Laser processing device, and laser processing method

Abstract

A laser processing device comprising: a light source for emitting laser light; a spatial light modulator for modulating the laser light emitted from the light source; a focusing unit for focusing the laser light that has passed through the spatial light modulator toward a target object; and a processing control unit for performing laser processing to form a modified region on a target object by moving the focusing spot of the laser light relative to the target object and irradiating the laser light onto the target object, wherein the target object comprises a first region and a second region located outside the first region, having a boundary with the first region, when viewed from the Z direction intersecting the incident plane of the laser light on the target object.

Description

Technology Field

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

[0002] Patent Document 1 describes a substrate processing system. In this substrate processing system, a modified layer is first formed in a ring shape by irradiating a laser light along the boundary between the peripheral edge portion and the central portion of the wafer to be removed. Subsequently, a modified surface is formed by irradiating a laser light along the unprocessed surface of the wafer to be processed, which is the surface bonded to the support wafer, and where the device layer is formed. Subsequently, the peripheral edge portion of the wafer to be processed is peeled off and removed starting from the modified layer and a crack extending from the modified layer in the plate thickness direction. At this time, since the modified surface is formed at the interface between the wafer to be processed and the support wafer, the bonding force between the wafer to be processed and the support wafer is reduced, and the peripheral edge portion can be properly removed. After that, finishing grinding is performed on the processed surface of the wafer to be processed. Prior art literature

[0003] Japanese Patent Publication No. 2022-002312 The problem to be solved

[0004] However, when forming a modification region on an object such as the above-mentioned wafer to be processed, if a crack extending from the modification region reaches the bottom surface of the object, such as the above-mentioned unprocessed surface, there is a risk of damage to the device layer formed on the bottom surface or to structures such as other wafers bonded to the bottom surface. Therefore, there is a need to suppress the propagation of cracks so that cracks extending from the modification region do not reach the bottom surface.

[0005] Therefore, the present disclosure aims to provide a laser processing apparatus and a laser processing method capable of suppressing the progression of cracks extending from a modified region. means of solving the problem

[0006] A laser processing device according to the present disclosure [1] comprises a light source that emits laser light, a spatial light modulator for modulating the laser light emitted from the light source, a focusing unit that focuses the laser light passing through the spatial light modulator toward a target object, and a processing control unit that performs laser processing to form a modified area on a target object by moving the laser light's focusing spot relative to the target object and irradiating the laser light onto the target object. The target object includes a first area and a second area located outside the first area, which has a boundary with the first area, when viewed from the Z direction that intersects the incident plane of the laser light on the target object. The processing control unit performs a first processing process of irradiating the laser light onto the target object to form a plurality of first modified areas arranged in the Y direction that intersects the Z direction from the end opposite to the boundary in the second area to the boundary, as the modified area, and after the first processing process, at the boundary, in the Y direction A second processing process is performed by irradiating the laser light onto the object to form a plurality of second modification regions that have an intersecting positional relationship with respect to a plurality of first modification regions listed therein as the modification regions, and in the second processing process, the processing control unit imparts a first aberration to the laser light by modulating the laser light through a spatial light modulator such that a third modification region, which is the second modification region closest to the first modification region among the plurality of second modification regions, becomes elongated in the Z direction, and the third modification region is the second modification region furthest from the incident surface among the plurality of second modification regions, and the first aberration is, when the aberration occurring in the direction of the optical axis of the laser light at the corresponding focusing position due to the focusing of the laser light onto the object by the focusing unit is taken as the reference aberration,A laser processing device having an aberration for forming a long, rectangular focused spot in the Z direction, rather than the focused spot of the laser light to which the corresponding standard aberration is applied.

[0007] A laser processing method according to the present disclosure [6] comprises a processing process for forming a modified region on an object by irradiating the laser light onto the object while moving the laser light collection spot relative to the object, wherein the object comprises a first region and a second region located outside the first region, having a boundary with respect to the first region when viewed from the Z direction that intersects the incident plane of the laser light on the object, and wherein the processing process comprises a first processing process for irradiating the laser light onto the object to form a plurality of first modified regions arranged in the Y direction that intersects the Z direction from the end opposite to the boundary in the second region to the boundary, as the modified region, and a second processing process for irradiating the laser light onto the object after the first processing process, wherein a plurality of second modified regions arranged in the Y direction at the boundary are positionally intersecting with the plurality of first modified regions arranged in the Y direction, as the modified region, wherein in the second processing process, a plurality of the second modified regions A laser processing method that applies a first aberration to the laser light such that the third modified region, which is the second modified region closest to the first modified region, becomes a long, rectangular shape in the Z direction, wherein the third modified region is the second modified region furthest from the incident surface among the plurality of second modified regions, and the first aberration is an aberration that forms a long, rectangular shape in the Z direction of the laser light, such that when the aberration occurring in the direction of the optical axis of the laser light at the corresponding focusing position due to focusing the laser light on the object is used as a reference aberration, the first aberration is an aberration for forming a focused spot that is longer than the focused spot of the laser light to which the reference aberration is applied.

[0008] In this apparatus and method, laser processing is performed on an object comprising a first region and a second region located further outward from the first region, with the boundary between the first region and the first region, when viewed from the Z direction intersecting the laser beam incident plane. Specifically, first, laser light is irradiated to form a plurality of first modified regions arranged in the Y direction intersecting the Z direction, extending from the end opposite to the boundary in the second region to the boundary. Subsequently, laser light is irradiated to form a plurality of second modified regions that are positionally intersecting with the first modified regions arranged in the Y direction at the boundary between the first region and the second region. In particular, when forming the second modified regions, a first aberration is imparted to the laser light by controlling a spatial light modulator to modulate the laser light so that the third modified region, which is the second modified region closest to the first modified region, becomes elongated in the Z direction.

[0009] By this, it is possible to lengthen the third modification region along the optical axis (Z direction) of the laser light. The lengthened third modification region formed in this way has the property that cracks extending from the third modification region are difficult to propagate in the Z direction (i.e., the cracks become short). Because it is difficult for cracks to extend from the third modification region, the propagation of cracks from the third modification region to the bottom surface of the object (the surface opposite to the incident surface) is suppressed.

