Laser machining device and laser machining method

Abstract

To provide a laser machining device and a laser machining method, capable of suppressing a positional deviation between a crack arrival position and a machining line.SOLUTION: A laser machining device includes a control unit that executes machining processing of forming a modified region along a second machining line by irradiating an object with laser light L while moving a condensing spot along the second machining line on a machining surface A along an incident surface 11a of the laser light L on the object 11. When the extension direction of the second machining line is an X direction, a direction intersecting the incident surface is a Z direction, and a direction intersecting the X direction and the Z direction is a Y direction, the object 11 has a crystal plane that is tilted to the Z direction in the YZ plane. The control unit executes such modulation processing that, in the machining processing, the beam shape of the laser light L at the condensing spot C in the XY plane becomes a tilted shape that is tilted on a side opposite the crystal plane relative to the Z direction at least closer on an incident surface side than the center of the condensing spot C.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a laser processing apparatus and a laser processing method. [Background technology]

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

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-016486 Summary of the Invention [Problem to be solved by the invention]

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

[0005] On the other hand, there are cases where the crack extending from the modified region is unintentionally tilted depending on the crystal plane of the workpiece. <111> Crystal orientation that is a plane <111> In the case of a wafer, when a modified region is formed by irradiating laser light along a processing line along the (110) plane perpendicular to the incident plane, cracks extending from the modified region are unlikely to tilt, but when a modified region is formed by irradiating laser light along another processing line perpendicular to the incident plane and the (110) plane, cracks extending from the modified region are likely to tilt 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, assuming that the direction in which the other processing line extends (processing direction) is the X direction, the direction intersecting the laser light incident plane 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 shift 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 (for example, 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 side, 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 invention is to provide a laser processing device and a laser processing method that can suppress misalignment between the crack arrival position and the processing line. [Means for solving the problem]

[0010] The laser processing device according to the present invention is [1] "a laser processing device 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 executing 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 of the present invention 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 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 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 focal 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 focal 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 focal spot. By inclining the beam shape at the focal 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 to each other in the Z direction, and as a result, the inclination of the crack can be suppressed. Therefore, according to 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 the laser light leaking through the incident back surface of the object) can be suppressed.

[0013] The laser processing device according to the present invention may be the laser processing device described in [1] above, [2] "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 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 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 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 into the above-mentioned inclined shape is a method of offsetting the center of the spherical aberration correction pattern displayed on the spatial light modulator with respect to the center of the entrance pupil plane of the condenser lens. In this case, the inclination 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 inclination 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 invention 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 invention may be the laser processing device according to 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 during multiple laser processing, it is possible to avoid increasing the offset amount required to ensure the inclination of the beam shape. This makes it possible to suppress the inclination of cracks extending from the modified region 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 invention 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 invention 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. 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 in 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 the crack 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 and the processing line (i.e., damage caused by the laser light escaping from the back surface of the object). [Effects of the Invention]

[0021] According to the present invention, 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. [Brief explanation of the drawings]

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

[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, moving 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 and Y directions. The X and Y directions are first and second horizontal directions that intersect (are perpendicular to) each other, and the Z direction is the 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 the 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 (orthogonal to) the Z direction, and a second moving unit 42 that moves the stage 2 in another direction within the plane intersecting (orthogonal 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. When the stage 2 and / or the irradiation unit 3 is moved 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 the 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. 1. 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 be configured not to have the light source 31, but 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, the spatial light modulator 7 displays the modulation pattern in accordance with the signal. The modulation pattern is for modulating the laser light L. When laser light L is incident from the outside, reflected, and emitted to the outside while a 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 target 11, thereby forming a modified region 12 and a crack extending from the modified region 12 in the target 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 target 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. (a) of FIG. 3 is a plan view, and (b) of FIG. 3 is a schematic diagram for explaining crystal orientation. The object 11 shown in FIG. 3 has, for example, a crystal orientation <111> The object 11 is a wafer (e.g., a silicon wafer). The object 11 includes a first surface 11a and a second surface 11b opposite to the first surface 11a. The object 11 is supported by the stage 2 so that the first surface 11a faces the irradiation unit 3 (see FIG. 5, etc.). Therefore, the first surface 11a is an incident surface of the object 11 onto which the laser light L is incident, and the second surface 11b is an incident back surface opposite to the incident surface of the object 11. 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 schedule for the above-mentioned laser processing. 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 parallel to each other and multiple second processing lines A2 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 with the first surface 11a is defined as the Z direction, and the direction intersecting with the X direction and the Z direction 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 direction and the Z direction.

[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 object 11 is irradiated with laser light L while the focused spot C is moved 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 with respect to the Z direction due to the influence of the crystal plane S1, which is a (111) plane inclined with respect to the Z direction in the YZ plane.

