A Novel Method for Determining Pressure Sensitivity of Underwater Shear-Stress Sensor Skins

This paper reports the development of a novel method for determining the pressure sensitivity of two types of surface micromachined underwater shear stress sensor skins for micro shear stress sensing applications. The two types of sensors consisted of a thin-diaphragm sensor and a thick-diaphragm sensor. The focus is on the use of a combination of metrology and numerical simulation to theoretically determine the pressure sensitivity of the sensors and compare to experimental data. Using this combination, the nitride diaphragm deflection, the intrinsic stress of the diaphragm, and the piezoresistive gauge factor of the polysilicon sensing element were successfully determined. For the thin-diaphragm sensor, the tensile intrinsic stress and gauge factor were determined to be 28 MPa and 4, respectively. For the thick diaphragm sensor, the average tensile intrinsic stress and gauge factor were 48 MPa and 12, respectively. Using these numbers, the pressure sensitivity of the shear stress sensors was successfully modeled and verified against experimental results.