JP7348647B2 - Laser irradiation device - Google Patents

Description

The present invention relates to a laser irradiation device.

In Patent Document 1, the cross section of the laser beam is shaped using a mask having a through hole with two mutually parallel sides, the beam is reflected by a reflecting mirror, and the beam is scanned in a two-dimensional direction by a galvano scanner. 2. Description of the Related Art A laser processing apparatus has been disclosed that performs processing to remove a part of a workpiece by forming an image of a through hole on the surface of the workpiece using a lens.

Japanese Patent Application Publication No. 2004-98120

However, in the invention described in Cited Document 1, a rectangular image (beam spot) is formed on the workpiece, but no consideration is given to reducing the size of the beam spot. That is, in the invention described in Cited Document 1, it is not possible to form a minute image of an arbitrary shape.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a laser irradiation device that can form a precise image while scanning with laser light.

In order to solve the above problems, a laser irradiation device according to the present invention includes, for example, a light source that emits laser light, a mask in which a slit is formed that allows a part of the laser light emitted from the light source to pass, and A scanning optical system through which the laser beam that has passed through the slit passes; and a reduction optical system that reduces the slit image that has passed through the scanning optical system and projects it onto a processing surface, the scanning optical system passing through the slit. a first optical member that converts the laser light into parallel light; a scan mirror that reflects the laser light that has passed through the first optical member, the scan mirror being rotatably provided; a second optical member that focuses the laser beam on an intermediate image plane; the reduction optical system includes a third optical member that reduces the slit image formed on the intermediate image plane; It is characterized by having an objective lens provided so that the aperture position is located at the focal point position of the optical member.

According to the laser irradiation device according to the present invention, the intensity distribution of the laser beam is made uniform and the laser beam is shaped by the slit, the laser beam that has passed through the slit is made into parallel light by the first optical member, and the laser beam is intermediated by the second optical member. An image is formed on the image plane, and the laser beam is scanned on the intermediate image plane by a scan mirror. Further, the reduction optical system reduces the slit image formed on the intermediate image plane and forms the image on the processing surface of the workpiece. With such a configuration, a precise image can be formed while scanning with laser light.

Here, the second optical member may be an fθ lens. Thereby, the distance between the third optical member and the objective lens can always be kept constant.

Here, the second optical member may be a telecentric fθ lens. As a result, all of the laser light is incident on the objective lens, so no energy loss occurs even if the laser light is scanned over a wide range.

Here, the scan mirror has a first mirror and a second mirror, and the first reflective surface that is the reflective surface of the first mirror and the second reflective surface that is the reflective surface of the second mirror are: The first reflective surface may face different directions, and the center of rotation of the first reflective surface and the center of rotation of the second reflective surface may be in twisted positions. This allows two-dimensional scanning with laser light with a simple configuration.

According to the present invention, a precise image can be formed while scanning with laser light.

1 is a diagram schematically showing a laser irradiation device 1 of the present invention. FIG. 2 is an optical path diagram of the laser irradiation device 1. FIG. It is a diagram schematically showing the optical path when a laser beam is swung by a scan mirror 16, in which (A) shows a state in which all the beams shown in (B), (C), and (D) are overlapped, and (B) ) shows the case where the angle formed by the principal ray before and after reflection on the scan mirror 16 is an obtuse angle, and (C) shows the case where the principal ray is on the optical axis (the angle formed between the principal ray before and after reflection on the scan mirror 16 is a right angle). (D) shows a case where the angle formed by the chief ray before and after reflection on the scan mirror 16 is an acute angle. 1A and 1B are diagrams schematically showing an outline of a workpiece 100, in which (A) is a side view and (B) is a plan view. 1 is a diagram schematically showing a conventional laser irradiation device 110. FIG. In the laser irradiation device 110, it is a diagram schematically showing the optical path when the laser beam is swung by the scan mirror 16, and (A) is a diagram in which all the light beams shown in (B), (C), and (D) are overlapped. (B) shows the case where the angle formed by the principal ray before and after reflection on the scan mirror 16 is an acute angle, and (C) shows the case where the principal ray is on the optical axis (the principal ray before and after reflection on the scan mirror 16). (D) shows the case where the angle between the chief rays before and after reflection on the scanning mirror 16 is an obtuse angle.

