JPH07169111A - Optical disc master exposure device - Google Patents

Abstract

(57) [Abstract] [Purpose] It is possible to always obtain a stable groove shape even with variations in light amount due to variations in the optical axis, and to perform stable control even for exposure with different resist sensitivities. [Structure] Light emitted from an argon laser 1 is split by a beam splitter 2 and, via a mirror M, A / O modulators 3a and 3b for light intensity modulation, and A / O modulators 4a and 4b for signal modulation. After passing through the beam expanders 5a and 5b so as to have a predetermined light diameter, one of them is combined via a λ / 2 plate 6, for example, by a polarization beam splitter (PBS) 7, and focused by a mirror M. The light is transmitted through the objective lens 9 in the actuator 8 to be servoed, and a spot is formed on the resist coated substrate 11 on the turntable 10 for exposure. A light amount sensor is inserted below the objective lens 9 to monitor the light amount.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk master exposure apparatus, and more specifically, it is possible to measure the light quantity by monitoring under the lens even with respect to the light quantity fluctuation due to the optical axis fluctuation. Optical disc master exposure apparatus.

[0002]

2. Description of the Related Art In optical disc master exposure,
The amount of incident light in the optical system is monitored or the amount of light reflected from the resist substrate is monitored.The set amount of light at the time of exposure is measured in advance by first measuring the correlation between the amount of light under the objective lens and the amount of monitor light. The light quantity is set based on the relationship between the light quantity and the groove shape.

[0003] For example, a "group manufacturing method of optical disk masters" described in Japanese Patent Laid-Open No. 4-311834.
In order to form a tracking group having a uniform width over the entire circumference of the disc when irradiating a laser beam on the photoresist film of the optical disc master to form a group, during the laser beam irradiation, The cutting power is gradually reduced at a desired ratio as the position goes to the outer circumference. Thus, CAV (Co
nstant Angular Velocity (constant rotation angle) etc., the groove shape has a different intensity distribution due to the difference in light intensity.
At present, it is necessary to control the light quantity because a uniform groove shape cannot be obtained with a simple light quantity setting.

[0004]

As described above, in the conventional light amount monitor, the incident light is controlled in the optical system or the light amount is controlled in the reflected light monitor from the resist substrate. The optical axis fluctuates due to fluctuations due to temperature changes or environmental conditions (temperature and humidity). The former is heated by increasing the current value in order to compensate for the laser output shortage, and the optical axis fluctuates.Therefore, the output of the acousto-optic modulator for light quantity control also fluctuates, and the axis to the objective lens also differs. ,
The amount of light emitted from the lens changes. Also in the latter case, the balance of the optical system is changed by a change of 1 ° C. and the optical axis is displaced, the amount of light under the objective lens is changed, and a stable groove shape cannot be obtained.

The incident light monitor cannot measure the influence of a slight inclination, and the reflected light monitor cannot be said to measure the actual exposure light amount due to vignetting of the reflected light due to the resist film thickness or the inclination of the substrate. . Further, due to the diversification of optical discs, it has become necessary to properly use resists having different sensitivities to light. It is necessary to reduce the amount of light for a high-sensitivity resist and to irradiate a low-sensitivity resist with a high amount of light. Low light control
Low voltage control is applied to the acousto-optic modulator, the degree of influence of noise and the like is large, and also an error is large with respect to the setting of the amount of light, so that a desired stable groove shape cannot be obtained.

The present invention has been made in view of the above circumstances, and provides an exposure means that can always obtain a stable groove shape even with respect to the unavoidable fluctuation of the optical axis in the optical disc master exposure apparatus. It is also an object of the present invention to provide an optical disk master exposure apparatus capable of more stable control of exposure with different resist sensitivities.

