Nine-fold density multiplication of hcp lattice pattern by directed self-assembly of block copolymer

Block copolymer assembly directed by electron beam (EB) lithography enhances both resolution and throughput of the EB-generated patterns and provides a feasible path to fabricating master molds of nanometer scale patterns over macroscopic areas. In our previous paper [27], we demonstrated that the self-assembly process can interpolate points in between the EB-generated pattern, thus attaining four-fold density multiplication. Here, we report a nine-fold feature density multiplication can be attained by the directed block copolymer assembly. The equilibrium formation of perpendicular cylindrical domains in registration with the pre-patterned surface is confined within a narrow thickness range once all other parameters are fixed as found in a four-fold feature density multiplication. The tolerance of the lattice mismatch between chemical pattern and d spacing of domains for nine-fold feature density multiplication is smaller than that for four-fold feature density multiplication. We also found that the critical dimension formed by the block copolymer domains is independent of that defined by the EB pre-patterned features.