JP2003296974A - Method for manufacturing master disk for optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a master disk for an optical recording medium capable of efficiently manufacturing the master disk for the optical recording medium of a high recording density with high reliability. <P>SOLUTION: The master disk for the optical recording medium is manufacturing by exposing and developing a photoresist 11 on a substrate 11 to form rugged patterns 12 and 13, regulating the photoresist 11 to a glass transition point or above by performing post baking and detecting the reflected and diffracted light obtained by irradiating the rugged patterns 13 of the photoresist 11 with the laser beam in the post baking process step. The master disk for the optical recording medium is manufactured by exposing and developing the photoresist on the substrate to form the first rugged patterns, subjecting the substrate to dry etching using the photoresist as a mask to form the second rugged patterns, removing the photoresist remaining on the substrate and detecting the reflected and diffracted light obtained by irradiating the second rugged patterns of the substrate with the laser beam in the dry etching process step. <P>COPYRIGHT: (C)2004,JPO

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 a master for an optical recording medium, and more particularly to an optical recording medium such as an optical disc and a card-shaped optical recording medium, particularly a magneto-optical recording medium and a phase change type optical recording medium. It is suitable for application to a master for a high-density optical recording medium.

[0002]

2. Description of the Related Art In recent years, higher density has been required for various optical recording media such as optical disks, magneto-optical disks and phase change type optical disks. There is a demand for miniaturization and formation. For example, there is a demand for an optical recording medium that has the same size (diameter and thickness) as a DVD (digital video disk) and has a larger information capacity than a DVD, for example, 15 GB (gigabytes) or more.

Along with this, it is required to form a finer concavo-convex pattern also on a master for producing an optical recording medium.

Conventionally, when a master for an optical recording medium is manufactured, a fine pattern is manufactured by applying a lithography technique or a dry etching technique which is generally used for manufacturing a semiconductor device. For example, a photosensitive material layer formed on a substrate, for example, a photoresist, is formed with a fine pattern by photolithography, or anisotropic etching by dry etching is performed on the substrate using the photoresist with the fine pattern as a mask. By performing the above, and forming a fine pattern on the substrate, a master for an optical recording medium can be manufactured.

Now, let us consider the case of forming pits on a read-only optical disk (so-called ROM disk), for example. When a fine pattern for forming such pits is produced by the photolithography technique, the wavelength λ of the exposure light source and the aperture of the objective lens that collects the light from the exposure light source are used to determine the resolution of the pattern. The number (hereinafter referred to as NA) is included. The resolution R of a pattern when a photoresist is used is expressed by R = 0.61 × λ / NA (1) by the Raighly's resolution limit equation.

FIG. 9 shows the relationship between the wavelength λ of the exposure light source and the minimum value of the concavo-convex pattern of the optical disk calculated from the resolution R of the photoresist based on this equation (1). FIG. 9 shows the relationship between the wavelength λ of the exposure light source and the minimum value of the concavo-convex pattern of the optical disk when the numerical aperture NA of the objective lens is 0.9, that is, the minimum pit length on the vertical axis and the track pitch on the horizontal axis. Shows the relationship.

From FIG. 9, when the wavelength λ is 351 nm,
From the formula (1), the resolution limit is about 0.24 μm, the minimum pit length of the disk capacity is 0.24 μm, the track pitch TP is 0.47 μm, and the information capacity is about 4.7 G.
An information capacity of about 12 GB can be achieved in the same size as the B DVD. Further, when the wavelength λ is 266 nm, the resolution limit is about 0.18 μm from the formula (1), and similarly, in terms of disk capacity, the minimum pit length is 0.18 μm.
m, the track pitch TP is 0.33 μm, and about 15 G in the same size as a DVD having an information capacity of about 4.7 GB.
The information capacity of B can be achieved.

An optical disc having an information capacity of 15 GB was actually exposed by using an optical system in which the wavelength λ of the exposure light source was 266 nm and the numerical aperture NA of the objective lens was 0.9 using a novolac photoresist. When manufactured, a practical jitter value of 6.6% was achieved. The reproducing optical system used at this time has a structure in which the wavelength of reproducing light is 532 nm and the numerical aperture NA of the objective lens is 0.943.

By the way, in recent years, in addition to simply forming a fine pattern on an optical disk as in the case of manufacturing a semiconductor device, further improving the uniformity of individual patterns in the formed pattern, There has been a demand for reducing the roughness of the pattern edge and controlling the inclination angle of the pattern side wall.

