JP2002367242A - Stamper for making optical recording medium and method of manufacturing for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stamper for making optical recording media which utilizes a negative type resist permitting the pattern exposure suitable for a higher recording density, eliminates the need for a transfer process step to a stamper for molding and is excellent in productivity. SOLUTION: The stamper for making the optical recording media for producing the optical recording medium having fine rugged patterns is constituted by providing the stamper with a substrate having a smooth main surface and fine rugged pattern layer which is different etching property from the substrate and has the uniform thickness corresponding to the depth of the fine rugged patterns and is subjected to the pattern etching corresponding to the fine rugged patterns on the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a CD (Compact Diode).
sc), DVD (Digital Versatile Disc), phase change type recording medium, stamper for producing optical recording media used for producing various optical recording media having fine irregularities such as pits and grooves formed on the substrate surface such as magneto-optical recording media And its manufacturing method.

[0002]

2. Description of the Related Art In recent years, demands for large-capacity recording on small-diameter discs and long-time recording of high definition (HD) images have been increasing, and optical recording media such as optical discs have been required to have higher densities. .

An optical recording medium having fine irregularities such as pits and grooves on a substrate surface is usually manufactured by injection molding using a stamper having inverted fine irregularities corresponding to the fine irregularities described above. This is based on a method for manufacturing a substrate that forms an optical recording medium having irregularities.

[0004] Alternatively, for example, an ultraviolet curable resin is applied on an optical recording medium substrate, and the above-described stamper is pressed on the resin layer to form desired fine irregularities, that is, a so-called 2.
A production method by a P (Photo-Polymerization) method is adopted.

[0005] In order to manufacture this stamper, a master on which fine irregularities are formed is usually manufactured, and a stamper is manufactured using the master, a so-called mastering process.

In the mastering process, that is, in the process of producing a master of a substrate of an optical recording medium such as a disk, fine irregularities are formed on the master substrate coated with a photoresist by exposure and development. In this photoresist master,
As described above, with the miniaturization of fine irregularities, a further reduction method of exposure and development of a photoresist has been an issue.

An example of such a photolithography technique will be described with reference to FIGS. First, as shown in FIG. 4A, a master substrate 71 made of glass or the like whose surface is polished flat and washed is prepared, and as shown in FIG. 4B, for example, as shown in FIG. The resist 72 is formed to a thickness of about 50 to
It is applied as 100 nm.

[0008] Then, as shown in FIG.
1 is rotated as indicated by an arrow a, and the recording light L having undergone intensity modulation in accordance with the recording signal is condensed on the surface of the photoresist 72 by the objective lens 73 to perform pattern exposure. At this time, for example, a spiral latent image 74 is formed by relatively moving the position of the master substrate 71 and the objective lens 73 in the radial direction of the substrate 71.

Thereafter, by developing the exposed photoresist 72, the exposed area is dissolved to form fine unevenness, as shown in FIG. 4D, a groove 76 in the illustrated example. Reference numeral 75 denotes a land between the grooves 76.

Next, a plating layer 78a is adhered and formed thereon by, for example, nickel plating, and the plating layer 78a is peeled off, whereby a stamper 78 made of nickel to which a reverse pattern of the concavo-convex pattern formed by the photoresist is transferred.
To form The thickness of the stamper 78 is 0.3
About 0.5 mm.

[0011] Nickel plating uses an electroplating method with a high plating growth rate. In this case, as a pretreatment for imparting conductivity to the substrate surface in advance, the surface is formed by a sputtering method or an electroless plating method in which nickel is deposited by a chemical reaction. Is given electrical conductivity and then nickel electroplated.

Then, the stamper 78 thus formed is placed in a cavity of a mold, and a disk-shaped substrate 80 made of a light-transmitting resin having desired fine irregularities is formed by injection molding or the like. I do.

Alternatively, using the stamper 78,
A similar substrate 80 is formed by the P method.

On this substrate 80, for example, a reflective layer, a recording layer made of a magneto-optical or phase-change material, a protective layer, and the like are successively deposited to form a light having a fine uneven pattern such as pits and grooves. A recording medium can be formed.

FIG. 5A shows a disk-shaped optical recording medium produced in this manner. On the surface of a substrate 80, a signal recording surface 81 provided with pits, grooves, and the like is formed. FIG.
B is an enlarged view of the groove 76, and p indicates a track pitch. FIG. 5C shows an enlarged view of the pit 77.

Incidentally, in a manufacturing site where such optical recording media are mass-produced, a plurality of stampers for forming the disk substrate 80 are often required. As a method of obtaining a plurality of stampers from a single stamper 78, a so-called master, a stamper is formed by transferring from the stamper using a nickel electroplating method in the same manner as in a normal process.
A transfer process called an MS (Master-Mother-Son) process is generally performed.

