Laser Processing Equipment

Abstract

To provide a laser processing device capable of adjusting a position of spots of two first laser beams on a street and a position of a spot of a second laser beam.SOLUTION: A laser processing device comprises: a laser beam outgoing radiation system (a laser beam source 22, a first beam formation element 32, and a second beam formation element 34) that emit two first laser beams L1 corresponded to edged processing and a second laser beam L2 corresponded to hollowing processing by a laser optical system 24; a first beam focusing lens 38 that focuses the two first laser beams L1 to a street C of a processing object; and second beam focusing lenses 40A and 40B that are positioned on the side opposite to a processing feeding direction with respect to the first beam focusing lens 38, and focuses the second laser beam L2 to the street C of the processing object. The second laser beam L2 has a strength distribution in a top-hat shape in a vertical direction vertical to the processing feeding direction and has a strength distribution in a Gaussian shape in the processing feeding direction.SELECTED DRAWING: Figure 12

Description

[Technical Field]

[0001] The present invention relates to a laser processing apparatus for performing laser processing on a wafer. [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 laminating a low-dielectric-constant insulating film (low-k film) made of a glassy material and a functional film that forms circuits on the surface of a substrate such as silicon. Such wafers are divided into multiple devices in a lattice pattern by lattice 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 a laser-processed area along the streets inside the wafer and then applying an external force along the streets whose strength has been reduced by the laser-processed area. However, in the case of wafers with low-k film, the material of the low-k film is different from that of the wafer, so the former method makes it difficult to simultaneously cut the insulating film and the substrate with a blade. Furthermore, the latter method makes it difficult to divide the wafer into individual devices with good quality when low-k film is present on the streets.

[0004] Therefore, Patent Document 1 discloses a laser processing device that performs edge cutting processing (see Patent Document 2), which forms two edge cutting grooves (blocking grooves) along the streets of a wafer, and center cutting processing, which forms a center cutting groove (division groove) between the two edge cutting grooves. This laser processing device includes a first laser beam application unit corresponding to the edge cutting processing and a second laser beam application unit corresponding to the center cutting processing, along a processing feed direction parallel to the streets of the wafer (see FIG. 15 of Patent Document 1). Then, by moving the first laser beam application unit and the second laser beam application unit relative to the wafer in one direction (e.g., the forward direction) in the processing feed direction, the two edge cutting grooves and the center cutting groove are simultaneously formed (parallel formation) along the same street, thereby removing a low-k film or the like.

[0005] Patent Document 3 discloses a laser processing device that performs first groove processing to form a first groove (fused portion) along the street of a wafer, and second groove processing to form a second groove (fused portion) at the bottom of the first groove. This laser processing device is equipped with a first laser beam head unit corresponding to the first groove processing and a second laser beam head unit corresponding to the second groove processing, along a processing feed direction parallel to the street of the wafer. Then, by moving the first laser beam head unit and the second laser beam head unit relative to the wafer in one direction in the processing feed direction (for example, the forward direction), the first groove and the second groove are simultaneously formed along the same street.

[0006] Patent Document 4 discloses a laser processing device that moves a chuck that holds a wafer relative to a laser optical system positioned opposite the wafer to form a pair of parallel trenches (two first grooves) along a dicing street and a furrow (second groove), which is a recess formed between the pair of trenches. The laser optical system of Patent Document 4 includes a laser light emitting system that emits laser beams (two first laser beams) corresponding to the processing of the pair of trenches and a laser beam (second laser beam) corresponding to the processing of the furrow, and a focusing optical system that focuses each laser beam on the wafer. This focusing optical system causes the laser beam corresponding to the processing of the trenches to precede the laser beam corresponding to the processing of the furrow, regardless of the processing feed direction (forward direction, backward direction) of the laser optical system (focusing optical system) relative to the wafer. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-182019 [Patent Document 2] U.S. Patent No. 5,922,224 [Patent Document 3] Japanese Patent Application Publication No. 58-143553 [Patent Document 4] Japanese Patent Application Laid-Open No. 2016-208035 Summary of the Invention [Problem to be solved by the invention]

[0008] However, as described in Patent Document 1, when forming two edge-cut grooves and a center-cut groove along a street, the two edge-cut grooves must be formed first, followed by the center-cut grooves. Therefore, the laser processing apparatus of Patent Document 1 can simultaneously form two edge-cut grooves and a center-cut groove along the same street only when the first laser beam application unit and the second laser beam application unit are moved relative to the wafer in one direction (e.g., the forward direction) in the processing feed direction. Therefore, the laser processing apparatus of Patent Document 1 cannot simultaneously form two edge-cut grooves and a center-cut groove along the same street when each laser beam application unit is moved relative to the wafer in the other direction (e.g., the backward direction) in the processing feed direction. As a result, the time required to process one wafer (takt time) increases.

[0009] Therefore, when each light beam application unit is moved relative to the wafer in the other direction in the processing feed direction in the laser processing apparatus of Patent Document 1, it is conceivable to perform edge cutting processing with the second laser beam application unit and perform hollow cutting processing with the first laser beam application unit. However, since the optical system corresponding to edge cutting processing and the optical system corresponding to hollow cutting processing are different, if each light beam application unit is made compatible with both edge cutting processing and hollow cutting processing, the optical system of each light beam application unit would become very complicated.

[0010] Even in the laser processing device of Patent Document 3, when each laser beam head unit is moved relative to the wafer in the other direction of the processing feed direction (for example, the return direction), it is not possible to simultaneously form the first groove and the second groove along the same street.

[0011] The laser processing apparatus of Patent Document 4 can perform edge cutting before hollow cutting regardless of the processing feed direction (forward or backward), thereby reducing the takt time compared to the laser processing apparatuses described in Patent Documents 1 to 3. However, the laser processing apparatus described in Patent Document 4 performs edge cutting and hollow cutting using a laser beam emitted from a common laser light source. The laser beam conditions (wavelength, pulse width, repetition frequency, etc.) suitable for edge cutting and hollow cutting differ from each other. Therefore, if the laser beam conditions deviate from the conditions suitable for either edge cutting or hollow cutting, the processing speed for one of the processes must be slowed down, and the processing speed for the other process must also be slowed down accordingly. Therefore, even with the laser processing apparatus described in Patent Document 4, there is a limit to how much the takt time required for laser processing of wafers can be reduced.

[0012] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a laser processing apparatus that can reduce the takt time required for laser processing of a wafer. [Means for solving the problem]

[0013] A laser processing apparatus for achieving the object of the present invention performs edge cutting processing for forming two parallel first grooves along the streets and center cutting processing for forming a second groove between the two first grooves for each street by irradiating a laser beam from the laser optical system onto the wafer while moving a table that holds a wafer and a laser optical system located opposite the table relatively in a processing feed direction along the streets of the wafer, the laser optical system comprising a first laser light source that emits laser beams under conditions corresponding to the edge cutting processing, a second laser light source that emits laser beams under conditions corresponding to the center cutting processing, a first light forming element that forms two first laser beams from the laser beams emitted from the first laser light source, and a laser beam forming element that forms two first laser beams from the laser beams emitted from the second laser light source. the laser beam forming element includes a second light forming element that forms a second laser beam from the first light forming element, a first condenser lens, two second condenser lenses that are arranged in a row along the processing feed direction together with the first condenser lens with the first condenser lens sandwiched therebetween, and a connection optical system that guides the two first laser beams emitted from the first light forming element to the first condenser lens and selectively guides the second laser beam emitted from the second light forming element to the two second condenser lenses, wherein when the laser optical system is moved relatively in the forward direction of the processing feed direction with respect to the table, the connection optical system guides the second laser beam to the second condenser lens located on the return direction side of the first condenser lens in the processing feed direction, and when the laser optical system is moved relatively in the return direction with respect to the table, the connection optical system guides the second laser beam to the second condenser lens located on the forward direction side of the first condenser lens.

[0014] This laser processing device can improve the wafer processing speed (reduce the takt time).

[0015] A laser processing apparatus for achieving the object of the present invention performs edge cutting processing for forming two parallel first grooves along the streets and center cutting processing for forming a second groove between the two first grooves for each street by irradiating a laser beam from the laser optical system onto the wafer while moving a table that holds a wafer and a laser optical system located opposite the table relatively in a processing feed direction along the streets of the wafer, the laser optical system comprising a first laser light source that emits laser beams under conditions corresponding to the edge cutting processing, a second laser light source that emits laser beams under conditions corresponding to the center cutting processing, a first light forming element that forms two first laser beams from the laser beams emitted from the first laser light source, and a laser beam forming element that forms a second groove from the laser beams emitted from the second laser light source. The laser beam forming device comprises a second light forming element that forms a second laser beam, two first focusing lenses arranged in a row along the processing feed direction, a second focusing lens arranged between the two first focusing lenses, and a connecting optical system that selectively guides the two first laser beams emitted from the first light forming element to the two first focusing lenses and guides the second laser beam emitted from the second light forming element to the second focusing lens, wherein when the laser optical system is moved relatively to the table in the forward direction of the processing feed direction, the connecting optical system guides the two first laser beams to the first focusing lens located on the forward direction side of the second focusing lens, and when the laser optical system is moved relatively to the table in the backward direction of the processing feed direction, the connecting optical system guides the two first laser beams to the first focusing lens located on the backward direction side of the second focusing lens.

[0016] This laser processing device can improve the wafer processing speed (reduce the takt time).

[0017] A laser processing apparatus according to another aspect of the present invention includes a first movement mechanism that moves a first condenser lens relative to a table in a first vertical direction that is parallel to the table and perpendicular to the processing feed direction, and a second movement mechanism that moves a second condenser lens relative to the table in the first vertical direction, thereby making it possible to move (trace) each processing point along an optimal movement trajectory regardless of the movement accuracy of the processing feed axis during laser processing.

[0018] In a laser processing device according to another aspect of the present invention, the first moving mechanism can move the first condenser lens relative to the table in a first vertical direction and a second vertical direction perpendicular to the table, and the second moving mechanism can move the second condenser lens relative to the table in the first vertical direction and the second vertical direction. This allows each processing point to move (trace) along an optimal movement trajectory regardless of the movement accuracy of the processing feed axis during laser processing.

[0019] A laser processing apparatus according to another aspect of the present invention includes a first moving mechanism that moves a first focusing lens relative to a table in a first vertical direction that is parallel to the table and perpendicular to the processing feed direction, and a second moving mechanism that moves two second focusing lenses together relative to the table in the first vertical direction.

[0020] In a laser processing apparatus according to another aspect of the present invention, a first moving mechanism is capable of moving a first focusing lens relative to a table in a first vertical direction and a second vertical direction perpendicular to the table, and a second moving mechanism is capable of moving two second focusing lenses together relative to the table in the first vertical direction and the second vertical direction.

