JP3749520B2 - Manufacturing method of stamper for manufacturing information medium, stamper, and stamper intermediate with master - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a stamper used when manufacturing an information medium such as an optical disc having an uneven pattern such as a groove or a prepit, a manufacturing method of the stamper, a stamper intermediate with a master in the process of manufacturing, and an information medium manufactured by the stamper .
[0002]
[Prior art]
Currently, there are two types of optical discs, which are one type of information medium, an optical recording disc that can be additionally written or rewritten, and a read-only disc on which information is recorded in advance.
[0003]
A groove (guide groove) used for tracking or the like is formed on a disk substrate in the optical recording disk, and a recording layer containing a phase change material or an organic dye material is laminated on the disk substrate. When the recording layer is irradiated with a laser beam, the recording layer undergoes a chemical change or a physical change to form a recording mark. On the other hand, recording marks (information pits) are formed in advance as part of the uneven pattern on the disk substrate of the read-only disk. When these recording marks are irradiated with a reading laser beam, the amount of reflected light fluctuates, and information can be read (reproduced) by detecting this fluctuation.
[0004]
In order to manufacture a disk substrate having a concavo-convex pattern such as a groove or an information pit, a stamper in which this concavo-convex negative pattern (which is also a kind of concavo-convex pattern) is formed in advance is used. For example, a general method is to manufacture a disk substrate by performing injection molding using a mold in which a stamper is fixed in a cavity, and transferring the negative pattern to a filled resin.
[0005]
A stamper having a concavo-convex pattern is usually constituted by a metal plate containing Ni or the like. As a process of manufacturing this stamper, first, a photoresist master having a negative pattern of the uneven pattern of the stamper is prepared in advance, and a metal film is formed on the photoresist master by plating. Thereafter, the metal film is peeled off from the photoresist master, and a predetermined process such as surface cleaning is performed to obtain a stamper.
[0006]
The manufacturing process of the photoresist master 1 will be described with reference to the conventional photoresist master 1 shown in FIG. First, a photoresist layer 4 is formed on the glass substrate 2. Next, the photoresist layer 4 is exposed using a patterning beam such as a laser, and the latent image pattern is developed. As a result, the photoresist master 1 in which the uneven pattern 6 is formed on the photoresist layer 4 is obtained.
[0007]
In order to produce the stamper 20 by plating using the photoresist master 1, as shown in FIG. 8, first, a metal thin film 8 containing Ni material or the like is formed on the surface of the concavo-convex pattern 6 by electroless plating or the like. Then, conductivity is imparted to the photoresist master 1.
[0008]
Thereafter, the metal thin film 8 is energized and plating is performed to form a metal film 10 containing Ni or the like. If the metal thin film 8 and the metal film 10 are peeled off from the photoresist master 1, the stamper 20 to which the concavo-convex pattern 6 is transferred can be obtained.
[0009]
[Problems to be solved by the invention]
In recent years, with the increase in capacity of information media, the concave and convex pattern such as a groove has become finer, and the shape error has a great influence on recording / reading accuracy. Therefore, it is required to form a sharp concavo-convex pattern on the disk substrate. To that end, it is necessary to form the concavo-convex pattern of the underlying photoresist layer 4 with high accuracy (sharpness).
[0010]
The minimum width of the latent image pattern formed on the photoresist layer 4 is limited by the spot diameter of the laser beam reaching the photoresist layer 4. The spot diameter w is represented by w = k · λ / NA where λ is the laser wavelength and NA is the numerical aperture of the objective lens of the irradiation optical system. Note that k is a constant determined by the aperture shape of the objective lens and the intensity distribution of the incident light beam.
[0011]
By the way, even if the pattern has a width that does not logically exceed the limit of the spot diameter, if the photoresist layer 4 is thin, the uneven pattern transferred to the stamper is shallow, or the uneven pattern is rounded. It is known that it will be sharp (this is called “sagging” of the pattern), resulting in insufficient sharpness. This is generally considered to be caused by fluctuations in the thickness of the photoresist layer 4 during exposure / development operations (this is called “film reduction”). This variation in thickness was thought to be caused by the fact that the laser beam was reflected between the photoresist layer 4 and the glass substrate 2 and the photoresist layer 4 was exposed more than necessary by this reflected light.
