Silane reduced chemical vapor deposition tungsten as a nucleating step in blanket W

Abstract

The SiH4–WF6 nucleation step of chemical vapor deposition blanket tungsten has been studied in the 10–100 Torr pressure range. The deposition rate, particle generation rate, and step coverage were studied as a function of the process parameters. The deposition rate was found to be mass transfer limited over the entire range of process conditions. Deposition rates from 300 to over 70 000 Å/min were observed. An in situ detector was used to measure gas phase particle levels. Particle generation rates were found to range from 0 to 108 particles/s over the parameter range studied. The strongest dependence seen was on the SiH4/WF6 flow ratio. At ratios of less than one, no detectable particles were produced. The particle generation rate increases rapidly at ratios above one. The particle rate also increases with increasing temperature and pressure. The step coverage was found to be ∼85% for 1000 Å films in 3:1 aspect ratio trenches. Overall, the results indicate that SiH4 nucleation in the 10–100 Torr range is an attractive alternative to the ≤1 Torr processes commonly in use today.