JPH10302300A - Manufacturing method of recording medium master, exposure method, recording and / or reproducing apparatus - Google Patents

Abstract

[PROBLEMS] To irradiate a photosensitive layer with light condensed by an objective lens to expose the photosensitive layer, while reducing the spot diameter smaller than a diffraction limit and reducing the influence of side lobes. I do. SOLUTION: When exposing a photosensitive layer by irradiating light condensed by an objective lens to the photosensitive layer, the photosensitive layer has three or more regions formed substantially concentrically around an optical axis, and adjacent regions. Are arranged in the exposure optical system. Then, after the phase shift mask causes a phase shift in the entrance pupil plane with respect to the light wavefront incident on the objective lens, the photosensitive layer is exposed.
As a result, the spot diameter becomes smaller than the diffraction limit,
In addition, the peak intensity of all side lobes generated near the main spot is set to be 5% or less of the peak intensity of the main spot.

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 recording medium master which serves as an information recording medium master. Further, the present invention relates to an exposure method for exposing a predetermined region of the photosensitive layer by irradiating light condensed by an objective lens to a photosensitive layer formed on a support. Further, the present invention relates to a recording and / or reproducing apparatus for optically recording and / or reproducing.
The present invention also relates to reducing the diameter of a spot formed when light is condensed in these.

[0002]

2. Description of the Related Art An optical disk has an optically transparent plastic disk substrate, on which a signal recording area for recording an information signal is formed. In the signal recording area, a continuous grooved groove,
A pit row composed of a large number of pits is formed in a spiral or concentric manner at a predetermined track pitch for each track. In an optical disk, one surface of a disk substrate is usually used as a signal recording surface on which grooves or pit rows are formed, and the other surface is used as a reading surface. That is, when a signal is reproduced from an optical disk, a side on which no groove or pit row is formed is set as a reading surface, and laser light is irradiated from the side of the reading surface.

In such an optical disk, the irregularities such as grooves and pit rows formed on the surface of the disk substrate affect the performance as an information recording medium. Therefore, in order to achieve particularly high recording density, it is required to manufacture a disk substrate with high precision.

[0004] When manufacturing such a disk substrate,
First, a photoresist serving as a photosensitive layer is applied on a glass master serving as a support, and the photoresist is exposed so as to correspond to a desired pattern of irregularities. At this time,
Exposure of the photoresist is performed by condensing laser light with an objective lens. In the following description, such a step of exposing the photosensitive layer is referred to as an exposing step.

[0005] Next, by developing the exposed photoresist, a predetermined pattern of irregularities is formed on the photoresist, and then, Ni plating is performed on the photoresist on which the predetermined pattern of irregularities has been formed. Then, by removing the Ni plating, a recording medium master, that is, a stamper, on which the irregularities of the predetermined pattern are transferred, is obtained. Thereafter, the disk substrate is formed by injection molding using the stamper thus formed as a mold.

When manufacturing a disk substrate as described above,
The exposure of the photoresist in the exposure step is performed by condensing the laser beam with the objective lens as described above. That is, when exposing the photoresist, an objective lens having a circular aperture pupil is used as a condensing lens for condensing laser light for exposing along a pit or groove shape. The light intensity distribution in the focal plane of the light condensed by the objective lens having such a circular aperture pupil is shown in FIG.
As shown in (1), the distribution has a peak at the center.
Here, the diameter d (hereinafter, referred to as spot diameter d) of the first dark ring formed around the main spot of the condensed light is minimized at the diffraction limit. In particular,
Assuming that the wavelength of the laser beam is λ and the numerical aperture of the objective lens is NA, the spot diameter d at the diffraction limit is given by the following equation (1-
It is represented by 1).

D = 1.22 × λ / NA (1-1) By the way, as the recording density of the optical disk is increasing, the disk area occupied by one bit of data is becoming smaller. Is coming. Therefore, in order to form finer pits or finer grooves,
It is required that the spot diameter d when exposing the photoresist in the exposure step be made smaller and the area exposed by the collected light be made smaller.

Since the minimum value defined as the diffraction limit of the spot diameter d is expressed by the above equation (1-1), in order to reduce the spot diameter d, the wavelength λ of the laser beam used must be shortened. do it. That is, conventionally, in the exposure step, light in the visible light region was used. However, if light in the ultraviolet region, which is light having a shorter wavelength, is used, the spot diameter d
Can be made smaller. However, when light in the ultraviolet region is used, there is a problem that adjustment of the optical system becomes difficult. Therefore, it is difficult to reduce the spot diameter d by shortening the wavelength λ of the laser beam used in the exposure step.

Further, since the minimum value defined as the diffraction limit of the spot diameter d is expressed by the above equation (1-1), in order to reduce the spot diameter d, the numerical aperture NA of the objective lens must be changed. You just need to increase it. However, the numerical aperture NA of the objective lens has already been increased to almost its limit at this stage, and cannot be increased further. Therefore, it is also difficult to reduce the spot diameter d by increasing the numerical aperture NA of the objective lens.

As described above, in the conventional optical system in which the spot diameter d is defined by the light wavelength λ and the numerical aperture NA, the reduction of the spot diameter has almost reached the limit, and the light is exposed in the exposure process. It is very difficult to make the area smaller. Therefore, the light wavelength λ and the numerical aperture NA
By changing parameters other than the above, the spot diameter d
There is a demand for a method of reducing the size.

As a method for realizing this, as shown in FIG. 22, an annular opaque plate 1 is placed on the entrance pupil plane of the objective lens 101.
JP-A-3-63947 discloses a method in which the spot diameter d can be made smaller than the diffraction limit defined by the light wavelength λ and the numerical aperture NA of the objective lens 101 by arranging 02. ing. As shown in FIG. 23, the annular light-shielding plate 102 includes a light-shielding portion 102a having a circular opening and a circular light-shielding portion 102b having a smaller diameter than the opening formed in the light-shielding portion 102a. The light shielding plate is disposed above, and has a ring-shaped opening 102c formed between the light shielding portion 102a and the light shielding portion 102b. The outer diameter of the annular opening 102c is referred to as an entrance pupil diameter d0, and the inner diameter of the annular opening 102c is referred to as an annular diameter d1.

When such an annular light shielding plate 102 is used,
When the wavelength λ of light is 413 nm and the NA of the objective lens 101 is 0.90, if the orbicular zone diameter d1 is 50% of the entrance pupil diameter of the objective lens 101, the spot diameter d is about 80% of the diffraction limit. If the orbicular zone diameter d1 is 80% of the entrance pupil diameter of the objective lens 101, the spot diameter d becomes about 70% of the diffraction limit as shown in FIG. In FIG. 24, the dotted line shows the light intensity distribution when the annular light shielding plate 102 is not used, and the solid line shows the annular light shielding plate whose annular diameter d1 is 80% of the entrance pupil diameter of the objective lens 101. 10 shows the light intensity distribution when the reference numeral 102 is used. The light intensity I is
The peak intensity of the main spot is standardized as 1.

