JP2001236696A - Optical disk master disk exposure method and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exposure device for glass master production which can expose the same pit or the same groove shape always on a photoresist film. SOLUTION: In an optical path from a laser light source 1 to an objective lens 11, a beam parallelism correction means 2, a beam parallelism detecting means 4 which detects the parallelism of the emission beam from the correction means, and beam modulators (an AOM 5 for light quantity adjustment and an AOM 8 for the optical modulations) are set. The beam parallelism is corrected by inputting the detection parallelism by the beam parallelism detecting means 4 in the beam parallelism correction means 2, and after treating a collimated beam after the correction by the beam modulator, it is made to condense on the photoresist film 102 formed in the glass base 101 with the adjective lens 11. A pinhole which transmits the central part of the beam from the laser light source can be used for the beam parallelism correction means 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure method and an exposure apparatus for producing a master for manufacturing an optical disk.

[0002]

2. Description of the Related Art Optical disks (CD, LD, MO, DV)
In an optical recording medium such as D), fine irregularities such as phase pits and pregrooves on which data information, tracking servo information, and the like are recorded are formed on the information recording layer. The production of an optical recording medium having such fine irregularities is performed by an injection molding method, a 2P method, or the like.

In these methods, a master stamper having fine irregularities for finally transferring and forming fine irregularities on the optical disk surface is used. This master stamper is manufactured using an optical disk manufacturing master (referred to as a glass master or a glass master) having irregularities formed of photoresist on the surface of a glass base as a base material master. That is, the master stamper is obtained by subjecting the surface of the glass master to Ni electroforming.
This is a copy of the irregularities on the glass master.

In the production of the above-mentioned glass master, first, a photoresist film is formed on a glass substrate, a laser beam is irradiated on the photoresist film by a master exposure apparatus, and then the photoresist film is developed to form irregularities. are doing. The master exposure apparatus includes an exposure laser (Ar laser, Kr laser, etc.), a modulator for adjusting the amount of laser light,
It is composed of a modulator that modulates according to an exposure pattern, that is, a pit pattern that is recorded information, an objective lens that focuses a laser beam on a photoresist (film), and the like. In such a master exposure apparatus, the size and shape of the irregularities on the glass master are determined by the spot size and spot shape of the laser beam focused on the photoresist.

FIG. 4 is an explanatory diagram showing the relationship between the parallelism of a laser beam and its focal position. As shown in this figure, when the collimated laser beam (parallel beam) L1 enters the objective lens 41, the glass substrate 42
The spot size is minimized by focusing on the upper photoresist film 43.

[0006]

[Problem 1 of Prior Art] However, as also shown in FIG. 4, in the conventional master exposure apparatus, when the convergent beam L2 or the divergent beam L3 is incident, the photoresist film 43 And the spot size increases. Normally, the optical system of the exposure device, which is the main body of the exposure apparatus, is adjusted so as to minimize the spot size, and the photoresist film 43 is exposed in this state. However, when the laser beam L2 or L3 that has converged or diverged due to the deviation of the parallelism of the laser beam is incident on the objective lens 41, the pit shape of the unevenness formed becomes large. Note that, in FIG. 4, reference numeral Lc indicates an optical axis.

[Problem 2 with prior art] As shown in FIG. 5, a laser beam incident on a modulator 51 for performing modulation (adjustment of the amount of laser beam) according to an exposure pattern, that is, a pit pattern as recording information. L11 is condensed by the lens 52 so that the spot size is minimized at the position of the modulator 51. Note that the modulator 51
AOM (Acoustic Optics Modulator)
(Acousto-optic modulator)).

However, when the spot size does not become minimum at the position of the modulator 51, as shown in FIG. 5, the laser beam L12 modulated by the modulator 51 is distorted such as astigmatism. The spot shape when such an inappropriate laser beam L12 having distortion such as astigmatism is focused on the photoresist by the objective lens 53 is as follows:
The symmetry is reduced as compared with the case without astigmatism, and the pit shape of the formed unevenness is deteriorated.

