JP2004334939A - Method for manufacturing stamper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent formation of defects caused by pit drop-off when a stamper is manufactured by peeling off an Ni peel film from an Si substrate in a method for manufacturing the stamper for a high-density optical disk. <P>SOLUTION: A thin film 102 is formed on a substrate 101. An electron beam resist film is formed on the thin film 102, the resist film is irradiated with an electron beam and the resist film is exposed, and the resist film is developed by developer. Using the developed resist film as a mask, the thin film 102 is subjected to reactive ion etching to form an irregular pattern on the thin film 102. A peel film 104 made of a material whose expansion rate is larger than that of the thin film 102 is formed on the thin film 102. The thin film 102 and the peel film 104 are cooled with a coolant such as liquid nitrogen or liquid helium, and the peel film 104 is peeled off from the substrate 101 to manufacture a stamper. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to, for example, a method of manufacturing a stamper used in a process of manufacturing an optical recording medium.
[0002]
[Prior art]
Substrates used for optical disks such as CDs (Compact Discs) and DVDs (Digital Versatile Discs) are mass-produced by compression molding or injection molding using a molding die called a stamper. Hereinafter, a method of manufacturing the stamper will be described.
[0003]
First, an ultraviolet-sensitive positive type photoresist is uniformly applied on a glass master having a thickness of several mm by spin coating. At this time, the rotation of the glass master is controlled so that the thickness of the photoresist becomes about 0.1 μm. Then, while rotating the glass master, the resist applied to the glass master is irradiated with laser light in the blue or ultraviolet region (wavelength: 350 nm to 460 nm) focused by an objective lens. At this time, the laser beam is turned on / off as appropriate to expose the resist to a desired pattern. Note that a gas laser such as an Ar or Kr laser is used as the laser.
[0004]
Thereafter, the resist is developed with a developer. As a result, a resist master having a pit or groove-shaped fine uneven pattern is formed. In a positive photoresist generally used in a process of manufacturing a resist master, a portion irradiated with laser light is exposed and dissolved in a developing solution, so that a concave pit shape can be obtained. Then, Ni plating having a thickness of several 100 μm is applied to the surface of the resist master having the unevenness. Thereafter, the Ni plating is peeled from the resist master. As a result, a Ni master stamper (molding die) having a thickness of several 100 μm is manufactured.
[0005]
For example, in a stamper for manufacturing a DVD-ROM (Digital Versatile Disc-Read Only Memory), information signal pits having a shortest pit length of 0.4 μm are formed spirally at a track pitch of 0.74 μm. By manufacturing a substrate having a diameter of 12 cm using this stamper, a recording capacity of 4.7 GB can be realized in a DVD-ROM (single-sided recording). For laser drawing (cutting), for example, a Kr (ion) laser that emits laser light having a wavelength of 413 nm is used.
[0006]
The shortest pit length P that can be cut, that is, the resolving power, generally depends on the wavelength λ of the laser beam, the NA (numerical aperture) of the objective lens, and the process factor K (0.8 to 0 depending on the resist characteristics and the like). .9) and
P = K · (λ / NA) (1)
Is approximately represented by For example, by substituting the wavelength λ = 413 nm, the numerical aperture NA = 0.9, and the process factor K = 0.8 into this equation (1), the shortest pit length P = 0.37 μm is obtained. This is a value that satisfies the shortest pit length of 0.4 μm in the DVD-ROM described above.
[0007]
By the way, with the rapid progress of information communication and image processing technology in recent years, it has been required to realize an optical disk having a recording capacity several times that of a conventional optical disk. For example, in order to achieve a recording capacity of 25 GB on one side of an optical disk having a diameter of 12 cm while maintaining a signal processing method similar to that of a DVD, the shortest pit length is reduced to 0.15 μm and the track pitch is reduced to about 0.32 μm. Need to be Also, the pit width needs to be about 1/3 of the track pitch, for example, about 0.1 μm.
[0008]
In order to form such fine pits, it is necessary to shorten the wavelength of the laser beam and increase the NA of the objective lens, as can be seen from the above equation (1). However, the NA value of the objective lens is almost at its current value of 0.9 from the viewpoint of lens manufacturing accuracy. Therefore, formation of fine pits by shortening the wavelength of laser light has been studied.
