The development of SiC wafers with properties suitable for electronic device fabrication is now well established commercially. A critical issue for developing metal-oxide-semiconductor field effect transistor devices of SiC is the choice of dielectric materials for surface passivation and insulating coatings. Although SiO2 grown thermally on SiC is a possibility for the gate dielectric, this system has a number of problems related to the higher band gap of SiC, which energetically favors more interface states than for SiO2 on Si, and the low dielectric constant of SiO2 leading to 2.5× higher electric fields across the oxide than in the surface of SiC, and to a premature breakdown at the higher fields and higher temperatures that SiC devices are designed to operate under. As a replacement for SiO2, amorphous Al2O3 thin film coatings have some strong advocates, both for n- and p-type SiC, due to the value of its band gap and the position of its band edges with respect to the band edges of the underlying semiconductor, a number of other material properties, and not the least due to the advances of the atomic-layer-deposition process. Exploring the fact that the chemical bonding of Al2O3 is the strongest among the oxides and therefore stronger than in SiO2, the authors have previously shown how to form an Al2O3 film on Si (111) and Si (100), by simply depositing a few atomic layers of Al on top of an ultrathin (0.8 nm) SiO2 film previously grown on Si surfaces [Si (111) and Si (100)] and heating this system up to around 600 °C (all in ultrahigh vacuum). This converts all the SiO2 into a uniform layer of Al2O3 with an atomically sharp interface between the Al2O3 and the Si surface. In the present work, the same procedures are applied to form Al2O3 on a SiC film grown on top of Si (111). The results indicate that a similar process, resulting in a uniform layer of 1-2 nm of Al2O3 with an atomically sharp Al2O3/SiC interface, also works in this case.
|Journal||Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films|
|Publication status||Published - Jan 2017|