This is because the wavelength of the light source is shortened from the near infrared region to the blue region and the numerical aperture NA of the objective lens of the optical pickup is increased in the reproduction (information reading) optical system of the optical disc. Along with this, the reading spot size is reduced and the MTF (modulation transfer function) is increased. Therefore, there arises a problem that the surface shape of the pattern, which cannot be a factor of jitter in the conventional optical disc, affects the jitter. This is because the. A reading spot size of a CD (compact disc) using an optical system having a reproduction light wavelength of 780 nm and an objective lens numerical aperture of 0.45, and an optical system having a reproduction light wavelength of 405 nm and an objective lens numerical aperture of 0.85 are used. A simple comparison with the reading spot size of the optical disk used shows that the latter is 0.2
It has been reduced by a factor of 7.

Here, the jitter factor of the optical disk is expressed by the following equation (2). (Jitter) ² = (Disk noise) ² + (Crosstalk) ² + (Intersymbol interference) ² + (Electrical noise) ² (2)

As shown in the equation (2), factors of optical disc jitter include disc noise caused by the shape of land areas and pits, the influence of crosstalk from adjacent tracks, and the influence of intersymbol interference before and after the pit. , And electrical noise that depends on the player.

Regarding the crosstalk and the intersymbol interference, a method for reducing the intersymbol interference noise and the crosstalk noise by introducing recording compensation has already been performed in a CD device or the like. In addition, in addition, the reproduced signal waveform is analyzed, the pit positions are slightly shifted back and forth, and simulation is performed to minimize intersymbol interference and crosstalk, and the results are fed back to the signal generation circuit formatter, A method of reducing crosstalk and intersymbol interference noise by repeating a series of processes of performing cutting (manufacturing of a master) again has been taken.

[0014]

On the other hand, the disk noise is randomly generated due to nonuniformity of the resist pattern formed by development, edge roughness, roughness of the resist itself, and the like. For this reason, it is very difficult to remove it in terms of an electric circuit, and it is often necessary to adjust the composition of the photoresist.

From the results of experiments conducted so far, it is known that the above-mentioned disk noise is the main cause of deterioration of jitter. In particular, as the recording density of an optical disk becomes higher due to the shortening of the wavelength and the higher NA, the disk noise has become more dominant as a factor for the deterioration of jitter.

Here, for example, a track pitch of 0.36 μ
m, bit length 0.13 μm / bit, film thickness of light transmission layer 1
Al formed on the surface of a pattern of 00 μm, pits, etc.
20GB with a disc structure with a reflectance of 20%
A read-only optical disk (ROM disk) having an information capacity of (gigabyte) was prepared, the total jitter value was measured, and each factor of jitter was analyzed. For the measurement, a reproducing optical system in which the light source was a Kr laser having a wavelength of 407 nm and the numerical aperture NA of the objective lens was 0.85 was used. As a result, the total jitter value was 8.6%, of which disk noise was 5.3% and crosstalk was 4.9%.
%, Intersymbol interference was 4.4%, and electrical noise was 1.5%. From this result, it is understood that the disk noise is the dominant factor of the jitter, but it is very difficult to reduce the disk noise by the conventional method for reducing the jitter. Also, it can be seen that the jitter component due to crosstalk and intersymbol interference is also large.

For this reason, in particular, in an optical disc having a structure in which recording and reproduction are performed by irradiating light from the side opposite to the substrate, a reflection film or a recording film formed on the substrate of the optical disc in order to reduce disc noise. The surface condition of is very important. Therefore, even in the manufacture of a master for an optical disk (for example, a glass master), the fine concavo-convex pattern of the master corresponding to the pits or grooves of the optical disk has the inclination angle and surface roughness of the side wall of the pattern and the shape of the pattern edge. It is essential to perform control so that a proper state is formed.

Conventionally, in order to control the state of the fine concavo-convex pattern formed on the master, recording compensation is introduced into the encoder and cutting (manufacturing of the master by a lithography technique or the like) is performed to reduce the width of each pit. Attempts have been made to make it narrower than the land area. However, this method has a problem that it requires a complicated process and that it takes time to set conditions. In addition, by forming a metal thin film on the master on which the fine concavo-convex pattern is formed by a sputtering method or the like, a master having smaller and narrower pits, grooves, etc. is produced, and a metal stamper is used by using this master. A method of making was also tried. However, the problem is that the pit shape changes due to thin film formation, and it is difficult to cleanly separate the metal stamper from the interface with the metal thin film (for example, the metal thin film remains attached to the stamper). Met.

As a method of solving the above-mentioned problems, there is a method of narrowing the groove width or the pit width by post-baking, that is, heat treatment after film formation to raise the temperature of the photoresist above the glass transition temperature to soften it. Conceivable. In this case, the photoresist having a glass transition temperature or higher finally becomes hemispherical due to the surface tension.

