Evolutionary Optimization of Directed Self-Assembly of Triblock Copolymers on Chemically Patterned Substrates

Abstract

Directed self-assembly of block copolymers on chemical patterns is of considerable interest for sublithographic patterning. The concept of pattern interpolation, in which a subset of features patterned on a substrate is multiplied through the inherent morphology of an ordered block copolymer, has enabled fabrication of extremely small, defect-free features over large areas. One of the central challenges in design of pattern interpolation strategies is that of identifying system characteristics leading to ideal, defect-free directed assembly. In this work we demonstrate how a coarse-grained many-body model of block copolymers, coupled to an evolutionary computation (EC) strategy, can be used to design and optimize substrate–copolymer combinations for use in lithographic patterning. The proposed approach is shown to be significantly more effective than traditional algorithms based on random searches, and its results are validated in the context of recent experimental observations. The coupled simulation–evolution method introduced here provides a general and efficient method for potential design of complex device-oriented structures.

Perspective: Evolutionary design of granular media and block copolymer patterns

“…More recently, design approaches using inverse methods have been implemented. [8][9][10][11]18 In these cases, the forward simulation consists of a numerical engine to solve various trial morphologies by implementing, e.g., a self-consistent field theory, 69 a mean field model based on the Cahn-Hilliard equation, 10 or a theoretically informed coarse-grain model for block copolymers. 70 As before, the forward simulation is coupled to an inverse process that optimizes the parameter set in order to achieve a solution that closely approximates the targeted design.…”

“…70 As before, the forward simulation is coupled to an inverse process that optimizes the parameter set in order to achieve a solution that closely approximates the targeted design. In this regard, our recent work 10,11,18 has shown that evolutionary strategies such as CMA-ES can be significantly faster and more efficient in finding optimized solutions than inverse methods based on Monte Carlo searches. 8,9 In a typical design task corresponding to Fig.…”

“…71 An alternative approach is to use a physics based model, be it a self-consistent field theory or a molecular simulation, to interpret the data. While such a consideration would be overly demanding for traditional Monte Carlo-based strategies, by relying on CMA-ES versions and our more recently proposed variants, 10,11,18 it is possible to interpret scattering in terms of a fully three-dimensional particle based model that includes fluctuations. 72 Again, we highlight the fact here that, from a computational point of view, a computational engine is charged with designing a material that scatters x-rays in a manner dictated by the experiments.…”

“…[4][5][6][7] Applied to polymers, such methods have paved the way towards optimizing directed self-assembly. [8][9][10][11] Similar methods have been employed to identify the crystal structures of patchy, colloidal particles. 12 For far-from-equilibrium systems like jammed, metastable aggregates of particles, 13 simulation-based optimization has been used to design bulk properties such as stiffness or packing density by tuning complicated microscale features like particle shape.…”

Critical Review of Current Trends in ASIC Writing and Layout Analysis

“…Chemical pre-patterns are defined using traditional lithographic materials and processes such as 193 nm immersion or e-beam lithography at the scale of 20 nm to 40 nm. By directing the assembly of block copolymer films on the chemical pre-patterns, the overall resolution of the lithographic process may be increased by three to four-fold or more [18,19].…”