Multiscale modeling of thin film deposition processes

Abstract

Ionized physical vapor deposition (IPVD) and electrochemical deposition (ECD) are two major thin film deposition processes in the microelectronics industry. The ion fluxes with high kinetic energies in IPVD process involve complex surface interactions that affect overall topology of the microscale features. Copper ECD process involves complex surface reactions and transport phenomena that ranges over different length scales. In this work, predictive simulation tools for these two processes have been developed by investigating the surface reaction and the transport phenomena in IPVD and ECD processes. In the IPVD process, molecular dynamics (MD) techniques with embedded-atom potentials are used to study the surface reactions for atoms with high impinging energies (30 - 50 eV). The surface reaction rates are combined with ballistic transport and level set methods. The resulting tool demonstrates the effect of the kinetic energy driven surface diffusion on the feature profile evolution. For the ECD process of copper, detailed surface kinetic mechanisms are developed based on the competitive adsorption/desorption model in the presence of three representative additives, poly ethylene glycol (PEG) and bis-(sodium sulfoprophyl) (SPS) and chloride. The proposed kinetic mechanism is capable of describing the synergistic effect of different additives on the copper deposition. Statistically designed experiments were performed with the rotating disk electrode (RDE) apparatus. A hydrodynamic model was developed for RDE and is used to fit the kinetic parameters that are independent of the transport effect.

(cont.) A reactor scale model is developed based on the Galerkin finite element method. The model includes momentum transport, transient mass transport, potential distribution and detailed surface kinetic mechanisms. The experimental film thickness uniformity on the blank wafer with commercial electrochemical deposition cell is compared with the simulation result. The reactor scale model is used to investigate the various effects on the film thickness uniformity including terminal effects and mass transport effects. The analysis shows the qualitative difference between two effects and how they can be eliminated. Also, the reactor scale simulation tool is used to model the pulse plating process. Improved performance of the pulse plating over the constant current operation suggests that the relaxation period is the critical parameter that determines the film thickness uniformity. A computationally efficient feature scale model is developed. Mass transport, potential distribution and detailed surface reactions are included in the model ...