By utilizing preexposure of helium plasma, a method of depositing a blanket
tungsten layer directly on SiO2 has been developed. When SiO2 films are ex
posed to a helium plasma, oxygen atoms are knocked on by active species in
the plasma and the surface becomes covered with reduced silicon. It is assu
med that this silicon reacts with WF6 to form tungsten nuclei, and that tun
gsten layers grow through the reaction of H-2 and WF6 at these nuclei. The
deposited tungsten layer is stable with a low resistivity in the form of th
e alpha-W crystal and shows strong adhesion to the SiO2 film due to the anc
horing effect of tungsten. (C) 1999 American Institute of Physics. [S0021-8
979(99)03912-2].