JPH11167752A - Optical disc manufacturing method - Google Patents

Abstract

(57) Abstract: The difference in thickness of a protective layer formed by sputtering between a land portion and a groove portion is reduced, and as a result, recording, erasing, and reproduction are performed on the land portion and the groove portion. Provided is a method for manufacturing an optical disc having a small difference in beam intensity at the time. A method of manufacturing an optical disc for recording information on both a land portion and a groove portion, the method comprising protecting a recording layer for recording information on a surface of a substrate on which the land portion and the groove portion are formed. When forming the protective layer, the protective layer is formed by performing sputtering using a sintered dielectric target.

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 disk, and more particularly to a method for forming a thin film as a component of an optical disk by sputtering.

[0002]

2. Description of the Related Art Information can be recorded at high density.
In addition, optical discs capable of high-speed reproduction have attracted attention as applications for audio and images, and as recording media for computers. Read-only CDs are widely used for audio and computers. Also, a write-once type in which information can be recorded only once and a rewritable type (re-writable type) in which information once recorded can be rewritten many times have become widespread. In particular, a magneto-optical disk, which is one type of rewritable type, is capable of rewriting information more than one million times, and is becoming popular mainly as a recording medium for computers.

[0003] Optical discs are classified according to their recording principle into a magneto-optical type in which information is recorded in the form of magnetization and a phase change type in which information is recorded in a crystalline or non-crystalline form. A guide for guiding a laser beam emitted from an optical pickup of a recording / reproducing apparatus along an information sequence, that is, for tracking, is formed in the optical disk in a spiral shape in a concave or convex shape. This concave or convex guide is called a guide groove. In the ISO standard, a concave portion, that is, a far side when viewed from the pickup is called a land, and a convex portion, that is, a near side when viewed from the pickup is called a groove. Conventionally, information is recorded on either a land or a groove. Recording on a land is called a land recording method, and recording on a groove is called a groove recording method. The distance from the center of the land to the center of the adjacent land or the distance from the center of the groove to the center of the adjacent groove is called a track pitch.

In recent years, the number of opportunities for recording image files on an optical disk has increased, and accordingly, there has been an increasing demand for increasing the recording capacity of the optical disk. That is, there is an increasing demand for increasing the recording density of optical disks. To increase the recording density of the optical disk, it is effective to reduce the track pitch. Of course, for this purpose, it is necessary to reduce the recording mark width. Conventional track pitch is 1.6μm
Was a standard, but recently, 1.4 μm and 1.2 μm,
A narrow track pitch of 1.0 μm has been proposed.

[0005] However, when the track pitch is reduced, a phenomenon (referred to as optical crosstalk) occurs in which information written in adjacent tracks is simultaneously read.
In addition, since a tracking error signal required for tracking becomes considerably small, there arises a problem that accurate tracking becomes difficult. Therefore, a land-groove recording method has been proposed as another approach for recording information at high density. This is because information has been recorded only on either the land or the groove, but by recording information on both the land and the groove, the track pitch is reduced by half and the recording density is increased. That is. For example, when the distance from the center of a land (or groove) to the center of an adjacent land (or groove) is 1.4 μm, by performing recording on both the land and the groove, the track pitch becomes 0.7 μm and the recording density is substantially reduced. Can be doubled.

In this method, if the groove depth is set to an appropriate value, it is possible to prevent information on adjacent groove (land) tracks from being simultaneously read during reproduction of a land (groove) track. That is,
Optical crosstalk can be prevented from occurring. In addition, since the distance between the centers of the lands (or grooves) is not small, the tracking error signal can secure a sufficient magnitude.

As described above, the prevention of optical crosstalk and the maintenance of the tracking error signal can be temporarily solved. However, in the optical recording, the information is recorded or erased on the track by the heat of the laser beam regardless of the magneto-optical type or the phase change type. Therefore, as the track pitch becomes smaller, the degree of heat generated when recording or erasing data on a certain track increases the temperature of an adjacent track increases. Eventually, there occurs a problem that information on an adjacent track is erased (referred to as cross erase or thermal crosstalk).
This cross erase determines how narrow the track pitch can be. Conventional optical discs with a step between land and groove of about 40 to 80 nm have a limit of about 0.8 μm for magneto-optical type and phase change type, and about 0.9 to 1.0 μm for optical modulation overwrite magneto-optical type. A narrower track than this was considered difficult.