Embodiments of the present invention will be described in detail below with reference to the drawings. The laser irradiation device of the present invention processes a workpiece by scanning a laser beam in the x and y directions.

FIG. 1 is a diagram schematically showing a laser irradiation device 1 of the present invention. The laser irradiation device 1 mainly includes a light source 10, a homogenizer 11, a mask 12, a scan optical system 13, and a reduction optical system 14, and irradiates the workpiece 100 with laser light.

Here, the workpiece 100 will be explained. FIG. 4 is a diagram schematically showing the outline of the workpiece 100, in which (A) is a side view and (B) is a plan view. The workpiece 100 has an LED chip 102 formed on a sapphire substrate 101. The laser irradiation device 1 irradiates the interface between the sapphire substrate 101 and the LED chip 102 with a laser to peel the LED chip 102 from the sapphire substrate 101. The LED chip 102 has a width d1 of about 30 to 70 μm and a height d2 of about 10 to 30 μm.

Since a display device is manufactured by removing the LED chips 102 and mounting them on a substrate (not shown), only the desired LED chips 102 must be peeled off from the sapphire substrate 101. For example, when RGB of the LED chips 102 are arranged in order on the sapphire substrate 101, first, only the R pixels are mounted on the substrate, then the G pixels are mounted, and finally the B pixels are mounted. In some cases, equipment may be manufactured. In such a case, every third LED chip 102 must be peeled off from the sapphire substrate 101.

FIG. 4 shows an example in which the LED chip 102a is first irradiated with the laser light L, and then the LED chips 102b arranged three chips apart are irradiated with the laser light L.

In order to peel off only the desired LED chip 102, the laser beam L emitted by the laser irradiation device 1 needs to substantially match the shape of the LED chip 102. Furthermore, in order to avoid irradiating adjacent LED chips 102 with laser light L, it is necessary to irradiate laser light L with an accuracy on the order of several tens of micrometers. Furthermore, in order to increase production efficiency, it is necessary to quickly change the irradiation position of the laser beam.

Returning to the explanation of FIG. The light source 10 is, for example, a solid-state laser oscillator, and emits pulsed laser light.

The homogenizer 11 is an optical system that equalizes the intensity distribution of the laser light emitted from the light source 10. Since the light emitted from the light source 10 generally has a non-uniform intensity distribution (for example, a Gaussian beam), the homogenizer 11 makes the intensity distribution of the laser beam uniform, and the laser beam with uniform intensity is applied to the LED chip 102. irradiation to ensure that one LED chip 102 is peeled off from the sapphire substrate 101.

The mask 12 is a substantially plate-shaped member in which a slit 12a is formed through which a portion of the laser light that has passed through the homogenizer 11 passes. The shape of the slit 12a is similar to the shape of the laser beam irradiated onto the workpiece 100, here the shape of the LED chip 102. Since the size of the slit 12a is reduced by the reduction optical system 14, the size of the slit 12a is larger than the shape of the laser beam irradiated onto the workpiece 100, and in this embodiment, it is approximately 20 times larger.

The scanning optical system 13 allows the laser light that has passed through the slit 12 a to pass therethrough, and forms an image of the irradiation pattern formed by the slit 12 a on an intermediate image plane 20 . The scan optical system 13 mainly includes a first lens 15, a scan mirror 16, and a second lens 17.

The first lens 15 is, for example, a tube lens, and converts the laser beam that has passed through the slit 12a into parallel light.

The scan mirror 16 reflects the laser beam that has passed through the first lens 15, and includes a first mirror 16a and a second mirror 16b. The first mirror 16a and the second mirror 16b each have reflective surfaces 16c and 16d on which the laser beam is reflected. The reflective surface 16c and the reflective surface 16d face different directions.

The first mirror 16a and the second mirror 16b are rotatably provided so that the directions of the reflective surfaces 16c and 16d can be changed, respectively. The rotation center 16e of the reflective surface 16c is a line along the short side of the first mirror 16a, and is located approximately at the center of the first mirror 16a in the longitudinal direction. Further, the rotation center 16f of the reflective surface 16d is a line along the short side of the second mirror 16b, and is located approximately at the center of the second mirror 16b in the longitudinal direction. The rotation center 16e and the rotation center 16f are in a twisted position.

