19 March 2015 Cross-sectional imaging of directed self-assembly block copolymers
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In this paper we address an important topic for the development of block copolymer directed self assembly, which is the lack of the third dimensional information. The three-dimensional shape of the DSA feature directly impacts the ability to transfer the DSA pattern into etched patterns. Through TEM sample preparation by in-situ focused ion beam (FIB) Pt deposition and milling, we show cross-sectional images for the two most elemental building blocks of directed self assembled block copolymers, namely, the single and double-hole (peanut shape) etched in Si structures with great contrast at the interface formed by PS and PMMA. Additionally, a hard-mask single hole structure processed with a different template material is shown as well. Elemental mapping with energy filtered TEM (EFTEM) was shown to assist interpretation of images. 3D reconstruction of the holes formed in the hard-mask sample was performed using dark field (DF) STEM. A reduction in the SOC and SOG thickness was observed post in-situ Pt deposition for the hard mask structure. Further TEM sample preparation improvements will be needed to minimize the compression observed.
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Kye Okabe, He Yi, Maryann Tung, Richard Tiberio, Joost Bekaert, Roel Gronheid, H.-S. Philip Wong, "Cross-sectional imaging of directed self-assembly block copolymers", Proc. SPIE 9423, Alternative Lithographic Technologies VII, 942318 (19 March 2015); doi: 10.1117/12.2087569; https://doi.org/10.1117/12.2087569

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