Osamu Kasono

High Density Mastering Using Electron Beam

A mastering system for the next-generation digital versatile disk (DVD) is required to have a higher resolution compared with the conventional mastering systems. We have developed an electron beam mastering machine which features a thermal field emitter and a vacuum sealed air spindle motor. Beam displacement caused by magnetic fluctuation with spindle rotation was about 60 nm(p-p) in both the radial and tangential directions. Considering the servo gain of a read-out system, it has little influence on the read-out signal in terms of tracking errors and jitters. The disk performance was evaluated by recording either the 8/16 modulation signal or a groove on the disk. The electron beam recording showed better jitter values from the disk playback than those from a laser beam recorder. The deviation of track pitch was 44 nm(p-p). We also confirmed the high density recording with a capacity reaching 30 GB.

Electron Beam Recording beyond 200 Gbit/in2 Density for Next Generation Optical Disk Mastering

We had developed an electron beam recorder for high-density mastering. The electron beam recorder has a capability to record high-density patterning beyond 200 Gbit/in2 density because it has characteristic of fine beam convergence. The behavior of electron scattering is important to realizing high-density patterning. Scattered electrons degrade patterning resolution and high-density patterning can not be realized. Thus, we adopted a new substrate made of a material that reduces the influence of the electron backscattering and attempted to record high density patterning beyond 200 Gbit/in2 density. As experimental result, 300 Gbit/in2 density patterning could be realized.

Nanopattern Profile Control Technology Using Reactive Ion Etching for 100 GB Optical Disc Mastering

We had developed an electron beam recorder (EBR) and studied a process technology for high-density optical disc mastering. In this study, we aimed at controlling a nanopattern profile by adopting inductively coupled plasma reactive ion etching (ICP-RIE) under simple conditions. To control a pattern inclination angle, we introduced an etching power ratio of antenna to bias and investigated the relationship. From the results of our investigation, we confirmed that inclination angle depended on etching power ratio linearly. Furthermore, in the case of a 100 GB read-only memory (ROM) equivalent pattern, we formed two kinds of inclined pattern by adopting ICP-RIE. We evaluated line edge roughness (LER) to determine the difference in pit profile accurately. As the result, we confirmed that LER was improved at a steep inclination angle. In addition, we applied ICP-RIE to a 300 GB ROM pattern.

Study of Chemically Amplified Resist Using an Electron Beam Recorder

We have been developing an electron beam recorder for next-generation optical disk mastering. Using a ZEP-520 resist that had high resolution, we fabricated read-only memory disks and obtained sufficient reproduction performance. But the recording velocity was 0.7 m/s to obtain sufficient jitter of the disk. We could not expect such low recording velocity to be used in mass production. Therefore we decided to use a chemically amplified resist, which had high sensitivity. To reduce the recording time, we adopted the resist to the optical disk mastering and investigated the process conditions. We examined the effect of development power and post-exposure banking (PEB) temperature on the jitter of the reproduced signals and obtained 6.4% jitter at a 2.5 m/s recording velocity.

Study of chemically amplified resist using an electron beam recorder

A user data capacity of more than 23 Gbytes (GB) is required for the next-generation optical disks to store HDTV signals for over 2 hours. To achieve such recording capacity, mastering recorders must have higher resolution performance than present ones. Therefore we have been developing an electron beam recorder (EBR) (Y. Kojima et al, Joint MORIS/ISOM 1997 Tech. Dig., Th-L-06, 1997). Previously we reported the high-resolution performance of the EBR using an electron beam (EB) resist (ZEP-520). At the same time we confirmed the performance of read-only memory (ROM) disks (M. Katsumura et al, ISOM 2000 Tech. Dig., We-C-02, 2000; Y. Wada et al, Jpn. J. Appl. Phys. vol. 40, pp. 1653-1660, 2001). We acquired sufficient process quality for next generation optical disks, but the recording speed in this process is not sufficient for mass production. Accordingly it is necessary to raise the recording speed in EB mastering. Although there are several proposals for high-speed recording, we propose a chemically amplified resist (CAR) method for the improvement of mass production. In this paper, we report the application of the CAR to high-speed EB recording and the reproduction performance of the 25 GB CAR disks.

Nano-Pattern Profile Control Technology Using Reactive Ion Etching for 100 GB Optical Disc Mastering

For high-density patterning, we tried to control the nano-pattern profile using a reactive ion etching technology. Line edge roughness could be improved and the line width fluctuation 7 nm could be realized.

Development of electron beam recorder with a /spl theta/-stage

In this paper, outline of EBR and the results of circle patterning were reported. Electron beam recorder with the /spl theta/-stage had a promising ability for high accuracy recording.

Improvement of recording positional accuracy in an electron beam recorder

A next generation optical disk is required to have over 23 Gbyte recording capacity for over 2 hour storage of digital high-definition television (HDTV) data. Since track pitch becomes narrower for such a large capacity disk, a high resolution and high accuracy mastering system is required. To realize this objective, we have developed an electron beam recorder (EBR) and have been studying fabrication of master stampers for next generation optical disks and for future optical disks (Y. Kojima et al, Jpn. J. Appl. Phys. vol. 37, p. 2137, 1998; Y. Wada et al, ibid., vol. 40, p. 1653, 2001). In this paper, we report an investigation of recording accuracy in the EBR and a trial for improvement.