Laser processing apparatus and laser processing method

Abstract

The laser processing apparatus of the present invention includes a laser irradiation unit and a control unit. The control unit is configured to perform: a first control, in which the laser irradiation unit is controlled to form a modified region for slicing along each of the lines extending in the X direction, and the crack extends from the modified region toward the surface; a second control, after the first control, in which the laser irradiation unit is controlled to form a modified region for slicing along each of the multiple lines extending in the Y direction, and the crack extends from the modified region toward the surface; and a third control, before the second control, in which the laser irradiation unit is controlled to reach the back surface from the multiple modified regions for warp suppression and is not continuously formed with the crack extending from the modified region for slicing.

Description

Technical Field

[0001] One aspect of the present invention relates to a laser processing apparatus and a laser processing method. Background Technology

[0002] A laser processing apparatus is known to cut a wafer having a semiconductor substrate and a functional element layer formed on one surface of the semiconductor substrate along multiple lines by irradiating the wafer with a laser from the other side of the semiconductor substrate, thereby forming multiple rows of slitting (cutting) modified regions along the multiple lines inside the semiconductor substrate (see, for example, Patent Document 1). In this laser processing apparatus, after the modified regions are formed, they can be ground to produce semiconductor chips with high flexural strength.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent No. 376209 Summary of the Invention

[0006] The technical problem that the invention aims to solve

[0007] In laser processing using the aforementioned laser processing apparatus, sometimes modified regions for segmentation are formed sequentially along multiple intersecting lines. In this case, wafer warping may occur due to the formation of modified regions along the first line irradiated by the laser (line 1). This wafer warping reduces the processing accuracy of the intersecting lines (line 2) irradiated by the laser later. That is, if processing of the second line irradiated by the laser is performed while the warped state is occurring, ensuring the accuracy of autofocus and other functions for adjusting the laser focus point during processing of line 2 becomes difficult, potentially making it impossible to properly form modified regions.

[0008] One aspect of the present invention is made in view of the above-mentioned matters, and its purpose is to appropriately form a modified region for segmentation on the object, thereby improving the precision of laser processing.

[0009] Technical means to solve the problem

[0010] One aspect of the laser processing apparatus of the present invention includes: a laser irradiation unit that irradiates a target object with a first surface including a first surface and a second surface opposite to the first surface as an incident surface; and a control unit configured to perform a first control, a second control, and a third control. The first control controls the laser irradiation unit to move the laser focusing point relative to each of a plurality of first lines extending in a first direction along the incident surface, thereby forming a first modified region for segmentation inside the target object through laser irradiation, and the crack extending from the first modified region toward the second surface. The second control controls the laser irradiation unit in the manner described in the first control. After control, the laser irradiation unit is controlled such that, while moving the laser focusing point relative to each of the multiple second lines that intersect the first direction and extend along the second direction of the incident surface, a second modified region for segmentation is formed inside the object by laser irradiation, and cracks extend from the second modified region toward the second surface; the third control, before the second control, is controlled such that, while forming multiple third modified regions for warping suppression inside the object by laser irradiation, cracks extending from the third modified region reach the first surface and are not continuously formed with cracks extending from the first modified region.

[0011] In one aspect of the laser processing apparatus of the present invention, by laser irradiation, first modified regions for segmentation are formed along each of a plurality of first lines extending in a first direction along the incident surface, and cracks extending from the first modified regions toward a second surface are formed. Then, by laser irradiation, second modified regions for segmentation are formed along each of a plurality of second lines intersecting the first direction and extending in a second direction along the incident surface, and cracks extending from the second modified regions toward a second surface are formed. Thus, when modified regions are formed sequentially along multiple intersecting lines, warping of the workpiece may occur due to the formation of the first modified regions along the lines first irradiated by the laser (first lines). This warping of the workpiece reduces the processing accuracy of the lines subsequently irradiated by the laser (second lines). Specifically, the warping of the workpiece is caused by stress concentration on a single surface of the workpiece (here, the second surface in the direction in which the cracks mainly extend) due to the formation of the first modified regions and the formation of cracks extending from the first modified regions toward the second surface. This warping of the object is particularly noticeable when the object is a tiny chip or when large cracks form. If the line (second line) to be irradiated by the laser is processed while the object is in a warped state, it may be difficult to guarantee the accuracy of automatic focusing and other methods used for adjusting the laser focus point during the processing of the second line, making it impossible to properly form the second modified region.

[0012] Regarding this, in one aspect of the laser processing apparatus of the present invention, before controlling the processing of the second line (second control), a plurality of third modified regions for warp suppression are formed inside the object by laser irradiation. Cracks extending from these third modified regions reach the first surface and are not continuous with cracks extending from the first modified regions. Thus, by forming the third modified regions in such a way that the cracks reach the first surface opposite to the second surface where stress is concentrated due to the formation of the first modified regions for segmentation, stress localization is alleviated, and warping of the object can be reduced. Therefore, in the second line processing performed after the formation of the third modified regions for warp suppression, the second modified regions can be appropriately formed. Here, by forming cracks extending from the third modified regions in a manner that are not continuous with cracks extending from the first modified regions, unintentional breakage of the object caused by the formation of the third modified regions for warp suppression can be appropriately suppressed. As described above, the laser processing apparatus according to one aspect of the present invention can suppress unintentional breakage of the object and can appropriately form a modified region for segmentation on the object, thereby improving the precision of laser processing.

[0013] Alternatively, in the third control, the control unit controls the laser irradiation unit to form the third modified region at a position different from the formation position of the first modified region in the second direction. This allows for the appropriate avoidance of the continuity between cracks in the first and third modified regions, and more effectively suppresses unintentional breakage of the object.

[0014] Alternatively, in the third control, the control unit controls the laser irradiation unit to form the third modified region at the midpoint of the formation positions of the two adjacent first lines in the second direction. By forming the third modified region at the midpoint between the two first lines, the separation distance between the modified regions of any first line and the third modified region can be increased, thus appropriately avoiding the continuity of cracks between the first and third modified regions. This appropriately suppresses unintentional breakage of the object.

[0015] Alternatively, the laser irradiation unit may include: a spatial light modulator that modulates the laser according to a set modulation pattern; and a control unit that, in a third control, sets the modulation pattern such that a third modified region is formed at a position different from the formation position of the first modified region in the second direction. In this way, by adjusting the formation position of the third modified region by setting the modulation pattern of the spatial light modulator, the processing time can be shortened compared to the case where the formation position of the modified region is changed by the movement of the stage.

[0016] Alternatively, the laser irradiation unit may include: a spatial light modulator that modulates the laser according to a set modulation pattern; and a control unit that, in at least one of a first control and a third control, sets the modulation pattern such that the position of the end of the crack extending from the first modified region on the first surface side differs from the position of the end of the crack extending from the third modified region on the second surface side. In this way, by adjusting the position of the end of the crack extending from the modified region through the setting of the modulation pattern of the spatial light modulator, the position of the crack end can be appropriately adjusted, and unintentional breakage of the object due to the interconnection of cracks can be more appropriately suppressed.

[0017] Alternatively, in the third control, the control unit controls the laser irradiation unit to make the cracks extending from the third modified region shorter than the cracks extending from the first modified region. Regarding the cracks extending from the third modified region for warp suppression, unlike the cracks extending from the first modified region for segmentation, these are not cracks that aid in segmentation. Therefore, by shortening them, unintentional breakage of the object caused by the continuity of the cracks can be more appropriately suppressed.

[0018] Alternatively, in the third control, the control unit controls the laser irradiation unit to form a greater number of third modified regions in the second direction than the number of first modified regions. As described above, it is desirable to shorten the cracks extending from the third modified regions for warp suppression when performing appropriate cutting. However, if the cracks extending from the third modified regions are shortened, the warp suppression effect may not be sufficiently achieved. To address this, by increasing the number of third modified regions in the second direction (more than the first modified regions), the warp suppression effect can be fully realized through numerous cracks extending from the third modified regions, and unintentional breakage of the object can be suppressed.

[0019] Alternatively, in the third control, the control unit controls the laser irradiation unit such that, when comparing the third modified region at the center of the object in the second direction with the third modified regions at both ends, the third modified region is formed in such a way that either the number of third modified regions in the second direction at both ends increases, or the length of the cracks extending from the third modified regions at both ends increases. The warping of the object caused by the formation of the first modified region becomes more pronounced closer to the two ends in the second direction. To address this, increasing the number of third modified regions at both ends, or increasing the length of the cracks extending from the third modified regions, compared to the center of the object in the second direction, can effectively suppress the significant warping of the object at the two ends in the second direction.

[0020] Alternatively, the control unit can control the laser irradiation unit by alternately implementing the formation of the first modified region of any first line under the first control and the formation of the third modified region under the third control. The warping of the object caused by the formation of the first modified region gradually progresses as the first modified regions of multiple first lines are formed. Therefore, the effect of the processing of the first line performed earlier also affects the processing of the first line performed later. That is, in the processing of the later half of the multiple first lines, the first modified region is formed in a warped state of the object. Therefore, it is possible, for example, for example, for cracks to extend obliquely relative to the second surface of the object, for deterioration of processing position accuracy, or for poor adsorption during processing. To address this, by alternately implementing the formation of the first modified region for segmentation and the formation of the third modified region for warping suppression, the effect of the processing of the first line performed earlier on the processing of the second line performed later can be suppressed, and the first modified region for segmentation can be appropriately formed on the object.

[0021] Alternatively, the control unit may be configured to further perform: a fourth control, wherein multiple fourth modified regions for warpage suppression are formed inside the object by laser irradiation, and cracks extending from these fourth modified regions reach the first surface and are not continuously formed with cracks extending from the second modified regions. The control unit controls the laser irradiation unit in a manner that alternately implements the formation of the second modified regions of any second line under the second control and the formation of the fourth modified regions under the fourth control. Thus, by alternately implementing the formation of the second modified regions of the second line and the formation of the fourth modified regions for warpage suppression, the influence of the processing of the first second line can be suppressed from affecting the processing of the second line implemented later, and second modified regions for segmentation can be appropriately formed on the object.

[0022] One aspect of the laser processing method of the present invention involves irradiating a workpiece with a first surface including a first surface and a second surface opposite to the first surface as the incident surface, and performing laser processing on the workpiece. The method comprises: a first step, in which, along each of a plurality of first lines extending in a first direction along the incident surface, the laser focusing point is relatively moved, and laser irradiation forms a first modified region for segmentation within the workpiece, thereby forming cracks extending from the first modified region toward the second surface; a second step, in the first step... Following the first step, along each of the plurality of second lines that intersect the first direction and extend along the second direction of the incident surface, while moving the laser focusing point relative to each other, a second modified region for segmentation is formed inside the object by laser irradiation, and a crack is formed extending from the second modified region toward the second surface; and in the third step, before the second step, a plurality of third modified regions for warping suppression are formed inside the object by laser irradiation, and a crack is formed that extends from the third modified region to the first surface and is not continuous with the crack extending from the first modified region.