FIGS. 6A to 6E show such a transfer step. First, as shown in FIG. 6A, a stamper 8 on which, for example, a pit pattern 77n and a land pattern 75n are formed is prepared, this is used as a master stamper, and this is transferred to form a mother stamper. That is, FIG.
As shown in B, the nickel layer is oxidized with, for example, dichromic acid to form a peeling layer 82.

Thereafter, as shown in FIG. 6C, a plating layer 83a is formed by electroplating in the same manner as in the step of manufacturing the stamper 78, and as shown in FIG. 6D, the plating layer 83a is peeled off to form a mother stamper 83. I do. The fine concavo-convex pattern of the mother stamper 83 is a pattern inverted from the fine concavo-convex pattern of the stamper 78. Thus, a plurality of mother stampers 83 can be obtained from one master stamper.

Similarly, a release layer 84 is formed on the mother stamper 83, and then a plating layer is formed by an electroplating method and then separated, thereby forming a stamper 85 used for manufacturing a substrate, a so-called grandchild stamper. (Or sun stamper).

In the above pattern exposure step, a method of condensing a laser beam with an objective lens and exposing a photoresist on a master substrate is generally employed. FIG. 7 shows an example of such an optical recording apparatus.

In FIG. 7, reference numeral 20 denotes a light source such as a gas laser.
After passing through the analyzer 22, it is partially reflected by the beam splitter 23. The laser light transmitted through the beam splitter 23 is detected by a photodetector 24 and input to a recording light power control circuit 25. In the recording light power control circuit 25, it is compared with the comparison voltage Ref and fed back to the modulator 21. Reference numeral 40 denotes a control unit.

The laser beam reflected by the beam splitter 23 enters the modulator 41. In the modulation unit 41,
The laser light is condensed by a lens 26, and AOM
An AO modulator 27 composed of (Acousto-Optic Modulator) is arranged. This AO modulator 2
The ultrasonic wave S corresponding to the recording signal is input to 7, and the intensity of the laser beam is intensity-modulated based on the ultrasonic wave. The laser light is diffracted by the diffraction grating of the AO modulator 27, and only the first-order diffracted light of the diffracted light is transmitted through the slit.

The intensity-modulated first-order diffracted light is transmitted through a lens 2
After being condensed by 8, the light is reflected by the beam splitter 29, passes through the 波長 wavelength plate 30, and enters the lenses 31 and 32 of the expander unit 42. Here, for example, the focal length of the lens 31 is
Assuming that f4, the magnification is enlarged as Me (= f4 / f3), and further focused by the objective lens 33 on the surface of the photoresist 72 on the master substrate 71, and exposure corresponding to a predetermined pattern is performed.

[0024]

The size and shape of the fine concavo-convex pattern of the photoresist formed by exposure and development by the above-mentioned optical recording apparatus are condensed by the objective lens 33 in the above-mentioned optical recording apparatus. It is almost equivalent to the spot shape of laser light. Therefore, the higher the spot size, the higher the recording density.

Here, since the spot diameter φ is given by φ = 1.22 · (λ / NA) from the wavelength λ and the numerical aperture NA of the objective lens, as described above, the blue laser is used as the recording light source. The use of a shorter wavelength has been the key to higher recording density.

In the early days of optical recording media such as CDs, a blue light source having a wavelength of about 400 nm was used as recording light. At present, however, an ultraviolet light source having a wavelength of about 350 nm is mainly used. Practical use of a deep ultraviolet light source is also being studied.

However, a light source with a shorter wavelength than this has not been obtained at present, and the numerical aperture NA of the objective lens is generally about 0.9, which is almost close to the theoretical limit (<1.0). Because of its use, the limit of recording density is beginning to be seen in conventional laser exposure.

On the other hand, as a method for easily obtaining a finer spot system for recording a higher density optical recording medium in the future, it has been proposed to expose a resist with an electron beam instead of light. .

As the next-generation lithography technology for semiconductors, the development of this electron beam sensitizing technology has been advanced, and the application to optical recording media has a short history.
Since the processes other than the exposure can be performed in the same manner as in the past, it is highly likely that the technology will become a mainstream technology in the near future.

FIG. 8 briefly describes the structure of an example of such an electron beam drawing apparatus. This electron beam drawing apparatus 50
The upper electron beam generation / convergence unit 51 and the lower mechanism unit 5
2 and rests on a vibration isolation table 53 for removing external vibrations at the installation location.

The electron beam is emitted from a thermionic beam gun 54 made of LaB ₆ or the like, and is several kV to 100 kV by the anode.
The electrons accelerated by the above are converged by the condenser lens 55 composed of an electrostatic lens, are modulated by the beam modulator 56, and reach the aperture 57.

After the electron beam narrowed by the aperture 57 passes through the beam deflection electrode 58, a resist 61 for an electron beam is applied by a focus adjusting lens 59, which is an electrostatic or electromagnetic lens, and an objective lens 60. A resist 61 for an electron beam is focused on a substrate 71 made of glass or the like and focused on a submicron spot size.

