Integrated multi-scale model for ionized plasma physical vapor deposition

In order to aid process development and address extendibility of ionized physical vapor deposition (IPVD) technology to future integrated circuit generations, an integrated model capable of simulating phenomena across the various length scales characteristic of these systems has been developed. The model is comprised of a two-dimensional equipment simulation, which relates process variables to characteristics of material fluxes to the wafer, and a three-dimensional Monte Carlo based feature scale model. The ion-surface interaction data required to model the surface processes is generated by a molecular dynamics based simulation. The integrated model is used to study the effect of various IPVD process parameters such as wafer bias, coil power, target power, and buffer gas composition on copper film profile inside a trench. Variations in film profile across the wafer are also examined. It is found that increasing the wafer bias results in an increase in the mean ion energy and the amount of sputtering inside the feature. This results in material transfer from the bottom of the feature to the sidewalls and faceting of the upper corners of the trench. Two variables, namely the total ion to Cu flux ratio (R(I/N)) and the mean ion energy, are found to play a crucial role in determining the effects of coil power and target power. Increasing the coil power enhances R(I/N) and slightly decreases the mean ion energy. This leads to more sputtering, and therefore a thicker film on the sidewalls relative to that on the bottom. Increase in target power causes R(I/N) to decrease, which decreases sputtering within the feature. Film profiles generally show evidence of enhanced sputtering as buffer gas ionization threshold decreases (He --> Ne --> Ar --> Xe) for the gases considered. These variations can be explained in terms of two factors: Cu flux ionization fraction, which decreases with buffer gas ionization threshold, and mean ion energy, which increases with ionization threshold. (C) 2001 American Institute of Physics.