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

Tungsten nitride (WxN) 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 N(2)and Ar gases. Experimental data demonstrate that different N(2)contents in gas mixture strongly affect microstructure, phase formation, texture morphology and resistivity of the WxN films. According to X-ray diffraction (XRD) patterns, the growth of tungsten nitride films promotes delta-WN phase for lower N(2)contents in gas mixture. At higher N(2)contents, a phase transition is observed in the tungsten nitride films. Both hexagonal delta-WN and cubic beta-W2N phases coexist, and WN phase approximately disappears with N(2)contents in the gas mixture increasing. Scanning electron microscope (SEM) images for deposited films at lower N(2)contents in gas mixture indicate a definite dense columnar nanostructure. The electrical resistivity results exhibit a significant drop for the WxN thin films with N(2)contents in the mixed gas increasing. The changes in N(2)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 N(2)contents in gas mixture has noncolumnar microstructure and lower resistivity, which may be used as a superior diffusion barrier.