Laser processing apparatus and laser processing method

Abstract

A laser processing apparatus includes a light source unit, a reflection-type spatial light modulator, a condensing section, a detection section, and a control section, the control section performing: a first process of causing a first branch pattern that branches laser light into a plurality of pieces to be displayed on the reflection-type spatial light modulator; a second process of controlling the light source unit in a manner that laser light is emitted in a state where the first branch pattern is displayed on the reflection-type spatial light modulator; a third process of controlling the detection section in a manner that reflected light of each of the pieces of laser light branched by the first branch pattern is detected; a fourth process of deriving luminance of the reflected light of each of the pieces of laser light branched based on a detection result of the detection section; and a fifth process of generating a second branch pattern in which the first branch pattern is corrected, in a manner that outputs of the pieces of laser light branched are homogenized, based on the derived luminance.

Description

TECHNICAL FIELD

[0001] The present application relates to a laser processing apparatus and a laser processing method. BACKGROUND

[0002] In Japanese Patent No. 6620976, a laser processing apparatus including a laser light source, a spatial light modulator, and a condensing correction unit different from the spatial light modulator is described. Such a laser processing apparatus forms a modification region in the inside of an object (wafer) by irradiation of laser light, thereby performing division and peeling of the object, and the like. In the technology described in Patent Literature 1 (Japanese Patent No. 6620976), a modification region is formed in the inside of an object by irradiation of laser light, and a part of reflected light from a condensing point is imaged, and a positional deviation amount of the condensing point is detected based on the imaging result, and a modulation pattern in the spatial light modulator is adjusted so as to make the positional deviation small. SUMMARY

[0003] In the laser processing apparatus as described above, sometimes a branch pattern is set in the spatial light modulator, and laser light is branched in accordance with the branch pattern, so as to form a plurality of modification regions at the same time. The branch pattern is set, for example, in accordance with an output target value of each laser light after branching. Here, in the case where branch processing is performed, for example, due to the influence of individual differences of optical characteristics such as the fact that the passing regions of each branch light in the lens are different from each other, it is difficult to make the output of each laser light after branching coincide with the above-described output target value. The output of each laser light after branching does not become the intended value, and thus the amount of cracks extending from the modification region does not become the desired amount of cracks, and it is possible that the object is not divided and peeled (deterioration of processing quality). Therefore, a technical problem of the present application is to provide a laser processing apparatus and a laser processing method capable of improving the processing quality by adjusting the output of branch light to the desired value.

[0004] The laser processing apparatus of one embodiment of the present application is a laser processing apparatus that forms a modified region in an object by irradiating the object with laser light, and includes a light source that emits laser light; a spatial light modulator that modulates the laser light emitted from the light source; a 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 light from the object; and a control unit that is configured to perform: a first process of setting and displaying, on the spatial light modulator, a first branch pattern that is a branch pattern for branching the laser light into a plurality of pieces and that corresponds to an output target value of each of the branched laser lights; a second process of controlling the light source so that the laser light is emitted in a state where the first branch pattern is displayed on the spatial light modulator; a third process of controlling the detection unit so that reflected light of each of the branched laser lights using the first branch pattern is detected; a fourth process of deriving luminance of the reflected light of each of the branched laser lights on the basis of a detection result of the detection unit; and a fifth process of generating a second branch pattern in which the output of each of the branched laser lights becomes the output target value, on the basis of the derived luminance, and in which the first branch pattern is corrected.

[0005] In the laser processing apparatus of one embodiment of the present application, reflected light of each of the laser lights branched in accordance with the first branch pattern from the object is detected, and luminance of the reflected light of each of the branched laser lights is derived on the basis of a detection result. Here, the luminance of the reflected light of each of the branched laser lights is proportional to the output (beam intensity) of each of the branched laser lights. Thus, by deriving the luminance, the output of each of the branched laser lights can be estimated with high accuracy. Then, on the basis of the output of each of the branched laser lights estimated with high accuracy in accordance with the luminance, a new branch pattern (the second branch pattern in which the first branch pattern is corrected) in which the output of each of the branched laser lights becomes the output target value is generated, whereby a branch pattern in which the output of each of the branched laser lights (branch light) is adjusted to a desired value (output target value) can be generated. As described above, according to the laser processing apparatus of one embodiment of the present application, the output of the branch light can be adjusted to a desired value, and the processing quality can be improved. In addition, if such a correction process of the branch pattern is performed once, the object is processed using the corrected branch pattern (the second branch pattern) in laser processing thereafter, so the time for generating the branch pattern can be reduced.

[0006] The control unit can be configured to further perform: a sixth process of setting and displaying the second branch pattern on the spatial light modulator; and a seventh process of controlling the light source so that the object is processed in a state where the laser light is emitted with the second branch pattern displayed on the spatial light modulator. In this case, the branch pattern (the second branch pattern) that is appropriate on the basis of the luminance is set on the spatial light modulator, and laser processing is actually performed, whereby high-quality processing of the object can be achieved in a state where the output of the branch light is adjusted to a desired value.

[0007] The control section can also control the light source in the second process so that the laser is irradiated at an output at which the object does not form a modified region. Thus, it is possible to prevent a modified region from being formed in the object at the stage of adjusting the outputs of the branched lights. Thus, it is possible to achieve high-quality processing of the object.

[0008] The laser processing apparatus described above can also include an input section that receives an input from a user, and the control section can determine the output target value based on information received by the input section in the first process, and set the first branch pattern corresponding to the determined output target value to the spatial light modulator. Thus, it is possible to set a branch pattern corresponding to a condition set by the user. That is, it is possible to achieve laser processing desired by the user.

[0009] The focal point of the laser light condensed by the condensing section can be set to a surface of a surface opposite to the surface of the laser light incident surface as the object, and the detection section can detect the reflected light on the back surface. The reflected light reflected on the surface has a relatively high brightness. By detecting such reflected light having a high brightness, it is possible to more accurately perform the output estimation of the laser light based on the brightness.

[0010] The focal point of the laser light condensed by the condensing section can be set to a surface of a surface opposite to the surface of the laser light incident surface as the object, and the detection section can detect the reflected light on the back surface. The reflected light reflected on the surface has a relatively high brightness. By detecting such reflected light having a high brightness, it is possible to more accurately perform the output estimation of the laser light based on the brightness.

[0011] The control section can also set the output target value of each of the branched laser lights to a common value in the first process, and set and display the first branch pattern corresponding to the common value to the spatial light modulator. In the branching process, it is sometimes desired to uniformize the outputs of the branched laser lights. In such a case, as described above, the output target value of each of the branched laser lights is set to a common value, and the second branch pattern is generated in the fifth process so that the outputs of the branched laser lights become the common value (i.e., so that the outputs of the laser lights are uniformized), whereby it is possible to suppress the deviation of the outputs of the branched laser lights, uniformize the outputs of the laser lights of the branched light, and improve the processing quality.

[0012] The laser processing method of one embodiment of the present application is a laser processing method of forming a modified region in an object by irradiating laser light to the object, including: a first step of setting and displaying, on a spatial light modulator, a first branch pattern as a branch pattern of branching laser light into a plurality of pieces, the first branch pattern corresponding to an output target value of each of the branched laser lights; a second step of emitting laser light to the spatial light modulator on which the first branch pattern is displayed, and irradiating the laser light branched into a plurality of pieces according to the first branch pattern to the object; a third step of detecting reflected light from the object of each of the branched laser lights; a fourth step of deriving the brightness of the reflected light of each of the branched laser lights on the basis of the detection result of the reflected light; and a fifth step of generating a second branch pattern in which the output of each of the branched laser lights is the output target value, by correcting the first branch pattern, on the basis of the derived brightness.

[0013] According to the present application, by adjusting the output of the branched light to a desired value, the processing quality can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is a perspective view of a laser processing apparatus of an embodiment.

[0015] Figure 2 is a front view of a laser processing apparatus. Figure 1

[0016] Figure 3 is a front view of a laser processing head of a laser processing apparatus. Figure 1

[0017] Figure 4 is a side view of a laser processing head. Figure 3

[0018] Figure 5 is a structure diagram of an optical system of a laser processing head. Figure 3

[0019] Figure 6 is a plan view for explaining a plurality of modified light points.

