Composite SiC Substrate Using Defect-Graded Bonded Layers
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Solution Overview
Problem
The high manufacturing costs and limited yield of silicon carbide (SiC) power devices due to defects in crystal growth and inefficient utilization of low-quality SiC ingots and wafers, restricting their application in various fields.
Innovation Solution
A composite substrate is created by bonding a high-quality monocrystalline silicon carbide layer with a low-quality silicon carbide layer, utilizing a method that includes hydrogen ion implantation and annealing to form a defect layer, allowing for efficient utilization of both types of silicon carbide layers, reducing waste, and improving electrical and thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If monocrystalline silicon carbide is grown using physical vapor transport (PVT) method, then the crystal has good electrical and thermal conductivity, but process condition fluctuations cause large quantities of defects and low yield
Solution Approach 1:
The invention divides the silicon carbide substrate into two distinct layers: a first silicon carbide layer with low defect density and a second silicon carbide layer with high defect density. This segmentation allows each layer to serve different functions - the first layer provides good electrical and thermal conductivity for device operation, while the second layer serves as a cost-effective base that absorbs mechanical stress and defects, thereby resolving the contradiction between maintaining high reliability and improving production yield.
Solution Approach 2:
The invention applies local quality by creating regions with different defect densities within the same substrate. The first silicon carbide layer near the epitaxial surface maintains low defect density to ensure device performance, while the second silicon carbide layer further from the surface has higher defect density acceptable for structural support. This local differentiation allows the substrate to simultaneously achieve high reliability where needed and cost-effectiveness where defects are tolerable.
2Ease of manufacture
If low-quality silicon carbide ingots are used to reduce costs, then manufacturing costs decrease, but the ingots contain defects that fail to meet quality requirements
Solution Approach 1:
The invention segments the silicon carbide material into two quality tiers within a single substrate structure. The first silicon carbide layer uses high-quality material suitable for epitaxial growth, while the second silicon carbide layer utilizes lower-quality material that would otherwise be discarded. This segmentation enables the system to achieve cost reduction through the use of low-quality material in the second layer while maintaining overall device quality through the first layer.
Solution Approach 2:
The invention converts the harmful effect of defects in low-quality silicon carbide into a beneficial structure. Instead of discarding defective ingots, the patent uses the defective second silicon carbide layer as a base substrate that provides mechanical support and stress relief. The defects in this layer are isolated from the active device region by the first high-quality layer, thereby converting waste material into a functional component that reduces overall manufacturing costs while maintaining device reliability.
3Ease of manufacture
If heterogeneous materials are stacked to form composite substrate, then cost reduction is achieved, but electrical and thermal conductivity deteriorate
Solution Approach 1:
The invention maintains homogeneity by using the same material type (silicon carbide) for both layers in the composite substrate. The first silicon carbide layer and the second silicon carbide layer are both silicon carbide with the same crystal structure and chemical composition, differing only in defect density. This material homogeneity ensures continuous electrical and thermal conductivity across the interface between layers, avoiding the conductivity deterioration that would occur with heterogeneous materials, while still achieving cost reduction through the use of lower-quality silicon carbide in the second layer.
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 composite substrate effectively reduces costs by utilizing low-quality silicon carbide, enhances electrical and thermal conductivity, and improves the yield of SiC power devices, promoting their wider application in fields such as aeronautics, smart grids, and electric vehicles.
Implementation Method 1
performing hydrogen ion implantation on a monocrystalline silicon carbide ingot from a back surface of the monocrystalline silicon carbide ingot, so that an implanted ion reaches a preset depth and forms a defect layer at the preset depth
Implementation Method 2
performing first annealing treatment on the first composite structure, so that the first silicon carbide layer is peeled off along the defect layer
Implementation Method 3
performing surface treatment on a surface of the first silicon carbide layer away from the second silicon carbide layer, to remove the damaged layer
Implementation Method 4
performing second annealing treatment on the third composite structure to repair a defect caused by hydrogen ion implantation in the first silicon carbide layer
Data Source
AI summary
Embodiments of this application relate to the field of semiconductor technologies, and provide composite substrate that comprises: a first silicon carbide layer comprising monocrystalline silicon carbide, and a second silicon carbide layer bonded to the first silicon carbide layer, wherein defect density of at least a part of the second silicon carbide layer is greater than defect density of the first silicon carbide layer.