[0007]

In order to achieve the above object, the present invention provides: (1) After dividing a laser beam as an exposure light source into two, an acousto-optic modulator for light quantity modulation and an acoustic wave for signal modulation respectively. In the optical disc master exposure device that creates an exposure latent image on the resist-coated substrate on the turntable after synthesizing after setting the required incident light diameter with the beam expander through the optical modulator and entering the objective lens for focus servo, A light amount sensor for measuring the amount of light after passing through the objective lens is provided, and the light amount sensor is inserted or ejected under the objective lens. Furthermore, (2) the objective lens substantially coincides with a normal resist coating substrate exposure position. The amount of light can be measured at the position, and (3) in (2) above, the amount of exposure light on each axis can be measured before and after the exposure, and further,
(4) In (1), (2) or (3) above, the voltage to each acousto-optic modulator for light quantity modulation is fed back so that a predetermined light quantity is obtained during pre-exposure measurement,
Exposure with the voltage, and after the exposure, measuring the amount of light at a predetermined voltage based on the voltage, and (5) the exposure in (1), (2), (3) or (4) The upper limit control voltage is applied to the acousto-optic modulator for light intensity modulation for each unit voltage before, and each output is measured by the light intensity sensor inserted under the objective lens, and the acousto-optic modulation is performed by the characteristic value measured by the light intensity sensor. Exposure is performed by controlling the output of the device, and (6) In (1), a filter for attenuating the light quantity is detachably provided in the optical path to the objective lens after the acousto-optic modulator for the light quantity modulation. And that
(7) In the above (1), an acousto-optic modulator for light quantity modulation as a filter is further provided after the acousto-optic modulator for light quantity modulation, and further, (8) above (6)
In, after setting the voltage of the acousto-optic modulator by the light quantity sensor under the objective lens, attach the filter at the time of exposure and perform the exposure with a constant attenuation rate, and after the exposure, measure the light quantity through the filter and the light quantity without the filter Or (9)
The thickness of the resist on the outer peripheral portion of the resist-coated substrate outside the recording area is always constant, and further, (10)
In (7), the outer peripheral portion of the resist-coated substrate is irradiated with exposure light, the amount of reflected and transmitted light is measured, the amount of absorption is calculated, and the result is fed back to an acousto-optic modulator as a filter. is there.

[0008]

In the optical disk master exposure apparatus according to the present invention, the light emitted from the argon laser is split by the beam splitter, and the light quantity modulation A / O modulator and the signal modulation A / O modulator are respectively passed through the mirrors. After passing through the beam expander, the beam passes through the beam expander, and one of them passes through the λ / 2 plate and is synthesized by, for example, a polarization beam splitter (PBS), and the focus servo is performed by the mirror. Through the objective lens, and a spot is formed on the resist-coated substrate on the turntable to be exposed. A light amount sensor is inserted below the objective lens to monitor the light amount and control the light amount so as to always obtain a groove shape that is stable even when the optical axis changes.

[0009]

Embodiments will be described below with reference to the drawings. FIG. 1 is a block diagram for explaining an embodiment of an optical disk master exposure apparatus according to the present invention. In the figure, 1 is an argon laser, 2 is a beam splitter, 3a and 3b are acousto-optics (A / O) for light quantity modulation. : Acousto-Optical) modulator, 4
a and 4b are A / O modulators for signal modulation, 5a and 5b are beam expanders, 6 is a λ / 2 plate, 7 is a polarization beam splitter (PBS), 8 is an actuator, 9 is an objective lens, 10 is a turntable, Reference numeral 11 is a resist coated substrate.

As a light source, for example, light emitted from an argon laser 1 is split by a beam splitter 2,
A / O modulator 3 for light amount modulation via each mirror M
a, 3b, A / O modulators 4a, 4b for signal modulation, and then beam expanders 5a, 5b, respectively, so as to have a predetermined light diameter, and one of them passes through a λ / 2 plate 6, For example, the light is transmitted by passing through the objective lens 9 in the actuator 8 which is composed by the polarization beam splitter (PBS) 7 and is focus-servoed by the mirror M, and a spot is formed on the resist coated substrate 11 on the turntable 10 for exposure. .

In this embodiment, when the resist substrate 11 is not present, the light quantity sensor 12 is inserted below the objective lens 9 as shown in FIG. The light amount sensor 12 is inserted before the exposure, and when it reaches a fixed position under the objective lens 9, the light of each optical axis emits a predetermined light amount. For this, the A / O modulators 4a and 4b for signal modulation may be turned on, and a shutter (not shown) may be used for opening and closing. Further, it is preferable that the position of the objective lens 9 is substantially aligned with the position where the resist substrate 11 is exposed. At the start of exposure,
The light amount sensor 12 is removed from below the objective lens 9, and the resist substrate 11 is inserted.

