MOCVD of High-Dielectric-Constant Lanthanum Oxide Thin Films

Abstract

Lanthanum oxide thin films were fabricated on Si substrates by the metallorganic chemical vapor deposition ͑MOCVD͒ method at substrate temperatures ranging from 400 to 650°C. From the results of X-ray photoelectron spectroscopy ͑XPS͒, X-ray diffraction ͑XRD͒, cross-sectional scanning transmission electron microscopy ͑STEM͒, and energy-dispersive X-ray ͑EDX͒ analyses, the enhanced chemical reaction at the interface between the Si substrate and the films was revealed, which results in the generation of an interfacial layer of SiO 2 ͑1-2 nm thick͒ and lanthanum silicate at all the experimental substrate temperatures. We found that a thin silicon oxynitride layer on the Si substrate is effective in suppressing the interfacial reaction and in increasing the dielectric constant of the lanthanum oxide deposited on it. The thin silicon oxynitride layer is also effective in reducing the leakage current through the film. For the stacked La-oxide/SiON film, the dielectric constant of the lanthanum oxide film was 19 and the leakage current density was 3 ϫ 10 Ϫ6 A/cm 2 at the oxide voltage of 1 V for a film with an equivalent oxide thickness of 2.4 nm.

Influence of postdeposition annealing on structural properties and electrical characteristics of thin Tm2O3 and Tm2Ti2O7 dielectrics

“…The as-deposited sample for Tm 2 O 3 film has high level of thulium as compared to the annealed sample. This result is due to the formation of silicate film during thermal annealing, which is in agreement with the literature reported [5][6][7]. In contrast, the Tm 2 Ti 2 O 7 film annealed at 700 and 800 8C has the highest thulium of all samples examined, as shown in Fig.…”

“…The HfO 2 -based dielectric is likely to employ within this process technology, but it is widely believed that HfO 2 -based technology permits the downscaling of equivalent oxide thickness no further than below $0.8 nm [4]. In addition to the HfO 2 -based dielectrics, rare-earth (RE) metal oxide, such as La 2 O 3 , Pr 2 O 3 , Nd 2 O 3 , Gd 2 O 3 , Dy 2 O 3 , and Er 2 O 3 [5][6][7][8][9][10], is being considered as one of the most promising high-k materials due to its superior properties including a high dielectric constant, a large bandgap, and good thermal stability in contact with the Si substrate. However, the moisture absorption is a major problem with RE oxides, leading to a thicker film and a larger flat-band voltage shift [11].…”

Improving the Si Impurity Tolerance of Pr0.1Ce0.9O2−δ SOFC Electrodes with Reactive Surface Additives

“…[43][44][45] This behavior is more clearly observed in the intentionally Si treated sample (Figure 5c), where the high energy peak becomes much larger and the low energy peak (Ce(IV)-O) decreases as the PCO film is covered by siliceous phase. After the La oxide treatment (Figure 5d), the intermediate peak is now by far the largest of all three peaks, and, for previous studies on the interface between La and Si oxides, has been assigned to oxygen bound to both La and Si (La-O-Si), with the high energy peak previously assigned to La-O-H. [46][47][48] In the present case, this result indicates that there is a significant reaction between the Si and La, possibly forming a lanthanum silicate compound. Though the temperature for reaction here is low (600 o C), the short diffusion lengths of the thin film layers of Si and La oxides likely facilitate reaction with La oxide.…”

Preparation and Evaluation of High-Purity La2O3

“…[6][7][8] Recently, high-purity La of 99.999 pct or higher is required for several high-technology applications, such as ultra-large-scale integrated (ULSI) gate insulation film materials. [9][10][11][12][13][14] Therefore, it is important to reduce the impurity levels as much as possible. Unfortunately, the mutual separation of rare earth elements is very difficult because of their similar physical and chemical properties.…”