[0020] Figure 7 is a diagram showing one example of a setting screen of a GUI.

[0021] Figure 8 is a diagram showing an example of a manager mode of a setting screen of a GUI.

[0022] Figure 9 is a diagram showing laser processing of a comparative example.

[0023] Figure 10 is a table showing the marking state of each branched light.

[0024] ​​​​Figure 11 is a diagram illustrating laser processing of an embodiment.

[0025] Figure 12 is a diagram illustrating laser processing of an embodiment.

[0026] Figure 13 is a table showing one example of correction of a branching pattern based on derived luminance and a result of correction.

[0027] Figure 14 is a diagram illustrating luminance measurement with a surface as a light condensing point.

[0028] Figure 15 is a diagram illustrating luminance measurement with a back surface as a light condensing point.

[0029] Figure 16 is a schematic diagram showing a state of laser processing in actual peeling processing.

[0030] Figure 17 is a diagram illustrating determination of a luminance measurement height of a branching that is uniform in the Z direction.

[0031] Figure 18 is a diagram illustrating determination of a luminance measurement height of a branching that is not uniform in the Z direction.

[0032] Figure 19 is a flowchart showing a correction (generation of a correction pattern) process of a branching pattern.

[0033] Figure 20 is a diagram showing a state of formation of a modification region and a crack extending from the modification region.

[0034] Figure 21 is a diagram illustrating synthesis of an AS pattern.

[0035] Figure 22 is a diagram illustrating synthesis of a slit pattern.

[0036] Figure 23 is a diagram illustrating synthesis of a horizontal branching pattern. DETAILED DESCRIPTION

[0037] Hereinafter, an embodiment of the present application will be explained in detail with reference to the drawings. In each drawing, the same or equivalent parts are denoted by the same reference symbols, and repeated explanation is omitted.

[0038] First, the basic structure of a laser processing apparatus will be explained.

[0039] [BASIC STRUCTURE OF LASER PROCESSING APPARATUS]

[0040] As shown in FIG. 1, the laser processing apparatus 1 includes a laser processing device 2, a control device 3, and a display device 4. Figure 1As shown, the laser processing apparatus 1 includes a plurality of moving mechanisms 5, 6, a support section 7, a pair of laser processing heads 10A, 10B, a light source unit 8, and a control section 9. Note that the following describes an example in which the laser processing heads are a pair, but the laser processing heads can be only one. Hereinafter, a first direction is referred to as an X direction, a second direction perpendicular to the first direction is referred to as a Y direction, and a third direction perpendicular to the first direction and the second 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.

[0041] The moving mechanism 5 has a fixed section 51, a moving section 53, and a mounting section 55. The fixed section 51 is mounted to the apparatus frame la. The moving section 53 is mounted to a rail provided in the fixed section 51 and is movable in the Y direction. The mounting section 55 is mounted to a rail provided in the moving section 53 and is movable in the X direction.

[0042] The moving mechanism 6 has a fixed section 61, a pair of moving sections 63, 64, and a pair of mounting sections 65, 66. The fixed section 61 is mounted to the apparatus frame la. The pair of moving sections 63, 64 are respectively mounted to rails provided in the fixed section 61 and are respectively independently movable in the Y direction. The mounting section 65 is mounted to a rail provided in the moving section 63 and is movable in the Z direction. The mounting section 66 is mounted to a rail provided in the moving section 64 and is movable in the Z direction. That is, the pair of mounting sections 65, 66 are respectively movable in the Y direction and the Z direction with respect to the apparatus frame la.

[0043] The support section 7 is mounted to a rotation shaft provided in the mounting section 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 section 7 is movable in the X direction and the Y direction and is rotatable about an axis parallel to the Z direction as a center line. The support section 7 supports an object 100. The object 100 is, for example, a wafer.

[0044] As shown in Figs. 1 and 2, the laser processing apparatus 1 includes a plurality of moving mechanisms 5, 6, a support section 7, a pair of laser processing heads 10A, 10B, a light source unit 8, and a control section 9. Note that the following describes an example in which the laser processing heads are a pair, but the laser processing heads can be only one. Hereinafter, a first direction is referred to as an X direction, a second direction perpendicular to the first direction is referred to as a Y direction, and a third direction perpendicular to the first direction and the second 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. Figure 1 and Figure 2 The laser processing head 10A is mounted to the mounting section 65 of the moving mechanism 6. The laser processing head 10A irradiates the laser LI toward the object 100 supported by the support section 7 in a state of facing the support section 7 in the Z direction. The laser processing head 10B is mounted to the mounting section 66 of the moving mechanism 6. The laser processing head 10B irradiates the laser L2 toward the object 100 supported by the support section 7 in a state of facing the support section 7 in the Z direction.

[0045] The light source unit 8 has a pair of light sources 81, 82. The light source 81 outputs the laser LI. The laser LI is emitted from an emission section 81a of the light source 81 and guided to the laser processing head 10A through an optical fiber 2. The light source 82 outputs the laser L2. The laser L2 is emitted from an emission section 82a of the light source 82 and guided to the laser processing head 10B through another optical fiber 2.

[0046] The control section 9 controls each section (the support section 7, the plurality of moving mechanisms 5, 6, the pair of laser processing heads 10A, 10B, and the light source unit 8, etc.) of the laser processing apparatus 1. The control section 9 is configured as a computer device including a processor, a memory, a storage, a communication device, and the like. In the control section 9, software (a program) read into the memory and the like is executed by the processor, reading and writing of data in the memory and the storage, and communication based on the communication device are controlled by the processor. Thus, the control section 9 realizes various functions.

[0047] One example of processing performed by the laser processing apparatus 1 configured as described above will be described. One example of the processing is an example of forming a modification region in the inside of the object 100 along a plurality of lines set in a lattice shape in order to cut the object 100 as a wafer into a plurality of chips. In addition, the laser processing apparatus 1 can also perform peeling processing of peeling a part of the object 100.

[0048] First, the moving mechanism 5 moves the support section 7 along the X direction and the Y direction, respectively, so that the support section 7 supporting the object 100 is opposed to the pair of laser processing heads 10A, 10B in the Z direction. Next, the moving mechanism 5 rotates the support section 7 with 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 aligned along the X direction.

[0049] Next, the moving mechanism 6 moves the laser processing head 10A along the Y direction, so that the focal point (a part of the focal region) of the laser L1 is positioned on one line extending in one direction. On the other hand, the moving mechanism 6 moves the laser processing head 10B along the Y direction, so that the focal point of the laser L2 is positioned on another line extending in one direction. Next, the moving mechanism 6 moves the laser processing head 10A along the Z direction, so that the focal point of the laser L1 is positioned in the inside of the object 100. On the other hand, the moving mechanism 6 moves the laser processing head 10B along the Z direction, so that the focal point of the laser L2 is positioned in the inside of the object 100.

[0050] Next, the light source 81 outputs the laser L1, the laser processing head 10A irradiates the laser L1 toward the object 100, and the light source 82 outputs the laser L2, the laser processing head 10B irradiates the laser L2 toward the object 100. At the same time, the moving mechanism 5 moves the support section 7 along the X direction, so that the focal point of the laser L1 relatively moves along one line extending in one direction and the focal point of the laser L2 relatively moves along another line extending in one direction. In this way, the laser processing apparatus 1 forms a modification region in the inside of the object 100 along each of a plurality of lines extending in one direction in the object 100.

[0051] Next, the moving mechanism 5 rotates the support section 7 with an axis parallel to the Z direction as a center line, so that a plurality of lines extending in another direction orthogonal to one direction in the object 100 are made to align along the X direction.

[0052] Next, the moving mechanism 6 moves the laser processing head 10A along the Y direction so that the focal point of the laser LI is located on a line extending in another direction. On the other hand, the moving mechanism 6 moves the laser processing head 10B along the Y direction so that the focal point of the laser L2 is located on another line extending in another direction. Next, the moving mechanism 6 moves the laser processing head 10A along the Z direction so that the focal point of the laser LI is located inside the object 100. On the other hand, the moving mechanism 6 moves the laser processing head 10B along the Z direction so that the focal point of the laser L2 is located inside the object 100.

