GRAIN-BOUNDARY DIFFUSION MODELING AND EFFICIENCY EVALUATION OF THIN-FILM DIFFUSION-BARRIERS CONSIDERING MICROSTRUCTURE EFFECTS

We have developed a novel grain-boundary diffusion model using the tra nsmission-line matrix method. in conjunction with a two-dimensional Mo nte Carlo thin-film growth simulator this model can be employed for th e analysis of impurity diffusion in thin-film diffusion barriers with realistic microstructures. in the model, the impurity at the upper sur face of the barrier layer may diffuse through rapid and irregularly sh aped grain-boundary diffusion paths to reach the bottom surface. Calcu lations of the impurity concentration and out-diffusion flux as a func tion of elapsed diffusion time and position enable the evaluation of t he effectiveness of the barrier layer at a microstructure level. Conse quently, the diffusion process is depicted with less assumptions and m ore precisely than previously available approaches. This paper details the grain-boundary diffusion modeling method outlined above, with the emphasis on the treatment of various boundary conditions. A represent ative application to titanium nitride (TiN) thin-film diffusion barrie rs is also demonstrated, as befits the high level of interest in this particular material for very large scale integrated devices. (C) 1995 American Institute of Physics.