JPH06150396A - Production of optical master disk - Google Patents

Abstract

PURPOSE:To enable the selection of a substrate having decreased drop-outs in the stage of the substrate to be reproduced by applying a photoresist to the substrate produced by reproducing the substrate formed with signal pits, then recording signals again thereon. CONSTITUTION:The positive type photoresist is applied by a method, such as spin coating, on the substrate 1 consisting of a glass, etc., subjected to flattening of the surface by a method, such as polishing, and is baked to form a photoresist layer 2. A conductive film 5 of nickel, etc., is then formed on the surface by a method, such as sputtering method and the number of the drop-outs is measured by making evaluation by reproduction. The stages are repeated from the beginning in case of the many drop-outs. The substrate having the decreased drop-outs is selected and is subjected to nickel plating by using the conductive film 5 as an electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical disc master.

[0002]

2. Description of the Related Art In general, a master disc of an optical disc is prepared by coating a photoresist on a glass substrate whose surface is polished, exposing it to light using a laser beam whose intensity is modulated by an information signal to be recorded, and developing it to correspond to its photosensitivity. It is manufactured by forming the uneven signal or groove or the uneven signal and groove. Hereinafter, the uneven signal or groove or the uneven signal and groove will be collectively referred to as a signal pit.

In order to achieve a high recording density, an optical disk having two kinds of signal pits having different depths has been devised (for example, Japanese Patent Laid-Open No. 54-136303).
In this optical disc, the depths of two types of signal pits having different depths are important. When the wavelength of the light for reading the signal is λ, the depth of the signal pit needs to be λ / 4 and λ / 8.

In order to manufacture such an optical disc, a method of obtaining two kinds of signal pits having different depths by changing the light intensity when recording a signal has been shown.
That is, two kinds of signal pits having different depths are formed by irradiating and developing light having low intensity when recording shallow signal pits and light having high intensity when recording deep signal pits.

FIG. 5A to FIG. 5C show steps of a conventional method for producing an optical disk master. As shown in FIG. 3A, a positive type photoresist is applied by a method such as spin coating to a substrate 1 made of glass or the like whose surface is flattened by a method such as polishing, and baked to form a photoresist layer 19. Form. Since the thickness of the photoresist is slightly reduced by the development even in the non-irradiated area, the photoresist thickness in the non-irradiated area after development should be deeper so that the depth of the signal pit becomes deeper. A photoresist is applied to the master so that the photoresist is slightly thicker than the signal pit depth.

Next, as shown in FIG. 1B, when recording deep signal pits, light having an intensity that completely removes the photoresist by development is irradiated, and when recording shallow signal pits, The photoresist is exposed to light of an intensity that removes about half of the film thickness by development. The exposed portion is indicated by the shaded portion 3.

Then, as shown in FIG. 1C, the exposed portion is removed by developing to form two kinds of signal pits 4 and 10 having different depths.

It is also possible to form two kinds of signal pits having different depths by repeating the steps of photoresist coating, signal recording and development twice.

[0009]

In the method of removing the photoresist film halfway by development by adjusting the irradiation light intensity, the depth of the signal pit changes due to variations in light intensity and development conditions. Sisters,
It is not possible to stably form signal pits of two kinds of depths. Further, in the method in which the steps of photoresist coating, signal recording, and development are repeated twice, many dropouts such as adhesion of foreign matters and chipping of photoresist occur.

An object of the present invention is to provide a method for manufacturing an optical disc master having two kinds of signal pits having different depths, which eliminates the above-mentioned drawbacks.

[0011]

The present invention has the above-mentioned objects.
This is achieved by applying a photoresist to the substrate prepared by duplicating the substrate on which the signal pit is formed and recording the signal again.

[0012]

When the steps of photoresist coating, signal recording and development are carried out, dropout such as adhesion of foreign matter or chipping of photoresist occurs. According to the method of the present invention, it is possible to select a substrate having a small number of dropouts at the stage of the substrate to be duplicated, and it is possible to produce a master disc having two types of signal pits having a small number of dropouts and different depths. It is also possible to stabilize the depth of two types of signal pits having different depths by defining the thickness of the photoresist when forming the signal pits on the substrate and when forming the signal pits on the duplicated substrate. it can.

