JP2005044459A - Exposing device for master disk of optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten the time for adjustment and to permit adjustment having reproducibility by systematizing an exposure spot diameter of a laser beam to a resist layer in an exposing device for a master disk of an optical disk. <P>SOLUTION: A stage 21 for exposure spot adjustment to be placed on with the disk for exposure spot adjustment previously formed with grooves is disposed in a position adjacent to the master disk 19 of the optical disk and the disk for the exposure spot adjustment on the stage 21 is irradiated with the laser beeam. The laser beam reflected by the grooves is read by a photodetector 17. The disk for exposure spot adjustment is moved in this state in a diametral direction by a sliding mechanism 36. The peak value of an amplitude level is detected from the detection signal of the photodetector 17 obtained by accompanying the movement thereof. As the sliding mechanism 36 moves, a lens 4 of, for example, an optical system for exposure is moved in order to change the exposure spot diameter and the position of the lens 4 at the time of the maximum amplitude of the peak detection signal is stored. The position of the lens 4 is moved and controlled in such a manner the lens attains the optimum state of the exposure spot diameter. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical disc master exposure apparatus that performs exposure recording by irradiating a resist layer formed on the surface of an optical disc master with an exposure laser beam in the step of manufacturing the master of the optical disc, and in particular, the exposure spot of the laser beam is optimized. The present invention relates to a device for adjusting to the above.

  In the manufacturing process of an optical disk, in the process of manufacturing a master for producing a stamper used when injection molding a disk substrate of an optical disk, an exposure emitted from a laser light source is applied to a resist layer formed on the surface of the optical disk master. The exposure laser beam is focused and irradiated by an objective lens to perform exposure recording.

  In order to perform reliable exposure in this optical disk master exposure apparatus, it is necessary to adjust the exposure spot to an optimum diameter. Conventionally, the adjustment of the exposure spot in this optical disc master exposure apparatus is performed by making an exposure laser reflected from the resist layer on the surface of the optical disc master incident on the CCD and visually observing the shape of the exposure spot projected on the monitor. I was going.

The exposure spot adjustment method as described above has the following drawbacks.
(Defect 1) Complicated adjustment process Especially after the optical axis adjustment, the optimum state of the exposure spot on the resist layer surface and the optimum state of the exposure spot observation image on the monitor detected by the CCD do not necessarily match. Therefore, complicated adjustment by the following processes 1 to 7 is required in order to match the optimum states of the two.
Process 1: Using an unused resist master, exposure is performed while changing the state of the exposure spot for each appropriate radius value.
Process 2: The exposed master is developed.
Process 3: The developed master is subjected to a diffracted light measuring device. Or visually.
Process 4: Record the radius value of the optimum exposure spot determined by the measurement result or visual judgment.
Process 5: Adjustment is made to the exposure spot setting state at the radius value recorded in process 4.
Process 6: After the optical disc master is reset in the apparatus, the state of the exposure spot is observed with the CCD.
Process 7: The position of the monitor optical system is adjusted so that the exposure spot observation image on the monitor is optimized.
Conventionally, since the complicated process as described above is required, considerable time is required for the optimization adjustment of the exposure spot.

(Disadvantage 2) Lack of reproducibility When performing optimization adjustment of an exposure spot, there are individual differences among observers in visual judgment on a monitor, and reproducibility is lacking.

(Disadvantage 3) Setting resolution is insufficient for high-density optical discs To increase the density, it is necessary to increase the NA of the objective lens. Since this works in the direction of reducing the depth of focus, an optimal adjustment process with higher resolution is required for optimal setting of the exposure spot. In the conventional method, the process of the above (defect 1) is followed. However, if the setting resolution is insufficient in process 1, the optimum value may not be detected as a result obtained in process 4. In this case, it is necessary to increase the setting resolution again and perform the entire process from process 1 to process 7. This effect may not be a problem with a low-density optical disc with a deep focal depth, but becomes more apparent with a high-density optical disc with a shallow focal depth.

