Structural studies of amorphous and crystallized tungsten nitride thin films by EFED, XRD and TEM

Energy-filtered electron diffraction (EFED), X-ray diffraction (XRD), and t ransmission electron microscopy (TEM) have been used to investigate the str uctural properties of amorphous and crystallized W1-xNx (0.12 less than or equal to x less than or equal to 0.35) thin films prepared by reactive magn etron sputtering in an Ar-N-2 atmosphere. XRD theta-2 theta scans combined with plan-view and cross-sectional TEM showed that the as-deposited W1-xNx films were amorphous in structure. Annealing of the as-deposited films at 6 00 degrees C or above resulted in crystallization of the amorphous phases, forming a two-phase structure consisting of W2N and bcc W or a single-phase structure of W2N, which was related to the initial nitrogen concentration in the films. The crystalline films (150 nm in thickness) near stoichiometr y of W2N had a columnar microstructure with an average column width of 15-2 0 nm near the film surface. For films with a lower N concentration, the col umn grains were larger. EFED data collected from a range of crystalline fil ms were Fourier transformed to a reduced density function (RDF), which was compared to the theoretical calculations based on the fraction of the cryst alline phases determined from the experiment. The transformed fraction was shown to agree with the calculations. (C) 2000 Elsevier Science B.V. All ri ghts reserved.