Wafer epitaxial growth is achieved through the metal organic chemical vapor deposition (MOCVD) technology, in which ultra-pure gases are injected into the reactor and finely metered, so that they combine at elevated temperatures to cause chemical interactions and are deposited onto semiconductor wafers in very thin atomic layers to form epitaxy of materials and compound semiconductors.
In CVD equipment, the substrate cannot be placed directly on metal or simply on a base for epitaxial deposition, because it will be affected by many factors. Therefore, a susceptor or tray is needed to hold the substrate, and then use CVD technology to perform epitaxial deposition on the substrate. This susceptor is a MOCVD graphite susceptor (also called MOCVD graphite tray).
Its structure is shown in the figure below :
Why does the graphite susceptor need CVD coating?
The graphite susceptor is one of the core components in MOCVD equipment. It is the carrier and heating element of the substrate. Its performance parameters such as thermal stability and thermal uniformity play a decisive role in the quality of epitaxial material growth, and directly determine the uniformity and purity of epitaxial thin film materials. Therefore, its quality directly affects the preparation of epitaxial wafers. At the same time, with the increase in the number of uses and the changes in the working conditions, it is very easy to wear and tear, it is a consumable. The excellent thermal conductivity and stability of graphite give it a great advantage as a base component of MOCVD equipment.
However, if it is only pure graphite, there will be some problems. In the production process, there will be residual corrosive gases and metal organic matter, and the graphite susceptor will corrode and fall off, which greatly reduces the service life of the graphite susceptor. At the same time, the falling graphite powder will also cause pollution to the wafer, so these problems need to be solved in the preparation process of the base. Coating technology can provide surface powder fixation, enhance thermal conductivity, and balance heat distribution, and has become the main technology to solve this problem.
According to the application environment and use requirements of the graphite base, the surface coating should have the following characteristics:
1. High density and full coverage: The graphite base is in a high temperature and corrosive working environment. The surface must be fully covered, and the coating must have good density to play a good protective role.
2. Good surface flatness: Since the graphite base used for single crystal growth requires a very high surface flatness, the original flatness of the base must be maintained after the coating is prepared, that is, 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 the graphite base to provide fast and uniform heat, so the coating material should have high thermal conductivity.
5. High melting point, high temperature oxidation resistance and corrosion resistance: The coating should be able to work stably in a high temperature and corrosive working environment.
The thermal stability, thermal uniformity and other performance parameters of the SiC coated graphite susceptor play a decisive role in the quality of epitaxial material growth, so it is the core key component of MOCVD equipment.
β-SiC (3C-SiC) crystal form is selected as the coating. Compared with other crystal forms, this crystal form has a series of excellent properties such as good thermodynamic stability, oxidation resistance and corrosion resistance. At the same time, it has a thermal conductivity that is basically consistent with that of graphite, thus giving the graphite base special properties. It can effectively solve the failure of the graphite base caused by high-temperature oxidation and corrosion and powder loss during service, and make the surface of the graphite base dense, non-porous, high-temperature resistant, anti-corrosion, anti-oxidation and other characteristics, thereby improving the crystal epitaxial quality and the service life of the graphite base (the service life of the SiC coated graphite base is measured in furnaces).
How to choose MOCVD graphite tray/susceptor that is resistant to high temperature and corrosion?
When choosing a graphite tray or susceptor for MOCVD that is resistant to high temperature corrosion, the following key factors should be considered:
1. Material purity: High-purity graphite materials can better resist corrosion and oxidation at high temperatures and reduce the impact of impurities on the deposition process.
2. Density and porosity: Graphite trays with high density and low porosity have better mechanical strength and corrosion resistance, and can effectively prevent gas penetration and material erosion.
3. Thermal conductivity: The high thermal conductivity graphite tray helps to evenly distribute heat, reduce thermal stress, and improve the stability and service life of the equipment.
4. Surface treatment: Graphite pallets that have undergone special surface treatment, such as coating or plating, can further enhance their corrosion resistance and wear resistance.
5. Size and shape: According to the specific requirements of the MOCVD equipment, select the appropriate size and shape to ensure the compatibility of the tray with the equipment and the convenience of operation.
6. Manufacturer’s reputation: Choose a manufacturer with a good reputation and rich experience to ensure the reliability of product quality and after-sales service.
7. Cost-effectiveness: On the premise of meeting technical requirements, consider cost-effectiveness and choose products with higher cost performance.
VET Energy is a high-purity graphite susceptor supplier, we offer a wide range of categories, and can be used in MOCVD equipment of different brands, models and specifications. The SiC coated graphite susceptor produced by VET Energy have no coating contact points and no weak links. In terms of service life, they can meet the requirements of customers with different needs (including the use of chlorine-containing atmospheres), and customers are welcome to consult and inquiry.
Post time: Mar-01-2025