Elastic Wave Device IDT Film Thickness Optimization
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Solution Overview
Problem
Existing elastic wave devices fail to sufficiently suppress degradation of frequency characteristics caused by unwanted waves, despite efforts to manage frequency fluctuations due to temperature changes.
Innovation Solution
The elastic wave device incorporates a piezoelectric substrate with multiple resonators having different wavelengths, where the film thickness of IDT electrodes in resonators with longer wavelengths is smaller than those with shorter wavelengths, utilizing a dielectric film with silicon oxide and silicon nitride for enhanced moisture resistance, effectively reducing unwanted waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If film thickness of IDT electrodes is increased to improve frequency characteristics, then frequency stability improves, but unwanted waves are enhanced
Solution Approach 1:
The patent applies local quality by setting different film thicknesses for IDT electrodes in different resonators based on their specific wavelength requirements. Each resonator's IDT electrode film thickness is locally optimized to suppress unwanted waves at its operating frequency while maintaining frequency stability, rather than using a uniform thickness across all resonators.
Solution Approach 2:
The patent changes the parameter of film thickness to resolve the contradiction. By adjusting the film thickness parameter of IDT electrodes according to the wavelength of each resonator, the patent achieves both frequency stability and unwanted wave suppression. The film thickness is set to specific ranges (e.g., 0.02λ to 0.05λ) to optimize performance.
2Adaptability or versatility
If multiple resonators with different wavelengths are added to broaden frequency response, then frequency coverage improves, but device complexity increases
Solution Approach 1:
The patent applies universality by designing a resonator structure that can operate across multiple frequency ranges. The resonators are configured with different wavelengths to cover broad frequency responses, and the common dielectric film and substrate provide a universal platform that simplifies the overall device architecture while enabling multi-frequency operation.
Solution Approach 2:
The patent segments the frequency response requirement into multiple resonators with different wavelengths. Each resonator handles a specific frequency range, and together they provide comprehensive frequency coverage. This segmentation allows independent optimization of each resonator while maintaining overall system performance.
3Ease of manufacture
If conventional IDT electrode thickness is used for all resonators, then manufacturing simplicity is maintained, but frequency characteristics degrade due to unwanted waves
Solution Approach 1:
The patent applies local quality by specifying different film thicknesses for IDT electrodes in different resonators based on their wavelength requirements. This local differentiation improves frequency characteristics and unwanted wave suppression while maintaining relatively simple manufacturing processes through standard thin-film deposition techniques.
Solution Approach 2:
The patent changes the film thickness parameter of IDT electrodes according to resonator wavelength to optimize frequency characteristics. This parameter adjustment is achieved through controlled deposition processes that can precisely regulate film thickness within specified ranges, balancing manufacturing simplicity with performance optimization.
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 significantly reduces unwanted waves by optimizing film thickness and dielectric materials, maintaining effective frequency characteristics and increasing moisture resistance.
Implementation Method 1
an elastic wave device includes a piezoelectric substrate, a plurality of elastic wave resonators provided on or in the piezoelectric substrate
Implementation Method 2
The plurality of elastic wave resonators include respective IDT electrodes disposed on the piezoelectric substrate
Implementation Method 3
a dielectric film disposed on the piezoelectric substrate and covering the plurality of elastic wave resonators
Data Source
AI summary
An elastic wave device includes a piezoelectric substrate, elastic wave resonators on or in the piezoelectric substrate, and a dielectric film disposed on the piezoelectric substrate and covering the elastic wave resonators. The elastic wave resonators includes respective IDT electrodes on the piezoelectric substrate. When a wavelength specified by an electrode finger pitch of the IDT electrode is denoted as λ, at least two of the elastic wave resonators have the different wavelengths. In two of the elastic wave resonators having different wavelengths, a film thickness of the IDT electrode in the elastic wave resonator having the longer wavelength is not greater than that of the IDT electrode in the elastic wave resonator having the shorter wavelength. Film thicknesses of the IDT electrodes in at least two of the elastic wave resonators are different from each other. The elastic wave device utilizes a Rayleigh wave.