Feasibility study on fabrication of piezoresistive pressure sensors using silicon micromachining technology

This paper describes a feasibility study on design and fabrication of piezoresistive pressure sensors for the pressure range 0.5 - 350 bar, using silicon micromachining technology. Different technological steps are studied in order to optimize the fabrication process and the electro-mechanical parameters of the device. The sensing membrane is etched in (100)-oriented silicon by anisotropic etching using different concentration of TMAH (tetramethyl anmmnium hydroxide) in water solution. The software package ISE-TCAD. based on the finite element method (FEM), has been used to calculate the stress distribution on the membrane in order to provide information for the proper location of the piezoresistors.Devices with different membrane thickness (between 120 and 40 um) have been investigated. All devices show a good linearity (better than 1%) and their sensibility ranges from 3 to 58 mV/Vbar depending on the membrane thickness.