Piezoelectric Resonator with Density-Gradient Mass Load Patterns
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Solution Overview
Problem
Existing piezoelectric thin-film resonators face challenges in effectively suppressing transverse mode spurious vibrations, which act as noise for the fundamental mode of vibration, particularly due to difficulties in arranging and designing hole patterns to achieve this suppression.
Innovation Solution
The implementation of a piezoelectric thin-film resonator design featuring a substrate with a lower electrode, a piezoelectric film, and an upper electrode with densely arranged concave or convex patterns in the central region and sparsely arranged patterns in the peripheral region, which reduces unwanted spurious vibrations by varying the pitch of these patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If holes are irregularly arranged with irregular sizes or shapes to suppress transverse mode spurious, then transverse mode spurious suppression is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent applies local quality by varying the hole diameter across different regions of the electrode. Specifically, holes in the central region have a first diameter while holes in the peripheral region have a second diameter that is different from the first. This spatial variation in hole size allows effective suppression of transverse mode spurious while using a regular, manufacturable pattern rather than irregular random arrangements.
2Object-affected harmful factors
If holes are provided in the upper electrode to suppress transverse mode spurious, then transverse mode spurious suppression is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent implements local quality through region-specific hole diameter design. The electrode is divided into a central region and a peripheral region, with each region having holes of a specific diameter optimized for its location. This approach maintains manufacturing precision by using uniform hole sizes within each region while achieving overall spurious suppression through the spatial gradient.
Solution Approach 2:
The patent applies segmentation by dividing the electrode into distinct regions (central and peripheral) with different hole characteristics. This segmentation allows each region to be optimized independently for its specific functional requirements while maintaining overall manufacturability through standardized hole patterns within each segment.
3Object-affected harmful factors
If densely arranged patterns are used in the central portion and sparsely arranged patterns in the peripheral portion, then transverse mode spurious suppression is improved, but device complexity increases
Solution Approach 1:
The patent applies local quality by creating a density gradient in the hole arrangement. The central region has a higher hole density with smaller pitch, while the peripheral region has lower density with larger pitch. This spatially varying density pattern is optimized to suppress transverse mode spurious effectively while maintaining regular, manufacturable geometry throughout the device.
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 reduces transverse mode spurious vibrations, enhancing the resonance characteristics and filter performance by minimizing unwanted noise and ripple in the frequency band, thereby improving the overall performance of the resonator at a lower cost.
Implementation Method 1
the vibration that propagates in a direction perpendicular to an electrode surface is defined as a fundamental mode of vibration
Implementation Method 2
The plurality of concave or convex patterns are densely arranged in a central portion of the region and are sparsely arranged in a peripheral portion of the region
Data Source
AI summary
A piezoelectric thin-film resonator includes a substrate, a lower electrode provided on the substrate, a piezoelectric film provided on the lower electrode and an upper electrode that is located opposite the lower electrode across at least a part of the piezoelectric film. A mass load film is provided on the upper electrode. The mass load film includes a plurality of concave or convex patterns in at least a region that faces the lower electrode. The plurality of concave or convex patterns are densely arranged in a central portion of the region and are sparsely arranged in a peripheral portion of the region.