JP2005011461A - Device of exposing optical master disk and its method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device of exposing an optical master disk which is used in order to form, by exposure to light, a groove whose width is relatively wider than a spot diameter and whose angles of wall faces are steep, and to provide its method. <P>SOLUTION: The exposure device of an optical master disk 1 draws, with a plurality of laser beams 8, a pattern on the resist film of the surface of the pertinent master disk along a track by irradiating the surface of the master disk which is rotated at a prescribed speed. The exposure device is constituted of: an acoustooptic optical deflector 4 which is arranged in the optical path of a laser beam; a plurality of radio-frequency (RF) generating means 6, 7; and a combining means 5 which combines signals from the plurality of the RF generating means 6, 7 and supplies the resultant signal to the acoustooptic optical deflector 4. When the beam spot diameter and the deflection distance on the master disk are defined respectively as d and l, the deflection direction θ (when a track direction is defined as 0°) of the deflector 4 is arranged to be within ¾sin<SP>-1</SP>(d/1)¾ ≤θ≤45° to the advancing direction of the beam. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical disk master exposure apparatus and method for exposing a master of a recording medium having pits and grooves on the same disk, and more particularly, to a groove groove that is relatively wider than a spot diameter and has a steep wall angle. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk master exposure apparatus and method for exposure.
[0002]
[Prior art]
Generally, in a recordable optical disc, a groove that is a concave groove is formed concentrically or spirally.
The information signal recording method includes a groove recording method for recording an information signal in a portion where a groove is formed and a land / groove recording method for recording an information signal in both a groove and a land. It has become mainstream.
In any of these methods, an optical disc master is formed by a so-called mastering process, a stamper is formed based on this optical disc master, an optical disc substrate is formed from the stamper, a recording material is applied, and an optical disc is produced.
[0003]
When manufacturing this optical disc master, for example, the shape of pits and grooves is exposed by irradiating a photoresist coated with a predetermined thickness on a glass substrate, and the desired shape is developed by development. A pit and a groove are formed.
In the above-described groove recording method or land / groove recording method, an information signal is recorded in a groove formed in a concave shape, so that noise is likely to occur near the edge of the groove.
In order to avoid this inconvenience, when these recording methods are employed, a groove having a pitch about ½ of the pitch is generally used.
[0004]
As a method of exposing such a groove, a method of preparing an exposure beam having a groove width of about the width can be considered. However, if the beam is made large, the beam is not steep, so that the exposed groove is not steep. There is.
In such a system, the tracking error signal, which is a role played by the groove, becomes unstable, resulting in a disc that easily causes track deviation. Therefore, in general, a beam having a diameter smaller than the groove width is used (see Patent Documents 1 to 4).
[0005]
[Patent Document 1]
Japanese Patent Publication No. 8-7883
[Patent Document 2]
Japanese Patent No. 2643159
[Patent Document 3]
JP 7-169115 A
[Patent Document 4]
JP 2000-149337 A
[0006]
[Problems to be solved by the invention]
Patent Document 1 discloses a method of using a diffraction grating or a prism as a method of realizing a plurality of spots with shifted centers, but when using either method, a master having a pit / groove groove on the same substrate is disclosed. For exposure, two optical paths corresponding to each are required, and the positional relationship of each spot becomes unstable with respect to room temperature and vibration. In addition, the loss of laser power is large. Further, since the relative intensity adjustment of a plurality of spots cannot be easily performed, the shape of both wall surfaces of the groove groove becomes asymmetric, and the disk tends to have a track error.
[0007]
In Patent Document 2, a groove having a width wider than the spot diameter is formed by subjecting the recording beam to high frequency vibration (wobbling) in the disk radial direction and multiple exposure of the groove groove area. The advantage of this method is that, as shown in FIG. 2, the groove width can be made variable by changing the wobble width.
[0008]
Even if the swing width is changed from 0.39 μm to 0.44 μm, the distribution of the exposure amount is not broken, and a steep wide groove can be exposed with the width being variable.
In this method, the vibration frequency fo required for the spot diameter d and the disk linear velocity v is
fo> v / d = (1.25 m / sec) / (0.5 μm) = 2.5 MHz
It is. This means that the wobbled beam moves to a position advanced by the beam diameter after one cycle.
In other words, since the beam is round, the edge of the groove becomes uneven at 2.5 MHz, so CD-R, MD, etc. are exposed to the wide groove by high frequency wobbling at a frequency of about 5 MHz, which is approximately twice this linear velocity. .
[0009]
In such an MD or the like, since there are pits in addition to the grooves on the board surface, the pits are exposed without being wobbled, and the grooves are wobbled to expose the wide groove. This high-frequency wobble can be realized by deflecting the laser beam at high speed with a very high-speed AO deflector (acousto-optic deflector) or EO deflector (electro-optic deflector) and irradiating the master. Is done.
