Ordering kinetics of lamella-forming block copolymers under the guidance of various external fields studied by dynamic self-consistent field theory

Abstract

Self-consistent field theory with a dynamic extension is exploited to investigate the kinetics of the lamellar formation of symmetric block copolymers under the direction of external fields. In particular, three types of directed self-assembly methods - a permanent field for chemo-epitaxy, a dynamic field for zone annealing and an integrated permanent/dynamic field - are examined. For the chemo-epitaxy involving sparsely prepatterned substrates or zone annealing, the block copolymers generally develop into polycrystalline nanostructures with multiple orientations due to the lack of strong driving forces for eliminating the long-lived imperfections in a limited time. As the integrated chemo-epitaxy and zone annealing method is applied to the block copolymer systems, single-crystalline nanostructures with precisely registered orientations are achieved in a short annealing time owing to the mutual acceleration of defect annihilations, which cannot be produced by the conventional techniques alone. Furthermore, the integrated method allows the rapid fabrication of well-ordered nanostructures on the extremely sparse prepatterned substrates. Our theoretical work may serve to rationalize the faster modern nanolithographic fabrication of smaller microelectronic components using lower-spatial-frequency templates.

Numerical Simulations of Directed Self-Assembly in Diblock Copolymer Films using Zone Annealing and Pattern Templating

“…A similar analysis was recently conducted by Wan et al . 48 , however here we consider chemical templating in two directions independently. A range of zone velocities were tested in systems that contained either horizontally- or vertically-aligned straight-line chemical templates with template spacing ranging between 5–7 lamellar periods (or 50–70 ).…”

“…In particular, mesoscopic field-based methods including self-consistent field theory and time-dependent Ginzburg-Landau (TDGL) models offer the required spatial resolution to represent the BCP domain structure while also allowing the computational efficiency to analyze fairly large sections of a BCP matrix. With regards to DSA, numerical simulations have been used to study BCP defect behavior in topologically and/or chemically patterned substrates 42, 43 , magnetic- and electric-field alignment with and without nanoparticle loading 44–46 , as well as a few studies of thermal gradient zone annealing alignment 30, 35, 47, 48 .…”

Impact of Molecular Asymmetry of Block Copolymers on the Stability of Defects in Aligned Lamellae

“…11,17,25 Although large-scale ordered lamellar structures can be obtained from the DSA by periodic chemical patterns, defects are still found in these stripe patterns over a macroscopic area, especially when the guiding pattern is imperfect. In contrast to the complex combinations of various defects observed in the perpendicular lamellar structures formed by a block copolymer film lying on a homogeneous neutral substrate, 26,27 lamellae mainly consist of various dislocations. 28−30 These dislocations with well-defined geometries provide prototypes for the study of defect stability in the ordered structures of block copolymers.…”

Developing Anisotropy in Self‐Assembled Block Copolymers: Methods, Properties, and Applications

“…[365] Briefly, the BCP domain alignment from zone annealing is accomplished by applying a moving thermal gradient across a BCP film where alignment occurs along the planar front of the cooling thermal gradient. [157,[366][367][368] Traditional zone annealing is carried out above the T ODT of the BCP system, but cold zone annealing, CZA, is performed in the temperature range between the T g of all segments and T ODT of BCPs. Karim et al demonstrated the successful use of CZA to enable cylinders to be perpendicularly aligned to the substrate in PS-b-PMMA films.…”

“…[148,149] Self-assembly of BCPs from conventional methods does not generically afford such long-range control of nanostructural orientation, and therefore numerous research efforts have been dedicated to this area. [150][151][152][153][154][155][156] These efforts include the use of theory and molecular simulation approaches, [157,158] paired with developing advanced processing techniques and in situ characterization techniques to explore assembly dynamics and pathway toward producing highly aligned BCPs. While several excellent contributions have already discussed directed self-assembly (DSA) of polymers within the scope of assembly physics and instrumentation in great detail, [30,105,[159][160][161][162][163] our goal here is to describe the physical phenomena and mechanisms of each experimental approach for BCP alignment, and more importantly to highlight the significance of the structure-property relationship in anisotropic block copolymers and their relevant applications.…”