JP2017174941A - Laser processing method and laser processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser processing method and a laser processing apparatus capable of suppressing meandering of cracks reaching a front surface or a back surface of an object to be processed with respect to a line to cut.SOLUTION: By simultaneously focusing laser beams L1 to L3 inside an object 1 to be processed, a first modified region 7a located on a line 5 to cut in a Y direction, a second modified region 7b located on one side of the first modified region 7a in the Y direction, and a third modified region 7c located on the other side of the first modified region 7a in the Y direction are simultaneously formed and a half cut Hc is generated from the first modified region 7a.SELECTED DRAWING: Figure 11

Description

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

  2. Description of the Related Art Conventionally, there is known a laser processing method for forming a modified region on a processing object along a planned cutting line by condensing laser light on the processing object. For example, in the laser processing method described in Patent Document 1, a modified region is formed along a planned cutting line, and a crack (so-called half cut) is generated from the modified region to the front surface or back surface of the workpiece. Let

JP 2012-130952 A

  In the laser processing method as described above, for example, while the demand for improving the processing quality is increasing, it is possible to suppress the meandering of the crack from the modified region to the front surface or the back surface of the object to be cut with respect to the line to be cut. Is required.

  An object of this invention is to provide the laser processing method and laser processing apparatus which can suppress that the crack from the modification | reformation area | region to the surface or back surface of a to-be-processed object meanders with respect to a cutting scheduled line.

  A laser processing method according to the present invention is a laser processing method in which a modified region is formed inside a processing object along a planned cutting line by condensing laser light inside the processing object. By simultaneously condensing at least three laser beams inside the object, it is located at a position corresponding to the planned cutting line in a predetermined direction orthogonal to the thickness direction of the processing target and the extending direction of the planned cutting line. One or a plurality of first reforming regions, one or a plurality of second reforming regions located on one side of the first reforming region in a predetermined direction, and the other side of the first reforming region in a predetermined direction And a laser beam condensing step of simultaneously generating one or a plurality of third modified regions located in the region and generating cracks reaching the front surface or the back surface of the workpiece from the first modified region.

  A laser processing apparatus according to the present invention is a laser processing apparatus for forming a modified region in a processing object along a scheduled cutting line by condensing a laser beam inside the processing object. A laser beam emitting unit that emits light, a condensing optical system that condenses the laser beam emitted from the laser beam emitting unit inside the object to be processed, and a light collecting unit that is emitted from the laser beam emitting unit and collected by the condensing optical system. A spatial light modulator that modulates the emitted laser light, and a control unit that controls at least the operation of the laser light emitting unit and the spatial light modulator, and the control unit causes the laser light to be emitted from the laser light emitting unit. The laser beam is modulated by a spatial light modulator so that the laser beam is branched into at least three parts and simultaneously condensed by the focusing optical system inside the workpiece, and the thickness direction and cutting of the workpiece are cut Orthogonal to the extension direction of the planned line One or more first modified regions located at a position corresponding to the line to be cut in the predetermined direction; and one or more second modified regions located on one side of the first modified region in the predetermined direction; One or a plurality of third modified regions located on the other side of the first modified region in the predetermined direction are simultaneously formed, and a crack reaching the front or back surface of the workpiece is generated from the first modified region The laser beam condensing control is executed.

  In the laser processing method and the laser processing apparatus, the first modified region is formed and a crack (hereinafter also referred to as “half cut”) from the first modified region to the front surface or the back surface is generated. At the same time, the second and third modified regions are respectively formed on one side and the other side in the predetermined direction of the first modified region. By forming the second and third modified regions, a strong compressive stress field that sandwiches the first modified region in a predetermined direction is instantaneously generated, and the half-cut progress in the predetermined direction can be suppressed by the compressive stress field. That is, the half cut progress direction can be stabilized and the half cut can be easily advanced from the first modified region along the thickness direction. Therefore, it is possible to prevent the half cut from meandering with respect to the line to be cut.

  In the laser processing method according to the present invention, the positions of the first to third modified regions in the extending direction of the planned cutting line may be equal to each other. In this case, the compressive stress field due to the formation of the second and third modified regions can be effectively applied to the progress of the half cut, and the progress of the half cut in a predetermined direction can be effectively suppressed. .

  In the laser processing method according to the present invention, the laser beam may be an ultrashort pulse laser beam. In this case, the compressive stress field due to the formation of the second and third modified regions can be generated more instantaneously.

  In the laser processing method according to the present invention, the positions of the first to third modified regions in the thickness direction of the workpiece may be equal to each other. In this case, the compression stress field can be effectively applied to the progress of the half cut, and the progress of the half cut in a predetermined direction can be effectively suppressed.

  A laser processing method according to the present invention is a laser processing method for forming a plurality of rows of modified regions in a thickness direction of a workpiece along a planned cutting line, and the laser beam focusing step includes: When a crack reaching the surface of the workpiece is generated from the first modified region, it is executed when forming a modified region closest to the surface of the workpiece among the plurality of rows of modified regions in the thickness direction of the workpiece. When a crack reaching the back surface of the workpiece is generated from the first modified region, a modified region closest to the back surface of the workpiece is formed in the plurality of rows of modified regions in the thickness direction of the workpiece. It may be executed when. In this case, the half cut can be generated efficiently.

  In the laser processing method according to the present invention, in the laser beam focusing step, the laser beam may be modulated by the spatial light modulator so that one laser beam is branched into at least three. In this case, the first to third modified regions can be formed simultaneously using a spatial light modulator.

  In the laser processing method according to the present invention, in the laser beam condensing step, the cracks reaching the front surface or the back surface of the processing target need not be generated from the second and third modified regions. In this case, it is possible to avoid that the stress in the compressive stress field is released and reduced due to a crack from the second and third modified regions to the front surface or the back surface.

  In the laser processing method according to the present invention, a plurality of scheduled cutting lines are set, the first modified region is located on the first scheduled cutting line, and the second modified region is a first cut in a predetermined direction. Located between the second scheduled cutting line and the first scheduled cutting line adjacent to one side with respect to the scheduled line, the third modified region is adjacent to the other side with respect to the first scheduled cutting line in a predetermined direction It may be located between the 3rd scheduled cutting line and the 1st scheduled cutting line. In this case, the workpiece can be accurately cut along the scheduled cutting line by using the first modified region and the half cut as the starting point of cutting.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the laser processing method and laser processing apparatus which can suppress that the crack which reaches the surface of a process target object meanders with respect to a cutting scheduled line.