[0010] Meanwhile, cracks extending from multiple first modified regions arranged in the Y direction may further advance by connecting with cracks extending from other modified regions if another modified region is formed close to the first modified region. In this regard, the second modified region closest to the first modified region is a third modified region where cracks are difficult to extend. In such a case, due to the formation of the third modified region, it is difficult for the phenomenon of cracks extending further from the first modified region to occur. That is, the advancement of cracks from the first modified region to the bottom surface of the object is suppressed. As described above, according to this apparatus and method, it is possible to suppress the advancement of cracks extending from the modified region.

[0011] The laser processing device according to the present disclosure may be [2] the laser processing device described in [1], wherein in the second processing process, the processing control unit irradiates the laser light onto the object such that the third modified region intersects the plurality of first modified regions. In this case, the progression of cracks extending from the first modified region located at the innermost side (first region side) of the object can be reliably suppressed.

[0012] The laser processing device according to the present disclosure may be [3] a laser processing device described in [2], wherein in the second processing step, the processing control unit irradiates the laser light onto the object such that the third modified area is opposite to the incident plane and intersects the plurality of first modified areas, with the center of the Z direction of the third modified area. In this case, most of the area on the incident plane side of the third modified area is located on the incident plane side rather than the first modified area. By doing so, the progression of cracks extending from the first modified area can be reliably suppressed.

[0013] The laser processing device according to the present disclosure may be [4] a laser processing device described in [2] or [3], wherein in the second processing step, the processing control unit irradiates the laser light onto the object such that no crack is included in the area opposite to the incident plane, rather than at the intersection position of the first modified area in the Z direction with the third modified area. In this case, the progression of a crack extending from the first modified area can be more reliably suppressed.

[0014] A laser processing device according to the present disclosure may be [5] a laser processing device described in any of [1] to [4], wherein the boundary comprises an inclined portion that is inclined with respect to the Z direction within a YZ plane including the Z direction and the Y direction, and the processing control unit modulates the laser light by controlling the spatial light modulator so that when forming the modification area in the inclined portion, the beam shape of the laser light at the focusing spot within the YZ plane is inclined along the inclined direction of the inclined portion at least on the incident plane side rather than the center of the focusing spot. In this case, it is possible to form a crack that extends obliquely with respect to the Z direction from the modification area along the inclined boundary. By doing so, it is possible to reduce the impact on structures on the bottom side, such as a device layer or another wafer, compared to the case where the crack extending from the modification area advances along the Z direction and reaches the bottom surface. Effects of the invention

[0015] According to the present disclosure, a laser processing apparatus and a laser processing method capable of suppressing the progression of cracks extending from a modified region can be provided. Brief explanation of the drawing

[0016] FIG. 1 is a schematic diagram showing the configuration of a laser processing device according to one embodiment. Figure 2 is a schematic diagram showing the configuration of the investigation unit illustrated in Figure 1. FIG. 3 is a drawing showing an object to be laser processed according to the present embodiment. Figure 4 is a drawing showing an example of an object depicted in Figure 3. FIG. 5 is a cross-sectional view showing an example of the formation of a modified area and a crack for the object shown in FIG. 4. FIG. 6 is a drawing for explaining a laser processing method according to the present embodiment. FIG. 6 (a) is a plan view, and FIG. 6 (b) is a side view. FIG. 7 is a drawing for explaining a laser processing method according to the present embodiment. FIG. 7 (a) is a cross-sectional view showing a state in which laser light is focused, and FIG. 7 (b) is a cross-sectional view showing a state in which a modified region is formed. FIG. 8 is a drawing for explaining a laser processing method according to the present embodiment. Specifically, it is a schematic cross-sectional view showing a state in which a modified region has been formed. FIG. 9 is a drawing for explaining a laser processing method according to the present embodiment. FIG. 9 (a) is a plan view, and FIG. 9 (b) is a side view. FIG. 10 is a drawing for explaining a laser processing method according to the present embodiment. FIG. 10 (a) is a cross-sectional view showing a state in which laser light is focused, and FIG. 10 (b) is a cross-sectional view showing a state in which a modified region is formed. FIG. 11 is a drawing for explaining a laser processing method according to the present embodiment. Specifically, FIG. 11 is a drawing for explaining aberrations occurring at the focusing position of laser light. FIG. 12 is a drawing for explaining a laser processing method according to the present embodiment. Specifically, FIG. 12 is a drawing showing the intensity and focusing spot of laser light when a plurality of aberrations are applied based on a reference aberration. FIG. 13 is a drawing for explaining a laser processing method according to the present embodiment. FIG. 13 (a) is a cross-sectional view showing a state in which laser light is focused, and FIG. 13 (b) is a cross-sectional view showing a state in which a modified region is formed. FIG. 14 is a drawing for explaining a laser processing method according to a modified example. Specifically, FIG. 14 (a) and (b) are schematic cross-sectional views showing the boundary between the effective area and the removal area in the object. FIG. 15 is a drawing for explaining a laser processing method according to a modified example. Specifically, FIG. 15 is a drawing showing a laser light focusing spot within the YZ plane. FIG. 16 is a drawing for explaining a laser processing method according to a modified example. Specifically, FIG. 16 (a) and (b) are schematic cross-sectional views showing a modified region and a state in which a crack extending obliquely from the modified region is formed. FIG. 17 is a drawing for explaining a laser processing method according to different variations. FIG. 17 (a) is a schematic cross-sectional view showing one example. FIG. 17 (b) is a schematic cross-sectional view showing another example. FIG. 18 is a drawing for explaining a laser processing method according to another variation. Specific details for implementing the invention

[0017] Hereinafter, an embodiment will be described with reference to the drawings. In addition, in each drawing, the same or equivalent parts are denoted by the same reference numerals, and redundant descriptions may be omitted. Also, each drawing may show an orthogonal coordinate system defined by the X-axis, Y-axis, and Z-axis.

