JP2000033487A - Laser beam cutting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To permit the formation of a latent image of a fine pattern on a resist layer by irradiating the resist layer formed on a board with laser beam applying high frequency superpose through an auto-focus mechanism and detecting this reflecting beam. SOLUTION: The laser beam emitted from a beam source 2 irradiates the resist layer 51 formed on the glass board 50 to form the latent image of the prescribed pattern on the resist layer 51. The high frequency convoluted laser beam emitted from the beam source 32 auto-focus, penetrates a correcting lens 33 to correct the chromatic aberration and further, penetrates a polarized- beam splitter 34 and a 1/4 wave length board 35 and directed to a reflecting mirror 36. The high frequency convoluted laser beam passed through the splitter 34 and the 1/4 wave length board 35, is made incident on objective lens 22 as p-polarized beam and the reflected beam of the high frequency superposed laser beam which irradiates the resist layer 51 through the objective lens 22, is used as s-polarized beam and the splippage amount of the focus is efficiently detected with a beam detector 37.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser cutting device used for producing a stamper used for molding a disk substrate of an optical disk.

[0002]

2. Description of the Related Art As a recording medium, an optical disk having a pit or the like indicating an information signal formed on the surface of a disk substrate and an Al reflective film or a protective film formed on the disk substrate having the pit or the like has been widely used. I have.

The disk substrate of this optical disk is mainly formed by an injection molding method. The injection molding method
For example, in a cavity of a pair of molds, a stamper in which the pits and the like of the disk substrate are formed in a concavo-convex pattern of an inverted pattern is disposed, and a disk material heated and melted is injected into the cavity of the mold, and the disk substrate It is a method of molding.

[0004] A stamper used in this injection molding method is manufactured as follows.

First, a photoresist having sufficient sensitivity to the wavelength of a recording laser light source is uniformly applied to the main surface of a disk-shaped glass substrate whose surface is precisely polished, via an adhesion reinforcing agent or the like. Then, the organic solvent of the photoresist is volatilized, and a photoresist layer is formed on the glass substrate.

Next, the glass substrate on which the photoresist layer has been formed is set in a laser cutting device. Then, the laser beam for recording is focused on the photoresist on the glass substrate by the laser cutting device.

The laser cutting device turns on / off the laser beam, scans the resist layer of the glass substrate in, for example, a spiral shape, and forms a latent image of a concavo-convex pattern corresponding to predetermined pits and grooves on the resist layer. Form.

Next, the resist layer on which the latent image is formed is developed with an alkaline developer to form a resist master having an uneven pattern corresponding to predetermined pits and grooves.

Next, a metal film such as silver or nickel is formed on the main surface of the resist master having an uneven pattern by a method such as sputtering, vapor deposition, or electroless plating.

Next, the resist master on which the metal coating is formed is set in an electroplating apparatus, and electroplating is performed using the metal coating as an electrode to form an electroplating layer on the main surface of the resist master. Is done.

Next, the resist master is peeled off from the metal film and the electroplating layer, and the excess metal film is removed by pressing to complete the stamper.

The laser cutting apparatus 100 used in the stamper manufacturing process described above is configured as shown in FIG. 4, for example. The laser cutting apparatus 100 shown in FIG. 4 includes a light source 101 that emits, for example, a Kr ion laser having a wavelength of 413 nm as recording laser light, and an output that controls the output of the recording laser light emitted from the light source 101. Control unit (APC: Auto Pow
er Controll) 102 and an acousto-optic modulator (AOM) for modulating a recording laser beam.
103, a position correction mechanism 104 for correcting the position of the recording laser light, and a resist layer 15 for condensing the recording laser light.
Objective lens 105 and objective lens 10 for irradiating
A beam expander 106 for expanding the beam diameter of the recording laser light incident on the laser beam 5 and an auto-focusing optical system 107 for detecting a focal position shift of the recording laser light on the resist layer 151 are provided.

The laser cutting device 10
At 0, the optical system from the light source 101 to the position correction mechanism 104 is mounted on a fixed optical surface plate, and the objective lens 105, the beam expander 106, and the autofocus optical system 107 are mounted on the glass substrate 150. It is mounted on a moving optical table that is moved in the radial direction.

The glass substrate 150 on which the resist layer 151 is formed is chucked on an air spindle that rotates with high rotational accuracy.

