JP2004213742A - Manufacturing method of stamper for optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a stamper for optical disk whose tilt angle of a groove side wall is made steep. <P>SOLUTION: Photoresist 2 is applied on a glass plate 1, after this photoresist 2 is irradiated with a laser beam, development is performed, a groove 4 of an inverse trapezoidal shape is formed, next, a shrinking rate being near the glass plate 1 of the photoresist 2 is made larger than that of the surface, the tilt angle of the photoresist 2 for the glass plate 1 is made steep, next, a nickel thin film 5 is formed on the glass plate 1 exposed on the photoresist 2 and the groove 4. Further, after a nickel electroforming film 6 is formed on the nickel thin film 5 by an electroforming method, the nickel electroforming film 6 is peeled off from the photoresist 2 with the nickel thin film 5. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a stamper for an optical disk that can steeply incline a groove side wall when an optical disk is manufactured.
[0002]
[Prior art]
2. Description of the Related Art In response to the multimedia era dealing with a large amount of information, the demand for optical discs capable of recording and reproducing a large amount of data is increasing. Such an optical disk is manufactured from a stamper. The method of manufacturing this stamper is disclosed in Patent Document 1.
[0003]
In Patent Document 1, after a photoresist film is coated on a substrate, a low-temperature heat treatment is performed to form a photoresist film, and then a spiral or concentric exposure and development with a laser beam is performed to form a groove. Then, the photoresist film is subjected to a heat treatment at 130 ° C. to 150 ° C. so as to smooth out minute irregularities on both side walls of the groove and also make the slope of the side wall gentle, thereby reducing a noise level of a reproduction signal. Is disclosed.
[0004]
[Patent Document 1]
Japanese Patent No. 2767638 (page 1-2, FIG. 2)
[0005]
[Problems to be solved by the invention]
However, in the optical disk manufactured by using the stamper described above, a groove corresponding to the groove portion formed in the resist master and a land corresponding to a portion other than the groove are formed, but the photoresist facing the groove described above is formed. Since the inclination angle of the side surface cannot be made steep, when the optical disc is made high-density, the inclination angle of the groove side wall does not become steep, that is, the land width becomes narrow, and the recording mark is recorded on the track composed of the land or the groove. When erasing or erasing, there is a problem that thermal crosstalk or cross-erase that erases a recording mark of an adjacent track occurs.
Further, in the case of recording in a groove, if the inclination of the groove side wall is gentle, the recording mark in the heat or thermomagnetic recording is blurred in the track direction (lateral direction). On the other hand, when the slope of the groove side wall is steep, the recording mark is cut off at the boundary between the groove and the land, and the recording mark becomes sharp in the lateral direction, thereby improving the recording characteristics. In order to prevent such thermal crosstalk, cross-erase, or bleeding of recording marks in the track direction, the inclination angle of the groove side wall must be 60 ° or more.
This tendency becomes more remarkable in the land / groove recording method in which recording marks are recorded on both lands and grooves.
[0006]
Accordingly, an object of the present invention is to provide a method of manufacturing a stamper for an optical disk that can steeply incline the groove side wall in order to solve the above problem.
[0007]
[Means for Solving the Problems]
The present invention is to apply a photoresist on a substrate, irradiate the photoresist with a laser beam having a high Gaussian distribution at the center of the irradiation intensity, and then perform development to form an inverted trapezoidal groove. a first step, by the wavelength band 380 nm to 450 nm, the light energy density is irradiated with light of ^{30kJ / m 2 ~50kJ / m 2} , the shrinkage ratio of the photoresist is increased by the substrate near the surface, the substrate A second step of steepening the inclination angle of the side surface of the photoresist with respect to the above, a third step of forming a nickel thin film on the photoresist and on the substrate exposed from the groove, and an electroforming method on the nickel thin film. Forming a nickel electroformed film on the substrate, and peeling the nickel electroformed film from the photoresist together with the nickel thin film. To provide a method of manufacturing a stamper for optical disc according to.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
A method for manufacturing an optical disk stamper according to an embodiment of the present invention will be described with reference to FIGS.
1A and 1B show a method of manufacturing a stamper for an optical disc according to an embodiment of the present invention. FIG. 1A is a cross-sectional view showing a (photoresist coating and groove forming step), and FIG. (C) is a cross-sectional view showing a (nickel film forming step), (D) is a cross-sectional view showing an (electroforming step), and (E) is a cross-sectional view showing a completed nickel stamper. . FIG. 2 is a diagram showing the relationship between the tilt angle of the photoresist side surface with respect to the glass plate and the light energy density.