The beam modulating section 5 above the aperture 57
Reference numeral 6 comprises a blanking electrode and the like, and serves to turn on and off the irradiation electron beam. That is, when a voltage is applied between the electrodes, the beam is largely deflected, and the aperture 5
7 and is turned off.

A voltage is also applied to the beam deflecting electrode 58 to deflect the beam. This is so-called wobbling, in which the irradiation beam is deflected on the resist surface in the order of nm to μm on the resist surface. Used for The objective lens 60 focuses the electron beam irradiated on the resist surface and narrows it down to a spot having a size of several nm to several μm.

In the mechanism section 52, an air spindle 62 holding a master substrate 71 is mounted on a slide 63, and the electron beam generating / focusing section 5 including the above-described electron gun 54 is provided.
1 and is mounted on the anti-vibration table 53.

The air spindle 62 has a high rotational accuracy of 3
High-speed rotation of about 600 rpm is possible, and the rotation speed is controlled by a servo mechanism using an optical rotary encoder with a rotation jitter of 10 ⁻⁷ or less (per rotation).

The slide speed of the slide 63 is controlled by using a linear motor type air slide or the like.
It can be precisely controlled by a length measuring mechanism using a laser scale mounted on the slide 63, and can be moved, for example, in the radial direction of a disk-shaped optical recording medium with a feeding accuracy of several nm. The master substrate 71 is moved to the air spindle 6
By moving the recording spot by the same distance per rotation in the radial direction while rotating with high accuracy by 2,
A latent image of a groove or a pit can be accurately formed in a spiral shape or concentric shape at a fixed track pitch.

Since the electron beam is scattered by collision with other atoms and molecules during propagation and has a spread or suffers an energy loss, it is usually necessary to keep the inside of the electron beam lithography apparatus 50 at a high vacuum. There is. The electron beam generating / focusing unit 51 requires an ultra-high vacuum of 10 ⁻⁶ Pa or less near the electron gun 54, and a vacuum degree of about 10 ⁻³ Pa near the objective lens 60 and the mechanism unit 52.

There has been reported an example in which mastering of a high-density optical disc, that is, fabrication of a substrate, was performed by the above-described electron beam drawing apparatus 50 (JAPANESE JOURNAL OF APPLIED PH).
YSICS / April 1998 / Vol.37 No.4B / P.2137-2143 / Article name "High Density Mastering Using Electron Beam" / Author Yoshiaki Kojima etc.).

According to this report, the surface density is about 6.4 times that of the current DVD (30 GB capacity on one side of CD = 21).
(Equivalent to Gbit / inch ² ). The signal uses the same EFM + signal as the DVD, and the shortest pit length is 0.16 μm and the track pitch is 0.29
μm. In addition, the half value width of the spot diameter of the electron beam was 80 nm.

In the conventional pattern exposure using a laser beam,
The spot half width cannot be narrowed down to about 165 nm, which is about twice as large. Therefore, it is expected that a method using an electron beam lithography apparatus will be the mainstream in producing a fine concavo-convex pattern in order to increase the recording density of an optical recording medium in the future.

However, pattern exposure by electron beam drawing has the following problems. In general, there are two types of photoresist, a "positive type" in which exposed areas are soluble in an alkaline developer and a "negative type" in which exposed areas are insoluble in an alkaline developer. The laser used in conventional laser exposure is advantageously a positive type in terms of resolution, and a negative type resist has not been used when producing an optical recording medium. However, for pattern exposure by electron beam lithography, a practical negative resist having a high resolution equal to or higher than that of a positive type (for example, "NEB series" of Sumitomo Chemical Co., Ltd.)
Exists.

However, when a negative resist is used,
The fine concavo-convex pattern formed on the resist, especially the shape of the pit, is concave in the stamper because the concavo-convex is inverted from the positive type. Therefore, after exposure and development, in the same mastering process as usual, that is, in the process of manufacturing a substrate from the above-described master or stamper by an injection molding method or the like, a plastic material such as polycarbonate, a so-called resin, is unlikely to enter the minute concave portion from the stamper. Therefore, accurate transfer is extremely difficult.

From the viewpoint of productivity, the transfer time allowed in the manufacturing process is at most about 20 seconds / sheet, and taking this into account, molding becomes almost impossible.

Therefore, as in the conventional case, it is necessary to invert the concavities and convexities so that the pits become convex. In the concavo-convex inversion process, it is conceivable to perform transfer from the master stamper to the mother stamper and use the mother stamper for substrate molding. However, productivity is reduced by spending time in a process of manufacturing the mother stamper. In addition, when producing a micropattern that can be drawn with an electron beam, the pattern shape may deteriorate during the transfer process, or the surface roughness may increase during the surface peeling process of the master stamper. Therefore, there is a possibility that a problem of causing a problem may occur. In order to maintain the quality of the substrate of the optical recording medium, it is desired to avoid an increase in the number of transfer steps.