[0010]
For example, in an AO deflector, an ultrasonic traveling wave is generated in a crystal when a signal having a frequency of about 100 MHz to 400 MHz is input, and the incident light is diffracted to change the angle. If the input frequency of 250 MHz is changed to 260 MHz, the emission angle changes, and the position of the beam irradiated on the master moves.
In order to wobble this at 5 MHz, it is necessary to switch between 250 MHz and 260 MHz at 5 MHz (this is called FM modulation).
[0011]
That is, a driver that generates a signal to be input to the AO deflector needs to be able to perform FM modulation at a frequency of 5 MHz or more, and an extremely expensive FM modulation transmitter is required.
Further, this exposure method has a problem that the groove width fluctuates as described above. FIG. 1 shows the variation of the exposure dose when the beam diameter (1 / e2 diameter) is 0.44 μm and 0.50 μm. In the case of 0.50 μm (in the case of a master exposure apparatus with an exposure wavelength of 458 nm), the fluctuation of the exposure due to wobble does not cause any problem of ± 0.6%, but in the case of 0.44 μm (the exposure wavelength is In the case of a 413 nm master exposure apparatus, the exposure amount fluctuation due to wobble is slightly ± 3.7%, but the groove width fluctuation occurs.
That is, if the beam is further reduced in diameter or the linear velocity is increased, 5 MHz is insufficient, and an FM modulation transmitter cannot be realized, and this exposure method cannot be used.
[0012]
In Patent Document 3, a plurality of signals having different frequencies are input to an AO deflector, and a wide groove groove is exposed with a plurality of focused beams. FIG. 3 shows the exposure distribution by this method.
In this system, if the distance between the two beams is slightly shifted, the exposure amount distribution is deformed as shown in FIG. 3B, and there is a problem that the resist remains even if the groove center is developed. As a result, the beam interval cannot be changed, so that the groove width that can be formed is determined by the beam diameter, and the groove width cannot be freely changed. Furthermore, in this method, two beams are generated simultaneously, so that a beat due to interference occurs in the overlapping portion of the beams.
[0013]
When two grooves are used as shown in FIG. 4 and the groove is exposed by this method, the overlap of the beams is not so much a problem because the intensity ratio is not as high as about 20%. There was a problem.
[0014]
In Patent Document 4, in order to avoid the occurrence of beats in Patent Document 3, a plurality of beams are not generated at the same time but are generated while being switched in time series. However, as in Patent Document 3, there is a problem that the beam interval cannot be changed, and the groove width that can be formed is determined by the beam diameter, and the groove width cannot be freely changed.
[0015]
The present invention has been made to solve the above-described problems, and can form a wide groove with a small beam diameter and a high linear velocity, and can change the groove width, and also has a steep and variable width. An object of the present invention is to provide an exposure apparatus and method for an optical disc master having a small size.
[0016]
[Means for Solving the Problems]
In order to solve the above problems, an exposure apparatus for an optical disc master according to claim 1 of the present invention irradiates a resist film on the surface of the master by irradiating the master surface rotating at a predetermined speed with a plurality of laser beams. In the master exposure apparatus for the master of the optical disc that draws a pattern along with the acousto-optic type optical deflector disposed in the optical path of the laser beam, a plurality of high frequency generators, and signals from the plurality of high frequency generators Combining means for combining and supplying to the acousto-optic type optical deflector, the deflection direction of the acousto-optic type optical deflector being arranged obliquely with respect to the track direction.
[0017]
According to a second aspect of the present invention, in the exposure apparatus for an optical disc master according to the first aspect, the deflection direction θ of the acousto-optic optical deflector (when the track direction is 0 °) is a beam spot diameter. d, where l is the deflection distance on the master,
For the direction of beam travel,
| Sin-1 (d / l) | ≦ θ ≦ 45 °
It is characterized by being.
[0018]
According to a third aspect of the present invention, in the exposure apparatus for an optical disc master according to the first or second aspect, when the signals from the plurality of high frequency generation means are combined by the combination means, the plurality of high frequency generation means. And a means for delaying the generation timing of the signal for each frequency.
[0019]
According to a fourth aspect of the present invention, there is provided an optical disc master exposure method in which a pattern is drawn along a track on a resist film on the master surface by irradiating a laser beam onto the master surface rotating at a predetermined speed. This exposure method is characterized in that exposure is performed while alternately switching between exposure with two beams evenly arranged on both sides from the track center and exposure with a beam arranged at the track center.
[0020]
According to a fifth aspect of the present invention, in the exposure method for an optical disk master according to the fourth aspect, the two beams that are equally arranged on both sides from the track center are arranged at different positions in the track direction. It is characterized by.
