Diffusion-reaction mechanisms of nitriding species inSiO2

Abstract

We study using first-principles total-energy calculations, diffusion-reaction processes involved in the thermal nitridation of SiO2. We consider NO, NH, N2 and atomic N in different charge states as the nitriding species in α-quartz. Our results show that none of neutral species react with the SiO2 network remaining at interstitial sites. Therefore, they are likely to diffuse through the oxide, incorporating nitrogen at near-interface (Si/SiO2) regions. Whereas, charged species are trapped by the network, nitriding bulk SiO2. For the diffusing species, we find that NH and atomic N show increasing diffusivities with temperatures, whereas for NO and N2 they are relatively constant. This result agree well with the finding of higher N concentration at the Si/SiO2 interface obtained by thermal processing of SiO2 in NH3 as compared with those obtained in N2O. Finally, we discuss spin-dependent incorporation reaction mechanisms of NH and atomic N with the SiO2 network.

Alternative techniques to reduce interface traps in n‐type 4H‐SiC MOS capacitors

“…small diffusion constant of N in SiC [41], we expect that N atoms diffuse into the oxide layer. Orellana et al [42] reported that neutral N atoms -opposite to positively charged N + ions, which form strong bonds with oxygen atoms -do not react chemically with the SiO 2 -network; they remain on interstitial sites and are able to diffuse through the oxide layer and finally to diffuse out. The SIMS data in combination with the electrical results are a strong hint that the fixed positive charge is accumulated at the SiC/SiO 2 -interface and is due to ionized N + donors.…”

Metal‐Insulator‐Insulator‐Metal Diodes with Responsivities Greater Than 30 A W−1 Based on Nitrogen‐Doped TiOx and AlOx Insulator Layers

“…Excess nitrogen at the interfaces would be expected to attract electrons due to the high electronegativity of nitrogen, resulting in the formation of dipole layers. [34,35] In Figure 3a,d the expected energy levels for the undoped TiO x and AlO x insulators are illustrated. The nitrogen dopant is expected to generate N2p states above the valence band [24] and shift the Fermi level (E F ) downward for NTiO x and NAlO x , as shown in Figure 3b,e.…”

Oxygen-induced atomic desorptions in oxynitrides: Density functional calculations

“…13 We consider the neutral reactants O 2 and NO since they are able to diffuse through SiO 2 with lower energy barriers with respect to charged ones, as recently suggested by firstprinciples calculations. 15 Two bonding configurations around the N atom are considered as our local oxynitride model ͑hereafter incorporated N structures͒: ͑i͒ the N atom binds to two Si atoms forming the Si-N-Si structure, and ͑ii͒ the N atom binds to two Si and one O atom, forming the Si-͓NO͔-Si structure. Si-͓NO͔-Si is commonly found at near interface regions of SiO x N y thermally grown on SiO 2 in N 2 O and NO atmospheres.…”