Surface processes during thin-film growth

The growth of thin films from low-temperature plasmas plays an important role in many applications such as optical or wear-resistant layers or for the fabrication of electronic devices. Albeit of great importance, the underlying growth mechanisms responsible for film formation from low-temperature plasmas are not well known. The direct identification of a growth mechanism is often hampered by the huge complexity of the bulk plasma processes and the plasma-surface interaction. The distribution of impinging species is very diverse, and ions, radicals and neutrals are interacting simultaneously with the growing film surface. A macroscopic quantity such as the growth rate can be the result of possible synergisms and anti-synergisms among a large variety of growth precursors. Due to the broad range of plasma-deposited materials as well as deposition methods, the objective of this paper is not to review them all, but to present a basic overview on the elementary surface mechanisms of radicals and ions. On the basis of these surface reactions, typical growth models will be discussed. As an example, for surface processes during thin-film growth, the current deposition models for amorphous hydrogenated carbon and silicon films are presented.