[0021]
According to a sixth aspect of the present invention, in the exposure method for an optical disc master according to the fourth or fifth aspect, the exposure time by two beams equally arranged on both sides from the track center and the center of the track are arranged. The exposure is performed by changing the ratio of the exposure time by the beam to a value determined by the beam interval between the two beams equally arranged on both sides from the track center.
[0022]
According to a seventh aspect of the present invention, in the exposure method for an optical disc master according to the fourth, fifth or sixth aspect, when the beam spot diameter is d and the exposure linear velocity is v, the beam is arranged at the center of the track. The exposure time t is defined as t <(d / 2v).
[0023]
According to an eighth aspect of the present invention, in the exposure method for an optical disc master according to the seventh aspect, the exposure with two beams that are equally arranged on both sides from the track center and the exposure with the beam that is arranged at the center of the track. The exposure is performed by changing the switching frequency to a value determined by the beam interval between two beams that are equally arranged on both sides from the track center.
[0024]
According to a ninth aspect of the present invention, there is provided an exposure apparatus for an optical disc master, which irradiates the surface of the master rotating at a predetermined speed with a laser beam to draw a pattern along a track on a resist film on the surface of the master. In the exposure apparatus, an acousto-optic type optical deflector disposed in the optical path of the laser beam, a first high frequency generating means for generating a drive signal having a predetermined frequency f0, and a drive signal having a predetermined frequency (f0 + f1). Second high frequency generating means for generating a signal, third high frequency generating means for generating a drive signal of a predetermined frequency (f0-f1), and combining means for combining the outputs of the second and third high frequency generating means Switching means for selectively supplying the output of the first high frequency generating means and the output of the synthesizing means to the acousto-optic type optical deflector, and timing for switching to the switching means Characterized by comprising the timing signal generating means for supplying a No..
[0025]
According to a tenth aspect of the present invention, in the exposure apparatus for an optical disc master according to the ninth aspect, the timing signal generating means includes a pulse generating means for generating a pulse signal of a predetermined frequency, and a duty ratio by the pulse signal. It is characterized by comprising a duty ratio adjusting means for switching between.
[0026]
According to an eleventh aspect of the present invention, in the exposure apparatus for an optical disc master according to the ninth aspect, the timing signal generating means includes a pulse generating means for generating a pulse signal of a predetermined frequency, and the pulse signal. It is characterized by comprising pulse generation means for converting into a pulse signal having a specific pulse width and outputting it regardless of the frequency of the pulse signal.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
The present invention was conceived by performing various experiments as described below using the above-described prior art to obtain the exposure dose distribution in the radial direction after exposure and the exposure dose distribution in the track direction after exposure. It is.
[0028]
2 and 3 are diagrams showing the exposure amount distribution in the radial direction by the techniques of Patent Document 2 and Patent Document 3, respectively.
2A shows a wobble frequency of 5 MHz, a linear velocity of 1.2 m / s, a beam spot diameter of 0.44 μm, and a wobble oscillation width of 0.39 μm. FIG. 2B shows a wobble frequency of 5 MHz and a linear velocity of 1.2 m. / S, exposure spot distribution when beam spot diameter is 0.44 [mu] m and swing width is 0.44 [mu] m.
[0029]
3A shows the exposure dose distribution when the beam spot diameter is 0.44 μm and the beam interval is 0.23 μm, and FIG. 3B shows the exposure amount distribution when the beam spot diameter is 0.44 μm and the beam interval is 0.26 μm. .
As is apparent from FIGS. 2 and 3, the exposure dose distribution in the radial direction is uniform in a wider range in FIG. 2, and various groove widths can be formed.
[0030]
1A and 1B are diagrams showing the exposure amount distribution in the track direction of Patent Document 2. FIG.
1A shows a wobble frequency of 5 MHz, a linear velocity of 1.2 m / s, and a beam spot diameter of 0.44 μm. FIG. 1B shows a wobble frequency of 5 MHz, a linear velocity of 1.2 m / s, and a beam spot diameter of 0. The exposure dose distribution at .5 μm is shown. As is apparent from FIG. 1, in the method of Patent Document 2, the exposure amount fluctuation in the track direction due to wobble occurs.
[0031]
Also in the method of Patent Document 3, exposure amount fluctuation due to beat occurs. FIG. 5 is a block diagram showing an example of the configuration of the exposure apparatus disclosed in Patent Document 3. 1 is an optical disc master, 2 is an objective lens, 3 is a turntable, 4 is an AO deflector (acoustooptic optical deflector), 5. Is synthesizing means (synthesizer), 6 and 7 are high frequency generating means, and 8 is a laser.
