Generalized method for perpendicular orientation of block copolymer microdomains in thin films with surface crosslinking process

Sub-10 nm pattern prepared by directed self-assembly of block copolymer (BCP) thin film can be a breakthrough beyond the resolution limitation of conventional photolithography. In the BCP thin film, the vertical orientation of the nanostructures is essential for pattern transfer and lithographic applications, but the surface and interfacial energies of the two domains of the BCPs are different and generally form parallel orientations. Here, we introduced more generalized method for the BCP films to form the perpendicular orientation by cross-linking process to the surface of the BCP film. By effectively cross-linking the surface of a randomly existing BCPs, the cross-linked BCP layer can be worked as natural-born fraction-tailored neutral brush. The cross-linking method can be directly applied to the poly(styrene-block-methyl methacrylate), poly(styrene-block-dimethylsiloxane) and poly(styrene-block-2-vinylpyrdine) films to realize perpendicular orientation from the top surface after thermal/solvent annealing on pristine Si or pre-patterned substrate for chemo-epitaxy directed self-assembly. Also, perpendicular orientation from the bottom interface can be also realized by introducing the new BCP film onto the cross-linked BCP layer.