Origin of Surface Morphological Defects in 4H-SiC Homoepitaxial Films

Plan-view transmission electron microscopy (TEM) was applied to investigate the origin of surface defects in 4H-SiC homoepitaxial films. Their origin existed at the substrate/epi-film interface. Hence, almost the entire thickness of the epi-film was removed by plasma etching leaving a very thin film. Then, the etched epi-crystal was thinned from the substrate side so that we could observe the crystallographic imperfections at the substrate/epi-film interface in plan-view TEM. Morphological features of the epi-film surface remained unchanged after the plasma etching process. Hence, one-to-one correspondence between surface defects and crystallographic imperfections was confirmed by comparing optical micrographs and TEM images. Crystallographic imperfections associated with “carrot defects” were observed. They were composed of stacking faults on the (0001) plane and partial dislocations bounding them. These imperfections originated from foreign particles at the interface. From X-ray energy-dispersive spectrometry (XEDS), it was confirmed that particles contained zirconium (Zr). Selected area diffraction patterns showed that the particles were crystalline.