What is a SiC Boat, and What are its Various Manufacturing Processes?

1. The Different Manufacturing Processes of SiC Boat

(1) Coating a layer of SiC film on the surface of graphite crystal boats through CVD

This type of boat has a graphite core, which is machined in one piece. However, graphite is porous and prone to particle generation, necessitating the application of a SiC film coating on its surface. Due to the mismatch in the Coefficient of Thermal Expansion (CTE) between the graphite body and the SiC film, the coating is likely to peel off after multiple heating and cooling cycles, leading to particle contamination. These boats are the least expensive and have a lifespan of about one year.

(2) Coating a layer of SiC film on recrystallized SiC crystal boats

Recrystallized SiC boats are also porous and can easily generate particles. Therefore, the individual components of the recrystallized SiC boats must be pre-formed, sintered, and then machined separately. Afterward, the components are bonded together at high temperatures using Si paste. Once assembled into a single boat, a SiC film is applied through CVD. This recrystallized SiC boat has the longest manufacturing process and is costly, but the surface CVD coating can also be damaged, with a lifespan of around three years.

(3) Monolithic SiC crystal boats

These boats are entirely composed of SiC material. SiC powder must be molded and sintered into the shape of a monolithic boat. Extremely costly, they are very durable and less likely to generate particles. However, these boats contain 10-15% free silicon, which is susceptible to erosion by fluorine and chlorine, leading to particle contamination.

2. Why Dry Cleaning is Not Recommended?

In summary, for SiC boats coated with a SiC film through CVD, the surface coating is prone to peeling during dry cleaning, which causes particle contamination. For monolithic SiC boats that contain a small amount of free silicon, exposure to gases containing fluorine or chlorine can lead to erosion and particle generation, thus causing contamination.**