[0013]

EXAMPLES The present invention will be described in detail below with reference to examples.

(Embodiment 1) The steps of a method for producing an optical disk master according to an embodiment of the present invention are shown in FIGS. 1A to 1L, and each step will be described in detail.

FIG. 1A: A positive type photoresist is applied by a method such as spin coating to a substrate 1 made of glass or the like whose surface is flattened by a method such as polishing, and baked to form a photoresist layer 2. To do.

FIG. 1B: Intensity modulation of a laser beam for signal recording is performed by an optical modulator utilizing an electro-optical effect according to a signal to be recorded, and the substrate 1 coated with a photoresist is narrowed down and irradiated. Exposing the photoresist layer to light. The exposed portion is indicated by the shaded portion 3.

FIG. 1C: The unexposed portion is removed by development to form the signal pit 4. The same figure (d): A conductive film 5 of nickel or the like is formed on the surface by a method such as a sputtering method, and reproduction is evaluated to measure the number of dropouts. If there are many dropouts, start over from step (a).

FIG. 3E: A substrate with few dropouts is selected, and the conductive film 5 is used as an electrode for nickel plating.

FIG. 2 (f): The stamper 6 is peeled off from the substrate.
To make. The stamper may be washed after peeling. Here, although the number of dropouts was measured by performing the reproduction evaluation at the stage of forming the conductive film, the reproduction evaluation may be performed at the stage of the stamper for selection.

FIG. 3G: The substrate 7 having signal pits is duplicated from the stamper 6 by a method such as an injection method or a photopolymer method.

FIG. 3H: A positive photoresist is applied to the substrate 7 having signal pits by a method such as spin coating and baked to form a photoresist layer 8.

FIG. 1I: Intensity modulation of a laser beam for signal recording is performed by an optical modulator or the like utilizing an electro-optical effect according to a signal to be recorded, and a substrate coated with a photoresist is narrowed down and irradiated with a photo. Exposing the resist layer to light. The exposed portion is indicated by the shaded portion 3.

FIG. 3J: The depression 9 is formed by developing. In the same figure (k): the signal pit 10 is formed by engraving the substrate by etching using the photoresist layer in which the depression is formed as a mask.

FIG. 1 (l): An optical disk master having two kinds of signal pits having different depths by removing the photoresist remaining on the substrate by a method such as ashing with an organic solvent such as remover or oxygen plasma. Get 11.

The substrate 1 may be made of a material such as nickel, copper or the like, a synthetic resin such as an acrylic resin or the like, which can have a flat surface, in addition to glass.

The thickness of the photoresist layer 2 is a value obtained by adding the value obtained by dividing the depth of the signal pit to be formed by the refractive index of the material of the optical disc manufactured from the master and the amount of film-deposition in the unexposed portion due to development. Try to be equal. The thickness of the photoresist layer 8 is set to a value obtained by dividing the depth of the other signal pit to be formed by the refractive index of the material of the optical disc manufactured from the master by the etching rate ratio of the photoresist and the substrate by development. The unexposed area should be larger than the sum of the amount of film slippage. Here, the etch rate ratio represents the etch rate of the substrate when the etch rate of the photoresist is 1. The amount of film slippage of the positive photoresist during development varies depending on the development conditions, but is about 5 to 15 nm in normal development.

When a photoresist is applied to the substrate 7,
If the signal pits formed on the substrate are deep, the flow of the photoresist is disturbed around the signal pits and the thickness of the photoresist becomes uneven. Therefore, it is better to use a substrate on which shallower signal pits are formed.

The etching is ion beam etching.
A method such as reactive ion beam etching or wet etching can be used. Desirably, anisotropic etching capable of engraving the substrate in the vertical direction, for example, ion beam etching with Ar ions using an ion gun is desirable.

In the method in which the steps of photoresist coating, signal recording and development are repeated twice, many dropouts such as adhesion of foreign matter and chipping of photoresist occur. A substrate with few dropouts can be produced in large quantity by selecting and duplicating one with few dropouts. A master with few dropouts can be produced by using a substrate with few dropouts and selecting a material with few dropouts even at the master stage.

