JP2005148243A - Exposure system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exposure system which can stably operate focus servo control by using laser light for exposure and makes high density recording possible. <P>SOLUTION: The exposure system is equipped with at least an objective lens 8 to condense laser light emitting from a laser light source 4 to a photoresist applied on a plate D to be exposed; and a focus servo controlling means 12 to control the focus by the reflected light from the photoresist. The system is also equipped with a main controlling means 13 to control the focus servo controlling means to change the position of the objective lens in such a manner that the laser light is rightly focused on the photoresist in an exposure period and that the laser light is defocused within the focus control range and does not expose the photoresist in a non-exposing period. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exposure apparatus, and more particularly to an exposure apparatus that exposes a glass master or the like used when mass-producing optical disks.

In general, an exposure apparatus is known as an apparatus for performing exposure by scanning a laser beam on an original plate coated with a photoresist. For example, in an exposure apparatus that exposes a glass master used for mass production of optical discs, a laser master spot is scanned relative to the glass master by rotating the glass master coated with a photoresist. On the other hand, exposure based on recorded data is performed (Patent Document 1, Patent Document 2).
At this time, in order to maintain a constant distance between the objective lens for condensing the laser beam and irradiating the glass master, and the photoresist surface of the glass master, an exposure laser that performs exposure for actual recording A laser beam for focus servo that is not exposed to a photoresist other than the light is used.
Specifically, apart from the exposure laser beam having a wavelength of 266 nm, a focus servo laser beam having a wavelength of 633 nm, which is not exposed to the photoresist, is used. Is doing.

JP 2002-342974 A Japanese Patent Laid-Open No. 7-199481

By the way, if the wavelength of the laser beam for exposure is shortened in order to increase the recording density, it becomes difficult to correct the color of the objective lens, and the focal length for the laser beam for exposure differs from the focal length for the laser beam for focus servo. End up. On the other hand, it is conceivable that the wavelength of the laser beam for focus servo is close to the wavelength of the laser beam for exposure. In this case, however, there arises a problem that the photoresist is exposed to light.
Therefore, it is conceivable to perform focus servo control using an exposure laser beam (hereinafter referred to as “direct focus servo method”). However, when forming a non-exposed portion, that is, a so-called mirror portion, an exposure laser is used. Since the irradiation of light must be stopped, there arises a problem that focus servo control is not applied at this time. Specifically, for example, when exposure for recording data is performed after the mirror portion, the focus servo control is not applied to the mirror portion that does not irradiate the exposure laser beam, so when data recording is started However, there is a problem that the pull-in for focusing does not go smoothly and the focus servo control becomes unstable, and it takes time to pull in.

  As a solution to this problem, as disclosed in Patent Document 2, there is a method in which the intensity of laser light is reduced when necessary so that the photoresist is not exposed. However, since this method forms the mirror part only by reducing the laser power, the load on the focus servo control due to the reduction of the laser power at the time of forming the mirror part becomes large and the servo control becomes unstable. In addition, it is difficult to form the mirror portion only by lowering the laser power when forming the mirror portion, and there is a case where even a slight amount of photoresist is exposed and the mirror portion is not formed.

  The present invention has been made in view of such circumstances, and for example, even in a mirror portion where exposure is not performed, focus servo control can be stably operated using laser light for exposure, and high-density recording is possible. An object of the present invention is to provide an exposure apparatus.

  According to a first aspect of the present invention, there is provided an objective lens for condensing laser light emitted from a laser light source onto a photoresist coated on an exposed plate, and a focus servo for performing focus control by reflected light reflected by the photoresist. In the exposure apparatus having at least a control means, at the time of exposure, the laser light is not exposed to the photoresist so that the laser light is just focused on the photoresist at the time of exposure, and within the focus control range. An exposure apparatus comprising: main control means for controlling the focus servo control means to change the position of the objective lens so as to defocus.

  In this case, for example, as defined in claim 2, it further includes intensity varying means for varying the intensity of the laser beam, and the main control means does not make the operation of the focus servo control means unstable during non-exposure. The intensity varying means is controlled so as to reduce the intensity of the laser beam within a range.

