Geometrical dimension impact for performance of CMOS based circular shape aluminum nitride (AlN) piezoelectric micromachined ultrasonic transducer (PMUT)

Abstract

This paper proposed impact of geometrical dimension for circular shaped aluminum nitride (AIN) based piezoelectric micromachined ultrasonic transducer (PMUT) for achieving best operating performance. The PMUT is focusing on 25–35 MHz frequency for biomedical application. Thus, this paper investigates the minimum geometrical dimension of PMUT with limitation of CMOS compatible process by using finite element analysis (FEA) ONSCALE software. This paper proposed comparative study that focused on AlN thickness and substrate diameter for PMUT in order to determine better design for better PMUT performance. Finite element analysis (FEA) of ONSCALE software was used for numerical analysis simulation. The simulation was carried out for AlN thickness and substrate diameter for impact study on PMUT performance with CMOS limitation. The PMUT displacement performances and frequencies for different AIN thickness and substrate diameter are analyzed. Firstly, the PMUT performance is analyzed for AlN thickness when the substrate diameter and cavity height are fixed. Secondly, the PMUT performance is analyzed for substrate diameter when the AlN thickness and cavity height are fixed. In this work, for frequency 25–35 MHz, the maximum PMUT displacement is achieved at AlN thickness $\mathbf{1.1} \mu\mathbf{m}$ , substrate diameter $\mathbf{22.5} \mu\mathbf{m}$ , and cavity height $\mathbf{3.0} \mu\mathbf{m}$ . The substrate diameter has no impact for PMUT displacement when the AlN thickness and cavity height is fixed. This work provides helpful information for designing PMUT for better performance of displacement.