Tatsundo Suzuki

XY stages driving an electron beam mastering system for high density optical recording

Abstract XY stages driving an electron beam (EB) mastering system for high density optical recording has been designed and prototyped. This system has some unique techniques for subnanometer accuracy, i.e. super-polygon approximation for spiral writing, auto focus adjusting, highly precise position-detecting, and a 32-bit data format. The system demonstrated fine pits writing with a small size of 50×80 nm and an accuracy of position of about 1.6 nm ( σ ) in a rotation direction. We confirmed that the mastering system can be applied to fabrication of 40 Gb/in 2 fine pit patterns. Furthermore, this system has the potential to write a fine pit pattern of over 100 Gb/in 2 .

Fine pit pattern formation by EB-writing for a high density optical recording

Abstract Possibility of fine pattern formation for an optical recording with a high recording density is researched using a conventional electro–optical system. Then, we checked whether conventional optics or near-field optics can read them out for high density recording. The conventional optics in a laser scanning optical microscope with a blue laser (a wavelength of 405 nm) and a high NA (numerical aperture) of 0.95 or 1.4 was used. The EB drawing technique provides patterns with a minimum size of 30 nm×100 nm. However, the advanced optics reads out fine pattern with a minimum size of 160 nm×320 nm using an NA of 0.95 and a wave length of 405 nm. We conclude that we have to develop multilevel memory technology and near-field optics to achieve 100 Gb/in 2 .

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.

XY-Stage-based electron-beam recorder for the single-carrier independent Pit-edge recording radial partial response format

An electron-beam recorder in an XY-stage-based architecture was developed for mastering optical disks. The recorder uses the single-carrier independent pit-edge recording radial partial response (SCIPER/RPR) format. An electron beam is irradiated onto a master disk on continuously moving X and Y stages that are controlled so as to draw circular traces in sine and cosine waveforms against time, respectively. High-accuracy pit recording was realized using electron-beam deflection with feedforward correction of stage positioning error. A 25-Gbit/in2 SCIPER/RPR read-only-memory test disk with an alternating pit-array pattern was fabricated using the recorder. The pit-edge accuracy was evaluated from a scanning-electron-microscope image of the pattern. The obtained accuracy values were 1.6 nm (σ) for mark pitch, 3.5 nm (σ) for track pitch, and 3.8 nm (σ) for index position, which are good values for 3-level pit-edge modulation with 30-nm steps.

XY-stage driving electron-beam mastering with nanometer-accuracy positioning for high-density optical disk

An XY-stage driving electron beam (EB) mastering system, having an improved EB deflector, was applied to high-density disk mastering with the 40-Gbit/in2 single-carrier independent pit-edge recording/radial-direction partial response (SCIPER/RPR) format. We evaluated the format for pit-edge positioning using an optical filtering technique. A pit-edge positioning accuracy of around 2-nm was obtained and this performed fairly well with the multilevel SCIPER/RPR format. A combination of 40-nm-width pits and nanometer-accuracy positioning has potential in achieving further high-density mastering.

Prototyped XY stages driving EB mastering for a high density optical recording

Prototyped XY-stages driving electron beam (EB) writing system is developed to research the possibility to write fine patterns. High density optical recording pattern with 25 Gbit/in/sup 2/ is demonstrated. It is also clear that EB writing (drawing) system has a potential to achieve a required fine pattern for 100 Gbit/in/sup 2/.