[0009]
(Photoresist coating and groove forming process)
First, the glass plate 1 is polished, washed with water, and exposed to hexamethyldisalazane vapor.
Next, as shown in FIG. 1A, a photoresist 2 having a thickness of 200 nm is applied on the glass plate 1 by spin coating. The photoresist 2 is 9900 NX manufactured by Spreeferist.
Subsequently, a krypton laser beam having a wavelength of 413 nm is irradiated onto the photoresist 2 in a spiral or circular shape, and then a latent image 3 is formed.
[0010]
(Lamp light irradiation process)
Thereafter, as shown in FIG. 1B, the latent image 3 is developed to form an inverted trapezoidal groove 4 having a track pitch of 0.75 μm and a width of 0.375 μm on the photoresist 2.
The groove 4 has an inverted trapezoidal shape for the following reason.
The irradiation intensity of the laser light has a Gaussian distribution that is strongest at the center and becomes weaker as the distance from the center increases. Since the absorption of the laser light by the photoresist 2 depends on the irradiation intensity, the laser light having the strong irradiation intensity The portion of the photoresist 2 exposed by the central portion is irradiated deeply, and the portion of the photoresist 2 irradiated with a laser beam having a low irradiation intensity and distant from the central portion is irradiated shallowly. Therefore, the latent image 3 formed on the photoresist 2 has the deepest portion irradiated at the center of the laser beam, and becomes shallower as the distance from the center increases. As a result, by developing this latent image 3, an inverted trapezoidal groove 4 is formed.
[0011]
Next, the entire photoresist 2 is irradiated using a tin-mercury metal halide lamp that emits lamp light in a wavelength band of 380 nm to 450 nm having a predetermined intensity, and the inclination angle of the side surface of the photoresist 2 facing the groove 4 (hereinafter, referred to as the inclination angle). (Hereinafter simply referred to as the inclination angle of the side surface of the photoresist 2).
[0012]
Here, the reason why the inclination angle of the side surface of the photoresist 2 can be made steep by irradiating light having a wavelength band of 380 nm to 450 nm will be described.
The photoresist 2 has an absorption band near the wavelength of 410 nm, and has a property that when irradiated with light in this wavelength band, the molecular bond chains in the photoresist 2 are cut to cause shrinkage. This shrinkage ratio also depends on the light energy density. When the photoresist 2 is irradiated with the above-described lamp light having the wavelength band of 380 nm to 450 nm from above, the entire thin portion is irradiated in the vicinity of the glass plate 2. Produces a shrinkage rate. As a result, the photoresist 2 near the glass plate 1 recedes, and the inclination angle of the photoresist 2 becomes steep.
[0013]
Next, the energy density of the lamp light emitted from the tin-mercury metal halide lamp was changed in the range of 0 kJ / cm ^{2 to} 100 kJ / cm ² , and the inclination angle of the side surface of the photoresist 2 was examined.
The inclination angle of the side surface of the photoresist 2 was measured using AFM-M5 manufactured by Park Science. The result is shown in FIG.
In FIG. 2, the horizontal axis represents the light energy density (kJ / m ² ) of the lamp light, and the vertical axis represents the inclination angle (°) of the photoresist 2 side surface. Here, the inclination angle of the side surface of the photoresist 2 refers to an angle formed by the inclined surface of the side surface of the photoresist 2 with the surface of the glass plate 1. When the light energy density is 0 kJ / cm ² , it means a state where only the laser beam is irradiated in the (photoresist coating and groove forming step) and the lamp light is not irradiated in the (lamp light irradiation step). At this time, the inclination angle of the side surface of the photoresist 2 is 50 °.
[0014]
As shown in FIG. 2, as the light energy density increases, the inclination angle of the photoresist 2 side surface increases and reaches saturation at 50 kJ / m ² .
When the light energy density is 50 kJ / m ² , the inclination angle of the side surface of the photoresist 2 is 68 °.
As described above, in order to prevent thermal crosstalk and cross-erase from occurring on the optical disk, it is necessary to secure an inclination angle of the groove wall surface of 60 ° or more. Therefore, the light energy density of the lamp light is 30 kJ / m ^2. It turns out that the above is necessary.
