JP2002150623A - Method for manufacturing stamper for optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method for manufacturing a stamper for optical disk, which suppresses surface wobbling (focus error) of a disk after forming as much as possible and manufactures the disk at a low cost. SOLUTION: In this method for manufacturing a stamper for optical disk, a protection tape P is stuck to a signal recording face of a stamper 10A for optical disk to be ground, and the rear face of this stamper 10A is ground to obtain the stamper for optical disk.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical disk stamper for molding an optical disk.

2. Description of the Related Art In recent years, with the advent of blue semiconductor lasers, demands for large-capacity recording on small-diameter discs and long-term recording of high-definition video have been increasing, and further densification of optical discs has been demanded. Accordingly, in the mastering process, a method of reducing pits recorded on a photoresist substrate has become an issue. The size of the bit depends on the spot diameter of the laser for exposing and recording the bit. Therefore, at present, when the recording density is about 2.5 GB or more, the NA (Num) of the objective lens for focusing the laser is used.
Exposure techniques using near-field recording in which the (Aperial Aperture) exceeds 1.0 are being studied. As another method of high-density recording, an EB (Electron B) capable of miniaturizing an exposure spot diameter is used.
eam) Exposure techniques are also being studied for practical use.

One of the problems in the process of manufacturing a high-density optical disk is a method of polishing the back surface of a stamper serving as a disk substrate. The stamper manufactured by the plating process is polished on the back surface, and then set in a mold of a disk forming machine. At this time, the state where the back surface of the stamper is polished is transferred to the front surface (signal recording surface), and further transferred to the disk during molding. In the case of a high-density optical disk, the transferred irregularities are reflected in the amount of surface deviation (remaining focus) at the time of signal reading, and jitter (Jitt) is obtained.
er) worsens. In a DVD-ROM, the surface runout is standardized as 230 nm as a format.
When the density becomes higher than 25 GB, it is not standardized yet, but if the surface runout is not suppressed to about 45 to 70 nm,
It may cause jitter deterioration. Since the surface runout tends to be deteriorated due to the formation of the protective layer on the signal recording surface, it is ideal that the surface runout of the formed substrate is suppressed to 20 nm or less.

An example of a conventional stamper backside polishing method will be described below.

FIG. 4 is a cross-sectional side view of a stamper to be polished before a back surface is polished for explaining a manufacturing process of a conventional stamper, and FIG. 5 is a polishing method for explaining a conventional method for polishing a thin plate-like work. FIG. 1A is a top view of a polishing machine in a state where a stamper to be polished is attached as a work, and FIG. 2B is a cross-sectional side view taken along line AA of FIG.

First, as a mastering step, as shown in FIG. 4, a stamper 10 to be polished is manufactured. Thickness 6
A photoresist 12 is applied to a substrate 11 such as soda lime glass or a silicon wafer (hereinafter, referred to as “Si wafer”) having a diameter of 200 mm to 220 mm, and after prebaking, exposing, and developing, a conductive film is formed by Ni electroless plating. 13, a stamper layer 14 having a thickness of about 0.3 mm is formed by electrolytic plating using this as a seed layer.

Next, while the stamper layer 14 is held on the substrate 11, the substrate 11 is mounted on a polishing machine 30 as shown in FIG. The polishing machine 30 includes a rotating shaft 31 that is rotationally driven by a driving motor (not shown), a surface perpendicular to the rotating shaft 31, and a spin stage 32 on which the polished stamper 10 as a work is fixed, A polishing head 33 for polishing the work W attached to the stage 32, a feed roller 34 for supplying a polishing tape T to the polishing head 33, a winding roller 35 for winding the polished polishing tape T, It comprises a water discharge nozzle 36 for discharging water onto the polishing surface, and a work holding jig 37.

As a method for polishing the back surface of the stamper 10 to be polished, first, the stamper 10 to be polished is placed on a spin stage 32 with a rubber sheet 38 interposed therebetween.
With the back surface 14B facing upward (toward the polishing head 33) and fixed with a work holding jig 37.

