JP2000339782A - Stamper for optical disk and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stamper for producing an optical disk having a higher density. SOLUTION: Grooves and land parts are concentrically or spirally and alternately disposed on the top face side of a disk substrate and a pair of side walls 14a, 14b are formed on both sides of the bottom face of the groove part at about <=90 deg. angle each to the plane direction of the disk to obtain the objective stamper 14 for an optical disk.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stamper for an optical disc used as a molding die when an optical information recording medium, particularly a video disc or the like is injection-molded, and a method of manufacturing the stamper.

[0002]

2. Description of the Related Art An optical disk capable of storing high-density data and capable of processing information at high speed has been attracting attention for audio and image applications, and as a computer memory. In such an optical disk, grooves and pits (hereinafter, collectively referred to as grooves) and lands are formed concentrically or spirally on the surface of a transparent disk substrate, and a recording layer, various protective layers, etc. are formed on this surface. Are laminated. FIG. 2 is a partially enlarged cross-sectional view of a conventional disk substrate. On the surface of the disk substrate 1, convex land portions 2 and groove portions 3 formed between adjacent land portions 2 are alternately formed. It is provided in. At this time, the angle θ formed by the side wall 3A defining the groove 3 and the bottom 3B is about 70 degrees, and the groove 3 and the land 2 are generally formed by molding a resin with a metal stamper. You.

Referring to FIG. 3, a conventional stamper for an optical disk and a method for manufacturing the same will be described. First,
As shown in FIG. 3A, a photoresist 6 is uniformly applied on the glass substrate 5 by, for example, a spin coating method.
Next, as shown in FIG. 3B, the laser beam L is condensed by the condensing lens 7 to form a condensed beam LB, thereby exposing the photoresist 6 along the groove to be formed. .

Next, as shown in FIG. 3C, the photoresist 6 is immersed in a developing solution (not shown) to remove a portion of the photoresist 6 exposed by the condensed beam LB, thereby forming a groove 8. To form Next, FIG.
As shown in (D), a stamper 9 to which the shape of the groove 8 is transferred is prepared by depositing a metal on the photoresist 6 by electroforming. Next, as shown in FIG. 3 (E), the groove 3 and the land 2 are formed on the surface by transferring and molding the surface shape of the stamper 9 onto the resin surface by using an injection molding method or a photopolymer molding method. Transparent disk substrate 1
make. Next, as shown in FIG. 3 (F), on the surface of the disk substrate 1 on which the grooves 3 are formed, for example, a recording film 10 used for a magneto-optical recording medium or the like and various protective layers (not shown) are formed. To complete the optical disk. The groove 3 and the land 2 or both of them are used as tracks.

In general, a stamper for an optical disk exposes a resist by condensing light such as a laser beam to form a pattern of grooves (grooves and pits) of the resist. It is well known that the pattern of the groove of the resist is transferred to metal to form a stamper. Further, as a method of manufacturing a stamper having an acute-angle groove or the like, for example, JP-A-6-290496, JP-A-10-92017, and JP-A-10-9
One disclosed in, for example, Japanese Patent Publication No. 2032 is known.

In the method of manufacturing a stamper disclosed in Japanese Patent Application Laid-Open No. 6-290496, a stamper having an acute angle is obtained by increasing the thickness of a resist and increasing the depth of a groove. Further, Japanese Patent Application Laid-Open No.
In the method of manufacturing a stamper disclosed in Japanese Patent Application Publication No. 7, a resist pattern having a width (w) and a depth (d) in a relationship of d ≧ w is formed, and this is transferred to form a stamper. Furthermore,
The method of manufacturing a stamper disclosed in Japanese Patent Application Laid-Open No. H10-92032 involves forming a resist pattern using two layers of photosensitive resin (resist) and transferring the same to form a stamper.

[0007]

However, a generally known method for manufacturing a stamper and the method disclosed in Japanese Patent Laid-Open No. 6-290 are disclosed.
496, JP-A-10-92017, JP-A-10-92032, etc. are disclosed in FIG.
In each case, since the resist pattern is formed by exposing the resist by condensing the laser light, even if the angle of the groove or pit is sharp, it is at most about 70 degrees as described above. However, there is a problem that it is not possible to manufacture a stamper on which grooves or pits having an angle of about 90 degrees are transferred. That is, there is a problem that a higher density optical disk cannot be manufactured.

In particular, in the case of a recordable optical disk, there is a problem that when data is written to or erased from a track, data on an adjacent track is also erased.
That is, since magneto-optical disks and phase-change disks are thermal recordings in which the temperature of the disk is raised by laser light, the smaller the distance between adjacent tracks, the greater the heat diffusion to adjacent tracks. Therefore, when writing or erasing information on a track, information written on an adjacent track is erased (thermal crosstalk or cross erase). In particular, in a land / groove recording method for recording information on both lands and grooves in order to reduce the track pitch, it is susceptible to cross-erase, and it is important to control cross-erase during multiple recordings.

In order to reduce the cross erase, there is a structure in which the depth of the groove is increased and the step due to the groove is increased to increase the heat propagation distance to an adjacent track, thereby improving the cross erase resistance. . However, even with this method, the surface roughness of the wall surface portion (a pair of side walls) of the groove of the stamper, which is the master of the optical disk substrate, is not sufficient, and this appears as unrecorded noise during reproduction. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems and has been created in order to effectively solve the problems. It is to provide a method.

