SiC Growth Substrate Structure for Crack-Resistant Crystal Growth
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Solution Overview
Problem
The high cost and impurity-related defects in silicon carbide (SiC) wafers hinder their widespread adoption in power electronics, particularly for electric vehicles, due to the limitations of current production methods like physical vapor transport (PVT) and the high purity requirements for SiC source material.
Innovation Solution
A SiC growth substrate and CVD reactor design that utilizes carbon fiber composite materials and controlled temperature profiles to facilitate high-purity, low-cost production of SiC, minimizing impurities and mechanical stress during crystal growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If acid leaching is used to purify SiC source material, then trace metals are extracted from the surface, but the purity is limited to 4N or 5N and particles need to be very small
Solution Approach 1:
The patent changes the purification method from acid leaching to a different process that allows achieving 6N purity with larger particles. This parameter change in the purification technique resolves the contradiction by enabling high purity without requiring small particle sizes.
Solution Approach 2:
The patent extracts trace metals from SiC particles through a purification process that goes beyond surface-level acid leaching. By taking out impurities more effectively throughout the particle, high purity is achieved without needing to reduce particle size to increase surface area.
2Productivity
If powder source material is used in PVT growth, then high initial sublimation rate is achieved, but parasitic polycrystalline depositions and nucleation occur
Solution Approach 1:
The patent changes the physical state of the source material from powder to larger particles or blocks. This parameter change reduces the initial sublimation rate to prevent parasitic depositions and vapor-phase nucleation, while maintaining adequate growth rates through controlled sublimation of the larger source material.
Solution Approach 2:
The patent uses a controlled, moderate sublimation rate rather than maximum rate. By using partial action (controlled sublimation) instead of excessive action (high initial rate from powder), the process avoids defects while maintaining productivity through optimized growth conditions.
3Reliability
If larger SiC particles are used as source material, then handling and contamination are reduced, but surface area for sublimation is decreased
Solution Approach 1:
The patent changes the particle size parameter to an optimal range that balances contamination resistance with adequate sublimation surface area. Rather than using very small or powder particles, larger particles are used with controlled surface area to prevent contamination while maintaining productivity.
4Productivity
If high sublimation rate is maintained, then crystal growth speed increases, but temperature gradients cause mechanical stress and cracking
Solution Approach 1:
The patent uses dynamic temperature control during the growth process. Temperature is adjusted throughout the growth cycle to maintain adequate growth rates while preventing excessive gradients that cause stress and cracking. The system adapts temperature conditions as the crystal develops.
Solution Approach 2:
The patent implements controlled temperature gradients from the beginning of growth to prevent excessive stress accumulation. By cushioning against thermal stress through pre-planned temperature profiles, the crystal can grow at high rates without developing cracks or mechanical defects.
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
Enables efficient, large-scale production of high-purity SiC with reduced defects and lower costs, suitable for power electronics applications.
Implementation Method 1
resist forces generated during growth of the SiC crust... having a thermal expansion coefficient at 1800° C. of less than 5.7×10−6K−1
Implementation Method 2
A SiC growth substrate and CVD reactor design that utilizes carbon fiber composite materials and controlled temperature profiles to facilitate high-purity, low-cost production of SiC
Data Source
AI summary
A SiC substrate includes a main body, a first power connection, and a second power connection. The main body has a length that extends between the first power connection and the second power connection. The first power connection is configured to conduct power into the main body for heating the main body. The second power connection is configured to conduct electric power conducted via the first power connection into the main body out of the main body. The main body forms a surface for deposition of SiC for growing a SiC crust. The main body is configured to resist forces generated during growth of the SiC crust having a minimal thickness for preventing cracking of the main body due to the generated forces at least in a volume section of the main body. The volume section is formed between a first plane and a second plane.