Laser processing device and laser processing method

Abstract

This laser processing device for forming a modified region on an object by irradiating the object with laser light includes: a support part for supporting the object; an irradiation part for irradiating the object supported by the support part with the laser light; a moving part for moving at least one among the support part and the irradiation part such that a condensing spot of the laser light moves relative to the object; and a control unit that executes machining processing for controlling the support part, the irradiation part, and the moving part to thereby irradiate the object with the laser light while moving the condensing spot along a processing line following the incident surface of the laser light on the object, thereby forming the modified region along the processing line. The irradiation part includes a spatial light modulator for modulating the laser light, and a condensing lens for condensing the laser light that has passed through the spatial light modulator toward the object.

Description

Laser processing device and laser processing method

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

[0002] Patent Document 1 describes a laser processing method for forming a modified region, which serves as a cutting start point, inside a plate-shaped workpiece along a line to be cut by irradiating the workpiece with a laser beam with a focal point aligned with the inside of the workpiece. This laser processing method includes the steps of forming a first modified region inside the workpiece and generating a first crack from the first modified region, the first crack extending parallel to the thickness direction of the workpiece and in a direction oblique to the plane including the line to be cut, and forming a second modified region inside the workpiece and generating a second crack from the second modified region, the second crack extending parallel to the thickness direction of the workpiece and in a direction oblique to the plane including the line to be cut so as to connect to the first crack.

[0003] Japanese Patent Application Laid-Open No. 2008-016486

[0004] In the laser processing method of Patent Document 1, in order to suppress warping of the object to be processed during laser processing, the cracks extending from the modified area are made parallel to the thickness direction of the object to be processed and inclined with respect to the plane including the planned cutting line.

[0005] On the other hand, depending on the crystal plane of the object to be processed, cracks extending from the modified region may be unintentionally tilted. As an example, when the object to be processed is a wafer with a crystal orientation of <111>, in which the incident plane of the laser light is the <111> plane, if a modified region is formed by irradiating the laser light along a processing line along the (110) plane perpendicular to the incident plane, the cracks extending from the modified region are unlikely to be tilted, but if a modified region is formed by irradiating the laser light along another processing line perpendicular to the incident plane and the (110) plane, the cracks extending from the modified region are likely to be tilted due to the influence of the (111) plane.

[0006] In this case, the (111) plane that affects the propagation of the crack is inclined with respect to the Z direction in the YZ plane, which includes the Y and Z directions, when the direction in which the other processing line extends (the processing direction) is the X direction, the direction intersecting the plane of incidence of the laser light is the Z direction, and the direction intersecting the X and Z directions is the Y direction. Therefore, the crack also tends to be inclined in the same direction. If the crack extending from the modified region is inclined with respect to the Z direction in the YZ plane, the following problems may occur.

[0007] That is, if a crack extending from the modified region is inclined with respect to the Z direction in the YZ plane, the arrival position of the crack on the incident back surface opposite the incident surface of the workpiece will be shifted in the Y direction from the processing line along which the focused spot of the laser light moves. Therefore, in the Y direction, the arrival position of the crack on the incident back surface of the workpiece and the damage caused by the escape light that occurs on the incident back surface directly below the processing line in the Z direction will be shifted in the Y direction. For this reason, if the arrival position of the crack on the incident back surface is positioned in the center of the street region (e.g., the region between devices on the incident back surface) in the Y direction, the damage caused by the escape light may be shifted from the center of the street region toward the device, potentially affecting the device.

[0008] From at least the above viewpoints, it is desirable to suppress the inclination of the crack in the Z direction within the YZ plane and to suppress the deviation between the arrival position of the crack on the back surface of the workpiece and the damage (i.e., the processing line) caused by the laser light escaping from the back surface of the workpiece.

[0009] Therefore, an object of the present disclosure is to provide a laser processing apparatus and a laser processing method that can suppress misalignment between the crack arrival position and the processing line.

[0010] A laser processing apparatus according to the present disclosure is [1] "a laser processing apparatus for forming a modified region in an object by irradiating the object with laser light, comprising: a support unit that supports the object; an irradiation unit that irradiates the object supported by the support unit with the laser light; a movement unit that moves at least one of the support unit and the irradiation unit so that a focused spot of the laser light moves relative to the object; and a control unit that controls the support unit, the irradiation unit, and the movement unit to irradiate the object with the laser light while moving the focused spot along a processing line that follows an incident surface of the laser light on the object, thereby performing a processing process to form the modified region along the processing line, and a focusing lens that focuses the laser light that has passed through the spatial light modulator toward the object, wherein the object includes a crystal plane that is inclined with respect to the Z direction in a YZ plane that includes the Y direction and the Z direction, where the extension direction of the processing line is defined as an X direction, the direction intersecting the incident plane is defined as a Z direction, and the direction intersecting the X direction and the Z direction is defined as a Y direction, and in the processing, the control unit modulates the laser light with the spatial light modulator, thereby performing a modulation process such that the beam shape at the focused spot of the laser light in the YZ plane becomes an inclined shape that is inclined with respect to the Z direction toward the opposite side to the crystal plane, at least on the incident plane side of the center of the focused spot.

[0011] The laser processing method according to the present disclosure is [6] "a laser processing method for forming a modified region in an object by irradiating the object with laser light, comprising a processing step of irradiating the object with the laser light while moving a focused spot of the laser light along a line along an incident surface of the laser light on the object, thereby forming the modified region along the line, wherein the object includes a crystal plane inclined with respect to the Z direction in a YZ plane containing the Y direction and the Z direction, where the extending direction of the line is defined as an X direction, a direction intersecting the incident surface is defined as a Z direction, and a direction intersecting the X direction and the Z direction is defined as a Y direction, and in the processing step, the laser light is modulated by a spatial light modulator, so that the beam shape at the focused spot of the laser light in the YZ plane is inclined toward the opposite side to the crystal plane with respect to the Z direction, at least on the incident surface side of the center of the focused spot."

[0012] In this laser processing apparatus and method, laser processing is performed to form a modified region along a processing line by irradiating the object with laser light while moving a focused spot along the processing line along the incident surface of the laser light on the object. When the extension direction of the processing line is the X direction, the direction intersecting the incident surface is the Z direction, and the direction intersecting the X and Z directions is the Y direction, the object includes a crystal plane inclined with respect to the Z direction in a YZ plane including the Y and Z directions. Therefore, depending on the crystal plane, a crack extending from the modified region may be inclined in the same direction as the crystal plane with respect to the Z direction in the YZ plane. In response to this, in this laser processing apparatus and method, the laser light is modulated by a spatial light modulator during laser processing so that the beam shape at the focused spot of the laser light in the YZ plane is inclined toward the opposite side of the crystal plane with respect to the Z direction, at least on the incident surface side of the center of the focused spot. By inclining the beam shape at the focused spot of the laser light in this manner, the crack extending from the modified region can be inclined in the same direction as the inclination direction of the beam shape. Therefore, in the YZ plane, the inclination of the crack according to the beam shape and the inclination of the crack according to the crystal plane of the object are opposite in the Z direction, and as a result, the inclination of the crack can be suppressed. Therefore, with this laser processing device and laser processing method, the inclination of the crack in the Z direction in the YZ plane can be suppressed, and the positional deviation between the arrival position of the crack on the incident back surface of the object and the processing line (i.e., damage caused by laser light leakage on the incident back surface of the object) can be suppressed.

[0013] The laser processing device according to the present disclosure may be the laser processing device described in [1] above, [2] "wherein the target object includes an incident back surface opposite to the incident surface, and in the processing, the control unit performs laser processing to form the modified region along the processing line by irradiating the target object with the laser light while moving the focused spot along the processing line, multiple times while varying the position of the focused spot in the Z direction, and the control unit performs the modulation process at least during the laser processing in which the position of the focused spot in the Z direction is closest to the incident back surface." In this case, misalignment between the arrival position of a crack on the incident back surface of the target object and the processing line can be more reliably suppressed.

