Abstract
Bulk fabrication of surface patterns with sub-20 nm feature sizes is immensely desirable for many existing and emerging technologies. Directed self-assembly (DSA) of block copolymers (BCPs) has been a recently demonstrated approach to achieve such feature resolution over large-scale areas with minimal defect populations. However, much work remains to understand and optimize DSA methods in order to move this field forward. This paper presents large-scale numerical simulations of zone annealing and chemo-epitaxy processing of BCP films to achieve long-range orientational order. The simulations utilize a Time-Dependent Ginzburg-Landau model and parallel processing to elucidate relationships between the magnitude and velocity of a moving thermal gradient and the resulting BCP domain orientations and defect densities. Additional simulations have been conducted to study to what degree orientational order can be further improved by combining zone annealing and chemo-epitaxy techniques. It is found that these two DSA methods do synergistically enhance long-range order with a particular relationship between thermal gradient velocity and chemical template spacing.
Highlights
The earliest implementation of zone annealing utilized temperatures in the hot zone above the order-disorder temperature (TODT) of the block copolymers (BCPs) film[31], designated as hot zone annealing (HZA)
We present large-scale time-dependent Ginzburg-Landau (TDGL) simulations to analyze the degree of BCP microdomain orientation and the defect populations during the cold zone annealing (CZA) process
Large-scale numerical simulations have been performed to improve our understanding of CZA as a directed self-assembly strategy for BCP thin films
Summary
The earliest implementation of zone annealing utilized temperatures in the hot zone above the order-disorder temperature (TODT) of the BCP film[31], designated as hot zone annealing (HZA). A sharp thermal gradient (∇T ~ 45 K/mm)[33] in CZA has been shown to produce vertical orientation (i.e. in the z-direction of the film) while broader thermal gradients (∇T ~ 17 K/mm) result in parallel alignment for similar velocities Computational studies including both particle-based and field-based simulations have expanded our understanding of many different DSA approaches to control BCP morphology[8, 35, 38,39,40,41]. We present large-scale TDGL simulations to analyze the degree of BCP microdomain orientation and the defect populations during the CZA process We systematically vary both the magnitude and the velocity of a moving thermal gradient translating across an initially disordered BCP film. The addition of templating patterns effectively allows increased CZA velocities while maintaining defect-free domains
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