Structure and reduction of large bumps formed on 4H-SiC epitaxial film originated from dislocations in substrate

Homo-epitaxial 4H-SiC films were grown by adding HCl gas with a high Cl/Si ratio and a low Si /H2 ratio in CVD process. A large number of large bumps originated from dislocations in bare substrate were observed for the film grown at Cl/Si ratio of 30 and at C/Si ratio of 1.05. Raman spectroscopy analysis and wet etching treatment for the film by mixed acid which consists of hydrofluoric acid (HF) and nitric acid (HNO3) revealed that the large bumps are Si islands. From the dependence of surface morphology of the films on C/Si ratio and Cl/Si ratio, it was found that the formation of Si islands is suppressed by decreasing C/Si ratio, even though large pits are formed by increasing Cl/Si ratio. From the results obtained in this study, formation mechanism of the Si island, originated from dislocations in the substrate, was also proposed.