Control of polystyrene-block-poly(methyl methacrylate) directed self-assembly by laser-induced millisecond thermal annealing

Abstract

Directed self-assembly of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) during laser thermal annealing at peak temperatures of 300°C-800°C for dwells of 1-10 ms has been explored. The enhanced mobility of polymer chains at these temperatures improves registration compared with conventional thermal anneals. PS-b-PMMA films (forming 15-nm line∕space standing lamellae) were cast on chemically patterned substrates with a copolymer neutral layer and annealed by laser and hot plate. Annealing by hot plate or multiple laser scans resulted in well-aligned features over micron length scales. By laser annealing multiple times, defectivity was reduced by ∼60%. However, laser annealing for only 10 ms before performing a hot plate anneal reduced defectivity by >80%. We believe that this reduction arises from improved interfacial alignment of the film to the template during laser annealing near the order-disorder transition. Jacobs et al.: Control of polystyrene-block-poly(methyl methacrylate) directed self-assembly. . . Downloaded From: http://nanolithography.spiedigitallibrary.org/ on 08/20/2015 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx Jacobs et al.: Control of polystyrene-block-poly(methyl methacrylate) directed self-assembly. . . Downloaded From: http://nanolithography.spiedigitallibrary.org/ on 08/20/2015 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx Jacobs et al.: Control of polystyrene-block-poly(methyl methacrylate) directed self-assembly. . . Downloaded From: http://nanolithography.spiedigitallibrary.org/ on 08/20/2015 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx

Photothermally Directed Assembly of Block Copolymers

“…Over the last five years, several groups have reported experiments using laser‐induced heating to anneal and thus order block copolymer thin films . Laser light can conveniently be used to focus light on a sample surface, leading to localized heating owing to the light absorption.…”

“…Jacobs et al used LSA to induce temperatures of ≈500 °C over millisecond timescales, in order to study the phase segregation of polystyrene‐b‐poly(methyl methacrylate) (PS‐b‐PMMA) films, noting evidence for an order–disorder transition above 420 °C . LSA was also combined with directed self‐assembly (DSA) methods by photothermally annealing films cast onto substrates with a chemical line pattern to guide the morphology.…”

“…Jacobs et al reported pathway dependence in LSA and hot plate processing of BCP films cast on chemical patterns . For the selected conditions, a single LSA scan was found to be insufficient to observe alignment of the morphology with respect to the underlying chemical template.…”

“…Over the last five years, several groups have reported experiments using laser-induced heating to anneal and thus order block copolymer thin films. [96,98,99,101,103] Laser light can conveniently be used to focus light on a sample surface, leading to localized heating owing to the light absorption. While the thermal field is generally larger than the illuminating optical field due to thermal diffusion in the substrate, this procedure can generate localized heating and thus large spatial thermal gradients.…”

“…Jacobs et al reported pathway dependence in LSA and hot plate processing of BCP films cast on chemical patterns. [98,103] For the selected conditions, a single LSA scan was found to be insufficient to observe alignment of the morphology with respect to the underlying chemical template. Nevertheless, this initial LSA step was found to have a dramatic influence on final ordering once the material was processed using isotropic thermal methods (hot plate annealing).…”