Low temperature plasma-assisted chemical vapor deposition of tantalum nitride from tantalum pentabromide for copper metallization

In this article, the authors report the development of a new low temperature plasma-assisted chemical vapor deposition (PACVD) process for the growth of low resistivity, cubic tantalum nitride (TaNx) for incorporation as a diffusion barrier/adhesion promoter in emerging ultralarge-scale integrated (ULSI) multilevel metallization (MLM) schemes. TaNx films were produced in a low density plasma using tantalum pentabromide, hydrogen, and nitrogen as coreactants. The films were grown at substrate temperatures of 350-450 degrees C, reactor working pressures of 0.9-1.6 Torr, hydrogen how rates between 250 and 1500 seem, nitrogen flow rates of 100-600 seem, and plasma power ranging from 10 to 60 W, corresponding to a power density of 0.06-0.33 W/cm(2). The films were subsequently characterized by Auger electron spectroscopy, Rutherford backscattering spectrometry, x-ray diffraction, atomic force microscopy, four-point resistivity probe, and cross-sectional scanning electron microscopy. These studies indicated that the TaNx films produced were stoichiometric and carbon and oxygen free, contained bromine concentrations below 3 at. %, and exhibited resistivities as low as 150 mu Omega cm. The conformality was higher than 95% in the nominally 0.3 mu m, 4.5:1 aspect ratio structures. These results indicate that in the case of halide-based Ta chemistries, PACVD in a (N-2 + H-2) plasma might be more viable than thermal CVD in a NH3 atmosphere for the deposition of TaNx for ULSI MLM applicatisns. (C) 1999 American Vacuum Society. [S0734-211X(99)00201-2].