MEMS Resonator Weight Structure for Stable Frequency Tuning
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Solution Overview
Problem
In MEMS vibrators, manufacturing variations can cause fluctuations in resonant frequency due to electric charges on insulator layers, which affect the accuracy of the resonant frequency adjustment.
Innovation Solution
A resonance device design with a resonator featuring a base and vibration arms, where the lower lid has a protruding portion with an insulating film, and the vibration arms have a weight portion with a conductive film, configured such that the distance between the weight portion and the protruding portion is larger than the distance between the weight portion and the holding portion, effectively canceling electric charges and stabilizing the resonant frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ion beam or similar methods are used to adjust resonant frequency by reducing mass parts, then resonant frequency can be adjusted, but electric charge accumulates on the insulator layer causing resonant frequency fluctuation
Solution Approach 1:
The patent extracts and removes the harmful electric charge from the insulator layer by introducing a conductive layer that neutralizes the charge. This allows the mass part to maintain its frequency-adjustment function while eliminating the charge accumulation problem that caused frequency fluctuation.
Solution Approach 2:
The conductive layer acts as an intermediary between the insulator layer and the external environment. It mediates the charge accumulation problem by providing a path for charge dissipation, thereby stabilizing the resonant frequency while preserving the mass part's structural integrity and frequency adjustment capability.
2Manufacturing precision
If mass part with insulator layer is formed on vibration arm, then resonant frequency can be adjusted, but Coulomb force from electric charge causes frequency fluctuation
Solution Approach 1:
The patent converts the harmful Coulomb force generated by electric charge on the insulator layer into a beneficial effect by introducing a conductive layer that attracts and neutralizes the charge. The conductive layer transforms the charge accumulation problem into a charge neutralization solution, eliminating frequency fluctuation while maintaining the mass part's weight and frequency adjustment properties.
3Manufacturing precision
If additional etching is performed during or after manufacturing to adjust frequency, then resonant frequency can be tuned, but manufacturing complexity increases
Solution Approach 1:
The patent merges the frequency adjustment function with the mass part formation process. By forming the mass part with both insulator and conductive layers in an integrated structure, the design combines charge neutralization and frequency adjustment into a single manufacturing step, eliminating the need for separate additional etching processes.
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 configuration suppresses the influence of electric charges on the insulator and conductive layers, reducing frequency fluctuations and enhancing the stability of the resonant frequency.
Implementation Method 1
a piezoelectric film, a lower electrode and an upper electrode provided so as to face each other with the piezoelectric film interposed therebetween
Implementation Method 2
the weight portion having a conductive film formed on the insulating film... suppresses influence of an electric charge in the insulator layer
Data Source
AI summary
A resonance device includes a resonator, an upper lid, and a lower lid. The resonator includes a vibration portion, a frame, and holding arms. The vibration portion includes a base and a plurality of vibration arms. The lower lid has a protruding portion protruding between two adjacent vibration arms, the protruding portion has an insulating film, the vibration arms have a weight portion that has a conductive film formed on the insulating film, and in a direction in which the plurality of vibration arms extend, a first distance between the weight portion of any one of the two adjacent vibration arms and the holding portion is less than a second distance between the weight portion and the protruding portion.