JPH07129998A - Production of optical master disk - Google Patents

Abstract

PURPOSE:To produce an optical master disk having high performance by easily and exactly setting the beam spacing between a laser beam for forming pits and a laser beam for forming grooves. CONSTITUTION:A laser cutting device is constituted to produce the optical master disk by irradiating a photoresist film 25 formed on a circular substrate 24 with the laser beam L1 (L2) modulated in accordance with recording data and exposing and recording the data patterns based on the recording data. The beam spacing between the laser beam for forming the grooves from a groove optical system 5 of this device and the laser beam for forming the pits from a pit optical system 10 is set on the basis of the luminance pattern detected by a luminance pattern detecting section 30 from a reference disk by inserting the optical element 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention irradiates a resist film formed on an optical disk substrate with a light beam which is modulated based on recording data, and a data pattern based on the recording data input to an optical modulator. By exposing and recording
The present invention relates to a method of manufacturing an optical disc master for manufacturing an optical disc master.

[0002]

2. Description of the Related Art Generally, an optical recording device using a laser beam, that is, a so-called laser cutting device is used in manufacturing a master disc of an optical disc.

Conventionally, a laser cutting apparatus for producing a master of this optical disk is, for example, as shown in FIG.
A gas laser light source 51 that uses gas as an amplification medium, a mirror 52 that guides the laser light L emitted from the gas laser light source 51 to an optical system in the subsequent stage, and a laser light L that is guided through the mirror 52 are input. electro-optical modulator for intensity modulation in accordance with that the recording signal S _W (Erectro optic Modulato
r; hereinafter simply referred to as EOM) 53, and mirrors 55 and 56 that guide the laser light L intensity-modulated by the EOM 53 to the objective lens 54. Objective lens 5
The mirror 4 and the mirror 56 are arranged on the photoresist film 58 formed on the circular substrate 57 so as to face each other at a predetermined interval, and move in the radial direction of the circular substrate 57 by a known moving mechanism.

Here, the EOM 53 is an electro-optic effect (a phenomenon in which the refractive index of a medium is changed by an applied signal electric field, and in particular, an effect in which the induced change in the refractive index is proportional to the first power of the electric field. And is also called the Pockels effect)
It is an optical modulator that utilizes the change in the refractive index of the medium due to. That is, the optical phase difference between the two orthogonal polarization components in the medium of the incident laser light (normally linearly polarized by the Brewster window) L is controlled by the applied signal electric field, It changes the polarization state of light. Since the laser light L transmitted through the EOM 53 is elliptically polarized light, the laser light L is converted into intensity-modulated light by the analyzer 59 composed of a ¼ wavelength plate and an analyzer in the subsequent stage.

When this EOM 53 is used, a wide modulation band can be obtained, high-speed modulation is possible, and the beam shape of the laser light L does not change. Therefore, the spot diameter of the laser light L irradiated on the photoresist film 58 is small. It becomes constant, and there is no variation in the leading width of the printed pattern.

As another conventional laser cutting device, as shown in FIG. 6, an acousto-optic modulator (hereinafter referred to simply as AOM) is used instead of the EOM 53 of the laser cutting device shown in FIG.
60) is arranged. That is, the laser light L of the parallel light flux emitted from the laser light source 51 is reduced in beam diameter by the beam reduction lens 61 and is incident on the AOM 60. Modulated) W
The light intensity is modulated in accordance with. The laser beam L intensity-modulated by the AOM 60 is restored to a parallel beam by the beam expanding lens 62 at the subsequent stage and becomes parallel light, and then the mirrors 55 and 56 and the objective lens 54.
The photoresist film 58 is irradiated with light through.

The AOM 60 utilizes the fact that the intensity of the first-order diffracted light in Bragg diffraction is almost proportional to the ultrasonic power, and the ultrasonic power is modulated based on a recording signal to optically modulate the laser light L. I do. This AOM6
0 uses the Bragg diffraction of the phase diffraction grating in the crystal generated by the supplied ultrasonic waves W, and therefore has the advantage that there is no temperature dependence and the operating point is stable.

The circular substrate 57 is rotatably driven by a CAV system, for example, by a rotative drive system (not shown).
By irradiating the photoresist film 58 with the laser beam L whose intensity is modulated based on the recording signal, the photoresist film 58 is irradiated with the recording signal along the concentric circles of the circular substrate 57 or along the spiral shape. A corresponding recording pattern is drawn.

That is, the photoresist film 58 is exposed along the drawn recording pattern, and the exposed portion is dissolved by the developing solution in the next developing step. Therefore, in the subsequent developing process, the exposed portion is removed and a mask made of the photoresist film 58 is formed. After that, electroless plating, nickel plating, a cleaning process, and the like are performed, so that a master for an optical disk is manufactured.