[0053] Next, the light source 81 outputs the laser LI, the laser processing head 10A irradiates the laser LI toward the object 100, and the light source 82 outputs the laser L2, the laser processing head 10B irradiates the laser L2 toward the object 100. At the same time, the moving mechanism 5 moves the support section 7 along the X direction so that the focal point of the laser LI relatively moves along a line extending in another direction and the focal point of the laser L2 relatively moves along another line extending in another direction. In this way, the laser processing apparatus 1 forms a modified region inside the object 100 along each of a plurality of lines extending in another direction orthogonal to one direction in the object 100.

[0054] In addition, in one example of the above processing, the light source 81 outputs the laser LI having a transmissivity with respect to the object 100, for example, by a pulse oscillation method, and the light source 82 outputs the laser L2 having a transmissivity with respect to the object 100, for example, by a pulse oscillation method. When such lasers are condensed inside the object 100, the laser is particularly absorbed in a portion corresponding to the focal point of the laser, and a modified region is formed inside the object 100. The modified region is a region in which density, refractive index, mechanical strength, other physical characteristics, and the like are different from those of a non-modified region around the modified region. As the modified region, for example, there are a fusion-processed region, a crack region, an insulation-destroyed region, a refractive index variation region, and the like.

[0055] If a laser output via pulse oscillation is applied to an object 100, and the laser's focal point moves relative to a line set on the object 100, multiple modified light spots are formed and arranged in a row along the line. A single modified light spot is formed by irradiation with a single laser pulse. A row of modified regions is a collection of multiple modified light spots arranged in a row. Adjacent modified light spots may be connected or separated depending on the relative movement speed of the laser's focal point relative to the object 100 and the laser's repetition frequency. The shape of the set line is not limited to a lattice pattern; it can also be a ring, a straight line, a curve, or a combination of at least one of these.

[0056] [Structure of laser processing head]

[0057] like Figure 3 and Figure 4 As shown, the laser processing head 10A includes a housing 11, an incident part 12, an adjustment part 13, and a focusing part 14.

[0058] The housing 11 has a first wall portion 21 and a second wall portion 22, a third wall portion 23 and a fourth wall portion 24, and a fifth wall portion 25 and a sixth wall portion 26. The first wall portion 21 and the second wall portion 22 are opposite to each other in the X direction. The third wall portion 23 and the fourth wall portion 24 are opposite to each other in the Y direction. The fifth wall portion 25 and the sixth wall portion 26 are opposite to each other in the Z direction.

[0059] In the laser processing head 10A, the first wall portion 21 is located on the opposite side of the fixed portion 61 of the moving mechanism 6, and the second wall portion 22 is located on the side of the fixed portion 61. The third wall portion 23 is located on the side of the mounting portion 65 of the moving mechanism 6, and the fourth wall portion 24 is located on the opposite side of the mounting portion 65 and on the side of the laser processing head 10B (see reference). Figure 2 The fifth wall portion 25 is located on the opposite side of the support portion 7, and the sixth wall portion 26 is located on the side of the support portion 7.

[0060] The housing 11 is configured such that it is mounted on the mounting portion 65 with the third wall portion 23 disposed on the mounting portion 65 side of the moving mechanism 6. Specifically, as described below, the mounting portion 65 has a base plate 65a and a mounting plate 65b. The base plate 65a is mounted on a track provided on the moving portion 63 (see reference). Figure 2 Mounting plate 65b is vertically mounted on the end of the laser processing head 10B side of base plate 65a (see reference). Figure 2 With the third wall portion 23 in contact with the mounting plate 65b, the bolt 28 is screwed into the mounting plate 65b via the base 27, thereby mounting the housing 11 onto the mounting portion 65. The base 27 is respectively provided on the first wall portion 21 and the second wall portion 22. The housing 11 can be attached to and detached from the mounting portion 65.

[0061] The incidence portion 12 is attached to the fifth wall portion 25. The incidence portion 12 causes the laser light LI to be incident into the casing 11. The incidence portion 12 is biased to the second wall portion 22 side (one wall portion side) in the X direction and is biased to the fourth wall portion 24 side in the Y direction.

[0062] The incidence portion 12 is configured so that the connection end portion 2a of the optical fiber 2 can be connected. A collimator lens that collimates the laser light LI emitted from the emission end of the optical fiber is provided at the connection end portion 2a of the optical fiber 2, and an isolator that suppresses return light is not provided. The isolator is provided midway through the optical fiber on the light source 81 side from the connection end portion 2a. Thus, miniaturization of the connection end portion 2a, and further, miniaturization of the incidence portion 12 are achieved. In addition, the isolator can be provided at the connection end portion 2a of the optical fiber 2.

[0063] The adjustment portion 13 is disposed inside the casing 11. The adjustment portion 13 adjusts the laser light LI incident from the incidence portion 12. Each structure that the adjustment portion 13 has is attached to an optical base 29 provided inside the casing 11. The optical base 29 is attached to the casing 11 in a manner that divides the region inside the casing 11 into a region on the third wall portion 23 side and a region on the fourth wall portion 24 side. The optical base 29 is integrated with the casing 11. Each structure that the adjustment portion 13 has is attached to the optical base 29 on the fourth wall portion 24 side. Details of each structure that the adjustment portion 13 has are described later.

[0064] The condensing portion 14 is disposed on the sixth wall portion 26. Specifically, the condensing portion 14 is disposed on the sixth wall portion 26 in a state of being inserted through a hole 26a formed in the sixth wall portion 26 (see Figure 5 ). The condensing portion 14 causes the laser light LI adjusted by the adjustment portion 13 to be emitted outside the casing 11 while condensing the laser light LI. The condensing portion 14 is biased to the second wall portion 22 side (one wall portion side) in the X direction and is biased to the fourth wall portion 24 side in the Y direction.

[0065] As shown in Figure 5 , the adjustment portion 13 has an attenuator 31, a beam expander 32, and a mirror 33. The incidence portion 12, and the attenuator 31, the beam expander 32, and the mirror 33 of the adjustment portion 13 are disposed on a straight line (first straight line) Al extending in the Z direction. The attenuator 31 and the beam expander 32 are disposed on the straight line Al between the incidence portion 12 and the mirror 33. The attenuator 31 adjusts the output of the laser light LI incident from the incidence portion 12. The beam expander 32 enlarges the diameter of the laser light LI whose output has been adjusted by the attenuator 31. The mirror 33 reflects the laser light LI whose diameter has been enlarged by the beam expander 32.

[0066] The adjustment section 13 also has a reflection-type spatial light modulator 34 and an imaging optical system 35. The reflection-type spatial light modulator 34 and the imaging optical system 35 of the adjustment section 13, and the condensing section 14 are arranged on a straight line (second straight line) A2 extending in the Z direction. The reflection-type spatial light modulator 34 is, for example, a reflection-type liquid crystal on silicon (LCOS: Liquid Crystal on Silicon) spatial light modulator (SLM: Spatial Light Modulator). The reflection-type spatial light modulator 34 modulates the laser light LI reflected by the mirror 33. The reflection-type spatial light modulator 34 modulates the laser light LI in accordance with a displayed modulation pattern. A branch pattern for branching the laser light LI into a plurality of laser lights is set and displayed in the reflection-type spatial light modulator 34. Thereby, the laser light LI incident on the reflection-type spatial light modulator 34 is branched into a plurality of laser lights in the reflection-type spatial light modulator 34 (refer to Figure 6 , described later in detail). The imaging optical system 35 constitutes a two-side telecentric optical system in which the reflecting surface 34a of the reflection-type spatial light modulator 34 and the entrance pupil surface 14a of the condensing section 14 are in an imaging relationship. The imaging optical system 35 is constituted by three or more lenses.

[0067] The straight line Al and the straight line A2 are located on a plane perpendicular to the Y direction. The straight line Al is located on the second wall section 22 side (one wall section side) with respect to the straight line A2. In the laser processing head 10A, the laser light LI is incident on the housing 11 from the entrance section 12 and travels on the straight line Al, is reflected by the mirror 33 and the reflection-type spatial light modulator 34 in this order, travels on the straight line A2, and is emitted to the outside of the housing 11 from the condensing section 14. In addition, the arrangement order of the attenuator 31 and the beam expander 32 can be reversed. In addition, the attenuator 31 can be arranged between the mirror 33 and the reflection-type spatial light modulator 34. In addition, the adjustment section 13 can have other optical sections (for example, a turning mirror arranged before the beam expander 32, and the like).

