Design and Application of a High Sensitivity Piezoresistive Pressure Sensor for Low Pressure Conditions.

Huiyang Yu,Jianqiu Huang

doi:10.3390/s150922692

Abstract

In this paper, a pressure sensor for low pressure detection (0.5 kPa–40 kPa) is proposed. In one structure (No. 1), the silicon membrane is partly etched to form a crossed beam on its top for stress concentration. An aluminum layer is also deposited as part of the beam. Four piezoresistors are fabricated. Two are located at the two ends of the beam. The other two are located at the membrane periphery. Four piezoresistors connect into a Wheatstone bridge. To demonstrate the stress concentrate effect of this structure, two other structures were designed and fabricated. One is a flat membrane structure (No. 2), the other is a structure with the aluminum beam, but without etched silicon (No. 3). The measurement results of these three structures show that the No.1 structure has the highest sensitivity, which is about 3.8 times that of the No. 2 structure and 2.7 times that of the No. 3 structure. They also show that the residual stress in the beam has some backside effect on the sensor performance.

Highlights

Nowadays, energy and environmental problems are of great concern and pressure sensors play an important role in environmental monitoring [1]
The usage of low pressure sensors can be expended to spatial orientation and 3-D
It was found after fabrication that the beam-membrane had residual stress and this induced some effects on the testing results

Summary

Introduction

Energy and environmental problems are of great concern and pressure sensors play an important role in environmental monitoring [1]. In early 1990s, Bao et al reported for the first time beam-membrane structures for stress concentration to improve the sensitivity of pressure sensors [5,6,7]. In 2010, Tian et al were the first to report a cross-beam structure [8]; the sensor is proved to show improved sensitivity under low pressure conditions. The piezoresistive pressure sensors are the most used because of their significant advantages such as high sensitivity, excellent linearity and repeatability [12] Their principle is that the resistance of a piezoresistor changes when the piezoresistor is exposed to stress. The membrane thickness cannot decrease infinitely, because it will lead to nonlinear effects between stress and applied pressure. When a beam-membrane deforms, the stress will concentrate in the beam

Experimental Section

The Beam-Thickness and the Stress

The Beam-Width and the Stress

The Residual Stress and the Stress

Results and Discussion

Conclusions