[0023] Alternatively, in the third process, a third modified region may be formed at a position different from the formation position of the first modified region in the second direction.

[0024] Alternatively, in the third process, the third modification zone can be formed at the midpoint of the formation positions of the two adjacent first lines in the second direction.

[0025] Alternatively, in the third step, by setting the modulation pattern of the spatial light modulator of the modulation laser, a third modification region is formed at a position different from the formation position of the first modification region in the second direction.

[0026] Alternatively, in at least one of the first and third steps, by setting the modulation pattern of the spatial light modulator of the modulation laser, the position of the end of the crack on the first surface extending from the first modified region is different from the position of the end of the crack on the second surface extending from the third modified region.

[0027] Alternatively, in the third process, the third modified region is formed in such a way that the cracks extending from the third modified region are shorter than those extending from the first modified region.

[0028] Alternatively, in the third process, a third modification zone is formed in the second direction, with a greater number of zones than the first modification zone.

[0029] Alternatively, in the third process, when comparing the third modified region in the central part of the object in the second direction with the third modified regions at both ends, the third modified region is formed in such a way that at least one of the following conditions is met: the number of third modified regions in the second direction at both ends becomes more and the length of the cracks extending from the third modified region at both ends becomes longer.

[0030] Alternatively, the formation of the first modified region of any first line in the first process and the formation of the third modified region in the third process can be carried out alternately.

[0031] The laser processing method described above further includes: a fourth step, in which multiple fourth modified regions for warping suppression are formed inside the object by laser irradiation, and cracks are formed extending from the fourth modified regions to the first surface and are not continuous with cracks extending from the second modified regions. The laser processing method alternately performs the formation of the second modified region of any second line in the second step and the formation of the fourth modified region in the fourth step.

[0032] Invention Effects

[0033] According to one aspect of the present invention, modified regions for segmentation can be appropriately formed on an object, thereby improving the precision of laser processing. Attached Figure Description

[0034] Figure 1 This is a structural diagram of an inspection device according to one embodiment.

[0035] Figure 2 This is a top view of a wafer in one implementation method.

[0036] Figure 3 yes Figure 2 A cross-sectional view of a portion of the wafer shown.

[0037] Figure 4 yes Figure 1 The diagram shows the structure of the laser irradiation unit.

[0038] Figure 5 It is shown Figure 4 The diagram shows the 4f lens unit.

[0039] Figure 6 It is shown Figure 4 The diagram shows a spatial light modulator.

[0040] Figure 7 yes Figure 1 The diagram shown is a structural diagram of the inspection camera unit.

[0041] Figure 8 yes Figure 1 The diagram shows the structure of the camera unit used for alignment correction.

[0042] Figure 9 This diagram illustrates the principle behind wafer warping.

[0043] Figure 10 This is a diagram showing the warping of the CH2 processing direction after CH1 processing.

[0044] Figure 11 This diagram illustrates poor AF (autofocus) tracking during CH2 processing.

[0045] Figure 12 This diagram illustrates the formation of the modified region used to suppress warping.

[0046] Figure 13 This diagram illustrates the formation of a modified region near the center of the chip to suppress warping.

[0047] Figure 14 This diagram illustrates the formation of the modified region used to suppress warping in multi-point branching processing.

[0048] Figure 15 This diagram illustrates a processing method used to specifically suppress warping of the outer periphery of a wafer.

[0049] Figure 16 This is a diagram showing the warping direction of CH2 processing after CH1 processing, in addition to the formation of the modified region for warping suppression.

[0050] Figure 17 This is a diagram illustrating the shift of the processing position set by the modulation pattern of the spatial light modulator.

[0051] Figure 18 This diagram illustrates the formation of oblique cracks by setting the modulation pattern through a spatial light modulator.

[0052] Figure 19 This diagram illustrates the deterioration of processing stability during the latter half of CH1 processing.

[0053] Figure 20 This diagram illustrates a processing method that alternately forms modified regions for segmentation and modified regions for warpage suppression.

[0054] Figure 21 This is a diagram illustrating the effects of this embodiment, showing the warping of the CH2 processing direction after CH1 processing.

[0055] Figure 22 This is a diagram illustrating the effects of this embodiment, showing the warping of the wafer after CH2 processing.

[0056] Figure 23 This is a diagram showing the warping of the CH1 processing direction after CH1 processing. Detailed Implementation

[0057] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Furthermore, in the drawings, the same or equivalent parts will be given the same reference numerals, and repeated descriptions will be omitted.

[0058] [Structure of the inspection device]

[0059] like Figure 1 As shown, the laser processing apparatus 1 includes: a stage 2; a laser irradiation unit 3; multiple camera units 4, 5, and 6; a drive unit 9; a control unit 8; and a display 150 (display unit). The laser processing apparatus 1 is a device that forms a modified region 12 on a workpiece 11 by irradiating the workpiece 11 with a laser L.

[0060] The stage 2 supports the object 11, for example, by adsorbing the film attached to it. The stage 2 can move along the X and Y directions and rotate about an axis parallel to the Z direction as its center line. Furthermore, the X and Y directions are mutually perpendicular first and second horizontal directions, and the Z direction is a vertical direction.

[0061] 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 stage 2, the laser L is specifically absorbed in the part corresponding to the focusing point C of the laser L, forming a modified region 12 inside the object 11.

[0062] 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, regions with insulation failure, and regions with refractive index changes. The modified region 12 has the characteristic that cracks easily extend from the modified region 12 towards the incident side of the laser L and the opposite side. This characteristic of the modified region 12 is utilized in the cutting of the object 11.

[0063] As an example, if platform 2 moves along the X direction and the focusing point C moves relative to 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 modified 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 their relative moving speeds relative to the focusing point C of object 11 and the repetition frequency of laser L.

[0064] The camera unit 4 is configured to capture images of the modified region 12 formed on the object 11 and the tip of the crack extending from the modified region 12. Furthermore, although the camera unit 4 is not an essential component, it will be described in this embodiment as being included in the laser processing apparatus 1.

[0065] Camera units 5 and 6, under the control of the control unit 8, capture images of the object 11 supported on the platform 2 using light transmitted through the object 11. The images obtained by camera units 5 and 6 are, for example, provided for aligning the position of the laser L. Furthermore, although camera units 5 and 6 are not essential components, in this embodiment, the laser processing apparatus 1 is described with camera units 5 and 6 included.

[0066] The drive unit 9 supports the laser irradiation unit 3 and multiple camera units 4, 5, and 6. The drive unit 9 moves the laser irradiation unit 3 and the multiple camera units 4, 5, and 6 along the Z direction.

[0067] The control unit 8 controls the operation of the stage 2, the laser irradiation unit 3, the multiple camera units 4, 5, and 6, and the drive unit 9. The control unit 8 is configured as a computer device including a processor, memory, storage device, and communication device. In the control unit 8, the processor executes software (programs) loaded into memory, etc., and controls the reading and writing of data in memory and storage device, as well as communication via the communication device.

[0068] The display 150 has the functions of an input section for receiving information from a user and a display section for displaying information to a user.

[0069] [Structure of the object]

[0070] The object 11 in this embodiment, such as Figure 2 as well as Figure 3As shown, a wafer 20 is depicted. The wafer 20 includes a semiconductor substrate 21 and a functional element layer 22. Although this embodiment describes the wafer 20 as having the functional element layer 22, the wafer 20 may or may not have the functional element layer 22, and may be a bare wafer. The semiconductor substrate 21 has a surface 21a and a back surface 21b. The semiconductor substrate 21 is, for example, a silicon substrate. The functional element layer 22 is formed on the surface 21a of the semiconductor substrate 21. The functional element layer 22 includes a plurality of functional elements 22a arranged two-dimensionally along the surface 21a. The functional elements 22a are, for example, light-receiving elements such as photodiodes, light-emitting elements such as laser diodes, and circuit elements such as memory. The functional elements 22a are sometimes stacked in multiple layers and three-dimensionally constructed. Furthermore, while the semiconductor substrate 21 has notches 21c indicating the crystal direction, an orientation flat may be provided instead of notches 21c.

[0071] The wafer 20 is cut along each of the plurality of lines 15 for each functional element 22a. The plurality of lines 15, when viewed from the thickness direction of the wafer 20, pass between each of the plurality of functional elements 22a. More specifically, the lines 15, when viewed from the thickness direction of the wafer 20, pass through the center (center in the width direction) of the dicing channel region 23. The dicing channel region 23 extends in the functional element layer 22 in a manner that passes between adjacent functional elements 22a. In this embodiment, the plurality of functional elements 22a are arranged in a matrix along the surface 21a. The plurality of lines 15 are configured in a lattice pattern. That is, the wafer 20 is provided with: a plurality of lines 15 extending in the X direction (first lines) and a plurality of lines 15 extending in the Y direction (second lines). Furthermore, the lines 15 can be virtual lines or actual lines.

[0072] [Structure of the laser irradiation unit]

[0073] like Figure 4 As shown, the laser irradiation unit 3 includes a light source 31, a spatial light modulator 7, a condenser lens 33, and a 4f lens unit 34. The light source 31 outputs laser light L, for example, via pulse oscillation. The spatial light modulator 7 modulates the laser light L output from the light source 31. The spatial light modulator 7 is, for example, a spatial light modulator (SLM) of a reflective liquid crystal on silicon (LCOS). The condenser lens 33 focuses the laser light L modulated by the spatial light modulator 7. Alternatively, the condenser lens 33 can also be a correction ring lens.

[0074] In this embodiment, the laser irradiation unit 3 forms modified regions 12 (e.g., two rows of modified regions 12a, 12b) inside the semiconductor substrate 21 by irradiating the wafer 20 with laser L along each of the plurality of lines 15 from the back side 21b side of the semiconductor substrate 21. Modified region 12a is the modified region closest to surface 21a among the two rows of modified regions 12a, 12b. Modified region 12b is the modified region closest to modified region 12a among the two rows of modified regions 12a, 12b, and is also the modified region closest to the back side 21b.

[0075] Two rows of modified regions 12a and 12b are adjacent in the thickness direction (Z direction) of wafer 20. These two rows of modified regions 12a and 12b are formed by moving two focusing points C1 and C2 relative to the semiconductor substrate 21 along line 15. For example, the laser L is modulated by a spatial light modulator 7 such that focusing point C2 is located behind the focusing point C1 in the forward direction and positioned on the incident side of the laser L. Furthermore, the formation of the modified regions can be single-focus or multi-focus; one row of modified regions (one pass) or multiple rows of modified regions (multiple passes) can be formed along a predetermined cutting line.

