JPH07287878A - Production of stamper for optical recording medium - Google Patents

Abstract

PURPOSE:To realize finer lines of grooves or pits by using current equipment by repeating >=2 times of a stage for executing etching of exposed parts by bringing a developer into contact with the surface of a resist layer and stopping of the etching by washing. CONSTITUTION:The surface of a glass master disk is subjected to mirror polishing, washing and drying, then to a surface treatment with a silane coupling agent. The resist layer is formed on this glass master disk. A positive type resist is used as the resist. While such master disk is kept rotated, the resist layer is spirally exposed at a feed pitch of 1.0mum from the inner periphery toward the outer periphery by a laser beam condensed according to prescribed information, by which the exposed parts are formed. The stage for executing the etching by bringing the developer into contact with the surface of the exposed parts on the resist and the stage for stopping the etching by washing are repeated >=2 times and thereafter, a post-baking treatment is executed to form rugged patterns on the resist layer. Ni is deposited by evaporation on the surface thereof and the Ni as an electrode is electroformed and thereafter, the electroforming layer is peeled. The inside and outside diameters of such electroforming layer are worked, by which the stamper is produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to the recording of information using light,
The present invention relates to a method for manufacturing a stamper for an optical recording medium used for an optical recording medium for reproducing or erasing.

[0002]

2. Description of the Related Art In an optical recording medium for recording and reproducing information with a minute light spot, guide grooves (grooves) for positioning the light spot, preformat signals (pits), etc. It is recorded as information. The general production of such a substrate is performed by transferring the uneven surface to a polycarbonate resin, an acrylic resin or the like using a stamper having an uneven surface corresponding to the information.

The most general conventional method of manufacturing a stamper for an optical recording medium is a manufacturing method to which a photolithography technique as shown in FIG. 4 is applied. That is, FIG. 4 (a)
After mirror-polishing the surface of the glass master 1 shown in Fig. 1B, cleaning the surface, and drying the surface well, in order to improve the adhesion with the resist, a silane coupling agent such as hexamethyldisilazane ( Treat the surface with HMDS). Next, as shown in FIG. 4B, a resist layer 2 is formed on the glass master 1 by spin coating or the like. This photoresist layer 2 is exposed by a laser beam obtained by focusing with an objective lens according to predetermined information of the optical recording medium. As a result, a photosensitive portion (latent image) 3 is formed on the resist layer 2 as shown in FIG. And
By developing this master, the photosensitive portion 3 is etched, and as shown in FIG.
That is, a groove or a pit is formed.

Thereafter, as shown in FIG. 4 (e), a metal is deposited on the surface of the resist layer 2 by means such as vacuum deposition to form a conductor film 5, thereby forming a conductor.
As shown in (f), the conductor film 5 is used as an electrode to electroform nickel or the like to form an electroformed layer 6, which is peeled from the glass master and processed to have inner and outer diameters by punching. Further, the stamper 7 is manufactured by cleaning.

Note that the related arts are described in, for example, "Points of optical disk process technology" published by Japan Industrial Technology Center.

[0006]

In recent years, along with the densification of grooves or pits for increasing the recording capacity of optical recording media, there has been a demand for finer grooves or pits.

However, in the above-mentioned conventional technique, the width of the formed groove or pit greatly depends on the spot diameter of the laser beam when the photoresist is exposed.
In order to realize a thin groove or pit,
Exposure must be performed with laser light having a smaller spot diameter.

It is generally known that the spot diameter of laser light is proportional to the wavelength of laser light and inversely proportional to the numerical aperture NA of the objective lens of the optical system. Therefore, as a means for reducing the spot diameter, it is conceivable to shorten the wavelength of the laser light or increase the NA of the objective lens.

However, since the objective lens of the optical system of the exposure apparatus in the above-mentioned conventional technique has already used NA of 0.9 or more, the width which can be improved by increasing the NA of the objective lens is small. In order to reduce the diameter, it is essential to shorten the wavelength of laser light. However, as a light source that can be used in the production of the above-mentioned conventional stamper for an optical recording medium, it is necessary to be able to continuously oscillate, so that a light source smaller than the near-ultraviolet region has not yet been put into practical use. Even with respect to the laser light in the near-ultraviolet region, there are problems that it is difficult to adjust the optical axis of the exposure apparatus, the focus margin is reduced, and the equipment cost is high because it is not visible light.

