Hitoshi Kurokawa

Quantum Chemical Molecular Dynamics Studies on the Chemical Mechanical Polishing Process of Cu Surface

The dynamic behavior of the oxidation reaction of the Cu surface during the Cu chemical-mechanical polishing (CMP) process was investigated by a novel tight-binding quantum chemical molecular dynamics method. We confirmed that our tight-binding quantum chemical molecular dynamics method with first-principles parameterization can calculate the structures, and electronic states of various molecules and solids related to the Cu-CMP process as accurately as the density functional calculations, while the CPU time of the new method is around 5,000 times faster than that of the first-principles molecular dynamics calculations. We employed hydrogen peroxide solution as a slurry and the Cu surface as a substrate to simulate the Cu-CMP process by using our accelerated quantum chemical molecular dynamics method. Three types of models were constructed to analyze the effect of the pH of the slurry and Miller plane of the Cu surface on the dynamic behaviors of the oxidation process of the Cu surface. We indicate that the pH of the slurry strongly affects the oxidation process of Cu surface. Moreover, we clarified that the oxidation mechanism depends on the Miller plane of the Cu surfaces.

A Theoretical Study on the Realistic Low Concentration Doping in Silicon Semiconductors by Accelerated Quantum Chemical Molecular Dynamics Method

We present a theoretical study of the structural and electronic properties of a realistic low concentration (<0.5%) doping model in silicon semiconductor. The density of states was calculated using our newly developed accelerated quantum chemical molecular dynamics method, based on our original tight-binding theory. Using this approach, the band structures of large-size silicon model including n-type and p-type dopants were successfully simulated. The results are in good agreement with the experimental results. Furthermore, we also performed quantum chemical molecular dynamics simulation of the dopants in silicon and observed the change of the dopant levels during the simulation. These results clearly suggest that our original quantum chemical molecular dynamics program is a very effective tool for not only the band structure of a realistically low concentration dopant model but also for the electronic states dynamics of silicon semiconductors.