Further, a method of manufacturing an optical disk master by developing the optical disk master manufacturing method applied to the laser cutting apparatus as described above and simultaneously exposing and recording the pit portion and the groove portion on the optical disk is also considered. There is.

In this case, the laser light from the gas laser light source is separated into two beams, and these two beams are applied to the photoresist film formed on the circular substrate. Here, the positional relationship of the pit portion and the groove portion in the radial direction of the disc must be arranged at regular regular intervals on the disc. Therefore, the two beams used to form the pit portion and the groove portion must be accurately separated.

[0012]

By the way, in the method of manufacturing the optical disc master by simultaneously exposing and recording the pit portion and the groove portion as described above, two beams used respectively for forming the pit portion and the groove portion are used. That is, the amount of separation between the pit forming laser beam and the groove forming laser beam could not be set accurately.

For this reason, after the disc is produced by simultaneous exposure of the pit portion and the groove portion, the positional relationship between the pit portion and the groove portion on the disc is confirmed by a secondary inspection method. It was

The confirmation by these secondary inspection methods is, for example, a method of confirming the shift of the pit portion and the groove portion on the master by an optical microscope, and the shift of them by an electron microscope on the stamper formed by this master. Has been performed, and for example, a method of performing signal evaluation using a polycarbonate (PC) molded product has been performed.

Then, by these methods, the separation amount of the above two beams is fixed while feeding back the displacement amount between the confirmed pit portion and the groove portion.

However, if the separation amount of the two beams is determined in this way, a lot of time is spent, and it is not possible to efficiently manufacture the master disc of the optical disc.

Further, when manufacturing master discs of optical discs having different pitches, the degree of pit modulation, the groove condition, etc. are different, and thus it is more troublesome to set (change) the separation amount of the two beams. become.

The present invention has been made in view of the above circumstances, and the amount of separation between the pit-forming laser beam and the groove-forming laser beam does not need to be spent much time.
It can be set easily and accurately, and when producing master discs of optical discs having different pitches, the separation amount can be easily changed, and as a result, an optical disc master disc can be efficiently produced. The purpose is to provide a method for manufacturing an optical disk master.

[0019]

According to the present invention, a reference disc having a luminance distribution corresponding to predetermined pits and grooves is irradiated with a parallel light beam to obtain a luminance distribution pattern, and then a pit forming laser beam is formed. The beam interval of the groove forming laser beam is set in contrast to the brightness distribution pattern, and the optical disk master is exposed.

[0020]

According to the method of manufacturing the optical disc master according to the present invention, the parallel luminous flux is applied to the reference disc having the luminance distribution corresponding to the predetermined pits and grooves.
The positional relationship between the pit portion and the groove portion on this reference disc can be obtained as a luminance distribution pattern, and by comparing this with the luminance distribution pattern, the beam interval between the pit forming laser beam and the groove forming laser beam on the optical disc master is determined. Since it is set, you can easily and accurately set the beam spacing between them without spending a lot of time.
Even when producing master discs of optical discs having different pitches, the separation amount of them can be easily changed.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method for manufacturing an optical disk master according to the present invention is applied to a laser cutting apparatus for manufacturing an optical disk master, which will be described as an embodiment with reference to the drawings.

The method of manufacturing an optical disk master according to the present invention is roughly divided into two steps. That is, a step of irradiating a reference disc having a luminance distribution corresponding to predetermined pits and grooves with a parallel light flux to obtain a luminance distribution pattern, and a beam interval between the pit forming laser beam and the groove forming laser beam is set to the luminance pattern. And the step of exposing the optical disk master to the setting.

The laser cutting apparatus according to the present embodiment is one in which the method of manufacturing an optical disk master including the above-described two steps is performed by one apparatus. The configuration of this laser cutting device will be described below with reference to FIG.

First, as shown in FIG. 1, the laser cutting apparatus includes a gas laser light source 1 using a gas as an amplifying medium and a laser light L emitted from the gas laser light source 1.
Is an electro-optic modulator (Erectro Optic Modulator; hereinafter referred to simply as EOM)
2), a half mirror 4 that divides the laser light L from the EOM 2 into two light components, and an optical system for groove drawing into which one light component L1 reflected by the half mirror 4 is incident. (Hereinafter, referred to as groove optical system) 5
And an optical system (hereinafter referred to as a pit optical system) 10 for pit drawing in which the other light component L2 transmitted through the half mirror 4 enters through a mirror 9, and the groove optical system 5 and the pit optical system. Laser light L1 and L2 from 10
Has a polarization beam splitter (PBS) 14 that guides the laser beams L1 and L2 into one optical path, and a mirror 16 that guides the laser beams (L1, L2) from the PBS 14 to the objective lens 15. It is configured.