Let R be the probability that a dropout will occur in a single photoresist coating / signal recording / development process.
R is 1 or less. In the conventional method in which this process is repeated twice, the probability of dropout occurrence is R × R, and even if an original disc with few dropouts is selected, there are not many original discs with few dropouts. In the method of the present invention, since the one with less dropout is selected for each step of photoresist coating / signal recording / development, the final probability of dropout is R, and a master with less dropout can be obtained.

In the method of the present invention, the depth of the signal pit can be defined by the thickness of the photoresist layer, and the one with less dropout can be selected when the substrate is duplicated. It is possible to manufacture an optical disc master having two kinds of signal pits with a small depth and a stable depth.

When forming signal pits of two kinds of depth, it is desirable to alternately form a signal pit row of one depth and a signal pit row of the other depth. When a signal pit having one depth is formed and then a signal pit having the other depth is formed, it is necessary to perform recording control for recording on the previously formed signal pit row. When a photoresist is applied to the substrate 7 on which signal pits of one type of depth are formed and a signal of another type of depth is recorded, the difference in the refractive index between the substrate and the photoresist is small, so that it is formed on the substrate 4. The tracking error signal obtained from the generated signal pit train becomes small.

If the tracking error signal is small, the control gain cannot be increased when the tracking control is applied, and the tracking control fluctuates. In order to solve this problem, a reflective layer is formed on the surface of the substrate 7 to increase the reflectance of the substrate 7, thereby increasing the tracking error signal obtained from the signal pit train formed on the substrate 7 to increase the tracking control gain. The tracking accuracy can be improved.

For the reflective layer, a metal such as gold, aluminum or nickel, a dielectric or the like can be used. As a method for forming the reflective layer, a vacuum vapor deposition method, a DC sputtering method, an AC sputtering method, or the like can be used. The thickness of the reflective layer may be greater than or equal to the thickness at which the reflectance that provides a tracking error signal sufficient for tracking control is obtained.

It is also possible to etch the reflective layer so that the thickness of the reflective layer is equal to or greater than the depth of the signal pits forming the reflective layer. In this case, the thickness of the photoresist layer 8 is a value obtained by dividing the depth of the other signal pit to be formed by the refractive index of the material of the optical disc manufactured from the master, by the etching rate ratio of the photoresist and the reflective layer. Try to be bigger. Forming the signal pits by etching the reflective layer has an advantage that the material of the substrate 4 to be duplicated can be selected without considering the etching rate ratio with the photoresist.

(Embodiment 2) FIGS. 2A to 2N show the steps of a method for producing an optical disk master according to an embodiment of the present invention. Hereinafter, the steps for each of the figures (a) to (n) will be described.

FIG. 3A: A positive type photoresist is applied by a method such as spin coating to a substrate 1 made of glass or the like whose surface is flattened by a method such as polishing and baked to form a photoresist layer 2. To do.

FIG. 2B: Laser light for signal recording is intensity-modulated by an optical modulator or the like utilizing an electro-optical effect according to a signal to be recorded, and the substrate 1 coated with photoresist is narrowed down and irradiated. Exposing the photoresist layer to light. The exposed portion is indicated by the shaded portion 3.

FIG. 3C: The depression 12 is formed in the photoresist layer 2 by developing. In the same figure (d): The substrate is engraved by etching with the photoresist layer in which the depressions are formed as a mask to form signal pits 4.

FIG. 5E: The photoresist remaining on the substrate is removed by a method such as ashing with an organic solvent such as remover or oxygen plasma to obtain a substrate having signal pits formed thereon.

FIG. 5F: A conductive film 5 made of nickel or the like is formed on the surface by a method such as a sputtering method, and reproduction is evaluated to measure the number of dropouts. If there are many dropouts, start over from step (a).

In the same figure (g), a substrate with few dropouts is selected, and the conductive film is used as an electrode for plating.

FIG. 6 (h): The stamper 6 is peeled off from the substrate.
To make. The stamper may be washed after peeling. Here, although the number of dropouts was measured by performing the reproduction evaluation at the stage of forming the conductive film, the reproduction evaluation may be performed at the stage of the stamper for selection.

