JPH059775A - Production of stamper - Google Patents

Abstract

(57) [Summary] [Object] To provide a stamper manufacturing method capable of easily obtaining a stamper having a uniform plate thickness. [Structure] A photoresist layer 2 is coated on a substrate 1 made of nickel ((A) of FIG. 1), and a fine pattern 2'is formed using a laser exposure apparatus. As a result, the master 3 having the fine pattern 2'is formed ((B) of FIG. 1). Subsequently, the insulating layer 4 is laminated on the fine pattern 2 '((C) in FIG. 1), and the conductive film 5 made of nickel is formed to make the master 3 conductive (((1) in FIG. 1). D)). Then, a nickel metal film 6 is formed on the conductive film 5 by electroforming ((E) in FIG. 1). Next, after undergoing a polishing step for making the plate thickness of the metal film 6 uniform, the conductive film 5 and the metal film 6 are integrally separated from the master 3 to form a stamper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stamper manufacturing method.

[0002]

2. Description of the Related Art Conventionally, as a stamper, a stamper for molding an optical recording medium in which information is recorded and reproduced by an optical means such as a laser beam is known. The stamper for molding the optical recording medium is provided with a concavo-convex pattern corresponding to the tracking groove, the information pit, etc. of the optical recording medium, and the concavo-convex pattern is formed by a polycarbonate resin or polymethyl resin which is a thermoplastic resin. The groove portion of the optical recording medium is formed by transferring to the methacrylic resin.

Such stampers for molding an optical recording medium are disclosed, for example, in Japanese Patent Laid-Open Publication No. 61-284843, Japanese Utility Model Laid-Open No. 58-141435, and "Main points of optical disk process technology No.
5 ”(issued March 15, 1985). A conventional method of manufacturing the stamper for molding the optical recording medium will be described with reference to FIG.

Generally, first, a photoresist layer 12 is formed by coating on the surface of the glass substrate 11 (FIG. 2A),
A glass master 13 is obtained by forming a fine pattern 12 'of unevenness corresponding to the tracking groove and the information pit thereon ((B) of FIG. 2). Next, glass master 1
A conductive film 14 is formed on the surface of 3 (FIG. 2C), and then a metal film 15 is formed by electroforming (FIG. 2D). Further, after polishing to make the plate thickness of the stamper uniform, the conductive film 14 and the metal film 15 are integrally separated from the glass master 13 at the same time to manufacture the stamper 16 for molding an optical recording medium (see FIG. 2). (E)).

The manufacturing process of a general optical recording medium molding stamper by the electroforming method is as described above. Particularly, the electroforming steps (C) to (D) will be described in detail. 14 is formed by a method such as vapor deposition of metal in a vacuum or sputtering, and silver, mostly nickel is often used as a material. For example, a nickel film is formed by a sputtering method at 500Å to 1000Å
A thick film is formed on the uneven fine pattern 12 'such as a tracking groove and an information pit.

Next, in the electroforming step (D), the glass master 13 on which the conductive film 14 is formed is held by a master holder and rotated at a rotation speed of 20 to 30 rpm in a nickel sulfamate electroforming liquid. Energize with the glass master 13
Then, nickel metal (metal film 15) is deposited on the conductive film 14 and electroforming is performed.

[0007]

However, the above-mentioned prior art has the following problems. The electroforming temperature in the electroforming process is set in consideration of the internal stress and the limiting current density, and is typically 45 to 50 ° C., but the master having the metal film formed in the electroforming process is For example, when taking out to room temperature of 25 ° C., a temperature difference of 20 ° C. to 25 ° C. occurs. At this time, the difference in the coefficient of thermal expansion between the substrate made of glass and the metal film made of nickel forming the master (9 to 10 × for glass).
10 ⁻⁶ / ° C., and nickel is 12.8 × 10 ⁻⁶ / ° C.), a bimetallic warp as shown in FIG. 3 is generated. Therefore, in the polishing step after electroforming, it is very difficult to perform polishing so that the plate thickness of the stamper becomes uniform. Further, in order to suppress the above-mentioned warpage, the glass master must be made thick, which causes problems in workability and cost.

The present invention has been made in view of the problems of the above conventional technique, and an object of the present invention is to provide a method of manufacturing a stamper which can easily obtain a stamper having a uniform plate thickness. .

[0009]

According to the present invention, there is provided a conductive step of forming a conductive film on a master having a fine uneven pattern on its surface, and a nickel film is formed on the conductive film by electroforming. An electroforming step for forming a film, a polishing step for making the film thickness of the nickel film uniform, and a peeling step for peeling the conductive film and the nickel film together from the master are included,
In the stamper manufacturing method, the master is made of a material whose coefficient of thermal expansion is substantially equal to that of the nickel film, and the coefficient of thermal expansion α of the material forming the master is 12 × 10 ^−6. There are cases where ≦ α ≦ 18 × 10 ⁻⁶ / ° C. and cases where the conductive film is formed after the insulating film is formed on the surface of the master in the conductive step.