It is a schematic block diagram of the laser processing apparatus used for formation of a modification area | region. It is a top view of the processing target object used as the object of formation of a modification field. It is sectional drawing along the III-III line of the workpiece of FIG. It is a top view of the processing target after laser processing. It is sectional drawing along the VV line of the workpiece of FIG. It is sectional drawing along the VI-VI line of the processing target object of FIG. It is a schematic block diagram of the laser processing apparatus which concerns on one Embodiment. It is a fragmentary sectional view of the reflection type spatial light modulator of the laser processing apparatus of FIG. It is a figure for demonstrating the branching and condensing of a laser beam. It is a top view of a processing target object. (A) is a top view of the processing target object for demonstrating the laser processing method which concerns on one Embodiment. (B) is sectional drawing which follows the BB line of Fig.11 (a). (C) is sectional drawing which follows the CC line of Fig.11 (a). It is a figure explaining the effect | action of the laser processing method and laser processing method which concern on one Embodiment. It is another figure explaining the effect | action of the laser processing method which concerns on one Embodiment, and a laser processing method. (A) is a photograph figure which shows the laser processing result concerning a comparative example. (B) is a photograph figure showing a laser processing result concerning one embodiment. (A) is the partially expanded photograph figure of Fig.14 (a). FIG. 14B is a partially enlarged photograph view of FIG. (A) is a photograph figure which shows the laser processing result concerning a comparative example. (B) is a photograph figure showing a laser processing result concerning one embodiment. It is a photograph figure which shows the laser processing result at the time of changing the output ratio of each laser beam after a branch in the laser processing which concerns on one Embodiment. It is a figure which shows the laser processing result at the time of changing the space | interval of a 1st-3rd modified region. It is a figure which shows the laser processing result at the time of changing the space | interval of a 1st-3rd modified region. It is a figure which shows the laser processing result at the time of changing the space | interval of a 1st-3rd modified region. It is a figure which shows the laser processing result at the time of changing the space | interval of a 1st-3rd modified region. It is a partially expanded photograph figure of the cut surface of a workpiece. It is a figure explaining the laser processing which concerns on a modification. It is a photograph figure which shows the laser processing result which concerns on a modification. It is a photograph figure which shows the laser processing result which concerns on a modification.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the same or an equivalent part, and the overlapping description is abbreviate | omitted.

  In the laser processing method and the laser processing apparatus according to the embodiment, the modified region is formed in the processing object along the planned cutting line by condensing the laser beam on the processing object. First, the formation of the modified region will be described with reference to FIGS.

  As shown in FIG. 1, the laser processing apparatus 100 is arranged so that the direction of the optical axis (optical path) of the laser light L and the laser light source 101 that is a laser light emitting unit that pulsates the laser light L is changed by 90 °. The dichroic mirror 103 and the condensing lens 105 for condensing the laser beam L are provided. Further, the laser processing apparatus 100 includes a support base 107 for supporting the workpiece 1 irradiated with the laser light L condensed by the condensing lens 105, and a stage 111 for moving the support base 107. A laser light source control unit 102 for controlling the laser light source 101 to adjust the output (pulse energy, light intensity), pulse width, pulse waveform, etc. of the laser light L, and a stage control unit 115 for controlling the movement of the stage 111 It is equipped with.

  In the laser processing apparatus 100, the laser light L emitted from the laser light source 101 is changed in the direction of its optical axis by 90 ° by the dichroic mirror 103, and is placed inside the processing object 1 placed on the support base 107. The light is condensed by the condensing lens 105. At the same time, the stage 111 is moved, and the workpiece 1 is moved relative to the laser beam L along the planned cutting line 5. Thereby, a modified region along the planned cutting line 5 is formed on the workpiece 1. Here, the stage 111 is moved in order to move the laser light L relatively, but the condensing lens 105 may be moved, or both of them may be moved.

  As the processing object 1, a plate-like member (for example, a substrate, a wafer, or the like) including a semiconductor substrate formed of a semiconductor material, a piezoelectric substrate formed of a piezoelectric material, or the like is used. As shown in FIG. 2, a scheduled cutting line 5 for cutting the workpiece 1 is set in the workpiece 1. The planned cutting line 5 is a virtual line extending linearly. When the modified region is formed inside the workpiece 1, the laser beam L is cut in a state where the condensing point (condensing position) P is aligned with the inside of the workpiece 1 as shown in FIG. 3. It moves relatively along the planned line 5 (that is, in the direction of arrow A in FIG. 2). Thereby, as shown in FIGS. 4, 5, and 6, the modified region 7 is formed on the workpiece 1 along the planned cutting line 5, and the modified region formed along the planned cutting line 5. 7 becomes the cutting start region 8.

  The condensing point P is a part where the laser light L is condensed. The planned cutting line 5 is not limited to a straight line, but may be a curved line, a three-dimensional shape in which these lines are combined, or a coordinate designated. The planned cutting line 5 is not limited to a virtual line but may be a line actually drawn on the surface 3 of the workpiece 1. The modified region 7 may be formed continuously or intermittently. The modified region 7 may be in the form of a line or a dot. In short, the modified region 7 only needs to be formed at least inside the workpiece 1. In addition, a crack may be formed starting from the modified region 7, and the crack and the modified region 7 may be exposed on the outer surface (front surface 3, back surface, or outer peripheral surface) of the workpiece 1. . The laser light incident surface when forming the modified region 7 is not limited to the front surface 3 of the workpiece 1 and may be the back surface of the workpiece 1.

  Incidentally, when the modified region 7 is formed inside the workpiece 1, the laser light L passes through the workpiece 1 and is near the condensing point P located inside the workpiece 1. Especially absorbed. Thereby, the modified region 7 is formed in the workpiece 1 (that is, internal absorption laser processing). In this case, since the laser beam L is hardly absorbed by the surface 3 of the workpiece 1, the surface 3 of the workpiece 1 is not melted. On the other hand, when the modified region 7 is formed on the front surface 3 or the back surface of the workpiece 1, the laser light L is absorbed particularly in the vicinity of the condensing point P located on the front surface 3 or the back surface, and the front surface 3 or the back surface. Then, a removed portion such as a hole or a groove is formed (surface absorption laser processing).

  The modified region 7 is a region where the density, refractive index, mechanical strength, and other physical characteristics are different from the surroundings. Examples of the modified region 7 include a melt treatment region (meaning at least one of a region once solidified after melting, a region in a molten state, and a region in a state of being resolidified from melting), a crack region, and the like. In addition, there are a dielectric breakdown region, a refractive index change region, and the like, and there is a region in which these are mixed. Further, the modified region 7 includes a region where the density of the modified region 7 in the material of the workpiece 1 is changed compared to the density of the non-modified region, and a region where lattice defects are formed. When the material of the workpiece 1 is single crystal silicon, the modified region 7 can be said to be a high dislocation density region.

The area where the density of the melt processing area, the refractive index changing area, the density of the modified area 7 is changed as compared with the density of the non-modified area, and the area where lattice defects are formed are further included in the interior of these areas or the modified areas. In some cases, cracks (cracks, microcracks) are included in the interface between the region 7 and the non-modified region. The included crack may be formed over the entire surface of the modified region 7, or may be formed in only a part or a plurality of parts. The workpiece 1 includes a substrate made of a crystal material having a crystal structure. For example, the workpiece 1 includes a substrate formed of at least one of gallium nitride (GaN), silicon (Si), silicon carbide (SiC), LiTaO ₃ , and sapphire (Al ₂ O ₃ ). In other words, the workpiece 1 includes, for example, a gallium nitride substrate, a silicon substrate, a SiC substrate, a LiTaO ₃ substrate, or a sapphire substrate. The crystal material may be either an anisotropic crystal or an isotropic crystal. Moreover, the workpiece 1 may include a substrate made of an amorphous material having an amorphous structure (amorphous structure), for example, a glass substrate.

