Single-Crystal SiC Wafer Defect Reduction via Doping Control
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Solution Overview
Problem
Current methods for producing high-quality single-crystal silicon carbide (SiC) wafers are hindered by defects such as micropipes and dislocation defects, which are inherited from seed crystals and exacerbated by thermal stress and doping element concentration mismatches, leading to suboptimal crystal quality and device performance.
Innovation Solution
A single-crystal silicon carbide growth process where the doping element concentration in the vicinity of the seed crystal is maintained between 2×10^19 cm^-3 and 6×10^20 cm^-3, with a concentration ratio of 5 or less across the seed-crystal interface, minimizing defects and stabilizing the 4H polytype growth, thereby reducing micropipe and dislocation densities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If single-crystal SiC is grown using the modified Lely process with a seed crystal, then the polytype, shape, and carrier type/concentration can be controlled, but micropipes and dislocation defects are inherited from the seed crystal and new defects arise during growth
Solution Approach 1:
The invention changes the doping element concentration parameter during the crystal growth process. By maintaining a high doping element concentration (2×10^19 cm^-3 to 6×10^20 cm^-3) in the vicinity of the seed crystal and controlling the concentration ratio across the interface to be 5 or less, the invention suppresses the formation of micropipes and dislocation defects while maintaining polytype control.
Solution Approach 2:
The invention performs preliminary action by pre-establishing the doping element concentration distribution before defects can form. By controlling the doping concentration in the region near the seed crystal interface before growth proceeds, the invention prevents the inheritance and formation of defects rather than addressing them after they occur.
2Area of stationary object
If large-diameter single-crystal SiC is produced, then wafer area and device fabrication capability are improved, but defect density increases due to thermal stress and growth challenges
Solution Approach 1:
The invention applies parameter changes by establishing a specific doping element concentration gradient during growth. The high concentration region near the seed crystal interface suppresses defect formation mechanisms that typically scale with crystal size, enabling large-diameter wafers to be produced with low defect densities.
Solution Approach 2:
The invention implements local quality by creating a non-uniform doping element concentration distribution specifically in the critical region near the seed crystal interface. This localized high concentration zone (2×10^19 cm^-3 to 6×10^20 cm^-3) provides defect suppression precisely where defects are most likely to originate, while allowing the rest of the crystal to grow with acceptable overall quality.
3Reliability
If doping element concentration is increased to suppress defects, then crystal quality improves, but polytype stability may be compromised
Solution Approach 1:
The invention carefully balances parameter changes by controlling both the absolute doping element concentration and the concentration gradient. By maintaining the concentration ratio across the interface at 5 or less while keeping the absolute concentration in the high range, the invention achieves defect suppression without disrupting polytype stability.
Solution Approach 2:
The invention applies dynamics by allowing the doping element concentration to vary spatially during growth rather than maintaining a uniform concentration. The concentration profile is dynamically optimized to be high near the seed crystal interface for defect suppression and can be adjusted in other regions to maintain polytype stability throughout the crystal.
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 approach results in high-quality single-crystal SiC wafers with significantly reduced defect densities, enhancing their performance and suitability for device applications by inhibiting defect occurrence at the seed-crystal interface and promoting stable polytype growth, even for larger diameter wafers.
Implementation Method 1
the sublimation recrystallization process (Lely process)
Implementation Method 2
cubic single-crystal SiC is being produced by heteroepitaxial growth, i.e., growth on a substrate of a different type like silicon (Si), using chemical vapor deposition (CVD)
Implementation Method 3
doping element concentration of the grown crystal at least in a region in the vicinity of the seed crystal is 2×10^19 cm−3 to 6×10^20 cm−3
Data Source
AI summary
A single-crystal silicon carbide and a single-crystal silicon carbide wafer of good-quality are disclosed that are low in dislocations, micropipes and other crystal defects and enable high yield and high performance when applied to a device, wherein the ratio of doping element concentrations on opposite sides in the direction of crystal growth of the interface between the seed crystal and the grown crystal is 5 or less and the doping element concentration of the grown crystal in the vicinity of the seed crystal is 2×1019 cm−3 to 6×1020 cm−3.