Transport of Sputtered Particles in Capacitive Sputter Sources

TL;DR

This paper simulates the transport of sputtered aluminum particles in a capacitively coupled plasma chamber using a kinetic multi-particle approach, highlighting the influence of chamber geometry and scattering parameters on particle behavior.

Contribution

It introduces a novel set of scattering parameters for aluminum and argon and applies an angular dependent energy distribution in kinetic simulations of sputtered particle transport.

Findings

Transport is effectively one-dimensional under typical conditions.

Geometric features significantly influence particle backscattering near electrode edges.

Backscattering from chamber outside volume is a key transport mechanism.

Abstract

The transport of sputtered aluminum inside a multi frequency capacitively coupled plasma chamber is simulated by means of a kinetic test multi-particle approach. A novel consistent set of scattering parameters obtained for a modified variable hard sphere collision model is presented for both argon and aluminum. An angular dependent Thompson energy distribution is fitted to results from Monte Carlo simulations and used for the kinetic simulation of the transport of sputtered aluminum. For the proposed configuration the transport of sputtered particles is characterized under typical process conditions at a gas pressure of p=0.5 Pa. It is found that -- due to the peculiar geometric conditions -- the transport can be understood in a one dimensional picture, governed by the interaction of the imposed and backscattered particle fluxes. It is shown that the precise geometric features play an important role only in proximity to the electrode edges, where the effect of backscattering from the outside chamber volume becomes the governing mechanism.