Usually, in the initial adjustment state of the exposure apparatus, the parallelism of the laser beam is not deviated, and there is no distortion such as astigmatism. However, the adjustment of the exposure laser (Ar laser, Kr laser, etc.) is deviated or deteriorated with time, so that the parallelism naturally deviates. Then, the size of the spot focused on the photoresist becomes large, the focusing position of the laser beam incident on the modulator shifts, and the spot shape deteriorates. In addition, when the tube of the exposure laser is deteriorated and replaced with a new tube, the parallelism of the laser beam differs before and after the replacement.
Also in this case, the spot size condensed on the photoresist increases, and the converging position of the laser beam incident on the modulator shifts, deteriorating the spot shape.

Particularly, in recent years, the density of an optical recording medium has been increased, and the density of an optical disk such as a DVD has been increased to about four times the capacity of a conventional CD. Therefore, it is required that the unevenness due to the photoresist film formed on the glass master is also fine, so that the increase in the spot size and the deterioration of the spot shape as described above are particularly problematic.

The present invention has been made in consideration of the above-mentioned problems of the prior art. An object of the present invention is to always adjust the beam to have the same parallelism so that the same pit or the same groove shape is always exposed. An object of the present invention is to provide an exposure method and an exposure apparatus for producing a master for manufacturing an optical disk.

[0012]

According to a first aspect of the present invention, there is provided a method for exposing an optical disc master, wherein a beam from a recording laser light source is condensed by an objective lens onto a photoresist film formed on a base master. In the method of exposing a master optical disc for forming a recording pattern, parallelism of a beam is detected from the laser light source, and when the detected parallelism is lower than a predetermined value, this is corrected to a predetermined value. Light is condensed on a photoresist film by the objective lens.

According to a second aspect of the present invention, there is provided an optical disc master exposing apparatus for forming an information recording pattern by condensing a beam from a recording laser light source on a photoresist film formed on a base master by an objective lens. An optical disc master exposure apparatus, comprising: a beam parallelism correction unit, a beam parallelism detection unit that detects a parallelism of a beam emitted from the correction unit, in an optical path from the laser light source to the objective lens, And a modulator for correcting the parallelism of the beam by inputting the parallelism detected by the beam parallelism detecting means to the beam parallelism correcting means, and processing the corrected parallel beam by the beam modulator. The objective lens focuses light on the photoresist film.

According to a third aspect of the present invention, there is provided an optical disk master exposure apparatus according to the second aspect, further comprising: a partially transmitting mirror on a beam emitting side of the beam parallelism correcting means; and a beam modulator on a reflected light side of the partially transmitting mirror. The beam parallelism detecting means is provided on the transmitted light side of the partially transmitting mirror, the beam parallelism detecting means is a half mirror, and a first beam diameter detection sensor provided on the transmitted light side of the half mirror. A second beam diameter detection sensor provided on the reflected light side of the half mirror, and the first sensor and the second sensor having different distances on the optical path from the half mirror. (With a difference in optical path length), and the parallelism of the beam from the laser light source is detected by the beam diameter measured by the first and second sensors. And wherein the door.

According to a fourth aspect of the present invention, there is provided an optical disk master exposure apparatus according to the second aspect, further comprising: a partial transmission mirror on a beam emission side of the beam parallelism correction means; and a beam modulator on a reflected light side of the partial transmission mirror. The beam parallelism detecting means is provided on the transmitted light side of the partially transmitting mirror, and the beam parallelism detecting means includes one convex lens provided on the transmitted light side of the partially transmitting mirror, and an output of the convex lens. On the emitting side,
And a beam diameter detection sensor provided at the focal position, wherein the parallelism of the beam from the laser light source is detected based on the beam diameter measured by the beam diameter detection sensor.

According to a fifth aspect of the present invention, in the optical disc master exposing apparatus according to the third or fourth aspect, the beam parallelism correcting means is a through-hole (pinhole) for transmitting a central portion of a beam from the laser light source. The beam parallelism is corrected by adjusting the aperture diameter.

According to a sixth aspect of the present invention, in the optical disc master exposure apparatus according to the third or fourth aspect, the beam parallelism correcting means comprises two convex lenses, and these convex lenses are
The optical axis (the central axis of the convex lens) is installed so as to coincide with the central axis of the beam from the laser light source, and the beam parallelism is corrected by adjusting the distance between these convex lenses. .

