Directed Self-Assembly of Binary AB/AB Diblock Copolymer Blends for Dense Nanopatterns with Density Multiplication

The directed self-assembly (DSA) of block copolymers is regarded as one of the most promising next-generation lithography techniques. One of the useful ordered patterns is the periodic lattice of nanodots, which can be produced by DSA of the cylinder-forming AB diblock copolymer. We propose to tune the volume fraction of the cylinder by blending two different AB diblock copolymers. In this work, we investigated the DSA of AB/AB binary blends using dissipative particle dynamics (DPD) simulations, aiming to obtain large-scale densely ordered cylinder patterns. In the DPD model, random copolymer/homopolymer brushes are explicitly included to constitute the guiding pattern on the substrate. By properly choosing the compositions of the two different diblock copolymers as well as their length ratio, perfectly ordered cylinder patterns with the volume fraction of cylinders as high as about 0.50 have been successfully obtained by one-to-one DSA. The one-to-one DSA exhibits a rather wide processing window with respect to the period of the guiding pattern. Large-scale ordered patterns composed of densely packed cylinders are also generated by DSA with 4x density multiplication, where the nonpatterned area is grafted by random copolymer brushes with a tailored composition. Our work demonstrates that blending two different AB diblock copolymers with tailored compositions and length ratios provides a feasible and inexpensive scheme for DSA to prepare densely arranged nanodot patterns.