Research of MEMS pressure sensor stability with PDA-NFL circuit

Abstract

The stability of pressure sensor chip output characteristics using the piezoresistive method in the form of microelectromechanical system (MEMS) is one of the most important features for sensors, which simultaneously demonstrates the relevance of the principles for design construction and the choice of fabrication technology for all element structures. The research analyzes the changes in the useful signal, as well as errors in mechanical and temperature characteristics of highly sensitive pressure sensor chips, which are more explicitly dependent on external factors. The main feature of this development is the application of a new electrical circuit in the form of piezoresistive differential amplifier with negative feedback loop (PDA-NFL) utilizing bipolar junction transistors (BjT), which allows to achieve a balance between high sensitivity, small chip area and low errors. This research considers the variations of two batch with pressure sensor chip PDA-NFL samples (area 4.00x4.00 mm2) for range of 1 kPa after 4.5 years (8 samples, sensitivity S1 after = (40.6 ± 6.4) mV/V/kPa, nonlinearity 2KNL 1 after = (0,81 ± 0.15) %/FS) and range of 5 kPa after 3.0 years (14 samples, sensitivity S5 after = (11.2 ± 1.8) mV/V/kPa, nonlinearity 2KNL 5 after = (0.10 ± 0.06) %/FS). The study demonstrates the unidirectional influence of residual mechanical stresses (RMS) from the pressure sensor assembly design on sensitivity and nonlinearity when pressure is applied from different sides of chip, initial membrane deflection, and temperature hysteresis errors.