Therefore, the present invention solves such a problem, and an object of the present invention is to provide a method for manufacturing a stamper for an optical recording medium, which realizes thinning of grooves or pits using existing equipment. Where it is.

[0011]

In order to solve such a problem, a method of manufacturing a stamper for an optical recording medium according to the present invention uses a positive type resist layer formed on a master as a predetermined information of the optical recording medium. In the method of manufacturing a stamper for an optical recording medium, a photosensitive portion is formed on the resist layer by exposure according to the above, and then the photosensitive portion is subjected to a development treatment to form an uneven pattern on the resist layer. In the development treatment, at least two steps of sequentially performing a step of bringing the developing solution into contact with the surface of the resist layer to etch the photosensitive portion and a step of stopping the etching by washing with water are performed.
The above-described etching of the photosensitive portion is intermittently performed by repeating the above-described times.

Further, as described above, the step of contacting a developing solution with the surface of the resist layer to etch the photosensitive portion and the step of stopping the etching by washing with water are repeated at least twice. As a result, when the photosensitive portion is intermittently etched, the wettability of the resist layer is reduced particularly from the second time onward, so that uneven development, spots, and defects are likely to occur. Even if it is transferred, the error rate of the recorded information on the stamper increases and the external appearance becomes defective.

Therefore, in the method of manufacturing a stamper for an optical recording medium of the present invention, at least the step of etching the photosensitive portion by bringing the developing solution into contact with the surface of the resist layer is performed.
From the second time onward, this etching step is performed after the step of performing a surface treatment with a substance that improves the wettability of the resist layer surface.

In this case, an aqueous solution prepared by adding a surfactant to pure water is used as the substance for improving the wettability of the resist layer surface.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiments 1 to 5) FIG. 1 is a process chart showing a method of manufacturing a stamper for an optical recording medium of the present invention.

Specifically, it was manufactured as follows.

First, the surface of a glass master is mirror-polished and then washed, and the surface is thoroughly dried, and then hexamethyldisilazane (a silane coupling agent) is used to improve adhesion to the resist. The surface was treated with HMDS). A resist was applied on this glass master by spin coating, and then prebaking was performed at about 90 ° C. to remove the solvent inside the resist layer to form a resist layer having a thickness of about 1500 Å. In addition to this, as the method for forming the resist layer, similar results were obtained by a dip method, a spray method, or a curtain coating method. In this embodiment,
As the resist, a novolak resin / quinonediazide derivative-based positive resist which can be developed with an aqueous alkaline solution was used.

Then, while rotating the master disk, the resist layer is spirally exposed from the inner circumference to the outer circumference at a feed pitch of 1.0 μm by a laser light focused according to predetermined information of the optical recording medium. By performing the above, a photosensitive portion was formed on this resist layer. Upon this exposure, NA = 0.
93 objective lens and λ = 442 for laser light source
A HeCd laser of nm was used.

The photosensitive portion thus obtained on the resist layer is subjected to a step of etching the photosensitive portion by bringing a developing solution into contact with the surface of the resist layer as shown in FIG. 1, and a step of stopping this etching by washing with water. After repeating the respective conditions shown in Table 1, post-baking treatment was performed at about 100 ° C. to form an uneven pattern on the resist layer.

[0021]

[Table 1]

(Embodiments 6 to 8) FIG. 2 is a process diagram showing a method for manufacturing a stamper for an optical recording medium, which has a step of performing a surface treatment with a substance that improves the wettability of the resist layer surface of the present invention. .

Specifically, it was manufactured as follows.

By the same method as in the first to fifth embodiments described above,
A photosensitive portion was formed on a resist layer provided on a glass master.

The photosensitive portion thus obtained on the resist layer is surface-treated with a substance for improving the wettability of the resist layer surface according to the process diagram of the method for manufacturing a stamper for an optical recording medium of the present invention shown in FIG. The development process was performed by repeating the step of applying, the step of contacting a developing solution with the surface of the resist layer to etch the photosensitive portion, and the step of stopping this etching by washing with water. Table 2 shows the development processing conditions at that time.