The optical surface plate, the movable optical table, the air spindle, and the like are all mounted on the air surface plate so as not to be affected by external vibration at the installation place.

When laser cutting is performed by the laser cutting apparatus 100 configured as described above, a Kr ion laser (recording laser light) having a wavelength of, for example, 413 nm is emitted from the light source 101.

The recording laser light emitted from the light source is applied to an electro-optical element (EOM: Elec)
trooptic modulator) 108 and a polarization beam splitter (PBS) 109, a part of which is reflected by a half mirror 110, and a part of which passes through the half mirror 110 to detect the output of the recording laser light. Incident on the photodetector 111.

The electro-optical element 108 changes the polarization angle of the transmitted recording laser beam based on the information fed back by the photodetector 111. As a result, the output of the recording laser light passing through the polarization beam splitter 109 is adjusted to be always constant.

The recording laser light reflected by the half mirror 110 passes through the condenser lens 112 and passes through the modulator 1
03. The modulation element 103 modulates the recording laser light by diffracting the incident recording laser light in a certain direction.

The recording laser light modulated by the modulation element 103 passes through the condenser lens 113 and sequentially enters the first position correction plate 114 and the second position correction plate 115 constituting the position correction mechanism 104. I do. The first and second position correction plates 114 and 115 are arranged to be inclined by a predetermined amount with respect to a direction orthogonal to the optical axis of the recording laser light, so that the optical axis of the recording laser light is adjusted. The shift is performed in the X direction or the Y direction by an amount corresponding to the amount of inclination.

The recording laser light whose position has been corrected by the position correcting mechanism 104 is partially reflected by the half mirror 116 and partially transmitted through the half mirror 116 to detect the beam position. 117.
The photodetector 117 feeds back information on the position of the incident recording laser light to the position correction mechanism 104.
Then, the position correction mechanism 104 is controlled by the first and second position correction plates 11 based on the information supplied from the photodetector 117.
The optical axis of the recording laser beam is controlled so as to be always at the correct position by changing the amount of inclination of 4,115.

The recording laser light reflected by the half mirror 116 is incident on a quarter-wave plate 118 and is converted into circularly polarized light.

The recording laser light converted into circularly polarized light by the １ ／ wavelength plate 118 is applied to the beam expander 1.
06 and the first lens 119 and the second lens 1
20, the first lens 119 and the second lens
The lens diameter of the lens 120 is enlarged.

The recording laser light whose beam diameter has been expanded by the beam expander 106 passes through a dichroic mirror 125 constituting an autofocus optical system 107, and its optical path is bent by a return mirror 121.
The light enters the objective lens 105 disposed so as to face the main surface of the glass substrate 150 on which the resist layer 151 is formed.

The objective lens 105 is formed by bonding a plurality of glass materials via an adhesive, thereby correcting chromatic aberration caused by a difference in wavelength for a plurality of laser beams having different wavelengths. The focal positions of the respective laser beams transmitted through the objective lens 105 are matched. The objective lens 105 has an anti-reflection coating on the lens surface so as to have a sufficient transmittance for each of a plurality of laser beams having different wavelengths.

The recording laser light incident on the objective lens 105 is condensed by the objective lens 105 and is deposited on the resist layer 151 of the glass substrate 150 which rotates in the direction of arrow B in FIG. 4 with the rotation of the air spindle. Irradiated.

Then, the laser cutting device 100
Moves the moving optical table on which the objective lens 105 and the beam expander are mounted in the radial direction of the glass substrate 150 while switching ON / OFF of the recording laser light, thereby forming the resist layer 151 of the glass substrate 150. The upper portion is scanned, for example, in a spiral shape, and a latent image having a concavo-convex pattern corresponding to predetermined pits and grooves is formed in the resist layer 151 in a spiral shape.

The laser cutting device 100
In irradiating the resist layer 151 with the recording laser light, focus control is performed so that the focal point of the recording laser light is always located on the resist layer 151. This focus control is performed by moving the objective lens 105 in a direction along the optical axis of the objective lens 105 in accordance with the amount of focus shift detected by the autofocus optical system 107.

The autofocus optical system 107 includes, for example, a semiconductor laser 122 that emits a laser beam having a wavelength of 680 nm, and a polarization beam splitter 123 disposed on the optical path of the laser beam emitted from the semiconductor laser 122.
A quarter-wave plate 124 disposed on the optical path of the laser light reflected by the polarizing beam splitter 123,
The dichroic mirror 12 disposed on the optical path of the laser beam transmitted through the four-wavelength plate 124 and the optical path of the recording laser beam whose beam diameter has been expanded by the beam expander 106.
5, and a photodetector 126 disposed on the optical path of the laser light (return light) reflected by the resist layer 151.

