461976 SiC Substrate Cleaning for Epitaxy Using a Thermally Generated Atomic Hydrogen Beam
Formation of an abrupt and effective interface is one of the basic requirements for integration of functional oxides on semiconductors. A reliable and effective cleaning procedure must be developed in order to produce consistent and well-characterized starting surfaces. Several SiC surface cleaning studies, including traditional wet cleaning, high-temperature hydrogen etching and hydrogen plasma treatment have been reported in order to remove contaminations and scratches made during polishing .
In our previous work, 6H-SiC (0001) substrates were cleaned in an ex-situ hydrogen furnace. Tantalum foil strip is used as heating element during furnace operation where the 6H-SiC sample is placed on it. The resulting 6H-SiC surfaces are smooth with a uniformly stepped surface and a √3×√3R30º surface reconstruction with a silicate adlayer, verified by reflection high energy electron diffraction (RHEED) and x-ray photoelectron spectroscopy (XPS) . This is consistent with that reported by Starke and coworkers . However, the high treatment temperature (~1600 ºC) and sensitivity to small thermal gradients makes it impractical for a low-cost and high-throughput production.
In this study we demonstrate the effects of atomic hydrogen produced by a hydrogen atom beam source (HABS). The HABS is a thermal gas-cracking cell consisting of a tungsten filament set in high purity tungsten tube. It has been found that the atomic hydrogen irradiation is productive for removal of carbon and oxygen on Si surfaces at relatively low temperature without any ion damage to the substrates . We compare the treatment of 6H-SiC surfaces with hydrogen atomic beam source and the hydrogen flow furnace, in order to understand the fundamental H-atom interactions with the surface and then use that knowledge to develop an optimized surface cleaning process.
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