Interdigital Transducer Electrode Stack for Higher Power Handling
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Solution Overview
Problem
Existing acoustic wave devices have insufficient electric power handling capability due to the use of AlCu alloy in interdigital transducer electrodes, which increases stress and deteriorates performance.
Innovation Solution
The acoustic wave device incorporates a piezoelectric substrate with an interdigital transducer electrode featuring a close-contact layer, a Cu—Al alloy layer, and an Al electrode layer, where the Al electrode layer has a weight-percentage concentration of Al greater than 50%, and all layers are epitaxial, with the Cu—Al alloy layer being 40% or less of the total thickness of the Cu—Al alloy layer and the Al electrode layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If AlCu alloy is used as the material for forming the interdigital transducer electrode, then the electrical resistance is decreased, but the electric power handling capability deteriorates due to increased stress
Solution Approach 1:
The electrode structure is segmented into multiple functional layers: a close-contact layer (Ti) for adhesion to the piezoelectric substrate, a Cu-Al alloy layer (5-20 wt% Cu) for optimized electrical and mechanical properties, and an Al electrode layer for low electrical resistance. This segmentation allows each layer to perform its specific function optimally, resolving the contradiction between stress resistance and electrical conductivity.
Solution Approach 2:
The invention uses composite material structure with Ti close-contact layer, Cu-Al alloy layer, and Al electrode layer. The Cu-Al alloy layer specifically uses copper and aluminum in controlled proportions to create a composite material that balances stress resistance and electrical conductivity, overcoming the limitations of pure AlCu alloy.
2Strength
If Ti film is disposed on the AlCu film, then adhesion is improved, but the stress applied to the AlCu film is increased, deteriorating electric power handling capability
Solution Approach 1:
The protective/adhesive Ti layer is segmented into a thin close-contact layer (1-5 nm) positioned only at the interface with the piezoelectric substrate, rather than covering the entire AlCu film. This minimal segmentation provides necessary adhesion while minimizing stress transmission to the AlCu alloy layer.
Solution Approach 2:
The Ti close-contact layer is applied locally only where adhesion is critical (at the substrate interface), with controlled thickness (1-5 nm). This local application provides sufficient adhesion strength without creating excessive stress across the entire electrode structure, preserving electric power handling capability.
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 decreases the electrical resistance of the electrode finger while enhancing the electric power handling capability of the acoustic wave device.
Implementation Method 1
the Cu—Al alloy layer and the Al electrode layer are epitaxial layers
Implementation Method 2
an acoustic wave device includes a piezoelectric substrate and an interdigital transducer electrode on the piezoelectric substrate
Data Source
AI summary
An acoustic wave device includes a piezoelectric substrate and an interdigital transducer electrode on the piezoelectric substrate. The interdigital transducer electrode includes a close-contact layer on the piezoelectric substrate, a Cu—Al alloy layer on the close-contact layer, and an Al electrode layer on the Cu—Al alloy layer and having a weight-percentage concentration, in % by weight, of Al of greater than about 50% by weight. The Cu—Al alloy layer and the Al electrode layer are epitaxial layers. A thickness of the Cu—Al alloy layer is about 40% or less of a total thickness of the Cu—Al alloy layer and the Al electrode layer.