By rotating the first mirror 16a around the rotation center 16e, the laser beam reflected by the reflective surface 16c moves along a line on the second mirror 16b, and the second mirror 16b is fixed. In this case, the laser beam reflected by the reflective surface 16d moves along a line on the second lens 17 (that is, on the intermediate image plane 20). Furthermore, by rotating the second mirror 16b around the rotation center 16f, the laser light incident on a certain point on the reflective surface 16d is converted into a line on the second lens 17 (that is, on the intermediate image plane 20). move along. The scanning direction of the laser beam when the first mirror 16a is rotated is substantially perpendicular to the scanning direction of the laser beam when the second mirror 16b is rotated. Thereby, the scan mirror 16 can two-dimensionally scan the irradiation pattern formed by the slit 12a on the intermediate image plane 20. Moreover, by configuring the scanning mirror 16 with two sheets, it is possible to perform two-dimensional scanning with laser light with a simple configuration.

The second lens 17 is a lens that focuses the laser beam reflected by the scan mirror 16 onto an intermediate image plane 20 . In this embodiment, when the laser beam reflected by the scan mirror 16 is incident at an angle θ, an fθ lens is used which establishes a proportional relationship (Y=f・θ) between the image height Y and the incident angle. 2 lens 17. In particular, in this embodiment, a telecentric fθ lens in which the output light beam forms an image on a point parallel to the optical axis is used as the second lens 17. The laser beam that has passed through the second lens 17 forms an image on the intermediate image plane 20 and enters the reduction optical system 14 .

FIG. 2 is an optical path diagram of the laser irradiation device 1. In FIG. 2, a principal ray, an upper ray, and a lower ray are illustrated. The solid line in FIG. 2 shows the case where the principal ray is on the optical axis, and the dotted line in FIG. 2 shows the case when the principal ray deviates from the optical axis (the laser beam is deflected by the scan mirror 16).

The light passing through the slit 12a enters the first lens 15 while expanding, the laser beam is converted into parallel light by the first lens 15, and the laser beam is reflected by the scan mirror 16. When the direction of the optical axis cannot be changed in the scan mirror 16 (the laser beam is not deflected), the direction of the chief ray does not change and remains on the optical axis, as shown by the solid line in FIG. On the other hand, when the direction of the optical axis is changed in the scan mirror 16 (the laser beam is deflected), the direction of the principal ray changes and the laser beam is directed to the second lens 17, as shown by the dotted line in FIG. incident at an angle.

The direction of the principal ray of the laser beam that is obliquely incident on the second lens 17 is approximately parallel to the direction of the principal ray of the laser beam that is not obliquely incident. That is, the second lens 17 makes the angle of the chief ray on the intermediate image plane 20 parallel even if the angle of the laser beam is changed by the scan mirror 16. Furthermore, since the distance between the second lens 17 and the reduction optical system 14 is telecentric, the deflection of the principal ray of the laser beam in the second lens 17 (positional deviation between the center of the second lens 17 and the principal ray of the laser beam) ) and the deflection of the principal ray of the laser beam at the intermediate image plane 20 (positional deviation between the center of the intermediate image plane 20 and the principal ray of the laser beam) substantially match.

Returning to the explanation of FIG. The reduction optical system 14 reduces the light that has passed through the scanning optical system, and mainly includes a third lens 18 and an objective lens 19. In this embodiment, the reduction optical system 14 reduces the irradiation pattern on the intermediate image plane 20 to approximately 1/20 times and projects it onto the processing surface of the workpiece 100.

The third lens 18 is a lens on which the slit image that has passed through the second lens 17 and is formed on the intermediate image plane 20 is incident, and is, for example, a tube lens. The distance between the intermediate image plane 20 and the third lens 18 substantially matches the focal length of the third lens 18. The third lens 18 reduces the irradiation pattern on the intermediate image plane 20 to approximately 1/20 times and makes it incident on the objective lens 19 .