[0014] Here, one example of a method for making the beam shape at the focused spot of laser light have the above-described tilted shape is to offset the center of the spherical aberration correction pattern displayed on the spatial light modulator from the center of the entrance pupil plane of the condenser lens. In this case, the tilt of the beam shape tends to increase as the amount of spherical aberration correction by the spherical aberration correction pattern increases, and also as the offset amount between the center of the spherical aberration correction pattern and the center of the entrance pupil plane of the condenser lens (hereinafter simply referred to as the "offset amount") increases. In other words, it is possible to maintain a constant tilt of the beam shape by increasing the offset amount when the amount of spherical aberration correction by the spherical aberration correction pattern is reduced, and by decreasing the offset amount when the amount of spherical aberration correction by the spherical aberration correction pattern is increased.

[0015] Therefore, the laser processing device according to the present disclosure may be the laser processing device described in [1] or [2] above, [3] "wherein the object includes an incident back surface opposite to the incident surface, and in the processing process, the control unit performs laser processing to form the modified region along the processing line by irradiating the object with the laser light while moving the focused spot along the processing line, multiple times while varying the position of the focused spot in the Z direction, and in the modulation process, the control unit offsets the center of a spherical aberration correction pattern to be displayed on the spatial light modulator with respect to the center of an entrance pupil plane of the focusing lens, thereby making the beam shape at the focused spot of the laser light in the YZ plane the inclined shape, and the control unit increases the offset amount of the center of the spherical aberration correction pattern with respect to the center of the entrance pupil plane in the multiple times of laser processing." In this case, in multiple laser processing operations, the closer the Z-direction position of the focused spot is to the incident surface, the more the tilt of the beam shape can be ensured even if the amount of spherical aberration correction by the spherical aberration correction pattern is reduced. This makes it possible to perform appropriate spherical aberration correction by adjusting the amount of spherical aberration correction by the spherical aberration correction pattern depending on the Z-direction position of the focused spot, while suppressing the tilt of cracks extending from the modified region formed at each position in the Z direction. As a result, it is possible to suppress unevenness in the cut surface of the object formed by connecting the cracks at each position in the Z direction.

[0016] Furthermore, the laser processing device according to the present disclosure may be the laser processing device described in any one of [1] to [3] above, [4] "wherein the object includes an incident back surface opposite to the incident surface, and in the processing, the control unit performs laser processing to form the modified region along the line by irradiating the object with the laser light while moving the focused spot along the line, multiple times while varying the position of the focused spot in the Z direction, and in the modulation processing, the control unit offsets the center of a spherical aberration correction pattern to be displayed on the spatial light modulator with respect to the center of an entrance pupil plane of the focusing lens, thereby making the beam shape at the focused spot of the laser light in the YZ plane the inclined shape, and the control unit over-corrects the amount of correction by the spherical aberration correction pattern in the multiple times of the laser processing." In this case, compared to when the amount of spherical aberration correction by the spherical aberration correction pattern is reduced as the Z-direction position of the focused spot is closer to the incident surface in multiple laser processing operations, it is possible to avoid increasing the offset amount to ensure the inclination of the beam shape. This makes it possible to suppress the inclination of cracks extending from the modified regions formed at each position in the Z direction while suppressing deterioration of processability due to an increase in the offset amount. As a result, it is possible to suppress unevenness in the cut surface of the object formed by connecting the cracks at each position in the Z direction.

[0017] Note that "the closer the position of the focused spot in the Z direction to the incident surface, the more over-corrected the correction amount by the spherical aberration correction pattern" means that the closer the position of the focused spot in the Z direction to the incident surface, the greater the excess of the correction amount of spherical aberration by the spherical aberration correction pattern from the appropriate correction amount according to the position of the focused spot in the Z direction. Therefore, for example, even if the correction amount of spherical aberration by the spherical aberration correction pattern is kept constant regardless of the position of the focused spot in the Z direction, the closer the position of the focused spot in the Z direction to the incident surface, the smaller the appropriate correction amount of spherical aberration, and therefore the greater the excess (i.e., more over-correction).

[0018] The laser processing device according to the present disclosure may be [5] "the laser processing device according to the above [1] or [2], wherein in the modulation process, the control unit causes the spatial light modulator to display a modulation pattern different from the spherical aberration correction pattern, and causes the beam shape at the focused spot of the laser light in the YZ plane to have the inclined shape by the different modulation pattern." In this case, the beam shape can be made into the inclined shape without affecting the correction of spherical aberration. Therefore, the beam shape can be stably made into the inclined shape.

[0019] The laser processing method according to the present disclosure is [7] "a laser processing method for forming a modified region in an object by irradiating the object with laser light, the method comprising: a first processing step of irradiating the object with the laser light while moving a focused spot of the laser light along a processing line along an incident surface of the laser light on the object, thereby forming the modified region along the processing line; an observation step of observing, after the first processing step, cracks extending from the modified region formed along the processing line; and, after the observation step, irradiating the object with the laser light while moving the focused spot of the laser light along another processing line along the incident surface of the laser light on the object, thereby forming the modified region along the processing line. and a second processing step of forming the modified region along the other processing line, wherein in the second processing step, when the extension direction of the processing line is defined as the X direction, the direction intersecting the incident surface is defined as the Z direction, and the direction intersecting the X direction and the Z direction is defined as the Y direction, if the crack inclined with respect to the Z direction is observed in the observation step within a YZ plane including the Y direction and the Z direction, the laser light is modulated by a spatial light modulator, so that the beam shape at the focused spot of the laser light in the YZ plane is inclined to the opposite side to the inclination direction of the crack with respect to the Z direction, at least on the incident surface side of the center of the focused spot.

[0020] According to this laser processing method, in an object with unknown characteristics, it is possible to suppress the inclination of cracks in the Z direction within the YZ plane, and to suppress the positional deviation between the arrival position of the crack on the back surface of the object where the laser beam is incident and the processing line (i.e., damage caused by the laser beam escaping from the back surface of the object where the laser beam is incident).

[0021] According to the present disclosure, it is possible to provide a laser processing device and a laser processing method that can suppress misalignment between the arrival position of a crack and the processing line.

