Transport of Sputtered Particles Through the Gas Phase

Knowledge of the transport of sputtered particles through the gas phase is not only a fundamental research topic, but also of main interest to know the properties of the arriving metal flux at the substrate or chamber walls as a function of the deposition geometry and deposition conditions. Characterisation or modelling of this metal flux is, e.g. of interest when a high thickness uniformity is needed [1], when complex substrates are to be deposited [2], or when the thin film composition has to be controlled [3]. However, not only the amount of arriving metallic particles has to be controlled, but also their direction and impact energy are influencing the final properties of the deposited thin films. Although some attempts have been done, characterisation of the incoming direction [4] or the energy [5] of metal particles experimentally is difficult to carry out.

A better attempt is to simulate the transport of the sputtered particles, and to verify the simulation code by the experimental much more accessible deposition profile [6].

An overview of the simulation of the transport of the sputtered particles through the gas phase is given in this article.

Section 6.2 describes the place wherefrom the sputtered particles leave the target. Section 6.3 discusses the different ways to describe the initial energy and direction of the sputtered particles, when leaving the target. In Sect. 6.4, the mean free path, and thus the distance to a collision with the background gas, is discussed. Also the collision and the interaction potential needed to describe the collision are treated in Sect. 6.4. Section 6.5 briefly discusses the possible ways to include the effect of gas rarefaction. Finally, in Sect. 6.6 a concrete simulation model is described and some typical results are shown.