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Directed self-assembly (DSA) of block co-polymers (BCPs) is a next-generation lithography technique that shows promise for extending Moore’s Law into the 10 nm regime and below. The minimum size of the features that can be produced by BCPs is controlled by the interaction parameter (chi) and the degree of polymerization (N). We have developed silicon containing BCPs for sub-20 nm line-and-space lithography. These BCPs were synthesized by living anionic polymerization, thermally annealed in thin films between neutral layers to generate the requisite perpendicular orientation [1, 2]. The silicon-containing blocks provide excellent development contrast under both oxidizing and reducing reactive ion etching (RIE) conditions. The developed patterns work well as masks for transfer of the developed patterns into useful substrate materials [3]. Through optimizing the design of the block copolymers and the “hybrid” DSA process [1], we have now obtained 10 nm full pitch gratings.
Recently we have studied silicon containing BCPs that incorporate a poly(2-vinylpyridine) block as a path to achieving still higher chi. For example, we have synthesized poly(4-pentamethyldisilylstyrene-block-2-vinylpyridine) (PDSS-b-P2VP) and found that this material has a chi parameter that is significantly higher than that of the BCP used for 10 nm lithography, meaning that even smaller feature sizes should be possible. Neutral top coats and cross-linked surface treatment layers were identified for PDSS-b-P2VP using the island and hole techniques that have been described previously [5]. We have succeeded in demonstrating 8 nm full pitch finger print patterns that are oriented perpendicular to the substrate. These are the smallest patterns we have managed to obtain in our system to date.
1. Blachut, G., et al. Chem. Mater (2016), 28 (24), 8951-8961.
2. Bates C. M., et al. Science (2012), 338 (6108), 775.
3. Azarnouchea, L., et al. J. Vac. Sci. Technol. B (2016) 34 (6), 061602/1-061602/10.
4. Lane A. P., et al. ACS Nano (2017), 11 (8), 7656-7665.
5. Maher, M. J., et al. Chemistry of Materials (2014), 26 (3), 1471-1479.
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