Laser processing apparatus and laser processing method

Abstract

The control section of the present application executes: a first process of irradiating the object with the laser while relatively moving the first focal point and the second focal point along a first line in a state where the distance between the first focal point and the second focal point is set to a first distance; and a second process of irradiating the object with the laser while relatively moving the first focal point and the second focal point along a second line in a state where the distance between the first focal point and the second focal point is set to a second distance smaller than the first distance.

Description

Technical Field

[0001] This disclosure relates to laser processing apparatus and laser processing methods. Background Technology

[0002] Patent Document 1 describes a laser processing apparatus. This apparatus includes a focusing lens, through which a processing layer is formed on a single-crystal component using laser light emitted from the focusing lens. The focusing lens comprises a sub-focusing system to which laser light is incident, and a main focusing system to which laser light emitted from the sub-focusing system is incident and irradiates the single-crystal component. The sub-focusing system includes a cylindrical lens array consisting of multiple cylindrical lenses arranged integrally, and a cylindrical convex lens through which light from the cylindrical lens array passes.

[0003] In this laser processing apparatus, the laser incident on the cylindrical lens is branched into multiple beams, forming a focusing point, and then incident on the cylindrical convex lens. The irradiated surface is formed into a long, narrow parallel beam that is incident on the main focusing system. The laser emitted from the main focusing system is branched onto the irradiated surface of the single crystal component and incident thereon, forming multiple focusing points inside the single crystal component.

[0004] Existing technical documents

[0005] Non-patent literature

[0006] Non-patent document 1: Japanese Patent Application Publication No. 2014-19120 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] In the aforementioned laser processing apparatus, the formation speed of the processing layer is improved by forming multiple laser focusing points simultaneously. That is, in this technical field, an increase in processing speed is desired. On the other hand, in this technical field, there is a processing requirement to cut out the central region (effective region) of the object by removing an annular region (removal region) containing the outer edge of the object. The effective region refers to, for example, the region where a device is formed. Therefore, in this technical field, it is also desirable to suppress the degradation of the quality of the effective region (i.e., processing quality).

[0009] Therefore, the purpose of this disclosure is to provide a laser processing apparatus and a laser processing method that can simultaneously increase processing speed and suppress the reduction of processing quality.

[0010] means for solving problems

[0011] The inventors of this case, through careful research, arrived at the following insights in order to solve the aforementioned problems. Specifically, when cutting an effective area from an object, two processing methods are considered. The first processing method involves irradiating the boundary between the effective area and the removal area with a laser to form a modified area at that boundary. The second processing method involves irradiating the annular removal area into multiple parts to facilitate its removal by irradiating the object with a laser from its outer edge to the boundary between the effective area and the removal area, thereby forming a modified area in the removal area from the outer edge of the object to the boundary between the effective area and the removal area.

[0012] From the perspective of increasing the formation speed of modified regions, consider forming multiple rows of modified regions in the thickness direction of the object by forming multiple focusing points. In this case, the amount of crack propagation from the modified regions can be increased by offsetting the focusing points relative to each other in the direction of focusing point travel (processing travel direction). If the amount of crack propagation increases, the number of rows of modified regions required to cut the object can be reduced in the thickness direction of the object. Therefore, in the first processing described above, when modified regions are formed at the boundary between the effective area and the removal area, the processing speed can be increased by offsetting the focusing points relative to each other.

[0013] In contrast, during the second processing described above, if the focal points are offset from each other in the processing direction, for example, when one focal point reaches the boundary between the effective area and the removal area, other focal points that are offset further forward in the processing direction than that focal point will travel into the effective area at a distance corresponding to the offset. In this case, a modified area is formed inside the effective area. Therefore, in this situation, by reducing the offset between the focal points, the modified area formed in the effective area can be reduced, and the degradation of the quality of the effective area can be suppressed.

[0014] On the other hand, if the laser irradiation is turned off when the other focusing point reaches the boundary between the effective region and the removal region without traveling into the effective region, then that focusing point will not reach the effective region by a distance corresponding to the offset. In this case, since the modified region is not formed in a way that reaches the effective region, the quality of the cut surface when cutting the object along the boundary between the effective region and the removal region may be reduced. Therefore, in this case, by reducing the offset between the focusing points, the reduction in the quality of the cut surface can be suppressed.

[0015] As described above, in the first processing step, the relative offset between the focal points is increased, and in the second processing step, the relative offset between the focal points is decreased. Thus, it is possible to simultaneously increase processing speed and suppress the reduction in processing quality. This invention was developed based on the above insights.

[0016] That is, the laser processing apparatus disclosed herein is a laser processing apparatus for irradiating an object with a laser to form a modified region, and includes: a support for supporting the object; a laser irradiation unit for forming a first laser focusing point and a second laser focusing point located on the object supported on the support, and irradiating the object with a laser; a moving mechanism for moving at least one of the support and the laser irradiation unit in a manner that moves relative to the first and second laser focusing points on the object; and a control unit for controlling the laser irradiation unit and the moving mechanism. Viewed from a direction intersecting the incident surface, the object includes: a first portion located inside the object, and a second portion located outside the first portion and including the outer edge of the object. The object is provided with: a portion extending from the direction intersecting the incident surface... Viewed from the fork direction, a first line extends in a ring shape at the boundary between the first and second parts; and a second line extends from the outer edge of the object toward the inner side of the object and reaches the boundary in the second part. The control unit performs: a first process, in which the laser irradiation unit and the moving mechanism are controlled to irradiate the object with laser while the distance between the first and second focusing points along the first line is set to a first distance; and a second process, in which the laser irradiation unit and the moving mechanism are controlled to irradiate the object with laser while the distance between the first and second focusing points along the second line is set to a second distance less than the first distance.

[0017] Furthermore, the laser processing method disclosed herein is a laser processing method for forming a modified region by irradiating an object with a laser, and includes: a laser irradiation step, forming a first laser focusing point and a second laser focusing point located on the object closer to the laser incident surface than the first laser focusing point, and irradiating the object with a laser, and, when viewed from a direction intersecting the incident surface, the object includes: a first part located inside the object and a second part located outside the first part and including the outer edge of the object, and a first line extending in a ring shape at the boundary between the first part and the second part when viewed from a direction intersecting the incident surface; In the second part, the laser irradiation process includes: a first irradiation process in which, with the distance between a first focal point and a second focal point set to a first distance along the direction of the first line, the first focal point and the second focal point are moved relative to each other along the first line while irradiating the object with laser; and a second irradiation process in which, with the distance between the first focal point and the second focal point set to a second distance less than the first distance along the direction of the second line, the first focal point and the second focal point are moved relative to each other along the second line while irradiating the object with laser.

