Phased Array Based on AlScN Piezoelectric Micromachined Ultrasound Transducers Monolithically Integrated on CMOS

In this work we present an array of piezoelectric micromachined ultrasound transducer (PMUT’s) based on AlScN piezoelectric layer, monolithically integrated on top of a 130 nm CMOS circuit. The ${7}\times {7}$ array along with the analog-front-end circuit has been configured to work as a linear phased array. Experiments carried out have demonstrated the homogeneous PMUT’s behavior, showing a small dispersion in terms of frequency, bandwidth, and sensitivity. The feasibility of easily performing a transmission beam steering and focusing has been proven. In particular, the beam directivity has been characterized in terms of the width of the main lobe. The integrated CMOS analog-front-end allows the reduction of parasitic elements and noise, improving the signal to noise ratio (SNR). As a proof of concept, a B-mode image, with a 16 dB dynamic range, using a single ${7}\times {1}$ AlScN PMUT-on-CMOS channel as a receiver has been obtained.

I. Introduction

The use of ultrasound has demonstrated a great potential in very diverse fields (medicine [1], range finding [2], [3], communication and power transfer channels [4], fingerprint sensor [5], [6]). Since the first medical application in the 1950s as imaging system, where ultrasound systems were used for diagnostic, nowadays their use in both surgical applications (where high intensity focused ultrasound is used for destruction of tissue [7]) and therapeutic applications (such as neuromodulation [8], [9]) is well known. In all these cases, miniaturization and resolution are a must.