[0012]
In order to solve this problem, the present inventor has clarified that it is effective to form a light absorption layer between the glass substrate 2 and the photoresist layer 4. In this case, the light absorption layer can absorb the laser beam and suppress light reflection, so that exposure / development can be performed more sharply than in the prior art.
[0013]
However, the present inventor has found through further research that the photoresist master 1 having the light absorption layer has a problem with the formation state of the metal thin film 8 by electroless plating. Specifically, it has been estimated that the photoresist master 1 in which the light absorption layer is partially exposed has a possibility of increasing minute irregularities (minute defects) during the electroless plating process. That is, it has been found that even if an attempt is made to form a metal thin film in the same way, there are cases where minute irregularities (minute defects) may be formed on the irregular pattern surface of the stamper after peeling for some reason. Since the minute irregularities appear as noise during reproduction, there is a problem that even if the light absorption layer is effectively used to increase the recording capacity, the recording / reproducing performance is deteriorated.
[0014]
If this problem is solved, a stamper having a sharp concavo-convex pattern can be manufactured by a photoresist master using a light absorption layer.
[0015]
The present invention has been made in view of the above problems, and a stamper manufacturing method in which fine unevenness is not formed on the uneven pattern surface of the stamper, a stamper manufactured by the manufacturing method, a stamper intermediate with a photoresist master, and It aims at providing the information medium manufactured from these.
[0016]
[Means for Solving the Problems]
The present inventor has intensively studied methods for manufacturing information media such as optical disks and magnetic disks (discrete media), and has devised a method for sharply forming an uneven pattern on a stamper while suppressing surface defects. That is, the above-described object can be achieved by the following invention.
[0017]
(1) At least a light absorption layer and a photoresist layer are formed in this order on a substrate, and a latent image is formed on the photoresist layer by irradiating light from the surface opposite to the surface in contact with the light absorption layer. Forming a concavo-convex pattern by developing the latent image and producing a photoresist master, and forming a metal thin film on the concavo-convex pattern in the photoresist master by a sputtering method or a vapor deposition method; And manufacturing a stamper for manufacturing an information medium, comprising: forming a metal film on the metal thin film; and forming a stamper by peeling the metal thin film and the metal film from the photoresist master. Method.
[0018]
(2) A stamper for manufacturing an information medium in which a concavo-convex pattern is previously formed on the surface, wherein the stamper is manufactured by the manufacturing method described in (1) above.
[0019]
(3) a substrate, a light absorption layer laminated on the substrate, and a photoresist layer laminated in contact with the light absorption layer and capable of forming a concavo-convex pattern by forming a latent image and developing the latent image. A stamper intermediate with a master, in which a metal thin film that forms a part of the stamper when peeled off from the photoresist layer is formed on the surface of the concavo-convex pattern in a photoresist master for manufacturing a stamper, the metal thin film Is a stamper intermediate with a master, characterized by being formed by sputtering or vapor deposition.
[0020]
(4) At least a light absorption layer and a photoresist layer are formed in this order on the substrate, and a latent image is formed by irradiating the photoresist layer with light from the side opposite to the surface in contact with the light absorption layer. Forming a concavo-convex pattern by developing the latent image and producing a photoresist master, and forming a metal thin film on the concavo-convex pattern in the photoresist master by a sputtering method or a vapor deposition method; A step of forming a metal film on the metal thin film, and a step of peeling the metal thin film and the metal film from the photoresist master to form a stamper. An information medium, wherein the final concavo-convex pattern is formed using the concavo-convex pattern as a negative pattern.
[0021]
(5) An information medium according to (4), comprising a final concavo-convex pattern formed by transferring a concavo-convex pattern directly from the stamper.
[0022]
(6) In (4), the final concavo-convex pattern is formed by transferring the concavo-convex pattern of the mother board. The concavo-convex pattern of the mother board is formed by transferring the concavo-convex pattern using the stamper as a master board. An information medium characterized by being made.
[0023]
(7) In (4), the final concavo-convex pattern is formed by transferring the concavo-convex pattern of the child board. The concavo-convex pattern of the child board is formed by transferring the concavo-convex pattern using the stamper as a master board. An information medium formed by transferring a concavo-convex pattern from a mother board.
[0024]
The present inventor presumed that applying a metal thin film forming process, which has been conventionally performed by electroless plating, to a photoresist master having a light absorption layer as it is, causes micro defects on the surface of the concavo-convex pattern. Then, a metal thin film is formed on the photoresist master using the light absorption layer by sputtering or vapor deposition.
