Development of SAW pressure sensor using ZnO/Si structure

SAW devices have been shown to be suitable for many sensor applications. One of these applications is the pressure sensor. In this study, we present our ZnO deposition process. We also investigate the performance of SAW pressure sensors formed with a ZnO/Si(001) structure. The pressure sensitivities of the Rayleigh mode as well as the Sezawa mode are studied as a function of normalized thickness (kh=2πh_ZnO/λ). The experimental results show an opposite strain effect in the ZnO layer and Si substrate. A theoretical approach was developed to show the particle displacement. For a low kh_ZnO value, the ZnO and Si medium contribute to the sensor sensitivity. For higher kh_ZnO values, the particle displacement is mainly confined in the ZnO layer. This confirmed the opposite behaviors of the sensitivity with the kh_ZnO value. Enhancement of the SAW sensitivity is also presented by the development of a pressure membrane based on the developed device.