Effect of internal stress on nonlinearity and sensitivity of a pressure sensor with SiN composite diaphragm

This paper presents a simulation model that predicts the nonlinearity behavior of a piezoresistive pressure sensor under different film internal stresses. The ultra-compact sensor has a sensing diaphragm geometry of only 360μm×80μm, thereby shrinking the sensor chip size to 840μm×840μm. The absolute-pressure sensor is designed and fabricated by a surface-micromachining process. Analytical models based on small- and large-deflection theories are applied to predict the nonlinearity of the pressure sensor. The measured nonlinearity data well validate the predicted result from the modeling. The simulation results show that internal stress in the film can improve the linearity of the pressure sensor by lowering the sensitivity. The ultra-miniaturized sensor is promising in consumer electronics in terms of low-cost applications.