JP2002251797A - Blank master and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable strict control at positions of boundaries with different thickness and to facilitate formation of signals with different depth in small mirror areas in the same disk, related to a disk in which a plurality of areas coexist. SOLUTION: This blank master is provided with a process to drop photoresist solution on a substrate rotated at a first rotation speed, a second process to form a first photoresist layer by throwing off the photoresist solution by rotating the substrate at a second rotation speed faster than the first one, a third process to drop the photoresist solution on the substrate from a prescribed position again at a state where the substrate is rotated at a third rotation speed and a fourth process to form a second photoresist layer by throwing off the photoresist solution dropped again by rotating the substrate at a fourth rotation speed faster than the third rotation speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blank master for producing a user-writable information recording medium and a method of manufacturing the blank master, and more particularly to a write-once optical disc, a rewritable optical disc, and a read-only optical disc. The present invention relates to a blank master applied to a so-called partial ROM optical disk in which a type optical disk or a rewritable optical disk is formed on the same surface of a single disk, and a method of manufacturing a blank master.

[0002]

2. Description of the Related Art Generally, an optical disk has a large recording capacity and can be reproduced without contact.
ROM-type recording media such as DVD, CD-R, DVD-
R and other write-once recording media, CD-RW, DVD-RA
It is widely used for rewritable recording media such as M and DVD-RW.

FIG. 6 is a diagram showing a manufacturing process of an optical disk. First, a photoresist layer 21 is formed on a glass substrate 20 whose surface is polished and cleaned by a spin coating method or the like, and a blank master is manufactured (FIG. 6A).

Next, a beam 22 such as an Ar, Kr, He—Cd laser or the like is condensed by a lens 23 and a reduced spot is irradiated on a glass substrate 20 on which a photoresist layer 21 is formed. At this time, the laser beam 22 is turned on while rotating the glass substrate 20 and moving it at a constant speed.
The latent image 24 of the pits and grooves is formed in a spiral shape by irradiating the laser light while switching between the state and the OFF state or continuously irradiating the laser beam 22 (FIG. 6B).

[0005] Then, a glass master 20 on which a pit and groove pattern 25 is formed is produced by performing development processing with an alkaline solution (FIG. 6C).

[0006] A conductive film 26 of nickel or the like is formed on the surface of the glass master 20 manufactured as described above by a method such as sputtering or electroless plating (FIG. 6D).

[0007] While this conductive film 26 is used as a cathode,
Nickel 27 is deposited on the glass master 20 by arranging nickel on the anode side and applying a current in a nickel sulfamate solution (e in FIG. 6).

[0008] Then, the nickel 27 deposited as described above is peeled from the glass master 20 to form a metal master on which a signal pattern is formed, that is, the stamper 2.
8 is produced (f in FIG. 6).

The above is an outline of the master disk manufacturing process. The optical disk is mass-produced by the disk forming process using the stamper 28 manufactured as described above. First, the stamper 28 is subjected to post-processing such as inner / outer diameter processing or back surface polishing, and then incorporated into a molding die installed in a molding machine.
As a molding method, a compression (compression molding) method, an injection (injection molding) method using a synthetic resin such as acrylic resin or polycarbonate resin having a light transmitting property as a material.
A male mold substrate 29 having the stamper 28 as a female mold is manufactured by a method or a photopolymer (2P) method (g in FIG. 6).

Next, a film forming step is performed. Stamper 2
The uneven pattern corresponding to the uneven pattern of No. 8 is transferred,
A concave portion corresponding to the convex portion of the stamper 28 based on the information signal, that is, the mold substrate 2 on which the pit 30 is formed.
9 is coated with aluminum or the like on one main surface side to form a reflective layer 3
1 is formed. In addition, as a film forming method, a vapor deposition or sputtering method is used (h in FIG. 6).

Further, in order to protect the reflective layer 31 described above, an acrylic UV curable resin or the like is applied and cured by a spray method, a rotocoal method, a spin coating method or the like to form a protective layer 32 (FIG. 1). 6i). Then, the label portion 3 is coated on the protective layer 32 with an ultraviolet curable ink or the like.
3 is completed to complete the optical disk (FIG. 6).
j).