[0046]

SUMMARY OF THE INVENTION The present invention relates to a stamper for manufacturing an optical recording medium for producing an optical recording medium having a fine concavo-convex pattern, comprising: a substrate having a smooth main surface; In this case, a fine uneven pattern layer having a uniform thickness corresponding to the depth of the fine uneven pattern and having a pattern etched corresponding to the fine uneven pattern is provided.

Further, according to the present invention, in the above stamper for producing an optical recording medium, a protective film is formed on the fine uneven pattern layer.

Further, according to the present invention, in the above stamper for producing an optical recording medium, at least the surface of the stamper is made of Ni.
And the fine uneven pattern layer is made of SiO ₂ .

The present invention also relates to a method of manufacturing a stamper for producing an optical recording medium, wherein a substantially uniform thickness is formed on a substrate having a smooth main surface and made of a material having a different etching property from the substrate. A step of depositing a layer to be etched having, a step of depositing a negative photosensitive layer on the layer to be etched, which becomes insoluble in a developing solution when exposed to light, and pattern-exposing a fine uneven pattern to the photosensitive layer. A step of developing the photosensitive layer; a step of performing anisotropic etching on the layer to be etched using the photosensitive layer on which the fine uneven pattern is formed as a mask; and removing the photosensitive layer on which the fine uneven pattern is formed. And

Further, according to the present invention, there is provided a method for manufacturing a stamper for producing an optical recording medium as described above, wherein the pattern exposure of the photosensitive layer is performed by electron beam drawing.

As described above, in the present invention, in the stamper for producing an optical recording medium, there is provided a substrate having a smooth main surface, and a substrate having a different etching property from the substrate and having a fine uneven pattern on the substrate. By providing a fine uneven pattern layer having a uniform thickness corresponding to the thickness and having been subjected to pattern etching corresponding to this fine uneven pattern, and forming a two-layer structure composed of materials having different etching properties, After a photosensitive layer made of, for example, a photoresist or an electron beam resist is applied on the uneven pattern, pattern exposure and development are performed to form a resist mask made of a photosensitive layer having a fine uneven pattern, and the patterned photosensitive layer is formed. By performing anisotropic etching with a mask as a mask, it is possible to form with high accuracy, that is, a shape that can reliably hold a fine uneven pattern. , Also it can be uniformly formed its depth.

In such a configuration, by providing a protective film on the fine uneven pattern layer, a substrate made of a resin or the like is manufactured from the stamper for manufacturing an optical recording medium by an injection molding method or the like. When the substrate is peeled, peeling of the fine concavo-convex pattern of the stamper having a two-layer structure can be reliably avoided, and fine concavo-convex patterns such as fine pits can be formed with a good shape. In addition, productivity and yield can be improved.

In particular, by using Ni for the substrate of the stamper, a stamper which is inexpensive and excellent in oxidation resistance, durability and strength can be obtained. Further, by forming the fine uneven pattern layer as SiO ₂ , In the case of applying by sputtering or the like, since the thickness can be suppressed to within about ± 1% on a so-called CD size substrate having a radius of about 20 mm to 60 mm, the depth of the fine uneven pattern can be more accurately adjusted. The optical recording medium can be provided uniformly, and the productivity of the optical recording medium and the yield can be further improved.

Further, by patterning the photosensitive layer made of a resist provided on the above-mentioned fine uneven pattern layer by electron beam drawing, it is possible to make the fine uneven pattern fine, and hence to increase the recording density of the optical recording medium. .

Further, by forming the photosensitive layer as a negative type resist, the fine uneven pattern layer formed by etching using the patterned photosensitive layer as a mask,
Since the shape of the pits is convex, when the substrate for an optical recording medium is molded by an injection molding method or the like, the transfer can be performed well, and fine pits can be formed with good controllability. As a result, it is possible to improve the productivity and yield of an optical recording medium with a particularly high recording density.

[0056]

Embodiments of the present invention will be described below in detail with reference to the drawings, but the present invention is not limited to the following embodiments.

First, as shown in FIG. 1, in the present invention, on a substrate 2 having a smooth main surface 2S made of, for example, Ni, the etching property is different from that of the substrate 2, and the depth of the fine uneven pattern 5 is increased. Fine uneven pattern layer 3 made of, for example, SiO ₂ , having a uniform thickness d corresponding to the thickness and subjected to pattern etching corresponding to the fine uneven pattern 5.
Is provided.

In this example, the protective layer 1 made of, for example, Ni is entirely covered over the fine uneven patterning layer 3.
1 is provided.

Such a stamper for producing an optical recording medium can be obtained by the following production method. That is, the substrate 2 having the smooth main surface 2S is prepared. As shown in FIG. 2A, the substrate 2 is formed, for example, on a glass master 1 used in a normal stamper manufacturing process.
After i-plating, it can be obtained by peeling off from the glass master.

Ni is difficult to etch with a normal gas, and a layer 3 to be etched made of a material having a different etching property is formed on the smooth main surface 2S of the substrate 2. As described above, by using SiO ₂ as the material of the layer 3 to be etched, it is possible to perform etching with a generally used safe fluorocarbon-based gas such as CF ₄ or CHF ₃ .

