A Zero TCF SAW Contact Stress Sensor in ZnO/SiO2/Si Structure
A thin sensor based on surface acoustic wave resonator (SAWR) in ZnO/SiO2/Si structure for wireless contact stress measurement in thin gap is numerically analyzed. Firstly, the scheme of the SAWR stress sensor and surface effective permittivity for analyzing surface acoustic wave (SAW) in ZnO/SiO2/Si structure are introduced. Then, the phase velocity and electromechanical coupling coefficient of ZnO(1µm)/SiO2(1.4µm)/Si structure for the fundamental and first Rayleigh mode are obtained. For both Rayleigh modes, the temperature coefficient of frequency (TCF) for the structure at different frequency is calculated. Good temperature stability for the structure is achieved at frequency 1GHz for the first Rayleigh mode with averaged TCF about 0.04ppm/°C and stress sensitivity about 22ppm/MPa.
Paul P. Lin and Chunliang Zhang
J. X. Ding et al., "A Zero TCF SAW Contact Stress Sensor in ZnO/SiO2/Si Structure", Applied Mechanics and Materials, Vols. 105-107, pp. 1894-1898, 2012