Observation of carbon clusters at the 4H-SiC/SiO2 interface

Analysis of the 4H SiC(0001)/SiO2 interface using atomic force microscopy revealed the presence of the nanometer-sized platelet-shaped inhomogeneities which are resistant to HF etching, but can be removed by ozone. These inhomogeneities are suggested to be carbon inclusions formed during thermal oxidation of SiC. Their density was found to be sensitive to the type of pre-oxidation surface cleaning, and to be correlated with the density of electrically active SiC/SiO2 interface states. This relationship between SiC/SiO2 interface defects and the interfacial carbon clusters explains the observed resistance of 4H SiC/SiO2 interface states against hydrogen passivation.