[0018] In these apparatuses and methods, the workpiece is provided with: a first line extending in a ring along the boundary between a first portion located on the inner side and a second portion located on the outer side of the first portion; and a second line extending from the outer edge of the workpiece toward the inner side of the workpiece and reaching the boundary in the second portion. Furthermore, in both processing along the first line and processing along the second line, two laser focusing points are formed on the workpiece, and the workpiece is irradiated with laser light. During processing along the first line, the distance between the focusing points along the first line relatively increases. Therefore, as described above, the processing speed can be increased. On the other hand, during processing along the second line, the distance between the focusing points along the second line relatively decreases. Therefore, as described above, a decrease in processing quality can be suppressed.

[0019] In the laser processing apparatus disclosed herein, the control unit may perform the second process multiple times on a second line while making the positions of the first and second focusing points in the direction intersecting the incident plane different. Therefore, performing the second process multiple times on one second line is effective for reducing the relative distance between the focusing points.

[0020] In the laser processing apparatus disclosed herein, the control unit may perform a second process (m being an integer greater than n) after executing the nth (n being an integer greater than or equal to 1) second process, with at least one of the first and second focusing points positioned between the first and second focusing points in the direction intersecting the incident plane during the nth second process. In this case, the modified region can be formed more tightly in the direction intersecting the incident plane, thereby improving the processing quality.

[0021] In the laser processing apparatus disclosed herein, the control unit may perform the (n+1)th second process after executing the nth (n being an integer greater than or equal to 1) second process, with the first focusing point positioned closer to the incident surface than during the nth second process, in the direction intersecting the incident surface. Therefore, by sequentially aligning the focusing points from the side farther from the incident surface during the second process, a modified region can be formed more appropriately.

[0022] The laser processing apparatus disclosed herein may further include an input unit for receiving input and a display unit for displaying information. Before performing the first processing, the input unit receives an input of a first distance. Before performing the first processing, if the first input value (the first distance received by the input unit) is less than a first threshold, the control unit causes the display unit to display information urging confirmation of the first input value. If the first input value is greater than or equal to the first threshold, the first processing is performed. In this case, during the first processing, it can be ensured that the first and second focusing points are greater than or equal to the threshold, and the amount of crack propagation can be reliably increased, thereby increasing the processing speed.

[0023] In the laser processing apparatus disclosed herein, the input unit may receive a second distance input before performing the second processing. Before performing the second processing, if the second input value (the second distance input value received by the input unit) is greater than a second threshold, the control unit may display information on the display unit to urge confirmation of the second input value. If the second input value is less than the second threshold, the second processing may be performed. In this case, during the second processing, it can be ensured that the distance between the first and second focusing points is less than the threshold, and the processing quality can be reliably improved.

[0024] Invention Effects

[0025] According to this disclosure, a laser processing apparatus and a laser processing method can be provided that can both increase processing speed and suppress the reduction of processing quality. Attached Figure Description

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[0042] Hereinafter, an embodiment will be described in detail with reference to the accompanying drawings. Furthermore, in the various figures, the same or equivalent parts are sometimes given the same symbols, and repeated descriptions are omitted. Additionally, in the various figures, an orthogonal coordinate system defined by the X-axis, Y-axis, and Z-axis is sometimes shown.

[0043] Figure 1 This is a schematic diagram of the structure of a laser processing apparatus according to one embodiment. Figure 1 As shown, the laser processing apparatus 1 includes: a stage (support) 2, a laser irradiation unit 3, a drive unit (moving unit) 4 and 5, and a control unit 6. The laser processing apparatus 1 is a device used to form a modified region 12 on an object 11 by irradiating the object 11 with a laser L.

[0044] The mounting stage 2 supports the object 11, for example, by holding the film attached to the object 11. The mounting stage 2 can rotate about an axis parallel to the Z direction. The mounting stage 2 can also move along the X and Y directions respectively. Furthermore, the X and Y directions are first and second horizontal directions that intersect (orthogonal), and the Z direction is a vertical direction.

[0045] The laser irradiation unit 3 focuses a laser L that is transmissible relative to the object 11 and irradiates the object 11. If the laser L is focused inside the object 11 supported on the mounting stage 2, the laser L is particularly absorbed in the part corresponding to the focusing point C of the laser L, and a modified region 12 is formed inside the object 11.

[0046] The modified region 12 is a region whose density, refractive index, mechanical strength, and other physical properties differ from the surrounding unmodified region. Examples of modified regions 12 include melt-processed regions, cracked regions, insulation-damaged regions, and regions with refractive index changes. The modified region 12 can be formed by cracks extending from the modified region 12 towards the incident side of the laser L and the opposite side. Such modified regions 12 and cracks are used for cutting the object 11.

[0047] As an example, if the stage 2 moves along the X direction and the focusing point C moves relative to the object 11 along the X direction, multiple modification points 12s are formed in a row along the X direction. Each modification point 12s is formed by irradiation with a single pulse of laser L. A row of modification regions 12 is a collection of multiple modification points 12s arranged in a row. Adjacent modification points 12s may be connected or separated depending on the relative moving speed of the focusing point C relative to the object 11 and the repetition frequency of the laser L.

[0048] The drive unit 4 rotates the stage 2 using an axis parallel to the Z direction as its rotation axis. The drive unit 4 can also move the stage 2 along the X and Y directions respectively. The drive unit 5 supports the laser irradiation unit 3. The drive unit 5 moves the laser irradiation unit 3 along the X, Y, and Z directions.

[0049] The control unit 6 controls the operation of the stage 2, the laser irradiation unit 3, and the drive units 4 and 5. The control unit 6 includes a processing unit 61, a storage unit 62, and an input receiving unit (display unit, input unit) 63. The processing unit 61 is configured as a computer device including a processor, memory, storage, and a communication device. In the processing unit 61, the processor executes software (programs) loaded into memory, etc., and controls the reading and writing of data in the memory and storage, as well as communication via the communication device. The storage unit 62 is, for example, a hard disk, which stores various types of data. The input receiving unit 63 is an interface unit that displays various data and receives various information input from the user. In this embodiment, the input receiving unit 63 constitutes a GUI (Graphical User Interface).

