Oxygen plasma etching of hydrocarbon‐like polymers: Part I Modeling

Abstract

This work on the etching of polymers in oxygen plasmas begins with a general review of experimental data and modeling attempts. Result analysis leads to an extended etching model based on the description of polymer surfaces composed of chain segments randomly distributed and taking into account the microscopic structure of polymers at the atomic and molecular level. Experimental data also suggest that thermally activated desorption of CO, in addition to CO 2 desorption, and UV-induced etching, in addition to ion-induced etching, must be incorporated in the modeling. The analytical results confirm the impossibility to reach perfect anisotropy in presence of UVinduced desorption and also to determine directly from Arrhenius plots the activation energies for CO and CO 2 thermal desorption.

Study of High-Density Polyethylene (HDPE) Kinetics Modification Treated by Dielectric Barrier Discharge (DBD) Plasma

“…Since the chemical modifications have aged over time, influencing the polar coordinate more clearly, due to the formation of functional groups with oxygen, the physical modification tends to be maintained, with the aging of morphological modifications not evident in polymers [ 1 , 33 ]. This change in surface roughness is due to the etching action promoted by the species present in the plasma, as reported in the literature [ 67 , 72 , 73 , 74 , 75 ].…”

A hybrid modeling framework for simulating plasma-surface interactions of rough polymeric substrates

“…These experimental results have led the way to the first self-consistent models of etching of polymers in O2 plasmas, which are based on a) a monolayer-type O adsorption on polymers [113,116,117], b) a negligible adsorption of O2 compared to O [113,114] and c) the balance of O fluxes (adsorption of O and desorption of reaction products) at the polymer surface [113][114][115]. Recently, the hypotheses and the mechanisms of the etching of polymers in O2 plasmas were reinvestigated in order to take into account the specificity of the nature of polymers and their fundamental structure at the molecular level by Bes et al [118]. Bes et al updated the model of Pons et al [114], which described correctly the kinetics of ion enhanced etching but only partially the kinetics of spontaneous etching, by including the terms arising from the thermal spontaneous desorption of CO above 100 °C (in addition to CO2 desorption) and the involvement of UV photons in photo induced desorption of reaction products.…”

“…Ultimately, the latest modeling approach for the etching of polymers in O2 plasmas of Bes et al [118] includes two steps: a) An initial quick step of direct oxidation 36 and/or ion-induced desorption 37 of volatile elements (i.e. O and H atoms) grafted along the polymer chains segments and the subsequent transformation of the latter to bare carbon chain segments.…”

“…The reactive species joining the surface processes are O and O + . The adsorption of O2 is negligible compared to the adsorption of Ο [206][207][208]. The dominant etching mechanism of PMMA is ion-enhanced etching which lies on a synergistic and nonlinear action of ions and (adsorbed) neutral species.…”

“…Ion-enhanced etching coexists with physical sputtering by O + , pure chemical and photo-induced (by UV photons) etching. However, the ion energy (close to 100 eV) and the surface temperature (300 -400 K) during plasma etching allows the neglect of sputtering [208] and pure chemical etching [206,207] respectively. Similarly, etching induced by UV photons [206,207] can be also neglected when compared to ion-enhanced etching.…”