CN114074214A

CN114074214A - Laser processing apparatus and laser processing method

Info

Publication number: CN114074214A
Application number: CN202110953949.3A
Authority: CN
Inventors: 坂本刚志; 是松克洋
Original assignee: Hamamatsu Photonics KK
Current assignee: Hamamatsu Photonics KK
Priority date: 2020-08-21
Filing date: 2021-08-19
Publication date: 2022-02-22
Also published as: TW202222458A; KR20220023716A; JP2022036013A; JP2022035948A

Abstract

The laser processing apparatus includes a light source unit, a reflective spatial light modulator, a condensing portion, a detecting portion, and a control portion that executes: a1 st process of displaying a1 st branch pattern, which is obtained by dividing laser light into a plurality of parts, on a reflective spatial light modulator; a2 nd process of controlling the light source unit so as to emit the laser light in a state where the 1 st branch pattern is displayed on the reflective spatial light modulator; a 3 rd process of controlling the detection unit to detect the reflected light of each laser beam branched by the 1 st branching pattern; a 4 th process of deriving the brightness of the reflected light of each laser beam after branching based on the detection result of the detection unit; and a 5 th process of generating a2 nd branching pattern in which the 1 st branching pattern is corrected so that the output of each laser beam after branching becomes uniform, based on the derived brightness.

Description

Laser processing apparatus and laser processing method

Technical Field

The present invention relates to a laser processing apparatus and a laser processing method.

Background

Japanese patent No. 6620976 describes a laser processing apparatus including a laser light source, a spatial light modulator, and a light-converging correction unit different from the spatial light modulator. Such a laser processing apparatus performs division, separation, and the like of an object (wafer) by forming a modified region inside the object by irradiation of laser light. In the technique described in patent document 1 (japanese patent No. 6620976), a modified region is formed inside an object by irradiation of laser light, a part of reflected light from a converging point is imaged, a positional deviation amount of the converging point is detected based on the imaging result, and a modulation pattern in a spatial light modulator is adjusted so that the positional deviation is small.

Disclosure of Invention

In the laser processing apparatus as described above, a branching pattern is set in the spatial light modulator, and the laser light may be branched in accordance with the branching pattern to simultaneously form a plurality of modified regions. The branching pattern is set, for example, in accordance with the output target value of each laser beam after branching. Here, when the branching processing is performed, it is difficult to make the output of each laser beam after branching match the above-described output target value due to the influence of individual differences in optical characteristics, such as the difference between the regions of passage of each branched light beam in the lens. Since the output of each laser beam after branching does not reach an assumed value, the amount of fractures extending from the modified region does not reach a desired amount of fractures, and there is a possibility that the object is not divided and does not peel (the processing quality is deteriorated). Therefore, an object of the present invention is to provide a laser processing apparatus and a laser processing method capable of improving processing quality by adjusting the output of the branched light to a desired value.

A laser processing apparatus according to an aspect of the present invention is a laser processing apparatus for forming a modified region in an object by irradiating the object with laser light, including: a light source for emitting laser light; a spatial light modulator for modulating laser light emitted from the light source; a light-condensing unit that condenses the laser light modulated by the spatial light modulator on an object; a detection unit for detecting the reflected light of the laser beam of the object; and a control unit configured to execute: a1 st process of setting and displaying a1 st branch pattern corresponding to an output target value of each of the branched laser beams, which is a branch pattern for branching the laser beams into a plurality of parts, on a spatial light modulator; a2 nd process of controlling the light source to emit the laser light in a state where the 1 st branch pattern is displayed on the spatial light modulator; a 3 rd process of controlling the detection unit to detect the reflected light of each laser beam branched by the 1 st branching pattern; a 4 th process of deriving the brightness of the reflected light of each laser beam after branching based on the detection result of the detection unit; and a 5 th process of generating a2 nd branching pattern in which the 1 st branching pattern is corrected so that the output of each laser beam after branching becomes an output target value, based on the derived brightness.

In the laser processing apparatus according to one aspect of the present invention, the reflected light of each laser beam branched in accordance with the 1 st branching pattern on the object is detected, and the brightness of the reflected light of each branched laser beam is derived based on the detection result. Here, the brightness of the reflected light of each branched laser beam is proportional to the output (beam intensity) of each branched laser beam. Therefore, by deriving the brightness, the output of each laser beam after branching can be estimated with high accuracy. Then, after the outputs of the branched laser beams are accurately estimated from the brightness, a new branch pattern (the 2 nd branch pattern in which the 1 st branch pattern is corrected) is generated so that the outputs of the branched laser beams become output target values, whereby a branch pattern in which the outputs of the branched laser beams (branched light) are adjusted to desired values (output target values) can be generated. As described above, according to the laser processing apparatus according to one aspect of the present invention, the output of the branched light can be adjusted to a desired value, and the processing quality can be improved. Further, if such a correction process of the branch pattern is performed once, the branch pattern (2 nd branch pattern) after the correction is processed by the laser processing, so that the time for generating the branch pattern can be reduced.

The control unit may be further configured to execute: a 6 th process of setting and displaying a2 nd branch pattern on the spatial light modulator; and a 7 th process of controlling the light source so as to emit laser light and process the object in a state where the 2 nd branch pattern is displayed on the spatial light modulator. In this way, by setting a branching pattern (2 nd branching pattern) optimized based on the brightness in the spatial light modulator and actually performing laser processing, it is possible to realize high-quality processing of the object in a state where the output of the branched light is adjusted to a desired value.

The control unit may control the light source so as to irradiate the object with the laser light at an output at which the modified region is not formed in the object in the 2 nd process. This prevents the modified region from being formed in the object at the stage of adjusting the output of the branched light. Thus, high-quality processing of the object can be realized.

The laser processing apparatus may further include an input unit that receives an input from a user, and the control unit may determine an output target value based on information received by the input unit in the 1 st process, and set the 1 st branching pattern corresponding to the determined output target value in the spatial light modulator. This enables setting of a branching pattern according to the condition set by the user. That is, laser processing desired by the user can be realized.

The converging point of the laser light converged by the converging unit may be set on the surface of the incident surface of the laser light as the object, and the detection unit may detect the reflected light on the surface. The brightness of the reflected light reflected at the surface is relatively high. By detecting such reflected light with high luminance, the output estimation of the laser light based on the luminance can be performed with higher accuracy.

The converging point of the laser beam converged by the converging unit may be set on the rear surface of the surface opposite to the incident surface of the laser beam as the object, and the detection unit may detect the reflected light on the rear surface. When laser processing such as lift-off processing is actually performed, a modulation pattern in which a light-converging correction pattern other than the branch pattern is combined is set in the spatial light modulator. In order to measure the brightness of the branched light (output of each branched light) in consideration of the modulation pattern in the spatial light modulator at the actual laser processing, it is preferable to measure the brightness of the reflected light on the back surface. Therefore, by detecting the reflected light on the back surface, it is possible to adjust each branched light output to a desired value in consideration of actual laser processing.

In the 1 st process, the control unit may set the output target values of the branched laser beams to a common value, and set and display a1 st branching pattern corresponding to the common value on the spatial light modulator. In the branching processing, it is sometimes desired to make the output of each laser light after branching uniform. In such a case, as described above, the target output values of the branched laser beams are set to a common value, and the 2 nd branching pattern is generated in the 5 th processing so that the output of the branched laser beams becomes the common value (that is, so that the output of the laser beams becomes uniform), whereby the variation in the output of the branched laser beams can be suppressed, the output of the laser beams of the branched light can be made uniform, and the processing quality can be improved.

A laser processing method according to an aspect of the present invention is a laser processing method for forming a modified region in an object by irradiating the object with laser light, the laser processing method including: a1 st step of setting and displaying a1 st branch pattern corresponding to an output target value of each of the branched laser beams, which is a branch pattern for branching the laser beams into a plurality of parts, on a spatial light modulator; a2 nd step of emitting laser light to the spatial light modulator on which the 1 st branch pattern is displayed, and irradiating the object with the laser light branched into a plurality of parts according to the 1 st branch pattern; a 3 rd step of detecting reflected light from the object of each of the branched laser beams; a 4 step of deriving the brightness of the reflected light of each laser beam after branching based on the detection result of the reflected light; and a 5 th step of generating a2 nd branch pattern in which the 1 st branch pattern is corrected so that the output of each laser beam after branching becomes the output target value, based on the derived brightness.

