Semiconductor Components--SiC Coated Graphite Pedestal

According to the Nikkei Chinese website, Toyo Carbon will increase production globally for core components of semiconductor manufacturing devices. In addition to strengthening plants in the United States and China, the company will begin production in Italy, which, along with increased investment in Japan, willA total of 36 billion yen will be invested in 2027. It has more than 50% of the global share in the field of trays (bases) carrying silicon carbide wafers and core components called "Susceptor.

So, what exactly is this tray carrying the wafers?
In the wafer fabrication process, some wafer substrates need to be further constructed with epitaxial layers to facilitate the fabrication of devices, typicallyLED light-emitting devices need to be prepared on silicon substrates.The epitaxial layer of GaAs; the SiC epitaxial layer is grown on the conductive SiC substrate for constructing devices such as SBD, MOSFET, etc., for power applications such as high voltage and high current; the GaN epitaxial layer is constructed on the semi-insulating SiC substrate, and further devices such as HEMT are constructed for radio frequency applications such as communications. This process is inseparable from the CVD equipment.

InIn CVD equipment, the substrate cannot be directly placed on the metal or simply placed on a base for epitaxial deposition, because it involves gas flow (horizontal, vertical), temperature, pressure, fixation, and other factors. Therefore, a pedestal is needed, and then the substrate is placed on the disk, and then the epitaxial deposition is carried out on the substrate by CVD technology. This pedestal is the SiC coated graphite pedestal (also called tray).

A SiC-coated graphite susceptor is commonly used as part of a metal-organic chemical vapor deposition (MOCVD) apparatus to support and heat a single crystal substrate. The performance parameters such as thermal stability and thermal uniformity of 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.
Metal organic chemical vapor deposition (MOCVD) technology is currently the mainstream technology for epitaxial growth of GaN films in blue LEDs. It has the advantages of simple operation, controllable growth rate, and high purity of the grown GaN films. The bearing base for epitaxial growth of GaN thin film, as an important part of the reaction chamber of MOCVD equipment, needs to have the advantages of high temperature resistance, uniform thermal conductivity, good chemical stability, strong thermal shock resistance, etc., and the graphite material can meet the above conditions.

Graphite baseOne of the core components in MOCVD equipment is the carrier and heating body of the substrate, which directly determines the uniformity and purity of the thin film material, so its quality directly affects the preparation of the epitaxial wafer, and at the same time, with the increase of the number of uses, the change of the working conditions, it is very easy to lose, which belongs to consumables.
Although graphite has excellent thermal conductivity and stability making itMOCVDThe base part of the equipment has a good advantage, but in the production process, the graphite will corrode the powder due to the residual of corrosive gas and metal organic matter, and the service life of the graphite base will be greatly reduced. At the same time, the falling graphite powder will pollute the chip.
The emergence of coating technology can provide surface powder fixation, enhance thermal conductivity, and balance heat distribution, which has become the main technology to solve this problem. Graphite Pedestal inIn the use environment of MOCVD equipment, the surface coating of graphite base should meet the following characteristics:
（1) The graphite base can be fully wrapped and compactness is good, otherwise the graphite base is easily corroded in the corrosive gas. (2) The high bonding strength with the graphite base ensures that the coating is not easy to fall off after multiple high temperature and low temperature cycles. (3) It has good chemical stability and avoids the failure of the coating in high temperature and corrosive atmosphere.
SiC has the advantages of corrosion resistance, high thermal conductivity, thermal shock resistance and high chemical stability, and can work well in GaN epitaxial atmosphere. In addition, the thermal expansion coefficient of SiC differs little from that of graphite, so SiC is the material of choice as a surface coating for graphite susceptors.
currently commonSiC is mainly 3C, 4H and 6H type, different crystal type of SiC uses different. For example, 4H-SiC can manufacture high-power devices; 6H-SiC is the most stable and can manufacture optoelectronic devices; 3C-SiC can be used to produce GaN epitaxial layers and manufacture SiC-GaN RF devices because of its similar structure to GaN. 3C-SiC is also commonly referred to as β-SiC, and an important use of β-SiC is as a thin film and coating material. Therefore, β-SiC is currently the main material for coating.