The laser light emitted from the semiconductor laser 122 is first reflected by the polarization beam splitter 123 and then transmitted through a quarter-wave plate to be converted into circularly polarized light. The circularly polarized laser light is reflected by the dichroic mirror 125. The dichroic mirror 125 reflects or transmits incident light according to its wavelength. The dichroic mirror 125 used here reflects light having a wavelength of 680 nm, and reflects light having a wavelength of 413 nm. Is configured to transmit this.

The laser light reflected by the dichroic mirror 125 is further reflected by the return mirror 121 and enters the objective lens 105. At this time, the laser light is incident on the optical axis of the objective lens 105 slightly obliquely, and is irradiated obliquely onto the resist layer 151 via the objective lens 105.

The laser beam irradiated on the resist layer 151 is reflected on the resist layer 151 at a reflection angle equal to the incident angle when the resist layer 151 is irradiated. The laser light (return light) reflected by the resist layer 151 passes through the objective lens 105 and is
1. The light is sequentially reflected by the dichroic mirror 125.

The return light reflected by the dichroic mirror 125 passes through the quarter-wave plate 124 and the polarization beam splitter 123 and enters the photodetector 126.

The photodetector 126 is constituted by, for example, a photodetector in which a light receiving portion is divided into two, and generates a signal corresponding to the incident position of the return light from the difference between the amounts of light received by the respective light receiving portions.

The laser beam reflected by the resist layer 151 takes a different return light path depending on the reflection position on the resist layer 151. Then, the reflection position of the laser light on the resist layer 151 changes according to the distance between the objective lens 105 and the resist layer 151. Therefore, the objective lens 105 and the resist layer 151
The distance between them is such that the focal point of the recording laser beam is the resist layer 151.
If the distance is different from the distance between the objective lens 105 and the resist layer 151 at the time of the so-called just focus, the return light takes an optical path different from the return light optical path at the time of the just focus. The incident position is different from the incident position at the time of just focus. The difference in the incident position is due to the photodetector 1
26 and is generated as a signal.

The laser cutting device 100 moves the position of the objective lens 105 based on the signal generated by the photodetector 126 to perform focus control.

The laser cutting device 100
A plurality of return mirrors 12 that reflect reflected light of the recording laser light irradiated onto the resist layer 151 of the glass substrate 150;
7, 128, 129, CCD through condenser lens 130
The focusing state of the recording laser light captured by the camera 131 and irradiated onto the resist layer 151 is monitored.

[0038]

In recent years, with the rapid development of information communication and image processing technologies, it has been desired to increase the recording capacity of optical discs. In order to increase the capacity of an optical disc while maintaining the existing external dimensions, it is necessary to improve the recording density by miniaturizing patterns such as pits and grooves.

In order to manufacture a stamper for an optical disk having such a high recording density, a pattern corresponding to a fine pattern of the optical disk must be obtained on the resist layer 131 of the recording laser beam of the laser cutting apparatus 100. It is necessary to reduce the spot size at.

Here, the recording laser beam resist layer 13
The spot size on 1 is determined by the numerical aperture NA of the objective lens 105 and the wavelength of the recording laser beam. However, there is a limit in increasing the numerical aperture NA of the objective lens 105 due to the lens design accuracy and the like. . Therefore, in order to reduce the spot size of the recording laser light, it is necessary to shorten the wavelength of the recording laser light.

However, if the wavelength of the recording laser beam is shortened, the difference between the wavelength of the recording laser beam and the wavelength of the laser beam used for focus control becomes large. It is difficult to apply an antireflection coat having a transmittance to the surface. For example, when an ultraviolet laser having a wavelength of about 250 nm is used as the recording laser light and a laser light having a wavelength of 680 nm is used as the focus control laser light, the transmittance for the recording laser light is 90%. In this case, the transmittance for the laser light for focus control is limited to about 60%.

Therefore, the laser beam for focus control reflected on the surface of the objective lens 105 becomes stray light, enters the photodetector 126 of the autofocus optical system 107, and is returned by the resist layer 151. In some cases, they act on light to form interference fringes and adversely affect focus control.

