AVS 51st International Symposium
    Thin Films Thursday Sessions
       Session TF-ThM

Paper TF-ThM9
Complex Target Poisoning Effects in Reactive Sputtering

Thursday, November 18, 2004, 11:00 am, Room 303C

Session: Modeling & Fundamentals in Thin Film Deposition
Presenter: D. Rosen, Uppsala University, Sweden
Authors: D. Rosen, Uppsala University, Sweden
O. Kappertz, Uppsala University, Sweden
T. Nyberg, Uppsala University, Sweden
I. Katardjiev, Uppsala University, Sweden
S. Berg, Uppsala University, Sweden
Correspondent: email address not available
Target poisoning is the major factor limiting the deposition rate in reactive sputtering processes. Chemisorption of the reactive gas at the target surface is the main poisoning mechanism which has been studied in detail and is realatively well understood. However, there are both experimental and theoretical indications that there exists an additional target poisoning process taking place simultaneously with chemisorption. This is implantation of ionized reactive gas molecules into the subsurface of the target. These ions will penetrate some 40-80 Angstrom beneath the surface depending on target voltage. At this position these molecules will also undergo chemical reactions with the target metal atoms and form compound molecules. The target is continously etched by the mixture of energetic argon ions and ionized reactive gas molecules. Thus, the compound molecules formed by ion implantation will be brought to the surface as the target is etched. In this way additional compound molecules will be brought to the surface as compared to the case when only chemisorption at the surface would have taken place. We present a simple treatment for how these two target poisoning mechanisms will affect the processing behaviour of the reactive sputtering process. Our results indicate that the chemical reactivity between the target metal atoms and reactive gas molecules will determine if chemisorption or ion implantation is the dominating mechanism for taget poisoning. The most surprising result, however, is that we found that due to recoil implantation with the energetic argon ions the depth of the partly formed compound sub-layer will be almost identical irrespective whether chemisorption or ion implantation is the dominating target poisoning mechanism.