  In the exposure apparatus according to the present invention, the exposure laser beam emitted from the laser light source is condensed by the objective lens and irradiated to the exposed plate to perform exposure for recording data, and from the exposed plate. When performing focus servo control (focus control) of the objective lens using the reflected light, the non-exposure part such as a mirror part that is not exposed, for example, is placed within the focus servo operation range (focus control) at a position where the photoresist is not exposed. Range)), or at the same time as this operation, the intensity of the laser beam is reduced within the range where the focus servo control does not become unstable. The problem of color correction is eliminated, the wavelength of the laser beam for exposure can be shortened, and high-density recording can be performed. Further, since one laser light source can be provided, the cost can be reduced as compared with the conventional apparatus.

Hereinafter, an embodiment of an exposure apparatus according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a block diagram illustrating an exposure apparatus according to the present invention, FIG. 2 is a diagram illustrating the relationship between the configuration of a photodetector for focus servo control and each signal, and FIG. 3 is a schematic diagram illustrating the waveform of each signal.
In the exposure apparatus according to the present invention, the exposure laser beam emitted from the laser light source is condensed by the objective lens and irradiated to the exposed plate, for example, exposure for recording data is performed, and the exposed plate When performing focus servo control of the objective lens using the reflected light from, for example, in a non-exposed part such as a mirror part that is not exposed, for example, the intensity of the laser light is kept at the time of exposure and the photoresist is not exposed Defocus the objective lens within the focus servo operating range. In this case, as will be described later, the intensity of the laser beam may be reduced within a range where the focus servo control does not become unstable, and the objective lens may be defocused within the focus servo operation range at a position where the photoresist is not exposed.

In the present embodiment, a case will be described in which the present invention is applied to an exposure apparatus that exposes a glass master in a so-called mastering process when mass-producing optical disks.
For example, as shown in FIG. 1, an exposure apparatus 2 to which the present invention is applied includes a laser light source 4 that emits an exposure laser beam L1, modulation means 6 that modulates the laser beam L1 based on recording data, and In order to scan the laser light spot irradiated to the objective lens 8 which condenses the laser beam modulated by the modulation means 6 and irradiates the glass master D which is a disc-shaped exposed plate, and the glass master D. A rotation turntable 10 as the scanning means, focus servo control means 12 for performing focus servo control of the objective lens 8 using reflected light from the glass master D, and an apparatus including the focus servo control means 12 It is mainly configured by main control means 13 made of, for example, a microcomputer or the like for controlling the entire operation. The surface of the glass master D is coated with a photoresist D1 for exposure with the modulated laser beam spot.

  The objective lens 8 is attached to and supported by a focus actuator 14 that operates uniaxially, and performs focus servo control that moves the objective lens 8 closer to and away from the glass master D in response to a command from the focus servo control means 12. The specific configuration of the focus actuator 14 is disclosed in, for example, Japanese Patent Application Laid-Open No. 61-57048. Further, the entire holding base 14A of the focus actuator 14 is supported by the movable surface plate 16, and the focus actuator 14 and the objective lens 8 can be moved integrally in the radial direction of the glass master D. Yes. The holding base 14A is provided with a radius sensor 18, detects the position (coordinates) of the objective lens 8 in the radial direction of the glass master D, and sends the detection result to the main control means 13. To get.

  Three mirrors 20, 22, and 24 for bending the optical axis are provided in the optical path of the laser light L1 emitted from the laser light source 4. A polarizing beam splitter (hereinafter referred to as “PBS”) for bending the reflected light reflected by the glass master D toward the focus servo control means 12 in the middle of the optical path between the modulation means 6 and the objective lens 8. 26) is also provided. A quarter-wave plate 28 that rotates the polarization plane of the laser light by 45 degrees is interposed in the middle of the optical path between the PBS 26 and the objective lens 8. The focus servo control means 12 to which the reflected light from the PBS 26 is directed is a photo detector 30 that directly receives the reflected light, and a focus that controls the operation of the focus actuator 14 based on an output signal from the photo detector 30. The servo control circuit 32 is included.

