultras.2012.10.018

Abstract

This paper describes an optimization method of the top electrode size for a thin film matrix ultrasonic transducer (M-UT) in the frequency range above 200 MHz. The goal of this work is to design an optimal top electrode size for an M-UT providing the maximal output peak-peak voltage (V(PP)) and the maximal signal-to-noise ratio (SNR) without additional electrical impedance matching. In order to reduce the complexity of the M-UT with more than 1000 elements, an intrinsic matching by electrode size variation is necessary. However, the size of a single element top electrode for an M-UT is related to the number of elements within a targeted sensor area, V(PP) and SNR of the transducer. In this paper, varying the active area of the top electrode from 0.09 to 25 mm(2) shows that for an Al-AlN-Al on silicon wafer configuration connected with a JSR Ultrasonics pulser/receiver (50 ohms), the optimal electrode size is 1 mm(2). With the optimal size electrode, the maximum output V(PP) of 0.08 V and the SNR of 42.93 dB are achieved at the resonance frequency of 225 MHz, and the bandwidth is 16.21 MHz.