[0050] Figure 2 and Figure 3 It is shown Figure 1 A schematic diagram of the structure of the laser irradiation unit is shown. Figure 2 , 3 As shown, the laser irradiation unit 3 includes a light source 31, a spatial light modulator 32, and a focusing lens 33. The light source 31 outputs laser light L through, for example, pulse oscillation. Alternatively, the laser irradiation unit 3 may not have a light source 31, and the laser light L may be introduced from outside the laser irradiation unit 3.

[0051] Spatial light modulator 32 modulates the laser L output from light source 31. Spatial light modulator 32 is a reflective liquid crystal on silicon (LCOS) spatial light modulator (SLM). Condensing lens 33 focuses the laser L modulated by spatial light modulator 32. Spatial light modulator 32 includes a liquid crystal layer (not shown), and modulates the laser L according to the modulation pattern displayed on the liquid crystal layer. Here, at least two branching patterns for branching the laser L into multiple (in this case, two) are displayed in spatial light modulator 32. Thus, the laser L incident on spatial light modulator 32 is branched into two lasers L1 and L2 in spatial light modulator 32, and focused by condensing lens 33 to form a first focusing point C1 and a second focusing point C2.

[0052] To elaborate further, the spatial light modulator 32 branches the laser L by forming a first focusing point C1 and a second focusing point C2 at mutually different positions in the Z direction, at least in the direction intersecting the incident surface (back face 11b) of the laser L of the object 11. Therefore, by moving the first focusing point C1 and the second focusing point C2 relative to the object 11, two rows of modified regions, namely modified region 121 and modified region 122, are formed at mutually different positions in the Z direction as modified regions 12.

[0053] Modified region 121 corresponds to laser L1 and its first focusing point C1, and modified region 122 corresponds to laser L2 and its second focusing point C2. The first focusing point C1 and modified region 121 are located on the opposite side of the back surface 11b (the surface 11a side of the object 11) relative to the second focusing point C2 and modified region 122. The spatial light modulator 32 sets the distance Dz (longitudinal branching amount) between the first focusing point C1 and the second focusing point C2 in the Z direction to be variable.

[0054] Furthermore, the spatial light modulator 32, when branching laser L into lasers L1 and L2, sets the horizontal distance Dx (horizontal branching amount) between the first focusing point C1 and the second focusing point C2 (in the illustrated example, the X direction) to be variable. Figure 2 For example, the spatial light modulator 32 sets the distance Dx to be greater than 0 so that the first focusing point C1 is positioned further forward than the second focusing point C2 in the X direction (processing travel direction). Figure 3 For example, the spatial light modulator 32 sets the distance Dx between the first focal point C1 and the second focal point C2 to 0.

[0055] Figure 4 This is a cross-sectional photograph showing the processing results when the distance Dx is set to 0. Figure 4 The processing results are as follows: the output of laser L is set to 2W (the pulse energy of lasers L1 and L2 is 10μJ each), the output ratio of laser L1 to laser L2 is set to 50:50, and the distance Dz (vertical branching) is varied from 15μm to 70μm. For example... Figure 4 As shown, when the distance Dx is set to 0, although a portion of the modified region 12 (modified region 121) is not formed on the surface 11a side when the distance Dz is 15 μm and 20 μm, a region 12N is formed. However, by setting the distance Dz to 25 μm, the modified region 121 is formed throughout. Furthermore, Figure 4 The specific irradiation conditions for lasers L1 and L2 in the example are: frequency 80kHz, processing speed 430mm / s, pulse spacing 5.375μm, and pulse width 700ns.

[0056] on the other hand, Figure 5 This is a cross-sectional photograph showing the results of other processing when the distance Dx is set to 0. Figure 5 The processing results are as follows: the output of laser L is set to 4W (the pulse energy of lasers L1 and L2 is 20μJ each), the output ratio of laser L1 to laser L2 is set to 50:50, and the distance Dz is varied from 15μm to 70μm. For example... Figure 5 As shown, with Figure 4Compared to the previous example, by increasing the output of laser L, the region 12N on the side where the modified region 12 is not formed on the surface 11a side is reduced, and the modified region 12 is formed over a substantially all-encompassing area for all cases with distances from 15 μm to 70 μm from Dz. Furthermore, Figure 5 The specific irradiation conditions for lasers L1 and L2 in the example are: frequency 80kHz, processing speed 430mm / s, pulse spacing 5.375μm, and pulse width 700ns.

[0057] Furthermore, according to the inventor's understanding, the closer the distance Dx is to 0, the less likely it is to form the modified region 12 (modified region 121) on the surface 11a due to the influence of the second focusing point C2 on the back side 11b and the modified region 12 (modified region 122). Therefore, as described above, since the modified region 121 can be sufficiently formed when the distance Dx is set to 0, the situation becomes more difficult when the distance Dx is set to a value greater than 0 (in...). Figure 2 (For example), the modified region 121 can be formed more reliably. In particular, by setting the distance Dx to 8 μm or more, the influence of the second focusing point C2 and the modified region 122 can be reduced, and the modified region 121 can be formed reliably.

[0058] As described above, the laser irradiation unit 3 can form a first focusing point C1 of laser L1 and a second focusing point C2 of laser L2 located on the side of the incident surface (back surface 11b) of laser L1 closer to the object 11 than the first focusing point C1, relative to the object 11 supported on the stage 2, and irradiate lasers L1 and L2. In particular, in the laser irradiation unit 3, laser L can be branched into lasers L1 and L2, and the distance between each first focusing point C1 and second focusing point C2 in each direction can be set to be variable.

[0059] Next, an example of the laser processing method performed by the laser processing apparatus 1 will be given, and the detailed structure of the laser processing apparatus will be described. Figure 6 This is a flowchart illustrating an example of the laser processing method of this embodiment. Here, the laser processing apparatus 1 performs trimming and cutting processes on the workpiece 11. Trimming is a process to remove unwanted portions from the workpiece 11 to form a modified region. Cutting is a process to separate the unwanted portions removed by the trimming process to form the modified region. Here, firstly, as... Figure 7 As shown, object 11 is supported on the mounting platform 2.

[0060] Figure 8 It is shown Figure 7 A diagram of the object shown. Figure 8 (a) is a top view. Figure 8 (b) is a side view. For example... Figure 7 ,8 As shown, the object 11 here includes, for example, a semiconductor wafer formed in the shape of a disc. However, the object 11 is not particularly limited and can be formed into various shapes depending on the material. Functional elements (not shown) are formed on the surface 11a of the object 11, for example. These functional elements include, for example, light-receiving elements such as light-emitting diodes, light-emitting elements such as laser diodes, and circuit elements such as memory. The object 11 is supported on the stage 2 with its back surface 11b, opposite to the surface 11a, facing the laser irradiation unit 3.