[0018]

Next, embodiments of the present invention will be described with reference to the drawings. First Embodiment FIG. 1 is an explanatory view showing a configuration of an optical disk master exposure apparatus according to the second aspect of the present invention and an exposure method according to the first aspect of the present invention using the same. As shown in FIG.
A beam parallelism correction means 2 and a partial transmission mirror 3 are provided in this order on the emission light side of a laser light source (laser) 1, and a beam parallelism detection means 4 is provided on the transmission light side of the partial transmission mirror 3.

An AOM (Acoustic Optics Modulator) for adjusting the amount of light is provided on the reflected light side of the partial transmission mirror 3.
A mirror (plane mirror) 6 is provided in this order. A first lens 7, a light modulation AOM 8, a second lens 9, and a second mirror (plane mirror) 10 are provided in this order on the reflected light side of the first mirror (plane mirror) 6. Further, an objective lens 11 is provided on the reflected light side of the second mirror 10. In FIG. 1, reference numeral 101 denotes a glass substrate, and reference numeral 102 denotes a photoresist film.

The operation of the exposure apparatus thus constructed will be described. The laser beam LB1 emitted from the laser 1 passes through the beam parallelism correcting means 2 and is reflected by the partially transmitting mirror 3. At the partially transmitting mirror 3, most (for example, 99%) of the laser beam is reflected (LB2), and a part of the laser beam is transmitted.

The reflected light LB2 from the partially transmitting mirror 3 is
The light is attenuated to a required light amount by the light amount adjusting AOM 5. The laser beam that has passed through the light amount adjusting AOM 5 is reflected by the first mirror 6, condensed by the first lens 7, and then enters the light modulating AOM 8, where it is modulated into recording information, that is, a pit pattern. The laser beam that has passed through the light modulation AOM 8 is returned to a parallel beam by the second lens 9, reflected by the second mirror 10, condensed on the photoresist film 102 by the objective lens 11, and exposed. On the other hand, the transmitted beam LB3 from the partially transmitting mirror 3 travels to the beam parallelism detecting means 4.

In the above exposure step, the parallelism of the laser beam LB1 emitted from the laser 1 is always detected by the beam parallelism detecting means 4, and this detection data is input to the beam parallelism correcting means 2 (feedback). You. In this case, the laser beam LB1 emitted from the laser 1
Is a parallel beam having a predetermined degree of parallelism, the beam parallelism correcting means 2 does not correct the beam parallelism. On the other hand, when the parallelism of the laser beam LB1 deviates from a predetermined value, the laser beam LB1 is automatically corrected to a predetermined parallelism by the beam parallelism correcting means 2.

As described above, in the above exposure apparatus, the laser 1
When the beam parallelism of the laser beam LB1 from the laser beam deviates from a predetermined value, it can be automatically returned to the parallel beam,
Therefore, in the exposure step, the spot size and the spot shape condensed on the photoresist film 102 can be constantly maintained.

Second Embodiment FIG. 2 is an explanatory view of the configuration of an optical disk master exposure apparatus according to a third aspect of the present invention. This exposure apparatus includes a partially transmitting mirror 3 on the laser beam emission side of the beam parallelism correcting means 2,
On the reflected light side of the partially transmitting mirror 3, an AOM or an objective lens (not shown) for adjusting the amount of light, which is the same element as in the first embodiment, is provided. The beam parallelism detecting means 4a having the above configuration is provided.

That is, the beam parallelism detecting means 4a
Comprises a half mirror 21, a first beam diameter detection sensor 22 on the transmitted light side of the half mirror 21, and a second beam diameter detection sensor 23 on the reflected light side of the half mirror 21. In this case, the distance between the first sensor 22 and the second sensor 23 on the optical path from the half mirror 21 is made different (the optical path length is made different).

In this exposure apparatus, the partially transmitting mirror 3
Is split into two by the half mirror 21. In this case, the first sensor 22 is the half mirror 2
The second sensor 23 is installed at a position where the distance from
Is installed at a position where the distance from the half mirror 21 is long. As described above, since the first and second sensors 22 and 23 have different optical path lengths from the half mirror 21, when the beam parallelism deviates from a normal value, the laser beams detected by these sensors 22 and 23 are changed. There is a difference in diameter. When the diameters of the laser beams detected by these sensors are equal to each other, the parallelism of the laser beams has a normal value (normal beam parallelism).

