THE LOW-TEMPERATURE CATALYZED CHEMICAL VAPOR-DEPOSITION AND CHARACTERIZATION OF ALUMINUM NITRIDE THIN-FILMS

Aluminum nitride thin films have been grown via low pressure chemical vapor deposition at substrate temperatures ranging from 584 to 732 K by the catalytic action of a heated tungsten filament. A tungsten filament heated to 2020 K was used to decompose ammonia, which reacted with trimethylaluminum introduced downstream of the filament to form aluminum nitride films at deposition rates between 50 and 200 nm/min. The resultant films were characterized by Fourier-transform infrared spectroscopy, x-ray photoelectron spectroscopy (XPS), scanning electron microscopy, and Raman spectroscopy. Infrared spectroscopy revealed hydrogen bonded to nitrogen in concentrations ranging from 2% to 8% on an atomic basis. Multiple internal reflection infrared spectra showed the presence of aluminum-oxygen bonds at the surface of the films. Surface-enhanced Raman spectra indicated that the films were a mixture of amorphous and polycrystalline phases. XPS sputter depth profiles revealed that the concentration of oxygen in the films decreased, and the concentration of carbon in the films increased with increased trimethylaluminum flow rates. The oxygen concentration in the aluminum nitride films could be reduced to levels below the limits of detection for XPS, while the carbon concentration could be reduced to 0.8% under the best growth conditions explored.