[0039] As a result, as shown in FIGS. 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 stray light that occurs on the second surface 11b directly below the second processing line A2 in the Z direction are shifted in the Y direction. For this reason, 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 stray light may be shifted from the center of the street region toward the device, which may affect the device. Therefore, there is a demand for suppressing 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 positioned inside the object 11 and the focused spot C is moved along the first processing line A1 (i.e., along the Y direction), 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, when laser processing is performed along the second processing line A2, the arrival position P13 of the crack 13 on the second surface 11b is prevented from shifting 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 multiple second processing lines A2 in the XY plane including the X and Y directions, and is positioned at a predetermined processing depth inside the object 11 in the Z direction (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 of the laser light L at the focused spot C 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 of the laser light L at the focused spot C in the YZ plane becomes an inclined shape (hereinafter, may be simply referred to as "inclined shape") inclined in the negative Y direction with respect to the Z direction at least on the first surface 11a side of the center Ca of the focused spot C (step S102). In the example of Fig. 7, the beam shape of the laser light L at the focused spot C in the YZ plane becomes an inclined shape inclined in the negative Y direction with respect to the Z direction on the first surface 11a side of the center Ca (an arc shape that is convex in the positive Y direction overall).

[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 the tilt direction with respect 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, 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 an inclined shape that is inclined toward the opposite side of the crystal plane S1 with respect to the Z direction, as shown in Fig. 8. Fig. 8(b) shows the beam shape (intensity distribution) in each cross section F1 to F7 in Fig. 8(a) (i.e., in the XY plane). Each diagram in Fig. 8(b) is the result of actual observation by a camera. Fig. 8 shows that the focused spot C gradually shifts to 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, as the Z-direction position moves toward the second surface 11b from 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 of 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 in the Z direction to the center Ca, and gradually shifts in the Y-negative direction at a position in the Z direction closer to the second surface 11b than the center Ca.

[0050] Alternatively, 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 loses 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 inside the object 11 in the Z direction (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 irradiate the object 11 with the laser light L while moving the focused spot C of the laser light L relative to the object 11 along the second processing line A2 (X direction), thereby forming the modified region 12 at the second position Z2 along the second processing line A2 (step S105: processing process, processing step). At this time, as described above, a modulation process may be performed so that the beam shape of 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 a modified region 12 along the second processing line A2. Then, the control unit 6 performs the above-mentioned modulation process at least during laser processing during 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, in the processing, the position of the focused spot C in the Z direction is changed sequentially from a first position Z1 toward the first surface 11a to a second position Z2, a third position Z3, a fourth position Z4, and a fifth position Z5, and five laser processing operations are performed to form modified regions 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 "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 "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 is to be reduced, and decreasing the offset amount when the amount of spherical aberration correction is to be 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 in multiple laser processing operations 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. 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, when performing 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. 12(a), 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. As a result, 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 beam 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 amount of the beam shape of the focused spot C of the laser beam L is maintained constant.

[0061] Furthermore, in the example of FIG. 12(b), the control unit 6 causes the spatial light modulator 7 to display a coma aberration pattern, which is a modulation pattern different 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 similarly to that of 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 other modulation pattern can be used, such as the above-mentioned astigmatism pattern, diffraction grating pattern, etc. 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 level notation, etc.) on an input / output unit that the laser processing apparatus 1 may be equipped 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] Note that 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] Fig. 13 is a diagram showing a cut surface when laser processing according to the first embodiment is performed. Fig. 13(a) shows the cut surface when viewed from the X direction, and Fig. 13(b) shows the cut surface when viewed from the Z direction. Note that the processing result in Fig. 13 shows a case where, 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 into an inclined shape.

[0066] 13, the laser processing according to the first embodiment suppresses the inclined propagation of the crack 13 extending from the modified region 12 closest to the second surface 11b, thereby suppressing 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. Therefore, 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, laser processing is performed to form a modified region 12 along the second processing line A2 by irradiating the target 11 with laser light L while moving the focused spot C along the second processing line A2 along the first surface 11a, which is the incident surface of the target 11 for the laser light L. 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 target 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 the laser processing method according to the first embodiment can suppress the tilt of the crack 13 in the Z direction within the YZ plane, and suppress the misalignment between the arrival position P13 of the crack 13 on the second surface 11b, which is the back surface of the object 11 onto which 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 scattering of the laser beam L 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. Then, the control unit 6 may 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, it is possible to more reliably suppress 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.

[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 condenser lens 33, thereby making the beam shape of the focused spot C of the laser light L in the YZ plane the inclined shape. In this case, the control unit 6 may increase the amount of 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 in multiple laser processing operations. In this case, even if the amount of spherical aberration correction by the spherical aberration correction pattern is reduced as the Z-direction position of the focused spot C approaches the first surface 11a in multiple laser processing operations, the inclination of the beam shape can be ensured. 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 an increase in the offset amount required to ensure the inclination of the beam shape, compared to a case in which 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 increase in the 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 (e.g., 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 above-mentioned inclined shape. In this case, the beam shape can be made the above-mentioned inclined shape without affecting the correction of spherical aberration. Therefore, the beam shape can be stably made the above-mentioned inclined shape. [Second embodiment]