In order to eliminate the above drawbacks, the present invention
In an optical disc master exposure apparatus configured to perform exposure recording by converging and irradiating a laser beam for exposure emitted from a laser light source by an objective lens onto a resist layer formed on the surface of the optical disc master,
An exposure spot adjustment stage which is provided at a position adjacent to the optical disk master and on which an exposure spot adjustment disk on which grooves have been previously formed is placed;
A light detection function of irradiating the exposure spot adjusting disk with laser light and reading the laser light reflected by the groove with a photodetector;
A slide mechanism for moving the exposure spot adjusting disk in the radial direction;
A peak detection function that detects and holds the peak value of the amplitude level from the detection signal of the photodetector obtained along with the movement of the exposure spot adjustment disk,
An electrical offset setting function for focus control that changes the size of the exposure spot of the laser light as the slide mechanism moves, or a position control function of the exposure optical system,
Memory that stores the electrical offset amount at the maximum amplitude or the position of the exposure optical system among the peak detection signals of the peak detection function obtained by the electrical offset setting function for focus control or the position control function of the exposure optical system Function and
A function of setting the electrical offset amount stored by the storage function or the position of the exposure optical system as the optimum state of the exposure spot diameter of the laser beam;
Is provided.
Further, in this optical disk master exposure apparatus, it is preferable to use a stepping motor for position control of the exposure optical system.

In the optical disc master exposure apparatus according to the present invention, the optimization adjustment of the exposure spot is closed only in the master exposure apparatus, so that the optimum exposure spot adjustment process is systematized and simplified, and the time required for the adjustment is greatly increased. Reduced.
Further, in this optical disc master exposure apparatus, all optimization adjustments of exposure spots are systematized and determined quantitatively, so that reliable reproducibility can be ensured.
Further, in this optical disk master exposure apparatus, it is possible to easily increase the setting resolution of the optimum exposure spot by adopting a stepping motor for position control of the exposure optical system.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
An optical disk master exposure apparatus according to the present invention is for creating a stamper used when injection molding a disk substrate of an optical disk having, for example, pits and grooves. As shown in FIG. The resist layer 18 formed in (1) is irradiated with an exposure laser beam, and a latent image having a predetermined pattern corresponding to the pits and grooves of the optical disk is recorded on the resist layer 18.

  This master exposure apparatus uses, for example, an ultraviolet laser having a wavelength of 266 nm as the exposure laser light source unit 1. The exposure laser light emitted from the laser light source unit 1 is modulated by an acousto-optic modulator or the like, then reaches the half mirror 2, partly reflected by the half mirror 2, and partly transmitted through the half mirror 2. Then, the light is incident on a photodetector 35 that detects the exposure power. On the optical path of the exposure laser beam reflected by the half mirror 2, a ¼ wavelength plate 3, a beam expander composed of a lens 4 and a lens 5 for enlarging the beam diameter of the exposure laser beam, and a dichroic A mirror 6 and an objective lens unit 7 for focusing the exposure laser beam and irradiating it on the resist layer 18 are provided.

  The exposure laser beam reflected by the half mirror 2 enters the quarter-wave plate 3 and becomes circularly polarized light. The exposure laser beam that has been circularly polarized by the quarter-wave plate 3 has its beam diameter enlarged by the first lens 4 and the second lens 5 that constitute the beam expander. The exposure laser beam whose beam diameter has been expanded by the beam expander has its optical path bent by the dichroic mirror 6 and is arranged so as to face the main surface of the optical disc master 19 on which the resist layer 18 is formed. 7 is incident. The exposure laser light incident on the objective lens unit 7 is focused by the objective lens unit 7 and irradiated onto the resist layer 18 formed on the optical disc master 19.

The optical disc master 19 on which the resist layer 18 is formed is chucked on an air spindle mechanism 37 that rotates with high rotational accuracy. As the air spindle mechanism rotates, the resist layer 18 on the optical disc master 19 is irradiated with an exposure laser.
In this master exposure apparatus, all the optical systems from the exposure laser light source 1 to the objective lens unit 7 are mounted on a fixed optical surface plate. On the other hand, the air spindle mechanism 37 and the optical disc master 19 are described later. The exposure spot adjusting stage 21 is mounted on an air slide mechanism 36 that is operated to move in the radial direction of the optical disc master 19. The movement of the air slide mechanism 36 is controlled by a slide position drive signal 32 from the slide control controller 23.

  Also, in this master exposure apparatus, the reflected light of the exposure laser light irradiated on the resist layer 18 on the optical disc master 19 is taken in by the CCD unit 15 via the half mirror 13 and the condenser lens 14 and is applied onto the resist layer 18. The spot image of the irradiated exposure laser beam is monitored.