A solution to this problem is a deep groove. That is, the distance of heat transfer is increased by increasing the step between the land and the groove, thereby reducing the amount of heat transfer to an adjacent track. When trying to reproduce a very small mark, with the conventional reproduction beam size, a plurality of marks are reproduced at once (crosstalk). Therefore, a necessary reproduction signal cannot be obtained. Therefore, a magnetic layer called a reproduction layer is provided separately from the memory layer to mask the information recorded in the memory layer, and the memory is stored only in a part of the temperature range of the temperature distribution generated by the irradiation of the reproduction beam. A technique has been proposed in which the magnetization of a layer is transferred to a reproducing layer for reproduction. This is referred to as magnetic super-resolution reproduction (MS
R).

In general, an optical disk has a layer (hereinafter, referred to as a layer) that functions for recording one or more layers of information on a transparent substrate on which projections and depressions corresponding to lands and grooves are formed in advance.
A recording layer) and a dielectric layer for protecting this layer are laminated, and a protective layer of resin is further formed thereon. These recording layers and protective layers are formed by sputtering. Sputtering is a method in which the surface of a target placed in a vacuum chamber is struck out as fine particles with argon ions, and the particles are attached to a substrate to form a thin film. The particles hit by the argon ions scatter radially. Therefore, particles flying from various angles adhere to the substrate.

[0010]

As described above, a step between a land portion and a groove portion is formed on the surface of an optical disk substrate. Therefore, at the time of sputtering, a phenomenon occurs in that particles struck out of the target are blocked by the lands, so that the particles hardly adhere to the grooves. When the step between the land portion and the groove portion is small as in a conventional optical disk, this phenomenon is not remarkable, so that it does not cause a serious problem. However, this phenomenon becomes more remarkable as the step between the land and the groove increases. That is, in the optical disk of the deep groove, compared with the thickness of the thin film formed on the land portion,
The thin film formed in the groove portion becomes considerably thin. This is shown in FIG.

In such an optical disk, since the heat capacity of the land portion and the groove portion is largely different, even if a beam of the same intensity is irradiated, the temperature reached at the irradiated portion is largely different between the land portion and the groove portion. Therefore, if recording is performed on the land portion and the groove portion with the same beam intensity, the thickness and length of the recording mark will differ. That is, the temperature (recording sensitivity) at which a recording mark is formed differs between the land portion and the groove portion. Therefore, in order to record the same state in both the land portion and the groove portion, it is necessary to set different beam intensities for each. This problem applies not only to recording but also to erasure. In an optical disc having a large step between the land and the groove, there is a problem that the erasing beam intensity must be changed between the land and the groove.

As described above, the heat capacity of the land is larger than that of the groove, so that recording or erasing on the land is relatively larger than when recording or erasing on the groove. It is necessary to irradiate an intense beam. Therefore, a large amount of heat is generated in the land portion and flows to the groove portion. Since the heat capacity of the groove portion is small, the temperature rises significantly even by a small amount of heat flowing from the land portion. As a result, there is a problem that information recorded in the groove is erased.

When performing MSR reproduction, the temperature distribution due to the reproduction beam is used. Therefore, if the heat capacity of the land and the groove is largely different, the intensity of the reproduction beam must be largely changed between the land and the groove. Occurs. Therefore, in order to make the recording, erasing, and reproducing conditions the same in the land portion and the groove portion, it is necessary to make the thicknesses of the recording layer and the protective layer the same.

The present invention solves the above problems, and when forming a protective layer by sputtering, reduces the difference in thickness between a land portion and a groove portion. As a result, recording, erasing, and recording on the land portion and the groove portion are performed. It is an object of the present invention to provide a method of manufacturing an optical disk having a small difference in beam intensity when performing reproduction.

[0015]

An object of the present invention is to provide a method for manufacturing an optical disk for recording information on both a land portion and a groove portion, wherein the surface of the substrate on which the land portion and the groove portion are formed is provided. Furthermore, when forming a protective layer for protecting a recording layer for information recording, the protective layer is formed by performing sputtering using a sintered dielectric target. With this configuration, when the protective layer is formed, particles sputtered from the target have a small component in a direction parallel to the substrate, and as a result, the difference in the thickness of the protective layer between the land and the groove is reduced. Can be reduced. That is, unlike the reactive sputtering, the particles that jump out of the target are not scattered by the reactive gas.