At this time, the reason why the inclination angle of the side surface of the photoresist 2 does not become steeper at 50 kJ / m ² or more is that when the light energy density increases, the entire photoresist 2 shrinks, and the shrinkage ratio in the thickness direction and the side direction is reduced. Are almost equal, and the inclination angle does not change. As described above, the reduction in the thickness of the photoresist 2 as a whole shrinks causes a problem that the depth of the groove 4 becomes shallow, and a stamper having a desired shape cannot be manufactured. For this reason, the lamp light irradiation needs to be performed at a light energy density in the range of 30 kJ / m ^{2 to} 50 kJ / m ² .
[0015]
(Nickel film forming step)
Next, as shown in FIG. 1C, a nickel thin film 5 is formed on the glass plate 1 opened from the photoresist 2 and the groove 4 by a sputtering method.
[0016]
(Electroforming process)
Next, as shown in FIG. 1D, a nickel electroformed film 6 is formed on the nickel thin film 5 by using nickel sulfamate by an electroforming method. Further, as shown in FIG. 1E, the nickel electroformed film 6 is peeled off from the photoresist 2 together with the nickel thin film 3 to produce a stamper 7 for an optical disk.
[0017]
As described above, according to the embodiment of the present invention, after irradiating the photoresist 2 with a laser beam having a Gaussian distribution, the photoresist 2 is developed to form the inverted trapezoidal groove 4, and further, the wavelength band is 380 nm to 380 nm. By irradiating the photoresist 2 with visible light having a wavelength of 450 nm and an energy density of 30 kJ / m ^{2 to} 50 kJ / m ² , the shrinkage ratio of the photoresist 2 is made larger in the vicinity of the glass plate 1 than in the surface, and the photoresist for the glass plate 1 is formed. Since the inclination angles of the two side surfaces are steep, a stamper 7 for an optical disk having a convex portion having a steep inclination corresponding to the groove 4 can be obtained. By using this optical disk stamper 7, an optical disk having a groove wall surface with an inclination angle of 60 ° or more, no thermal crosstalk or cross-erase, and good recording characteristics without blurring of recording marks in the track direction is obtained. be able to.
[0018]
【The invention's effect】
According to the present invention, a photoresist is coated on a substrate, and the photoresist is irradiated with a laser beam having a Gaussian distribution, and then developed to form an inverted trapezoidal groove. The photoresist is irradiated with light having a wavelength of 450 nm and a light energy density of 30 kJ / m ^{2 to} 50 kJ / m ² , and the shrinkage ratio of the photoresist is increased near the glass plate from the surface, and the inclination angle of the photoresist side surface with respect to the substrate is reduced. Because of the steepness, it is possible to obtain an optical disk stamper having a convex portion having a steep slope corresponding to the groove. By using the stamper for an optical disc, it is possible to obtain an optical disc having a groove side wall having an inclination angle of 60 ° or more, free of thermal crosstalk and cross-erase, and having good recording characteristics without bleeding of a recording mark in a track direction. Can be.
[Brief description of the drawings]
FIG.
FIGS. 4A and 4B illustrate a method of manufacturing a stamper for an optical disc according to an embodiment of the present invention, in which FIG. 5A is a cross-sectional view illustrating a (photoresist coating and groove forming step), FIG. (C) is a sectional view showing a (nickel film forming step), (D) is a sectional view showing an (electroforming step), and (E) is a sectional view showing a completed nickel stamper.
FIG. 2 is a diagram showing a relationship between a tilt angle of a side surface of a photoresist with respect to a glass plate and a light energy density.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Glass plate (substrate), 2 ... Photoresist, 3 ... Latent image, 4 ... Groove, 5 ... Nickel thin film, 6 ... Nickel electroformed film, 7 ... Stamper for optical discs

Claims (1)

A first step of applying a photoresist on a substrate, irradiating the photoresist with a laser beam having a high Gaussian distribution in the irradiation intensity at the center, and then performing development to form an inverted trapezoidal groove,
By irradiating light having a wavelength band of 380 nm to 450 nm and a light energy density of 30 kJ / m ^{2 to} 50 kJ / m ² , the shrinkage ratio of the photoresist is increased near the substrate from the surface, and the photoresist with respect to the substrate is increased. A second step of steepening the inclination angle of the side surface;
A third step of forming a nickel thin film on the photoresist and on the substrate exposed from the groove,
After forming a nickel electroformed film on the nickel thin film by electroforming, a fourth step of removing the nickel electroformed film from the photoresist together with the nickel thin film,
A method of manufacturing a stamper for an optical disk, comprising:

Images