Masaharu Fukuda

Developing Quartz Wafer Mold Manufacturing Process for Patterned Media

Recently, patterned media have gained attention as a possible candidate for use in the next generation of hard disk drives (HDD). Feature sizes on media are predicted to be 20-25 nm half pitch (hp) for discrete-track media in 2010. One method of fabricating such a fine pattern is by using a nanoimprint. The imprint mold for the patterned media is created from a 150-millimeter, rounded, quartz wafer. The purpose of the process introduced here was to construct a quartz wafer mold and to fabricate line and space (LS) patterns at 24 nmhp for DTM. Additionally, we attempted to achieve a dense hole (HOLE) pattern at 12.5 nmhp for BPM for use in 2012. The manufacturing process of molds for patterned media is almost the same as that for semiconductors, with the exception of the dry-etching process. A 150-millimeter quartz wafer was etched on a special tray made from carving a 6025 substrate, by using the photo-mask tool. We also optimized the quartz etching conditions. As a result, 24 nmhp LS and HOLE patterns were manufactured on the quartz wafer. In conclusion, the quartz wafer mold manufacturing process was established. It is suggested that the etching condition should be further optimized to achieve a higher resolution of HOLE patterns.

Si-mold fabrication for patterned media using high-resolution chemically amplified resist

Nanoimprint lithography (NIL) is one promising candidate for fabricating a patterned media to be used in the next generation of hard disk drives. It is expected that the pitch, characterizing the feature size of the media will become as low as 40-50 nm for Discrete-Track Media (DTM) by 2010 and 25 nm for Bit-Patterned Media (BPM) by 2012. Electron beam lithography is usually employed for fabricating the nanoimprint mold used for nanoimprint lithography. ZEP520A, the high-resolution resist that is commonly used for this fabrication has a low throughput; caused by the low sensitivity when used at the high acceleration voltage of 100 kV. To solve this problem, we evaluated a new high-resolution, chemically amplified resist (CAR) developed by TOKYO OHKA KOGYO Co., LTD., that was specifically developed for high resolution, instead of high sensitivity, with over twice the sensitivity of ZEP520A and a resolution of 50 nm pitch or less. A spot-electron beam (EB) writer with an acceleration voltage of 100 kV (100 kV-SB) was employed and the new CAR and ZEP520A were compared for resolution and sensitivity. Results indicated that the new CAR patterns were resolved down to a 48 nm pitch, but were collapsed even at a64 nm pitch. To prevent the collapse, we attempted to optimize the baking conditions and examined the primers as promoters of the adhesion between the resist patterns and the substrate surface. As a result, a resist pattern as low as a 48 nm pitch was obtained. We report on the performance of the new CAR and the fabrication of the Si mold by using the new CAR.

6-inch circle template fabrication for patterned media using a conventional resist and new chemically amplified resists

Nanoimprint lithography (NIL) is one promising candidate for fabricating a patterned media to be used in the next generation of hard disk drives. It is expected that the pitch, characterizing the feature size of the media will become as small as about 50 nm for discrete-track recording (DTR) in 2010 or 2011. There are two major issues, one is fine groove formation and the other is long e-beam writing time. Writing time is estimated more than one week if we use ZEP520A-resist. To solve these problems, master template fabrication processes using combination of silicon substrate and new CAR were evaluated. As a result, the capability of 1:2 groove and land ratio 50 nm pitch LS pattern formation with new CAR which sensitivity is approximately 2.5 times higher than ZEP520A was shown.

Adhesion control between resist patterns and photomask blank surfaces

Most problems in photomask fabrication such as pattern collapse, haze, and cleaning damage are related to the behavior of surfaces and interfaces of resists, opaque layers, and quartz substrates. Therefore, it is important to control the corresponding surface and interface energies in photomask fabrication processes. In particular, adhesion analysis in microscopic regions is strongly desirable to optimize material and process designs in photomask fabrication. We applied the direct peeling (DP) method with a scanning probe microscope (SPM) tip and measured the adhesion of resist patterns on Cr and quartz surfaces for photomask process optimization. We measured adhesion and frictional forces between the resulting collapsed resist pillar and the Cr or the quartz surface before and after the sliding. We also studied the effect of surface property of the Cr and quartz surfaces to resist adhesion. The adhesion could be controlled by surface modification using silanes and surface roughness on Cr blanks. We also discuss the relationship between the adhesion observed with the DP method and the properties of the modified surfaces including water contact angles and local adhesive forces measured from force-distance curves with an SPM.