FIG. 10 shows the groove width when the resist pattern and the groove width are changed to a hemispherical shape in the rectangular resist pattern having a track pitch of 300 nm. As an example, when the resist has a thickness of 100 nm, a track pitch of 300 nm, and a land width of 150 nm, post-baking can be performed to finally reduce the groove width to 104.5 nm as indicated by a circle in FIG. it can.

Then, dry etching is performed on the substrate by using the resist pattern whose shape is changed as described above, thereby making it possible to form narrow grooves and pits with less crosstalk. Become.

Further, as a method for forming a fine uneven pattern on the master, by dry etching a substrate constituting the master, for example, a glass master or a silicon substrate, using a photoresist having the uneven pattern as a mask,
A method of forming smaller pits and grooves can be considered. In particular, when dry etching is performed under the condition of containing a gas species having a low vapor pressure and hydrogen, a deposit is further deposited on the side wall of the pattern that is normally formed, so a pattern smaller than the resist mask pattern is transferred by etching. It

However, when the above method is used,
The following problems occur. First, in the method of performing post-baking on the photoresist, depending on the shape of the concavo-convex pattern of the photoresist (for example, in the case of a rectangular shape with a track pitch of 300 nm, a resist thickness of 150 nm, and a land width of 250 nm), the land may be post-baked. The groove may disappear when connected.

Further, in the method of dry etching the substrate constituting the master, depending on the dry etching conditions, that is, gas species, source power, temperature, pressure and flow rate,
The etching rate, the inclination angle, and the etching selection ratio between the mask material (photoresist) and the substrate are variously changed, and there is a case where deposits without etching are prioritized. .

Due to the above-mentioned problems, it is necessary to measure the change of the surface shape due to post-baking or etching with the AFM (Atomic Force Microscope) every time when manufacturing the master, that is, for each master. In the AFM, since the measurement is performed by contacting with the sample, it is necessary to interrupt or terminate the post-baking process or the etching process before performing the measurement. In addition, it takes time and effort to adjust the sample for measurement in the AFM, and it is difficult to incorporate the AFM into a device that performs a post-baking process or an etching process. Therefore, it is difficult to efficiently manufacture a master for an optical disc having a high recording density.

Further, in the AFM, since the needle is brought into contact with the surface to perform the measurement, the accuracy of measurement in the direction parallel to the needle, that is, the vertical direction is highly reliable, but depending on the thickness of the needle, the direction perpendicular to the needle, that is, the horizontal direction. The accuracy of is affected. Therefore, it is difficult to accurately detect the width of the groove or pit of the fine pattern, for example. Therefore, it is difficult to accurately control the width of the groove or pit after the surface shape is changed by post-baking or etching.

In order to solve the above-mentioned problems, in the present invention, a master for an optical recording medium having a high recording density can be manufactured efficiently and with high reliability. It provides a method.

[0028]

A method of manufacturing a master for an optical recording medium according to the present invention comprises a step of exposing and developing a photoresist on a substrate to form a concavo-convex pattern by the substrate and the photoresist, and a step on the substrate. A step of performing post-baking on the photoresist on which the concavo-convex pattern is formed to reach the glass transition point or higher, and irradiating the concavo-convex pattern of the photoresist with laser light in the step of performing post-baking on the photoresist. Then, the obtained reflected diffracted light is detected.

According to the above-described method for producing a master for an optical recording medium of the present invention, post-baking is performed on the photoresist on the substrate on which the concavo-convex pattern is formed so as to reach the glass transition point or above, thereby making the photoresist. The shape of the concavo-convex pattern changes to a hemisphere due to surface tension. Then, in the step of performing this post-baking, the uneven pattern of the photoresist is irradiated with laser light and the resulting reflected diffracted light is detected to detect the size of the uneven pattern (for example, the width of the groove or pit) in real time. It becomes possible to do.

The method of manufacturing a master for an optical recording medium of the present invention comprises:
A step of exposing and developing the photoresist on the substrate to form a first uneven pattern formed by the substrate and the photoresist, and dry etching the substrate using the photoresist as a mask to form a second uneven pattern. Reflected diffracted light obtained by irradiating the second concave-convex pattern of the substrate with laser light in the step of performing dry etching on the substrate, which includes a step and a step of removing the photoresist remaining on the substrate. Is to detect.

According to the above-described method of manufacturing the master for an optical recording medium of the present invention, the reflection diffraction obtained by irradiating the second concave-convex pattern of the substrate with laser light in the step of performing dry etching on the substrate. By detecting the light, it becomes possible to detect the dimension of the concave-convex pattern (for example, the width of the groove or the pit) in real time during the dry etching process.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a step of exposing and developing a photoresist on a substrate to form an uneven pattern formed by the substrate and the photoresist, and a photoresist having the uneven pattern formed on the substrate. And a step of post-baking the glass transition point or higher. In the step of post-baking the photoresist, the uneven pattern of the photoresist is irradiated with laser light, and the obtained reflected diffraction light is detected. It is a method for manufacturing a master for an optical recording medium.

