X-ray photoelectron spectroscopy study of high-k CeO2/La2O3 stacked dielectrics

Abstract

This work presents a detailed study on the chemical composition and bond structures of CeO2/La2O3 stacked gate dielectrics based on x-ray photoelectron spectroscopy (XPS) measurements at different depths. The chemical bonding structures in the interfacial layers were revealed by Gaussian decompositions of Ce 3d, La 3d, Si 2s, and O 1s photoemission spectra at different depths. We found that La atoms can diffuse into the CeO2 layer and a cerium-lanthanum complex oxide was formed in between the CeO2 and La2O3 films. Ce3+ and Ce4+ states always coexist in the as-deposited CeO2 film. Quantitative analyses were also conducted. The amount of CeO2 phase decreases by about 8% as approaching the CeO2/La2O3 interface. In addition, as compared with the single layer La2O3 sample, the CeO2/La2O3 stack exhibits a larger extent of silicon oxidation at the La2O3/Si interface. For the CeO2/La2O3 gate stack, the out-diffused lanthanum atoms can promote the reduction of CeO2 which produce more atomic oxygen. This result confirms the significant improvement of electrical properties of CeO2/La2O3 gated devices as the excess oxygen would help to reduce the oxygen vacancies in the film and would suppress the formation of interfacial La-silicide also.

Electronic Structure and Room Temperature Ferromagnetism in Gd‐doped Cerium Oxide Nanoparticles for Hydrogen Generation via Photocatalytic Water Splitting

“…All peak positions for “ u ” and “ v ” of pure CeO 2 and Ce 1− x Gd x O 2 ( x = 0.02, 0.04, 0.06, 0.08, and 0.10) samples have been tabulated in Table 3 . The total concentration of Ce 3+ and Ce 4+ in the samples has been calculated using the following formula…”

Supports materialization of Pd based catalysts for NOx removal by hydrogen assisted selective catalytic reduction in the presence of oxygen

“…By a peak-fitting deconvolution, the Ce 3d core-level spectra displayed in Figure 3 (i) corresponding to 3d 3/2 peaks at 882. 36 [60,61] In general, the presence of Ce 3 + is related to the formation of oxygen vacancies conferring to charge compensation. Therefore, the relatively high Ce 3 + content in CeO 2 À MgO specifies the formation of more oxygen vacancies.…”

On the scaling of subnanometer EOT gate dielectrics for ultimate nano CMOS technology

“…Most of the high-k silicides are conductive. The interfacial silicide layer would not affect the EOT but the interface metal-Si bonding is one of the interface trap precursors and results in the channel mobility degradation and in other instabilities [2,[59][60][61][62][63][64][65][66][67][68][69][70]. Most of the high-k materials, including hafnium oxide and lanthanum oxide are only marginally stable against the formation of silicates.…”

“…It was proposed that the oxygen in W may diffuse into the La 2 O 3 film to fill up the oxygen vacancies there. Oxygen vacancies are the major defect centers in La 2 O 3 which result in several instability issues and enhance the gate leakage current [59][60][61][62][63][64][65][66][67][68][69][70][71]. Post-metallization annealing may cause an reverse effect.…”

“…Yet, amongst all these issues, the interface properties and their thermal instabilities need to be resolved firstly [64][65][66][67][68][69][70][71][72]. Transition metal (TM) or rare-earth metal (RE) based high-k dielectrics are extrinsic materials to the substrate silicon.…”