[0068] The laser processing head 10A also includes a dichroic mirror 15, a measurement section 16, a detection section 17, a drive section 18, and a circuit section 19.

[0069] The dichroic mirror 15 is arranged between the imaging optical system 35 and the condensing section 14 on the straight line A2. That is, the dichroic mirror 15 is arranged between the adjustment section 13 and the condensing section 14 in the housing 11. The dichroic mirror 15 is attached to the optical base 29 on the fourth wall section 24 side. The dichroic mirror 15 transmits the laser light LI. From the viewpoint of suppressing astigmatism, the dichroic mirror 15 is, for example, preferably a cubic type, or a 2-plate type arranged in a twisted relationship.

[0070] The measurement section 16 is disposed on the first wall section 21 side (the side opposite the one wall section side) with respect to the adjustment section 13 inside the housing 11. The measurement section 16 is attached to the optical base 29 on the fourth wall section 24 side. The measurement section 16 outputs measurement light L10 for measuring the distance from the surface of the object 100 (for example, the surface on the side on which the laser light L1 is incident) to the condensing section 14, and detects the measurement light L10 reflected on the surface of the object 100 via the condensing section 14. That is, the measurement light L10 output from the measurement section 16 is irradiated onto the surface of the object 100 via the condensing section 14, and the measurement light L10 reflected on the surface of the object 100 is detected by the measurement section 16 via the condensing section 14.

[0071] More specifically, the measurement light L10 output from the measurement section 16 is reflected on the beam splitter 20 and the dichroic mirror 15 attached to the optical base 29 on the fourth wall section 24 side in this order, and is emitted outside the housing 11 from the condensing section 14. The measurement light L10 reflected on the surface of the object 100 is incident into the housing 11 from the condensing section 14, is reflected on the dichroic mirror 15 and the beam splitter 20 in this order, is incident into the measurement section 16, and is detected by the measurement section 16.

[0072] The detection section 17 is disposed on the first wall section 21 side (the side opposite the one wall section side) with respect to the adjustment section 13 inside the housing 11. The detection section 17 is attached to the optical base 29 on the fourth wall section 24 side. The detection section 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 the observation light L20 reflected on the surface of the object 100 via the condensing section 14. That is, the observation light L20 output from the detection section 17 is irradiated onto the surface of the object 100 via the condensing section 14, and the observation light L20 reflected on the surface of the object 100 is detected by the detection section 17 via the condensing section 14. The detection section 17 is, for example, a camera that detects (images) the reflected observation light L20.

[0073] More specifically, the observation light L20 output from the detection section 17 is reflected on the dichroic mirror 15 after passing through the beam splitter 20, and is emitted outside the housing 11 from the condensing section 14. The observation light L20 reflected on the surface of the object 100 is incident into the housing 11 from the condensing section 14, is reflected on the dichroic mirror 15, passes through the beam splitter 20, is incident into the detection section 17, and is detected by the detection section 17. Furthermore, the respective wavelengths of the laser light L1, the measurement light L10, and the observation light L20 are different from each other (at least the respective central wavelengths are offset from each other).

[0074] In addition, the detection section 17 detects a portion of the laser light L1 reflected on the surface of the object 100 (details are described later). The portion of the laser light L1 reflected on the surface of the object 100 refers to only a small amount of the laser light L1 reflected on the dichroic mirror 15 toward the detection section 17 among the laser light L1 reflected on the surface of the object 100.

[0075] The driving section 18 is attached to the optical base 29 on the side of the fourth wall section 24. The driving section 18 moves the condensing section 14 disposed on the sixth wall section 26 in the Z direction by a driving force of a piezoelectric element, for example.

[0076] The circuit section 19 is disposed on the side of the third wall section 23 with respect to the optical base 29 in the housing 11. That is, the circuit section 19 is disposed on the side of the third wall section 23 with respect to the adjusting section 13, the measuring section 16, and the detecting section 17 in the housing 11. The circuit section 19 is a plurality of circuit boards, for example. The circuit section 19 processes a signal output from the measuring section 16 and a signal input to the reflection-type spatial light modulator 34. The circuit section 19 controls the driving section 18 on the basis of the signal output from the measuring section 16. As one example, the circuit section 19 controls the driving section 18 in such a manner that the distance between the surface of the object 100 and the condensing section 14 is maintained constant (that is, in such a manner that the distance between the surface of the object 100 and the condensing point of the laser light L1 is maintained constant) on the basis of the signal output from the measuring section 16. Further, a connector (not shown) is provided in the housing 11, and a wiring for electrically connecting the circuit section 19 and the control section 9 (refer to FIG. 1) and the like is connected to the connector. Figure 1

[0077] The laser processing head 10B includes the housing 11, the incident section 12, the adjusting section 13, the condensing section 14, the dichroic mirror 15, the measuring section 16, the detecting section 17, the driving section 18, and the circuit section 19 similarly to the laser processing head 10A. However, as shown in FIG. 6, the respective structures of the laser processing head 10B are arranged in a face-symmetrical relationship with respect to the respective structures of the laser processing head 10A with respect to an imaginary plane passing through the midpoint between the pair of attachment sections 65, 66 and being perpendicular to the Y direction. Figure 2

[0078] For example, the housing (first housing) 11 of the laser processing head 10A is attached to the attachment section 65 in such a manner that the fourth wall section 24 is located on the side of the laser processing head 10B with respect to the third wall section 23 and the sixth wall section 26 is located on the side of the support section 7 with respect to the fifth wall section 25. In contrast to this, the housing (second housing) 11 of the laser processing head 10B is attached to the attachment section 66 in such a manner that the fourth wall section 24 is located on the side of the laser processing head 10A with respect to the third wall section 23 and the sixth wall section 26 is located on the side of the support section 7 with respect to the fifth wall section 25.

[0079] ​​The housing 11 of the laser processing head 10B is configured to be attached to the attachment portion 66 in a state where the third wall portion 23 is disposed on the attachment portion 66 side. Specifically, as described below. The attachment portion 66 has a base plate 66a and an attachment plate 66b. The base plate 66a is attached to the rail provided in the moving portion 63. The attachment plate 66b is vertically disposed at the end portion 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 third wall portion 23 is in contact with the attachment plate 66b. The housing 11 of the laser processing head 10B is detachable with respect to the attachment portion 66.

[0080] [Branch pattern correction processing]

[0081] Hereinafter, a description will be given of processing of correcting the branch pattern set and displayed on the reflective spatial light modulator 34 so that the output of each of the branched lasers becomes an output target value in a case where the laser is branched and irradiated to the object 100 for the purpose of cutting and peeling of the object 100 and the like. Hereinafter, a description will be mainly given of processing of correcting the branch pattern so that the output target value of each of the branched lasers is a common value and the output of each of the branched lasers becomes the common value (i.e., so that the output of each of the lasers is uniformized). This correction processing is performed before the modification region is formed in the object 100 for the purpose of cutting of the object and the like.

[0082] First, a description will be given of the branch of the laser LI with reference to Figures 6 to 8 Fig. 6. As described above, the laser LI is branched in accordance with the branch pattern set and displayed on the reflective spatial light modulator 34.

[0083] Figure 6 is a view for explaining a plurality of modification spots SA in a case where the laser LI is branched into four. In the example shown in Figure 6 , the laser LI is branched so that a plurality of (four) modification spots SA are formed in the object 100 in a row along a tilt direction C2 inclined with respect to an orthogonal direction orthogonal to the processing direction Cl. The branching of the laser LI is achieved by the branch pattern (modulation pattern) set and displayed on the reflective spatial light modulator 34 (see Fig. 4). Figure 5

[0084] In the illustrated example, the laser LI is branched into four, and four modification spots SA are formed. With respect to an adjacent pair of modification spots SA among the four modification spots SA after the branching, the interval in the processing direction Cl is a branch pitch Bpx, and the interval in the direction orthogonal to the processing direction Cl is a branch pitch Bpy. With respect to a pair of modification spots SA formed by irradiation of the laser LI by two continuous pulses, the interval in the processing direction Cl is a pulse pitch PP. The angle between the processing direction Cl and the tilt direction C2 is a branch angle a. ​

[0085] Figure 7 is a setting screen of the GUI 111 for realizing Figure 6 the branch of the laser L1 as illustrated. The GUI 111 functions as an input section that receives an input from a user. Figure 7 The setting screen of the GUI 111 illustrated includes a machining condition selection button 211 that selects a machining condition, a branch number field 212 that inputs or selects a branch number of the laser L1, an index field 213 that inputs an index as a distance of movement from after laser machining along one machining line to the next machining line, an impression chart 214 that performs input or display of the branch number and the index, a machining Z height field 215 that inputs a position of a modification spot SA in the Z direction, a machining speed field 216 that inputs a machining speed, and a condition switching method button 217 that selects a switching method of the machining condition.

