What Is the Core Material for Next-Gen LED Epitaxy Susceptors?

By Sera Lee (Sales) @ semicera semiconductor technology co., ltd.

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Driven by emerging technologies such as Micro LED, Mini LED, and high-power general lighting, the manufacturing of LED epi-wafers is facing unprecedented challenges. Every small improvement in luminous efficiency and uniformity places increasingly higher requirements on the key components inside MOCVD (Metal-Organic Chemical Vapor Deposition) reactors.

Among them, the LED Epitaxy Susceptor—the base on which the epi-wafer grows—directly determines the yield and uniformity of the final chip.

Why can’t traditional graphite susceptors meet these demanding requirements anymore?
The answer lies in their intrinsic limitations under ultra-high-temperature and high-purity process environments. Bottlenecks in uniformity and yield are forcing the industry to find a revolutionary alternative.

Silicon Carbide (SiC), with its exceptional physical and chemical characteristics, is rapidly becoming the core material for next-generation LED epitaxy susceptors. This article explores the advantages of SiC, its application forms, and how it helps manufacturers break through yield limitations.

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The Challenge of Current Susceptors

1.1 The Rise and Fall of Traditional Graphite

For decades, polycrystalline graphite has been the mainstream susceptor material due to its low cost and ease of machining. However, as demand for higher-quality and lower-defect-density epi-wafers has surged, its weaknesses have become increasingly visible:

• Poor thermal uniformity:
  Graphite has relatively low and unstable thermal conductivity, making it difficult to achieve an ideal temperature distribution inside MOCVD reactors. This leads to variations in growth rate and composition at different wafer positions—far from the near-perfect uniformity $(\Delta T\approx 0)$ that epitaxy engineers aim for.

• Susceptible to corrosion and contamination:
  Under high-temperature hydrogen and halogen-containing precursors, graphite reacts chemically and releases carbon particles, creating surface defects that severely reduce yield.

• Short service life & high maintenance cost:
  Frequent cleaning, decontamination, and replacement increase downtime and significantly raise production costs.

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1.2 Strict Requirements for Next-Generation Materials

Next-generation susceptor materials must satisfy a set of demanding performance requirements to support GaN-based epitaxy and new substrates such as SiC and sapphire:

• Ultra-high thermal conductivity for rapid thermal response and excellent temperature uniformity

• Extremely low particle generation to meet the zero-defect tolerance of Micro LED manufacturing

• Superior corrosion resistance and chemical inertness to maintain structural integrity in aggressive MOCVD environments

• Outstanding mechanical stability for repeated high-temperature cycling without deformation or cracking

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The Next-Gen Champion — Silicon Carbide (SiC)

2.1 Why SiC? A Deeper Look

Silicon Carbide (SiC) is the ideal material that meets all of the above criteria, thanks to its unique covalent-bond crystal structure:

• Exceptional thermal management:
  SiC offers thermal conductivity several times higher than graphite, enabling precise control of wafer temperature fluctuations and thus ensuring excellent uniformity in epi-layer thickness and composition.

• Outstanding chemical stability:
  Extremely inert, SiC is highly resistant to corrosion from precursors and by-products in MOCVD reactions, minimizing interference with the process atmosphere.

• High purity with minimal contamination:
  High-purity SiC significantly reduces particle release and impurity introduction, directly contributing to higher LED chip yields.

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2.2 Two Forms of SiC Susceptors and Their Applications

To meet varying requirements and budgets, SiC susceptors are available in two primary forms:

1) SiC-Coated Graphite

• Principle:
  A dense, high-purity CVD-SiC coating is grown on a graphite substrate.

• Advantages:
  Combines graphite’s machinability with SiC’s superior surface properties.
  Industry leaders such as SGL Carbon and Tokai Carbon have achieved advancements including:

  • Ultra-high-purity coatings (>99.9999%)

  • High-adhesion, low-stress CVD processes
    These ensure the coating does not peel or generate particles during harsh thermal cycling, a key factor affecting epi-wafer yield.

2) Bulk SiC

• Principle:
  The entire susceptor is made of high-purity SiC.

• Advantages:
  Maximum purity and longest lifespan, making it ideal for extremely strict processes such as Micro LED—even though the initial cost is highest.

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2.3 Why SiC Is Critical for Micro LED Epitaxy

Micro LED allows zero tolerance for pixel defects. Even slight contamination or temperature non-uniformity may cause massive transfer failure.

SiC’s:

• high purity

• ultra-low particle generation

• perfect thermal uniformity

make it the foundation for high-yield Micro LED -Epitaxie, dramatically reducing defect density caused by the susceptor and paving the way for commercial-scale production.

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 Head-to-Head Comparison — SiC vs. Graphite

A direct comparison of key performance indicators:

Industry data shows that upgrading from graphite to high-quality SiC-coated susceptors increases high-power blue LED -Epitaxie yield by 5–15%, while particle count decreases by over 80%.

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Implementation and Buying Considerations

4.1 Challenges in Implementation

Despite its advantages, adopting Sic is not without obstacles:

• Higher initial investment

• More difficult machining due to material hardness

Manufacturers must balance upfront cost against long-term gains in yield and lifecycle.

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4.2 How to Select the Best SiC Solution

When sourcing SiC susceptors, decision-makers should evaluate:

• Coating quality (for coated graphite):
  Thickness, density, and adhesion must meet international standards.

• Purity level:
  Supplier must provide detailed purity reports—trace metal impurities directly impact LED device performance.

• Custom design capabilities:
  Geometry significantly affects thermal management and airflow matching inside the MOCVD chamber.

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4.3 Maintenance Tips

Even SiC susceptors require specialized maintenance:

• Use gentle but effective chemical or high-energy physical cleaning

• Proper cleaning protocols can extend SiC lifespan by more than 50%

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For next-generation LED -Epitaxie processes seeking ultimate uniformity and yield, Silicon Carbide (SiC) is unequivocally the core material of choice.

By overcoming the long-standing bottlenecks of graphite—thermal management and particle contamination—SiC provides a solid foundation for breakthroughs in Micro LED and high-power LED manufacturing.

If your production line is facing stagnant yield or you’re planning the next upgrade of your MOCVD system, adopting SiC susceptors will be one of the highest-ROI investments you can make.