Next, while the spin stage 32 is rotated, and thus the stamper 10 to be polished is rotated, the polishing tape T is pressed against the back surface thereof, and the polishing tape T is moved while being sprinkled with water. By doing so, the polishing tape T
The back surface 14B of the stamper layer 14 is only in line contact with the polishing tape T, but the entire surface is uniformly polished. In this case, as shown in FIG. 4, the stamper layer 14 formed by Ni electrolytic plating is formed so as to hang from the front side to the back side of the substrate 11 and firmly embrace the substrate 11, so that the back side is polished. The polishing tape T can be pressed, and the stamper layer 14 does not peel off from the substrate 11 even when a force is applied in a direction parallel to the surface of the substrate 11.

[0009]

However, in the high-density optical disk mastering process by laser exposure, the substrate 11 is used in order to minimize the influence of the above-mentioned surface runout.
As a result, a quartz glass substrate having a surface roughness Ra of 5 mm or less is used. In such a case, it is difficult to reuse the glass substrate by polishing like soda lime glass, and a quartz glass substrate having a thickness of 6 mm is very expensive to dispose the glass substrate. Therefore, it has been studied to use a quartz glass substrate having a thickness of about 1 mm in a disposable manner. When EB exposure is used, a conductive Si wafer is used in order to prevent charge-up on the back surface of the photoresist 12 during exposure. Therefore, in either case of exposure, a thin substrate 11 having a thickness of about 1 mm is used. When the substrate 11 is made thinner, as shown in FIG. 4, it is possible to form a Ni plating layer from the back surface to the front surface of the substrate 11, but the area for holding the outer peripheral end surface of the stamper layer 14 is simply increased. Since it is 1/6, there is a disadvantage that the stamper layer 14 is easily peeled off from the substrate 11 due to the frictional force at the time of polishing the back surface. Further, the stress of the plating film is reduced by the thin substrate 11.
However, there is also a problem that the stamper layer 14 is peeled off from the substrate 11 before polishing the back surface because the substrate cannot be completely retained.

[0010] Accordingly, the present invention is intended to solve such a problem, and it is possible to minimize surface runout (focus error) of a molded disk and to manufacture an optical disk stamper at low cost. The purpose of the present invention is to obtain a manufacturing method.

[0011]

According to the first aspect of the present invention, a protective tape is applied to a signal recording surface of a stamper for an optical disc to be polished, and the back surface of the stamper for an optical disc to be polished is polished. The above-mentioned problem is solved by adopting a method of manufacturing a stamper for an optical disc, characterized by obtaining a stamper for an optical disc.

According to the second aspect of the present invention, an ultraviolet curing resin is applied to the signal recording surface of the stamper for an optical disc to be polished, and a glass plate is bonded to the surface of the ultraviolet curing resin. The object has been achieved by a method of manufacturing a stamper for an optical disk, characterized in that after curing by irradiation, a stamper for an optical disk is obtained by polishing the back surface of the stamper for an optical disk.

According to a third aspect of the present invention, in the method of manufacturing an optical disk stamper according to the second aspect, the surface roughness of the glass is 5 nm or less.

Further, in the invention according to claim 4,
In the method of manufacturing a stamper for an optical disk according to claim 2 or 3, the glass is subjected to a primer treatment.

Further, in the invention according to claim 5, the stamper for an optical disk to be polished in the method for manufacturing an optical disk stamper according to claim 1 or 2 is coated with a photoresist only on the surface of a substrate. After pre-baking, exposing, and developing the photoresist layer, a conductive film is formed on the surface of the photoresist layer by electroless plating, and a stamper layer is formed by Ni electrolytic plating using the conductive film as a seed layer. The layer is obtained by peeling off the substrate.

Therefore, according to the first aspect of the present invention,
The signal recording surface of the stamper for polished optical discs can be protected with a protective tape. Even if the disc is molded with a stamper whose back surface has been polished with the polished stamper peeled off from the substrate, the surface deflection of the disc after molding Can be kept as low as possible.