[0021] A laser processing apparatus according to another aspect of the present invention includes a first moving mechanism that moves two first focusing lenses relative to a table together in a first vertical direction that is parallel to the table and perpendicular to the processing feed direction, and a second moving mechanism that moves a second focusing lens relative to the table in the first vertical direction.

[0022] In another aspect of the laser processing apparatus of the present invention, the first moving mechanism is capable of moving two first focusing lenses together relative to the table in a first vertical direction and a second vertical direction perpendicular to the table, and the second moving mechanism is capable of moving the second focusing lens relative to the table in the first vertical direction and the second vertical direction.

[0023] In the laser processing apparatus according to another aspect of the present invention, the first movement mechanism moves the table in a first vertical direction.

[0024] In the laser processing device according to another aspect of the present invention, the second movement mechanism moves the table in a first vertical direction.

[0025] In the laser processing device according to another aspect of the present invention, the first movement mechanism moves the table in a first vertical direction and a second vertical direction.

[0026] In the laser processing device according to another aspect of the present invention, the second movement mechanism moves the table in a first vertical direction and a second vertical direction. [Effects of the Invention]

[0027] The present invention can reduce the takt time required for laser processing of a wafer with a simple configuration. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a schematic diagram of a laser processing device according to a first embodiment. [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] 4 is a flowchart showing the flow of laser processing for each street of a wafer by the laser processing apparatus of the first embodiment. [Figure 8] 10 is an explanatory diagram for explaining adjustment of the distance between the two edge cutting grooves in the Y direction by the first rotation mechanism. FIG. [Figure 9] 10 is an explanatory diagram for explaining adjustment of the distance between the two edge cutting grooves in the Y direction by the first rotation mechanism. FIG. [Figure 10] 10 is an explanatory diagram for explaining adjustment of the width of the hollow groove in the Y direction by the second rotation mechanism. FIG. [Figure 11] 10 is an explanatory diagram for explaining adjustment of the width of the hollow groove in the Y direction by the second rotation mechanism. FIG. [Figure 12] FIG. 10 is a schematic view of a laser processing device according to a third embodiment. [Figure 13] 10 is an explanatory diagram for explaining edge cutting and hollowing by a laser optical system that is moved relatively to the wafer in the forward direction in the fourth embodiment. FIG. [Figure 14] 10 is an explanatory diagram for explaining edge cutting and hollowing by a laser optical system that is moved relatively to the wafer in the backward direction in the fourth embodiment. FIG. [Figure 15] FIG. 10 is an explanatory diagram for explaining a specific example 1 of a connection switching element according to the fourth embodiment. [Figure 16] FIG. 13 is an explanatory diagram for explaining specific example 2 of the connection switching element according to the fourth embodiment. [Figure 17] FIG. 13 is an explanatory diagram for explaining a specific example 3 of the connection switching element according to the fourth embodiment. [Figure 18] 13 is an explanatory view for explaining edge cutting and hollowing by a laser optical system that is moved relatively to the wafer in the forward direction in the fifth embodiment. FIG. [Figure 19] 10 is an explanatory view for explaining edge cutting and hollowing by the laser optical system 24 that is moved relatively to the wafer in the backward direction in the fifth embodiment. FIG. [Figure 20] 13 is an explanatory diagram for explaining edge cutting and hollowing by a laser optical system that is moved relatively to the wafer in the forward direction in the sixth embodiment. FIG. [Figure 21] 13 is an explanatory diagram for explaining edge cutting and hollowing by the laser optical system 24 that is moved relatively to the wafer in the backward direction in the sixth embodiment. FIG. [Figure 22]10 is an explanatory diagram for explaining a problem that occurs when the intensity distribution of the second laser light has a Gaussian shape. FIG. [Figure 23] FIG. 4 is an explanatory diagram showing an example of an ideal intensity distribution of the second laser light. [Figure 24] FIG. 10 is an explanatory diagram showing an example of an actual intensity distribution of the second laser light. [Figure 25] Reference symbol XXVA is an explanatory diagram showing an example of the intensity distribution (E) of the second laser light in the Y direction, and reference symbol XXVB is an explanatory diagram showing an example of the intensity distribution (E) of the second laser light in the X direction. [Figure 26] 13 is an explanatory diagram showing an example of the intensity distribution of the second laser light L2 in the XY plane according to the seventh embodiment. FIG. [Figure 27] FIG. 13 is a schematic diagram of a laser optical system of a laser processing apparatus according to an eighth embodiment. [Figure 28] FIG. 13 is an explanatory diagram for explaining the effect of the laser processing device of the eighth embodiment. [Figure 29] 13 is an explanatory view for explaining edge cutting and hollowing by the laser optical system of the laser processing device of the ninth embodiment, which is moved relatively in the forward direction with respect to the wafer. FIG. [Figure 30] 13 is an explanatory view for explaining edge cutting and hollowing by the laser optical system of the laser processing device of the ninth embodiment, which is moved relatively in the backward direction with respect to the wafer. FIG. [Figure 31] 10 is an explanatory diagram for explaining the function of the connection optical system when the laser optical system is moved relatively to the wafer in the forward direction by the relative movement mechanism. FIG. [Figure 32] 10 is an explanatory diagram for explaining the function of the connection optical system when the laser optical system is moved relatively to the wafer in the backward direction by the relative movement mechanism. FIG. [Figure 33] 13 is an explanatory view for explaining edge cutting and hollowing by a laser optical system that is moved relatively to the wafer in the forward direction in the first modification of the ninth embodiment. FIG. [Figure 34]13 is an explanatory view for explaining edge cutting and hollowing by a laser optical system that is moved relatively to the wafer in the backward direction in the first modification of the ninth embodiment. FIG. [Figure 35] 13 is an explanatory view for explaining edge cutting and hollowing by a laser optical system that is moved relatively to the wafer in the forward direction in the second modification of the ninth embodiment. FIG. [Figure 36] 13 is an explanatory view for explaining edge cutting and hollowing by a laser optical system that is moved relatively to the wafer in the backward direction in the second modification of the ninth embodiment. FIG. [Figure 37] 13 is an explanatory diagram for explaining edge cutting processing and hollowing processing by the laser optical system of the laser processing device of the tenth embodiment. FIG. [Figure 38] 11 is an explanatory diagram for explaining edge cutting and hollowing by the laser optical system of the laser processing device of the eleventh embodiment, which is moved relatively in the forward direction with respect to the wafer. FIG. [Figure 39] FIG. 39 is an enlarged view of the area within the dotted circle K1 in FIG. 38. [Figure 40] 11 is an explanatory diagram for explaining edge cutting and hollowing by the laser optical system of the laser processing device of the eleventh embodiment, which is moved relatively in the backward direction with respect to the wafer. FIG. [Figure 41] FIG. 41 is an enlarged view of the area within the dotted circle K2 in FIG. 40. [Figure 42] FIG. 23 is an explanatory diagram for explaining a modified example of the eleventh embodiment. [Figure 43] FIG. 43 is an explanatory diagram for explaining a modified example of the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0029] [Overall configuration of the laser processing device of the first embodiment] Figure 1 is a schematic diagram of a laser processing apparatus 10 according to a first embodiment. 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 perpendicular to one another, 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 of the present invention.

[0030] 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 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.

[0031] 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.

[0032] At this time, in order to reduce the takt time required for laser processing of the wafer 12, the laser processing apparatus 10 alternates the relative movement direction when moving a laser optical system 24 (described later) relative to the wafer 12 in the X direction for each street C.

[0033] 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.

[0034] 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.

[0035] As shown in Figures 3 and 4, in this embodiment, edge cutting and hollow cutting are performed simultaneously (in parallel) as laser processing. The edge cutting is performed using two first laser beams L1, and forms two parallel edge cutting grooves 18 (ablation grooves corresponding to the two first grooves of the present invention) along the street C. The hollow cutting is performed using one second laser beam L2 having a diameter larger than the two first laser beams L1, and forms a hollow cutting groove 19 (ablation groove corresponding to the second groove of the present invention) between the two edge cutting grooves 18 formed in the edge cutting processing. Note that the two edge cutting grooves 18 and hollow cutting groove 19, which are ablation grooves, are publicly known technologies, so detailed description thereof will be omitted (see Patent Document 1).

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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 beams of first laser light L1 for edge cutting and one beam of second laser light L2 for hollowing out. The laser optical system 24 then emits (irradiates) the two beams of first laser light L1 from a first condenser lens 38 toward the street C. Under the control of the control device 30, the laser optical system 24 also selectively emits (irradiates) the second laser light L2 from two second condenser lenses 40A, 40B toward the street C.

[0041] 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.

[0042] 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).

[0043] 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).

[0044] 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.

[0045] 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.

[0046] 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.

[0047] [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.

[0048] As shown in Figures 5 and 6, the laser optical system 24 includes a safety shutter 100, a safety shutter drive mechanism 102, a branching element 31, a first light forming element 32, a second light forming element 34, a connection switching element 36, a first focusing lens 38, two second focusing lenses 40A, 40B, a first high-speed shutter 47A and a second high-speed shutter 47B, and a high-speed shutter drive mechanism 47C.

[0049] The safety shutter drive mechanism 102 is an actuator that, under the control of the control device 30, inserts and removes the safety shutter 100 into and from the optical path between the laser light source 22 and the branching element 31. The safety shutter drive mechanism 102 inserts the safety shutter 100 into the optical path except during laser processing, thereby stopping the emission of the two laser beams, the first laser beam L1 and the second laser beam L2, from the laser optical system 24. Furthermore, during laser processing, the safety shutter drive mechanism 102 retracts the safety shutter 100 from the optical path, thereby enabling the emission of the two laser beams, the first laser beam L1 and the second laser beam L2, from the laser optical system 24.

[0050] 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, and emits one of the two branched laser lights L to the first light forming element 32 and the other laser light L to the second light forming element 34. Note that the branching ratio of "two-branch" in this specification is not limited to 50:50 and can be changed as appropriate.

[0051] The first light forming element 32 may be, for example, a diffractive optical element (DOE). The first light forming element 32 forms two first laser beams L1 corresponding to edge cutting processing from the laser beam L incident from the branching element 31, and emits the two first laser beams L1 toward a first condenser lens 38. As a result, the two first laser beams L1 are condensed on street C (outbound and return paths) by the first condenser lens 38, and two spots (also referred to as condensing points or processing points) spaced apart in the Y direction are formed on street C. Although not shown, the optical paths of the two first laser beams L1 from the first light forming element 32 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.

[0052] The second light forming element 34 may be, for example, a diffractive optical element or a mask. The second light forming element 34 forms a second laser light L2 corresponding to the hollowing process from the laser light L incident from the branching element 31. The second laser light L2 forms a single rectangular (or other shape such as circular) spot (see FIGS. 10 and 11 ) between the two edge cutting grooves 18 on the wafer 12. The width of this spot in the Y direction is adjusted to match the spacing between the two edge cutting grooves 18. The second light forming element 34 then emits the second laser light L2 to the connection switching element 36.

