JP3439272B2 - Laser processing equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing apparatus for performing processing such as punching and cutting by irradiating a workpiece such as a photomask with a laser beam.

[0002]

2. Description of the Related Art Conventionally, a photomask used for manufacturing a liquid crystal display (LCD) or the like is composed of a metal thin film having a desired light shielding portion and a transparent portion on the surface of a glass substrate. Then, a photomask made of such a metal thin film has come to be corrected by a laser processing apparatus generally called a laser repair when a light shielding part remains at a position which should originally be a transparent part. There is.

FIG. 10 shows an example of a laser processing apparatus used to correct such a photomask. 1 is a laser oscillator, 2 is a driver, and these laser oscillators 1 are
Further, the driver 2 constitutes a processing light source for pulse oscillation. Then, the laser light flux emitted from the laser oscillator 1 is applied to the optical attenuator 3 and adjusted to an appropriate intensity, and then the slit 7 is illuminated through the dichroic mirror 4.
Here, the slit 7 is composed of an opening of a generally square shape constituted by a knife edge. And this slit 7
And the workpiece 15 between the imaging lens 11 and the objective lens 14.
The optical system makes an optically conjugate positional relationship, and the laser light flux passing through the slit 7 is formed into a reduced projection image of the shape of the slit 7 and is formed on the surface of the workpiece 15 such as the metal thin film described above. The surface of the metal thin film located in the image formation range is removed. In this case, if the laser beam diameter is smaller than the slit 7, a beam expander is provided between the laser oscillator 1 and the slit 7 so that a sufficient beam diameter can be obtained.

In this case, the surface of the workpiece 15 is illuminated by the light emitted from the visible light source 13 through the objective lens 14 from the semitransparent mirror 12 arranged between the imaging lens 11 and the objective lens 14, and is illuminated. The surface image of the work piece 15 is passed through the objective lens 14, the imaging lens 11 and the semi-transparent mirror 8 by the semi-transparent mirror 8 arranged between the slit 7 and the imaging lens 11 and CC.
An image is formed on the image pickup surface of D10 and is observed by the monitor TV9. Further, the light emitted from the visible light source 5 is reflected by the dichroic mirror 4 and illuminates the slit 7, so that the image of the slit 7 is projected on the surface of the workpiece 15, and the monitor TV 9 is irradiated with the laser light flux. The area to be displayed is also displayed.

However, an operator who operates such a laser processing apparatus adjusts the position of the workpiece 15 and the shape of the slit 7 while observing the screen of the monitor TV 9 to cause the laser oscillator 1 to pulse-oscillate. The unnecessary portion on the surface of the workpiece 15 is removed.

[0006]

However, in such a laser processing apparatus, the workpiece 7 is processed from the slit 7 to the workpiece 15.
The relationship between the optical system and the laser light flux 19 can be expressed as shown in FIG. Here, the semi-transparent mirror, which is not essential for imaging the slit, is omitted.

In this case, the light beam emitted from the laser oscillator 1 is a substantially parallel light beam and is incident on the slit 7 as a parallel light beam even after the light beam diameter is expanded by the beam expander. Then, the imaging lens 11 passes through the slit 7.
Is converted into a convergent light flux, and the degree of convergence is increased by the objective lens 14 and is once converged at the convergence point 22 and then spreads to reach the surface of the workpiece 15. The convergence point 22 here is
The focus position is on the front side (workpiece 15 side) of the imaging system including the objective lens 14 and the imaging lens 11 (hereinafter, the workpiece side is referred to as the front side, and the laser oscillator 1 side is referred to as the rear side).

Here, an optical microscope in which an objective lens 14 for so-called infinity correction and an image forming lens 11 constitutes an image forming system has been described as an example, but the so-called objective lens alone constitutes an image forming system. The same applies to those using an objective lens with finite correction. In this case, the convergence point can be on the front focus of the objective lens.

