Laser processing device

Abstract

To provide a laser processing device that can further improve processing accuracy, in performing punching processing for forming a punched groove (a divided grove) between two edge-cut grooves by laser light, along a street of a semiconductor wafer.SOLUTION: A laser processing device is provided with: a laser light source 22; a first light forming element 32 that forms first laser light L2 having an arbitrary spot shape, from laser light L1 emitted from the laser light source 22; a second light forming element 33 that forms second laser light L3 having a spot shape expanded and contracted in one direction that is perpendicular to an optical axis, from the first laser light L2 and enables a length of the expansion / contraction to be changed; and a light condensing lens 40A that makes the second laser light L3 emitted from the second light forming element 33 condense on a wafer.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a laser processing device. [Background technology]

[0002] In recent years, in the field of semiconductor device manufacturing, wafers (semiconductor wafers) have become known in which multiple devices are formed by stacking, for example, a low-dielectric-constant insulating film (low-k film) made of a glassy material and a functional film that forms a circuit on the surface of a substrate such as silicon. In such wafers, multiple devices are partitioned in a lattice pattern by lattice-like streets, and individual devices are manufactured by dividing the wafer along the streets.

[0003] Known methods for dividing a wafer into multiple devices (chips) include using a high-speed rotating blade and forming laser-processed areas along the streets inside the wafer and then applying an external force along the streets whose strength has been reduced by the laser-processed areas. However, for example, in the case of wafers with low-k films, the former method makes it difficult to simultaneously cut the insulating film and the substrate with a blade because the low-k film and the wafer are made of different materials. Furthermore, the latter method makes it difficult to divide the wafer into individual devices with good quality when low-k films are present on the streets. This problem can occur not only with low-k films but also with films made of other materials.

[0004] Therefore, Patent Documents 1 and 2 describe a laser processing device that performs edge cutting processing to form two edge cutting grooves (blocking grooves) along the streets of a wafer, and core cutting processing to form a core cutting groove (division groove) between the two edge cutting grooves. This laser processing device removes low-k films and the like by simultaneously forming (parallel forming) two edge cutting grooves and a core cutting groove along the same street using the laser optical system while moving the laser optical system relative to the wafer in one direction in the processing feed direction (for example, the forward direction).

[0005] In Patent Documents 1 and 2, the grooves are formed by irradiating a laser beam adjusted to form a rectangular spot. However, the width of the grooves may need to be changed to accommodate changes in the specifications of the semiconductor wafer. In this case, it is necessary to adjust the shape of the laser beam spot, particularly the width. In Patent Documents 1 and 2, the shape of the laser beam spot is rotated around the optical axis of the laser beam, thereby adapting to changes in the width of the grooves. However, in Patent Documents 1 and 2, an optical element known as a light forming element needs to be mechanically rotated to rotate the shape of the spot. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-71402 [Patent Document 2] Patent Publication No. 2021-192922 Summary of the Invention [Problem to be solved by the invention]

[0007] As explained above, when performing a core cutting process to form a core cut groove (division groove) between two edge cutting grooves along the streets of a semiconductor wafer, the width dimension of the core cut groove may be changed in accordance with changes in the specifications of the semiconductor wafer. In Patent Documents 1 and 2, by mechanically rotating an optical element called a light forming element, the shape of the laser light spot is rotated, making it possible to form the desired core cut groove. While the resulting processing accuracy is sufficient, further improvements in processing accuracy are desired as semiconductors become increasingly miniaturized.

[0008] The present invention has been made in consideration of the above circumstances, and its object is to provide a laser processing device that enables further improvement in processing accuracy when performing a hollowing process in which a hollow groove (division groove) is formed between two edge-cutting grooves along the streets of a semiconductor wafer using laser light. [Means for solving the problem]

[0009] [1] a laser light source; a first light forming element that forms a first laser light having an arbitrary spot shape from the laser light emitted from the laser light source; a second light forming element that forms a second laser light having a spot shape expanded or contracted in one direction perpendicular to an optical axis from the first laser light, and that makes the length of the expansion or contraction variable; a condenser lens that condenses the second laser light emitted from the second light forming element onto a wafer; A laser processing device comprising: [2] The laser processing device according to [1], wherein the second light forming element is any one of a cylindrical lens group, a cylindrical mirror group, and a deformable mirror group. [3] The laser processing device according to [1], wherein the first light forming element is any one of a diffractive optical element, a refractive optical element, a reflective liquid crystal spatial light modulator, and a cylindrical lens. [4] The laser processing device according to [1], wherein the first light forming element generates a first laser beam having a linear spot shape parallel to the one direction. [5] The laser processing device is a laser processing device that performs, for each street, an edge cutting process that forms two parallel first grooves along the street of the wafer, and a hollowing process that forms a second groove between the two first grooves, The laser processing device according to [1], wherein hollowing is performed using the second laser beam. [Effects of the Invention]

