What is SiC coated graphite susceptor?

In order to introduce the SiC coated graphite susceptor, it's important to understand its application. When manufacturing devices, further epitaxial layers are required to be built on some wafer substrates. For instance, LED light-emitting devices require the preparation of GaAs epitaxial layers on silicon substrates; while SiC layer growth on SiC substrates is needed, the epitaxial layer helps to construct devices for power applications such as high voltage and high current, for instance SBD, MOSFET, etc. Conversely, the GaN epitaxial layer is constructed on the semi-insulating SiC substrate to further construct devices such as HEMT for radio frequency applications like communications. To do this, a CVD equipment (among other technical methods) is required. This equipment can deposit the III and II group elements and V and VI group elements as growth source materials on the substrate surface.

In CVD equipment, the substrate cannot be placed directly on metal or simply placed on a base for epitaxial deposition. This is because gas flow direction (horizontal, vertical), temperature, pressure, fixation, shedding of contaminants, etc. are all factors that can influence the process. Therefore, a susceptor is needed where the substrate is placed on the disk, and then CVD technology is used to perform epitaxial deposition on the substrate. This susceptor is a SiC-coated graphite susceptor (also known as a tray).

The graphite susceptor is a crucial component in MOCVD equipment. It acts as the carrier and heating element of the substrate. Its thermal stability, uniformity, and other performance parameters are important factors that determine the quality of epitaxial material growth, and directly affect the uniformity and purity of the thin film material. Therefore, the quality of the graphite susceptor is vital in the preparation of epitaxial wafers. However, due to the consumable nature of the susceptor and changing working conditions, it is easily lost.

Graphite has excellent thermal conductivity and stability, making it an ideal base component for MOCVD equipment. However, pure graphite faces some challenges. During production, residual corrosive gases and metal organic matter can cause the susceptor to corrode and powder away, thereby greatly reducing its service life. Additionally, the falling graphite powder can cause pollution to the chip. Hence, these problems need to be resolved during the preparation process of the base.

Coating technology is a process that can be used to fix powder on surfaces, enhance thermal conductivity, and distribute heat evenly. This technology has become the primary way to solve this problem. Depending on the application environment and usage requirements of the graphite base, the surface coating should have the following characteristics:

1. High density and full wrapping: The graphite base is in a high-temperature, corrosive working environment, and the surface must be fully covered. The coating must also have good density to provide good protection.

2. Good surface flatness: Since the graphite base used for single crystal growth requires a high surface flatness, the original flatness of the base must be maintained after the coating is prepared. This means that the coating surface must be uniform.

3. Good bonding strength: Reducing the difference in thermal expansion coefficient between the graphite base and the coating material can effectively improve the bonding strength between the two. After experiencing high and low temperature thermal cycles, the coating is not easy to crack.

4. High thermal conductivity: High-quality chip growth requires fast and uniform heat from the graphite base. Therefore, the coating material should have high thermal conductivity.

5. High melting point, high temperature resistance to oxidation, and corrosion resistance: The coating should be able to work stably in high-temperature and corrosive working environments.

At present, Silicon Carbide (SiC) is the preferred material for coating graphite, owing to its exceptional performance in high-temperature and corrosive gas environments. Moreover, its close thermal expansion coefficient with graphite enables them to form strong bonds. Additionally, Tantalum Carbide(TaC) coating also is a good choice, and it can stand in more high temperature(>2000℃) environments.

Semicorex offers high-quality SiC and TaC coated graphite susceptors. If you have any inquiries or need additional details, please don't hesitate to get in touch with us.

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Email: sales@semicorex.com