CN114730075A

CN114730075A - Laser irradiation device

Info

Publication number: CN114730075A
Application number: CN202080081247.4A
Authority: CN
Inventors: 下浦厚志; 铃木良和
Original assignee: V Technology Co Ltd
Current assignee: Tokai Rika Co Ltd
Priority date: 2019-12-20
Filing date: 2020-12-14
Publication date: 2022-07-08
Also published as: JP7348647B2; KR20220110484A; WO2021125141A1; TW202124075A; JP2021099419A

Abstract

The invention aims to provide a laser irradiation device capable of forming a delicate image while scanning laser. The laser irradiation device of the invention homogenizes the intensity distribution of laser light and forms the laser light by a slit (12a), the laser light passing through the slit (12a) is converted into parallel light by a first optical component (15), the laser light is imaged on an intermediate image surface (20) by a second optical component (17), and the laser light is scanned on the intermediate image surface (20) by scanning reflection mirrors (16a, 16 b). In addition, the reducing optical system (14) reduces the slit image formed on the intermediate image surface (20) and forms an image on the processing surface of the object (100).

Description

Laser irradiation device

Technical Field

The present invention relates to a laser irradiation apparatus.

Background

Patent document 1 discloses a laser processing apparatus that shapes a cross section of a laser beam using a mask having a through hole having two parallel sides, reflects the beam using a mirror, scans the beam in two dimensions using a Galvano scanner (Galvano scanner), forms an image of the through hole on a surface of an object to be processed using an f θ lens, and performs processing for removing a part of the object to be processed.

Prior art documents

Patent document

Patent document 1: japanese patent laid-open publication No. 2004-98120

Disclosure of Invention

Problems to be solved by the invention

However, in the invention described in cited document 1, a rectangular image (beam spot) is formed on the object to be processed, but no consideration is given to reducing the size of the beam spot. That is, in the invention described in cited document 1, a minute image of an arbitrary shape cannot be formed.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a laser irradiation device capable of forming a fine image while scanning a laser beam.

Means for solving the problems

In order to solve the above problem, a laser irradiation device according to the present invention includes, for example: a light source that emits laser light; a mask having a slit formed therein, the slit allowing a part of the laser light emitted from the light source to pass therethrough; a scanning optical system through which the laser light having passed through the slit passes; and a reduction optical system that reduces the size of the slit image passing through the scanning optical system and projects the slit image onto a processing surface, the scanning optical system including: a first optical member that makes the laser light passing through the slit parallel; a scanning mirror provided to be rotatable, which reflects the laser light having passed through the first optical member; and a second optical member that images the laser light reflected by the scanning mirror on an intermediate image plane, the reduction optical system including: a third optical member that reduces the slit image formed on the intermediate image plane; and an objective lens disposed so that an opening position of the objective lens is at a focal position of the third optical member.

According to the laser irradiation apparatus of the present invention, the intensity distribution of the laser light is uniformized and shaped by the slit, the laser light passing through the slit is made into parallel light by the first optical member, the laser light is imaged on the intermediate image plane by the second optical member, and the laser light is scanned on the intermediate image plane by the scanning mirror. The reduction optical system reduces the slit image formed on the intermediate image surface and forms an image on the processing surface of the object. With such a configuration, a fine image can be formed while the laser beam is scanned.

Here, the second optical member may be an f θ lens. This makes it possible to keep the distance between the third optical member and the objective lens constant.

Here, the second optical member may be an f θ lens of a telecentric structure type. Thus, all the laser light is incident on the objective lens, and therefore, no energy loss occurs even if the laser light is scanned over a wide range.

Here, the scanning mirror may include a first mirror and a second mirror, a first reflecting surface that is a reflecting surface of the first mirror and a second reflecting surface that is a reflecting surface of the second mirror face in different directions, and a rotation center of the first reflecting surface and a rotation center of the second reflecting surface may be located at twisted positions. This enables the laser beam to be scanned two-dimensionally with a simple configuration.

Effects of the invention

According to the present invention, a fine image can be formed while the laser light is scanned.

Drawings

Fig. 1 is a schematic diagram of a laser irradiation device 1 according to the present invention.

