Formation of thermal decomposition cavities in physical vapor transport ofsilicon carbide

The relationship between seed mounting and the formation of thermal decompo sition cavities in physical vapor transport grown silicon carbide was inves tigated. Scanning electron microscopy, energy dispersive x-ray spectroscopy , Auger electron spectroscopy, and optical microscopy were used to characte rize 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 deco mposes at void locations and Si-bearing species are transported through the void. The decomposition produces a cavity in the seed; the silicon is depo sited on and diffuses into the graphite lid. The formation of thermal decom position cavities can be suppressed by the application of a diffusion barri er on the seed crystal backside.