Using this exposure apparatus, the laser light from the laser 8 using a Kr laser (wavelength 413 nm) is deflected in the radial direction by the AO deflector 4, condensed by the objective lens 2, and irradiated onto the optical disc master 1. When the signals generated by the two high-frequency generators 6 and 7 are combined by the combiner 5 and input to the AO deflector 4, the laser light is irradiated into the optical disk master 1 as two beams aligned in the radial direction. Is done. When the two frequencies are adjusted so that the interval between the two beams is as shown in FIG. 4 (beam interval 0.23 μm), the exposure dose distribution becomes a wide shape with a flat center as shown in FIG. It was.
[0032]
Each of the two thin peaks in FIG. 4 indicates the shape of one beam. The two frequencies at this time were 185 MHz and 190 MHz, and the frequency difference was 5 MHz. Although the two beams overlap each other, a slight beat of 5 MHz is generated, and an exposure amount fluctuation of ± 3% is generated.
[0033]
(1) First principle of the present invention:
In Patent Document 3, since exposure is simultaneously performed with two beams arranged in the radial direction as described above, when the exposure distribution in the radial direction is optimal as shown in FIG. Therefore, a beat is generated (see FIG. 6A).
However, as shown in FIG. 6B, when the beams arranged in the radial direction are shifted in the track direction, the apparent beam interval (radial beam interval) does not change. 6 (A) and 6 (B), there is no overlap because the beams are not overlapped, so that interference does not occur, and fluctuations in exposure due to beats are eliminated.
In the case of this exposure method, as can be seen from FIG. 6, the beam spacing in the radial direction when the exposure dose distribution in the radial direction is optimal is in the range from 1/2 of the beam diameter to 60% of the beam diameter.
[0034]
FIG. 7 shows the positional relationship of the exposure beam when the radial exposure amount distribution is optimum and when the radial beam interval is maximized, and the deflection direction is tilted at 45 ° with respect to the track direction. The intensity distribution of the two beams in the deflection direction at that time is shown in FIG. When tilted to 45 °, there is almost no overlap of the beams and the beat disappears.
[0035]
Thus, if the deflection direction of the AO deflector is arranged obliquely rather than in the radial direction, the overlap of the beams can be reduced compared to the case where the AO deflector is arranged in the radial direction, and beats generated in the two-beam exposure can be suppressed. Therefore, it is possible to provide an exposure apparatus capable of exposing a groove having a steep and no width variation even with a small beam and a high linear velocity. This method does not involve switching between two beam and one beam exposure methods as in Principle 2 described later, so that exposure can be performed without causing fluctuations in width even if the beam diameter and linear velocity change.
[0036]
As is clear from FIG. 9, when the maximum deflection distance is 1 and the beam spot diameter is d, the minimum value of the angle θ of the deflection direction with respect to the track direction is
sin-1 (d / l)
It becomes. That is, when the beat disappears, the angle θ with respect to the track direction of the deflection direction is
| Sin-1 (d / l) | ≦ θ ≦ 45 ° (Formula 1)
It is.
[0037]
By setting the deflection direction of the AO deflector to a predetermined angle θ within the range represented by Equation 1, the beam interval can be increased without disturbing the exposure distribution, so that the overlap of the beams can be eliminated, that is, the beat is Since it does not occur, it is possible to expose a groove with a small diameter beam at a high linear velocity, a steep and no width variation.
[0038]
As described above, when the deflection direction is tilted with respect to the track direction, the groove is inclined at the exposure start position and end position of the groove as shown in FIG. In order to eliminate this, assuming that the linear velocity v (m / s), the beam interval b (μm) in the radial direction, and the angle θ with respect to the track direction in the deflection direction, one beam (the upper beam in FIG. 7) is b. By starting exposure with a delay of / v / tan θ (μsec) and performing an extra exposure by b / v / tan θ (μsec), grooves aligned in the radial direction can be formed.
[0039]
As described above, when the deflection direction of the AO deflector is arranged obliquely, the groove exposure start and end shapes are inclined, but the signal generation timing of the high frequency generation means is sequentially delayed. As a result, the shape of the beginning and end of exposure can be made uniform in the radial direction.
[0040]
(2) Second principle of the present invention:
As described above, the method of inputting a composite signal of two frequencies to an AO deflector as in Patent Document 3 and performing exposure has the advantage that the fluctuation of the width does not occur even if the linear velocity and the beam diameter are small, Even if the amount of information increases and the groove becomes finer, it is possible to cope with it.
However, there is a problem that the width that can be formed is almost determined by the beam spot diameter. In order to solve this, in the present invention, exposure is performed by alternately using a method of exposing with a composite signal of two frequencies (two beams) and a method of exposing with one frequency (one beam), The width of the groove that can be formed can be made variable.