[0076] The formation of these two modified regions 12a and 12b and the crack 14 is carried out in the following cases. That is, in subsequent processes, sometimes the semiconductor substrate 21 is thinned and the crack 14 is exposed on the back side 21b by grinding, for example, and the wafer 20 is cut into multiple semiconductor devices along each of the multiple lines 15.

[0077] like Figure 5 As shown, the 4f lens unit 34 has a pair of lenses 34A and 34B arranged in the optical path of the laser L from the spatial light modulator 7 toward the condenser lens 33. The pair of lenses 34A and 34B constitute a bilateral telecentric optical system in which the modulation surface 7a of the spatial light modulator 7 and the entrance pupil surface 33a of the condenser lens unit 33 are in an imaging relationship. Thus, the image of the laser L at the modulation surface 7a of the spatial light modulator 7 (the image of the laser L modulated by the spatial light modulator 7) is imaged onto the entrance pupil surface 33a of the condenser lens 33. Furthermore, Fs in the figure represents the Fourier surface.

[0078] like Figure 6As shown, the spatial light modulator 7 is a spatial light modulator (SLM) of reflective liquid crystal on silicon (LCOS). The spatial light modulator 7 is constructed by sequentially stacking a driving circuit layer 72, a pixel electrode layer 73, a reflective film 74, an alignment film 75, a liquid crystal layer 76, an alignment film 77, a transparent conductive film 78, and a transparent substrate 79 on a semiconductor substrate 71.

[0079] The semiconductor substrate 71 is, for example, a silicon substrate. The driving circuit layer 72 is located on the semiconductor substrate 71 and forms an active matrix circuit. The pixel electrode layer 73 includes a plurality of pixel electrodes 73a arranged in a matrix along the surface of the semiconductor substrate 71. Each pixel electrode 73a is formed, for example, from a metallic material such as aluminum. A voltage is applied to the pixel electrode 73a via the driving circuit layer 72.

[0080] The reflective film 74 is, for example, a dielectric multilayer film. An alignment film 75 is disposed on the surface of the liquid crystal layer 76 on the side of the reflective film 74, and an alignment film 77 is disposed on the surface of the liquid crystal layer 76 opposite to the reflective film 74. Each alignment film 75 and 77 is formed, for example, from a polymer material such as polyimide, and the contact surfaces between each alignment film 75 and 77 and the liquid crystal layer 76 are subjected to, for example, a rubbing treatment. The alignment films 75 and 77 align the liquid crystal molecules 76a contained in the liquid crystal layer 76 in a specific direction.

[0081] A transparent conductive film 78 is disposed on the surface of the transparent substrate 79 on the side of the alignment film 77, facing the pixel electrode layer 73 across the liquid crystal layer 76. The transparent substrate 79 is, for example, a glass substrate. The transparent conductive film 78 is formed, for example, from a light-transmitting and conductive material such as ITO. The transparent substrate 79 and the transparent conductive film 78 allow laser light L to pass through.

[0082] In the spatial light modulator 7 configured as described above, if a signal representing a modulation pattern is input from the control unit 8 to the drive circuit layer 72, a voltage corresponding to that signal is applied to each pixel electrode 73a, forming an electric field between each pixel electrode 73a and the transparent conductive film 78. If this electric field is formed, in the liquid crystal layer 76, in each region corresponding to each pixel electrode 73a, the alignment direction of the liquid crystal molecules 76a changes, and in each region corresponding to each pixel electrode 73a, the refractive index changes. This state is the state in which the modulation pattern is displayed in the liquid crystal layer 76. The modulation pattern is used to modulate the laser L.

[0083] That is, if, with the modulation pattern displayed on the liquid crystal layer 76, laser L is incident on the liquid crystal layer 76 from the outside via the transparent substrate 79 and the transparent conductive film 78, reflected by the reflective film 74, and emitted from the liquid crystal layer 76 to the outside via the transparent conductive film 78 and the transparent substrate 79, then laser L is modulated according to the modulation pattern displayed on the liquid crystal layer 76. Thus, according to the spatial light modulator 7, the modulation pattern displayed on the liquid crystal layer 76 can be appropriately set, thereby enabling modulation of laser L (e.g., modulation of the intensity, amplitude, phase, polarization, etc. of laser L). Furthermore, Figure 5 The modulation surface 7a shown is, for example, a liquid crystal layer 76.

[0084] As described above, the laser L output from the light source 31 is incident on the condenser lens 33 via the spatial light modulator 7 and the 4f lens unit 34. The condenser lens 33 focuses the light onto the object 11, thereby forming a modified region 12 and cracks extending from the modified region 12 on the object 11 at the focusing point C. Furthermore, the stage 2 is controlled by the control unit 8 to move the focusing point C relative to the wafer 20, forming the modified region 12 and cracks along the moving direction of the focusing point C.

[0085] like Figure 4 As shown, the laser irradiation unit 3 also includes an AF (autofocus) unit 91 (measuring unit). The AF unit 91 is a structure designed to ensure that the focusing point of the laser L is accurately aligned to a position at a predetermined distance from the back surface 21b, even when there is displacement (undulation) in the thickness direction (Z direction) on the incident surface (back surface) 21b of the wafer 20. The AF unit 91 measures the displacement of the back surface 21b (the surface to be measured) in order to adjust the focusing point of the laser L irradiated onto the wafer 20 by the light source 31. Specifically, the AF unit 91 irradiates the back surface 21b with an AF laser LA (measuring light) and receives and detects the reflected light of the AF laser LA from the back surface 21b, thereby obtaining displacement data (measured displacement) of the back surface 21b.

[0086] The AF unit 91 includes an AF light source 91a that outputs an AF laser LA, and a displacement detection unit 91b that receives and detects the reflected light of the AF laser LA. The AF laser LA emitted from the AF light source 91a is reflected by an AF beam splitter 92 and illuminates the back surface 21b via a condenser lens 33. Thus, the AF laser LA and laser L are illuminated on the wafer 20 (coaxial) from the same condenser lens 33. Furthermore, the reflected light of the AF laser LA on the back surface 21b is reflected by the AF beam splitter 92 and detected by the displacement detection unit 91b. The displacement detection unit 91b is configured to include, for example, a 4-segment light-emitting diode. The 4-segment light-emitting diode is a structure that divides and receives the concentrated image of the reflected light of the AF laser LA and outputs a voltage value corresponding to the amount of light of each segment. Because the concentrated image adds astigmatism to the reflected light of the AF laser LA, its shape (longitudinal length, circular shape, transverse length) changes depending on the position of the back surface 21b of the wafer 20 relative to the focal point of the AF laser LA. That is, the focused image varies depending on the position of the back surface 21b of the wafer 20 relative to the focusing point. Therefore, the voltage value output from the 4-segment light-emitting diode varies depending on the position of the back surface 21b of the wafer 20 relative to the focusing point of the AF laser LA.

[0087] The voltage value output from the four-segment LED of the displacement detection unit 91b is input to the control unit 8. The control unit 8 calculates a value based on the voltage value output from the four-segment LED of the displacement detection unit 91b, as position information regarding the position of the back surface 21b of the wafer 20 relative to the focusing point of the AF laser LA. Furthermore, based on this calculated value, the control unit 8 controls the drive unit 9 (actuator) to finely adjust the position of the focusing lens 33 in the vertical direction so that the position of the focusing point of the laser L irradiated from the light source 31 is at a predetermined depth from the back surface 21b. Thus, through laser processing by the laser L and control based on the distance measurement results from the AF unit 91 (performed before laser processing), even when there are undulations in the incident surface, i.e., the back surface 21b, the focusing point of the laser L can be accurately aligned to a predetermined distance from the back surface 21b.

[0088] [Inspection of the camera unit's structure]

[0089] like Figure 7As shown, the imaging unit 4 (imaging section) includes: a light source 41, a reflector 42, an objective lens 43, and a light detection unit 44. The imaging unit 4 captures images of the wafer 20. The light source 41 outputs light I1 that is transmissive relative to the semiconductor substrate 21. The light source 41 is configured, for example, by a halogen lamp and a filter, and outputs light I1 in the near-infrared region. The light I1 output from the light source 41 is reflected by the reflector 42 and passes through the objective lens 43, and illuminates the wafer 20 from the back side 21b side of the semiconductor substrate 21. At this time, the stage 2 supports the wafer 20 on which two rows of modified regions 12a and 12b are formed, as described above.

[0090] Objective lens 43 allows light I1 reflected from the surface 21a of semiconductor substrate 21 to pass through. That is, objective lens 43 allows light I1 propagating within semiconductor substrate 21 to pass through. The numerical aperture (NA) of objective lens 43 is, for example, 0.45 or higher. Objective lens 43 includes a correction ring 43a. The correction ring 43a corrects aberrations generated by light I1 within semiconductor substrate 21, for example, by adjusting the distance between the plurality of lenses constituting objective lens 43. Furthermore, the means of correcting aberrations is not limited to the correction ring 43a, but may also include other correction means such as a spatial light modulator. Light detection unit 44 detects light I1 that has passed through objective lens 43 and mirror 42. Light detection unit 44 is, for example, composed of an InGaAs camera, and detects light I1 in the near-infrared region. Furthermore, the means of detecting (capturing) light I1 in the near-infrared region is not limited to an InGaAs camera; if it is a transmission-type confocal microscope or other means of transmission-type imaging, other imaging means may be used.

[0091] The camera unit 4 is capable of capturing images of the front ends of each of the two modified regions 12a and 12b, and each of the multiple cracks 14a, 14b, 14c, and 14d. Crack 14a extends from the modified region 12a toward the surface 21a. Crack 14b extends from the modified region 12a toward the back surface 21b. Crack 14c extends from the modified region 12b toward the surface 21a. Crack 14d extends from the modified region 12b toward the back surface 21b.

[0092] [Structure of the camera unit for alignment correction]

[0093] like Figure 8 As shown, the imaging unit 5 includes a light source 51, a reflector 52, a lens 53, and a light detection unit 54. The light source 51 outputs light I2 that is transmissive to the semiconductor substrate 21. The light source 51 is configured, for example, by a halogen lamp and a filter, and outputs light I2 in the near-infrared region. The light source 51 may also be common to the light source 41 of the imaging unit 4. The light I2 output from the light source 51 is reflected by the reflector 52 and passes through the lens 53, and illuminates the wafer 20 from the back side 21b of the semiconductor substrate 21.

[0094] Lens 53 allows light I2 reflected from the surface 21a of the semiconductor substrate 21 to pass through. That is, lens 53 allows light I2 propagating within the semiconductor substrate 21 to pass through. The number of apertures in lens 53 is 0.3 or less. That is, the number of apertures in the objective lens 43 of the imaging unit 4 is greater than the number of apertures in lens 53. Light detection unit 54 detects the light I2 that has passed through lens 53 and reflector 52. Light detection unit 54, for example, is constructed using an InGaAs camera and detects light I2 in the near-infrared region. Alternatively, light detection unit 54 can be an SD camera or a component that detects non-transparent light.