As described above, when the annular light shielding plate 102 is used, the spot diameter d can be made equal to or smaller than the diffraction limit. However, this method is very difficult to actually apply to the exposure step because the loss of the incident light amount due to the annular light shielding plate 102 is large. Therefore, while suppressing the loss of the incident light amount,
As a method for making the spot diameter d equal to or less than the diffraction limit, FIG.
As shown in (2), a method of disposing a phase shift mask 103 in front of the objective lens 101 and changing the phase of an optical wavefront incident on the entrance pupil plane of the objective lens 101 by an appropriate amount in a partial area in the entrance pupil plane is as follows. It is disclosed in JP-A-7-153120. Here, the phase shift mask 103 is an optical element that causes a phase shift in a part of an equal phase plane of light.

For example, the center is shared with the radius R0 of the entrance pupil of the objective lens 101, and the radius r is 0 ≦ r ≦ R0.
Using a phase shift mask 103 that advances or delays the phase of the circular region R1 of × 30% by π from the other regions, as shown in FIG. 26, makes the spot diameter d 89% of the diffraction limit. Can be reduced to Note that, in the example shown in FIG.
13 nm, and the numerical aperture NA of the objective lens 101 is 0.9.
It is set to 0. In FIG. 26, the dotted line shows the light intensity distribution when the phase shift mask 103 is not used, and the solid line shows the light intensity distribution when the phase shift mask 103 is used. The light intensity I is normalized with the peak intensity of the main spot as 1.

[0015]

As described above, narrowing the spot diameter d to the diffraction limit or less by using an annular light shielding plate, a phase shift mask, or the like is generally called super-resolution.
Attempting to perform such super-resolution increases the intensity of the side lobe. Here, the side lobe is a portion having a slight light intensity distribution as a concentric annular zone outside the main spot. There are a plurality of side lobe peaks, and primary, secondary, tertiary,...
Called side lobes.

When a laser beam is focused by an objective lens without applying super-resolution, the peak intensity of the primary side lobe is about 1.7% with respect to the peak intensity of the main spot. The peak intensity of the side lobes after the second order is almost negligible. On the other hand, in the example shown in FIG. 26, by using the phase shift mask, the spot diameter d of the main spot is reduced to 89% of the diffraction limit, but the peak intensity of the primary side lobe is reduced. And the peak intensity of the main spot is increased to about 10%. Then, when the photoresist is exposed in the exposure step, if the side lobe intensity is large, even if the spot diameter d is reduced, appropriate exposure cannot be performed.

In practice, FIG.
When the exposure step was performed as a light intensity distribution as shown by the solid line in FIG.
%, And the effect of super-resolution was certainly recognized, but the side lobe whose intensity was significantly increased exposed not only a portion to be exposed but also a portion in the vicinity thereof. Specifically, for example, when the groove portion is exposed, even the land portions, which are both side portions of the groove, are exposed, and the land portion becomes rough.

As described above, a recording medium master is manufactured based on the photoresist exposed by the side lobe not only at the portion to be exposed but also in the vicinity thereof, and an optical disk is formed based on the recording medium master. In this case, roughness caused by side lobes remains on the disk substrate. Therefore, in such an optical disc,
The noise of the reproduced signal is greatly increased. For this reason,
Even if the spot diameter d is reduced in the exposure step, it is impossible to increase the recording density. Further, when the roughness caused by the side lobe is severe, the focus control and the tracking control cannot be performed, and the reproduction itself may be hindered.

As described above, conventionally, when the spot diameter d is made smaller than the diffraction limit in the exposure step, a large side lobe is generated, and roughness caused by the side lobe is formed on the photoresist. Was. Then, since the roughness is transferred to the recording medium master or the disk substrate, it is impossible to increase the recording density of the optical disk.

The present invention has been proposed in view of the above-mentioned conventional circumstances. In the exposure step in the production of a recording medium master, the spot diameter d is made smaller than the diffraction limit and the side lobe is reduced. It is an object of the present invention to provide a method of manufacturing a recording medium master that can reduce the influence and manufacture a recording medium such as an optical disk with higher recording density.

The problem of the side lobe is not limited to the exposure step when manufacturing a recording medium master, and for example, a photosensitive layer made of a photoresist or the like is spotted as in a patterning step when manufacturing a semiconductor device. This is a common problem in a field where it is desired to perform exposure with a smaller diameter d.

Therefore, the present invention is not limited to the exposing step for producing a master recording medium, but is capable of exposing the photosensitive layer by reducing the influence of side lobes while reducing the spot diameter d. It is also intended to provide a method.

Furthermore, reducing the spot diameter d and reducing side lobes is desired not only in the case of exposing the photosensitive layer but also in a recording and / or reproducing apparatus. That is, in a recording and / or reproducing device,
In order to increase the recording density, it is desired that light can be more finely condensed and irradiated onto a recording medium.

Accordingly, it is another object of the present invention to provide a recording and / or reproducing apparatus capable of irradiating a recording medium with light while reducing the side lobe while reducing the spot diameter d.

[0025]

According to a method of manufacturing a recording medium master according to the present invention, a light condensed by an objective lens is irradiated on a photosensitive layer formed on a support, and a predetermined area of the photosensitive layer is formed. An exposure step of exposing, a development step of developing the exposed photosensitive layer to form a predetermined pattern of irregularities on the photosensitive layer, and transferring the irregularities formed on the photosensitive layer to produce a recording medium master. Transfer step. Then, in the above exposure step, when the diameter of the first dark ring formed around the main spot of the light condensed on the photosensitive layer is d, the wavelength of the light is λ, and the numerical aperture of the objective lens is NA, d <
It is incident on the light wave front incident on the objective lens such that the peak intensity of all side lobes generated in the vicinity of the main spot is 1.22 × λ / NA and 5% or less of the peak intensity of the main spot. After causing a phase shift in the pupil plane, the photosensitive layer is exposed.

In the method of manufacturing a recording medium master according to the present invention as described above, the diameter d of the first dark ring formed around the main spot of light is set smaller than 1.22 × λ / NA. I have. That is, the spot diameter d is smaller than the diffraction limit. Therefore, a finer area can be exposed. In addition, the peak intensity of the side lobe is set to 5% or less of the peak intensity of the main spot. Therefore, roughness due to side lobes can be suppressed.

In the exposure method according to the present invention, the light condensed by the objective lens is irradiated on the photosensitive layer formed on the support to expose a predetermined area of the photosensitive layer so that the optical axis is adjusted. A phase shift mask having at least three concentrically formed regions at the center and different in the amount of phase shift between adjacent regions is disposed in the exposure optical system. Then, after the phase shift mask causes a phase shift within the entrance pupil plane with respect to the light wavefront incident on the objective lens, the photosensitive layer is exposed.

In the exposure method according to the present invention as described above, the light for exposure is incident on the objective lens after a phase shift is caused by the phase shift mask, and is then condensed by the objective lens and exposed to light. The layer is irradiated. Here, the phase shift mask has three or more regions formed substantially concentrically about the optical axis, and is formed so that adjacent regions have different amounts of phase shift. Therefore, the peak intensity of the side lobe generated when the light is condensed by the objective lens is very low.