The thickness d of the layer 3 to be etched is
It is selected so as to match the desired depth of the fine concavo-convex pattern, and is formed by sputtering or the like so as to have a substantially uniform thickness. In the etching process described later, since the etching is stopped at the interface between the layer 3 to be etched and the substrate 2, it is necessary to suppress the variation in the depth of the fine uneven pattern caused by the in-plane variation of the etching rate on the substrate 2. Thus, a fine uneven pattern having a uniform depth can be formed over almost the entire surface.

Thereafter, a photosensitive layer 4 made of a negative resist which becomes insoluble in a developing solution when exposed to light is coated on the entire surface of the layer 3 to be etched.

Then, as shown in FIG. 2C, the photosensitive layer 4 is subjected to pattern exposure of a fine concavo-convex pattern using, for example, an electron beam drawing apparatus 50. As the electron beam lithography apparatus 50, an apparatus having the same configuration as the apparatus described with reference to FIG. 8 can be used.

In FIG. 2C, the electron beam generating / focusing unit in FIG. 8 is schematically shown as an electron beam lithography apparatus 50. The substrate 2 is mounted on an air spindle in a mechanism unit, and the required vacuum is set in the apparatus. It is kept every time. 54 is an electron gun, 55 is a condenser lens, 56 is a beam modulator,
57 is an aperture, 58 is a beam deflection electrode, 59 is a focus adjustment lens, and 60 is an objective lens.

The substrate 2 is rotated by an air spindle on which the substrate 2 is mounted, and the substrate 2 is moved in the radial direction of the substrate 2 by a slide mechanism. 5a is formed.

After the development, the photosensitive layer 4 on the layer to be etched 3 is patterned to form a fine uneven pattern 5 as shown in FIG. 2D.

Then, as shown in FIG. 3A, anisotropic etching such as RIE (reactive ion etching) is performed on the layer 3 to be etched using the photosensitive layer 4 having the fine uneven pattern 5 as a mask. In FIG. 3A, 6 is a mounting table on which the substrate 2 is mounted, 7 is a counter electrode, 8 is a high-frequency power supply connected to the mounting table 6, 9 is active gas ions, and arrow e schematically shows the movement of the ions 9. It is shown.

Thereafter, as shown in FIG. 3B, the photosensitive layer on which the fine uneven pattern is formed is removed to expose the fine uneven pattern layer 3. As a removing method, a stripping solution treatment such as oxygen plasma asher or sulfuric acid water can be employed. In FIG. 3B, reference numeral 10 denotes O ₂ ion, and arrow f denotes O 2
₂ schematically shows the movement of _two ions 10.

Then, as shown in FIG. 3C, a protective layer 11 made of Ni or the like is formed on the fine concavo-convex pattern layer 3 by sputtering or the like, and the optical recording medium of the present invention described with reference to FIG. The production stamper 12 can be obtained.

As described above, by applying the protective layer 11 on the fine uneven pattern layer 3, even when the adhesion strength between the fine uneven pattern layer 3 and the substrate 2 is insufficient,
It is possible to reliably prevent the fine uneven pattern layer 3 from being separated from the substrate 2 by the force applied when the molded substrate is separated from the stamper.
The durability of No. 2 can be significantly improved.

Since the stamper for manufacturing an optical recording medium according to the present invention manufactured as described above uses a negative resist when forming its fine uneven pattern, the pits formed after etching are convex. Thus, there is no problem in the transferability of the molding, that is, it is possible to perform the transfer while maintaining the good shape with a good yield, and it is possible to improve the productivity and the yield.

Further, after the formation of the fine concavo-convex pattern by pattern exposure, development and etching, the molded substrate can be manufactured without passing through the transfer step in the usual stamper manufacturing process, so that the shape of the fine concavo-convex pattern is deteriorated. It has the advantage of being kept to a minimum. As described above, when the recording density of the optical recording medium is increased, and the present invention is applied when the fine uneven pattern is further miniaturized,
Since the transfer step is not required, it is very advantageous in terms of productivity and yield.

Further, as compared with the conventional stamper manufacturing process, the equipment requires a new sputtering apparatus and an etching apparatus for the layer to be etched, and a new apparatus for removing the resist, that is, the photosensitive layer. Since the size of the stamper does not need to be changed, the machine can be used as it is.

Further, as described with reference to FIG. 4D, the sputtering apparatus used for applying the above-described protective layer 11 includes a sputtering apparatus for conducting the surface treatment of the master disk immediately before the conventional electroplating step. If used, this can be diverted. When using the electroless plating method,
It is also possible to form by deposition instead of sputtering. Thus, it is also an advantage of the present invention that there is no need to modify the conventionally used device or to discard the conventional device.

The photosensitive means of the photosensitive layer 4 is not limited to the above-described pattern exposure using an electron beam, but is performed by using a conventional optical recording apparatus using a laser beam or the like as described with reference to FIG. You can also.