[0061] In object 11, an effective region R (part 1) and a removal region E (part 2) are defined. The effective region R is the device region where functional elements are formed. For example, when viewed from the thickness direction of object 11 (the direction from surface 11a to back surface 11b, Z direction), the effective region R is a circular plate-shaped portion including the central part. That is, the effective region R is the portion located further inside object 11 than the removal region E.

[0062] The removal area E is located outside the effective area R of the object 11 and includes the outer edge of the object 11. Here, the removal area E is the portion outside the effective area R of the object 11, and viewed from the Z direction, it is an annular portion surrounding the effective area R. Viewed from the Z direction, the removal area E includes the peripheral portion (the beveled portion of the outer edge) of the object 11. The removal area E is the radiation cutting area that becomes the object of the radiation cutting process.

[0063] On object 11, lines (first line) M1 and (second line) M2 are defined. Line M1 is a predetermined line for forming the modified region during finishing processing. Viewed from the Z direction, line M1 extends in a loop (ring shape) at the boundary between the effective region R and the removal region E. Viewed from the Z direction, line M1 coincides with the outer edge of the effective region R (inner edge of the removal region E). That is, line M1 shows the boundary between the effective region R and the removal region E. Line M2 is a predetermined line for forming the modified region during radial cutting processing. Viewed from the Z direction, line M2 extends in a straight line (radial shape) along the radial direction of object 11.

[0064] Viewed from the Z direction, line M2 extends from the outer edge of object 11 toward the inner side of object 11 in the removal area E, reaching the boundary between the effective area R and the removal area E. Line M2 stops at the intersection with line M1 before reaching the effective area R. Lines M2a and M2b in line M2 are aligned on a straight line. Lines M2c and M2d in line M2 are aligned on a straight line in a direction that intersects (orthogonals) lines M2a and M2b. The settings of lines M1 and M2 can be performed in the control unit 6. Lines M1 and M2 can be either imaginary lines or lines specified by coordinates.

[0065] For the object 11 described above, a finishing process is first performed. Therefore, the control unit 6 first receives input for the finishing processing conditions (process S1). More specifically, in this process S1, the control unit 6 causes the input receiving unit 63 to display information urging the input of the finishing conditions. The input receiving unit 63 receives the input of the finishing conditions. At this time, the input receiving unit 63 receives at least the input of the finishing distance Dx (first distance). An example of the input value for distance Dx is 110 μm.

[0066] Input receiving unit 63, in addition to the above, as described later Figure 11 Similarly, each value can accept input from various conditions. That is, as an example, the input receiving unit 63 accepts inputs of the number of focal points, the number of passes, the processing speed, the pulse width, and the frequency as basic processing conditions. The number of focal points is the number of branches of the laser L through the spatial light modulator 32, which is mainly 2 here. The number of passes is the number of times the line M1 is trimmed, that is, the number of times the first processing of line M1 (described later) is performed, and the number of scans of lasers L1 and L2 is 4 times, for example. Therefore, in the trimming process, a modified region 12 is formed in the Z direction with a column number equivalent to the number of focal points × the number of passes.

[0067] Furthermore, the input receiving unit 63 can accept detailed processing conditions for each scan. Here, since the number of passes is input as 4, the input receiving unit 63 can accept the processing conditions for each of the four scans. An example of the input values ​​for each scan is as follows.

[0068] [First scan]

[0069] ZH (lower point): 176.

[0070] ZH (upper point): 160.

[0071] Processing output (bottom point): 2.6W.

[0072] Processing output (top point): 2.6W.

[0073] Frequency: 120kHz.

[0074] Speed: 800 mm / s.

[0075] Pulse width: 700 nsec.

[0076] Vertical branch distance (VD): 16.

[0077] [Second scan]

[0078] ZH (lower point): 140.

[0079] ZH (upper point): 115.

[0080] Processing output (bottom point): 2.6W.

[0081] Processing output (top point): 2.6W.

[0082] Frequency: 120kHz.

[0083] Speed: 800 mm / s.

[0084] Pulse width: 700 nsec.

[0085] Vertical branch distance (VD): 25.

[0086] [Third scan]

[0087] ZH (lower point): 78.

[0088] ZH (upper point): 40.

[0089] Processing output (bottom point): 2.6W.

[0090] Processing output (top point): 2.6W.

[0091] Frequency: 120kHz.

[0092] Speed: 800 mm / s.

[0093] Pulse width: 700 nsec.

[0094] Vertical branch distance (VD): 38.

[0095] [4th scan] (focus 1 here)

[0096] ZH (lower point): 22.

[0097] ZH (upper point): -.

[0098] Processing output (bottom point): 2.6W.

[0099] Processing output (top point): -.

[0100] Frequency: 120kHz.

[0101] Speed: 800 mm / s.

[0102] Pulse width: 700 nsec.

[0103] Vertical branch distance (VD): -.

[0104] ZH (lower point) corresponds to the position of the first focusing point C1 in the Z direction. ZH (upper point) corresponds to the position of the second focusing point C2 in the Z direction. Since ZH (lower point) and ZH (upper point) are based on the incident surface of lasers L1 and L2, i.e., the back surface 11b, a larger value indicates a greater distance from the back surface 11b. The longitudinal branch distance (VD) is the distance Dz, which is equivalent to the difference between ZH (lower point) and ZH (upper point). The machining output (lower point) is the output of laser L1, and the machining output (upper point) is the output of laser L2. Here, the same value is input for both the machining output (lower point) and the machining output (upper point). Therefore, the output ratio of laser L1 to laser L2 is set to 50:50.

[0105] In the next step, the control unit 6 determines whether the input value of distance Dx received by the input receiving unit 63, i.e., the first input value, is above a first threshold (step S2). The first threshold is, for example, 50 μm. If the determination result of step S2 is that the first input value of distance Dx is above the first threshold (step S2: YES), the control unit 6 sets (generates) a branch pattern corresponding to the first input value of distance Dx (step S3). Furthermore, if the determination result of step S2 is that the first input value of distance Dx is not above the first threshold (step S2: NO), the control unit 6 causes the input receiving unit 63 to display information urging confirmation of the first input value (step S9), and proceeds to step S1 to urge the re-input of distance Dx.