Fig. 2 is an optical path diagram of the laser irradiation device 1.

Fig. 3 is a diagram schematically showing an optical path when the scanning mirror 16 deflects the laser beam, (a) shows a state in which all the light beams shown in (B), (C), and (D) are superimposed, (B) shows a case in which an angle formed by principal rays before and after reflection at the scanning mirror 16 is an obtuse angle, (C) shows a case in which the principal ray is on an optical axis (an angle formed by principal rays before and after reflection at the scanning mirror 16 is a right angle), and (D) shows a case in which an angle formed by principal rays before and after reflection at the scanning mirror 16 is an acute angle.

Fig. 4 is a schematic view of the object 100, where (a) is a side view and (B) is a top view.

Fig. 5 is a diagram schematically showing a conventional laser irradiation device 110.

Fig. 6 is a diagram schematically showing an optical path in the laser irradiation device 110 in a case where the scanning mirror 16 deflects the laser beam, (a) shows a state where all the light beams shown in (B), (C), and (D) are superimposed, (B) shows a case where an angle formed by the principal rays before and after reflection at the scanning mirror 16 is an acute angle, (C) shows a case where the principal ray is on the optical axis (an angle formed by the principal rays before and after reflection at the scanning mirror 16 is a right angle), and (D) shows a case where an angle formed by the principal rays before and after reflection at the scanning mirror 16 is an obtuse angle.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The laser irradiation device of the present invention processes a processing object by scanning laser light in an xy direction.

Fig. 1 is a schematic diagram of a laser irradiation device 1 according to the present invention. The laser irradiation device 1 mainly includes a light source 10, a homogenizer 11, a mask 12, a scanning optical system 13, and a reduction optical system 14, and irradiates the object 100 with laser light.

Here, the object 100 will be described. Fig. 4 is a schematic view of the object 100, where (a) is a side view and (B) is a top view. The object 100 is a sapphire substrate 101 on which LED chips 102 are formed. The laser irradiation device 1 irradiates laser light to the interface between the sapphire substrate 101 and the LED chip 102 and peels the LED chip 102 from the sapphire substrate 101. Regarding the size of the LED chip 102, the width d1 is about 30 to 70 μm, and the height d2 is about 10 to 30 μm.

Since the display device is manufactured by mounting the LED chips 102 on a substrate (not shown) after being detached, only the desired LED chips 102 need to be peeled off from the sapphire substrate 101. For example, when RGB of LED chips 102 are sequentially arranged on a sapphire substrate 101, a display device may be manufactured by first mounting only pixels of R, then pixels of G, and finally pixels of B on the substrate. In such a case, the LED chips 102 must be peeled off from the sapphire substrate 101 every 3.

Fig. 4 shows an example in which the LED chip 102a is first irradiated with the laser beam L, and then the LED chips 102b arranged at positions 3 away from each other are irradiated with the laser beam L.

In order to peel off only a desired LED chip 102, the laser light L irradiated by the laser irradiation device 1 needs to substantially conform to the shape of the LED chip 102. In order to avoid irradiation of the adjacent LED chips 102 with the laser light L, the laser light L must be irradiated with accuracy of several tens of μm. In addition, in order to improve the production efficiency, the irradiation position of the laser beam needs to be changed quickly.

The description returns to fig. 1. The light source 10 is, for example, a solid-state laser oscillator, and emits pulsed laser light.

The homogenizer 11 is an optical system for homogenizing 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, gaussian beam), the intensity distribution of the laser light is made uniform by the homogenizer 11, and the laser light of uniform intensity is emitted to the LED chips 102, so that 1 LED chip 102 is reliably peeled from the sapphire substrate 101.

The mask 12 is a substantially plate-shaped member formed with a slit 12a, and the slit 12a allows a part of the laser beam passing through the homogenizer 11 to pass therethrough. The shape of the slit 12a is similar to the shape of the laser beam irradiated to the object 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 is larger than the shape of the laser beam irradiated to the object 100, and in the present embodiment, the size of the slit 12a is approximately 20 times larger than the shape of the laser beam irradiated to the object 100.