  The main control means 13 outputs a non-exposure focus point offset signal S1 for defocusing to the focus servo control circuit 32 when necessary, whereby the above-mentioned main control means 13 at the time of non-exposure. The objective lens 8 is defocused within the focus servo operation range to a position where the photoresist D1 is not exposed. More specifically, the intensity of the laser beam is set to the intensity at which the photoresist D1 applied to the glass master D is exposed at the time of exposure, and the intensity at which the photoresist D1 is exposed at the time of non-exposure, and the photoresist D1 is not exposed. The objective lens 8 is defocused at a position within the focus servo operation range.

Next, the operation of the exposure apparatus of the present invention configured as described above will be described.
First, the laser light source 4 has an element that outputs a Deep UV (short wavelength ultraviolet) laser beam having a short wavelength, for example, 266 nm, in order to perform high-density recording. The laser light L1 emitted from the laser light source 4 is: The light is reflected by the mirror 20 and enters the modulation means 6. The modulation means 6 is composed of, for example, an electro-optic effect (EO) modulator or an acousto-optic effect (AO) modulator, and is driven based on, for example, recording data under the control of the main control means 13 to pulse-modulate the laser light L1. The pulse-modulated laser light is reflected by the mirror 22, passes through the PBS 26, and enters the quarter-wave plate 28. That is, for example, if the laser light L1 from the laser light source 4 is P-polarized light, the PBS 26 is set to transmit P-polarized light.

  The pulse-modulated laser light is reflected by the mirror 24 after the polarization plane is rotated 45 degrees by the quarter wavelength plate 28 and is incident on the objective lens 8 attached to the focus actuator 14. The objective lens 8 is moved in the radial direction of the disk-shaped glass master D by the moving surface plate 16, condenses the pulse-modulated laser light and irradiates the glass master D. The glass master D is mounted on the turntable 10 and is rotated by the turntable 10. Therefore, the spot of the laser beam scans relative to the glass master D. Then, the photoresist D1 applied to the surface of the glass master D is exposed with a laser beam modulated based on the recording data. At this time, part of the laser light is reflected on the surface of the glass master D, and this reflected light is incident on the quarter-wave plate 28 through the objective lens 8 and the mirror 24, and this quarter-wave plate At 28, the plane of polarization is further rotated 45 degrees. That is, the reflected light becomes S-polarized light by passing through the quarter-wave plate 28, is reflected by the PBS 26, and enters the photodetector 30 of the focus servo control means 12.

  The photodetector 30 forms a focus error signal FS1 and a focus lock detection output signal FS2 by an astigmatism method using, for example, a condensing lens and a cylindrical lens (not shown), and based on both the signals FS1 and FS2. The focus servo control circuit 32 drives and controls the focus actuator 14 that supports the objective lens 8. As shown in FIG. 2, the photodetector 30 has a substantially square photosensor 36 divided into four parts, and the outputs on the diagonal planes are added by the addition amplifiers 40A and 40B, respectively. Opposite surface addition outputs A and B are output. Then, the difference between the outputs A and B is obtained by the differential amplifier 42A and the focus error signal FS1 is created, and the sum is obtained by the addition amplifier 42B and the focus lock detection output signal FS2 is created.

The waveforms of the signals FS1 and FS2 at this time are shown in FIG. FIG. 3A shows the waveform of the focus error signal FS1, and represents the S-characteristic. The area between the + peak and the − peak of the S-characteristic is the focus servo pull-in area “S range”. FIG. 3B shows the waveform of the focus lock detection output signal FS2, and shows an upward convex characteristic that peaks at the in-focus position. Both abscissas represent the distance between the objective lens 8 and the glass master D. In FIG. 3A, the detection system is such that when the output is zero, it corresponds to the in-focus position of the recording beam. It has been adjusted.
In the operation of the focus control system, first, a glass master D coated with a photoresist D1 is set on the turntable 10. The objective lens 8 attached to the focus actuator 14 is retracted upward so as not to contact the glass master D at first. Next, when the DC power is supplied to the focus actuator 14 and the objective lens 8 is slowly lowered so as to approach the glass master D, the reflected light from the glass master D irradiated with the laser light is received by the photodetector 30. Will come to be.

