Fujio Asa

Monte Carlo simulation of damascene electroplating: effects of additives

The influence of additives on the filling process of via holes in damascene electroplating is investigated with use of a kinetic Monte Carlo method. The basic system is the solid-by-solid model for crystal growth which includes the vacancy formation during the growth of thin film. Three kinds of additives are included in the model to control the local surface growth rate. Inhibitors and levelers have the effect of preventing the deposition, while accelerators increase the local growth rate. Levelers are modeled to stick to the tips of the surface. We performed a series of simulations by changing the parameters which characterize the additives to see their influence on the filling mechanism. It is shown that void-free filling is possible by the combination of the effects of the additives.

Molecular dynamics—Monte Carlo hybrid simulation of thin film growth and void formation in electrodeposition process

The surface structure and the void formation during electrodeposition process are investigated using the hybridized method of molecular dynamics and Monte Carlo simulations. In this approach, adsorption and desorption reactions are simulated by means of the Monte Carlo method within the molecular dynamics simulation of solution-electrode interface. The adsorption (desorption) is regarded as the change of metal ions (atoms) to metal atoms (ions). We performed the simulations of crystal growth on FCC (111) and (100) surfaces to study the surface structure depending upon the deposition conditions. The growth mechanism is discussed in relation to the surface diffusion of adatoms. In order to study the void formation in the deposition process, we performed the simulation of filling V-shaped grooves. It is shown that large voids appear in the middle of the grooves when they are filled with deposited atoms and some of the ions are embedded in the film.

Kinetic Monte Carlo Approach to the Effects of Additives in Electrodeposition

The effects of additives in copper electrodeposition have been studied by using the multi-scale kinetic Monte Carlo simulation. Recently we have extended the solid-by-solid model for crystal growth to a multiple scale model for the simulation of the copper deposition from electrolytic solution. The system consists of the electrode, the solution and the diffusion layer. The solution contains copper ions and the model additives of chloride ions, polyethylene glycol (PEG) and bis(3-sulfopropyl) disulfide (SPS). We have performed the simulations of copper deposition with different combinations of the additives and studied the surface morphology. The suppressing effect of PEG and the accelerating effect of SPS have been confirmed.

Simulation of Three-Dimensional Solid-by-Solid Model and Application to Electrochemical Engineering

A multi-scale kinetic Monte Carlo method has been developed for the molecular simulation of electrodeposition. The basic system is the solid-by-solid model which is a new model for crystal growth with vacancy formation. This model is extended to include the solution and the diffusion layer to take into account the concentration overpotential. The migration of ions in solution is simulated by the coarse-grained random walk. Since the time and length scales in the diffusion layer are largely different from those of the atomic events on the electrode surface, a multi-scale simulation method has been used for the diffusion layer. We have performed the simulation of copper electrodeposition and confirmed that the shape evolution of the surface can be simulated with the formation of the concentration gradient in the diffusion layer.

Kinetic Monte Carlo Simulation of Via Filling : Role of Chloride Ions

The influence of chloride ions on the filling process of via holes has been studied with use of a kinetic Monte Carlo method. Four kinds of additives (inhibitors, accelerators, levelers and chloride ions) are included in the solid-by-solid model for crystal growth as a model of copper electrodeposition. It is assumed that the chloride ions are adsorbed on the metal surface and the adsorption of the inhibitors and the accelerators occurs through the interaction with the surface chloride ions. The binding energy of the chloride ions with the accelerators is assumed to be larger than that with the inhibitors. We performed a series of simulations to study the synergistic effects of the chloride ions and the other additives on the film structures. The effect of convection is also taken into account to improve the filling condition. The mechanism of superfilling is discussed from a microscopic point of view.

Molecular Simulation Approach to the Effects of Additives in Electrodeposition Process

The leveling effect of additives in electrodeposition has been studied using a simplified model for inhibitors by the combined method of molecular dynamics and Monte Carlo simulations. The additive molecule is assumed to be a spherical particle which has an action range around its center in which the metal deposition is inhibited. The interaction between the additives and the electrode is modeled by a simple Lennard-Jones potential. The dependence of the leveling efficiency on the action range and the interaction energy has been studied by a series of simulations of filling grooves. It is shown that high throwing power is obtained for the additives with large interaction energy with the electrode.