We grew epitaxial layers on 4H-silicon carbide (SiC) Si-face substrates with a 1° off-angle. The suppression of 3C-inclusion formation during growth at a high C/Si ratio was investigated, because a growth technique with a high C/Si ratio is needed to decrease residual nitrogen incorporation. 3C inclusions were generated both at the interface between the substrate and epitaxial layer, and during epitaxial growth. 3C-SiC nucleation is proposed to trigger the formation of 3C inclusions. We suppressed 3C-inclusion formation by performing deep in situ etching and using a high C/Si ratio, which removed substrate surface damage and improved the 4H-SiC stability, respectively. The as-grown epitaxial layers had rough surfaces because of step bunching due to the deep in situ etching, but the rough surface became smooth after chemical mechanical polishing treatment. These techniques allow the growth of epitaxial layers with 1° off-angles for a wide range of doping concentrations.
Keywords: 3C inclusion; C/Si ratio; epitaxial growth; in situ etching; low off-angle; silicon carbide.