Silicon carbide (SiC) substrates are inherently defective and cannot be processed directly. They require the growth of specific single-crystal thin films through an epitaxial process to produce chip wafers. This layer of thin film is known as the epitaxial layer. Nearly all SiC devices are fabricated on epitaxial materials, and the quality of the SiC homoepitaxial material is fundamental to the development of SiC devices. The performance of the epitaxial material directly determines the achievable performance of SiC devices.
For high current and high-reliability SiC devices, the epitaxial materials must meet more stringent requirements regarding surface morphology, defect density, doping uniformity, and thickness uniformity. Large size, low defect density, and high uniformity of SiC epitaxy have become key challenges for the growth of the SiC industry.
Achieving high-quality SiC epitaxy relies on advanced processes and equipment. The most commonly used method for SiC epitaxial growth is Chemical Vapor Deposition (CVD), a technique that allows precise control of film thickness, doping concentration, minimal defects, moderate growth rates, and automated process control. CVD has been successfully commercialized and has become a reliable technology for SiC device production.
SiC CVD epitaxy is generally performed using hot-wall or warm-wall CVD systems. These systems operate at high growth temperatures (1500–1700°C) to ensure the continuity of the 4H-SiC crystal structure. Over the years, CVD systems have been developed with horizontal or vertical reaction chamber designs, depending on the direction of the incoming gas flow relative to the substrate surface.
The quality of SiC epitaxial reactors is measured by three main indicators:
Epitaxial Growth Performance: Includes thickness uniformity, doping uniformity, defect density, and growth rate.
Temperature Performance: Includes the heating/cooling rates, maximum temperature, and temperature uniformity.
Cost-effectiveness: Includes the unit price and production capacity.
Three types of SiC epitaxial reactors have been commercially deployed: Hot-wall Horizontal CVD, Warm-wall Planetary CVD, and Near-hot-wall Vertical CVD. Each has its own characteristics, making it suitable for specific applications. Below is a summary of each type:
Hot-wall Horizontal CVD Systems:
Typically, this system uses a gas-floating-driven single-wafer growth process, suitable for large-diameter wafers. The LPE Pe1O6 system from Italy is a representative model. This system can achieve high growth rates, short epitaxial cycles, and excellent consistency across wafers. In China, companies like Jing Sheng Mechanical & Electrical, CETC 48, North Huachuang, and NASE have developed similar systems.
Performance Metrics (as reported by LPE):
Thickness uniformity across wafer ≤ 2%
Doping concentration uniformity ≤ 5%
Surface defect density ≤ 1 cm²
Defect-free surface area (2mm x 2mm unit) ≥ 90%
In February 2023, Jing Sheng Mechanical & Electrical launched a 6-inch dual-wafer SiC epitaxy system, overcoming the limitations of single-wafer systems by allowing two wafers to be grown per chamber with independent gas control for each layer, reducing temperature differences to under 5°C.
Warm-wall Planetary CVD Systems:
These systems feature a planetary base arrangement, allowing the growth of multiple wafers simultaneously, significantly improving production efficiency. A typical model is the Aixtron AIXG5WWC (8×150mm) and G10-SiC series from Aixtron (Germany).
Performance Metrics (as reported by Aixtron):
Thickness deviation between wafers ± 2.5%
Thickness uniformity ≤ 2%
Doping concentration deviation between wafers ± 5%
Doping concentration uniformity < 2%
However, this system is less commonly used in China, with insufficient batch production data and high technical barriers in temperature and flow control. Domestic development is still in the R&D stage, and no direct alternative has been developed.
Near-hot-wall Vertical CVD Systems:
These systems use a high-speed rotating substrate with external mechanical assistance. They operate under lower chamber pressures, which reduces the viscosity layer thickness, thus increasing growth rates. The absence of an upper wall in the reaction chamber minimizes SiC particle deposition, improving defect control. The EPIREVOS6 and EPIREVOS8 from Nuflare (Japan) are representative models.
Performance Metrics (as reported by Nuflare):
Growth rate above 50μm/h
Surface defect density controlled below 0.1 cm²
Thickness and doping concentration uniformity within 1% and 2.6%, respectively
Although this technology has shown excellent results, it has not yet been widely adopted in China, and large-scale use remains limited. Domestic manufacturers such as Xin San Dai and Jing Sheng Mechanical & Electrical have designed similar systems, but the technology is still under evaluation.
The three reactor structures each have their strengths and limitations, serving specific market demands:
Hot-wall Horizontal CVD: Known for fast growth rates, excellent quality, and uniformity. It is simple to operate and maintain, with well-established production processes, but efficiency can be limited due to single-wafer operation and frequent maintenance.
Warm-wall Planetary CVD: Supports multiple wafer growth in a single chamber, increasing production efficiency, but uniformity control across multiple wafers remains a challenge, affecting overall yield.
Near-hot-wall Vertical CVD: Features excellent defect control and high growth rates, but its complex structure requires advanced maintenance and operational expertise, limiting its widespread adoption.
In conclusion, each reactor type plays an important role in different stages of SiC device production, with choices influenced by factors like production scale, cost, and specific performance requirements. As the SiC industry evolves, advancements in epitaxial technology will continue to shape the future of high-performance SiC devices.