The scanning optical system 13 is a system through which the laser beam having passed through the slit 12a passes, and images the irradiation pattern formed by the slit 12a on the intermediate image plane 20. The scanning optical system 13 mainly includes a first lens 15, a scanning mirror 16, and a second lens 17.

The first lens 15 is, for example, a tube lens, and collimates the laser beam passing through the slit 12 a.

The scanning mirror 16 reflects the laser beam having passed through the first lens 15, and includes a first mirror 16a and a second mirror 16 b. The first mirror 16a and the second mirror 16b have reflecting

surfaces

16c and 16d for reflecting laser light, respectively. The reflective surface 16c faces a different direction than the reflective surface 16 d.

The first reflector 16a and the second reflector 16b are rotatably provided so that the orientations of the reflecting

surfaces

16c and 16d can be changed. The rotation center 16e of the reflection surface 16c is a line along the short side of the first mirror 16a, and is disposed substantially at the center in the longitudinal direction of the first mirror 16 a. The rotation center 16f of the reflecting surface 16d is a line along the short side of the second reflecting mirror 16b, and is disposed substantially at the center in the longitudinal direction of the second reflecting mirror 16 b. The rotation center 16e and the rotation center of the rotation center 16f are in a twisted position.

When the first mirror 16a is rotated about the rotation center 16e, the laser beam reflected by the reflection surface 16c moves on the second mirror 16b along the line, and when the second mirror 16b is fixed, the laser beam reflected by the reflection surface 16d moves on the second lens 17 (i.e., on the intermediate image plane 20) along the line. Further, by rotating the second mirror 16b about the rotation center 16f, the laser beam incident on a certain point of the reflection surface 16d moves along a line on the second lens 17 (i.e., on the intermediate image surface 20). The scanning direction of the laser beam when the first reflecting mirror 16a is rotated is substantially orthogonal to the scanning direction of the laser beam when the second reflecting mirror 16b is rotated. Thereby, the scanning mirror 16 can two-dimensionally scan the irradiation pattern formed by the slit 12a on the intermediate image plane 20. In addition, by configuring the scanning mirror 16 as two pieces, the laser beam can be two-dimensionally scanned with a simple configuration.

The second lens 17 is a lens for forming an image of the laser beam reflected by the scanning mirror 16 on the intermediate image plane 20. In the present embodiment, an f θ lens is used as the second lens 17, which has a proportional relationship (Y ═ f · θ) between the image height Y and the incident angle when the laser light reflected by the scanning mirror 16 enters at the angle θ. In particular, in the present embodiment, as the second lens 17, a f θ lens of a telecentric structure type in which output light is imaged at a point parallel to the optical axis is used. The laser beam having passed through the second lens 17 is formed into 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 main ray, an upper ray, and a lower ray are illustrated. The solid line in fig. 2 indicates the case where the principal ray is on the optical axis, and the broken line in fig. 2 indicates the case where the principal ray is shifted from the optical axis (the laser light is laterally shifted at the scanning mirror 16).

The light having passed through the slit 12a enters the first lens 15 while spreading, and the laser light is converted into parallel light by the first lens 15 and reflected by the scanning mirror 16. When the direction of the optical axis of the scanning mirror 16 is not changed (the laser light is not laterally deviated), the direction of the principal ray is on the optical axis without being changed as shown by the solid line in fig. 2. On the other hand, when the direction of the optical axis of the scanning mirror 16 is changed (the laser beam is laterally deviated), the direction of the principal ray changes as shown by the broken line in fig. 2, and the laser beam is obliquely incident on the second lens 17.

The direction of the principal ray of the laser light obliquely incident on the second lens 17 is substantially parallel to the direction of the principal ray of the laser light not obliquely incident on the second lens 17. That is, even if the angle of the laser beam is changed by the scanning mirror 16, the second lens 17 makes the angle of the principal ray on the intermediate image plane 20 parallel. Since the second lens 17 and the reduction optical system 14 are telecentric, the lateral shift of the principal ray of the laser beam (the positional shift between the center of the second lens 17 and the principal ray of the laser beam) in the second lens 17 and the lateral shift of the principal ray of the laser beam (the positional shift between the center of the intermediate image plane 20 and the principal ray of the laser beam) in the intermediate image plane 20 substantially coincide with each other.