[0026]

[Table 2]

In this embodiment, an aqueous solution prepared by adding about 100 ppm of sodium dialkylsulfosuccinate to pure water was used as the substance for improving the wettability of the resist layer surface. It is not limited to this. Further, it is desirable to use a substance that has a small effect of inhibiting the photosensitive portion etching by the developing solution in the next etching step. Examples thereof include other alkyl sulfosuccinates, alkyl sulfocarboxylates, α-olefin sulfonates, polyoxyethylene alkyl ether carboxylates, N-acyl amino acids and their acids, N-acyl methyl taurine salts, alkyls. Sulfate polyoxyalkyl ether sulfate, alkyl sulfate polyoxyethylene alkyl ether phosphate, rosin acid soap, castor oil sulfate ester salt, lauryl alcohol sulfate ester salt, alkylphenol phosphate ester,
An aqueous solution prepared by adding a surfactant such as an alkyl type phosphoric acid ester or an alkylallyl sulfonate to pure water in an amount of several to several thousand ppm can be mentioned, and the same effect was actually obtained. Moreover,
Similar effects were obtained even when the developing solution used in the etching step of the photosensitive portion was diluted several to several tens of times.

Further, in Examples 7 and 8, the step of performing the surface treatment with the substance that improves the wettability of the resist layer surface in the first cycle was omitted.

After the intermittent etching under the above conditions was completed, a post-baking treatment was continued at about 100 ° C. to obtain a master having an uneven pattern formed on the resist layer.

Comparative Example By the same method as in Examples 1 to 5 described above, a photosensitive portion was formed on the resist layer provided on the glass master.

The photosensitive portion on the resist layer thus obtained was subjected to the conventional general method as shown in FIG.
After continuously performing etching with a developing solution for 60 seconds,
Washing with water was performed for 60 seconds, and post-baking treatment was performed at about 100 ° C. to form an uneven pattern on the resist layer.

In each of Examples 1 to 8 and Comparative Example described above, about 1000 Å of nickel was formed on the surface of the resist layer having an uneven pattern obtained by a vacuum film forming method.
A conductive film was formed by forming a film having a thickness of about this. In addition to this, as the vacuum film forming method, there are vapor deposition, sputtering, CVD, ion plating and the like, and the same effect was obtained in each case. As a method of forming the conductor film, the same effect was obtained by the electroless plating method as well as the vacuum film forming method.

Then, by using this conductor film as an electrode and electroforming nickel, an electroformed layer having a thickness of about 0.3 mm is formed, which is peeled off from the glass master and the back surface is polished, The inner and outer diameters were processed by punching and further washed to prepare a stamper.

FIG. 3 shows an AFM (Atomic Force) groove formed on a substrate prepared by transferring an uneven surface on a glass substrate by the 2P method using each stamper obtained by the above method. Microscope: Atomic force microscope) is the result of width and depth obtained by measurement. The width tends to expand as the depth increases. Comparing the widths at the same depth in FIG. 3, the developing solution is applied to the surface of the resist layer of the present invention as compared with the comparative example in which the photosensitive portion formed on the resist layer is continuously etched by the conventional technique. It is better to intermittently etch the photosensitive part by repeating the step of contacting and etching the photosensitive part and the step of stopping this etching by washing with water for the same optical system. It can be seen that thinning can be realized. Furthermore, the width can be adjusted at the same depth by appropriately selecting the repeating conditions of the step of contacting a developing solution with the surface of the resist layer to etch the photosensitive portion and the step of stopping the etching by washing with water. It is possible.

By intermittently etching the photosensitive portion by repeatedly performing the step of etching the photosensitive portion by bringing the developing solution into contact with the surface of the resist layer and the step of stopping this etching by washing with water, The reason why the formed groove or pit is thinned is explained as follows.

In the novolak resin / quinonediazide derivative-based positive resist which can be developed with an aqueous alkali solution, the alkali-insoluble quinonediazide derivative alone is in a state of suppressing the alkali solubility of the alkali-soluble novolak resin. The quinonediazide derivative not only decomposes by light irradiation to be converted into an alkali-soluble indenecarboxylic acid by itself, but also has an effect of promoting alkali solubility of the novolac resin. Therefore, when a resist of such a system is applied in a film form and exposed according to predetermined information, there is a difference in solubility in an alkaline aqueous solution between the exposed part (photosensitive part) and the unexposed part.
By developing under an appropriate condition with an alkaline aqueous solution, it is possible to selectively dissolve and remove the photosensitive portion to form an uneven pattern. However, in reality, when the photosensitive portion is dissolved and removed by the developing solution, the formation of the hardly soluble layer against the developing solution is competitively occurring on the resist layer surface,
It is considered that the developing solution dissolves and removes the photosensitive portion while breaking through the poorly soluble layer.