[0053] The connection switching element 36, together with the branching element 31 and the like, constitutes the connection optical system of the present invention. As this connection switching element 36, for example, a known optical switch or various optical elements (such as a half-wave plate 52 and a polarizing beam splitter 54, a half mirror 58 and shutters 62A, 62B, and mirrors 66A, 66B) shown in Figures 15 to 17 described below can be used. Under the control of the control device 30, the connection switching element 36 selectively guides the second laser beam L2 emitted from the second light forming element 34 to the second focusing lenses 40A, 40B.

[0054] 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.

[0055] The first condenser lens 38 condenses the two first laser beams L1 incident from the first light forming element 32 onto street C (outward path and return path). The second condenser lens 40A condenses the second laser beam L2 incident from the connection switching element 36 onto street C (outward path). The second condenser lens 40B condenses the second laser beam L2 incident from the connection switching element 36 onto street C (return path).

[0056] When the relative movement mechanism 28 moves the laser optical system 24 relative to the wafer 12 in one of the forward direction side X1 and the return direction side X2, the connection switching element 36 guides the second laser light L2 emitted from the second light forming element 34 to the lens among the second focusing lenses 40A, 40B that is located on the other side of the forward direction side X1 and the return direction side X2 relative to the first focusing lens 38.

[0057] 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 L2 emitted from the second light forming element 34 to the second condenser lens 40A. This causes the second laser beam L2 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.

[0058] 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 L2 emitted from the second light forming element 34 to the second condenser lens 40B. This causes the second laser beam L2 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), thereby forming two edge cutting grooves 18, and then causes center cutting processing to be performed, thereby forming a center cutting groove 19 between the two edge cutting grooves 18.

[0059] The first high-speed shutter 47A is provided so as to be insertable into and detachable from the optical path of the laser light L between the branching element 31 and the first light forming element 32 (it may also be the optical path between the first light forming element 32 and the first condenser lens 38). When the first high-speed shutter 47A is inserted into the optical path between the branching element 31 and the first light forming element 32, it blocks the laser light L entering the first light forming element 32 from the branching element 31, thereby stopping the emission of the two first laser lights L1 from the first condenser lens 38.

[0060] The second high-speed shutter 47B is provided so as to be insertable into and detachable from the optical path of the laser light L between the branching element 31 and the second light forming element 34 (it may also be the optical path between the second light forming element 34 and the connection switching element 36). When the second high-speed shutter 47B is inserted into the optical path between the branching element 31 and the second light forming element 34, it blocks the laser light L entering the second light forming element 34 from the branching element 31, thereby stopping the emission of the second laser light L2 from the second condenser lenses 40A, 40B.

[0061] The high-speed shutter drive mechanism 47C is an actuator that inserts and removes the first high-speed shutter 47A and the second high-speed shutter 47B into and from the aforementioned respective optical paths under the control of the control device 30. The high-speed shutter drive mechanism 47C retracts the first high-speed shutter 47A from the optical path of the laser light L during edge cutting processing, and inserts the first high-speed shutter 47A into the optical path of the laser light L at times other than edge cutting processing. In addition, the high-speed shutter drive mechanism 47C retracts the second high-speed shutter 47B from the optical path of the laser light L during hollow cutting processing, and inserts the second high-speed shutter 47B into the optical path of the laser light L at times other than hollow cutting processing.

[0062] 7 is a flowchart showing the flow of laser processing for each street C of the wafer 12 by the laser processing apparatus 10 of the first embodiment configured as described above (a method for controlling the laser processing apparatus 10). Note that in the initial state, the first high-speed shutter 47A, the second high-speed shutter 47B, and the safety shutter 100 are each inserted in the optical path of the laser light L. Also, it is assumed that emission of the laser light L from the laser source 22 begins in conjunction with startup of the laser processing apparatus 10.

[0063] 7, when the wafer 12 to be laser processed is held on the table 20, the control device 30 first drives the safety shutter drive mechanism 102 to retract the safety shutter 100 from the optical path of the laser light L (step S0). This enables the laser optical system 24 to emit two laser beams, the first laser beam L1 and the second laser beam L2. At this point, the first high-speed shutter 47A and the second high-speed shutter 47B are inserted in the optical path of the laser light L, and therefore the first laser beam L1 and the second laser beam L2 are not emitted from the laser optical system 24.

[0064] Next, the control device 30 drives the relative movement mechanism 28 to move the microscope 26 relative to the wafer 12 to a position where an image of an alignment fiducial (not shown) of the wafer 12 can be captured, and then controls the microscope 26 to capture an image of the alignment fiducial. The control device 30 then performs alignment detection, detecting the position of each street C in the wafer 12, based on the captured image of the alignment fiducial captured by the microscope 26. Next, the control device 30 drives the relative movement mechanism 28 to align the optical axis of the first condenser lens 38 of the laser optical system 24 with the processing start position of the first street C (outward pass) (step S1).

[0065] Furthermore, the control device 30 drives the connection switching element 36 to switch the lens that emits the second laser light L2 to the second condenser lens 40A (step S2). Note that the order of steps S0 to S3 may be changed as appropriate, or these processes may be performed in parallel.

[0066] Upon completion of step S2, the control device 30 drives the high-speed shutter drive mechanism 47C to retract the first high-speed shutter 47A from the optical path of the laser light L (step S3). As a result, two first laser beams L1 are emitted from the first condenser lens 38 via the branching element 31 and the first light forming element 32, and the two first laser beams L1 are condensed at the processing start position on the street C (outward path).

[0067] Next, the control device 30 drives the relative movement mechanism 28 to move the laser optical system 24 relative to the wafer 12 in the forward direction X1 (step S4). Then, when the optical axis of the second condenser lens 40A reaches the processing start position on street C (forward path), the control device 30 drives the high-speed shutter drive mechanism 47C to retract the second high-speed shutter 47B from the optical path of the laser light L (step S5). As a result, the second laser light L2 is emitted from the second condenser lens 40A via the branching element 31, the second light forming element 34, and the connection switching element 36, and the second laser light L2 is focused at the above-mentioned processing start position. In addition, by shifting the timing of the start of the hollowing process, laser processing (holing process) on the outside of the wafer 12 is prevented.

[0068] When the relative movement of the laser optical system 24 in the forward direction X1 continues, the two spots of the first laser beam L1 and the second laser beam L2 move along the street C (forward path) in the forward direction X1, as shown in Figures 3 and 5. As a result, along the street C (forward path), the formation of two edge cutting grooves 18 by edge cutting processing and the formation of a hollow groove 19 by hollow cutting processing are simultaneously performed with an interval between them.

[0069] Then, the control device 30 drives the high-speed shutter drive mechanism 47C to insert the first high-speed shutter 47A into the optical path of the laser beam L in synchronization with the timing at which the spots of the two first laser beams L1 emitted from the first condenser lens 38 reach the processing end position of street C (outward pass) (steps S6 and S7). Furthermore, the control device 30 drives the high-speed shutter drive mechanism 47C to insert the second high-speed shutter 47B into the optical path of the laser beam L in synchronization with the timing at which the spots of the second laser beam L2 emitted from the second condenser lens 40A reach the processing end position, and stops driving the relative movement mechanism 28 (step S8). This completes laser processing of the first street C (outward pass). Note that if the outer side of the wafer 12 may be laser processed (edge cutting processing), the timing at which the first high-speed shutter 47A is inserted into the optical path of the laser beam L may be synchronized with the timing at which the second high-speed shutter 47B is inserted into the optical path of the laser beam L.

[0070] When laser processing of the first street C (outbound path) is completed, the control device 30 drives the relative movement mechanism 28 to align the optical axis of the first focusing lens 38 with the processing start position of the second street C (return path) (YES in step S9, step S10).

[0071] Furthermore, the control device 30 drives the connection switching element 36 to switch the lens that emits the second laser light L2 to the second condenser lens 40B (step S11). Note that steps S10 and S11 may also be executed in the reverse order or simultaneously.

[0072] Upon completion of step S11, the control device 30 drives the high-speed shutter drive mechanism 47C to retract the first high-speed shutter 47A from the optical path of the laser light L (step S12). As a result, two first laser beams L1 are emitted from the first condenser lens 38 via the branching element 31 and the first light forming element 32, and the two first laser beams L1 are condensed at the processing start position on the street C (return path).

[0073] Next, the control device 30 drives the relative movement mechanism 28 to move the laser optical system 24 relative to the wafer 12 in the backward direction X2 (step S13). Then, when the optical axis of the second condenser lens 40B reaches the processing start position of normal street C (backward), the control device 30 drives the high-speed shutter drive mechanism 47C to retract the second high-speed shutter 47B from the optical path of the laser light L (step S14). As a result, the second laser light L2 is emitted from the second condenser lens 40B via the branching element 31, the second light forming element 34, and the connection switching element 36, and the second laser light L2 is focused at a position shifted from the above-mentioned processing start position toward the forward direction X1. In addition, by shifting the timing of the start of the hollowing process, laser processing (holing) of the outer side of the wafer 12 is prevented.

[0074] When the relative movement of the laser optical system 24 toward the return direction side X2 continues, the two spots of the first laser beam L1 and the second laser beam L2 move toward the return direction side X2 along the street C (return direction) as shown in Figures 4 and 6. As a result, along the street C (return direction), the formation of two edge cutting grooves 18 by edge cutting processing and the formation of a hollow groove 19 by hollowing processing are simultaneously performed with an interval between them.

[0075] Then, the control device 30 drives the high-speed shutter drive mechanism 47C to insert the first high-speed shutter 47A into the optical path of the laser beam L in synchronization with the timing at which the spots of the two first laser beams L1 emitted from the first condenser lens 38 reach the processing end position of street C (return pass) (steps S15 and S16). Furthermore, the control device 30 drives the high-speed shutter drive mechanism 47C to insert the second high-speed shutter 47B into the optical path of the laser beam L in synchronization with the timing at which the spots of the second laser beam L2 emitted from the second condenser lens 40B reach the processing end position, and stops driving the relative movement mechanism 28 (step S17). This completes laser processing of the second street C (return pass). As described above, the timing at which the first high-speed shutter 47A is inserted into the optical path of the laser beam L may be synchronized with the timing at which the second high-speed shutter 47B is inserted into the optical path of the laser beam L.

[0076] Similarly, laser processing (edge cutting and hollowing) is repeatedly performed along all of the streets C parallel to the X direction (YES in step S9, YES in step S18). Next, the control device 30 drives the relative movement mechanism 28 to rotate the table 20 by 90°, thereby making the remaining streets C parallel to the Y direction on the wafer 12 parallel to the X direction. Then, the control device 30 repeatedly performs the above-described series of processes. As a result, laser processing is performed along each of the lattice-shaped streets C.