The description returns to fig. 1. The reduction optical system 14 is for reducing the light after passing through the scanning optical system, and mainly has a third lens 18 and an objective lens 19. In the present embodiment, the reduction optical system 14 reduces the irradiation pattern of the intermediate image plane 20 to approximately 1/20 times and projects the reduced pattern onto the processing surface of the object 100.

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

The objective lens 19 forms the irradiation pattern of the intermediate image plane 20 reduced by the third lens 18 on the processing plane of the object 100. The objective lens 19 is disposed such that the opening position of the objective lens 19 is at the focal position of the third lens 18. In the present embodiment, the second lens 17 is an f θ lens, and the distance between the third lens 18 and the objective lens 19 is always constant because the second lens 17 and the third lens 18 are telecentric.

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

Fig. 3 is a diagram schematically showing an optical path in a case where the scanning mirror 16 deflects the laser beam side, (a) shows a state where all the light beams shown in (B), (C), and (D) are superimposed, (B) shows a case where an angle formed by principal rays before and after reflection at the scanning mirror 16 is an obtuse angle, (C) shows a case where the principal ray is on the optical axis (an angle formed by principal rays before and after reflection at the scanning mirror 16 is a right angle), and (D) shows a case where an angle formed by principal rays before and after reflection at the scanning mirror 16 is an acute angle.

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

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

Further, according to the present embodiment, since the slit image is formed on the intermediate image plane 20 by the f θ lens of the telecentric structure type and reduced by the reduction optical system 14, even if the laser light is laterally deviated on the intermediate image plane 20 by the scanning mirror 16, the laser light enters the same position on the pupil of the objective lens 19. Therefore, the 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 scanning mirror 16, and an objective lens 22 (here, an f θ lens).

In the laser irradiation device 110, since the angle of the beam of the laser light changes when scanning around the scanning mirror 16, a part of the laser light may deviate from the opening of the objective lens 22 at the opening of the objective lens 22.

Fig. 6 is a diagram schematically showing an optical path in the laser irradiation device 110 in a case where the scanning mirror 16 deflects the laser beam side, (a) shows a state where all the light beams shown in (B), (C), and (D) are superimposed, (B) shows a case where an angle formed by the principal rays before and after reflection at the scanning mirror 16 is an acute angle, (C) shows a case where the principal ray is on the optical axis (an angle formed by the principal rays before and after reflection at the scanning mirror 16 is a right angle), and (D) shows a case where an angle formed by the principal rays before and after reflection at the scanning mirror 16 is an obtuse angle.

When the principal ray is on the optical axis, as shown in fig. 6 (C), all the rays enter the objective lens 22, and therefore no energy loss occurs, but when the principal ray is not on the optical axis, as shown in fig. 6 (B) and (D), some of the rays deviate from the objective lens 19.

For example, the magnification is 20 times, the N/A is 0.36, and the actual visual field is

Opening diameter of

The objective lens of (1). When the scanning position is set to. + -. 0.6mm, the incident angle of the principal ray to the objective lens 22 becomes. + -. 3.43 ℃. When the position of the scanning mirror 16 is separated from the opening portion of the objective lens 22 by 50mm, the positional deviation of the principal ray at the opening portion of the objective lens 22 is ± 3 mm.

I.e. the diameter of the opening relative to the objective lens

The chief ray offset amounts to + -3 mm. Therefore, when the laser beam is laterally deflected as shown in fig. 6 (B) and (D), a part of the laser beam does not enter the objective lens, and energy loss occurs.

In contrast, in the present embodiment, even if the laser light is laterally deflected by the scanning mirror 16, the laser light enters the same position on the pupil of the objective lens 19, and therefore no energy loss occurs.

In the present embodiment, since the intensity distribution of the laser light is uniformized by the homogenizer 11 and the beam is shaped by the slit 12a, the laser light having a uniform intensity can be irradiated to the entire LED chip 102.