  In the embodiment, the modified region 7 can be formed by forming a plurality of modified spots (processing marks) along the planned cutting line 5. In this case, the modified region 7 is formed by collecting a plurality of modified spots. The modified spot is a modified portion formed by one pulse shot of pulsed laser light (that is, one pulse of laser irradiation: laser shot). Examples of the modified spot include a crack spot, a melting treatment spot, a refractive index change spot, or a mixture of at least one of these. For the modified spot, the size and length of cracks to be generated are appropriately determined in consideration of the required cutting accuracy, required flatness of the cut surface, thickness, type, crystal orientation, etc. of the workpiece 1. Can be controlled. In the embodiment, the modified spot can be formed as the modified region 7 along the planned cutting line 5.

  Next, a laser processing method and a laser processing apparatus according to the embodiment will be described. In the following description, the extending direction of the planned cutting line 5 (direction along the processing progress direction) along which the laser light L is moved relative to the processing target 1 is defined as the X direction, and the thickness of the processing target 1 is determined. A direction is a Z direction, and a direction orthogonal to the X direction and the Z direction is a Y direction (predetermined direction).

  As shown in FIG. 7, the laser processing apparatus 300 includes a laser light source (laser light emitting unit) 202, a reflective spatial light modulator (spatial light modulator) 203, a 4f optical system 241, and a condensing optical system 204. It is provided in the housing 231. The laser processing apparatus 300 focuses the laser beam L on the workpiece 1 to form the modified region 7 on the workpiece 1 along the planned cutting line 5.

  The laser light source 202 emits laser light L. The laser light source 202 emits an ultrashort pulse laser beam, which is a laser beam having a pulse width of 20 ps or less, as a laser beam L. The laser light source 202 includes an ultrashort pulse laser light source as a laser oscillator. As the laser oscillator, for example, a solid laser, a fiber laser, an external modulation element, or the like can be used. The laser light source 202 includes an output adjusting unit that adjusts the output of the laser light L. The output adjustment unit can be composed of a λ / 2 wavelength plate unit, a polarizing plate unit, and the like. Further, the laser light source 202 includes a beam expander that parallelizes the laser light L while adjusting the diameter thereof.

  The wavelength of the laser light L emitted from the laser light source 202 is included in any of the wavelength bands of 500 to 550 nm, 1000 to 1150 nm, or 1300 to 1400 nm. Here, the wavelength of the laser beam L is 1030 nm. Such a laser light source 202 is fixed to the top plate 236 of the housing 231 with screws or the like so as to emit the laser light L in the horizontal direction.

  The reflective spatial light modulator 203 modulates the laser light L emitted from the laser light source 202. The reflective spatial light modulator 203 is, for example, a reflective liquid crystal on silicon (LCOS) spatial light modulator (SLM). The reflective spatial light modulator 203 modulates the laser beam L incident from the horizontal direction and reflects the laser beam L obliquely upward with respect to the horizontal direction.

  As shown in FIG. 8, the reflective spatial light modulator 203 includes a silicon substrate 213, a drive circuit layer 914, a plurality of pixel electrodes 214, a reflective film 215 such as a dielectric multilayer mirror, an alignment film 999a, and a liquid crystal layer 216. , An alignment film 999b, a transparent conductive film 217, and a transparent substrate 218 such as a glass substrate are stacked in this order.

  The transparent substrate 218 has a surface 218a along a predetermined plane. The surface 218 a of the transparent substrate 218 constitutes the surface of the reflective spatial light modulator 203. The transparent substrate 218 is made of a light transmissive material such as glass, for example. The transparent substrate 218 transmits the laser light L having a predetermined wavelength incident from the surface 218 a of the reflective spatial light modulator 203 into the reflective spatial light modulator 203. The transparent conductive film 217 is formed on the back surface of the transparent substrate 218. The transparent conductive film 217 is made of a conductive material (for example, ITO) that transmits the laser light L.

  The plurality of pixel electrodes 214 are arranged in a matrix on the silicon substrate 213 along the transparent conductive film 217. The plurality of pixel electrodes 214 are formed of a metal material such as aluminum, for example. The surfaces 214a of the plurality of pixel electrodes 214 are processed flat and smoothly. The plurality of pixel electrodes 214 are driven by an active matrix circuit provided in the drive circuit layer 914.

  The active matrix circuit is provided between the plurality of pixel electrodes 214 and the silicon substrate 213. The active matrix circuit controls the voltage applied to each pixel electrode 214 in accordance with the light image to be output from the reflective spatial light modulator 203. For example, the active matrix circuit includes a first driver circuit that controls an applied voltage of each pixel column aligned in one direction along the surface 218a, and each pixel column orthogonal to the one direction and aligned in the other direction along the surface 218a. And a second driver circuit for controlling the applied voltage. Such an active matrix circuit is configured such that a predetermined voltage is applied to the pixel electrode 214 of the pixel specified by both driver circuits by the control unit 250 (see FIG. 7).

  The alignment films 999a and 999b are disposed on both end faces of the liquid crystal layer 216, and align liquid crystal molecule groups in a certain direction. The alignment films 999a and 999b are formed of a polymer material such as polyimide, for example. The contact surfaces of the alignment films 999a and 999b with the liquid crystal layer 216 are rubbed.

  The liquid crystal layer 216 is disposed between the plurality of pixel electrodes 214 and the transparent conductive film 217. The liquid crystal layer 216 modulates the laser light L in accordance with the electric field formed by each pixel electrode 214 and the transparent conductive film 217. That is, when a voltage is applied to each pixel electrode 214 by the active matrix circuit of the drive circuit layer 914, an electric field is formed between the transparent conductive film 217 and each pixel electrode 214, and the electric field formed in the liquid crystal layer 216. The alignment direction of the liquid crystal molecules 216a changes depending on the size of the liquid crystal molecules. When the laser light L passes through the transparent substrate 218 and the transparent conductive film 217 and enters the liquid crystal layer 216, the laser light L is modulated by the liquid crystal molecules 216 a while passing through the liquid crystal layer 216, and is reflected on the reflective film 215. After reflection, the light is again modulated by the liquid crystal layer 216 and emitted.

  At this time, the voltage applied to each pixel electrode 214 is controlled by the control unit 250 (see FIG. 7), and a portion sandwiched between the transparent conductive film 217 and each pixel electrode 214 in the liquid crystal layer 216 according to the voltage. The refractive index of the liquid crystal layer 216 at the position corresponding to each pixel changes. With this change in refractive index, the phase of the laser light L can be changed for each pixel of the liquid crystal layer 216 in accordance with the applied voltage. That is, phase modulation corresponding to the hologram pattern can be applied to each pixel by the liquid crystal layer 216. In other words, a modulation pattern (also referred to as a phase pattern) as a hologram pattern for applying modulation can be displayed on the liquid crystal layer 216 of the reflective spatial light modulator 410. The wavefront of the laser light L that enters and passes through the modulation pattern is adjusted, and the phase of the component in the direction orthogonal to the traveling direction is shifted in each light beam constituting the laser light L. Therefore, by appropriately setting the modulation pattern to be displayed on the reflective spatial light modulator 203, the laser light L can be modulated (for example, the intensity, amplitude, phase, polarization, etc. of the laser light L can be modulated).