However, when laser processing is performed using such an optical system, there are the following problems. (1) A component of the laser beam that illuminates the workpiece 15 that is absorbed by the metal thin film contributes to the removal of the metal thin film, and the remaining component is reflected or transmitted. Of these, the reflected light flux is converged at the convergence point 23 on the front side of the slit 7 through the objective lens 14 and the imaging lens 11, as shown by the broken line in FIG. However, if the position of the converging point 23 overlaps the positions of the imaging lens 11 and the semi-transparent mirror 8 shown in FIG. 10 described above, the imaging lens 11 and the semi-transparent mirror 8 may be damaged. Further, even if the positions of the converging points 23 do not overlap, as the beam diameter becomes smaller, the energy density thereof increases and the possibility of damage increases. Then, such damage particularly occurs on the coated surface or the cemented surface of the lens, and since cracks or fogging can occur at that portion, the function as an optical system is significantly impaired and the laser processing performance deteriorates. .

(2) When the surface of the workpiece 15 is machined, it does not matter so much, but the surface to be machined is the workpiece 15
If it is on the back surface or inside, the convergence point 22 may be formed inside the workpiece 15. In this case, in the above-described photomask, the glass substrate has higher durability against the laser light flux than the metal thin film, and thus the above-described processing is established. However, the energy density of the laser light flux at the converging point 22 is the surface to be processed. Since it is much larger than that in, the glass substrate is also damaged.

(3) Imaging lens 11 through slit 7
If the laser light flux entering the objective lens 14 is larger than the respective lens diameters, the shape of the slit 7 may not be reproduced on the surface of the workpiece 15. The cause is mainly the problem that occurs in the objective lens 14, and when the opening of the rectangular slit 7 is gradually increased, the corners of the image are blurred first, and finally a rounded blurred image is formed. Will end up.
The laser light flux that has passed through the slit 7 spreads little by little due to diffraction, but in order to obtain a clear image, a lens diameter that can take in the laser light flux is required. There is an upper limit.

Therefore, a first object of the present invention is to provide a laser processing apparatus capable of reliably preventing damage to an optical system. A second object of the present invention is to provide a laser processing apparatus capable of reliably preventing damage to a work piece.

[0013]

The present invention according to claim 1
Is a laser output means for emitting a parallel laser beam, and
The slit for forming the laser light flux into a predetermined shape and the slit
Laser light flux to a divergent light flux
An imaging lens that converges the divergent light beam emitted from the
The light flux that has passed through the imaging lens of
After converging to the convergence point, project the slit image on the surface of the work piece.
It is characterized by including an objective lens that casts a shadow.

[0014]

According to a fifth aspect of the present invention, a parallel laser beam is emitted.
Laser output means for emitting the laser beam
Conversion means for converting to and the convergence emitted from this conversion means
A slit that forms a light beam into a predetermined shape and this slit
Convergent light flux formed by passing through the converging point of the conversion means
After that, it converges to a convergence point distant from the back side of the work piece.
And project the slit image on the inside or back of the workpiece.
And an image forming optical system including an objective lens
It is characterized by having.

According to a sixth aspect of the present invention, a parallel laser beam is emitted.
Laser output means to emit and this laser light into a convergent light flux
A convex lens that is converted and focuses on a position away from the back surface of the workpiece.
Lens and the convergent light flux emitted from this convex lens to a predetermined shape
And the slit formed on the
The convergent light flux is converted into a diffused light flux on the surface of the workpiece and the added light flux is added.
An imaging lens and a pair for projecting a slit image on the surface of the work
And an image forming optical system including an object lens.
is doing.

