Photo-Induced Atomic Layer Deposition of Tantalum Oxide Thin Films from Ta(OC[sub 2]H[sub 5])[sub 5] and O[sub 2]

Abstract

The growth of tantalum oxide thin films by photoinduced atomic layer deposition was investigated in the temperature range of 170-350°C using Ta(OC 2 H 5 ) 5 and O 2 as precursors. A self-limiting growth rate of 0.37 Å/cycle was achieved at the substrate temperature range of 190-285°C. All the films grown in this temperature range were amorphous and very smooth ͑Ͻ0.31 nm root-mean-square͒ as examined by X-ray diffractometer and atomic force microscopy. X-ray photoelectron spectroscopy analysis showed that the films grown at 260-350°C were almost stoichiometric. The refractive index ͑at 550 nm͒ and the optical bandgap were found to be ϳ2.13 and ϳ4.20 eV, while an average transmittance of ϳ90% in the visible region was obtained. Electrical measurements performed on Pt/Ta 2 O 5 (10 nm)/Ru/SiO 2 /Si capacitors exhibited high dielectric constant ͑22-25͒ and a remarkably low leakage current density of 0.8 Ϫ 1 ϫ 10 Ϫ8 A/cm 2 at an applied field of 1 MV/cm, probably due to the presence of reactive oxygen atom species. The low leakage current was dominated by the Poole-Frenkel emission mechanism.

Flash-Enhanced Atomic Layer Deposition: Basics, Opportunities, Review, and Principal Studies on the Flash-Enhanced Growth of Thin Films

“…The related increase in reactivity and/or the enhancement of the adsorption behavior largely affect the film formation. With respect to ALD, the photo-assisted ALD of tantalum oxide 19,20 and boron nitride 21 thin films using an UV lamp and an ArF laser, respectively, has been reported in literature. Compared to thermal ALD, the application of UV light has led to a higher growth rate, a broadening of the ALD window towards lower temperatures, and partially different film properties.…”

Electrical and optical properties of tantalum oxide thin films prepared by reactive magnetron sputtering

“…In microelectronic applications, Ta 2 O 5 thin film is used in highdensity dynamic-random-access memories (DRAMs) as well as in metal-oxide-semiconductor field-effect transistors (MOSFETs) due to its high dielectric constant, high chemical, thermal stability, low leakage-current density and being compatible with the microelectronic processing technology [6,7]. Deposition techniques such as thermal evaporation [8], rf and dc reactive magnetron sputtering [9,10], electron beam evaporation [11], pulsed laser deposition [12], atomic layer deposition [13], and metal-organic chemical vapor deposition [14] are employed for deposition of Ta 2 O 5 thin films. Among these techniques, reactive magnetron sputtering has the advantage in the preparation of uniform films on large area substrates by sputtering of metallic tantalum target in the presence of reactive gas of oxygen.…”

Photoassisted atomic layer deposition of oxides employing alkoxides as single-source precursors

“…The growth rate is lower than that reported by Lee et al (0.26 Å/cycle both at 220 and 260°C) for the same precursor in photo-ALD, most likely due to different UV emissions employed. Our lamp has a broad spectrum from 190 to 800 nm, whereas Lee et al 15 utilized a lamp with 185 nm emission. The lamp or emission details were not, however, described in their paper, but it is evident that the different spectra lead to different photochemistry and thereby result in different growth rates of Ta 2 O 5 .…”

“…Lee et al deposited Ta 2 O 5 from tantalum ethoxide. 15 They studied two process approaches utilizing a UV lamp with 185-nm emission. The single-source approach, using a process sequence of Ta(OEt) 5 purge irradiation, resulted in a growth rate of 0.26 Å/cycle, which increased to 0.37 Å/cycle when O 2 was used as a reactant during the irradiation.…”