Silicon carbide (SiC) substrates are inherently defective and cannot be processed directly. They require the growth of specific single-crystal thin films through an epitaxial process to produce chip wafers. This layer of thin film is known as the epitaxial layer. Nearly all SiC devices are fabricated on epitaxial materials, and the quality of the SiC homoepitaxial material is fundamental to the development of SiC devices. The performance of the epitaxial material directly determines the achievable performance of SiC devices.
For high current and high-reliability SiC devices, the epitaxial materials must meet more stringent requirements regarding surface morphology, defect density, doping uniformity, and thickness uniformity. Large size, low defect density, and high uniformity of SiC epitaxy have become key challenges for the growth of the SiC industry.
Achieving high-quality SiC epitaxy relies on advanced processes and equipment. The most commonly used method for SiC epitaxial growth is Chemical Vapor Deposition (CVD), a technique that allows precise control of film thickness, doping concentration, minimal defects, moderate growth rates, and automated process control. CVD has been successfully commercialized and has become a reliable technology for SiC device production.
SiC CVD epitaxy is generally performed using hot-wall or warm-wall CVD systems. These systems operate at high growth temperatures (1500–1700°C) to ensure the continuity of the 4H-SiC crystal structure. Over the years, CVD systems have been developed with horizontal or vertical reaction chamber designs, depending on the direction of the incoming gas flow relative to the substrate surface.
The quality of SiC epitaxial reactors is measured by three main indicators:
Epitaxial Growth Performance: Includes thickness uniformity, doping uniformity, defect density, and growth rate.
Temperature Performance: Includes the heating/cooling rates, maximum temperature, and temperature uniformity.
Cost-effectiveness: Includes the unit price and production capacity.
Three types of SiC epitaxial reactors have been commercially deployed: Hot-wall Horizontal CVD, Warm-wall Planetary CVD, and Near-hot-wall Vertical CVD. Each has its own characteristics, making it suitable for specific applications. Below is a summary of each type:
Hot-wall Horizontal CVD Systems:
Typically, this system uses a gas-floating-driven single-wafer growth process, suitable for large-diameter wafers. The LPE Pe1O6 system from Italy is a representative model. This system can achieve high growth rates, short epitaxial cycles, and excellent consistency across wafers. In China, companies like Jing Sheng Mechanical & Electrical, CETC 48, North Huachuang, and NASE have developed similar systems.
Performance Metrics (as reported by LPE):
Thickness uniformity across wafer ≤ 2%
Doping concentration uniformity ≤ 5%
Surface defect density ≤ 1 cm²
Defect-free surface area (2mm x 2mm unit) ≥ 90%
In February 2023, Jing Sheng Mechanical & Electrical launched a 6-inch dual-wafer SiC epitaxy system, overcoming the limitations of single-wafer systems by allowing two wafers to be grown per chamber with independent gas control for each layer, reducing temperature differences to under 5°C.
Warm-wall Planetary CVD Systems:
These systems feature a planetary base arrangement, allowing the growth of multiple wafers simultaneously, significantly improving production efficiency. A typical model is the Aixtron AIXG5WWC (8×150mm) and G10-SiC series from Aixtron (Germany).
Performance Metrics (as reported by Aixtron):
Thickness deviation between wafers ± 2.5%
Thickness uniformity ≤ 2%
Doping concentration deviation between wafers ± 5%
Doping concentration uniformity < 2%
However, this system is less commonly used in China, with insufficient batch production data and high technical barriers in temperature and flow control. Domestic development is still in the R&D stage, and no direct alternative has been developed.
Near-hot-wall Vertical CVD Systems:
These systems use a high-speed rotating substrate with external mechanical assistance. They operate under lower chamber pressures, which reduces the viscosity layer thickness, thus increasing growth rates. The absence of an upper wall in the reaction chamber minimizes SiC particle deposition, improving defect control. The EPIREVOS6 and EPIREVOS8 from Nuflare (Japan) are representative models.
Performance Metrics (as reported by Nuflare):
Growth rate above 50μm/h
Surface defect density controlled below 0.1 cm²
Thickness and doping concentration uniformity within 1% and 2.6%, respectively
Although this technology has shown excellent results, it has not yet been widely adopted in China, and large-scale use remains limited. Domestic manufacturers such as Xin San Dai and Jing Sheng Mechanical & Electrical have designed similar systems, but the technology is still under evaluation.
The three reactor structures each have their strengths and limitations, serving specific market demands:
Hot-wall Horizontal CVD: Known for fast growth rates, excellent quality, and uniformity. It is simple to operate and maintain, with well-established production processes, but efficiency can be limited due to single-wafer operation and frequent maintenance.
Warm-wall Planetary CVD: Supports multiple wafer growth in a single chamber, increasing production efficiency, but uniformity control across multiple wafers remains a challenge, affecting overall yield.
Near-hot-wall Vertical CVD: Features excellent defect control and high growth rates, but its complex structure requires advanced maintenance and operational expertise, limiting its widespread adoption.
In conclusion, each reactor type plays an important role in different stages of SiC device production, with choices influenced by factors like production scale, cost, and specific performance requirements. As the SiC industry evolves, advancements in epitaxial technology will continue to shape the future of high-performance SiC devices.
