Macrosteps formation on 4H-SiC surfaces via Si melting within a sandwich configuration

Abstract

With a view to designing a homogeneous and controlled step-bunched morphology on large monocrystalline 4H-SiC(0001) surfaces, a sandwich configuration was investigated. A piece of silicon was melted between two 4H-SiC 4° off wafers, allowing a better spreading of the liquid than with a Si drop approach. Using as low liquid Si thickness as 30 µm, homogeneously highly step-bunched surfaces were obtained, though with irregular step shapes. This was found to be the result of time dependent dissolution of the SiC-bottom wafer under the natural vertical thermal gradient of the setup. The most parallel step and terrace structures were generated using 400 µm thick liquid Si though this led to long range inhomogeneities associated with complex mass transport. The proposed mechanism includes the combined effects of H2 etching at the edges acting as C pump and electromagnetic convection rolls for long range transport of these dissolved C atoms.