[0022] FIG. 1 is a schematic diagram showing the configuration of a laser processing apparatus according to one embodiment. FIG. 2 is a schematic diagram showing the configuration of the irradiation unit shown in FIG. 1. FIG. 3 is a diagram showing a laser processing apparatus and an object to be processed by the laser processing method according to the first embodiment. FIG. 3(a) is a plan view, and FIG. 3(b) is a schematic diagram for explaining crystal orientation. FIG. 4 is a diagram showing a cut surface when laser processing is performed on the object shown in FIG. 3. FIG. 4(a) shows the cut surface as viewed from the X direction, and FIG. 4(b) shows the cut surface as viewed from the Z direction. FIG. 5 is a schematic cross-sectional view showing a step of the laser processing method according to the first embodiment. In particular, FIG. 5 shows the XZ plane. FIG. 6 is a schematic cross-sectional view showing a step of the laser processing method according to the first embodiment. In particular, FIG. 6 shows the YZ plane. FIG. 7 is a diagram showing the relationship between the beam shape at the focused spot of laser light in the YZ plane and the crystal plane. FIG. 8 is a diagram showing an example of the beam shape at the focused spot. FIG. 8A shows the beam shape (intensity distribution) in the YZ plane, and FIG. 8B shows the beam shape (intensity distribution) in each cross section F1 to F7 in FIG. 8A (i.e., the XY plane). FIG. 9 shows an example of a beam shape at a focused spot. FIG. 9A shows the beam shape (intensity distribution) in the YZ plane, and FIG. 9B shows the beam shape (intensity distribution) in each cross section F1 to F8 in FIG. 9A (i.e., the XY plane). FIG. 10 is a schematic cross-sectional view showing a step of the laser processing method according to the first embodiment. FIG. 11 shows an example of processing conditions and processing results of the laser processing method according to the first embodiment. FIG. 11A is a photograph of a cut surface showing the processing results, and FIG. 11B is a table showing the relationship between the processing position in the Z direction and various conditions in the modulation process. FIG. 12 is a graph showing an example of processing conditions of the laser processing method according to the first embodiment. 12A is a graph showing various conditions for overcorrecting spherical aberration as the machining position in the Z direction becomes shallower, and FIG. 12B is a graph showing various conditions for modulation processing when a coma aberration pattern different from the spherical aberration correction pattern is used. FIG. 13 is a diagram showing a cut surface when laser machining according to the first embodiment is performed.FIG. 13(a) shows a cut surface as viewed from the X direction, and FIG. 13(b) shows a cut surface as viewed from the Z direction. FIG. 14 is a flowchart showing each step of the laser processing method according to the second embodiment. FIG. 15 is a schematic diagram for explaining each step shown in FIG. 14. FIG. 15(a) is a plan view, FIG. 15(b) shows a YZ cross section of the object shown in FIG. 15(a), and FIG. 15(c) shows an XZ cross section of the object shown in FIG. 15(a). FIG. 16 is a schematic diagram for explaining each step shown in FIG. 14. FIG. 16(a) is a plan view, FIG. 16(b) is an enlarged view of region R1 of FIG. 16(a), and FIG. 16(c) is an enlarged view of region R2 of FIG. 16(a).

[0023] An embodiment will be described below with reference to the drawings. In each drawing, the same or corresponding parts are designated by the same reference numerals, and redundant explanations may be omitted. Each drawing may also show a Cartesian coordinate system defined by an X-axis, a Y-axis, and a Z-axis.

[0024] Fig. 1 is a schematic diagram showing the configuration of a laser processing apparatus according to one embodiment. As shown in Fig. 1, the laser processing apparatus 1 includes a stage (support unit) 2, an irradiation unit 3, movement units 4 and 5, a control unit (processing control unit) 6, and an imaging unit 8. The laser processing apparatus 1 is an apparatus for forming a modified region 12 in an object 11 by irradiating the object 11 with laser light L.

[0025] The stage 2 supports the object 11, for example, by holding a film attached to the object 11. The stage 2 is rotatable about an axis parallel to the Z direction. The stage 2 may be movable along both the X direction and the Y direction. The X direction and the Y direction are first and second horizontal directions that intersect (are perpendicular to) each other, and the Z direction is a vertical direction.

[0026] The irradiation unit 3 is for irradiating the object 11 supported on the stage 2 with laser light L. The irradiation unit 3 focuses the laser light L, which is transparent to the object 11, and irradiates the object 11. When the laser light L is focused inside the object 11 supported on the stage 2, the laser light L is particularly absorbed in a portion corresponding to a focused spot C of the laser light L (for example, the center Ca shown in FIG. 7 ), and a modified region 12 is formed inside the object 11. The focused spot C is a position where the beam intensity of the laser light L is highest or a region within a predetermined range from the center Ca, which is the center of gravity of the beam intensity.

[0027] The modified region 12 is a region whose density, refractive index, mechanical strength, and other physical properties differ from those of the surrounding unmodified region. Examples of the modified region 12 include a melt-treated region, a crack region, a dielectric breakdown region, and a refractive index change region. The modified region 12 can be formed so that a crack extends from the modified region 12 to the incident side of the laser light L and to the opposite side. Such modified region 12 and cracks are used, for example, to cut the object 11.

[0028] As an example, when the stage 2 is moved along the X direction and the focused spot C is moved along the X direction relative to the object 11, multiple modified spots 12s are formed lined up in a row along the X direction. One modified spot 12s is formed by irradiating one pulse of laser light L. A row of modified regions 12 is a collection of multiple modified spots 12s lined up in a row. Adjacent modified spots 12s may be connected to each other or separated from each other depending on the relative moving speed of the focused spot C with respect to the object 11 and the repetition frequency of the laser light L.

[0029] The moving unit 4 includes a first moving unit 41 that moves the stage 2 in one direction within a plane intersecting (perpendicular to) the Z direction, and a second moving unit 42 that moves the stage 2 in another direction within the plane intersecting (perpendicular to) the Z direction. As an example, the first moving unit 41 moves the stage 2 along the X direction, and the second moving unit 42 moves the stage 2 along the Y direction. The moving unit 4 also rotates the stage 2 around an axis parallel to the Z direction. The moving unit 5 supports the irradiation unit 3. The moving unit 5 moves the irradiation unit 3 along the X direction, Y direction, and Z direction. By moving the stage 2 and / or the irradiation unit 3 while the focused spot C of the laser light L is formed, the focused spot C is moved relative to the object 11. That is, the moving units 4 and 5 move at least one of the stage 2 and the irradiation unit 3 to move the focused spot C of the laser light L relative to the object 11.

[0030] The imaging unit 8 captures an image of the object 11 supported on the stage 2 using light (e.g., light in the near-infrared region) that passes through the object 11. More specifically, the imaging unit 8 is used to capture images of the modified region 12 formed in the object 11 and the cracks extending from the modified region 12.

[0031] The control unit 6 controls the operations of the stage 2, the irradiation unit 3, the moving units 4 and 5, and the imaging unit 8. The control unit 6 has a processing unit, a memory unit, and an input receiving unit (not shown). The processing unit is configured as a computer device including a processor, memory, storage, a communication device, etc. In the processing unit, the processor executes software (programs) loaded into the memory, etc., and controls reading and writing of data in the memory and storage, as well as communication via the communication device. The memory unit is, for example, a hard disk, and stores various types of data. The input receiving unit is an interface unit that displays various types of information and receives input of various types of information from the user. The input receiving unit constitutes a GUI (Graphical User Interface).

[0032] FIG. 2 is a schematic diagram showing the configuration of the irradiation unit shown in FIG. 2. FIG. 2 shows a virtual processing line A indicating the planned laser processing. As shown in FIG. 2, the irradiation unit 3 has a light source 31, a spatial light modulator 7, and a condensing lens 33. The light source 31 outputs laser light L, for example, by a pulse oscillation method. Note that the irradiation unit 3 may not have the light source 31 and may be configured to introduce the laser light L from outside the irradiation unit 3. The spatial light modulator 7 modulates the laser light L output from the light source 31. The condensing lens 33 condenses the laser light L modulated by the spatial light modulator 7 and output from the spatial light modulator 7 (i.e., the laser light L that has passed through the spatial light modulator 7) toward the object 11.

[0033] When a signal indicating a modulation pattern is input from the control unit 6 to the spatial light modulator 7, the modulation pattern is displayed in accordance with the signal. The modulation pattern is for modulating the laser light L. When the laser light L is incident from the outside, reflected, and emitted to the outside while the modulation pattern is displayed on the spatial light modulator 7, the laser light L is modulated in accordance with the displayed modulation pattern. In this way, the spatial light modulator 7 makes it possible to modulate the laser light L (for example, modulate the intensity, amplitude, phase, polarization, etc. of the laser light L) by appropriately setting the modulation pattern to be displayed.