When the wavelength of the recording laser beam is shortened, the glass material applicable to the objective lens 105 is limited.
For example, when an ultraviolet laser having a wavelength of about 250 nm is used as the recording laser light, the glass material applicable to the objective lens 105 is limited to synthetic quartz or fluorite. Actually, it is extremely difficult to produce a uniform lens having a sufficient size as the objective lens 105 using fluorite. Therefore, the objective lens 105 needs to be produced from a single glass material made of only synthetic quartz.

The objective lens 105 used in the conventional laser cutting apparatus 100 is configured so that the chromatic aberration of a plurality of transmitted laser beams can be corrected by combining a plurality of glass materials. When the lens 105 is made of a single glass material, the objective lens 105 cannot have a function of correcting chromatic aberration of a plurality of laser beams transmitted through the objective lens 105.

Therefore, an object of the present invention is to solve the above-mentioned problems and to provide a laser cutting apparatus capable of forming a latent image having a fine pattern on a resist layer.

[0046]

According to the present invention, there is provided a laser cutting apparatus for irradiating a resist layer formed on a substrate with a recording laser beam to form a latent image on the resist layer. An auto-focus mechanism that positions the focal point of the laser light for use on the resist layer. The auto-focus mechanism irradiates the resist layer formed on the substrate with the laser light that has been subjected to high-frequency superposition, and detects the reflected light. In this case, the defocus of the recording laser light is detected.

In this laser cutting apparatus, focus control is performed using a laser beam on which high-frequency superposition is applied, so that light reflected by an optical element arranged on the optical path of the laser beam is applied to the substrate. The inconvenience of forming interference fringes by acting on the light reflected on the resist layer formed thereon is avoided.

Therefore, according to this laser cutting apparatus, an appropriate latent image can be formed on the resist layer even when a laser beam having a short wavelength such as an ultraviolet laser is used as the recording laser beam. it can.

In the laser cutting apparatus according to the present invention, it is preferable that the autofocus mechanism includes a correction lens for correcting chromatic aberration caused by a wavelength difference between the laser light subjected to high-frequency superposition and the recording laser light.

In the laser cutting device, the auto focus mechanism is provided with the correction lens as described above,
Even if a laser beam having a short wavelength, such as an ultraviolet laser, is used as a recording laser beam and an objective lens cannot have a function of correcting chromatic aberration, an appropriate latent image can be formed on the resist layer. .

[0051]

Embodiments of the present invention will be described below with reference to the drawings.

The laser cutting device according to the present invention comprises:
For example, it is for producing a stamper used for injection molding a disk substrate of an optical disk having pits, grooves, and the like. As shown in FIG.
This is for irradiating a recording laser beam on the resist layer 51 formed on the resist layer 51 to form a latent image of a predetermined pattern corresponding to pits and grooves of the optical disc on the resist layer 51.

This laser cutting device uses, for example, a YAG quadruple-wave laser which is an ultraviolet laser having a wavelength of 266 nm as the recording laser light. In this specification, a laser beam having a wavelength of 200 to 400 nm is referred to as an ultraviolet laser.

The light source 2 that emits the recording laser light includes:
As shown in FIG. 2, a laser generator 3 for converting a YAG laser having a wavelength of about 1064 nm to about 532 nm, which is a second harmonic of the YAG laser, by a SHG crystal, and generating a laser beam generated by the laser generator 3 in phase. A phase modulator 4 that modulates the laser beam and an external resonator 5 that converts the laser light whose phase is modulated by the phase modulator 4 into an ultraviolet laser of about 266 nm, which is a second harmonic of the laser light, using a BBO crystal. Further, the external resonator 5 includes a voice coil motor inside, so that the length of the resonator can be accurately servo-controlled.

The light source 2 configured as described above can emit a high-output and stable YAG fourth-harmonic laser.

An output control unit (APC: Auto Power Control) 6 for controlling the output of the recording laser light is provided on the optical path of the recording laser light emitted from the light source 2. The output control unit 6 includes an electro-optical element (EO)
M: Electrooptic modulator) 7, a polarization beam splitter (PBS) 8, a half mirror 9, and a photodetector 10.

The recording laser light emitted from the light source 2 is
First, the light passes through the electro-optical element 7 and the polarizing beam splitter 8 that constitute the output control unit 6, is partially reflected by the half mirror 9, and partially passes through the half mirror 9 and enters the photodetector 10. .

