Simulation of selective tungsten chemical vapour deposition

A detailed numerical model is presented for the simulation of hydrodynamics and chemistry in selective tungsten low pressure chemical vapour deposition. It combines models for multicomponent transport phenomena in the gas phase and ab initio elementary reactions at the wafer surface. A mechanism and model are proposed to relate non-selective tungsten nucleation on oxide surfaces to the gaseous by-product WF₅. Model predictions of gas temperatures and composition as well as deposition rates have been validated quantitatively with (in situ laser diagnostic) experiments. Predictions for the dependence of selectivity loss on operating conditions show excellent qualitative agreement with experimentally observed trends. The use of the model in the optimization of selective tungsten deposition processes is illustrated.