Influence of Temperature on the Sensitivity of ZnO-Based MEMS Acoustic Sensor

摘要

This study investigates the temperature dependence of the sensitivity of ZnO-based MEMS acoustic sensor. The structure contains a capacitor using ZnO dielectric layer, on a 25 μm-thick silicon diaphragm. One micron-thick Al was used as top and bottom electrodes for the fabrication of capacitor. The value of dielectric constant of ZnO layer was found to be 12.5 by measuring the capacitance value at room temperature and 1 kHz frequency. The investigations showed that the value of dielectric constant of ZnO layer increases with temperature. A variation of 11 to 16.2 was observed in dielectric constant on changing the temperature of the device from -25℃ to 120℃. The corresponding dielectric loss (tan δ) also increased from 0.03 to 0.1. This variation of capacitance and the corresponding loss affects the sensitivity of the device, which was found to decrease from 432 μV/Pa at -25℃ to 290 μV/Pa at 120℃.