Design of AlN and PZT pMUT for high-quality ultrasound imaging

Piezoelectric micromachined ultrasound transducer (PMUT) technology has been investigated as a promising alternative to conventional bulk piezoelectric transducer for medical imaging, mainly due to its low cost, high density and easier integration with CMOS circuits. In PMUT design, transmit efficiency is one of the key concerns to achieve high-quality imaging. In this paper, we present a quantitative study of both the pMUT configurations and the material characteristics of their piezoelectric layers in terms of the transmit efficiency. Considering the material-related issues, we compared PZT and AlN as the piezoelectric layers in pMUT design. As the radius of the pMUT reaches 40 µm, the transmit efficiency peaks while the properties of PZT-based pMUT is 34 times higher than that of AlN-based pMUT. Moreover, the sealed pMUT with 8 holes at the radius of 3.5 um enables the transmit efficiency 1.8 times higher than the clamped one does.