According to the present invention, in the above-described method for manufacturing a master for an optical recording medium, after the step of post-baking, the substrate is dry-etched using the photoresist as a mask to form the second uneven pattern on the substrate. A step of forming and a step of removing the photoresist remaining on the substrate are performed thereafter.

The present invention also provides a reflection diffraction pattern obtained by irradiating the second concave-convex pattern of the substrate with laser light in the step of dry etching the substrate in the method for manufacturing a master for optical recording medium. Detect light.

According to the present invention, the steps of exposing and developing a photoresist on a substrate to form a first concave-convex pattern formed of the substrate and the photoresist, and performing dry etching on the substrate using the photoresist as a mask are performed. 2 has a step of forming a concave-convex pattern and a step of removing the photoresist remaining on the substrate. In the step of performing dry etching on the substrate, the second concave-convex pattern of the substrate is irradiated with laser light. And a method for manufacturing a master for an optical recording medium, which detects the obtained reflected diffracted light.

As one embodiment of the present invention, a method of manufacturing a master for an optical recording medium and a method of manufacturing an optical recording medium using the master for an optical recording medium will be described with reference to FIGS. The present embodiment applies the present invention to the case where an optical disk master is manufactured as a master for an optical recording medium.

First, the substrate 10 is placed on a turntable (not shown), and the substrate 10 is rotated at a predetermined rotation speed by the turntable. And this rotating substrate 1
0, a photoresist 11, for example, a photosensitive material layer that becomes alkali-soluble by exposure to light, a so-called positive photoresist, is applied to a uniform thickness by, for example, a spin coating method (see FIG. 1A above).

As the substrate 10, for example, a glass substrate, a quartz substrate, a silicon substrate, a metal substrate or the like whose surface is polished and washed to be flat can be used. Of these, for example, an alkali-containing glass substrate can be used as the glass substrate. The photoresist 11 may be a negative type, and may be of any type such as a novolac type resist or a chemically amplified resist.

Next, the substrate 10 coated with the photoresist 11 is rotated by a turntable at a predetermined number of revolutions, and an energy beam, such as a laser beam, an electron beam, or an X-ray, whose intensity is modulated in accordance with a recording signal is applied. Then, the light is focused on the photoresist 11 by an objective lens (not shown), and the photoresist 11 is exposed as shown in FIG. 1B. The shaded area 11A in the figure indicates the exposed portion.

Subsequently, this exposed photoresist 1
1 is developed with an organic or inorganic alkaline developing solution to remove the exposed portion 11A, and as shown in FIG. 1C, corresponds to an uneven structure composed of grooves or pits recorded on an optical recording medium. The uneven pattern thus formed is formed on the photoresist 11.

At this time, as shown in FIG. 2, as the concavo-convex pattern of the photoresist 11, the concavo-convex pattern 12 of the signal area is formed by the concavo-convex pattern of grooves or pits.
In addition to the above, an uneven pattern for monitoring (for example, monitor groove) 13 for monitoring the pattern of the photoresist 11 is formed on the outer peripheral portion of the substrate 10. Therefore, in the step of exposing the photoresist (FIG. 1B), the exposure is performed so as to correspond to the monitor concavo-convex pattern 13.

After that, the substrate 10 and the photoresist 11 are post-baked by using a hot plate type or convection type baking device. As a result, the rectangular concavo-convex pattern of the photoresist 11 shown in FIG. 3A changes into a hemispherical concavo-convex pattern as shown in FIG. 3B. By changing from the rectangular shape to the hemispherical shape in this manner, the thickness D1 of the uneven pattern of the photoresist 11 after the change becomes thinner than the thickness D of the uneven pattern before the change. Further, the width GW1 of the groove between the concavo-convex patterns after the change is smaller than the width GW of the groove before the change. TP in Figure 3
Indicates the track pitch, and LW indicates the width of the land. The track pitch TP does not change before and after post baking.

The substrate 1 and the photoresist 1 having a hemispherical concavo-convex pattern formed thereon are manufactured in this manner.
The master disk for the optical disk can be constructed as it is with 1.