[0086] In the machining condition selection button 211, a specific machining condition can be selected from a plurality of options. According to the index field 213, in a case where the branch number is 1, the laser machining head 10A is caused to automatically move in the index direction by the input value. In a case where the branch number is made greater than 1, the laser machining head 10A is caused to automatically move in the index direction by an index amount based on the following calculation formula.

[0087] Index = (branch number) x index input value

[0088] The impression chart 214 includes a display section 214a of the index input value and an output input field 214b that inputs an output of each modification spot SA.

[0089] Figure 8 is a diagram that shows an example of a manager mode of the setting screen of the GUI 111. Figure 8 The setting screen illustrated includes a branch direction selection button 221 that selects a branch direction of the laser L1, a branch number field 222 that inputs or selects a branch number of the laser L1, a branch pitch input field 223 that inputs a branch pitch Bpx, a branch pitch column number input field 224 that inputs a column number of the branch pitch Bpx, a branch pitch input field 225 that inputs a branch pitch BPy, an index field 226 that inputs an index, an optical axis impression chart 227 based on the branch number, a go-back selection button 228 that selects whether a scanning direction of the laser L1 is one direction (go) or the other direction (back), and a balance adjustment start button 229 that automatically adjusts a balance of various values.

[0090] The control section 9 decides the output target value of each of the branched lasers (in this case, the value common to each of the branched lasers) based on the information received from the user in the GUI 111, and derives a first branch pattern (modulation pattern) for branching the laser LI corresponding to the decided output target value. In this case, the control section 9 can select one branch pattern from among a plurality of branch patterns prepared in advance as the first branch pattern, or can newly generate a branch pattern as the first branch pattern based on the information received from the user. The control section 9 sets and displays the derived first branch pattern in the reflective spatial light modulator 34.

[0091] As shown in (a), when the information for branching the laser LI into four is input from the user to the GUI 111, the output target value is decided by the control section 9 so that the laser output at each branch processing point (each focal point of the branched lasers) becomes the same degree as each other (see (b)). Figure 9 Figure 9 As shown in (c), the first branch pattern 340 is generated (automatically generated) according to the decided output target value, and is set and displayed in the reflective spatial light modulator 34. Figure 9 Figure 9 (b), (c), and (d) of (a) are the same as those of FIG. 8. Figure 9 (e), Figure 11 (b), Figure 11 (e), Figure 12 (b), and Figure 12 (d) of (a) are the same as those of FIG. 8. Figure 9 As shown in (d) of (a), the laser LI is branched according to the first branch pattern 340 and irradiated to the object 100, and processing (automatic processing) of the object 100 is performed. In this case, as for each of the lasers LI branched according to the first branch pattern 340, the output is theoretically set to be the same as each other, but in reality, as shown in (e) of (a), the output (actual input output) is not the same degree as each other. Figure 9

[0092] Figure 10 is a table showing one example of the mark state (in detail, the presence or absence of a modified region) in the case where the laser LI is branched into four and irradiated to the object 100 according to the first branch pattern. In Figure 10 , for each of the four branched lasers, the value of the theoretical pulse energy and whether or not a modified region is generated (in the case where a modified region is generated, "0", and in the case where a modified region is not generated, "x") are shown. As shown in Figure 10 ​​​As shown, even when laser L1 is branched according to a first branch pattern configured to make the output of each branch beam equal, modified regions are generated in the branches of focus points 2 and 3 when the pulse energy is 5.71 μJ or higher. Conversely, in the branch of focus point 3, modified regions are generated when the pulse energy is 5.96 μJ or higher, and in the branch of focus point 1, modified regions are generated when the pulse energy is 6.48 μJ or higher. Thus, even when laser L1 is branched in a way that makes the output of each branch beam equal, there are actually cases where the laser output of the branch beams is not equal to each other. Such differences in laser output are caused by individual differences in optical characteristics, such as the different transmission areas of each branch beam in the lens, and it is difficult to completely eliminate the influence of such individual differences. Furthermore, it is difficult to control such individual differences without laser irradiation.

[0093] Therefore, in the laser processing apparatus 1 of this embodiment, before processing the object 100 to form a modified region, the following correction process is performed: the object 100 is irradiated with a laser beam branching from the first branch pattern, the reflected light of the laser beam is detected (image captured) to derive the brightness, and the first branch pattern is corrected based on the brightness. Specifically, the laser processing apparatus 1 estimates the output of each branch light based on the brightness, corrects the first branch pattern to generate a second branch pattern as a new branch pattern, so that the output of the branch light becomes the output target value (here, the output of each branch light is homogenized).

[0094] This correction process is based on the premise that the brightness of the reflected light from the detected (camera) branch light is proportional to the output (beam intensity) of the branch light. In the above... Figure 10 In the example, if the pulse energy of the focal points 2 and 3 that produce the modified region when the pulse energy is 5.71 μJ or higher is set to 100% (maximum intensity), then, relatively speaking, the pulse energy of the focal point 4 that produces the modified region when the pulse energy is 5.96 μJ or higher is considered 96%, and the pulse energy of the focal point 1 that produces the modified region when the pulse energy is 6.48 μJ or higher is considered 88%. In this case, such as Figure 13(a) shows, if the brightness of the maximum condensing point 3 is set to 100%, the brightness of the reflected light of the branched light detected (imaged) by the detection section 17 is 89% for the condensing point 1, 98% for the condensing point 2, and 96% for the condensing point 4. In other words, as for the condensing point 1 and the condensing point 3, although there is a slight difference in the intensity of the reflected light from the output, it can be said that there is a proportional relationship between the brightness of the reflected light and the output. Therefore, by estimating the output of each branched light based on the brightness, the process of correcting the first branched pattern so that the output of the branched light is uniformized, can appropriately reduce the deviation of the output of the branched light at the time of laser processing.

[0095] Figure 11 and Figure 12 is a diagram illustrating the process of the laser processing device 1 that performs the above-described correction process. As Figure 11 (a) shows, when information for branching the laser L1 into 4 is input from the user to the GUI 111, using the control section 9, a first branched pattern 340 is generated (automatically generated) so that the laser output at each branched processing point (each condensing point of the branched laser) becomes theoretically the same degree as each other (see Figure 11 (b)), and this first branched pattern 340 is set and displayed on the reflective spatial light modulator 34 (see Figure 11 (c)). Then, the laser L1 is branched according to the first branched pattern 340, and each branched light is irradiated to the object 100, and the reflected light (see Figure 11 (d)) of each branched light in the object 100 is detected (imaged) by the detection section 17. As Figure 11 (d) shows, using the control section 9, the brightness of the detected reflected light is derived, and the brightness of each point (the brightness of each branched light) is compared (see Figure 11 (e)).

[0096] Then, using the control section 9, based on the derived brightness, a second branched pattern 341 that corrects the first branched pattern 340 is generated so that the output of the branched light is uniformized, and this second branched pattern 341 is set and displayed on the reflective spatial light modulator 34 (see Figure 12 (a)). In this case, as shown in (b) of Figure 12 , as the second branched pattern 341, a modulation pattern is set so that the output of the branched light with lower brightness is increased compared to the branched light with higher brightness. Specifically, for example, as for the brightness of the reflected light of each branched light, as shown in Figure 13 (a), if the brightness of the maximum condensing point 3 is set to 100%, the brightness of the condensing point 1 is 89%, the brightness of the condensing point 2 is 98%, and the brightness of the condensing point 4 is 96%, as Figure 13(b) As shown, regarding the 2nd branch pattern, the pulse energy of the focal point 1 is set to 100% (the maximum intensity) in consideration of the magnitude and difference of the brightness, and adjustment is made so that the pulse energy of the focal point 2 is 91%, the pulse energy of the focal point 3 is 89%, and the pulse energy of the focal point 4 is 93%. In this example, the 2nd branch pattern is generated so that the value obtained by multiplying the value of the % of the brightness before correction by the value of the % of the pulse energy of the 2nd branch pattern (after correction) is the same degree in all the focal points.