Third Embodiment FIG. 3 is an explanatory view of a configuration of an optical disk master exposure apparatus according to a fourth aspect of the present invention. This exposure apparatus includes a partially transmitting mirror 3 on the laser beam emission side of the beam parallelism correcting means 2,
On the reflected light side of the partial transmission mirror 3, an AOM or an objective lens (not shown) for adjusting the amount of light, which is the same element as in the first embodiment, is provided. A beam parallelism detecting means 4b having the following configuration is provided.

That is, the beam parallelism detecting means 4b
Is composed of one convex lens 31 provided on the transmitted light side of the partially transmitting mirror, and a beam diameter detection sensor 32 provided on the outgoing light side of the convex lens 31 and at its focal position.

In this exposure apparatus, the laser beam transmitted through the partially transmitting mirror 3 is focused by a convex lens 31 toward a beam diameter detection sensor 32. In this case, when the parallelism of the laser beam is deviated, the laser beam does not converge at the focal position of the convex lens 31. On the other hand, when the parallelism of the laser beam is correct, the laser beam is focused at the focal position of the convex lens 31 (the position of the sensor 32). Therefore, the time when the diameter of the laser beam detected by the sensor 32 is minimized is when the parallelism of the laser beams is matched. In this embodiment, in order to improve the detection accuracy of the beam parallelism, it is desirable to use a convex lens 31 having a short focal length. This is because the shorter the focal length, the shallower the focal depth, so that a slight shift in the beam parallelism can be detected.

Fourth Embodiment The present embodiment is directed to a fifth aspect of the present invention. In this exposure apparatus, the beam parallelism correcting means 2 (see FIG. 1) of the laser beam LB1 from the laser 1 is used. A pinhole that allows the central portion to pass through and allows fine adjustment of the opening diameter is provided.

In this exposure apparatus, when the laser beam LB1 passes through the pinhole, the pinhole blocks the outer peripheral portion of the laser beam and transmits only the inner peripheral portion, thereby adjusting the parallelism. However, when the diameter of the pinhole becomes smaller than a certain diameter, the parallelism of the laser beam is not further improved, and only the intensity of the laser beam is reduced. As described above, since there is an optimum value for the diameter of the pinhole, the optimum value should be determined by the beam parallelism detecting means. In addition, as the pinhole, several types having various diameters may be prepared, or a pinhole capable of increasing or decreasing the diameter may be provided, but the latter is preferable, and the diameter can be easily adjusted. There are advantages.

Fifth Embodiment The present embodiment is directed to a sixth aspect of the present invention. In this exposure apparatus (see FIG. 1), two convex lenses are arranged such that their optical axes (the central axes of the convex lenses) are lasers. The beam parallelism correcting means 2 is configured by being installed so as to coincide with the central axis of the laser beam from No. 1. In addition, one or both of these convex lenses is installed on a movable table that can be moved in the optical axis direction. Further, the movement control mechanism of the movable table is connected to the beam parallelism detection means 4 and the detection data of the beam parallelism is input to the movement control mechanism, whereby the distance between the two convex lenses can be finely adjusted to an optimum value. To do.

In this exposure apparatus, the laser beam LB1 emitted from the laser 1 passes through two convex lenses.
In this case, the beam parallelism is adjusted to a predetermined value by appropriately increasing or decreasing the distance between these two convex lenses. The distance between the convex lenses is controlled by the beam parallelism detecting means and the movement control mechanism of the movable table so that the laser beams become parallel. With these two convex lenses, the longer the focal length, the deeper the focal depth, so that the adjustment of the distance between the convex lenses becomes easier. If the center axis of the laser beam from the laser does not coincide with the optical axis of the two convex lenses, changing the distance between the two lenses may cause a change in the emission direction of the laser beam.

[0034]

EXAMPLES Hereinafter, the present invention will be described more specifically based on examples. Example 1 (Claim 5: See FIGS. 1 and 2) A laser beam emitted from an Ar laser was passed through the center of a pinhole sufficiently larger than the laser beam diameter. Most of the transmitted light is transmitted through a partially transmitting mirror having a transmittance of 99%, the transmitted laser beam is split into two by a half mirror, and the diameter of these laser beams is reduced using two commercially available spot size detectors. It was measured.

