SiC-GaN SAW Filter Stack for 5G Bandwidth and Thermal Control
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Solution Overview
Problem
The existing SAW technology faces limitations in achieving high frequency, large bandwidth, and low loss required for 5G communication due to insufficient electromechanical coupling coefficient and quality factor of conventional piezoelectric materials, and silicon substrates fail to meet thermal conductivity needs.
Innovation Solution
An integrated device using a SiC substrate with stacked GaN film layers and a piezoelectric material layer, optimized by a piezoelectric multi-layer film structure, which includes a SiC substrate, buffer layer, GaN film, and piezoelectric material, enabling improved electromechanical coupling and thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional piezoelectric materials (lithium tantalate and lithium niobate) are used in SAW filters, then the device structure is simple and manufacturing is easy, but the electromechanical coupling coefficient and quality factor are insufficient to meet 5G communication requirements for large bandwidth and low loss
Solution Approach 1:
The patent employs a composite piezoelectric multi-layer film structure consisting of alternating layers of lithium niobate (LN) and lithium tantalate (LT) with specific thickness ratios. This composite structure combines the high electromechanical coupling coefficient of LT with the high quality factor of LN, achieving both large bandwidth and low loss performance required for 5G communication while maintaining a manageable device structure through systematic layer design
Solution Approach 2:
The patent systematically varies the thickness parameters of individual layers within the piezoelectric multi-layer film, specifically optimizing the thickness ratio between LN and LT layers. By adjusting these physical parameters, the patent achieves optimal electromechanical coupling and quality factor performance for 5G frequency bands, transforming the fixed-performance conventional materials into a tunable high-performance structure
2Reliability
If silicon substrate is used for SAW filters, then manufacturing cost is low and processing is simple, but the thermal conductivity is insufficient to handle high input power and prevent device burnout
Solution Approach 1:
The patent introduces an aluminum nitride (AlN) thermal management layer as an intermediary between the piezoelectric film and the silicon substrate. This AlN layer serves as a thermal conduit with high thermal conductivity, efficiently transferring heat away from the high-power SAW filter region while maintaining electrical isolation and mechanical stability, thus enabling effective thermal management without requiring complete replacement of the silicon substrate infrastructure
Solution Approach 2:
The patent creates a composite substrate structure combining silicon base substrate with an aluminum nitride thermal management layer. This composite approach leverages the cost-effectiveness and成熟 manufacturing of silicon while adding the high thermal conductivity of AlN specifically where needed for heat dissipation, achieving thermal management capability without entirely abandoning the economical silicon substrate platform
3Manufacturing precision
If heteroepitaxy of SiC and GaN is performed to reduce lattice mismatch, then material quality improves, but the backside process is required to complete the integrated device
Solution Approach 1:
The patent segments the device fabrication into distinct front-side and back-side processing regions. By carefully designing the epitaxial structure and bonding interfaces, the patent enables completion of the integrated device primarily through front-side processes, minimizing or eliminating the need for complex backside processing while maintaining high material quality through controlled heteroepitaxy of SiC and GaN layers
4Reliability
If SAW technology is expanded to 5G frequency bands, then communication performance improves, but the heat generation from increased input power causes device burnout
Solution Approach 1:
The patent introduces an aluminum nitride (AlN) thermal management layer as an intermediary heat dissipation pathway between the high-power SAW filter and the substrate. This AlN layer acts as a thermal bridge with high thermal conductivity, efficiently conducting heat away from the active device region while maintaining electrical isolation, thus enabling 5G frequency operation with high input power without causing device burnout
Solution Approach 2:
The patent replaces conventional passive thermal management approaches with an active thermal conduction system using high-performance AlN material. This substitution transforms the thermal management mechanism from relying on natural convection and radiation to utilizing controlled thermal conduction through the AlN layer, enabling effective heat removal at the high power densities required for 5G communication performance
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 enhances the frequency and coupling coefficient of SAW filters, allowing them to meet 5G requirements, reduces processing costs, and integrates SAW filters and radio frequency devices without a backside process, suitable for 5G and sub-6G frequency bands.
Implementation Method 1
a piezoelectric material layer stacked on the first GaN film layer; wherein the first SiC substrate, the first buffer layer, the first GaN film layer and the piezoelectric material layer which are stacked are used for forming a piezoelectric multi-layer film, and the piezoelectric multi-layer film is used for forming an SAW filter
Implementation Method 2
bonding a hundred nanometer piezoelectric film onto a silicon substrate with higher sound velocity, so that sound waves can be more confined to the surface of the substrate
Implementation Method 3
enhancing the cooling ability of the device at high input power by utilizing the thermal conductivity of silicon
Data Source
AI summary
An integrated device based on a third-generation semiconductor and a manufacturing method thereof are provided. The integrated device at least includes a SiC substrate, a buffer layer, a GaN film layer and a piezoelectric material layer; the SiC substrate includes a first buffer layer stacked on a first SiC substrate and a second buffer layer stacked on a second SiC substrate; the GaN film layer at least includes a first GaN film layer stacked on the first buffer layer and a second GaN film layer stacked on the second buffer layer; the first SiC substrate, the first buffer layer, the first GaN film layer and the piezoelectric material layer which are stacked are used for forming a piezoelectric multi-layer film; the piezoelectric multi-layer film is used for forming a surface acoustic wave (SAW) filter.