In recent years, as an application of a write-once optical disk or a rewritable optical disk, an optical disk in which an information reproduction-only area and an information recordable area in which a user can record information has been proposed and commercialized. For example, there is an optical disc in which pits are recorded on an inner peripheral side as a read-only area, and a guide groove for tracking is recorded on an outer peripheral side to be a recordable area. The information recorded in the read-only area of the optical disc is, for example, address information of a recording groove, information for indicating the type and manufacturer of a recording disc, and disc management for preventing unauthorized copying. Or information.

Usually, in an optical disk having pits, a signal is detected by using a phase difference between a pit portion and a non-pit portion, so that the pit depth is λ / 4n (λ: wavelength of a reproducing laser beam, n: (Refractive index of the substrate).
On the other hand, in an optical disk having a groove, the groove exists as a guide groove for an optical head to accurately follow the groove during recording, and after information is recorded, tracking is performed by relying on a recorded mark row. Therefore, the depth of the groove is set to a depth at which tracking can be easily performed before recording, and the signal quality of the recording mark after recording is good.

In the case of the land / groove recording method,
When detecting a mark recorded on a land, the depth is set so that the influence of a signal from an adjacent groove is reduced. In general, the depth is around λ / 6n or less. Set to value.

As described above, since the pit and the groove have an optimum depth for each, in the case of an optical disk in which the pit and the groove are mixed, the depth is set in the pit and the groove. I have to change. However, in an optical disk manufactured through the above-described ordinary optical disk master manufacturing process, the depths of the pit portion and the groove portion are naturally the same.

For example, in a DVD-RW optical disk, the signal quality (modulation degree, jitter) of a recorded mark is
Is taken into consideration, the groove depth becomes very shallow, and λ / 10n to λ / 18n are selected. Here, if a read-only area using pits is to be provided, a signal from the pit portion cannot have a sufficient phase difference.

As described above, in order to achieve both the reproduction signal quality in the read-only area and the recordable area, the depth of the pit portion and the groove portion must be changed in the same disk. However, improvement of the manufacturing process is required.

Japanese Patent Laid-Open No. Sho 60-1 discloses a method for forming signals having different depths in the same disk.
No. 70045. According to the publication, it is described that two types of photosensitive materials having different photosensitive characteristics are applied one on top of the other and exposed under exposure conditions suitable for each photosensitive material to form pits and guide grooves.

As a well-known material, according to “Magneto-Optical Disk by Dry Etching” described in Optics Vol. 23, No. 6, June 1994, pp. 371-372, a positive-type photo-resist is formed on a substrate. A resist is applied, and exposure and development corresponding to pits and guide grooves (grooves) are performed by a laser cutting method. The pit portion is fully exposed and completely developed to expose the substrate, but the guide groove is in an insufficiently exposed state compared to the pit, and the photoresist of a certain thickness remains without being completely developed. And Subsequently, pits and guide grooves having different depths are formed by a two-stage dry etching process including etching, ashing, etching, and ashing.

Further, after one area (for example, a pit area) is formed by applying, exposing, developing, and etching a photosensitive agent, the other area (for example, a groove area) is formed by using a substrate having the formed area. A method of forming by applying, exposing, developing and etching a photosensitive agent, or applying, exposing, developing and etching a photosensitive agent has been proposed before.

[0021]

However, the above-mentioned prior art has the following problems. JP-A-60-17
According to Japanese Patent Publication No. 0045, an intermediate layer of SiO ₂ or the like is attached between the two layers of photosensitive material by a sputtering method or a vacuum evaporation method. May occur. The solvent of the photosensitive material applied on the intermediate layer from the pinholes permeates the underlying photosensitive material layer and attacks the underlying photosensitive material layer. Further, although the intermediate layer is removed by etching, the surface of the underlying photosensitive material from which the intermediate layer has been removed is roughened by etching.
There was a problem that the ratio became worse. Further, in general, the sensitivity of a photosensitive material such as a photoresist changes depending on the temperature of the environment used, the storage period, and the like. In this prior art, since the depth is controlled by utilizing the sensitivity difference between two types of photosensitive materials having different sensitivities, there has been a problem that condition management becomes complicated.

