JPH1177344A - Optical machining device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase utilization efficiency of a laser beam and to enlarge tolerance against misalignment by providing a laser generator with an unstable type resonator, and thereby making a beam spot diameter smaller for a laser beam with which a mask is irradiated. SOLUTION: A laser beam from a laser generator 1 is split into laser beams that advance in a number of arbitrary directions, with each laser beam converged by a condensing lens 3 and emitted onto a pattern mask 4. The laser beam, which penetrates the transfer pattern of the pattern mask 4 and which is shaped into a machining configuration, is image-formed as a transferred image on a machining target 6 through a transfer lens 5, providing required machining. In making the beam spot diameter smaller on the pattern mask 4, the divergence angle of the laser beam needs to be smaller; for this purpose, an unstable type resonator is used for the laser generator 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical processing apparatus using a laser.

[0002]

2. Description of the Related Art FIG. 17 shows, for example, Japanese Patent Application No. 8-59471.
This is a conventional optical processing apparatus using the hologram shown in FIG.
In the figure, 1 is a laser oscillator, 2 is a phase hologram for dividing a laser beam emitted from the laser oscillator into a number of laser beams, 3 is a condenser lens, 4 is a pattern mask, and 5 is an image of the pattern mask 4 is transferred. Transfer lens,
Reference numeral 6 denotes a processing target to be processed, and 7 denotes a laser beam.

Next, the operation will be described. The laser beam 7 emitted from the laser oscillator 1 is divided into a large number of laser beams traveling in arbitrary directions by the hologram 2,
Thereby, the respective laser beams are condensed and irradiated on the pattern mask 4. The laser beam that has passed through the transfer pattern of the pattern mask 4 is imaged as a transfer image on a processing target 6 by a transfer lens 5 to be processed. At this time, the beam spot diameter irradiated onto the pattern mask 4 is determined by the focal length of the condenser lens and the divergence angle of the laser beam.

[0004]

In a conventional processing optical system using a hologram (a processing optical system used in a laser transfer processing apparatus disclosed in Japanese Patent Application No. 8-59471), a mask is formed at a mask opening. When the laser beam divided by the hologram is irradiated, if the focused spot diameter of the laser beam is larger than the diameter of the mask hole, the part blocked by the mask increases and the light utilization efficiency (the laser output emitted from the laser oscillator) increases. On the other hand, the ratio of the laser output actually applied to the processing target decreases.

In a conventional processing optical system using a hologram, when a mask has a plurality of discrete openings,
When the distance between the openings is narrow, when irradiating the laser beam focused on the mask openings, the beam spots applied to the respective mask openings overlap each other, and the intensity distribution on the mask openings becomes uneven. Become. As a result, accurate processing cannot be performed.

In a conventional processing optical system using a hologram, when a laser beam divided by the hologram is irradiated to the mask opening, if the focused spot diameter of the laser beam is smaller than the mask hole diameter, the mask opening will be damaged. The light intensity at the edge decreases. In addition, it is necessary to perform alignment between the mask and the beam spot with high precision, and even if a slight misalignment occurs, accurate processing cannot be performed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. In an optical processing apparatus for simultaneously processing a plurality of processing positions by using a laser and a hologram, a mask aperture is reduced by reducing a beam spot diameter. It is an object of the present invention to obtain an optical processing apparatus in which the beam intensity distribution in the inside is made uniform and the beam use efficiency is enhanced.

[0008]

According to a first aspect of the present invention, there is provided an optical processing apparatus comprising: a laser light source having a laser oscillator;
A hologram for dividing the laser beam emitted from the laser light source into a plurality of directions, a mask for shaping the laser beam divided by the hologram into a processing shape, and a transfer lens for transferring the laser beam transmitted through the mask onto a processing target. In the optical processing apparatus provided, the laser oscillator includes an unstable resonator.

Further, in the optical machining apparatus according to the second configuration of the present invention, the unstable resonator is a one-dimensional unstable resonator.

