Norikatsu Sasao

Fabrication of 5 Tdot/in.2 bit patterned media with servo pattern using directed self-assembly

The fabrication of an etching template for 5 Td/in.2 bit patterned media using a self-organization material, namely, poly(styrene)-poly(dimethylsiloxane) (PS-PDMS), was investigated. The molecular weight of the PS-PDMS for forming the areal density of 5 Td/in.2 dot pattern was estimated from the polymerization index related to the Flory–Huggins interaction parameter. Annealing was carried out to obtain a fine-order dot pattern. PS-PDMS films were subjected to thermal treatment or solvent annealing. The ordering of the dot array in these films was evaluated by using Voronoi diagrams. The results indicate that the film annealed in N-methylpyrrolidone (NMP) vapor showed finer ordering than did the thermally treated film. This seemed to be attributable to the high solubility parameter of NMP. The soaking of NMP into the PS phase slightly shifted the phase separation energy of the polymer matrix. The lattice spacing of the obtained hexagonal pattern was 11 nm. By using low-molecular-weight PS-PDMS with solvent...

Orientation and Position Control of Self-Assembled Polymer Pattern for Bit-Patterned Media

Directed self-assembly (DSA) is expected to be a solution for the fabrication process of high-density bit-patterned media. A DSA pattern of polystyrene-b-polydimethylsiloxane diblock copolymer with 20 nm pitch was fabricated on a 2.5 in disk substrate using a postguide. Uniformity of the dot alignment as well as dot-pitch fluctuation and linearity of pseudodot tracks are estimated using image analyses of SEM photographs. Uniformity along the circumferential direction was confirmed. All the SEM images at eight different angles at r=29.4 mm showed single domain. Pitch distribution and linearity error were estimated to be 14% and 7.8%, respectively. Uniformity along the radius direction was estimated with the moiré method. The single-domain region is expected to be 5 mm in width. Margin of the postguide pitch for the single-domain formation is revealed to be more than 15% of the self-assembled dot pitch.

Wide-range directed self-assembly lithography enabling wider range of applicable pattern size for both hexagonal multi-hole and line/space

One of technical issues of directed self-assembly lithography is extremely narrow patterning range. It is really difficult to make not only smaller patterns (pitch of less than 30nm) because of self-assembling limit but also middle patterns (pitch of more than 60nm) because of material synthesis issues. This paper describes wide–range directed self-assembly lithography which enables not only narrow patterns but also wide patterns using newly developed block copolymer. One block of the new block copolymer is easily metalized selectively by metalize technology and it is confirmed that dry etching resistance is markedly improved.

Sub-15nm patterning technology using directed self-assembly on nano-imprinting guide

In next generation lithography to make sub-15nm pattern, Directed self-assembly (DSA) and Nano-imprint lithography (NIL) are proposed. The current DSA process is complicated and it is difficult to decrease width and line edge roughness of a guide pattern for sub-15nm patterning. In the case of NIL, it is difficult to make the master template having sub- 15nm pattern. This paper describes cost-effective lithography process for making sub-15nm pattern using DSA on a guide pattern replicated by Nano-imprinting (NIL + DSA). Simple process for making sub-15nm pattern is proposed. The quartz templates are made and line/space patterns of half pitch (hp) 12nm and hp9.5nm are obtained by NIL + DSA.

Orientation and position-controlled block copolymer nanolithography for bit-patterned media

Bit-patterned media (BPM) is a candidate for high-density magnetic recording media. Directed self-assembly (DSA) is expected to be a solution for the fabrication process of high-density BPM. A BPM with 20 nm-pitch dot pattern is fabricated. A 100 nm-pitch triangle lattice dot pattern, which is fabricated by EB lithography, is used as a guide post to order PS-PDMS self-assembled diblock co-polymer with 20 nm pitch. Dot-pitch fluctuation and linearity of pseudo dot tracks are estimated. The standard deviation of the dot-pitch variation including the post guide is 8% of the self-assembled dot pitch. The dot-position deviation is estimated to be about 8% of the pseudo dot track pitch. In both cases, variation of the size and pitch of the post guides is found to increase the dot-pitch fluctuation and dot-position deviation from pseudo dot-track.