[0009]
However, it is difficult to achieve the shortest pit length and pit width that enable the above-mentioned 25 GB capacity only by shortening the wavelength of the laser beam. For example, even when far-ultraviolet laser light having a wavelength λ = 250 nm is used, according to the above equation (1), the shortest pit length P is 0.22 μm (where K = 0.8 and NA = 0.9). ), And the desired shortest pit length of 0.15 μm cannot be realized.
[0010]
As described above, it is very difficult to manufacture a resist master for manufacturing a high-density optical disk having a capacity of 25 GB using a conventional laser cutting apparatus using an ultraviolet laser as a light source. Therefore, in recent years, a manufacturing method of exposing a resist using an electron beam drawing apparatus (EBR; Electron Beam Recorder) has been proposed. In this electron beam writing apparatus, a beam finer than a light beam can be obtained.
[0011]
Conventionally, this electron beam writing apparatus has been used for pattern writing of a photomask or direct writing on a wafer in the semiconductor field, but with the recent rapid increase in the density of optical disks, fine pits or fine pits are formed on an optical disk master. It is also used for patterning grooves and the like.
[0012]
In fact, it has been reported that a glass disk having good signal characteristics can be manufactured by a manufacturing method using this electron beam writing apparatus. In the manufacturing method according to this report, a pit pattern of a ROM disk having a capacity of 25 to 30 GB is first drawn on an electron beam resist applied to a master (silicon substrate) using an electron beam drawing apparatus. Then, the resist is developed with a developer to produce a resist master. Thereafter, a Ni master stamper is manufactured from the resist master by a Ni plating process similar to the conventional one. Finally, a glass disk is manufactured from the Ni master stamper by a replication process using a photopolymer. Since a positive type resist is used for the resist as in the case of the conventional cutting by the ultraviolet laser, a portion irradiated by the electron beam is dissolved in the developing solution to form a concave pit pattern. That is, in the Ni master stamper, the pit pattern is convex.
[0013]
However, in the manufacturing method using the above-described electron beam drawing apparatus, it is easy to experimentally produce a glass disk having good signal characteristics, but a substrate made of a plastic resin having good signal characteristics is used. It is difficult to mass-produce by injection molding. This is because when the substrate is actually injection-molded using a plastic resin, the transferability of the pits in the injection molding process is deteriorated. In general, pits formed by electron beam writing have a very sharp and nearly vertical edge shape compared to pits formed by conventional ultraviolet laser writing. It is very difficult to transfer such a very sharp pit to a substrate by injection molding. Further, the pits are miniaturized and become extremely high density, which also causes deterioration of pit transferability of injection molding.
[0014]
In view of such a situation, a method of manufacturing a stamper using reactive ion etching (RIE) has been proposed. In this manufacturing method, first, a resist for an electron beam uniformly applied to a Si master is drawn by an electron beam and developed by a developing solution. Then, the Si master is subjected to reactive ion etching using the developed resist as a mask. Then, the etched Ni master is plated with Ni, and the Ni plating is peeled off to produce a Ni master stamper. In this manufacturing method, the pit shape obtained by the etching, that is, the edge angle can be easily controlled by adjusting the etching gas and the etching conditions (RF power, pressure, etc.) when performing the reactive ion etching. . That is, a stamper having an appropriate pit shape can be manufactured in consideration of the transferability of the stamper in the subsequent injection molding process.
[0015]
[Problems to be solved by the invention]
However, when the present inventor produced a Ni master stamper having a thickness of about 0.3 mm using the master on which pits were formed by reactive ion etching, when the Ni master stamper was peeled off from the Si master, Then, they came to find out the problem that the fine pit portions collapsed and separated from the surface of the Ni master stamper. This is because when a convex pit portion made of Ni having relatively low hardness is peeled from a concave pit portion made of Si having high hardness, a large stress is applied momentarily and locally, and the convex pit portion is broken. It is thought to be.
[0016]
In the conventional laser cutting using ultraviolet light, when the Ni master stamper is peeled off from the master having pits made of photoresist, the resist adheres to the Ni master stamper side. I never did. This is because the photoresist is softer than Ni, so that a large stress is not applied locally, and the resist is carried to the stamper side at the time of peeling, and a large force is not required at the time of peeling unlike the Si master. That's why.
[0017]
Therefore, an object of the present invention is to prevent a defect from being formed due to pit dropout when a Ni master stamper is separated from a Si master in a method for manufacturing a stamper for a next-generation high-density optical disk. An object of the present invention is to provide a method for manufacturing a stamper.