[0010] According to the present invention, a laser processing device can be provided that enables further improvement in processing accuracy when performing hollowing processing in which a hollow groove (division groove) is formed between two edge-cutting grooves along the streets of a semiconductor wafer using laser light. [Brief explanation of the drawings]

[0011] [Figure 1]1 is a schematic diagram of a laser processing apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a plan view of a wafer to be processed by the laser processing device. [Figure 3] FIG. 10 is an explanatory diagram for explaining laser processing along odd-numbered streets. [Figure 4] FIG. 10 is an explanatory diagram for explaining laser processing along even-numbered streets. [Figure 5] 10 is an explanatory diagram for explaining edge cutting and hollowing by a laser optical system that is moved relatively in the forward direction with respect to the wafer. FIG. [Figure 6] 10 is an explanatory diagram for explaining edge cutting and hollowing by a laser optical system that is moved relatively in the backward direction with respect to the wafer. FIG. [Figure 7] 1 is a perspective schematic view showing a laser optical system of a laser processing apparatus according to an embodiment of the present invention. [Figure 8] 1 is a plan view schematically illustrating a laser optical system of a laser processing apparatus according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Figure 1 is a schematic diagram of a laser processing apparatus 10 according to an embodiment of the present invention. As shown in Figure 1, the laser processing apparatus 10 performs laser processing (ablation groove processing) on ​​a wafer 12 as a pre-process before dividing the wafer 12 into a plurality of chips 14 (see Figure 2). Note that the X, Y, and Z directions in the figure are mutually orthogonal, with the X and Y directions being horizontal directions and the Z direction being the up-down direction. Here, the X direction corresponds to the processing feed direction.

[0013] Fig. 2 is a plan view of a wafer 12 to be processed by the laser processing apparatus 10. As shown in Fig. 2, the wafer 12 is a laminate in which, for example, a low-k film and a functional film forming a circuit are laminated on the surface of a substrate such as silicon. The wafer 12 is divided into a plurality of regions by a plurality of streets C (planned division lines) arranged in a grid pattern. Devices 16 that constitute chips 14 are provided in each of these divided regions.

[0014] The laser processing apparatus 10 removes low-k films and the like on the substrate by performing laser processing (ablation groove processing) on ​​the wafer 12 along each street C, as indicated by the parenthesized numbers (1) to (4), ... in the figure.

[0015] At this time, in order to reduce the takt time required for laser processing of the wafer 12, the laser processing apparatus 10 may alternately switch the relative movement direction when moving the laser optical system 24 (described later) relative to the wafer 12 in the X direction for each street C.

[0016] For example, when laser processing is performed along odd-numbered streets C indicated by parenthesized numbers (1), (3), etc. in the figure, the laser optical system 24, which will be described later, is moved relative to the wafer 12 in the forward direction X1 (see FIG. 5), which is one side in the X direction. When laser processing is performed along even-numbered streets C indicated by parenthesized numbers (2), (4), etc. in the figure, the laser optical system 24 is moved relative to the wafer 12 in the backward direction X2 (see FIG. 6), which is the other side in the X direction.

[0017] Fig. 3 is an explanatory diagram for explaining laser processing along odd-numbered streets C. Fig. 4 is an explanatory diagram for explaining laser processing along even-numbered streets C.

[0018] 3 and 4, in this embodiment, edge cutting and hollowing are performed simultaneously (in parallel) as laser processing. The edge cutting is performed using two laser beams L4, and forms two parallel edge cutting grooves 18 along the street C.

[0019] The hollowing out process is laser processing performed using one laser beam L3 (second laser beam) having a larger diameter than the two laser beams L4 used for the edge cutting process, and forms a hollowing out groove 19 (an ablation groove corresponding to the second groove of the present invention) between the two edge cutting grooves 18 formed by the edge cutting process. Note that the two edge cutting grooves 18 and the hollowing out groove 19, which are ablation grooves, are publicly known techniques, and therefore detailed description thereof will be omitted (see JP 2009-182019 A, etc.).

