Influence of deposition parameters on the texture of chemical vapor deposited tungsten films by a WF6/H2/Ar gas source

In order to investigate the relationship between the film texture and the deposition parameters including gas composition, temperatures, and substrate materials, polycrystalline tungsten films were prepared by reduction of tungsten hexafluoride with hydrogen. The experimental results show that the orientations of the textured films correlate closely with WF6 concentrations in the gas mixture and deposition temperatures. High WF6 concentrations enhance the formation of the <100> textured films, while low WF6 concentrations facilitate the formation of the <111> textured films. The <111> texture, usually observed in tungsten films deposited at high temperatures (greater than or equal to 400 degrees C) and high ratios of H-2 to WF6, can also form at low deposition temperatures (370 degrees C) when the WF6 concentration used is low enough (0.6 vol %). The WF6 concentration for obtaining a <100> textured film increases with increasing deposition temperatures. On the other hand. the concentrations of hydrogen gas have minimal influence on the formation of the film textures. Therefore, in terms of gas composition, the WF6 concentration, riot the ratio of H-2 to WF6 is a compact factor which directly dominates the texture of the films. The effect of substrate on the film texture was only found in the initial growth stage. The crystals formed at the beginning of the film growth were randomly oriented. A. preferential orientation became pronounced with increasing film thickness through the competitive crystal growth.