[0095] The imaging unit 5, under the control of the control unit 8, images the functional element layer 22 by irradiating the wafer 20 with light I2 from the back side 21b and detecting the light I2 returning from the surface 21a (functional element layer 22). Similarly, under the control of the control unit 8, the imaging unit 5 also acquires images of the regions including the modified regions 12a and 12b by irradiating the wafer 20 with light I2 from the back side 21b and detecting the light I2 returning from the formation locations of the modified regions 12a and 12b in the semiconductor substrate 21. These images are used for alignment of the irradiation position of the laser L. The imaging unit 6 has the same structure as the imaging unit 5, except that the lens 53 has a lower magnification (e.g., 6x in imaging unit 5, 1.5x in imaging unit 6), and is used for alignment in the same way as the imaging unit 5.

[0096] [Detailed explanation of laser processing methods]

[0097] The following describes in detail the laser processing method performed by the laser processing apparatus 1. The laser processing method of this embodiment is a laser processing method in which the back surface 21b of a wafer 20 (object) containing a back surface 21b (first surface) and a surface 21a (second surface) opposite to the back surface 21b is used as the incident surface, and laser L is irradiated onto the wafer 20 to perform laser processing on the wafer 20. This laser processing method includes: a first step; and a second step performed after the first step. As described above, the wafer 20 is cut along each of the plurality of lines 15 to each functional element 22a. In the first step, the plurality of lines 15 (first line, reference line, etc.) extending in the X direction (first direction) along the back surface 21b are cut. Figure 2 Each of the parts is subjected to laser irradiation. In the second process, multiple lines 15 (second lines, reference lines) extending along the Y direction (second direction) along the back surface 21b are irradiated with lasers. Figure 2 Each of the components is subjected to laser irradiation. The following will explain the process as CH1 and the process as CH2.

[0098] In detail, during the first processing step (CH1 processing), along each of the multiple lines 15 extending in the X direction, the focusing point of the laser L is moved relative to each other, and the laser L irradiates the interior of the wafer 20 to form a dicing modified region 12 (first modified region), forming a crack 14 extending from the modified region 12 toward the surface 21a. The control unit 8 controls the laser irradiation unit 3 (first control) to form such a crack 14. Here, in the first process, the modified region 12 is formed in a so-called BHC (Bottom side half-cut) state where the crack 14 reaches the surface 21a. Alternatively, in the first process, the modified region 12 can also be formed in a so-called ST (Stealth) state where the crack 14 does not reach the surface 21a. Furthermore, in the second processing step (CH2 processing), along each of the multiple lines 15 extending in the Y direction, while the focusing point of the laser L is moved relative to each other, the laser L irradiates the interior of the wafer 20 to form a dicing modified region 12 (second modified region), and forms a crack 14 extending from the modified region 12 toward the surface 21a. The control unit 8 controls the laser irradiation unit 3 (second control) in such a way as to form this crack 14. Here, in the second process, the modified region 12 is formed in a so-called BHC state where the crack 14 reaches the surface 21a. Alternatively, in the second process, the modified region 12 can also be formed in a so-called ST state where the crack 14 does not reach the surface 21a.

[0099] Here, as described above in the CH1 and CH2 processing, when the modified regions 12 are formed sequentially along multiple intersecting lines 15, warping sometimes occurs on the wafer 20 due to the formation of the modified regions 12 along the line 15 (first line) that is first irradiated by the laser L and extends in the X direction. Figure 9 This diagram illustrates the principle behind the warping of wafer 20. Specifically, as shown... Figure 9 As shown, the warping of wafer 20 is caused by the formation of the modified region 12 and the formation of cracks 14 extending from the modified region 12 toward surface 21a, resulting in stress concentration on one side of wafer 20 (here, surface 21a reached by crack 14). Figure 9 In the example shown, during CH1 processing, modified regions 12 are sequentially formed on multiple lines 15 (the first line) that extend along the X direction and are adjacent to each other in the Y direction, and the cracks 14 extend towards the surface 21a. Particularly at the two ends of the wafer 20 in the Y direction, the warpage is increased. That is, due to CH1 processing, warpage occurs in the Y direction, the processing direction of CH2 processing. This warpage of the wafer 20 is particularly significant when the wafer 20 is a small chip, or when a large crack 14 is formed on the wafer 20.

[0100] Figure 10 This diagram shows the warping in the CH2 processing direction after CH1 processing and before CH2 processing. Figure 10 In the diagram, the horizontal axis represents the processing direction of CH2 (the width direction of wafer 20), and the vertical axis represents the displacement expressed in voltage values. A voltage value of 1V on the vertical axis corresponds to, for example, a displacement of approximately 8μm. Figure 10 The image shows an example of the results of CH1 machining under the following conditions: workpiece size: 775μm (65mm × 36mm wafer), chip size: 1mm, finished thickness after grinding: 80μm, modified area for slicing: 3 strokes (total cracks approximately 300μm, BHC cracks approximately 80μm), and measurement point: 1.5mm from the end of the wafer. Figure 10 It can be seen that after CH1 processing, the warpage increases at both ends (wafer edges) of the CH2 processing direction.

[0101] Figure 11 This diagram illustrates the poor AF (autofocus) tracking during CH2 processing after CH1 processing. As described above, in the laser irradiation unit 3, the displacement data of the back surface 21b is obtained by detecting the reflected light from the back surface 21b using the AF unit 91. However, after CH1 processing, as mentioned above, the warpage at the wafer edge increases, potentially causing poor AF tracking. Even with the AF unit 91, accurate displacement data of the back surface 21b cannot be obtained. Consequently, the accuracy of the modified region 12 (second modified region) formed during CH2 processing may deteriorate.

[0102] Therefore, in the laser processing method of this embodiment, a third step for warpage suppression is performed before the second step. In the third step, before the second step, a warpage suppression modification region 12 (the third modification region) is formed inside the wafer 20 by irradiation with laser L. A crack 114 (see reference) is formed extending from this modification region 12 to the incident surface, i.e., the back surface 21b, and is not continuous with the crack 14 extending from the dicing modification region 12. Figure 12 In this case, the control unit 8 controls the laser irradiation unit 3 (third control) in such a way that multiple warpage suppression modified regions 12 are formed by irradiation of the laser L, and the cracks 114 extending from the modified regions 12 reach the back surface 21b and are not formed continuously with the cracks 14 extending from the modified regions 12 for segmentation.

[0103] Figure 12 This diagram illustrates the formation of the modified region 12 used for warpage suppression. (See diagram for example.) Figure 12As shown, in the CH1 process, a modified region 12 for segmentation is formed, and cracks 14 are formed from this modified region 12 toward the surface 21a. The modified region 12 for segmentation in the CH1 process and the cracks 14 extending from this modified region 12 are formed at the center of, for example, a street region 23 in which a line 15 (first line) extending in the X direction is formed. In this case, in the third process, as... Figure 12 As shown, a warp-suppressing modified region 12 (the modified region 12 involving crack 114) is formed at a position different from the modified region 12 for segmentation in the Y direction (the modified region 12 involving crack 14) (a position offset from the modified region 12 for segmentation). That is, in the third control, the control unit 8 controls the laser irradiation unit 3 to form the warp-suppressing modified region 12 at a position different from the formation position of the modified region 12 for segmentation in the Y direction. In the third process, the warp-suppressing modified region 12 is formed in a so-called HC (Half-cut) state, where crack 114 reaches the back surface 21b. In this way, by becoming HC state, warping of the warp-suppressing modified region 12 can be reduced, further mitigating the warping of the modified region 12 for segmentation (details will be described later). The offset method between the position of the modified region 12 for segmentation and the position of the modified region 12 for warp suppression (and the positions of crack 14 and crack 114) is not particularly limited. For example, it can be implemented by the operation of the stage 2 or the Y-shift pattern of the spatial light modulator 7 (details are described later).

[0104] Alternatively, in the third process, a warp-suppressing modified region 12 can be formed at the midpoint in the Y-direction of the formation positions of the two adjacent lines 15 (first lines) in the Y-direction. In this case, the control unit 8, in the third control, controls the laser irradiation unit 3 to form the warp-suppressing modified region 12 at the midpoint in the Y-direction of the formation positions of the two adjacent lines 15 (first lines) in the Y-direction. As described above, in the CH1 processing, the lines 15 (first lines) that are adjacent in the Y-direction and extend along the X-direction form the modified region 12 for slicing and the cracks 14 extending from the modified region 12. Therefore, the midpoint in the Y-direction of the formation positions of the two adjacent lines 15 in the Y-direction becomes the central position of the chip after cutting (slicing). Figure 13 This diagram illustrates the formation of a warp-suppressing modified region 12 near the center of the chip. In the third process, by forming the warp-suppressing modified region 12 at the center of the chip, the separation distance between the cracks 14 extending from the dicing modified region 12 and the cracks extending from the warp-suppressing modified region 12 can be maximized, thereby reducing the risk of wafer breakage caused by the continuity of these crack phases. Furthermore, as... Figure 13As shown in (a), since the functional element 22a is located near the center of the chip where the warp suppression modified region 12 is formed, the warp suppression modified region 12 is formed on the active region. Because the distance from the focusing point in the third process to the functional element 22a is sufficiently large, the functional element 22a will not be damaged by the light passing through it from the laser irradiation in the third process. Furthermore, as... Figure 13 As shown in (b), the modified region 12 for warpage suppression is removed in the subsequent polishing process. Therefore, even if the modified region 12 for warpage suppression is formed on the active region in the third process, it will not affect the chip-based semiconductor device.

[0105] Alternatively, in the third step, the cracks 114 extending from the warp suppression modified region 12 may be formed in a way that makes them shorter than the cracks 14 extending from the modified region 12 for segmentation. Furthermore, in the third step, the length of the cracks 114 may be shortened as described above, and in the second direction, a greater number of warp suppression modified regions 12 may be formed than the number of modified regions 12 for segmentation. Figure 14 This diagram illustrates the formation of warp suppression modified regions in multi-point branching processing. As a processing method that shortens the length of the cracks 114 extending from the warp suppression modified regions 12 and increases the number of warp suppression modified regions 12, multi-point branching processing can also be implemented, for example, using a modulation pattern (multi-point branching pattern) set on the spatial light modulator 7. In this case, the control unit 8 sets the modulation pattern (multi-point branching pattern) on the spatial light modulator 7 in such a way that the cracks 114 are shorter than the original cracks 14, and the number of warp suppression modified regions 12 is greater than the number of segmented modified regions 12. Figure 14 As shown, a plurality of warp suppression modified regions 12 are formed in one step through multi-point branching processing of the spatial light modulator 7. Furthermore, by increasing the number of focusing points and dispersing energy, the vertical crack 114 can be shortened (reducing the risk of wafer breakage). Based on this multi-point branching processing using a modulation pattern (multi-point branching pattern) set in the spatial light modulator 7, warp suppression processing can be performed without reducing the cycle time and thus reducing the risk of wafer breakage. Moreover, the method of shortening the crack 114 and forming more warp suppression modified regions 12 than the number of segmented modified regions 12 is not limited to multi-point branching processing using the spatial light modulator 7; it can also be performed line-by-line processing, for example, using a conveyor table.