[0018] FIG. 1 is a schematic diagram showing the configuration of a laser processing device according to one embodiment. As shown in FIG. 1, the laser processing device (1) is equipped with a stage (support part) (2), an irradiation part (3), a moving part (4, 5), and a control part (processing control part) (6). The laser processing device (1) is a device for forming a modified area (12) on an object (11) by irradiating a laser light (L) onto an object (11).

[0019] The stage (2) supports the object (11) by, for example, holding a film attached to the object (11). The stage (2) can rotate with an axis parallel to the Z direction as the axis of rotation. The stage (2) may be movable along the X direction and the Y direction, respectively. Additionally, the X direction and the Y direction are a first horizontal direction and a second horizontal direction that intersect (orthogonally) each other, and the Z direction is a vertical direction.

[0020] The irradiation unit (3) is intended to irradiate a laser beam (L) onto an object (11) supported on the stage (2). The irradiation unit (3) concentrates a laser beam (L) that is permeable to the object (11) and irradiates it onto the object (11). When the laser beam (L) is concentrated inside the object (11) supported on the stage (2), the laser beam (L) is particularly absorbed in a portion corresponding to the concentration spot (C) of the laser beam (L) (e.g., the center (Ca) shown in FIG. 18), and a modified region (12) is formed inside the object (11). Additionally, the concentration spot (C) is a region within a predetermined range from the position where the beam intensity of the laser beam (L) is highest or the center of gravity of the beam intensity.

[0021] The modified region (12) is a region in which the density, refractive index, mechanical strength, and other physical properties differ from those of the surrounding non-modified region. Examples of the modified region (12) include a melting region, a crack region, an dielectric breakdown region, and a refractive index change region. The modified region (12) may be formed such that cracks extend from the modified region (12) toward the incident side of the laser light (L) and the opposite side. Such modified region (12) and cracks are used, for example, for cutting an object (11).

[0022] For example, by moving the stage (2) along the X direction, the focusing spot (C) is moved relative to the object (11) along the X direction, and a plurality of modification spots (12s) are formed to be arranged in a row along the X direction. One modification spot (12s) is formed by irradiation with a single pulse of laser light (L). A row of modification areas (12) is a collection of a plurality of modification spots (12s) arranged in a row. Adjacent modification spots (12s) may be connected to each other or separated from each other depending on the relative movement speed of the focusing spot (C) relative to the object (11) and the repetition frequency of the laser light (L).

[0023] The moving unit (4) includes a first moving unit (41) that moves the stage (2) in one direction within a plane intersecting (orthogonal) the Z direction, and a second moving unit (42) that moves the stage (2) in another direction within a plane intersecting (orthogonal) the Z direction. As an example, the first moving unit (41) moves the stage (2) along the X direction, and the second moving unit (42) moves the stage (2) along the Y direction. Additionally, the moving unit (4) rotates the stage (2) using an axis parallel to the Z direction as the axis of rotation. The moving unit (5) supports the irradiation unit (3). The moving unit (5) moves the irradiation unit (3) along the X direction, the Y direction, and the Z direction. When the stage (2) and / or the irradiation unit (3) are moved while the laser light (L) is in a state where the light-gathering spot (C) is formed, the light-gathering spot (C) is moved relative to the object (11). That is, the moving part (4, 5) moves at least one of the stage (2) and the irradiation part (3) in order to move the focusing spot (C) of the laser light (L) relative to the object (11).

[0024] The control unit (6) controls the operation of the stage (2), the investigation unit (3), and the movement unit (4, 5). The control unit (6) has a processing unit, a memory unit, and an input receiving unit (not shown). The processing unit is configured as a computer device including a processor, memory, storage, and communication device. In the processing unit, the processor executes software (program) read into memory, etc., and controls the reading and writing of data in memory and storage, as well as communication by the communication device. The memory unit is, for example, a hard disk, and stores various data. The input receiving unit is an interface unit that displays various information and receives input of various information from the user. The input receiving unit is configured as a GUI (Graphical User Interface).

[0025] FIG. 2 is a schematic diagram showing the configuration of the irradiation unit illustrated in FIG. 1. FIG. 2 shows a hypothetical line (A) indicating the planned laser processing. As shown in FIG. 2, the irradiation unit (3) has a light source (31), a spatial light modulator (7), and a focusing lens (focusing unit) (33). The light source (31) outputs laser light (L) by, for example, a pulse oscillation method. Additionally, the irradiation unit (3) may be configured to introduce laser light (L) from outside the irradiation unit (3) without having a light source (31). The spatial light modulator (7) modulates the laser light (L) output from the light source (31). The focusing lens (33) focuses the laser light (L) output from the spatial light modulator (7) (i.e., laser light that has passed through the spatial light modulator (7)) that has been modulated by the spatial light modulator (7) toward the target object (11).

[0026] In the spatial light modulator (7), when a signal indicating a modulation pattern is input from the control unit (6), the modulation pattern is displayed according to the signal. The modulation pattern is intended to modulate the laser light (L). In the spatial light modulator (7), when the modulation pattern is displayed, the laser light (L) is incident from the outside, reflected, and emitted outward, and the laser light (L) is modulated according to the displayed modulation pattern. In this way, according to the spatial light modulator (7), by appropriately setting the displayed modulation pattern, it is possible to modulate the laser light (L) (for example, modulation of the intensity, amplitude, phase, polarization, etc. of the laser light (L)).

[0027] As described above, laser light (L) output from the light source (31) passes through the spatial light modulator (7) and is incident on the focusing lens (33), and is focused within the object (11) by the focusing lens (33), thereby forming a modified area (12) and a crack extending from the modified area (12) in the object (11) at the focused spot (C). Additionally, by the control unit (6) controlling the moving unit (4, 5), the focused spot (C) is moved relative to the object (11), thereby forming a modified area (12) and a crack along the direction of movement of the focused spot (C).

[0028] FIG. 3 is a drawing showing an object for laser processing according to the present embodiment. FIG. 3(a) is a plan view, and FIG. 3(b) is a side view. As shown in FIG. 3, the object (100) includes the object (11) described above and an object (11R) which is a different component from the object (11). The object (11R) is, for example, a silicon wafer. The object (11) includes a first surface (11a) and a second surface (11b) opposite to the first surface (11a). The object (11) includes a plurality of functional elements and a device layer (110) formed on the second surface (11b). The object (11R) includes a plurality of functional elements and a device layer (110R) formed on the first surface (11Ra) of the object (11R). The object (11) and the object (11R) are stacked by arranging the device layer (110) and the device layer (110R) so as to face each other and joining them together, and constitute the object (100).