According to a second aspect of the present invention, in the method for manufacturing an optical disk according to the first aspect, the step between the land and the groove is 80 to 600 nm. With this configuration, the difference in the thickness of the protective layer formed between the land and the groove can be reduced even for a substrate having a large step between the land and the groove. According to a third aspect of the present invention, in the method for manufacturing an optical disk according to the first or second aspect, the sintered dielectric target is a silicon nitride target (Si3N4). With this configuration, when the protective layer is formed, particles sputtered from the target have a small component in a direction parallel to the substrate, and as a result, the difference in the thickness of the protective layer between the land and the groove is reduced. Can be reduced.

According to a fourth aspect of the present invention, in the method for manufacturing an optical disk according to the first, second and third aspects, a bias voltage is applied to the substrate or the substrate holder when the protective layer is formed by performing sputtering. It is characterized by doing. With such a configuration, the particles sputtered from the target are accelerated in a direction perpendicular to the substrate, so that the influence of the velocity component in the oblique direction is reduced. As a result, the protective layer is easily formed also in the groove portion, and the difference in the thickness of the protective layer formed in each of the land portion and the groove portion can be reduced.

[0018] The invention according to claim 5 is the invention according to claims 1, 2,
The method for manufacturing an optical disk according to any one of Items 3 and 4, wherein the substrate is stationary when the protective layer is formed by performing sputtering. With such a configuration, the relationship that particles sputtered from the target move in a direction perpendicular to the substrate is maintained,
The difference in the thickness of the protective layer formed between the land and the groove can be further reduced.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram of a sputtering apparatus used in the method for manufacturing an optical disk according to the present invention. 1 includes a vacuum chamber 1, a vacuum pump 2, a sputtering gas inlet 3, a cathode 4, a substrate holder 5, an RF power source 6 for discharge, a DC power source 7 for bias, and a gas pressure gauge 8.

Inside the vacuum chamber 1, a cathode 4 is provided.
And a substrate holder 5. A target T can be mounted on the cathode 4, and a substrate S can be mounted on the substrate holder 5. The vacuum pump 2 exhausts the air in the vacuum chamber 1 to lower the pressure. The vacuum chamber 1 is provided with one or more sputtering gas inlets 3 so that a sputtering gas or a reactive gas can be supplied into the vacuum chamber 1. The discharge RF power source 6
An RF voltage is applied to the target through the cathode. The bias DC power supply 7 applies a DC voltage to the substrate holder 5. Gas pressure gauge 8 indicates the pressure in the vacuum chamber.

When an RF voltage is applied to the target from the discharge RF power supply 6 through the cathode, the plasma-generated sputtering gas (eg, argon gas) collides with the target surface and strikes out particles of the target material.
In the optical disk manufacturing method of the present invention, a DC voltage (bias voltage) is applied to the substrate holder by the bias DC power supply 7 when performing sputtering.

FIG. 2 is a vertical sectional view showing the structure of an optical disk manufactured by the method of manufacturing an optical disk according to the present invention using the sputtering apparatus shown in FIG. As shown in FIG. 2, the difference in the thickness of the thin film formed between the land portion and the groove portion is smaller than that of the optical disk manufactured by the conventional manufacturing method (shown in FIG. 3).

[0023]

Embodiment 1 (Production of a magneto-optical disk) A sputtering apparatus is prepared. This sputtering apparatus has a configuration in which a plurality of the sputtering apparatuses shown in FIG. 1 are continuous and can be moved from one vacuum chamber to another vacuum chamber while maintaining a vacuum state. A sintered silicon nitride target is mounted on the cathode 4 in the vacuum chamber 1, and two types of GdFeCo target and GdFe target as magnetic materials are mounted on the cathode 4 inside one vacuum chamber 1. , And a TbFeCo target. An RF voltage can be applied to the cathode 4 by a discharge RF power supply 6. Alternatively, a DC voltage can be applied by another DC (not shown) power supply.

Next, a plurality of types of optical disc substrates having various sizes having a step between the land portion and the groove portion on the surface in the range of 50 nm to 800 nm are prepared. The land and groove pitches of these substrates are 1.4 μm, and are formed in a spiral shape. Next, the above substrate is set on a substrate holder 5 provided in the vacuum chamber 1, and the inside of the vacuum chamber 1 is subjected to 1 × ex by a vacuum pump 2.
Evacuate to a vacuum of p (-6) Pa or less. Next, an argon gas is introduced into the chamber, the pressure in the vacuum chamber 1 is set to 3 × exp (−3) Pa, and sputtering is performed in this state using a sintered silicon nitride target to form a silicon nitride protective layer having a thickness of 3 nm. Form 75 nm. At this time, the power supplied to the discharge RF power supply 6 is set to 600 W, and no bias voltage is applied. Since silicon nitride is an insulator, R
This is because discharge occurs only by the F power source, and sputtering can be performed by that. That is, sputtering cannot be performed with a DC power supply.