According to a seventh aspect of the present invention, a parallel laser beam is emitted.
Laser output means for emitting the laser beam
And the conversion means for converting into
This slit and the slit that forms the convergent light flux into a predetermined shape
The convergent light flux formed by
The rear focus is formed on the imaging lens and the virtual convergence point of the conversion means.
They are arranged so that they pass through the imaging lens.
Converts the bundled light flux into parallel light flux, and the slit image on the workpiece surface.
Characterized by having an objective lens for projection
It

[0018]

As a result, according to the present invention,
By expanding the imaging optical system with the reflected laser beam,
Concentration of laser beam energy density on imaging optics
Laser beam that can prevent
Make sure that the bundle does not damage the imaging optics.
You can stop. According to the invention, the slit
The converging light flux formed by the
The slit image is made by converging to a converging point away from the back side of the work piece.
Is projected on the back surface of the work piece,
Do not damage parts other than the work part by the laser beam.
In addition, the back surface of the workpiece can be laser processed.

[0019]

[0020]

[0021]

[0022]

[0023]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 shows a schematic configuration of the first embodiment, and the same parts as those in FIG. 10 are designated by the same reference numerals. In this case, a concave lens 6 is arranged between the dichroic mirror 4 and the slit 7 so as to be close to the slit 7 side. Others are the same as in FIG.

Then, in such a structure, the relationship between the optical system from the slit 7 to the workpiece 15 and the laser beam 19 can be expressed as shown in FIG. Again, the semi-transparent mirror, which is not essential for the imaging of the slit, is omitted.

However, in this configuration, the concave lens 6 is
It is arranged on the rear side of the slit 7 and converts the laser light flux 19 passing through the slit 7 from a parallel light flux to a divergent light flux. Then,
The laser light flux that has passed through the slit 7 is incident on the imaging lens 11 with a light flux diameter larger than that described with reference to FIG. 11, is once converged, and then is converged by the objective lens 14 to increase at a convergence point 22. After being converged once, it spreads and forms a slit image on the surface of the workpiece 15.

In this case, the concave lens 6 acts so as to bring the parallel light flux, that is, the light source position of the laser, which is apparently at infinity, close to the focal position of the concave lens 6. As a result, the convergence point 22 obtained from the objective lens 14 becomes a position which is optically conjugate with the focal position of the concave lens 6 and the image forming system, and may be closer to the workpiece 15 side than the position described in FIG. Become. As a result, the convergence point 23 of the light beam reflected on the surface of the workpiece 15 also moves largely to the slit 7 side.

In this case, the amount of movement of the convergence points 22 and 23 is
It can be increased as the focal length of the concave lens 6 is shortened. However, since the diameter of the light beam entering the imaging lens 11 and the objective lens 14 is also increased accordingly, it may not be too large.
Incidentally, in the case of this embodiment, the focal length f of the concave lens 6 is
The optimum value is in the range of f = -250 mm to -500 mm.

Therefore, according to such a first embodiment,
The concave lens 6 is arranged on the rear side of the slit 7, the laser light flux 19 passing through the slit 7 is changed from a parallel light flux to a divergent light flux, and this divergent light flux forms an image on the surface of the workpiece 15 through an imaging system and By moving the convergence point 23 of the light flux reflected on the surface of the workpiece 15 to the slit 7 side,
Since the diameter of the light beam passing through the image forming system can be increased, the concentration of energy density in the image forming system can be avoided. This is because compared with a conventional imaging lens in which the coating surface or the cemented surface is damaged, cracks or fogging can be formed in that portion, which significantly impairs the function of the optical system. The damage of the optical system can be surely prevented, and the deterioration of the laser processing performance can be prevented. Further, since the concentration of energy density can be prevented, a laser having large radiant energy can be used. (Second Embodiment) FIG. 3 shows a schematic configuration of the second embodiment, and the same parts as those in FIG. 2 are designated by the same reference numerals. In this case, although the concave lens 6 is arranged on the rear side of the slit 7 in the first embodiment, the convex lens 61 is arranged instead of the concave lens 6.