[0010]

According to the stamper manufacturing method of the present invention, since the master is made of a material having a thermal expansion coefficient substantially equal to that of the nickel film formed in the electroforming step, the electroforming step moves to the polishing step. Warping of the master on which the conductive film and the nickel film are formed is eliminated due to the temperature change at the time of performing. The temperature change during the transition from the electroforming step to the polishing step is 20 to 25 ° C.
Since the change in the coefficient of thermal expansion of the nickel film due to the temperature change is considered to be 12 × 10 ⁻⁶ to 18 × 10 ⁻⁶ / ° C., a material having a coefficient of thermal expansion within that range is used as the master material. You can choose.

[0011]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a diagram showing a manufacturing process in an embodiment of a stamper manufacturing method of the present invention. In the stamper manufacturing method of this embodiment, a nickel film is formed as a conductive film by sputtering on a master 3 having a fine pattern corresponding to tracking grooves and information pits of an optical recording medium formed on the surface of the substrate 1. Is formed, and further, on the conductive film,
Nickel is deposited as a metal film by electroforming. After that, the conductive film and the metal film are integrally peeled off from the master 3 to manufacture the stamper 7 for molding the optical recording medium.

The substrate 1 of the master 3 used in this embodiment is the same nickel plate (coefficient of thermal expansion: 12.8 × 10) as the metal film.
^-6 / ° C) (300 x 340 x 10 mm),
The surface has a surface roughness of 0.1 μm or less due to mirror polishing. Here, a manufacturing process of the stamper for molding an optical recording medium in the present embodiment will be described.

First, Az1370 (manufactured by Hoechst Japan Co., Ltd.) is applied as a photoresist layer 2 on the substrate 1 by spinner coating to a film thickness of about 3000 Å (FIG. 1).
(A)). Then, prebaking was performed under the conditions of 30 ° C. and 30 minutes. Next, laser exposure apparatus MPA-1
500 (manufactured by Canon Inc.) is used to expose a stripe-shaped preformat pattern of, for example, four optical recording media on the photoresist layer 2 to develop a developer Az312.
Develop with MIF (Hoechst Japan). As a result, the master 3 having the fine pattern 2'formed on the substrate 1 is completed ((B) of FIG. 1).

Subsequently, on the fine pattern 2 ', 500 Å-thick SiO ₂ is laminated as the insulating layer 4 by the sputtering method (FIG. 1C), and then a metal film is formed by the electroforming method. As a pretreatment of
A conductive film 5 of 0Å nickel was formed by a sputtering method to make the master 3 conductive ((D) of FIG. 1). Next, a metal film 6 is formed on the conductive film 5 by electroforming ((E) in FIG. 1).

This electroforming method will be described. First, a nickel chip in an electroforming tank (not shown) is set as a + side electrode, and a conductive master 3 is set as a − side electrode. Next, in the nickel sulfamate electroforming liquid in the electroforming tank, while rotating the master 3 provided with the conductive film 5 at 20 to 30 rpm, the time integral value of the energizing current was 160 to 240 AH (ampere hour). Under the conditions of 1), nickel metal of 200 to 300 μm was deposited to form the metal film 6. The liquid temperature during electroforming was 50 ° C.

The electroforming liquid used here has the following composition. Nickel sulfamate tetrahydrate [Ni (NH ₂ SO ₃ ) 2.4H ₃ ] 500 g / l Boric acid [H ₃ BO ₃ ] 35 to 38 g / l Pit inhibitor 2.5 ml / l Thus the metal film 6 is formed. The master 3 was taken out from the electroforming tank, washed with water, returned to room temperature, and then polished to make the stamper uniform in plate thickness. There was no warp and there was no problem during polishing.

After that, the conductive film 5 and the metal film 6 are integrally peeled off from the master 3 to complete the stamper 7 for molding the optical recording medium ((E) in FIG. 1). In this example, when the master 3 having the metal film 6 formed thereon was taken out of the electroforming tank and returned to room temperature, the metal film 6 and nickel on the substrate 1 both had nickel and had the same coefficient of thermal expansion. It was possible to obtain a stamper 7 having a uniform plate thickness without any polishing. Further, the substrate 1 and the conductive film 5 are made of the same nickel, but the insulating layer (SiO ₂ ) 4 is laminated on the substrate 1 before the conductive film 5 is formed. The conductive film 5 and the metal film 6 can be easily peeled off from the surface 3.

Next, a second embodiment of the present invention will be described. In this embodiment, 1 is used as the material of the substrate forming the master.
8-8 stainless steel plate (coefficient of thermal expansion: 16.4 × 10 ^-6
/ ° C.) was used to form a fine pattern, an insulating layer, a conductive film, and a metal film along the steps shown in FIGS.