  When it further descends and approaches the in-focus position, the focus lock detection output signal FS2 exceeds the level of the reference value Vref (see FIG. 3B), and as a result, the focus error signal FS1 becomes the focus servo pull-in area “S range”. Enter. After confirming that the focus lock detection output signal FS2 exceeds the level of the reference value Vref, the focus servo control circuit 32 is turned on. Then, the objective lens 8 and the glass are placed so that the focus error signal FS1 becomes zero, that is, the focus position of the beam light comes to the surface of the photoresist D1 applied to the surface of the glass master D. The focus servo control circuit 32 operates so that the distance from the master D is kept constant. Then, laser light is irradiated with focus servo control applied, and exposure based on the recording data is performed. Although the astigmatism method has been described here as the focus servo method, the present invention is not limited to this, and various focus servo methods such as a knife edge method and a critical angle method can be used.

  Here, a case where a portion not exposed, for example, a mirror portion is formed will be described. First, the main control means 13 stores in advance, for example, the start radius and end radius of the mirror portion to be formed. The main control means 13 recognizes the position of the objective lens 8 in the radial direction with respect to the glass master D based on the output of the radius sensor 18 made of, for example, a so-called laser scale, and the objective lens moved by the moving surface plate 16. When 8 is located at the start radius of the mirror portion, the main control means 13 outputs a non-exposure offset signal S1 for defocusing to the focus servo control circuit 32. Accordingly, the objective lens 8 is defocused within the focus servo operation range to a position where the photoresist D1 is not exposed while keeping the intensity of the laser beam exposed by the photoresist D1.

  That is, since the spot of the laser beam irradiated to the photoresist D1 is not in focus, the photoresist D1 is not exposed during this period, but the reflected light is normally detected by the photodetector 30. The focus servo control is operating normally with the focus out of focus. The main control means 13 performs control to maintain the above operation until the objective lens 8 is located at the end radius of the mirror portion. As a result, since the region from the start radius to the end radius of the mirror portion is not exposed, the mirror portion is formed in this portion, and the focus servo control can be normally operated during this time.

Here, the amount and direction of defocusing the objective lens 8 from the in-focus position will be described.
The amount to be defocused is within the S range in FIG. 3A and does not deviate from this S range. Usually, in a high-density exposure apparatus, the objective lens 8 uses a lens having a NA (numerical aperture) of 0.9. In addition, the astigmatism condensing lens, the focal length of a cylindrical lens (not shown), and the photo Although it varies depending on the size of the sensor cell of the detector 30, the S range is generally about ± 5 μm. The laser beam diameter obtained from the diagram of the NA0.9 objective lens when defocused by 3 μm within the S range is about 12 μm, and the energy density reduction (area expansion) is NA of 0.9. This is about 1/1000 for an objective lens having a laser beam wavelength of 266 nm and a focused beam diameter of less than 0.4 μm, which is sufficient for non-exposure of the photoresist D1. The direction of defocusing from the in-focus position is usually that of an objective lens (NA 0.9, wavelength 266 nm) manufactured by Tropell, Inc. in a high-density exposure apparatus. The working distance of this objective lens 8 is about The amount of about 5 μm to be defocused is very small, and may be either in the direction closer to the glass master D or in the direction away from it.

  Next, when the objective lens 8 reaches the end radius of the mirror portion, the main control means 13 stops the output of the non-exposure focus point offset signal S1, and as a result, the photoresist D1 is exposed to the laser beam power. The objective lens 8 is focused on the exposure position of the photoresist D1 while keeping the intensity at a predetermined level. That is, the laser beam spot is focused on the photoresist D1. Simultaneously with this control, the modulation means 6 is driven again based on the recording data. In other words, since the focus servo control is applied even when the laser beam irradiates the mirror part (at the time of non-exposure), the transition from the mirror formation state to the data recording state, that is, the transition from the non-exposure state to the exposure state However, the focus servo control can be operated stably.