[0041]
For example, as shown in FIG. 11, an experiment was conducted at an exposure linear velocity of 1.2 m / s, a beam spot diameter of 0.44 μm, a beam interval of two beams of 0.44 μm, and switching between two beams and one beam at 5 MHz. It was.
[0042]
At this time, when the duty ratio of one beam is 30%, the beam shape in the radial direction becomes an optimum shape in which the peak of the exposure amount is flat (see FIG. 11A), and the exposure amount fluctuation in the track direction is ± 0. .9%, no problem (see FIG. 11B). Here, a duty ratio of 30% means that 30% of the cycle is exposed with one beam and 70% of the cycle is exposed with two beams.
When the duty ratio is 20%, the track center falls (see FIG. 11C), and when the duty ratio is 40%, the track center pops out (see FIG. 11D).
[0043]
Further, as shown in FIG. 12, an experiment was conducted at an exposure linear velocity of 1.2 m / s, a beam spot diameter of 0.44 μm, a beam interval of two beams of 0.25 μm, and switching between two beams and one beam at 5 MHz.
At this time, when the duty ratio of one beam was 10%, the beam shape in the radial direction became an optimum shape in which the peak of the exposure amount was flat (see FIG. 12). FIG. 13 shows the relationship between the beam interval / beam diameter and the duty ratio. By changing the beam interval in this relationship, it is possible to form a groove having a very wide range.
[0044]
Further, when the linear velocity is v (m / s) and the beam spot diameter is d (μm), the exposure time t of one beam is
t <d / 2v
Then, it was confirmed that the variation in the track direction was not a problem regardless of the switching frequency (see FIG. 14). This means that one beam exposure time is suppressed to ¼ or less of the beam spot diameter.
[0045]
Thus, by setting the exposure time for one beam to a predetermined value or less, fluctuations in the amount of light in the track direction can be suppressed to a problem-free level. Therefore, a groove with a small diameter beam, a high linear velocity, a steep and no width fluctuation can be formed. Can be exposed.
[0046]
That is, fixing one beam exposure time and making the switching frequency variable is the same as making the duty ratio variable, so the relationship between the switching frequency and the beam interval / beam diameter is shown in FIG. In this case, a groove having a very wide range can be formed by changing the switching frequency according to the beam interval.
[0047]
As described above, since the switching frequency between the two-beam exposure and the one-beam exposure can be varied while keeping the exposure time for one beam at a predetermined time, it is possible to suppress the light amount fluctuation in the track direction to a level with no problem. In addition, when the beam interval is changed, the exposure frequency can be changed to the corresponding switching frequency so that exposure can be performed with a uniform exposure amount distribution even if various groove widths are exposed. Grooves with no width variation can be exposed with various groove widths.
[0048]
(Example 1)
Using the exposure apparatus configured as shown in FIG. 5, the experimental results of the present invention and the prior art are compared.
In the case of the present invention, the AO deflector 4 is arranged so that the deflection direction is inclined by 45 ° from the radial direction of the optical disc master 1.
In the case of the prior art, the AO deflector 4 is arranged so that the deflection direction is the radial direction of the optical disc master 1.
The two beams in such a configuration are as shown in FIG. 6A in the case of the prior art, and as shown in FIG. 6B in the case of the present invention.
[0049]
In the case of the prior art, when the exposure is performed with a beam diameter of 0.42 μm and a beam interval of 0.23 μm, the exposure distribution has an optimum shape as shown in FIG. Fluctuation occurred.
Further, in the case of the present invention, when exposure is performed with a beam diameter of 0.42 μm and a beam interval of 0.37 μm, the exposure amount distribution becomes an optimum shape as in FIG. 4, and no beat is generated, and exposure in the track direction is performed. There was no change in quantity.
[0050]
(Example 2)
FIG. 16 is a block diagram showing another configuration of the present invention, in which 1 is an optical disc master, 2 is an objective lens, 3 is a turntable, 4 is an AO deflector, 5 is a synthesizing means, 6, 7 and 9 are high-frequency waves. Generation means, 8 is a laser, 10 is a switching means, 11 is a pulse generation means, 12 is a delay means, 13 is an AND circuit, 14 is a control means, and 17 is a duty variable means. Here, the AO deflector 4 is arranged so that the deflection direction is the radial direction of the optical disc master 1.
Further, the duty variable means 17 is an AND of the delay means 12 whose delay amount can be changed by a signal from the control means 14, and the signal obtained by delaying the output of the pulse generating means 11 and the output of the pulse generating means 11 by the delay means 12. It is composed of an AND circuit 13 for extracting a signal.
