Tantalum carbide ceramics -- key materials for semiconductor equipment and aerospace
Recently, Hengpu Technology launched a new thermal field material for SiC crystal growth - porous tantalum carbide in Guanwei. It is reported that this material is conducive to defect control during crystal growth.
What kind of material is tantalum carbide?
Tantalum carbide (TaC) is an ultra-high temperature ceramic material. The so-called ultra-high temperature ceramics (UHTCs) usually refer to a class of ceramic materials, such as ZrC, HfC, TaC, HfB2, ZrB2, HfN, etc., whose melting point exceeds 3000 ℃ and which are used in high temperature and corrosive environments (such as oxygen atom environment) above 2000 ℃.
TaC properties
The melting point of tantalum carbide is up to 3880 ℃, with high hardness (Mohs hardness 9~10), large thermal conductivity (22W · m-1 · K-1), large bending strength (340~400MPa), and small coefficient of thermal expansion (6.6 × 10-6K-1), and exhibits excellent thermochemical stability and excellent physical properties. It has good chemical compatibility and mechanical compatibility with graphite and C/C composites. Therefore, TaC coatings are widely used in aerospace thermal protection, single crystal growth, energy electronics, medical devices and other fields.
Applied to semiconductor equipment
At present, wide bandgap semiconductors represented by silicon carbide are strategic industries facing the main economic battlefield and major national needs. At the same time, silicon carbide semiconductor is an industry with complex processes and high equipment requirements, among which the preparation of silicon carbide single crystals is the most fundamental and important link in the entire industry chain.
At present, the most commonly used method for SiC crystal growth is the physical gas phase transfer method (PVT method). PVT method uses induction heating to heat silicon carbide powder in a closed growth chamber at high temperatures above 2300 ° C and near vacuum low pressure, causing it to sublime and produce reaction gases containing different gaseous components such as Si, Si2C, SiC2, etc. Through solid-gas reaction, a silicon carbide single crystal reaction source is generated. Silicon carbide seed crystals (seeds) are set at the top of the growth chamber, The gas-phase components transported to the seed crystal are driven by the supersaturation of the gas-phase components to deposit atoms on the surface of the seed crystal and grow into silicon carbide single crystals.
This process has a long growth cycle, high difficulty in control, and is prone to defects such as microtubules and inclusions. For the control of defects, small adjustments or drifts in the furnace's thermal field can lead to changes in crystals or an increase in defects. In the later stage, we will face the challenge of "growing fast, growing thick, and growing up". In addition to theoretical and engineering improvements, we also need more advanced thermal field materials as support.
The materials used for crucibles in the thermal field mainly include graphite and porous graphite. However, graphite is prone to oxidation when exposed to oxygen at high temperatures and can be corroded by molten metals. TaC has excellent thermochemical stability and excellent physical properties, and has good chemical compatibility and mechanical compatibility with graphite. The preparation of TaC coating on the surface of graphite can effectively enhance its oxidation resistance, corrosion resistance, wear resistance and mechanical properties. Especially suitable for growing GaN or AlN single crystals in MOCVD equipment and SiC single crystals in PVT equipment, the quality of the grown single crystals is significantly improved.
Image source: Hengpu Technology
In addition, during the preparation process of silicon carbide single crystals, the Si/C stoichiometric ratio varies with the thermal field distribution after generating a reaction source through solid-gas reaction. It is necessary to distribute and transport the gas phase components according to the designed thermal field and temperature gradient. The permeability of porous graphite is insufficient, and additional holes need to be opened to increase the permeability. However, porous graphite with high permeability faces challenges such as processing, powder shedding, and etching. Porous tantalum carbide ceramics can better realize vapor component filtration, adjust local temperature gradient, guide material flow direction, control leakage, etc
Image source: Hengpu Technology
Due to the excellent acid and alkaline resistance of TaC coatings to H2, HCl, and NH3, in the silicon carbide semiconductor industry chain, TaC can also fully protect graphite matrix materials and purify the growth environment during epitaxial processing such as MOCVD.
Application in Aerospace
With the development of modern aircraft such as aerospace, rockets, and missiles towards high speed, high thrust, and high altitude, the requirements for their surface materials to have high temperature resistance and oxidation resistance under extreme conditions are also increasing. When an aircraft enters the atmosphere, it faces extreme environments such as high heat flux density, high stagnation point pressure, and fast airflow erosion, as well as chemical erosion caused by reactions with oxygen, water vapor, and carbon dioxide. When an aircraft flies out and into the atmosphere, the air around its nose cone and wings is subjected to severe compression and generates significant friction with the aircraft surface, resulting in the surface being heated by airflow. In addition to aerodynamic heating during flight, the surface of the aircraft is also affected by solar radiation, environmental radiation, and other factors, resulting in a continuous increase in surface temperature. This change will seriously affect the service condition of the aircraft.
TaC is a member of the ultra-high temperature resistant ceramic family. Its high melting point and excellent thermodynamic stability make it widely used in the hot end of aircraft, such as protecting the surface coating of rocket engine nozzles.
Other applications
TaC also has broad application prospects in fields such as cutting tools, grinding materials, electronic materials, and catalysts. For example, adding TaC to hard alloys can prevent grain growth, increase hardness, and improve their service life; TaC has good conductivity and can form non stoichiometric compounds. The conductivity varies with the composition, making it an attractive application prospect in the field of electronic materials; In terms of catalytic dehydrogenation of TaC, some researchers have studied the catalytic performance of TiC and TaC, indicating that TaC has little catalytic activity at lower temperatures, but its catalytic activity significantly increases above 1000 ℃. Research on the catalytic performance of CO has found that the catalytic products of TaC at 300 ℃ include methane, water, and a small amount of olefins.
Reference source: [1] Liu Xingliang et al. Research progress of carbon based materials modified based on tantalum carbide coating [2] Zhang Li et al. Preparation of dense tantalum carbide coating by high-temperature chemical vapor deposition [3] Cuan Bingchen et al. Research progress of preparation methods of tantalum carbide ceramic materials [4] Liu Dandan et al. Research progress of ultra-high temperature ceramic coating [5] Tianyue Advanced Prospectus [6] Hengpu Technology
The 2nd 2023 Semiconductor Industry Ceramic Materials Technology Seminar
In semiconductor chip equipment, the cost of precision ceramic components accounts for about 10%, and the current market is basically monopolized by developed countries such as the United States and Japan. How to achieve the localization of advanced ceramic components in semiconductor equipment such as lithography machines and solve the current bottleneck problem in the chip industry is an important part, and it is also a huge opportunity and challenge faced by advanced ceramic enterprises in China.
At the same time, with the vigorous development of industries such as new energy vehicles, 5G, artificial intelligence, and the Internet of Things, the scale of the third-generation wide bandgap semiconductor material industry represented by silicon carbide and gallium nitride continues to expand, and advanced ceramics will usher in a larger application market in the semiconductor industry.
In this context, China Powder Network will hold the "Second Semiconductor Industry Ceramic Material Technology Seminar" in Suzhou on June 14, 2023, aiming to build a communication platform for the semiconductor and advanced ceramic industries, exchange advanced technologies, exchange industry information, promote industry chain cooperation, and promote the process of domestic substitution.
The conference warmly welcomes industry experts, scholars, technical personnel, and representatives from the business community to attend. At the same time, companies and institutions are welcome to showcase their technological achievements and negotiate cooperation in production, academia, and research.