Further, in the stamper for producing an optical recording medium according to the present invention, when the optical recording medium to be produced is composed only of a groove, a positive resist is used as a resist for pattern exposure of the groove. It is also possible. It is effective for the purpose of forming a groove that is thinner than a resist pattern by controlling the type and pressure of an etching gas or the power of a high-frequency power supply, for example, by using the pattern miniaturization effect by etching.

Next, the above-described stamper for producing an optical recording medium according to the present invention is replaced with an existing DVD-ROM (Read Only Memory).
mory) at a recording density equivalent to 10 times the depth d = 70n
An embodiment in which an optical recording medium having an m pit pattern, in this example, a substrate of an optical disk will be described in detail.

First, a substrate made of Ni having an outer diameter conforming to the standard of a general molding stamper is manufactured. In this example, a disk-shaped substrate having an outer diameter of 130 mm and a thickness of 295 μm is subjected to the same stamper manufacturing process on a pattern-unexposed glass master, that is, a Ni layer is applied by electroplating after forming a conductive layer. After peeling,
Ni having a smooth principal surface whose surface is a so-called mirror surface
A substrate can be obtained.

Thereafter, SiO ₂ is entirely formed as a layer to be etched on the smooth main surface of the substrate by sputtering. At this time, the sputtered film thickness of SiO ₂ is adjusted so as to match the desired pit pattern depth.
70 nm. When deposited on a substrate having an outer diameter of 130 mm by sputtering, the variation in the film thickness is 1%.
It could be suppressed to the following degree.

Then, a photosensitive layer made of a negative resist for electron beam drawing is applied on the layer to be etched by spin coating. As a material for the photosensitive layer, NEB-22 (trade name) manufactured by Sumitomo Chemical Co., Ltd. is used.
The thickness of the photosensitive layer is set to dr = 200 nm.

After that, the pit pattern was subjected to pattern exposure by the electron beam lithography apparatus described with reference to FIG. The conditions of the exposure at this time are shown below. [1] Pattern a. Modulation signal: EFM + signal. This is a modulation signal generally used for DVD-ROM, and is 3T, 4T, 5T,.
T consists of 12 pit lengths. b. Recording density: 3T pit length = 0.126 μm, track pitch TP = 0.234 μm. This corresponds to ten times the areal density of a DVD.

[2] Electron beam drawing apparatus a. The electron gun: Material LaB ₆ b. Accelerating voltage: 50 kV c. Current: 20 nA d. Beam diameter: 100 nm e. Recording linear velocity: 0.2 m / s

Next, the developing conditions are shown below. [3] Development conditions a. Developer: Organic alkali developer / tetramethylammonium 2.38% (trade name: NMD-3) b. Development time: 60 seconds

When development was performed under the above conditions, a pit pattern having a depth of 70 nm could be formed. Since a negative resist is used, the pits have a convex shape.

Then, the layer to be etched was subjected to anisotropic etching by RIE using the photosensitive layer having the fine concavo-convex pattern thus formed, in this case, the pit pattern, as an etching mask. In the RIE apparatus, as described with reference to FIGS. 3A and 3B described above, a high voltage is applied by a high-frequency power supply 8 between the mounting table 6 and the counter electrode 7 that constitute two planar electrodes, so that A plasma is generated in the reactive gas.

The generated active gas ions 9 are vertically incident along the electric field on the sample surface provided on one of the electrodes, ie, the mounting table 6, in this case, the layer to be etched on the substrate 2, and the photosensitive layer 4. Then, a chemical reaction occurs and the etching proceeds in the vertical direction. The use of etching characteristics and a chemical reaction that allows etching to be performed almost vertically has a high degree of freedom in the selectivity of an etching substance, and further has the advantage of high productivity, which is a feature of dry etching.

In this embodiment, the layer to be etched 3a
Is composed of SiO ₂ , so that the main reaction gas is CF 2
₄ or CHF ₃ is used. An example of the etching conditions is described below.

A. Etching gas and flow rate: CHF ₃ 2
5 sccm / Ar 25 sccm b. Degree of vacuum: 0.25 mPa c. Gas pressure: 0.50 Pa d. High frequency RF power output: antenna unit 130W / bias unit 30W

When etching was performed under the above conditions,
The etching rate was 40 nm / min. The thickness of the layer to be etched 3a corresponding to the depth of the pit pattern is 7
Since it was 0 nm, that is, the time required for etching the target pit pattern was 1 minute and 45 seconds. Thus, the layer to be etched is patterned to form the fine uneven pattern layer 3.

Since the etching gas described above does not etch Ni of the substrate material, as described above, S
Since the thickness of the layer to be etched made of iO ₂ is made to coincide with the depth of the target fine concavo-convex pattern, in this case, the pit pattern, even if the etching time is set longer, the pattern having a substantially uniform depth is obtained. Can be obtained.