On the other hand, in the case of the "optical" magneto-optical disk by dry etching, the photoresist is left by insufficient exposure to form the guide groove. The width and depth of the provided guide groove are likely to vary. In this prior art, the above-described variation is eliminated by ashing, but the ashing does not generally eliminate the variation in width generated in the photoresist. The surfaces of the pits and guide grooves formed by etching are roughened. However, since the reflected light from the pits is small, the roughness does not have a great effect. However, when recording and reproducing information in the guide groove, there is a problem that the influence of surface roughness is large and the reproduction S / N ratio is deteriorated.

In the above-described method of performing the second exposure with the etching interposed therebetween, the substrate is removed from the cutting device after the first exposure, and the second exposure is performed by mounting the substrate again after the etching. A non-signal area (mirror area) is formed between the read-only area and the recording / reproduction area. In other words, both the recording in the read-only area and the recording in the recording / reproducing area are recorded in a spiral or concentric manner. ) Occurs. Therefore, in order for the optical head to follow this boundary during recording and reproduction, it is very difficult to reduce the mirror area as the allowable amount of the eccentricity to 20 μm or less.

[0024]

In order to solve the above-mentioned problems, a step of dropping a photoresist solution onto a substrate rotated at a first rotation speed, and a step of dropping a photoresist solution at a higher speed than the first rotation speed. A second step of forming a first photoresist layer by rotating the substrate at a second rotation speed,
A third step of dropping a photoresist solution onto the substrate again from a predetermined position on the first photoresist layer while the substrate is rotating at a third rotation speed; and A fourth step of forming a second photoresist layer by rotating the substrate at a fourth rotation speed higher than the rotation speed.

In the third step, the photoresist solution is started to be dropped from an outer peripheral side of a position to be an inner peripheral end of the second photoresist layer, and the substrate is rotated at a third rotational speed. The method for manufacturing a blank master according to claim 1, further comprising a step of moving a dropping nozzle to a position that is an inner peripheral end of the second photoresist layer while rotating.

Further, the present invention provides the blank master manufacturing method according to claim 1 or 2, wherein the third rotation speed is higher than the first rotation speed.

Still further, the third rotational speed is 50 rpm.
The method for manufacturing a blank master according to any one of claims 1 to 3 is provided.

Further, the third step and the fourth step are repeated.
The present invention provides a method for producing a blank master according to any one of the above.

Further, the present invention provides a blank master manufactured by the blank master manufacturing method according to any one of claims 1 to 5.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A blank master according to the present invention and a method for manufacturing the same will be described below with reference to the drawings. FIG. 1 is a view for explaining an outline of a process of applying a photoresist layer in a blank master and a method for manufacturing the same according to the present invention. (Step 1-1) First, after polishing and cleaning the surface, a dried glass substrate 1 having a diameter of 200 mm and a thickness of 10 mm was prepared.
Is fixed on a spinner 2 by suction, and a nozzle 3 provided at the end of an arm of a photoresist dropping device is set at the center thereof. (Step 1-2) Next, the spinner 2 is rotated at a low speed, for example, 10 minutes.
The photoresist liquid 4 is dropped onto the glass substrate 1 while the nozzle 3 is moved from the center of the glass substrate 1 to the outer peripheral side in a state where the glass substrate 1 is rotationally driven at about rpm. (Step 1-3) When the photoresist solution 4 spreads evenly on the glass substrate 1, the dripping of the photoresist solution 4 is stopped, and the excess photoresist solution 5 is shaken off by centrifugal force by rotating the spinner 2 at high speed. By removing, the first photoresist layer 6 was formed. In the above steps, for example, a mixture of a photoresist stock solution and a solvent at a ratio of 1:10 is used as a photoresist solution, and the high-speed rotation is performed at 1000 rpm for 40 seconds, so that the thickness of the first photoresist layer 6 is reduced. Is about 70 nm. (Step 1-4) With respect to the glass master 1 on which the first photoresist layer 6 is formed as described above, the nozzle 7 is set at a predetermined position A on the outer peripheral side from the center. (Step 1-5) First, with the nozzle 7 fixed at the position A, the photoresist liquid 8 is dropped while the spinner 2 is rotated at a low speed. (Step 1-6) After the photoresist liquid 8 is dropped while the spinner rotates one or more turns, the photoresist liquid 8 is dropped on the glass substrate 1 while moving the nozzle 7 to the outer peripheral side. I do. By dropping the photoresist liquid 8, the first photoresist layer 6 formed on the outer peripheral side from the position A elutes. (Step 1-7) The spinner 2 is rotated at high speed to remove excess photoresist liquid 9 by centrifugal force and removed therefrom.
To form