(I) of the same figure: The substrate 7 having signal pits is duplicated from the stamper 6 by a method such as an injection method or a photopolymer method.

In the same figure (j): A positive type photoresist is applied to the substrate 7 having signal pits by a method such as spin coating and baked to form a photoresist layer 8.

(K): Laser light for signal recording is intensity-modulated by an optical modulator or the like utilizing an electro-optical effect according to a signal to be recorded, and the substrate 7 coated with a photoresist is narrowed down and irradiated. Exposing the photoresist layer to light. The exposed portion is indicated by the shaded portion 3.

FIG. 1 (l): The depression 9 is formed by developing. In the figure, (m): the signal pit 10 is formed by engraving the substrate by etching using the photoresist layer having the depressions as a mask.

(N): The optical disc master having two kinds of signal pits having different depths by removing the photoresist remaining on the substrate by a method such as ashing with an organic solvent such as remover or oxygen plasma at the end. Get 11.

As the substrate, the same substrate as that described in the first embodiment can be used, but it is desirable to use a material having a different etching rate from that of the photoresist.

The thickness of the photoresist layer 2 is a value obtained by dividing the depth of the signal pits to be formed by the refractive index of the material of the optical disc manufactured from the master by the etching rate ratio of the photoresist and the substrate, by development. The unexposed area should be larger than the sum of the amount of film slippage. The thickness of the photoresist layer 8 is set to a value obtained by dividing the depth of the other signal pit to be formed by the refractive index of the material of the optical disc manufactured from the master by the etching rate ratio of the photoresist and the substrate by development. The unexposed area should be larger than the sum of the amount of film slippage.

When a photoresist is applied to the substrate 7,
If the signal pits formed on the substrate are deep, the flow of the photoresist is disturbed around the signal pits and the thickness of the photoresist becomes uneven. Therefore, it is better to use a substrate on which shallower signal pits are formed.

For etching, the same method as that described in Example 1 is used. In this method in which signal pits are formed by etching using the depressions of the photoresist as a mask, the pit depth can be controlled by the etching time, and fluctuations in the film thickness of the photoresist layer and film thickness of the photoresist due to development can be prevented. A stable signal pit depth can be obtained without being affected. Also, if you choose the etching conditions,
The shape of the signal pit can also be improved.

Since it is possible to select a substrate having a small number of dropouts when replicating the substrate, the number of dropouts is small, and the pit depth can be controlled by the etching time. An optical disc master having two types of signal pits can be manufactured.

Also in the case of the present embodiment, by forming a reflection layer on the surface of the substrate 7 to increase the reflectance of the substrate 7, the tracking error signal obtained from the signal pit row formed on the substrate 7 is increased and tracking is performed. It is possible to increase the control gain and the tracking accuracy. It is also possible to etch the reflective layer so that the thickness of the reflective layer is greater than or equal to the depth of the signal pits that form it.

(Embodiment 3) FIG. 3 (a) to FIG. 3 (c) show steps of a method for producing an optical disk master in another embodiment of the present invention.
In addition to being shown in (j), the steps of FIGS. (A) to (j) will be described below.

FIG. 5A: A positive type photoresist is applied to a substrate 1 made of glass or the like whose surface is flattened by a method such as polishing by a method such as a spin coating method and baked to form a photoresist layer 2. To do.

FIG. 5B: A laser beam for signal recording is focused on the substrate 1 coated with the photoresist and irradiated to expose the photoresist layer. The exposed area is the shaded area 1
3 shows.

FIG. 6C: Grooves 14 are formed by developing. The same figure (d): A conductive film 5 of nickel or the like is formed on the surface by a method such as a sputtering method, and reproduction is evaluated to measure the number of dropouts. If there are many dropouts, start over from step (a).

FIG. 6E: A substrate with few dropouts is selected, and the conductive film is used as an electrode for plating.

FIG. 6 (f): The stamper 1 is peeled off from the substrate.
5 is produced. The stamper may be washed after peeling.

(G): The substrate 16 having the groove is duplicated from the stamper 15 by a method such as an injection method or a photopolymer method.