When the light quantity monitored by the light quantity sensor 12 is different from the set light quantity, the A / O modulators 3a, 3 for light quantity modulation are used.
The voltage is input to the driver of b in a controlled manner so that the set light amount is obtained. Exposure is performed based on the voltage value applied to the A / O modulators 3a and 3b for light amount modulation. After exposure, resist substrate 11
After removing, the voltage value is input to the A / O modulator, the light amount sensor 12 is again inserted under the objective lens 9, and the light amount is monitored.

In the second embodiment, when the light quantity monitor 12 is inserted under the objective lens 9, the driver of the A / O modulators 3a and 3b for light quantity modulation has a voltage of 0 V to an upper limit voltage (for example,
1V, 5V) is given for each unit voltage (for example, 0.1V),
As shown in FIG. 3, A / O characteristics are measured. The relationship of the voltage value with respect to the light amount at this time is calculated, the light amount necessary for forming the groove at the time of CAV exposure is calculated, and the light amount corresponding to the radial position as shown in FIG. 4 is emitted.

FIG. 5 is a view showing another embodiment (third embodiment) of the optical disk master exposure apparatus according to the present invention, in which 13 is shown.
Is a resist substrate, 14 and 15 are filters, and other parts having the same functions as those in FIG. For example, when a highly sensitive resist substrate 13 is used, the required exposure light amount is small. At this time, if the input voltage to the A / O modulators 3a and 3b for light quantity modulation is reduced in accordance with the required light quantity, the influence of noise becomes large and the light quantity varies.
As shown in FIG. 5, the A / O modulators 3a and 3 for light quantity modulation
The input voltage to b is made substantially equal, and filters 14 and 15 are inserted to attenuate the light quantity. In this case, the light quantity before and after the exposure is measured with the filter removed.

FIG. 6 is a view showing still another embodiment (embodiment 4) of the optical disk master exposure apparatus according to the present invention.
Reference numerals 16a and 16b are A / O modulators, and other parts having the same functions as those in FIG. 1 are designated by the same reference numerals. Additional A / O modulators 16a and 16b are provided after the A / O modulators 3a and 3b.
Can be inserted to electrically act the same function as the filter described in the third embodiment.

FIG. 7 is a view showing still another embodiment (embodiment 5) of the optical disk master exposure apparatus according to the present invention.
Reference numeral 17 is a resist substrate, 18 and 19 are detectors, 20 is a polarization beam splitter, 21 is an AMP (amplifier), 22
Is an arithmetic circuit, 23 is a feedback circuit, and 24 is an A / O
Other parts of the driver that have the same functions as those in FIG. 1 are denoted by the same reference numerals. A resist substrate 17 is prepared by spinner coating so that the outer peripheral portion of the resist substrate always has the same thickness regardless of whether the resist has low sensitivity or high sensitivity. By irradiating a part of the exposure light (a part of the optical system with a constant light amount) to the outer peripheral portion, measuring the transmitted light or the reflected light with the detector 18 or 19, and calculating the light absorption rate,
As a substitute value for the sensitivity, the appropriate amount of light is automatically determined by the value even when exposing a resist having sensitivity such as feeding back to the input voltage of the A / O modulators 16a and 16b described in the fourth embodiment. Can be emitted.

[0017]