Further, the recording and / or reproducing apparatus according to the present invention comprises a light source for emitting light of a predetermined wavelength, an objective lens for condensing light from the light source, and a light wave front incident on the objective lens. A phase shift mask that causes a phase shift in the entrance pupil plane. Then, the light from the light source is incident on the objective lens via the phase shift mask,
The recording and / or reproduction is performed by irradiating the recording medium with the light collected by the objective lens. Here, as the phase shift mask, for example, a mask having three or more regions formed substantially concentrically with the optical axis as the center and having different amounts of phase shift between adjacent regions is used.

In the recording and / or reproducing apparatus according to the present invention as described above, light from a light source is incident on an objective lens after a phase shift is caused by a phase shift mask, and then collected by the objective lens. The recording medium is irradiated with light. Here, the phase shift mask has three or more regions formed substantially concentrically about the optical axis,
Further, it is formed so that the phase shift amounts of adjacent regions are different. Therefore, the peak intensity of the side lobe generated when the light is condensed by the objective lens is very low.

[0031]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the following description, an example in which the method of manufacturing a recording medium master according to the present invention and the exposure method according to the present invention are applied to the manufacture of an optical disk will be described.

First, an optical disk manufactured by applying the present invention will be described.

As shown in FIG. 1, the optical disk 1 has an optically transparent disk substrate 2 on which a signal recording area 3 for recording information signals is formed. You. In the signal recording area 3, a continuous groove-shaped groove 4 as shown in FIG. 2 and a continuous pit 5 as shown in FIG. 3 are formed in a spiral or concentric manner at a predetermined track pitch P for each track. Is done. Here, the track pitch P is, for example, about 0.7 to 1.6 μm.

In such an optical disk 1, usually, one surface of the disk substrate 2 is a signal recording surface 2a on which grooves 4 and pits 5 are formed, and the other surface is a reading surface 2b. That is, when a signal is reproduced from the optical disc 1, the side on which the grooves 4 and the pits 5 are not formed is set as the reading surface 2b, and laser light is irradiated from the side of the reading surface 2b.

In a recordable optical disk such as a phase change optical disk and a magneto-optical disk, the groove 4
The land 6 which is the both side portions is a recording area, and the groove 4 is a tracking light reflection area. Such a system is called a land recording system. In a recordable optical disk, the groove 4 may be used as a recording area, and the lands 6 on both sides of the groove 4 may be used as reflection areas for tracking. Such a method is called a groove recording method. Further, in a recordable optical disk, both the groove 4 and the land 6 may be used as recording areas. Such a method is called a land / groove recording method. In the land / groove recording method, the recording density can be increased to about twice that of land recording or groove recording.

On the other hand, in a read-only optical disk in which pits indicating information signals are formed in advance, the pits 5 formed on the signal recording surface 2a are used as a recording area and a tracking diffraction grating. That is, in the read-only optical disk, tracking control is performed based on the diffracted light from the pit 5 indicating the information signal. However, also in a read-only optical disk, it is possible to form the groove 4 and the land 6 and use the groove 4 and the land 6 as a reflection area for tracking.

In such an optical disk 1, a thin film layer necessary for recording and / or reproduction is formed on the signal recording surface 2a of the disk substrate 2. Specifically, when the optical disc 1 is a phase change optical disc, a thin film layer having a phase change recording layer and a reflective layer is formed, and when the optical disc 1 is a magneto-optical disc, magneto-optical recording is performed. When the optical disc 1 is a read-only optical disc in which a pit row indicating an information signal is formed in advance, a thin film layer having a reflective layer is formed. Further, a protective layer made of an ultraviolet curable resin or the like is formed on these thin film layers.

When reproducing an information signal from the optical disk 1, a laser beam from the optical pickup is irradiated from the side of the reading surface 2b while rotating the optical disk 1, and the reflected light is detected. When the optical disc 1 is a phase-change optical disc or a read-only optical disc in which pits 5 indicating information signals are formed in advance,
The information signal is reproduced by detecting a change in the intensity of the reflected light. When the optical disk 1 is a magneto-optical disk, the information signal is reproduced by detecting a change in the Kerr rotation angle of the reflected light.

On the other hand, when recording an information signal on the optical disk 1, a laser beam from the optical pickup is irradiated from the side of the reading surface 2a while rotating the optical disk 1. At this time, when the optical disk 1 is a phase-change type optical disk, a laser beam whose intensity has been modulated corresponding to an information signal to be recorded is irradiated from the reading surface 2b side. Thereby, an information signal is recorded in the area irradiated with the laser light. When the optical disk 1 is a magneto-optical disk, laser light is applied from the reading surface 2b side, and a magnetic field is applied to an area irradiated with the laser light.
At this time, intensity modulation is performed on the laser light or the magnetic field in accordance with the information signal to be recorded. As a result, an information signal is recorded in a region where the magnetic field is applied and the laser beam is irradiated.

When performing recording and / or reproduction as described above, the optical pickup detects reflected light from the optical disc 1 and performs tracking control so that laser light is always irradiated onto a predetermined track. I do. In particular,
If the groove 4 or the land 6 is formed on the optical disc 1, tracking control is performed by detecting the diffracted light from the groove 4 or the land 6. In the case of a read-only optical disk in which only the pits 5 are formed, tracking control is performed by detecting diffracted light from the pits.

Next, an example of a method for manufacturing the above optical disk will be described.

When manufacturing the above optical disk, first, as shown in FIG. 4, a glass master disk 10 whose surface is sufficiently polished and cleaned is prepared. And this glass master 10
Then, as shown in FIG. 5, a photoresist 11 which becomes alkali-soluble by exposure treatment is applied thereon. here,
The thickness of the photoresist 11 is about 0.1 μm.

Next, as an exposure step, as shown in FIG. 6, the laser beam 13 condensed by the objective lens 12 is irradiated on the photoresist 11 using a laser cutting device described later. At this time, when the wavelength of the laser light 13 is λ and the numerical aperture of the objective lens 12 is NA, the spot diameter d of the laser light 13 condensed by the objective lens 12 is 1.22 × λ / diffraction limit. Lower than NA. Further, the peak intensity of all side lobes generated near the main spot is set to 5% or less of the peak intensity of the main spot. Note that such light collection is realized, for example, by using a phase shift mask described later.

Here, the irradiation of the laser beam 13 is performed while rotating the glass master disk 10 and moving the irradiation position of the laser beam 13 in the radial direction. That is, the irradiation position of the laser beam 13 is continuously moved so as to move by an amount corresponding to the predetermined track pitch P per rotation of the glass master disk 10. As a result, the photoresist 11 is exposed in a spiral shape at a predetermined track pitch, and a latent image 14 of the groove 4 or the pit 5 is formed on the exposed portion of the photoresist 11. When performing concentric exposure, the irradiation position of the laser beam 13 may be intermittently moved so as to move by an amount corresponding to a predetermined track pitch P every time the glass master 10 is rotated once.

When forming the latent image 14 as described above, when forming the latent image of the groove 4, the laser beam 13 is used.
Are continuously performed, and when the latent image of the pit 5 is formed, the irradiation of the laser beam 13 is performed intermittently. That is, if the irradiation with the laser light 13 is performed continuously, a latent image corresponding to the continuous groove 4 is formed on the photoresist 11, and if the irradiation with the laser light 13 is performed intermittently, the pits 5 correspond to many pits 5. A latent image is formed on photoresist 11.