[0034] As described above, the laser light L output from the light source 31 is incident on the condenser lens 33 via the spatial light modulator 7 and is focused by the condenser lens 33 within the object 11, thereby forming a modified region 12 and a crack extending from the modified region 12 in the object 11 at the focused spot C. Furthermore, the control unit 6 controls the moving units 4 and 5 to move the focused spot C relative to the object 11, thereby forming a modified region 12 and a crack along the movement direction of the focused spot C. [First Embodiment]

[0035] Next, the laser processing apparatus 1 and the laser processing method according to the first embodiment will be described. FIG. 3 is a diagram showing an object of the laser processing apparatus and the laser processing method according to the first embodiment. FIG. 3(a) is a plan view, and FIG. 3(b) is a schematic diagram for explaining crystal orientation. The object 11 shown in FIG. 3 is, for example, a wafer (e.g., a silicon wafer) with a crystal orientation <111>. The object 11 includes a first surface 11a and a second surface 11b opposite to the first surface 11a. The object 11 is supported on the stage 2 so that the first surface 11a faces the irradiation unit 3 (see FIG. 5, etc.). Therefore, the first surface 11a is the incident surface of the object 11 for the laser light L, and the second surface 11b is the back surface of the object 11 opposite to the incident surface. For example, a device layer including a plurality of devices arranged two-dimensionally along the second surface 11b may be formed on the second surface 11b.

[0036] On the object 11, a first processing line A1 and a second processing line A2 are set as virtual processing lines A indicating the above-mentioned laser processing schedule. The first processing line A1 and the second processing line A2 extend perpendicular to each other when viewed from a direction intersecting the first surface 11a (Z direction). Here, the extension direction of the first processing line A1 is defined as the Y direction, and the extension direction of the second processing line A2 is defined as the X direction. Note that while FIG. 3 illustrates only a pair of the first processing line A1 and the second processing line A2, multiple first processing lines A1 that are parallel to each other and multiple second processing lines A2 that are parallel to each other are set on the object 11.

[0037] The first surface 11a of the object 11 is, for example, a (111) surface. The object 11 also includes crystal surfaces S0 and S1 that intersect with the first surface 11a. The crystal surface S0 is, for example, a (110) surface, and the crystal surface S1 is, for example, a (111) surface that forms an angle of 70.5° with respect to the first surface 11a. Alternatively, the crystal surface S1 is, for example, a (110) surface that forms an angle of 35.3° with respect to the first surface 11a. The following describes an example in which the crystal surface S1 is a (111) surface. Thus, when the extension direction of the second processing line A2 is defined as the X direction, the direction intersecting the first surface 11a is defined as the Z direction, and the direction intersecting the X and Z directions is defined as the Y direction, the object 11 includes a crystal surface S1 that is inclined with respect to the Z direction in a YZ plane that includes the Y and Z directions.

[0038] 4A and 4B are diagrams showing a cut surface obtained by laser processing the object shown in FIG. 4A. FIG. 4A shows a cut surface viewed from the X direction, and FIG. 4B shows a cut surface viewed from the Z direction. As shown in FIG. 4A, when a focused spot C is positioned inside the object 11 and the laser beam L is irradiated onto the object 11 while moving the focused spot C along the second processing line A2 (i.e., along the X direction), a crack 13 extending from the modified region 12 formed at the focused spot C toward the second surface 11b tends to propagate in the YZ plane at an angle in the same direction as the inclination direction of the crystal plane S1 relative to the Z direction due to the influence of the crystal plane S1, which is a (111) plane inclined relative to the Z direction in the YZ plane.

[0039] 4A and 4B, the arrival position P13 of the crack 13 on the second surface 11b may be shifted in the Y direction from the second processing line A2 on which the focused spot C of the laser light L is aligned. Therefore, in the Y direction, the arrival position P13 of the crack 13 on the second surface 11b of the object 11 and the damage caused by the light leakage on the second surface 11b directly below the second processing line A2 in the Z direction are shifted in the Y direction. Therefore, if the arrival position P13 of the crack 13 is positioned in the center of a street region (e.g., a region between devices on the second surface 11b) in the Y direction, the damage caused by the light leakage may be shifted from the center of the street region toward the device, potentially affecting the device. Therefore, there is a need to suppress the inclination of the crack 13.

[0040] In addition, when the laser beam L is irradiated onto the object 11 while the focused spot C is moved along the first processing line A1 (i.e., along the Y direction) with the focused spot C positioned inside the object 11, the crack 13 extending from the modified region 12 tends to propagate in the Z direction along the crystal plane S0, which is the (110) plane, and the propagation of the crack 13 is less affected by the crystal plane S1, which is the (111) plane. Therefore, there is relatively little need to suppress the inclination of the crack 13 during laser processing along the first processing line A1.

[0041] From the above viewpoint, in the first embodiment, during laser processing along the second processing line A2, the arrival position P13 of the crack 13 on the second surface 11b is prevented from deviating from the second processing line A2 on which the focused spot C of the laser light L is aligned.

[0042] Next, a specific example of the laser processing method according to the first embodiment will be described. In this method, first, as shown in Figures 5 and 6, the object 11 is supported on the stage 2 so that the first surface 11a of the object 11 faces the irradiation unit 3 (condenser lens 33) of the laser processing device 1. As a result, the first surface 11a of the object 11 serves as the incident surface of the laser light L, and the second surface 11b serves as the back surface onto which the laser light L is incident.

[0043] Next, the control unit 6 controls the moving units 4 and 5 to move the irradiation unit 3 and / or the stage 2 so that the focused spot C of the laser light L is positioned on one of the second processing lines A2 in the XY plane including the X and Y directions, and is positioned at a predetermined processing depth in the Z direction inside the object 11 (step S101). The position of the focused spot C in the Z direction at this time is defined as a first position Z1.

[0044] Next, as laser processing proceeds along the second processing line A2, the beam shape at the focused spot C of the laser light L is controlled. That is, as shown in Fig. 7, the control unit 6 modulates the laser light L using the spatial light modulator 7, thereby performing a modulation process (step S102) so that the beam shape at the focused spot C of the laser light L in the YZ plane becomes an inclined shape (hereinafter, sometimes simply referred to as an "inclined shape") that is inclined toward the opposite side of the crystal plane S1 with respect to the Z direction, at least on the first surface 11a side from the center Ca of the focused spot C. In the example of Fig. 7, the beam shape at the focused spot C of the laser light L in the YZ plane becomes an inclined shape that is inclined in the negative Y direction with respect to the Z direction, at the first surface 11a side from the center Ca (an arc shape that is convex overall in the positive Y direction).

[0045] Such an arc-shaped beam shape can be formed, for example, by controlling the spatial light modulator 7 to offset the center of the spherical aberration correction pattern displayed on the spatial light modulator 7 in an oblique direction relative to the center of the entrance pupil plane of the condenser lens 33, or by displaying a coma aberration pattern for imparting coma aberration to the laser light L on the spatial light modulator 7 and controlling the magnitude and direction of the coma aberration in the coma aberration pattern.

[0046] Furthermore, in step S102, as shown in FIG. 8 , the laser light L may be modulated by the spatial light modulator 7 so that the entire beam shape at the focused spot C of the laser light L in the YZ plane is inclined toward the opposite side of the crystal plane S1 with respect to the Z direction. (b) of FIG. 8 shows the beam shape (intensity distribution) in each cross section F1 to F7 in (a) of FIG. 8 (i.e., in the XY plane). Each diagram in (b) of FIG. 8 is an actual observation result obtained by a camera. It can be seen from FIG. 8 that the focused spot C gradually shifts toward one side in the Y direction (here, the positive Y direction) as the position in the Z direction changes from F1 to F7.

[0047] In the case of the arc-shaped beam shape shown in Figure 7, it can be seen that, within the XY plane, the focused spot C gradually shifts in the Y-positive direction as the Z-direction position moves from the first surface 11a to the center Ca, and that when the Z-direction position moves closer to the second surface 11b than the center Ca, the focused spot C gradually shifts in the Y-negative direction.