As is apparent from the above description, the present invention has the following effects. (1) Effect corresponding to claim 1: Even if a small amount of vignetting occurs in the objective lens due to the thermal stability of the laser collapsed or the optical axis of the optical system slightly shifts due to changes in the ambient temperature and humidity, By monitoring, the amount of light in that state can be measured. (2) Effect corresponding to claim 2: Since it substantially matches the position of the exposure surface, the amount of light including the optical axis shift of the optical system including the objective lens can be measured. (3) Effect corresponding to claim 3: Since the amount of light on each axis of the optical system can be measured separately, the influence of each optical axis or the like can be seen. (4) Effect corresponding to claim 4: After measuring the light quantity, it can be fed back to the A / O modulator, so that the deviation of the optical axis can be compensated by the light quantity, and the groove shape becomes stable. Also, because it is done before exposure,
Smaller fluctuation correction is required. Further, since the light amount at a predetermined voltage is output after the exposure, the change in the light amount before and after the exposure can be clearly grasped. (5) Effect corresponding to claim 5: When the laser optical axis fluctuates, the incident angle with respect to the A / O modulator shifts, and the emitted light quantity efficiency with respect to the control voltage changes. In the embodiment, even if there is a change, the correction is made each time, so that the output light amount can always be correctly output even when the light amount is changed toward the outer periphery like CAV. (6) Effect corresponding to claim 6 and solving means 8: Since a filter having a constant attenuation rate can be selected, it is possible to select it according to the sensitivity. Further, since the input voltage to the A / O modulator does not change, the degree of influence on noise (electro-optic) is constant. Since the set light amount is obtained by removing the filter, the above effect does not change. Further, since the result of the presence or absence of the filter can be monitored after the exposure, the change during the exposure can be grasped. (7) Effect corresponding to solution means 7: Since the attenuation factor of the filter can be electrically changed by using the A / O modulator, it can be performed without changing the characteristics of the original A / O modulator. . (8) Effects corresponding to solving means 9: By coating the outer peripheral portion of the resist substrate with a resist having a constant thickness, the reflectance caused by the thickness can be made constant at all times. Further, the coating on the outer periphery can be easily performed even by the usual spinner coating. (9) Effect corresponding to solving means 10: The amount of transmitted / reflected light can be measured for a resist having a constant thickness, and the absorbance of the resist can be grasped. Further, since the attenuation rate of the filter can be determined by feeding back to the A / O according to the value, adjustment of the optical system can be made unnecessary for a resist having any sensitivity.

[Brief description of drawings]

FIG. 1 is a configuration diagram for explaining an embodiment of an optical disk master exposure apparatus according to the present invention.

FIG. 2 is a diagram showing a state without a resist substrate according to the present invention.

FIG. 3 is a diagram showing A / O characteristics in the present invention.

FIG. 4 is a diagram showing a light amount according to a radial position in the present invention.

FIG. 5 is a diagram showing another embodiment of the optical disk master exposure apparatus according to the present invention.

FIG. 6 is a diagram showing still another embodiment of the optical disk master exposure apparatus according to the present invention.

FIG. 7 is a diagram showing still another embodiment of the optical disk master exposure apparatus according to the present invention.

[Explanation of symbols]

1 ... Argon laser, 2 ... Beam splitter, 3a, 3
b ... A / O modulator for light intensity modulation, 4a, 4b ... A / O modulator for signal modulation, 5a, 5b ... Beam expander, 6
... λ / 2 plate, 7 ... Polarizing beam splitter (PBS), 8
... Actuator, 9 ... Objective lens, 10 ... Turntable, 11 ... Resist coated substrate.

Claims (6)

[Claims] 1. A laser beam as an exposure light source is divided into two,
Via the acousto-optic modulator for light quantity modulation and the acousto-optic modulator for signal modulation respectively, after making the required incident light diameter with the beam expander, and synthesizing, incident on the objective lens for focus servo, and then on the turntable In an optical disc master exposure device that creates an exposure latent image on a resist coated substrate,
An optical disc master exposure apparatus, comprising a light amount sensor for measuring the amount of light after passing through the objective lens, and the light amount sensor is inserted or ejected under the objective lens. 2. The optical disk master exposure apparatus according to claim 1, wherein the objective lens is capable of measuring the light quantity at a position which substantially coincides with a normal resist coating substrate exposure position. 3. The optical disk master exposure apparatus according to claim 2, wherein the exposure light amount of each axis is measured before and after the exposure. 4. The voltage to each acousto-optic modulator for light quantity modulation is fed back so that a predetermined set light quantity is obtained during pre-exposure measurement, exposure is performed with the voltage, and after exposure, a predetermined value based on the voltage is applied. The optical disc master exposure apparatus according to claim 1, 2 or 3, wherein the amount of light at a voltage is measured. 5. An upper limit control voltage is applied to an acousto-optic modulator for light quantity modulation for each unit voltage before exposure, and each output is measured by a light quantity sensor inserted under an objective lens, and measured by the light quantity sensor. The exposure is performed by controlling the output of the acousto-optic modulator according to the characteristic value.
Alternatively, the optical disc master exposure apparatus according to the item 4. 6. The optical disk master exposure apparatus according to claim 1, wherein a filter for attenuating the light amount is detachably provided in the optical path to the objective lens after the acousto-optic modulator for the light amount modulation.