Next, the substrate carrier is moved to another vacuum chamber, and argon gas is introduced again to make the pressure in the chamber 5 × exp (−3) Pa. In this state, sputtering is performed with a GdFeCo alloy target, and Gd25Fe60
Co15 (atomic%, Gd25%, Fe60%, Co15%, and so on)
A 30 nm thick reproducing layer is formed on the silicon nitride layer. At this time, the power supplied to the discharge RF power supply 6 is set to 400 W, and a DC voltage of 20 V is applied to the substrate holder 5 by the bias DC power supply 7.

Next, sputtering is performed with a GdFe alloy target in a state in which an argon gas is introduced and the pressure in the chamber is set to 5 × exp (−3) Pa, so that an intermediate layer of Gd29Fe71 is formed on the reproducing layer. Form 50 nm thick. At this time, the power supplied to the discharge RF power supply 6 is set to 400 W, and a DC voltage of 20 V is applied to the substrate holder 5 by the bias DC power supply 7.

Next, sputtering is performed with a TbFeCo alloy target in a state in which an argon gas is introduced and the pressure in the chamber is set to 5 × exp (−3) Pa, to obtain Tb21Fe63.
A memory layer of Co16 is formed to a thickness of 50 nm on the intermediate layer. At this time, the power supplied to the discharge RF power supply 6 is set to 400 W, and a DC voltage of 20 V is applied to the substrate holder 5 by the bias DC power supply 7.

Next, a protective layer made of silicon nitride is formed to a thickness of 70 nm on the memory layer in the same procedure as the first formation of the protective layer made of silicon nitride. That is, no bias voltage is applied. After the film is formed by sputtering according to the above procedure, a resin protective film is further applied to manufacture a magneto-optical disk capable of magnetic super-resolution reproduction (MSR). (Recording) Next, a magneto-optical recording / reproducing apparatus is prepared. This device uses a 680 nm wavelength semiconductor laser light source and a numerical aperture (NA).
An optical pickup with an optical system of 0.55 is equipped.
It also has a spindle motor for rotating the disk, a magnetic field application unit, and a signal processing circuit.

A magneto-optical disk having various land and groove steps is set in a magneto-optical recording / reproducing apparatus and rotated at a linear velocity of 9.0 m / s. While tracking the land, a laser beam of 9.0 mW intensity is condensed by the optical system of the optical pickup and irradiated to the magneto-optical disk. At the same time, a magnetic field having a strength of 300 Oe is applied in the erasing direction, and the magnetization direction of the memory layer in the land is aligned in one direction in the erasing direction, thereby performing initialization.

Next, the same operation is performed while tracking the groove portion, and the magnetization direction of the memory layer in the groove portion is aligned with the erasing direction in one direction for initialization. next,
While tracking the land, the laser beam is irradiated to the magneto-optical disk while pulse-modulating it at a 15 MHz duty ratio of 50% between the optimum recording level on the land and 1.0 mW to form a single-period mark of 0.3 μm length Record.

Next, while tracking the groove portion, the laser beam is irradiated on the magneto-optical disk while pulse-modulating the laser beam between the optimum recording level in the groove and 1.0 mW at a duty ratio of 50% at a 15 MHz duty cycle. Record a single cycle mark. (Evaluation by reproduction) A laser beam is irradiated to the magneto-optical disk while tracking the land where the mark is recorded, reproduction is performed, and the C / N (carrier level / noise level) value of the reproduction signal is measured. At this time, the reproducing laser beam intensity is increased from 1.5 mW to 4.0 mW at intervals of 0.1 mW, and the C / N value at each intensity is evaluated.

Next, a laser beam is applied to the magneto-optical disk to perform reproduction while tracking the groove portion where the mark is recorded, and the C / N (carrier level / noise level) value of the reproduced signal is measured. At this time, the reproducing laser beam intensity is increased from 2.0 mW to 4.0 mW every 0.1 mW, and the C / N value at each intensity is evaluated. These results are shown in FIG. FIG. 4 shows the reproduction signal C / N of a sample in which the step between the land and the groove is 60 to 600 nm. In FIG. 4, when the reproduction beam intensity is low, C / N
It is considered that the value is low because the magnetization of the memory layer is not transferred to the reproduction layer because the MSR reproduction is not performed.
Also, the reason why the C / N value is low when the reproducing beam intensity is high is considered to be that MSR reproduction is not performed because the temperature in the entire area of the reproducing beam spot becomes high.