[0097] The laser LI is branched with the 2nd branch pattern 341 thus set, and the branched light is irradiated to the object 100, whereby the object 100 is processed (refer to Figure 12 (c)). In this case, as shown in Figure 12 (d), the output of each branched light at the time of processing (actual input output) is set to the same degree as each other, and the object 100 is processed. For example, as shown in Figure 13 (a), the brightness is measured, and as shown in Figure 13 (b), correction of the branch pattern is performed. In this case, as shown in Figure 13 (c), a modified region is generated in a case where the pulse energy of an arbitrary focal point is 5.71 μj or more. In this way, by homogenizing the output of each branched light with the 2nd branch pattern, it is possible to make the generation conditions of the modified region for each branched light the same. Thereby, it is possible to suppress the deviation of the amount of cracks extending from the modified region, to suppress the generation of unseparation-unpeeling of the object, and to improve the processing quality.

[0098] Hereinafter, the function of the control section 9 which realizes the above-described branch pattern correction processing will be described.

[0099] The control section 9 is configured to execute the following processes: a 1st process of setting and displaying, on the reflective spatial light modulator 34, a 1st branch pattern corresponding to the output target value of each laser after branching as a branch pattern for branching the laser LI into a plurality of; a 2nd process of controlling the light source unit 8 to emit the laser LI in a state where the 1st branch pattern is displayed on the reflective spatial light modulator 34; a 3rd process of controlling the detection section 17 to detect the reflected light of each laser after branching by the 1st branch pattern; a 4th process of deriving the brightness of the reflected light of each laser after branching based on the detection result of the detection section 17; and a 5th process of generating a 2nd branch pattern in which the 1st branch pattern is corrected so that the output of each laser after branching becomes the output target value, based on the derived brightness.

[0100] In the 1st process, the control section 9 derives the output target value of each laser after branching based on the setting screen of the GUI 111 (refer to Figure 7 and Figure 8The control section 9 decides the output target value of each of the branched lasers based on the information received in the step S101, and sets the first branched pattern corresponding to the decided output target value in the reflective spatial light modulator 34. The control section 9 sets the output target value of each of the branched lasers to a common value, and sets and displays the first branched pattern corresponding to the common value in the reflective spatial light modulator 34. In this case, the first branched pattern is a branched pattern in which the outputs of each of the branched lasers are theoretically the same degree as each other.

[0101] In the second process, the control section 9 controls the light source unit 8 so that the laser LI is irradiated at the output at which the object 100 does not form a modified region (below the modification threshold value) while the first branched pattern is displayed in the reflective spatial light modulator 34. Further, the branched laser can also be irradiated to an object (a modification process object) different from the object 100 on which the laser processing is performed after the branched pattern correction process.

[0102] Here, in the second process, the control section 9 can set the focal points of each of the branched lasers to the surface 100a which is the incident surface of the laser for the object 100 by controlling the moving mechanism 6 so that the laser processing head 10A moves in the Z direction. Figure 14 In this case, the detection section 17 detects the reflected light on the surface 100a. The reflected light reflected on the surface 100a has a high brightness. By detecting such reflected light having a high brightness, the output estimation of the laser based on the brightness can be performed with high accuracy.

[0103] Alternatively, the control section 9 can control the moving mechanism 6 so that the laser processing head 10A moves in the Z direction, thereby setting the focal points of each of the branched lasers to the back surface 100b which is the surface on the opposite side of the surface 100a which is the incident surface of the laser for the object 100 (see FIG. 10). Figure 15 In this case, the detection section 17 detects the reflected light on the back surface 100b. Figure 16 is a diagram showing the state of the laser processing in the actual peeling process. As shown in Figure 16 In the case where the laser processing such as the peeling process is actually performed, in the reflective spatial light modulator 34, not only the branched pattern but also a modulation pattern which synthesizes a focal point correction pattern corresponding to the depth (Z height) of the focal point and the like is set. In this regard, as shown in Figure 15 In the case where the back surface 100b is the focal point, in the reflective spatial light modulator 34, a modulation pattern which synthesizes the branched pattern and a focal point correction pattern corresponding to the thickness t of the object 100 and the like is set to detect the brightness, so as in the actual laser processing, the brightness of the reflected light of each of the branched lasers can be detected in a state in which the focal point correction pattern is also taken into account. Thus, the brightness (i.e., the laser output) can be judged in an environment similar to that in the actual laser processing.

[0104] Further, the control section 9 can determine the luminance measurement height based on the intensity of the reflected light detected (imaged) by the detection section 17 while moving the laser processing head 10A in the Z direction by controlling the moving mechanism 6. That is, as shown in Figure 17 , the control section 9 can determine the Z height at which the intensity (luminance) of all the branched lights becomes large as the luminance measurement height in the case where the respective branched lights are branched at the same height in the Z direction. Further, as shown in Figure 18 , the control section 9 can determine the Z height at which the intensity of each of the respective branched lights becomes large as the luminance measurement height in the case where the respective branched lights are branched at different heights in the Z direction. Further, the control section 9 can determine the final luminance measurement height by taking into account the amount of deviation of the condensing position in the case where the amount of deviation can be determined in advance. The amount of deviation is, for example, the amount of deviation caused by chromatic aberration of the objective lens of the reticle used at the time of height setting, and the like.

[0105] In the third process, the control section 9 controls the detection section 17 so that the reflected light of each of the branched lasers on the object 100 can be detected (imaged) at least during the period in which the respective branched lasers are irradiated onto the object 100. The control section 9 acquires the image imaged by the detection section 17 from the detection section 17.

[0106] In the fourth process, the control section 9 determines the region in which the luminance is higher than in other regions corresponding to the number of branches in the imaged data acquired by the detection section 17. The region here is a region that also includes the region around the point having the highest luminance as the center. Then, the control section 9 derives the luminance also taking into account the luminance of the surroundings for the region corresponding to each of the branched lights.

[0107] The control section 9 is configured to further perform: a sixth process of setting and displaying the second branched pattern in the reflective spatial light modulator 34; and a seventh process of controlling the light source unit 8 so that the laser L1 is emitted in a state in which the second branched pattern is displayed in the reflective spatial light modulator 34 to process the object 100.

[0108] Next, the branched pattern correction process will be described with reference to the flowchart of Figure 19 .

[0109] As shown in Figure 19 , in the branched pattern correction process, first, the first branched pattern is derived based on the information accepted in the setting screen of the GUI 111, and the first branched pattern is set / displayed in the reflective spatial light modulator 34 (step S1: first process).

[0110] Next, the laser light L1 is emitted to the reflection-type spatial light modulator 34 on which the first branch pattern is displayed, and the laser light branched into a plurality according to the first branch pattern is irradiated to the surface 100a or the back surface 100b of the object 100 (Step S2: second process).

[0111] Next, the reflected light of the branched light from the surface 100a or the back surface 100b is detected (imaged) by the detection section 17 (Step S3: third process). Then, based on the imaged data (detection result of the reflected light), the brightness at the condensing point of each of the branched laser lights is measured (Step S4: fourth process).

[0112] Finally, based on the derived brightness data, a corrected pattern (second branch pattern) in which the first branch pattern is corrected is generated so that the output of each of the branched laser lights becomes the output target value (in the case where the output target value is a common value, the output is uniformized) (Step S5: fifth process).

[0113] Next, the effects of the laser processing apparatus 1 of the present embodiment will be described.