[0074] Next, a laser processing method according to the second embodiment will be described. Fig. 14 is a flowchart showing each step of the laser processing method according to the second embodiment. Figs. 15 and 16 are schematic diagrams for explaining each step 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 plan for 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 target 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 direction and the Y direction 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 laser light L at the focused spot C 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 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 of the laser light L at the focused spot C in the XZ plane when performing laser processing along the first processing line A1 are determined (step S205). In the example shown in (b) of FIG. 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 in laser processing along the first processing line A1, no crack 13 is formed that propagates from the modified region 12 at an incline with respect to the Z direction, i.e., no crack 13 is formed 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, there is no need 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 of the laser light L at the focused spot C in the YZ plane when performing laser processing along the second processing line A2 are determined (step S207). In the example shown in (c) of FIG. 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 factors other 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 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 object 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 for making 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 target 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 relative 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 defined as the X direction, the direction intersecting with the first surface 51a is defined as the Z direction, and the direction intersecting with the X and Z directions is defined as 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 lines (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 has described one aspect of the laser processing apparatus and laser processing method according to the present invention. Therefore, the laser processing apparatus and laser processing method according to the present invention are not limited to the above embodiment and can be modified as desired.

[0093] For example, in the first embodiment described above, an example has been described in Fig. 11 in which 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 entrance surface, in multiple laser processing operations, and an example has been described in Fig. 12(a) in which 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 entrance surface, in multiple laser processing operations. However, by adjusting the degree of increase in the offset amount and the degree to which the spherical aberration correction amount is overcorrected, the example of Fig. 11 and the example of Fig. 12(b) may be combined to increase the offset amount and to perform overcorrection as the position of the focused spot C in the Z direction is closer to the first surface 11a, which is the entrance surface. [Explanation of symbols]

[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, a support portion that supports the object; an irradiation unit that irradiates the laser light onto the object supported by the support unit; a moving 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; a control unit that controls the support unit, the irradiation unit, and the moving 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 executing a processing process to form the modified region along the processing line, the irradiation unit includes a spatial light modulator for modulating the laser light; a condenser lens that condenses the laser light that has passed through the spatial light modulator toward the target; Including, When an extension direction of the processing 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, the object includes a crystal plane inclined with respect to the Z direction in a YZ plane including the Y direction and the Z direction, In the processing, the control unit performs a modulation process in which the spatial light modulator modulates the laser light so that the beam shape at the focused spot of the laser light in the YZ plane becomes an inclined shape that 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. Laser processing equipment.

2. the object includes an incident back surface opposite the incident surface, In the processing, the control unit irradiates the object with the laser light while moving the focused spot along the processing line, thereby performing laser processing to form the modified region along the processing line multiple times while changing the position of the focused spot in the Z direction; the control unit executes 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, among the plurality of times of the laser processing. The laser processing device according to claim 1 .

3. the object includes an incident back surface opposite the incident surface, In the processing, the control unit irradiates the object with the laser light while moving the focused spot along the processing line, thereby performing laser processing to form the modified region along the processing line multiple times while changing the position of the focused spot in the Z direction; In the modulation process, the control unit offsets a center of a spherical aberration correction pattern to be displayed on the spatial light modulator with respect to a center of an entrance pupil plane of the condenser lens, thereby making the beam shape of the condensed spot of the laser light in the YZ plane the inclined shape; the control unit increases an offset amount of the center of the spherical aberration correction pattern with respect to the center of the entrance pupil plane as the position of the focused spot in the Z direction approaches the entrance surface in a plurality of times of the laser processing; 3. The laser processing device according to claim 1 or 2.

4. the object includes an incident back surface opposite the incident surface, In the processing, the control unit irradiates the object with the laser light while moving the focused spot along the line, thereby performing laser processing to form the modified region along the line a plurality of times while varying the position of the focused spot in the Z direction; In the modulation process, the control unit offsets a center of a spherical aberration correction pattern to be displayed on the spatial light modulator with respect to a center of an entrance pupil plane of the condenser lens, thereby making the beam shape of the condensed spot of the laser light in the YZ plane the inclined shape; the control unit, in the multiple laser processing operations, causes the amount of correction by the spherical aberration correction pattern to be overcorrected as the position of the focused spot in the Z direction becomes closer to the incident surface.

3. The laser processing device according to claim 1 or 2.

5. In the modulation process, the control unit causes the spatial light modulator to display a modulation pattern different from a spherical aberration correction pattern, and causes the beam shape at the focused spot of the laser light in the YZ plane to be the inclined shape by the different modulation pattern.

3. The laser processing device according to claim 1 or 2.

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 object with the laser light, thereby forming the modified region along the line, When an extension direction of the line is defined as an X direction, a direction intersecting the plane of incidence is defined as a Z direction, and a direction intersecting the X direction and the Z direction is defined as a Y direction, 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, In the processing step, the laser light is modulated by a spatial light modulator, so that a beam shape of the focused spot of the laser light in the YZ plane is tilted toward an 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. Laser processing method.

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 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 cracks extending from the modified region formed along the processing line after the first processing step; a second processing step of, after the observation step, irradiating the object with the laser light while moving a 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 another processing line; Equipped with In the second processing step, when the extension direction of the processing line is defined as an X direction, the direction intersecting the incident surface is defined as a Z direction, and the direction intersecting the X direction and the Z direction is defined as a 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. Laser processing method.

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