[0020] In this way, in the laser processing apparatus 10 of this embodiment, whether the laser optical system 24 described below is moved relative to the wafer 12 in the forward direction X1 (see Figure 5) or in the return direction X2 (see Figure 6), the edge cutting process is performed before the hollowing process.

[0021] Returning to FIG. 1, the laser processing apparatus 10 includes a table 20, a laser light source 22, a laser optical system 24, a microscope 26, a relative movement mechanism 28, and a control device 30.

[0022] The table 20 holds the wafer 12. Under the control of the control device 30, the table 20 is moved by a relative movement mechanism 28 in the X direction, which is the processing feed direction parallel to the street C of the processing target, and is rotated around a central axis (rotation axis) of the table 20 parallel to the Z direction.

[0023] The laser light source 22, together with the laser optical system 24 described below, constitutes the laser optical system of the present invention. This laser light source 22 constantly emits laser light L under conditions (wavelength, pulse width, repetition frequency, etc.) suitable for both edge cutting processing and hollow cutting processing. The laser light L emitted from the laser light source 22 enters the laser optical system 24.

[0024] The laser optical system 24 (also referred to as a laser unit), which will be described in detail later, splits the laser light L from the laser light source 22 into two laser lights L4 for edge cutting and one laser light L3 (second laser light) for core cutting. The laser optical system 24 then emits (irradiates) the two laser lights L4 for edge cutting from a first condenser lens 38 toward the street C. Under the control of the control device 30, the laser optical system 24 also adjusts the spot shape of the one laser light L3 for core cutting to a shape suitable for core cutting, and adjusts the dimension of the spot shape in the groove width direction (Y direction) of the core cut groove 19 to match the groove width of the core cut groove 19. Under the control of the control device 30, the laser optical system 24 also selectively emits (irradiates) the one laser light L3 for core cutting from two second condenser lenses 40A, 40B toward the street C.

[0025] Moreover, the laser optical system 24 is moved in the Y and Z directions by a relative movement mechanism 28 under the control of the control device 30.

[0026] The microscope 26 is fixed to the laser optical system 24 and moves integrally with the laser optical system 24. The microscope 26 photographs an alignment reference (not shown) formed on the wafer 12 before edge cutting and hollowing processing of the wafer 12. The microscope 26 also photographs the two edge cutting grooves 18 and hollowing groove 19 formed along the street C by the edge cutting and hollowing processing. The photographed image (image data) taken by the microscope 26 is output to the control device 30, and is displayed by the control device 30 on a monitor (not shown).

[0027] The relative movement mechanism 28 is composed of an XYZ actuator, a motor, etc. (not shown), and under the control of the control device 30, moves the table 20 in the X direction and rotates it about the rotation axis, and moves the laser optical system 24 in the Y and Z directions. This allows the relative movement mechanism 28 to move the laser optical system 24 relative to the table 20 and the wafer 12 held on the table 20. Note that instead of moving the table 20 in the X direction and moving the laser optical system 24 in the Y and Z directions, for example, the laser optical system 24 may be moved in the Z direction and the table 20 in the X and Y directions. The method of relative movement is not particularly limited as long as it allows the laser optical system 24 to be moved relative to the table 20 (wafer 12) in each direction (including rotation).

[0028] By driving the relative movement mechanism 28, it is possible to repeatedly align the laser optical system 24 with the processing start position, which is one end of the street C to be processed, and relatively move the laser optical system 24 in the X direction [the forward direction side X1 (see FIG. 5) or the backward direction side X2 (see FIG. 6)] along the street C. In addition, by driving the relative movement mechanism 28 to rotate the table 20 by 90°, it is possible to make each street C along the Y direction of the wafer 12 parallel to the X direction, which is the processing feed direction.

[0029] The control device 30 is configured by a computing device such as a personal computer, and includes a computing circuit configured by various processors, memories, etc. The various processors include a central processing unit (CPU), a graphics processing unit (GPU), an application specific integrated circuit (ASIC), and a programmable logic device (e.g., simple programmable logic device (SPLD), complex programmable logic device (CPLD), and field programmable gate array (FPGA)). The various functions of the control device 30 may be realized by a single processor, or by multiple processors of the same or different types.