After the metal film was formed, the master was taken out of the electroforming tank, washed with water, and then returned to room temperature. The warp accompanying the temperature change was m.
With ax of 10 μm, there was no problem during polishing. Next, a third embodiment of the present invention will be described. In the present embodiment, lead calico soda glass (coefficient of thermal expansion: 12.3 × 10 ⁻⁶ / ° C.) (manufactured by Corning Japan) is used as the material of the substrate forming the master.

The shape of the substrate is 300 × 340 × 10 mm
Then, the fine pattern and the conductive film were formed in the same manner as in the first embodiment described above. After that, a nickel metal film having a thickness of 200 to 300 μm was deposited on the conductive film by electroforming in the same manner as described above. In this example, the electroforming liquid (nickel sulfamate) at the time of electroforming was set to 45 ° C.

In this way, the master having the metal film formed thereon was taken out of the electroforming tank, washed with water, returned to room temperature, and measured for warpage, which showed a maximum of 35 μm, and there was no problem during polishing. Next, as a comparative example, a case where soda lime glass (coefficient of thermal expansion: 9.2 × 10 ⁻⁶ / ° C.) is used for the substrate of the master will be described. In this case, a fine pattern, a conductive film and a metal film were formed on the substrate in the same manner as in the third embodiment, the master was taken out of the electroforming tank, washed with water and returned to room temperature. At this time, the warp was measured to be 90 μm at maximum, and when the warp was returned during polishing and polishing was performed,
The conductive film was peeled off from the master and it was difficult to polish.

In the first to third embodiments described above,
Although an example in which nickel, 18-8 stainless steel plate, and lead calico soda glass are used as the substrate material of the master is shown, the coefficient of thermal expansion α is 12 × 10 ⁻⁶ ≦ α ≦ 18 × 10 ⁻⁶ /
As those satisfying the temperature, cobalt, gold, iron, copper, palladium, aluminum bronze, carbon steel, yellow, constantan, bronze, gun metal, monel metal, phosphor bronze, ceramics having a high expansion coefficient, or the like can be used. Also, among the above-mentioned metals and alloys, those without acid resistance,
For those which are more easily ionized than nickel, the surface thereof may be covered with a thin film of plastic, ceramics or the like, or passivated. In this case, since the coating film also acts as a protective film, it also has an effect of preventing contamination of the electroforming liquid.

As a method for forming a fine pattern, there is a method using mask exposure or etching in addition to using a laser exposure apparatus. It is also conceivable that a pattern formed on an ultraviolet curable resin or a thermosetting resin is transferred onto a master and patterned without using a resist. Further, in each of the above-described embodiments, the stamper for molding the optical recording medium has been described as an example, but the present invention is not limited thereto.

[0024]

As described above, the present invention has the following effects. (1) Since the master is formed of a material having a thermal expansion coefficient substantially equal to that of the nickel film formed by electroforming, the warpage of the master due to the temperature change during the transition from the electroforming step to the polishing step can be ignored. The workability is improved and the thickness of the stamper is made uniform. In addition, since warpage can be suppressed without increasing the thickness of the master, it is economically advantageous.

(2) When a metal whose coefficient of thermal expansion is substantially the same as that of the nickel film is used as the master material, the strength against impact during transportation or installation is improved. (3) After forming an insulating film on the master surface in the conductive step,
By forming the conductive film, the conductive film and the nickel film can be easily peeled from the master in the peeling step even when the master and the conductive film are made of the same material.

[Brief description of drawings]

FIG. 1 is a diagram showing steps in an embodiment of a stamper manufacturing method of the present invention.

FIG. 2 is a diagram showing steps in an example of a conventional stamper manufacturing method.

FIG. 3 is a sectional view showing an example of a conventional master having a conductive film and a metal film formed thereon.

[Explanation of symbols]

1 substrate 2 Photoresist layer 3 master 4 insulating layers 5 Conductive film 6 metal film 7 Stamper

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshiya Yuasa             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation (72) Inventor Hisanori Hayashi             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation (72) Inventor Hirofumi Kamikohara             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation (72) Inventor Naoki Kushida             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation

Claims (3)

[Claims] 1. A conductive step of forming a conductive film on a master having a fine concavo-convex pattern on its surface, and an electroforming step of forming a nickel film on the conductive film by electroforming. In the method of manufacturing a stamper, which comprises a polishing step for making the film thickness of the nickel film uniform and a peeling step for peeling the conductive film and the nickel film together from the master, The expansion coefficient is formed of a material substantially equal to the thermal expansion coefficient of the nickel film,
Stamper manufacturing method. 2. The coefficient of thermal expansion α of the material forming the master is 1
2. The method for manufacturing a stamper according to claim 1, wherein 2 × 10 ⁻⁶ ≦ α ≦ 18 × 10 ⁻⁶ / ° C. 3. The stamper manufacturing method according to claim 1, wherein the conductive film is formed after the insulating film is formed on the surface of the master in the conductive step.