According to the present invention, the processing quality can be improved by adjusting the output of the branched light to a desired value.

Drawings

Fig. 1 is a perspective view of a laser processing apparatus according to an embodiment.

Fig. 2 is a front view of a part of the laser processing apparatus shown in fig. 1.

Fig. 3 is a front view of a laser processing head of the laser processing apparatus shown in fig. 1.

Fig. 4 is a side view of the laser processing head shown in fig. 3.

Fig. 5 is a structural diagram of an optical system of the laser processing head shown in fig. 3.

Fig. 6 is a plan view for explaining a plurality of modified light spots.

Fig. 7 is a diagram showing an example of a GUI setting screen.

Fig. 8 is a diagram showing an example of the administrator mode of the GUI setting screen.

Fig. 9 is a diagram illustrating laser processing of a comparative example.

Fig. 10 is a table showing the state of the scratches of each branched light.

Fig. 11 is a diagram illustrating laser processing according to the embodiment.

Fig. 12 is a diagram illustrating laser processing according to the embodiment.

Fig. 13 is a table showing an example of correction of the branch pattern based on the derived luminance and a result after the correction.

Fig. 14 is a diagram for explaining the measurement of the brightness with the surface as the focal point.

Fig. 15 is a diagram for explaining the measurement of the luminance with the rear surface as the focal point.

Fig. 16 is a schematic view showing a laser processing state in an actual peeling process.

Fig. 17 is a diagram illustrating determination of the luminance measurement height of the branches uniform in the Z direction.

Fig. 18 is a diagram illustrating determination of the luminance measurement height of the branches that are not uniform in the Z direction.

Fig. 19 is a flowchart showing a process of correcting a branch pattern (generating a correction pattern).

Fig. 20 is a diagram showing a modified region and a fracture formation state extending from the modified region.

Fig. 21 is a diagram illustrating the composition of the AS pattern.

Fig. 22 is a diagram illustrating the synthesis of a slit pattern.

Fig. 23 is a diagram illustrating the composition of the lateral branch pattern.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference numerals, and redundant description thereof is omitted.

First, a basic configuration of a laser processing apparatus will be described.

[ basic Structure of laser processing apparatus ]

As shown in fig. 1, the laser processing apparatus 1 includes a plurality of moving mechanisms 5, 6, a support 7, a pair of laser processing heads 10A, 10B, a light source unit 8, and a control section 9. In addition, although the following description will be given of an example in which the laser processing heads are a pair, the number of the laser processing heads may be only 1. Hereinafter, the 1 st direction is referred to as an X direction, the 2 nd direction perpendicular to the 1 st direction is referred to as a Y direction, and the 3 rd direction perpendicular to the 1 st direction and the 2 nd direction is referred to as a Z direction. In the present embodiment, the X direction and the Y direction are horizontal directions, and the Z direction is a vertical direction.

The moving mechanism 5 has a fixed portion 51, a moving portion 53, and a mounting portion 55. The fixing portion 51 is attached to the apparatus frame 1 a. The moving unit 53 is attached to a rail provided in the fixed unit 51 and is movable in the Y direction. The mounting portion 55 is mounted on a rail provided in the moving portion 53 and is movable in the X direction.

The moving mechanism 6 has a fixed portion 61, a pair of moving

portions

63, 64, and a pair of mounting

portions

65, 66. The fixing portion 61 is attached to the apparatus frame 1 a. The pair of moving

portions

63 and 64 are respectively attached to rails provided on the fixed portion 61 and can independently move in the Y direction. The mounting portion 65 is mounted on a rail provided in the moving portion 63 and is movable in the Z direction. The mounting portion 66 is mounted on a rail provided in the moving portion 64 and is movable in the Z direction. That is, the pair of mounting

portions

65, 66 are movable in the Y direction and the Z direction, respectively, with respect to the apparatus frame 1 a.

The support portion 7 is attached to a rotary shaft provided in the attachment portion 55 of the moving mechanism 5 and is rotatable about an axis parallel to the Z direction as a center line. That is, the support portion 7 is movable in the X direction and the Y direction, respectively, and is rotatable about an axis parallel to the Z direction as a center line. The support portion 7 supports the object 100. The object 100 is, for example, a wafer.

As shown in fig. 1 and 2, the laser processing head 10A is attached to an attachment portion 65 of the moving mechanism 6. The laser processing head 10A irradiates the object 100 supported by the support 7 with the laser light L1 in a state of facing the support 7 in the Z direction. The laser processing head 10B is attached to the attachment 66 of the moving mechanism 6. The laser processing head 10B irradiates the object 100 supported by the support 7 with the laser light L2 in a state of facing the support 7 in the Z direction.

The light source unit 8 has a pair of

light sources

81, 82. The light source 81 outputs laser light L1. The laser light L1 is emitted from the emission portion 81a of the light source 81 and guided to the laser processing head 10A through the optical fiber 2. The light source 82 outputs laser light L2. The laser light L2 is emitted from the emission portion 82a of the light source 82 and guided to the laser processing head 10B through the other optical fiber 2.

The control unit 9 controls each unit (the support unit 7, the plurality of moving mechanisms 5 and 6, the pair of laser processing heads 10A and 10B, the light source unit 8, and the like) of the laser processing apparatus 1. The control unit 9 is configured as a computer device including a processor, a memory, a storage, a communication device, and the like. In the control unit 9, software (program) read into a memory or the like is executed by the processor, and reading and writing of data in the memory or the storage and communication by the communication device are controlled by the processor. Thereby, the control section 9 realizes various functions.

An example of the processing performed by the laser processing apparatus 1 configured as described above will be described. One example of this processing is an example in which a modified region is formed inside an object 100, which is a wafer, along a plurality of lines set in a lattice shape in order to cut the object 100 into a plurality of chips. The laser processing apparatus 1 may perform a peeling process of peeling off a part of the object 100.

First, the moving mechanism 5 moves the support 7 in the X direction and the Y direction, respectively, so that the support 7 supporting the object 100 faces the pair of laser processing heads 10A and 10B in the Z direction. Next, the moving mechanism 5 rotates the support 7 about an axis parallel to the Z direction as a center line so that a plurality of lines extending in one direction in the object 100 are along the X direction.

Next, the moving mechanism 6 moves the laser processing head 10A in the Y direction so that the condensed point (a part of the condensed region) of the laser light L1 is positioned on a line extending in one direction. On the other hand, the moving mechanism 6 moves the laser processing head 10B in the Y direction so that the converging point of the laser light L2 is located on another line extending in one direction. Next, the moving mechanism 6 moves the laser processing head 10A in the Z direction so that the focal point of the laser light L1 is positioned inside the object 100. On the other hand, the moving mechanism 6 moves the laser processing head 10B in the Z direction so that the converging point of the laser light L2 is positioned inside the object 100.

Next, the light source 81 outputs the laser beam L1, the laser machining head 10A irradiates the object 100 with the laser beam L1, the light source 82 outputs the laser beam L2, and the laser machining head 10B irradiates the object 100 with the laser beam L2. At the same time, the moving mechanism 5 moves the support 7 in the X direction so that the focal point of the laser light L1 relatively moves along one line extending in one direction and the focal point of the laser light L2 relatively moves along another line extending in one direction. In this way, the laser processing apparatus 1 forms a modified region in the object 100 along each of a plurality of lines extending in one direction in the object 100.

Next, the moving mechanism 5 rotates the support 7 about an axis parallel to the Z direction as a center line so that a plurality of lines extending in the other direction orthogonal to the one direction in the object 100 are along the X direction.

