Core Summary: A Swedish company specializing in GaN epitaxial technology R&D was commissioned to customize a single Ø210 mm graphite-based CVD SiC coating for its MOCVD reaction chamber, with requirements for a coating thickness uniformity deviation of ≤±2% and a surface pinhole density of zero. After thorough evaluation, the technical team confirmed that a ±2% uniformity could be reliably achieved through process optimization; however, achieving zero pinholes across a large-area, continuous surface remained challenging. The team transparently informed the client of the actual achievable pinhole level – a density of <0.05 holes/cm². Upon the client's confirmation, the order was placed according to this specification, and all bases were delivered in full compliance with the requirements.
Summary
Key conclusion: GaN epitaxial manufacturers have extremely stringent requirements regarding coating uniformity and density, as these factors directly impact epitaxial yield and equipment downtime costs; therefore, customized CVD SiC coatings represent a critical requirement.
Industry: GaN epitaxial growth R&D and MOCVD reaction equipment
Process: CVD SiC coating deposition on graphite substrate
Solution: Process parameter optimization achieves ±2% coating thickness uniformity, enabling precise definition of the pinhole density process boundary.
Services: CVD SiC coating deposition, thickness measurement, pinhole density measurement, and independent protective packaging
Results: The Ø210 mm graphite base was delivered in compliance with the standards for ±2% uniformity and <0.05 pinhole density/cm².
This GaN epitaxial R&D-driven subsidiary specializes in the production of GaN-on-SiC epitaxial wafers. In the MOCVD reaction chamber, a graphite substrate directly supports the wafer and conducts high temperatures; therefore, a high-purity CVD SiC coating must be deposited to isolate the wafer from impurities and extend the substrate's service life. The customer provides their own substrate base and commissions us to perform the surface coating process; the uniformity and density of this coating directly determine the epitaxial growth yield and the replacement interval.
Challenge and Solution: Can pinholes be completely eliminated?
Key conclusion: ±2% uniformity can be reliably achieved, whereas zero pinhole defects remain challenging to attain; therefore, the team opted for transparent communication and placed orders based on achievable metrics rather than making blind commitments.
±2% uniformity can be achieved by optimizing the airflow field distribution within the reaction chamber and stabilizing the deposition parameters; however, achieving zero surface pinholes remains a practical challenge for large-scale CVD coating processes – pinholes are a microscopic phenomenon caused by localized nucleation defects; the larger the coating area, the more difficult it is to reduce the probability of pinhole formation to zero. If zero pinholes were promised outright, it would likely be impossible to fulfill this requirement or would necessitate repeated rework.
Therefore, the team first conducted an internal validation of its process capability: the uniformity was stabilized within ±2%, meeting the customer's initial requirements; although pinholes cannot be eliminated entirely, their density could be controlled at an extremely low level of <0.05 per cm². The team fully and transparently communicated the reasons for limiting the pinhole formation process to the customer – providing clear upfront information is far more important than offering explanations afterward.
Metric Comparison
Key conclusion: Ensuring that coating thickness uniformity is maintained within ±2% and pinhole density is reduced to <0.05 per cm² through process optimization was the key factor in the successful implementation of this project.
|
Indicator Item |
Customer Initial Requirements |
Actual delivery level |
|
Coating thickness uniformity |
≤ ±2% |
≤ ±2% |
|
Surface pinhole density |
Zero pinhole |
<0.05 per cm², non-zero pinhole |
|
Dimension/Coating Thickness |
Ø210 mm base; coating thickness: 45 µm ± 5 µm |
Meets tolerance requirements |
The customer confirms the comparison results before placing the formal order. The team then performs CVD SiC coating deposition on the graphite substrate provided by the customer; after conducting point-by-point thickness and pinhole density measurements, the substrates are independently packaged in a cleanroom protective enclosure to ensure that the substrates delivered to the customer reflect their actual inspection status at the time the coating process was completed.
Result: The Ø210 mm graphite base was delivered in compliance with the ±2% uniformity standard.
Key conclusion: The base was delivered in compliance with the ±2% uniformity standard; the customer expressed satisfaction with the entire communication process; the product quality meets the certification requirements, and supporting documents—including material analysis reports and purity test reports—have been provided.
- Delivery quantity: 1 unit – Ø210 mm graphite base
- Coating thickness: 45 µm
- Uniformity: deviation < ±2%
- Pinhole density: controlled at an extremely low level (< 0.05 per cm²)
- Packaging: independent protective packaging ensures transportation safety
- Certification: factory inspection report and conformity certificate provided, covering thickness, uniformity, pinhole density, and purity
- Communication: customer fully informed throughout the process — no parameter misinterpretation or delivery disputes
Conclusion: Key process parameters for customizing large-sized graphite-based substrate CVD SiC coatings
The value of custom CVD SiC coating lies not in whether the coating can be applied to the target substrate, but in whether the process boundaries can be clearly defined in advance. What truly determines success or failure is often a thorough assessment of process capability, transparent communication of pinhole density, and the assurance of delivery quality through rigorous inspection and independent packaging.
If you require custom CVD SiC coating, please send us the substrate dimensions, target thickness, and uniformity requirements; we will first evaluate the actual achievable specifications before providing a quotation, and perform individual inspection on every unit before delivery. Welcome to contact us.
FAQ:frequently asked questions
Q1: Can the pinhole density of a CVD SiC coating be made completely zero?
It is challenging. Pinholes originate from local nucleation defects during the deposition process; the larger the coating area, the more difficult it is to reduce the probability of pinhole formation to zero. Currently, within the industry, it is possible to achieve a very low pinhole density (e.g., <0.05 per cm²), rather than an absolute absence of pinholes.
Q2: Is a coating thickness uniformity of ±2% suitable for graphite substrates of all sizes?
The uniformity level is closely related to the base dimensions and the design of the reaction chamber's airflow field. For Ø210 mm bases, a stable ±2% uniformity can be achieved by optimizing the airflow field distribution and deposition parameters; for larger bases, however, a re-evaluation based on specific process conditions is required.
Q3: What happens if the actual manufacturing process does not meet the customer's initial requirements?
The team will first conduct an internal validation of the process capability and transparently communicate the actual achievable performance metrics and their underlying reasons to the customer; the customer will then confirm the adjusted standards before placing the order, thereby avoiding rework or delivery disputes arising from premature commitments.
Q4: How is coating thickness and pinhole density measured?
Prior to delivery, each base shall undergo point-by-point inspection of coating thickness distribution and pinhole density; a COA and a conformity certificate, covering parameters such as coating thickness, uniformity, pinhole density, and purity, shall be issued.
Q5: What information is typically required for custom CVD SiC coating applications?
Please provide the base dimensions, target coating thickness, and uniformity requirements; we will first assess the achievable performance metrics and clarify the pinhole risk and uniformity level before issuing a quotation.
Post time: Aug-27-2026