From dissolution to controlled macrostepping of 4H-SiC during liquid Si-induced structuring in a sandwich configuration

The structuring of Si face 4 degrees off 4H-SiC surfaces was investigated using Si melting in a SiC/Si/SiC sandwich configuration. The stacks were treated at 1550-1600 degrees C under H-2 in a RF-heated cold-wall reactor. By fixing the liquid Si thickness to 30 mu m, the vertical thermal gradient inside the stack generates carbon transport from the bottom to the top SiC wafer. The constant dissolution of the bottom SiC wafer (1.7 mu m/h at 1550 degrees C) leads to surface structuring in macrosteps. The regularity of these macrosteps can be reproducibly controlled when performing the process on an epitaxial layer thanks to the pre-structuration in parallel microsteps of such kind of surfaces. The best regularity of the steps was obtained after a structuring process of 2 h, with an average terrace width of similar to 3-5 mu m.