Influence of annealing environment on the ALD-Al2O3/4H-SiC interface studied through XPS

The instability of Al2O3/4H-SiC interface at various process temperatures and ambient is investigated by the annealing of Al2O3/4H-SiC in low vacuum conditions as well as in N2 environments. Atomic layer deposited Al2O3 on a 4H-SiC substrate with 3, 6 and 10 nm of thicknesses is treated at 300, 500, 700 and 900 °C under the vacuum level of 10−1 torr. The as-deposited and annealed structures are analyzed using x-ray photoelectron spectroscopy. It is hypothesized that the minute quantity of oxygen present in low vacuum conditions diffuses through thin layers of Al2O3 and helps in forming SiO2 at the interface even at low temperatures (i.e. 300 °C), which plays a pivotal role in determining the electrical properties of the interface. It is also proved that the absence of oxygen in the ambient prevents the formation of SiO2 at low temperatures. Additionally, it is observed that Al–OH is present in as-deposited layers, which gradually reduces after annealing. However, at around 700 °C, the concentration of oxygen in the whole structure increases to maximum and reduces at 900 °C.