Next, the exposed portion, that is, the exposed portion of the photoresist 11 is removed by developing the photoresist 11 exposed in the exposure step with an alkaline developer. As a result, irregularities having a predetermined pattern are formed on the photoresist 11. Here, the unevenness of the predetermined pattern is, for example, a continuous groove corresponding to the groove 4 in a recordable optical disk, and a large number of concave portions corresponding to pits 5 indicating an information signal in a read-only optical disk. That is, in a recordable optical disk, as shown in FIG. 7, a concave portion 15 corresponding to the groove 4 formed on the disk substrate 2 and a convex portion 16 corresponding to the land 5 formed on the disk substrate 2. It is formed. Alternatively, in a read-only optical disk, a concave portion 17 corresponding to the pit 5 formed on the disk substrate 2 is formed as shown in FIG.

Next, as shown in FIG. 9, a plating layer 18 is formed by plating the photoresist 11 with Ni or the like. Thereafter, by peeling off the plating layer 18,
As a result, a recording medium master, that is, a stamper 19, on which the predetermined pattern of irregularities formed on the photoresist 11 is transferred, is obtained.

Next, as shown in FIG.
Is used as a mold to form the disk substrate 2. Thus, the disk substrate 2 on which the irregularities formed on the stamper 10 are transferred, that is, the disk substrate 2 on which the grooves 4, the lands 6, the pits 5, and the like are formed is manufactured. The method of producing the disk substrate 2 on which the irregularities formed on the stamper 19 are transferred may be a method other than injection molding. For example, the irregularities may be formed by pressing a resin material softened by heating to the stamper 19. The transfer may be performed by thermal transfer. The material of the disk substrate 2 is not particularly limited, but a plastic material is preferable in consideration of moldability, cost, and the like.

Thereafter, the groove 4 is formed on the disk substrate 2.
The optical disk 1 is completed by forming a predetermined thin film layer on the surface on which the lands 6 and the pits 5 are formed, and further forming a protective layer made of an ultraviolet curable resin or the like on the thin film layer. Here, as described above, as the thin film layer,
In the case of a phase-change optical disk, a phase-change recording layer and a reflection layer are formed. In the case of a magneto-optical disk, a magneto-optical recording layer and a reflection layer are formed. In the case of a read-only optical disk, a reflection layer and the like are formed.

Next, an example of a laser cutting device used in the above-described exposure step will be described.

As shown in FIG. 11, this laser cutting apparatus includes a laser light source 21 for emitting laser light of a predetermined wavelength and a recording for controlling the laser light intensity so that the laser light intensity is at a predetermined stable level. A light intensity control unit 22,
A light intensity modulation unit 23 that modulates the intensity of the laser light applied to the photoresist 11 applied to the glass master 10,
The apparatus includes a beam splitter 24, a beam expander 25 for expanding a beam diameter, and a condensing unit 26 for condensing laser light on the photoresist 11.

The laser light source 21 emits laser light having a predetermined wavelength. Here, the wavelength of the laser beam emitted from the laser light source 21 is preferably shorter from the viewpoint of reducing the spot diameter on the photoresist 11, but if the wavelength is in the ultraviolet region, the adjustment of the optical system is required. It will be difficult. Therefore, this laser light source 21
It is preferable to emit a laser beam having a wavelength in the visible light region and as short as possible. Specifically, a Kr ion laser emitting a wavelength of 413 nm is preferable.

The laser light emitted from the laser light source 21 enters a recording light intensity control unit 22, and the intensity is controlled by the recording light intensity control unit 22. The recording light intensity control unit 22 removes the instability of the output of the laser light source 21,
This is for stabilizing the light intensity of the laser beam applied to the photoresist 11, and includes an electro-optic crystal element 31, an analyzer 32, and a beam splitter 33.
, Photodetector 34 and recording light power control circuit 3
5 is provided.

Then, the laser light from the laser light source 21 passes through the electro-optic crystal element 31 and the analyzer 32 and enters the beam splitter 33, and the intensity of the light transmitted through the beam splitter 33 is detected by the photo detector 34. The photodetector 34 converts the level of the detected light intensity of the laser light into a voltage level, and supplies the voltage level to the recording light power control circuit 35. The recording light power control circuit 35 compares the input from the photodetector 34 with the reference voltage level Ref so that the light intensity of the laser light transmitted through the electro-optic crystal element 31 is always constant. A voltage is applied to the element 31. Accordingly, the laser light emitted from the recording light intensity controller 22, that is, the light intensity of the laser light reflected by the beam splitter 33, is stable even if the output of the laser light source 21 is unstable.
Always at a stable level.

The laser light reflected by the beam splitter 33 enters the light intensity modulator 23, where the light intensity is modulated. The light intensity modulator 23 includes a first convex lens 36 and a light intensity modulator 37.
And a second convex lens 38.

The laser beam reflected by the beam splitter 33 has a first focal length f1.
After being condensed by the convex lens 36, the light enters the light intensity modulator 37. The laser light that has been subjected to light intensity modulation by the light intensity modulator 37 is incident on a second convex lens 38 having a predetermined focal length f2, and is converted into parallel light by the second convex lens 38.

Here, the light intensity modulator 37 transmits or blocks light corresponding to a pit row when forming a pit corresponding to an information signal, for example. That is, the light intensity modulator 37 modulates light intensity by transmitting laser light when forming a pit, and shielding the laser light when not forming a pit. As described above, the light intensity modulator 37 converts a recording signal voltage level into a light intensity in order to form a pit having a length corresponding to, for example, an electric recording signal. As the light intensity modulator 37,
A modulator using an electro-optic crystal element or an acousto-optic crystal element that can be used in a high frequency band of several tens of MHz is preferable.

The laser light modulated by the light intensity modulator 37 is converted into parallel light by the second convex lens 38 and then enters the beam splitter 24. Then, the laser light reflected by the beam splitter 24 enters the beam expander 25. The beam expander 25 is an optical system that enlarges the beam diameter of the laser beam, and includes a third convex lens 39 having a predetermined focal length f3 and a fourth convex lens 4 having a predetermined focal length f4.
0. In the beam expander 25, when the gap between the third convex lens 39 and the fourth convex lens 40 is changed, the magnification of the beam diameter by the beam expander 25 changes. In this laser cutting apparatus, the photoresist 1 is adjusted by adjusting the magnification of the beam diameter by the beam expander 25.
It is possible to adjust the spot diameter d of the laser light condensed on 1.

The laser beam whose beam diameter has been adjusted by the beam expander 25 is incident on the condenser 26. The condensing unit 26 is for condensing the laser light on the photoresist 11 and includes a phase shift mask 41 and an objective lens 42. The phase shift mass 41 is for causing a predetermined phase shift within the entrance pupil plane with respect to the light wavefront incident on the objective lens 42. The phase shift mask 41 will be described later in detail. Then, the laser light transmitted through the phase shift mask 41 is incident on the objective lens 42, is condensed by the objective lens 42, and is irradiated on the photoresist 11.