[0077] When laser processing of all the grid-shaped streets C is completed (NO in step S9, NO in step S18), the wafer 12 is sent to a subsequent process where it is divided into a plurality of chips 14 (devices 16). Note that in this embodiment, an example is given of a flow under the fastest conditions in which the formation of the two edge-cutting grooves 18 and the center-cutting grooves 19 is completed in one laser processing operation in one direction (outgoing path: X1 direction, returning path: X2 direction) for each street C (forward path and return path), but the present invention is not limited to this. For example, depending on the processing depth of each of the two edge-cutting grooves 18 and the center-cutting grooves 19, at least one of the edge-cutting processing and the center-cutting processing may be performed multiple times for each street C (forward path and return path).

[0078] [Effects of the first embodiment] As described above, the laser processing apparatus 10 of the first embodiment can perform hollow cutting by selectively using the second condenser lenses 40A and 40B depending on the relative movement direction of the laser optical system 24 with respect to the wafer 12. This allows edge cutting and hollow cutting to be performed simultaneously along the same street C, regardless of the forward or backward movement. Therefore, laser processing of two streets C (forward and backward movements) can be completed by moving the laser optical system 24 back and forth once in the X direction, thereby reducing the takt time required for laser processing of the wafer 12. Furthermore, simply operating the connection switching element 36 can switch between hollow cutting using the second condenser lens 40A and hollow cutting using the second condenser lens 40B depending on the relative movement direction of the laser optical system 24, preventing the laser optical system 24 (optical system) from becoming complicated. As a result, the takt time required for laser processing of the wafer 12 can be reduced with a simple configuration.

[0079] [Second embodiment] Next, a laser processing apparatus 10 according to a second embodiment will be described. The laser processing apparatus 10 according to the second embodiment has a function of adjusting the Y-direction spacing of the two edge-cutting grooves 18 and the Y-direction width of the core-cut grooves 19. The laser processing apparatus 10 according to the second embodiment has basically the same configuration as the laser processing apparatus 10 according to the first embodiment, except that it is provided with a first rotation mechanism 44 (see FIGS. 8 and 9) and a second rotation mechanism 46 (see FIGS. 10 and 11), which will be described later. Therefore, components that are the same in function or configuration as those according to the first embodiment will be assigned the same reference numerals, and their description will be omitted.

[0080] 8 and 9 are explanatory diagrams illustrating adjustment of the Y-direction spacing between the two edge-cutting grooves 18 by the first rotation mechanism 44. As shown in FIGS. 8 and 9, the first rotation mechanism 44 is configured, for example, with a motor and a drive transmission mechanism, and rotates the first light forming element 32 in a direction around its optical axis under the control of the control device 30. This allows the spots of the two first laser beams L1 focused on the street C by the first condenser lens 38 to be rotated around the optical axis of the first condenser lens 38 when the wafer 12 is viewed from above in the Z direction. As a result, the Y-direction spacing between the spots of the two first laser beams L1 focused on the street C can be widened or narrowed, thereby adjusting the Y-direction spacing between the two edge-cutting grooves 18.

[0081] 10 and 11 are explanatory diagrams illustrating the adjustment of the Y-direction width of the recessed groove 19 by the second rotation mechanism 46. As shown in FIGS. 10 and 11, the second rotation mechanism 46, like the first rotation mechanism 44, is configured, for example, with a motor and a drive transmission mechanism. Under the control of the control device 30, the second rotation mechanism 46 rotates the second light forming element 34 in a direction around its optical axis. As a result, when the wafer 12 is viewed from above in the Z direction, the spot of the second laser light L2 focused on the street C by the second focusing lenses 40A and 40B can be rotated around the optical axis of the second focusing lenses 40A and 40B. The spot of the second laser light L2 formed on the street C is rectangular, i.e., noncircular. Therefore, by rotating this rectangular spot, the Y-direction width of the recessed groove 19 formed on the street C can be adjusted, for example, by widening or narrowing it. The shape of the spot of the second laser light L2 is not limited to rectangular, as long as it is noncircular.

[0082] Based on adjustment instructions input by the operator to an operating unit (not shown), the control device 30 drives the first rotation mechanism 44 and the second rotation mechanism 46, respectively, to rotate the first light forming element 32 and the second light forming element 34, respectively, thereby adjusting the spacing between the two edge cutting grooves 18 and the width of the center cut groove 19.

[0083] [Third embodiment] 12 is a schematic diagram of a laser processing apparatus 10 of a third embodiment. The laser processing apparatus 10 of each of the above embodiments performs edge cutting and hollowing along the street C of the wafer 12. At this time, the laser processing apparatus 10 of each of the above embodiments has a total of three processing points, including the processing points for edge cutting (spots of the two first laser beams L1 focused on the street C by the first focusing lens 38) and the two processing points for hollowing (spots of the second laser beam L2 focused on the street C by the second focusing lenses 40A and 40B), which are independent of each other, and therefore the respective processing points are spaced apart by several tens of millimeters. Therefore, if the positions of the first focusing lens 38 and the second focusing lenses 40A, 40B within the laser optical system 24 are fixed as in the above embodiments, there is a problem that, depending on the movement accuracy of the processing feed axis (X axis) during laser processing, there will be a deviation in the horizontal direction (Y direction) and vertical direction (Z direction) between the processing points of the two edge-cutting grooves 18 and the processing point of the hollowed-out groove 19 (deviation from the optimal processing point).

[0084] Therefore, the laser processing apparatus 10 of the third embodiment has a function of individually adjusting the Y-direction and Z-direction positions of the processing point for edge cutting and the two processing points for hollowing. The laser processing apparatus 10 of the third embodiment has basically the same configuration as the laser processing apparatus 10 of each of the above embodiments, except that it is equipped with three mirrors 37, 39A, 39B and three movement mechanisms 48, 49A, 49B. Therefore, parts that are the same in function or configuration as those of the above embodiments are given the same reference numerals and their description will be omitted.

[0085] The mirror 37 (first reflecting element) is positioned above the first focusing lens 38 in the Z direction, and reflects the two first laser beams L1 incident from the laser light source 22 via the branching element 31 and the first light forming element 32 toward the first focusing lens 38.

[0086] The mirrors 39A and 39B correspond to second reflecting elements of the present invention. The mirror 39A is disposed above the second collecting lens 40A in the Z direction, and reflects the second laser light L2 incident from the laser light source 22 via the connection switching element 36, etc., toward the second collecting lens 40A. The mirror 39B is disposed above the second collecting lens 40B in the Z direction, and reflects the second laser light L2 incident from the laser light source 22 via the connection switching element 36, etc., toward the second collecting lens 40B.

[0087] The moving mechanism 48 corresponds to the first moving mechanism of the present invention, and the moving mechanisms 49A and 49B correspond to the second moving mechanism of the present invention. Known linear actuators, for example, are used as the moving mechanisms 48, 49A, and 49B. Under the control of the control device 30, the moving mechanism 48 moves the mirror 37 and the first focusing lens 38 together in the Y direction (corresponding to the first vertical direction of the present invention) and moves the first focusing lens 38 in the Z direction (corresponding to the second vertical direction of the present invention). Under the control of the control device 30, the moving mechanism 49A moves the mirror 39A and the second focusing lens 40A together in the Y direction and moves the second focusing lens 40A in the Z direction. Under the control of the control device 30, the moving mechanism 49B moves the mirror 39B and the second focusing lens 40B together in the Y direction and moves the second focusing lens 40B in the Z direction.

[0088] Instead of moving the first condenser lens 38 and the second condenser lenses 40A and 40B in the Y direction by the movement mechanisms 48, 49A and 49B, respectively, the first condenser lens 38 and the second condenser lenses 40A and 40B may be tilted.

[0089] As described above, in the third embodiment, the mirror 37 and the first condenser lens 38, the mirror 39A and the second condenser lens 40A, and the mirror 39B and the second condenser lens 40B can be moved individually in the Y direction and the Z direction. As a result, the Y direction and Z direction positions of the two spots of the first laser beam L1 formed on the street C and the spots of the second laser beam L2 formed by each of the second condenser lenses 40A and 40B can be adjusted individually. This allows, for example, the manufacturer of the laser processing apparatus 10 to adjust the Y direction position and the Z direction position of each spot (adjust the parallelism).

[0090] Furthermore, based on images of the street C, the two edge cutting grooves 18 (the spots of the two first laser beams L1), and the center cutting groove 19 (the spot of the second laser beam L2) photographed by the microscope 26 during laser processing of the wafer 12, the processing point (spot) for edge cutting processing can be traced relative to the street C, and the processing point (spot) for center cutting processing can be traced relative to the center of the two edge cutting grooves 18. Furthermore, based on the above-mentioned photographed images, the amount of deviation in the Z direction (amount of deviation of the focusing position) of the spots of the two first laser beams L1 and the spot of the second laser beam L2 relative to the surface of the wafer 12 (street C) can be adjusted.

[0091] In this case, a camera capable of simultaneously photographing the processed grooves (the two edge-cutting grooves 18 and the hollow groove 19) and the spots may be provided for each of the first condenser lens 38 and the second condenser lenses 40A, 40B.

[0092] As described above, in the third embodiment, the Y- and Z-direction positions of three processing points, including the processing point for edge cutting and the two processing points for hollowing, can be adjusted individually, so that each processing point can be moved (traced) along an optimal movement trajectory regardless of the movement accuracy of the processing feed axis (X-axis) during laser processing.

[0093] In the above third embodiment, the positions of three processing points, including the processing point for edge cutting and two processing points for hollowing out, in the Y and Z directions can be adjusted individually, but it is also possible to make only one of the Y and Z directions adjustable.

[0094] In the third embodiment, the positions of three processing points including the edge cutting processing point and the two hollowing processing points in the Y direction and the Z direction can be adjusted individually by the movement mechanisms 48, 49A, 49B, but the position of the edge cutting processing point may be adjusted by the movement mechanism 48, and the positions of the two hollowing processing points may be adjusted by the relative movement mechanism 28. In other words, the positions of the two hollowing processing points may be adjusted by moving the table 20 in at least one of the Y direction and the Z direction by the relative movement mechanism 28.

[0095] Conversely, the position of the edge cutting point may be adjusted by moving the table 20 using the relative movement mechanism 28, and the positions of the two hollowing points may be adjusted by the movement mechanisms 49A and 49B.

[0096] FIG. 43 is an explanatory diagram for explaining a modified example of the third embodiment. The first laser light source 22A and the second laser light source 22B in FIG. 43 will be described in the fourth embodiment. In the third embodiment, the Y- and Z-direction positions of the two hollowing processing points can be adjusted individually by the movement mechanisms 49A and 49B. Alternatively, as shown by reference numerals 1000A and 1000B in FIG. 43, the second condenser lenses 40A and 40B and mirrors 39A and 39B corresponding to the two hollowing processing points may be mounted on the same frame (not shown), and the positions of the two hollowing processing points may be adjusted together in at least one of the Y and Z directions by the single movement mechanism 49. Because the two hollowing processing points do not perform processing simultaneously, there is no problem with moving the positions of the two hollowing processing points together.