[0051]
In such a configuration, the outputs of the high frequency generating means 6 and the high frequency generating means 7 whose transmission frequency can be changed by a signal from the control means 14 are synthesized by the synthesizing means 5 and input to the switching means 10, and the output of the high frequency generating means 9 is output. Are alternately switched and input to the AO deflector 4.
This switching timing is controlled by a signal a obtained by adjusting the duty ratio of the output of the pulse generating means 11 by the duty variable means 17.
[0052]
The laser light from the laser 8 is deflected by the AO deflector 4, condensed by the objective lens 2, irradiated onto the optical disc master 1, and when the frequency of the high frequency generating means 9 is supplied to the AO deflector 4, it is centered on the track. Irradiated.
The frequencies of the high-frequency generator 6 and the high-frequency generator 7 are set so that the average of the two frequencies becomes the frequency of the high-frequency generator 9, so that the two beams are roughly separated from the track center. The control unit 14 can determine the beam interval of the two beams based on the difference in frequency between the high-frequency generation unit 6 and the high-frequency generation unit 7 to make the beam interval variable.
[0053]
As described above, in the two-beam exposure, when the beam interval is widened, the exposure amount at the center of the track is reduced, so that a uniform groove cannot be formed, and the groove width that can be formed is variable only within a small range. By performing exposure while switching between 2-beam exposure and 1-beam exposure, it is possible to suppress a decrease in exposure amount at the center of the track even if the beam interval is widened. Unexposed grooves can be exposed with various groove widths.
Since this method only switches high-frequency signals, even if the switching frequency is 20 MHz, it can be configured with a general-purpose analog switch, so even if the beam diameter is 0.42 μm and the linear velocity is 4 m / s, a wide groove can be exposed without problems. it can.
[0054]
Further, the control unit 14 always obtains an optimal exposure amount distribution by controlling the beam interval and the duty ratio so as to have the relationship shown in FIG.
For example, when the beam diameter is varied by setting the beam diameter to 0.44 μm, the exposure amount distribution shown in FIG. 17 is obtained.
[0055]
In addition, the fluctuation of the exposure amount in the track direction was stable at ± 0.9% and ± 0.6% without a beat when the duty ratio was 30% and 28%, but the duty ratio was 20%, In the cases of 15% and 10%, the exposure amount in the track direction fluctuated ± 1.0%, ± 1.8%, ± 2.4% due to the influence of the beat.
[0056]
In this way, when exposing a sharp wide groove by switching between two-beam exposure and one-beam exposure, the ratio of the two-beam exposure and one-beam exposure on the time axis is changed at the same time. Therefore, even when various groove widths are exposed, exposure can be performed with a uniform exposure amount distribution, so that a groove having a small diameter and a high linear velocity can be exposed with various groove widths without steep width fluctuation.
[0057]
Example 3
In this embodiment, the AO deflector 4 is arranged so that the deflecting direction is inclined by 45 ° from the radial direction of the optical disc master 1, and the control means 14 has a beam interval. / The beam diameter and duty ratio were controlled so as to be in the relationship of FIG.
As a result, when the beam diameter was varied by changing the beam diameter to 0.44 μm, the exposure amount distribution as shown in FIG. 19 was obtained.
Further, the fluctuation of the exposure amount in the track direction did not generate a beat, and was stable at ± 0.9% even when the duty was the largest 30%.
[0058]
In this way, if the two beams are arranged obliquely rather than in the radial direction, the overlap of the beams at the time of two-beam exposure can be reduced compared to the case of arranging the two beams at the radial direction, so that beat can be suppressed. It is possible to expose a groove with a small diameter beam at a high linear velocity and with no steep width variation.
[0059]
In this embodiment, when the deflection direction is tilted with respect to the track direction, the groove is inclined at the exposure start position and end position of the groove as shown in FIG.
In order to eliminate this, as shown in FIG. 20, the exposure start position and end position of the two beams are controlled.
[0060]
In FIG. 20, when the high frequency generating means 6 is the upper beam of FIG. 10 and the high frequency generating means 7 is the lower beam of FIG. 10, 16 is an output signal from the high frequency generating means 7 when exposing with two beams. A switch for controlling the rise and fall, and 19 is a switch for controlling the rise and fall of the output signal from the high-frequency generator 6 when exposure is performed with two beams.
[0061]
The rising timings of the switch 16 and the switch 19 are the linear velocity v (m / s), the beam interval b (μm) in the radial direction, and the angle θ with respect to the track direction in the deflection direction. / Tan θ (μsec) is delayed, and the falling edge of the switch 19 is also exposed by b / v / tan θ (μsec). The time from the rise of the switch 16 to the fall of the switch 19 is the exposure time with two beams.
Thereby, it is possible to form grooves aligned in the radial direction.