[0029] The object (11) includes an effective region (first region) (R) and a removal region (second region) (E). The effective region (R) is a portion corresponding to the semiconductor device to be acquired. The effective region (R) here is a disc-shaped portion that includes the central portion of the object (11) when viewed from the Z direction, which is the thickness direction of the object (11). The removal region (E) has a boundary (B) with the effective region (R) and is a region located outside the effective region (R) of the object (11). In this embodiment, the removal region (E) is an outer edge portion other than the effective region (R) of the object (11). The removal region (E) here is a round ring-shaped portion that surrounds the effective region (R).

[0030] In this embodiment, a modified area (12) and a crack extending from the modified area (12) are formed in the boundary (B) between the effective area (R) and the removal area (E), and in the horizontal area extending from the outer edge portion of the removal area (E) (the end opposite to the boundary (B)) to the boundary (B), and a trimming process is performed to cut the removal area (E) of the object (11) using these modified areas (12) and cracks. Accordingly, the boundary (B) is also one of the above lines (A) where laser light (L) is to be irradiated.

[0031] FIG. 4 is a drawing showing an example of an object illustrated in FIG. 3. FIG. 4 (a) is a perspective view with a portion cut away, and FIG. 4 (b) is a schematic cross-sectional view. As shown in FIG. 4, the object (11) is, for example, a crystal orientation <100> It is a wafer (e.g., a silicon wafer). That is, in the object (11), the first surface (11a) (main surface) is the (100) surface. The object (11) is supported on a stage (2) such that the first surface (11a) becomes the incident surface of the laser light (L). The object (11) includes a (110) surface that is orthogonal to the first surface (11a), which is the (100) surface, and a (111) surface that intersects the (110) surface at an angle of 125.25°. The angle between the (111) surfaces extending in the direction of mutual intersecting is 70.5°.

[0032] FIG. 5 is a cross-sectional view showing an example of the formation of a modified region and a crack in an object shown in FIG. 4. As shown in FIG. 5 (a), when a laser light (L) is irradiated onto an object (11) with the first surface (11a), which is the (100) plane, as the incident surface of the laser light (L), thereby forming a plurality of modified regions (12) arranged along the Y direction (i.e., the (100) plane) within the YZ plane, it is preferable to also advance a crack (13) extending from the modified region (12) along the Y direction (i.e., the (100) plane). This is because if the crack (13) extending from the modified area (12) advances obliquely with respect to the (100) plane and reaches, for example, the second plane (11b), there is a risk of adverse effects on the device layer (110) formed on the second plane (11b) or on other objects (11R) joined to the second plane (11b) side through the device layer (110).

[0033] However, the object (11) includes a plane (111) that is easier to cleave than the plane (100). Therefore, as shown in FIG. 5 (b), in practice, when a laser beam (L) is irradiated onto the object (11) with the first plane (11a), which is the plane (100), as the incident plane of the laser beam (L), thereby forming a plurality of modified regions (12) arranged along the Y direction (i.e., the plane (100)) within the YZ plane, cracks (13) extending from the modified regions (12) tend to advance along the plane (111). In this case, there is a risk that the cracks (13) will reach the second plane (11b). Therefore, there is a need to suppress the progression of cracks (13) extending from the modified regions (12) to the second plane (11b). Next, laser processing to suppress the progression of cracks (13) is described.

[0034] FIGS. 6 to 13 are drawings for explaining a laser processing method according to the present embodiment. The laser processing method according to the present embodiment is carried out by the laser processing device (1) described above. Therefore, the laser processing method described below is an example of processing performed by the laser processing device (1). In addition, in the present embodiment, the control unit (6) irradiates the laser light (L) onto the target object (11) while moving the focusing spot (C) of the laser light (L) relative to the target object (11) (processing process). That is, as shown in FIGS. 6 to 8, first, horizontal processing is performed from the end opposite to the boundary (B) of the removal area (E) to the vicinity of the boundary (B) (process S101: first processing process, first processing treatment).

[0035] More specifically, in process S101, first, as shown in FIGS. 6 and 7, the control unit (6) controls the moving unit (4, 5) so that the focusing spot (C) of the laser light (L) is located on one of a plurality of lines (A) that extend in a circular shape concentric with the boundary (B) from the end opposite to the boundary (B) of the removal area (E) to the vicinity of the boundary (B), and the irradiation unit (3) and / or stage (2) are moved so that it is located at a predetermined depth (Z-direction position) from the first surface (11a) of the object (11). Additionally, FIGS. 6 and 7 show an example in which the line (A) coincides with the boundary (B).

[0036] In that state, the control unit (6) controls the moving unit (4) to rotate the stage (2) with an axis parallel to the Z direction as the axis of rotation, and simultaneously controls the light source (31) to initiate the irradiation of the laser light (L) and to move the focused spot (C) of the laser light (L) relative to the object (11) along the line (A). By doing so, a first modification area (121) arranged in a circular shape along the circular line (A) viewed from the Z direction is formed as a modification area (12).

[0037] This process S101 is performed multiple times while sequentially changing the position of the light-gathering spot (C0) in the Y direction, for example, from the end side opposite to the boundary (B) of the removal area (E) toward the boundary (B) side (or from the boundary (B) side toward the end side opposite to the boundary (B) of the removal area (E). That is, laser light (L) is irradiated on each of the multiple lines (A). By this, as shown in FIG. 8, multiple first modification areas (121) arranged in the Y direction within the YZ plane are formed as modification areas (12). That is, here, multiple first modification areas (121) arranged in a two-dimensional shape within a virtual plane (planned slice plane) along the first plane (11a) (XY plane) are formed.