In the above steps, the ratio of the photoresist solution to the solvent is, for example, 1: 1.
Using high-speed rotation at 500 rpm
m for 40 seconds, the thickness of the second photoresist layer will be about 100 nm.

In the above-described first to fifth steps, the rotation speed of the spinner 2 is changed to change the second photoresist layer 10.
FIG. 2 shows the result of measuring the amount of change in one round of the radius at the position A when is applied. FIG. 4 is a diagram for explaining the definition of the amount of change in one round of the radius. The top view of the blank master in which the photoresist is applied on the glass substrate 1 by the method shown in FIG. It is. The distance R from the center to the boundary 13 between the first photoresist layer 12 and the second photoresist layer 11 is measured over one round, and the difference (R max−R) between the maximum value and the minimum value is measured.
min) was defined as the amount of change in one round.

In FIG. 2, “a” represents a dilution ratio of the photoresist solution of 1:10, and a high-speed rotation condition in the first to third steps at 1000 rpm for 40 seconds (film thickness 70 nm).
The results are obtained when the high-speed rotation conditions in the seven steps are set to 500 rpm for 40 seconds (film thickness 100 nm), that is, when the thickness of the photoresist layer is set such that the thickness on the inner side is smaller than the thickness on the outer side, b Is the dilution ratio of the photoresist solution to 1:
10. The high-speed rotation condition in the 1-3 step is set to 500 rpm.
m for 40 seconds (film thickness 100 nm), and the high-speed rotation conditions in the first to seventh steps were changed to 1000 rpm for 40 seconds (film thickness 70 nm).
nm), that is, the thickness of the photoresist layer is
The result is obtained when the thickness on the inner peripheral side is greater than the thickness on the outer peripheral side.
In any case, by setting the low-speed rotation speed to 50 rpm or more, the accuracy of the position A is remarkably improved, and the one-round variation can be suppressed to 20 μm or less.

FIG. 3 shows that the high-speed rotation condition is 1000 r.
The results are obtained when the thickness of the first photoresist layer and the thickness of the second photoresist layer were changed by changing the ratio of the dilution of the photoresist solution while fixing at 40 pm for 40 seconds. c
Sets the dilution ratio of the photoresist solution used for the first application to 1:10 (film thickness 70 nm), and sets the dilution ratio of the photoresist solution used for the second application to 1: 6 (100 nm film thickness).
m), that is, when the thickness of the photoresist layer is such that the thickness on the inner peripheral side is smaller than the thickness on the outer peripheral side,
Sets the dilution ratio of the photoresist solution used for the first application to 1: 6 (film thickness 100 nm) and the dilution ratio of the photoresist solution used for the second application to 1:10 (film thickness 70 n).
m), that is, when the thickness of the photoresist layer is such that the thickness on the inner peripheral side> the thickness on the outer peripheral side. As shown in FIG. 2, by setting the low-speed rotation speed to 50 rpm or more, the result that the accuracy of the position A was remarkably improved was obtained.

In FIG. 1, during the second application, the photoresist solution is dropped after the nozzle position is brought to a predetermined position A. In this case, the photoresist solution is dropped when the photoresist is dropped. There is a case where the liquid rebounds and falls to the inner peripheral side from the position A, and the blank master itself becomes a defective product.

Such a problem can be solved by moving the photoresist liquid dropping start position to the outer peripheral side from the position A. In other words, for example, starting dropping of the photoresist liquid from the outermost peripheral portion of the glass substrate,
The nozzle is moved to the inner peripheral side while dripping, stops at the position A, and moves to the outer peripheral side.

