Design and fabrication of a tiny micro-pressure sensor with improved linearity and sensitivity

Abstract

With the rapid development of key industries such as new energy vehicles, smart homes, smart phones and consumer grade drones, the demand for high performance miniature micro-pressure sensors is also growing promptly. At prssent, most of the pressure sensors of this type adopt a C-type structure, and the thickness of the sensitive diaphragm needs to be continuously thinned in order to improve the sensitivity of this type sensor, which leads to its sensitivity to etching errors and makes it difficult to ensure the linearity of the pressure sensor. Based on this, we designed a tiny micro-pressure half active Wheatstone bridge piezoresistive pressure sensor with C-type square diaphragm structure, whose area is reduced by shortening the number of leads and pads, through ion impantation on the surface of the diaphragm to create piezoresistors, using deep reactive ion etching (DRIE) technology to release the pressure sensitive diaphragm with length of 460 μm × 460 μm, thinkness of 7.5 μm. The buried oxygen layer in the SOI (silicon on insulator) can play a role of stopping the etching, which assures the uniformity of the released sensitive diaphragm and the linearity of the sensor while maintains its sensitivity. Before preparing a pressure sensor, simulation data is used to predict whether the test results meet the design requirements. In this paper, the influence of piezoresistors position offset on the performance of the pressure sensor is analyzed by means of simulation, which improves the accuracy of the designed model and guarantees its performance parameters can meet the design indicators. Finally, the static characteristics of the sensor is calibrated. The experimental results show that the sensitivity of the sensor is up to 0.538 mV/kPa in the range of 40 kPa at room temperature, and the nonlinear error is only 0.386% FS. This study provides some new ideas and references for the design work of high performance micro-pressure sensors.