[0038] As described above, in process S101, the control unit (6) performs a process (first processing process) of irradiating laser light (L) onto an object (11) to form a plurality of first modification areas (121) arranged in the Y direction intersecting the Z direction from the end opposite to the boundary (B) in the removal area (E) to the boundary (B), as modification areas (12).

[0039] Next, as illustrated in FIG. 9 and FIG. 13, after the first processing step, laser processing is performed to form a plurality of second modified regions (122) arranged in the Z direction along the boundary (B) within the YZ plane as modified regions (12) (Process S102: second processing step, second processing step). More specifically, in process S102, as illustrated in FIG. 9, first, by controlling the moving unit (4, 5) with the control unit (6), the irradiation unit (3) and / or stage (2) are moved so that the focusing spot (C) of the laser light (L) is located at the boundary (B) and also at a predetermined depth (position in the Z direction) from the first surface (11a) of the object (11).

[0040] In that state, the control unit (6) controls the moving unit (4) to rotate the stage (2) with an axis parallel to the Z direction as the axis of rotation, and simultaneously controls the light source (31) to initiate irradiation of the laser light (L) and to move the focused spot (C) of the laser light (L) relative to the object (11). By doing so, a modified area (12) arranged in a circular shape is formed at the circular boundary (B) when viewed from the Z direction.

[0041] At this time, as illustrated in FIG. 10 (a), the control unit (6) modulates the laser light (L) by controlling the spatial light modulator (7) so that a laser light spot (C1) in the Z direction is formed as a laser light spot (C), compared with the laser light spot (C0) formed when the first modification area (121) is formed in process S101, thereby imparting a first aberration to the laser light (L). By doing so, as illustrated in FIG. 10 (b), a third modification area (123) in the Z direction can be formed as a modification area (12) (and a second modification area (122)) at the boundary (B). That is, in process S102, the control unit (6) performs a process of irradiating laser light (L) onto the object (11) so as to form a third modified area (123) in the Z direction as a modified area (12) at the boundary (B) between the effective area (R) and the removal area (E).

[0042] The first aberration imparted to the laser light in process S102 is described. FIG. 11 is a diagram illustrating the aberration occurring at the focusing position of the laser light. When the laser light (L) is a plane wave (a plane wavefront (phase)), it is geometrically focused at a single point. On the other hand, since the wavefront of the laser light (L) of a plane wave usually changes due to various influences, there are cases where the laser light (L) focused on the object (11) does not focus at a single point, i.e., aberration occurs naturally. The aberration includes, for example, Seidel aberration (astigmatism, coma aberration, spherical aberration, image plane curvature and distortion aberration), and also includes longitudinal aberration, which is an aberration in the longitudinal direction (a direction following the optical axis direction), and transverse aberration, which is an aberration in a direction intersecting the longitudinal direction.

[0043] For example, as illustrated in FIG. 11, when a laser beam (L) is focused onto an object (11) by a focusing lens (33) or the like, when it is incident on the object (11) during the focusing process, spherical aberration naturally occurs in which light rays of different angles of incidence are focused at different locations due to refraction (Snell's Law). That is, as illustrated, due to the laser beam (L) being focused onto the object (11), aberration naturally occurs at the corresponding focusing location without relying on the spatial light modulator (7), and a range of aberration along the optical axis direction (a range in which the intensity of the corresponding laser beam (L) is greater than or equal to the processing threshold value (α)) exists as a reference aberration (H).

[0044] By modulating the laser light (L) containing such a reference aberration (H) using a spatial light modulator (7), it becomes possible to impart an aberration different from the reference aberration (H) to the laser light (L). FIG. 12 is a diagram showing the intensity and focusing spot of the laser light when a plurality of aberrations are imparted based on the reference aberration. The intensity distributions D10, D11, D12, and D13 shown in FIG. 12 represent, in order, the case where a reference aberration H10 corresponding to the reference aberration (H) is imparted, the case where a first aberration H11 with a longer range (negative side) than the reference aberration H10 is imparted, the case where a first aberration H12 with a longer range (more negative side) than the reference aberration H10 is imparted, and the case where a second aberration H13 with a shorter range (positive side) than the reference aberration H10 is imparted. In addition, the concentrating spots C10, C11, C12, and C13 are, for example, regions that are greater than or equal to the processing threshold (α) for each of the corresponding intensity distributions D10, D11, D12, and D13.

[0045] As illustrated in FIG. 12, the control unit (6) can impart a first aberration H11 and H12 to the laser light (L) by controlling the spatial light modulator (7) to modulate the laser light (L), so that a long, narrow-shaped focusing spot C11 and C12 are formed in the Z direction, compared to the focusing spot C10 of the laser light (L) to which a reference aberration H10 is imparted. Examples of such modulation include, for instance, phase modulation that realizes the action of an axicon lens, phase modulation that realizes the action of a diffraction grating, and phase modulation that generates a predetermined spherical aberration. Each of the examples of such phase modulation can be implemented, for instance, by displaying an axicon lens pattern, a diffraction grating pattern, and a predetermined spherical aberration pattern, respectively, as modulation patterns to the spatial light modulator (7).

[0046] As described above, in process S102, the control unit (6) controls the spatial light modulator (7) to modulate the laser light (L) so that when the aberration occurring in the direction of the optical axis of the laser light (L) at the corresponding focusing position is set as a reference aberration H10, the laser light (L) is given a reference aberration H10, and the focusing spots C11 and C12 are formed in the Z direction more elongated than the focusing spot C10 of the laser light (L) to which the reference aberration H10 is given, thereby giving the first aberration H11 and H12 to the laser light (L). By doing so, as shown in FIG. 10 (b), at the boundary (B), a third modified region (123) in the Z direction is formed as a modified region (12) and a second modified region (122).

[0047] It has been confirmed that the third modified region (123), formed in this manner, has a property that makes it difficult for cracks extending from the third modified region (123) to advance in the Z direction (i.e., the cracks become shorter) compared to the modified region (12) formed by a laser light (L) to which, for example, a reference aberration H10 or a second aberration H13 is applied. By this, when the third modified region (123) is formed near another modified region (12), it has the effect of suppressing the cracks extending from the third modified region (123) from connecting to cracks extending from the other modified region (12) and causing further advancement. In other words, as described above, by making the second modification area (122) formed near the first modification area (121) where the progression of the crack (13) extending along the (111) plane is predicted to be such a third modification area (123), it is possible to suppress the progression of the crack (13) extending from the first modification area (121) so that it does not reach the second plane (11b).