When the wavelength of the laser beam is λ and the numerical aperture of the objective lens 42 is NA, the spot diameter d of the laser beam condensed by the objective lens 42 is 1.22 × λ, which is the diffraction limit. / NA. Further, the peak intensity of all side lobes generated near the main spot is set to 5% or less of the peak intensity of the main spot. Note that such light collection is performed by using the phase shift mask 41 and the objective lens 42 as described in detail later.
This is realized by arranging it in the preceding stage of.

Although not shown, the laser cutting apparatus is provided with a turntable for holding and rotating the glass master 10 coated with the photoresist 11, and moving the laser beam irradiation position in the radial direction of the glass master 10. And a servo mechanism for always keeping the distance between the exposure surface of the photoresist 11 and the objective lens 42 constant. Here, the servo mechanism performs focusing servo using, for example, a focusing laser having a wavelength to which the photoresist 11 is not exposed so that the distance between the objective lens 42 and the exposed surface of the photoresist 11 is constant.

Then, with this laser cutting device,
When exposing the photoresist 11, the glass master 1 coated with the photoresist 11 is turned by a turntable.
While rotating 0, the moving position of the laser beam is moved by the moving mechanism in the radial direction of the glass master 10 by an equal distance per rotation. Then, with the servo mechanism keeping the distance between the exposure surface of the photoresist 11 and the objective lens 42 always constant, the photoresist 11 is irradiated with laser light that has been subjected to predetermined modulation by the light intensity modulator 37. . As a result, latent images of grooves and pits are formed in the photoresist 11 on the glass master 10 in a spiral or concentric manner at a fixed track pitch P.

In the laser cutting apparatus, the peak intensity of the side lobe is specified to be 5% or less of the peak intensity of the main spot. The reason will be described below.

If the side lobe is large, when the groove portion is exposed, the land portions, which are both side portions of the groove, become rough. Therefore, an experiment was conducted to determine how much side lobes would cause roughness in the land when the side lobes were formed.

This experiment was carried out by exposing at an exposure intensity several times the normal exposure intensity with the spot diameter d being the diffraction limit in the exposure step, thereby creating a state where the peak intensity of the side lobe was large. . Then, when the groove was exposed in this manner, the roughness generated on the land was examined.

When the diffraction limit is set, the peak intensity of the primary side lobe is about 1.7% of the peak intensity of the main spot. Therefore, for example, when the exposure is performed at six times the normal exposure intensity, the peak intensity of the primary side lobe is six times 1.7%, based on the peak intensity of the main spot at the normal exposure intensity. It is about 10%.
That is, when the spot diameter d is set to the diffraction limit and the exposure is performed at six times the normal exposure intensity, the peak intensity of the primary side lobe becomes smaller than the peak intensity of the main spot by using a phase shift mask. This corresponds to a value of about 10%.

The above experiments were performed under the conditions shown in Table 1. In Table 1, the normal strength ratio is
The ratio of the exposure intensity when the normal exposure intensity is 1 is shown. The primary side lobe peak intensity converted value is
It represents the ratio of the peak intensity of the primary side lobe with reference to the peak intensity of the main spot at the normal exposure intensity.

[0068]

[Table 1]

As shown in Table 1, Experiment A was performed when exposure was performed at a normal exposure intensity, Experiment B was performed when exposure was performed at 2.8 times the normal exposure intensity, and Experiment C was performed when exposure was performed at a normal exposure intensity. In the case of exposing at an exposure intensity of 3.0 times, Experiment D is the case of exposing at an exposure intensity of 3.3 times the normal exposure intensity. Experiment B corresponds to the case where the peak intensity of the primary side lobe becomes 4.8% of the peak intensity of the main spot by using the phase shift mask. Experiment C corresponds to the case where the peak intensity of the primary side lobe becomes 5.1% of the peak intensity of the main spot by using the phase shift mask. Experiment D corresponds to the case where the peak intensity of the primary side lobe becomes 5.6% of the peak intensity of the main spot by using the phase shift mask.

Here, the wavelength λ of the light was 351 nm, and the numerical aperture NA of the objective lens was 0.90. Since the diffraction limit is set, the spot diameter d is 1.22 × (λ / N
A) = 0.48 μm. The track pitch was 1.0 μm and the linear velocity was 3.0 m / s. In addition, a photoresist for i-line was used as the photoresist, and the film thickness was about 0.1 μm. The development time of the photoresist was 20 seconds. As for the photoresist used for producing a high-density optical disk, there is not much choice in the photoresist, and there is no photoresist having a greatly different characteristic. Therefore, it is possible to obtain a general conclusion from this experiment without considering the difference in characteristics depending on the type of photoresist.

Under the above conditions, the groove portion was exposed, and the roughness of the land caused by the side lobe was examined with a scanning electron microscope. As a result, in Experiment A, the land surface was very smooth, and there was no appearance of exposure due to side lobes. In experiment B, a slight increase in surface roughness was observed on the land surface near the boundary with the groove. However, this surface roughness is about the same as the surface roughness of a photoresist used for manufacturing a practically used optical disk, and has not reached the level of forming irregularities that affect the reproduction signal. . In the experiment C, the roughness was further increased in a region where the surface was slightly roughened in the experiment B, and granular irregularities were being formed. The unevenness was large enough to affect the reproduction signal. In experiment D,
It is in a state where it has been completely exposed to the land,
The edge of the groove has an abnormal shape that pulls the hem toward the center of the land.

From the above experimental results, if the peak intensity of the side lobe is smaller than in the case of the experiment C, it can be considered that there is no problem in the land roughness in practical use. Therefore, even when exposed at a normal exposure intensity using a phase shift mask,
If the peak intensity of the side lobe is 5% or less of the peak intensity of the main spot, it can be said that there is no problem. When super-resolution is performed using a phase shift mask, it is not necessary to consider that the exposure intensity is made higher than the normal exposure intensity. This is because the purpose of super-resolution is to form a finer pattern, and it is not necessary to use super-resolution when increasing the exposure intensity and forming large pits or thick grooves. It is.

From the above results, when the photoresist is exposed by making the spot diameter d smaller than the diffraction limit by super-resolution, the peak intensity of the side lobe becomes 5% or less of the peak intensity of the main spot. It is understood that it is necessary to do so.

By the way, while making the spot diameter d smaller than the diffraction limit, the peak intensity of the side lobe is set to be 5% or less of the peak intensity of the main spot.
The phase shift mask can be realized by causing a phase shift in the entrance pupil plane with respect to the light wavefront incident on the objective lens. However, the spot diameter d and the peak intensity of the side lobe greatly change depending on the phase shift method. Therefore, the relationship between the phase shift and the spot diameter d or the peak intensity of the side lobe will be described below.

In the following description, the ratio of the peak intensity of the n-th side lobe to the peak intensity of the main spot is expressed as Sn. That is, for example, the ratio of the peak intensity of the primary side lobe to the peak intensity of the main spot is S1, and the ratio of the peak intensity of the secondary side lobe to the peak intensity of the main spot is S2.
It is. The light wavelength λ was 413 nm, and the numerical aperture NA of the objective lens was 0.90.

Comparative Example First, as a comparative example, as shown in FIG. 12, a case where the equal phase region on the entrance pupil is divided into two concentric circles by a circular region 51 having a phase difference π will be described. In the following description, the structure as shown in FIG. 12 is referred to as a double ring structure. In the double ring structure, when the entrance pupil radius is R0 and the distance from the entrance pupil center is r,
The phase difference π is added to the circular area 51 in the range represented by the following equation (2-1).
Gave. However, 0% <α <100%.

