MODELING OF BIAS SPUTTER-DEPOSITION PROCESSES

The Monte-Carlo-based ''high dose'' program I DYN has been used to sim ulate bias sputter deposition processes. T-DYN follows the collision c ascades caused by energetic ions in a solid. The changes in the target caused by each collision sequence are stored and the target compositi on modified accordingly for the next incoming ion. The program also al lows the addition of five different non-energetic atomic fluxes to the surface. Calculations of the continuous deposition and resputtering m ake it possible to simulate the substrate-film interface formation as well as the build-up of a coating on the substrate surface. In this pr esentation we focus on some phenomena which occur during bias sputter deposition in the limit where the resputtering rate is close to the ar rival rate of the deposition species. We shall present simulation stud ies that illustrate that substrate-dependent preferential sputtering e ffects frequently appear during film-substrate interface formation. Th e resputtering yield of the deposition species from the interface may differ by an order of magnitude for different substrates. This effect is so pronounced that for identical processing conditions it is possib le to obtain zero net him growth at certain substrates but substantial net film growth at other substrate materials. It is well known that b ecause of preferential resputtering the film composition obtained duri ng bias sputter deposition from an binary alloy target may differ sign ificantly from the target composition. What is less known, however, is that for very thin coatings the resulting film composition may also d epend on the underlying substrate. We shall describe how the substrate -dependent resputtering rate effect also may explain this substrate '' memory'' effect in film composition during bias sputter deposition of binary alloys.