In-Situ Synchrotron X-Ray Topography Study on the Stress Relaxation Process in 4H-SiC Homoepitaxial Layers

Abstract

During 4H silicon carbide (4H-SiC) homoepitaxy and post-growth processes, the development of stress relaxation has been observed, in which interfacial dislocations (IDs) are formed at the epilayer/substrate interface, relaxing the misfit strain induced by the nitrogen doping concentration difference between the epilayer and substrate. It is widely believed that an interfacial dislocation is created by the glide of a mobile segment of a basal plane dislocation (BPD) in the substrate or epilayer towards the interface, leaving a trailing edge component right at the interface. However, direct observation of such mechanisms has not been made in SiC before. In this work, we present an in situ study of the stress relaxation process, in which a specimen cut from a commercial 4H-SiC homoepitaxial wafer undergoes the stress relaxation process during a high-temperature heat treatment while sequential synchrotron white beam X-ray topographs were recorded simultaneously. Based on the dynamic observation of this process, it can be concluded that thermal stress plays a role in the relaxation process while the increased misfit strain at elevated temperature most likely drives the formation of an interfacial dislocation.

Anisotropic deformation of 4H-SiC wafers: insights from nanoindentation tests

“…Nanoindentation has been regarded as an ideal approach to investigate the mechanical properties and deformation mechanisms of semiconductors [11,12]. By combining the nanoindentation tests and transmission electron microscope (TEM) observations, the nucleation and slip of basal plane dislocations (BPDs) are found to dominate the plastic deformation of 4H-SiC [13,14]. The formation and propagation of cracks give rise to the brittle deformation of 4H-SiC, which is characterized by the fracture toughness [15][16][17][18].…”