The electro-optical element 7 changes the polarization angle of the transmitted recording laser beam based on the information fed back by the photodetector 10. As a result, the output of the recording laser light passing through the polarization beam splitter 8 is adjusted to be always constant.

On the optical path of the recording laser light reflected by the half mirror 9, a condensing lens 11, an acousto-optic modulator (AOM) 12, a condensing lens 13, a position correcting mechanism 14, a half Mirrors 15 are provided.

The recording laser light reflected by the half mirror 9 passes through the condenser lens 11 and passes through the acousto-optic modulator 1.
2 is incident. The acousto-optic modulator 12 modulates the recording laser light by diffracting the incident recording laser light in a certain direction.

The recording laser light modulated by the acousto-optic modulator 12 passes through the condenser lens 13 and is transmitted to the first position correction plate 16 and the second position correction plate 17 constituting the position correction mechanism 14. Inject sequentially. The first and second position correction plates 16 and 17 are each disposed at a predetermined angle with respect to a direction orthogonal to the optical axis of the recording laser light so that the optical axis of the recording laser light is adjusted. X according to the amount of inclination
In the direction or the Y direction.

The recording laser light whose position has been corrected by the position correction mechanism 14 is partially reflected by the half mirror 15 and partially transmitted through the half mirror 15 to detect a beam position. 18 is incident. The light detector 18 feeds back information on the position of the incident recording laser light to the position correction mechanism 14. Then, the position correcting mechanism 14 changes the amount of inclination of the first and second position correcting plates 16 and 17 based on the information supplied from the photodetector 18, so that the optical axis of the recording laser light is always correct. Controlled to be in position.

On the optical path of the recording laser light reflected by the half mirror 15, a quarter-wave plate 19 and a beam expander 20 for expanding the beam diameter of the recording laser light are provided.
, A dichroic mirror 21 and an objective lens 22 for condensing a recording laser beam and irradiating the resist layer 51 with the laser beam.

The recording laser light reflected by the half mirror 15 is incident on the quarter-wave plate 19 and is converted into circularly polarized light. Then, the recording laser light converted into circularly polarized light by the 波長 wavelength plate 19 sequentially enters the first lens 23 and the second lens 24 constituting the beam expander 20, and the first lens The beam diameter is enlarged by the lens 23 and the second lens 24.

The recording laser beam whose beam diameter has been expanded by the beam expander 20 has its optical path bent by a dichroic mirror 21 which will be described in detail later, and faces the main surface of the glass substrate 50 on which the resist layer 51 is formed. To the objective lens 22 arranged as described above.

The objective lens 22 is made of a single glass material made of only synthetic quartz, and its surface is provided with an antireflection coat for sufficiently transmitting the recording laser light. The objective lens 22 is provided with an anti-reflection coating on its surface in this way, so that it has a transmittance of 90% or more with respect to the recording laser light.

The recording laser light incident on the objective lens 22 is condensed by the objective lens 22 and is irradiated on a resist layer 51 formed on the glass substrate 50.

Glass substrate 5 on which resist layer 51 is formed
0 is chucked on an air spindle that rotates with high rotational accuracy. Then, with the rotation of the air spindle, the resist layer 51 on the glass substrate 50 rotating in the direction of arrow A in FIG. 1 is irradiated with the recording laser light.

In this laser cutting device 1,
The optical system from the light source 2 to the quarter-wave plate 19 is mounted on a fixed optical base, and the beam expander 2
0, the folding mirror 21 and the objective lens 22 are mounted on a moving optical table that is operated to move in the radial direction of the glass substrate 50. The optical surface plate, the movable optical table, the air spindle, and the like are all mounted on the air surface plate so as not to be affected by external vibration at the installation location.

Then, the laser cutting apparatus 1 moves the movable optical table 25 in the radial direction of the glass substrate 50 while switching ON / OFF of the recording laser beam, thereby transmitting the recording laser beam to the glass substrate. 5
For example, a spiral image is formed on the 0 resist layer 51 to form a latent image of a concavo-convex pattern corresponding to predetermined pits and grooves on the resist layer 51 in a spiral shape.

Further, this laser cutting device 1
The reflected light of the recording laser light applied to the resist layer 51 of the glass substrate 50 is reflected by a plurality of folding mirrors 26 and 2.
7, 28, and are captured by the CCD camera 30 via the condenser lens 29, and the focusing state of the recording laser light irradiated onto the resist layer 51 is monitored.