  Returning to FIG. 7, the 4f optical system 241 is an adjustment optical system that adjusts the wavefront shape of the laser light L modulated by the reflective spatial light modulator 203. The 4f optical system 241 includes a first lens 241a and a second lens 241b. In the first lens 241a and the second lens 241b, the distance of the optical path between the reflective spatial light modulator 203 and the first lens 241a is the first focal length f1 of the first lens 241a. The distance of the optical path between the second lens 241b is the second focal distance f2 of the second lens 241b, and the distance of the optical path between the first lens 241a and the second lens 241b is the first focal distance f1 and the second focal distance. on the optical path between the reflective spatial light modulator 203 and the condensing optical system 204 so that the first lens 241a and the second lens 241b are both-side telecentric optical systems. Has been placed. According to the 4f optical system 241, the laser beam L modulated by the reflective spatial light modulator 203 can be suppressed from changing its wavefront shape due to spatial propagation and increasing aberration.

  The condensing optical system 204 condenses the laser light L emitted from the laser light source 202 and modulated by the reflective spatial light modulator 203 inside the workpiece 1. The condensing optical system 204 includes a plurality of lenses, and is installed on the bottom plate 233 of the housing 231 via a drive unit 232 configured to include a piezoelectric element and the like.

  In the laser processing apparatus 300 configured as described above, the laser light L emitted from the laser light source 202 travels in the horizontal direction in the housing 231, is then reflected downward by the mirror 205 a, and is reflected by the attenuator 207. Strength is adjusted. Thereafter, the laser light L is reflected in the horizontal direction by the mirror 205 b, the intensity distribution of the laser light L is made uniform by the beam homogenizer 260, and is incident on the reflective spatial light modulator 203.

  The laser beam L incident on the reflective spatial light modulator 203 is modulated in accordance with the modulation pattern by transmitting the modulation pattern displayed on the liquid crystal layer 216. Thereafter, the laser light L is reflected upward by the mirror 206a, the polarization direction is changed by the λ / 2 wave plate 228, reflected by the mirror 206b in the horizontal direction, and enters the 4f optical system 241.

  The wavefront shape of the laser light L incident on the 4f optical system 241 is adjusted so as to be incident on the condensing optical system 204 as parallel light. Specifically, the laser light L is transmitted and converged through the first lens 241a, reflected downward by the mirror 219, diverged through the confocal O, and transmitted through the second lens 241b to become parallel light. Will converge again. Then, the laser light L sequentially passes through the dichroic mirrors 210 and 238 and enters the condensing optical system 204, and is condensed by the condensing optical system 204 in the workpiece 1 placed on the stage 111. .

  The laser processing apparatus 300 also includes a surface observation unit 211 for observing the laser light incident surface of the workpiece 1 and an AF (AutoFocus) for finely adjusting the distance between the condensing optical system 204 and the workpiece 1. ) Unit 212 and housing 231.

  The surface observation unit 211 includes an observation light source 211a that emits visible light VL1, and a detector 211b that receives and detects the reflected light VL2 of the visible light VL1 reflected by the laser light incident surface of the workpiece 1. Have. In the surface observation unit 211, the visible light VL 1 emitted from the observation light source 211 a is reflected and transmitted by the mirror 208 and the dichroic mirrors 209, 210, and 238, and condensed toward the workpiece 1 by the condensing optical system 204. Is done. The reflected light VL2 reflected from the laser light incident surface of the workpiece 1 is condensed by the condensing optical system 204, transmitted and reflected by the dichroic mirrors 238 and 210, and then transmitted through the dichroic mirror 209 to be detected. Light is received at 211b.

  The AF unit 212 emits the AF laser light LB1, receives and detects the reflected light LB2 of the AF laser light LB1 reflected by the laser light incident surface, thereby detecting the laser light incident surface along the planned cutting line 5 Get the displacement data. When forming the modified region 7, the AF unit 212 drives the drive unit 232 based on the acquired displacement data, and reciprocates the condensing optical system 204 in the optical axis direction so as to follow the undulation of the laser light incident surface. Move.

  Furthermore, the laser processing apparatus 300 includes a control unit 250 that controls the operation of each unit of the laser processing apparatus 300. The control unit 250 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like.

  The controller 250 controls the operation of the laser light source 202 and emits the laser light L from the laser light source 202. The controller 250 controls the operation of the laser light source 202 and adjusts the output, pulse width, and the like of the laser light L emitted from the laser light source 202. When the control unit 250 forms the modified region 7, the condensing point P of the laser light L is located at a predetermined distance from the front surface 3 or the back surface 21 of the workpiece 1 and the condensing point P of the laser light L is cut. At least one of the housing 231, the position of the stage 111, and the drive of the drive unit 232 is controlled so as to move relatively along the scheduled line 5. The control unit 250 has functions of the laser light source control unit 102 and the stage control unit 115.

  When forming the modified region 7, the controller 250 applies a predetermined voltage to each pixel electrode 214 in the reflective spatial light modulator 203 and causes the liquid crystal layer 216 to display a predetermined modulation pattern. Thereby, the control unit 250 modulates the laser light L as desired by the reflective spatial light modulator 203. The modulation pattern displayed on the liquid crystal layer 216 includes, for example, the position where the modified region 7 is to be formed, the wavelength of the laser beam L to be irradiated, the material of the workpiece 1, and the condensing optical system 204 or the workpiece 1. Is derived in advance based on the refractive index and the like and stored in the control unit 250. The modulation pattern includes an individual difference correction pattern for correcting individual differences generated in the laser processing apparatus 300 (for example, distortion generated in the liquid crystal layer 216), a spherical aberration correction pattern for correcting spherical aberration, and the like.

  In the present embodiment, the control unit 250 controls at least the operations of the laser light source 202 and the reflective spatial light modulator 203, and executes laser beam focusing control (details will be described later). The control unit 250 controls the reflective spatial light modulator 203 to convert the laser beam L into at least three branches and simultaneously branch into a processing object 1 by the focusing optical system 204 using the modulation pattern. Is displayed on the liquid crystal layer 216. Thereby, for example, as shown in FIG. 9, the reflective spatial light modulator 203 splits the laser light L into three laser lights L1 to L3. In the workpiece 1, the laser beam L is simultaneously focused at three desired positions in the three-dimensional direction by the focusing optical system 204, and the modified regions 7 as modified spots are simultaneously focused at the three locations. Let it form. Specifically, one or more first modified regions 7a located at positions corresponding to the planned cutting line 5 in the Y direction, and one or more located on one side of the first modified region 7a in the Y direction. The second modified region 7b and one or more third modified regions 7c located on the other side (opposite side of the one side) in the Y direction are formed simultaneously.

  The positions of the first to third modified regions 7a to 7c in the X direction are equal to each other. In other words, the first to third modified regions 7a to 7c are formed so as to be linearly arranged along the Y direction. The positions of the first to third modified regions 7a to 7c in the Z direction are equal to each other. In other words, the first to third modified regions 7a to 7c are formed at the same depth position.

  The distance between the first modified region 7a and the second modified region 7b in the Y direction is equal to the distance between the first modified region 7a and the third modified region 7c in the Y direction. That is, the intervals between the first to third modified regions 7a to 7c in the Y direction are equal to each other. The interval between the first to third modified regions 7 a can be adjusted as appropriate by the branch pattern displayed on the liquid crystal layer 216. Although the space | interval of the 1st-3rd modified area | region 7a is not specifically limited, For example, it can be set as 1 micrometer-10 micrometers.