  Further, this master exposure apparatus is configured to perform focus control so that the focus of the exposure laser beam is always on the resist layer 18 when the exposure laser beam is irradiated onto the resist layer 18. This focus control is performed by moving the objective lens unit 7 in the direction along the optical axis in accordance with the focus shift amount detected by the autofocus optical system.

  The autofocus optical system includes, for example, a focus laser light source 8 that emits laser light having a wavelength of about 680 nm, a quarter-wave plate 10 and a folding mirror disposed on the optical path of the laser light that has passed through the polarization beam splitter 9. 11, the dichroic mirror 6 disposed on the optical path of the laser light reflected by the folding mirror 11, and the optical path of the reflected light of the laser light irradiated on the resist layer 18 through the objective lens unit 7. And a photodetector 12.

The detector 12 converts an optical signal into an electrical signal using, for example, a two-divided type photodetector, and the converted signal is input to the focus control controller 22 as a gap error signal 25. Here, for example, a change in the condensing state in the resist layer 18 of the focus light source 8 is detected as a change in reflected light by a generally well-known off-axis method or the like, and the change from the focus control controller 22 based on the detection signal is detected. The movement actuator 20 of the objective lens unit 7 is driven by the control signal, and the objective lens unit 7 is moved and adjusted in the optical axis direction to perform focus control.
In this master exposure apparatus, the focus control controller 22 is controlled by a focus sequence control signal 33 from the host computer 24. The slide control controller 23 is controlled by a slide sequence control signal 34 from the host computer 24.

Next, in the master exposure apparatus as described above, a configuration for realizing the optimization adjustment of the exposure spot, which is the key of the present invention, will be described.
The exposure spot of the exposure laser on the resist layer 18 on the optical disc master 19 has a smaller margin with respect to the gap control of the focus system as its diameter is smaller. In the present invention, as a means for adjusting the exposure spot diameter on the resist layer 18, the exposure spot adjusting stage 21 is disposed on the air slide mechanism 36 at a position adjacent to the air spindle 37.

  On the exposure spot adjusting stage 21, an exposure spot adjusting disk is installed as a sample in which grooves are engraved in a spiral shape at predetermined intervals. The height of the exposure spot adjustment stage 21 is adjusted in advance so that the surface of the exposure spot adjustment disk is the same height as the surface of the adjacent optical disk master. Here, it is determined whether or not the thickness of the photoresist layer 18 on the optical disc master 19 is taken into consideration from the ratio to the focal depth determined by the employed exposure optical system.

Next, the air slide mechanism 36 is moved in the radial direction of the optical disc master 19 so that the position of the objective lens unit 7 is on the exposure spot adjustment stage 21.
Subsequently, the objective lens unit 7 is lowered on the exposure spot adjustment stage 21 and stopped at a position where the focus servo starts to work. A part of the reflected light from the surface of the exposure spot adjustment disk on the exposure spot adjustment stage 21 of the exposure laser is transmitted by the half mirror 13 and enters the photodetector 17 through the condenser lens 16.

  The exposure pattern detection signal 28 output from the photodetector 17 is observed as a SIN wave having a constant amplitude at a constant period when the air slide mechanism 36 is moved at a constant speed. The period of the SIN wave is determined from the pattern interval on the exposure spot adjusting disk and the air slide feed speed, and the amplitude is determined by the spot diameter of the exposure laser on the surface of the exposure spot adjusting disk. . The smaller the spot diameter of the exposure laser, the larger the amplitude level.

Therefore, if the exposure spot diameter on the exposure spot adjustment disk surface is changed as the air slide mechanism 36 moves at a constant speed, the amplitude level of the exposure pattern detection signal 28 changes according to the diameter of the exposure spot. Can be caught.
In this case, examples of the method for changing the exposure spot diameter include the following two methods.
(1) The focus gap 27 is adjusted by electrically adding an offset to the gap error signal 25 for focus control.
(2) The position of the lens 4 or the lens 5 arranged on the optical path of the exposure laser beam is adjusted in the optical axis direction of the exposure laser.

