Shear-Mode Electroacoustic Component for Frequency-Temperature Stability
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Solution Overview
Problem
The complexity of physical interactions between RF-waves and acoustic waves with piezoelectric materials in electroacoustic components makes it challenging to achieve desired properties such as small thickness, low insertion loss, frequency-temperature compensation, high coupling coefficient, wide-band capability, and spectral purity, due to the numerous parameters involved.
Innovation Solution
An electroacoustic component is designed with a carrier wafer, a piezoelectric layer, and an interdigitated transducer, where a passivation layer of silicon dioxide reduces temperature coefficients, and the piezoelectric material is oriented for specific cuts like (YX1)/α to enhance frequency-temperature compensation and spectral purity, using lithium niobate or lithium tantalate substrates with optimized thickness and metallization ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a piezoelectric layer with optimized thickness is used to achieve small spatial dimensions, then the component size is reduced, but the frequency-temperature compensation and spectral purity deteriorate
Solution Approach 1:
The patent employs a composite structure consisting of a piezoelectric layer (lithium niobate or lithium tantalate) bonded to a carrier wafer (silicon or sapphire) with a specific cut orientation ((YX1)/α where 45°≤α≤60°). This composite configuration enables the thin piezoelectric layer to maintain small spatial dimensions while the specific crystal orientation and substrate combination provide frequency-temperature compensation and spectral purity, thus resolving the contradiction between miniaturization and performance stability.
2Reliability
If the piezoelectric material orientation is optimized for spectral purity, then spectral purity is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent specifies a particular range for the cut orientation angle α (45°≤α≤60°) of the piezoelectric layer relative to the carrier wafer. By defining this specific parameter range, the invention achieves spectral purity through the optimized acoustic wave propagation characteristics while providing clear manufacturing guidelines that reduce complexity. The interdigitated transducer geometry parameters (electrode width, spacing, and length) are also optimized to excite single-mode acoustic waves, further enhancing spectral purity with manufacturable dimensions.
3Reliability
If multiple parameters are optimized to achieve desired component properties, then performance is improved, but the device complexity increases
Solution Approach 1:
The patent optimizes specific local parameters of the piezoelectric layer and carrier wafer combination, particularly the cut orientation angle α in the range of 45° to 60°. This localized optimization of the crystal cut angle and layer configuration enables frequency-temperature compensation and spectral purity without requiring optimization of all possible parameters. The interdigitated transducer design with specific electrode geometry further locally optimizes the electroacoustic coupling, achieving high performance while managing complexity through focused parameter optimization rather than comprehensive adjustment.
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
The solution achieves improved frequency-temperature compensation, high coupling coefficients, and spectral purity, enabling efficient conversion of RF signals to acoustic waves while maintaining small spatial dimensions, thus addressing the complexity of parameter dependencies in electroacoustic components.
Implementation Method 1
Utilizing the piezoelectric effect, the electrode structures can convert electromagnetic RF-signals into acoustic waves and vice versa
Implementation Method 2
The passivation layer can be amorphous and have a thickness of 1 μm. It is preferably pure, e.g. without ionic pollution, and dense to provide elastic properties of the layer as close as possible from the ones of the bulk material
Data Source
AI summary
An improved electroacoustic component is provided. The component includes a carrier wafer with a passivation layer, a piezoelectric layer above the passivation layer and an interdigitated transducer in an electrode layer on the piezoelectric layer. The component is configured to work with a shear mode.