Coplanar IDT Acoustic Wave Filter With Local Thickness Tuning
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Solution Overview
Problem
Existing acoustic wave devices with multiple filters having different pass bands require complex fabrication processes due to non-uniform light exposure during IDT electrode formation on piezoelectric substrates with varying levels, leading to non-homogeneous electrodes and increased complexity in manufacturing.
Innovation Solution
The acoustic wave device incorporates a piezoelectric laminate with an intermediate layer and a support substrate, where the first and second exciting electrodes are disposed in the same plane with varying thicknesses, utilizing a low acoustic velocity film and high acoustic velocity substrate to effectively confine energy and adjust filter characteristics, allowing for the easy fabrication of multiple filters with different pass bands on the same chip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If IDT electrodes are formed at different levels in thick and thin portions of the piezoelectric substrate simultaneously by photolithography, then fabrication process is simplified, but light exposure becomes non-uniform resulting in non-homogeneous electrodes
Solution Approach 1:
The patent transitions from forming electrodes at different vertical levels (3D arrangement) to forming all electrodes in the same horizontal plane (2D arrangement). By making all IDT electrodes coplanar on the piezoelectric substrate surface, the invention eliminates the light exposure non-uniformity problem that occurred when electrodes were at different levels, while still enabling multiple filters with different pass bands to be fabricated simultaneously in a simplified process
2Adaptability or versatility
If multiple acoustic wave filters with different pass bands are fabricated in the same chip, then device integration is improved, but fabrication process complexity increases
Solution Approach 1:
The patent applies local quality by creating regions with different piezoelectric film thicknesses in specific areas of the substrate while maintaining a uniform coplanar electrode structure. By locally varying the piezoelectric layer thickness rather than the electrode positions, the invention enables different filters with distinct pass bands to be formed in different regions of the same chip, all using the same simplified coplanar photolithography process
Solution Approach 2:
The invention changes the physical parameter of piezoelectric film thickness in different regions of the substrate to achieve different filter characteristics. By controlling the piezoelectric layer thickness locally while keeping all electrodes in the same plane, the patent enables multiple filters with different pass bands to be fabricated simultaneously without increasing process complexity
3Manufacturing precision
If IDT electrodes are formed in separate steps at different times to ensure homogeneity, then electrode homogeneity is improved, but fabrication process becomes complex
Solution Approach 1:
The patent resolves the need for separate formation steps by changing from a vertical arrangement (electrodes at different levels requiring sequential processing) to a horizontal arrangement (all electrodes in the same plane). This dimensional change allows all IDT electrodes to be patterned simultaneously in a single photolithography step while maintaining uniform electrode quality across the entire chip
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 simplifies the fabrication process by ensuring homogeneous electrode formation and allows for easy adjustment of filter characteristics, reducing the likelihood of cracks and separation during processing, while enabling efficient energy confinement and improved reflection performance.
Implementation Method 1
an acoustic wave device includes a piezoelectric laminate, a first exciting electrode, and a second exciting electrode
Implementation Method 2
utilizing a low acoustic velocity film and high acoustic velocity substrate to effectively confine energy
Data Source
AI summary
An acoustic wave device includes a support substrate, a piezoelectric laminate, and first and second interdigital transducer electrodes. The piezoelectric laminate includes an intermediate layer provided directly or indirectly on the support substrate and a piezoelectric thin film provided on the intermediate layer. The first and second interdigital transducer electrodes are provided on the piezoelectric thin film of the piezoelectric laminate so as to be disposed in an identical or substantially identical plane. In the piezoelectric laminate, a thickness of a portion where the first interdigital transducer electrode is provided is different from a thickness of a portion where the second interdigital transducer electrode is provided.