  As described above, in the exposure apparatus to which the present invention is applied, the focus servo control is stably performed using the laser light source 4 that emits the laser beam L1 for exposure including the formation of the mirror portion (at the time of non-exposure). Can be done. In other words, the focus servo control can always be applied using the exposure laser beam L1, the problem of color correction of the objective lens, which has been a problem in the conventional apparatus, is eliminated, and the wavelength of the exposure laser beam is shortened. And high density recording can be performed. Further, the number of laser light sources can be made one, and the cost can be reduced as compared with the conventional apparatus.

Next, a modified example of the present invention will be described.
In the embodiment described above, the intensity of the laser light L1 emitted from the laser light source 4 is always kept constant during both exposure and non-exposure (when the mirror portion is formed), but is not limited thereto. During non-exposure, the objective lens 8 may be defocused, and at the same time, the intensity of the laser light L1 may be reduced (dropped) to reliably prevent the photoresist D1 from being exposed.
FIG. 4 is a block diagram showing a modification of the exposure apparatus of the present invention. The same components as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted. As shown in FIG. 4, here, a power controller 50 is provided in the middle of the optical path between the laser light source 4 and the mirror 20 as intensity varying means for varying the intensity of the laser light L1 emitted from the laser light source 4. The intensity of the laser beam L1 can be changed as needed under the control of the main control means 13.

  The power controller 50 includes, for example, an electro-optic effect (EO) modulator and a polarizing plate. As described above, the laser light L1 from the laser light source 4 has a necessary power under the control of the main control unit 13. Adjust to. Specifically, the main controller 13 controls the power controller 50 during non-exposure (when the mirror portion is formed) so that the intensity of the laser light L1 is within a range where the focus servo control does not become unstable. The focus servo control circuit 32 defocuses the objective lens 8 within the focus servo operation range to a position where the photoresist D1 is not exposed.

Then, when the formation of the mirror portion is completed, the power controller 50 increases the power of the laser light L1 passing therethrough to the original power. By operating in this way, it is possible not only to exhibit the same effects as the previous embodiments, but also to reliably prevent the photoresist D1 from being exposed during non-exposure.
The present invention is not limited to the above-described embodiments, and can be applied to various exposure apparatuses that employ the self-focus method. For example, the present invention can also be applied to a two-dimensional image drawing exposure apparatus that performs exposure by scanning a laser beam spot two-dimensionally on an original plate coated with a photoresist.

It is a block block diagram which shows the exposure apparatus which concerns on this invention. It is a figure which shows the structure of the photodetector of focus servo control, and the relationship of each signal. It is a schematic diagram which shows the waveform of each signal. It is a block block diagram which shows the modification of the exposure apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Exposure apparatus, 4 ... Laser light source, 6 ... Modulation means, 8 ... Objective lens, 10 ... Turntable (scanning means), 12 ... Focus servo control means, 13 ... Main control means, 14 ... Focus actuator, 16 ... Movement Surface plate, 18 ... radius sensor, 30 ... photo detector, 32 ... focus servo control circuit, 50 ... power controller (intensity varying means), D ... glass master, D1 ... photoresist, L1 ... laser beam.

Claims (2)

An exposure having at least an objective lens for condensing laser light emitted from a laser light source onto a photoresist coated on an exposed plate, and focus servo control means for performing focus control with reflected light reflected by the photoresist In the device
The focus servo control means so that the laser light is just focused on the photoresist during exposure, and the laser light is not exposed to the photoresist and is defocused within a focus control range during non-exposure. An exposure apparatus comprising: main control means for performing control for changing the position of the objective lens. It further includes intensity varying means for varying the intensity of the laser light, and the main control means reduces the intensity of the laser light within a range in which the operation of the focus servo control means does not become unstable during non-exposure. The exposure apparatus according to claim 1, wherein the intensity varying unit is controlled.

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