[0030] The control device 30 comprehensively controls the operations of the laser light source 22, the laser optical system 24, the microscope 26, and the relative movement mechanism 28.

[0031] [Laser optics] Fig. 5 is an explanatory diagram for explaining edge cutting and hollow cutting by the laser optical system 24 that is moved relatively in the outgoing direction side X1 with respect to the wafer 12. Fig. 6 is an explanatory diagram for explaining edge cutting and hollow cutting by the laser optical system 24 that is moved relatively in the return direction side X2 with respect to the wafer 12. Hereinafter, odd-numbered streets C that are the processing target of the laser optical system 24 that is moved relatively in the outgoing direction side X1 with respect to the wafer 12 will be referred to as the "outgoing path" as appropriate, and even-numbered streets C that are the processing target of the laser optical system 24 that is moved relatively in the return direction side X2 with respect to the wafer 12 will be referred to as the "returning path" as appropriate.

[0032] As shown in Figures 5 and 6, the laser optical system 24 includes at least a branching element 31, a first light forming element 32, a second light forming element 33, a third light forming element 34, a connection switching element 36, a first focusing lens 38, and two second focusing lenses 40A and 40B.

[0033] A half mirror or the like is used as the branching element 31. The branching element 31 branches the laser light L emitted from the laser light source 22 into two laser lights L1 and L5, and emits one laser light L1 to the first light forming element 32 and the other laser light L5 to the third light forming element 34. Note that the branching ratio of "two-way branching" in this specification is not limited to 50:50 and can be changed as appropriate.

[0034] The first light forming element 32 forms a first laser light L2 having an arbitrary spot shape from the laser light L1 emitted from the laser light source 22. For example, a diffractive optical element (DOE), a refractive optical element (ROE), a spatial light modulator, or a cylindrical lens can be used as the first light forming element 32. For example, an LCOS (liquid crystal on silicon) can be used as the spatial light modulator.

[0035] The second light forming element 33 may be, for example, a group of cylindrical lenses, a group of cylindrical mirrors, or a group of deformable mirrors. The second light forming element 33 forms, from the first laser light L2 emitted from the first light forming element 32, a second laser light L3 having a spot shape expanded or contracted in one direction perpendicular to the optical axis and corresponding to the hollowing process. The second laser light L3 is a laser light whose Y-direction length of the spot shape at the focal position of the condenser lens 40 is longer than the Y-direction length of the spot shape at the focal position when the second light forming element 33 is not installed. Alternatively, the second laser light L3 may be a laser light whose Y-direction length of the spot shape at the focal position of the condenser lens 40 is shorter than the Y-direction length of the spot shape at the focal position when the second light forming element 33 is not installed. The second light forming element 33 is also capable of changing the Y-direction length of the spot shape of the second laser light L3. That is, the second laser light L3 forms one rectangular (or other shape such as circular) spot (see FIG. 8) between the two edge-cutting grooves 18 on the wafer 12, and the width of this spot in the Y direction is adjusted by the second light forming element 33 to match the spacing between the two edge-cutting grooves 18. Then, the second light forming element 33 emits the formed second laser light L3 to the connection switching element 36.

[0036] The connection switching element 36, together with the branching element 31 and the like, constitutes the connection optical system of the present invention. For example, a known optical switch or various optical elements (such as a half-wave plate and a polarizing beam splitter, a half mirror and a shutter) can be used as this connection switching element 36. Under the control of the control device 30, the connection switching element 36 selectively guides the second laser light L3 emitted from the second light forming element 33 to the second focusing lenses 40A, 40B.

[0037] Next, for example, a diffractive optical element (DOE) is used for the third light forming element 34. This third light forming element 34 converts the laser light L5 into two laser light beams L4 corresponding to the edge cutting process, and emits the two laser light beams L4 toward the first condenser lens 38. As a result, the two laser light beams L4 are focused on the street C (outward and return paths) by the first condenser lens 38, and two spots (also referred to as focused points or processing points) spaced apart in the Y direction are formed on the street C. Although not shown, the optical paths of the two laser light beams L4 from the third light forming element 34 to the first condenser lens 38 (including various optical elements provided on the optical paths) constitute a part of the connection optical system of the present invention.

