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The main goal of this project is to develop molecular-level understanding, control, and predict chemical reactions relevant for the formation and properties of complex ultra-thin diffusion barrier films on semiconductor substrates. The current technologies dictate that the thickness of diffusion barriers will approach just a few nanometers within the next 15 years, as estimated by the International Technology Roadmap for Semiconductors. Therefore the questions of scaling the physical properties of the films enter a qualitatively new era: these properties now have to be analyzed and understood at the atomic level. The key objective of this project is to promote desired surface chemical reactions for clean Ta- and Ti-based film deposition, while preventing impurity incorporation (C, O, F) at the interfaces formed during this process. Our group employs thermal and photochemical methods to achieve this control. The structure of these amorphous or polycrystalline films presents many challenges. Our group has developed a novel approach to understand their properties. It combines a newly established experimental strategy with novel computational models designed recently in our laboratory to investigate local interactions in these complex systems, as summarized in Figures 1 and 2. Modern deposition and characterization techniques designed for and tested on Ti-based films will be further applied to investigate the poorly characterized Ta-, Hf-, and W-based materials. With the new deposition precursor molecules becoming available, this project will both rely on the materials that are currently predicted to be suitable as diffusion barriers and branch into novel materials.

1. Rodríguez-Reyes, J. C. F. and Teplyakov, A. V. Role of surface strain in the subsurface migration of adsorbates on silicon. Phys. Rev. B 2008, 78, 165314-1-165314-14.

2. Rodríguez-Reyes, J. C. F. and Teplyakov, A. V. Chemisorption of tetrakis-dimethylamido-titanium on Si(100)-2x1: C-H and C-N bond reactivity leading to low-temperature decomposition pathways. J. Phys. Chem. C 2008, 112, 9695-0705.

3. Perrine , K. A., Skliar, D. B., Willis, B. G. and Teplyakov, A. V. Molecular level investigation of 2,2,6,6-tetramethyl-3,5-heptanedione on Si(100)-2x1: Spectroscopic and computational studies, Surf. Sci. 2008, 602, 2222-2231.

4. Rodríguez-Reyes, J. C. F. and Teplyakov, A. V. Surface transamination reaction for tetrakis(dimethylamido)titanium with NH_X-terminated Si(100) surfaces. J. Phys. Chem. C 2007, 111(44), 16498-16505.

5. Rodríguez-Reyes, J. C. F. and Teplyakov, A. V. Chemistry of diffusion barrier film formation: Adsorption and dissociation of tetrakis-(dimethylamino)-titanium on Si(100)-2x1. J. Phys. Chem. C 2007, 111, 4800-4808.

6. Ni, C.; Zhang, Z.; Wells, M.; Beebe, T. P., Jr.; Pirolli, L.; Méndez De Leo, L. P., and Teplyakov, A. V. Effect of Film Thickness and the Presence of Surface Fluorine on the Structure of a Thin Barrier Film Deposited from tetrakis-(dimethylamino)-titanium onto a Si(100)-2x1 Substrate. Thin Solid Films 2007, 515, 3030-3039.

7. Pirolli, L. and Teplyakov, A. V. Adsorption and Thermal Chemistry of 1,1,1,5,5,5,-hexafluoro-2,4-pentanedione (hfacH) and (hexafluoroacetylacetonate)Cu (vinyltrimethylsilane) ((hfac)Cu(VTMS)) on TiCN-covered Si(100) Surface. Surf. Sci. 2006, 601, 155-164.

8. Pirolli, L. and Teplyakov, A. V. Molecular View of Copper Deposition Chemistry: (hexafluoroacetylacetonate)Cu(vinyltrimethylsilane) on a Si(100)-2x1 Surface. Surf. Sci. 2006, 600, 3313-3320.

9. Pirolli, L. and Teplyakov, A. V. Vinyltrimethylsilane (VTMS) as a Probe of Chemical Reactivity of a TiCN Diffusion Barrier-Covered Silicon Surface. J. Phys. Chem. B. 2006, 110, 4708-4716.

10. Pirolli, L. and Teplyakov, A. V. Complex Thermal Chemistry of Vinyltrimethylsilane (VTMS) on Si(100)-2´1. J. Phys. Chem. B 2005, 109(17), 8462-8468.


Figure 1. Atomically resolved TEM studies of the TiCN film deposited onto a Si(100) single crystal.	Figure 2. Schematic representation of the chemical role of the diffusion barrier.