%0 Journal Article
%T Surface Roughening of Polystyrene and Poly(methyl methacrylate) in Ar/O2 Plasma Etching
%A Yuk-Hong Ting
%A Chi-Chun Liu
%A Sang-Min Park
%A Hongquan Jiang
%A Paul F. Nealey
%A Amy E. Wendt
%J Polymers
%D 2010
%I MDPI AG
%R 10.3390/polym2040649
%X Selectively plasma-etched polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer masks present a promising alternative for subsequent nanoscale patterning of underlying films. Because mask roughness can be detrimental to pattern transfer, this study examines roughness formation, with a focus on the role of cross-linking, during plasma etching of PS and PMMA. Variables include ion bombardment energy, polymer molecular weight and etch gas mixture. Roughness data support a proposed model in which surface roughness is attributed to polymer aggregation associated with cross-linking induced by energetic ion bombardment. In this model, RMS roughness peaks when cross-linking rates are comparable to chain scissioning rates, and drop to negligible levels for either very low or very high rates of cross-linking. Aggregation is minimal for very low rates of cross-linking, while very high rates produce a continuous cross-linked surface layer with low roughness. Molecular weight shows a negligible effect on roughness, while the introduction of H and F atoms suppresses roughness, apparently by terminating dangling bonds. For PS etched in Ar/O 2 plasmas, roughness decreases with increasing ion energy are tentatively attributed to the formation of a continuous cross-linked layer, while roughness increases with ion energy for PMMA are attributed to increases in cross-linking from negligible to moderate levels.
%K diblock copolymer
%K plasma etching
%K surface roughness
%K cross-linking
%K polymer aggregation
%U http://www.mdpi.com/2073-4360/2/4/649