Further, this laser cutting device 1
When irradiating the resist layer 51 with the recording laser beam,
The focus control is performed so that the focal point of the recording laser beam is always located on the resist layer 51. This focus control is performed by moving the objective lens 22 in a direction along the optical axis according to the amount of focus shift detected by the autofocus optical system.

The auto-focusing optical system is provided on the moving optical table, and has a wavelength of 680 nm, for example.
an autofocus light source 32 that superimposes high-frequency laser light on the order of m and emits the high-frequency laser light;
The correction lens 33 and the polarization beam splitter 34 disposed on the optical path of the high-frequency superposed laser light emitted from the autofocus light source 32, and the polarization beam splitter 3
A quarter-wave plate 35 and a return mirror 36 disposed on the optical path of the high-frequency superimposed laser light transmitted through 4, and the dichroic mirror disposed on the optical path of the high-frequency superimposed laser light reflected by the return mirror 36 21 and a photodetector 37 disposed on the optical path of the reflected light (return light) of the high-frequency superimposed laser light applied to the resist layer 51 via the objective lens 22.

The autofocus light source 32 includes, for example, a semiconductor laser that generates a laser beam having a wavelength of about 680 nm, applies a high-frequency superimposed pulse to the laser beam generated from the semiconductor laser, and emits it as a high-frequency superposed laser beam. I do. In the autofocus light source 32, the frequency of the high-frequency superimposed pulse applied to the laser light generated from the semiconductor laser is set in the range of 200 to 600 MHz, and the duty of the high-frequency superimposed pulse applied to the laser light generated from the semiconductor laser is set. It is desirable that the ratio be set in the range of 1 to 50%. The autofocus light source 32 can emit an appropriate high-frequency superimposed laser light by setting the frequency and the duty ratio of the high-frequency superimposed pulse applied to the laser light generated from the semiconductor laser as described above.

The high-frequency superimposed laser light emitted from the autofocus light source 32 sequentially passes through the first lens 38 and the second lens 39 constituting the correction lens 33.
Chromatic aberration is corrected by transmitting the high-frequency superimposed laser light through the first and second lenses 38 and 39 constituting the correction lens 33. That is, since the high-frequency superimposed laser light has a longer wavelength than the above-described recording laser light, when it is applied to the resist layer 51 through the same objective lens 22 as the recording laser light, chromatic aberration occurs and focus The distance is different from the focal length of the recording laser light. Therefore, unless this chromatic aberration is corrected, it is difficult to detect an appropriate amount of defocus. Therefore, in the optical system for autofocus of the laser cutting device 1, a correction lens 33 is disposed on the optical path of the high frequency superimposed laser beam emitted from the autofocus light source 32 to correct chromatic aberration.

The high-frequency superposed laser light whose chromatic aberration has been corrected by the correction lens 33 passes through the polarizing beam splitter 34, passes through the １ ／ wavelength plate 35, and
Go to 6.

The polarization beam splitters 34 and 1 /
The four-wavelength plate 35 causes the high-frequency superimposed laser light to enter the objective lens 22 as p-polarized light, and the return light of the high-frequency superposed laser light applied to the resist layer 51 via the objective lens 22 is converted to s-polarized light by the photodetector 37. This is provided for efficient detection.

The high frequency superimposed laser light reflected by the folding mirror 36 passes through the dichroic mirror 21.

The dichroic mirror 21 transmits or reflects the incident light according to its wavelength, is on the optical path of the recording laser light transmitted through the beam expander 20, and is reflected by the folding mirror 36. It is disposed at a position on the optical path of the high frequency superimposed laser light. The dichroic mirror 21 reflects recording laser light having a wavelength of about 266 nm, and transmits high frequency superposed laser light having a wavelength of about 680 nm.

The high-frequency superimposed laser light transmitted through the dichroic mirror 21 is applied to the resist layer 51 via the objective lens 22. Then, the high-frequency superimposed laser light (return light) reflected by the resist layer 51 is incident on the photodetector 37, whereby the amount of defocus is detected.