However, in such a configuration, the laser light flux 19 is converted from a parallel light flux into a convergent light flux by the action of the convex lens 61, passes through the slit 7, and then once converges at the convergence point 2.
21 and then the imaging lens 11 and the objective lens 1
After passing through 4, a slit image is formed on the surface of the workpiece 15. In this example, the convex lens 61 is determined so that the convergence point 221 can be located further rearward than the focal point 20 on the rear side of the imaging system.

Then, the light flux on the surface of the workpiece 15 converges after that, but the convergence point 22 is the convergence point 2 described above.
21 and a position optically conjugate with the imaging system. Further, the convergence point 23 of the light flux reflected from the surface of the workpiece 15 is
The convergence point 22 and the mirror image have a positional relationship with the surface of the workpiece 15.

However, if this is done, the convergence point 22
Can be formed on the opposite side of the workpiece 15 from the objective lens 14, and thus is suitable for processing the back surface of the workpiece 15. That is, when a slit image is formed on the back surface (lower side surface) of the workpiece 15 as shown in FIG. 4, the convergence point 22 can be located outside the workpiece 15, so that the workpiece 15 is It has the advantage of not being damaged.

Therefore, according to such a second embodiment,
Even if the surface to be processed is on the back surface or inside the work piece 15, the converging point 22 can be formed on the back surface (lower side surface) side of the work piece 15, so that parts other than the work surface are damaged. Can be reliably prevented. (Third Embodiment) FIG. 5 shows a schematic configuration of the third embodiment. The same parts as those in FIG. 3 are designated by the same reference numerals. In this case, the virtual convergence point 2 of the laser light flux by the convex lens 61
The focal length of the convex lens 61 is determined so that 6 can be located in front of the focus 20 on the rear side of the imaging system.

In this case, the actual convergence point (not shown) is
It is formed on the rear side of the focus 25 on the front side of the imaging system,
Is illuminated with a divergent light beam, and a slit image is formed on its surface. As a result, a convergence point of the laser light flux cannot be formed in the vicinity of the object to be processed 15, so that even when processing the back surface or the inside of the object to be processed 15, damage other than the surface to be processed can be prevented. Further, since the diameter of the laser light flux incident on the objective lens 14 can be reduced, an image of the slit 7 larger than that described with reference to FIG. 11 can be formed on the surface of the workpiece 15, and the size of the processing area can be reduced. The inconvenience of having an upper limit can be eliminated. (Fourth Embodiment) FIG. 6 shows a schematic configuration of the fourth embodiment. The same parts as those in FIG. 3 are designated by the same reference numerals. In this case, the virtual convergence point 2 of the laser light flux by the convex lens 61
6 is made to coincide with the focal point 20 on the rear side of the image forming system. In this case, the actual convergence point 221 of the convex lens 61
Can be formed behind the focal point 20 by the action of the imaging lens 11. Further, the laser light flux that has passed through the objective lens 14 is imaged on the workpiece 15 as a parallel light flux.

Therefore, the same effect as that of the above-described third embodiment can be realized also by such a fourth embodiment. (Fifth Embodiment) FIG. 7 shows a schematic configuration of the fifth embodiment. The same parts as those in FIG. 3 are designated by the same reference numerals. In this case, the convex lens 61 is deleted, and the front focus 21 of the imaging lens 11 and the rear focus 21 of the objective lens 14 are made to coincide with each other.

However, when such an afocal imaging system is used, the laser light flux 19 incident on the slit 7 as a parallel light flux becomes a parallel light flux with respect to the workpiece 15, and a convergence point is provided in the vicinity thereof. Does not happen. Therefore, even in this case, the same effect as that of the fourth embodiment can be realized. (Sixth Embodiment) FIG. 8 shows a schematic structure of the sixth embodiment. The same parts as those in FIG. 1 are designated by the same reference numerals. In this case, the laser light flux from the laser oscillator 1 has the same optical path from the optical attenuator 3 to the slit 7 through the dichroic mirror 4 and the arrangement of the visible light source 5 as described in FIG. The generated light flux is once transferred as a slit image 17 by the relay lens 16, and this is imaged on the surface of the workpiece 15 by the imaging system including the imaging lens 11 and the objective lens 14.
In this case, the laser light flux 19 of the laser oscillator 1 is once converged at the front focus 24 of the relay lens 16 and then enters the imaging lens 11 as a divergent light flux.