[0025]
According to the present invention, micro defects on the surface of the concave / convex pattern of the stamper are drastically reduced. In the case of sputtering or vapor deposition, it is not necessary to pre-process the photoresist master, and the stamper manufacturing process itself can be simplified.
[0026]
Therefore, a sharp concavo-convex pattern can be faithfully transferred to the stamper as compared with the conventional one by the synergistic effect of the advantage of the light absorption layer and the reduction of minute defects by the sputtering method or the vapor deposition method. As a result, even if the concavo-convex pattern is miniaturized, it is possible to maintain a surface state that can withstand such a pattern. By using this stamper, grooves and information pits of information media such as optical disks are sharply formed. Therefore, the recording / reproducing characteristics can be improved. In addition, since it becomes possible to cope with the miniaturization of the uneven pattern which will be developed more and more in the future, the information storage (recording) capacity of the information medium can be increased.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.
[0028]
FIG. 1 shows a photoresist master 100 used in a stamper manufacturing method according to an example of an embodiment of the present invention. The photoresist master 100 includes a glass substrate 102, a light absorption layer 103 laminated on the glass substrate 102, and a photoresist layer 104 laminated on the light absorption layer 103. The photoresist layer 104 is exposed by a patterning laser beam from the opposite side (upper side in FIG. 1) of the light absorption layer 103 to form a latent image of a concavo-convex pattern, and a part of the latent image is removed by developing this latent image. Thus, an uneven pattern 106 is formed. Note that after the development, a part of the light absorption layer 103 is exposed on the bottom surface of the concave portion of the concave-convex pattern 106. Reference numeral 107 in FIG. 1 indicates a non-recessed area, which is an area where the uneven pattern is not formed.
[0029]
As will be described later, the uneven pattern 106 becomes the pattern surface 206 of the stamper 120. Further, the region where the uneven pattern is not formed becomes the mirror surface 207 of the stamper 120.
[0030]
During the exposure, the patterning beam is absorbed by the light absorption layer 103, light reflection is suppressed, and fine irregularities can be formed sharply.
[0031]
FIG. 2A shows a state in which the stamper 120 is formed using the photoresist master 100.
[0032]
In this forming step, first, a Ni thin film 108 is formed on the surface of the concavo-convex pattern 106 by sputtering or vapor deposition. At this point, the master stamper intermediate 118 can be obtained in which the photoresist master 100 and the Ni thin film 108 that is a part of the stamper 120 to be peeled off in a later process are integrated.
[0033]
Thereafter, the surface is energized with the Ni thin film 108 as a base, and the Ni film 110 is formed by electroplating. When the Ni thin film 108 and the Ni film 110 are peeled off from the photoresist master 100, as shown in FIG. 2B, a stamper 120 to which the uneven pattern 106 is accurately transferred can be obtained.
[0034]
In the stamper 120, a pattern surface 206 is formed corresponding to the region of the uneven pattern 106, and a mirror surface 207 is formed corresponding to the non-recessed region 107.
[0035]
Although not particularly illustrated, an optical disk substrate having a final concavo-convex pattern in which the concavo-convex pattern 106 is transferred as a negative pattern is manufactured by, for example, injection molding or the like by installing the stamper 120 in a mold. In addition to manufacturing an optical disk substrate using the stamper 120, a mother board may be created by an electroforming process using the stamper 120 as a master board, and an optical disk may be manufactured using the mother board. Further, a child disk may be created using this mother disk as a master disk, and an optical disk may be manufactured using this.
[0036]
In other words, the stamper 120 in the present invention is not limited to the case where the stamper 120 is actually used directly for manufacturing an optical disk, but is used indirectly for manufacturing an optical disk by creating a mother board or the like as a master disk. It doesn't matter.
[0037]
In the photoresist layer 104 of the example of the present embodiment, a clear latent image can be drawn by laminating the light absorption layer 103, and a sharp uneven pattern 106 can be obtained. In addition, since the metal thin film is formed by the sputtering method or the vapor deposition method, it is possible to form the Ni thin film 108 in which the state of the concavo-convex pattern 106 including the surface defect state is transferred very faithfully. Since almost no surface defects are formed in the concavo-convex pattern 106 formed in the photoresist layer 104, the number of micro defects on the concavo-convex pattern surface transferred to the stamper 120 is also greatly reduced. By using this stamper 120, it is possible to obtain an information medium with high recording / reading (reproduction) accuracy in which noise is suppressed.
