High-carbon concentrations at the silicon dioxide–silicon carbide interface identified by electron energy loss spectroscopy

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Abstract
High carbon concentrations at distinct regions at thermally-grown SiO 2 / 6H – SiC(0001) interfaces have been detected by electron energy loss spectroscopy(EELS). The thickness of these C-rich regions is estimated to be 10–15 Å. The oxides were grown on n-type 6H–SiC at 1100 °C in a wet O 2 ambient for 4 h immediately after cleaning the substrates with the complete RCA process. In contrast, C-rich regions were not detected from EELSanalyses of thermally grown SiO 2 / Si interfaces nor of chemical vapor deposition deposited SiO 2 / SiC interfaces. Silicon-rich layers within the SiC substrate adjacent to the thermally grown SiO 2 / SiC interface were also evident. The interface state density D it in metal–oxide–SiC diodes (with thermally grown SiO 2 ) was approximately 9×10 11 cm −2 eV−1 at E−E v =2.0 eV, which compares well with reported values for SiC metal–oxide–semiconductor (MOS) diodes that have not received a postoxidation anneal. The C-rich regions and the change in SiC stoichiometry may be associated with the higher than desirable D it ’s and the low channel mobilities in SiC-based MOS field effect transistors.

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