Next, the moving mechanism 6 moves the laser processing head 10A in the Y direction so that the converging point of the laser light L1 is positioned on a line extending in the other direction. On the other hand, the moving mechanism 6 moves the laser processing head 10B in the Y direction so that the converging point of the laser light L2 is positioned on another line extending in the other direction. Next, the moving mechanism 6 moves the laser processing head 10A in the Z direction so that the focal point of the laser light L1 is positioned inside the object 100. On the other hand, the moving mechanism 6 moves the laser processing head 10B in the Z direction so that the converging point of the laser light L2 is positioned inside the object 100.

Next, the light source 81 outputs the laser beam L1, the laser machining head 10A irradiates the object 100 with the laser beam L1, the light source 82 outputs the laser beam L2, and the laser machining head 10B irradiates the object 100 with the laser beam L2. At the same time, the moving mechanism 5 moves the support 7 in the X direction so that the focal point of the laser light L1 relatively moves along one line extending in the other direction and the focal point of the laser light L2 relatively moves along another line extending in the other direction. In this way, the laser processing apparatus 1 forms the modified region in the object 100 along each of the plurality of lines extending in the other direction orthogonal to the one direction in the object 100.

In the above-described processing example, the light source 81 outputs the laser light L1 that is transmissive to the object 100, for example, by a pulse oscillation method, and the light source 82 outputs the laser light L2 that is transmissive to the object 100, for example, by a pulse oscillation method. When such a laser beam is condensed inside the object 100, the laser beam is particularly absorbed in a portion corresponding to the condensing point of the laser beam, and a modified region is formed inside the object 100. The modified region is a region having a density, refractive index, mechanical strength, and other physical properties different from those of the surrounding unmodified region. Examples of the modified region include a melt-processed region, a crack region, an insulation breakdown region, and a refractive index change region.

When the object 100 is irradiated with the laser light output by the pulse oscillation method and the converging point of the laser light is relatively moved along a line set on the object 100, a plurality of modified spots are formed to be arranged in 1 line along the line. The 1 modified spots are formed by irradiation of 1 pulse of laser light. The 1-column modified region is a set of a plurality of modified light spots arranged in 1 column. The adjacent modified spots may be connected to each other or separated from each other depending on the relative movement speed of the converging point of the laser light with respect to the object 100 and the repetition frequency of the laser light. The shape of the set line is not limited to the lattice shape, and may be a ring shape, a straight line shape, a curved line shape, or a combination of at least any of these.

[ Structure of laser processing head ]

As shown in fig. 3 and 4, the laser processing head 10A includes a housing 11, an incident portion 12, an adjusting portion 13, and a light condensing portion 14.

The housing 11 has 1 st and 2

nd wall portions

21 and 22, 3 rd and 4

th wall portions

23 and 24, and 5 th and 6

th wall portions

25 and 26. The 1 st wall portion 21 and the 2 nd wall portion 22 are opposed to each other in the X direction. The 3 rd wall portion 23 and the 4 th wall portion 24 are opposed to each other in the Y direction. The 5 th wall portion 25 and the 6 th wall portion 26 are opposed to each other in the Z direction.

In the laser processing head 10A, the 1 st wall portion 21 is located on the opposite side of the fixing portion 61 of the moving mechanism 6, and the 2 nd wall portion 22 is located on the fixing portion 61 side. The 3 rd wall portion 23 is located on the mounting portion 65 side of the moving mechanism 6, and the 4 th wall portion 24 is located on the laser processing head 10B side opposite to the mounting portion 65 (see fig. 2). The 5 th wall portion 25 is located on the opposite side of the support portion 7, and the 6 th wall portion 26 is located on the support portion 7 side.

The housing 11 is configured such that the housing 11 is attached to the attachment portion 65 of the moving mechanism 6 in a state where the 3 rd wall portion 23 is disposed on the attachment portion 65 side. Specifically, the following is described. The mounting portion 65 has a bottom plate 65a and a mounting plate 65 b. The bottom plate 65a is attached to a rail provided in the moving unit 63 (see fig. 2). The mounting plate 65B is erected on the end of the base plate 65a on the laser processing head 10B side (see fig. 2). In a state where the 3 rd wall portion 23 is in contact with the attachment plate 65b, the bolt 28 is screwed to the attachment plate 65b via the base 27, whereby the housing 11 is attached to the attachment portion 65. The mounts 27 are provided on the 1 st wall portion 21 and the 2 nd wall portion 22, respectively. The housing 11 is detachable from the mounting portion 65.

Incident portion 12 is attached to 5 th wall portion 25. The incident unit 12 causes the laser beam L1 to enter the housing 11. The incident portion 12 is biased toward the 2 nd wall portion 22 (one wall portion side) in the X direction and biased toward the 4 th wall portion 24 in the Y direction.

The incident portion 12 is configured to be connectable to the connection end portion 2a of the optical fiber 2. A collimator lens for collimating the laser light L1 emitted from the emission end of the optical fiber is provided at the connection end 2a of the optical fiber 2, and no isolator for suppressing the return light is provided. The isolator is provided in the middle of the optical fiber on the light source 81 side of the connection end 2 a. This realizes the miniaturization of the connection end portion 2a and further the miniaturization of the incident portion 12. Further, an isolator may be provided at the connection end portion 2a of the optical fiber 2.

The adjustment portion 13 is disposed in the housing 11. The adjustment unit 13 adjusts the laser light L1 incident from the incident unit 12. Each of the components of the adjustment unit 13 is attached to an optical base 29 provided in the housing 11. The optical base 29 is attached to the housing 11 so as to partition the region inside the housing 11 into a region on the 3 rd wall portion 23 side and a region on the 4 th wall portion 24 side. The optical base 29 is integrated with the housing 11. Each configuration of the adjustment portion 13 is attached to the optical base 29 on the 4 th wall portion 24 side. The details of each configuration of the adjusting unit 13 will be described later.

The light-condensing portion 14 is disposed on the 6 th wall portion 26. Specifically, the light converging portion 14 is disposed on the 6 th wall portion 26 in a state of being inserted through a hole 26a (see fig. 5) formed in the 6 th wall portion 26. The light-condensing unit 14 emits the laser light L1 adjusted by the adjusting unit 13 to the outside of the housing 11 while condensing the laser light. The light collecting portion 14 is biased toward the 2 nd wall portion 22 (toward one wall portion) in the X direction and biased toward the 4 th wall portion 24 in the Y direction.

As shown in fig. 5, the adjusting section 13 has an attenuator 31, a beam expander 32, and a mirror 33. The attenuator 31, the beam expander 32, and the mirror 33 of the incident section 12 and the adjusting section 13 are arranged on a straight line (1 st straight line) a1 extending in the Z direction. The attenuator 31 and the beam expander 32 are disposed between the incident portion 12 and the mirror 33 on a straight line a 1. The attenuator 31 adjusts the output of the laser light L1 incident from the incident unit 12. The beam expander 32 expands the diameter of the laser light L1 whose output is adjusted by the attenuator 31. The mirror 33 reflects the laser light L1 whose diameter is expanded by the beam expander 32.

The adjustment section 13 also has a reflective spatial light modulator 34 and an imaging optical system 35. The reflective spatial light modulator 34, the imaging optical system 35, and the light condensing unit 14 of the adjustment unit 13 are arranged on a straight line (2 nd straight line) a2 extending in the Z direction. The reflective Spatial Light Modulator 34 is, for example, a Spatial Light Modulator (SLM) of a reflective Liquid Crystal (LCOS). The reflective spatial light modulator 34 modulates the laser light L1 reflected by the mirror 33. The reflective spatial light modulator 34 modulates the laser light L1 according to the displayed modulation pattern. A branching pattern for branching at least the laser light L1 into a plurality of beams is set and displayed on the reflective spatial light modulator 34. Thus, the laser light L1 incident on the reflective spatial light modulator 34 is branched into a plurality of laser lights in the reflective spatial light modulator 34 (details will be described later with reference to fig. 6). The imaging optical system 35 constitutes a bilateral telecentric optical system in which the reflection surface 34a of the reflection type spatial light modulator 34 and the entrance pupil surface 14a of the light condensing portion 14 are in an imaging relationship. The imaging optical system 35 is constituted by 3 or more lenses.

