Modelling of Reactive Sputtering Processes

Sputtering is a widely used technique to fabricate thin film coatings. Equipment for large area coatings is easy to set up and film uniformity may be satisfactory controlled over large processing areas. Sputtering is normally carried out in an argon ambient. Not only elemental pure single metal targets may be used, but also metal alloys can be sputtered which offers the possibility to deposit also complex coatings. Common for all inert argon sputtering processes is that the simplicity of the process only requires rather rudimentary process control. These properties make sputtering an attractive and competitive coating process.

By adding a reactive gas to the sputtering process, it is possible to form a compound between sputtered metal atoms and reactive gas molecules. In this way, it is possible to form oxides, nitrides, borides, carbides, etc. To distinguish inert argon sputtering from the process where reactive gases are added, the latter process is commonly referred to as a reactive sputtering process. At first glance, one may believe that reactive sputtering processes may be as easy to carry out as the simple and straightforward inert sputtering processes. Unfortunately this is not the case. The addition of the reactive gas significantly changes the behaviour of the sputtering process. Both deposition rate as well as the composition of the film will be heavily influenced by the flow of the reactive gas [1–3]. Typical processing curves are shown in Figs. 4.1 and 4.2.