0 ≦ r ≦ α × R0 (2-1) In the double ring structure as described above, α is 0%, 20%,
Table 2 shows the calculation results of the spot diameter d and the peak intensity of the side lobe for each of 25% and 30%. Table 2 and Tables 3 to 5 below
In the above, the spot diameter d is represented by a relative value when the spot diameter d when the diffraction limit is set to 100. In these tables, "-" indicates that the peak intensity of the side lobe was negligibly small.

[0078]

[Table 2]

In the double ring structure, when α is made larger than shown in Table 2, the spot diameter d becomes smaller. However, the peak intensity of the side lobe further increases, and the side lobe eventually has an intensity higher than the main spot. When α is further increased, the spot diameter d of the main spot eventually increases, and the side lobe intensity decreases. Therefore, from the viewpoint of reducing the spot diameter d, only a structure within the range shown in Table 2 is practical. However, as can be seen from Table 2, when Sn ≦ 5.0%,
The spot diameter d is only about 95% of the diffraction limit. That is, it is impossible to obtain a sufficient super-resolution effect while maintaining the condition of Sn ≦ 5.0% with the double ring structure as shown in FIG.

Embodiment 1 Next, as Embodiment 1, a case will be described in which an equiphase region on the entrance pupil is concentrically divided into three by an annular region 52 having a phase difference π as shown in FIG. . In addition,
In the following description, the structure shown in FIG. 13 is referred to as a triple ring structure.

In the triple ring structure, when the radius of the entrance pupil is R0 and the distance from the center of the entrance pupil is r, a phase difference π is given to the annular zone 52 in the range represented by the following equation (2-2). Was. However, 0% <α1 <α2 <100%.

Α1 × R0 ≦ r ≦ α2 × R0 (2-2) In the triple ring structure as described above, a solution that can reduce the spot diameter of the main spot while satisfying Sn ≦ 5.0% As a result of the calculation, for example, a solution shown in Table 3 was obtained.

[0083]

[Table 3]

As can be seen from Table 3, the use of the triple ring structure makes it possible to reduce the spot diameter d by the super-resolution effect while maintaining the condition of Sn ≦ 5.0%.
Specifically, in the example of Table 3, it is possible to reduce the spot diameter d to 90% of the diffraction limit while setting the maximum value of the peak intensity of the side lobe to 4.8%.

Second Embodiment Next, as a second embodiment, as shown in FIG. 14, the equal phase region on the entrance pupil is divided into four concentric circles by a circular region 53 and a ring zone 54 having a phase difference of π. The case will be described. In the following description, the structure as shown in FIG. 14 is referred to as a quadruple ring structure. In the quadruple ring structure, when the radius of the entrance pupil is R0 and the distance from the center of the entrance pupil is r, a circular region 53 in the range represented by the following equation (2-3) and the following equation (2-4) Zone 5 in the range indicated by
4 with a phase difference π. However, 0% <α1 <α2 <
α3 <100%.

0 ≦ r ≦ α1 × R0 (2-3) α2 × R0 ≦ r ≦ α3 × R0 (2-4) In the above quadruple ring structure, Sn ≦ 5.0 %, A solution that can reduce the spot diameter d of the main spot was calculated. As a result, for example, a solution as shown in Table 4 was obtained.

[0087]

[Table 4]

As can be seen from Table 4, the spot diameter d can be reduced by the super-resolution effect while maintaining the condition of Sn ≦ 5.0% by adopting the quadruple ring structure.
Specifically, in the example shown in the upper column of Table 4, it is possible to reduce the spot diameter d to 92% of the diffraction limit while setting the maximum value of the peak intensity of the side lobe to 3.3%. In the example shown in the lower column of Table 4, it is possible to reduce the spot diameter d to 90% of the diffraction limit while setting the maximum value of the peak intensity of the side lobe to 3.8%. It has become.

Third Embodiment Next, as a third embodiment, as shown in FIG. 15, the equi-phase regions on the entrance pupil are concentrically formed by the circular region 55, the annular region 56, and the annular region 57 having the phase difference π. A case where the image is divided into six parts will be described. In the following description, FIG.
The structure shown in FIG. 5 is referred to as a hexacyclic structure. When the radius of the entrance pupil is R0 and the distance from the center of the entrance pupil is r in the hexacyclic structure, a circular region 55 in the range represented by the following equation (2-5) and the following equation (2-6) The phase difference π was given to the annular zone region 56 in the range indicated by the symbol and the annular zone 57 in the range indicated by the following formula (2-7). However, 0% <α1
<Α2 <α3 <α4 <α5 <100%.

0 ≦ r ≦ α1 × R0 (2-5) α2 × R0 ≦ r ≦ α3 × R0 (2-6) α4 × R0 ≦ r ≦ α5 × R0 (2- 7) In the above-described six-ring structure, a solution that can reduce the spot diameter d of the main spot while satisfying Sn ≦ 5.0% was calculated. For example, a solution as shown in Table 5 was obtained. Was.

[0091]

[Table 5]

As can be seen from Table 5, the use of the hexacyclic structure allows the spot diameter d to be reduced by the super-resolution effect while maintaining the condition of Sn ≦ 5.0%.
More specifically, in the example shown in the upper column of Table 5, it is possible to reduce the spot diameter d to 89% of the diffraction limit while setting the maximum value of the peak intensity of the side lobe to 3.8%. In the example shown in the lower column of Table 5, it is possible to reduce the spot diameter d to 88% of the diffraction limit while setting the maximum value of the peak intensity of the side lobe to 4.0%. It has become.

As can be seen from the above-described first to third embodiments, the equal-phase region on the entrance pupil is divided into three or more by a circular region or an annular region having a phase difference π, so that the side of each order can be obtained. A spot diameter d that is significantly smaller than the diffraction limit can be realized while suppressing the peak intensity of all the lobes to 5% or less of the peak intensity of the main spot. In the above example, the phase difference between the divided regions is π, but the phase difference may be an odd multiple of π.

Here, the light intensity distribution when using the above-mentioned double ring structure with α being 30% and the light intensity distribution when using the hexacyclic ring structure listed in the upper column of Table 5 are shown. As shown in FIG.
FIG. 16 also shows that the peak intensity of the side lobe can be suppressed to be very low in the hexacyclic structure as compared with the double ring structure.

Next, a phase shift mask which causes the above-described phase shift will be specifically described.

In the laser cutting apparatus shown in FIG. 11, the phase shift mask 41 is an optical such that an appropriate amount of phase shift occurs in a partial area on the entrance pupil plane with respect to the light wavefront incident on the objective lens 42. Subject to proper treatment. This phase shift mask 41 is arranged between the fourth convex lens 40 and the objective lens 42 in the exposure optical system. That is, the laser light whose optical wavefront is made substantially flat by the fourth convex lens 40 is incident on the phase shift mask 41, and the phase shift mask 41 causes a phase shift with respect to the laser light.

