The use of process modelling for optimum design of reactive sputtering processes

• Published in: Surface & coatings technology 1989-12, Vol.39, p.465-474
• Main Authors: Berg, S., Moradi, M., Nender, C., Blom, H.-O.
• Format: Article
• Language: English
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/S0257-8972(89)80008-8

The reactive sputtering process has been successfully described in a quite simple mathematical model in some recent articles. By the use of such a model it has been possible to predict the partial pressure of the reactive gas, the rate and also the composition of the deposited film. In such a complex process it is not easy to experimentally verify all aspects of the model. Numerous experiments have, however, been carried out which support the validity of the model. In this article we will apply this model to investigate the problem of target poisoning. We will calculate the composition of the deposited film, the deposition rate and the poisoning of the target surface. We will mathematically show that by introducing a pressure gradient in the processing chamber it is possible to obtain compound film formation while minimizing the target poisoning effect. This effect has earlier been experimentally observed by several authors. These theoretical findings explain quite satisfactorily the expected improvement in performance of the reactive sputtering of compound films, as far as deposition rate is concerned. However, the most favourable conditions only exist at non-stable processing operating points. To be able to operate the process at optimum conditions a feedback control system for the partial pressure of reactive gas vs. gas mass flow has to be incorporated.