The two spot size detectors were respectively installed at positions 10 cm and 1 m away from the half mirror, and the difference in optical path length was about 90 cm. The measured spot diameter was about 1800 μm in both cases. At this point, the parallelism of the laser beam was matched, and the minimum width of the exposed pit pattern was about 0.4 μm.

However, as the time elapses, a shift occurs in the adjustment of the Ar laser, and the parallelism of the laser beam shifts. The measured spot diameters at the time of deviation are, for example, about 1850 μm and 1950 μm, respectively, and the minimum width of the exposed pit pattern is about 0.45 μm. Then, as a result of reducing the pinhole diameter to 1.7 mm, the parallelism of the laser beam was improved, and the minimum width of the exposed pit pattern could be returned to about 0.4 μm.

Embodiment 2 (refer to claim 6 and FIG. 1) A laser beam emitted from an Ar laser has a focal length of 100 mm.
2 mm convex lenses. At this time, the central axis of the laser beam emitted from the Ar laser was made to coincide with the optical axes of the two convex lenses. The laser beam transmitted through the partially transmitting mirror having a transmittance of 99% was observed with a device such as an autocollimator capable of accurately detecting the parallelism, and the distance between the two convex lenses was adjusted so that the parallelism of the laser beam was matched. .

Next, the autocollimator was removed, and a convex lens having a focal length of 30 mm and a commercially available CCD camera were installed. At this time, the convex lens and the CC are so arranged that the spot diameter observable by the CCD camera is minimized.
The distance of the D camera was set correctly. The spot diameter measured at this time was about 100 μm. At this point,
The parallelism of the laser beam was matched, and the minimum width of the exposed pit pattern was about 0.4 μm.

However, as time elapses, the adjustment of the Ar laser is shifted, and the parallelism of the laser beam is shifted. The measured spot diameter at the time of displacement was, for example, about 120 μm, and the minimum width of the exposed pit pattern was about 0.45 μm. At this time, the parallelism of the laser beam is improved by adjusting the distance between the two convex lenses so as to minimize the measured spot diameter, and the minimum width of the exposed pit pattern is set to 0.4 μm.
It was able to return to the degree.

[0040]

As apparent from the above description, the following effects can be obtained according to the present invention. (1) Effects of the optical disk master exposure method of claim 1:
When the parallelism of the detected laser beam is lower than a predetermined value, it is corrected to a predetermined value, and the corrected beam is focused on the photoresist film. Therefore, pits or grooves having the same shape and dimensions can always be recorded on the photoresist film.

(2) Effect of the optical disk master exposure apparatus according to the second aspect: beam parallelism correcting means, beam parallelism detecting means for detecting parallelism of a beam emitted from the correcting means, and a beam modulator. The parallelism of the beam is corrected by inputting the parallelism detected by the beam parallelism detecting means to the beam parallelism correcting means, and the corrected parallel beam is processed by a beam modulator, and then focused on a photoresist film. Since it is possible to always perform exposure with a beam having good parallelism, pits or grooves having the same shape and dimensions can be always recorded on the photoresist film.

(3) Advantage of the optical disk master exposure apparatus according to the third aspect: Since the parallelism of the beam from the laser light source is detected based on the beam diameter measured by the first and second sensors, the parallelism is always maintained. Pits or grooves having the same shape and dimensions can always be recorded on the photoresist film.

(4) Advantage of the optical disk master exposure apparatus according to claim 4: The parallelism of the beam from the laser light source is detected by the convex lens and the beam diameter detection sensor provided at the focal position of the convex lens. Exposure can always be performed with a beam having good parallelism, and pits or grooves having the same shape and dimensions can always be recorded on the photoresist film.

(5) Effect of the optical disk master exposure apparatus of claim 5: Since the beam parallelism is corrected by narrowing the beam from the laser light source with a pinhole, the parallelism is always kept by an extremely simple configuration. A good beam is obtained, and pits or grooves having the same shape and dimensions can always be recorded on the photoresist film.