At this time, in addition to the return light reflected by the resist layer 51, the high-frequency superimposed laser light reflected by the objective lens 22 enters the photodetector 37 as stray light. That is, the laser cutting device 1 according to the present invention
As described above, an ultraviolet laser having a short wavelength is used as a recording laser beam, and a laser beam having a wavelength of 6
When a laser beam of about 80 nm is used, since the wavelengths of these laser beams are greatly different, an anti-reflection coat having a sufficient transmittance for both the recording laser beam and the autofocus laser beam is used for the objective lens. 22 is difficult to apply. For example, as described above, when an anti-reflection coat is applied so as to have a transmittance of 90% or more with respect to the recording laser light, a transmittance of approximately 60% is secured with respect to the autofocus laser light. That is the limit. Then, without passing through the objective lens 22, the objective lens 2
The laser light for autofocus reflected by the laser beam 2 becomes stray light and enters the photodetector 37.

Here, when a laser beam not subjected to high-frequency superposition is used as the laser beam for autofocus, its coherent distance is relatively long, about several tens of cm, so that it is reflected by the objective lens 22 and becomes stray light. The laser beam for autofocus incident on the photodetector 37 is
In some cases, interference fringes may be formed by acting on the return light reflected by 1 and entering the photodetector 37. If focus control is to be performed in such a state in which interference fringes are formed, frequent oscillation of the servo makes it difficult to perform normal focus control.

However, the laser cutting device 1 according to the present invention uses laser light on which high-frequency superposition has been applied as the laser light for autofocus, and its coherence length is extremely short. Even when the laser beam for autofocus enters the photodetector 37 as stray light, the objective lens 22
The laser light for autofocus reflected by the laser beam does not interfere with the return light reflected by the resist layer 51.

Therefore, the laser cutting apparatus 1 can perform focus control normally even when a short-wavelength laser such as an ultraviolet laser is used as the recording laser light.

In the optical system for autofocus, the amount of defocus is detected by a method called an off-axis method. Here, the principle of detecting the amount of defocus by the off-axis method will be described with reference to FIG.
This will be described with reference to FIG.

The high-frequency superimposed laser light reflected by the folding mirror 36 and transmitted through the dichroic mirror 21 enters the objective lens 22. At this time, in the autofocus optical system using the off-axis method, the high-frequency superimposed laser light is incident on the optical axis of the objective lens 22 slightly obliquely, and is incident on the surface of the resist layer 51 at a predetermined incident angle. Irradiated obliquely. Therefore, in the autofocus optical system using the off-axis method, when the distance between the objective lens 22 and the surface of the resist layer 51 changes, the irradiation position of the high-frequency superimposed laser light on the resist layer 51 changes. Will be. The return light reflected by the resist layer 51 takes a different optical path depending on the irradiation position on the resist layer 51.

For example, assuming that the position of the objective lens 22 does not change, when the surface of the resist layer 51 is at the first height position indicated by h1 in FIG. A first irradiation position 51 is indicated by p1 in FIG. Then, the return light reflected by the resist layer 51 passes through the first return light path L1 and passes through the objective lens 2.
2, dichroic mirror 21, folding mirror 36,
The light enters a photodetector 37 via a quarter-wave plate 35 and a polarizing beam splitter 34.

On the other hand, the surface of the resist layer 51 corresponds to h in FIG.
When the laser beam is at the second height position indicated by reference numeral 2, the high-frequency superimposed laser light is applied to the second irradiation position indicated by p2 in FIG. Then, the return light reflected by the resist layer 51 passes through the second return light path L2 and passes through the objective lens 22, the dichroic mirror 21, and the return mirror 3
The light enters a photodetector 37 via a 6, 1/4 wavelength plate 35 and a polarizing beam splitter 34. At this time, the incident position of the return light incident on the photodetector 37 through the second return optical path L2 is determined by the light detector 37 through the first return optical path L1.
Will be different from the incident position of the return light incident on the.

The photodetector 37 is constituted by, for example, a photodetector in which a light receiving portion is divided into two, and generates a signal corresponding to the incident position of the return light from the difference in the amount of light received by each light receiving portion.

As described above, in the optical system for auto-focusing using the off-axis method, when the height position of the surface of the resist layer 51 changes due to the deflection of the surface of the glass substrate 50, etc.
Return light passes through different optical paths and enters, for example, different positions of a photodetector 37 constituted by a photodetector in which a light receiving section is divided into two. Then, the difference between the incident positions is detected by the photodetector 37 and is generated as a signal.
That is, in the optical system for auto-focusing using the off-axis method, the distance between the resist layer 51 and the objective lens 22 changes due to the surface deflection of the glass substrate 50, and the focus of the recording laser light is shifted to the resist layer. When it deviates from above 51, the incident position of the return light of the high-frequency superimposed laser light on the photodetector 37 changes, and the amount of change is detected as a focus shift amount.