The straight line a1 and the straight line a2 are located on a plane perpendicular to the Y direction. The straight line a1 is located on the 2 nd wall portion 22 side (one wall portion side) with respect to the straight line a 2. In the laser processing head 10A, the laser light L1 enters the housing 11 from the entrance section 12, travels on the straight line a1, is sequentially reflected by the mirror 33 and the reflective spatial light modulator 34, travels on the straight line a2, and is emitted from the light collection section 14 to the outside of the housing 11. The order of arrangement of the attenuator 31 and the beam expander 32 may be reversed. The attenuator 31 may be disposed between the mirror 33 and the reflective spatial light modulator 34. The adjusting unit 13 may have another optical component (for example, a steering mirror disposed in front of the beam expander 32).

The laser processing head 10A further includes a dichroic mirror 15, a measuring section 16, a detecting section 17, a driving section 18, and a circuit section 19.

The dichroic mirror 15 is disposed between the imaging optical system 35 and the light collecting unit 14 on the straight line a 2. That is, the dichroic mirror 15 is disposed between the adjustment unit 13 and the light collection unit 14 in the housing 11. The dichroic mirror 15 is attached to the optical base 29 on the 4 th wall portion 24 side. The dichroic mirror 15 transmits the laser light L1. From the viewpoint of suppressing astigmatism, the dichroic mirror 15 is preferably of a cubic type or a 2-plate type arranged so as to have a twisted relationship, for example.

The measuring portion 16 is disposed on the 1 st wall portion 21 side (the side opposite to the one wall portion side) with respect to the adjusting portion 13 in the housing 11. The measurement unit 16 is attached to the optical base 29 on the 4 th wall portion 24 side. The measuring unit 16 outputs measurement light L10 for measuring the distance between the surface of the object 100 (for example, the surface on the side on which the laser light L1 is incident) and the light converging unit 14, and detects the measurement light L10 reflected on the surface of the object 100 via the light converging unit 14. That is, the measurement light L10 output from the measurement unit 16 is irradiated to the surface of the object 100 via the light condensing unit 14, and the measurement light L10 reflected by the surface of the object 100 is detected by the measurement unit 16 via the light condensing unit 14.

More specifically, the measurement light L10 output from the measurement unit 16 is sequentially reflected by the beam splitter 20 and the dichroic mirror 15 attached to the optical base 29 on the 4 th wall portion 24 side, and is emitted from the light collection unit 14 to the outside of the housing 11. The measurement light L10 reflected by the surface of the object 100 enters the housing 11 from the light collecting unit 14, is sequentially reflected by the dichroic mirror 15 and the beam splitter 20, enters the measurement unit 16, and is detected by the measurement unit 16.

The detection unit 17 is disposed on the 1 st wall portion 21 side (the side opposite to the one wall portion side) with respect to the adjustment unit 13 in the housing 11. The detection unit 17 is attached to the optical base 29 on the 4 th wall portion 24 side. The detector 17 outputs observation light L20 for observing the surface of the object 100 (for example, the surface on the side on which the laser light L1 is incident), and detects observation light L20 reflected by the surface of the object 100 via the light condenser 14. That is, the observation light L20 output from the detection unit 17 is irradiated to the surface of the object 100 via the light condensing unit 14, and the observation light L20 reflected by the surface of the object 100 is detected by the detection unit 17 via the light condensing unit 14. The detection unit 17 is, for example, a camera that detects (captures) the reflected observation light L20.

More specifically, the observation light L20 output from the detection unit 17 passes through the beam splitter 20, is reflected by the dichroic mirror 15, and is emitted from the light collection unit 14 to the outside of the housing 11. The observation light L20 reflected by the surface of the object 100 enters the housing 11 from the light collecting unit 14, is reflected by the dichroic mirror 15, passes through the beam splitter 20, enters the detection unit 17, and is detected by the detection unit 17. The laser light L1, the measurement light L10, and the observation light L20 have different wavelengths (at least their center wavelengths are shifted from each other).

The detection unit 17 detects a part of the laser beam L1 reflected by the surface of the object 100 (details will be described later). The part of the laser light L1 reflected on the surface of the object 100 is the laser light L1 that is slightly reflected toward the detector 17 by the dichroic mirror 15, among the laser light L1 reflected on the surface of the object 100.

The driving portion 18 is attached to the optical base 29 on the 4 th wall portion 24 side. The driving unit 18 moves the condensing unit 14 disposed on the 6 th wall 26 in the Z direction by the driving force of the piezoelectric element, for example.

The circuit portion 19 is disposed on the 3 rd wall portion 23 side with respect to the optical base 29 in the housing 11. That is, the circuit portion 19 is disposed on the 3 rd wall portion 23 side with respect to the adjusting portion 13, the measuring portion 16, and the detecting portion 17 in the housing 11. The circuit portion 19 is, for example, a plurality of circuit boards. The circuit unit 19 processes the signal output from the measurement unit 16 and the signal input to the reflective spatial light modulator 34. The circuit unit 19 controls the drive unit 18 based on the signal output from the measurement unit 16. For example, the circuit unit 19 controls the driving unit 18 so as to maintain a constant distance between the surface of the object 100 and the light converging unit 14 (that is, so as to maintain a constant distance between the surface of the object 100 and the light converging point of the laser light L1) based on the signal output from the measurement unit 16. The housing 11 is provided with a connector (not shown) to which wiring for electrically connecting the circuit unit 19 and the control unit 9 (see fig. 1) is connected.

The laser processing head 10B includes a housing 11, an incident portion 12, an adjusting portion 13, a condensing portion 14, a dichroic mirror 15, a measuring portion 16, a detecting portion 17, a driving portion 18, and a circuit portion 19, similarly to the laser processing head 10A. However, as shown in fig. 2, the respective structures of the laser processing head 10B are arranged in a plane-symmetric relationship with the respective structures of the laser processing head 10A with respect to a virtual plane passing through a midpoint between the pair of mounting

portions

65, 66 and perpendicular to the Y direction.

For example, the housing (1 st housing) 11 of the laser processing head 10A is attached to the attachment portion 65 such that the 4 th wall portion 24 is located on the laser processing head 10B side with respect to the 3 rd wall portion 23 and the 6 th wall portion 26 is located on the support portion 7 side with respect to the 5 th wall portion 25. On the other hand, the housing (2 nd housing) 11 of the laser processing head 10B is attached to the attachment portion 66 such that the 4 th wall portion 24 is located on the laser processing head 10A side with respect to the 3 rd wall portion 23 and the 6 th wall portion 26 is located on the support portion 7 side with respect to the 5 th wall portion 25.

The housing 11 of the laser processing head 10B is configured such that the housing 11 is attached to the attachment 66 in a state where the 3 rd wall portion 23 is disposed on the attachment 66 side. Specifically, the following is described. The mounting portion 66 has a bottom plate 66a and a mounting plate 66 b. The bottom plate 66a is attached to a rail provided in the moving portion 63. The attachment plate 66b is provided upright on the end of the base plate 66a on the laser processing head 10A side. The housing 11 of the laser processing head 10B is attached to the attachment portion 66 in a state where the 3 rd wall portion 23 is in contact with the attachment plate 66B. The housing 11 of the laser processing head 10B is detachable from the mounting portion 66.

[ Branch pattern correction processing ]

Next, a process of correcting the branching pattern set and displayed on the reflective spatial light modulator 34 so that the output of each laser beam for which the score is given becomes an output target value when the laser beam is branched and irradiated to the object 100 for the purpose of cutting, peeling, or the like of the object 100 will be described. In the following, a process of correcting the branching pattern so that the output target values of the branched laser beams are a common value and the output of the branched laser beams becomes the common value (that is, so that the output of the laser beams becomes uniform) will be mainly described. This correction processing is performed before the object 100 is formed into the modified region for the purpose of cutting the object or the like.

First, the branching of the laser beam L1 will be described with reference to fig. 6 to 8. As described above, the laser light L1 branches according to the branching pattern set and displayed on the reflective spatial light modulator 34.

