Structure, morphology and electrical resistance of W_xN thin film synthesized by HFCVD method with various N₂ contents

Tungsten nitride (W_xN) thin films with good crystalline structure, high quality and relatively low resistivity were deposited by hot filament chemical vapor deposition (HFCVD) technique at different mixtures of N₂ and Ar gases. Experimental data demonstrate that different N₂ contents in gas mixture strongly affect microstructure, phase formation, texture morphology and resistivity of the W_xN films. According to X-ray diffraction (XRD) patterns, the growth of tungsten nitride films promotes δ-WN phase for lower N₂ contents in gas mixture. At higher N₂ contents, a phase transition is observed in the tungsten nitride films. Both hexagonal δ-WN and cubic β-W₂N phases coexist, and WN phase approximately disappears with N₂ contents in the gas mixture increasing. Scanning electron microscope (SEM) images for deposited films at lower N₂ contents in gas mixture indicate a definite dense columnar nanostructure. The electrical resistivity results exhibit a significant drop for the W_xN thin films with N₂ contents in the mixed gas increasing. The changes in N₂ content in gas mixture are found to be responsible for variation in the film resistivity values. Thus, the deposited tungsten nitride thin film at higher N₂ contents in gas mixture has noncolumnar microstructure and lower resistivity, which may be used as a superior diffusion barrier.