[0106] In the next process, control unit 6 actually performs the processing (process S4: laser irradiation process, first irradiation process). More specifically, as... Figure 9 and Figure 10 As shown in (a), the control unit 6 moves the laser irradiation unit 3 by controlling the drive unit 5 (and / or drive unit 4) so ​​that, when viewed from the Z direction, the first focusing point C1 and the second focusing point C2 are located on line M1. Simultaneously, the control unit 6 controls the spatial light modulator 32 so that the first focusing point C1 is positioned in front of the second focusing point C2 in the X direction at a distance Dx, and the second focusing point C2 is positioned behind the first focusing point C1 at a distance Dz. Furthermore, Figure 9 (a) is a top view. Figure 9 (b) is along Figure 9 (a) Cross-sectional view of line B1-B1. Figure 10 (a) and (c) are side views. Figure 10 (b) is a top view.

[0107] Next, in step S4, the control unit 6 controls the drive unit 4 to rotate the stage 2 around the rotation axis A, and controls the laser irradiation unit 3 to irradiate the object 11 with lasers L1 and L2. The rotation axis A is the center of the object 11 and line M1. As a result, the first focusing point C1 and the second focusing point C2 move relative to the object 11 in the opposite direction (in this case, the X direction) to the rotation direction AR of the stage 2 along line M1. That is, here, the distance Dx is the distance between the first focusing point C1 and the second focusing point C2 along the direction of line M1 (the tangential direction of line M1).

[0108] Here, the control unit 6 rotates the stage 2 at a certain rotational speed and controls the start and stop of the irradiation of lasers L1 and L2 based on the rotation angle of the stage 2. The control unit 6 irradiates the object 11 with lasers L1 and L2 throughout the entire circumference of line M1. As a result, at least inside the object 11, modified regions 12 (modified regions 121) corresponding to laser L1 and the first focusing point C1, and modified regions 12 (modified regions 122) corresponding to laser L2 and the second focusing point C2 are formed on line M1.

[0109] That is, in the laser processing apparatus 1, the drive units 4 and 5 are moving mechanisms that move the stage 2 by moving the first focusing point C1 and the second focusing point C2 relative to the object 11. The control unit 6 controls the laser irradiation unit 3 and the drive units 4 and 5. Furthermore, the control unit 6 performs the first process of controlling the laser irradiation unit 3 and the drive units 4 and 5 by moving the first focusing point C1 and the second focusing point C2 relative to each other along the line M1 while irradiating the object 11 with laser L, with the distance Dx between the first focusing point C1 and the second focusing point C2 along the line M1 set to a first input value (first distance).

[0110] Furthermore, the control unit 6, under the control of the drive unit 5, moves the laser irradiation unit 3 along the Z direction, enabling it to perform the first process (the aforementioned number of passes) multiple times while simultaneously differentiating the Z-direction positions of the first focusing point C1 and the second focusing point C2. Thus, as... Figure 10 As shown in (b) and (c), a modified region 12 and cracks extending from the modified region 12 can be formed from the surface 11a of the object 11 to the back surface 11b. However, the modified region 12 and the cracks may or may not reach at least one of the surface 11a and the back surface 11b. Based on the above, the finishing process is completed. Next, a radiation cutting process is performed.

[0111] In the next step, the control unit 6 receives input of the processing conditions for the radiation cutting process (step S5). More specifically, in this step S5, the control unit 6 causes the input receiving unit 63 to display information urging the input of processing conditions. The input receiving unit 63 accepts the input of processing conditions. At this time, the input receiving unit 63 accepts at least the input of the radiation cutting distance Dx (second distance). The input receiving unit 63 also accepts other and various processing conditions. This will be explained in detail.

[0112] Figure 11 This diagram shows an example of a settings screen displayed on the input receiving unit. (Example) Figure 11 As shown, here, as the selection option Q, the inputs for wafer thickness, LBA-X offset, LBA-Y offset, and horizontal branch distance (distance Dx) are accepted. LBA-X offset is the offset in the X direction (along the direction of line M1) between the center of the spherical aberration correction pattern displayed in various patterns of the spatial light modulator 32 and the center of the entrance pupil surface of the condenser lens 33. Similarly, LBA-Y offset is the offset in the Y direction (the direction intersecting line M1) between the center of the spherical aberration correction pattern and the center of the entrance pupil surface of the condenser lens 33. Here, as the horizontal branch distance (distance Dx), 0 is input.

[0113] In addition, the input receiving unit 63 receives inputs of the number of focal points, number of passes, processing speed, pulse width, and frequency as basic processing conditions H0. The number of focal points is the number of branches of the laser L through the spatial light modulator 32, which is 2 in this case. The number of passes is the number of times the radiation cutting process is performed on one line M2, that is, the number of times the second processing of one line M2 is performed, and the number of scans of lasers L1 and L2. Therefore, in the radiation cutting process, a modified region 12 is formed in the Z direction with a number of columns corresponding to the number of focal points × the number of passes. The processing speed is the speed of relative movement of the first focusing point C1 and the second focusing point C2 relative to the object 11.

[0114] Furthermore, the input receiving unit 63 can accept detailed processing conditions for each scan. Here, since the number of passes is input as 6, the input receiving unit 63 can accept the processing conditions H1 to H6 for each of the 6 scans. In the processing conditions H1 to H6, ZH (lower point) corresponds to the position of the first focusing point C1 in the Z direction. ZH (upper point) corresponds to the position of the second focusing point C2 in the Z direction. Since ZH (lower point) and ZH (upper point) are based on the incident surface of lasers L1 and L2, i.e., the back surface 11b, a larger value indicates a greater distance from the back surface 11b.

[0115] The vertical branch distance (VD) is the distance Dz, equivalent to the difference between ZH (lower point) and ZH (upper point). The machining output (lower point) is the output of laser L1, and the machining output (upper point) is the output of laser L2. Here, the same value is input for both the machining output (lower point) and the machining output (upper point). Therefore, the output ratio of laser L1 to laser L2 is set to 50:50.

[0116] In the next step, the control unit 6 determines whether the second input value (used for radiation cutting) of distance Dx received by the input receiving unit 63 is below the second threshold (step S6). The second threshold is a value smaller than the first threshold during the trimming process (first process), for example, 15 μm. If the determination result of step S6 is that the second input value of distance Dx is below the second threshold, the control unit 6 sets (generates) a branch pattern corresponding to the second input value of distance Dx (step S7). Furthermore, if the determination result of step S6 is that the second input value of distance Dx is not below the second threshold (step S6: NO), the control unit 6 causes the input receiving unit 63 to display information urging confirmation of the second input value (step S10), and proceeds to step S5 to urge the re-input of distance Dx.