The EOM 2 is made of, for example, ADP or KDP crystal, and a variable DC power source (not shown) is connected between the electrodes of the EOM 2. Usually, a constant level DC voltage V is output from this variable DC power supply.
Then, the linearly polarized laser beam L incident on the EOM 2,
In particular, the optical phase difference Δφ between the two orthogonal polarization components in the medium is controlled by the supply of the DC voltage V from the variable DC power supply, and this control changes the polarization state of the laser light L.

Since the laser light L transmitted through the EOM 2 becomes elliptically polarized light, it is converted into intensity-modulated light by the analyzer 3 consisting of a 1/4 wavelength plate and an analyzer in the subsequent stage. That is,
The elliptically polarized laser light L output from the EOM 2 is first returned to the linearly polarized laser light L by the quarter-wave plate, but the oscillating surface of the electric vector has a DC voltage V compared to the incident light.
Since it has rotated by an angle Δφ / 2 proportional to, it is converted into intensity-modulated light by the analyzer next.

Also, the groove optical system 5 and the PBS 14 are used.
In the meantime, the laser light L1 from the groove optical system 5 is supplied to the PBS.
Two mirrors 17 and 18 leading to the
Between the mirror 18 and the mirror 18, for example, the focal length f
The optical element 19 of about 70 to 100 mm is inserted.

The pit optical system 10 and the PBS 14 are also used.
In the meantime, the laser light L2 from the pit optical system 10 is supplied to the PBS.
PBS1 as it is guided to 14 and reflected from the circular substrate 24
A half mirror 20 that transmits the reflected laser light that has passed through 4 and a half-wave plate 21 are provided.

The objective lens 15 and the mirror 16 are arranged on the photoresist film 25 formed on the circular substrate 24 so as to face each other with a predetermined gap, and are moved in the radial direction of the circular substrate 24 by a known moving mechanism. . Here, when the photosensitive material of the photoresist film 24 is a positive type, the laser light L is 458 nm with an Ar laser and He-Cd.
A laser having an oscillation wavelength of 442 nm is selected.
Recently, K having an oscillation wavelength near 400 nm
r lasers may also be used. Further, these gas lasers are emitted as linearly polarized laser light L through the Brewster window.

The groove optical system 10 is based on the beam reduction lens 6 for narrowing the beam diameter of the laser light (parallel light flux) L1 reflected by the half mirror 4 and the ultrasonic wave modulated by the groove recording signal. , An acousto-optic modulator (Acousto Optic Modulator; hereinafter simply referred to as AOM) 7 for intensity-modulating the laser beam L1 from the beam reduction lens 6 and the intensity-modulated laser beam (diffused light flux) from the AOM 7 are parallel to each other. The beam expanding lens 8 converts the light beam to return it to the original beam diameter.

The pit optical system 10 includes a mirror 9
The intensity of the laser beam L2 from the beam reduction lens 11 is modulated based on the beam reduction lens 11 that narrows the beam diameter of the laser beam (parallel light flux) L2 reflected by the beam reduction lens 11 and the ultrasonic wave modulated by the pit recording signal. AOM12 and this AO
The beam expanding lens 13 converts the intensity-modulated laser light (diffused light flux) from M12 into a parallel light flux and restores the original beam diameter.

The AOMs 7 and 12 are made of, for example, TeO ₂ crystal, and use the phase diffraction grating due to the change in the refractive index generated in the crystal by the ultrasonic wave supply from the ultrasonic wave generation circuit, and the Bragg diffraction 1 The secondary diffracted light is used for signal recording. The intensity of the diffracted light is determined by the ultrasonic power, and the diffraction direction is determined by the carrier frequency.

Further, between the PBS 14 and the mirror 16, laser light (L1, L2) incident from the PBS 14 is entered.
A converging lens element 22 for changing the focal length of the
A wave plate 23 is arranged.

Here, the laser cutting apparatus according to the present embodiment irradiates the reference disc having a luminance distribution corresponding to predetermined pits and grooves with a parallel light beam,
It also has a luminance pattern detection unit 30 for performing a step of obtaining a luminance distribution pattern.

The brightness pattern detecting section 30 includes a mirror 31 for reflecting the reflected laser light from the circular substrate 24 that has passed through the half mirror 20, and a lens 32 for converging the reflected laser light reflected by the mirror 31. A light receiving element 35 for receiving the reflected laser light converged by the lens 32, and mirrors 33 and 34 for guiding the reflected laser light converged by the lens 32 to the light receiving element 35,
And a monitor device 36 for displaying a luminance distribution pattern by the reflected laser light received by the light receiving element 35 on a monitor.