Fig. 6 is a diagram illustrating a plurality of modified spots SA in the case where the laser light L1 is branched into 4. In the example shown in fig. 6, the laser light L1 is branched so that a plurality of (4) modified spots SA are formed in the object 100, the modified spots SA being aligned in a line along an oblique direction C2 that is oblique to a direction orthogonal to the machining direction C1. Branching of the laser light L1 is realized by a branching pattern (modulation pattern) set and displayed on the reflective spatial light modulator 34 (see fig. 5).

In the illustrated example, the laser light L1 is branched into 4 beams, and 4 modified spots SA are formed. In the adjacent pair of modified spots SA out of the 4 modified spots SA after branching, the interval in the processing direction C1 is the branching pitch BPx, and the interval in the direction orthogonal to the processing direction C1 is the branching pitch BPy. The interval in the machining direction C1 between the pair of modified spots SA formed by irradiation of the continuous 2-pulse laser light L1 is the pulse pitch PP. The angle between the machining proceeding direction C1 and the oblique direction C2 is a branch angle α.

Fig. 7 is a setting screen of the GUI111 for realizing branching of the laser beam L1 as shown in fig. 6. The GUI111 functions as an input unit that receives an input from a user. The setting screen of the GUI111 shown in fig. 7 includes: a processing condition selection button 211 for selecting a processing condition; a branch number column 212 for inputting or selecting the branch number of the laser light L1; an index column 213 for inputting an index as a distance moved to the next processing line after laser processing along 1 processing line; an impression map 214 for inputting or displaying the number of branches and index; a processing Z-height column 215 for inputting the position of the modified spot SA in the Z direction; a processing speed column 216 for inputting a processing speed; and a condition switching method button 217 for selecting a method of switching the processing conditions.

The machining condition selection button 211 enables selection of a specific machining condition from a plurality of options. According to the index column 213, when the number of branches is 1, the laser processing head 10A is automatically moved in the index direction by the input value. When the number of branches is greater than 1, the laser processing head 10A is automatically moved in the index direction by an index amount based on the following calculation formula.

Index (number of branches) × index input value

The icon 214 includes a display unit 214a for inputting an index input value and an output input field 214b for inputting the output of each modified spot SA.

Fig. 8 is a diagram showing an example of the administrator mode of the setting screen of the GUI 111. The setting screen shown in fig. 8 includes: a branch direction selection button 221 for selecting the branch direction of the laser light L1; a branch number column 222 for inputting or selecting the branch number of the laser light L1; a branch pitch input field 223 for inputting the branch pitch BPx; a branch pitch row number input field 224 for inputting the row number of the branch pitch BPx; a branch pitch input field 225 for inputting the branch pitch BPy; an index bar 226 for inputting an index; an optical axis impression map 227 based on the number of branches; an outgoing/returning selection button 228 for selecting whether the scanning direction of the laser light L1 is one direction (outgoing) or the other direction (returning); and a balance adjustment start button 229 that automatically adjusts the balance of the various values.

The control unit 9 determines the output target value of each laser beam after branching (here, a value common to each laser beam after branching) based on information received from the user in the GUI111, and derives the 1 st branching pattern (modulation pattern) for branching the laser beam L1 in accordance with the determined output target value. In this case, the control section 9 may select 1 branch pattern as the 1 st branch pattern from a plurality of branch patterns prepared in advance, or may newly generate a branch pattern as the 1 st branch pattern based on information received from the user. The control unit 9 sets and displays the derived 1 st branching pattern on the reflective spatial light modulator 34.

As shown in fig. 9 a, when information for branching the laser light L1 into 4 pieces is input from the user to the GUI111, the control unit 9 determines an output target value so that the laser outputs at the branching processing points (the converging points of the branched laser light) are the same (see fig. 9 b), generates (automatically generates) the 1 st branching pattern 340 based on the determined output target value, and sets and displays the 1 st branching pattern 340 on the reflective spatial light modulator 34 (see fig. 9 c). The graphs in fig. 9(b), 9(e), 11(b), 11(e), 12(b), and 12(d) show the output of the laser light (or the brightness of the reflected light) at each converging point of the branched laser light. Then, as shown in fig. 9 d, the laser beam L1 is branched according to the 1 st branching pattern 340 and irradiated to the object 100, and the object 100 is processed (automatic processing). Here, the respective laser beams branching the laser beam L1 according to the 1 st branching pattern 340 are theoretically set to the same output, but actually, as shown in fig. 9(e), it is considered that the outputs (actually input outputs) are not the same.

Fig. 10 is a table showing an example of a marking state (specifically, presence or absence of generation of a modified region) when the object 100 is irradiated with 4 laser beams L1 branched in accordance with the 1 st branching pattern. In fig. 10, the values of the theoretical pulse energy and whether or not a modified region is generated are shown for each of the 4 laser beams after branching (good for the case where a modified region is generated, and good for the case where a modified region is not generated, and x for the case where a modified region is not generated). As shown in fig. 10, even when the laser light L1 is branched in accordance with the 1 st branching pattern set so that the outputs of the respective branched lights are the same, the modified region is generated when the pulse energy is 5.71 μ j or more in the branched lights of the converging point 2 and the converging point 3, whereas the modified region is generated when the pulse energy is 5.96 μ j or more in the branched light of the converging point 3, and the modified region is generated when the pulse energy is 6.48 μ j or more in the branched light of the converging point 1. As described above, even when the laser light L1 is branched so that the outputs of the branched lights are substantially the same, the laser outputs of the branched lights may not be substantially the same. Such a difference in laser output is caused by the influence of individual differences in optical characteristics, such as the difference in the passage area of each of the branched lights in the lens, and it is difficult to completely eliminate the influence of such individual differences. In addition, it is difficult to grasp such individual differences without actually performing laser irradiation.

Therefore, in the laser processing apparatus 1 of the present embodiment, the following correction processing is performed before the processing for forming the modified region in the object 100 is performed: the object 100 is irradiated with laser light branched according to the 1 st branching pattern, the reflected light of the laser light is detected (imaged) to derive the luminance, and the 1 st branching pattern is corrected based on the luminance. Specifically, the laser processing apparatus 1 estimates the output of each of the branched lights based on the brightness, and generates the 2 nd branched pattern as a new branched pattern by correcting the 1 st branched pattern so that the output of the branched light becomes an output target value (here, the output of each of the branched lights is made uniform).

This correction processing is based on the premise that the brightness of the reflected light of the detected (imaged) branched light is proportional to the output (beam intensity) of the branched light. In the example of fig. 10, if the pulse energy of the converging point 2 and the converging point 3 that generate the modified region is 100% (maximum intensity) when the pulse energy is 5.71 μ j or more, the pulse energy of the converging point 4 that generates the modified region when the pulse energy is 5.96 μ j or more is regarded as 96%, and the pulse energy of the converging point 1 that generates the modified region when the pulse energy is 6.48 μ j or more is regarded as 88%, respectively. In this case, as shown in fig. 13(a), if the brightness of the maximum focused spot 3 is set to 100%, the brightness of the reflected light of the branched light detected (imaged) by the detection unit 17 is 89% of the focused spot 1, 98% of the

focused spot

2, and 96% of the focused spot 4. In other words, the intensity of the reflected light is slightly different from the output with respect to the condensed point 1 and the condensed point 3, but it can be said that the brightness of the reflected light is roughly proportional to the output. Therefore, by estimating the output of each of the branched lights based on the brightness and correcting the 1 st branched pattern so that the output of the branched light becomes uniform, it is possible to appropriately reduce the variation in the output of the branched light during the laser processing.

Fig. 11 and 12 are diagrams for explaining the processing of the laser processing apparatus 1 that performs the correction processing described above. As shown in fig. 11 a, when information for branching the laser light L1 into 4 is input from the user to the GUI111, the control unit 9 generates (automatically generates) the 1 st branching pattern 340 so that the laser outputs at the branching processing points (the converging points of the branched laser light) are theoretically the same (see fig. 11 b), and sets and displays the 1 st branching pattern 340 on the reflective spatial light modulator 34 (see fig. 11 c). Then, the laser light L1 is branched in accordance with the 1 st branching pattern 340, each branched light is irradiated to the object 100, and the reflected light (see fig. 11 d) of each branched light in the object 100 is detected (imaged) by the detection unit 17. As shown in fig. 11(d), the control unit 9 derives the brightness of the detected reflected light, and compares the brightness of each point (the brightness of each branched light) (see fig. 11 (e)).