FIG. 4 shows that in the optical disk manufactured by the optical disk manufacturing method of the present invention, the optimum reproduction beam intensity at the land and the optimum reproduction beam intensity at the groove are both about 3.0 mW, and the difference between the two is extremely small. This is because the difference in heat capacity between land and groove is small.
That is, the difference between the thicknesses of the thin films is small. Of course, the difference between the optimum recording beam intensity and the optimum erasing beam intensity between the land portion and the groove portion is extremely small.

Note that the step between the land and the groove is 600
In the case of the sample exceeding nm, the gap between the appropriate values of the reproduction beam intensity in the land portion and the groove portion becomes large. This is presumably because when the step between the land and the groove exceeds 600 nm, a protective layer is hardly formed on the groove and the heat capacity of the land and the groove greatly differs.

[0035]

Embodiment 2 (Preparation of a magneto-optical disk) A magneto-optical disk is manufactured by using the same sputtering apparatus shown in FIG. 1 as in the embodiment, and using the same optical disk substrate as in the embodiment. Next, a protective layer is formed. At this time, only the following contents are changed as compared with the first embodiment. That is, a DC voltage of 30 V is applied to the substrate holder 5 by the DC power supply 7 for bias.

Next, the substrate carrier is moved to another vacuum chamber, and a reproducing layer, an intermediate layer, and a memory layer are formed under the same conditions as in the first embodiment. Next, a silicon nitride layer is formed to a thickness of 70 nm on the memory layer by the same procedure as that for forming the first silicon nitride layer. That is, a DC voltage of 30 V is applied to the substrate holder 5 by the DC power supply 7 for bias.

After forming a film by sputtering according to the above procedure, a resin protective film is further applied to manufacture a magneto-optical disk capable of magnetic super resolution reproduction (MSR). (Evaluation by recording and reproduction)
Recording is performed in exactly the same manner as in Example 1, and is reproduced to evaluate the C / N value.

FIG. 5 shows the results. FIG. 5 shows the reproduction signal C / N of a sample in which the step between the land and the groove is 60 to 600 nm. In FIG. 5, the reason why the C / N value is low when the reproduction beam intensity is low is considered that the magnetization of the memory layer is not transferred to the reproduction layer because the MSR reproduction is not performed. Also, the reason why the C / N value is low when the reproducing beam intensity is high is considered to be that MSR reproduction is not performed because the temperature in the entire area of the reproducing beam spot becomes high. These are the same as those described with reference to FIG.

FIG. 5 shows that in the optical disk manufactured by the optical disk manufacturing method of the present invention, the optimum reproduction beam intensity in the land and the optimum reproduction beam intensity in the groove are both about 3.0 mW, and the difference between the two is compared with FIG. And even smaller. This is probably because the difference in heat capacity between the land portion and the groove portion is smaller, that is, the difference in the thickness of the protective layer between the land portion and the groove portion is smaller. Of course, the difference between the optimum recording beam intensity and the optimum erasing beam intensity between the land portion and the groove portion is further reduced.

[0040]

Comparative Example (Production of Magneto-Optical Disk) FIG. 1 Same as Example
A magneto-optical disk is manufactured by using the sputtering apparatus shown in FIG.
When forming the protective layer, a magneto-optical disk is manufactured in the same manner as in the example except that a normal silicon nitride target that is not sintered is used.

Next, sputtering is performed in the same manner as the first formation of the silicon nitride layer, and a silicon nitride layer is formed to a thickness of 70 nm on the memory layer. That is, a normal non-sintered silicon nitride target is used. After the film is formed by sputtering according to the above procedure, a resin protective film is further applied to manufacture a magneto-optical disk capable of magnetic super-resolution reproduction (MSR). (Evaluation by recording and reproduction)
Recording is performed in exactly the same manner as in Example 1, and is reproduced to evaluate the C / N value.

FIG. 6 shows the result. FIG. 6 shows a reproduction signal C / N of a sample in which the step between the land portion and the groove portion is 60 to 600 nm. As shown in FIG. 6, in the optical disk of the comparative example, the optimum reproduction beam intensity in the land was 3.0 mW, while the optimum reproduction beam intensity in the groove was 2.
It is 7 mW, and it can be seen that there is a great difference between the two.
This indicates that the heat capacity of the groove portion is smaller than the heat capacity of the land portion, that is, the thickness of the protective layer of the groove portion is smaller than the thin film of the land portion. Of course, the optimum recording beam intensity and the optimum erasing beam intensity are considerably smaller in the groove portion than in the land portion.