On the other hand, the photoresist 11 is further added.
Substrate 1 using the hemispherical uneven pattern of
By performing dry etching on 0, the substrate 1
It is also possible to fabricate a master for an optical disc by forming a second concave-convex pattern at 0. That is, as shown in FIG. 7A, by using the photoresist 11 having a hemispherical concavo-convex pattern as a mask, dry etching is performed on the substrate 10 to correspond to the concavo-convex pattern (first concavo-convex pattern) of the photoresist 11. The second uneven pattern 10B is formed on the substrate 10. Then, the photoresist remaining on the substrate 10 can be removed to prepare the substrate 10 having the second uneven pattern 10B as shown in FIG. 7B, which can be used as a master for an optical disc. You can

In the present embodiment, particularly in the above post-baking step, as shown in FIG. 4, a monitor means including a light source 15 and a detector 16 is provided for a monitor uneven pattern (monitor groove or the like) 13. To place.
Then, laser light is emitted from the light source 15, and the reflected diffracted light is detected by the detector 16.

As a result, it is possible to monitor the change in size and shape in the concavo-convex pattern of the photoresist 11 by post-baking, for example, the change in groove width (GW → GW1 in FIG. 3).

Furthermore, by adjusting the post-baking conditions (for example, temperature and time) based on the detection result by the monitor, it becomes possible to accurately control the size and shape of the concavo-convex pattern, for example, the groove width.

Further, while monitoring in real time during the post-baking process, the post-baking process is stopped or the temperature or the time of the post-baking process is increased based on the detection result of the monitor. It is possible to control so that an uneven pattern is formed in the groove width.

Then, in order to improve the accuracy of this control,
It is desirable that the track pitch TP of the monitor concavo-convex pattern (monitor groove or the like) 13 be equal to the track pitch TP of the concavo-convex pattern 12 in the signal area.

When the track pitch TP is 320 nm, for example, the first-order diffracted light is finally observed using light in the ultraviolet region having a wavelength λ of 266 nm or 351 nm. However, ultraviolet light damages the photoresist 11 and the like and must be avoided. Therefore, a blue semiconductor laser having a long wavelength but a small wavelength of 405 nm is used as the light source 15 of the monitor laser light.

For example, when the laser light is incident on the substrate 10 and the photoresist 11 from the light source 15 at the incident angle ω1 = 30 degrees, the reflected diffracted first-order light is observed in the direction of about 50 degrees (emission angle ω2). To be done. Then, for example, the light source 15 and the detector 16 are respectively arranged at positions 10 cm apart from the surface of the photoresist 11 on the substrate 10 in the vertical direction, and the laser is inclined from the light source 15 by 30 degrees with respect to the normal to the substrate surface. Make light incident (incident angle ω1 = 30 degrees)
Thus, the reflected diffracted light can be detected at a position that is 6.1 cm away from the light source 15 in the horizontal direction. The position of the detector 16 is determined by the wavelength λ, the incident angle ω1, and the track pitch TP.
Is calculated. Detector 1 in this position
The diffracted light intensity I detected in 6 can be calculated by the following equation 1. In Equation 1, N is the number of grooves, k is a wave number vector (= 2π / λ), a is the track pitch (TP), and b is the groove width.

[0052]

[Equation 1]

Here, for example, the track pitch TP is set to 32.
0 nm and the wavelength λ of the laser light from the light source 15 is 405 nm
5 shows the relationship between the reflected diffraction angle and the diffracted light intensity I when the incident angle ω1 of the laser light is 30 degrees and the number of tracks N is 10,000. From FIG. 5, it can be seen that the first-order diffracted light is detected in the −49.96 degrees (about −50 degrees) direction.

Further, in the post-baking process, the shape of the concave-convex pattern changes as described above, so that, for example, the groove duty ratio changes, so that the intensity of the first-order diffracted light changes. 6 shows changes in the diffracted light intensity I of the first-order diffracted light due to changes in the groove width under the same conditions (track pitch TP, laser light wavelength λ, incident angle ω1) as in FIG. From FIG. 6, when the groove width changes from 150 nm to 196 nm, the intensity ratio before and after the change is 0.
Since it is 485, it is possible to detect a sufficient change.

According to the above-described present embodiment, by performing the post-baking, the concavo-convex pattern formed by the photoresist 11 becomes hemispherical, the width thereof widens, and the interval between the patterns becomes narrow. As a result, a master having a narrow concave-convex pattern can be manufactured by directly manufacturing the master, or by performing dry etching on the substrate using the concave-convex pattern having the wide width as a mask to manufacture the master. You can

Further, according to the present embodiment, particularly in the post-baking step, the uneven pattern of the photoresist 11 is irradiated with the laser light from the light source 15 and the reflected diffracted light is detected by the detector 16. This makes it possible to monitor the uneven pattern and estimate the dimension and shape of the uneven pattern. As a result, the detection result obtained by the monitor can be fitted to the diffracted light intensity pattern corresponding to the uneven pattern to be formed, and the conditions (temperature, time, etc.) of the post-baking step can be controlled,
It is possible to control the dimensional shape of the uneven pattern of the photoresist 11 with higher accuracy.