[0038] The first condenser lens 38 and the second condenser lenses 40A, 40B are arranged in a row along the X direction (processing feed direction). The first condenser lens 38 is arranged between the second condenser lenses 40A and 40B. The second condenser lens 40A is arranged on the backward direction side X2 relative to the first condenser lens 38. The second condenser lens 40B is arranged on the forward direction side X1 relative to the first condenser lens 38.

[0039] The first condenser lens 38 condenses the two laser beams L4 incident from the third light forming element 34 onto street C (outward path and return path). The second condenser lens 40A condenses the second laser beam L3 incident from the connection switching element 36 onto street C (outward path). The second condenser lens 40B condenses the second laser beam L3 incident from the connection switching element 36 onto street C (return path).

[0040] 5, when the relative movement mechanism 28 moves the laser optical system 24 relative to the wafer 12 in the forward direction X1, the connection switching element 36 guides the second laser beam L3 emitted from the second light forming element 33 to the second condenser lens 40A. This causes the second laser beam L3 to be condensed on the street C (forward path) by the second condenser lens 40A. As a result, the relative movement of the laser optical system 24 in the forward direction X1 causes edge cutting processing to be performed first along the street C (forward path), forming two edge cutting grooves 18, and then causes center cutting processing to be performed, forming a center cutting groove 19 between the two edge cutting grooves 18.

[0041] 6, when the relative movement mechanism 28 moves the laser optical system 24 relative to the wafer 12 in the return direction side X2, the connection switching element 36 guides the second laser beam L3 emitted from the second light forming element 33 to the second condenser lens 40B. This causes the second laser beam L3 to be condensed on street C (return direction) by the second condenser lens 40B. As a result, the relative movement of the laser optical system 24 in the return direction side X2 causes edge cutting processing to be performed first along street C (return direction), forming two edge cutting grooves 18, and then causes center cutting processing to be performed, forming a center cutting groove 19 between the two edge cutting grooves 18.

[0042] A specific example of the laser optical system 24 in which a diffractive optical element DOE is used as the first light forming element 32 and a cylindrical lens group is used as the second light forming element 33 will be described below.

[0043] 7 and 8, the laser beam L1 emitted from the branching element 31 has a spot shape S1 that is approximately circular and is substantially parallel. Furthermore, the focal length of the X-direction component of the laser beam L1 is the same as the focal length of the Y-direction component. Therefore, for example, when the laser beam L1 is converged by a general focusing lens, the resulting spot shape is similar to the spot shape S1, i.e., is substantially circular.

[0044] The laser light L1 emitted from the branching element 31 is incident on the first light forming element 32 (diffractive optical element (DOE)). When a reflective liquid crystal on silicon (LCOS) spatial light modulator is used as the first light forming element 32, the laser light L1 incident on the element is reflected by the LCOS and emitted as reflected light as first laser light L2, the focal length of which is different between the X-direction component and the Y-direction component. As a result, for example, when the first laser light L2 is a laser light whose focal length in the Y-direction component is longer than that in the X-direction component, if the first laser light L2 is converged by a general focusing lens, the X-direction component is converged at the focal position of the focusing lens, but the Y-direction component is not completely converged. Therefore, when the first laser light L2 is converged by a general focusing lens, the spot shape at the focal position of the lens becomes a shape elongated in the Y direction compared to the spot shape S1. That is, the first light forming element 32 generates the first laser light L2 having a linear spot shape parallel to the Y direction.

[0045] The first laser beam L2 emitted from the first light forming element 32 is incident on the cylindrical lens group that constitutes the second light forming element 33. As shown in FIGS. 7 and 8, the cylindrical lens group includes a cylindrical convex lens 33A disposed on the first light forming element 32 side and a cylindrical concave lens 33B disposed on the second condenser lenses 40A and 40B side. The inter-lens distance between the cylindrical convex lens 33A and the cylindrical concave lens 33B can be changed by a drive mechanism (not shown). The drive mechanism is connected to the control device 30, which controls the inter-lens distance. Adjusting the inter-lens distance can make the Y-direction length of the spot shape of the second laser beam L3 at the focal position longer than the Y-direction length of the spot shape of the second laser beam L3 at the focal position when the second light forming element 33 is not installed. Furthermore, by adjusting the inter-lens distance, the length of the spot shape S2 of the second laser light L3 in the Y direction can be changed arbitrarily.