In general, the etching rate may have a non-uniformity of about ± 5% in a plane or between samples.
The thickness of the sputtering varies only about 1%. Therefore, as described above, by selecting the thickness of the layer to be etched so as to match the pattern depth and setting the etching time longer, the pattern depth caused by the in-plane variation of the etching rate Can be avoided, and the shape of the fine uneven pattern can be accurately controlled.

After the completion of the etching, the unnecessary photosensitive layer 4, that is, the so-called resist mask is removed.
Since the resist after etching is deteriorated under plasma, it cannot be easily removed with a developing solution or an organic solvent such as acetone. Therefore, a method of using an effective stripper such as sulfuric acid or the like, or a method of burning the remaining resist by O ₂ plasma, so-called ashing, is generally adopted.

Alternatively, if oxygen is used as the reactive gas in the above-described etching apparatus, the etching of SiO ₂ does not proceed with the oxygen gas, so that the resist, that is, the photosensitive layer 4 is removed while the pattern shape of the fine uneven pattern layer 3 is maintained. Can be removed. In this embodiment, the remaining resist, that is, the photosensitive layer 4 was removed by this method under the following etching conditions.

A. Etching gas: O ₂ b. Degree of vacuum: 0.3 mPa c. Gas pressure: 0.5 Pa d. Gas flow rate: 25 sccm e. High frequency RF power output: antenna unit 130W / bias unit 30W (frequency 13.56MHz)

By performing the treatment for 5 minutes under the above etching conditions, the photosensitive layer 4, in this case, the negative resist could be completely removed. As a result, it is possible to obtain an optical recording medium producing stamper in which the fine uneven pattern layer 3 on which the fine uneven pattern 5 is formed is formed on the substrate 2 made of Ni, and the pit pattern is convex.

In this embodiment, in particular, the fine uneven pattern layer 3 made of SiO ₂ on the substrate 2 made of Ni has a structure in which only the bottom surfaces of the pits are adhered to the substrate 2. Therefore, when the so-called resin molded substrate such as plastic is peeled from the stamper, the protective layer 11 made of Ni or the like is formed with a thickness of, for example, several tens nm in order to reliably prevent the fine uneven pattern layer from peeling. It is formed by sputtering or the like.

Thereafter, if necessary, the outer peripheral portion is punched according to the size of the molding machine, for example, so that the photosensitive layer is patterned and etched by using this as a mask.
A so-called direct patterning type stamper for producing an optical recording medium can be obtained. In the above punching,
While observing the patterning with a microscope, the eccentricity can be suppressed to a standard value or less, for example, 20 μmP-P or less based on the patterning standard.

Then, using this stamper, a substrate is formed by an injection molding method or a 2P (Photo-Polymmerization) method or the like, and a reflective layer, a recording layer, a protective layer, and the like are adhered to produce an optical recording medium. be able to.

It is estimated that the total working time of the etching step, the resist removing step, and the step of forming the protective layer on the stamper surface in the respective manufacturing steps described above is about 30 minutes.
The time is much shorter than the 2-3 hours required for manufacturing the mother stamper described with reference to FIGS. 6A to 6E, which is extremely advantageous in terms of productivity.

That is, it is possible to manufacture a plurality of stampers for producing an optical recording medium in about the same time as producing a molding stamper by the conventional transfer process. Therefore, even when a plurality of molding stampers are required for mass production, a stamper for producing an optical recording medium can be manufactured in a short time without performing a transfer step.
By applying the present invention when the deterioration of the fine uneven pattern in the transfer step becomes a problem with the increase in the recording density, the yield can be remarkably improved.

The present invention is not limited to the above-described embodiment, but can be applied to various stampers for producing optical recording media. Needless to say, the present invention is not limited to electron beam exposure, and may take various other forms such as using an optical recording device using a normal laser beam.

[0102]

As described above, according to the present invention, in a stamper for producing an optical recording medium, a substrate having a smooth main surface and an etching property different from that of the substrate are provided on the substrate.
In addition, a two-layer structure made of materials having different etching properties is provided by providing a fine concavo-convex pattern layer having a uniform thickness corresponding to the depth of the fine concavo-convex pattern and being subjected to pattern etching corresponding to the fine concavo-convex pattern. By applying a photosensitive layer made of, for example, a photoresist or an electron beam resist on the fine concavo-convex pattern, pattern exposure and development are performed to form a resist mask composed of a photosensitive layer having a fine concavo-convex pattern, By performing anisotropic etching using the patterned photosensitive layer as a mask, it is possible to perform molding with high precision, that is, a shape that can surely hold a fine uneven pattern, and to uniformly form the depth.

In such a configuration, by providing a protective film on the fine uneven pattern layer, a substrate made of resin or the like is manufactured from the stamper for manufacturing an optical recording medium by an injection molding method or the like. When peeling a substrate in the form of a substrate, it is possible to reliably avoid the peeling of the fine uneven pattern of the stamper having a two-layer structure, and to form the fine uneven pattern such as minute pits with a good shape. As a result, productivity and yield can be improved.