[0106] Alternatively, in the third process, a warp suppression modification region 12 can be formed by focusing on suppressing warping of the outer periphery of the wafer 20 (the two ends of the CH2 processing direction, i.e., the wafer edge). Figure 15This diagram illustrates a processing method used to specifically suppress warping of the outer periphery of wafer 20. It can also be seen as... Figure 15 As shown in (a), in the third process, when comparing the warp suppression modification region 12 at the center of the wafer 20 in the Y direction with the warp suppression modification regions 12 at both ends, the number of warp suppression modification regions 12 at both ends in the second direction is increased. The processing index is changed according to the location to form the warp suppression modification regions 12. In this case, the control unit 8, in the third control, controls the laser irradiation unit 3 to increase the number of warp suppression modification regions 12 at both ends in the Y direction. Alternatively, it can be as follows... Figure 15 As shown in (b), in the third process, the warp suppression modified region 12 is formed such that, when comparing the warp suppression modified region 12 at the center of the wafer 20 in the Y direction with the warp suppression modified region 12 at both ends, the length of the crack 114 at both ends (i.e., crack 114L) becomes longer than the crack 114 at the center (i.e., crack 114S). In this case, the control unit 8, in the third control, controls the laser irradiation unit 3 such that the length of the crack 114 extending from the warp suppression modified region 12 at both ends in the Y direction becomes longer.

[0107] Figure 16 This is a diagram illustrating the warping in the CH2 processing direction after CH1 processing, showing the formation of the modified region used for warping suppression. Figure 16 In the diagram, the horizontal axis represents the processing direction of CH2 (the width direction of wafer 20), and the vertical axis represents the displacement expressed in voltage values. A voltage value of 1V on the vertical axis corresponds to, for example, a displacement of approximately 8μm. Figure 16 The image shows an example of the results of CH1 processing under the following conditions: workpiece size: 775μm (65mm × 36mm wafer), chip size: 1mm, finished thickness after grinding: 80μm, modified area for slicing: 3 strokes (total cracks approximately 300μm, BHC cracks approximately 80μm), and measurement point: 1.5mm from the end of the wafer. Figure 16 The diagram illustrates the warpage amount (displacement amount) for three cases: forming only the modified region 12 for segmentation (Pattern 1); forming the modified region 12 for segmentation and forming the same number of modified regions 12 for warpage suppression (Pattern 2); and forming two lines of modified regions 12 for warpage suppression on the outer periphery of the wafer 20, i.e., the edge 10mm portion, except for Pattern 2 (Pattern 3). Figure 16 As shown, when using pattern 3, warpage can be suppressed even in the outer periphery of wafer 20, where warpage is prone to increase.

[0108] In addition, it can also be like Figure 15 As shown in (c), in the third process, each warp suppression modification region 12 is formed in such a way that the warp suppression modification region 12 in the center of the wafer 20 is made sparse. For example, if the warp amount in the center of the wafer 20 is extremely small and the warp amount only increases at both ends, then even if the warp suppression modification region 12 in the center of the wafer 20 is made sparse, the warp of the wafer 20 can be appropriately suppressed.

[0109] Alternatively, in the third step, by setting the modulation pattern (modulation pattern that shifts the focus point) of the spatial light modulator 7 that modulates the laser L, the warp suppression modified region 12 can be formed at a position different from the segmentation modified region 12 in the Y direction. That is, in the third control, the control unit 8 sets the modulation pattern so that the warp suppression modified region 12 is formed at a position different from the formation position of the segmentation modified region 12 in the Y direction. Figure 17 This diagram illustrates the shift in processing position set by the modulation pattern of the spatial light modulator 7. Figure 17 In the example shown, in the first step, the focusing point of the modified region 12 for segmentation is shifted from the reference focusing position in the -Y direction, and in the third step, the focusing point of the modified region 12 for warpage suppression is shifted from the reference focusing position in the +Y direction. This allows the modified regions 12 for segmentation and warpage suppression to be shifted in opposite directions in the Y direction, effectively separating the relative positions of these modified regions 12 and the cracks 14, 114 extending from them. Furthermore, in the first and third steps, the processing position can be shifted simply by switching the modulation pattern; therefore, compared to the case where the stage 2 is operated, the processing time required can be shortened.

[0110] Alternatively, in at least one of the first and third steps, the modulation pattern of the spatial light modulator 7 can be set such that the position of the end of the crack 14 extending from the modified region 12 for segmentation on the back side 21b side is different from the position of the end of the crack 114 extending from the modified region 12 for warp suppression on the surface side 21a side. That is, the control unit 8 sets the modulation pattern in at least one of the first and third controls such that the position of the end of the crack 14 extending from the modified region 12 for segmentation on the back side 21b side is different from the position of the end of the crack 114 extending from the modified region 12 for warp suppression on the surface side 21a side. Here, the example of setting the modulation pattern of the spatial light modulator 7 in the first step to make the position of the end of the crack 14 on the back side 21b side different from the position of the end of the crack 114 on the surface side 21a side will be explained. Specifically, in the first step, by forming cracks 14 inclined in the Z and Y directions, the position of the end on the back side 21b of the crack 14 is different from the position of the end on the surface side 21a of the crack 114 (see reference). Figure 18 (a)

[0111] Figure 18 This diagram illustrates the formation of oblique cracks based on a modulation pattern set by a spatial light modulator. (In...) Figure 18 In the example shown in (a), in the first step, two rows of modified regions 12 for segmentation are formed. Cracks 14A extending from the modified region 12 on the surface 21a side are formed along line 15. Cracks 14B extending from the modified region 12 on the back side 21b side are formed as oblique cracks continuous with cracks 14A and inclined relative to the Z and Y directions. Thus, for example... Figure 18 As shown in (a), in the third step, even when the modified region 12 for warping suppression is formed in such a way that the crack 114 is formed at the same position in the Y direction as the crack 14A, the position of the end of the crack 14 (specifically, crack 14B) extending from the modified region 12 for segmentation on the back side 21b side can be different from the position of the end of the crack 114 on the surface side 21a side. Furthermore, the crack 14A connected to the crack 14B extends along the line 15, so the crack 14 (specifically, crack 14A) can be appropriately extended in the required position and direction for the crack 14 for segmentation.

[0112] In such Figure 18 In the example shown in (b), three columns of modified regions 12 are formed for segmentation, with the modified region 12 closest to the surface 21a being the most prominent. Figure 18 (b) of SD1), the crack 14A is formed in a manner that extends along line 15. Furthermore, by setting the modulation pattern (Y-shift and coma aberration settings) of the spatial light modulator 7, the central modified region 12 ( Figure 18(b) of SD2), shifted from SD1 in the Y direction, and oblique crack 14B extends from there, to the modified region 12 closest to the back side 21b. Figure 18 (b) SD3), further shifted in the Y direction from SD2, and oblique crack 14C extends from there. Oblique crack 14B is continuous with crack 14A and oblique crack 14C, and oblique crack 14B and oblique crack 14C extend in the same direction (oblique direction).

[0113] It has been explained that, in order to suppress the adverse effects of warpage on the second processing step (CH2 processing) caused by warpage during the first processing step (CH1 processing) on ​​the second processing step, a warpage suppression modification region 12 (third modification region) is formed inside the wafer 20 in the third processing step before the second processing step. Here, the warpage of the wafer 20 caused by the formation of the modification region 12 during CH1 processing gradually progresses as the modification region 12 for dicing the multiple lines 15 is formed. Therefore, in CH1 processing, the effect of processing the lines 15 processed first also affects the processing of the lines 15 processed later. That is, in CH1 processing, during the processing of the lines 15 processed later in the process, the dicing modification region 12 may form while the wafer 20 is warped, which could lead to a deterioration in processing stability.

[0114] Figure 19 This diagram illustrates the deterioration of processing stability during the latter half of CH1 processing. (For example...) Figure 19 As shown, when multiple lines have been modified with regions 12 and cracks 14 extend from these modified regions 12, warping occurs in the wafer 20. In this state, if laser L is used in CH1 processing to further form the modified regions 12 for dicing, problems arise such as the cracks 14 extending obliquely onto the device surface of the wafer 20, leading to deterioration of processing position accuracy. Furthermore, with the wafer 20 warped, poor adhesion of the wafer 20 to the stage 2 sometimes occurs. Thus, in the latter half of CH1 processing, stable and accurate processing is sometimes difficult.

[0115] In view of this, in the laser processing method of this embodiment, the formation of the modified region 12 for dividing any line 15 in the first step and the formation of the modified region 12 for warp suppression in the third step can be performed alternately. That is, the control unit 8 controls the laser irradiation unit 3 in a manner that alternately performs the formation of the modified region 12 for dividing any line 15 under the first control and the formation of the modified region 12 for warp suppression under the third control. This alternate implementation is not only the case of a completely one-to-one alternation, but also the case of alternately performing the formation of multiple modified regions 12 for dividing and multiple modified regions 12 for warp suppression.

[0116] Figure 20 This diagram illustrates a processing method in which alternating modified regions 12 for segmentation and modified regions 12 for warpage suppression are formed. Figure 20 (a) to Figure 20 In (c), the numbers 1 through 9 represent the processing order. In such cases... Figure 20 In the example shown in (a), the third process involves the formation of the modified region 12 for warpage suppression and the cracks 114 extending from the modified region 12 (processing sequence 1). Next, the first process involves the formation of the modified region 12 for segmentation and the cracks 14 extending from the modified region 12 (processing sequence 2). Then, the third and first processes are performed sequentially, one at a time. In this case, the processed parts are arranged in the processing sequence in the Y direction. Figure 20 In the example shown in (b), initially, the third step involves two processing steps (processing sequence 1, 2) to form the modified region 12 for warpage suppression and the cracks 114 extending from the modified region 12. Then, the first step involves two processing steps (processing sequence 3, 4) to form the modified region 12 for segmentation and the cracks 14 extending from the modified region 12. This process is then repeated twice. In this case, if the first and third steps are observed separately, the processed parts are arranged in the Y direction according to the processing sequence. Figure 20 In the example shown in (c), the third step involves three processing steps (processing sequence 1, 2, 3) to form the modified region 12 for warpage suppression and the cracks 114 extending from the modified region 12. Then, the first step involves three processing steps (processing sequence 4, 5, 6) to form the modified region 12 for segmentation and the cracks 14 extending from the modified region 12. In this case, if the first and third steps are observed separately, the processed parts are arranged in the Y direction according to the processing sequence.

