A hybrid modeling framework for the investigation of surface roughening of polymers during oxygen plasma etching

Abstract

Oxygen and oxygen-containing plasmas offer great potential for the surface functionalization of polymeric substrates: thermal reactive neutral species are combined with high energy ions to alter both the micro/nanomorphology and composition of polymeric surfaces in a dry process. Although plasma processing is an attractive option for polymer surface modification, plasma–surface interactions are complex and the process design is usually based on a trial-and-error procedure. Toward a comprehensive process design, a hybrid modeling framework, addressing both effects of plasmas on polymeric surfaces, is developed and applied to an investigation of the oxygen-plasma-induced surface roughening of poly(methyl methacrylate). A kinetic Monte Carlo surface model, considering the synergy of neutral species and ions, is used for the calculation of the local etching rate. The novel element of the model is that it takes into account the surface morphology through the calculation of the trajectories of the species joining the surface reactions. The local etching rate is utilized by a profile evolution module based on the level set method to predict the surface roughness evolution. A method for tracking the local variables of the evolving surface profile (e.g. surface coverage), treating a fundamental weakness of the level set method, is proposed and used to effectively reduce the computational time. The results of the framework are validated by comparison to a theoretical model. The prediction of roughness evolution is consistent with measurements vs time and at different operating conditions. The potential of the framework to additionally handle the chemical composition (oxidation) of the surface is demonstrated, enabling the study of the wetting behavior of plasma-etched polymeric surfaces.

Tailoring Wetting Properties at Extremes States to Obtain Antifogging Functionality

“…The PMMA samples were plasma etched in a high‐density plasma reactor equipped with a helicon source (at 13.56 MHz), the MET system of Adixen. The conditions used induce fast anisotropic etching, which in combination with the co‐deposition of small amount of sputtered material coming from the reactor ring and walls result in roughness formation which increases with etching time [ 44,45 ] Etching conditions were the following: plasma power 1900 W, pressure 0.75 Pa, oxygen flow rate 100 sccm, bias power 250 W, and electrode temperature 15 °C. Samples were glued with thermal paste on silicon wafers.…”

Etching of iron and iron–chromium alloys using ICP-RIE chlorine plasma

“…This approach was already performed for the simulation of InP etching by Cl 2 /N 2 /Ar plasma mixtures [35]. Multiscale approach has been developed by several authors [50,51,52,53,54].…”

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

“…Profile evolution simulators have been used to predict the evolution and explore origins of the surface roughness during plasma etching: Cell-based methods [52,[85][86][87][88][89][90][91][92][93], molecular dynamics simulations [19,94,95] and the level set method [82,83,[96][97][98][99][100] have been encompassed for the evolution of surface roughness.…”

“…• A kinetic Monte Carlo (kMC) surface etching model [100], in order to consider the synergy of neutral species and ions for the calculation of the local etching rate in the case of O2 plasma etching (i.e. ion enhanced etching), taking into account the surface morphology.…”

“…• A profile evolution module [170], which is based on a continuum description of the profile and the level set method; the latter module has been used for conventional (microelectronic) structures in previous works not only for plasma etching [170], but also for wet etching [53], and chemical vapor deposition [171]. In this dissertation, it is modified in order to α) handle also the evolution of unconventional (rough) profiles and b) treat a fundamental weakness of the level set method, and generally of all methods using an implicit representation of the surface profile, namely the tracking of local profile properties during evolution [100].…”