Further, since the uneven pattern (dimensional shape) can be monitored in a non-contact manner, the process can be speeded up. Then, in the device that performs post bake,
Since it is possible to incorporate monitoring means such as the light source 15 and the detector 16, it is possible to monitor in real time.

Therefore, it is possible to control the size and shape of the concavo-convex pattern of the photoresist 11 to produce a concavo-convex pattern having a desired size and shape with higher accuracy, and to shorten the time required for the post-baking process. Will be possible.

Then, using the master thus manufactured, an optical recording medium such as an optical disk is produced,
In the recording layer of the optical recording medium, a concavo-convex pattern having a narrow width (for example, groove width) can be formed. This makes it possible to realize a high recording density in the optical recording medium and reduce crosstalk between adjacent tracks during reproduction.

In the above-described present embodiment, the photoresist 11 is formed into a hemispherical shape by post-baking and spreads to the outside to narrow the groove width. On the contrary, the photoresist 11 contracts by post-baking to expand the groove width. Even with the photoresist having the structure, the change in the groove width can be detected by monitoring as in the present embodiment.

Next, an optical recording medium master according to the present embodiment was actually manufactured, the surface condition of the master was observed, and the characteristics of the optical recording medium manufactured using this master were evaluated.

Example 1 An 8-inch silicon wafer having a thickness of 0.725 mm was prepared as a substrate 10, and a chemically amplified resist (ZEP520 manufactured by ZEON CORPORATION) was used as a photoresist 11 on the silicon wafer to a thickness of 20 nm.
Was applied at a thickness of. Next, the photoresist 11 is exposed to an accelerating voltage of 15 kV to obtain a 20 GB density EFM modulation pattern (track pitch 0.3.
2 μm) is recorded in a region of radius r = 20 to 30 mm from the center, and a radius r = 6 corresponding to the outer peripheral portion of the optical disc.
A groove structure having a track pitch of 0.32 μm to be the monitor concavo-convex pattern 13 was recorded in a region of 6 to 69 mm. In addition, an organic alkaline developer (Tokyo Oka NMD-
By 3), development was performed for 15 seconds to form fine uneven patterns 12 and 13 on the photoresist 11.

It was observed by AFM that the groove width of the monitor concavo-convex pattern 13 was 150 nm. Then, in order to reduce the surface roughness of the photoresist 11 and the bottom of the pits, post baking was performed on a hot plate at 150 ° C. At that time, the light source 1
The blue semiconductor laser of No. 5 (wavelength 405 nm) is irradiated on the monitor groove structure formed on the outer peripheral portion to detect the detector 1.
In step 6, the reflected first-order diffracted light was detected, and the intensity was controlled to be 1.57 compared to the initial value. As a result, 150 nm
It was possible to narrow the groove width to 100 nm as calculated.

An optical disk was manufactured using a disk substrate manufactured from a master plate made of the silicon wafer thus obtained and a photoresist on the silicon wafer, and an EFM having a density of 20 GB was prepared.
The modulation pattern was reproduced. As a result, it was confirmed that the jitter was reduced by 1% as compared with the 20 GB density optical disc manufactured by the conventional manufacturing method.

Next, another embodiment of the present invention will be described. First, similarly to the previous embodiment (see FIGS. 1A to 1C), as shown in FIG. 8A, a fine uneven pattern is formed on the photoresist 11 on the substrate 10. This fine concavo-convex pattern has a concavo-convex pattern 12 in the signal area and a concavo-convex pattern (monitor groove or the like) 13 for monitoring in the outer peripheral portion similar to FIG.

After that, the concavo-convex pattern of the photoresist 11 (referred to as a first concavo-convex pattern) is used as a mask.
Dry etching is performed on the substrate 10 using an etching gas having a low vapor pressure or an etching gas having a deposition rate equal to or higher than the etching rate.

At this time, the etching rate in the dry etching depends on the inclination angle of the object, and the etching rate is good in the direction perpendicular to the incident direction of the ion gas, but in the direction parallel to the incident direction. Is low. As a result, by using the above-described etching gas, it becomes possible to fabricate the groove and pit concavo-convex pattern to be smaller than the mask pattern. By the dry etching process under such conditions, as shown in FIG. 8B, the second uneven pattern 10C smaller than the opening of the photoresist 11 used as the mask is formed on the substrate 10.

At this time, by arranging monitor means (for example, the same as the light source 15 and the detector 16 in FIG. 4) in the etching chamber, the monitor groove 13 formed on the outer peripheral portion of the substrate 10 is irradiated with the laser from the light source. It becomes possible to irradiate light, detect reflected diffracted light, and monitor in real time. As a result, it is possible to indirectly grasp the shape change of the substrate 10 due to etching, which has not been known by the conventional etching plasma gas emission spectrum.

