Vanadium carbide coatings were deposited on steel substrates by MOCVD in the temperature range 400-550 °C using bis(arene)vanadium as precursors. The films are polycrystalline and exhibit the cubic structure V₈C₇. Their crystallinity increases with the temperature. The composition of the films grown using V(C₆H₆)₂ does not change significantly in the whole temperature range and is typically V_0.52C_0.48. No significant difference of composition was observed for a coating grown using V(C₆H₅CH₃)₂ indicating that a methyl group bound to the aromatic rings does not increase the C content. SIMS profiles have shown the uniform depth distribution of the elements.

Addition of C₆Cl₆ in the gas phase allows to decrease the C content and to increase the growth rate of the coatings. Then, depending on the composition of the initial mixture V(C₆H₆)₂/C₆Cl₆/H₂/He the different phases of the V-C phase diagram have been deposited at 400 °C, including the growth of coatings exhibiting the cubic structure of metal vanadium. However the C content of such films is about 14 at % that is far beyond its solubility in vanadium. Therefore they must be considered as a supersaturated metastable solid solution.

Vanadium nitride coatings were grown at 550 °C using the input gas phase V(C₆H₆)₂/NH₃ in the same isothermal low pressure reactor. The films exhibit the cubic structure δ-VN with a (111) texture. The C content is lower than 5 at %. The deposition process and the main features of these V-based coatings are presented and discussed.

Protective films of ZrN and its derivative Zr(C,N) deposited by MOCVD (metallorganic chemical vapor deposition) are among the less investigated hard-coating materials. In comparison to TiN, which is widely used for cutting tool coatings, these films display a smaller coefficient of friction while possessing comparable hardness and chemical properties. Advantages of ZrN in the machining of non-ferrous metals (brass, Ti alloys) have been reported. Systematic investigations concerning the tribological properties, the substrate-layer interface, and the deposition of gradient layers or multilayers are still lacking.

Until now, Zr(NEt₂)₄ has mainly been used, by other groups, as a precursor for MOCVD of zirconium nitride. Three new precursors, Zr(NEtMe)₄, Zr(pip)₄ and Zr(pyrr)₄, have been synthesized and characterized in our laboratory. The substituents in these volatile molecules have been chosen such that thermal decomposition occurs at lower temperatures, thus reducing loss of substrate hardness during deposition. The compounds already contain direct zirconium-nitrogen bonds.

Coatings were deposited on both silicon wafers and HSS tool-steel samples in the temperature range of 350 to 700°C using a low-pressure cold-wall reactor. Decomposition byproducts were investigated using an in-line mass spectrometer. Coatings and interfaces were chemically characterized employing XPS analysis and depth profiling. Phase analysis was carried out using XRD.

Coating thickness and growth rate were evaluated. Hardness was determined from both micro- and nanoindentation techniques. Surface roughness was measured by AFM and the morphology of the film surface and cross-section characterized by FE-SEM. Tribological results were obtained using a pin-on-disk tribometer.

Both precursors proved to be suitable for use with the MOCVD technique and our experimental set-up. The concentration of carbon and oxygen impurities, however, had a remarkable impact on the established hardness values.

Currently CVD Tungsten plug technology is optimized for contact and via interconnect applications. Tungsten has been proposed to be used as gate electrode material and bit line contact in the source and drain regions for the next generation devices. A reduction of W resistivity by Diborane (B₂H₆), published by Hara¹ et. al., will be advantageous to these advanced applications that require device speed enhancement and geometry shrinkage.

A novel Tungsten (W) CVD process was developed which includes B₂H₆ doping in various stages of the process recipe performed on an Applied Materials Centura^TM WxZ Tungsten chamber. The bulk resistivity of the CVD W film was measured at 8.5 μΩ-cm which represented a 38% reduction at 2000 Å thickness over the resistivity of a standard W CVD process. This work will report the W CVD process conditions and the metrics developed to measure the film density and thickness for a W CVD film resistivity verification. Other film properties such as: step coverage, reflectivity, surface roughness, stress , impurity content and crystal size of the obtained films will be compared to the standard W CVD film. A proposed model for the resistivity reduction was developed to explain the observed changes in the W films. Other possible applications of these novel low resistivity W films in future IC designs will also be discussed.

¹ T. Hara, T. Ohba, H. Yagi, H. Tsuchikawa in: Proc. Advanced Metallization for ULSI Applications in 1993, Edts.: D.P. Favreau, Y. Shachman-Diamond and Y. Horiike, Materials Research Society, Pittsburgh, PA, 1994, p. 353