[0038]
In the present embodiment, only sputtering or vapor deposition using Ni has been described, but the present invention is not limited thereto, and other metals may be used.
[0039]
The stamper is generally applied not only to optical discs but also to the production of information media including, for example, magnetic discs (discrete media and the like).
[0040]
【Example】
(Example: Stamper No. 1)
After a coupling agent layer was formed on the polished glass substrate, a light absorption layer was formed by spin coating. As the coating solution, SWK-T5D60 (Tokyo Ohka Kogyo Co., Ltd.) containing 4.4'-bis (diethylamino) benzophenone as a light absorber was used. This coating film was baked and cured at 200 degrees for 15 minutes, and the residual solvent was removed to obtain a light absorption layer having a thickness of 140 nm. Next, a photoresist (DVR100 manufactured by Nippon Zeon Co., Ltd.) was spin-coated on the light absorption layer, and the residual solvent was evaporated by baking to obtain a photoresist layer having a thickness of 25 nm.
[0041]
Then, using a cutting machine manufactured by Sony Corporation, the photoresist layer is exposed with a Kr laser (wavelength = 351 nm) and further developed for the purpose of forming a groove pattern with a track pitch of 320 nm and a groove width of 150 nm. A concavo-convex pattern was formed by using a photoresist master.
[0042]
A Ni thin film was formed on the surface of the photoresist layer of this photoresist master by sputtering. Electroplating was performed using this Ni thin film as a base to form a Ni film. The Ni thin film and the laminate composed of the Ni film were peeled off from the master, and back surface polishing and surface cleaning were performed. 1 was obtained.
[0043]
(Comparative example: Stamper No. 2)
Except for the condition that the Ni thin film was formed by electroless plating, the stamper no. The stamper No. 1 was prepared in the same manner as in the production of No. 1. 2 was produced. Specifically, the surface of the photoresist layer of the photoresist master was activated with a surfactant without sputtering, and then a catalyst (Pd, Sn colloid) was applied as a pretreatment for electroless plating. Then Accelerator (HBF ₄ solution) to precipitate Pd on the surface to remove the Sn by, then immersing the photoresist master in NIC1 ₂ bath to form a Ni thin film by electroless plating.
[0044]
(Comparative example: Stamper No. 3)
Except for the condition that there is no light absorption layer, the stamper no. The stamper No. 1 was prepared in the same manner as in the production of No. 1. 3 was produced.
[0045]
(Evaluation result 1)
About the uneven | corrugated pattern formed in each stamper, the shape was confirmed using AFM (atomic force microscope). A silicon nitride (SiN) needle was used as the AFM probe. The measurement was performed in a non-contact mode, and the change in atomic force between the sample and the probe was imaged.
[0046]
In FIG. The AFM image of No. 1 is shown in FIG. Further, in FIG. The AFM image of No. 3 is shown in FIG. In the AFM image, a region with high dot density is a concave portion in the concavo-convex pattern, and a region with low dot density or a white region is a convex portion, corresponding to the convex portion and concave portion of the concavo-convex pattern in the photoresist master, respectively. ing. 3B and 4B, the unevenness is formed at a pitch of 0.32 μm.
[0047]
As is clear from a comparison of FIGS. 3 and 4, the stamper No. manufactured by applying the present invention is shown in FIG. 1 shows that a sharp pattern was formed and that the pattern was faithfully transferred.
[0048]
(Evaluation result 2)
With a scanning electron microscope (10,000 times), the stamper No. 1 and stamper no. FIG. 5 and FIG. 6 show the concavo-convex state in which 2 is measured. From the comparison between FIG. 5 and FIG. No fine irregularities are seen in No. 1, but stamper no. In FIG. 2, it can be seen that minute irregularities are clearly recognized as depressions having a width of about 1 μm around 3 μm and 8.5 μm in the horizontal axis. 5 and 6 is an uneven pattern to be formed in the present invention.