According to the second aspect of the present invention, the signal recording surface can be protected by bonding the stamper for the polished optical disk and the glass plate with an ultraviolet curing resin as an adhesive layer, and the protected surface is made of glass. The back surface of the polished optical disk stamper can be polished while maintaining a state of good surface roughness, and after the back surface polishing, the glass plate and the ultraviolet curing resin can be easily peeled off from the polished optical disk stamper. it can.

According to the third aspect of the invention, in addition to the effect of the second aspect of the invention, the surface roughness of the surface protecting the signal recording surface can be reduced.

According to the fourth aspect of the present invention, in addition to the function of the second or third aspect of the present invention, it is possible to improve the adhesion of the ultraviolet curing resin to the surface of the glass. it can.

According to the fifth aspect of the present invention, in addition to the effects of the first and second aspects of the present invention, it is necessary to form the conductive film on the outer peripheral end face and the back surface peripheral portion of the substrate. Therefore, there is no need to perform a pretreatment on those portions, and the number of processing steps for forming a conductive film can be reduced.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a stamper for an optical disk according to an embodiment of the present invention will be described below with reference to the drawings.

First, a method of manufacturing a stamper for an optical disk of the present invention using a protective tape will be described.

FIG. 1 is a sectional side view for explaining a method of manufacturing a stamper to be polished according to a first embodiment of the present invention suitable for molding an optical disk, and FIG. 2 is a sectional view of the stamper to be polished shown in FIG. FIG. 7A shows the state of the disk runout when the disk is formed by the stamper obtained by the manufacturing method. FIG. 7A shows that when the back surface of the stamper to be polished is polished, the protective tape laminated to the signal recording surface is laminated in a good state. B is a plan view of a disk formed by a stamper formed by polishing and polishing. FIG. B is a diagram showing a state in which a protective tape laminated on the signal recording surface is laminated and polished in an unfavorable state at the time of polishing the back surface of the stamper to be polished. FIG. 3 is a plan view of a disk formed by the stamper, and FIG. 3 illustrates a method of manufacturing a stamper to be polished according to a second embodiment of the present invention. It is a process diagram for.

First, a method of manufacturing a stamper to be polished according to the first embodiment of the present invention will be described with reference to FIG.

In FIG. 1, reference numeral 10A indicates a stamper to be polished at a stage before the stamper for an optical disk of the present invention is manufactured. In manufacturing the stamper 10A to be polished, first, a thin glass or Si wafer substrate 1 having a thickness of about 1 mm is prepared. A photoresist 2 is applied to the surface of the substrate 1, and after pre-baking, exposing, and developing,
i. A conductive film 3 is formed by electroless plating, and a stamper layer 4 (a polished stamper 10A) having a thickness of about 0.3 mm is formed by Ni electrolytic plating using the conductive film 3 as a seed layer.

In this case, the conductive film 3 need only be grown only on the surface of the substrate 1 in consideration of peeling off from the substrate 1, and the conductive film 3 may be formed like a stamper 10 shown in FIG. It is not necessary to grow the outer peripheral end surface of the substrate 1 and the peripheral portion of the back surface. Therefore, the stamper layer 4 does not need to be formed up to the photoresist 2, the outer peripheral end surface of the substrate 1, and the peripheral portion of the back surface of the substrate 1. Therefore, it is not necessary to perform the pre-processing (catalyst activation processing) when the conductive film 3 is formed by Ni electroless plating up to the photoresist 2, the outer peripheral end surface of the substrate 1, and the peripheral portion of the back surface of the substrate 1.

Also, when the stamper layer 4 is formed by Ni sputtering, it is possible to form the stamper layer 4 from the principle of sputtering itself to the photoresist 2 and the outer peripheral end surface of the substrate 1 and the peripheral portion of the back surface of the substrate 1 at one time. Since it is impossible, the method of manufacturing the stamper layer 4 (the stamper 10A to be polished) of the present invention is useful, and also a pretreatment step for forming the conductive film 3 on the outer peripheral end face and the rear face of the substrate 1. Can be reduced.

