Kinetic simulation of metal chemical-vapor deposition on high aspect ratio features in modern very-large-scale-integrated processing

Abstract

Chemical-vapor deposition of tungsten is extensively used for very-large-scalae-integrated metallization because of its ability to adequately coat the bottom of high aspect ratio features. Despite this, a detailed model of the surface kinetics is not yet widely accepted. Such a model is essential for predicting film coverage over deep topography where fluxes and adsorbate coverage can be very different from those on flat surfaces. By considering the dissociative adsorption of H2 and WF6 and the desorption of H2 and HF molecules, a new surface kinetic model for tungsten deposition is presented. The model includes temperature- and coverage-dependent sticking coefficients of adsorbing reactions, the inhibiting effects of F on H2 adsorption, and multiple reaction pathways. Predictions of the model show reasonable agreement with experimental measurements of H2 partial pressure dependence of tungsten deposition rate over a wide pressure range. Particularly, the model explains the recently observed effect of reduced deposition rate when the H2 pressure becomes comparable to the WF6 pressure. This kinetic model is used by a kinetic thin-film simulator, GROFILMS, to study the W film deposition over high aspect ratio topography. The film growth profile, the coverage of F and H, and the impingement fluxes along the film surface are analyzed.