[0010]

That is, in the first invention, grooves 3 and lands 2 are alternately provided concentrically or spirally on the upper surface side of a disk substrate 1, and both sides of the bottom surface of the groove 3 are provided. In the optical disk stamper 14 having a pair of side walls 14a, 14b having substantially the same angle with respect to the disk plane direction, the pair of side walls 14a, 14b
The present invention provides an optical disk stamper 14 that is set within a range of approximately 90 degrees with respect to the disk plane direction. The second invention provides an electronic stamper on a glass master 5 coated with a photoresist 6. A beam EB is irradiated to form a groove 11 having an overhang structure, and then the groove 11 is formed.
A chromium metal 12 is formed thereon, and then the photoresist 6 and the chromium metal 12 on the photoresist 6 are removed to form a chromium metal pattern 12b having an acute angle. Thereafter, the chromium metal pattern 12b is transferred. The present invention provides a method of manufacturing a stamper 14 for an optical disc in which a stamper having grooves 14a, 14b and pits with acute angles is formed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a stamper for an optical disk and a method of manufacturing the same according to the present invention will be described in detail with reference to FIG. Note that the same components as those in the related art are denoted by the same reference numerals, and detailed description thereof is omitted.

FIG. 1 is a sectional view showing steps of an optical disk stamper and a method of manufacturing the same according to the present invention. First, as shown in FIG. 1A, a photoresist 6 is uniformly applied on a glass substrate 5 by, for example, a spin coating method, and then, as shown in FIG. 1B, an electron beam EB is focused. The light is focused by the lens 7 to form a focused electron beam LEB, and the photoresist 6 is exposed along the groove to be formed.

Next, as shown in FIG. 1C, the exposed photoresist 6 is immersed in a developing solution (not shown) to remove a portion of the photoresist 6 exposed by the focused electron beam LEB. Thus, an overhang structure, that is, a groove portion 11 having a narrow entrance and a large depth is formed.

Here, the overhang structure will be described. The electron beam EB has a very short wavelength of several tens of angstroms, and the focused electron beam LEB is several angstroms. Further, the photon energy is large, and a phenomenon called back scattering occurs at the interface between the photoresist 6 and the glass substrate 5. It is considered that this is because the energy that has been absorbed by the photoresist 6 but not absorbed is scattered inside the photoresist 6 and the surface of the glass substrate 5 to naturally create an overhang structure.

Next, as shown in FIG. 1D, chromium metal 12 is formed on the resist pattern of the overhang structure.
Is formed to a thickness of about 80% of the thickness of the photoresist 6 by sputtering. During this sputtering, the photoresist 6 plays the role of a mask, and the chromium metal 12b is vertically deposited inside the overhang structure. When depositing by sputtering, chromium metal 1
When the deposition amount of 2 is increased, the chromium metal 12 on the surface of the photoresist 6 becomes gradually spilled outward. As a matter of course, the chromium metal 12 is not vertically deposited inside the overhang structure.
That is, it is considered that the mask effect of the photoresist 6 is lost when the deposition amount of the chromium metal 12 exceeds 80% of the height. If it is less than 80%, the pattern of chromium metal
Peels off and cannot be transferred by electroforming.

Next, as shown in FIG. 1E, the chromium metal 12a on the photoresist 6 is removed together with the photoresist 6, and thereafter, as shown in FIG. Is formed on the chromium metal 12b, and a nickel conductive film 13 is formed thereon by sputtering to a thickness of about 50 nm to form a nickel metal stamper 14.

Next, as shown in FIG. 1 (G), by removing the chromium metal 12b on the nickel metal stamper 14, a metal stamper having a groove or pit angle of about 90 degrees is formed. If necessary, a stamper having a pattern inverted by the nickel metal stamper 14 can be formed.

[0018]

As described above, according to the stamper for an optical disk and the method of manufacturing the same according to the present invention, a metal pattern is formed by depositing a chromium metal on a resist pattern having an overhang structure. As a result, the angle of the groove or pit is 9
A stamper close to 0 degrees can be manufactured, and a higher density optical disc can be formed.

[Brief description of the drawings]

FIG. 1 is a sectional view showing steps of a method for manufacturing a stamper according to the present invention.

FIG. 2 is a partially enlarged sectional view of a conventional disk substrate.

FIG. 3 is a cross-sectional view showing steps of a conventional stamper manufacturing method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Disk board 2 Land part 3,11 Groove part 14 Stamper 14a, 14b for optical disk Side wall

Claims (2)

[Claims] A groove and a land are alternately provided concentrically or spirally on the upper surface side of a disk substrate, and a pair of side walls having substantially the same angle with respect to the disk plane direction are formed on both sides of the bottom surface of the groove. An optical disk stamper according to claim 1, wherein said pair of side walls are respectively set within a range of approximately 90 degrees with respect to the disk plane direction. 2. A glass master coated with a photoresist is irradiated with an electron beam to form grooves or pits having an overhang structure, and then chromium metal is formed on the grooves or pits. The chromium metal on the resist and the photoresist was removed to form a chromium metal pattern having an acute angle, and then this chromium metal pattern was transferred to form a stamper having grooves and pits with an acute angle. A method for manufacturing a stamper for an optical disk, which is characterized by the following.