Silicon Mold Etching with Hard Mask Stack Using Spherical Structure of Block Copolymer for Bit-Patterned Media with 2.8 Tbit/in.2

We investigated a silicon mold fabrication that uses a hard mask stack by using poly(methyl methacrylate)-block-poly(methacrylate polyhedral oligomeric silsesquioxane) (PMMA-b-PMAPOSS) as the block copolymer (BCP) to assemble nano-patterns for a nano-imprint lithography process during bit-patterned media manufacturing. We developed a dry development process comprised of a single step by taking both the selectivity and anisotropy into consideration, which enables us to create hole patterns by using an array of PMMA spheres embedded in a PMAPOSS matrix. The availability of this process was evaluated from the experimental results that showed that hole patterns at several areal densities were successfully obtained by adjusting the process time under a fixed etching condition. The capability of the pattern transfer to a hard mask from the hole patterns of residual PMAPOSS could be improved by changing the hard mask material from SiO2 to amorphous carbon based on the results from an X-ray photoelectron spectroscopy (XPS) surface analysis. Silicon molds with areal densities of up to 2.8 Tbit/in.2 were successfully fabricated by using an optimized process condition and the hard mask stack.