Phase map, composition and resistivity of reactively magnetron sputtered and annealed Ta-N films

• Published in: Journal of physics. D, Applied physics Applied physics, 2016-05, Vol.49 (19), p.195301-195310
• Main Authors: Salamon, K, Radi, N, Bogdanovi Radovi, I, O ko, M
• Format: Article
• Language: English
• Subjects: Annealing; Atomic properties; Crystal defects; Density; Deposition; Electrical resistivity; magnetron sputtering; phase composition; resistivity; Tantalum; tantalum nitride; thermal annealing; Thin films
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/0022-3727/49/19/195301

Thin films of tantalum nitride (Ta-N) have been prepared by reactive magnetron deposition under various nitrogen partial pressures pN2 (0−1) and subsequently annealed (Ta  =  450-950 °C). The structure, density, composition and electrical resistivity of the prepared films were systematically investigated. A pN2−Ta phase map was constructed from the results of structural analysis. With increasing of pN2 from 0 to 0.2, a single-phase or two-phase mixture films of tetragonal Ta, Ta2N (Ta 450 °C), -TaN (Ta 850 °C), θ-TaN (Ta 850 °C) and fcc δ-TaN are sequentially observed. For pN2=0.25-0.45, the as grown and annealed films exhibit δ-TaN structure. Amorphous films grown in the pN2=0.45-0.75 range crystallize as cubic Ta2N3 upon annealing at Ta 650 °C or as δ-TaN at Ta 850 °C. A cubic Ta2N3 is grown at highest pN2 ( 0.85), which decomposes to δ-TaN at Ta 850 °C. The N     / Ta atomic ratio in the film linearly increases for pN2=0-0.5, ranging from 0 to 2.1, while the mass density monotonically decreases with pN2. Upon annealing, a part of N atoms out-diffuses from the films deposited at pN2 0.3. The electrical resistivity strongly depends on both pN2 and Ta. However, in the as grown and annealed δ-TaN films the resistivity was of the order of 100-1000 μΩcm. In these films, a correlation between the resistivity and the average number of defects (Ta vacancies and N atom excess) is observed. Finally, the influence of thermally introduced oxygen on the films resistivity has been revealed.