Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making named article
Reexamination Certificate
2000-08-03
2004-03-16
Angebranndt, Martin (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making named article
C430S321000, C216S024000, C216S058000, C216S074000, C216S075000
Reexamination Certificate
active
06706465
ABSTRACT:
BACKGROUND OF THE INVENTION
A process of forming a master for optical disks, generally referred to as “mastering”, is where a nickel or the like metallic master, i.e., “stamper”, is formed at its final step. A large number of optical disks are duplicated with use of the stamper as a mold in a succeeding molding process. Through dry etching, the present invention relates to a direct dry mastering stamper for optical disks, a method and an apparatus for direct dry mastering a stamper for optical disks whereby the stamper is manufactured in a reduced number of steps in a short time at low costs with a high yield as compared with the prior art, and an optical disk formed with use of the stamper.
A conventional mastering process will be described with reference to
FIGS. 5A-5G
.
In
FIG. 5A
,
31
is a glass substrate to which a positive type photoresist is applied thereby forming a resist layer
32
. A signal-modulated laser beam
3
is converged to a size of sub microns by a recording lens
4
to expose the glass substrate as shown in
FIG. 5B. A
developing solution is applied from a nozzle
33
onto the glass substrate
31
, whereby the exposed part is etched and removed, as shown in FIG.
5
C. Fine dents
34
called “pits”, namely, signal pits, are formed on the photoresist layer
32
. The glass substrate
31
is then heated by baking, so that a film of the photoresist layer
32
is stabilized (FIG.
5
D). A metallic conductive coat
35
is formed onto the photoresist layer
32
by sputtering or the like manner (FIG.
5
E). Thereafter, with using the metallic conductive coat
35
as an electrode, nickel plating is carried out when a nickel thick film
36
of a thickness of approximately 0.3 mm is formed on the metallic conductive coat
35
(FIG.
5
F). A replica of the pits on the photoresist layer is formed to the nickel thick film
36
.
The nickel thick film
36
is peeled off the glass base
31
as shown in
FIG. 5G. A
rear face of the thick film is polished, and inner and outer diameters are punched to conform to a molding machine. An optical disk master, that is, stamper, is thus completed.
The mastering process of forming the stamper as described hereinabove includes chemical treatment steps such as development, electroforming, and the like. In general, the chemical treatment is varied in quality and worsened in yield without strict management on production environments such as chemical liquids to be used, devices to be used, temperatures, humidities, and the like. According to the inventors' experience, further, a wet process such as the aforementioned ones cause defects on the stamper with high probability because most surface foreign particles and specks adhere or are generated when the stamper is dried from the wet state. Particularly, in accordance with a signal density increase of optical disks, the pits are required to be formed in a micro-structure of a size of sub microns, and therefore, even a minute speck or a little quantity of adhering foreign particles impairs the stamper.
Pits are formed in a chemical liquid in the conventional process. More specifically, the pits are formed to a front face of the resist layer in the developing solution and signal projections of nickel along the pits are formed in the plating solution. Under these circumstances, a degree of cleanness is hard to manage and the foreign particles or the like are prone to adhere.
Then, the pits (dents) formed to the photoresist layer on the glass base through exposure and development are transferred as projections (bumps) to a metal plate of nickel by electroforming to form the stamper. The number of steps is large and, a quality and a yield are decreased due to defects brought about in the process. Facility costs and material costs are also disadvantageously high.
The object of the present invention is, therefore, to provide a direct dry mastering stamper for optical disks, a method and an apparatus for direct dry mastering a stamper for optical disks whereby a degree of cleanness is easy to manage, adhesion of foreign particles or the like can be reduced, the number of production steps for the stamper is reduced by directly dry etching a metallic, ceramic, or the like substrate without electroforming or the like process, and a quality and a productivity can be improved and, an optical disk formed with use of the stamper.
SUMMARY OF THE INVENTION
In order to achieve the aforementioned objective, the present invention is constituted as follows.
According to a first aspect of the present invention, there is provided a method for mastering a stamper for optical disks. The method includes: irradiating laser beams signal-modulated and converged by a recording lens to a surface of a substrate while rotating the substrate having a resist layer formed of a negative type photoresist, thereby forming exposed and unexposed parts; thereafter, continuously executing heating, developing in a dry process, etching in a dry process, and removing the resist in a dry process, thereby forming signal projections to the surface of the substrate; and thereafter, machining the substrate to a stamper size conforming to a mold of an optical disk-molding machine, thereby forming an optical disk stamper.
According to a second aspect of the present invention, there is provided a method for mastering a stamper for optical disks. This method includes: irradiating laser beams signal-modulated and converged by a recording lens to a surface of a substrate while rotating the substrate having a resist layer formed of a negative type resist and machined to a stamper size conforming to a mold of an optical disk-molding machine, thereby forming exposed and unexposed parts; and thereafter, heating, and then carrying out developing in a dry process, etching in a dry process, and removing the resist in a dry process, thereby forming an optical disk stamper.
According to a third aspect of the present invention, there is provided a method for mastering a stamper for optical disks according to the first aspect, wherein the heating after irradiating the laser beams is carried out in an organic Si gas ambience of hexamethyl dislazane or the like.
According to a fourth aspect of the present invention, there is provided a method for mastering a stamper for optical disks according to the first aspect, wherein the developing, the etching, and the removing of the resist are carried out in the same chamber by changing reaction gases.
According to a fifth aspect of the present invention, there is provided a method for mastering a stamper for optical disks according to the first aspect, wherein the stamper substrate having the negative type resist layer provided to a front face thereof is formed of a material essentially consisting of at least one of nickel, chromium, aluminum, titanium, cobalt, iron, molybdenum, tungsten, boron, copper, and tantalum.
According to a sixth aspect of the present invention, there is provided a method for mastering a stamper for optical disks according to the first aspect, wherein the stamper substrate having the negative type resist layer provided to a front face thereof is formed of a silicon compound of Si, SiO
2
, SiC, or the like.
According to a seventh aspect of the present invention, there is provided a method for mastering a stamper for optical disks according to the first aspect, wherein the stamper substrate having the negative type resist layer provided to a front face thereof is formed of glass.
According to an eighth aspect of the present invention, there is provided a method for mastering a stamper for optical disks according to the first aspect, wherein the stamper substrate having the negative type resist layer provided to a front face thereof is formed of a material essentially consisting of carbon.
According to a ninth aspect of the present invention, there is provided a method for mastering a stamper for optical disks according to the first aspect, wherein the dry etching layer of the stamper substrate having the negative type resist layer provided to a front face thereof is formed of titani
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