Crystal Growth

There are two primary technologies employed today to grow silicon carbide:

• Physical Vapor Transport (PVT) – This is the most commonly used growth technique. During PVT high purity silicon carbide powder is sublimed from a crucible in order to deposit SIC material along the length of a crystalline silicon carbide seed. This method is used to produce 4H and 6H silicon carbide crystals. The major advantage of this approach is that the growth process is fairly well understood. The primary disadvantage centers around the difficulty controlling the stoichiometry of the sublimed silicon carbide, which leads to high defect densities.
• High Temperature Chemical Vapor Deposition (HTCVD) – In this technique, the solid source materials are replaced by gases such as silane and propane. The strength of this approach is that it offers greater control over the sublimation process, resulting in fewer defects. In addition, HTCVD is able to cover pre-existing cracks in material, leading to higher quality wafers. A significant challenge facing this approach is to reduce the impurities generated from the degradation of the graphite containers in which the material is produced, making it difficult to grow long boules.

After an extensive R&D effort, a new bulk growth method was discovered by Caracal scientists in 2005. This approach leverages the advantages of HTCVD while overcoming its limitations. Specifically, the process is designed to lower the required growth temperature and thermal gradient, which puts less strain on the materials, resulting in lower defects. The degradation rate of the graphite crucible is also reduced. The net effect is higher purity silicon carbide of greater boule length. We have applied for 3 different patents covering both the process and apparatus of this new growth technique.

Our new growth process occurs in bulk reactors custom designed by Caracal scientists, and built in-house to exacting specifications.  We believe these reactors are unique in the world, and set a new standard in silicon carbide bulk reactor technology.  In the design of the reactors, a particular emphasis has been placed on efficiency of operation.  Reactor runtime is maximized and operator involvement is minimized through a recipe-driven, fully automated control system.