[0117] In the next step, actual processing is carried out (Step S8: Laser irradiation step, second irradiation step). More specifically, such as... Figure 12 and Figure 13 As shown in (a), the control unit 6 moves the laser irradiation unit 3 by controlling the drive unit 5 (and / or drive unit 4) in a manner that, when viewed from the Z direction, the first focusing point C1 and the second focusing point C2 move along the line M2 as they enter the object 11 from the outside of the object 11. Simultaneously, the control unit 6 controls the spatial light modulator 32 to display a branching pattern on the spatial light modulator 32 such that the second focusing point C2 is located on the back side 11b relative to the first focusing point C1 at a distance Dz. Here, as described above, 0 is input as the second input value for the distance Dx. Therefore, the position of the first focusing point C1 along the line M2 is aligned with the position of the second focusing point C2. Furthermore, Figure 12 (a) is a top view. Figure 12 (b) is along Figure 12 (a) Cross-sectional view of line B2-B2. Figure 13 (a) is a side view. Figure 13 (b) is a top view.

[0118] Here, the control unit 6 irradiates the object 11 with lasers L1 and L2 by moving the first focusing point C1 and the second focusing point C2 relative to each other from the outer edge of the object 11 toward the inner side of the object 11 along one of the lines M2a. The object 11 is arranged such that line M2a is along the X direction. As a result, the first focusing point C1 and the second focusing point C2 move relative to each other along the X direction. That is, here, the distance Dx is the distance between the first focusing point C1 and the second focusing point C2 along the X direction of line M2a (which is 0 in this case).

[0119] Thus, the control unit 6, with the distance Dx between the first focusing point C1 and the second focusing point C2 along the direction of line M2 (line M2a) set to a second input value (second distance) smaller than the distance Dx (first distance) during the finishing process, performs the second processing of controlling the laser irradiation unit 3 and the drive unit 5 (and / or the drive unit 4) in a manner that moves the first focusing point C1 and the second focusing point C2 relative to each other along line M2 while irradiating the object 11 with lasers L1 and L2.

[0120] The control unit 6 continuously moves the first focusing point C1 and the second focusing point C2 relative to each other. When the first focusing point C1 and the second focusing point C2 reach the intersection of line M2a and line M1, the irradiation of lasers L1 and L2 is turned off. Then, when the positions (X-direction positions) of the first focusing point C1 and the second focusing point C2 reach the intersection of line M1 and another line M2b that is on the same straight line as line M2a in line M2, the control unit 6 turns the irradiation of lasers L1 and L2 on. Similar to line M2a, while moving the first focusing point C1 and the second focusing point C2 relative to each other along the X-direction on line M2b, lasers L1 and L2 are irradiated onto the object 11. In addition, the control unit 6 performs the second process similarly on the other lines M2c and M2d in line M2.

[0121] Furthermore, as described above, here, the number of scans (passes) of lasers L1 and L2 for each line M2 is input as 6. Therefore, the control unit 6 moves the laser irradiation unit 3 along the Z direction for each line M2 by controlling the drive unit 5, thereby performing the second process multiple times (6 times in this case) while making the Z-direction positions of the first focusing point C1 and the second focusing point C2 different.

[0122] Specifically, when performing multiple second processes on a line M2, the control unit 6 can, after performing the nth (n is an integer greater than 1) second process, perform the mth (m is an integer greater than n) second process while at least one of the first focusing point C1 and the second focusing point C2 is located between the first focusing point C1 and the second focusing point C2 in the Z direction during the nth second process.

[0123] Reference Figure 11 For the ZH (lower point) value of the second scan, input a value between the ZH (lower point) and ZH (upper point) of the first scan. Additionally, for the ZH (upper point) value of the second scan, input a value smaller than the ZH (upper point) of the first scan. The relationship between the fourth and third scans, and between the sixth and fifth scans, is the same.

[0124] That is, in Figure 11 In the example, after the control unit 6 performs the second processing for the first, third, and fifth times, it performs the second processing for the second, fourth, and sixth times while keeping the first focusing point C1 at a position between the first focusing point C1 and the second focusing point C2 in the Z direction during the second processing for the first, third, and fifth times.

[0125] In other words, in Figure 11 In the example, after the control unit 6 performs the second process for the 2n-1th time (n is an integer greater than or equal to 1), it performs the second process for the 2nth time in a state where the first focusing point C1 is located between the position of the first focusing point C1 in the Z direction during the second process for the 2n-1th time and the position of the second focusing point C2, and the second focusing point C2 is located further back to the back side 11b than the position of the second focusing point C2 in the Z direction during the second process for the 2n-1st time.

[0126] In addition, Figure 11 In the example, if we focus on each of the first focusing point C1 and the second focusing point C2, the position in the Z direction moves sequentially towards the back side 11b from the first to the sixth time. That is, in Figure 11 In the example, after the control unit 6 performs the second process for the nth time (n being an integer greater than or equal to 1), it performs the second process for the (n+1)th time, with the first focusing point C1 positioned further towards the back surface 11b in the Z direction than it was in the second process for the nth time. Furthermore, after the control unit 6 performs the second process for the nth time (n being an integer greater than or equal to 1), it performs the second process for the (n+1)th time, with the second focusing point C2 positioned further towards the back surface 11b in the Z direction than it was in the second process for the nth time.

[0127] Based on the above, such as Figure 13 As shown in (b), a modified region 12 is formed for all lines M2. Specifically, as... Figure 14As shown in (a), a modified region 12 (modified area 121) on the surface 11a side of the second scan P2 is formed between a pair of modified regions 12 (modified regions 121, 122) formed by the first scan P1, a modified region 12 on the surface 11a side of the fourth scan P4 is formed between a pair of modified regions 12 formed by the third scan P3, and a modified region 12 on the surface 11a side of the sixth scan P2 is formed between a pair of modified regions 12 formed by the fifth scan P5.

[0128] Thus, a modified region 12 and cracks extending from the modified region 12 are formed from the surface 11a of the object 11 to the back surface 11b. However, the modified region 12 and the cracks may or may not reach at least one of the surface 11a and the back surface 11b. Furthermore, Figure 14 It is a photograph showing the cross-section after the modified region was formed.

[0129] Then, as Figure 15 As shown, the removal region E is cut and removed (separation removal) using, for example, a jig or air, with the modified region 12 on line M1 as the boundary, thereby forming object 11A from object 11 (cutting out the effective region R). Then, a peeling process can be performed in the laser processing apparatus 1. Next, the peeling process will be described. Furthermore, Figure 15 (a) is a top view, (b) is a side view, and (c) is a side view.