In particular, by using Ni for the substrate of the stamper, a stamper which is inexpensive and excellent in oxidation resistance, durability and strength can be obtained. Further, by forming the fine uneven pattern layer as SiO ₂ , In the case of applying by sputtering or the like, since the thickness can be suppressed to within about ± 1% on a so-called CD size substrate having a radius of about 20 mm to 60 mm, the depth of the fine uneven pattern can be more accurately adjusted. The optical recording medium can be uniformly provided, and the productivity and the yield of the optical recording medium can be further improved.

Further, by patterning the photosensitive layer made of a resist provided on the above-mentioned fine uneven pattern layer by electron beam drawing, it is possible to make the fine uneven pattern fine, and thus to increase the recording density of the optical recording medium. .

Further, by forming the photosensitive layer as a negative type resist, the fine uneven pattern layer formed by etching using the patterned photosensitive layer as a mask,
Since the shape of the pits is convex, when the substrate for an optical recording medium is molded by an injection molding method or the like, the transfer can be performed well, and fine pits can be formed with good controllability. As a result, it is possible to improve the productivity and yield of an optical recording medium with a particularly high recording density.

Further, after the formation of the fine concavo-convex pattern by pattern exposure, development and etching, a molded substrate can be manufactured without passing through a transfer step in a normal stamper manufacturing process, so that the shape of the fine concavo-convex pattern is deteriorated. It has the advantage of being kept to a minimum. As described above, when the recording density of an optical recording medium is increased and the fine uneven pattern is further miniaturized, when the present invention is applied, a plurality of optical recordings can be performed in a much shorter time than in the past. Since a stamper for manufacturing a medium can be manufactured, a transfer step can be omitted in this process, and the working time can be reduced, or the yield and productivity can be improved.

In addition, as compared with the conventional stamper manufacturing process, equipment requires a new apparatus for sputtering a layer to be etched and an apparatus for etching, and a new apparatus for removing a resist, that is, a photosensitive layer. Since the size of the stamper does not need to be changed, the machine can be used as it is.

Further, the sputtering apparatus used for depositing the above-mentioned protective layer can be formed by depositing instead of the conventional sputtering apparatus used for conducting the surface of the master substrate. For example, there is no need to make changes to a device that has been used conventionally and to discard the device.

[Brief description of the drawings]

FIG. 1 is a schematic enlarged sectional view of an example of a stamper for producing an optical recording medium.

FIG. 2 is a manufacturing process diagram of an example of a method for manufacturing a stamper for manufacturing an optical recording medium.

FIG. 3 is a manufacturing process diagram of an example of a method for manufacturing a stamper for manufacturing an optical recording medium.

FIG. 4 is a manufacturing process diagram of the optical recording medium.

FIG. 5 is an explanatory diagram illustrating a configuration of an example of an optical recording medium.

FIG. 6 is an explanatory diagram of a transfer step of a stamper for producing an optical recording medium.

FIG. 7 is an explanatory diagram of an example of an optical recording device.

FIG. 8 is an explanatory diagram of an example of an electron beam drawing apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Glass master, 2 board | substrate, 2S smooth main surface, 3 micro uneven pattern layer, 3a etching layer, 4 photosensitive layer, 5
Fine uneven pattern, 5a latent image, 6 mounting table, 7
Counter electrode, 8 High frequency power supply, 9 Active gas ion, 10
O ₂ ion, 11 protective layer, 12 stamper for producing optical recording medium, 50 electron beam drawing apparatus

Claims (5)

[Claims] An optical recording medium producing stamper for producing an optical recording medium having a fine concavo-convex pattern, comprising: a substrate having a smooth main surface; A stamper for producing an optical recording medium, comprising: a fine uneven pattern layer having a uniform thickness corresponding to the depth of the uneven pattern and being subjected to pattern etching corresponding to the fine uneven pattern. 2. The stamper for producing an optical recording medium according to claim 1, wherein a protective film is formed on the fine uneven pattern layer. 3. The substrate according to claim 1, wherein at least a surface of the substrate is Ni.
The stamper for producing an optical recording medium according to claim 1, wherein the fine uneven pattern layer is made of SiO ₂ . 4. A step of depositing a layer to be etched made of a material having a different etching property from the substrate and having a substantially uniform thickness on a substrate having a smooth main surface; A step of applying a negative photosensitive layer which becomes insoluble in a developer when exposed to light, a step of pattern-exposing a fine uneven pattern to the photosensitive layer, a step of developing the photosensitive layer, and a step of developing the fine unevenness Using the photosensitive layer on which the pattern is formed as a mask, performing anisotropic etching on the layer to be etched, and removing the photosensitive layer on which the fine uneven pattern is formed. A method for manufacturing a stamper for producing an optical recording medium. 5. The method for producing a stamper for producing an optical recording medium according to claim 4, wherein the pattern exposure of the photosensitive layer is performed by electron beam drawing.