[0097] 43, the position of the processing point for edge cutting may be adjusted by moving the table 20 using the relative movement mechanism 28. Furthermore, the positions of the two processing points for hollowing may be adjusted by moving the table 20 using the relative movement mechanism 28.

[0098] [Fourth embodiment] Next, a fourth embodiment of the laser processing apparatus 10 will be described. In the laser processing apparatus 10 of each of the above embodiments, two laser beams, a first laser beam L1 for edge cutting and a second laser beam L2 for hollow cutting, are formed from the laser beam L emitted from the common laser light source 22. However, the conditions (wavelength, pulse width, repetition frequency, etc.) of the laser beam L suitable for edge cutting and hollow cutting differ from each other. For this reason, if the conditions of the laser beam L deviate from the conditions suitable for either edge cutting or hollow cutting, it is necessary to slow down the processing speed of one of the processes, and accordingly, it is also necessary to slow down the processing speed of the other process.

[0099] In other words, when performing edge cutting groove machining and center through groove machining using a single laser light source 22, the speed of edge cutting groove machining can be improved depending on the laser light conditions, but the speed of center through groove machining cannot be improved, and machining must be performed at the center through groove machining speed that cannot be improved. Furthermore, the opposite may be true depending on the laser light conditions. Therefore, the lower speed in each process becomes the upper limit of the machining speed. In this way, edge cutting groove machining, which forms two edge cutting grooves 18 (blocking grooves) along the street C of the wafer 12, and groove machining, which forms a center through groove 19 (dividing groove) between the two edge cutting grooves 18, each have laser light conditions that are suitable for machining speed and machining finish, so it is difficult to satisfy both conditions with a single laser light source 22.

[0100] For this reason, in the fourth embodiment, different light sources are used for the first laser light L1 and the second laser light L2.

[0101] Fig. 13 is an explanatory diagram for explaining edge cutting and hollow cutting by the laser optical system 24 that is moved relatively to the wafer 12 in the outward direction side X1 in the fourth embodiment. Fig. 14 is an explanatory diagram for explaining edge cutting and hollow cutting by the laser optical system 24 that is moved relatively to the wafer 12 in the backward direction side X2 in the fourth embodiment.

[0102] 13 and 14, the laser processing apparatus 10 of the fourth embodiment has basically the same configuration as the laser processing apparatus 10 of each of the above-described embodiments, except that it is equipped with a first laser light source 22A, a second laser light source 22B, a first safety shutter 100A, a second safety shutter 100B, and a safety shutter drive mechanism 102A instead of the laser light source 22 and the branching element 31. For this reason, components that are the same in function or configuration as those of the above-described embodiments are given the same reference numerals, and their description will be omitted.

[0103] The first laser light source 22A constantly emits laser light LA under conditions (wavelength, pulse width, repetition frequency, etc.) suitable for edge cutting processing to the first light forming element 32. As a result, similar to the above-described embodiments, the first light forming element 32 forms two first laser light beams L1, and the first focusing lens 38 focuses the two first laser light beams L1 onto the street C.

[0104] The second laser light source 22B constantly emits laser light LB under conditions (wavelength, pulse width, repetition frequency, etc.) suitable for hollow cutting to the second light forming element 34. As a result, similar to the above-described embodiments, the second light forming element 34 forms the second laser light L2, the connection switching element 36 switches between the second condenser lenses 40A and 40B, the second condenser lens 40A focuses the second laser light L2 onto street C (outward path), and the second condenser lens 40B focuses the second laser light L2 onto street C (return path).

[0105] The first safety shutter 100A is provided so as to be insertable and detachable on the optical path of the laser light LA between the first laser light source 22A and the first light forming element 32. The second safety shutter 100B is provided so as to be insertable and detachable on the optical path of the laser light LB between the second laser light source 22B and the second light forming element 34.

[0106] The safety shutter drive mechanism 102A is an actuator that, under the control of the control device 30, inserts and removes the first safety shutter 100A into and from the optical path of the laser beam LA, and inserts and removes the second safety shutter 100B into and from the optical path of the laser beam LB. The safety shutter drive mechanism 102A inserts the first safety shutter 100A into the optical path of the laser beam LA, except during edge cutting processing, thereby stopping the emission of the two first laser beams L1 from the laser optical system 24. Furthermore, during edge cutting processing, the safety shutter drive mechanism 102A retracts the first safety shutter 100A from the optical path of the laser beam LA, thereby allowing the two first laser beams L1 to be emitted from the laser optical system 24.

[0107] Similarly, the safety shutter drive mechanism 102A inserts the second safety shutter 100B into the optical path of the laser light LB during times other than the hollow cutting process, thereby stopping the emission of the second laser light L2 from the laser optical system 24. Furthermore, the safety shutter drive mechanism 102A retracts the second safety shutter 100B from the optical path of the laser light LB during the hollow cutting process, thereby causing the second laser light L2 to be emitted from the laser optical system 24.

[0108] The flow of laser processing for each street C by the laser processing apparatus 10 of the fourth embodiment is basically the same as the flow of laser processing in the first embodiment shown in Fig. 7. However, in step S0 of the fourth embodiment, the control device 30 controls the safety shutter drive mechanism 102A to retract the first safety shutter 100A from the optical path of the laser beam LA and the second safety shutter 100B from the optical path of the laser beam LB.

[0109] As described above, in the fourth embodiment, by separately providing the first laser light source 22A corresponding to the edge cutting process and the second laser light source 22B corresponding to the hollow cutting process, a decrease in the processing speed of each of the edge cutting process and the hollow cutting process is prevented. As a result, the above-mentioned takt time can be further reduced. In addition, the processing quality of each of the edge cutting process and the hollow cutting process can be optimized.

[0110] Furthermore, by using laser beams LA and LB of different wavelengths for edge cutting and hollow cutting, and optimizing the processing conditions for those wavelengths, the processing speed can be improved. As a result, the laser processing apparatus 10 using the first laser light source 22A and the second laser light source 22B of the fourth embodiment can process at a faster speed than the laser processing apparatus 10 using a single laser light source 22 as in the first embodiment.

[0111] In the fourth embodiment, similarly to the third embodiment, the Y-direction and Z-direction positions of the edge cutting processing point and the two hollowing processing points can be individually adjusted to obtain the same effect as the third embodiment. Furthermore, not only can the Y-direction and Z-direction positions of the three processing points including the edge cutting processing point and the two hollowing processing points be individually adjustable, but also only one of the Y-direction and Z-direction positions can be adjusted.

[0112] [Specific example of connection switching element of the fourth embodiment] Next, specific examples 1 to 3 of the connection switching element 36 of the fourth embodiment will be described. Note that the configuration other than the connection switching element 36 is basically the same as that of the laser processing apparatus 10 of the fourth embodiment (first to third embodiments). Therefore, components that are the same in function or configuration as those of the above embodiments are given the same reference numerals and their description will be omitted. Furthermore, these specific examples 1 to 3 can also be applied to the connection switching element 36 of the above first to third embodiments.

[0113] <Specific Example 1 of Connection Switching Element 36> 15 is an explanatory diagram for explaining a first specific example of the connection switching element 36 of the fourth embodiment. As shown in FIG. 15, the connection switching element 36 of the first specific example includes a λ / 2 plate 52, a plate rotation mechanism 53, and a polarization beam splitter 54.

[0114] The λ / 2 plate 52 rotates the polarization direction of the second laser light L2 (linearly polarized light) emitted from the second light forming element , and then emits this second laser light L2 toward the polarizing beam splitter .

[0115] The plate rotation mechanism 53 adjusts the polarization direction of the second laser light L2 by rotating the λ / 2 plate 52 about its optical axis under the control of the control device 30. As a result, when the relative movement mechanism 28 moves the laser optical system 24 relative to the wafer 12 in the outward direction side X1, the plate rotation mechanism 53 adjusts the rotation angle of the λ / 2 plate 52 so that the second laser light L2 becomes S-polarized. Furthermore, when the relative movement mechanism 28 moves the laser optical system 24 relative to the wafer 12 in the backward direction side X2, the plate rotation mechanism 53 adjusts the rotation angle of the λ / 2 plate 52 so that the second laser light L2 becomes P-polarized.

[0116] The polarizing beam splitter 54 reflects the S-polarized light toward the second condenser lens 40A and transmits the P-polarized light as is, causing it to exit toward the second condenser lens 40B. This makes it possible to perform hollowing by selectively using the second condenser lenses 40A and 40B depending on the relative movement direction (the outward direction side X1 or the backward direction side X2) of the laser optical system 24 with respect to the wafer 12.

[0117] <Specific Example 2 of Connection Switching Element 36> 16 is an explanatory diagram for explaining a second specific example of the connection switching element 36 of the fourth embodiment. As shown in FIG. 16, the connection switching element 36 of the second specific example includes a half mirror 58, a mirror 60, shutters 62A and 62B, and a shutter drive mechanism 64.

[0118] The half mirror 58 is disposed on the optical path of the second laser light L2 emitted from the second light forming element 34 and at a position facing the second condenser lens 40A. The half mirror 58 splits the second laser light L2 incident from the second light forming element 34 into two, reflects one of the split second laser light L2 toward the second condenser lens 40A, and transmits the other second laser light L2 to be emitted toward the mirror 60.

[0119] The mirror 60 is disposed in a position facing the second condenser lens 40B on the optical path of the second laser light L2 that has passed through the half mirror 58. The mirror 60 reflects the second laser light L2 that has passed through the half mirror 58 toward the second condenser lens 40B.

[0120] The shutter 62A is provided so as to be insertable into and removable from the optical path of the second laser light L2 between the half mirror 58 and the second condenser lens 40A. Thus, when the shutter 62A is inserted into the optical path of the second laser light L2, the second laser light L2 reflected by the half mirror 58 is blocked by the shutter 62A. On the other hand, when the shutter 62A is retracted from the optical path of the second laser light L2, the second laser light L2 reflected by the half mirror 58 is incident on the second condenser lens 40A.

[0121] The shutter 62B is provided so as to be freely insertable and detachable on the optical path of the second laser light L2 between the mirror 60 and the second collecting lens 40B. As a result, when the shutter 62B is inserted on the optical path of the second laser light L2, the second laser light L2 reflected by the mirror 60 is blocked by the shutter 62B. On the other hand, when the shutter 62B is retracted from the optical path of the second laser light L2, the second laser light L2 reflected by the mirror 60 is incident on the second collecting lens 40B.

[0122] The shutter drive mechanism 64 is a known actuator that inserts and removes (opens and closes) the shutters 62A and 62B on the optical path of the second laser light L2 under the control of the control device 30. When the relative movement mechanism 28 moves the laser optical system 24 relative to the wafer 12 in the forward direction side X1, the shutter drive mechanism 64 retracts the shutter 62A from the optical path of the second laser light L2 and inserts the shutter 62B into the optical path of the second laser light L2.

