Theoretical study of the mechanism of dry oxidation of4H-SiC

Abstract

Possible defect structures, arising from the interaction of O 2 molecules with an ideal portion of the SiC/ SiO 2 interface, have been investigated systematically using density functional theory. Based on the calculated total energies and assuming thermal quasiequilibrium during oxidation, the most likely routes leading to complete oxidation have been determined. The defect structures produced along these routes will remain at the interface in significant concentration when stopping the oxidation process. The results obtained for their properties are well supported by experimental findings about the SiC/ SiO 2 interface. It is found that carbon-carbon bonds can explain most of the observed interface states but not the high density near the conduction band of 4H-SiC.

Al2O3/SiO2 films prepared by electron-beam evaporation as UV antireflection coatings on 4H-SiC

“…It is possibly contribute to the difference of growth mechanism between thermal oxidation and electron-beam evaporation. The thermal oxidation consists of complex chemical reactions between oxygen and 4H-SiC [17]. The components of thermally grown SiO 2 layers and interfaces depend greatly on heating temperature, oxygen exposure and surfaces of 4H-SiC substrates.…”

Structural and electronic properties of the transition layer at the SiO2/4H-SiC interface

“…It is clear that the DOS of the abrupt interface structure exhibits a band gap of approximately 2.2 eV, which is comparable to the value of the 4H-SiC band gap from standard DFT calculations. 21,25 This result indicates that the perfect abrupt interface structure does not produce defect states. When the interface structure contains a transition layer, significant interface states emerge in the gap region.…”

“…[5][6][7][8][9][10][11] Considerable effort has been devoted to the identification and characterization of interface defects at the SiO 2 /SiC interface. 6,[12][13][14][15][16][17][18][19][20][21] These investigations drew a conclusion that intrinsic oxide defects and excess carbon are the most dominant contributions to interface states. Intrinsic defects in SiO 2 that are independent of the polytype and orientation of SiC substrate, can account for the D it near the bottom of the SiC conduction band gap, so-called near-interface trap (NIT) levels.…”

“…Such defective structures have not yet been considered in the previous theoretical studies. 20,21,24,27,30 Apart from that, our non-abrupt interface model also include excited configurations, such as fivefold-coordinated Si atoms (SiO 5 ) and threefold-coordinated O atoms. The SiO 5 center does not mean the O enrichment of the interface because a fivefold-coordinated silicon event is accompanied by the generation of threefold-coordinated oxygen atoms.…”

“…Knaup et al studied the oxidation mechanism of 4H-SiC and proposed several possible defects occurring on both the SiC and oxide sides of the interface. 20,21 Gavrikov et al subsequently presented a kinetic mechanism of dry SiC oxidation based on the first-principles investigation. 24 They suggested that the carbon dimer generated during SiC oxidation probably is responsible for the NITs.…”