[0018]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a first invention of the present application is a step of forming a concavo-convex pattern on a thin film laminated on one main surface of a substrate,
Forming a release film made of a material having a higher coefficient of expansion than the material constituting the thin film on the concave / convex pattern;
At least cooling the thin film and the release film, and peeling the release film from the thin film to produce a stamper.
[0019]
According to the first aspect of the present invention, a concavo-convex pattern is formed on a thin film laminated on one principal surface of a substrate, and a release film made of a material having a larger expansion coefficient than the material constituting the thin film is formed on the concavo-convex pattern. Then, at least the thin film and the release film are cooled, and the release film is separated from the thin film. Therefore, after a gap is formed between the thin film and the release film, the release film can be separated from the thin film.
[0020]
The second invention of the present application includes a step of forming a concavo-convex pattern on one main surface of the substrate;
Forming a release film made of a material having a higher expansion coefficient than the material forming the substrate on the concave / convex pattern;
Cooling the substrate and the release film, and removing the release film from the substrate to produce a stamper.
[0021]
According to the second aspect of the present invention, a release film made of a material having a higher expansion coefficient than the material constituting the substrate is formed on the concave / convex pattern formed on one main surface of the substrate, and the substrate and the release film are cooled. Since the separation film is separated from the substrate, the separation film can be separated from the substrate after a gap is formed between the substrate and the separation film.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, an electron beam writing apparatus used in the method for manufacturing a stamper according to the first embodiment of the present invention will be described.
[0023]
FIG. 1 shows an example of the configuration of an electron beam writing apparatus. As shown in FIG. 1, the electron beam writing apparatus mainly includes an electron beam column 1 and a mechanical unit 2 installed in a vacuum chamber 3. This electron beam lithography apparatus is mounted on a vibration isolation table 4 in order to eliminate external vibrations at the installation location. It should be noted that a computer control device that performs beam-related control for turning on / off the electron beam and adjusting the focused beam size and the like and control of the mechanism unit 2 is omitted from the drawing.
[0024]
The electron beam column 1 has a cylindrical shape. In the electron beam column 1, an electron gun 11, a condenser lens 12, a blanking electrode (beam modulator) 13, an aperture 14, a beam deflection electrode 15, a focus adjustment lens 16 And an objective lens 17.
[0025]
The electron gun 11 includes a thermal field emission type electron beam source made of a material ZrO / W, an anode for accelerating electrons emitted from the electron beam source at several tens of kV, and the like. Electrons emitted from the electron gun 11 are focused by a condenser lens 12 which is an electrostatic lens, and pass between blanking electrodes 13. The blanking electrode 13 turns on / off the electron beam emitted from the electron beam column 1 under the control of a computer controller (not shown). Specifically, when a voltage is applied between the blanking electrodes 13, the irradiation electron beam is largely deflected, deviates from the aperture 14, and the electron beam emitted from the electron beam column 1 is turned off.
[0026]
The electron beam that has passed between the blanking electrodes 13 is narrowed by the aperture 14 and passes between the beam deflection electrodes 15. The beam deflection electrode 15 deflects the electron beam passing between the beam deflection electrodes 15 under the control of a computer controller (not shown). The electron beam passing between the beam deflection electrodes 15 is collected by an objective lens 17 which is an electrostatic or electromagnetic lens. Thus, the resist film 103 formed on the substrate 101 is irradiated with a spot having a diameter of about several tens nm.
[0027]
Further, the mechanism section 2 includes a spindle motor 21 configured to be capable of chucking the substrate 101 on an upper portion, and an air slide 22 on which the spindle motor 21 is mounted. The spindle motor 21 is configured to be able to rotate with high accuracy and high speed, and the rotation speed is controlled by a servo mechanism using an optical rotary encoder. The air slide 22 is configured to be drivable in the radial direction of the substrate 101 with a feed accuracy of several nm.
[0028]
Next, a method for manufacturing a stamper according to the first embodiment of the present invention will be described. 2 and 3 show respective manufacturing steps of the method of manufacturing the stamper according to the first embodiment. Hereinafter, a method of manufacturing the stamper according to the first embodiment will be described with reference to FIGS.