[0123] Conversely, when the relative movement mechanism 28 moves the laser optical system 24 relative to the wafer 12 in the backward direction X2, the shutter drive mechanism 64 inserts the shutter 62A into the optical path of the second laser light L2 and moves the shutter 62B out of the optical path of the second laser light L2. This makes it possible to perform hollow cutting by selectively using the two second condenser lenses 40A, 40B depending on the relative movement direction (the forward direction X1 or the backward direction X2) of the laser optical system 24 relative to the wafer 12.

[0124] <Specific Example 3 of Connection Switching Element 36> 17 is an explanatory diagram for explaining a third specific example of the connection switching element 36 of the fourth embodiment. As shown in FIG. 17, the connection switching element 36 of the third specific example includes a mirror 66A, a mirror 66B, and a mirror driving mechanism 68.

[0125] The mirror 66A is removably provided on the optical path of the second laser light L2 emitted from the second light forming element 34 and at a position facing the second condenser lens 40A. When the mirror 66A is inserted on the optical path of the second laser light L2, the mirror 66A reflects the second laser light L2 incident from the second light forming element 34 toward the second condenser lens 40A. When the mirror 66A is retracted from the optical path of the second laser light L2, the second laser light L2 emitted from the second light forming element 34 is incident on the mirror 66B.

[0126] The mirror 66B is provided at a position facing the second condenser lens 40B on the optical path of the second laser light L2 emitted from the second light formation element 34. The mirror 66B reflects the second laser light L2 incident from the second light formation element 34 toward the second condenser lens 40B.

[0127] The mirror driving mechanism 68 is a known actuator that inserts and removes a mirror 66A on the optical path of the second laser light L2 under the control of the control device 30. The mirror driving mechanism 68 inserts the mirror 66A into the optical path of the second laser light L2 when the relative movement mechanism 28 moves the laser optical system 24 in the forward direction X1 relative to the wafer 12. As a result, all of the second laser light L2 emitted from the second light forming element 34 is reflected by the mirror 66A toward the second condenser lens 40A.

[0128] Conversely, when the relative movement mechanism 28 moves the laser optical system 24 relative to the wafer 12 in the backward direction X2, the mirror drive mechanism 68 retracts the mirror 66A from the optical path of the second laser light L2. As a result, all of the second laser light L2 emitted from the second light forming element 34 is reflected by the mirror 66B toward the second condenser lens 40B. As a result, hollowing can be performed by selectively using the two second condenser lenses 40A, 40B depending on the relative movement direction (the forward direction X1 or the backward direction X2) of the laser optical system 24 relative to the wafer 12.

[0129] [Fifth embodiment] Next, a laser processing apparatus 10 according to a fifth embodiment will be described. The laser processing apparatus 10 according to the fourth embodiment is provided with two types of laser light sources, a first laser light source 22A and a second laser light source 22B. However, if a malfunction occurs in either the first laser light source 22A or the second laser light source 22B, laser processing of the wafer 12 becomes impossible. Therefore, the laser processing apparatus 10 according to the fifth embodiment has a function that allows laser processing of the wafer 12 to continue even if a malfunction occurs in either the first laser light source 22A or the second laser light source 22B.

[0130] Fig. 18 is an explanatory diagram for explaining edge cutting and hollow cutting by the laser optical system 24 that moves relatively to the wafer 12 in the outward direction side X1 in the fifth embodiment. Fig. 19 is an explanatory diagram for explaining edge cutting and hollow cutting by the laser optical system 24 that moves relatively to the wafer 12 in the backward direction side X2 in the fifth embodiment. Note that Figs. 18 and 19 show a case where there is a malfunction in the second laser light source 22B.

[0131] 18 and 19, the laser processing apparatus 10 of the fifth embodiment has basically the same configuration as the laser processing apparatus 10 of the fourth embodiment (including specific examples 1 to 3) except for the inclusion of bypass optical systems 72 and 74. Therefore, components that are the same in function or configuration as those of the fourth embodiment are given the same reference numerals and descriptions thereof will be omitted.

[0132] The bypass optical system 72 is composed of one or more optical elements, and is provided on the optical path of the laser light LA between the first laser light source 22A and the first light forming element 32. Under the control of the control device 30, when there is no malfunction in the second laser light source 22B, the bypass optical system 72 emits all of the laser light LA emitted from the first laser light source 22A toward the first light forming element 32. Note that the presence or absence of a malfunction in the second laser light source 22B can be determined by monitoring the operation of the second laser light source 22B and the light amount of the laser light LB, etc.

[0133] On the other hand, under the control of the control device 30, when a malfunction occurs in the second laser light source 22B, the bypass optical system 72 splits the laser light LA emitted from the first laser light source 22A into two, and emits one of the split laser light LA toward the first light forming element 32, while emitting the other laser light LA toward the second light forming element 34. As a result, the second laser light L2 is formed from the laser light LA in the second light forming element 34. This second laser light L2 passes through the connection switching element 36, and is selectively emitted from the second condenser lenses 40A, 40B depending on the relative movement direction of the laser optical system 24, as in the fourth embodiment.

[0134] The bypass optical system 74 is configured by one or more optical elements, similar to the bypass optical system 72, and is provided on the optical path of the laser light LB between the second laser light source 22B and the second light forming element 34. Under the control of the control device 30, when there is no malfunction in the first laser light source 22A, the bypass optical system 74 emits all of the laser light LB emitted from the second laser light source 22B toward the second light forming element 34. Note that the presence or absence of a malfunction in the first laser light source 22A can also be determined by monitoring the operation of the first laser light source 22A and the light amount of the laser light LA, etc.

[0135] On the other hand, under the control of the control device 30, when a malfunction occurs in the first laser light source 22A, the bypass optical system 74 splits the laser light LB emitted from the second laser light source 22B into two, and emits one of the split laser light LB toward the second light forming element 34, while emitting the other laser light LB toward the first light forming element 32. As a result, two first laser beams L1 are formed from the laser light LB by the first light forming element 32. These two first laser beams L1 are emitted from the first condenser lens 38, similar to the fourth embodiment.

[0136] As described above, in the laser processing apparatus 10 of the fifth embodiment, by providing the bypass optical systems 72 and 74, even if a malfunction occurs in either the first laser light source 22A or the second laser light source 22B, it is possible to continue laser processing of the wafer 12. As a result, the downtime of the laser processing apparatus 10 can be reduced.

[0137] [Sixth embodiment] Next, a sixth embodiment of the laser processing apparatus 10 will be described. The laser processing apparatus 10 of each of the above embodiments includes one first condenser lens 38 for edge cutting and two second condenser lenses 40A, 40B for hollowing out, sandwiching the first condenser lens 38 therebetween, but the first condenser lens 38 and the second condenser lenses 40A, 40B may be interchanged.

[0138] Fig. 20 is an explanatory diagram for explaining edge cutting and hollow cutting by the laser optical system 24 that is moved relatively to the wafer 12 in the outward direction side X1 in the sixth embodiment. Fig. 21 is an explanatory diagram for explaining edge cutting and hollow cutting by the laser optical system 24 that is moved relatively to the wafer 12 in the backward direction side X2 in the sixth embodiment.

[0139] 20 and 21, in the laser processing apparatus 10 of the sixth embodiment, one second condenser lens 40 for hollowing out processing is provided instead of the first condenser lens 38, two first condenser lenses 38A and 38B for edge cutting processing are provided instead of the second condenser lenses 40A and 40B, and further the positions of the first light forming element 32 and the second light forming element 34 are interchanged. Note that other configurations are basically the same as those of the laser processing apparatus 10 of the first to third embodiments, so a detailed description thereof will be omitted here.

[0140] The first condenser lenses 38A, 38B and the second condenser lens 40 are arranged in a row along the X direction (processing feed direction). The second condenser lens 40 is arranged between the two first condenser lenses 38A, 38B. The first condenser lens 38A is arranged on the outgoing direction side X1 relative to the second condenser lens 40. The first condenser lens 38B is arranged on the returning direction side X2 relative to the second condenser lens 40.

[0141] The first condensing lens 38A condenses the two first laser beams L1 input from the connection switching element 36 via the first light forming element 32 onto the street C (outward path). The first condensing lens 38B condenses the two first laser beams L1 input from the connection switching element 36 via the first light forming element 32 onto the street C (return path). The second condensing lens 40 condenses the second laser beam L2 input from the second light forming element 34 onto the street C (outward path and return path).

[0142] The connection switching element 36 of the sixth embodiment guides the two first laser beams L1 emitted from the first light forming element 32 to one of the two first focusing lenses 38A, 38B that is located on the one side of the second focusing lens 40 when the relative movement mechanism 28 moves the laser optical system 24 relative to the wafer 12 in either the forward direction side X1 or the backward direction side X2.

[0143] 20 , 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, under the control of the control device 30, guides the two first laser beams L1 emitted from the first light forming element 32 to the first condenser lens 38A. As a result, the two first laser beams L1 are condensed onto the street C (forward path) by the first condenser lens 38A. Furthermore, the second laser beam L2 is condensed by the second condenser lens 40. As a result, the relative movement of the laser optical system 24 in the forward direction X1 executes edge cutting and hollowing along the street C (forward path).

[0144] 21 , when the relative movement mechanism 28 moves the laser optical system 24 relative to the wafer 12 in the return direction X2, the connection switching element 36, under the control of the control device 30, guides the two first laser beams L1 emitted from the first light forming element 32 to the first condenser lens 38B. As a result, the two first laser beams L1 are condensed onto street C (return direction) by the first condenser lens 38B. In addition, the second laser beam L2 is condensed by the second condenser lens 40. As a result, edge cutting and hollowing are performed along street C (return direction) by the relative movement of the laser optical system 24 in the return direction X2.

[0145] In addition, in the above-mentioned fourth embodiment (including specific examples 1 to 3) and fifth embodiment, as in the sixth embodiment, the positions of the first condensing lens 38 and the second condensing lenses 40A, 40B may be interchanged, and the positions of the first light forming element 32 and the second light forming element 34 may be interchanged.

[0146] Furthermore, the positions of the two processing points for edge cutting may be adjusted by moving the table 20 using the relative movement mechanism 28, and the position of the processing point for hollowing may be adjusted by moving the table 20 using the relative movement mechanism 28. Furthermore, as a modification of the embodiment shown in Fig. 43, the first condenser lenses 38A, 38B and the like corresponding to the two processing points for edge cutting may be installed on the same frame (not shown), and the positions of the two processing points for edge cutting may be adjusted together in at least one of the Y direction and the Z direction using a single movement mechanism 48.

