Modification of 4H-SiC and 6H-SiC(0001)Si surfaces through the interaction with atomic hydrogen and nitrogen

The interaction of 4H-SiC(0001)Si and 6H-SiC(0001)Si surfaces with atomic hydrogen and atomic nitrogen produced by remote radio-frequency plasmas is investigated. The kinetics of the surface modifications is monitored in real time using ellipsometry, while chemical modifications of the surface are characterized using x-ray photoelectron spectroscopy (XPS). Film morphological properties are assessed with atomic force microscopy (AFM). A two-stage sub-strate preparation procedure is described that effectively removes oxygen from the SiC surface at low (200°C) temperature. In the first step, the SiC surface is etched with an HCl/HF acid solution as an alternative to the conventional HF(1%)-H2O solution. The HCl/HF etch provides effective hydrogen passivation of the SiC surface. In the second step, the SiC surface is exposed to atomic hydrogen that selectively interacts with residual oxygen. In addition, the temperature dependence of the nitridation of SiC surfaces has also been investigated. It is found that interaction of SiC surfaces with atomic hydrogen at 200°C provides clean, smooth, and terraced surfaces suitable for epitaxial growth. In contrast, SiC surface exposure at high temperature (750°C) to atomic hydrogen and nitrogen results in very rough and disordered Si-rich surfaces. Finally, we find that the 4H-SiC surface is more reactive than the 6H-SiC surface to both species studied, independent of temperature. Surface geometry and electronic factors responsible for the observed reactivities are discussed.

Duke Scholars

Author April S. Brown Electrical and Computer Engineering