A high quality factor piezoelectric cantilever beam density sensor chip and its working method and preparation method

Abstract

The invention discloses a high-quality factor piezoelectric cantilever beam density sensor chip and its working method and preparation method, including a silicon substrate and a silicon micro-cantilever resonator, wherein the silicon micro-cantilever resonator includes a micro-cantilever suspension structure, a solid Support beam structure, piezoresistive beam structure and piezoresistive connecting beam structure. The silicon microresonant cantilever beam structure is covered with a low-stress aluminum nitride piezoelectric film through the MEMS process. The double piezoelectric electrodes are used to pass through a certain frequency of alternating voltage and generate piezoelectric driving force based on the inverse piezoelectric effect. Four piezoelectric electrodes The four sensitive resistance strips on the resistance beam are connected by the metal leads on the piezoresistive beam to form a Wheatstone full bridge, which is used to detect the resonant stress and convert it into a voltage signal output by arranging the Wheatstone bridge. The method can obtain the out-of-plane vibration mode of the cantilever beam. The density sensor chip has high sensitivity and high quality factor in the fluid, which can significantly improve the application range of fluid density measurement, and has high measurement accuracy and sensitivity.

Description

technical field [0001] The present invention relates to the field of MEMS (Micro Electromechanical Systems, micro-mechanical electronic systems) sensors, more specifically, to a high-quality factor piezoelectric cantilever beam density sensor chip and its working method and preparation method. Background technique [0002] The resonant density sensor based on MEMS technology detects the density characteristics of the fluid, relying on the change of the resonant frequency of the resonant device caused by the change of the additional mass of the attached fluid molecules. Compared with the traditional density meter, it has the advantages of small size, easy operation and high sensitivity. Measure performance. However, by affecting the quality factor of the density resonator, the fluid viscosity also has a non-negligible effect on the vibration stability of the resonator, as well as the applicability and measurement accuracy of the density measurement of medium and high viscosit...

AI Technical Summary

Problems solved by technology

However, by affecting the quality factor of the density resonator, the fluid viscosity also has a non-negligible effect on the vibration stability of the resonator, as well as the applicability and measurement accuracy of the density measurement of medium and high viscosity fluids. Due to the high requirements for density detection, MEMS density sensors still face significant problems such as narrow application range, low sensitivity, and poor convenience.

[0003] Quality factor and density measurement sensitivity are important indicators of MEMS resonant density sensors. Newtonian, non-Newtonian liquids, and low-viscosity liquids all have a significant impact on the resonator quality factor of MEMS resonant density sensors, and density resonators based on out-of-plane vibration and When the fluid molecules interact, the larger length-width surface is dominant, which increases the density sensitivity and at the same time, the quality factor is strongly affected by the fluid damping due to the larger compression film fluid damping; Although the density resonance can significantly improve the anti-fluid damping characteristics due to the damping effect of the synovial film, its vibration form makes the interaction with the fluid molecules only the width-thickness surface of the resonator, which greatly reduces the frequency caused by the change of fluid density changes, reducing the density measurement sensitivity

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