[0049]
【The invention's effect】
In the present invention, a sharp concavo-convex pattern can be formed on the photoresist master by the light absorption layer in contact with the photoresist layer. Further, the concavo-convex pattern is formed on the stamper while suppressing micro defects on the surface by a metal thin film by sputtering or vapor deposition. Can be transferred faithfully.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a photoresist master according to an example of an embodiment of the present invention. FIG. 2A is a cross-sectional view showing a state in the middle of manufacturing a stamper using the photoresist master. FIG. 3A is a cross-sectional view showing the manufactured stamper. FIG. 3A is a view showing a state in which the uneven pattern formed on the stamper according to the embodiment of the present invention is analyzed by AFM. FIG. FIG. 4A is a diagram showing a cross-sectional shape of a concavo-convex pattern based on the analysis. FIG. 4A is a diagram showing a state in which the concavo-convex pattern formed on the stamper according to the comparative example of the present invention is analyzed by AFM. FIG. 5 is a diagram showing a concavo-convex state obtained by measuring the stamper surface of the above-described embodiment with a scanning electron microscope. FIG. 6 is a diagram showing a scan of the stamper surface of the comparative example. Concave measured with electron microscope Diagram showing the state 7 is a sectional view showing a state of manufacturing a stamper using a conventional cross-sectional view showing a photoresist master of Figure 8 a conventional photoresist master EXPLANATION OF REFERENCE NUMERALS
DESCRIPTION OF SYMBOLS 100 ... Photoresist original disk 102 ... Glass substrate 103 ... Light absorption layer 104 ... Photoresist layer 106 ... Irregular pattern 107 ... Non-irregular area 108 ... Ni thin film 110 ... Ni film 118 ... Stamper intermediate 120 with original disc ... Stamper 206 ... Pattern surface 207 ... Mirror surface

Claims (7)

On the substrate, at least a light absorption layer and a photoresist layer are formed in this order, and the latent image is formed by irradiating the photoresist layer with light from the side opposite to the surface in contact with the light absorption layer, A step of forming a concavo-convex pattern by developing the latent image to produce a photoresist master, a step of forming a metal thin film on the concavo-convex pattern in the photoresist master by a sputtering method or a vapor deposition method, and the metal A method for manufacturing a stamper for manufacturing an information medium, comprising: forming a metal film on a thin film; and forming a stamper by peeling the metal thin film and the metal film from the photoresist master. A stamper for manufacturing an information medium in which a concavo-convex pattern is previously formed on a surface, wherein at least a light absorption layer and a photoresist layer are formed in this order on a substrate, and the light absorption layer and the light absorption layer are formed on the photoresist layer. A step of forming a latent image by irradiating light from the opposite surface side of the contacting surface, and developing the latent image to form a concave / convex pattern, and manufacturing the photoresist master, and the concave / convex pattern in the photoresist master A step of forming a metal thin film by sputtering or vapor deposition, a step of forming a metal film on the metal thin film, and a step of separating the metal thin film and the metal film from the photoresist master to form a stamper And a stamper characterized by being manufactured through A stamper having a substrate, a light absorption layer laminated on the substrate, and a photoresist layer laminated in contact with the light absorption layer and capable of forming a concavo-convex pattern by forming a latent image and developing the latent image A stamper intermediate with a master, in which a metal thin film that forms a part of a stamper when peeled off from the photoresist layer is formed on the surface of the concave / convex pattern in a photoresist master for use, wherein the metal thin film is sputtered Alternatively, a stamper intermediate with a master, which is formed by a vapor deposition method. On the substrate, at least a light absorption layer and a photoresist layer are formed in this order, and the latent image is formed by irradiating the photoresist layer with light from the side opposite to the surface in contact with the light absorption layer, A step of forming a concavo-convex pattern by developing the latent image to produce a photoresist master, a step of forming a metal thin film on the concavo-convex pattern in the photoresist master by a sputtering method or a vapor deposition method, and the metal A step of forming a metal film on the thin film, and a step of forming a stamper by peeling the metal thin film and the metal film from the photoresist master, and forming an uneven pattern of the metal thin film and the metal film in the stamper manufactured An information medium, wherein a final uneven pattern is formed as a negative pattern. 5. The information medium according to claim 4, further comprising a final concavo-convex pattern formed by transferring the concavo-convex pattern directly from the stamper. 5. The final uneven pattern according to claim 4, wherein the final uneven pattern is formed by transferring an uneven pattern of a mother board, and the uneven pattern of the mother board is formed by transferring an uneven pattern using the stamper as a master board. An information medium characterized by being. 5. The final concavo-convex pattern is formed by transferring a concavo-convex pattern of a child board, and the concavo-convex pattern of the child board is a mother formed by transferring the concavo-convex pattern using the stamper as a master board. An information medium formed by further transferring a concavo-convex pattern from a board.

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