Multi-Layer SAW Substrate for Heat Dissipation and Spurious Control
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Solution Overview
Problem
Surface acoustic wave (SAW) resonators with multi-layer piezoelectric substrates face challenges in achieving high ruggedness and power handling while maintaining low thermal heat dissipation and minimizing high frequency spurious responses.
Innovation Solution
The SAW resonators incorporate a single crystal support layer, a z-propagation quartz layer, and a lithium-based piezoelectric layer, along with an interdigital transducer electrode, where the support layer has higher thermal conductivity than the quartz and piezoelectric layers, and the quartz layer is oriented to confine acoustic energy and reduce spurious responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a multi-layer piezoelectric substrate is used to achieve high quality factor, then the quality factor is improved, but thermal heat dissipation increases and power handling capability deteriorates
Solution Approach 1:
The device is divided into distinct functional layers: a first piezoelectric layer for generating surface acoustic waves and a second piezoelectric layer for thermal management. This segmentation allows each layer to specialize in its primary function, with the second layer providing thermal conduction path without interfering with the acoustic wave generation in the first layer.
Solution Approach 2:
The second piezoelectric layer acts as an intermediary thermal conduction path between the interdigital transducer electrode and the substrate. It mediates the thermal management function while maintaining the necessary acoustic wave propagation characteristics, effectively decoupling thermal and acoustic functions.
2Reliability
If a multi-layer piezoelectric substrate is used to achieve high quality factor, then the quality factor is improved, but ruggedness and power handling capability deteriorate
Solution Approach 1:
The device structure is segmented into a first piezoelectric layer for acoustic wave generation and a second piezoelectric layer for mechanical support and thermal conduction. This segmentation allows the second layer to provide enhanced ruggedness and power handling capability while the first layer maintains high quality factor performance.
Solution Approach 2:
The device uses a composite structure with two different piezoelectric layers having different orientations and properties. The first layer (e.g., lithium niobate) provides high piezoelectric coupling for quality factor, while the second layer provides mechanical strength and thermal conduction, creating a composite material system that achieves multiple performance goals simultaneously.
3Ease of manufacture
If conventional substrate structures are used, then manufacturing is simpler, but high frequency spurious responses cannot be minimized
Solution Approach 1:
The patent applies different local qualities to different regions of the device. The first piezoelectric layer has specific crystal orientation optimized for acoustic wave generation, while the second piezoelectric layer has different orientation optimized for thermal conduction and mechanical support. This local differentiation allows suppression of spurious responses while maintaining manufacturing feasibility.
Solution Approach 2:
The solution adds a vertical dimension to the structure by stacking two piezoelectric layers with different orientations. This dimensional approach allows independent optimization of acoustic wave properties in one layer and thermal/mechanical properties in another layer, effectively suppressing spurious responses that would occur in conventional single-layer structures.
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 effective electromechanical coupling coefficient, quality factor, and power durability, while reducing high frequency spurious responses, making the SAW resonators suitable for wide bandwidth filters and compatible with higher frequency bands.
Implementation Method 1
the support layer has higher thermal conductivity than the quartz and piezoelectric layers
Implementation Method 2
the quartz layer is oriented to confine acoustic energy and reduce spurious responses
Implementation Method 3
a lithium based piezoelectric layer positioned over the intermediate single crystal layer, and an interdigital transducer electrode positioned over the lithium based piezoelectric layer. The surface acoustic wave device is configured to generate a surface acoustic wave
Data Source
AI summary
A surface acoustic wave device is disclosed. The surface acoustic wave device can include a single crystal support layer, an intermediate single crystal layer positioned over the single crystal support layer, a lithium based piezoelectric layer positioned over the intermediate single crystal layer, and an interdigital transducer electrode positioned over the lithium based piezoelectric layer, the surface acoustic wave device configured to generate a surface acoustic wave. The single crystal layer can be a quartz layer, such as a z-propagation quartz layer. A thermal conductivity of the single crystal support layer is greater than a thermal conductivity of the intermediate single crystal layer, and the thermal conductivity of the single crystal support layer is greater than a thermal conductivity of the lithium based piezoelectric layer.