Therefore, when the etching with the developing solution is interrupted by a method such as rinsing with water, since the insolubilizing layer for the developing solution is formed on the surface of the resist layer, the etching of the photosensitive portion is subsequently restarted with the developing solution. Then, the existence of this hardly soluble layer suppresses etching in the width direction. As a result, thinning of the groove or pit is realized.

Next, when each 20 stampers were produced by the method described in Examples 2, 4, 5, 6 to 8 and Comparative Example in Table 3, the rate of non-defective products of the stamper appearance (= number of non-defective products ÷ Two
0x100). In Table 3, Examples 2, 4, 5
Comparing, as the number of repetitions of the step of contacting a developing solution to the resist layer surface and etching the photosensitive portion and the step of stopping this etching by washing with water increases,
The non-defective rate tends to decrease.

[0039]

[Table 3]

This is because the wettability of the resist layer is reduced by repeatedly contacting a developing solution with the surface of the resist layer and etching the photosensitive portion. It can be improved by subjecting the resist layer surface to a surface treatment with a substance that improves the wettability of the resist layer before etching with a developing solution.

From the comparison of the non-defective product ratios of Examples 6 and 7,
Even if the step of subjecting the surface of the resist layer to the surface treatment with a substance that improves the wettability is performed before the step of etching the photosensitive portion with the developer from the second cycle onward, a sufficient effect can be obtained.

[0042]

As described above, according to the present invention, the step of etching a photosensitive portion by bringing a developing solution into contact with the surface of a resist layer and the step of stopping this etching by washing with water are sequentially performed. By repeating the etching at least twice or more, the etching of the photosensitive portion is intermittently performed, and it becomes possible to realize the thinning of the groove or the pit by using the existing equipment.

Furthermore, from at least the second step of the step of contacting a developing solution with the surface of the resist layer to etch the photosensitive portion, a step of performing a surface treatment with a substance improving the wettability of the surface of the resist layer is performed. By performing this etching process later, the error rate of recorded information is small,
The effect that a stamper for a high-performance and high-quality optical recording medium having a good appearance can be manufactured was obtained.

[Brief description of drawings]

FIG. 1 is a process drawing showing a method for manufacturing a stamper for an optical recording medium of the present invention.

FIG. 2 is a process drawing showing another method of manufacturing a stamper for an optical recording medium of the present invention.

FIG. 3 is an explanatory diagram of measurement results of groove width and depth obtained in Examples and Comparative Examples.

FIG. 4 is a process drawing showing a conventional method for manufacturing a general stamper for an optical recording medium.

[Explanation of symbols]

 1 Master 2 Resist Layer 3 Photosensitive Part 4 Concavo-convex Pattern (Groove or Pit) 5 Conductor Film 6 Electroformed Layer 7 Stamper for Optical Recording Medium

Claims (3)

[Claims] 1. A photosensitive portion is formed on the resist layer by exposing a positive resist layer formed on a master according to predetermined information of an optical recording medium, and then the photosensitive portion is developed. In the method for manufacturing a stamper for an optical recording medium in which a concave-convex pattern is formed on the resist layer, the developing treatment includes a step of contacting a developing solution with the surface of the resist layer to etch the photosensitive portion, and the etching. A method of manufacturing a stamper for an optical recording medium, characterized in that the photosensitive portion is intermittently etched by repeating a step of stopping by washing with water at least twice. 2. A step of performing a surface treatment with a substance that improves the wettability of the resist layer surface from at least the second step of the step of contacting a developing solution with the resist layer surface and etching the photosensitive portion. The method for manufacturing a stamper for an optical recording medium according to claim 1, wherein the etching step is performed after the etching. 3. The method for producing a stamper for an optical recording medium according to claim 2, wherein an aqueous solution containing a surfactant is used as the substance for improving the wettability of the resist layer surface.