The phase shift mask 41 has, for example,
As shown in FIGS. 17 and 18, one having the above-described triple ring structure is used. In the phase shift mask 41 shown in FIGS. 17 and 18, a flat plate-like substrate 41a made of an optically transparent material is subjected to step processing by etching, so that the concave portion 41b corresponding to the above-mentioned annular zone is formed. Thus, the above-described triple ring structure is obtained. Here, the substrate 41a is made of a material having a refractive index different from that of the optical path medium, and is made of, for example, quartz (SiO ₂ ).

FIG. 19 schematically shows a state in which light having a wavelength λ is incident on the phase shift mask 41.

Here, the step between the concave portion 41b formed in the phase shift mask 41 and other portions is h, the wavelength of the incident light is λ, the refractive index of the optical path medium is N0, and the refraction of the phase shift mask 41 is Let the rate be N1. Here, the phase shift mask 41 has a different refractive index from the optical path medium. That is, N1 ≠ NO. In a normal exposure optical system, the optical path medium is air, and its refractive index N0 is 1.0. Also, since the refractive index of quartz is about 1.5, when the phase shift mask 41 is made of quartz, the refractive index N1
Is about 1.5.

At this time, the concave portion 4 of the phase shift mask 41
The light passing through 1b has the following formula (2)
A phase difference Δφ indicated by -8) occurs.

Δφ = (2π / λ) × {(N1−N0) × h} (2-8) Therefore, for example, wavelength λ = 413 nm, N1 = 1.
5, when N0 = 1.0, in order to generate a phase difference π between the concave portion 41b and other portions, the step h may be set to 413 nm as shown in the following equation (2-9).

H = λ / {2 × (N1−N0)} = 413 [nm] (2-9) The phase shift mask 4 having a triple ring structure as described above.
By using 1, as described above, it is possible to realize a super-resolution in which the spot diameter d is significantly smaller than the diffraction limit while suppressing the side lobe peak intensity to 5% or less. And adopting such super-resolution,
By performing the above-described exposure process, it is possible to reduce the influence of side lobes around the main spot, for example,
Even when a fine groove is formed, the land portion does not become rough. Further, the method of realizing super-resolution using the above-described phase shift mask 41 is such that super-resolution is realized by disposing a ring-shaped light shielding plate at a part of the entrance pupil of the objective lens 42. Compared to the method, there is no loss of the amount of incident light, so that it is very superior in actual use.

In the phase shift mask 41 having a triple ring structure, almost the same super-resolution effect can be obtained even if the above-mentioned α1 and α2 vary by about ± 1%. Then, the entrance pupil radius R0 of the objective lens 42 used for a normal laser cutting device is about 2 mm.
It is. Accordingly, the processing accuracy in the radial direction required when forming the concave portion 41b by etching is ± 20 μm.
m. Further, in a phase shift mask that generates a phase difference π by forming the step h, an allowable range of an error of the step h is about ± 20 nm. Therefore,
The processing accuracy in the depth direction required when forming the concave portion 41b by etching is about ± 20 nm. The processing accuracy in the radial direction within ± 20 μm and the processing accuracy in the depth direction within ± 20 nm can be easily realized by existing etching techniques. Therefore, the above-described phase shift mask 41 can be easily manufactured.

Further, as the material of the phase shift mask 41, any material other than quartz may be used as long as it has a sufficient transmission characteristic from the visible light region to the ultraviolet light region. However, quartz is inexpensive and has excellent workability,
It is very suitable as a material for the phase shift mask 41.

In the above description, the phase shift mask 41 has a triple ring structure as an example. However, as is apparent from the above embodiment, a mask having a quadruple or more ring structure is also used. It is possible. In the case of a quadruple or more ring structure, similarly to the above-mentioned phase shift mask 41, a substrate having a refractive index different from that of the optical path medium is etched,
It goes without saying that it can be easily manufactured by forming a step h between the circular region or the annular zone region and other portions.

Further, the structure of the phase shift mask 41 may be such that a circular area or an annular area is not a concave part but a convex part, and these parts are formed as openings. It may be. That is, the shape of the phase shift mask 41 is not particularly limited, as long as the phase shift mask 41 causes a predetermined phase difference between the portion of the circular region or the annular region and the other portion.

Next, an embodiment of the recording and / or reproducing apparatus according to the present invention will be described. Here,
As an example of a recording and / or reproducing apparatus to which the present invention is applied, a recording and reproducing apparatus that performs recording and reproduction on a magneto-optical disk will be described.

As shown in FIG. 20, this recording / reproducing apparatus is a recording / reproducing apparatus for recording / reproducing information on / from a magneto-optical disk 60. It has a similar configuration. That is, the recording / reproducing apparatus includes a light source 62 composed of a semiconductor laser or the like that emits a laser beam of a predetermined wavelength,
Collimator lens 63 that converts the laser light from 2 into parallel light
A beam splitter 64 for separating laser light from the light source 62 and return light from the magneto-optical disk 60;
A phase shift mask 61 for generating a phase difference with respect to the laser light from the optical disk 2; an objective lens 65 for condensing the laser light having a predetermined phase difference with the phase shift mask 61 onto the magneto-optical disk 60; A magnetic head 66 for applying a magnetic field to the magnetic disk 60. Here, the phase shift mask 61 has a triple or more ring structure as described above, and the spot diameter d of the light collected by the objective lens 65 is smaller than the diffraction limit.

The recording / reproducing apparatus is also capable of providing a return light from the magneto-optical disk 60 with a λ / 2 phase difference.
A wavelength plate 67, a polarization beam splitter 68 that separates the return light transmitted through the half-wave plate 67 into a P-polarization component and an S-polarization component, and one of the polarization components separated by the polarization beam splitter 68. A first condensing lens 69 for condensing, a first photodetector 70 for detecting polarized light condensed by the first condensing lens 69, and a polarization component split by the polarization beam splitter 68. A second condenser lens 71 for condensing the other, a second condenser lens 71
Photodetector 72 for detecting polarized light collected by
And

When an information signal is recorded on the magnetic disk 60 by the recording / reproducing apparatus, the laser light from the light source 62 is applied to the magnetic disk 60 while a magnetic field is applied to the magnetic disk 60 by the magnetic head 66. Irradiation. At this time, the magnetic field from the magnetic head 66 or the intensity of the laser beam from the light source 62 is modulated in accordance with the information signal to be recorded. Thus, information signals are recorded on the magnetic disk 60. On the other hand, the magneto-optical disk 6
When reproducing the information signal from 0, the laser light from the light source 62 is applied to the magnetic disk 60. Then, the return light is detected by the first photodetector 70 and the second photodetector 72, thereby reproducing the information signal.

In the recording / reproducing apparatus as described above, the light from the light source 62 can be condensed more finely and applied to the magneto-optical disk 60 by the super-resolution by the phase shift mask 61. Therefore, higher recording density can be achieved.

It should be noted that the method of condensing the light from the light source more finely and irradiating the recording medium with the super-resolution by the phase shift mask is not limited to the recording / reproducing apparatus for the magneto-optical disk, but also for the optical recording and reproducing. The present invention can be widely applied to an apparatus for performing reproduction. That is, super-resolution by a phase shift mask having a triple or more ring structure can be applied to a recording / reproducing device for a phase-change optical disk, a reproducing device for a read-only optical disk, and the like. Further, it is possible to further increase the recording density.

