Surface processes during thin-film growth

Abstract

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.

Surprising temperature dependence of the dust particle growth rate in low pressure Ar/C2H2 plasmas

“…However, the critical density and radius of dust particles before coagulation do not vary with temperature. 11 Second, the residence time of radicals on the particle's surface decreases with gas/particle temperature 9 radicals finding an open bond to strongly chemisorb with becomes less probable, fewer radicals chemisorb and R p is decreased. (below) as a function of time after plasma ignition.…”

Synergistic etch rates during low-energetic plasma etching of hydrogenated amorphous carbon

“…A qualitative explanation for the etching mechanisms in these plasma systems are likewise formulated in this part, with the understanding that the processes and variables involved in plasma-surface interactions are -even if only due to the wide range in properties of amorphous carbon -numerous and intrinsically interconnected. 18,[84][85][86] The roughness evolution during a-C:H etching is discussed in part two of this section.…”

Plasma processing and chemistry

“…If the loading is critical, no hard radical as CH or C are produced in a secondary reaction chain. The main radical produced in the first charge transfer and dissociative recombination cycle are CH 3 and CH 2 radicals, both believed to be soft radicals [7]. These reflect from the substrate surface and enter the recirculating background, where they reside until they react in the volume or at the vessel wall.…”

“…Fragmentation patterns are difficult to predict, recirculation and wall production of new monomers may partially replace injected monomers [5], and surface interactions may vary with the radical fluxes, which on their turn may be altered by the changing surface processes. Models have been designed, which may explain what is observed [6][7][8], but they cannot always be used to predict new routes. Therefore, it is useful to analyze the problem of plasma deposition and/or catalysis in a principal way and to inquire how far one can get with a general picture.…”