Further, in the optical processing apparatus according to the third configuration of the present invention, the unstable type resonator is a phase matching type unstable type resonator.

An optical processing apparatus according to a fourth configuration of the present invention is a laser light source having a laser oscillator, a hologram for dividing a laser beam emitted from the laser light source into a plurality of directions, and a laser emitted from the hologram. In an optical processing apparatus including a mask irradiated with a beam and a transfer lens for transferring a laser beam transmitted through the mask onto a processing target, the laser oscillator includes a Gaussian resonator.

According to a fifth aspect of the present invention, there is provided an optical processing apparatus, comprising: a laser light source for emitting a laser beam; a hologram for dividing the laser beam emitted from the laser light source into a plurality of directions; An optical processing apparatus comprising: a mask irradiated with a laser beam; and a transfer lens for transferring a laser beam transmitted through the mask onto a processing target, wherein the laser light source includes a laser system having a laser oscillator and at least one optical amplifier. It is a thing.

An optical processing apparatus according to a sixth aspect of the present invention provides a laser light source having a laser oscillator, a hologram for dividing a laser beam emitted from the laser light source into a number of arbitrary directions, and an hologram emitted from the hologram. A laser beam irradiating the mask, the optical processing apparatus having a transfer lens for transferring the laser beam transmitted through the mask onto a processing target, wherein the laser beam irradiating on the mask comprises a plurality of beam spots is there.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. Hereinafter, a first embodiment of the present invention will be described. FIG. 1 is a view showing a laser transfer processing apparatus according to an embodiment of the present invention. In the figure, 1 is a laser oscillator, 2 is a hologram for dividing a laser beam into a number of laser beams, 3 is a condenser lens, 4 is a pattern mask, 5 is a transfer lens for transferring an image of the pattern mask 4,
Reference numeral 6 denotes a processing target to be processed, and 7 denotes a laser beam. The first laser oscillator is KrF, XeCl, ArF
And processing lasers such as an excimer laser, a CO ₂ laser, and a YAG laser (including a fundamental wave, a second harmonic, a third harmonic, a fourth harmonic, and a fifth harmonic). FIG. 2 is a diagram showing the relationship between the opening of the mask and the beam spot. FIG.
2A shows a case where the beam spot diameter irradiated on the mask opening is large, and FIG. 2B shows a case where the beam spot diameter irradiated on the mask opening is small. However, the hole diameter, the number of holes, and the hole arrangement pattern of the mask are arbitrary. In the figure, 8 is a mask opening, and 9 is an irradiation beam spot. FIG. 3 is a diagram showing the relationship between the beam spot size and the divergence angle when a laser beam having a divergence angle is converged by a lens. In the figure, 10 is a light ray, f is the focal length of the lens, and θ is the angle of the light ray with respect to the optical axis.

Next, the operation will be described. The light emitted from the laser oscillator 1 is divided into a large number of laser beams traveling in arbitrary directions by a hologram 2, and the respective laser beams are condensed by a condenser lens 3 and radiated onto a pattern mask 4. The laser beam transmitted through the transfer pattern of the pattern mask 4 and shaped into a processing shape is formed as a transfer image on a processing target 6 by a transfer lens 5, and necessary processing is performed.

In the hologram 2, the laser beam can be divided into laser beams traveling in arbitrary directions. Therefore, each of the divided laser beams is condensed by the condensing lens 3 and, as shown in FIG. Since it is possible to selectively dispose them only in a large number of openings and thereby reduce the energy for irradiating the light-shielding portion of the mask, high-efficiency processing with high light use efficiency can be performed.

