SCFT Simulations of Thin Film Blends of Block Copolymer and Homopolymer Laterally Confined in a Square Well

Abstract

Recently there has been significant interest in manipulating the self-assembly behavior of block copolymers to obtain structures that are not observed in the bulk. Here we explore the conditions for which self-assembly in laterally confined thin block copolymer films results in tetragonal square arrays of standing up cylinders. More specifically, we used self-consistent field theory (SCFT) to study the equilibrium phase behavior of thin films composed of a blend of AB block copolymer and A homopolymer laterally confined in square wells. By using suitable homopolymer additives and appropriately sized wells, we observed square lattices of upright B cylinders that are not stable in pure 1 AB block copolymer systems. We further investigated the optimal conditions and parameters that lead to defect-free, in-plane tetragonal ordering. Considering the potential application of such films in block copolymer lithography, we also conducted numerical SCFT simulations of the role of line edge roughness at the periphery of the square well on feature defect populations. Our results indicate that the tetragonal ordering observed under square confinement is robust to a wide range of boundary perturbations.

The Hole Shrink Problem: Directed Self-Assembly Using Self-Consistent Field Theory

“…In addition to enforcing a vanishingly small polymer density in the wall region, the implemented mask enables various selectivity conditions at the sidewalls and top and bottom surfaces of the prepattern, modeled herein using a Flory-like parameter, χ w = (χ wA -χ wB )/2, where χ wA and χ wB describe interactions between the wall and blocks A and B, respectively. [13][14] All simulations are started from random initial field configurations. …”

Field-theoretic Simulations of Directed Self-assembly for Contact Multiplication

“…Since the total free energy of a resulting morphology is readily available from our SCFT calculations, the stability of defective and perfect structures can be established from measurements of the defect formation energy, computed as F = F defect -F perfect 5 . Our molten block copolymers have N monomers per chain, N = N PS + N PMMA , and the volume fraction of the minor PMMA block is denoted, f. In addition, the interaction between monomers of different types are modeled using a Flory parameter, , resulting in a dimensionless segregation strength, N. Furthermore, masking walls 17,18 provide the flexible designs for templates with various selectivity conditions using a Flory-like parameter w . In this study, we are in particular interested in wall affinity effect to the defectivity so that we vary w N as described below: All PMMA-attractive and all neutral templates are modeled with w N = -15 and w N = 0, respectively.…”

Advances in square arrays through self‐assembly and directed self‐assembly of block copolymers

“…Hur et al conducted twodimensional SCFT simulations of a lateral square-well confinement on a diblock copolymer in thin films. 72 It is predicted that the edges of confined wells direct the orientation of block copolymer grains when the walls of wells are coated with a homopolymer consistent with one of the blocks, and the bottom and top of wells remains neutral to both blocks. When the size of square wells commensurates with a 3 Â 3 square lattice of 9 cylinders and smaller, square arrays can be thermodynamically stable for a simple AB diblock copolymer.…”