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

Abstract

The structuring of Si face 4°off 4H-SiC surfaces was investigated using Si melting in a SiC/Si/SiC sandwich configuration. The stacks were treated at 1550–1600 °C under H2 in a RF-heated cold-wall reactor. By fixing the liquid Si thickness to 30 µm, 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 µm/h at 1550 °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 ∼3–5 µm.