[0048] The beam shape shown in Fig. 8 can be realized, for example, by controlling the spatial light modulator 7 so that the modulation pattern displayed on the spatial light modulator 7 is asymmetric in the Y direction with respect to the X direction. An example of a pattern asymmetric in the Y direction is a modulation pattern that includes a diffraction grating pattern only on one side of the center in the Y direction. This makes it possible to prevent modulated light of the laser light L that has been modulated by the diffraction grating pattern from entering the condenser lens 33, and the beam shape shown in Fig. 8 can be obtained.

[0049] Furthermore, in step S102, as shown in FIG. 9 , even when forming an arc-shaped beam shape similar to that shown in FIG. 7 , the intensity of the modulation pattern displayed on the spatial light modulator 7 can be asymmetric in the Y direction relative to the X direction. An example of such a modulation pattern includes a relatively weak astigmatism pattern on one side of the center in the Y direction and a relatively strong astigmatism pattern on the other side of the center in the Y direction. (b) of FIG. 9 shows the beam shape (intensity distribution) in each cross section F1 to F8 in (a) of FIG. 9 (i.e., in the XY plane). Each diagram in (b) of FIG. 9 shows the results of actual observations by a camera. It can be seen from FIG. 9 that, in the XY plane, the focused spot C gradually shifts in the Y-positive direction from the first surface 11a to the center Ca in the Z direction, and gradually shifts in the Y-negative direction when the focused spot C is closer to the second surface 11b than the center Ca in the Z direction.

[0050] In addition, the beam shape can be made inclined by any known method, such as modulating the laser light L using a modulation pattern displayed on the spatial light modulator 7 to form multiple focal points of the laser light L along a line inclined in the opposite direction to the crystal plane S1 with respect to the Z direction in the YZ plane, so that the entire focal spot C, which is a collection of multiple focal points, has an inclined shape.

[0051] The beam shape at the focused spot C refers to the intensity profile near the focused point (including a slightly defocused position). The inclined beam shape means that the intensity profile has lost symmetry in the XY plane, and when the XY plane is viewed at each point in the Z direction, the position where the intensity profile is highest in the XY plane is located on the opposite side from the crystal plane S1, at least in the region closer to the first surface 11a (incident surface), compared to the position where the intensity profile is highest in the XY plane at the focused point.

[0052] In the next step, as shown in Fig. 5, the control unit 6 controls the irradiation unit 3 and the moving units 4 and 5 to irradiate the target 11 with the laser light L while moving the focused spot C of the laser light L relative to the target 11 along the second processing line A2 (X direction), thereby forming a modified region 12 along the second processing line as shown in Fig. 10 (step S103: processing treatment, processing step). At this time, as described above, a modulation process is performed so that the beam shape of the focused spot C of the laser light L in the YZ plane becomes an inclined shape inclined toward the opposite side of the crystal plane S1 with respect to the Z direction, at least on the first surface 11a side of the center Ca of the focused spot C.

[0053] Next, the control unit 6 controls the moving units 4 and 5 to move the irradiation unit 3 and / or the stage 2 so that the focused spot C of the laser light L is located on the second processing line A2 that formed the modified region 12 at the first position Z1 in the XY plane including the X and Y directions, and is located at another predetermined processing depth in the Z direction inside the object 11 (step S104). The position of the focused spot C in the Z direction at this time is a second position Z2 that is closer to the first surface 11a than the first position Z1.

[0054] Next, the control unit 6 controls the irradiation unit 3 and the moving units 4 and 5 to move the focused spot C of the laser light L relative to the object 11 along the second processing line A2 (X direction) while irradiating the object 11 with the laser light L, thereby forming a modified region 12 along the second processing line A2 at the second position Z2 (step S105: processing process, processing step). At this time, as described above, a modulation process may be performed so that the beam shape at the focused spot C of the laser light L becomes an inclined shape.

[0055] Thereafter, similar laser processing is performed multiple times while varying the Z-direction position of the focused spot C toward the first surface 11a. That is, in the processing, the control unit 6 performs laser processing multiple times while varying the Z-direction position of the focused spot C to irradiate the target object 11 with laser light L while moving the focused spot C along the second processing line A2, thereby forming the modified region 12 along the second processing line A2. Then, the control unit 6 performs the above-mentioned modulation process at least during the laser processing of the multiple times in which the Z-direction position of the focused spot C is at the first position Z1 closest to the second surface 11b (i.e., the back surface of incidence).

[0056] 11 , the laser processing is performed five times while sequentially changing the position of the focused spot C in the Z direction from the first position Z1 toward the first surface 11a to the second position Z2, the third position Z3, the fourth position Z4, and the fifth position Z5, forming the modified region 12 at each position. Also, in the example of FIG. 11 , modulation processing is performed over all of the first position Z1 to the fifth position Z5. Specifically, the modulation processing involves offsetting the center of the spherical aberration correction pattern in the spatial light modulator 7 from the center of the entrance pupil plane of the focusing lens 33, thereby imparting a predetermined coma aberration to the laser light L, thereby forming the beam shape of the focused spot C of the laser light L into the above-mentioned inclined shape.

[0057] Here, the tilt of the beam shape tends to increase as the amount of spherical aberration correction by the spherical aberration correction pattern (hereinafter sometimes simply referred to as the "spherical aberration correction amount") increases, and also as the amount of offset between the center of the spherical aberration correction pattern and the center of the entrance pupil plane of the condenser lens (hereinafter sometimes simply referred to as the "offset amount") increases. In other words, it is possible to maintain a constant tilt of the beam shape by increasing the offset amount when the spherical aberration correction amount is reduced, and by decreasing the offset amount when the spherical aberration correction amount is increased.

[0058] 11 , the control unit 6 increases the offset amount of the center of the spherical aberration correction pattern relative to the center of the entrance pupil plane when laser processing is performed multiple times, as the Z-direction position of the focused spot C approaches the first surface 11a, which is the entrance surface (as the Z-direction position value decreases). Specifically, when laser processing is performed at the first position Z1, where the Z-direction position value of the focused spot C is the largest, the spherical aberration correction amount is set to 80, and the offset amount is accordingly set to +3.5. Furthermore, when laser processing is performed at the second position Z2, where the Z-direction position value of the focused spot C is the second largest after the first position Z1, the spherical aberration correction amount is reduced to 69, and the offset amount is accordingly increased to +4.5.

[0059] Furthermore, during laser processing at the third position Z3, fourth position Z4, and fifth position Z5, where the Z direction position value of the focused spot C is even smaller than the second position Z2, the spherical aberration correction amount is reduced to 12, and the offset amount is accordingly increased to +25. As a result, the amount of coma aberration imparted to the laser light L is constant at −0.037 over the five laser processing operations from the first position Z1 to the fifth position Z5, and as a result, the amount of tilt of the beam shape of the laser light L at the focused spot C is maintained constant.

[0060] In the example of FIG. 12A , the control unit 6 overcorrects the spherical aberration correction amount as the Z-direction position of the focused spot C approaches the first surface 11a, which is the incident surface, during multiple laser processing operations. Specifically, the spherical aberration correction amount is kept constant at 80 across all of the first position Z1 to the fifth position Z5. As a result, the closer the Z-direction position of the focused spot C approaches the first surface 11a across the first position Z1 to the fifth position Z5, the smaller the appropriate spherical aberration correction amount becomes. Therefore, the amount of spherical aberration correction exceeds the appropriate amount, resulting in overcorrection. Accordingly, the offset amount is also kept constant across all of the first position Z1 to the fifth position Z5. As a result, the amount of coma aberration imparted to the laser light L is kept constant at −0.037 across five laser processing operations at the first position Z1 to the fifth position Z5. As a result, the tilt of the beam shape of the focused spot C of the laser light L is maintained constant.

