Directed Self-Assembly of Block Copolymers for Nanolithography: Fabrication of Isolated Features and Essential Integrated Circuit Geometries

Abstract

Self-assembling block copolymers are of interest for nanomanufacturing due to the ability to realize sub-100 nm dimensions, thermodynamic control over the size and uniformity and density of features, and inexpensive processing. The insertion point of these materials in the production of integrated circuits, however, is often conceptualized in the short term for niche applications using the dense periodic arrays of spots or lines that characterize bulk block copolymer morphologies, or in the long term for device layouts completely redesigned into periodic arrays. Here we show that the domain structure of block copolymers in thin films can be directed to assemble into nearly the complete set of essential dense and isolated patterns as currently defined by the semiconductor industry. These results suggest that block copolymer materials, with their intrinsically advantageous self-assembling properties, may be amenable for broad application in advanced lithography, including device layouts used in existing nanomanufacturing processes.

A Path to Ultranarrow Patterns Using Self-Assembled Lithography

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Templated self-assembly of block copolymer thin films can generate periodic arrays of microdomains within a sparse template, or complex patterns using 1:1 templates [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] . However, arbitrary pattern generation directed by sparse templates remains elusive.

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“…As a result, both chemical and topographical substrate features have been used to template or guide block copolymer self-assembly, imposing long-range order and generating microdomain geometries not observed in untemplated films [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] . These templates are often defined using electronbeam lithography (EBL) [3][4][5]7,8,11 , because of its ability to pattern small features of arbitrary geometry. However, the serial nature of EBL makes it clearly advantageous to minimize the density of the EBL-written features required to template a given arrangement of block copolymer microdomains.…”

“…Most work on the templated self-assembly of block copolymers for nanolithography has focused on the generation of periodic patterns of parallel lines, close-packed dots or concentric rings, using shallow trenches 1,6,9,10,[12][13][14]22,24,26 , sparse post arrays 3 or chemical templates with a periodicity either similar to that of the BCP 2,7,8,15 or a factor two, three or four times larger [3][4][5] . Nealey and colleagues have shown that non-regular features such as lamellae with bends 2,11 or square-packed dots 15 could be formed using a chemical pattern of the same density as the desired block copolymer pattern. Meanwhile, Cheng and colleagues have used discontinuous chemical lines to direct the locations of lamellae 4 .…”

Enabling complex nanoscale pattern customization using directed self-assembly

“…The large relative area of the central HSQ masking feature is expected to promote the orientation of lamellae parallel to the substrate to minimize non-preferential interfacial interactions 28 . This local control of lamellae orientation with respect to the chemically patterned substrate has been explored previously as a means to discretize pattern regions or create isolated pattern geometries using one-to-one organic chemical patterns 24 . However, when combined with feature density multiplication, it is challenging to generate reliable and well-defined customizations based on the imperfect orientation control of lamellae using entirely organic chemical patterns 25 .…”

“…An alternative, selfaligned strategy for generating complex patterns is to form them directly through DSA, avoiding the scaling limits associated with lithographic overlay. This strategy has been demonstrated previously using one-to-one 4,24 or two-to-one 25 chemical pattern templates. Complex self-assembled patterns may also be created using sparse topographical templates of post arrays with locally modified spacings, shapes or orientations to adjust the preferred commensurability conditions controlling lateral alignment of BCP domains 14,15 , which can be designed using configurable square post lattice template tiles 26 .…”