| AVS 63rd International Symposium & Exhibition | |
| Plasma Science and Technology | Thursday Sessions |
| Session PS1-ThM |
| Session: | Modeling of Plasmas and Plasma-Surface Interactions |
| Presenter: | Akito Kumamoto, Osaka University, Japan |
| Authors: | A. Kumamoto, Osaka University, Japan N. Mauchamp, Osaka University, Japan M. Isobe, Osaka University, Japan K. Mizotani, Osaka University, Japan H. Li, Osaka University, Japan T. Ito, Osaka University, Japan K. Karahashi, Osaka University, Japan S. Hamaguchi, Osaka University, Japan |
| Correspondent: | Click to Email |
Magnetic random access memory (MRAM) is a nonvolatile storage device of high speed operation with low operating voltage. It has the potential to replace static random access memory (SRAM), dynamic access memory (DRAM), and flash memory if the MRAM integration becomes comparable to that of DRAMs. One of the key challenges for high integration of memory cells in an MRAM device is to establish low-damage highly anisotropic etching technologies for magnetic thin films. Although Ar ion milling processes have been widely used to etch magnetic thin films for MRAM chip manufacturing, plasma etching based on chemically reactive gases such as CO/NH3 and CH3OH have been also studied as possible reactive ion etching (RIE) processes. In this study, we have used molecular dynamics (MD) simulations and ion beam experiments to understand etching mechanisms of magnetic thin films by chemically reactive plasmas. More specifically the current goal of this research is to develop classical interatomic reactive potential functions for MD simulation to emulate etching processes of magnetic thin films (Ni, Co, Fe, and CoFeB alloys) with high accuracy. In this study, we have used Ni as a sample film and developed Ni-C-O interatomic potential functions to examine self-sputtering and physical sputtering by energetic inert gas ions as well as oxidation and carbonization of Ni surfaces by incident O+, C+, and CO+ ions. The metal-metal interactions are modeled with embedded atom method (EAM). However, the existing EAM potentials for most metals do not reproduce their self-sputtering yields well and therefore require modification of the functions in the short range. The metal-oxygen or metal-carbon interaction model used in our MD simulation is based on bond-order potential functions or Stillinger-Weber type angle dependent three-body functions. The potential function model also includes coordination bonds to allow the possible formation of metal carbonyls such as Ni(CO)4. The parameters of these potential models have been optimized based on experimental data of sputtering yields as well as potential energy data obtained from first-principle quantum mechanical (QM) simulations. The MD simulation results for Ni etching based on the newly developed reactive potential functions are also compared with data obtained from ion beam experiments.