[0061] 12(b), the control unit 6 causes the spatial light modulator 7 to display a coma aberration pattern, which is a modulation pattern separate from the spherical aberration correction pattern, during modulation processing, and the coma aberration pattern tilts the beam shape of the laser light L at the focused spot C in the YZ plane. In this example, the spherical aberration correction amount is set in the same manner as in FIG. 11, while the offset amount is kept constant at 0 across multiple laser processing operations from the first position Z1 to the fifth position Z5, and coma aberration is imparted to the laser light L by the coma aberration pattern. The amount of coma aberration in the coma aberration pattern is constant at −0.037. As a result, the amount of coma aberration imparted to the laser light L is constant at −0.037 across multiple laser processing operations, and as a result, the amount of tilt of the beam shape of the laser light L at the focused spot C is maintained constant.

[0062] 12(b), a coma aberration pattern is illustrated as a modulation pattern separate from the spherical aberration correction pattern, but any pattern such as the above-mentioned astigmatism pattern, diffraction grating pattern, etc. may be used as the separate modulation pattern. Also, in FIG. 12(b), the amount of coma aberration in the coma aberration pattern is displayed as an actual value of −0.037, but the laser processing apparatus 1 may display a value that corresponds to the actual value and is easy for the user to recognize (for example, an integer value such as −37, or an arbitrary Lv notation, etc.) on an input / output unit that the laser processing apparatus 1 may be provided with.

[0063] As shown in the above example, when the beam shape at the focal spot C of the laser light L in the YZ plane is made to be an inclined shape, the control unit 6 can make the amount of inclination of the beam shape constant by making various adjustments to the modulation pattern to be displayed on the spatial light modulator 7 across multiple laser processing operations in which the Z-direction positions of the focal spot C are different from each other.

[0064] Laser processing along the first processing line A1 (i.e., the Y direction) can be performed at any timing. When processing the first processing line A1, the control unit 6 does not need to perform modulation processing to make the beam shape of the focused spot C of the laser light L in the XZ plane an inclined shape.

[0065] 13A and 13B are diagrams illustrating a cut surface when laser processing according to the first embodiment is performed. (a) of Fig. 13A illustrates the cut surface as viewed from the X direction, and (b) of Fig. 13A illustrates the cut surface as viewed from the Z direction. The processing result in Fig. 13A illustrates a case in which, among multiple laser processing operations performed with different positions of the focused spot C in the Z direction, modulation processing is performed only during processing at the first position Z1 closest to the second surface 11b, and the beam shape of the focused spot C of the laser light L in the YZ plane is made inclined.

[0066] 13 , according to the laser processing of the first embodiment, the crack 13 extending from the modified region 12 closest to the second surface 11b is prevented from growing at an angle, and as a result, the deviation in the Y direction of the arrival position P13 of the crack 13 on the second surface 11b from the second processing line A2 on which the focused spot C of the laser light L is aligned is suppressed. Therefore, in the Y direction, the deviation in the Y direction between the arrival position P13 of the crack 13 on the second surface 11b of the object 11 and damage caused by light leakage occurring on the second surface 11b directly below the second processing line A2 in the Z direction is suppressed.

[0067] As described above, in the laser processing apparatus 1 and laser processing method according to the first embodiment, the laser beam L is irradiated onto the object 11 while moving the focused spot C along the second processing line A2 along the first surface 11a, which is the incident surface of the laser beam L on the object 11, thereby forming a modified region 12 along the second processing line A2. When the direction in which the second processing line A2 extends is defined as the X direction, the direction intersecting the first surface 11a is defined as the Z direction, and the direction intersecting the X and Z directions is defined as the Y direction, the object 11 includes a crystal plane S1 that is inclined with respect to the Z direction in a YZ plane that includes the Y and Z directions. Therefore, there is a risk that the crack 13 extending from the modified region 12 will be inclined in the same direction as the crystal plane S1 with respect to the Z direction in the YZ plane, depending on the crystal plane S1.

[0068] In contrast, in the laser processing apparatus 1 and laser processing method according to the first embodiment, during laser processing, the spatial light modulator 7 modulates the laser light L so that the beam shape at the focal spot C of the laser light L in the YZ plane is tilted toward the opposite side of the crystal plane S1 with respect to the Z direction, at least on the first surface 11a side of the center Ca of the focal spot C. By tilting the beam shape at the focal spot C of the laser light L in this manner, the cracks 13 extending from the modified region 12 can be tilted in the same direction as the tilt direction of the beam shape. Therefore, in the YZ plane, the tilt of the cracks 13 according to the beam shape and the tilt of the cracks 13 according to the crystal plane S1 of the object 11 are opposite to each other with respect to the Z direction, and as a result, the tilt of the cracks 13 can be suppressed.

[0069] Therefore, the laser processing apparatus 1 and laser processing method according to the first embodiment can suppress the tilt of the crack 13 in the Z direction within the YZ plane, thereby suppressing misalignment between the arrival position P13 of the crack 13 on the second surface 11b, which is the back surface of the object 11 where the laser beam L enters, and the second processing line A2 (i.e., damage caused by the laser beam L leaking through the second surface 11b of the object 11). Note that suppressing the tilt of the crack 13 in the Z direction can suppress damage (splash damage) that occurs at a position away from the position directly below the second processing line A2 due to the laser beam L being scattered by the tilted crack 13.

[0070] Furthermore, in the laser processing apparatus 1 (laser processing method) according to the first embodiment, in the processing step (processing step, step S103), the control unit 6 irradiates the target object 11 with laser light L while moving the focused spot C along the second processing line A2, thereby performing laser processing to form the modified region 12 along the second processing line A2 multiple times while varying the Z-direction position of the focused spot C. The control unit 6 may then perform the modulation process (step S102) at least during the laser processing step in which the Z-direction position of the focused spot C is closest to the second surface 11b (first position Z1). In this case, misalignment between the arrival position P13 of the crack 13 on the second surface 11b of the target object 11 and the second processing line A2 can be more reliably suppressed.

[0071] Furthermore, in the laser processing apparatus 1 (laser processing method) according to the first embodiment, in the modulation process (step S102), the control unit 6 may offset the center of the spherical aberration correction pattern displayed on the spatial light modulator 7 from the center of the entrance pupil plane of the focusing lens 33, thereby forming the beam shape of the focused spot C of the laser light L in the YZ plane into the above-described inclined shape. In this case, the control unit 6 may increase the offset of the center of the spherical aberration correction pattern from the center of the entrance pupil plane as the Z-direction position of the focused spot C approaches the first surface 11a during multiple laser processing operations. In this case, the closer the Z-direction position of the focused spot C approaches the first surface 11a during multiple laser processing operations, the more the inclination of the beam shape can be ensured even if the amount of spherical aberration correction by the spherical aberration correction pattern is reduced. This makes it possible to perform appropriate spherical aberration correction by adjusting the amount of spherical aberration correction by the spherical aberration correction pattern depending on the Z-direction position of the focused spot C, while suppressing the inclination of the cracks 13 extending from the modified regions 12 formed at each position in the Z direction. As a result, it is possible to suppress irregularities in the cut surface of the object 11 formed by connecting the cracks 13 at each position in the Z direction.

[0072] Furthermore, in the laser processing apparatus 1 (laser processing method) according to the first embodiment, in the modulation process (step S102), the control unit 6 may overcorrect the amount of correction by the spherical aberration correction pattern as the Z-direction position of the focused spot C approaches the first surface 11a during multiple laser processing operations. In this case, it is possible to avoid increasing the offset amount required to ensure the inclination of the beam shape compared to when the Z-direction position of the focused spot C approaches the first surface 11a during multiple laser processing operations. This makes it possible to suppress the inclination of the cracks 13 extending from the modified regions 12 formed at each position in the Z direction while suppressing deterioration of processability due to an increased offset amount. As a result, it is possible to suppress unevenness in the cut surface of the object 11 formed by connecting the cracks 13 at each position in the Z direction.

