MEMS Resonator Structure for Precise Temperature-Frequency Tuning
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Solution Overview
Problem
Conventional MEMS resonators face challenges in precisely adjusting frequency temperature characteristics, which are influenced by the film thickness in the spring and mass regions, leading to suboptimal performance.
Innovation Solution
A MEMS resonator design featuring a vibration portion with a piezoelectric film and two temperature characteristic adjustment films, one with a positive temperature coefficient and the other with a negative temperature coefficient, exposed in specific regions to adjust frequency temperature characteristics with high precision, along with a frequency adjustment film in the mass region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single type of adjustment film is formed in the spring portion, then the manufacturing process is simple, but the frequency temperature characteristics cannot be adjusted with high precision
Solution Approach 1:
The patent applies local quality by forming different types of adjustment films (first adjustment film and second adjustment film) in different regions of the spring portion. The first adjustment film has different etching speed characteristics than the second adjustment film, allowing independent optimization of temperature characteristics in different areas. This enables precise control of frequency temperature characteristics while maintaining a manageable device structure.
Solution Approach 2:
The patent uses composite materials by combining multiple adjustment films with different material properties in the spring portion. Each adjustment film type responds differently to etching processes and temperature variations, creating a composite structure that achieves superior frequency stability across temperature ranges compared to single-material solutions.
2Manufacturing precision
If adjustment films with high mass reduction speed are formed in regions with large displacement, then frequency adjustment is effective, but temperature characteristics deteriorate
Solution Approach 1:
The patent applies local quality by assigning different adjustment film types to different functional regions. In regions with large displacement, one type of adjustment film is used to achieve effective frequency adjustment, while in the spring portion, another type is used to maintain temperature characteristics. This spatial differentiation of material properties resolves the conflict between frequency adjustment effectiveness and temperature stability.
3Manufacturing precision
If frequency adjustment is performed by etching, then the resonant frequency can be tuned, but the temperature characteristics change unfavorably
Solution Approach 1:
The patent applies local quality by forming adjustment films with specific etching resistance properties in the spring portion. These films are designed to resist etching in regions critical for temperature stability, while allowing controlled etching in other regions for frequency tuning. This enables frequency adjustment through etching while preserving temperature characteristics in critical areas.
Solution Approach 2:
The adjustment films act as intermediaries between the etching process and the underlying structure. By controlling the etching speed and mass reduction characteristics of these films, the patent mediates the effect of etching on both frequency and temperature characteristics, allowing frequency tuning while minimizing adverse temperature effects.
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 allows for precise adjustment of frequency temperature characteristics and resonant frequency, enhancing the precision and stability of the resonator's performance.
Implementation Method 1
a piezoelectric film formed between the first electrode and the second electrode
Implementation Method 2
a first temperature characteristic adjustment film having a positive temperature coefficient of frequency and a second temperature characteristic adjustment film having a negative temperature coefficient of frequency
Data Source
AI summary
A resonator is provided that includes a vibration portion having a first and second electrodes, a piezoelectric film disposed therebetween and having a first face opposing the first electrode, and at least two temperature characteristic adjustment films formed to oppose the first face of the piezoelectric film with the first electrode interposed therebetween. Moreover, the resonator includes a frame that surrounds at least part of the vibration portion; and a holding arm connecting the vibration portion to the holding portion. The vibration portion includes a surface opposing the first face of the piezoelectric film and having first and second regions in which an average amount of displacement is larger than an average amount of displacement in the first region when the vibration portion vibrates.