Aligned Sub-10-nm Block Copolymer Patterns Templated by Post Arrays
- Category: Nanotechnology
- Tags: jae-byum chang, karl berggren
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Download as PDFTopographic templates can be used for guiding the self-assembly of block copolymers to produce complex nanoscale patterns. In our previous work, sub-20-nm bends or meander structures were achieved based on topographic templates using 45.5 kg/mol polystyrene polydimethylsiloxane (PS-PDMS) block copolymer [1] . To template the self-assembly of 16 kg/mol PS-b-PDMS with a sub-10-nm periodicity, so as to scale down the resolution to sub-10-nm, the diameter of the templates must also be scaled down to the sub-10-nm range. However, the fabrication of sub-10-nm posts is challenging even with state-of-the-art lithography.
In this study, we demonstrate aligned sub-10-nm block copolymer patterns, based on the understanding of the interaction between the block copolymer cylinders and posts with a range of diameters and heights. Figure 1 shows how the orientation of the block copolymer cylinders depended on the post diameter for a given spacing, Lx = 48 nm and Ly = 32 nm. The commensurate orientation of the 16 kg/mol PS-b-PDMS block copolymer cylinders for this array period is depicted in Figure 1(b), giving a cylinder orientation of 53.1˚ with respect to the x-axis. The area fraction of the block copolymer oriented along the commensurate orientation was over >75% when templated by posts with a height of 16 nm and diameters from 8 nm to 12 nm. The cylinders were not aligned in a preferential orientation when templated by posts with a diameter of 6 nm. However, the cylinders were aligned parallel to the y-axis when templated by large (diameter > 13 nm) or tall (height > 24 nm) posts.
Based on the preceding result, we demonstrated every possible commensurate condition for the 18-nm period PS-b-PDMS. As shown in Figure 2, the orientation of the block copolymer cylinders could be varied between 0o and 90o with respect to the x-axis by using posts with a height of 19 nm and a diameter of 10 nm.
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- Figure 1: (a) The change of area fraction of the block copolymer cylinders templated by a post array with Lx = 48 nm and Ly = 32 nm depending on the post diameter and height. (b) The commensurate orientation for a post array with Lx = 48 nm and Ly = 32 nm. (c) SEM image of the PDMS cylinders templated by the post array with a post diameter of 12 nm and a post height of 16 nm.
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- Figure 2: SEM images of PDMS cylinders templated by post arrays. The height of the posts was 19 nm and the diameter was 10 nm. Arrows indicate the direction of the PDMS cylinders. Each figure is annotated Lx, Lx/Ly. Scale bar = 100 nm.
- J. K. Yang, Y. S. Jung, J. Chang, R. A. Mickiewicz, A. Alexander-Katz, C. A. Ross, and K. K. Berggren, “Complex self-assembled patterns using sparse commensurate templates with locally varying motifs,” Nature Nanotechnology, vol. 5, pp. 256-260, Mar. 2010. [↩]