Here, the light use efficiency is a ratio of light reaching the processing surface in the laser beam emitted from the laser oscillator, and the cause of the decrease in the use efficiency is most likely to be blocked by the mask. In this optical system, the diffraction efficiency of the hologram (which indicates the ratio at which laser beams can be divided and arranged at desired positions when the laser beam is divided by the hologram) is 60 to 70%, and the loss of the condenser lens and the transfer lens is the optical element ( (Lens) is only the reflection and absorption loss, which is 10% or less. The loss due to the mask varies depending on the mask pattern. For example, a fine hole (100
If it is desired to open the mask opening (μm or less), the mask opening is inevitably small, and the beam spot diameter applied to the mask opening becomes too large with respect to the mask opening.

The spot diameter of the laser beam focused on the pattern mask 4 is determined by the focal length of the focusing lens 3 and the divergence angle of the laser beam when entering the focusing lens as shown in FIG.

Here, the divergence angle of the laser beam will be described. A laser beam can be thought of as a bundle of rays flying in different directions. The angle of the light beam included within a certain ratio of the laser beam energy when the angle distribution of the light beam in the laser beam is obtained is defined as the divergence angle. In other words, a laser beam having a smaller angle component with respect to the optical axis among light beams in the laser beam has a larger divergence angle. The effect of the divergence angle becomes remarkable when the laser beam is focused by a lens.

For example, as shown in FIG. 3, light incident on a lens having a focal length f at a divergence angle θ (one side θ / 2) has a spot diameter substantially represented by fθ on a mask separated from the lens by f. That is, the larger the divergence angle of the laser beam, the more light is distributed to a position farther from the center. Therefore, when a laser beam with a large divergence angle is used,
The spot diameter of the laser beam formed on the pattern mask 4 as shown in FIG. If the spot diameter is too large with respect to the mask opening, the portion blocked by the mask of the laser beam will increase, and the light use efficiency will decrease.

In order to reduce the spot diameter on the mask, it is necessary to reduce the divergence angle of the laser beam. Therefore, an unstable resonator is used for the laser oscillator 1.

Next, the effect of the unstable resonator will be described. FIG. 4 shows an example of a normal stable resonator.
This is called a confocal type. This is total reflection on one side,
The other uses a partially reflecting spherical mirror. As can be seen from the light ray 10 shown in the figure, a light ray traveling within a certain angle with respect to the optical axis 11 is always confined in the resonator. This is because it is called a stable type. In this case, a group of rays whose angles are within a certain range are always confined in the resonator and are amplified in the same manner as rays traveling parallel to the optical axis. Therefore, the light emitted from the oscillator has a large divergence angle distribution. Further, in the case of the confocal type stable resonator shown in FIG. 4, there are two types of light extracted out of the resonator from the partial reflecting mirror: light parallel to the optical axis and light passing through the confocal point. This also causes a large divergence angle distribution.

FIG. 5 is a diagram showing an unstable type resonator. This shows a one-dimensional unstable type resonator in which cylindrical mirrors having different outer diameters and curvatures are opposed to each other. As shown by the rays in the figure, this resonator cannot always keep the light confined in the resonator. Optical axis 11
A light ray having a larger angle component with respect to the laser beam jumps out of the resonator earlier. This is because a light beam having a small angle with respect to the optical axis is amplified to and fro to some extent inside the resonator and then jumps out, whereas a light beam having a large angle is not amplified enough inside the resonator before being amplified. And the intensity of light decreases. That is, of the light extracted from the resonator to the outside, a component having a large intensity is limited to a component having a small angle with the optical axis and capable of repeating reciprocating reflection many times. As a result, a laser beam having a small divergence angle is obtained.

For example, FIG. 6 shows what is shown in the book "Development of Excimer Laser and Application Techniques / Examples" (Applied Technology Publishing) (P51, FIG. 1.68). It is a figure showing the laser output concentrated in the spread angle at the time of using the oscillator by synchronization. Here, the divergence angle indicates the angle of the light beam included in the laser beam with respect to the optical axis, and FIG. 6 shows the ratio of the beam energy within the angle. In FIG. 6, the laser output is more concentrated within a narrower spread angle when the unstable resonator is used than when the stable resonator is used.
It can be seen that the focused spot can be made smaller when the unstable resonator is used.

