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Properties of lanthanum oxide thin films deposited by cyclic chemical vapor deposition using tris(isopropyl-cyclopentadienyl)lanthanum precursor

Lanthanum oxide thin films were deposited at deposition temperatures ranging from 170to370°C using alternate injection of tris(isopropyl-cyclopentadienyl)lanthanum and various reactants (H2O, O2, and NH3). It was possible to deposit films containing a carbon impurity concentration <1at.%. The residual carbon could be further reduced by postdeposition annealing. X-ray photoelectron spectroscopy (XPS) showed that after rapid thermal annealing (RTA) at 870°C the films transformed to silicate which increased the band gap of the films (7.0±0.15eV). With changing the RTA ambient from O2 to N2, a binding energy shift of the substrate’s Si peaks by 0.9eV was observed in the XPS spectra relative to the signals from the oxide layer. The shift was attributed to the electric field in the oxide film caused by the fixed charge distribution. A flat band voltage shift indicating the change of the fixed charge was also observed according to the RTA ambient. From Pt∕La-oxide∕p-Si(100) structures, the dielectric constant an...

Electronic properties of atomic-layer-deposited Al2O3/thermal -nitrided SiO2 stacking dielectric on 4H SiC

We report the first electronic-property results on atomic-layer deposited Al 2 O 3 /thermal-nitrided SiO 2 stacking dielectric on n-type 4H SiC. The effects of the ultrathin thermal-nitrided SiO 2 (2, 4. and 6 nm) on the SiC-based metal oxide semiconductor (MOS) characteristics have also been investigated, compared, and explained. A significant improvement in dielectric reliability and dielectric breakdown field has been observed after an ultrathin nitrided oxide has been introduced between Al 2 O 3 and SiC. The best reported results were obtained from Al 2 O 3 stacked with the thickest nitrided oxide (6 nm).

Properties of Aluminum Nitride Thin Films Deposited by an Alternate Injection of Trimethylaluminum and Ammonia under Ultraviolet Radiation

Aluminum nitride (AlN) thin films were prepared on p-type Si (100) wafers using a sequential injection of trimethylaluminum (TMA) and ammonia under ultraviolet (UV) radiation at a temperature of 370°C. Films containing low carbon concentration ( <0.5 atom%) were deposited with a dielectric constant of ∼7.9. UV radiation effects were investigated for two different radiation conditions (UV exposure during the TMA and NH 3 injection step, respectively). A reduction in the hydrogenated nitrogen concentration was observed by X-ray photoelectron spectroscopy when UV photons were radiated during the TMA injection step. The leakage current of a 9.5-nm-thick AlN film followed the Poole-Frenkel conduction mechanism, and an optical dielectric constant of 4.2 and a trap energy depth of 0.83 eV were extracted from the Poole-Frenkel fitting of the current-density-voltage results at temperatures ranging from 20 to 170°C. The film deposited under UV radiation during TMA injection showed a higher dielectric constant than the films deposited without radiation.

Property Changes of Aluminum Oxide Thin Films Deposited by Atomic Layer Deposition under Photon Radiation

Aluminum oxide thin films were deposited by atomic layer deposition (ALD) using trimethyl aluminum and water under UV radiation. Films were prepared at two different deposition temperatures of 260 and 370°C. The films deposited at 370°C had a higher O/Al atomic ratio than those deposited at 260°C. The upper valence band (VB) spectrum, observed by X-ray photoelectron spectroscopy (XPS), of the aluminum oxide thin film deposited under UV radiation during water purge was different from that of a nonradiated thin film, indicating a structural change by the UV radiation. For the film deposited at 370°C, the effective mass (m*) was estimated to be larger than 0.35m 0 , and an effective electron barrier height of 3.8 eV was obtained for m = 0.4m 0 by fitting the I-V curve with the Fowler-Nordheim (FN) tunneling model. The films, of which leakage current densities were reduced by UV radiation, showed an increase in electron barrier height for FN tunneling conduction. In addition, the conduction band offset with Si, calculated from the VB offsets and the bandgap values obtained by XPS, was also increased for the UV-radiated sample.

