We fabricated SiO2/4H-SiC (0001) metal-oxide-semiconductor capacitors with nearly ideal capacitance-voltage characteristics, simply by the control of thermal oxidation conditions which were selected based on thermodynamic and kinetic considerations of SiC oxidation. The interface with low interface defect state density <1011 cm−2 eV−1 for the energy range of 0.1–0.4 eV below the conduction band of SiC was obtained by thermal oxidation at 1300 °C in a ramp-heating furnace with a short rise/fall time, followed by low temperature O2 anneal at 800 °C.
Growth kinetics of nanometer-thick thermal oxides on 4H-SiC (0001), Si-face, was investigated. A linear oxide growth was clearly observed in this thickness region, indicating the oxide growth is limited by interface reaction. The activation energy of the interface reaction was estimated to be 3.8 ± 0.1 eV. The rate-limiting step in this reaction was discussed from both the value of activation energy and the oxygen partial pressure dependence of the growth rate. The enhanced growth limited only to the initial <2 nm region was also observed, which is suggesting the change of the rate-limiting step for the interface reaction in the ultrathin region.
Control of thermal oxidation conditions is inevitable to achieve a high-quality MOS interface on SiC substrates. We investigated the kinetics and thermodynamics of 4H-SiC oxidation for nanometer-thick SiO2/SiC system, to find out thermodynamically preferred conditions for a smooth elimination of carbon byproduct from the interface. A linear regime of thermal oxidation of 4H-SiC (0001) was clearly observed with a high activation energy corresponding to direct CO ejection from the interface. Based on our understanding of oxidation kinetics, we found that nearly-ideal MOS characteristics with reduced interface state density ~1011 cm-2eV-1 or less, were achievable on 4H-SiC (0001) only by dry oxidation processes.
We fabricated SiO2/4H-SiC (0001) MOS capacitors with nearly-ideal capacitance-voltage characteristics, simply by the control of thermal oxidation conditions which were selected based on thermodynamic and kinetic considerations of SiC oxidation. The interface with low interface defect state density <1011 cm-2eV-1 for the energy range 0.1 – 0.4 eV below the conduction band of SiC was obtained by thermal oxidation at 1300oC in a ramp-heating furnace with a short rise/fall time, followed by low temperature O2 anneal at 800oC.
Fig. 1 (a) Temperature-pO 2 phase diagram for the reaction between surface SiC and O 2. (b) Arrhenius plot of oxide growth rate. The inset shows the oxidation time dependence of SiO 2 film thickness grown on 4H-SiC (0001) at 1300 o C.
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