  The first modified region 7a is formed on the planned cutting line (first cutting planned line) 5, that is, at a position overlapping the planned cutting line 5 when viewed from the Z direction. The second modified region 7b includes a scheduled cutting line 5 corresponding to the first modified region 7a and another scheduled cutting line 5 (second scheduled cutting line) adjacent to the scheduled cutting line 5 on one side in the Y direction. ). The third modified region 7c includes a planned cutting line 5 corresponding to the first modified region 7a and another planned cutting line 5 (third planned cutting line) adjacent to the planned cutting line 5 on the other side in the Y direction. ).

  The control part 250 controls each part of the laser processing apparatus 300, and when the first to third modified regions 7a to 7c are formed, the half cut Hc that is a crack reaching the surface 3 of the workpiece 1 is first modified. It is generated from the quality region 7a. At this time, the half cut Hc is not generated from the second and third modified regions 7b and 7c. The half cut Hc is a surface crack exposed on the surface 3.

  As an example, the control unit 250 controls the laser light source 202 and adjusts the output of the laser light L so that the half cut Hc is generated only from the first modified region 7a. Specifically, the control unit 250 has an output of the laser beam L1 that is collected for forming the first modified region 7a larger than the HC threshold that is the minimum output value that can generate the half cut Hc. Thus, the output of the laser beam L1 is controlled. In addition, generation | occurrence | production of the half cut Hc from the 1st modification | reformation area | region 7a is the characteristic of the laser beam L1 (laser beam L), the position (distance from the surface 3) which condenses the laser beam L in the process target object 1, This can be realized by appropriately adjusting at least one of the modulation pattern and other processing conditions by the control unit 250. Generation | occurrence | production of the half cut Hc is realizable using various well-known methods.

  The control unit 250 controls the laser light source 202 and adjusts the output ratios of some or all of the laser beams L1 to L3 after branching to be the same or different from each other. For example, the control unit 250 sets the output of the laser beam L1 that is the first laser beam that forms the first modified region 7a as the first output, and the second and second modified regions 7b and 7c that form the second and third modified regions 7c. The outputs of both the laser beams L2 and L2, which are three laser beams, are set as a second output smaller than the first output.

  Next, a laser processing method performed in the laser processing apparatus 300 will be described.

  The laser processing method of this embodiment is used as a chip manufacturing method for manufacturing a plurality of chips by laser processing the workpiece 1. The workpiece 1 has a plate shape. The workpiece 1 is, for example, a sapphire substrate, a SiC substrate, a glass substrate (tempered glass substrate), a silicon substrate, a semiconductor substrate, a transparent insulating substrate, or the like. The processing object 1 here is a sapphire substrate.

  As shown in FIG. 10, the functional element layer 15 is formed on the surface 3 side that is the laser light incident surface side in the workpiece 1. The functional element layer 15 includes a plurality of functional elements 15a (for example, a light receiving element such as a photodiode, a light emitting element such as a laser diode, or a circuit element formed as a circuit) arranged in a matrix. On the surface 3 of the workpiece 1, a plurality of cutting lines 5 extending so as to pass between adjacent functional elements 15 a are set. The plurality of scheduled cutting lines 5 extend in a lattice shape. In addition, when the workpiece 1 is a sapphire substrate, the C surface is set as a main surface (the front surface 3 and the back surface 21), and the planned cutting line 5 is set to extend in a direction along the R surface of the sapphire substrate. .

  In the laser processing method of this embodiment, first, the processing object 1 is placed on the support base 107 of the stage 111 so that the surface 3 becomes a laser light incident surface. The control unit 250 causes the modulation pattern to be displayed on the liquid crystal layer 216 (see FIG. 8). In this state, the laser light L is emitted from the laser light source 202, and the laser light L is condensed inside the workpiece 1. At the same time, the movement of the stage 111 is controlled by the control unit 250, and the laser light L is moved (scanned) relatively in the processing progress direction along the planned cutting line 5 to be modified inside the processing target 1. One row of the regions 7 is formed along the planned cutting line 5.

  Such scanning of the laser beam L along the planned cutting line 5 is performed a plurality of times while changing the condensing position in the Z direction. Thus, a plurality of rows of modified regions 7 whose positions in the Z direction are different from each other are formed inside the workpiece 1 along the planned cutting line 5. Then, a knife edge is pressed against the workpiece 1 along the planned cutting line 5, a force is applied to the processing target 1 from the outside along the planned cutting line 5, and the processing target 1 is made into a plurality of chips. Disconnect.

  Here, in the scan for forming the modified region 7 in the row closest to the surface 3 among the modified regions 7 in a plurality of rows in the Z direction, the next laser beam focusing step (laser beam focusing control) is performed. Execute. That is, the laser beams L1 to L3 are simultaneously condensed inside the workpiece 1. Here, the first focusing point on the planned cutting line 5, the second focusing point on one side in the Y direction with respect to the planned cutting line 5, and the third set on the other side in the Y direction with respect to the planned cutting line 5. The laser beam L is simultaneously focused on the light spot. As a result, as shown in FIG. 11, the first to third modified regions 7a to 7c are simultaneously formed at the first to third condensing points, respectively, and half-cut from the first modified region 7a. Hc is generated.

  Specifically, with the control unit 250 displaying the branch pattern on the liquid crystal layer 216, the control unit 250 emits the laser light L from the laser light source 202 and modulates the laser light L with the branch pattern of the liquid crystal layer 216. Then, it is branched into three laser beams L1 to L3. The laser beam L1 to L3 is irradiated onto the workpiece 1 through the condensing optical system 204, and the laser beams L1 to L3 are simultaneously condensed on the first to third condensing points, respectively. The first to third modified regions 7a to 7c are simultaneously formed on the basis of the positions of the first to third condensing points.

  At this time or in advance, for example, the control unit 250 controls the laser light source 202 so that the output of the laser light L1 becomes equal to or higher than the HC threshold. Thereby, the half cut Hc is generated from the first modified region 7a simultaneously with the formation of the first to third modified regions 7a to 7c. In addition, the control unit 250 controls the movement of the stage 111 and the like, and relatively moves the laser beams L1 to L3 in the processing progress direction along the planned cutting line 5. As described above, the first to third modified regions 7 a to 7 c are formed along the planned cutting line 5 in the workpiece 1, and the half cut Hc is advanced along the planned cutting line 5.

  12 and 13 are diagrams for explaining the operation of the laser processing method and the laser processing apparatus 300 according to an embodiment. FIG. 12 is a cross-sectional view along the XY plane at a position in the Z direction where the modified region 7 is formed in the workpiece 1. FIG. 13A is a side sectional view of the workpiece 1 after laser processing according to the comparative example. FIG. 13B is a side sectional view of the workpiece 1 after laser processing according to this embodiment. In the laser processing according to the comparative example, the laser beam L is condensed on the processing object 1 without branching (for example, without displaying the branch pattern on the liquid crystal layer 216 of the reflective spatial light modulator 203), and the line to be cut 5, the modified region 7 is formed without forming the second and third modified regions 7b, 7c (the same applies to the following comparative examples).

