Fabrication of templates with rectangular bits on circular tracks by combining block copolymer directed self-assembly and nanoimprint lithography

We combine block copolymer directed self-assembly with nanoimprint lithography to generate templates with rectangular patterns through an original double imprint process. We use a rotary e-beam tool to separately expose circumferential and radial line/space chemical contrast patterns with periodicities commensurate to the natural period of two lamellae-forming poly(styrene-b-methyl methacrylate) (PS-b-PMMA) block copolymers. Line patterns are formed by directed self-assembly of PS-b-PMMA on chemical patterns on two separate submaster templates, one with circumferential lines to define concentric tracks, and a second template on which the block copolymer is used to form radial lines at constant angular pitch. The patterns are subsequently transferred to their underlying Si substrates to form submaster templates. Using two sequential nanoimprinting steps, we combine the radial and circumferential submaster line patterns into a final quartz master template with rectangular bits on circular tracks.