Yasumitsu Wada

High-Density Recording Using an Electron Beam Recorder

A high-density optical disk fabricated using electron beam mastering exhibited excellent performance. Read-only disks with the recording capacity of 25 to 30 GB were fabricated by electron beam mastering and their jitter values were evaluated by a blue laser read out system. As a result, very low jitter values of 5.4, 6.2 and 7.7% were obtained for the disks whose capacity was 25, 27.5 and 30 GB, respectively. Characteristics of the disks such as track pitch variation, track roundness and recording stability are also shown. The electron beam recorder used in the experiments is described. In particular, details of the electron beam column, properties of the beam, how to adjust and evaluate the beam and a beam blanker are presented. Finally, several problems are addressed.

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 Recorder for Patterned Media Mastering

Patterned media are promising technologies to realize the next-generation hard disk drives (HDD) with an areal density beyond 1 Tbit/in.2. Two types of patterned media have been proposed: one is the discrete track medium (DTM) and the other is the bit-patterned medium (BPM). Both DTM and BPM require very small feature sizes and extremely tight tolerances. The mastering process is a key technology for production of patterned media, and electron beam mastering is the only means to carry out the process. We developed a new electron beam recorder (EBR) for patterned media mastering. In this paper, we introduce the technologies and the recording performance of the EBR. The EBR has four primary technical features: a 100 kV EB column, a high-precision r–θ stage system, a stage error correction system, and an EBR formatter for patterned media. In experimentals, the EBR demonstrated the following recording performance. The EBR achieved sufficient recording accuracy for the requirements of DTM with 1 Tbit/in.2 areal density. The EBR succeeded in high-density recording of a DTM pattern with 35-nm track pitch for over 1.5 Tbit/in.2 areal density. The EBR showed high throughput and good recording stability by recording a 1.8-in. DTM master. In this experiment, the EBR achieved a line width uniformity of less than 1 nm and a short exposure time of about 50 h for whole-area recording. We proved the practicality of the EBR for patterned media production.

Practical electron beam recorder for high-density optical and magnetic disk mastering

Electron beam mastering is a promising technique to realize next-generation disk media. We have been developing electron beam recorders since 1993 and have proved their effectiveness for high-density disk fabrication. To introduce electron beam mastering technology into practical application in next-generation disk mastering, we developed a new electron beam recorder as a commercial prototype. The electron beam recorder was improved in terms of recording resolution, beam-blanking characteristic and recording stability. For production use, a load-lock system was adopted to improve throughput, and the recording and substrate exchange operations were automated through computer control. The recording stability was proved experimentally by fabricating 100-GB-capacity stampers recorded on the whole recording area of 22 to 58 mm radius with a good pattern size uniformity. A superhigh-density patterning of 350 Gbit/in.2 density (510 GB capacity/layer) was realized for the next-generation optical disk, and a 35 nm line and space pattern could be fabricated for the next-generation magnetic disk.

Improvement of Electron Beam Recorder for Mastering of Future Storage Media

An electron beam recorder for optical disk mastering was improved for future storage media. One improvement was related to a formatter to record constant angular velocity formats like servo patterns of hard disks. The formatter draws patterns with constant linear velocity by controlling the translation stage, the rotation stage, the beam blanker, and the high-speed deflector synchronously. The operation of the formatter was demonstrated by test drawing standard servo patterns that aligned in the radial direction and along the arc trajectory of a swing-arm actuator. Another improvement was a reduction in electron beam size. An electron beam column with a 50 kV acceleration voltage for optical disk mastering was improved by incorporating a new objective lens, the magnification of which was about 40% of the former lens. As a result, 58.5-nm pitch land-and-grooves were resolved with a linear velocity of 0.55 m/s. Furthermore a 100 kV electron beam column was developed to reduce the beam size to 10 nm or less. The width of fabricated grooves drawn by the column was about 12 nm.

Electron Beam Recorder with Nanometer-Scale Accuracy for 100 Gbit/in2 Density Mastering

An electron beam recorder (EBR) was developed for mastering optical disks with a recording density of 100 Gbit/in2 using a multilevel recording format. In this recording format, a nanometer-scale accuracy of relative pit edge position is required in both radial and tangential directions. To achieve the recording position accuracy, a rotation stage with a noncontact vacuum seal and a correction system for rotation errors were developed. In addition, an active magnetic shield system and a learning compensation for beam displacement were adopted to improve the stability of the beam position. As a result, the ability to record with high accuracy and high resolution was confirmed from experimental results. A fine pit pattern with a minimum pit length of 70 nm was formed precisely. The recording accuracy of the EBR was evaluated to be approximately 2 nm (standard deviation) in both radial and tangential directions. Furthermore, a carrier-to-noise ratio of 64 dB was also obtained by reproducing an etched silicon master with a 240 nm monotone pit pattern.

Application of Retarding Technology to Electron Beam Recorder

The paper reports the outline of the developed electron beam recorder (EBR) for the purpose of developing future optical disk storage media. A rotation stage is developed and is installed to the EBR. The EBR using the retarding field can vary the beam energy only by adjusting the high voltage for the substrate (10 keV to 50 keV)

Development of Practical Electron Beam Recorder for High-Density Optical and Magnetic Disc Mastering

We developed a practical electron beam recorder, which was improved recording stability, resolution and throughput. The stable recording performance for the whole recording area and the capability for high-density recording beyond 200 Gbit/in2 were realized.