[0048] In the subsequent process, laser processing is performed to form a plurality of second modification regions (122) arranged in the Z direction along the boundary (B) within the YZ plane as modification regions (12) (Process S102: second processing process, second processing treatment). More specifically, first, the irradiation unit (3) and / or stage (2) are moved so that the focusing spot (C) of the laser light (L) is located at the boundary (B) and also at a predetermined depth (position in the Z direction) from the first surface (11a) of the object (11) by the control unit (6) controlling the moving unit (4, 5). At this time, as shown in FIG. 13 (a), the position in the Z direction of the focusing spot (C) is positioned closer to the first surface (11a), which is the incident surface of the laser light (L), than the position in the Z direction of the focusing spot (C1) when the third modification region (123) is formed.

[0049] In that state, the control unit (6) controls the moving unit (4) to rotate the stage (2) with an axis parallel to the Z direction as the axis of rotation, and simultaneously controls the light source (31) to initiate irradiation of the laser light (L) and to move the laser light (L) concentration spot (C) relative to the object (11). At this time, the concentration spot (C) becomes a concentration spot (C2) that is shorter in the Z direction than the concentration spot (C1) when the third modification area (123) is formed. By this, at the circular boundary (B) viewed from the Z direction, the second modification area (122) arranged in a circular shape is formed as the modification area (12).

[0050] The formation of this second modified region (122) is carried out multiple times while sequentially changing the position of the light-concentrating spot (C2) in the Z direction from the second surface (11b) side toward the first surface (11a) side. By doing so, a plurality of second modified regions (122) arranged along the Z direction at the boundary (B) within the YZ surface are formed as modified regions (12). The second modified region (122) including the third modified region (123) has an intersecting positional relationship with respect to a plurality of first modified regions (121) arranged in the Y direction. The intersecting positional relationship is a positional relationship in which a virtual line (plane) connecting a plurality of first modification regions and a virtual line (plane) connecting a plurality of second modification regions (122) intersect each other. There may be cases where the plurality of first modification regions (121) and the plurality of second modification regions (122) actually intersect, or cases where they do not intersect (for example, a gap is formed in the Z direction). Additionally, the third modification region (123) becomes the second modification region (122) located closest to the second plane (11b) among the plurality of second modification regions (122).

[0051] As a result of this process S102, a crack (13) is formed that extends across a plurality of second modification regions (122) including a third modification region (123) at the boundary (B). The crack (13) may extend to the first surface (11a). As described above, in process S102, the control unit (6) performs a process (second processing) of irradiating laser light (L) onto the object (11) so as to form a plurality of second modification regions (122) as modification regions (12) that have an intersecting positional relationship with respect to a plurality of first modification regions (121) arranged in the Y direction at the boundary (B). In particular, the control unit (6) modulates the laser light (L) by controlling the spatial light modulator (7) so that the third modification region (133), which is the second modification region (122) closest to the first modification region (121) among the plurality of second modification regions (122), becomes elongated in the Z direction, thereby imparting first aberrations H11 and H12 to the laser light (L).

[0052] In addition, when laser processing is performed by moving the focused spot (C) in a circular direction as in the laser processing method according to the present embodiment, the processing direction (i.e., the circumference direction of the circle) (PD), which is the direction of travel of the focused spot (C), can be set as the X direction, and the direction perpendicular to the processing direction (PD) (i.e., the diameter direction of the circle) can be set as the Y direction.

[0053] As described above, in the laser processing method according to the present embodiment, in process S101, <100> For a wafer-like object (11), a plurality of first modification regions (121) are formed along the Y direction (i.e., plane (100)). Therefore, if another modification region (12) is formed in close proximity to the first modification region (121), there is a risk that a crack (13) extending from the first modification region (121) may further advance along plane (111). In this regard, in the present embodiment, as described above, in process S102, the third modification region (123) on the side of the second plane (11b) is formed to be elongated in the Z direction as the second modification region (122) closest to the first modification region (121) among the plurality of second modification regions (122). In this embodiment, the third modified region (123) is located near the innermost (effective region (R) side) of the first modified region (121) among the plurality of first modified regions (121) arranged in the Y direction. Therefore, when the third modified region (123) is formed, the crack extending from the third modified region (123) is connected to the crack (13) extending from the corresponding first modified region (121), thereby preventing further progression along the (111) surface of the crack (13).

[0054] In addition, in the laser processing device (1) according to the present embodiment, processing conditions can be set as follows for each of the formation of the first modification region (121), the formation of the second modification region (122), and the formation of the third modification region (123).

[0055] Formation of the first modification region (121): wavelength of laser light (L) 1099 nm, frequency 60 kHz, pulse width 45 nsec, output 0.14 W, relative movement speed of the focusing spot (C) 300 mm / sec, spacing of the line (A) in the Y direction 5 μm, and aberration correction to remove spherical aberration of Si.

[0056] Formation of the second modification region (122): wavelength of laser light (L) 1099 nm, frequency 120 kHz, pulse width 700 nsec, output 3 W, relative movement speed of the focusing spot (C) 800 mm / sec, and aberration correction to remove spherical aberration of Si.

[0057] Formation of the third modified region (123): wavelength of the laser light (L) is 1099 nm, frequency is 60 kHz, pulse width is 45 nsec, output is 1.5 W, relative movement speed of the focusing spot (C) is 300 mm / sec, and aberration correction is performed to remove the spherical aberration of Si. Aberration is imparted so that a focusing region with a longer shape than the focusing region at the reference aberration is formed.

[0058] As described above, in the laser processing apparatus (1) and laser processing method according to the present embodiment, laser processing is performed on an object (11) that includes an effective area (R) and a boundary (B) between the effective area (R) and a removal area (E) located outside the effective area (R), when viewed from the Z direction intersecting the first surface (11a) which is the laser light incident surface. That is, first, a laser light (L) is irradiated to form a plurality of first modification areas (121) arranged in the Y direction intersecting the Z direction, extending from the end opposite to the boundary (B) in the removal area (E) to the boundary (B).