[0073] Furthermore, in the laser processing apparatus 1 (laser processing method) according to the first embodiment, in the modulation process (step S102), the control unit 6 may cause the spatial light modulator 7 to display a modulation pattern (for example, a coma aberration pattern) different from the spherical aberration correction pattern, and may use this different modulation pattern to make the beam shape at the focused spot of the laser light L in the YZ plane the inclined shape. In this case, the beam shape can be made the inclined shape without affecting the correction of spherical aberration. Therefore, the beam shape can be stably made the inclined shape. [Second Embodiment]

[0074] Next, a laser processing method according to the second embodiment will be described. FIG. 14 is a flowchart showing the steps of the laser processing method according to the second embodiment. FIGS. 15 and 16 are schematic diagrams for explaining the steps shown in FIG. 14. In the laser processing method shown in FIGS. 14 to 16, laser processing is performed on an object 51. The object 51 includes a first surface 51a and is supported on the stage 2 so that the first surface 51a faces the irradiation unit 3 (condenser lens 33). A first processing line A1 and a second processing line A2 are set on the object 51 along the first surface 51a as virtual processing lines A indicating the planned laser processing.

[0075] Here, the extension direction of the first processing line A1 is the Y direction, the extension direction of the second processing line A2 is the X direction, and the direction intersecting with the first surface 51a is the Z direction. Note that although only a pair of the first processing line A1 and the second processing line A2 is shown in Fig. 15, a plurality of first processing lines A1 parallel to each other and a plurality of second processing lines A2 parallel to each other are set on the object 51.

[0076] In the laser processing method according to the second embodiment, first, alignment and height setting are performed (step S201). Specifically, in step S201, for example, the control unit 6 controls the moving units 4 and 5 to determine the irradiation position of the laser light L in the X and Y directions as alignment based on images of the object 51 and the laser light L captured by a camera (not shown), and adjust the position of the focused spot C of the laser light L in the Z direction as height setting.

[0077] 15B, the control unit 6 controls the moving units 4 and 5 to move the irradiation unit 3 and / or the stage 2 so that the focused spot C of the laser light L is positioned on one of the plurality of first processing lines A1 (for example, the first processing line A1 located at the end of the object 51) in the XY plane and at a predetermined processing depth inside the object 51 in the Z direction.

[0078] Thereafter, the control unit 6 controls the irradiation unit 3 and the moving units 4 and 5 to irradiate the target object 51 with the laser light L while moving the focused spot C along the first processing line A1 (i.e., the Y direction), thereby forming a modified region 12 in the target object 51 along the first processing line A1. Note that in step S202, no modulation process is performed to tilt the beam shape of the focused spot C of the laser light L in the XZ plane with respect to the Z direction.

[0079] 15C, the control unit 6 controls the moving units 4 and 5 to move the irradiation unit 3 and / or the stage 2 so that the focused spot C of the laser light L is positioned on one of the plurality of second processing lines A2 (for example, the second processing line A2 located at the end of the object 51) in the XY plane and at a predetermined processing depth inside the object 51 in the Z direction.

[0080] Thereafter, the control unit 6 irradiates the target object 51 with the laser light L while moving the focused spot C along the second processing line A2 (i.e., the X direction), thereby forming a modified region 12 in the target object 51 along the second processing line A2. Note that in step S203, no modulation process is performed to tilt the beam shape of the laser light L at the focused spot C in the YZ plane with respect to the Z direction.

[0081] Subsequently, in step S202, the processed first processing line A1 is observed (step S204, observation step). More specifically, in step S204, as shown in FIG. 16(b), the control unit 6 controls the imaging unit 8 to image the region R1 including the processed first processing line A1 in step S202 using light transmitted through the object 51. Based on the image thus obtained, the first processing line A1 can be observed.

[0082] Next, the inclination direction and inclination amount of the beam shape at the focused spot C of the laser light L in the XZ plane when laser processing is performed along the first processing line A1 are determined (step S205). In the example shown in (b) of Figure 16, no crack 13 extending with an X-direction component from the modified region 12 is confirmed in the first processing line A1 extending along the Y direction. Therefore, it is confirmed that laser processing along the first processing line A1 does not form a crack 13 that propagates from the modified region 12 at an incline with respect to the Z direction, i.e., a crack 13 that propagates from the modified region 12 at an incline with respect to the Z direction in the XZ plane.

[0083] Therefore, when performing laser processing along the first processing line A1, it is not necessary to consider the inclination of the crack 13 extending from the modified region 12. For this reason, in step S205, it can be determined that the beam shape at the focused spot C of the laser light L in the XZ plane will not be an inclined shape. Note that, as an example, determining the inclination direction and inclination amount of the beam shape at the focused spot C of the laser light L means determining the strength and direction of the coma aberration when the beam shape is to be an inclined shape due to the coma aberration imparted to the laser light L.

[0084] In the next step, the second processing line A2 processed in step S203 is observed (step S206, observation step). More specifically, in step S206, as shown in Fig. 16(c), the control unit 6 controls the imaging unit 8 to image the region R2 including the second processing line A2 processed in step S203 using light transmitted through the object 51. Based on the image obtained in this way, the second processing line A2 can be observed.

[0085] Next, the inclination direction and inclination amount of the beam shape at the focused spot C of the laser light L in the YZ plane when laser processing is performed along the second processing line A2 are determined (step S207). In the example shown in (c) of Figure 16, a crack 13 extending with a Y-direction component from the modified region 12 is confirmed in the second processing line A2 extending along the X direction. Therefore, it is confirmed that laser processing along the second processing line A2 forms a crack 13 that propagates from the modified region 12 at an incline with respect to the Z direction, i.e., a crack 13 that propagates from the modified region 12 in the YZ plane at an incline with respect to the Z direction.

[0086] Therefore, when performing laser processing along the second processing line A2, it is necessary to take into consideration the inclination of the crack 13 extending from the modified region 12. For this reason, in step S207, the inclination direction of the beam shape (here, the negative Y direction) is determined so that at least the portion of the beam shape at the focused spot C of the laser light L in the YZ plane that is closer to the first surface 51a than the center Ca is inclined in the opposite direction to the inclination direction of the crack 13 confirmed in step S206 (here, the positive Y direction), and the inclination amount of the beam shape is also determined so as to be able to offset the inclination of the crack 13. Note that factors that cause the inclination of the crack 13 may be the crystal plane of the object 51, as in the first embodiment, or may be other factors than the crystal plane of the object 51, such as warpage of the object 51, device structure, or stress due to bumps.

[0087] Thereafter, laser processing of the unprocessed first processing line A1 and the second processing line A2 is performed (step S208, second processing step). In particular, in step S208, when processing the first processing line A1, based on the determination in step S205, the control unit 6 irradiates the target 51 with the laser light L while moving the focused spot C of the laser light L along the unprocessed first processing line A1, without performing modulation processing to make the beam shape at the focused spot C of the laser light L in the XZ plane an inclined shape, thereby forming a modified region 12 along the first processing line A1.

[0088] Also, in step S208, when processing the second processing line A2, based on the decision made in step S207, the control unit 6 performs modulation processing so that the beam shape at the focal spot C of the laser light L in the YZ plane becomes an inclined shape, and irradiates the laser light L onto the object 51 while moving the focal spot C of the laser light L along the unprocessed second processing line A2, thereby forming a modified area 12 along the second processing line A2.