[0113]

As is apparent from the above description, according to the method of manufacturing a recording medium master according to the present invention, in the exposure step of manufacturing the recording medium master, the spot diameter is reduced to less than the diffraction limit, and The influence of side lobes can be reduced. Therefore, it is possible to manufacture a recording medium with higher recording density.

According to the exposure method of the present invention, when exposing the photosensitive layer, the spot diameter can be made smaller than the diffraction limit, and the influence of side lobes can be reduced. Accordingly, a semiconductor device with higher integration, a recording medium with higher recording density, and the like can be manufactured.

Further, according to the recording and / or reproducing apparatus of the present invention, it is possible to irradiate the recording medium with light while keeping the spot diameter smaller than the diffraction limit and keeping the side lobe peak intensity low. it can. That is, light can be more finely condensed and applied to the recording medium. Therefore, it is possible to further increase the recording density.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of an optical disk.

FIG. 2 is an enlarged view showing a portion of a disk substrate of a recording / reproducing optical disk on which grooves are formed.

FIG. 3 shows a disk substrate of a read-only optical disk;
It is a figure which expands and shows the part in which a pit is formed.

FIG. 4 is a view showing a glass master.

FIG. 5 is a diagram showing a state in which a photoresist is applied on a glass master.

FIG. 6 is a view showing an exposure step of exposing a photoresist.

FIG. 7 is a diagram showing a state in which unevenness corresponding to grooves and lands is formed on a photoresist.

FIG. 8 is a diagram showing a state in which unevenness corresponding to a pit row is formed on a photoresist.

FIG. 9 is a diagram showing a state where a plating layer is formed on a photoresist.

FIG. 10 is a diagram showing a state in which a pattern formed on a stamper is transferred to produce a disk substrate.

FIG. 11 is a diagram showing an optical system of an example of a laser cutting device.

FIG. 12 is a diagram showing a phase shift mask having a double ring structure.

FIG. 13 is a diagram showing a phase shift mask having a triple ring structure.

FIG. 14 is a diagram showing a phase shift mask having a quadruple ring structure.

FIG. 15 is a diagram showing a phase shift mask having an example of a hexacyclic ring structure.

FIG. 16 is a diagram showing a light intensity distribution when a phase shift mask having a double ring structure is used and a light intensity distribution when a phase shift mask having a hexacyclic structure is used.

FIG. 17 is a plan view illustrating an example of a phase shift mask having a triple ring structure.

18 is a cross-sectional view of the phase shift mask taken along line AA of FIG.

FIG. 19 is a schematic diagram showing a state of a phase shift by the phase shift mask shown in FIGS. 17 and 18.

FIG. 20 is a diagram illustrating an example of a recording / reproducing device to which the present invention has been applied.

FIG. 21 is a diagram showing an intensity distribution of a condensed spot by an objective lens having a circular aperture pupil.

FIG. 22 is a view showing a conventional exposure optical system using an annular light shielding plate.

FIG. 23 is a plan view showing a ring-shaped light shielding plate.

FIG. 24 is a diagram showing a light intensity distribution when an annular aperture is formed using an annular light shielding plate and a light intensity distribution when a circular aperture is formed without using an annular light shielding plate.

FIG. 25 is a diagram showing a conventional exposure optical system using a phase shift mask.

FIG. 26 is a diagram showing a light intensity distribution when a phase shift is performed using a phase shift mask and a light intensity distribution when a circular aperture is formed without using a phase shift mask.

[Explanation of symbols]

10 glass substrate, 11 photoresist, 21
Laser light source, 22 recording light intensity control unit, 23 light intensity modulation unit, 24 beam splitter, 25 beam expander, 26 focusing unit, 41 phase shift mask, 42 objective lens

Claims (12)

[Claims] An exposure step of irradiating a light-sensitive layer formed on a support with light condensed by an objective lens to expose a predetermined area of the photosensitive layer; and developing the exposed photosensitive layer. A developing step of forming irregularities of a predetermined pattern on the photosensitive layer, and a transfer step of transferring the irregularities formed on the photosensitive layer to produce a master recording medium. Where d is the diameter of the first dark ring formed around the main spot of the light to be condensed, λ is the wavelength of the light, and NA is the numerical aperture of the objective lens.
It is incident on the light wavefront incident on the objective lens so that 1.22 × λ / NA and the peak intensity of all side lobes generated near the main spot is 5% or less of the peak intensity of the main spot. A method for manufacturing a recording medium master, comprising exposing the photosensitive layer after causing a phase shift in a pupil plane. 2. In the exposure step, by disposing a phase shift mask having a plurality of regions having different phase shift amounts in the exposure optical system, a phase shift in a plane of an entrance pupil with respect to a wavefront incident on the objective lens is achieved. 2. The method according to claim 1, wherein a shift occurs. 3. The phase shift mask according to claim 2, wherein the phase shift mask has three or more regions formed substantially concentrically about the optical axis, and adjacent regions have different amounts of phase shift. Of producing a master recording medium. 4. The method for manufacturing a master recording medium according to claim 3, wherein the phase shift mask has a difference in the amount of phase shift between adjacent regions is an odd multiple of π. 5. The master recording medium according to claim 3, wherein the phase shift mask is made of a material having a different refractive index from that of the exposure optical path medium, and has different thicknesses in the optical axis direction in adjacent regions. Manufacturing method. 6. A method of irradiating light condensed by an objective lens to a photosensitive layer formed on a support to expose a predetermined area of the photosensitive layer, wherein the light is formed substantially concentrically about an optical axis. A phase shift mask having three or more regions and different amounts of phase shift between adjacent regions is disposed in the exposure optical system, and the phase shift mask causes an entrance pupil plane with respect to a light wave front incident on the objective lens. An exposure method, wherein the photosensitive layer is exposed after a phase shift has occurred in the photosensitive layer. 7. The exposure method according to claim 6, wherein in the phase shift mask, a difference between phase shift amounts of adjacent regions is an odd multiple of π. 8. The exposure method according to claim 6, wherein the phase shift mask is made of a material having a different refractive index from that of the exposure optical path medium, and adjacent regions have different thicknesses in the optical axis direction. 9. A light source for emitting light of a predetermined wavelength, an objective lens for condensing light from the light source, and a phase shift in an entrance pupil plane with respect to a light wavefront incident on the objective lens. A phase shift mask, wherein light from a light source is incident on an objective lens through the phase shift mask, and light condensed by the objective lens is irradiated on a recording medium to perform recording and / or reproduction. Recording and / or playback device. 10. The phase shift mask has three or more regions formed substantially concentrically about an optical axis,
10. The recording and / or reproducing apparatus according to claim 9, wherein adjacent regions have different amounts of phase shift. 11. The recording and / or reproducing apparatus according to claim 10, wherein in the phase shift mask, a difference between phase shift amounts of adjacent regions is an odd multiple of π. 12. The phase shift mask according to claim 10, wherein the phase shift mask is made of a material having a different refractive index from that of the exposure optical path medium, and adjacent regions have different thicknesses in the optical axis direction.
A recording and / or reproducing apparatus as described in the above.