Silicon carbide (SiC) powder is a critical upstream material for third-generation semiconductor crystal growth. Its purity, particle morphology, and volatilization behavior directly influence sublimation rate stability, defect formation, and the overall crystal quality for 6–12 inch wafers. Today, two mainstream synthesis routes dominate the industry: Chemical Vapor Deposition (CVD) and the traditional Acheson Si+C solid-state reaction. This review provides a technical comparison of their mechanisms, powder characteristics, long-crystal compatibility, and future evolution trends.

1. Process Principles and Key Mechanistic Differences

CVD Route

Gas-phase reaction using high-purity silane (SiH₄) and hydrocarbons (CH₄/C₂H₂) at 1200–1600 °C.
Key characteristics:
• Fully gas-phase mechanism minimizes impurity sources.
• SiC particles form directly without mechanical crushing.
• Narrow particle size control from 40 nm to several micrometers.
• Stable morphology and excellent crystallinity.

Acheson Route (Si + C Solid-State Reaction)

Solid-state diffusion between silicon powder and carbon black at 2000–2500 °C, followed by crushing and classification.
Key characteristics:
• Mature, high-throughput method.
• Requires post-processing, leading to broader particle distribution.
• Higher furnace wear and oxygen incorporation.
• Particle sizes from ~10 µm to several millimeters.

2. Powder Quality Comparison and Impact on Crystal Growth

Implications for sublimation crystal growth:
Large-diameter (8–12 in.) SiC crystal growth requires extremely low impurity levels and stable sublimation rates. CVD powders offer superior uniformity and purity, while coarse Acheson grains provide better bed permeability. As a result, hybrid blends (CVD fine powder + Acheson coarse powder) are commonly used to balance sublimation uniformity and thermal stability.

3. Process Matching and Powder Selection Strategy

≤6-inch SiC crystal growth

Acheson high-purity powders remain sufficient due to wider growth windows and lower sensitivity to impurity fluctuations.

8-inch sublimation furnaces

A mixed-powder system becomes advantageous:
• 20–40% CVD fine powder improves purity and uniform sublimation.
• Coarse Acheson grains maintain optimal permeability and thermal flow.

12-inch R&D lines

Higher reliance on CVD powder:
• 60–100% CVD fine powder used to achieve ultra-low defect densities.
• Ensures stable vapor species distribution and minimized oxygen incorporation.

4. Technology Evolution and Future Trends

CVD cost-down pathways

• Localization of high-temperature CVD reactors and corrosion-resistant hot-zone materials
• Closed-loop recovery of H₂ and SiHx byproducts
• Plasma-assisted CVD to reduce deposition temperature by 100–200 °C

Acheson process optimization

• Coupled continuous vacuum purification and advanced acid-leaching
• Target purity improvement toward 7N levels
• Reduced oxygen pickup through optimized furnace design

Intelligent powder blending

• Machine-learning-based control of sublimation curves
• Real-time adjustment of fine-powder ratios
• Predictive modeling of powder bed permeability and crystal morphology

Industry outlook

As SiC moves into the 8–12 inch era, CVD powder’s market share is expected to increase rapidly due to:
• Stricter purity and uniformity requirements
• Improved cost structures as CVD falls below the threshold where it is ≤2× the cost of Acheson powder
• Better correlation between high CVD fraction and large-diameter crystal yield

This shift indicates that future high-end SiC crystal growth will increasingly rely on CVD-based or hybrid-engineered powder systems optimized for sublimation stability, defect suppression, and scalable wafer production.