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

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-mu-OMEGA-cm with the addition of SiH4 (SiH4/WF6 ratio = 1) even at a lower temperature (220-degrees-C) than in the previous works. For the further reduction of resistivity, with increasing deposition temperature from 220 to 360-degrees-C, 40-mu-OMEGA-cm is reduced to 10-mu-OMEGA-cm, and (110), (200) and (211) oriented alpha-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 beta peaks are observed at the expense of the alpha-phase. The Auger in-depth profile indicates that 20 atomic % is incorporated into the deposition process.