FIG. 6H: A positive type photoresist is applied to the substrate 16 having grooves by a method such as spin coating,
The photoresist layer 17 is formed by baking.

(I): Two laser beams for signal recording are intensity-modulated by an optical modulator or the like utilizing the electro-optical effect according to the signals to be recorded, and are respectively applied to the substrate 16 coated with photoresist. The photoresist layer is exposed by squeezing it down.

FIG. 11 (j): signal pits 4 and 10 having two kinds of depths are formed by developing.

In the present embodiment, the substrate 1 may be made of a material such as nickel, copper or the like, a synthetic resin such as an acrylic resin, or the like, whose surface can be made flat, in addition to glass.

The thickness of the photoresist layer 2 is a value obtained by dividing the difference between the depths of two kinds of signal pits to be formed by the depth of the signal pits by the refractive index of the material of the optical disc manufactured from the master, and the unexposed portion is filmed by the development. Make it equal to the sum of the amount of sliding. The thickness of the photoresist layer 17 is equal to the value obtained by dividing the depth of the shallower signal pit by the refractive index of the material of the optical disc manufactured from the master to the value obtained by adding the amount by which the unexposed portion is film-thickened by the development. To do so.

If the groove width of the groove formed in the stamper and the width between the grooves are made equal, the photoresist applied to the substrate 1 is the same for the negative type. However, in this case, the film thickness of the photoresist layer 2 should be equal to the value obtained by dividing the difference in the depth of the signal pits of the two kinds of depths to be formed by the refractive index of the material of the optical disc manufactured from the master. There is a need to.

According to the method of the present invention, the depth of the signal pit can be defined by the thickness of the photoresist layer, and a dropout can be selected when the substrate is duplicated. It is possible to manufacture an optical disc master having two kinds of signal pits with a small depth and a stable depth. Further, the duplicated substrate 16 having the groove formed therein can be manufactured in large numbers with a small dropout, and since no signal is recorded, it is a general-purpose product. .

Also in the case of the present embodiment, by forming a reflective layer on the surface of the substrate 16 to increase the reflectance of the substrate 16, the tracking error signal obtained from the groove formed in the substrate 16 is increased and the tracking control gain is increased. The tracking accuracy can be improved.

(Embodiment 4) The steps of the method for producing an optical disk master according to an embodiment of the present invention are shown in FIGS. 4 (a) to 4 (l), and each step will be described in detail.

FIG. 9A: A positive type photoresist is applied by a method such as spin coating to a substrate 1 made of glass or the like whose surface is flattened by a method such as polishing, and baked to form a photoresist layer 2. To do.

FIG. 7B: Laser light for signal recording is focused on the substrate 1 coated with the photoresist and irradiated to expose the photoresist layer. The exposed area is the shaded area 1
3 shows.

FIG. 7C: Groove-shaped depression 18 is formed by developing. In the same figure (d): The substrate is engraved by etching and the groove 14 is formed by etching using the photoresist layer having the depressions as a mask.

FIG. 7E: The photoresist remaining on the substrate is removed by a method such as ashing with an organic solvent such as remover or oxygen plasma to obtain a substrate having signal pits formed thereon.

FIG. 6F: A conductive film 5 made of nickel or the like is formed on the surface by a method such as a sputtering method, and reproduction is evaluated to measure the number of dropouts. If there are many dropouts, start over from step (a).

FIG. 7G: A substrate with few dropouts is selected, and the conductive film is used as an electrode for plating.

FIG. 6H: The stamper 1 is peeled off from the substrate.
5 is produced. The stamper may be washed after peeling.

Here, the number of dropouts was measured by performing the reproduction evaluation at the stage of forming the conductive film, but the reproduction evaluation may be performed at the stage of the stamper for selection.

(I) of the same figure: The substrate 16 having the groove is duplicated from the stamper 15 by a method such as an injection method or a photopolymer method.

FIG. 11J: A positive type photoresist is applied to the substrate 16 having grooves by a method such as spin coating and baked to form a photoresist layer 17.