(6) Advantage of the optical disk master exposure apparatus according to claim 6: Two convex lenses are provided, and the beam parallelism is corrected by adjusting the distance between the convex lenses. A beam with good parallelism is obtained, and pits or grooves having the same shape and dimensions can always be recorded on the photoresist film.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a second embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a third embodiment of the present invention.

FIG. 4 is an explanatory diagram of Problem 1 of the related art.

FIG. 5 is an explanatory diagram of Problem 2 of the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser light source (laser) 2 Beam parallelism correction means 3 Partial transmission mirror 4 Beam parallelism detection means 4a Beam parallelism detection means 4b Beam parallelism detection means 5 AOM for light quantity adjustment 6 First mirror (plane mirror) 7 First lens Reference Signs List 8 AOM for light modulation 9 Second lens 10 Second mirror (plane mirror) 11 Objective lens 21 Half mirror 22 First beam diameter detection sensor 23 Second beam diameter detection sensor 31 Convex lens 32 Beam diameter detection sensor 41 Objective lens 42 Glass Base 43 Photoresist film 51 Modulator 52 Lens 53 Objective lens 101 Glass base 102 Photoresist film L1 Parallel beam L2 Convergent beam L3 Divergent beam L11 Laser beam L12 Laser beam LB1 Laser beam LB2 Reflected beam LB3 Transmitted beam Lc Optical axis

Claims (6)

[Claims] An exposure method for an optical disk master for forming an information recording pattern by condensing a beam from a recording laser light source on a photoresist film formed on a base material master with an objective lens. Detecting the parallelism of the beam, correcting the beam to a predetermined value when the detected parallelism is lower than a predetermined value, and condensing the corrected beam on a photoresist film by the objective lens. Optical disc master exposure method. 2. An exposure apparatus for a master optical disc, wherein an information recording pattern is formed by converging a beam from a recording laser light source on a photoresist film formed on a master substrate by an objective lens. Beam parallelism correcting means, a beam parallelism detecting means for detecting parallelism of a beam emitted from the correcting means, and a beam modulator in an optical path from a laser light source to the objective lens; The parallelism of the beam is corrected by inputting the parallelism detected by the means to the beam parallelism correction means, and the corrected parallel beam is processed by the beam modulator, and then is placed on a photoresist film by the objective lens. An optical disk master exposure apparatus characterized in that light is condensed. 3. A partially transmitting mirror on the beam emitting side of the beam parallelism correcting means, the beam modulator on a reflected light side of the partially transmitting mirror, and the beam parallelism detection on a transmitted light side of the partially transmitting mirror. Means, the beam parallelism detecting means includes a half mirror, a first beam diameter detection sensor provided on a transmitted light side of the half mirror, and a second beam provided on a reflected light side of the half mirror. A diameter detection sensor, and the first sensor and the second sensor.
And the distance from the half mirror on the optical path is made different, and the parallelism of the beam from the laser light source is detected by the beam diameter measured by the first and second sensors. The optical disk master exposure apparatus according to claim 2, wherein: 4. A partial transmission mirror on the beam exit side of the beam parallelism correction means, the beam modulator on the reflected light side of the partial transmission mirror, and the beam parallelism detection on the transmitted light side of the partial transmission mirror. And a beam parallelism detecting means, wherein the beam parallelism detecting means includes one convex lens provided on the transmitted light side of the partial transmission mirror, and a beam diameter detection sensor provided on the outgoing light side of the convex lens and at a focal position thereof. The optical disk master exposure apparatus according to claim 2, wherein the parallelism of the beam from the laser light source is detected based on the beam diameter measured by the beam diameter detection sensor. 5. The method according to claim 1, wherein the beam parallelism correcting means is a through-hole for transmitting a central portion of the beam from the laser light source, and corrects the beam parallelism by adjusting the opening diameter. A feature according to claim 3 or claim 4.
3. The optical disc master exposure apparatus according to claim 1. 6. The beam parallelism correcting means comprises two convex lenses, and these convex lenses are installed such that an optical axis coincides with a central axis of a beam from the laser light source.
5. The optical disk master exposure apparatus according to claim 3, wherein the beam parallelism is corrected by adjusting the distance between the convex lenses.