[0147] [Seventh embodiment] Fig. 22 is an explanatory diagram for explaining a problem that occurs when the intensity distribution (E) of the second laser light L2 has a Gaussian shape. Fig. 23 is an explanatory diagram showing an example of an ideal intensity distribution (E) of the second laser light L2. Fig. 24 is an explanatory diagram showing an example of an actual intensity distribution (E) of the second laser light L2.

[0148] As shown by reference symbol XXIIA in Fig. 22, the intensity distribution of the laser beam L emitted from the laser source 22 has a Gaussian shape. Therefore, when the center cutting process is performed using the second laser beam L2 having a Gaussian shape, the cross-sectional shape of the center cut groove 19 (the two edge cutting grooves 18 are not shown) also has a Gaussian shape, as shown by reference symbol XXIIB. In this case, in the cutting process in which the wafer 12 is cut along the center cut groove 19 (streets C) by the blade 110 rotating at high speed after the laser processing, uneven wear of the blade 110 may occur depending on the positional relationship of the blade 110 with respect to the center cut groove 19. For this reason, it is required to form the bottom of the center cut groove 19 flat (including approximately flat).

[0149] 23, in order to form a flat bottom of the hollow groove 19, for example, a method of forming the intensity distribution of the second laser beam L2 into an isotropic top hat shape using a DOE and a refractive beam shaper can be considered. However, while optical elements such as the above-mentioned DOE and refractive beam shaper are designed on the premise that the laser beam L (beam) has an ideal perfect circle (cross-sectional shape), the cross-sectional shape of the actual laser beam L is not a perfect circle but an ellipse (a state in which the divergence angle is anisotropic) due to individual differences in the laser light source 22, etc. In this case, as shown in FIG. 24, the intensity distribution (E) of the second laser beam L2 has a shape other than a top hat shape, making it difficult to form a flat bottom of the hollow groove 19.

[0150] Furthermore, as described above, when the divergence angle of the laser beam L is anisotropic, astigmatism occurs, and the Z position at which the top hat shape is formed differs in each of the X and Y directions. Furthermore, when performing core cutting using the second laser beam L2 having the intensity distribution (E) shown in Figure 23, the cross-sectional shape of the core cut groove 19 becomes a shape obtained by integrating the spots of the second laser beam L2 according to the overlap rate in the processing feed direction (X direction). As a result, it is difficult to estimate the cross-sectional shape of the core cut groove 19 from the shape of the spot of the second laser beam L2 alone.

[0151] Therefore, in the laser processing apparatus 10 of the seventh embodiment, the intensity distribution (E) of the second laser beam L2 is adjusted by the second light forming element 34 so that the intensity distribution (E) of the second laser beam L2 has a stable top hat shape and the cross-sectional shape of the hollow groove 19 can be easily estimated. The laser processing apparatus 10 of the seventh embodiment has basically the same configuration as the laser processing apparatus 10 of each of the above embodiments except for the difference in the function of the second light forming element 34. Therefore, parts that are the same in function or configuration as those of each of the above embodiments will be assigned the same reference numerals and their description will be omitted.

[0152] 25 is an explanatory diagram showing an example of the intensity distribution (E) in the Y direction of the second laser light L2 of the seventh embodiment, and XXVB is an explanatory diagram showing an example of the intensity distribution (E) in the X direction of the second laser light L2 of the seventh embodiment. Fig. 26 is an explanatory diagram showing an example of the intensity distribution in the XY plane of the second laser light L2 of the seventh embodiment.

[0153] 25 and 26, the second laser beam L2 formed by the second beam forming element 34 of the seventh embodiment has a top-hat intensity distribution in a first direction (e.g., the Y direction perpendicular to the processing feed direction) and a Gaussian intensity distribution in a second direction (e.g., the X direction parallel to the processing feed direction). As such a second beam forming element 34, for example, an optical element such as a DOE or a refractive beam shaper (a combination of multiple types of optical elements is also possible) is used.

[0154] In this way, forming the second laser beam L2 having a top hat-shaped intensity distribution in only one direction (here, the Y direction) reduces the difficulty of adjusting the second laser beam L2 to form a top hat shape compared to forming the second laser beam L2 having a top hat-shaped intensity distribution in multiple directions as shown in Fig. 23. As a result, it becomes possible to form the second laser beam L2 in a stable top hat shape, and therefore the bottom of the hollow groove 19 can be formed flat.

[0155] Furthermore, by forming the intensity distribution of the second laser beam L2 in the X direction (processing feed direction) into a Gaussian shape, the profile shape of the spot of the second laser beam L2 in the Y direction (i.e., an inverted top hat shape) can be directly reflected in the processed shape of the center hole groove 19. As a result, the processed shape of the center hole groove 19 can be easily estimated from the shape of the spot of the second laser beam L2 alone.

[0156] 25 and 26, the first direction is the Y direction and the second direction is the X direction, but the first direction and the second direction can be any direction within the XY plane (within a horizontal plane) by rotating the second light formation element 34 using the second rotation mechanism 46 of the second embodiment (see FIGS. 10 and 11). That is, when the first direction and the second direction are directions parallel to the table 20 (perpendicular to the traveling direction of the second laser light L2 emitted from the second light formation element 34) and orthogonal to each other, the second light formation element 34 forms the second laser light L2 having a top-hat intensity distribution in the first direction and a Gaussian intensity distribution in the second direction.

[0157] In the seventh embodiment, the second light forming element 34 forms the second laser light L2 having a top-hat shaped intensity distribution in only one direction, but the first light forming element 32 may also form two first laser lights L1 having a top-hat shaped intensity distribution in only one direction. Furthermore, the invention of the seventh embodiment can be applied to various laser processing of the wafer 12 other than edge cutting and hollowing.

[0158] [Eighth embodiment] Fig. 27 is a schematic diagram of the laser optical system 24 of the laser processing apparatus 10 of the eighth embodiment. In each of the above embodiments, edge cutting is performed using one of the first condenser lenses 38, 38A, 38B, and hollow cutting is performed using one of the second condenser lenses 40, 40A, 40B. In contrast, as shown in Fig. 27, the laser processing apparatus 10 of the eighth embodiment performs edge cutting using the first condenser lens group 120, and hollow cutting using one of the second condenser lens groups 122A, 122B.

[0159] The laser processing apparatus 10 of the eighth embodiment has basically the same configuration as the laser processing apparatus 10 of each of the above-described embodiments (here, excluding the sixth embodiment) except for the fact that it includes a first condenser lens group 120 and second condenser lens groups 122A, 122B. Therefore, components that are the same in function or configuration as those of the above-described embodiments are given the same reference numerals, and their description will be omitted. The first condenser lens group 120 and second condenser lens groups 122A, 122B, together with the already-described connection switching element 36 and the like, constitute a condensing optical system.

[0160] The first condenser lens group 120 is provided in place of the first condenser lens 38 in each of the above embodiments. The first condenser lens group 120 includes a branching element 124 and three first condenser lenses 38.

[0161] The branching element 124 branches the two first laser beams L1 incident from the first light forming element 32 into three beams, which are emitted respectively toward the three first condenser lenses 38. The three first condenser lenses 38 are arranged in a row along the X direction (processing feed direction), and simultaneously condense the two first laser beams L1 incident from the branching element 124 onto the street C (outward and return paths).

[0162] The second collective lens group 122A is provided in place of the second collective lens 40A in each of the above embodiments. The second collective lens group 120A includes a branching element 126A and three second collective lenses 40A.

[0163] The branching element 126A branches the second laser light L2 incident from the second light forming element 34 into three beams, which are emitted toward the three second condenser lenses 40A. The three second condenser lenses 40A are arranged in a row along the X direction (processing feed direction), and simultaneously condense the second laser light L2 incident from the branching element 126A onto the street C (outward path).

[0164] The second collective lens group 122B is provided in place of the second collective lens 40B in each of the above embodiments. The second collective lens group 120B includes a branching element 126B and three second collective lenses 40B.

[0165] The branching element 126B branches the second laser light L2 incident from the second light forming element 34 into three beams, which are emitted toward the three second condenser lenses 40B. The three second condenser lenses 40B are arranged in a row along the X direction (processing feed direction), and simultaneously condense the second laser light L2 incident from the branching element 126B onto street C (return path).

[0166] Figure 28 is an explanatory diagram for explaining the effect of the laser processing apparatus 10 of the eighth embodiment. Note that reference numeral XXVIIIA in Figure 28 indicates movement of the spots SP of each laser beam (two first laser beams L1 and second laser beam L2) focused on the street C during edge cutting processing and hollow cutting processing by the laser processing apparatus 10 of each of the above embodiments. Also, reference numeral XXVIIIB in Figure 28 indicates movement of the spots SP1 to SP3 of each laser beam focused on the street C during edge cutting processing and hollow cutting processing by the laser processing apparatus 10 of the eighth embodiment.

[0167] As shown by reference symbol XXVIIIA in Fig. 28, due to the relative movement of the laser optical system 24 in the forward direction X1 or the backward direction X2 during edge cutting and hollow cutting, the two spots SP of the first laser beam L1 and the second laser beam L2 formed on the street C (forward and backward paths) by the laser optical system 24 move along the street C. If the speed of the relative movement of the laser optical system 24 is increased at this time, the spacing between the spots SP in the processing feed direction will increase, resulting in unevenness on the bottom surfaces of the processing grooves (the two edge cutting grooves 18 and the hollow cutting groove 19). For this reason, in each of the above embodiments, it is necessary to limit the speed of the relative movement of the laser optical system 24 so that adjacent spots SP in the processing feed direction partially overlap each other.

[0168] In contrast, in the laser processing apparatus 10 of the eighth embodiment, by arranging a plurality of first condenser lenses 38 and a plurality of second condenser lenses 40A, 40B along the processing feed direction, it is possible to simultaneously condense the two first laser beams L1 and the two second laser beams L2 at a plurality of locations on the street C (forward and return passes), as shown by reference symbol XXVIIIB in Fig. 28. For this reason, in the eighth embodiment, by relatively moving the laser optical system 24 in the forward pass direction side X1 or the return pass direction side X2, the three spots SP1, SP2, SP3 of the two first laser beams L1 formed on the street C (forward and return passes) and the three spots SP1, SP2, SP3 of the second laser beam L2 move along the street C.

[0169] In this way, in the eighth embodiment, by increasing the number of spots per laser processing, it is possible to make adjacent spots SP1, SP2, and SP3 in the processing feed direction partially overlap each other even when the relative movement speed of the laser optical system 24 is increased. This makes it possible to form processed grooves with a stable shape. As a result, in the eighth embodiment, it is possible to reduce the takt time required for laser processing of the wafer 12 compared to the above embodiments.

[0170] In the eighth embodiment, three first condenser lenses 38, three second condenser lenses 40A, and three second condenser lenses 40B are arranged along the processing feed direction, but the number of lenses arranged may be two or four or more. Also, similar to the sixth embodiment (see FIGS. 21 and 22), the first condenser lens group 120 and the second condenser lens groups 122A and 122B may be interchanged.

