Effect of Ar post-oxidation annealing on oxide–4H-SiC interfaces studied by capacitance to voltage measurements and photoemission spectroscopy

The effect of post-oxidation annealing in Ar atmosphere (Ar POA) on 4H-SiC–oxide interfaces has been studied by capacitance to gate-bias voltage $(C–V)$ measurements and photoemission spectroscopy (PES). It was found from the $C–V$ measurements that the shift of the $C–V$ curve disappears when the Ar POA temperature is higher than 600 °C. On the other hand, angle-resolved x-ray photoelectron spectroscopy measurements revealed that the thickness of the intermediate layers containing $Si1+$ oxidation states observed at the interfaces decreases abruptly when the Ar POA temperature exceeds 500 °C. In ultraviolet photoelectron spectra, $O2p$ peaks were changed by Ar POA at temperatures higher than 600 °C, which is the temperature where the shift of the $C–V$ curve disappears in $C–V$ measurements. This shows that the change in $O2p$ bonding by Ar POA is the origin of the shift observed in $C–V$ characteristics. A model of structural changes in the interfaces by Ar POA has been proposed based on the results of PES measurements and those of $C–V$ measurements.