Piezoelectric Resonator Layout for Stray Capacitance Control
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Solution Overview
Problem
Piezoelectric resonators connected in parallel experience decreased characteristics due to stray capacitance, which affects their performance in small-sized electronic devices.
Innovation Solution
A resonance device with a substrate, insulating film, and vibration regions featuring lower electrodes with differing electric potentials to prevent antiphase vibration, and a package that includes a ground terminal for grounding the substrate to mitigate stray capacitance effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If vibration area is decreased to reduce device size, then device size is reduced, but resonant resistance increases and oscillation margin decreases
Solution Approach 1:
The patent combines multiple vibration arms (first vibration arm and second vibration arm) into a single integrated structure that shares common electrodes. This merging approach increases the effective vibration area without proportionally increasing device footprint, thereby maintaining oscillation margin while achieving size reduction through efficient space utilization
2Quantity of substance
If parallel connection structure is used to increase capacitance, then combined capacitance increases, but stray capacitance occurs due to low resistivity silicon layer causing short circuit
Solution Approach 1:
The patent introduces an insulating layer as an intermediary between the lower electrodes and the silicon layer. This mediator prevents direct electrical contact that would cause short circuits, thereby eliminating the harmful stray capacitance effect while preserving the beneficial parallel connection capacitance increase
Solution Approach 2:
The patent extracts the problematic direct connection between lower electrodes and silicon layer by removing the conductive path through the silicon layer. By taking out this harmful electrical connection while maintaining the mechanical and electrical functionality through the insulating layer, the stray capacitance is eliminated
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 enhances the coupling coefficient and oscillation margin of the piezoelectric resonator by utilizing stray capacitance as additional capacitance, while maintaining the resonator's size and performance.
Implementation Method 1
a piezoelectric resonance device for which a MEMS (Micro Electro Mechanical Systems) technique is used
Implementation Method 2
at least one vibration region vibrates in antiphase with another vibration region
Data Source
AI summary
A resonator that includes a substrate, an insulating film that is formed on the substrate, and vibration regions each of which is formed on the insulating film and includes lower electrodes that are formed on the insulating film, a piezoelectric film that is formed on the lower electrodes, and an upper electrode that is formed on the piezoelectric film. At least one lower electrode of the lower electrodes that are formed on the insulating film has an electric potential that differs from an electric potential of another lower electrode such that at least one vibration region vibrates in antiphase with another vibration region. Moreover, a package seals a resonator and includes the substrate, the insulating film, and the vibration regions and includes a ground terminal for grounding the substrate.