Acoustic Wave Electrode Gap Cavities for Stable Linearity
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Solution Overview
Problem
Acoustic wave devices with IDT electrodes on piezoelectric members suffer from deteriorated linear characteristics due to electric fields reaching semiconductor substrates, causing nonlinear responses.
Innovation Solution
The acoustic wave device includes a semiconductor support with a piezoelectric layer directly or indirectly on its surface and an IDT electrode. Cavities are provided in the semiconductor support to overlap gaps in the IDT electrode, reducing the electric field's impact on the semiconductor substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the IDT electrode is formed on the piezoelectric member with the silicon containing substrate, then the acoustic wave device can be manufactured with standard semiconductor processes, but the electric field generated at the gaps reaches the silicon containing substrate and causes nonlinear response
Solution Approach 1:
The invention divides the semiconductor support into multiple regions: a first region with a cavity underneath the gaps and a second region without a cavity underneath the IDT electrode. This segmentation allows the electric field to be isolated in specific areas while maintaining structural integrity and manufacturability in other areas.
Solution Approach 2:
The cavity is provided only in the first region overlapping the gaps, not in the second region overlapping the IDT electrode. This local differentiation allows the structure to have different properties in different locations: the cavity region manages electric field effects while the non-cavity region maintains strong mechanical support and linear characteristics.
2Device complexity
If the electric field reaches the silicon containing substrate, then the device structure is simple, but the silicon containing substrate produces a nonlinear response which deteriorates the linear characteristics
Solution Approach 1:
The semiconductor support is segmented into regions with and without cavities. The cavity in the first region prevents the electric field from reaching the silicon containing substrate in that area, while the second region maintains direct contact for structural support. This segmentation resolves the contradiction by localizing the electric field management.
Solution Approach 2:
The cavity acts as an intermediary structure between the gaps and the silicon containing substrate. It physically separates the electric field generation area from the semiconductor substrate, preventing direct interaction that causes nonlinear response, while still allowing the overall device structure to remain relatively simple.
3Reliability
If a cavity is provided in the semiconductor support to prevent electric field from reaching the substrate, then the linear characteristics are maintained, but the mechanical strength may be reduced
Solution Approach 1:
The cavity is provided only in the first region underneath the gaps, while the second region underneath the IDT electrode maintains full structural integrity. This segmentation ensures that the mechanical strength is preserved in the critical load-bearing area while still providing electric field management where needed.
Solution Approach 2:
The structural properties are locally optimized: the first region has a cavity for electric field management, while the second region has solid structure for mechanical strength. This local differentiation allows the device to simultaneously achieve good linear characteristics and maintain adequate mechanical strength.
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 prevents the deterioration of linear characteristics and mechanical strength in acoustic wave devices by minimizing the electric field's nonlinear response in the semiconductor substrate.
Implementation Method 1
an IDT (interdigital transducer) electrode is formed on a piezoelectric member
Implementation Method 2
An electric field is generated at each gap due to a potential difference between the electrode fingers and the dummy electrode fingers
Data Source
AI summary
An acoustic wave device includes a semiconductor support including a principal surface, a piezoelectric layer on the principal surface of the semiconductor support, and an IDT electrode on a principal surface of the piezoelectric layer. The IDT electrode includes first and second busbars, and first and second electrode fingers. The IDT electrode includes first gaps between the first busbar and respective second electrode fingers. A recess is provided in at least a portion of the semiconductor support substrate overlapping the first gaps as viewed in plan. No recess is provided in at least a portion of the semiconductor support substrate overlapping the IDT electrode as viewed in plan. The recess opens toward the piezoelectric layer.