Power Generation and Distribution

High purity silicon carbide source material is typically defined as silicon carbide with a purity level of 6N (99.9999%) or greater. The purity of this source material (among other factors including its form) can influence the resulting silicon carbide crystal (or ingot) uniformity and quality from which the SiC wafers are produced. Such wafer uniformity defects can negatively affect the performance of the subsequent semiconductor power device.

Solid CVD silicon carbide (SiC) wafer holders or wafer carriers are often preferred over holders made of graphite that are coated with SiC, for a variety of reasons:

1. A monolithic material design can provide greater temperature uniformity resulting in a more consistent epitaxy layer deposited upon the wafer being held.
2. The surface morphology of a machined, solid CVD SiC holder can be easier to control versus a coated surface morphology
3. Besides being inert to the hot process gasses of the epitaxy reaction, the holder must also be able to resist the cleaning process (such as wet etching) employed to remove materials that deposit themselves onto the holder surface during the epitaxial reaction. A solid SiC carrier is considered more durable versus a SiC coated holder in both these circumstances.

Physical vapour transport (PVT) is a process where a source material is heated to its sublimation point, transforming the material into a gas or vapour. The PVT tube directs the flow of the resultant hot vapour to a surface upon which the vapour will be deposited, typically to form a film. Because such hot gasses can be corrosive, the tubes must be constructed of a material that is chemically inert to the hot gasses so the tube itself does not become a source of impurities in the resulting deposited film.