Piezoelectric Resonator Layout for Charge-Stable Frequency Adjustment
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Solution Overview
Problem
In MEMS vibrators, variations in resonant frequency occur due to manufacturing variations and electric charges on insulator layers, affecting the resonant frequency, which existing technologies have not effectively addressed.
Innovation Solution
A resonator design featuring a piezoelectric film between electrodes, a protective insulator film, and a conductive frequency adjusting film connected to the electrodes, which suppresses the impact of electric charges on the resonant frequency by allowing charge transfer and adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a mass portion including an insulator layer and conductive layer is formed on the vibration arm for frequency adjustment, then the resonant frequency can be adjusted, but the insulator layer becomes charged and generates Coulomb force that causes resonant frequency fluctuation
Solution Approach 1:
The patent introduces a conductive layer between the insulator layer and the vibration arm to serve as an intermediary that prevents charge accumulation. This conductive layer acts as a charge drain path, allowing accumulated charges to be discharged through the conductive layer and ground connection, thereby eliminating the Coulomb force that causes frequency instability while preserving the mass loading effect for frequency adjustment
Solution Approach 2:
The patent changes the electrical parameter (conductivity) of the mass portion by adding a conductive layer with specific conductivity properties. This modification transforms the mass portion from an insulating structure that accumulates charge to a conductive structure that can dissipate charge, thereby resolving the frequency stability issue while maintaining the ability to adjust resonant frequency through mass variation
2Adaptability or versatility
If ion beam or pyroelectric material is used for frequency adjustment, then the resonant frequency can be tuned, but electric charge accumulates on the insulator layer causing frequency fluctuation
Solution Approach 1:
The conductive layer serves as a mediator between the insulator layer and the external environment, providing a controlled path for charge dissipation. When ion beam or pyroelectric material is used for frequency adjustment, any accumulated charges are rapidly discharged through the conductive layer, preventing Coulomb force generation and maintaining frequency stability throughout the tuning process
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design effectively stabilizes the resonant frequency by transferring and releasing electric charges, reducing frequency variations and improving the reliability of MEMS vibrators.
Implementation Method 1
a piezoelectric film that is provided between the first electrode and the second electrode, has an upper surface opposing the first electrode, and vibrates in a predetermined vibration mode when a voltage is applied between the first electrode and the second electrode
Implementation Method 2
a conductive film made of an conductor and provided opposing the upper surface of the piezoelectric film with the protective film interposed therebetween, wherein the conductive film is electrically connected to any one of the first electrode and the second electrode
Data Source
AI summary
A resonator is provided having a first electrode and a second electrode; and a piezoelectric film that is disposed between the first and second electrodes, has an upper surface opposing the first electrode, and that vibrates in a predetermined vibration mode when a voltage is applied between the first and second electrodes. Moreover, the resonator includes a protective film made of an insulator and disposed opposing the upper surface of the piezoelectric film with the first electrode interposed therebetween. Furthermore, a conductive film made of a conductor is provided that is disposed opposing the upper surface of the piezoelectric film with the protective film interposed therebetween, where the conductive film is electrically connected to any one of the first and second electrodes.