Growth characteristics and electrical resistivity of chemical vapor-deposited tungsten film

Abstract

The chemical vapor-deposited (CVD) tungsten films using H 2/WF 6 chemistry were studied. A wide range of deposition temperatures and gas compositions was changed to investigate the boundary separating mass transport-controlled and surface reaction-controlled regimes, in which the latter is preferred to get the optimum properties of films. The experimental results show that with increasing WF 6 and/or decreasing H 2 concentrations the surface reaction-controlled region is expanded toward high temperatures, which can be explained by the different order dependence of deposition rate with respect to H 2 and WF 6 concentrations. The grain size of the tungsten films is not sensitive to deposition temperature of 370–610°C, while is larger for films deposited at higher WF 6 concentrations in hydrogen-rich atmospheres. Electrical resistivity of films of about 0.5 μm thickness was measured by four-point probe. Low film resistivity of 8.1–14.7 μΩ cm was obtained as deposited over a wide range of H 2/WF 6 ratio between 5 and 40 at 490°C and 2.7×10 4 Pa (200 Torr). Larger electrical resistivity was obtained for the films deposited either by extra high H 2/WF 6 ratio or low ratio near 3, in which the former is attributed to the small grain size effect, while the latter is possible due to the fluorine incorporated into the film during deposition.