The objective lens 19 images the irradiation pattern of the intermediate image plane 20 reduced by the third lens 18 on the processing surface of the workpiece 100. The objective lens 19 is provided so that the aperture position of the objective lens 19 is located at the focal position of the third lens 18. In this embodiment, the second lens 17 is an fθ lens, and the distance between the second lens 17 and the third lens 18 is telecentric, so the distance between the third lens 18 and the objective lens 19 is always constant. .

As shown in FIG. 2, energy loss can be eliminated by setting the intersection of the principal rays at the pupil position of the objective lens 19.

FIG. 3 is a diagram schematically showing the optical path when the laser beam is swung by the scan mirror 16, and (A) shows the state in which all the beams shown in (B), (C), and (D) are overlapped. (B) shows the case where the angle formed by the principal ray before and after reflection on the scan mirror 16 is an obtuse angle, and (C) shows the case where the principal ray is on the optical axis (the angle formed by the principal ray before and after reflection on the scan mirror 16). (D) shows the case where the angle between the principal rays before and after reflection on the scan mirror 16 is acute.

The principal ray, the upper ray, and the lower ray are incident on the same position on the objective lens 19, whether the principal ray is on the optical axis or not on the optical axis. Therefore, no energy loss occurs at the aperture of the objective lens 19.

According to this embodiment, a slit image is formed on the intermediate image plane 20 by the scanning optical system 13, and is reduced by the reduction optical system 14, so that a precise image is formed while scanning the laser beam. be able to.

Further, according to the present embodiment, a slit image is formed on the intermediate image plane 20 by a telecentric fθ lens, and is reduced by the reduction optical system 14, so that the laser beam is focused on the intermediate image plane 20 by the scanning mirror 16. Even if the light is waved, the laser light enters the same position on the pupil of the objective lens 19. Therefore, loss of laser energy can be eliminated.

FIG. 5 is a diagram schematically showing a conventional laser irradiation device 110. The laser irradiation device 110 mainly includes a light source 10, a homogenizer 11, a mask 12, an imaging lens 21, a scan mirror 16, and an objective lens 22 (here, an fθ lens).

In the laser irradiation device 110, since the angle of the laser beam during scanning changes around the scan mirror 16, there is a risk that a portion of the laser beam may deviate from the opening of the objective lens 22. .

FIG. 6 is a diagram schematically showing the optical path when the laser beam is swung by the scanning mirror 16 in the laser irradiation device 110, and (A) is a diagram schematically showing the optical path when the laser beam is swung by the scanning mirror 16 in the laser irradiation device 110. The state in which the light rays are overlapped is shown, (B) shows the case where the angle formed by the principal ray before and after reflection on the scan mirror 16 is an acute angle, and (C) shows the case where the principal ray is on the optical axis (the angle formed by the principal ray before and after reflection on the scan mirror 16 is acute). (D) shows the case where the angles formed by the principal rays before and after reflection on the scan mirror 16 are obtuse angles.

When the principal ray is on the optical axis, no energy loss occurs because all the rays enter the objective lens 22, as shown in FIG. 6(C), but when the principal ray is not on the optical axis, As shown in FIGS. 6(B) and 6(D), some of the light rays miss the objective lens 19.

For example, assume that an objective lens with a magnification of 20 times, an N/A of 0.36, an actual field of view of 1.2 mm, and an aperture diameter of 7.7 mm is used. If the scan position is ±0.6 mm, the angle of incidence of the chief ray on the objective lens 22 is ±3.43°. Assuming that the scan mirror 16 is located 50 mm away from the aperture of the objective lens 22, the positional deviation of the chief ray at the aperture of the objective lens 22 is ±3 mm.

In other words, the principal ray deviates by ±3 mm with respect to the aperture diameter of the objective lens of φ7.7 mm. Therefore, when the laser beam is deflected as shown in FIGS. 6(B) and (D), a portion of the laser beam does not enter the objective lens, resulting in energy loss.

In contrast, in this embodiment, even if the laser beam is swung by the scan mirror 16, the laser beam is incident on the same position on the pupil of the objective lens 19, so no energy loss occurs.

Furthermore, in this embodiment, the homogenizer 11 equalizes the intensity distribution of the laser beam, and the slit 12a shapes the beam, so the entire LED chip 102 can be irradiated with a laser beam of uniform intensity.