Next, in the present invention, the stamper layer 4 (the stamper 10A to be polished) is peeled from the substrate 1, and the attached photoresist 2 is removed by acetone, NaOH, plasma ashing or the like.

Next, the cleaned stamper 1
A protective tape P is stuck on the signal recording side of 0A. Then, the stamper 10A to be polished is placed and fixed on the polishing machine 30 shown in FIG. In the backside polishing of the stamper 10 of the prior art, as shown in FIG. 5, a rubber sheet 38 such as silicon rubber is laid below the stamper 10 to be polished. When only 10A (stamper layer 4) is placed on the spin stage 32, a glass plate, a metal plate such as stainless steel, a plastic plate, or the like may be placed. In that case, the surface roughness Ra of the substrate 1
It is preferably equal to or less than that of, for example, 5 nm or less.

The polishing of the back surface of the stamper 10A to be polished is an example, but was performed under the following conditions.

1. 1. Pressing force of polishing tape T: 3 kg / cm2 2. Number of rotations of spin stage 32 during polishing: 500 rpm 3. Number of rotations of polishing head 33: 10 rpm or less 4. Rough polishing with polishing tape T of # 1000: 5 min Finish polishing with # 2000 polishing tape T: 5 min As the protective tape P to be used, a tape having no unevenness in the thickness of the tape and no unevenness in application of the adhesive is preferable. In this embodiment,
Nitto Denko Corporation's BT-150E-CM and Furukawa Electric Corporation's SP
-510B-140 or the like was used. Nitto Denko's BT-
150E-CM (base material: ethylene pinyl acetate, adhesive:
In the case of acrylic), the tape is polished with a stamper 10.
After peeling from A, adhesive residue may be generated, and it is desirable to remove the adhesive residue by UV (ultraviolet) ashing, plasma ashing, or the like. Further, like SP-510B-140 (base material: polyolefin, adhesive: acrylic type) of Furukawa Electric Co., Ltd., the protective tape P is polished on the stamper 10A without irradiating UV so that the adhesive remains. Some have features that allow them to be peeled off.

Here, the base material of the protective tape P may be ethylene vinyl acetate, polyolefin, polyvinyl chloride, polyamide, acrylic, acrylic rubber, nitrocellulose, polyvinylidene chloride, or a combination thereof. It may be a polymer. The adhesive of the protective tape P may be acrylic, silicone, nitrile, phenol, NBR, olefin, or polyester.

The protective tape P is applied to the stamper 10 to be polished.
If wrinkles or bubbles remain when pasting on the signal recording surface of A, the step is transferred to the surface of the stamper 10A to be polished at the time of polishing the back surface, causing an increase in surface runout.
Therefore, it is necessary to apply the reef retention tape P to the signal recording surface of the polished stamper 10A with a uniform pressure using a laminator.

For example, when a protective tape P is mechanically affixed to the signal recording surface of the stamper 10A to be polished with a roller having a constant pressure and a constant speed, and the back surface is polished, the surface deviation of the disk formed by the polished stamper is measured. 45-7
0 nm could be suppressed. However, manually apply the protective tape P with a roller (the worker holds the roller,
When the protective tape P appears to be applied evenly, micro wrinkles are formed at the point where the pressing force of the roller is unevenly generated and the speed is changed, even if it appears that the protective tape P is evenly applied. The surface runout of the disk after molding using such a stamper becomes larger than 70 nm.

FIG. 2 shows examples of these measurements. FIG. 2A shows the surface of a disk that was mechanically laminated and polished on the back and the resulting stamper formed, and FIG. 2B shows the surface manually laminated and polished on the back and molded with the resulting stamper. FIG. The black portion indicates that the surface runout (focus error) is large. In FIG. 2A, 45
The surface runout amount is suppressed to about 70 nm. However, FIG.
In the case of B, the amount of runout is linearly increased at the point where the pressing force and speed of the roller are manually changed, and the runout amount is numerically 70 nm or more. The laminator used here is not limited to the roller type as long as it can be made of a uniform laminate.

