Bulk-micromachined, SOI-based half-bridge silicon strain gauges for high pressure applications

Abstract

This paper presents a new half-bridge silicon strain gauge fabricated on a silicon-on-insulator (SOI) substrate by MEMS bulk-micromachining technology. These gauges have holes etched through the wafer by deep reactive ion etching (DRIE) and a closed shape with four sides, unlike the current competitive devices with open structures. This unique design minimizes the shifting or rotation of gauge position and enhances the bonding strength during glass-frit bonding, leading to an improved sensor performance and yield, and hence, a reduction in sensor cost. The prototype half-bridge gauges were tested under strains ranging from -170 to 170 mu m m(-1) and were shown to have a linear output with a typical gauge factor of about 112 and an average hysteresis of 0.0192% FS. In addition, the full bridge output for 0-50 bar pressure shows a typical sensitivity of about 0.345 mVN/bar, a maximum thermal zero shift of -7.33% FS, and a thermal sensitivity shift of -0.17% FS/degrees C.