[0062]
(Example 4)
FIG. 21 is a block diagram showing another configuration of the present invention, in which 1 is an optical disc master, 2 is an objective lens, 3 is a turntable, 4 is an AO deflector, 5 is a synthesizing unit, and 6, 7 and 9 are high-frequency components. Generation means 8 is a laser, 10 is a switching means, 11 is a pulse generation means, 12 is a delay means, 14 is a control means, 15 is a pulse generation means (mono multivibrator), and 18 is a pulse length control means. Except for the means for generating the timing signal a to be supplied to the switching means 10, it is the same as FIG.
[0063]
The timing signal a supplied to the switching unit 10 is supplied from the pulse length control unit 18. The pulse length control means 18 converts the output d from the pulse generation means 11 that generates pulses of various frequencies in response to a command from the control means 14 into a signal a having a constant pulse length regardless of the frequency by the mono multivibrator 15. (See FIG. 22).
[0064]
When the pulse length is 0.05 μsec and the beam spot diameter is 0.44 μm, the optimum exposure dose distribution as shown in FIG. 23 can be obtained by controlling the relationship between the beam interval / beam diameter and frequency as shown in FIG. .
Further, the beam fluctuation in the track direction was as good as ± 0.6% or less at any frequency.
[0065]
In this way, when a pulse signal of a predetermined frequency is generated, a specific pulse width is output regardless of the frequency of this pulse signal, and the beam interval is always made constant with one beam exposure time constant. In addition, since it can be replaced with a switching frequency between the two-beam exposure and the one-beam exposure corresponding to it, it is possible to expose a groove with a small diameter beam, a high linear velocity, a steep and no width fluctuation, with various groove widths.
[0066]
Note that the present invention is not limited to the above-described embodiment, and various modifications and corrections can be made without departing from the scope of the present invention.
[0067]
【The invention's effect】
As described above, according to the present invention, it is possible to expose a master optical disc with various groove widths, with a small beam and a high linear velocity, with a steep and no width variation.
[Brief description of the drawings]
FIG. 1 is a diagram showing an exposure amount distribution in a track direction according to the technique of Patent Document 2. FIG.
FIG. 2 is a diagram showing an exposure amount distribution in the radial direction according to the technique of Patent Document 2;
FIG. 3 is a view showing an exposure amount distribution in the radial direction according to the technique of Patent Document 3;
FIG. 4 is a diagram showing an exposure amount distribution when a distance between two beams is set to 0.23 μm by the technique of Patent Document 3.
FIG. 5 is a block diagram showing a configuration example of an exposure apparatus disclosed in Patent Document 3.
FIGS. 6A and 6B are diagrams for explaining beam intervals when two beams arranged in the radial direction are exposed simultaneously and when the beams arranged in the radial direction are shifted in the track direction; FIGS.
FIG. 7 shows the positional relationship of the exposure beam when the deflection direction is inclined at 45 ° with respect to the track direction when the radial exposure amount distribution is optimum and the radial beam interval is maximized. FIG.
FIG. 8 is a diagram showing the intensity distribution of two beams when the two beams are in the positional relationship of FIG.
FIG. 9 is a diagram for explaining a relationship between angles between a deflection direction of two beams and a track direction;
FIG. 10 is a view for explaining exposure regions at the exposure start position and end position of the groove when the deflection directions of two beams are tilted with respect to the track direction;
FIG. 11 is a diagram showing an exposure amount distribution when exposure is performed by alternately using a method of exposing with two beams and a method of exposing with one beam.
FIG. 12 is a diagram showing another exposure amount distribution when exposure is performed by alternately using a method of exposing with two beams and a method of exposing with one beam.
FIG. 13 is a diagram showing a relationship between a beam interval / beam diameter and a duty ratio.
FIG. 14 is a diagram showing a change in the light amount ratio and the track direction under the condition of exposure time t <d / 2v for one beam.
FIG. 15 is a diagram showing the relationship between the switching frequency and the beam interval / beam diameter when the one-beam exposure time is 0.1 μsec and 0.05 μsec.
FIG. 16 is a block diagram showing another configuration of the present invention.
FIG. 17 is a view showing an exposure amount distribution when the beam diameter is controlled to be 0.44 μm and the beam interval is variable and controlled as shown in FIG.
FIG. 18 is a diagram showing a relationship between a beam interval / beam diameter and a duty ratio.
FIG. 19 is a view showing an exposure amount distribution when the beam diameter is controlled to be 0.44 μm and the beam interval is variable and controlled as shown in FIG.
FIG. 20 is a block diagram showing a configuration of a main part when controlling an exposure start position and an end position of two beams.
FIG. 21 is a block diagram showing another configuration of the present invention.
