High-quality-factor piezoelectric cantilever beam density sensor chip and working method and preparation method thereof

Abstract

The invention discloses a high-quality-factor piezoelectric cantilever beam density sensor chip and a working method and a preparation method thereof. The high-quality-factor piezoelectric cantileverbeam density sensor chip comprises a silicon substrate and a silicon micro-cantilever beam resonator, wherein the silicon micro-cantilever beam resonator comprises a micro-cantilever beam suspension structure, a clamped beam structure, a piezoresistive beam structure and a piezoresistive connection beam structure. The silicon micro-resonance cantilever beam structure is covered with a low-stress aluminum nitride piezoelectric film through an MEMS process, double piezoelectric electrodes are used for introducing alternating voltage with a certain frequency and generating piezoelectric driving force based on an inverse piezoelectric effect, four sensitive resistor strips on four piezoresistive beams are connected through metal leads on piezoresistive connecting beams to form a Wheatstone full bridge,and are used for detecting resonance stress and converting the resonance stress into voltage signals to be output by arranging the Wheatstone bridge, and a cantilever beam out-of-plane vibration mode can be obtained in a piezoelectric excitation mode. The density sensor chip has high sensitivity and high-quality factors in fluid, an application range of fluid density measurement can be remarkably widened, and measurement precision and sensitivity are high.

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...

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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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