[0089] This completes the laser processing of the object 51. After step S208, the second processing line A2 processed in step S208 may be observed again to check whether the propagation of the crack 13 at an angle with respect to the Z direction has been improved.

[0090] As described above, in step S208, when the extension direction of the processing lines (first processing line A1 and second processing line A2) is the X direction, the direction intersecting with the first surface 51a is the Z direction, and the direction intersecting with the X and Z directions is the Y direction, if a crack 13 inclined with respect to the Z direction in the YZ plane including the Y and Z directions is observed in the observation step (steps S204 and S206), the control unit 6 modulates the laser light L using the spatial light modulator 7, so that the beam shape at the focal spot C of the laser light L in the YZ plane is inclined to the opposite side to the inclination direction of the crack 13 with respect to the Z direction, at least on the incident surface (first surface 51a) side of the center Ca of the focal spot C.

[0091] As described above, according to the laser processing method of the second embodiment, even if the characteristics of the object 51 such as the crystal structure or warpage are unknown, the inclination of the crack 13 in the Z direction within the YZ plane (or within the XZ plane) can be suppressed, and the positional deviation between the arrival position P13 of the crack 13 on the incident back surface of the object 51 and the processing line (first processing line A1 and second processing line A2), i.e., damage caused by the laser light L leaking through the incident back surface of the object 51, can be suppressed.

[0092] The above embodiment describes one aspect of the laser processing apparatus and laser processing method according to the present disclosure. Therefore, the laser processing apparatus and laser processing method according to the present disclosure are not limited to the above embodiment and may be modified as desired.

[0093] 11 has described an example in which, in multiple laser processing operations, the offset amount is increased as the position of the focused spot C in the Z direction is closer to the first surface 11a, which is the incident surface, and FIG. 12(a) has described an example in which, in multiple laser processing operations, the spherical aberration correction amount is overcorrected as the position of the focused spot C in the Z direction is closer to the first surface 11a, which is the incident surface. However, by adjusting the degree of increase in the offset amount and the degree to which the spherical aberration correction amount is overcorrected, the offset amount may be increased and overcorrected as the position of the focused spot C in the Z direction is closer to the first surface 11a, which is the incident surface, by combining the example of FIG. 11 and the example of FIG. 12(b).

[0094] 1...laser processing device, 2...stage (support part), 3...irradiation part, 4, 5...movement part, 6...control part, 7...spatial light modulator, 11, 51...object, 11a, 51a...first surface (incident surface), 11b...second surface (incident back surface), 12...modified area, 13...crack, A...processing line, A1...first processing line, A2...second processing line, C...focus spot, Ca...center, L...laser light.

Claims

1. A laser processing device for forming a modified region in an object by irradiating the object with laser light, comprising: a support section for supporting the object; an irradiation section for irradiating the object supported by the support section with the laser light; a movement section for moving at least one of the support section and the irradiation section so that a focused spot of the laser light moves relative to the object; and a control section for controlling the support section, the irradiation section, and the movement section to irradiate the object with the laser light while moving the focused spot along a processing line along an incident surface of the laser light on the object, thereby executing a processing process to form the modified region along the processing line, wherein the irradiation section includes: a spatial light modulator for modulating the laser light; and a focusing lens for focusing the laser light that has passed through the spatial light modulator toward the object, the target object includes a crystal plane inclined with respect to the Z direction in a YZ plane including the Y direction and the Z direction, where the extension direction of the processing line is defined as an X direction, the direction intersecting the incident plane is defined as a Z direction, and the direction intersecting the X direction and the Z direction is defined as a Y direction; and in the processing, the control unit performs a modulation process by modulating the laser light with the spatial light modulator so that the beam shape at the focused spot of the laser light in the YZ plane becomes an inclined shape inclined with respect to the Z direction toward the opposite side to the crystal plane, at least on the incident plane side of the center of the focused spot.

2. The laser processing device according to claim 1, wherein the object includes an incident back surface opposite to the incident surface, and in the processing, the control unit performs laser processing to form the modified region along the processing line multiple times while varying the Z-direction position of the focused spot by irradiating the object with the laser light while moving the focused spot along the processing line, and the control unit performs the modulation process at least during the laser processing of the multiple times in which the Z-direction position of the focused spot is closest to the incident back surface.

3. The laser processing device according to claim 1 or 2, wherein the object includes an incident back surface opposite to the incident surface, and wherein in the processing, the control unit performs laser processing to form the modified region along the processing line multiple times while varying the position of the focused spot in the Z direction by irradiating the object with the laser light while moving the focused spot along the processing line, and in the modulation process, the control unit offsets the center of a spherical aberration correction pattern to be displayed on the spatial light modulator with respect to the center of an entrance pupil plane of the focusing lens, thereby making the beam shape at the focused spot of the laser light in the YZ plane the inclined shape, and the control unit increases the offset amount of the center of the spherical aberration correction pattern with respect to the center of the entrance pupil plane in the multiple times of laser processing as the position of the focused spot in the Z direction is closer to the incident surface.

4. The laser processing device according to any one of claims 1 to 3, wherein the object includes an incident back surface opposite to the incident surface, and in the processing step, the control unit performs laser processing to form the modified region along the line by irradiating the object with the laser light while moving the focused spot along the line, multiple times while varying the position of the focused spot in the Z direction, and in the modulation step, the control unit offsets the center of a spherical aberration correction pattern to be displayed on the spatial light modulator with respect to the center of an entrance pupil plane of the focusing lens, thereby making the beam shape of the focused spot of the laser light in the YZ plane the inclined shape, and the control unit over-corrects the amount of correction made by the spherical aberration correction pattern in the multiple times of laser processing as the position of the focused spot in the Z direction is closer to the incident surface.

5. A laser processing device according to claim 1 or 2, wherein in the modulation process, the control unit causes the spatial light modulator to display a modulation pattern different from the spherical aberration correction pattern, and uses this modulation pattern to make the beam shape at the focused spot of the laser light in the YZ plane the inclined shape.

6. A laser processing method for forming a modified region in an object by irradiating the object with laser light, comprising a processing step of irradiating the object with laser light while moving a focused spot of the laser light along a line along an incident surface of the laser light on the object, thereby forming the modified region along the line, wherein the object includes a crystal plane inclined with respect to the Z direction in a YZ plane containing the Y direction and the Z direction, where the extending direction of the line is defined as an X direction, a direction intersecting the incident surface is defined as a Z direction, and a direction intersecting the X direction and the Z direction is defined as a Y direction, and wherein in the processing step, the laser light is modulated by a spatial light modulator, so that the beam shape at the focused spot of the laser light in the YZ plane is inclined to the opposite side of the crystal plane with respect to the Z direction, at least on the incident surface side of the center of the focused spot.

7. A laser processing method for forming a modified region in an object by irradiating the object with laser light, comprising: a first processing step of irradiating the object with laser light while moving a focal spot of the laser light along a processing line along an incident surface of the laser light on the object, thereby forming the modified region along the processing line; an observation step of observing, after the first processing step, cracks extending from the modified region formed along the processing line; and a second processing step of irradiating the object with laser light while moving the focal spot of the laser light along another processing line along the incident surface of the laser light on the object, thereby forming the modified region along the other processing line, after the observation step. In the second processing step, when the extension direction of the processing line is defined as the X direction, the direction intersecting the incident surface is defined as the Z direction, and the direction intersecting the X direction and the Z direction is defined as the Y direction, if the crack inclined with respect to the Z direction is observed in the observation step within a YZ plane including the Y direction and the Z direction, the laser light is modulated by a spatial light modulator so that the beam shape at the focused spot of the laser light within the YZ plane is inclined to the opposite side to the inclination direction of the crack with respect to the Z direction, at least on the incident surface side of the center of the focused spot.

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