(K): Laser light for signal recording is intensity-modulated by an optical modulator or the like utilizing an electro-optical effect according to a signal to be recorded, and the substrate 16 coated with a photoresist is narrowed down and irradiated, Exposing the photoresist layer to light.

(L) of the same figure: By developing, signal pits 4 and 10 of two kinds of depth are formed.

The thickness of the photoresist layer 2 is obtained by dividing the difference between the depths of two kinds of signal pits to be formed by the depth of the signal pits by the refractive index of the material of the optical disc manufactured from the master, and the etching rate of the photoresist and the substrate. It should be larger than the value obtained by dividing the value obtained by dividing the ratio by the amount of film-developing in the unexposed portion by the development. The thickness of the photoresist layer 17 is made equal to the value obtained by dividing the depth of the shallower signal pit by the refractive index of the material of the optical disc manufactured from the master, plus the amount of film-deposition in the unexposed portion due to development. .

As the substrate, the same ones as those described in the first embodiment can be used, but it is desirable to use a material having a different etching rate from that of the photoresist.

According to the method of the present invention, the depth of the signal pit can be defined by the thickness of the photoresist layer, and it is possible to select one having a small number of dropouts when the substrate is duplicated. It is possible to manufacture an optical disc master having two kinds of signal pits with a small depth and a stable depth.

As the etching method, the method described in Example 2 can be used. In this method of forming a groove by etching using the depression of the photoresist as a mask,
The groove depth can be controlled by the etching time, and a stable groove depth can be obtained without being affected by the variation of the film thickness of the photoresist layer 2 and the film thickness of the photoresist film due to the development.

According to the method of the present invention, the depth of the signal pit can be defined by the thickness of the photoresist layer, and it is possible to select one having a small number of dropouts when the substrate is duplicated. It is possible to manufacture an optical disc master having two kinds of signal pits with a small depth and a stable depth.

Also in the case of this embodiment, by forming a reflective layer on the surface of the substrate 16 to increase the reflectance of the substrate 16, the tracking error signal obtained from the groove formed in the substrate 16 is increased, and the tracking control gain is increased. The tracking accuracy can be improved.

[0089]

According to the method of the present invention, a substrate formed by duplicating a signal pit is duplicated and a photoresist is applied to the substrate to record a signal again. One can be selected, and a master having two kinds of signal pits with few dropouts and different depths can be manufactured. Also,
It is also possible to stabilize the depth of two kinds of signal pits having different depths by defining the thickness of the photoresist when forming the signal pits on the substrate and when forming the signal pits on the duplicated substrate.

[Brief description of drawings]

FIG. 1 is a process diagram showing an embodiment of a method for manufacturing an optical disc master according to the present invention.

FIG. 2 is a process chart showing another embodiment of the present invention.

FIG. 3 is a process chart showing still another embodiment of the present invention.

FIG. 4 is a process chart showing still another embodiment of the present invention.

FIG. 5 is a process diagram showing a conventional method for producing an optical disc master.

[Explanation of symbols]

 1 Substrate 2 Photoresist Layer 4 Signal Pit 5 Conductive Film 6 Stamper 7, 16 Substrate 8 Photoresist Layer 9 Dimple 10 Signal Pit 11 Optical Disc Master

Front page continuation (72) Inventor Takashi Shunho 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. Inventor Shinya Abe 1006 Kadoma, Kadoma-shi, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] 1. Two kinds of signal pits having different depths are formed by applying a photoresist to a second substrate produced by duplicating a first substrate having signal pits formed thereon and recording a signal again. A method for manufacturing an optical disk master. 2. The method of manufacturing an optical disk master according to claim 1, wherein a substrate having shallow signal pits is used as the second substrate. 3. A substrate having signal pits formed by etching is used as the first substrate.
Alternatively, the method for producing the optical disk master according to the item 2. 4. A photoresist is applied to a second substrate produced by duplicating a first substrate having a groove corresponding to the difference in depth of signal pits, and a signal is recorded so that the depth of the signal can be reduced. A method for manufacturing an optical disc master in which two different types of signal pits are formed. 5. The method for producing an optical disk master according to claim 1, wherein a reflective layer is further formed on the surface of the duplicated substrate.