Next, the operation of the laser cutting apparatus having such a structure will be described with reference to FIGS.

First, in FIG. 1, the groove optical system 5 is used.
The optical element 19 having a focal length f = 70 to 100 mm, which is inserted between the mirror 14 and the PBS 14, and between the mirror 17 and the mirror 18, causes the laser beam L1 from the groove optical system 5 to pass through the objective lens 15 as shown in FIG. Focus on the pupil plane. Then, the laser light flux irradiated from the objective lens 15 to the irradiation target surface 40 becomes a parallel light flux and is uniformly irradiated to the irradiation target surface 40.

In this state, that is, the optical element 19 is inserted between the groove optical system 5 and the PBS 14, and further between the mirror 17 and the mirror 18, and the objective lens 15 to the illuminated surface 40 is inserted.
A reference disc having a uniform luminance distribution such that the positional relationship in the disc radial direction between the pits and the grooves, that is, the spacing is used as a reference while the parallel light flux is being radiated onto the illuminated surface 40 (Hereinafter, referred to as the reference disk 40). Then, the pattern of the pit portion and the groove portion of the reference disk 40 is enlarged by the objective lens 15 and the converging lens elements 22 and 32, and an image is formed on the image receiving element 35. That is, the objective lens 15 and the light receiving element 35
When is focused, a brightness distribution image of the illuminated surface of the reference disk 40 patterned at the reference intervals is obtained on the light receiving surface of the light receiving element 35.

Here, the reference interval of the reference disc 40 is
Beam interval Δ between two required beams, that is, a pit forming laser beam and a groove forming laser beam
Alternatively, it is desirable to use a highly reflective object patterned at intervals of pitch.

The brightness distribution image of the illuminated surface of the reference disk 40 formed on the light receiving surface of the light receiving element 35 can be confirmed by the monitor device 36. The process up to this point is the process of obtaining the above-described brightness distribution pattern.

The brightness distribution pattern of the reference disk 40 obtained in the brightness distribution pattern detecting step indicates the positional relationship in the disk radial direction between the pit portion and the groove portion of the reference disk 40.

Therefore, in contrast to the brightness distribution pattern obtained here, the photoresist film 2 of the circular substrate 24 is formed.
The separation amount of the pit forming laser beam and the groove forming laser beam for irradiating 5 may be set by adjusting the PBS 14, for example. This is because the optical image formation relationship between the irradiated surface of the reference disk 40 and the light receiving element 35 does not change even when setting the beam separation amount of the two beams, so that the optical element 19 is excluded. This is because the same confirmation can be performed.

In this way, as shown in FIG. 3, the laser beam for forming the groove and the laser beam for forming the pit have respective spots G and P on the photoresist film 25 with a constant beam interval Δ. Will be formed in.

That is, in FIG. 3, the parallel laser beam from the groove optical system 5 and the parallel laser beam from the pit optical system 10 which do not pass through the optical element 19 reflected by the mirror 18 are incident on the PBS 14. To do.
The parallel laser beam from the groove optical system 5 reflected by the mirror 18 is reflected by the PBS 14,
It goes to the converging lens 22 together with the parallel laser beam from the pit optical system 10 that has passed through S14. The two laser beams converged by the converging lens 22 are the objective lens 1
5, the photoresist film 25 is separated and irradiated so as to have a constant beam interval Δ.

In contrast to the result of this irradiation, that is, the brightness distribution pattern obtained in the brightness distribution pattern detection process using the reference disk 40, two lasers are formed on the photoresist film 25 of the circular substrate 24 by the exposure process. A groove portion and a pit portion obtained by irradiating a beam and then undergoing a developing process and the like have exactly the same waveform image as shown in the enlarged image of FIG. Here, in FIG.
Shows a case where the pitch is 1.6 μm and the distance between the pit and the groove is 0.8 μm, and FIG. 4B shows that the pitch is 1.3 μm and the distance between the pit and the groove is The waveform image in the case of 0.65 μm is shown.

In this way, while setting the two laser beams to have a constant beam interval Δ, the respective laser beams, that is, the pit forming laser beam and the groove forming laser beam, are transmitted through the PBS 14 to the circular substrate. By irradiating the photoresist film 25 on 24, the pit portion and the groove portion can be exposed at the same time while accurately maintaining the positional relationship between the pit portion and the groove portion in the disk radial direction.

