Ellipsometric Examination of Growth and Dissolution Rates of Ta2 O 5 Films Formed by Metalorganic Chemical Vapor Deposition

Abstract

The formation process of Ta2O5 films in MOCVD using pentamethoxy tantalum (PMT) as a metal organic source and O2 as reactant gas has been analyzed by in situ ellipsometry at deposition temperatures of 473–773 K. According to the change in the growth rate of the films, the formation process can be divided into three stages, the initial, the transition, and the final stages. The growth rate and the optical constant of the films were found to depend on the deposition temperature and the deposition time. All the films obtained at temperatures of 473–773 K had amorphous structures. The corrosion resistance of the films against a buffered HF solution depended on the deposition temperature. By annealing at 923 K in the air for 3.6 ks, amorphous Ta2O5 films deposited at temperatures higher than 673 K were transformed into polycrystalline structures. Ta2O5 films crystallized by annealing showed extremely high corrosion resistances.

Corrosion resistance of Fe2O3-Cr2O3 artificial passive films formed with LP-MOCVD

“…Namely, the refractive index in the complex optical constant decreased with increasing immersion time. The decrease in the refractive index is attributed to an increase in the surface roughness of the films with the progression of the dissolution [6,8,[11][12][13]. The amount of decrease in film thickness with immersion time was determined from the theoretical curve which best fit the experimental plots.…”

“…This suggests that an increase in the order of atomic structure increases the corrosion resistance of the material even in an amorphous structure. It has been reported that the corrosion resistance of oxide films formed by MOCVD depends on the crystallinity of the films [6][7][8]12,14]. For example, the corrosion resistance of ZrO 2 films deposited at temperatures higher than the crystallization temperature is higher than that of the films deposited at temperatures lower than the crystallization temperature.…”

“…For example, the corrosion resistance of ZrO 2 films deposited at temperatures higher than the crystallization temperature is higher than that of the films deposited at temperatures lower than the crystallization temperature. The corrosion resistance of Al 2 O 3 [7] and Ta 2 O 5 [8] films formed at temperatures lower than the crystallization temperature is markedly improved by annealing at temperatures higher than the crystallization temperature.…”

“…For example, Amano et al [6] have reported that the corrosion resistance of ZrO 2 films formed by MOCVD remarkably increased in both 12.0 M HCl and 10.0 M NaOH solutions when they were formed at temperatures higher than the crystallization temperature. The corrosion resistance of the films improves with raising the annealing temperature even in a temperature range lower than the crystallization temperature [7,8].…”

Corrosion Resistance of Artificial Passive Film and Real Passive Film on Fe-Ti Alloy

“…For example, the corrosion resistance of ZrO2 films [20] formed by MOCVD remarkably increased when their formation temperature exceeded the crystallization temperature. The corrosion resistance of A1203 [21] and Ta205 films [22], formed at temperatures lower than the crystallization temperature, were markedly improved by annealing at temperatures higher than the crystallization temperature. It is reasonable to suggest that the crystallinity of the Fe203-TiO2 films formed at 350~ would be higher than that of the passive films formed at 25~ and that this should be the reason why the FezO3-TiO2 artificial passive films have a higher corrosion resistance.…”