Semi-Insulating SiC Transfer Substrate for Low-Loss III-N Epitaxy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge lies in fabricating substrates for epitaxial growth of III-N alloys like gallium nitride, aluminum gallium nitride, or indium gallium nitride, which face issues with high RF losses and poor heat dissipation, particularly due to the limitations of semi-insulating silicon carbide substrates, including high costs and limited size, as well as the presence of thermal barriers in composite structures.
Innovation Solution
A process involving a base substrate of single-crystal silicon carbide, where a layer of semi-insulating SiC is grown epitaxially and then transferred to a high-resistivity receiver substrate, minimizing thermal barriers and optimizing crystal quality, allowing for efficient heat dissipation and reduced RF losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If semi-insulating silicon carbide substrates are used for heteroepitaxy of III-N alloys, then RF losses are minimized and thermal conductivity is improved, but substrate cost increases and substrate size is limited
Solution Approach 1:
The substrate structure is segmented into multiple functional layers: a large-area polycrystalline SiC substrate for cost-effectiveness and heat dissipation, an intermediate layer of single-crystal SiC for epitaxial growth, and a thin semi-insulating SiC layer for RF performance. This segmentation allows each layer to optimize its specific function without requiring the entire substrate to be expensive semi-insulating material.
Solution Approach 2:
The invention uses composite substrate structures combining different SiC crystal forms (polycrystalline and single-crystal) and electrical properties (semi-insulating and conductive). This composite approach allows the substrate to simultaneously achieve low cost, high thermal conductivity, good RF losses, and suitable crystal quality for epitaxial growth.
2Loss of energy
If semi-insulating silicon carbide substrates are used for heteroepitaxy of III-N alloys, then RF losses are minimized, but substrate size is limited
Solution Approach 1:
The substrate is segmented into a large-area polycrystalline SiC base substrate and a thinner single-crystal SiC layer. This allows the overall substrate to be large in area for cost-effectiveness while the critical epitaxial growth occurs on a high-quality single-crystal surface.
3Ease of manufacture
If composite structures like SopSiC or SiCopSiC are used, then substrate cost decreases and heat dissipation is improved, but thermal barriers form at interfaces
Solution Approach 1:
The invention extracts and eliminates the problematic silicon oxide interface layer from composite substrate structures. By using direct bonding between single-crystal SiC and polycrystalline SiC without intermediate oxide layers, the thermal barrier is removed while maintaining the cost and heat dissipation advantages of composite structures.
Solution Approach 2:
The single-crystal SiC layer serves as an intermediary between the polycrystalline SiC substrate and the III-N alloy epitaxial layer. This intermediate layer provides a high-quality crystal surface for epitaxy while maintaining good thermal contact with the polycrystalline substrate, avoiding the formation of thermal barriers.
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 process enables the creation of substrates with high electrical resistivity and thermal conductivity, suitable for high-frequency, high-power electronic devices, by eliminating thermal barriers and utilizing high-quality semi-insulating SiC layers for epitaxial growth, thereby enhancing heat dissipation and reducing RF losses.
Implementation Method 1
performing epitaxial growth of a layer of semi-insulating SiC on the layer of single-crystal SiC to form a donor substrate
Implementation Method 2
implanting ionic species into the layer of semi-insulating SiC so as to form a weakened region that defines a thin layer of single-crystal semi-insulating SiC to be transferred
Implementation Method 3
bonding the layer of semi-insulating SiC to a receiver substrate having a high electrical resistivity
Data Source
AI summary
A method of fabricating a substrate for epitaxial growth of a layer of gallium nitride (GaN), aluminum gallium nitride (AlGaN) or indium gallium nitride (InGaN), comprises the following successive steps:providing a base substrate comprising at least one layer of single-crystal silicon carbide,performing epitaxial growth of a layer of semi-insulating SiC having a thickness larger than 1 μm on the layer of single-crystal SiC to form a donor substrate,implanting ionic species into the layer of semi-insulating SiC so as to form a weakened region defining a thin layer of single-crystal semi-insulating SiC to be transferred,bonding the layer of semi-insulating SiC directly to a receiver substrate having a high electrical resistivity, anddetaching the donor substrate along the weakened region so as to transfer the thin layer of single-crystal semi-insulating SiC to the receiver substrate.