Investigation of interface trap states in TiN/Al2O3/p-Si capacitor by deep level transient spectroscopy

The minority carrier (electron) capture process and the interface trap density of a TiN/Al2O3/p-Si metal–oxide–semiconductor capacitor were examined by deep level transient spectroscopy (DLTS). It was found that the activation energies of the large peaks detected at higher temperatures with gate bias voltages of 1.8, 1.5, 1.3, and 1.1 V were 0.19, 0.24, 0.29, and 0.37 eV, respectively. These energies were related to the electron-capture process from the conduction band by interface states in the upper half of the Si band gap. The interface state passivation effect of postannealing in a hydrogen ambient was studied from the minority carrier capture process and the usual DLTS signals. The Dit at an energy of 0.35 eV from the valence bandedge decreased from 1×1012 cm−2 eV−1 at the as-fabricated state to 4×1011 cm−2 eV−1 after H2 annealing at 450 °C. It was also found that the Dit at an energy of 0.3 eV from the conduction bandedge decreased to the same amount by the same annealing process.

Deposition Characteristics and Annealing Effect of La2O3 Films Prepared Using La ( iPrCp ) 3 Precursor

Lanthanum oxide thin films were deposited using alternate injections of La(iPrCp) 3 and H 2 O at various substrate temperatures. The leakage current density increased with decreasing substrate temperature, although the films showed similar equivalent oxide thickness (EOT). The proper substrate temperature, at which La 2 O 3 thin films with a low EOT and low leakage current were deposited, was 300°C. During post-deposition annealing (PDA) in an N 2 atmosphere, a remarkable amount of Si diffusion occurred. However, annealing in an NH 3 atmosphere improved the thermal stability and dielectric constant of the La 2 O 3 thin films, due to the incorporation of nitrogen. The typical EOT and leakage current of the La 2 O 3 thin films, annealed in NH 3 at 800°C, were 2.2 nm and 1.7 X 10 -8 A/cm 2 at -1 V, respectively. The amount of Si atoms which diffused into the La 2 O 3 films decreased in the sequence: O 2 -annealed, NH 3 -annealed, and pre-nitrided samples. A pre-nitridation step to form an SiN x reaction barrier was effective at increasing the thermal stability.

Thermal Annealing Effects on the Atomic Layer Deposited LaAlO3 Thin Films on Si Substrate

The changes in film structure of amorphous atomic layer deposited LaAlO 3 thin films after thermal annealing were examined by medium-energy ion-scattering measurements and angle-resolved X-ray photoelectron spectroscopy. Thermal annealing induces Si-rich LaSiO and Al-deficient LaAl x Si y O z layers on a few monolayers of SiO 2 . Al atoms do not participate in silicate formation during annealing. Instead, they migrate toward the film surface, which induces nonhomogeneity in the films along the vertical direction. The concentrations of Al and La on the film surface increase and decrease, respectively, as a result of Si diffusion from the substrate and silicate formation.

Enhanced Nucleation Behavior of Atomic-Layer-Deposited Ru Film on Low-k Dielectrics Afforded by UV-O3 Treatment

The effect of UV-O 3 treatment on the nucleation behavior of ruthenium (Ru) film on low-k dielectrics was investigated. A continuous Ru film was not formed on the as-deposited or N 2 -annealed low-k layer, but after the UV-O3 treatment, full coverage with a continuous Ru layer was obtained. The microstructure and Ru/Row-k interface were studied using transmission electron microscopy, specular X-ray reflectivity, and Auger electron spectroscopy. The enhanced nucleation behavior of Ru may be due to the increased chemisorption probability of the Ru precursor on the low-k film surface, which comes from a modified oxygen-based dense layer (SiO x ).

The Role of the Methyl and Hydroxyl Groups of Low-k Dielectric Films on the Nucleation of Ruthenium by ALD

Nucleation of the ruthenium (Ru) precursor on low-k film surfaces during atomic layer deposition (ALD) of Ru was investigated. The adsorption tendency of the precursor decreased with increasing concentration of methyl groups on the low-k film surface, resulting in poor nucleation of Ru. The electron-deficient hydroxyl groups act as preferential adsorption sites for the electron-rich ligands of the aromatic Ru precursor through the formation of π-bonds. This leads to the enhanced nucleation of Ru. The roles of the functional groups were corroborated by silylation experiments.

Improvement in Thermal Stability of Stacked Structures of Aluminum Nitride and Lanthanum Oxide Thin Films on Si Substrate

AIN films were deposited as capping (deposited on top of) and reaction barrier layers (placed between the Si substrate and La 2 O 3 film) to improve the thermal stability of La 2 O 3 films. The film structures were investigated by high-resolution transmission electron microscopy and angle-resolved X-ray photoelectron spectroscopy. The AlN-capped La 2 O 3 film did not change its structure after thermal annealing, while that with the AlN barrier films showed a slight increase in the film thickness. The Al atoms diffuse onto the film surface during annealing in the La 2 O 3 /AlN/Si stack, which makes the bottom AlN barrier layer less effective than the capping layer.