The laser cutting device 1 drives an electromagnetic actuator that holds the objective lens 22 in accordance with the amount of defocus detected by the autofocus optical system 31, and moves the objective lens 22 in the direction of its optical axis. Focus control is performed.

Although the optical system for autofocus which detects the amount of defocus by the off-axis method has been described above, the present invention is not limited to this example. For example, the amount of defocus is determined by the astigmatism method. You may make it detect. In this case, the high-frequency superimposed laser light is applied to the resist layer 51 along the optical axis of the objective lens 22, and a cylindrical lens is arranged on the optical path of the return light to cause astigmatism in the return light. What should be done is.

As described above, the laser cutting apparatus 1 according to the present invention uses a high-frequency superimposed laser beam obtained by superimposing a high-frequency laser beam having a wavelength of about 680 nm as a laser beam for autofocusing. Therefore, the laser light for autofocus reflected by the objective lens 22 may interfere with the return light reflected by the resist layer 51 to form interference fringes, thereby causing a problem that normal focus control is obstructed. Absent.

Therefore, the laser cutting apparatus 1 can appropriately perform focus control even when a short-wavelength laser such as an ultraviolet laser is used as a recording laser beam, and can provide a latent image of a fine pattern. Can be appropriately formed.

Further, this laser cutting device 1
A correction lens 33 is provided as an auto-focusing optical system, and the correction lens 33 corrects chromatic aberration caused by a wavelength difference between the auto-focusing laser light and the recording laser light. Therefore, even if the objective lens 22 cannot have a function of correcting chromatic aberration, the focus control can be appropriately performed.

[0096]

The laser cutting apparatus according to the present invention irradiates a resist layer formed on a substrate with a laser beam subjected to high-frequency superposition and detects the reflected light, thereby defocusing the recording laser beam. Is detected, the light reflected by the objective lens disposed on the optical path of the laser light acts on the reflected light reflected by the resist layer to form interference fringes, Inconvenience such as hindering normal focus control is avoided.

Therefore, according to this laser cutting apparatus, even when a laser beam having a short wavelength, such as an ultraviolet laser, is used as the recording laser beam, the focus control is appropriately performed, and the fineness of the resist layer is reduced. A latent image having a simple pattern can be appropriately formed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a state in which a latent image having a predetermined pattern is formed on a resist layer.

FIG. 2 is a schematic diagram showing a schematic configuration of a laser cutting device according to the present invention.

FIG. 3 is a schematic diagram illustrating a principle of detecting a focus position shift using an off-axis method.

FIG. 4 is a schematic diagram illustrating an outline of a conventional laser cutting device.

[Description of Signs] 1 Laser cutting device, 2 light source, 22 objective lens, 32 autofocus light source, 33 correction lens, 50 glass substrate, 51 resist layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hisayuki Yamazu 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Motohiro Furuki 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Yasuyuki Takeshita 6-7-35 Kita Shinagawa, Shinagawa-ku, Tokyo Sony Corporation (72) Inventor Kiyoshi Osato 6-35, Kita Shinagawa, Shinagawa-ku, Tokyo Sony F term in reference company (reference) 4E068 AB00 CA11 CB08 CC01 CD13 DB07 5D121 BB21 BB38

Claims (4)

[Claims] 1. A laser cutting apparatus for irradiating a resist layer formed on a substrate with a recording laser beam to form a latent image on the resist layer, wherein a focal point of the recording laser beam is positioned on the resist layer. An auto-focus mechanism for causing the resist layer formed on the substrate to be irradiated with a laser beam subjected to high-frequency superposition,
A laser cutting device for detecting a defocus of a recording laser beam by detecting the reflected light. 2. The laser cutting device according to claim 1, wherein an ultraviolet laser is used as the recording laser light. 3. The laser cutting device according to claim 1, further comprising an objective lens for converging the recording laser light and the high-frequency superimposed laser light, wherein the objective lens is made of a single glass material. apparatus. 4. The laser cutting apparatus according to claim 1, wherein the autofocus mechanism includes a correction lens for correcting chromatic aberration between the laser light on which the high-frequency superposition is applied and the recording laser light.