First-principles study on the effect of SiO2 layers during oxidation of 4H-SiC

Abstract

The effect of SiO2 layers during the thermal oxidation of a 4H-SiC(0001) substrate is examined by performing the first-principles total-energy calculations. Although it is expected that a CO molecule is the most preferable product during the oxidation, CO2 molecules are mainly emitted from the SiC surface at the initial stage of the oxidation. As the oxidation proceeds, CO2 emission becomes less favorable and CO molecules are emitted from the interface. We conclude that the interface stress due to the lattice constant mismatch between 4H-SiC(0001) and SiO2 is responsible for the removal of C during the oxidation, resulting in the characteristic electronic property of the interface fabricated by the thermal oxidation.

First-Principles Study on Interlayer States at the 4H-SiC/SiO2Interface and the Effect of Oxygen-Related Defects

“…It is interesting to consider the influence of O defects, which are introduced during thermal oxidation, since they exist within or just below the first SiC bilayer; the region where the interface types differ. We focus on the most stable defects identified in our previous study 6 for each stage of one oxidation cycle. Structures for each are shown in Fig.…”

“…Theoretical studies report that C and O-related defects 15 are created during the thermal oxidation process. 3,4,6 Of these, the density of C-related defects is measurable since they generate gap states. Recent experimental studies have reported that the density of defects which generate these states is less than 10 −12 cm −2 eV −1 .…”

“…However, its use in practical devices has been hampered by the low channel mobility of the SiC/SiO 2 interface compared with bulk SiC. 1,2 Interfacial defects [3][4][5][6] have attracted a lot of attention, with the aim of identifying and removing the most detrimental. Traditionally, research has focused on defects which contribute interface gap states, but advances in interface growth techniques mean that these gap states no longer make a significant contribution to reductions in mobility.…”

Ab initio calculation of the evolution of [SiN4‐nOn] tetrahedron during β‐Si3N4(0001) surface oxidation

“…Since the oxidation of Si 3 N 4 usually happens under high‐temperature conditions (>1000 K), oxygen has sufficient energy to dissociate near the surface of Si 3 N 4 . Therefore, we simulate the oxidation of Si 3 N 4 surface using O atom as an adsorption unit instead of the O 2 molecule, which is also employed in many literatures . Besides, the dissociation energy is very small (0.189 eV), indicating it has little influence on the adsorption energy.…”

“…which is also employed in many literatures. [35][36][37] Besides, the dissociation energy is very small (0.189 eV), indicating it has little influence on the adsorption energy. What's more, E nO is half of the energy of an isolated O 2 molecule, so the dissociation energy has been included in the formula of adsorption energy, excluding the error form the ignorance of dissociation energy.…”