FIG. 7 is a diagram showing a hologram processing optical system using a one-dimensional unstable resonator. More specifically, FIG. 7 shows a processing apparatus combining a hologram processing optical system and a one-dimensional unstable resonator. In the drawing, reference numeral 20 denotes an excitation region in which a population inversion is formed, and reference numeral 12 denotes a one-dimensional unstable resonator provided for the excitation region. The one-dimensional unstable resonator has a cylindrical concave mirror on one side and a cylindrical convex mirror on the other side, and can reduce only the divergence angle in the direction of curvature. The one-dimensional unstable type resonator includes a one-side extraction system shown in the drawing (a laser beam is extracted from one side of an extraction mirror) and a system which extracts a laser beam from both sides.

Next, the effect when a one-dimensional unstable type resonator is used will be described. For example, in an excimer laser or the like, the cross-sectional shape of the excitation region is often rectangular, and the profile of the laser beam may be different depending on the direction. The divergence angle at this time usually differs depending on the direction,
In a processing optical system using a conventional hologram, a spot diameter in a direction in which a divergence angle is large may be a problem. By using a one-dimensional unstable resonator as the laser oscillator in this way, the divergence angle can be reduced only for the larger divergence angle, and the spot diameter on the mask can be reduced equally in the vertical and horizontal directions. In addition, the portion that is blocked by the laser beam mask can be reduced.

Embodiment 2 FIG. A second embodiment according to the present invention will be described. FIG. 8 is a diagram showing a hologram processing optical system using a two-dimensional unstable resonator. In the figure, reference numeral 13 denotes a two-dimensional unstable type resonator. By using a two-dimensional unstable resonator, the diameter of the focused beam spot on the mask can be reduced. The two-dimensional unstable resonator has a spherical concave mirror on one side and a spherical convex mirror on the other. By using a two-dimensional unstable resonator, the beam spot diameter can be reduced, the transmittance of the mask is improved, and processing with high light use efficiency can be performed. The two-dimensional unstable resonator is effective for a system in which the cross section of the excitation region is close to a square or a circle, and can always obtain an axially symmetric beam spot.

Embodiment 3 A third embodiment according to the present invention will be described. FIG. 9 is a diagram showing a hologram processing optical system using a phase matching type resonator. In the drawing, reference numeral 14 denotes a phase-matching type unstable resonator (JP-A-63-2).
No. 65479). FIG. 10 is a diagram illustrating a phase matching type resonator. In the figure, 15 is a spherical mirror, 16 is a totally transmitting film, and 17 is a partially reflecting spherical mirror. The phase-matching type unstable resonator has a structure as shown in FIG. 10. In a normal unstable type resonator, the intensity distribution becomes a donut at the outlet of the oscillator. The stable resonator allows the laser beam to be extracted from the center so that the intensity distribution does not have a donut shape. This is effective in eliminating side ropes, while a conventional two-dimensional unstable resonator has side spots formed in a spot when a laser beam is focused. The stable resonator has the effect of suppressing the divergence angle in the same manner as a normal unstable resonator. As in the first embodiment, the divergence angle of the laser beam is reduced by using a phase-matching type unstable resonator for the laser oscillator, and the beam converging spot diameter on the mask is reduced.
This improves the mask transmittance and enables processing with high light use efficiency.

Embodiment 4 A fourth embodiment according to the present invention will be described. FIG. 11 is a diagram showing a hologram processing optical system using a Gauss core resonator. In the figure, reference numeral 18 denotes a Gauss core resonator (laser research, Vo)
l. 23, no. 9 (1995)). The Gauss core resonator is an ordinary stable type resonator, and it is necessary to limit the laser beam width in the resonator when trying to select the mode (removing the component with a large divergence angle). On the other hand, in the Gauss core type resonator, the mode can be selected without restricting the width of the laser beam, and a laser beam with a small divergence angle can be extracted without greatly reducing the output of the laser. As in the first embodiment, the divergence angle of the laser beam is reduced by using a Gaussian-type stable resonator as the laser oscillator, and the beam spot diameter on the mask is reduced. This improves the mask transmittance and enables processing with high light use efficiency.