[0117] Furthermore, within the same process (CH1 processing in the above example), the effects of the earlier processing can affect the later processing, and this will also occur in CH2 processing. Therefore, to further suppress the deterioration of processing stability during the latter half of CH2 processing, the following fourth process can be implemented. That is, the laser processing method of this embodiment also includes: a fourth process in which multiple warp suppression modified regions 12 (fourth modified regions) are formed inside the wafer 20 by laser irradiation, and cracks 114 are formed extending from the modified regions 12 to the back surface 21b and are not continuous with the cracks 14 extending from the segmentation modified regions 12 formed by CH2 processing. In this case, the formation of the segmentation modified regions 12 for any line 15 in the second process and the formation of the warp suppression modified regions 12 in the fourth process can be performed alternately.

[0118] Next, the effects of the laser processing apparatus 1 in this embodiment will be explained.

[0119] The laser processing apparatus 1 of this embodiment includes a laser irradiation unit 3 and a control unit 8. The control unit 8 performs: a first control, which controls the laser irradiation unit 3 to move the focusing point of the laser L relative to each of the plurality of lines 15 extending in the X direction along the back surface 21b, thereby forming a modified region 12 for dicing inside the wafer 20 by irradiation of the laser L, and causing the crack 14 to extend from the modified region 12 toward the surface 21a; and a second control, which, after the first control, controls the laser irradiation unit 3 to move along the plurality of lines 15 extending in the Y direction intersecting the X direction and along the back surface 21b. Each laser irradiation unit 3 is controlled to move the focusing point of the laser L relative to the wafer 20 while forming a modified region 12 for dicing by irradiation of the laser L, and to extend the crack 14 from the modified region 12 toward the surface 21a. The third control is to control the laser irradiation unit 3 in such a way that, before the second control, multiple modified regions 12 for warpage suppression are formed inside the wafer 20 by irradiation of the laser L, and the crack 114 extending from the modified region 12 reaches the back surface 21b and is not formed continuously with the crack 14 extending from the modified region 12.

[0120] In the laser processing apparatus 1 of this embodiment, by irradiation with laser L, a modified region 12 for slicing is formed along each of a plurality of lines 15 extending in the X direction along the back surface 21b, and a crack 14 extending from the modified region 12 toward the surface 21a is formed. Then, by irradiation with laser L, a modified region 12 for slicing is formed along each of a plurality of lines 15 extending in the Y direction, and a crack 14 extending from the modified region 12 toward the surface 21a is formed. Thus, when the modified regions 12 are formed sequentially along a plurality of intersecting lines 15, warping may occur in the wafer 20 due to the formation (CH1 processing) of the modified region 12 along the line 15 (first line) that was first irradiated by laser L. Due to the effect of the warping of the wafer 20, the processing accuracy of the line 15 (second line) that was subsequently irradiated by laser L is reduced. Specifically, the warping of wafer 20 is caused by the formation of the modified region 12 and the formation of cracks 14 extending from the modified region 12 toward surface 21a, resulting in stress concentration on one side of wafer 20 (here, the main direction of the extension of crack 14 is surface 21a). This warping of wafer 20 is particularly noticeable when wafer 20 is a tiny chip and when large cracks are formed. Furthermore, if the processing of line 15 (second line) after being irradiated by laser L (CH2 processing) is performed in a warped state, it may be difficult to guarantee the accuracy of autofocus, etc., used for adjusting the focus point of laser L during the processing of line 15, and the formation of modified region 12 may become inadequate during CH2 processing.

[0121] Regarding this, in the laser processing apparatus 1 of this embodiment, before performing control of CH2 processing (second control), a plurality of warp-suppressing modified regions 12 are formed inside the wafer 20 by irradiation with laser L. Cracks 114 extending from these modified regions 12 are formed in such a way that they reach the back surface 21b and are not continuous with the cracks 14 extending from the dicing modified regions 12. In this way, by forming the warp-suppressing modified regions 12 in such a way that the cracks 141 reach the back surface 21b opposite to the surface 21a where stress is concentrated due to the formation of the dicing modified regions 12, the localization of stress is alleviated, and the warping of the wafer 20 can be reduced. Therefore, in CH2 processing performed after the formation of the warp-suppressing modified regions 12, the modified regions 12 can be appropriately formed. Furthermore, by forming the crack 141 extending from the warp suppression modified region 12 in a manner that is not continuous with the crack 14 extending from the dicing modified region 12, unintentional breakage of the wafer 20 due to the formation of the warp suppression modified region 12 can be appropriately suppressed. As described above, the laser processing apparatus 1 according to this embodiment can suppress unintentional breakage of the wafer 20, and the dicing modified region 12 can be appropriately formed on the wafer 20, thereby improving the laser processing accuracy.

[0122] Figure 21 This diagram illustrates the effect of the laser processing apparatus 1 in this embodiment, showing the warping of the CH2 processing direction after CH1 processing. Figure 21 In the diagram, the horizontal axis represents the processing direction of CH2 (the width direction of wafer 20), and the vertical axis represents the displacement expressed in voltage values. A voltage value of 1V on the vertical axis corresponds to, for example, a displacement of approximately 8μm. Figure 21 The diagram shows the warpage amount after CH1 processing and before CH2 processing, in the case where the modified region 12 for warpage suppression is not formed (in... Figure 21 In the case where the crack 114 extending from the modified region 12 for warpage suppression is in the ST state (as recorded in the text, "BHC only"), the situation is as follows: Figure 21 In the text, it is recorded as "BHC+warpage suppression SD(ST)" and the case where the HC state extends from the modified region 12 for warpage suppression to the back surface 21b is reached (in the case of the HC state). Figure 21 In the text, each item labeled "BHC+Warbage Inhibition SD(HC)" shows the results for the amount of warp. Figure 21 This illustrates an example of the processing results under the following conditions: workpiece size: 775μm (65mm × 36mm wafer), chip size: 1mm, finished thickness after grinding: 80μm, modified area for slicing: 3 strokes (total cracking approximately 300μm, BHC cracking approximately 80μm), modified area for warpage suppression: 1 stroke (total cracking approximately 60μm). Figure 21 It is known that by forming a warp suppression modified region 12 and extending the crack 114 from the warp suppression modified region 12 to the back surface 21b in an HC state, the warp of the wafer 20 caused by the formation of BHC in the segmentation modified region 12 can be significantly reduced.

[0123] Figure 22 This diagram illustrates the effect of the laser processing apparatus 1 according to this embodiment, showing the warping of the wafer 20 after CH1 and CH2 processing. Figure 22 In the diagram, the horizontal axis represents the position of wafer 20 along its width, and the vertical axis represents the surface displacement. This surface displacement was measured using a microscope. Figure 22 The diagram shows the surface displacement representing the warpage of wafer 20 after CH1 and CH2 processing, specifically for the case where the modified region 12 for warpage suppression is not formed (in...). Figure 22 In the case of "SD for slicing only" and in the case where the modified region 12 for warp suppression is formed in the center of the chip (in Figure 22 In the text, each element described as "SD for segmentation + SD for warpage suppression (processed in the center of the chip)" shows the surface displacement representing the amount of warpage. Figure 22The image shows an example of the processing results under the following conditions: workpiece size: 775 μm (12 inches), chip size: 1 mm, finished thickness after grinding: 80 μm, modified area for slicing: 3 strokes (total cracking approximately 300 μm, BHC cracking approximately 80 μm), modified area for warpage suppression: 3 strokes (total cracking approximately 150 μm). Figure 22 As shown, when the warp suppression modification region 12 is formed in the center of the chip, the warp amount (displacement) at both ends of the wafer 20 can be reduced to less than half compared to the case where the warp suppression modification region 12 is not formed. If the warp amount at both ends of the wafer 20 is large, it is possible that the wafer 20 cannot be properly held onto the transport arm after processing, resulting in transport defects such as the wafer 20 falling off. Regarding this, as described above, for a wafer 20 whose warp amount is reduced to less than half by the warp suppression modification region 12, the wafer 20 can be properly transported. Furthermore, the wafer 20 does not break after transport.

[0124] Alternatively, in the third control, the control unit 8 controls the laser irradiation unit 3 to form the warp suppression modified region 12 at a position different from the formation position of the modified region 12 for segmentation in the Y direction. This can appropriately avoid the continuity between the crack 14 from the modified region 12 for segmentation and the crack 114 from the modified region 12 for warp suppression, and can more appropriately suppress unintentional breakage of the wafer 20.

[0125] Alternatively, in the third control, the control unit 8 controls the laser irradiation unit 3 to form a warp-suppressing modified region 12 at the midpoint of the Y-direction of the formation positions of the two adjacent lines 15 in the Y-direction. By forming the warp-suppressing modified region 12 at the midpoint between the two lines 15, the separation distance between the arbitrarily divided modified region 12 and the warp-suppressing modified region 12 can be increased, thus appropriately avoiding the continuity of cracks 14 and 114. This appropriately suppresses unintentional breakage of the wafer 20.

[0126] Alternatively, in the third control, the control unit 8 sets a modulation pattern such that the warp suppression modified region 12 is formed at a position different from the formation position of the modified region 12 for segmentation in the Y direction. In this way, by adjusting the formation position of the warp suppression modified region 12 by setting the modulation pattern of the spatial light modulator 7, the processing time can be shortened compared to the case where the formation position of the modified region 12 is changed by the operation of the stage 2.

[0127] Alternatively, the control unit 8 may, in at least one of the first and third controls, set a modulation pattern such that the position of the end of the crack 14 on the back side 21b is different from the position of the end of the crack 114 on the surface side 21a. In this way, by adjusting the position of the ends of the cracks 14 and 114 extending from the modified region 12 by setting the modulation pattern of the spatial light modulator 7, the positions of the ends of the cracks 14 and 114 can be appropriately adjusted, and unintentional breakage of the wafer 20 caused by the continuity of the cracks 14 and 114 can be more appropriately suppressed.

[0128] Alternatively, in the third control, the control unit 8 controls the laser irradiation unit 3 to make the crack 114 extending from the warp suppression modified region 12 shorter than the crack 14 extending from the slitting modified region 12. The crack 114 extending from the warp suppression modified region 12 is different from the crack 14 extending from the slitting modified region 12; it is not a crack that aids in slitting. Therefore, by shortening it, unintentional breakage of the wafer 20 caused by the continuity of cracks 14 and 114 can be more appropriately suppressed.