Preparation method of silicon carbide coating

at present,The preparation methods of SiC coating mainly include gel-sol method, embedding method, brush coating method, plasma spraying method, chemical vapor reaction method (CVR) and chemical vapor deposition method (CVD).

embedding method

This method is a kind of high temperature solid phase sintering, mainly based onSi powder and C powder are mixed as embedded powder, the graphite matrix is placed in the embedded powder, and sintered at high temperature in inert gas, and finally the SiC coating is obtained on the surface of the graphite matrix. The process is simple, and the combination between the coating and the substrate is better, but the uniformity of the coating along the thickness direction is poor, and more holes are easy to produce, resulting in poor oxidation resistance.

brush coating method

The brush coating method is mainly to paint the liquid raw material on the surface of the graphite substrate, and then solidify the raw material at a certain temperature to prepare the coating. The process is simple and the cost is low, but the combination of the coating and the substrate prepared by the brush coating method is weak, the coating uniformity is poor, the coating is thin and the oxidation resistance is low, and other methods are needed to assist.

plasma spraying method

The plasma spraying method is mainly a plasma gun that sprays molten or semi-molten raw materials on the surface of the graphite substrate, and then solidifies and bonds to form a coating. The method is simple to operate and can produce denser silicon carbide coatings, but the silicon carbide coatings prepared by this method are often too weak to resist oxidation, so they are generally usedSiC composite coating was prepared to improve the quality of the coating.

Gel-Sol method

Gel-Sol method is mainly to prepare a uniform transparent sol solution covered on the surface of the substrate, dried into a gel after sintering to obtain a coating. The method is simple and low cost, but the prepared coating has the disadvantages of low thermal shock resistance and easy cracking, and cannot be widely used.

Chemical vapor reaction method (CVR）

CVR is mainly through the use of Si and SiO₂Powder generated at high temperatureSiO vapor, a series of chemical reactions occur on the surface of the C material substrate, resulting in the formation of SiC coating. The SiC coating prepared by this method is closely bonded to the substrate, but the reaction temperature is higher and the cost is higher.

Chemical vapor deposition (CVD）

CVD is currently the main technology for preparing SiC coatings on the surface of substrates. The main process is that a series of physical and chemical reactions occur on the surface of the substrate, and finally the SiC coatings are deposited on the surface of the substrate. The SiC coating prepared by CVD technology is closely combined with the surface of the substrate, which can effectively improve the oxidation resistance and ablation resistance of the substrate material, but the deposition time is longer, and there is a certain amount of toxic gas in the reaction gas.

Market Situation of SiC Coated Graphite Pedestal
When foreign manufacturers started earlier, they had obvious leading advantages and high market share.. Internationally,The mainstream suppliers of SiC coated graphite susceptor include Dutch Xycard, German SGL Carbon (SGL), Japanese Toyo Carbon, American MEMC and other enterprises, which basically occupy the international market. Although China has broken through the key core technology of uniform growth of SiC coating on the surface of graphite substrate, high-quality graphite substrate still depends on German SGL, Japanese Toyo Carbon and other enterprises. The graphite substrate provided by domestic enterprises cannot meet the requirements of MOCVD equipment for SiC coated graphite substrate due to quality problems such as thermal conductivity, elastic modulus, rigid modulus, lattice defects and so on.
China's semiconductor industry is developing rapidly,MOCVD epitaxial equipment localization rate gradually increased, and other process application expansion, the future SiC coated graphite base product market is expected to grow rapidly. According to preliminary estimates by industry insiders, the domestic graphite base market will exceed 0.5 billion yuan in the next few years.
As the core component of compound semiconductor industrialization equipment, SiC coated graphite base has important strategic significance for ensuring the development of China's semiconductor industry by mastering the key core technology of its production and manufacturing and realizing the localization of the whole industrial chain of raw materials, process and equipment. The field of domestic SiC coated graphite susceptor is in the ascendant, and the product quality is just around the corner to reach the international advanced level.

In semiconductor chip equipment, the cost of precision ceramic components accounts for aboutAbout 10%, the current market is basically monopolized by developed countries such as the United States and Japan. How to realize the localization of advanced ceramic components in semiconductor equipment such as lithography machines and solve the current "stuck neck" problem in the chip industry is also an important part of the great opportunities and challenges faced by domestic advanced ceramic enterprises.

At the same time, with new energy vehicles,With the vigorous development of 5G, artificial intelligence, Internet of things and other industries, the scale of the third generation wide band gap semiconductor material industry represented by silicon carbide and gallium nitride is expanding, and advanced ceramics will usher in a larger application market in the semiconductor industry.