In the above method for polishing the back surface of the stamper to be polished, a method is employed in which a protective tape P is adhered to the signal recording surface side of the stamper 10A which has been peeled off from the substrate 1 and the back surface is polished. A method of protecting the signal recording surface of the stamper 10A to be polished using an ultraviolet curing resin (hereinafter, referred to as “UV resin”) and a glass plate and polishing the back surface thereof can be adopted. Next, referring to FIG.
The stamper 1 to be polished by the UV resin and the glass plate
A method for protecting the 0A signal recording surface will be described.

FIG. 3 is a process diagram of a method for protecting a signal recording surface of a stamper to be polished with a UV resin and a glass plate according to another embodiment of the present invention.

First, as shown in FIG. 1, the polished stamper 10A is peeled off from the substrate 1, and the polished stamper 1A is removed.
The photoresist 2 adhering to the 0A signal recording surface is removed by acetone, NaOH, plasma ashing, or the like, and the cleaned stamper 10A is placed on the surface plate 40 with the signal recording surface facing up. I do. And then
For example, an acrylic UV resin R is applied to the signal recording surface using the UV resin discharge nozzle 41 (FIG. 3A).

Next, as shown in FIG. 3B, the area is approximately the same as the area of the stamper 10A to be polished, and the thickness is 1 mm.
A glass plate G is placed on the applied UV resin R.

The surface roughness Ra of the glass plate G is equal to or less than that of the substrate 1, and for example, it is preferable that Ra is about 5 nm or less. Here, the surface of the glass plate G is subjected to a primer treatment such as a silane coupling treatment, a titanium coupling treatment, and an HMDS treatment in order to improve the adhesion to the UV resin R.

Next, as shown in FIG. 3C, a roller 42 made of silicon rubber or the like is pressed onto the glass plate G at a constant pressure and a constant speed, and the UV resin R is applied between the glass plate G and the stamper 10A to be polished. Spread evenly.

Thereafter, as shown in FIG. 3D, ultraviolet rays (UV) are irradiated to cure the UV resin R.

By the above steps, the stamper 10 to be polished is
A and the glass plate G are bonded together using the UV resin R as an adhesive layer. In this state, the stamper 10A to be polished is placed on the spin stage 32 of the polishing machine 30 shown in FIG. 5 with the back surface 4B side up, and the back surface 4B is polished.

After polishing the back surface, the glass plate G and the UV resin R are peeled off from the polished stamper. As mentioned above,
Since the glass plate G has been subjected to the silane coupling treatment, the glass plate G is strongly chemically bonded (eg, covalently bonded) to the UV resin R which is an organic substance. Therefore, since the bonding is stronger than the adhesion between the Ni surface of the stamper and the UV resin R, the glass plate G and the UV resin R can be easily peeled off from the stamper.

Thereafter, if necessary, if there is any remaining UV resin R, the surface of the stamper may be cleaned by ashing, plasma ashing, or the like.

By adhering the stamper 10A to be polished and the glass plate G via the UV resin R in this manner, it is possible to obtain a stamper having a structure substantially equivalent to that of the stamper 10 shown in FIG. That is, the signal recording surface is protected, and the back surface can be polished while the protected surface is kept in a state of good surface roughness by glass.

Therefore, even when actually measuring the surface runout of a disk manufactured from a stamper whose back surface is polished by this method, a value smaller than 45 nm which is the same amount of surface runout (focus error) as in FIG. 2A is obtained. be able to.

As the glass plate G, the glass plate after the stamper has been peeled off can be used. Washing of the glass after peeling off the stamper is performed by dissolving Ni residue adhering to the surface with, for example, ferric chloride or the like, and then removing the resist by dissolving with, for example, NaOH. Then, pure water cleaning may be performed.