[0129] Alternatively, in the third control, the control unit 8 controls the laser irradiation unit 3 to form a greater number of warp suppression modified regions 12 in the Y direction than the number of modified regions 12 used for dicing. As described above, it is desirable to shorten the cracks 114 extending from the warp suppression modified regions 12 when performing appropriate dicing. However, if the cracks 114 extending from the warp suppression modified regions 12 are shortened, the warp suppression effect may not be sufficiently obtained. To address this, by increasing the number of warp suppression modified regions 12 (more than the number of modified regions 12 used for dicing), the warp suppression effect can be fully realized through the numerous cracks 114 extending from the warp suppression modified regions 12, and unintentional breakage of the wafer 20 can be suppressed.

[0130] Alternatively, in the third control, the control unit 8 controls the laser irradiation unit 3 to form the warp suppression modified region 12 in such a way that, when comparing the warp suppression modified region 12 at the center of the wafer 20 in the Y direction with the warp suppression modified region 12 at both ends, the warp suppression modified region 12 is formed in a manner that either the number of warp suppression modified regions 12 at both ends in the Y direction is increased, or the length of the cracks 114 extending from the warp suppression modified region 12 at both ends is increased. Warp of the wafer 20 caused by the formation of the sizing modified region 12 becomes more pronounced closer to the two ends in the Y direction. To address this, by increasing the number of warp suppression modified regions 12 at both ends compared to the center of the wafer 20 in the Y direction, or by increasing the length of the cracks 114 extending from the warp suppression modified region 12, the significant warp of the wafer 20 at the two ends in the Y direction can be effectively suppressed.

[0131] Alternatively, the control unit 8 can control the laser irradiation unit 3 to alternately implement the formation of the modified region 12 for dividing any line 15 under the first control and the formation of the modified region 12 for warpage suppression. Warpage of the wafer 20 caused by the formation of the modified region 12 for dividing the line 15 gradually progresses as the modified regions 12 for dividing multiple lines 15 are formed. Therefore, the effect of processing the lines 15 processed first also affects the processing of the lines 15 processed later. That is, in the processing of the later half of the multiple lines 15, the modified region 12 is formed in the warped state of the wafer 20. Therefore, it is possible, for example, that cracks 14 extend obliquely relative to the surface 21a of the wafer 20, or that the processing position accuracy deteriorates, or that poor adhesion occurs during processing. In response to this, by alternately forming the modified region 12 for segmentation and the modified region 12 for warpage suppression, the influence of the processing of the line 15 performed first can be suppressed from affecting the processing of the line 15 performed later, and the modified region 12 for segmentation can be formed more appropriately on the wafer 20.

[0132] Furthermore, the formation of the warp suppression modified region 12 within such CH1 processing (alternating processing of the segmentation modified region 12 and the warp suppression modified region 12) is not necessarily required. For example, it can be implemented only when the wafer 20 is uneven in the CH1 processing direction after CH1 processing. Figure 23 This is a diagram showing the warping of the CH1 machining direction after CH1 machining. In Figure 23 The horizontal axis represents the machining direction of CH1, and the vertical axis represents the displacement expressed in voltage values. Figure 23The image shows an example of the results of CH1 processing under the following conditions: workpiece size: 775μm (65mm × 36mm wafer), chip size: 1mm, finished thickness after grinding: 80μm, modified area for slicing: 3 strokes (total cracks approximately 300μm, BHC cracks approximately 80μm), and measurement point: 1.5mm from the end of the wafer. Figure 23 In the example shown, although the warpage amount changes before and after processing, no unevenness or concavity in the processing direction is observed in CH1 after processing. In this case, it is not necessary to form the modified region 12 for warpage suppression within the CH1 processing; it is sufficient to form the modified region 12 for warpage suppression before the CH2 processing.

[0133] Alternatively, the control unit 8 may be configured to further perform: a fourth control, in which multiple warp-suppressing modified regions 12 are formed inside the wafer 20 by irradiation with laser L, and cracks 114 extending from these modified regions 12 reach the back surface 21b and are not continuously formed with cracks extending from the CH2 processing dicing modified region 12 (the second modified region), and the control unit controls the laser irradiation unit 3 in a manner that alternately implements the formation of the modified region 12 of any line 15 under the second control and the formation of the modified region 12 under the fourth control. In this way, by alternately implementing the formation of the CH2 processing modified region 12 and the warp-suppressing modified region 12, the influence of the processing of the line 15 performed first can be suppressed from affecting the processing of the line 15 performed later, and the dicing modified region 12 can be appropriately formed on the wafer 20.

[0134] Symbol Explanation

[0135] 1…laser processing apparatus, 3…laser irradiation unit (laser irradiation section), 7…spatial light modulator, 8…control unit, 12…modification regions (first modification region, second modification region, third modification region), 14, 114…cracks; 15…lines (first line, second line), 20…wafer (object).

Claims

1. A laser processing device, It comprises: a laser irradiation unit that irradiates a target object with a laser beam onto the target object using the first surface of the target object, which includes a first surface and a second surface opposite to the first surface, as the incident surface; and Control Department The control unit is configured to execute: a first control, a second control, and a third control. The first control involves moving the focal point of the laser relative to each of a plurality of first lines extending along a first direction along the incident surface, while simultaneously forming a first modified region for segmentation within the object through laser irradiation, with cracks extending from this first modified region toward the second surface. The second control, following the first control, involves controlling the laser irradiation unit in such a manner that, while relatively moving the focal point of the laser along each of a plurality of second lines extending in a second direction that intersects the first direction and extends along the incident surface, the laser irradiation forms a second modified region for segmentation inside the object, and cracks extend from this second modified region toward the second surface. The third control, prior to the second control, controls the laser irradiation section to form multiple third modified regions for warpage suppression inside the object through laser irradiation, such that cracks extending from these third modified regions reach the first surface and do not form continuously with cracks extending from the first modified regions. The control unit controls the laser irradiation unit in at least one of the first control and the third control in such a way that the position of the end of the crack on the first surface extending from the first modified region is different from the position of the end of the crack on the second surface extending from the third modified region.

2. The laser processing apparatus according to claim 1, wherein, The control unit, in the third control, controls the laser irradiation unit to form the third modified region at a position different from the formation position of the first modified region in the second direction.

3. The laser processing apparatus according to claim 2, wherein, The control unit, in the third control, controls the laser irradiation unit in such a way that the third modified region is formed at the midpoint of the formation positions of the two adjacent first lines in the second direction.

4. The laser processing apparatus according to claim 2, wherein, The laser irradiation unit includes a spatial light modulator that modulates the laser according to a set modulation pattern. The control unit, in the third control, sets the modulation pattern such that the third modified region is formed at a position different from the formation position of the first modified region in the second direction.

5. The laser processing apparatus according to claim 3, wherein, The laser irradiation unit includes a spatial light modulator that modulates the laser according to a set modulation pattern. The control unit, in the third control, sets the modulation pattern such that the third modified region is formed at a position different from the formation position of the first modified region in the second direction.

6. The laser processing apparatus according to claim 1, wherein, The laser irradiation unit includes a spatial light modulator that modulates the laser according to a set modulation pattern. The control unit sets the modulation pattern in at least one of the first control and the third control in such a way that the position of the end of the crack on the first surface extending from the first modified region is different from the position of the end of the crack on the second surface extending from the third modified region.

7. The laser processing apparatus according to claim 2, wherein, The laser irradiation unit includes a spatial light modulator that modulates the laser according to a set modulation pattern. The control unit sets the modulation pattern in at least one of the first control and the third control in such a way that the position of the end of the crack on the first surface extending from the first modified region is different from the position of the end of the crack on the second surface extending from the third modified region.

8. The laser processing apparatus according to claim 3, wherein, The laser irradiation unit includes a spatial light modulator that modulates the laser according to a set modulation pattern. The control unit sets the modulation pattern in at least one of the first control and the third control in such a way that the position of the end of the crack on the first surface extending from the first modified region is different from the position of the end of the crack on the second surface extending from the third modified region.

9. The laser processing apparatus according to claim 4, wherein, The laser irradiation unit includes a spatial light modulator that modulates the laser according to a set modulation pattern. The control unit sets the modulation pattern in at least one of the first control and the third control in such a way that the position of the end of the crack on the first surface extending from the first modified region is different from the position of the end of the crack on the second surface extending from the third modified region.

10. The laser processing apparatus according to claim 5, wherein, The laser irradiation unit includes a spatial light modulator that modulates the laser according to a set modulation pattern. The control unit sets the modulation pattern in at least one of the first control and the third control in such a way that the position of the end of the crack on the first surface extending from the first modified region is different from the position of the end of the crack on the second surface extending from the third modified region.

11. The laser processing apparatus according to any one of claims 1 to 10, wherein, In the third control, the control unit controls the laser irradiation unit in such a way that the cracks extending from the third modified region become shorter compared to the cracks extending from the first modified region.

12. The laser processing apparatus according to claim 11, wherein, The control unit, in the third control, controls the laser irradiation unit in such a way that the number of the third modified regions in the second direction is greater than the number of the first modified regions.

13. The laser processing apparatus according to any one of claims 1 to 10, wherein, The control unit, in the third control, controls the laser irradiation unit such that, when comparing the third modified region of the central portion of the object in the second direction with the third modified regions of the two ends, the third modified region is formed in such a way that at least one of the following conditions is met: the number of the third modified regions in the second direction of the two ends becomes more, and the length of the cracks extending from the third modified regions of the two ends becomes longer.

14. The laser processing apparatus according to claim 11, wherein, The control unit, in the third control, controls the laser irradiation unit such that, when comparing the third modified region of the central portion of the object in the second direction with the third modified regions of the two ends, the third modified region is formed in such a way that at least one of the following conditions is met: the number of the third modified regions in the second direction of the two ends becomes more, and the length of the cracks extending from the third modified regions of the two ends becomes longer.

15. The laser processing apparatus according to claim 12, wherein, The control unit, in the third control, controls the laser irradiation unit such that, when comparing the third modified region of the central portion of the object in the second direction with the third modified regions of the two ends, the third modified region is formed in such a way that at least one of the following conditions is met: the number of the third modified regions in the second direction of the two ends becomes more, and the length of the cracks extending from the third modified regions of the two ends becomes longer.

16. The laser processing apparatus according to any one of claims 1 to 10, wherein, The control unit controls the laser irradiation unit by alternately implementing the formation of the first modified region of any of the first lines under the first control and the formation of the third modified region under the third control.

17. The laser processing apparatus according to claim 11, wherein, The control unit controls the laser irradiation unit by alternately implementing the formation of the first modified region of any of the first lines under the first control and the formation of the third modified region under the third control.

18. The laser processing apparatus according to claim 12, wherein, The control unit controls the laser irradiation unit by alternately implementing the formation of the first modified region of any of the first lines under the first control and the formation of the third modified region under the third control.

19. The laser processing apparatus according to claim 13, wherein, The control unit controls the laser irradiation unit by alternately implementing the formation of the first modified region of any of the first lines under the first control and the formation of the third modified region under the third control.