In the present embodiment, the second lens 17 is an f θ lens, and the second lens 17 and the third lens 18 are telecentric, but the second lens 17 is not limited to the f θ lens. However, when a lens having a non-telecentric structure 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 needs to be changed in accordance with a change in the focal length of the third lens 18.

In the present embodiment, the scanning mirror 16 includes two mirrors (the first mirror 16a and the second mirror 16b), but the configuration of the scanning mirror 16 is not limited to this. For example, the scanning mirror may have one mirror. The one mirror can perform one-dimensional scanning when it can be rotated in 1 direction, and can perform two-dimensional scanning when it can be rotated in two directions. However, since the structure for performing two-dimensional scanning of laser light by using one mirror becomes complicated, it is desirable to perform two-dimensional scanning by using two mirrors.

In the present embodiment, the intensity distribution of the laser light emitted from the light source 10 is uniformized by the homogenizer 11, and a part of the laser light having passed through the homogenizer 11 passes through the slit 12a, but the homogenizer 11 is not essential. For example, even when only a portion (through the slit 12a) of the laser beam (gaussian beam) emitted from the light source 10 having a strong intensity is used, uniform irradiation can be performed to some extent. However, in order to reduce the occurrence of energy loss, it is desirable to use a laser beam whose intensity distribution is uniformized by the homogenizer 11.

While the embodiments of the present invention have been described in detail with reference to the drawings, the specific configuration is not limited to the embodiments, and design changes and the like are included within a range not departing from the gist of the present invention.

For example, the laser irradiation apparatus of the present invention can be used in various apparatuses that scan a laser beam in the xy direction to process an object to be processed, for example, a laser annealing apparatus. That is, the present invention can be applied to various apparatuses that require the laser beam to be rapidly scanned in two-dimensional directions using a scanning mirror.

In the present invention, "substantially" includes not only the strict identity but also an error or a distortion to the extent that the identity is not lost. For example, the substantially parallel is not limited to the case of being strictly parallel. For example, the substantially rectangular shape is not limited to a case of being strictly rectangular. For example, when only parallel, orthogonal, identical, or the like is expressed, the terms include not only strictly parallel, orthogonal, identical, or the like, but also substantially parallel, substantially orthogonal, substantially identical, or the like.

Description of the reference numerals

1: laser irradiation device

10: light source

11: homogenizer

12: mask and method for manufacturing the same

12 a: slit

13: scanning optical system

14: reduction optical system

15: first lens

16: scanning mirror

16 a: first reflector

16 b: second reflecting mirror

16c, 16 d: reflecting surface

16e, 16 f: center of rotation

17: second lens

18: third lens

19: objective lens

20: intermediate image plane

21: imaging lens

22: objective lens

100: object to be processed

101: sapphire substrate

102. 102a, 102 b: LED chip

110: a laser irradiation device.

Claims

1. A laser irradiation apparatus is characterized in that,

the laser irradiation device is provided with:

a light source that emits laser light;

a mask having a slit formed therein, the slit allowing a part of the laser light emitted from the light source to pass therethrough;

a scanning optical system through which the laser light having passed through the slit passes; and

a reduction optical system for reducing the slit image passing through the scanning optical system and projecting the image onto a processing surface,

the scanning optical system has: a first optical member that makes the laser light passing through the slit parallel; a scanning mirror provided to be rotatable, which reflects the laser light having passed through the first optical member; and a second optical member that images the laser light reflected by the scanning 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 surface; and an objective lens disposed so that an opening position of the objective lens is at a focal position of the third optical member.

2. The laser irradiation apparatus according to claim 1,

the second optical member is an f θ lens.

3. The laser irradiation apparatus according to claim 1 or 2,

the second optical member is an f θ lens of a telecentric structure type.

4. The laser irradiation apparatus according to any one of claims 1 to 3,

the scanning mirror has a first mirror and a second mirror,

the reflecting surface of the first mirror (first reflecting surface) faces in a different direction from the reflecting surface of the second mirror (second reflecting surface),

the rotation center of the first reflecting surface and the rotation center of the second reflecting surface are in a torsional position.