New method for preparing large-area, defect-free block copol
Professor So Youn Kim from Ulsan Institute of Science and Technology, Su-Mi Hur from Chonnam University, and Professor Seok Joon Kwon from Korea Academy of Science and Technology have proposed a new experimental method. The ordered self-assembled film of block copolymer was obtained in the region. After only 15 minutes of solvent annealing, the defect density can be reduced to about 1.37 ea / μm2. Related work was published in Science Advances, a sub-issue of Science, under the title "Shear-solvo defect annihilation of diblock copolymer thin films over a large area".
Films formed by self-assembly of block copolymers have potential application prospects in many industrial fields. Among them, people pay special attention to the use of block copolymers to self-assemble to form large-area ordered structures of 10-100 nm. The thin film obtained by this method has good resolution, functionality, and scalability, so it is expected to break through traditional lithography. Limitations of technology. However, films formed by self-assembly generally lack long-range ordering of orientation, and the films have a high defect density over a large area.
Directed self-assembly technology (DSA), including mapping epitaxy, surface chemical patterning, and laser-assisted patterning, has made landmark progress in the study of obtaining block copolymers with ordered nanostructures. However, DSA requires more steps, which limits its industrial application. In addition, reducing the defects in the nanopatterns prepared using DSA to make them practical (for example, down to 1 ea / cm2) remains to be experimentally proven.
The method used by the author is shown in Figure 1: First, the mechanical shear force is used to induce the block copolymer to be oriented, and the shear force can induce the macroblock orderly arrangement of the block copolymer; then the solvent vapor is used for annealing and the solvent annealing is performed. Microscopic defects can be eliminated without disrupting the long-range ordering induced by shear. The authors call this method shear-solvo annealing, or SS annealing.
Figure 1. SS annealing process
Figure 2. Long-range ordered regulation of columnar structures after SS annealing
(A) SEM image and grazing incidence two-dimensional image after SS annealing after shear orientation and (B) toluene solvent, (C) tetrahydrofuran, (D) mixed solvent; (E) one-dimensional grazing incidence Figure; (F) the integrated width of the first-order peak and (G) the normalized period size as a function of annealing time.
Figure 3.Micro-ordering of columnar structures after SS annealing
(A) SEM image after shear orientation and (B) SS annealing using a mixed solvent of toluene solvent, (C) tetrahydrofuran, and (D), an orientation pixel image after dyeing, and a SEM image marked with a defect number SEM image of the defect area and the orientation fringe pattern after dyeing; (E) Hermans parameter P2 as a function of annealing time; (F) Correlation function g (r) as a function of position; (G) defect area density And defect number density as a function of annealing time; (H) stripe pattern uniformity, (I) Hermans parameter P2, (J) the degree of agreement with the scale after shearing, toluene annealing, tetrahydrofuran annealing, and both Changes after mixed solvent annealing.
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