Then, by feeding back the detection result to the dry etching condition, it becomes possible to accurately control the dimensional shape, such as the groove width, of the concavo-convex pattern 10C of the substrate 10 formed by the dry etching.

Further, while monitoring in real time during the dry etching process, from the detection result by the monitor, for example, the dry etching process is stopped, the time of the dry etching process is extended, or the condition is changed (for example, the condition related to the etching rate is changed). Change)
It is possible to control so that the concavo-convex pattern is formed in a predetermined groove width.

According to the above-described present embodiment, the substrate 1 is formed by using the etching gas having a low vapor pressure or the etching gas having a deposition rate equal to or higher than that of the etching rate.
By dry etching 0, a pattern 10C having a width narrower than the opening of the photoresist 11 used as the mask is formed. As a result, a master having a narrow uneven pattern can be manufactured by the substrate 10 on which the pattern 10C having the narrow width is formed.

According to the present embodiment, particularly in the dry etching process for the substrate 10, the substrate 10 is
Irradiate laser light from the light source to the uneven pattern 10C of
Since the reflected diffracted light is detected by the detector, it is possible to monitor the uneven pattern 10C and estimate the size and shape of the uneven pattern. As a result, the detection result obtained by the monitor can be fitted to the diffracted light intensity pattern corresponding to the uneven pattern to be formed, and the conditions of the dry etching process can be controlled, and the dimensional shape of the uneven pattern 10C of the substrate 10 can be controlled. Can be controlled with higher accuracy.

Further, since the uneven pattern 10C (the size and shape) can be monitored in a non-contact manner, the process can be speeded up. Further, since it becomes possible to incorporate monitor means such as a light source and a detector into the apparatus for performing dry etching, it becomes possible to monitor in real time.

Therefore, it is possible to control the size and shape of the uneven pattern 10C of the substrate 10 to form an uneven pattern having a desired size and shape with higher accuracy, and to shorten the time required for the dry etching process. Will be possible.

Then, using the master thus manufactured, an optical recording medium such as an optical disk is produced,
In the recording layer of the optical recording medium, a concavo-convex pattern having a narrow width (for example, groove width) can be formed. This makes it possible to realize a high recording density in the optical recording medium and reduce crosstalk between adjacent tracks during reproduction.

It is also possible to combine the two embodiments described above. That is, a step of forming a hemispherical concavo-convex pattern on the photoresist 11 by post-baking, and a step of performing dry etching on the substrate 10 under the condition that the groove width is narrowed by using the photoresist 11 as a mask, The size and shape of the uneven pattern of the photoresist 11 is detected by the monitor means in the post-baking process, and the substrate 1 is further processed in the dry etching process.
It is also possible to detect the dimensional shape (groove width, etc.) of the uneven pattern of 0 by the monitor means.

In this case, the photoresist 11
The semi-spherical concavo-convex pattern can be transferred to the substrate 10 by normal dry etching to form the second concavo-convex pattern on the substrate 10 (FIG. 7), and the groove width can be made narrower. It becomes possible to control the narrowed groove width with dimensional accuracy by the monitor.

In each of the above-described embodiments, in order to monitor the state of the concavo-convex pattern, the monitor groove is formed in the outer peripheral portion separately from the signal area. However, the monitor groove is not formed and the signal area is not formed. It is also conceivable to irradiate the uneven pattern with laser light for monitoring. For example, in the post-baking process, when monitoring the condition of the uneven pattern, as long as the monitoring means (light source and detector) are arranged so as not to interfere with the post-baking, the uneven pattern of the signal area can be directly measured. It is also possible to irradiate laser light for monitoring.

However, in the dry etching process,
When monitoring the state of the concavo-convex pattern, it is necessary that the dry etching by the etching means and the irradiation of the laser light and the detection of the reflected diffracted light by the monitoring means do not intersect with each other. This is because in the post-baking step, the direction of heat transfer can be arbitrarily controlled by selecting the configuration of the heating means, whereas the dry etching by the etching means is performed linearly. Therefore, in the dry etching process, as shown in FIG.
As shown in FIG. 3, a mask pattern is formed on the outer peripheral portion of the substrate 10 so as to form the concave-convex pattern 13 for monitoring, and the monitor means (for example, the light source 15 and the detector 16) is arranged outside the substrate 10, It is desirable that the laser beam is obliquely irradiated from the outside of the substrate 10 to perform the dry etching while monitoring the state of the uneven pattern.