Then, the control unit 9 generates the 2 nd branching pattern 341 in which the 1 st branching pattern 340 is corrected so that the output of the branched light becomes uniform, based on the derived luminance, and sets and displays the 2 nd branching pattern 341 on the reflective spatial light modulator 34 (see fig. 12 (a)). In this case, as shown in fig. 12(b), as the 2 nd branch pattern 341, a modulation pattern is set such that the output of the branch light having a lower luminance is increased as compared with the branch light having a higher luminance. Specifically, for example, as shown in fig. 13(a), if the brightness of the maximum focused spot 3 is 100%, the brightness of the focused spot 1 is 89%, the brightness of the focused spot 2 is 98%, and the brightness of the focused spot 4 is 96%, as shown in fig. 13(b), the pulse energy of the focused spot 1 is 100% (maximum intensity) in the 2 nd branch pattern, taking into account the magnitude and difference of the brightness, and the pulse energy of the focused spot 1 is adjusted so that the pulse energy of the focused spot 2 is 91%, the pulse energy of the focused spot 3 is 89%, and the pulse energy of the focused spot 4 is 93%. In this example, the 2 nd branch pattern is generated such that the value obtained by multiplying the value of% of the luminance before the correction by the value of% of the pulse energy of the 2 nd branch pattern (after the correction) is the same at all the converging points.

The object 100 is processed by branching the laser beam L1 with the 2 nd branching pattern 341 set in this manner and irradiating the object 100 with the branched light (see fig. 12 c). In this case, as shown in fig. 12 d, the object 100 is machined while the outputs (actual input outputs) of the respective branched lights during machining are set to be the same. For example, when the luminance is measured as shown in fig. 13(a) and the branch pattern is corrected as shown in fig. 13(b), the modified region is generated when the pulse energy of any converging point is 5.71 μ j or more as shown in fig. 13 (c). In this way, by uniformizing the output of each branched light by the 2 nd branching pattern, the generation conditions of the modified regions for each branched light can be made the same. This suppresses variation in the amount of fractures extending from the modified region, suppresses occurrence of undivided objects and non-peeling, and improves the processing quality.

The function of the control unit 9 for realizing the branch pattern correction process will be described below.

The control unit 9 is configured to execute the following processing: a1 st process of setting and displaying a1 st branching pattern corresponding to an output target value of each of the branched laser beams, which is a branching pattern for branching the laser beam L1 into a plurality of parts, on the reflective spatial light modulator 34; a2 nd process of controlling the light source unit 8 to emit laser light L1 in a state where the reflective spatial light modulator 34 displays the 1 st branch pattern; a 3 rd process of controlling the detection unit 17 to detect the reflected light of each laser beam branched by the 1 st branching pattern; a 4 th process of deriving the brightness of the reflected light of each laser beam after branching based on the detection result of the detection unit 17; and a 5 th process of generating a2 nd branching pattern in which the 1 st branching pattern is corrected so that the output of each laser beam after branching becomes an output target value, based on the derived luminance.

In the process 1, the control unit 9 determines an output target value based on information received on the setting screen (see fig. 7 and 8) of the GUI111, and sets the 1 st branching pattern corresponding to the determined output target value in the reflective spatial light modulator 34. The control unit 9 sets the output target values of the branched laser beams to a common value, sets the 1 st branching pattern corresponding to the common value, and displays the pattern on the reflective spatial light modulator 34. In this case, the 1 st branching pattern is a branching pattern in which outputs of the laser beams after the branching are theoretically the same as each other.

In the process 2, the control unit 9 controls the light source unit 8 to irradiate the laser light L1 with an output (below the modification threshold) such that no modified region is formed in the object 100, while the reflective spatial light modulator 34 displays the 1 st branch pattern. Further, the branched laser beam may be irradiated to an object (object for correction) different from the object 100 subjected to the laser processing after the branching pattern correction processing.

In the process 2, the control unit 9 may control the moving mechanism 6 so that the laser processing head 10A moves in the Z direction, and set the converging point of each of the branched laser beams on the surface 100A (see fig. 14) which is the incident surface of the laser beam on the object 100. In this case, the detection portion 17 detects the reflected light on the surface 100 a. The brightness of the reflected light reflected at the surface 100a is relatively high. By detecting such reflected light with high luminance, it is possible to estimate the output of the laser light with high accuracy.

Alternatively, the control unit 9 may control the movement mechanism 6 to move the laser processing head 10A in the Z direction, thereby setting the converging point of each of the branched laser beams to the back surface 100b, which is the surface opposite to the front surface 100A, which is the incident surface of the laser beam of the object 100 (see fig. 15). In this case, the detection unit 17 detects the reflected light on the back surface 100 b. Fig. 16 is a schematic view showing a laser processing state in an actual peeling process. As shown in fig. 16, when laser processing such as lift-off processing is actually performed, the reflective spatial light modulator 34 is set with not only a branching pattern but also a modulation pattern in which a condensed light correction pattern or the like corresponding to the depth (Z height) of the condensed point is combined. In this regard, as shown in fig. 15, when the rear surface 100b is a converging point, the reflection type spatial light modulator 34 is set with a modulation pattern in which a branching pattern and a converging correction pattern corresponding to the thickness t of the object 100 are combined to detect the brightness, and therefore, similarly to laser processing such as actual peeling processing, the brightness of the reflected light of each laser beam after branching can be detected in consideration of the converging correction pattern. This makes it possible to determine the brightness (i.e., laser output) in an environment similar to that in actual laser processing.

The control unit 9 may determine the luminance measurement height based on the intensity of the reflected light detected (imaged) by the detection unit 17 while moving the laser processing head 10A in the Z direction by controlling the movement mechanism 6. That is, as shown in fig. 17, the control unit 9 may determine, as the luminance measurement height, a Z height at which the intensity (luminance) of all the branched lights becomes large when the branched lights are branched to the same height in the Z direction. As shown in fig. 18, when the branched lights are branched at different heights in the Z direction, the control unit 9 may determine the Z height at which the intensity is increased as the luminance measurement height for each of the branched lights. In addition, when the deviation amount of the light converging position can be determined in advance, the control unit 9 may determine the final luminance measurement height in consideration of the deviation amount with respect to the determined luminance measurement height. The amount of deviation is, for example, a deviation due to chromatic aberration of the objective lens of the reticle used for setting the height.

In the 3 rd process, the control unit 9 controls the detection unit 17 so that the reflected light of each of the branched laser beams on the object 100 can be detected (imaged) at least while each of the branched laser beams is irradiated on the object 100. The control unit 9 acquires the image captured by the detection unit 17 from the detection unit 17.

In the 4 th process, the control unit 9 specifies a region having a higher luminance than the other regions according to the number of branches in the imaging data acquired by the detection unit 17. The region here is a region that also includes a region around the point of highest brightness. Then, the control unit 9 derives the brightness in consideration of the surrounding brightness for the region corresponding to each branched light.

The control unit 9 is configured to further execute: a 6 th process of setting and displaying a2 nd branch pattern on the reflective spatial light modulator 34; and a 7 th process of controlling the light source unit 8 so as to emit the laser light L1 to process the object 100 in a state where the 2 nd branch pattern is displayed on the reflective spatial light modulator 34.

Next, the branch pattern correction process will be described with reference to a flowchart of fig. 19.

As shown in fig. 19, in the branch pattern correction process, first, the 1 st branch pattern is derived based on the information received on the setting screen of the GUI111, and the 1 st branch pattern is set and displayed on the reflective spatial light modulator 34 (step S1: step 1).

Then, the laser beam L1 is emitted to the reflective spatial light modulator 34 on which the 1 st branch pattern is displayed, and the laser beam branched into a plurality according to the 1 st branch pattern is irradiated to the front surface 100a or the back surface 100b of the object 100 (step S2: 2 nd step).

