Applications of TaC Coated Graphite Components

1. Crucible, seed crystal holder and guide ring in SiC and AIN single crystal furnace grown by PVT method

In the process of growing SiC and AlN single crystals by the physical vapor transport method (PVT), components such as the crucible, seed crystal holder and guide ring play a vital role. During the preparation process of SiC, the seed crystal is located in a relatively low temperature region, while the raw material is in a high temperature region exceeding 2400°C. The raw materials decompose at high temperatures to form SiXCy (including Si, SiC₂, Si₂C and other components). These gaseous substances are then transferred to the low-temperature seed crystal area, where they nucleate and grow into single crystals. In order to ensure the purity of SiC raw materials and single crystals, these thermal field materials must be able to withstand high temperatures without causing contamination. Similarly, the heating element during the AlN single crystal growth process also needs to be able to withstand the corrosion of Al vapor and N₂, and should have a high enough eutectic temperature to reduce the crystal growth cycle.

Research has proven that graphite thermal field materials coated with TaC can significantly improve the quality of SiC and AlN single crystals. The single crystals prepared from these TaC-coated materials contain less carbon, oxygen, and nitrogen impurities, reduced edge defects, improved resistivity uniformity, and significantly reduced density of micropores and etching pits. In addition, TaC-coated crucibles can maintain almost unchanged weight and intact appearance after long-term use, can be recycled multiple times, and have a service life of up to 200 hours, which greatly improves the sustainability and safety of single crystal preparation. Efficiency.

2. Application of MOCVD technology in GaN epitaxial layer growth

In the MOCVD process, the epitaxial growth of GaN films relies on organometallic decomposition reactions, and the performance of the heater is crucial in this process. It not only needs to be able to heat the substrate quickly and evenly, but also maintain stability at high temperatures and repeated temperature changes, while being resistant to gas corrosion and ensuring the quality and thickness uniformity of the film, which affects the performance of the final chip.

In order to improve the performance and service life of heaters in MOCVD systems, TaC-coated graphite heaters were introduced. This heater is comparable to traditional pBN-coated heaters in use, and can bring the same quality of GaN epitaxial layer while having lower resistivity and surface emissivity, thus improving heating efficiency and uniformity, reducing reduced energy consumption. By adjusting process parameters, the porosity of the TaC coating can be optimized, further enhancing the heater's radiation characteristics and extending its service life, making it an ideal choice in MOCVD GaN growth systems.

3. Application of epitaxial coating tray (wafer carrier)

As a key component for the preparation and epitaxial growth of third-generation semiconductor wafers such as SiC, AlN, and GaN, wafer carriers are usually made of graphite and coated with SiC coating to resist corrosion by process gases. In the epitaxial temperature range of 1100 to 1600°C, the corrosion resistance of the coating is critical to the durability of the wafer carrier. Studies have shown that the corrosion rate of TaC coatings in high-temperature ammonia is significantly lower than that of SiC coatings, and this difference is even more significant in high-temperature hydrogen.

The experiment verified the compatibility of the TaC-coated tray in the blue GaN MOCVD process without introducing impurities, and with appropriate process adjustments, the performance of LEDs grown using TaC carriers is comparable to traditional SiC carriers. Therefore, TaC-coated pallets are an option over bare graphite and SiC-coated graphite pallets due to their longer service life.