Embodiment 5 A fifth embodiment according to the present invention will be described. FIG. 16 is a diagram illustrating a hologram processing optical system using an injection-type laser oscillator. In the figure, reference numeral 20 denotes an excitation region where a population inversion is formed, and reference numeral 21 denotes an excitation electrode. As shown in FIG.
By using a laser oscillator (injection method) in which the laser resonance portion and the laser amplification portion are independent from each other in the processing optical system according to the present invention, a laser beam having a small divergence angle can be extracted. By using an injection-type laser oscillator as the laser oscillator as in the first embodiment, the divergence angle of the laser beam is reduced, and the beam spot diameter on the mask is reduced. This improves the mask transmittance and enables processing with high light use efficiency.

Embodiment 6 FIG. A sixth embodiment according to the present invention will be described. FIG. 12 is a diagram showing the influence when the intensity distribution of the laser beam is present in the mask opening. In the figure, reference numeral 19 denotes a laser beam intensity profile after transmission through the mask. FIG. 12A shows a case where the divergence angle is reduced as described in Embodiments 1 to 4 or a case where the beam spot diameter on the mask is smaller than the mask opening even when the divergence angle is not controlled. As described above, the light intensity differs between the central portion and the edge portion of the mask opening, and there is a possibility that accurate processing cannot be performed. In other words, as shown in FIG. 12B, even if the laser beam is slightly shifted laterally, the intensity of the edge changes, and the intensity of light transferred to the object to be processed has an intensity distribution, so that the processing pattern is distorted. I will. Even if the beam spot is reduced by using an unstable resonator or the like to increase the transmittance of the mask, there is a limit in reducing the spot because the intensity distribution of the laser beam changes smoothly. .

When a plurality of beam spots are superimposed on one mask opening as shown in FIG. 13A by using a hologram without using an unstable resonator,
If the mask opening is small, sufficient uniformity cannot be obtained even when laser beams are superimposed.

In this case, as shown in FIG. 13B, the beam spot is made sufficiently small by using an unstable resonator, and a plurality of beam spots are superimposed on one mask opening by a hologram. An intensity distribution close to a top hat shape with a sharp rise can be created at the mask opening, and a beam profile with high mask transmittance and high uniformity can be formed. Further, this can increase the tolerance for misalignment.

Embodiment 7 FIG. 14 is a diagram showing the effect of irradiating a relatively large beam spot when the mask openings are close to each other. As shown in the figure,
When the mask openings are close to each other, a part of the beam spot applied to the mask opening is also applied to another adjacent opening at the same time, and the beam intensity after transmission through the mask is indicated by 19 in the figure. The distribution changes. For this reason,
Precise processing cannot be performed.

In such a case, as shown in the fifth embodiment, the divergence angle is made sufficiently small with respect to the mask opening by the unstable resonator, and a large number of beam spots are overlapped at the mask opening by the hologram. An intensity distribution close to a top hat shape with a steep rise can be created, and the intensity distribution can be controlled so as not to affect the adjacent mask opening as shown in FIG.

[0036]

According to the optical processing apparatus according to the first to fifth aspects of the present invention, the beam spot diameter of the laser beam applied to the mask can be reduced, so that the utilization efficiency of the laser beam can be increased. The tolerance against misalignment can be increased.

According to the optical processing apparatus of the sixth aspect of the present invention, it is possible to irradiate a laser beam having a uniform intensity distribution within the opening of the mask, and to increase the tolerance for misalignment. .

[Brief description of the drawings]

FIG. 1 is a diagram of a transfer processing optical system using a hologram according to the present invention.

FIG. 2 is a diagram illustrating a relationship between a mask opening and a beam spot.