[0114] The laser processing apparatus 1 of the present embodiment is a laser processing apparatus that forms a modified region in an object 100 by irradiating laser light to the object 100, and includes a light source unit 8 that emits laser light, a reflection-type spatial light modulator 34 that modulates the laser light emitted from the light source unit 8, a condensing section 14 that condenses the laser light modulated by the reflection-type spatial light modulator 34 to the object 100, a detection section 17 that detects the reflected light of the laser light of the object 100, and a control section 9 that includes a first process of setting and displaying, in the reflection-type spatial light modulator 34, a first branch pattern that is a branch pattern for branching the laser light into a plurality corresponding to an output target value of each of the branched laser lights, a second process of controlling the light source unit 8 so that the laser light is emitted in a state where the first branch pattern is displayed in the reflection-type spatial light modulator 34, a third process of controlling the detection section 17 so as to detect the reflected light of each of the branched laser lights using the first branch pattern, a fourth process of deriving the brightness of the reflected light of each of the branched laser lights based on the detection result of the detection section 17, and a fifth process of generating a second branch pattern in which the first branch pattern is corrected so that the output of each of the branched laser lights becomes the output target value based on the derived brightness.

[0115] In the laser processing apparatus 1 of the present embodiment, the reflected light of each laser light branched according to the first branch pattern on the object 100 is detected, and the brightness of the reflected light of each branched laser light is derived based on the detection result. Here, the brightness of the reflected light of each branched laser light is proportional to the output (beam intensity) of each branched laser light. Therefore, by deriving the brightness, the output of each branched laser light can be estimated with high accuracy. Then, on the basis of the output of each branched laser light estimated with high accuracy according to the brightness, a new branch pattern (a second branch pattern in which the first branch pattern is corrected) is generated so that the output of each branched laser light becomes the output target value, whereby a branch pattern that adjusts the output of each branched laser light (branched light) 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.

[0116] The control section 9 can also be configured to further perform: a sixth process of setting and displaying the second branch pattern to the reflective spatial light modulator 34; and a seventh process of controlling the light source unit 8 so that the laser light is emitted to process the object 100 in a state where the second branch pattern is displayed to the reflective spatial light modulator 34. In this way, the branch pattern (second branch pattern) that is appropriately based on the brightness is set to the reflective spatial light modulator 34, and the laser processing is actually performed, whereby high-quality processing of the object 100 can be achieved in a state where the output of the branched light is adjusted to a desired value.

[0117] The control section 9 can also control the light source unit 8 in the second process so that the laser light is irradiated at an output at which the modified region is not formed in the object 100. Thereby, it is possible to prevent the modified region from being formed in the object 100 at the stage of adjusting the output of the branched light. Thereby, high-quality processing of the object 100 can be achieved.

[0118] The above-described laser processing apparatus 1 can also further include a GUI 111 that receives an input from a user, and the control section 9 decides the output target value based on the information received by the GUI 111 in the first process, and sets the first branch pattern corresponding to the decided output target value to the reflective spatial light modulator 34. Thereby, it is possible to set the branch pattern corresponding to the condition set by the user. That is, it is possible to achieve laser processing desired by the user.

[0119] It can also be that the condensing point of the laser light condensed by the condensing section 14 is set to the surface 100a, which is the incident surface of the laser light, of the object 100, and the detection section 17 detects the reflected light on the surface 100a. The brightness of the reflected light reflected by the surface 100a is relatively high. By detecting such reflected light with high brightness, the estimation of the output of the laser light based on the brightness can be performed with higher accuracy.

[0120] It is also possible to set the condensing point of the laser light condensed by the condensing section 14 to the back surface 100b of the surface 100a of the object 100, and the detection section 17 detects the reflected light on the back surface 100b. In the case of actually performing laser processing such as peeling processing, a modulation pattern in which a condensing correction pattern other than the branch pattern is synthesized is set in the reflective spatial light modulator 34. In this case, in which the brightness of the branch light (the output of each branch light) of the modulation pattern in the reflective spatial light modulator 34 at the time of actual laser processing is considered, it is preferable to measure the brightness of the reflected light on the back surface 100b. Therefore, by detecting the reflected light on the back surface 100b, it is possible to adjust the output of each branch light to a desired value in consideration of the actual laser processing.

[0121] Thus, as mainly described in the present embodiment, the control section 9 can set the output target value of each laser light after branching to a common value in the first process, and set and display the first branch pattern corresponding to the common value in the reflective spatial light modulator 34. In the branching processing, it is sometimes desired to uniformize the output of each laser light after branching. In this case, as described above, the output target value of each laser light after branching is set to a common value, and the second branch pattern is generated in the fifth process so that the output of each laser light after branching becomes the common value (i.e., so that the output of each laser light is uniformized), whereby it is possible to suppress the deviation of the output of each laser light after branching, uniformize the output of each laser light of the branch light, and improve the processing quality.

[0122] The above describes the embodiment of the present application, but the present application is not limited to the above-described embodiment. For example, in the above-described embodiment, mainly described is the generation of the second branch pattern so that the output target value of each laser light after branching is a common value, and the output of each laser light after branching becomes the common value (i.e., so that the output of each laser light is uniformized), but it is not limited thereto, and the output target value of each laser light after branching can be mutually different values. In this case, by generating the second branch pattern so that the output of each laser light after branching becomes the output target value of each laser light based on the brightness, it is possible to adjust the output of the branch light to a desired value and improve the processing quality.

[0123] In addition, for example, the object 100 for which the luminance measurement is performed can be a mirror wafer (a bare wafer without a pattern) or an actual device (a wafer with a pattern) in which, for example, a peeling process is actually performed. In the actual device, a laminated film of SiN, SiO2, or the like is sometimes provided on the laser incidence surface side, but it is considered that the reflectance is lower than that of the mirror wafer due to the influence of multiple reflection in the laminated film. For example, in the mirror wafer, the reflectance of the 1099 nm laser is about 30%, whereas in the actual device in which a 100 nm SiN film is provided, the reflectance of the laser of the same wavelength is reduced to about 8%. Therefore, in such an actual device, it is considered that the luminance measurement value is reduced. In this regard, for example, in the case of determining the deviation of the output of each branch light, or the like, only the relative comparison of the luminance at each point is necessary, and thus the reduction in the luminance measurement value due to the reduction in the reflectance hardly becomes a problem. However, in the case where the amount of reflected light is so low that the luminance measurement cannot be performed, it is necessary to perform a correction of increasing the laser output at the time of measurement. In this case, the output that becomes the luminance value most suitable for the measurement can be set by making the attenuator variable while monitoring the luminance value, or the luminance value (reflectance) of the mirror wafer, the optimum luminance value, can be grasped in advance, and the output corresponding to the amount of deviation from the luminance value is adjusted.

[0124] Further, in the case where the above-described 7th process (laser-based processing of an object) is performed using an actual device, the output setting correction can be performed taking the above-described reflectance into consideration.

[0125] As described above, as one example of laser processing using the laser processing apparatus 1, there is processing for forming a modification 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. One example of the processing conditions of this processing will be described below. In this processing, two columns of modification regions are formed inside the object 100 in the thickness direction. The two columns of modification regions can be formed by irradiating laser light respectively, or can be formed by branching the processing points into two with a 2-focus branch pattern by one scan.

[0126] Processing object material: silicon wafer; wafer thickness: 300 μm; crystal orientation: <100>; resistivity: 1 Ω-cm or more

[0127] Laser wavelength of the laser processing apparatus 1: 1099 nm; pulse width: 700 nsec; frequency: 120 kHz; stage speed: 800 mm / sec; pulse pitch: 6.67 μm

[0128] Depth (Z height) of the condensing point of SD1 which is the modification region on the side away from the incidence surface: Z64; output: 2.78 W; display pattern of the spatial light modulator: a spherical aberration correction pattern was used

[0129] The depth (Z-height) of the focusing point of SD2, the modified region near the incident plane, is Z24; output: 1.85W; display pattern of the spatial light modulator: using a spherical aberration correction pattern.

