Cell-Based Design Methods for Directed Self-Assembly

Abstract

Topographic templates can direct the self-assembly of block copolymers to achieve nanoscale patterns with high order. Previously, we have demonstrated well-aligned periodic lines, bends, and meshes using a sparse array of lithographically defined posts [1,2]. However, it is generally challenging to fabricate complex and non-periodic patterns using a sparse post array because the key information contained in the final pattern must be encoded in the sparse template. In this work, we present two cell-based design methods for fabricating complex patterns using directed self-assembly of polystyrene-b-polydimethylsiloxane (PS-b-PDMS) block copolymer thin films. For the first approach, we developed a set of template tiles consisting of square post lattices with a restricted range of geometric features. For all possible tile arrangements, we examined the resulting block copolymer patterns. We were able to predict a relatively simple template that will result in a desired complex pattern by combining tiles in different ways. For the second approach, we designed a binary-state system with ladder-shaped block copolymer structures using a square confinement. We developed design-rules for controlling alignment direction of the ladder-shaped structures by introducing openings around the square cells. These methods could provide a new template design method for a complex non-trivial block copolymer patterns.