  According to the present embodiment described above, the first modified region 7a is formed on the planned cutting line 5, and the first modified region 7a is generated at the same time as the first modified region 7a is generated. Second and third modified regions 7b and 7c are formed on one side and the other side in the Y direction of 7a, respectively. By forming the second and third modified regions 7b and 7c, one side and the other side in the Y direction of the first modified region 7a can be locally expanded in the workpiece 1. Thereby, as shown in FIG. 12, a strong compressive stress field (see the arrow in the figure) that sandwiches the first modified region 7a in the Y direction can be instantaneously and intentionally generated. The compressive stress field can suppress the progress of the half cut Hc in the Y direction, and the half cut Hc generated from the modified region 7 is inclined in the Y direction and deviates from the line 5 to be cut (see FIG. 13A). ) Can be suppressed. That is, as shown in FIG. 13B, the direction of progress of the half-cut Hc can be stabilized, and the half-cut Hc can be easily straightened from the first modified region 7a to the surface 3 in the Z direction. Therefore, it is possible to suppress the half-cut Hc from meandering with respect to the scheduled cutting line 5.

  In the present embodiment, the positions of the first to third modified regions 7a to 7c in the X direction are equal to each other. Thereby, the half cut Hc is positioned within a range in which the compressive stress field generated by the formation of the second and third modified regions 7b effectively extends, and the compressive stress field is effectively developed into the half cut Hc. Can act. It is possible to effectively suppress the progress of the half cut Hc in the Y direction.

  In the present embodiment, the laser beam L is an ultrashort pulse laser beam. Thereby, the compressive stress field due to the formation of the second and third modified regions 7b can be generated more instantaneously. Further, in the irradiation of one pulse of the branched laser beams L1 to L3, the irradiation of the laser beams L1 to L3 can be terminated before the thermal effect (influence) appears at each condensing point. As a result, the compressive stress field is effectively generated, and the above action of suppressing the progress of the half-cut Hc in the Y direction becomes remarkable by the compressive stress field.

  In the present embodiment, the positions of the first to third modified regions 7a to 7c in the Z direction are equal to each other. Thereby, the half cut Hc is positioned within a range in which the compressive stress field generated by the formation of the second and third modified regions 7b effectively extends, and the compressive stress field is effectively developed into the half cut Hc. Can act. It is possible to effectively suppress the progress of the half cut Hc in the Y direction.

  In the present embodiment, a plurality of rows of modified regions 7 are formed in the Z direction along the planned cutting line 5. The laser beam condensing step (laser beam focusing control) for generating the half-cut Hc reaching the surface 3 is performed in the modified region 7 closest to the surface 3 of the workpiece 1 among the modified regions 7 in a plurality of rows in the Z direction. Run when forming. Thereby, the half cut Hc from the 1st modification area | region 7a to the surface 3 can be generated efficiently.

  In the present embodiment, the laser beam L is modulated by the reflective spatial light modulator 203 so as to be branched into three laser beams L1 to L3, and these laser beams L1 to L3 are simultaneously condensed in the workpiece 1. . Thus, in the present embodiment, the first to third modified regions 7a to 7c can be simultaneously formed using the reflective spatial light modulator 203.

  In the present embodiment, the half cut Hc is generated only from the first modified region 7a without being generated from the second and third modified regions 7b, 7c. Thereby, it is possible to avoid that the stress of the compressive stress field is released and reduced due to the influence of the half cut Hc from the second and third modified regions 7b and 7c.

  In the present embodiment, the second and third modified regions 7 b and 7 c are not located on the planned cutting line 5. That is, the second modified region 7b is located between the planned cutting line 5 corresponding to the first modified region 7a and the planned cutting line 5 adjacent to the planned cutting line 5 on one side in the Y direction. ing. The third modified region 7c is located between the planned cutting line 5 corresponding to the first modified region 7a and the planned cutting line 5 adjacent to the scheduled cutting line 5 on the other side in the Y direction. . In this case, the workpiece 1 is cut along the planned cutting line 5 by using the first modified region 7a and the half cut Hc as the starting point of cutting without using the second and third modified regions 7b, 7c. Can be cut accurately. That is, the first modified region 7a and the half cut Hc are regions used as a starting point for cutting. The second and third modified regions 7b and 7c are not regions that are used as starting points for cutting (in other words, regions that are not used as starting points for cutting).

  FIG. 14 and FIG. 15 are photographic views showing the laser processing results relating to the presence / absence of the second and third modified regions 7b and 7c. FIG. 14A is a photograph showing the surface 3 of the workpiece 1 after laser processing according to a comparative example in which the second and third modified regions 7b and 7c are not formed. FIG. 14B is a photograph showing the surface 3 of the workpiece 1 after laser processing according to the present embodiment in which the second and third modified regions 7b and 7c are formed. FIG. 15 (a) is a partially enlarged view of FIG. 14 (a), and FIG. 15 (b) is a partially enlarged view of FIG. 14 (b).

  In the laser processing of FIGS. 14 and 15, the processing object 1 is sapphire. As processing conditions, the pulse width of the laser light L is 2 ps, the repetition frequency of the laser light L is 50 kHz, and the scanning speed of the laser light L (relative speed with respect to the processing object 1) is 500 mm / s. In the laser processing shown in FIGS. 14B and 15B, the interval (pitch) between the first to third modified regions 7a to 7c is set to 3 μm, and the output (energy) of the laser beams L1 to L3 after branching. ) Are equal to each other.

  As shown in FIGS. 14 and 15, in the present embodiment, the half-cut Hc is more stable along the planned cutting line 5 than the laser processing in the case where the second and third modified regions 7 b and 7 c are not formed. And extend. Thereby, the said effect that it can suppress that the half cut Hc meanders with respect to the cutting scheduled line 5 in this embodiment can be confirmed.

  FIG. 16 is another photograph showing the laser processing result relating to the presence or absence of the second and third modified regions 7b and 7c. FIG. 16 shows a cross-sectional view along the XY plane at a position in the Z direction where the modified region 7 is formed in the workpiece 1. FIG. 16A is a photograph showing a cross-sectional view after laser processing according to a comparative example in which the second and third modified regions 7b and 7c are not formed. FIG. 16B is a photograph showing a cross-sectional view after laser processing according to the present embodiment in which the second and third modified regions 7b and 7c are formed.

  In the laser processing of FIG. 16, the workpiece 1 is quartz glass. As processing conditions, the pulse width of the laser light L is 2 ps, the repetition frequency of the laser light L is 50 kHz, and the scanning speed of the laser light L is 500 mm / s. The output of the laser beam L is 6 μJ, and the modified region 7 is formed at a position 10 μm from the surface 3. In the laser processing shown in FIG. 16B, the interval between the first to third modified regions 7a to 7c is set to 1 μm, and the outputs of the branched laser beams L1 to L3 are made equal to each other.

  As shown in FIG. 16, according to the present embodiment, the width W of the internal crack can be narrowed compared to the laser processing in the case where the second and third modified regions 7 b and 7 c are not formed. Thereby, the said effect that it can suppress that the half cut Hc meanders with respect to the cutting scheduled line 5 in this embodiment can be confirmed.

