Modeling the Sensitive Element of the Sandwich Construction of a Capacitive Micromechanical Accelerometer, Taking into Account the Change in the Dielectric Constant

• Published in: Russian microelectronics Vol. 50; no. 7; pp. 549 - 554
• Main Authors: Ye Koh Koh Aung, Simonov, B. M., Timoshenkov, S. P.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.12.2021; Springer Nature B.V
• Subjects: Accelerometers; Capacitance; Capacitors; Circuits; Electrical Engineering; Electrodes; Engineering; Feedback control; Low noise; Modelling; Movement; Parameter sensitivity; Permittivity; Power consumption; Sandwich structures; Sensitivity; Stability; Ultimate tensile strength; relative dielectric constant of capacitors; sandwich construction; sensitive element of a capacitive micromechanical accelerometer
• ISSN: 1063-7397; 1608-3415
• DOI: 10.1134/S1063739721070027

By using the capacitive measurement principle, high-performance micromechanical accelerometers provide low noise and power consumption, cost efficiency, and reliability. Capacitive sensors based on changes in the gap between the electrodes, as a rule, require closed-loop control, which increases the level of complexity of the measurement circuit and increases power consumption. Capacitive sensitive elements with a change in the electrode overlap area have a good linearity of the capacitance versus displacement and a large measurement range, but they are more difficult to manufacture. This paper presents and investigates a model of a sensitive element of a sandwich design of a capacitive micromechanical accelerometer, the functioning of which is based on the use of a change in the relative dielectric constant of the dielectric of capacitors due to the introduction of a movable inertial mass between the electrodes of the capacitors, moving under the action of acceleration. As a result, there is a change in capacitance in the output measuring circuit. It is shown that the considered model is sensitive to acceleration and resistant to temperature changes, with low residual mechanical stress in the sensitive element. The modeling and calculations are performed using the Ansys and SolidWorks software. It is found that the movement of the moving mass along the axis of sensitivity X is more than five times the movement of the moving mass along the nonworking axes, and the change in the capacitance between the electrodes along the axis X is almost 2500 times more than the changes in capacitance between electrodes along the nonworking axes Z and Y . Calculations have shown that for all values of the acting acceleration (up to 30 g), the mechanical stress in the sensitive element is much less than the ultimate strength of silicon, equal to 440 MPa. It is found that variation of the temperature from –40 to 85°C leads to minor changes in capacitance along the working axis (0.0025–0.003 pF). This indicates the temperature stability of the investigated micromechanical accelerometer sensing element. The results of the analysis show that the developed and investigated model of the sensitive element of the sandwich design ensures the sensitivity of the micromechanical accelerometer and the stability of its parameters.