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

The chemical vapor-deposited (CVD) tungsten films using H-2/WF6 chemistry w ere studied. A wide range of deposition temperatures and gas compositions w as changed to investigate the boundary separating moss 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 WF6 and/or decreasing H-2 concentrations the surface reacti on-controlled region is expanded toward high temperatures, which can be exp lained by the different order dependence of deposition rate with respect to H-2 and WF6 concentrations. The grain size of the tungsten films is not se nsitive to deposition temperature of 370-610 degrees C, while is larger for films deposited at higher WF6 concentrations in hydrogen-rich atmospheres. Electrical resistivity of films of about 0.5 mu m thickness was measured b y four-paint probe. Low film resistivity of 8.1-14.7 mu Omega cm was obtain ed as deposited over a wide range of H-2/WF6 ratio between 5 and 40 at 490 degrees C and 2.7 x 10(4) Pa (200 Torr). Larger electrical resistivity was obtained for the films deposited either by extra high H-2/WF6 ratio or low ratio near 3, in which the former is attributed to the small grain size eff ect, while the latter is possible due to the fluorine incorporated into the film during deposition. (C) 1998 Elsevier Science S.A. All rights reserved .