Reaction mechanisms at 4H-SiC/SiO₂interface during wet SiC oxidation

Abstract

The reaction processes at the interface between SiC with 4H structure (4H-SiC) and SiO 2 during wet oxidation are investigated by electronic structure calculations within the density functional theory. Our calculations for 4H-SiC/SiO 2 interfaces with various orientations demonstrate characteristic features of the reaction depending on the crystal orientation of SiC: On the Si-face, the H 2 O molecule is stable in SiO 2 and hardly reacts with the SiC substrate, while the O atom of H 2 O can form Si-O bonds at the C-face interface. Two OH groups are found to be at least necessary for forming new Si-O bonds at the Si-face interface, indicating that the oxidation rate on the Si-face is very low compared with that on the C-face. On the other hand, both the H 2 O molecule and the OH group are incorporated into the C-face interface, and the energy barrier for OH is similar to that for H 2 O. By comparing the calculated energy barriers for these reactants with the activation energies of oxide growth rate, we suggest the orientation-dependent rate-limiting processes during wet SiC oxidation.

Ab initio study for orientation dependence of nitrogen incorporation at 4H-SiC/SiO2 interfaces

“…A cristobalite-like structure is used as a representative of SiO 2 generated by thermal oxidation of SiC, which has been obtained by our previous calculations. [22][23][24][25] For the m-face interface, (1 × 3) slab model consisting of four 4H-SiC bilayers and two SiO 2 monolayers with tridymite structure is adopted. By using present slab models, similar atomic configurations at 4H-SiC/SiO 2 interfaces to those reported in previous calculations are successfully obtained.…”

“…Detailed frameworks of present slab models and their validity are described elsewhere. [22][23][24][25] The ab initio calculations are performed within the generalized gradient approximation in density-functional theory. For the exchange-correlation functional, we employ the Perdew-Burke-Ernzerhof functional within the generalized gradient approximation including spin degrees of freedom.…”

“…In our previous study, the reaction processes of dry and wet oxidation at the 4H-SiC/SiO 2 interface have been theoretically investigated on the basis of ab initio calculations. [22][23][24] We have revealed characteristic features of the reaction of O 2 and H 2 O molecules at the interface depending on the crystal orientation of SiC. Furthermore, we have investigated the reaction of NO molecule at 4H-SiC/SiO 2 interface during NO-POA and found that stable Si 4 -N (four Si-N) and Si 3 -N (three Si-N) bonds are formed in addition to the CO 2 desorption on the Si-face and C-face, respectively.…”

Behavior of Silicon Carbide Materials under Dry to Hydrothermal Conditions

“…It is important to point out that the discussion is based on studies using the Deal-Grove model, as it is still the most used model to describe SiC oxidation. Recent studies on the parameters influencing SiC oxidation and using the Si and C emission model include several references [19][20][21][22][23][24].…”

Reaction of NO molecule at 4H-SiC/SiO2 interface: an ab initio study for the effect of NO annealing after dry oxidation

“…[4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Indeed, we have previously reported on the SiC-oxidation mechanisms during dry and wet oxidations on the basis of ab initio calculations. 20,21) We have suggested metastable structures consisting of C-C or C=C bonds at the interface during dry oxidation as possible candidates for the origin of high D it . 20) Regarding the physical origin of D it , density functional theory calculations have also revealed that the defects related to C-C bonds, which create energy levels close to the valence band maximum and/or conduction band minimum, are stably formed in either the SiO 2 region, SiC substrate or SiC/SiO 2 interface, depending on the oxygen chemical potentials.…”