In the above-mentioned embodiments and examples, description is made by applying to the case where an optical disc, for example, a read-only optical disc (ROM disc) is produced from the optical recording medium master according to the present invention. The optical recording medium having the structure, for example, not only a disc shape but also an optical recording medium of other shapes (such as a card shape), for example, a write-once type optical recording medium, a magneto-optical recording medium, a phase change type optical recording medium, etc. The present invention can be applied.

The present invention is not limited to the above-mentioned embodiments, and various other configurations can be adopted without departing from the gist of the present invention.

[0082]

According to the present invention described above, in the post-baking step and the dry etching step for the substrate, that is, the step of changing the shape of the concavo-convex pattern, the concavo-convex pattern is irradiated with laser light to detect reflected diffracted light. Due to
The uneven pattern can be monitored and its size and shape can be estimated. As a result, the detection result obtained by the monitor is fitted to the diffracted light intensity pattern corresponding to the uneven pattern to be formed, and the post-baking process and the dry etching process on the substrate are controlled to determine the dimensional shape of the uneven pattern. It becomes possible to control with higher accuracy.

Since the means for monitoring the concave-convex pattern can be incorporated in the apparatus for performing post-baking or dry etching, it is possible to monitor in real time. This makes it possible to control the post-baking process and the dry etching process for the substrate in real time.

Therefore, according to the present invention, it becomes possible to control the size and shape of the concavo-convex pattern formed on the master for optical recording medium with higher accuracy. Then, for example, an uneven pattern having a narrow width is formed on the master, and an optical recording medium is manufactured using this master so that the pattern has a narrow width (such as a groove), a high recording density, and a crosstalk at the time of reproduction. It is possible to obtain an optical recording medium with reduced

Further, since the uneven pattern can be monitored in a non-contact manner, the process can be speeded up and the master for an optical recording medium can be efficiently manufactured.

[Brief description of drawings]

1A to 1C are process diagrams illustrating a method for manufacturing an optical recording medium master according to an embodiment of the present invention.

FIG. 2 is a view showing a state in which a monitor concavo-convex pattern is formed on an outer peripheral portion of a substrate.

FIG. 3 is a diagram illustrating changes in the shape of the photoresist before and after A and B post-baking.

FIG. 4 is a diagram showing a configuration in which monitor means is arranged with respect to the uneven pattern of photoresist.

FIG. 5 is a diagram showing a relationship between a reflection diffraction angle and a diffracted light intensity.

FIG. 6 is a diagram showing a change in diffracted light intensity of first-order diffracted light due to a change in groove width under the same conditions as in FIG.

7A and 7B are process diagrams showing a method for producing a master by dry-etching a substrate using an uneven pattern of a photoresist having a hemispherical shape.

8A and 8B are process diagrams illustrating a method for manufacturing an optical recording medium master according to another embodiment of the present invention.

FIG. 9 is a diagram showing the relationship between the wavelength λ of the exposure light source and the minimum value of the concavo-convex pattern of the disk calculated from the resolution of the photoresist.

FIG. 10 is a diagram showing a relationship between a resist thickness and a groove width in a rectangular resist pattern having a track pitch of 300 nm, and a groove width when the resist pattern finally becomes hemispherical after post baking.

[Explanation of symbols]

10 substrate, 10B, 10C, 12, 13 uneven pattern, 11 photoresist, 15 light source, 16 detector, GW, GW1 groove width, TP track pitch

Claims (4)

[Claims] 1. A step of exposing and developing a photoresist on a substrate to form an uneven pattern of the substrate and the photoresist, and a post-baking process for the photoresist having the uneven pattern on the substrate. And a step of setting the glass transition point or higher, and in the step of post-baking the photoresist, irradiating the concavo-convex pattern of the photoresist with laser light to detect reflected diffracted light obtained. A method of manufacturing a master for an optical recording medium, comprising: 2. A step of dry etching the substrate using the photoresist as a mask after the step of performing the post-baking to form a second concavo-convex pattern on the substrate, and thereafter forming a second uneven pattern on the substrate. The step of removing the remaining photoresist is performed.
A method for manufacturing a master for an optical recording medium according to. 3. The step of performing dry etching on the substrate, irradiating the second concave-convex pattern of the substrate with laser light to detect the reflected diffracted light obtained. A method for producing a master for an optical recording medium as described above. 4. A step of exposing and developing a photoresist on a substrate to form a first uneven pattern of the substrate and the photoresist, and dry etching the substrate using the photoresist as a mask. Forming a second uneven pattern on the substrate, and removing the photoresist remaining on the substrate. In the step of dry etching the substrate, the second uneven pattern on the substrate is formed. A method of manufacturing a master for an optical recording medium, which comprises irradiating a laser beam on the substrate and detecting the resulting reflected diffracted light.