Heat flow modeling of chemical vapor deposition of tungsten for improved film thickness uniformity

Abstract

The boundary element method is used to model the heat flow in a tungsten chemical vapor deposition (CVD W) reactor to determine the origin of the tungsten film thickness variation across a 125 mmp-type silicon wafer. The typical thickness nonuniformity is 7-10%. The model predicts temperature variations in the graphite susceptor which heats the wafers. The resulting temperature difference between the center and edge of a wafer can be up to 20 °C. Deposition rate experiments in a CVD W reactor confirm this. Experiments involving changes in the gas flow geometry have been conducted. It is concluded that the temperature gradient across the wafer, not the gas flow geometry, is the dominant factor controlling film thickness uniformity for this CVD W reactor.