[0029]
First, as shown in FIG. 2A, a thin film 102 is formed on a substrate 101 by, for example, a thermal oxidation method. Here, the substrate 101 is made of, for example, Si. The thin film 102 is, for example, an oxide film having a thickness of several 100 nm, and the material of the oxide film is, for example, SiO ₂ .
[0030]
Next, as shown in FIG. 2B, a resist for an electron beam is uniformly applied on the thin film 102 by, for example, a spin coating method. Thus, a resist film 103 having a thickness of, for example, 80 nm is formed on the thin film 102. As the resist for the electron beam, a positive resist is selected. Here, a case where a positive resist is used will be described as an example, but it goes without saying that a negative resist can also be used.
[0031]
Next, the substrate 101 is placed on a turntable provided above the spindle motor 21 of the electron beam writing apparatus. Then, while the substrate 101 is being rotated at a high speed, the focused electron beam is concentrically or spirally spot-irradiated onto the electron beam resist film 103 applied on the substrate 101.
[0032]
Next, the resist film 103 is developed with, for example, an alkaline aqueous solution or a dedicated developer. As a result, as shown in FIG. 2C, the portion irradiated with the electron beam is dissolved, and a mask having a desired resist pattern is formed on the thin film 102.
[0033]
Next, as shown in FIG. 2D, the thin film 102 is subjected to, for example, reactive ion etching with a resist-based film 103 as a mask using a Freon-based gas such as CF ₄ or CHF ₃ or a chlorine-based gas such as Cl ₂ . By this etching, for example, a concave portion having a depth of about 80 nm is formed in the thin film 102. It is preferable that etching conditions such as an etching gas, an RF (Radio Frequency) power, and a pressure be appropriately adjusted in consideration of a pit inclination angle. By appropriately adjusting the etching conditions in this manner, the inclination angle of the pit can be relaxed even when the resist pattern is nearly 90 degrees. In consideration of the subsequent steps, it is preferable to reduce the inclination angle of the pit after etching to about 70 degrees.
[0034]
Next, the resist film 103 is removed. Thereby, as shown in FIG. 3A, a substrate 101 having a pit pattern on the thin film 102 can be obtained. When a positive resist is used, a substrate 101 having a concave pit pattern on the thin film 102 can be obtained.
[0035]
Next, as shown in FIG. 3B, a metal is deposited on the thin film 102 by, for example, an electroforming method. Thus, a release film 104 having a thickness of, for example, about 300 μm is formed on the thin film 102. As a material for forming the peeling film 104, a material having a higher expansion coefficient than the material for forming the thin film 102 is selected, and for example, Ni is selected.
[0036]
Next, the substrate 101 and the release film 104 are cooled by a coolant such as liquid nitrogen or liquid helium. Thereby, a gap is formed between the substrate 101 and the release film 104. The degree to which the pit portion (convex portion) of the peeling film 104 contracts more than the pit portion (concave portion) of the substrate 101 due to cooling can be easily obtained by calculation using the coefficient of thermal expansion. For example, when the pit width is 100 nm, when the substrate 101 made of Si and the release film 104 made of Ni are cooled from room temperature 22 ° C. (295 K) to a low temperature of −196 ° C. (77 K) with liquid nitrogen, the release film 104 The width of the pit (convex) shrinks by about 1.2 nm more than the width of the pit (concave) of the substrate 101. The expansion coefficients of Ni and SiO ₂ are 5.3 × 10 ⁻⁵ / K and 5.5 × 10 ⁻⁷ / K, respectively.
[0037]
Next, as shown in FIG. 3C, the separation film 104 is separated from the substrate 101. Thereby, a master stamper is formed. Then, a metal such as Ni is laminated on the surface of the master stamper on which the irregularities are formed by, for example, electroforming. Thereby, a metal film is formed on the master stamper. Thereafter, the metal film is peeled from the master stamper. Thus, a mother stamper having irregularities opposite to the master stamper is formed.
[0038]
Next, a metal such as Ni is laminated on the surface of the mother stamper on which the irregularities are formed by, for example, electroforming. As a result, a metal film is formed on the mother stamper. Thereafter, the metal film is peeled from the mother stamper. As a result, a target stamper having irregularities opposite to that of the mother stamper is formed.
[0039]
According to the above-described first embodiment of the present invention, the following effects can be obtained.
