Multi-Layer Piezoelectric Substrate for SAW Heat Dissipation
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Solution Overview
Problem
Surface acoustic wave devices experience self-heating due to the thermal conductivity mismatch between quartz substrates and lithium tantalate or lithium niobate piezoelectric layers, leading to undesirable temperature increases and performance degradation.
Innovation Solution
Incorporating a thermally conductive layer with higher thermal conductivity than the support substrate, positioned between the support substrate and the piezoelectric layer, to dissipate heat effectively, along with a temperature compensating layer to manage temperature coefficients, thereby reducing surface temperatures and improving electrical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a quartz substrate is used with lithium tantalate or lithium niobate piezoelectric layers, then the device achieves good electrical performance, but thermal conductivity mismatch causes self-heating and temperature increase
Solution Approach 1:
A thermally conductive layer is introduced as an intermediary between the quartz substrate and the piezoelectric layer. This layer has higher thermal conductivity than the quartz substrate, acting as a thermal bridge to conduct heat away from the piezoelectric layer, thereby reducing self-heating while maintaining the electrical performance benefits of the quartz-piezoelectric structure.
Solution Approach 2:
The device structure is transformed into a composite multi-layer system combining quartz substrate, thermally conductive layer, and piezoelectric layer. This composite structure leverages the complementary properties of each material: quartz for electrical performance, thermally conductive layer for heat dissipation, and piezoelectric layer for acoustic wave generation, resolving the thermal-electrical performance contradiction.
2Temperature
If the thermally conductive layer thickness is increased to improve heat dissipation, then temperature reduction is enhanced, but the device structure becomes more complex and acoustic performance may be affected
Solution Approach 1:
The thickness of the thermally conductive layer is optimized within a specific range (greater than 10 nanometers but less than the piezoelectric layer thickness, and less than 0.03λ where λ is the acoustic wavelength). This parameter optimization ensures sufficient thermal conductivity while minimizing impact on acoustic wave propagation and maintaining structural simplicity.
Solution Approach 2:
Rather than making the thermally conductive layer very thick to maximize heat dissipation, a thin layer (greater than 10 nm) is sufficient to provide the necessary thermal bridge function. This partial action approach achieves adequate heat dissipation without excessive thickness that would complicate the structure or degrade acoustic performance.
3Stability of the object's composition
If a temperature compensating layer is added to improve temperature stability, then frequency stability is enhanced, but the device structure and manufacturing process become more complex
Solution Approach 1:
A temperature compensating layer with positive temperature coefficient of frequency is strategically positioned between the piezoelectric layer and the thermally conductive layer (or between piezoelectric layer and substrate). This localized compensation targets the temperature drift issue specifically without requiring complete structural redesign, providing temperature stability with minimal added complexity.
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 effectively reduces surface temperatures below 60°C and enhances the quality factor and temperature stability of surface acoustic wave devices, improving their operational durability and performance.
Implementation Method 1
a thermally conductive layer configured to dissipate heat associated with the acoustic wave device. The thermally conductive layer has a higher thermal conductivity than the support substrate
Implementation Method 2
A surface acoustic wave resonator can include an interdigital transductor electrode on a piezoelectric substrate. The surface acoustic wave resonator can generate a surface acoustic wave on a surface of the piezoelectric layer
Data Source
AI summary
Aspects of this disclosure relate to a filter that includes an acoustic wave device with a multi-layer substrate with heat dissipation. The multi-layer substrate includes a support substrate (e.g., a quartz substrate), a piezoelectric layer, an interdigital transducer electrode on the piezoelectric layer, and a thermally conductive layer configured to dissipate heat associated with the acoustic wave device. The thermally conductive layer is disposed between the support substrate and the piezoelectric layer. The thermally conductive layer has a thickness that is greater than 10 nanometers and less than a thickness of the piezoelectric layer.