Numerical analysis of SAW pressure sensors based on AIN/Si structure

Abstract

The performance of the AlN/Si-based Surface Acoustic Wave (SAW) device is explored as a pressure sensor. The device structure is investigated and discussed using a finite element method (FEM) applied by Comsol Multiphysics. A thin chemically resistive polyisobutylene (PIB) is used as a sensing layer. The results show that the working frequency of the device has significantly improved to a value up to ∼1.257 GHz at normalized thicknesses of the AIN piezoelectric substrate (kh AlN=3) for the Rayleigh wave mode. The device response of the pressure sensor of the Rayleigh mode wave is examined under a range of pressure varying from 5 atm to 15 atm, using several kh AlN up to 5. The relationship between the particle displacement and the penetration depth into the AlN film on Si for the Rayleigh mode is also investigated. The present AIN/Si based SAW device results in electromechanical coupling coefficient, for the fundamental Rayleigh mode in the range of 0.13% to 0.21% as the kh AlN decreases from 5.0 to 0.5. The simulation results conveyed the merits of employing the AIN to implement SAW pressure sensors and other high-efficiency energy harvesting devices. Furthermore, the results reveal the consistency of the negative sign of the e 15 piezoelectric constant.