  FIG. 17 is a photograph showing the result of laser processing by changing the output ratio of the branched laser beams L1 to L3. FIG. 17 shows a cross-sectional view along the XY plane at a position in the Z direction where the modified region 7 is formed in the workpiece 1. In the laser processing in the figure, the processing object 1 is quartz glass. The processing conditions are the same as the laser processing in FIG. 17A, the output ratio of the laser beams L1 to L3 is set to 3: 3: 3, and in FIG. 17B, the output ratio of the laser beams L1 to L3 is set to 2: 3: 2, and FIG. ), The output ratio of the laser beams L1 to L3 is 1: 3: 1.

  In the present embodiment, laser processing may be performed by changing the output ratio of the laser beams L1 to L3. Even in this case, as shown in FIG. 17, the width of the internal crack can be reduced, and the half-cut Hc can be prevented from meandering with respect to the planned cutting line 5. In particular, when the output of the laser beam L1 for forming the first modified region 7a is larger than the outputs of the laser beams L2 and L3 for forming the second and third modified regions 7b and 7c, a half cut is made in the X direction. Hc can be easily developed.

  18-21 is a figure which shows the laser processing result at the time of changing the space | interval of the 1st-3rd modification area | regions 7a-7c. In the result column in FIGS. 18 and 19, a photograph of the surface 3 of the workpiece 1 is shown. 20 and 21 are cross-sectional views along the XY plane at the position in the Z direction where the modified region 7 is formed in the workpiece 1. In the figure, the interval is the interval between the first to third modified regions 7a to 7c. “None” is the case where the laser beam L is condensed at one point without branching, and means laser processing according to a comparative example in which the second and third modified regions 7b and 7c are not formed. . The processing energy is the output of the laser beam L. In the laser processing of FIGS. 18 to 21, the processing object 1 is sapphire. The processing conditions are the same as the laser processing in FIGS. The modified region 7 is formed at a position 20 μm from the surface 3.

  As shown in FIGS. 18 to 21, in the present embodiment, the control unit 250 can control the effect of suppressing the meandering of the half cut Hc by controlling the interval between the first to third modified regions 7 a. I understand. Further, in the present embodiment, the processing energy necessary for generating the half cut Hc is larger than the laser processing result (when there is no interval) according to the comparative example in which the second and third modified regions 7b and 7c are not formed. It can be confirmed that it is reduced. In addition, it can be seen that when the interval between the first to third modified regions 7a to 7c is equal to or greater than a certain value (8 μm in the drawing), the processing energy increases.

  In the present embodiment, the control unit 250 may control at least one of laser characteristics such as a focused spot diameter of the laser light L and a wavelength of the laser light L. Also in this case, it can be seen that the effect of suppressing the meandering of the half cut Hc can be controlled.

  Here, the bending strength comparison test which compares the bending strength of the workpiece 1 which performed the laser processing was done. In the bending strength comparison test, the bending strength was compared between the comparative example in which the second and third modified regions 7b and 7c were not formed and the present embodiment in which the second and third modified regions 7b and 7c were formed. . The bending strength was measured in accordance with JIS1603. In the laser processing of the bending strength comparison test, five rows of modified regions 7 were formed in the Z direction. In the laser processing according to the comparative example, five rows of the modified regions 7 were formed without branching the laser beam L. In the laser processing according to the present embodiment, the first to third modified regions 7a to 7c are simultaneously formed by branching the laser beam L only when forming the modified region 7 on the most surface 3 side. When the other four regions of the modified region 7 were formed, the modified region 7 was formed without branching the laser beam L.

  According to the result of such a bending strength comparison test, when the result of the comparative example is used as a reference, in the case of the present embodiment, the average strength of the workpiece 1 is 118%, and the strength of the fracture probability is 10%. 128%. Thereby, in this embodiment, it has confirmed that high bending strength was obtained. Moreover, in this embodiment, it has confirmed that the dispersion | variation in bending strength was very small.

  FIG. 22 (a) is an enlarged photograph showing a part of the cut surface when the workpiece 1 is cut by performing laser processing according to a comparative example in which the second and third modified regions 7b and 7c are not formed. FIG. FIG. 22B is an enlarged photographic view showing a part of the cut surface when the workpiece 1 is cut by performing the laser processing according to the present embodiment. As shown in FIG. 22, in this embodiment, since the meandering of the half-cut Hc can be suppressed as compared with the laser processing that does not form the second and third modified regions 7b and 7c, the edge Eg that is a stress concentration portion It can be seen that it is possible to suppress the formation on the cut surface. Thereby, in this embodiment, it can be considered that the bending strength can be reduced and, in turn, variation can be suppressed.

  In addition, the number and arrangement | positioning relationship of the 1st-3rd modification area | regions 7a-7c to form are not limited to the said embodiment. For example, as shown in FIG. 23A, the second and third modified regions 7b and 7c may be located on the rear side in the processing progress direction with respect to the first modified region 7a. For example, as shown in FIG. 23B, the second and third modified regions 7b and 7c may be located on the front side in the processing progress direction with respect to the first modified region 7a.

  For example, as shown in FIG. 23C, two first modified regions 7a may be formed apart from each other in the X direction. In this case, the second and third modified regions 7b and 7c may be positioned between the two first modified regions 7a in the X direction. For example, as shown in FIG. 23 (d), the second modified region 7b is located on the front side in the processing progress direction with respect to the first modified region 7a, and the third modified region 7c is the first modified region. You may be located in the back side of a process progress direction with respect to 7a. In this case, the intervals in the X direction of the first to third modified regions 7a to 7c may be equal to each other. In the example shown in FIG. 23D, the second modified region 7b is located on the rear side in the processing progress direction with respect to the first modified region 7a, and the third modified region 7c is in the first modified region. You may be located in the front side of a process progress direction with respect to the quality area | region 7a.

  24 and 25 are photographic diagrams showing the results of laser processing by the laser processing method and laser processing apparatus according to the modification. 24 and 25 show cross-sectional views along the XY plane at the position in the Z direction where the modified region 7 is formed in the workpiece 1. In the laser processing shown in FIGS. 24 and 25, the processing object 1 is quartz glass. The processing conditions are the same as the laser processing in FIG.

  FIG. 24A shows the laser processing result when the number and arrangement relationship of the first to third modified regions 7a to 7c are shown in FIG. FIG. 24B shows the laser processing result when the number and arrangement relationship of the first to third modified regions 7a to 7c are shown in FIG. FIG. 25A shows the laser processing result when the number and arrangement relationship of the first to third modified regions 7a to 7c are shown in FIG. 23C. FIG. 25B shows the laser processing result when the number of the first to third modified regions 7a to 7c and the arrangement relationship are narrower than the case shown in FIG. 25A. It is. FIG. 25 (c) shows the laser processing result when the number and arrangement relationship of the first to third modified regions 7a to 7c are shown in FIG. 23 (d).

  As shown in FIGS. 24 and 25, also in the laser processing apparatus and the laser processing method according to the modified example, the width of the internal crack is reduced, and the half cut Hc is prevented from meandering with respect to the scheduled cutting line 5. It becomes possible.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments. The present invention can be modified without departing from the scope described in the claims or applied to other embodiments. May be.

