Long-term stability of output characteristics of piezoresistive pressure sensor chips in the form of microelectromechanical system (MEMS) is one of the most important parameters. The research analyzes the variation of useful signal of high sensitive pressure sensor chips and its errors in mechanical and temperature characteristics, which are also time-dependent. The main feature of this study is the application of the previously developed construction of mechanical part, which allows to achieve a balance between extremely high sensitivity and low error rates for ultra-low pressure range. The research demonstrates the changes after 5 years of aging for 24 pressure sensor chip samples (chip dimension 6.15x6.15 mm 2) for pressure range of 0.5 kPa with sensitivity S0,5 after = (34.5 ± 6.0) mV/V/kPa, nonlinearity 2KNL 0.5 after = (0.71 ± 0.47) %/FS and temperature hysteresis up to 0.5% in the temperature range from-30 ⁰C to +60 ⁰C. The results of long-term stability of useful signal shows that the errors for 10 out of 24 samples does not exceed the values of 1.5%, which mostly connects with influence of residual mechanical stresses (RMS) from the assembly design of pressure sensor.

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 mm 2) 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.

The investigation of the pressure sensor chip’s design developed for operation in ultralow differential pressure ranges has been conducted. The optimum geometry of a membrane has been defined using available technological resources. The pressure sensor chip with an area of 6.15х6.15 mm has an average sensitivity S of 34.5 mV/кPa/V at nonlinearity 2KNL = 0.81 %FS and thermal hysteresis up to 0.6 %FS was created. Owing to the chip connection with stop elements, the burst pressure reaches 450 кPa.

A mathematical model of an ultrahigh sensitivity piezoresistive chip of a pressure sensor with a range from -0.5 to 0.5 kPa has been developed. The optimum geometrical dimensions of a specific silicon membrane with a combination of rigid islands to ensure a trade-off relationship between sensitivity (Ssamples = 34.5 mV/kPa/V) and nonlinearity (2KNL samples = 0.81 %FS) have been determined. The paper also studies the range of the membrane deflection and makes recommendations on position of stops limiting diaphragm deflection in both directions; the stops allow for increasing burst pressure Pburst up to 450 кPa. The simulated data has been related to that of experimental samples and their comparative analysis showed the relevance of the mathematical model (estimated sensitivity and nonlinearity errors calculated on the basis of average values are 1.5% and 19%, respectively).