Acoustic Wave Electrode Patterning for Leakage Mode Suppression
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Solution Overview
Problem
Acoustic wave devices with an excitation portion on an acoustic reflector often experience leakage mode propagation due to manufacturing errors, leading to spurious components in the device.
Innovation Solution
The acoustic wave device incorporates a periodic pattern on at least one of the extraction electrodes, which reduces or prevents leakage mode propagation by Bragg-reflection, thereby enhancing resonance characteristics without increasing manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the lower electrode and upper electrode extend beyond the cavity region due to manufacturing errors, then the electrode coverage is improved, but leakage mode propagation occurs causing spurious components
Solution Approach 1:
The invention converts the harmful leakage mode propagation into a beneficial effect by introducing a periodic pattern that causes Bragg reflection. The periodic structure with specific pitch (lambda/2n) reflects the leakage acoustic waves back toward the excitation portion, preventing spurious mode generation while utilizing the extended electrode region that would otherwise be harmful.
Solution Approach 2:
The periodic pattern acts as an intermediary element between the extended electrodes and the extraction electrodes. This intermediate structure mediates the acoustic wave propagation by reflecting leakage modes through Bragg reflection, preventing direct coupling between the extended electrode regions and the output ports.
2Object-generated harmful factors
If a periodic pattern is added to the extraction electrode to prevent leakage mode propagation, then spurious components are reduced, but device complexity increases
Solution Approach 1:
The extraction electrode is segmented into multiple periods of the periodic pattern, creating a distributed Bragg reflector structure. This segmentation approach allows the electrode to simultaneously serve as both an electrical connection element and an acoustic wave management element, reducing spurious modes without requiring separate dedicated structures.
Solution Approach 2:
The periodic pattern on the extraction electrode provides multi-functionality: it serves as both the electrical extraction path and the acoustic wave reflector. This universal structure eliminates the need for separate components to address leakage mode propagation, maintaining manufacturing simplicity while achieving the desired acoustic isolation.
3Object-generated harmful factors
If the periodic pattern pitch is set to lambda/2n to achieve Bragg reflection, then leakage mode propagation is prevented, but manufacturing precision requirements increase
Solution Approach 1:
The invention specifies the periodic pattern pitch as lambda/2n, where lambda is the acoustic wavelength and n is the refractive index. This parameter relationship provides a clear design guideline that can be implemented through standard photolithography processes, balancing the need for precise Bragg reflection with manufacturability using conventional fabrication techniques.
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
The periodic pattern effectively reduces leakage mode propagation, improving the resonance characteristics of the acoustic wave device and preventing spurious modes from appearing in the resonance characteristics.
Implementation Method 1
A periodic pattern is provided along a direction separating from the excitation portion on at least one of the first extraction electrode and the second extraction electrode. Acoustic wave devices according to the preferred embodiments of the present invention are each able to reduce or prevent leakage mode propagation toward at least one of the first extraction electrode and second extraction electrode.
Data Source
AI summary
An acoustic wave device in which a cavity defining an acoustic reflector is formed on a first main surface side of a substrate, an excitation portion is structured above the cavity in a manner that a first electrode, a piezoelectric thin film, and a second electrode are laminated, and a periodic pattern is provided in a normal direction of a side of the excitation portion on at least one of a first extraction electrode and a second extraction electrode.