MODELING OF SELECTIVE TUNGSTEN LOW-PRESSURE CHEMICAL-VAPOR-DEPOSITION

A comprehensive numerical model for selective low-pressure chemical va por deposition (LPCVD) of tungsten from hydrogen and WF6 in a single-w afer reactor has been developed. The computational fluid dynamics (CFD ) code PHOENICS-CVD is used for transient solutions of the two-dimensi onal transport equations of heat, momentum and chemical species in the reactor. A detailed model is used for the kinetics of tungsten deposi tion at the surface. A model for the nucleation of intermediates, whic h are formed at the surfaces where tungsten is deposited and are trans ported through the gas phase, is used to describe the loss of selectiv ity. This opens the way for qualitative study of the influence of proc ess conditions and reactor configurations on the selectivity of this p rocess. The selectivity is found to improve at high how rates, low tot al pressures and low partial pressures of WF6.