When 30 sheets were coated by each of the following methods, the yield for the rebound of the photoresist solution to the inner peripheral portion was 80%, 90% and 97%, respectively. Start dropping from position A (method in FIG. 1). Start dropping from the outermost periphery of the glass substrate. Turned back after stopping the nozzle at position A. The nozzle is moved to the inner peripheral side while the photoresist liquid is dropped from the outside of the glass substrate, and stopped at the position A and then turned back.

Although an example in which two types of photoresist layers are formed in the same glass substrate has been described above, three types of photoresist layers are formed by repeating steps 1-4 to 1-7. It is also possible to form a photoresist layer having the above depth.

With respect to the blank master for the information recording medium obtained as described above, for example, pits exclusively for reproduction are formed in a thick region of the photoresist layer by laser beam exposure, and a thin region of the photoresist layer is formed. To
For example, a recording groove is formed by laser beam exposure to produce an information recording medium master. And FIG.
A stamper is manufactured by the same method as that of the prior art shown in FIG. 1, and a large number of information recording medium substrates are copied from the stamper. The recording material is applied to the pit or groove formation surface of the copied substrate by a spin coating method or a vacuum film forming method (sputtering method or vacuum evaporation method). As a recording material, in the case of a write-once optical disc, a dye or the like is used. In the case of a magneto-optical disc, a rare earth / transition metal alloy or the like is used. In the case of a phase change optical disc, a chalcogenite-based material is selected. Further, a protective film is applied thereon, or two substrates are bonded together. Then, label printing is performed as needed, and the information recording medium is completed.

FIG. 5 shows an example of the information recording medium thus manufactured. A pit 15 in a read-only area and a groove 16 in a recording / reproducing area are formed on a plastic substrate 14, and a recording film 17, a protective film 18, and a label 1 are formed thereon.
9 are formed in order. The pits 15 in the reproduction-only area are formed deeper than the grooves 16 in the recording / reproduction area.

[0041]

As described above in detail, according to the present invention, in a glass master for an optical disk formed such that the thickness of a photoresist layer is varied stepwise in a plane,
It is possible to strictly control the positions of boundaries having different thicknesses. As a result, there is an effect that signals having different depths can be easily formed in the same disk with a small mirror area.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an outline of a process of applying a photoresist layer in a blank master and a method of manufacturing the same according to the present invention.

FIG. 2 is a view showing the result of measuring the amount of change in one round of a radius at a position A of a blank master according to the present invention.

FIG. 3 is a diagram showing the result of measuring the amount of change in one round of a radius at a position A of a blank master according to the present invention.

FIG. 4 is a diagram for explaining the definition of the amount of change in one round of a radius;

FIG. 5 is a diagram showing an example of an information recording medium manufactured using the blank master according to the present invention.

FIG. 6 is a diagram showing a conventional method for manufacturing a blank master, a stamper, and an information recording medium.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass base 2 Spinner 3,7 Nozzle 4,8 Photoresist solution 5,9 Excess photoresist solution 6,11 First photoresist layer 10,12 Second photoresist layer

Claims (6)

[Claims] 1. A step of dropping a photoresist solution onto a substrate rotated at a first rotation speed, and rotating the substrate at a second rotation speed higher than the first rotation speed. A second step of forming a first photoresist layer by, in a state where the substrate is rotating at a third rotation speed, the photoresist solution again from a predetermined position on the first photoresist layer A third step of dropping on the substrate, and a fourth step of forming a second photoresist layer by rotating the substrate at a fourth rotation speed higher than the third rotation speed And a method for producing a blank master. 2. The method according to claim 1, wherein in the third step, the photoresist solution is dropped from an outer peripheral side of a position to be an inner peripheral end of the second photoresist layer, and the substrate is rotated at a third rotational speed. The method for manufacturing a blank master according to claim 1, further comprising a step of moving the dropping nozzle to a position that is an inner peripheral end of the second photoresist layer while rotating. 3. The blank master manufacturing method according to claim 1, wherein the third rotation speed is higher than the first rotation speed. 4. The blank master manufacturing method according to claim 1, wherein said third rotation speed is 50 rpm or more. 5. The method according to claim 1, wherein the third step and the fourth step are repeated. 6. A blank master manufactured by the blank master manufacturing method according to any one of claims 1 to 5.