Research of Long-Term Stability of High-Sensitivity Piezoresistive Pressure Sensors for Ultralow Differential Pressures

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 S-0,S-5 after = (34.5 +/- 6.0) mV/V/kPa, nonlinearity 2K(NL 0.5 after) = (0.71 +/- 0.47) %/FS and temperature hysteresis up to 0.5% in the temperature range from-30 degrees C to +60 degrees C. 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.