[0130] Figure 20 (a) is a diagram showing the formation state of the modified regions 12a, 12b and the cracks 14 extending from the modified regions 12a, 12b when the object 100 is processed under the aforementioned processing conditions. Figure 20 In the example shown in (a), it cannot be said that the modified regions 12a and 12b and the cracks 14 extending from the modified regions 12a and 12b are in a good state of formation. Specifically, with Figure 20 Compared to the formation state of the modified regions 12a and 12b shown in (b) and the cracks 14 extending from the modified regions 12a and 12b, Figure 20 The formation state of cracks 14 shown in (a) cannot be described as good. Figure 20 As shown in (b), by effectively forming cracks 14, the unevenness (end-face unevenness) during cutting is reduced, enabling cutting with high straightness. Furthermore, by suppressing end-face unevenness, it has the effects of preventing crack residue during cutting, reducing the occurrence rate of modified lamellars (silicon microparticles) generated from the cutting surface, and improving bending strength. The following describes the methods used to achieve this. Figure 20 (b) illustrates an example where, in addition to the processing conditions described above, a predetermined pattern is synthesized in a spatial light modulator and the processing is performed while displaying the predetermined pattern.

[0131] Figure 21 This is a diagram illustrating an example of an AS pattern synthesized from the pattern specified above, which is a pattern for applying astigmatism. Figure 21 This indicates the shape of the light beam L150 at the focal point. Figure 21 In the example shown, by synthesizing an AS pattern that serves as the pattern for applying astigmatism, the intensity distribution of the beam L150 is elliptical; specifically, the processing direction is elliptical in the longitudinal direction. When the ellipticity is set as the ratio of the major axis to the minor axis of the beam shape, this ellipticity is, for example, set to 1.5. Thus, by synthesizing the AS pattern, the laser beam becomes elliptical in the processing direction, thereby enabling cuts with higher straightness. It should be noted that the effect of improving straightness is achieved, for example, by setting the ellipticity to 1.05 or higher.

[0132] Figure 22is a view illustrating an example of synthesizing a slit pattern as the above-described prescribed pattern. The slit pattern here refers to a pattern in which both ends in a direction intersecting the processing direction are cut in a laser beam. That is, for example, in a case where the processing direction is set as the left-right direction, the slit pattern cuts the upper and lower ends of the laser beam in the up-down direction. The size of the region where the cutting is performed here can be set to, for example, about 10% of the entire beam. In this way, by synthesizing slit patterns that cut both ends in a direction intersecting the processing direction, the shape of the beam is the same as when the above-described AS pattern is synthesized, and cutting with high straightness can be performed. Figure 22 In the example shown in the view, in a case where the left-to-right direction in the view is the processing direction, the upper and lower ends of the beam L180 are cut by the slit patterns 500, 600. The size of the region where the cutting is performed here can be set to, for example, about 10% of the entire beam. In this way, by synthesizing slit patterns that cut both ends in a direction intersecting the processing direction, the shape of the beam is the same as when the above-described AS pattern is synthesized, and cutting with high straightness can be performed.

[0133] Figure 23 is a view illustrating an example of synthesizing a lateral branch pattern as the above-described prescribed pattern. The lateral branch here refers to branching of a laser in a direction intersecting the thickness direction (Z direction) of the object 100, and more specifically, refers to branching in the processing direction. In Figure 23 In the example shown in the view, the pulse pitch is set to 6.67 μm, and a lateral branch pattern that branches the beam in the processing direction is synthesized, and a lateral branch pattern in which the distance between the beams branched to 2 is set to 3 μm. In this case, the distance between the beams L201, L202 branched to 2 is 3 μm, the distance between the beam L201 and the beam L203 (pulse pitch) is 6.67 μm, and the distance between the beams L203, L204 branched to 2 is 3 μm. In this way, by processing in a manner in which the lateral branch is performed at a distance smaller than the pulse pitch, the above-described straightness can be improved.

[0134] Each of the above-described prescribed patterns can improve the straightness even when used alone, but by using them in combination, the straightness can sometimes be further improved. In addition, the effects of the above-described prescribed patterns can be achieved without using a spatial light modulator. That is, for example, the same effects as the AS pattern can be achieved by a cylindrical lens, and the same effects as the slit pattern can be achieved by cutting the ends of the beam with a mechanical knife.

Claims

1. A laser processing apparatus characterized by, being a laser processing apparatus that forms a modified region in an object by irradiating a laser to the object, comprising: a light source that emits the laser; a spatial light modulator that modulates the laser emitted from the light source; a condensing section that condenses the laser modulated by the spatial light modulator to the object; a detection section that detects reflected light of the laser from the object; and a control section, the control section configured to execute: a first process of setting and displaying a first branch pattern on the spatial light modulator, the first branch pattern being a branch pattern that branches the laser into a plurality, and corresponding to an output target value of each of the branched lasers; a second process of controlling the light source so as to emit the laser in a state where the first branch pattern is displayed on the spatial light modulator; a third process of controlling the detection section so as to detect the reflected light of each of the branched lasers using the first branch pattern; a fourth process of deriving a brightness of the reflected light of each of the branched lasers based on a detection result of the detection section; and a fifth process of generating a second branch pattern in which the first branch pattern is corrected so that the output of each of the branched lasers becomes the output target value, based on the derived brightness.

2. The laser processing apparatus according to claim 1, characterized in that, the control section is configured to further execute: a sixth process of setting and displaying the second branch pattern on the spatial light modulator; and a seventh process of controlling the light source so as to process the object by emitting the laser in a state where the second branch pattern is displayed on the spatial light modulator.

3. The laser processing apparatus according to claim 1, characterized in that, the control section controls the light source in the second process so that the laser is irradiated at an output at which no modified region is formed in the object.

4. The laser processing apparatus according to claim 2, characterized in that, the control section controls the light source in the second process so that the laser is irradiated at an output at which no modified region is formed in the object.

5. The laser processing apparatus according to claim 1, characterized in that, the laser processing apparatus further comprises an input section that receives an input from a user, the control section decides the output target value based on information received by the input section in the first process, and sets the first branch pattern corresponding to the decided output target value on the spatial light modulator.

6. The laser processing apparatus according to claim 2, characterized in that, the laser processing apparatus further comprises an input section that receives an input from a user, the control section decides the output target value based on information received by the input section in the first process, and sets the first branch pattern corresponding to the decided output target value on the spatial light modulator.

7. The laser processing apparatus according to claim 3, characterized in that, the laser processing apparatus further comprises an input section that receives an input from a user, The control section decides the output target value based on information received by the input section in the first process, and sets the first branch pattern corresponding to the decided output target value in the spatial light modulator.

8. The laser processing apparatus according to claim 4, wherein the laser processing apparatus further includes an input section that receives input from a user, the control section decides the output target value based on information received by the input section in the first process, and sets the first branch pattern corresponding to the decided output target value in the spatial light modulator.

9. The laser processing apparatus according to any one of claims 1 to 8, wherein a condensing point of the laser light condensed by the condensing section is set on a surface on the opposite side of the surface of the object as an incident surface of the laser light, the detection section detects the reflected light on the surface.

10. The laser processing apparatus according to any one of claims 1 to 8, wherein a condensing point of the laser light condensed by the condensing section is set on a back surface of a surface on the opposite side of the surface of the object as an incident surface of the laser light, the detection section detects the reflected light on the back surface.

11. The laser processing apparatus according to any one of claims 1 to 8, wherein the control section sets the output target value of each of the branched laser lights to a common value in the first process, and sets and displays the first branch pattern corresponding to the common value in the spatial light modulator.

12. The laser processing apparatus according to claim 9, wherein the control section sets the output target value of each of the branched laser lights to a common value in the first process, and sets and displays the first branch pattern corresponding to the common value in the spatial light modulator.

13. The laser processing apparatus according to claim 10, wherein the control section sets the output target value of each of the branched laser lights to a common value in the first process, and sets and displays the first branch pattern corresponding to the common value in the spatial light modulator.

14. A laser processing method, wherein the laser processing method is a laser processing method of forming a modified region in an object by irradiating laser light to the object, the laser processing method includes: a first process of setting and displaying a first branch pattern in a spatial light modulator, the first branch pattern being a branch pattern of branching laser light into a plurality, and corresponding to an output target value of each of the branched laser lights; a second process of emitting laser light to the spatial light modulator on which the first branch pattern is displayed, and irradiating laser light branched into a plurality according to the first branch pattern to an object; a third process of detecting reflected light of each of the branched laser lights from the object; a fourth process of deriving a brightness of the reflected light of each of the branched laser lights based on a result of detection of the reflected light; and a fifth process of generating a second branch pattern in which the output of each of the branched laser lights becomes the output target value, based on the derived brightness, by correcting the first branch pattern.

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