That is, the laser beam L1 from the groove optical system 5 is reflected by the polarization plane of the PBS 14 toward the objective lens 15 side while the positional relationship between the groove portion and the pit portion in the disc radial direction is maintained accurately. The laser beam L2 from the pit optical system 10 that has been guided passes through the polarization plane of the polarization beam splitter 14 as it is and is guided to the objective lens 15 side. The laser beams L1 and L2 are finally collected by the objective lens 15 and the photoresist film 2
5 is illuminated.

The circular substrate 24 is rotationally controlled in one direction by, for example, the CAV method by a spindle motor (not shown), and the mirror 18 and the objective lens 15 are moved in the radial direction of the circular substrate 24 by a known moving mechanism. Therefore, for example, by supplying the groove recording signal and the pit recording signal for the optical disc to the input terminals of the ultrasonic wave generating circuits in the AOMs 7 and 12, the circular substrate 2
A recording pattern based on the signal is written on the photoresist film 25 on the surface 4 along the concentric circles of the circular substrate 24 or along the spiral shape.

Then, the photoresist film 2 on which the recording pattern is drawn by the above-mentioned exposure process while accurately maintaining the positional relationship between the groove portion and the pit portion in the disc radial direction.
5 is exposed along the drawn recording pattern,
The exposed portion will be dissolved in the developing solution in the next developing step. Therefore, in the subsequent developing process, the exposed portion is removed and a mask made of the photoresist film 25 is formed. After that, electroless plating, nickel plating, a cleaning step, and the like are performed on the basis of a normal master disk manufacturing process to manufacture an optical disk master.

As described above, the laser cutting apparatus according to the present embodiment irradiates the reference disc having the luminance distribution corresponding to the predetermined pits and grooves with the parallel light flux, thereby illuminating the reference disc. The positional relationship between the pit portion and the groove portion can be obtained as a luminance distribution pattern. In contrast to this luminance distribution pattern,
The beam interval between the pit forming laser beam and the groove forming laser beam of the optical disc master is set. For this reason, the beam interval can be set easily and accurately without spending a lot of time, so that the obtained pit portion and groove portion have an accurate positional relationship and an accurate address can be set. Further, even when the masters of the optical discs having different pitches are manufactured, the separation amount thereof can be easily changed, so that the influence of the crosstalk amount can be suppressed even if the track pitch becomes narrower, for example.

In the embodiment of the laser cutting apparatus according to the present invention, the optical element 19 is inserted on the groove optical system 5 side. However, if the optical element 19 is inserted on the pit optical system 10 side, the reference disk is the same as in the present embodiment. It is possible to obtain 40 luminance distribution patterns.

[0052]

As described above, according to the method of manufacturing an optical disc master according to the present invention, a parallel light flux is irradiated to a reference disc having a luminance distribution corresponding to predetermined pits and grooves to form a luminance distribution pattern. After obtaining, the beam interval between the pit forming laser beam and the groove forming laser beam is set in contrast to the brightness distribution pattern, and the optical disc master is exposed.
The amount of separation from the groove forming laser beam can be easily and accurately set without spending a lot of time. Therefore, the positional relationship between the pit portion and the groove portion in the radial direction of the disc can be accurately maintained, and a high-performance optical disc master can be manufactured. Further, when producing master discs of optical discs having different pitches, the separation amount of them can be easily changed.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a laser cutting apparatus as an embodiment of a method for manufacturing an optical disc according to the present invention.

FIG. 2 is a diagram for explaining a principle of obtaining a luminance distribution pattern of a reference disc by a laser cutting device according to an embodiment.

FIG. 3 is a diagram for explaining a separation amount between two laser beams generated in a laser cutting device according to an embodiment.

FIG. 4 is a diagram showing enlarged waveforms of a pit portion and a groove portion obtained by a laser cutting device according to an embodiment.

FIG. 5 is a configuration diagram of a laser cutting device according to a conventional example.

FIG. 6 is a configuration diagram of a laser cutting device according to another conventional example.

[Explanation of symbols]

 1 ... Laser light source 2 ... EOM 5 ... Groove optical system 7, 12 ... AOM 10 ... Pit optical system 14 ... PBS 15 ... Lens 24 ... Circular substrate 25 ... Photoresist film 30 ... Luminance pattern detector 35 ... Light receiving element 36 ... Monitor device

Claims (1)

[Claims] 1. A beam interval between a pit forming laser beam and a groove forming laser beam after a parallel light beam is irradiated onto a reference disk having a brightness distribution corresponding to predetermined pits and grooves to obtain a brightness distribution pattern. Is set in contrast with the brightness distribution pattern, and the optical disk master is exposed.