Piezoelectric Resonator Wiring Layout for Harmonic Stability
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Solution Overview
Problem
The polarity of piezoelectric thin film resonators in acoustic wave devices affects electric characteristics, leading to issues with harmonic and power durability characteristics, and existing connection methods result in wiring layer disconnection or increased resistance due to inadequate coverage of the level difference by the wiring layer.
Innovation Solution
The acoustic wave device design includes a wiring layer with a thickness greater than the piezoelectric film, extending from the upper surface of the lower electrode to the upper surface of the upper electrode, ensuring comprehensive coverage and connection between the electrodes, thereby preventing disconnection and resistance issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the wiring layer thickness is less than the piezoelectric film thickness, then the device structure is simpler and manufacturing is easier, but the wiring layer becomes disconnected or exhibits increased resistance
Solution Approach 1:
The patent changes the critical parameter of wiring layer thickness from being less than the piezoelectric film thickness to being greater than the piezoelectric film thickness. This parameter change ensures that the wiring layer completely covers the piezoelectric film and underlying structures, eliminating disconnection issues and reducing resistance while maintaining manufacturing feasibility
Solution Approach 2:
The patent transitions from a two-dimensional planar connection to a three-dimensional layered structure where the wiring layer extends vertically above the piezoelectric film surface. This dimensional change allows the wiring layer to encompass the entire piezoelectric film thickness and underlying structures, ensuring reliable electrical connection
2Ease of manufacture
If the polarity of piezoelectric films is not uniformly controlled, then manufacturing flexibility is improved, but harmonic characteristics and power durability deteriorate
Solution Approach 1:
The patent applies preliminary action by forming the piezoelectric film with predetermined polarity orientation before subsequent electrode and wiring layer fabrication. The piezoelectric film is deposited with controlled polarity (e.g., first surface positive, second surface negative) in advance, ensuring that subsequent processing steps maintain consistent electrical characteristics and harmonic performance
Solution Approach 2:
The patent applies local quality by ensuring that different regions of the piezoelectric film maintain consistent polarity characteristics. The piezoelectric film exhibits uniform polarity distribution across its surface, with the first surface having a specific polarity and the second surface having the opposite polarity, which is maintained throughout the device structure to ensure consistent harmonic characteristics
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 enhances the static dynamic characteristic, such as second harmonic characteristics, and power durability by ensuring reliable connections and reduced resistance across the piezoelectric film level differences, improving the overall performance of the acoustic wave device.
Implementation Method 1
a first piezoelectric thin film resonator including a first lower electrode located on the substrate, a first piezoelectric film located on the first lower electrode, and a first upper electrode located on the first piezoelectric film
Data Source
AI summary
An acoustic wave device includes: a substrate; a first piezoelectric thin film resonator including a first resonance region in which a first lower electrode and a first upper electrode sandwich a first piezoelectric film; a second piezoelectric thin film resonator including a second resonance region in which a second lower electrode and a second upper electrode sandwich a second piezoelectric film; and a wiring layer that is located from an upper surface of the first lower electrode in a first extraction region, in which the first lower electrode is extracted from the first resonance region, to an upper surface of the second upper electrode located in a second extraction region, in which the second upper electrode is extracted from the second resonance region, and has a film thickness on the first lower electrode greater than a film thickness of the second piezoelectric film.