[0130] like Figure 15 As shown, an imaginary surface M3 is provided on the object 11A as a predetermined peeling surface. The imaginary surface M3 is the surface from which a modified region is to be formed through the peeling process. The imaginary surface M3 is the surface opposite to the laser incident surface, i.e., the back surface 11b, of the object 11A. The imaginary surface M3 is a surface parallel to the back surface 11b, and for example, it is circular in shape. The imaginary surface M3 is an imaginary region, not limited to a plane, and can also be a curved surface or even a three-dimensional surface. The setting of the imaginary surface M3 can be performed in the control unit 6. The imaginary surface M3 can also be a surface specified by coordinates.

[0131] During the peeling process, the control unit 6, by controlling the drive unit 4, rotates the stage 2 at a certain rotational speed while irradiating the laser L3 from the laser irradiation unit 3. Simultaneously, the control unit 6, by controlling the drive unit 5, moves the laser irradiation unit 3 such that the focusing point C3 of the laser L3 moves from the outer edge of the imaginary surface M3 inwards. Thus, as... Figure 16 As shown in (a), inside the object 11A along the imaginary surface M3, a rotation axis A is formed (refer to...). Figure 9 The modified region 12 extends in a spiral (involute) shape centered on the location of the point. The formed modified region 12 contains multiple modified points. Furthermore, Figure 16 (a) is a top view, and the others are side views.

[0132] Next, as Figure 16 As shown in (b) and (c), a portion of the object 11A is peeled off using, for example, an adsorption jig, with the modified region 12 covering the imaginary surface M3 as the boundary. The peeling of the object 11A can be performed on the stage 2 or moved to a dedicated peeling area. The peeling of the object 11A can also be performed using air blowing or tape. If the object 11A cannot be peeled off by external stress alone, the modified region 12 can be selectively etched using an etching solution (KOH or TMAH, etc.) that reacts with the object 11A. Thus, the object 11A can be easily peeled off. Figure 16 As shown in (b), the peeling surface 11h of the object 11A is finely ground, or even ground with an abrasive material KM such as a grinding stone. This grinding process can be simplified when the object 11A is peeled off by etching. Based on the above results, a semiconductor device 11B is obtained.

[0133] As explained above, in the laser processing apparatus 1 and its laser processing method, the workpiece 11 is provided with: a line M1 extending in a ring along the boundary between the effective region R located inside and the removal region E located outside the effective region R; and a line M2 extending from the outer edge of the workpiece 11 toward the inner side of the workpiece 11 and reaching the boundary in the removal region E. Furthermore, in both the processing along line M1 (trimming processing) and the processing along line M2 (radiation cutting processing), a first focusing point C1 and a second focusing point C2 of laser L are formed on the workpiece 11, and the workpiece 11 is irradiated with laser L. At this time, when processing along line M1 is performed, the distance Dx between the first focusing point C1 and the second focusing point C2 along line M1 relatively increases. Therefore, the processing speed can be increased. Conversely, when processing along line M2 is performed, the distance Dx between the first focusing point C1 and the second focusing point C2 along line M2 relatively decreases. Therefore, a decrease in processing quality can be suppressed.

[0134] Figure 14 (b) is a photograph showing a cross-section of the boundary between the effective region R and the removed region E. For example... Figure 14As shown in (b), when processing along line M2, by relatively reducing the distance Dx between the first focusing point C1 and the second focusing point C2 (for example, to 0), the end of the modified region 12 corresponding to the first focusing point C1 is aligned with the end of the modified region 12 corresponding to the second focusing point C2. That is, in this case, it is possible to prevent either the first focusing point C1 or the second focusing point C2 from entering the effective region R and forming the modified region 12 within the effective region R, or the other focusing point C1 or the second focusing point C2 from not reaching the effective region R and generating an unmodified region in the removal region E.

[0135] Furthermore, in the laser processing apparatus 1, the control unit 6 can perform a second process multiple times on a line M2, making the positions of the first focusing point C1 and the second focusing point C2 in the Z direction, which intersects with the back surface 11b, different. In this way, it is effective to perform the second process, which relatively reduces the distance Dx between the first focusing point C1 and the second focusing point C2, multiple times on a single line M2.

[0136] Furthermore, in the laser processing apparatus 1, the control unit 6 can perform the m-th (m is an integer greater than n) second process after performing the nth (n is an integer greater than 1) second process, with at least one of the first focusing point C1 and the second focusing point C2 positioned between the first focusing point C1 and the second focusing point C2 in the Z direction during the nth second process. In this case, the modified region 12 can be formed more tightly in the Z direction, thereby improving the processing quality.

[0137] Furthermore, in the laser processing apparatus 1, the control unit 6 can perform the (n+1)th second process after performing the nth (n is an integer greater than or equal to 1) second process, with the first focusing point C1 positioned further towards the back surface 11b in the Z direction than during the nth second process. Therefore, by sequentially aligning the focusing points from a side farther from the back surface 11b during the second process, the modified region 12 can be formed more appropriately.

[0138] Furthermore, the laser processing apparatus 1 also includes an input receiving unit 63 for receiving and displaying input information. Before performing the first processing, the input receiving unit 63 receives the distance Dx for the first processing. Before performing the first processing, if the input value of the distance Dx received by the input receiving unit 63, i.e., the first input value, is less than a first threshold, the control unit 6 displays information urging confirmation of the first input value; and if the first input value is greater than or equal to the first threshold, the first processing is performed. Therefore, in the first processing, it can be ensured that the distance Dx is greater than or equal to the threshold, and the amount of crack progression can be reliably increased, thereby improving the processing speed.

[0139] Furthermore, in the laser processing apparatus 1, the input receiving unit 63 receives the distance Dx for the second processing before performing the second processing. Before performing the second processing, if the input value of the distance Dx received by the input receiving unit 63, i.e., the second input value, is greater than a second threshold, the control unit 6 displays information to urge confirmation of the second input value; and if the second input value is less than the second threshold, the second processing is performed. Therefore, in the second processing, it can be ensured that the distance Dx between the first focusing point C1 and the second focusing point C2 is less than the threshold, and the processing quality can be reliably improved.

[0140] The above embodiments are one way of illustrating this disclosure. Therefore, the present invention is not limited to the above embodiments and any modifications can be made.

