Removal of surface contaminants from SiC Substrate Using Thermally Generated Atomic Hydrogen

Introduction Wide bandgap semiconductors are becoming the new platform of choice for devices with greater power density and higher energy efficiency than silicon. In particular, Silicon carbide (SiC) is ideal for high power and high temperature (>150 oC) electronic applications because of its excellent properties as a high critical electric field for operate under high applied operating voltages (2500 kV/cm) and good thermal conductivity (4.9 W/cmK) [1]. However, heteroepitaxial film growth of functional oxides on SiC, is a challenging and yet critical goal to achieve the overall success of utilizing SiC in next-generation electronics. Formation of an abrupt and effective interface is one of the basic requirements for integration of functional oxides on semiconductors. A reliable and successful cleaning procedure must be developed in order to produce consistent and well-characterized starting surfaces. Several SiC surface cleaning studies, including high-temperature hydrogen etching and hydrogen plasma treatment, have been reported to remove contaminations and scratches made during polishing [2]. In our previous work, 6H-SiC (a polymorph of SiC with the hexagonal structure) substrates were cleaned in an ex-situ hydrogen (H2) furnace [3]. A tantalum foil strip placed under the sample is used as a heating element during furnace operation. X-ray photoelectron spectroscopy (XPS) scans of resulting 6HSiC surfaces repeatedly show 10 at% oxygen contamination on the surface. This aspect, along with the sharp non-diffusive spots known as intermediate Laue rings observed in the reflection high energy electron diffraction (RHEED) pattern, confirm the √3×√3 R30° surface reconstruction which corresponds to the presence of a silicate adlayer on the surface. These results are consistent with previous reports for cleaning of SiC [2]. However, the high treatment temperature (~1600 oC) and high sensitivity to small thermal gradients makes this process impractical for low-cost, high-throughput production. In this study we demonstrate the effects of atomic hydrogen produced by a hydrogen atom beam source (HABS) used for cleaning substrates in order to understand the fundamental H-atom interactions with the surface. This knowledge will be used to develop an optimized surface cleaning process at relatively low substrate temperature.