Roughness evolution during a-C:H film growth in methane plasmas

Abstract

The roughness evolution during plasma deposition of amorphous hydrogenated carbon (a-C:H) films is investigated. Films were deposited from an inductively coupled methane plasma using a wide range of process parameters. Plasma deposition is uniquely described by the dissipated energy per source gas molecule Emean. Depending on Emean, a specific set of radicals contributes to film growth causing a characteristic roughness development. The film roughness is measured using atomic force microscopy and spectroscopic ellipsometry and is expressed using the static and dynamic scaling coefficients α and β, respectively. For low Emean<20eV, α∼0.65 and β∼0.19 indicating film deposition via a growth precursor with a large surface diffusion length. For Emean>20eV, α∼0.9 and β∼0.25 indicating film deposition via a growth precursor with a small surface diffusion length.

Relationship between scaling behavior and porosity of plasma-depositedTiO2thin films

“…16 Such an approach has been successfully applied for thin films grown by evaporation, 18 sputtering, 19 thermal CVD, 35 or PECVD. 20,21,24 Here, besides applying this methodology, we will try to correlate the obtained information with the porosity and microstructure of the films.…”

“…The evolution of the roughness ͑␣͒ and growth ͑␤͒ exponents deduced from this analysis provides information about the influence of the different surface processes controlling the thin film growth ͑surface diffusion, surface reactivity, shadowing effects, etc.͒ and, therefore, in the shaping of the surface morphology. [18][19][20][21] Roughness evolution of films prepared by plasma deposition usually behave in an "anomalous" way with regard to the values of roughness and growth exponents ͑i.e., these exponents do not follow the basic Family-Vicsec relation that holds for a "normal" scaling behavior of surface evolution 22,23 ͒. As evidenced for SiO 2 and SiO x Cy films prepared by PECVD, a factor that contributes to the appearance of such an "anomalous" behavior in plasma films is the fact that species coming from the plasma may reach the surface under off-diagonal directions.…”

Investigation of the Growth Mechanisms of a-CHx Coatings Deposited by Pulsed Reactive Magnetron Sputtering

“…A self-affine surface seems to have both short range space scaling and long-range time scaling. By measuring the roughness evolution through the scaling coefficients (α roughness and β growth exponents), it is possible to deduce the main growth mechanisms, such as a "ballistic deposition" (direct chemisorption of a growth precursor upon impact) or a "surface diffusion mediated deposition" (chemisorption, which is mediated by a preceding surface diffusion step) [21].…”

“…proposed [1,[19][20][21]. However, the growth of a-CH x films is a complicated nonequilibrium set of processes.…”

“…Dynamic scaling hypothesis has been recently applied in the smooth a-C:H x films formation [20,21,[27][28][29][30]. As example, Zhu et al [27] have proposed a set of processes responsible for the formation of amorphous diamond-like carbon under ion beam growth conditions: a dense diamond-like phase generation takes place during the slowing-down process of ion collision simultaneously to some relaxation mechanisms, such as the asymmetric displacement of sp 2 /sp 3 carbon atoms, thermally activated density, and stress relaxation processes.…”