Real-time spectroscopic ellipsometry study of Ta-Si-N ultrathin diffusion barriers
- Department of Physics, Southern Illinois University, Carbondale, Illinois 62901-4401 (United States)
This article reports on the use of real-time spectroscopic ellipsometry (RTSE) to (1) understand the growth process of ultrathin (10 nm thick) Ta-Si-N diffusion barriers and to (2) monitor their thermal stability up to a temperature of 800 deg. C. Thin films of Ta-Si-N diffusion barriers and Cu overlayers were deposited on Si(111) substrates using reactive unbalanced magnetron sputtering. In order to reduce roughness and interdiffusion between consecutive surfaces, a modulated low energy and high flux ion assistance was utilized. The initial part of the films (2 nm) of each layer was deposited with a high flux of low energy ions (<10 eV) to reduce intermixing, while higher energies (between 40 and 130 eV) were utilized for the remainder of the layer to decrease the percolation thickness. RTSE data were simulated using the Drude-Lorentz model to obtain information about the growth mechanism and the conduction electron transport properties for these structures. The films were annealed at 800 deg. C and the diffusion of copper into silicon was evaluated by monitoring changes in the optical properties of the bilayers. The pseudodielectric function of the films was found to be altered whenever diffusion proceeded. Thermal stability at 800 deg. C was achieved for samples produced using the ion-assistance technique. The results deduced from RTSE were verified by characterizing the elemental composition of the as-deposited and heat-treated films using Rutherford backscattering and time-of-flight secondary ion mass spectrometry.
- OSTI ID:
- 20723045
- Journal Information:
- Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films, Vol. 23, Issue 5; Other Information: DOI: 10.1116/1.1996612; (c) 2005 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0734-2101
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
COPPER
CRYSTAL GROWTH
DEPOSITION
DIFFUSION BARRIERS
ELLIPSOMETRY
ION MICROPROBE ANALYSIS
LAYERS
MASS SPECTROSCOPY
NANOSTRUCTURES
OPTICAL PROPERTIES
ROUGHNESS
RUTHERFORD BACKSCATTERING SPECTROSCOPY
SEMICONDUCTOR MATERIALS
SILICON
SILICON COMPOUNDS
SPUTTERING
SUBSTRATES
TANTALUM COMPOUNDS
THIN FILMS
TIME-OF-FLIGHT METHOD