Highly Conductive Tungsten Thin Films Prepared by the Plasma-Assisted Silane Reduction Process

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Abstract
We have studied the properties of plasma-enhanced chemical vapor deposited tungsten (PECVD-W) thin films according to the variations of reactant mixtures, SiH4/WF6 ratio, deposition temperature and RF power density. As the result, it is found that the resistivity of PECVD-W is reduced from 70 to 40 µΩ-cm with the addition of SiH4 (SiH4/WF6 ratio=1) even at a lower temperature (220°C) than in the previous works. For the further reduction of resistivity, with increasing deposition temperature from 220 to 360°C, 40 µΩ-cm is reduced to 10 µΩ-cm, and (110), (200) and (211) oriented α-phase grain growth is observed. The deposition rate is increased with the increase of the SiH4/WF6 ratio up to 1.5. However, at the SiH4/WF6 ratio of 2, the deposition rate decreases and β peaks are observed at the expense of the α-phase. The Auger in-depth profile indicates that 20 atomic % is incorporated into the deposition process.