Radiant energy – Irradiation of objects or material – Irradiation of semiconductor devices
Reexamination Certificate
2001-08-31
2004-02-03
Lee, John R. (Department: 2881)
Radiant energy
Irradiation of objects or material
Irradiation of semiconductor devices
C369S272100
Reexamination Certificate
active
06686597
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a substrate rotating device and a manufacturing method and apparatus of a recording medium master.
2. Description of the Related Art
A variety of large-capacity recording media are under development for recording image/audio data and digital data thereon. An optical disc such as a DVD (Digital Versatile Disc) is one example of the recording media. Research and development are now under progress for increasing the recording capacity to, for example, 30 GB (Giga-Bytes) for the optical disc having a diameter of 12 cm. Also, a hard disk platter for magnetic recording having large capacity is also under development.
Recording resolution, however, is limited by the spot diameter of a laser beam for recording in the manufacturing process of a master (i.e., an original master or a stamper) of a recording medium using a conventional laser beam in a visible or ultraviolet wavelength range. Investigations have been made for manufacturing the master (i.e., cutting of the master) with a master manufacturing apparatus using an electron beam for increasing the recording density of the disc, since the electron beam has a smaller spot diameter than a visible or ultraviolet laser beam.
The manufacturing method of the master through exposure to the electron beam involves coating of a master-disc substrate (hereinafter, simply referred to as “substrate”) with an electron beam resist, and irradiating the substrate with the electron beam in a vacuum environment. The electron beam is applied to form a latent image of miniature patterns (i.e., electron beam exposure) in the electron beam resist. The substrate undergoes a development, patterning and removal processing of the resist, resulting in formation of miniature concave/convex patterns on the substrate.
For achieving a high resolution in the electron beam exposure, the electron beam must be converged into a thin beam which however travels at a higher velocity. A fast electron beam is hardly absorbed in an electron beam resist layer but pass therethrough, thereby resulting in a reduced amount of exposure and a lower resolution.
It is contemplated to perform a constant angular velocity exposure in the electron beam method in which exposure (i.e., recording) is performed on a substrate rotated at a constant rotating speed, because of its simple control feature for a substrate rotating system. However, the line velocity greatly varies depending on a radial position of the substrate when the substrate is rotated at a constant angular velocity for exposure. For example, when using a substrate in which a recording radial position varies in a range of 20 to 60 mm (electron beam irradiation range), the line velocity varies approximately three times.
It is therefore necessary to control the velocity of the electron beam in accordance with variations in the line velocity. For example, when the velocity of the electron beam is changed by changing an accelerating voltage applied to an electron gun, the beam diameter also changes simultaneously, resulting in variations in the size of recorded pits, the width of grooves and so on. Further, the axis and focus of the electron beam also fluctuate by changing the accelerating voltage applied to the electron gun. On the other hand, there is a method to use a condenser lens to control the amount of the electron beam current. However, there arises a problem that the structure of the electron beam irradiating system becomes complicated.
The electron beam is used in a vacuum atmosphere since the electron beam has properties of greatly diffusing and attenuating in an atmospheric pressure and the existence of another medium on a beam propagation path is not preferred. Consequently, the electron gun, a substrate rotating device, a substrate transporting device are all accommodated in a vacuum chamber and used in a vacuum.
The driving devices must be extremely accurately controlled for positioning and driving the substrate, since the master manufacturing apparatus forms a latent image of miniature concave/convex patterns at an extremely small pitch on the substrate.
The substrate must be rotated with high accuracy when manufacturing a high-density master disc in a master manufacturing apparatus using the electron beam.
Also, when the substrate is fixed by a mechanical chucking mechanism, the center of the substrate is susceptible to shifting, thereby causing a lower accuracy.
For recording (cutting) information on a substrate for an information recording medium, the substrate is placed on a turntable, and an electron beam is emitted from an electron beam irradiating means to irradiate the surface of the substrate with the electron beam. In this event, since an electromagnetic motor is used as a substrate rotating device for applying the turntable with a rotating force, an electromagnetic field is generated near the motor. The electromagnetic field, however, adversely affects a direction of the emitted electron beam, thereby reducing a recording or cutting accuracy.
To solve this problem, there is disclosed in Japanese Patent No. 3040887 (Japanese Unexamined Patent Publication Kokai No. H06-131706), a master manufacturing apparatus in which an electromagnetic motor is surrounded by a magnetic shielding means in order to avoid the influence of an electromagnetic field generated by the motor to the electron beam.
In a substrate rotating device of a conventional master manufacturing apparatus, a spindle shaft is supported by a static pressure air bearing in a housing, and rotated by a motor. A magnetic fluid seal is provided in a gap along the radial direction between the housing and the spindle shaft for blocking air for the bearing from a vacuum chamber.
In the conventional substrate rotating device, heat generated from a magnetic fluid seal and a motor transfers to a spindle shaft and its surroundings when it is used at a high rotational speed. The heat thus generated causes the spindle shaft to expand thermally and the shaft length to change. This results in a change in the height of a turntable attached on the shaft for carrying the substrate, leading to unstable focusing of an electron beam which should be converged on the substrate. In addition, the temperature distribution fluctuates in the magnetic fluid, causing unstable rotation of the spindle shaft. Consequently, the recording accuracy is deteriorated such as variations in track pitch of a resulting master and an increased amount of jitter in a reproduced signal.
Likewise, miniature patterns are formed through exposure of an electron beam or direct drawing with the electron beam in the manufacturing process of a master for magnetically recording hard discs. The rotation driving system and electron beam must be controlled with high accuracy in the manufacturing process of the master for forming miniature patterns using the electron beam.
OBJECT AND SUMMARY OF THE INVENTION
The present invention is made in view of the problems mentioned above, and the object of the present invention is to provide a highly-accurate substrate rotating device, and a master manufacturing apparatus and a method which are capable of manufacturing a high-density master disc.
It is another object of the present invention to provide a substrate rotating device which suppresses the influence of variations in temperature during driving, and a master manufacturing apparatus using the same.
To achieve the object, according to one aspect of the present invention, there is provided an apparatus for manufacturing a master of a recording medium by irradiation of an electron beam on a substrate placed on a turntable disposed within a chamber, which comprises an electron-beam emitting portion for emitting the electron beam; an electron-beam converging portion for converging the electron beam; a retarding voltage applying portion for applying the substrate with a retarding voltage having a magnitude of decelerating electron rays of the electron beam; and a vacuum atmosphere producing portion for evacuating the chambe
Iwata Takeharu
Kamimura Kenji
Kaneda Hiroki
Kobayashi Masaki
Kumasaka Osamu
Johnston Phillip A
McGinn & Gibb PLLC
Pioneer Corporation
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