High-Sensitivity Saw Pressure Sensor Based on Single Crystal Linbo3 Film with Silicon Cavities

Abstract

In this paper, we proposed a surface acoustic wave (SAW) pressure sensor based on a 4-inch silicon-based single-crystal LiNbO3 film. Firstly, finite element simulation was carried out to obtain resonant frequency and diaphragm force variation. The sensor was then designed based on the simulation results. Pressure changes cause substrate deformation, primarily changing the Interdigital transducer (IDT) structure, which results in a frequency shift of the SAW pressure sensor. Our sensor is compatible with micro-electro-mechanical system (MEMS) process. Deep reactive ion etching (DRIE) process enables cavity fabrication, which simplifies the process and avoids additional fabrication of the chamber. After encapsulating the devices with ultraviolet (UV) adhesive, resonant frequency is measured as 91.592MHz at atmospheric pressure. We tested the devices in the range of 0-300kPa. The device is capable of maintaining high sensitivity of 873.437ppm/MPa with linear behavior. The proposed SAW pressure sensor has promising applications in confined production monitoring systems.

Keywords: MEMS, single-crystal LiNbO3, surface acoustic wave, pressure sensor