Sublimation Anisotropic Etching of Silicon Carbide in Aluminum Nitride Vapors

Abstract

Specific features of sublimation etching of crystalline silicon carbide (SiC) in the presence of aluminum nitride (AlN) vapors have been reported. The etching is shown to be essentially anisotropic. Abnormally high speed of sublimation in a lateral direction, which weakly depends on surface orientation and polarity, is revealed through increasing artificial holes and flattening out surface elevations prepared in the shape of rectangular mesa structures. A high-rate etching is observed at outcrops of micropipes and closed-core screw dislocations, which leads to the formation of pits on () C-terminated faces. During annealing, the pits evolve into holes that might provoke the formation of pores inside free-standing AlN layers grown in one process with the sublimation of SiC substrates. The sublimation kinetics of a Si-terminated face is evidently different from that of a C-terminated face. It is found that a liquid phase is formed on the etched surfaces and it plays a key role in interpreting the etching anisotropy on SiC crystal faces of different orientations. It is shown that the sublimation of mesa-shaped SiC substrates can be used with the aim of optimizing the fabrication of thick freestanding AlN layers.