[0046] The second laser light L3 emitted from the second light forming element 33 is converged by the second condenser lenses 40A and 40B to form a single spot S3 on the street C.

[0047] As described above, according to the laser processing apparatus 10 of the present embodiment, the first light forming element 32 adjusts the focal lengths of the X-direction component and the Y-direction component contained in the laser beam, thereby enabling the shape of the spot of the first laser beam L2 to be shaped into a shape suitable for forming the center cut groove 19, such as a rectangular shape, and the second light forming element 33 enables the length of the Y-direction of the spot shape of the second laser beam L3 to be enlarged to an arbitrary length, thereby enabling the spot shape of the second laser beam L3 to be adjusted to a spot shape with a length that matches the width of the center cut groove 19. As a result, even if it becomes necessary to change the width dimension of the center cut groove 19 in accordance with a change in the specifications of the semiconductor wafer, the dimension of the spot shape of the second laser beam L3 that corresponds to the groove width direction of the center cut groove 19 can be adjusted arbitrarily by using the first and second light forming elements 32, 33 without mechanically rotating the light forming elements, thereby further improving the processing accuracy of the center cut groove 19.

[0048] Furthermore, in this embodiment, the second light forming element 33 makes it possible to change the dimension of the spot shape of the second laser light L3 corresponding to the groove width direction of the hollow groove 19, so that, for example, there is no need to block part of the laser light using a slit or the like as in the conventional method, and energy loss of the laser light can be prevented.

[0049] Furthermore, according to this embodiment, the widthwise dimension of the center-cut groove 19 in the spot shape of the second laser light L3 can be changed while keeping the energy density of the second laser light L3 in the longitudinal direction of the center-cut groove 19 constant.

[0050] It is also possible to provide a rotation mechanism in the laser optical system 24 of this embodiment to switch the X and Y directions in the laser optical system. This makes it possible to change the longitudinal dimension of the groove 19 in the spot shape of the second laser beam L3, for example, while keeping the energy density of the second laser beam L3 in the width direction of the groove 19 constant.

[0051] 1 and 5 show the laser light source 22 that emits the laser light for edge cutting and the laser light L3 for center cutting, but the present invention is not limited to this, and a laser light source that emits the laser light for edge cutting and a laser light source that emits the laser light L3 for center cutting (second laser light) may be provided separately. In this case, the branching element 31 in FIG. 5 may be omitted. [Explanation of symbols]

[0052] 10...Laser processing equipment, 12...wafer, 14...chip, 16...device, 18...Edge cutting groove (first groove), 19...Cutout groove (second groove), 20...table, 22...laser light source, 24...Laser optical system, 26...microscope, 28...Relative movement mechanism, 30...control device, 31...branching element, 32...first light forming element, 33...second light forming element, 34...Third light forming element, 36...Connection switching element, 38...First condenser lens, 40A, 40B...second condenser lens, L2: First laser beam L3: Second laser beam S1, S2, S3...spot, X... Machining feed direction (longitudinal direction of the second groove) X1...Outbound direction side, X2...Returning direction side, Y...Direction perpendicular to the machining feed direction (width direction of the second groove).

Claims

1. a laser light source; a first light forming element that forms a first laser light having an arbitrary spot shape from the laser light emitted from the laser light source; a second light forming element that forms a second laser light having a spot shape expanded or contracted in one direction perpendicular to an optical axis from the first laser light, and that makes the length of the expansion or contraction variable; a condenser lens that condenses the second laser light emitted from the second light forming element onto a wafer; A laser processing device comprising:

2. 2. The laser processing device according to claim 1, wherein the second light forming element is any one of a cylindrical lens group, a cylindrical mirror group, and a deformable mirror group.

3. 2. The laser processing device according to claim 1, wherein the first light forming element is any one of a diffractive optical element, a refractive optical element, a reflective liquid crystal spatial light modulator, and a cylindrical lens.

4. The laser processing device according to claim 1 , wherein the first light forming element generates the first laser light having a linear spot shape parallel to the one direction.

5. the laser processing device is a laser processing device that performs, for each street, an edge cutting process for forming two first grooves parallel to each other along the street of the wafer, and a hollowing process for forming a second groove between the two first grooves; The laser processing device according to claim 1 , wherein hollowing is performed by the second laser beam.

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