Formation of thermal decomposition cavities in physical vapor transport of silicon carbide

The relationship between seed mounting and the formation of thermal decomposition cavities in physical vapor transport grown silicon carbide was investigated. Scanning electron microscopy, energy dispersive x-ray spectroscopy, Auger electron spectroscopy, and optical microscopy were used to characterize thermal decomposition cavities at various stages of their development. The observations indicate that the attachment layer that holds the seed to the graphite crucible lid frequently contains voids. The seed locally decomposes at void locations and Si-bearing species are transported through the void. The decomposition produces a capacity in the seed; the silicon is deposited on and diffuses into the graphite lid. The formation of thermal decomposition cavities can be suppressed by the application of a diffusion barrier on the seed crystal backside.