Subsequently, the detection unit 17 detects (images) the reflected light of the branched light from the front surface 100a or the back surface 100b (step S3: step 3). Then, based on the imaging data (detection result of the reflected light), the brightness at the converging point of each branched laser beam is measured (step S4: step 4).

Finally, a correction pattern (2 nd branch pattern) in which the 1 st branch pattern is corrected is generated based on the derived luminance data so that the output of each laser beam after branching becomes an output target value (when the output target values are a common value, the output is made uniform) (step S5: step 5).

Next, the operational effects of the laser processing apparatus 1 of the present embodiment will be described.

The laser processing apparatus 1 of the present embodiment is a laser processing apparatus for forming a modified region in an object 100 by irradiating the object 100 with laser light, and includes: a light source unit 8 that emits laser light; a reflective spatial light modulator 34 that modulates laser light emitted from the light source unit 8; a light-condensing unit 14 for condensing the laser light modulated by the reflective spatial light modulator 34 on the object 100; a detection unit 17 for detecting the reflected light of the laser beam from the object 100; and a control unit 9, the control unit 9 including: a1 st process of setting and displaying on the reflective spatial light modulator 34a 1 st branching pattern corresponding to an output target value of each of the branched laser beams, which is a branching pattern for branching the laser beams into a plurality of parts; a2 nd process of controlling the light source unit 8 so that laser light is emitted in a state where the reflective spatial light modulator 34 displays the 1 st branch pattern; a 3 rd process of controlling the detection unit 17 to detect the reflected light of each laser beam after branching by the 1 st branching pattern; a 4 th process of deriving the brightness of the reflected light of each laser beam after branching based on the detection result of the detection unit 17; and a 5 th process of generating a2 nd branching pattern in which the 1 st branching pattern is corrected so that the output of each laser beam after branching becomes an output target value, based on the derived brightness.

In the laser processing apparatus 1 of the present embodiment, the reflected light of each laser beam branched in accordance with the 1 st branching pattern on the object 100 is detected, and the brightness of the reflected light of each branched laser beam is derived based on the detection result. Here, the brightness of the reflected light of each branched laser beam is proportional to the output (beam intensity) of each branched laser beam. Therefore, by deriving the brightness, the output of each laser beam after branching can be estimated with high accuracy. Then, after the output of each laser beam after branching is estimated with high accuracy from the brightness, a new branching pattern (the 2 nd branching pattern in which the 1 st branching pattern is corrected) is generated so that the output of each laser beam after branching becomes an output target value, whereby a branching pattern in which the output of each laser beam after branching (branched light) is adjusted to a desired value (output target value) can be generated. As described above, according to the laser processing apparatus 1 of the present embodiment, the output of the branched light can be adjusted to a desired value, and the processing quality can be improved.

The control unit 9 may be configured to further execute: a 6 th process of setting and displaying a2 nd branch pattern on the reflective spatial light modulator 34; and a 7 th process of controlling the light source unit 8 so as to emit laser light in a state where the 2 nd branch pattern is displayed on the reflective spatial light modulator 34, thereby processing the object 100. In this way, by setting the branching pattern (2 nd branching pattern) optimized based on the brightness in the reflective spatial light modulator 34 and actually performing the laser processing, it is possible to realize high-quality processing of the object 100 while adjusting the output of the branching light to a desired value.

The control unit 9 may control the light source unit 8 so as to irradiate the object 100 with the laser light at an output at which the modified region is not formed in the 2 nd process. This prevents the modified region from being formed in the object 100 at the stage of adjusting the output of the branched light. This enables high-quality processing of the object 100.

The laser processing apparatus 1 may further include a GUI111 that receives an input from a user, and the control unit 9 may determine an output target value based on information received by the GUI111 in the 1 st process, and set the 1 st branching pattern corresponding to the determined output target value in the reflective spatial light modulator 34. This enables setting of a branching pattern according to the condition set by the user. That is, laser processing desired by the user can be realized.

The converging point of the laser beam converged by the converging unit 14 may be set on the surface 100a, which is the incident surface of the laser beam of the object 100, and the detection unit 17 may detect the reflected light on the surface 100 a. The brightness of the reflected light reflected by the surface 100a is relatively high. By detecting such reflected light with high luminance, the output estimation of the laser light based on the luminance can be performed with higher accuracy.

The converging point of the laser light converged by the converging unit 14 may be set on the rear surface 100b, which is the surface opposite to the front surface 100a of the object 100, and the detection unit 17 may detect the reflected light on the rear surface 100 b. When laser processing such as lift-off processing is actually performed, a modulation pattern in which a light-converging correction pattern other than the branch pattern is combined is set in the reflective spatial light modulator 34. In this way, the brightness of the branched light (output of each branched light) in consideration of the modulation pattern in the reflective spatial light modulator 34 at the actual laser processing is preferably measured, and the brightness of the reflected light on the back surface 100b is preferably measured. Therefore, by detecting the reflected light on the back surface 100b, the output of each branched light can be adjusted to a desired value in consideration of actual laser processing.

As described mainly in the present embodiment, the control unit 9 may set the output target values of the laser beams after branching to a common value in the 1 st processing, and set and display the 1 st branching pattern corresponding to the common value on the reflective spatial light modulator 34. In the branching processing, it is sometimes desired to make the output of each laser light after branching uniform. In such a case, as described above, the target output values of the branched laser beams are set to a common value, and the 2 nd branching pattern is generated in the 5 th processing so that the output of the branched laser beams becomes the common value (that is, so that the output of the laser beams becomes uniform), whereby the variation in the output of the branched laser beams can be suppressed, the output of the laser beams of the branched light can be made uniform, and the processing quality can be improved.

The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments. For example, in the above-described embodiment, the 2 nd branching pattern is mainly generated so that the output target values of the branched laser beams are a common value and the output of the branched laser beams is the common value (that is, so that the output of the laser beams is uniform). In this case, too, the 2 nd branching pattern is generated based on the brightness so that the output of each laser beam after branching becomes the output target value of each laser beam, whereby the output of the branched light can be adjusted to a desired value and the processing quality can be improved.

For example, the object 100 to be measured for brightness may be a mirror wafer (a bare wafer without a pattern) or an actual device (a wafer with a pattern) to which a peeling process or the like is actually performed. In an actual device, a multilayer film of SiN, SiO2, or the like may be provided on the laser light incident surface side, but it is considered that the reflectance is lower than that of a mirror wafer due to the influence of multiple reflections in the multilayer film. For example, the reflectivity of 1099nm laser light is about 30% in a mirror wafer, whereas the reflectivity of laser light of the same wavelength is reduced to about 8% in an actual device provided with a SiN film of 100 nm. Therefore, in such an actual device, it is considered that the luminance measurement value is decreased. In this regard, for example, when determining the variation in the output of each branched light, it is sufficient if the relative comparison of the luminance of each point is possible, and therefore, the decrease in the luminance measurement value due to the decrease in the reflectance hardly becomes a problem. However, when the amount of reflected light is so low that the luminance cannot be measured, it is necessary to perform correction for increasing the laser output at the time of measurement. In this case, the attenuator may be variably set to an output having a luminance value optimum for measurement while monitoring the luminance value, or the luminance value (reflectance) of the mirror wafer and the optimum luminance value may be grasped in advance, and the output corresponding to the amount of variation in the luminance value may be adjusted.

When the above-described process 7 (processing of the object by the laser beam) is performed using an actual device, the output setting correction may be performed in consideration of the above-described reflectance.

As described above, an example of laser processing using the laser processing apparatus 1 is processing for forming a modified region inside the object 100 along a plurality of lines set in a lattice shape in order to cut the object 100, which is a wafer, into a plurality of chips. An example of the processing conditions for this processing is shown below. In this processing, 2 rows of modified regions are formed in the object 100 in the thickness direction. The modified regions in 2 rows may be formed by irradiating each with laser light, or may be formed by branching the processing points 2 by 2 times of scanning using a 2-focus branching pattern.

