In this study, a series of perpendicular lamellae-forming poly(polyhedral oligomeric silsesquioxane methacrylate-block-2,2,2-trifluoroethyl methacrylate)s (PMAPOSS-b-PTFEMAs) was developed based on the bottom-up concept of creating a simple yet effective material by tailoring the chemical properties and molecular composition of the material. The use of silicon (Si)-containing hybrid high-χ block copolymers (BCPs) provides easy access to sub-10 nm feature sizes. However, as the surface free energies (SFEs) of Si-containing polymers are typically vastly lower than organic polymers, this tends to result in the selective segregation of the inorganic block onto the air interface and increased difficulty in controlling the BCP orientation in thin films. Therefore, by balancing the SFEs between the organic and inorganic blocks through the use of poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA) on the organic block, a polymer with an SFE similar to Si-containing polymers, orientation control of the BCP domains in thin films becomes much simpler. Herein, perpendicularly oriented BCP thin films with a χ value of 0.45 were fabricated using simple spin-coating and thermal annealing processes under ambient conditions. The thin films displayed a minimum domain size of L = 11 nm, as observed via atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Furthermore, directed self-assembly (DSA) of the BCP on a topographically prepatterned substrate using the grapho-epitaxy method was used to successfully obtain perpendicularly oriented lamellae with a half pitch size of ca. 8 nm.

Bit patterned media (BPM) is fabricated by a directed self-assembled polymer mask. CoPt magnetic dots with 17 nm pitch (2.5 Tb/in 2 ) consists of ridge-and-groove servo patterns as well as circular data tracks. Distribution of dot size and dot pitch is 16% and 15%, respectively. The position error signal (PES) is estimated numerically employing a simulation model using estimated deviation of dot size and pitch. PES linearity was found to be fairly good in spite of large dot pitch deviation. Distribution of dot size and dot pitch causes distortion in the reproduced waveform, but it does not degrade the phase information of the servo signal. This result indicates that the ridge-and-groove servo has a high tolerance to the amplitude noise and is suitable for BPM. When the width of the read head is close to the dot pitch, the linearity error increases owing to the dot size and dot pitch deviation. Reduction of these distributions is necessary in order to apply BPM to hard disk drives.Index Terms-Bit patterned media, HDD, self-assembled polymer, servo pattern.

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