[0141] For example, in such Figure 6 In the operation of the laser processing apparatus 1 shown, at least a distance Dx is received as input in both the first and second processes. A branching pattern corresponding to the received distance Dx is set and displayed on the spatial light modulator 32. However, the branching pattern can also be set automatically. That is, in the laser processing apparatus 1, the branching pattern can be automatically set in each of the first and second processes in such a way that the distance Dx of the first process becomes relatively larger than the distance Dx of the second process (in other words, the distance Dx of the second process becomes relatively smaller than the distance Dx of the first process), and the first and second processes can be executed.

[0142] Furthermore, in the above embodiment, the case where laser L is branched into two lasers L1 and L2 to form a first focusing point C1 and a second focusing point C2 has been described. However, in the laser processing apparatus 1, laser L can also be branched into three or more lasers to form their respective focusing points. In this case, for two of the three or more focusing points, the relationship that the distance Dx of the first processing is greater than the distance Dx of the second processing is sufficient.

[0143] Furthermore, in the above embodiment, line M1 extends along the boundary between the device region where the functional element is formed, i.e., the effective region R, and the removal region E outside it. However, line M1 may also be set on the boundary between a region wider than the device region described above (a region that expands the effective region R towards the removal region E) and a region further outward from that region. Alternatively, line M1 may be independent of the effective region R and the removal region E, and can be set on the boundary between any first and second portions of the object 11.

[0144] [Potential for Industrial Applications]

[0145] It can provide laser processing equipment and laser processing methods that can both improve processing speed and prevent the reduction of processing quality.

[0146] [Symbol Explanation]

[0147] 1…laser processing device, 2…stage (support), 3…laser irradiation unit, 4, 5…drive unit (moving mechanism), 6…control unit, 11…object, 63…input receiving unit (input unit, display unit), C1…first focusing point, C2…second focusing point, Dx…distance, L, L1, L2…laser, M1…line (first line), M2…line (second line).

Claims

1. A laser processing apparatus, wherein, It is a laser processing device used to irradiate an object with a laser to form a modified area. The laser processing apparatus includes: A support portion, used to support the object; A laser irradiation unit is used to form a first focusing point of the laser and a second focusing point of the laser located on the object supported on the support unit, which is located closer to the object than the first focusing point on the incident surface of the laser, and to irradiate the object with the laser. A moving mechanism that moves at least one of the support and the laser irradiation part in a manner that allows relative movement of the first focusing point and the second focusing point relative to the object; and The control unit controls the laser irradiation unit and the moving mechanism. Viewed from a direction intersecting the incident plane, the object comprises: a first portion located inside the object, and a second portion located outside the first portion and including the outer edge of the object. The object is provided with: a first line extending in a ring shape at the boundary between the first part and the second part when viewed from a direction intersecting the incident plane; and a second line extending from the outer edge of the object toward the inner side of the object and reaching the boundary in the second part. The control unit performs: The first process involves controlling the laser irradiation unit and the moving mechanism to irradiate the object while the distance between the first focusing point and the second focusing point along the first line is set to a first distance; and the laser is used to irradiate the object while the relative movement of the first focusing point and the second focusing point along the first line is achieved. The second process involves controlling the laser irradiation unit and the moving mechanism to irradiate the object with laser light while setting the distance between the first and second focusing points along the second line to a second distance smaller than the first distance. This is done by moving the first and second focusing points relative to each other along the second line from the outer edge of the object to the boundary between the first and second parts. The first distance is greater than 0.

2. The laser processing apparatus according to claim 1, wherein, The control unit performs the second process multiple times on a second line, making the positions of the first focusing point and the second focusing point in the direction intersecting the incident surface different.

3. The laser processing apparatus according to claim 2, wherein, After performing the second process for the nth time, the control unit performs the second process for the mth time, with at least one of the first focusing point and the second focusing point positioned between the first focusing point and the second focusing point in the direction intersecting the incident surface during the second process for the nth time, where n is an integer greater than or equal to 1 and m is an integer greater than n.

4. The laser processing apparatus according to claim 2, wherein, After performing the second process for the nth time, the control unit performs the second process for the (n+1)th time, in a state where the first focusing point is located closer to the incident surface than the position of the first focusing point in the direction intersecting the incident surface during the second process for the nth time, where n is an integer greater than or equal to 1.

5. The laser processing apparatus according to claim 3, wherein, After performing the second process for the nth time, the control unit performs the second process for the (n+1)th time, in a state where the first focusing point is located closer to the incident surface than the position of the first focusing point in the direction intersecting the incident surface during the second process for the nth time, where n is an integer greater than or equal to 1.

6. The laser processing apparatus according to any one of claims 1 to 5, wherein, It also has: The input section used to receive input; and The display unit used to show information. The input unit receives the first distance as input before performing the first process. Before performing the first process, if the first input value, which is the first distance received by the input unit, is less than a first threshold, the control unit causes the display unit to display information urging confirmation of the first input value, and if the first input value is greater than or equal to the first threshold, the control unit performs the first process.

7. The laser processing apparatus according to claim 6, wherein, The input unit receives the second distance as input before performing the second processing. Before performing the second process, if the second input value, which is the input value of the second distance accepted by the input unit, is greater than the second threshold, the control unit causes the display unit to display information to urge confirmation of the second input value, and if the second input value is less than the second threshold, the control unit performs the second process.

8. A laser processing method, wherein, It is a laser processing method used to irradiate an object with a laser to form a modified area. The laser processing method includes a laser irradiation step, wherein a first focusing point of the laser and a second focusing point of the laser located on the object, closer to the incident surface of the laser than the first focusing point, are formed on the object, and the laser is irradiated. Viewed from a direction intersecting the incident plane, the object comprises: a first portion located inside the object, and a second portion located outside the first portion and including the outer edge of the object. The object is provided with: a first line extending in a ring shape at the boundary between the first part and the second part when viewed from a direction intersecting the incident plane; and a second line extending from the outer edge of the object toward the inner side of the object and reaching the boundary in the second part. The laser irradiation process includes: In the first irradiation step, with the distance between the first focusing point and the second focusing point along the first line set to a first distance, the object is irradiated with the laser while the first focusing point and the second focusing point are moved relative to each other along the first line; and In the second irradiation step, with the distance between the first focusing point and the second focusing point along the second line set to a second distance smaller than the first distance, the laser is used to irradiate the object while moving the first focusing point and the second focusing point relative to each other along the second line from the outer edge of the object to the boundary between the first part and the second part. The first distance is greater than 0.

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