Comparison of tungsten films grown by CVD and hot-wire assisted atomic layer deposition in a cold-wall reactor

In this work, the authors developed hot-wire assisted atomic layer deposition (HWALD) to deposit tungsten (W) with a tungsten filament heated up to 1700-2000 degrees C. Atomic hydrogen (at-H) was generated by dissociation of molecular hydrogen (H-2), which reacted with WF6 at the substrate to deposit W. The growth behavior was monitored in real time by an in situ spectroscopic ellipsometer. In this work, the authors compare samples with tungsten grown by either HWALD or chemical vapor deposition (CVD) in terms of growth kinetics and properties. For CVD, the samples were made in a mixture of WF6 and molecular or atomic hydrogen. Resistivity of the WF6-H-2 CVD layers was 20 mu Omega.cm, whereas for the WF6-at-H-CVD layers, it was 28 mu Omega.cm. Interestingly, the resistivity was as high as 100 mu Omega.cm for the HWALD films, although the tungsten films were 99% pure according to x-ray photoelectron spectroscopy. X-ray diffraction reveals that the HWALD W was crystallized as beta-W, whereas both CVD films were in the alpha-W phase. (C) 2015 American Vacuum Society.