An uneven pattern is formed on the thin film 102 laminated on one main surface of the substrate 101, and a release film 104 made of a material having a higher expansion coefficient than the material forming the thin film 102 is formed on the uneven pattern. Since at least the separation film 104 is cooled and the separation film 104 is separated from the thin film 102, the separation film 104 can be separated from the thin film 102 after a gap is formed between the thin film 102 and the separation film 104. Thereby, when manufacturing a stamper for a high-density optical disk, it is prevented that the pits (concave portions) of the thin film 102 bite into the pits (convex portions) of the release film 104 and the pit portions of the release film 104 fall off. be able to. That is, defects generated when the release film 104 is separated can be prevented. Further, the separation film 104 can be smoothly separated from the thin film 102. Further, a stamper for a high-density optical disk can be manufactured with high yield.
[0040]
Further, a gap is formed between the thin film 102 and the release film 104 due to a difference in the coefficient of thermal expansion (shrinkage) between the material forming the thin film 102 and the material forming the release film 104. When the peeling film 104 is peeled off, the local stress applied to the pits is reduced, and a master stamper having almost no defects due to pits falling off can be manufactured.
[0041]
Further, even when the aspect ratio of the pit is high, when the peeling film 104 is peeled from the thin film 102, the pit portion (convex portion) of the peeling film 104 may be significantly collapsed or separated to cause a defect. Can be prevented. In other words, a stamper having desired pits and other irregularities can be formed.
[0042]
Next, a second embodiment of the present invention will be described. In the second embodiment, first, a resist film for an electron beam is formed on a substrate, and the resist film is exposed by irradiating the resist film with an electron beam. Next, the resist film is developed using a dedicated developer or the like. The substrate is etched using the developed resist film as a mask to form an uneven pattern on one main surface of the substrate. On this concavo-convex pattern, a release film made of a material having a higher expansion coefficient than the material constituting the substrate is formed. Next, the release film and the substrate are cooled by a coolant such as liquid nitrogen or liquid helium, and the release film is separated from the substrate to produce a master stamper. After that, a stamper is manufactured in the same manner as in the manufacturing method according to the first embodiment.
[0043]
As described above, the first and second embodiments of the present invention have been specifically described. However, the present invention is not limited to the above-described first and second embodiments. Various modifications are possible.
[0044]
For example, the numerical values given in the first and second embodiments are merely examples, and different numerical values may be used as needed.
[0045]
In the first and second embodiments described above, an example in which the present invention is applied to the method of manufacturing a stamper having a pit pattern has been described. However, the method of manufacturing a stamper having a wobbled guide groove or the like is described. However, it goes without saying that the present invention is applicable.
[0046]
【The invention's effect】
As described above, according to the present invention, the substrate and the release film are cooled, and the release film is released from the substrate. Therefore, a gap is created between the substrate and the release film, and the release film is released from the substrate. be able to. Thereby, it is possible to prevent a defect from occurring at the time of peeling of the peeling film. Therefore, the stamper can be manufactured with high yield.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an example of a configuration of an electron beam writing apparatus according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view for explaining a method of manufacturing a stamper according to the first embodiment of the present invention.
FIG. 3 is a cross-sectional view for explaining the method of manufacturing the stamper according to the first embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Electron beam column, 2 ... Mechanical part, 3 ... Vacuum tank, 4 ... Vibration isolation table, 11 ... Electron gun, 12 ... Condenser lens, 13 ... Blanking Electrode, 14: aperture, 15: beam deflection electrode, 16: focus adjustment lens, 17: objective lens, 21: spindle, 22: air slide, 101: substrate, 102: silicon oxide film, 103: electron beam resist film, 104: metal film

Claims (4)

Forming a concavo-convex pattern on a thin film laminated on one main surface of the substrate,
Forming a release film made of a material having a higher expansion coefficient than the material constituting the thin film on the uneven pattern;
At least cooling the thin film and the release film, and separating the release film from the thin film to produce a stamper. 2. The method according to claim 1, wherein the thin film and the release film are cooled by liquid nitrogen or liquid helium. A step of forming an uneven pattern on one main surface of the substrate,
A step of forming a release film made of a material having a higher expansion coefficient than the material constituting the substrate on the uneven pattern;
Cooling the substrate and the release film, and separating the release film from the substrate to produce a stamper. 4. The method according to claim 3, wherein the substrate and the release film are cooled by liquid nitrogen or liquid helium.

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