Material to be processed: a silicon wafer; thickness of the wafer: 300 mu m; crystal orientation: < 100 >; resistance value: 1 omega cm or more

Laser wavelength of the laser processing apparatus 1: 1099 nm; pulse width: 700 nsec; frequency: 120 kHz; the speed of the workbench: 800 mm/sec; pulse interval: 6.67 μm

Depth (Z height) of converging point of SD1 as the modified region on the side far from the incident surface: z64; and (3) outputting: 2.78W; display pattern of spatial light modulator: using spherical aberration correction patterns

Depth (Z height) of converging point of SD2 as the modified region on the side closer to the incident surface: z24; and (3) outputting: 1.85W; display pattern of spatial light modulator: using spherical aberration correction patterns

Fig. 20(a) is a diagram showing the modified

regions

12a, 12b and the formation states of fractures 14 extending from the modified

regions

12a, 12b when the object 100 is machined under the machining conditions. In the example shown in fig. 20(a), it cannot be said that the modified

regions

12a and 12b and the fractures 14 extending from the modified

regions

12a and 12b are formed in good condition. Specifically, the formation state of the fracture 14 or the like shown in fig. 20(a) is not said to be good compared with the formation states of the modified

regions

12a, 12b and the fractures 14 extending from the modified

regions

12a, 12b shown in fig. 20 (b). As shown in fig. 20(b), by forming the crack 14 or the like well, unevenness (end surface unevenness) at the time of cutting is reduced, and cutting with high straightness can be performed. Further, suppressing the unevenness of the end face has an effect of preventing the remaining of cracks at the time of division, an effect of reducing the occurrence rate of modified layer pieces (silicon microparticles) generated from the divided face, an effect of improving the flexural strength, and the like. In the following, an example will be described in which, in order to realize the formation state of the crack 14 and the like shown in fig. 20(b), a predetermined pattern is synthesized in the spatial light modulator in addition to the above-described processing conditions, and processing is performed in a state where the predetermined pattern is displayed.

Fig. 21 is a diagram illustrating an example of combining AS patterns AS the patterns to which astigmatism is applied AS the predetermined patterns described above. Fig. 21 shows the shape of the light flux L150 at the condensing point. In the example shown in fig. 21, the intensity distribution of the light beam L150 is an elliptical shape by combining AS patterns to which astigmatism is applied, and more specifically, the processing direction is an elliptical shape such AS the longitudinal direction. When the ellipticity is defined as the ratio of the major axis/minor axis of the beam shape, the ellipticity of the elliptical shape is, for example, 1.5. In this way, by combining the AS patterns, the laser beam becomes elliptical in the machining direction, and thus cutting with higher linearity can be performed. The effect of improving the straightness is exhibited by setting the ellipticity to 1.05 or more, for example.

Fig. 22 is a diagram illustrating an example in which a slit pattern is synthesized as the predetermined pattern. The slit pattern here refers to a pattern obtained by cutting both end portions in a direction intersecting the processing direction in the laser beam. That is, for example, when the machining direction is set to the left-right direction, the slit pattern cuts the end portion of the laser beam in the up-down direction. In the example shown in fig. 22, when the direction from left to right in the drawing is the machining direction, the upper and lower ends of the light beam L180 are cut by the

slit patterns

500 and 600. The size of the region to be cut here may be, for example, about 10% of the entire beam. By combining slit patterns that cut both end portions in the direction intersecting the direction of progress of the processing in this way, the beam shape can be cut with high straightness AS in the case of combining the AS patterns described above.

Fig. 23 is a diagram illustrating an example of synthesizing a lateral branch pattern as the predetermined pattern described above. Here, the lateral branching means that the laser beam is branched in a direction intersecting the thickness direction (Z direction) of the object 100, and more specifically, in the processing direction. In the example shown in fig. 23, the pulse pitch was set to 6.67 μm, and a lateral branch pattern in which the light beams were branched in the machining direction was synthesized, and a lateral branch pattern in which the distance between the 2 light beams was 3 μm was set as a branch. In this case, the distance between the light beams L201 and L202 branched into 2 is 3 μm, the distance between the light beams L201 and L203 (pulse pitch) is 6.67 μm, and the distance between the light beams L203 and L204 branched into 2 is 3 μm. In this way, the straightness can be improved by performing the machining so as to branch in the lateral direction at a distance smaller than the pulse pitch.

The predetermined patterns described above can improve the linearity even when used individually, but may further improve the linearity when used in combination. The effect of the predetermined pattern described above can be achieved without using a spatial light modulator. That is, for example, the same effect AS the AS pattern can be achieved by a cylindrical lens, and the same effect AS the slit pattern can be achieved by cutting the end of the beam with a mechanical knife.

Claims

1. A laser processing apparatus is characterized in that,

a laser processing apparatus for forming a modified region in an object by irradiating the object with laser light,

the method comprises the following steps:

a light source for emitting the laser light;

a spatial light modulator for modulating the laser light emitted from the light source;

a light-condensing unit that condenses the laser light modulated by the spatial light modulator on the object;

a detection unit that detects reflected light of the laser beam from the object; and

a control part for controlling the operation of the display device,

the control unit is configured to execute:

a1 st process of setting and displaying a1 st branch pattern corresponding to an output target value of each of the branched laser beams, which is a branch pattern for branching the laser beams into a plurality of parts, on the spatial light modulator;

a2 nd process of controlling the light source so as to emit the laser light in a state where the 1 st branch pattern is displayed on the spatial light modulator;

a 3 rd process of controlling the detection unit so as to detect the reflected light of each laser beam branched by the 1 st branching pattern;

a 4 th process of deriving the brightness of the reflected light of each of the branched laser beams based on a detection result of the detection unit; and

and a 5 th process of generating a2 nd branch pattern in which the 1 st branch pattern is corrected so that the output of each of the branched laser beams becomes the output target value, based on the derived brightness.

2. Laser processing apparatus according to claim 1,

the control unit is configured to further execute:

a 6 th process of setting and displaying the 2 nd branch pattern on the spatial light modulator; and

and a 7 th process of controlling the light source so as to emit the laser beam and process the object in a state where the 2 nd branch pattern is displayed on the spatial light modulator.

3. Laser processing apparatus according to claim 1 or 2,

the control unit controls the light source so that the laser light is irradiated at an output at which a modified region is not formed in the object in the process 2.

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

the laser processing apparatus further includes an input section that receives an input from a user,

the control unit determines the output target value based on the information received by the input unit in the 1 st process, and sets the 1 st branch pattern corresponding to the determined output target value in the spatial light modulator.

5. The laser processing apparatus according to any one of claims 1 to 4,

the converging point of the laser beam converged by the converging unit is set on the surface of the incident surface of the laser beam as the object,

the detection section detects the reflected light on the surface.

6. The laser processing apparatus according to any one of claims 1 to 4,

the converging point of the laser beam converged by the converging unit is set on the back surface of the surface opposite to the incident surface of the laser beam as the object,

the detection section detects the reflected light on the back surface.

7. The laser processing apparatus according to any one of claims 1 to 6,

in the 1 st process, the control unit sets the output target values of the branched laser beams to a common value, and sets and displays the 1 st branching pattern corresponding to the common value on the spatial light modulator.

8. A laser processing method is characterized in that,

a laser processing method for forming a modified region in an object by irradiating the object with a laser beam,

the method comprises the following steps:

a1 st step of setting and displaying a1 st branch pattern corresponding to an output target value of each of the branched laser beams, the 1 st branch pattern being a branch pattern for branching the laser beams into a plurality of parts, on a spatial light modulator;

a2 nd step of emitting laser light to the spatial light modulator on which the 1 st branch pattern is displayed, and irradiating an object with the laser light branched into a plurality of parts according to the 1 st branch pattern;

a 3 rd step of detecting reflected light from the object of each of the branched laser beams;

a 4 th step of deriving the brightness of the reflected light of each of the branched laser beams based on the detection result of the reflected light; and

and a 5 th step of generating a2 nd branching pattern in which the 1 st branching pattern is corrected so that the output of each of the branched laser beams becomes the output target value, based on the derived brightness.