  That is, in the method (1), the focus control controller 22 adds an electrical offset for focus control to the gap error signal 25, and the objective lens unit 7 receives the gap control signal 26 from the focus control controller 22. The moving actuator 20 is driven to adjust the focus gap 27. Alternatively, the focus gap 27 may be adjusted by changing the height of the exposure spot adjustment stage 21 by the stage height position drive signal 31 from the focus control controller 22. In this way, by adjusting the focus gap 27 so as to change the exposure spot diameter as the air slide mechanism moves at a constant speed, exposure pattern detection according to the diameter of the exposure spot on the surface of the exposure spot adjustment disk is performed. It can be understood as a change in the amplitude level of the signal 28.

  In the method (2), as the air slide mechanism moves at a constant speed, the lens 4 of the exposure optical system is moved in the optical axis direction of the exposure laser by the lens position drive signal 30 from the focus control controller 22. By controlling the movement of the exposure pattern, it can be grasped as a change in the amplitude level of the exposure pattern detection signal 28 in accordance with the diameter of the exposure spot on the exposure spot adjustment disk surface. Here, for the position control mechanism of the lens 4, for example, a microstepping motor capable of detecting the relative position is used. In this case, if the pulse counter is cleared by the origin signal 29 built in the stepping motor unit and the output pulses of the lens position driving signal 30 are counted, the optical axis direction of the exposure optical system of the lens 4 corresponding to the count value is obtained. The relative position of can be known.

  The exposure pattern detection signal 28 captured as a change in amplitude level by the method (1) or (2) is input to the focus control controller 22 where peak detection processing is performed and the amplitude level becomes maximum. Or the pulse count value of the lens position driving signal 30 is stored. The value stored here is finally determined as the electrical offset amount that optimizes the exposure spot on the exposure spot adjustment disk surface or the position where the lens 4 is to be fixed, and the focus gap 27 or the lens 4 based on the setting. The movement of the position is controlled.

In this manner, in the master exposure apparatus according to the present invention, the exposure spot of the laser beam irradiated on the resist layer 18 of the optical disc master 19 can be adjusted to an optimum diameter.
In this master exposure apparatus, the exposure spot optimization adjustment is closed only in the master exposure apparatus, so that the optimum exposure spot adjustment process is systematized and simplified, and the time required for the adjustment is greatly reduced. The
Further, in this master exposure apparatus, since all optimization adjustments of exposure spots are systematized and quantitatively determined, reliable reproducibility can be ensured.
Further, in this master exposure apparatus, the setting resolution of the optimum exposure spot can be easily increased by adopting the micro stepping motor in the position control mechanism of the lens 4 that is the exposure optical system.

  Although the embodiment of the present invention has been described above, it is needless to say that the present invention is not limited to this and can take other various embodiments.

1 is a system block diagram of a disc master exposure apparatus according to the present invention.

Explanation of symbols

1 Laser light source unit 4 Lens (optical system for exposure)
7 Objective Lens Unit 17 Photodetector 18 Resist Layer 19 Optical Disc Master 21 Exposure Spot Adjustment Stage 22 Focus Control Controller 23 Slide Control Controller 36 Air Slide Mechanism

Claims (2)

In an optical disc master exposure apparatus configured to perform exposure recording by converging and irradiating an exposure laser beam emitted from a laser light source by an objective lens onto a resist layer formed on the surface of the optical disc master,
An exposure spot adjustment stage which is provided at a position adjacent to the optical disk master and on which an exposure spot adjustment disk on which grooves are formed in advance is placed;
A light detection function of irradiating the exposure spot adjusting disk with the laser light and reading the laser light reflected by the groove with a photodetector;
A slide mechanism for moving the exposure spot adjusting disk in the radial direction;
A peak detection function for detecting and holding the peak value of the amplitude level from the detection signal of the photodetector obtained along with the movement of the exposure spot adjustment disk,
An electrical offset setting function for focus control or a position control function of the exposure optical system that changes the size of the exposure spot of the laser light as the slide mechanism moves,
Of the peak detection signal of the peak detection function obtained by the electrical offset setting function for focus control or the position control function of the exposure optical system, the electrical offset amount at the maximum amplitude or the exposure optical system A memory function to memorize the position;
A function of setting the electrical offset amount stored by the storage function or the position of the exposure optical system as an optimum state of the exposure spot diameter of the laser beam;
An optical disc master exposure apparatus comprising:   2. The optical disk master exposure apparatus according to claim 1, wherein a stepping motor is used for position control of the exposure optical system.

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