Note that in this embodiment, the second lens 17 is an fθ lens, and the space between the second lens 17 and the third lens 18 is telecentric, but the second lens 17 is not limited to an fθ lens. However, if a lens that is not telecentric between the second lens 17 and the third lens 18 is used as the second lens 17, the distance between the third lens 18 and the objective lens 19 will change depending on the change in the focal length of the third lens 18. It is necessary to move the distance between the

Further, in this embodiment, the scan mirror 16 has two mirrors (the first mirror 16a and the second mirror 16b), but the configuration of the scan mirror 16 is not limited to this. For example, the scan mirror may have only one mirror. If the single mirror is rotatable in one direction, one-dimensional scanning is possible, and if it is rotatable in two directions, two-dimensional scanning is possible. However, since attempting two-dimensional scanning with a laser beam using one mirror would complicate the configuration, it is desirable to perform two-dimensional scanning using two mirrors.

Further, in this embodiment, the intensity distribution of the laser light emitted from the light source 10 is made uniform by the homogenizer 11, and a part of the laser light that has passed through the homogenizer 11 passes through the slit 12a, but the homogenizer 11 is not essential. do not have. For example, even when only a high-intensity portion of the laser light (Gaussian beam) emitted from the light source 10 is used (passed through the slit 12a), uniform irradiation is possible to some extent. However, in order to reduce the occurrence of energy loss, it is desirable to use a laser beam whose intensity distribution has been made uniform by the homogenizer 11.

Although the embodiment of this invention has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes, etc. within the scope of the gist of this invention are also included. .

For example, the laser irradiation device of the present invention can be used in various devices, such as laser annealing devices, that process a workpiece by scanning laser light in the x and y directions. That is, the present invention can be applied to various devices that require a scanning mirror to quickly scan a laser beam in two-dimensional directions.

Furthermore, in the present invention, "substantially" is a concept that includes not only strictly the same case but also errors and deformations to the extent that the sameness is not lost. For example, "substantially parallel" is not limited to strictly parallel. Further, for example, a substantially rectangular shape is not limited to a strictly rectangular shape. Furthermore, for example, when simply expressing parallel, perpendicular, identical, etc., it includes not only cases of strictly parallel, orthogonal, identical, etc., but also cases of substantially parallel, substantially orthogonal, substantially identical, etc.

1: Laser irradiation device 10: Light source 11: Homogenizer 12: Mask 12a: Slit 13: Scanning optical system 14: Reduction optical system 15: First lens 16: Scanning mirror 16a: First mirror 16b: Second mirror 16c, 16d: Reflective surfaces 16e, 16f: Rotation center 17: Second lens 18: Third lens 19: Objective lens 20: Intermediate image plane 21: Imaging lens 22: Objective lens 100: Workpiece 101: Sapphire substrates 102, 102a, 102b: LED chip 110: Laser irradiation device

Claims (4)

a light source that emits laser light;
a mask in which a slit is formed through which a portion of the laser light emitted from the light source passes;
a scanning optical system through which the laser beam that has passed through the slit passes;
a reduction optical system that reduces the slit image that has passed through the scanning optical system and projects it onto the processing surface;
Equipped with
The scan optical system includes a first optical member that converts the laser light that has passed through the slit into parallel light, and a scan mirror that reflects the laser light that has passed through the first optical member, and is rotatably provided. comprising a scan mirror and a second optical member that images the laser beam reflected by the scan mirror on an intermediate image plane,
The reduction optical system includes a third optical member that reduces the slit image formed on the intermediate image plane, and an objective lens provided such that an aperture position is located at a focal position of the third optical member. A laser irradiation device characterized by: The laser irradiation device according to claim 1, wherein the second optical member is an fθ lens. 3. The laser irradiation device according to claim 1, wherein the second optical member is a telecentric fθ lens. The scan mirror has a first mirror and a second mirror,
A first reflective surface that is a reflective surface of the first mirror and a second reflective surface that is a reflective surface of the second mirror face different directions,
The laser irradiation device according to any one of claims 1 to 3, wherein a center of rotation of the first reflective surface and a center of rotation of the second reflective surface are at twisted positions.

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