On the role of ion potential energy in low energy HiPIMS deposition: An atomistic simulation

TL;DR

This study uses molecular dynamics simulations to explore how ion potential energy influences the structure and defect formation in low energy HiPIMS Cu deposition, revealing effects on interface mixing, defects, and pore formation.

Contribution

It introduces the role of ion potential energy in low energy HiPIMS deposition, showing its impact on film structure and defect dynamics, which was not previously well understood.

Findings

Including ion potential reduces interface mixing and point defects.

Ion potential increases resputtering and twinning.

Temporary pore formation observed with ion potential inclusion.

Abstract

We study the effect of the so-called ion potential or non-kinetic energies of bombarding ions during ionized physical vapor deposition of Cu using molecular dynamics simulations. In particular we focus on low energy HiPIMS deposition, in which the potential energy of ions can be comparable to their kinetic energy. The ion potential, as a short-ranged repulsive force between the ions of the film-forming material and the surface atoms (substrate and later deposited film), is defined by the Ziegler-Biersack-Littmark potential. Analyzing the final structure indicates that, including the ion potential leads to a slightly lower interface mixing and fewer point defects (such as vacancies and interstitials), but resputtering and twinning have increased slightly. However, by including the ion potential the collision pattern changes. We also observed temporary formation of a ripple/pore with 5~nm height when the ion potential is included. The latter effect can explain the pores in HiPIMS deposited Cu thin films observed experimentally by atomic force microscopy.