FIG. 3 is a diagram illustrating a relationship between a divergence angle and a spot diameter of a laser beam when the mask is irradiated with the laser beam through a condenser lens.

FIG. 4 is a diagram illustrating a stable resonator.

FIG. 5 is a diagram illustrating an unstable resonator.

FIG. 6 is a diagram illustrating laser output concentrated within a spread angle when a stable resonator, an unstable resonator, and an oscillator using injection locking are used.

FIG. 7 is a diagram illustrating a hologram processing optical system using a one-dimensional unstable resonator.

FIG. 8 is a diagram illustrating a hologram processing optical system using a two-dimensional unstable resonator.

FIG. 9 is a diagram illustrating a hologram processing optical system using a phase matching type resonator.

FIG. 10 is a diagram illustrating a phase matching type unstable resonator.

FIG. 11 is a diagram illustrating a hologram processing optical system using a Gaussian resonator.

FIG. 12 is a diagram illustrating an influence when a laser beam intensity distribution exists in a mask opening.

FIG. 13 is a diagram illustrating a difference between a case where the spot diameter is large and a case where the beam diameter is small when beam spots are superimposed on the hologram at the mask opening.

FIG. 14 is a diagram showing the effect of irradiating a relatively large beam spot when the mask openings are close to each other.

FIG. 15 is a diagram showing an effect when a beam spot is reduced by an unstable resonator when mask openings are close to each other and a large number of beam spots are superimposed on the mask openings by holograms.

FIG. 16 is a diagram illustrating a hologram processing optical system using an injection-type laser oscillator.

FIG. 17 is a diagram of a transfer processing optical system using a conventional hologram.

[Explanation of symbols]

1 laser oscillator, 2 hologram, 3 condenser lens,
Reference Signs List 4 pattern mask, 5 transfer lens, 6 processing target, 7 laser beam, 8 mask opening, 9 irradiation beam spot, 10 light beam, 11 optical axis, 12 one-dimensional unstable resonator, 13 two-dimensional unstable resonator, 14
Phase matching type resonator, 15 spherical mirror, 16 total transmission film, 17 partially reflecting spherical mirror, 18 Gauss core type resonator, 19 laser beam intensity profile after mask transmission, 20 excitation region where population inversion is formed,
21 Excitation electrode.

Claims (6)

[Claims] 1. A laser light source having a laser oscillator, a hologram for dividing a laser beam emitted from the laser light source into a plurality of directions, a mask for shaping the laser beam divided by the hologram into a processed shape, and a mask transmitted through the mask. An optical processing apparatus including a transfer lens for transferring a laser beam onto a processing target, wherein the laser oscillator includes an unstable resonator. 2. The optical processing apparatus according to claim 1, wherein the unstable resonator is a one-dimensional unstable resonator. 3. An optical machining apparatus according to claim 1, wherein said unstable resonator is a phase-matching unstable resonator. 4. A laser light source having a laser oscillator, a hologram for dividing a laser beam emitted from the laser light source into a plurality of directions, a mask irradiated with the laser beam emitted from the hologram, and a laser beam transmitted through the mask An optical processing apparatus provided with a transfer lens for transferring a laser beam onto a processing target, wherein the laser oscillator includes a Gaussian-type resonator. 5. A laser light source for emitting a laser beam, a hologram for dividing the laser beam emitted from the laser light source into a plurality of directions, a mask irradiated with the laser beam emitted from the hologram, and a laser transmitted through the mask An optical processing apparatus including a transfer lens for transferring a beam onto a processing target, wherein the laser light source includes a laser system having a laser oscillator and at least one optical amplifier. 6. A laser light source having a laser oscillator, a hologram for dividing a laser beam emitted from the laser light source into a number of arbitrary directions, a mask irradiated with the laser beam emitted from the hologram, and a mask transmitted through the mask 6. An optical processing apparatus comprising a transfer lens for transferring a laser beam onto a processing target, wherein the laser beam irradiated on the mask is constituted by a plurality of beam spots. Optical processing equipment.