Directed self-assembly is emerging as a promising technology to define sub-20nm features. However, a straightforward
path to scale block copolymer lithography to single-digit fabrication remains challenging given the diverse material
properties found in the wide spectrum of self-assembling materials. A vast amount of block copolymer research for
industrial applications has been dedicated to polystyrene-b-methyl methacrylate (PS-b-PMMA), a model system that
displays multiple properties making it ideal for lithography, but that is limited by a weak interaction parameter that
prevents it from scaling to single-digit lithography. Other block copolymer materials have shown scalability to much
smaller dimensions, but at the expense of other material properties that could delay their insertion into industrial
lithographic processes. We report on a line doubling process applied to block copolymer patterns to double the
frequency of PS-b-PMMA line/space features, demonstrating the potential of this technique to reach single-digit
lithography.
We demonstrate a line-doubling process that starts with directed self-assembly of PS-b-PMMA to define line/space
features. This pattern is transferred into an underlying sacrificial hard-mask layer followed by a growth of self-aligned
spacers which subsequently serve as hard-masks for transferring the 2x frequency doubled pattern to the underlying
substrate. We applied this process to two different block copolymer materials to demonstrate line-space patterns with a
half pitch of 11nm and 7nm underscoring the potential to reach single-digit critical dimensions. A subsequent patterning
step with perpendicular lines can be used to cut the fine line patterns into a 2-D array of islands suitable for bit patterned
media. Several integration challenges such as line width control and line roughness are addressed.
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