Incident ion characteristics in ionized physical vapor deposition using molecular dynamics simulation

This paper presents the use of molecular dynamics (MD) simulation to investigate incident ion characteristics within the ionized physical vapor deposition (IPVD) process. The study focuses upon the influence of different compositions of Ar+ and Cu+ ions within the incident source on the filling morphology, and on the trench filling mechanisms. This paper also presents the filling morphology associated with a conventional deposition process for comparison purposes. The MD simulation incorporates a trench model and a deposition model, and uses the many-body, tight-binding potential method to represent the inter-atomic force which acts between the neutral atoms. Meanwhile, the inter-atomic force acting between the ions and the neutral atoms is modeled by the pairwise Molière potential method. The results of the simulation indicate that an increase in either the argon or the copper ion composition in the incident source is beneficial to improving trench coverage. The main function of these two incident ions is to impart kinetic energy to previously deposited atoms within the trench. Of the two types of incident ions, it is found that the copper ion has the greater influence on the filling pattern. The principal effects of the incident copper ion include improving coverage of the trench bottom, providing a beveling effect of the overhanging clusters at the trench opening, and causing a sputtering of the atoms deposited at the bottom of the trench. By contrast, the incident argon ion plays more of an assisting role in the IPVD process, and tends to promote the dragging of the overhanging clusters towards the trench. The simulation results demonstrate that increasing the incident copper ion composition is more effective in improving trench coverage than increasing the incident argon ion composition. However, it is noted that the most significant improvement in trench coverage is made by increasing the kinetic energy of the incident atoms, particularly when the percentage of ions within the total incident source is high.