  In the above embodiment, the positions where the second and third modified regions 7b and 7c are formed are not limited to the above. The second and third modified regions 7b and 7c may be formed simultaneously on one side and the other side in the Y direction with respect to the first modified region 7a. The position where the second and third modified regions 7b and 7c are formed may be a position where each stress due to the formation of the second and third modified regions 7b and 7c acts on the half cut Hc. The arrangement relationship of the first to third modified regions 7a to 7c can be controlled by appropriately setting the modulation pattern of the reflective spatial light modulator 203, for example.

  In the said embodiment, the number of each of the 1st-3rd modification area | regions 7a-7c is not limited above. A plurality of first modified regions 7a may be formed at positions corresponding to the scheduled cutting lines 5. A plurality of second modified regions 7b may be formed on one side in the Y direction of the first modified region 7a. A plurality of third modified regions 7c may be formed on the other side in the Y direction of the first modified region 7a. The number of each of the first to third modified regions 7a to 7c can be controlled by appropriately setting the modulation pattern of the reflective spatial light modulator 203, for example.

  The above embodiment includes the reflective spatial light modulator 203 as the spatial light modulator. However, the spatial light modulator is not limited to the reflective type, and may include a transmissive spatial light modulator. . In the said embodiment, although the surface 3 of the workpiece 1 was made into the laser beam incident surface, it is good also considering the back surface 21 of the workpiece 1 as a laser beam incident surface. The position corresponding to the planned cutting line 5 includes not only the case where it coincides with the planned cutting line 5 in the Y direction, but also the case where it substantially matches the planned cutting line 5 and the case where it is close to the planned cutting line 5. The position corresponding to the planned cutting line 5 includes a position separated from the planned cutting line 5 to such an extent that the quality of the workpiece 1 after cutting is not affected.

  In the above embodiment, the half cut Hc from the first modified region 7a to the front surface 3 is generated, but a half cut from the first modified region 7a to the back surface 21 may be generated. In the above embodiment, a laser beam condensing step (laser beam concentrating) that generates a half-cut Hc reaching the surface 3 during the scan for forming the modified region 7 in the column closest to the surface 3 among the plurality of columns in the Z direction. The laser beam condensing step (laser) that generates a half cut reaching the back surface 21 during the scan for forming the modified region 7 in the row closest to the back surface 21 among the plurality of columns in the Z direction. (Light condensing control) may be executed.

  In the above embodiment, the laser beam L is branched to the laser beams L1 to L3 by the reflective spatial light modulator 203 and focused on the workpiece 1. However, the present invention is not limited to this. For example, by using at least three laser light sources and irradiating laser light L from each of them, at least three laser lights may be simultaneously condensed inside the workpiece 1. In the said embodiment, the space | interval of the 1st-3rd modification area | regions 7a-7c in a Y direction may mutually differ.

  In the above embodiment, the knife edge is used to cut the workpiece 1, but the method of cutting the workpiece 1 is not particularly limited. For example, an expanding tape may be affixed on the front surface 3 or the back surface 21 of the processing object 1, and this expanding tape may be expanded and the processing object 1 may be cut | disconnected. For example, the workpiece 1 may be cut using a breaker device or a roller device. In the above embodiment, the laser light source 202 includes the output adjustment unit that adjusts the output of the laser light L, but may include another output adjustment unit. In any of these cases, the output of the laser beam L (laser beams L1 to L3) can be controlled by the controller 250.

  DESCRIPTION OF SYMBOLS 1 ... Processing object, 3 ... Surface, 5 ... Planned cutting line (1st scheduled cutting line-3rd scheduled cutting line), 7 ... Modified region, 7a ... 1st modified region, 7b ... 2nd modified region 7c ... third modified region, 21 ... back surface, 100, 300 ... laser processing apparatus, 101, 202 ... laser light source (laser light emitting part), 203 ... reflective spatial light modulator (spatial light modulator), 204 ... Condensing optical system, 250 ... Control unit, Hc ... Half cut (crack), L, L1, L2, L3 ... Laser light.

Claims (9)

A laser processing method for forming a modified region in the processing object along the line to be cut by condensing laser light inside the processing object,
By simultaneously condensing at least three laser beams inside the workpiece, the planned cutting line in a predetermined direction orthogonal to the thickness direction of the processing target and the extending direction of the planned cutting line One or more first reforming regions located at positions corresponding to the above, one or more second reforming regions located on one side of the first reforming region in the predetermined direction, and in the predetermined direction Simultaneously forming one or a plurality of third modified regions located on the other side of the first modified region and generating cracks from the first modified region to the front surface or the back surface of the workpiece A laser processing method including a laser beam focusing step.   2. The laser processing method according to claim 1, wherein positions of the first to third modified regions in an extending direction of the scheduled cutting line are equal to each other.   The laser processing method according to claim 1, wherein the laser beam is an ultrashort pulse laser beam.   The laser processing method according to claim 1, wherein positions of the first to third modified regions in a thickness direction of the processing target are equal to each other. A laser processing method for forming a plurality of the modified regions in a thickness direction of the workpiece along the planned cutting line,
The laser beam condensing step includes
When a crack reaching the surface of the workpiece is generated from the first modified region, the closest to the surface of the workpiece among a plurality of the modified regions in the thickness direction of the workpiece. Executed in forming the modified region,
When the crack reaching the back surface of the workpiece is generated from the first modified region, it is closest to the back surface of the workpiece among a plurality of the modified regions in the thickness direction of the workpiece. The laser processing method as described in any one of Claims 1-4 performed when forming a modification | reformation area | region.   The laser processing according to claim 1, wherein in the laser beam condensing step, the laser beam is modulated by a spatial light modulator so that one laser beam is branched into at least three. Method.   The laser processing according to any one of claims 1 to 6, wherein in the laser beam condensing step, a crack reaching the front surface or the back surface of the workpiece is not generated from the second and third modified regions. Method. A plurality of the scheduled cutting lines are set,
The first modified region is located on a first scheduled cutting line,
The second modified region is located between the second planned cutting line and the first planned cutting line adjacent to one side with respect to the first planned cutting line in the predetermined direction,
The third modified region is located between the third planned cutting line and the first planned cutting line adjacent to the other side of the first planned cutting line in the predetermined direction. The laser processing method as described in any one of -7. A laser processing apparatus that forms a modified region in the processing object along the line to be cut by condensing laser light inside the processing object,
A laser beam emitting section for emitting the laser beam;
A condensing optical system for condensing the laser light emitted from the laser light emitting portion inside the workpiece;
A spatial light modulator that modulates the laser light emitted from the laser light emitting portion and condensed by the condensing optical system;
A control unit that controls at least the operation of the laser beam emitting unit and the spatial light modulator,
The controller is
The laser light is emitted from the laser light emitting portion, and the laser light is branched into at least three parts, and the laser light is condensed in the processing object at the same time by the condensing optical system. One or a plurality of first revisions that are modulated by an optical modulator and located at a position corresponding to the planned cutting line in a predetermined direction orthogonal to the thickness direction of the workpiece and the extending direction of the planned cutting line. A quality region, one or more second reformed regions located on one side of the first modified region in the predetermined direction, and 1 located on the other side of the first modified region in the predetermined direction Alternatively, a laser processing apparatus that simultaneously forms a plurality of third modified regions and generates a crack reaching the front surface or the back surface of the workpiece from the first modified region.