Therefore, according to the sixth embodiment, the same effect as that of the first embodiment can be realized.
Further, by disposing a convex lens (not shown) at the position of the slit image 17, the same effect as in the second to fourth embodiments can be realized. (Seventh Embodiment) FIG. 9 shows a schematic configuration of the seventh embodiment. The same parts as those in FIG. 1 are designated by the same reference numerals. In this case, the beam expander 18 is arranged between the optical attenuator 3 and the dichroic mirror 4. Usually, the beam expander 18 is an afocal system, which expands the diameter of the incident parallel light flux and emits it as a parallel light flux. However, in this example, the outgoing light flux is made to be the convergent light flux 19 by shifting from the afocal condition.

Therefore, according to such a seventh embodiment,
The same effects as those of the second to fourth embodiments can be realized. Also,
If the light beam emitted from the beam expander 18 is a divergent light beam, the same effect as that of the first embodiment can be realized.

Although the above description is based on the embodiments, the present invention also includes the following inventions. (1) Laser output means for emitting a substantially parallel laser beam, a convex lens for converting the laser beam into a convergent beam, a slit for shaping the convergent beam emitted by the convex lens into a predetermined shape, and a slit formed by this slit An image forming optical system for forming an image of the shape of the slit on the surface to be processed while the convergent light beam is incident, and a virtual convergence point of the laser light beam by the convex lens is set to the rear of the image forming optical system. It is characterized in that the focal length of the convex lens is determined so that it can be located in front of the side focus.

(2) Laser output means for emitting a substantially parallel laser beam, a convex lens for converting this laser beam into a convergent beam, a slit for shaping the convergent beam emitted by this convex lens into a predetermined shape, and this slit. An image forming optical system for forming an image of the shape of the slit on the surface to be processed while the formed convergent light beam is incident, and the virtual converging point of the laser light beam by the convex lens is formed in the image forming optical system. It is characterized by matching the focal point of the rear side.

(3) Laser output means for emitting a substantially parallel laser beam, a convex lens for converting this laser beam into a convergent beam, a slit for shaping the convergent beam emitted by this convex lens into a predetermined shape, and this slit. A focusing optical system including an objective lens and an image forming lens for forming an image of the shape of the slit on the surface to be processed while the shaped convergent light beam is incident, and a focus on the front side of the image forming lens The rear focus of the objective lens is matched.

[0041]

As described above, according to the present invention, the energy in the optical system is increased by moving the convergence point of the light beam reflected by the surface to be processed and increasing the diameter of the laser light beam passing through the imaging optical system. Concentration of density can be avoided and damage to the optical system can be reliably prevented.

Further, by moving the converging point of the light flux by the imaging optical system to the opposite side of the surface to be processed from the side of the imaging optical system, even if the surface to be processed is on the back surface or inside of the processing object, This ensures that damage to parts other than the machined surface can be prevented.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between an optical system of Example 1 and a laser beam.

FIG. 3 is a diagram showing a schematic configuration of a second embodiment of the present invention.

FIG. 4 is a diagram for explaining a second embodiment.

FIG. 5 is a diagram showing a schematic configuration of a third embodiment of the present invention.

FIG. 6 is a diagram showing a schematic configuration of a fourth embodiment of the present invention.

FIG. 7 is a diagram showing a schematic configuration of a fifth embodiment of the present invention.

FIG. 8 is a diagram showing a schematic configuration of a sixth embodiment of the present invention.

