SAW Resonator Structure With LiNbO3 Overcoat and Raised Frame
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Solution Overview
Problem
Current surface acoustic wave (SAW) devices with lithium tantalate piezoelectric materials face limitations in effective electromechanical coupling coefficient and temperature stability, leading to degraded performance and increased susceptibility to temperature changes.
Innovation Solution
The use of lithium niobate piezoelectric materials with an overcoat layer of silicon dioxide and a raised frame structure, which improves the effective electromechanical coupling coefficient and suppresses transverse modes, while maintaining thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If lithium tantalate piezoelectric materials are used in SAW devices, then the device structure is simpler, but the electromechanical coupling coefficient is lower and temperature stability is poor
Solution Approach 1:
The patent employs a composite structure consisting of lithium niobate piezoelectric material combined with silicon dioxide overcoat layer and metal electrode layers. This composite material approach enables simultaneous achievement of high electromechanical coupling coefficient (k² > 8%) and improved temperature stability, resolving the contradiction between simple structure and reliable performance.
Solution Approach 2:
The patent optimizes critical parameters including the thickness of the lithium niobate layer (40-80 nm), silicon dioxide layer (10-50 nm), and metal electrode thickness (10-100 nm). By precisely controlling these dimensional parameters, the device achieves enhanced electromechanical coupling while maintaining thermal stability, thus resolving the performance trade-off.
2Reliability
If lithium niobate piezoelectric materials with overcoat layer and raised frame structure are used, then the electromechanical coupling coefficient is enhanced, but the device structure becomes more complex
Solution Approach 1:
The patent divides the device into functionally distinct segments: the lithium niobate piezoelectric layer for high coupling coefficient, the silicon dioxide overcoat layer for thermal stability and protection, and the metal electrode layers for electrical connection. This segmentation allows each layer to be optimized independently, achieving high performance while managing structural complexity through functional specialization.
Solution Approach 2:
The patent introduces a vertical dimension by stacking multiple thin layers (lithium niobate, silicon dioxide, metal electrodes) with controlled thicknesses in the range of 10-100 nm each. This multi-layer vertical structure enhances the electromechanical coupling coefficient through improved field confinement while managing complexity through precise dimensional control in the thickness dimension.
3Ease of manufacture
If conventional SAW device structures are used, then the manufacturing process is simpler, but the energy transfer efficiency is lower
Solution Approach 1:
The patent optimizes the thickness parameters of each layer to enhance energy transfer efficiency. The lithium niobate layer thickness (40-80 nm) and silicon dioxide layer thickness (10-50 nm) are specifically controlled to maximize piezoelectric coupling and minimize energy loss, achieving high efficiency while maintaining compatibility with standard thin-film fabrication processes.
Solution Approach 2:
The composite structure of lithium niobate with silicon dioxide overcoat and metal electrodes creates favorable acoustic impedance matching and enhanced piezoelectric coupling. This material combination improves energy transfer efficiency by reducing energy leakage and enhancing the conversion between electrical and mechanical energy, while still using conventional thin-film deposition techniques for manufacturing.
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 enhances the energy transfer efficiency and suppresses spurious modes, resulting in improved performance and stability of SAW devices across varying temperatures.
Implementation Method 1
a piezoelectric layer that includes lithium niobate; an interdigital transducer electrode including a plurality of interdigitated fingers separated by gaps. The piezoelectric layer can be disposed between the substrate and the interdigital transducer electrode
Implementation Method 2
The device can include an overcoat layer that includes silicon dioxide. The interdigital transducer electrode can be disposed between the piezoelectric layer and the overcoat layer
Data Source
AI summary
An acoustic wave device configured to generate a surface acoustic wave having a wavelength L is disclosed. The acoustic wave device can include a substrate, a piezoelectric layer that includes lithium niobate, an interdigital transducer electrode, an overcoat dielectric layer, and/or a raised frame structure. The piezoelectric layer can have a trench in an edge region within 0.25L and 0.45L from an edge of an active region where the surface acoustic wave is generated. The piezoelectric layer is disposed at least partially between the substrate and the interdigital transducer electrode. The overcoat dielectric layer is positioned over the interdigital transducer electrode. The raised frame structure is positioned over the overcoat dielectric layer. The raised frame structure is positioned in an edge region of the active region. The acoustic wave device can include a trap-rich layer over the substrate and an intervening dielectric layer over the trap-rich layer.