[0059] Next, laser light (L) is irradiated to form a plurality of second modification regions (122) that intersect with the first modification regions (121) arranged in the Y direction at the boundary (B) between the effective region (R) and the removal region (E). In particular, when forming the second modification regions (122), the laser light (L) is modulated by controlling the spatial light modulator (7) so that the third modification region (123), which is the second modification region (122) closest to the first modification region (121), becomes elongated in the Z direction, thereby imparting first aberrations H11 and H12 to the laser light (L).

[0060] By this, it is possible to lengthen the third modified region (123) in the direction of the optical axis (Z direction) of the laser light (L). The lengthened third modified region (123) formed in this way has the property that cracks extending from the third modified region (123) are difficult to advance in the Z direction (i.e., the cracks become short). Because of this, since it is difficult for cracks to extend from the third modified region (123), the progression of cracks from the third modified region (123) to the bottom surface of the object (the second surface (11b) opposite to the incident surface) is suppressed.

[0061] Meanwhile, cracks (13) extending from multiple first modified regions (121) arranged in the Y direction may further advance by connecting with cracks extending from other modified regions (12) when another modified region (12) is formed close to the first modified region (121). In this regard, the second modified region (122) closest to the first modified region (121) is a third modified region (123) where cracks are difficult to extend. In this case, due to the formation of the third modified region (123), it is difficult for the phenomenon of cracks (13) extending from the first modified region (121) to further advance to occur. That is, the advancement of cracks (13) from the first modified region (121) to the bottom surface of the object (11) is suppressed. As described above, the advancement of cracks (13) extending from the modified region (12) is suppressed.

[0062] The above embodiments describe one aspect of a laser processing apparatus and a laser processing method according to the present disclosure. Accordingly, the present disclosure is not limited to what has been described above and may be modified at will. Modified examples will be described below.

[0063] FIG. 14 is a drawing for explaining a laser processing method according to a modified example. As shown in FIG. 14, the boundary (B) between the effective area (R) and the removal area (E) may include an inclined portion (B1) that is inclined with respect to the Z direction within the YZ plane. In the example of FIG. 14 (a), a part of the boundary (B) on the second plane (11b) side is the inclined portion (B1). In the example of FIG. 14 (b), the entire boundary (B) is the inclined portion (B1). Thus, when the boundary (B) includes the inclined portion (B1), when forming the modification area (12) in the inclined portion (B1), there is a requirement to form a crack (13) that extends obliquely along the inclined portion (B1) (with respect to the Z direction) from the modification area (12).

[0064] Thus, the control unit (6) can modulate the laser light (L) by controlling the spatial light modulator (7) so that when forming a modified region (12) in the inclined portion (B1) during the second forming process (process S102) as shown in FIG. 15, the beam shape of the laser light (L) at the concentrating spot (C) in the YZ plane is inclined in the inclined direction of the inclined portion (B1) (here, in the Y minus direction) at least on the side of the incident plane (first plane (11a)) rather than the center (Ca) of the concentrating spot (C).

[0065] Various methods can be conceived and any method can be selected as a method for modulating such laser light (L), but examples include a method of offsetting the center of a spherical aberration correction pattern in an inclined direction with respect to the center of the incident plane of a focusing lens (33), a method of controlling the magnitude of coma aberration in a coma aberration pattern for imparting coma aberration to the laser light (L), or a method of modulating the laser light (L) by a modulation pattern that is asymmetric with respect to an axis line along the X direction of processing progress.

[0066] By controlling the shape of the light-concentrating spot (C) as described above, as shown in FIG. 16 (a), it is possible to form a third modified region (123) in process S102, and also to form a crack (13a) that extends obliquely along the inclined portion (B1) between the third modified region (123) and the second modified region (122) closest to the third modified region (123). In addition, in the example of FIG. 16 (a), in process S102, a second modified region (122) arranged in the Z direction is formed without inclining the light-concentrating spot (C), thereby forming a crack (13b) that extends in the Z direction from the second modified region (122).

[0067] Meanwhile, in the example of FIG. 16 (b), in process S102, the concentrating spot (C) is inclined, and a plurality of second modified regions (122) and third modified regions (123) are formed along the entire boundary (B) inclined with respect to the Z direction, thereby forming a crack (13a) that extends in an inclined direction with respect to the Z direction along the entire boundary (B). In this way, by forming a crack (13a) that extends obliquely with respect to the Z direction from the modified region (12) along the inclined boundary (B), it is possible to reduce the impact on structures on the bottom side, such as the device layer (110, 110R) or other objects (11R), compared to the case where the crack (13) extending from the modified region (12) advances along the Z direction and reaches the bottom surface (second surface (11b)).

[0068] FIGS. 17 and 18 are drawings for explaining a laser processing method according to a different variant. As shown in FIG. 17 (a), within the YZ plane, the first modified region (121) arranged in the Y direction may be formed inward (effective region (R) side) within, for example, within a range of 1 mm from the second modified region (122) arranged in the Z direction along the boundary (B). In this case, the line (A) when forming the innermost first modified region (121) is located inward from the boundary (B). Also, as shown in FIG. 17 (b), within the YZ plane, the first modified region (121) arranged in the Y direction and the second modified region (122) arranged in the Z direction along the boundary (B) may be spaced apart with respect to the Z direction, for example, with an unmodified region within 50 μm.

[0069] Additionally, as illustrated in FIG. 18, within the YZ plane, a first modification area (121) arranged in the Y direction and a plurality of second modification areas (122) arranged in the Z direction may actually intersect. In the illustrated example, the first modification area (121) arranged in the Y direction and the third modification area (123) intersect. That is, along the Y direction, the first modification area (121) and the third modification area (123) overlap. In this way, the control unit (6) may irradiate a laser light (L) onto the object (11) in process S101 so that the third modification area (123) intersects the plurality of first modification areas (121). In this case, the progression of the crack (13) extending from the first modification area (121) located at the innermost side (effective area (R) side) of the object (11) can be reliably suppressed.