20. The laser processing apparatus according to claim 14, wherein, The control unit controls the laser irradiation unit by alternately implementing the formation of the first modified region of any of the first lines under the first control and the formation of the third modified region under the third control.

21. The laser processing apparatus according to claim 15, wherein, The control unit controls the laser irradiation unit by alternately implementing the formation of the first modified region of any of the first lines under the first control and the formation of the third modified region under the third control.

22. The laser processing apparatus according to claim 16, wherein, The control unit, The configuration further includes: a fourth control, wherein the laser irradiation unit is controlled to form multiple fourth modified regions for warpage suppression within the object through laser irradiation, such that cracks extending from these fourth modified regions reach the first surface and are not continuously formed with cracks extending from the second modified regions. The laser irradiation section is controlled in a manner that alternately implements the formation of the second modified region of any of the second lines under the second control and the formation of the fourth modified region under the fourth control.

23. The laser processing apparatus according to claim 17, wherein, The control unit, The configuration further includes: a fourth control, wherein the laser irradiation unit is controlled to form multiple fourth modified regions for warpage suppression within the object through laser irradiation, such that cracks extending from these fourth modified regions reach the first surface and are not continuously formed with cracks extending from the second modified regions. The laser irradiation section is controlled in a manner that alternately implements the formation of the second modified region of any of the second lines under the second control and the formation of the fourth modified region under the fourth control.

24. The laser processing apparatus according to claim 18, wherein, The control unit, The configuration further includes: a fourth control, wherein the laser irradiation unit is controlled to form multiple fourth modified regions for warpage suppression within the object through laser irradiation, such that cracks extending from these fourth modified regions reach the first surface and are not continuously formed with cracks extending from the second modified regions. The laser irradiation section is controlled in a manner that alternately implements the formation of the second modified region of any of the second lines under the second control and the formation of the fourth modified region under the fourth control.

25. The laser processing apparatus according to claim 19, wherein, The control unit, The configuration further includes: a fourth control, wherein the laser irradiation unit is controlled to form multiple fourth modified regions for warpage suppression within the object through laser irradiation, such that cracks extending from these fourth modified regions reach the first surface and are not continuously formed with cracks extending from the second modified regions. The laser irradiation section is controlled in a manner that alternately implements the formation of the second modified region of any of the second lines under the second control and the formation of the fourth modified region under the fourth control.

26. The laser processing apparatus according to claim 20, wherein, The control unit, The configuration further includes: a fourth control, wherein the laser irradiation unit is controlled to form multiple fourth modified regions for warpage suppression within the object through laser irradiation, such that cracks extending from these fourth modified regions reach the first surface and are not continuously formed with cracks extending from the second modified regions. The laser irradiation section is controlled in a manner that alternately implements the formation of the second modified region of any of the second lines under the second control and the formation of the fourth modified region under the fourth control.

27. The laser processing apparatus according to claim 21, wherein, The control unit, The configuration further includes: a fourth control, wherein the laser irradiation unit is controlled to form multiple fourth modified regions for warpage suppression within the object through laser irradiation, such that cracks extending from these fourth modified regions reach the first surface and are not continuously formed with cracks extending from the second modified regions. The laser irradiation section is controlled in a manner that alternately implements the formation of the second modified region of any of the second lines under the second control and the formation of the fourth modified region under the fourth control.

28. A laser processing method, A laser processing method that uses the first surface of an object, which includes a first surface and a second surface opposite to the first surface, as the incident surface to irradiate the object with a laser, thereby performing laser processing on the object. It includes: process 1, process 2, and process 3. In the first process, along each of a plurality of first lines extending in a first direction along the incident surface, the focusing point of the laser is moved relative to each other, and the laser irradiation forms a first modified region for segmentation inside the object, forming cracks extending from the first modified region toward the second surface. The second step, following the first step, involves moving the laser's focal point relative to each of several second lines extending along a second direction that intersects the first direction and runs along the incident surface. Simultaneously, the laser irradiates the interior of the object, forming a second modified region for segmentation, and creating cracks extending from this second modified region toward the second surface. In the third step, prior to the second step, multiple third modified regions for warpage suppression are formed inside the object by laser irradiation, forming cracks that extend from the third modified regions to the first surface and are not continuous with cracks extending from the first modified regions. In at least either the first step or the third step, the position of the end of the crack on the first surface extending from the first modified region is different from the position of the end of the crack on the second surface extending from the third modified region.

29. The laser processing method according to claim 28, wherein, In the third step, the third modified region is formed at a position different from the formation position of the first modified region in the second direction.

30. The laser processing method according to claim 29, wherein, In the third step, the third modification region is formed at the midpoint of the formation positions of the two adjacent first lines in the second direction.

31. The laser processing method according to claim 29, wherein, In the third step, by setting the modulation pattern of the spatial light modulator that modulates the laser, a third modified region is formed at a position different from the formation position of the first modified region in the second direction.

32. The laser processing method according to claim 30, wherein, In the third step, by setting the modulation pattern of the spatial light modulator that modulates the laser, a third modified region is formed at a position different from the formation position of the first modified region in the second direction.

33. The laser processing method according to claim 28, wherein, In at least one of the first and third steps, by setting a modulation pattern for the spatial light modulator that modulates the laser, the position of the end of the crack on the first surface extending from the first modified region is different from the position of the end of the crack on the second surface extending from the third modified region.

34. The laser processing method according to claim 29, wherein, In at least one of the first and third steps, by setting a modulation pattern for the spatial light modulator that modulates the laser, the position of the end of the crack on the first surface extending from the first modified region is different from the position of the end of the crack on the second surface extending from the third modified region.

35. The laser processing method according to claim 30, wherein, In at least one of the first and third steps, by setting a modulation pattern for the spatial light modulator that modulates the laser, the position of the end of the crack on the first surface extending from the first modified region is different from the position of the end of the crack on the second surface extending from the third modified region.

36. The laser processing method according to claim 31, wherein, In at least one of the first and third steps, by setting a modulation pattern for the spatial light modulator that modulates the laser, the position of the end of the crack on the first surface extending from the first modified region is different from the position of the end of the crack on the second surface extending from the third modified region.

37. The laser processing method according to claim 32, wherein, In at least one of the first and third steps, by setting a modulation pattern for the spatial light modulator that modulates the laser, the position of the end of the crack on the first surface extending from the first modified region is different from the position of the end of the crack on the second surface extending from the third modified region.

38. The laser processing method according to any one of claims 28 to 37, wherein, In the third step, the third modified region is formed such that the cracks extending from the third modified region are shorter than those extending from the first modified region.

39. The laser processing method according to claim 38, wherein, In the third step, in the second direction, the number of the third modified regions is greater than the number of the first modified regions.

40. The laser processing method according to any one of claims 28 to 37, wherein, In the third step, the third modified region is formed such that, when comparing the third modified region of the central portion of the object in the second direction with the third modified regions of the two ends, at least one of the following conditions is met: the number of the third modified regions in the second direction of the two ends becomes more, and the length of the cracks extending from the third modified regions of the two ends becomes longer.

41. The laser processing method according to claim 38, wherein, In the third step, the third modified region is formed such that, when comparing the third modified region of the central portion of the object in the second direction with the third modified regions of the two ends, at least one of the following conditions is met: the number of the third modified regions in the second direction of the two ends becomes more, and the length of the cracks extending from the third modified regions of the two ends becomes longer.

42. The laser processing method according to claim 39, wherein, In the third step, the third modified region is formed such that, when comparing the third modified region of the central portion of the object in the second direction with the third modified regions of the two ends, at least one of the following conditions is met: the number of the third modified regions in the second direction of the two ends becomes more, and the length of the cracks extending from the third modified regions of the two ends becomes longer.

43. The laser processing method according to any one of claims 28 to 37, wherein, The formation of the first modified region of any of the first lines in the first process and the formation of the third modified region in the third process are carried out alternately.

44. The laser processing method according to claim 38, wherein, The formation of the first modified region of any of the first lines in the first process and the formation of the third modified region in the third process are carried out alternately.

45. The laser processing method according to claim 39, wherein, The formation of the first modified region of any of the first lines in the first process and the formation of the third modified region in the third process are carried out alternately.

46. ​​The laser processing method according to claim 40, wherein, The formation of the first modified region of any of the first lines in the first process and the formation of the third modified region in the third process are carried out alternately.

47. The laser processing method according to claim 41, wherein, The formation of the first modified region of any of the first lines in the first process and the formation of the third modified region in the third process are carried out alternately.

48. The laser processing method according to claim 42, wherein, The formation of the first modified region of any of the first lines in the first process and the formation of the third modified region in the third process are carried out alternately.

49. The laser processing method according to claim 43, wherein, It also includes: a fourth step, in which multiple fourth modified regions for warpage suppression are formed inside the object by irradiation with the laser, and cracks are formed extending from the fourth modified regions to the first surface that are not continuous with cracks extending from the second modified regions. The formation of the second modified region of any of the second lines in the second process and the formation of the fourth modified region in the fourth process are carried out alternately.

50. The laser processing method according to claim 44, wherein, It also includes: a fourth step, in which multiple fourth modified regions for warpage suppression are formed inside the object by irradiation with the laser, and cracks are formed extending from the fourth modified regions to the first surface that are not continuous with cracks extending from the second modified regions. The formation of the second modified region of any of the second lines in the second process and the formation of the fourth modified region in the fourth process are carried out alternately.

51. The laser processing method according to claim 45, wherein, It also includes: a fourth step, in which multiple fourth modified regions for warpage suppression are formed inside the object by irradiation with the laser, and cracks are formed extending from the fourth modified regions to the first surface that are not continuous with cracks extending from the second modified regions. The formation of the second modified region of any of the second lines in the second process and the formation of the fourth modified region in the fourth process are carried out alternately.

52. The laser processing method according to claim 46, wherein, It also includes: a fourth step, in which multiple fourth modified regions for warpage suppression are formed inside the object by irradiation with the laser, and cracks are formed extending from the fourth modified regions to the first surface that are not continuous with cracks extending from the second modified regions. The formation of the second modified region of any of the second lines in the second process and the formation of the fourth modified region in the fourth process are carried out alternately.

53. The laser processing method according to claim 47, wherein, It also includes: a fourth step, in which multiple fourth modified regions for warpage suppression are formed inside the object by irradiation with the laser, and cracks are formed extending from the fourth modified regions to the first surface that are not continuous with cracks extending from the second modified regions. The formation of the second modified region of any of the second lines in the second process and the formation of the fourth modified region in the fourth process are carried out alternately.

54. The laser processing method according to claim 48, wherein, It also includes: a fourth step, in which multiple fourth modified regions for warpage suppression are formed inside the object by irradiation with the laser, and cracks are formed extending from the fourth modified regions to the first surface that are not continuous with cracks extending from the second modified regions. The formation of the second modified region of any of the second lines in the second process and the formation of the fourth modified region in the fourth process are carried out alternately.

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