[0049]

As described above, according to the method of manufacturing a stamper for an optical disk of the present invention, An optical disk stamper, in particular, a high-density optical disk stamper can be manufactured at low cost, and even when molded using the optical disk stamper obtained by this manufacturing method, the surface runout of the optical disk is reduced to 45 to 70 mm or less. 1. Can be suppressed The method of manufacturing the stamper for an optical disc according to the first embodiment may be a simple process of simply attaching a protective tape to the signal recording surface of the stamper. Furthermore, when punching the inner and outer diameters of the stamper according to the mold before molding the disc, it is necessary to apply a protective tape or apply a protective film to protect the signal recording surface. 2. In the method of manufacturing the stamper for an optical disk according to the second embodiment, the surface roughness of the surface for protecting the signal recording surface is determined by the glass to be bonded, so that the surface wobble can be reliably and stably suppressed. Backside polishing becomes possible. The glass used as the substrate has a surface roughness Ra of 5
3. Since it is as small as nm or less, it is possible to reuse the glass of the substrate from which the stamper has been peeled off. In the case of the present invention, Ni electrolytic plating for producing a stamper need only be performed on the substrate surface only. Therefore, the conductive layer for that purpose also needs to be formed only on the substrate surface.
The step of forming the conductive film on the back surface and the outer peripheral end surface can be omitted. This leads to a number of excellent effects such as lowering the cost of equipment for forming the conductive film.

[Brief description of the drawings]

FIG. 1 is a sectional side view for explaining a method of manufacturing a stamper to be polished according to a first embodiment of the present invention suitable for molding an optical disc.

FIG. 2 shows a surface run-out state of a disk when it is formed by a stamper obtained by the method of manufacturing a stamper to be polished shown in FIG. 1, and FIG. A plan view of a disk formed by a stamper formed by laminating and polishing a protective tape laminated on a surface in a good condition, and FIG. B shows a disk laminated on a signal recording surface of the stamper when the back surface of the stamper is polished. FIG. 2 is a plan view of a disk formed by a stamper formed by laminating and polishing a protective tape in an undesirable state.

FIG. 3 is a process chart for explaining a method of manufacturing a stamper to be polished according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional side view of a stamper to be polished before a back surface polishing, for explaining a manufacturing process of a conventional stamper.

5A and 5B show a polishing machine for explaining a conventional method of polishing a thin plate-like work, wherein FIG. 5A is a top view of the polishing machine with the work attached, and FIG. 5B is A of FIG. -It is a sectional side view on the A line.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Photoresist, 3 ... Conductive film, 10A
(4) The stamper to be polished (stamper layer) in the present invention, 30 ... Polisher, 32 ... Spin stage, 33 ... Polishing head, 36 ... Water discharge nozzle, 40 ... Surface plate, 41 ... UV
Resin discharge nozzle, 42: roller, G: glass plate, R
... UV resin, T ... Polishing tape

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Mitsuru Toyokawa 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation (72) Inventor Shingo Ishinishi 6-35-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Incorporated F term (reference) 4F202 AH79 CA01 CA11 CD25 5D121 AA02 CA03 CB03 CB08 EE22 EE28 FF03 FF11 FF13 GG02 GG22 GG28

Claims (5)

[Claims] 1. A method of manufacturing a stamper for an optical disk, comprising: attaching a protective tape to a signal recording surface of a stamper for an optical disk to be polished; and polishing the back surface of the stamper for an optical disk to obtain a stamper for an optical disk. 2. An ultraviolet-curable resin is applied to a signal recording surface of a stamper for an optical disc to be polished, a glass plate is bonded to a surface of the ultraviolet-curable resin, and the ultraviolet-curable resin is cured by irradiating ultraviolet rays. A method of manufacturing a stamper for an optical disc, characterized in that a stamper for an optical disc is obtained by polishing the back surface of the stamper for an optical disc. 3. The method according to claim 2, wherein the surface roughness of the glass is 5 nm or less. 4. The method of manufacturing an optical disk stamper according to claim 2, wherein the glass is subjected to a primer treatment. 5. The stamper for an optical disc to be polished,
A photoresist is applied only to the surface of the substrate, and the photoresist layer is pre-baked, exposed, developed, and then a conductive film is formed on the surface of the photoresist layer by electroless plating.
3. The method according to claim 1, wherein a stamper layer is formed by Ni electrolytic plating using the conductive film as a seed layer, and then the stamper layer is peeled off from the substrate. .