Reactor-scale models for rf diode sputtering of metal thin films

Abstract

This article describes the development of an integrated physical model for the rf diode sputtering of metal thin films. The model consists of: (1) a computational fluid dynamic finite element model for the velocity and pressure distribution of the working gas Ar flow in the chamber, (2) a steady-state plasma model for the flux and energy of Ar ions striking the target and the substrate, (3) a molecular dynamics sputtering model for the energy distribution, angle distribution, and yield of the sputtered atoms (Cu) from the target, and (4) a direct simulation Monte Carlo (DSMC) model for the transport of Cu atoms through the low-pressure argon gas to the deposition substrate. The individual models for gas flow, plasma discharge, Cu sputtering, and DSMC-based Cu atom transport are then integrated to create a detailed, steady-state, input–output model capable of predicting thin-film deposition rate and uniformity as a function of the process input variables: power, pressure, gas temperature, and electrode spacing. Deposition rate and uniformity in turn define the characteristics of thin films exploited in applications, for example, the saturation magnetic field for a giant magnetoresistive multilayer. This article also describes the development of an approximate input–output model whose CPU time is several orders-of-magnitude faster than that of the detailed model. Both models were refined and validated against experimental data obtained from rf diode sputtering experiments.