[0070] In addition, at this time, the control unit (6) may irradiate the object (11) with a laser light (L) such that the third modification area (123) is located on the opposite side of the incident plane (first plane (11a)) from the center of the Z direction of the third modification area (123) and intersects the first modification area (121). In this case, most of the area on the incident plane side of the third modification area (123) is located on the incident plane side more than the first modification area (121). By doing so, the progression of the crack (13) extending from the first modification area (121) can be reliably suppressed.

[0071] In addition, at this time, the control unit (6) may irradiate the object (11) with laser light (L) so that cracks are not included in the area opposite to the incident surface (first surface (11a)) compared to the Z-direction intersection position with the first modification area (121) in the third modification area (123). In this case, the progression of cracks (13) extending from the first modification area (121) can be suppressed more reliably. In addition, for example, the first modification area (121) that is the innermost (effective area (R) side) among the plurality of first modification areas (121) may be in contact (overlapping) with the third modification area (123).

[0072] Although various modified examples have been described above, these modified examples and embodiments may be applied in any combination. For example, in an example of forming a crack (13a) that extends obliquely with respect to the Z direction, the first modified region (121) and the third modified region (123) may be formed to intersect.

[0073] In addition, any modification other than the above modification example may be additionally applied. For example, in the above embodiment and modification example, an example of processing based on the boundary (B) between the effective area (R) and the removal area (E) in the trimming process was described, but in processing based on the boundary between any first area and a second area outside the first area in the object, the laser processing device (1) and laser processing method according to the above embodiment and modification example may be applied. Furthermore, the object (11) for laser processing is not limited to being joined to another object (11R). Explanation of the symbols

[0074] 1… Laser processing device 6… Control unit 7… Spatial optical modulator 11… object 11a… First plane (plane of incidence) 11b… Second side (bottom) 12… modification zone 13, 13a, 13b… cracks 31… light source 33… Concentrating lens (concentrating part) 121… 1st Reforming Zone 122… 2nd reforming zone 123… Third modification zone L… Laser light H, H10… Reference Water Cycle H11, H12… 1st water turbine

Claims

Claim 1 A light source for emitting laser light, a spatial light modulator for modulating the laser light emitted from the light source, a focusing unit for focusing the laser light that has passed through the spatial light modulator toward a target object, and a processing control unit for performing laser processing to form a modification area on a target object by moving the focused spot of the laser light relative to the target object and irradiating the laser light onto the target object, wherein the target object comprises a first area when viewed from the Z direction intersecting the incident plane of the laser light on the target object, and a second area having a boundary with the first area and located further outward from the first area, wherein the processing control unit comprises a first processing process of irradiating the laser light onto the target object to form a plurality of first modification areas arranged in the Y direction intersecting the Z direction from the end opposite to the boundary in the second area to the boundary, and a position intersecting the plurality of first modification areas arranged in the Y direction at the boundary after the first processing process A second processing process is performed by irradiating the laser light onto the object to form a plurality of related second modification regions as the modification regions, and in the second processing process, the processing control unit imparts a first aberration to the laser light by modulating the laser light through a spatial light modulator such that a third modification region, which is the second modification region closest to the first modification region among the plurality of second modification regions, becomes elongated in the Z direction, wherein the third modification region is the second modification region furthest from the incident plane among the plurality of second modification regions, and the first aberration is, when the aberration occurring in the direction of the optical axis of the laser light at the focusing position due to the focusing of the laser light onto the object by the focusing unit is taken as the reference aberration,A laser processing device having an aberration for forming a long, rectangular focused spot in the Z direction, rather than the focused spot of the laser light to which the above reference aberration is applied. Claim 2 A laser processing device according to claim 1, wherein in the second processing step, the processing control unit irradiates the laser light onto the object such that the third modification area intersects the plurality of first modification areas. Claim 3 A laser processing device according to claim 2, wherein in the second processing step, the processing control unit irradiates the laser light onto the object such that the third modification area intersects a plurality of the first modification areas on the side opposite to the incident plane, rather than the center of the Z direction of the third modification area. Claim 4 A laser processing device according to claim 2 or claim 3, wherein in the second processing step, the processing control unit irradiates the laser light onto the object such that no crack is included in the area opposite to the incident surface, compared to the Z-direction intersection position with the first modified area in the third modified area. Claim 5 A laser processing apparatus according to any one of claims 1 to 4, wherein the boundary comprises an inclined portion inclined with respect to the Z direction within a YZ plane including the Z direction and the Y direction, and the processing control unit modulates the laser light by controlling the spatial light modulator such that, when forming the modification region in the inclined portion, the beam shape of the laser light at the focusing spot within the YZ plane is inclined along the inclined direction of the inclined portion at least on the incident plane side rather than the center of the focusing spot. Claim 6 A processing process is provided for forming a modification region on an object by irradiating the object with the laser light while moving the focused spot of the laser light relative to the object, wherein the object comprises a first region and a second region located outside the first region, having a boundary with respect to the first region when viewed from the Z direction intersecting the incident plane of the laser light on the object, and wherein the processing process comprises a first processing process for irradiating the laser light on the object to form a plurality of first modification regions arranged in the Y direction intersecting the Z direction as the modification region, extending from the end opposite to the boundary in the second region to the boundary, and a second processing process for irradiating the laser light on the object after the first processing process to form a plurality of second modification regions as the modification region, having a positional relationship intersecting with the plurality of first modification regions arranged in the Y direction at the boundary, wherein in the second processing process, the second A laser processing method comprising: applying a first aberration to the laser light such that a third modified region, which is a modified region, becomes a long, rectangular shape in the Z direction; wherein the third modified region is the second modified region furthest from the incident surface among a plurality of second modified regions; and wherein the first aberration is an aberration for forming a long, rectangular shape in the Z direction of the laser light, such that when the aberration occurring in the direction of the optical axis of the laser light at the focusing position due to focusing the laser light on the object is used as a reference aberration, the first aberration is an aberration for forming a focused spot that is longer than the focused spot of the laser light to which the reference aberration is applied.

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