Linewidth fluctuations caused by polymer aggregates in resist films.

Enhanced resolution of poly(methyl methacrylate) electron resist by thermal processing

“…An almost linear relation between the surface roughness and line edge roughness ( Fig. 2.a) observed which substantiates a common source for both of them and the mentioned theory of PMMA granules 17,18,19 . In samples which have been baked at temperatures lower than 230°C, surface roughness and line edge roughness were improving by increasing the baking time ( Fig.2.…”

“…The most important problem that had limited the resolution of PMMA was its granular structure 17,18,19 (Fig.1.a). Given the fact that all the PMMA molecules in the resist solution are not exactly the same length; granules can form as fallows: after the spin coating and during the backing process, bigger PMMA molecules fold on themselves, due to the attraction between the monomers on the same chain.…”

Resist Homogeneity

“…The ultimate homogeneity of a resist layer is dictated by the structure of the polymer material itself. In most of these resists the Steric compatibilities between the tactic sequences of the polymer molecules [19] and Van der Waals attractions [17] drives the smaller polymer molecules to diffuse and attach to the bigger molecules and make granules of about 20 nm big (figure 1). If the mentioned forces be enough strong, and the polymer chain be enough long and flexible; they can even make the polymer chain to collapse on itself.…”

“…Consequently, the size and solubility of these granules will limit the lithography resolution and line edge roughness (figure 2) [9,19]. So, in order to increase the resist homogeneity, it is necessary to reduce the aggregation and formation of these granules; or choose a resist with less aggregation or smaller granules.…”

Chemically Amplified Main Chain Scission: New Concept to Reduce Line Edge Roughness and Outgassing.

“…[ 15] Polymer aggregates with a diameter of 20-30nm in resist films were reported by Yamaguchi et al, who found aggregates remaining at the pattern edge after development cause linewidth fluctuations. [ 16] The main chain scission concept is expected to overcome problems occurring from phase separation phenomena and from the size of polymer coils or polymer aggregates. Fig.…”