Note that the step between the land and the groove is 60 n.
For samples smaller than m, the gap between the appropriate values of the reproduction beam intensity at the lands and grooves is small.
This is presumably because in the sample in which the step between the land portion and the groove portion is smaller than 60 nm, a thin film is easily formed in the groove portion in the first place, so that the heat capacity in the land portion and the groove portion is small. The step between the land and groove is
Needless to say, in the case of a sample exceeding 600 nm, the gap between the appropriate values of the reproduction beam intensity in the land portion and the groove portion is further increased.

[0044]

As described above, according to the first aspect of the present invention, a protective layer for protecting a recording layer for information recording is formed on the surface of a substrate on which lands and grooves are formed. At this time, sputtering is performed using a sintered dielectric target. Thereby, the components of the particles sputtered from the target in the direction parallel to the substrate can be reduced. As a result, it is possible to provide an optical disc having a small difference in the thickness of the protective layer between the land and the groove.

According to the second aspect of the invention, the step between the land and the groove is 80 to 600 nm. This makes it possible to provide an optical disc having a small difference in the thickness of the protective layer between the land and the groove, even if the optical disc has a large step between the land and the groove. According to the third aspect of the present invention, the target used for forming the protective layer is made of sintered silicon nitride. Thereby,
During the formation of the protective layer, particles sputtered from the target have a small component in a direction parallel to the substrate. As a result, it is possible to provide an optical disk having a small difference in the thickness of the thin film between the land and the groove.

According to the fourth aspect of the present invention, when forming the protective layer by sputtering, a bias voltage is applied to the substrate or the substrate holder. Thereby, the particles sputtered from the target are accelerated in a direction perpendicular to the substrate, so that the influence of the oblique velocity component is reduced. As a result, a protective layer is easily formed also in the groove portion,
The difference in the thickness of the protective layer formed between the land and the groove can be reduced.

According to the fifth aspect of the present invention, when forming a recording layer or a protective layer for information recording by sputtering, the substrate is in a stationary state. Thereby, the relation that the particles sputtered from the target move in the direction perpendicular to the substrate is maintained. As a result, it is possible to provide an optical disc having a small difference in the thickness of the protective layer between the land and the groove.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a basic configuration of a sputtering apparatus used for a method of manufacturing an optical disc according to the present invention.

FIG. 2 is a vertical sectional view illustrating the structure of an optical disk manufactured by the method for manufacturing an optical disk of the present invention.

FIG. 3 is a vertical sectional view illustrating a structure of an optical disk manufactured by a conventional optical disk manufacturing method.

FIG. 4 is a graph illustrating a relationship between a reproduction beam intensity and a C / N value in lands and grooves of an optical disk manufactured by the method for manufacturing an optical disk of the present invention.

FIG. 5 is a graph illustrating a relationship between a reproduction beam intensity and a C / N value in lands and grooves of an optical disk manufactured by the method for manufacturing an optical disk of the present invention.

FIG. 6 is a graph illustrating a relationship between a reproduction beam intensity and a C / N value in lands and grooves of an optical disk manufactured by a conventional optical disk manufacturing method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Vacuum chamber 2 ... Vacuum pump 3 ... Sputtering gas introduction part 4 ... Cathode 5 ... Substrate holder 6 ... RF power supply for discharge 7 ... DC power supply for bias 8 ... Gas pressure gauge S ... Substrate T ... Target

Claims (5)

[Claims] 1. A method for manufacturing an optical disk for recording information on both a land portion and a groove portion, the method comprising protecting a recording layer for recording information on a surface of a substrate on which the land portion and the groove portion are formed. A method for manufacturing an optical disk, wherein the protective layer is formed by sputtering using a dielectric target when forming the protective layer. 2. The method for manufacturing an optical disk according to claim 1, wherein a step between the land and the groove is 80 to 600 nm. 3. The method for manufacturing an optical disc according to claim 1, wherein the dielectric target is a silicon nitride target. 4. The method for manufacturing an optical disk according to claim 1, wherein a bias voltage is applied to a substrate or a substrate holder when the protective layer is formed by performing sputtering. Manufacturing method. 5. The method for manufacturing an optical disk according to claim 1, wherein the substrate is stationary when the protective layer is formed by performing sputtering. Production method.