Configuration improvement for micropressure sensor with vibration interference

Presented is the configuration design for piezoresistive absolute micropressure sensors. A figure of merit called the performance factor (PF) is defined as a quantitative index to describe the comprehensive performances of a sensor including sensitivity, resonant frequency and acceleration interference. Two configurations are proposed through introducing islands and sensitive beams into the typical flat diaphragm. The stress distributions of sensitive elements are analysed by a finite element method. Multivariate fittings based on ANSYS simulation results are performed to establish the equations on surface stresses and deflections of the two sensors. Optimisation by MATLAB is carried out to determine the dimensions of the configurations. Convex corner undercutting is analysed to estimate the final dimensions of the islands. Each PF of the two configurations with the determined dimensions has been calculated and compared. Silicon bulk micromachining is utilised to fabricate the prototypes of the sensors. The outputs of the sensors under both static and dynamic conditions are tested. Experimental results reveal that the configuration with quad islands presents the highest PF of 210.947 Hz^1/4. The favourable overall performances make the sensor more suitable for altimetry.