Oxygen isotopic exchange occurring during dry thermal oxidation of 6H SiC

Abstract

SiC is a large band gap semiconductor, promising for high power and high frequency devices. The thermal oxide is SiO 2 however the growth rates of thermal oxide on SiC are substantially slower than on Si, and different along the polar directions ( 〈0 0 0 1〉 and 〈0 0 0 1〉 in the hexagonal polytypes). Thorough understanding of the oxide growth mechanisms may give us new insights into the nature of the SiO 2/SiC interface, crucial for device applications. We have determined growth kinetics for ultra-dry thermal oxidation of 6H SiC at 1100 °C for pressures from 3 to 200 mbar. At 3 mbar, the lowest pressure studied, the oxide growth rates along the two polar directions are virtually the same. At higher pressures growth is faster on the carbon-terminated (0 0 0 1 ) face. After consecutive oxidations at 1100 °C and 100 mbar in 18 O 2 and 16 O 2 gases, 18 O depth profiles show significant isotopic exchange and oxygen movement within the oxide during oxidation.