FIG. 22 is a diagram for explaining the relationship between the output signal from the pulse generating means and the output signal from the mono multivibrator.
FIG. 23 is a diagram showing an exposure amount distribution when the pulse length is 0.05 μsec, the beam spot diameter is 0.44 μm, and the beam interval is variable and control is performed as shown in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Optical disc master, 2 ... Objective lens, 3 ... Turntable, 4 ... AO deflector (acousto-optic type optical deflector), 5 ... Synthesis means, 6, 7, 9 ... High frequency generation means, 8 ... Laser, 10 ... Switching means 11... Pulse generating means 12. Delaying means 13. AND circuit 14 Control means 15 Pulse generating means (mono multivibrator) 16 19 Switch 17 Duty variable means 18 Pulse Long control means.

Claims (11)

In an exposure apparatus for an optical disc master that draws a pattern along a track on a resist film on the master surface by irradiating a plurality of laser beams onto the master surface rotating at a predetermined speed, the optical disc master is disposed in the optical path of the laser light. The acousto-optic light deflector, a plurality of high-frequency generating means, and a combining means for synthesizing signals from the plurality of high-frequency generating means and supplying the signals to the acousto-optic light deflector. An exposure apparatus for an optical disc master, wherein the deflecting direction of the deflector is arranged obliquely with respect to the track direction. 2. The exposure apparatus for an optical disc master according to claim 1, wherein the deflection direction θ of the acousto-optic type optical deflector (when the track direction is 0 °) is a beam spot diameter d and a deflection distance on the master is l. When
For the direction of beam travel,
| Sin-1 (d / l) | ≦ θ ≦ 45 °
An exposure apparatus for an optical disc master, characterized in that: 3. The exposure apparatus for an optical disc master according to claim 1, wherein when the signals from the plurality of high frequency generation means are combined by the combining means, the generation timing of the signals from the plurality of high frequency generation means is set for each frequency. An exposure apparatus for an optical disc master, characterized by having means for delaying. In an exposure method of an optical disc master that draws a pattern along a track on a resist film on the master surface by irradiating the surface of the master rotating at a predetermined speed, 2 is arranged evenly on both sides from the track center. An exposure method for an optical disc master, wherein exposure is performed while alternately switching between exposure with one beam and exposure with a beam arranged at the center of a track. 5. The exposure method for an optical disc master according to claim 4, wherein the two beams equally arranged on both sides from the track center are arranged at different positions in the track direction. 6. The exposure method for an optical disc master according to claim 4 or 5, wherein a ratio of an exposure time by two beams evenly arranged on both sides from the track center and an exposure time by the beam arranged at the track center is defined as the track. An exposure method for an optical disc master, wherein exposure is performed by changing the value to a value determined by a beam interval between two beams that are uniformly arranged on both sides from the center. 7. An exposure method for an optical disc master according to claim 4, wherein when the beam spot diameter is d and the exposure linear velocity is v, the exposure time t by the beam arranged at the center of the track is expressed as t <(d / 2v), a method for exposing an optical disc master. 8. The exposure method for an optical disc master according to claim 7, wherein the frequency of switching between exposure with two beams arranged uniformly on both sides from the track center and exposure with the beam arranged at the track center is set from the track center. An exposure method for an optical disc master, characterized in that exposure is performed by changing the value to a value determined by a beam interval between two beams equally arranged on both sides. In an exposure apparatus for an optical disc master that draws a pattern along a track on a resist film on the master surface by irradiating the master surface rotating at a predetermined speed, an acoustic wave disposed in the optical path of the laser light An optical type optical deflector, first high frequency generating means for generating a drive signal with a predetermined frequency f0, second high frequency generation means for generating a drive signal with a predetermined frequency (f0 + f1), and a predetermined frequency (f0) -F1) a third high frequency generation means for generating a drive signal; a synthesis means for synthesizing outputs of the second and third high frequency generation means; an output of the first high frequency generation means; A switching means for selectively supplying an output to the acousto-optic type optical deflector, and a timing signal generating means for supplying a timing signal for switching to the switching means. Exposure apparatus of the optical disc master to be. 10. The exposure apparatus for an optical disc master according to claim 9, wherein the timing signal generating means comprises pulse generating means for generating a pulse signal having a predetermined frequency and duty ratio adjusting means for switching the duty ratio by the pulse signal. An optical disk master exposure apparatus characterized by the above. 10. The exposure apparatus for an optical disc master according to claim 9, wherein the timing signal generating means includes a pulse generating means for generating a pulse signal having a predetermined frequency, and the pulse signal is specified regardless of the frequency of the pulse signal. An exposure apparatus for an optical disc master, comprising pulse generation means for converting to a pulse signal having a pulse width and outputting the pulse signal.

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