FIG. 9 is a diagram showing a schematic configuration of a seventh embodiment of the present invention.

FIG. 10 is a diagram showing a schematic configuration of an example of a conventional laser processing apparatus.

FIG. 11 is a diagram showing a relationship between an optical system of the laser processing apparatus and a laser beam.

[Explanation of symbols]

1 ... Laser oscillator, 2 ... Driver, 3 ... Optical attenuator, 4 ...
Dichroic mirror, 5 ... Visible light source, 6 ... Concave lens,
61 ... Convex lens, 7 ... Slit, 8 ... Semi-transparent mirror, 9 ... Monitor TV, 10 ... CCD, 11 ... Imaging lens, 12 ... Semi-transparent mirror, 13 ... Visible light source, 14 ... Objective lens, 15 ... Workpiece, 16 … Relay lens, 17… Slit image, 18…
Beam expander, 19 ... Laser beam, 20 ... Focus,
21 ... Focus, 22 ... Convergence point, 221 ... Convergence point, 23 ... Convergence point, 24 ... Focus point, 25 ... Focus point, 26 ... Convergence point.

Claims (8)

(57) [Claims] 1. A laser output for emitting parallel laser beams.
Means, a slit for forming the laser light flux into a predetermined shape, a conversion means for converting the laser light flux into a divergent light flux, and an imaging lens for converging the divergent light flux emitted from the conversion means.
One and lens, the light beam passed through the imaging lens in the vicinity of the workpiece surface
After converging to the convergent point, the slit image is formed on the surface of the workpiece.
A laser processing apparatus comprising: an objective lens for projecting . 2. The conversion means is configured so that the laser beam of the slit is
This is composed of a concave lens arranged on the laser output means side.
The focal length f of the lens is f = -250 mm to -500 mm
2. The laser processing according to claim 1, wherein
apparatus. 3. The converting means comprises a concave lens and a convex lens.
A beam exhaust that expands the diameter of the laser beam
It consists of a spanner and shifts the afocal condition to
A laser light flux is converted into a diffused light flux.
1. The laser processing device according to 1. 4. The converting means passes through the slit.
Converts laser light flux into diffused light flux and enters it into the imaging lens
2. A relay lens that allows the relay lens to move.
The laser processing device described. 5. A laser output device for emitting parallel laser light.
A step, a converting means for converting the laser light flux into a convergent light flux, and a convergent light flux emitted from the converting means into a predetermined shape.
And a converging light flux formed by the slit
After passing through the convergence point of
The slit image is focused on the inner surface of the workpiece by converging on the convergence point.
Or an imaging lens and an objective lens that project on the back side.
An image forming optical system according to claim 1 . 6. A laser output device for emitting parallel laser light.
Step and convert this laser light into a convergent light beam to separate it from the back surface of the workpiece.
A convex lens that focuses on a certain position and a convergent light flux emitted from this convex lens is formed into a predetermined shape.
And a convergent light flux formed by this slit
On the surface of the workpiece to convert it into a diffused light flux
Imaging light consisting of an imaging lens for projecting light and an objective lens
Laser machining apparatus being characterized in that comprising the academic system, the. 7. A laser output device for emitting parallel laser light.
A step, a converting means for converting the laser light flux into a convergent light flux, and a convergent light flux formed by the slit into a predetermined shape.
A slit formed, a convergent light beam formed by the slit once the convergence point
The rear-side focal point is aligned with the virtual focusing point of the converting means and the focusing lens for converging.
The converging light flux that has been placed and has passed through the imaging lens is collimated.
An objective lens that converts it into a bundle and projects the slit image onto the surface of the workpiece.
A laser processing apparatus comprising: 8. The converting means comprises a concave lens and a convex lens.
A beam exhaust that expands the diameter of the laser beam
It consists of a spanner and shifts the afocal condition to
A laser beam is converted into a convergent beam.
7. The laser processing device according to 7.