[0171] [Ninth embodiment] Fig. 29 is an explanatory diagram for explaining edge cutting and hollow cutting by the laser optical system 24 of the laser processing apparatus 10 of the ninth embodiment, which is moved relatively in the forward direction side X1 with respect to the wafer 12. Fig. 30 is an explanatory diagram for explaining edge cutting and hollow cutting by the laser optical system 24 of the laser processing apparatus 10 of the ninth embodiment, which is moved relatively in the backward direction side X2 with respect to the wafer 12.

[0172] In each of the above embodiments, laser processing is performed by selectively using three types of first condenser lenses 38 (38A, 38B) and second condenser lenses 40A, 40B (40) depending on the relative movement direction of the laser optical system 24 with respect to the wafer 12. In contrast to this, in the ninth embodiment, as shown in Figures 29 and 30, laser processing is performed using the first condenser lens 38 and the second condenser lens 40. In the ninth embodiment, edge cutting processing by the first condenser lens 38 and hollow cutting processing by the second condenser lens 40 and hollow cutting processing by the first condenser lens 38 are switched between edge cutting processing by the second condenser lens 40 and hollow cutting processing by the first condenser lens 38 depending on the relative movement direction of the laser optical system 24 with respect to the wafer 12.

[0173] The laser optical system 24 of the ninth embodiment has basically the same configuration as the laser processing apparatus 10 of the first embodiment, except that it includes a first condenser lens 38 and a second condenser lens 40 instead of the first condenser lens 38 and the second condenser lenses 40A, 40B, and a connection optical system 200 instead of the connection switching element 36. For this reason, parts that are the same in function or configuration as those of the first embodiment are given the same reference numerals, and their description will be omitted.

[0174] The first condenser lens 38 and the second condenser lens 40 are arranged in a row along the X direction (processing feed direction). The first condenser lens 38 is arranged on the forward direction side X1 with respect to the second condenser lens 40. The first condenser lens 38 condenses two first laser beams L1 or second laser beams L2 incident from a connecting optical system 200 (described later) onto the street C. In addition, the second condenser lens 40 condenses two first laser beams L1 or second laser beams L2 incident from the connecting optical system 200 onto the street C.

[0175] When the relative movement mechanism 28 moves the laser optical system 24 relatively in the outward direction side X1 with respect to the wafer 12, the connection optical system 200 guides the two first laser beams L1 emitted from the first light formation element 32 to the first condenser lens 38 and guides the second laser beam L2 emitted from the second light formation element 34 to the second condenser lens 40 (see FIG. 29). Conversely, when the relative movement mechanism 28 moves the laser optical system 24 relatively in the backward direction side X2 with respect to the wafer 12, the connection optical system 200 guides the two first laser beams L1 emitted from the first light formation element 32 to the second condenser lens 40 and guides the second laser beam L2 emitted from the second light formation element 34 to the first condenser lens 38 (see FIG. 30).

[0176] Fig. 31 is an explanatory diagram for explaining the function of the connection optical system 200 when the relative movement mechanism 28 moves the laser optical system 24 relative to the wafer 12 in the outward direction side X1. Fig. 32 is an explanatory diagram for explaining the function of the connection optical system 200 when the relative movement mechanism 28 moves the laser optical system 24 relative to the wafer 12 in the backward direction side X2.

[0177] 31 and 32, symbol PP1 indicates that the two first laser beams L1 are P-polarized, symbol SP1 indicates that the two first laser beams L1 are S-polarized, symbol PP2 indicates that the second laser beam L2 is P-polarized, and symbol SP2 indicates that the second laser beam L2 is S-polarized. In addition, in this embodiment, the two first laser beams L1 emitted from the first light formation element 32 and the second laser beam L2 emitted from the second light formation element 34 will be described as being P-polarized.

[0178] As shown in FIGS. 31 and 32, the connection optical system 200 includes a polarizing beam splitter 202, a λ / 2 plate 204, a polarizing beam splitter 206, a λ / 2 plate 208, polarizing beam splitters 210 and 212, a λ / 2 plate 214, and mirrors 220 and 222.

[0179] The polarizing beam splitter 202, the λ / 2 plate 204, and the polarizing beam splitter 206 are arranged along the optical path from the first light forming element 32 to the first condenser lens 38. The λ / 2 plate 208, the polarizing beam splitters 210 and 212, and the λ / 2 plate 214 are arranged along the optical path from the second light forming element 34 to the second condenser lens 40. The mirror 220 is arranged on the optical path between the polarizing beam splitter 202 and the polarizing beam splitter 210. The mirror 222 is arranged on the optical path between the polarizing beam splitter 206 and the polarizing beam splitter 212.

[0180] Each of the polarizing beam splitters 202, 206, 210, and 212 transmits P-polarized light and reflects S-polarized light.

[0181] The λ / 2 plates 204, 208, and 214 are switchable between a reference state in which they transmit P-polarized light and S-polarized light without changing their polarization state, and a rotated state in which the optical axis is rotated 45 degrees from the reference state. In the rotated state, the λ / 2 plates 204, 208, and 214 convert incident P-polarized light into S-polarized light and convert incident S-polarized light into P-polarized light.

[0182] Mirror 220 guides the S-polarized light reflected by polarizing beam splitter 210 to polarizing beam splitter 202. Mirror 222 guides the S-polarized light reflected by polarizing beam splitter 206 to polarizing beam splitter 212. Note that if polarizing beam splitters 202 and 210 are arranged opposite each other in the X direction, mirror 220 can be omitted, and if polarizing beam splitters 206 and 212 are arranged opposite each other in the X direction, mirror 222 can be omitted.

[0183] As shown in Figure 31, the control device 30 (see Figure 1) of the ninth embodiment sets the λ / 2 plates 204, 208, and 214 to their respective reference states when performing laser processing on street C (outward path), i.e., when the relative movement mechanism 28 moves the laser optical system 24 relative to the wafer 12 in the outward direction side X1.

[0184] The two first laser beams L1 (P polarized) emitted from the first light forming element 32 are transmitted through the polarizing beam splitter 202, the λ / 2 plate 204, and the polarizing beam splitter 206 in this order, and are then guided to the first condenser lens 38. As a result, the two first laser beams L1 are condensed onto street C (outward path) by the first condenser lens 38.

[0185] The second laser light L2 (P polarized light) emitted from the second light forming element 34 is transmitted in order through the λ / 2 plate 208, the polarizing beam splitters 210 and 212, and the λ / 2 plate 214, and is guided to the second condenser lens 40. As a result, the second laser light L2 is condensed onto street C (outward path) by the second condenser lens 40.

[0186] As in the above-described embodiments, edge cutting is performed first along the street C (outward path) by the relative movement of the laser optical system 24 toward the outward direction side X1, and then hollowing is performed. Note that the timing of emission and stoppage of emission of the two laser beams, the first laser beam L1 and the second laser beam L2, during laser processing of the street C (outward path) is the same as in the above-described first embodiment, and therefore a detailed description thereof will be omitted here (the same applies to the tenth and eleventh embodiments described below).

[0187] As shown in Figure 32, the control device 30 of the ninth embodiment sets the λ / 2 plates 204, 208, and 214 to a rotating state when performing laser processing on street C (return path), i.e., when the relative movement mechanism 28 moves the laser optical system 24 relative to the wafer 12 in the return path direction X2.

[0188] The two first laser beams L1 (P polarized) emitted from the first light forming element 32 pass through the polarizing beam splitter 202 and are then converted into S polarized light by the λ / 2 plate 204. The two first laser beams L1 converted into S polarized light are reflected by the polarizing beam splitter 206 toward the mirror 222, and are further reflected by the mirror 222 to enter the polarizing beam splitter 212. The two first laser beams L1 (S polarized) that enter the polarizing beam splitter 212 are reflected by the polarizing beam splitter 212 toward the λ / 2 plate 214, and are then converted into P polarized light by this λ / 2 plate 214, and are then guided to the second condenser lens 40. As a result, the two first laser beams L1 are condensed onto street C (return path) by the second condenser lens 40.

[0189] The second laser light L2 (P polarized light) emitted from the second light forming element 34 is converted into S polarized light by the λ / 2 plate 208, then reflected by the polarizing beam splitter 210 toward the mirror 220, and further reflected by the mirror 220 to enter the polarizing beam splitter 202. The second laser light L2 (S polarized light) that entered the polarizing beam splitter 202 is reflected by the polarizing beam splitter 202 toward the λ / 2 plate 204, and converted into P polarized light by this λ / 2 plate 204, then passes through the polarizing beam splitter 206 and is guided to the first condenser lens 38. As a result, the second laser light L2 is condensed onto street C (return path) by the first condenser lens 38.

[0190] As in the above-described embodiments, edge cutting is performed first along street C (returning path) by the relative movement of the laser optical system 24 toward the return direction side X2, followed by hollowing. Note that the timing of emission and stoppage of emission of the two first laser beams L1 and second laser beam L2 during laser processing of street C (returning path) is the same as in the above-described first embodiment, and therefore a detailed description thereof will be omitted here (the same applies to the tenth and eleventh embodiments described later).

[0191] In the ninth embodiment, a λ / 2 plate 214 is provided to align the polarization state of the two first laser beams L1 that perform edge cutting processing on street C (return path) to P polarization, similar to that during edge cutting processing on street C (outward path), but if there is no need to align to P polarization, the λ / 2 plate 214 may be omitted.

[0192] As described above, in the ninth embodiment, it is possible to switch between edge cutting using the first condenser lens 38 and hollow cutting using the second condenser lens 40, and edge cutting using the second condenser lens 40 and hollow cutting using the first condenser lens 38, depending on the relative movement direction of the laser optical system 24 with respect to the wafer 12. As a result, the same effects as those of the above embodiments can be obtained.

[0193] [Modification of the ninth embodiment] <Variation 1> Fig. 33 is an explanatory diagram for explaining edge cutting and hollow cutting by the laser optical system 24 that is moved relatively to the outgoing direction side X1 with respect to the wafer 12 in Modification 1 of the ninth embodiment. Fig. 34 is an explanatory diagram for explaining edge cutting and hollow cutting by the laser optical system 24 that is moved relatively to the homeward direction side X2 with respect to the wafer 12 in Modification 1 of the ninth embodiment.

[0194] In the ninth embodiment, two laser beams, a first laser beam L1 for edge cutting and a second laser beam L2 for hollow cutting, are formed from the laser beam L emitted from the laser beam source 22. In contrast, as shown in Figures 33 and 34, in Modification 1 of the ninth embodiment, a first laser beam source 22A for edge cutting and a second laser beam source 22B for hollow cutting are separately provided, similar to the fourth embodiment (see Figures 13 and 14). Note that components that are the same in function or configuration as those in the fourth embodiment are given the same reference numerals, and descriptions thereof will be omitted.

[0195] In this way, in variant example 1 of the ninth embodiment, by separately providing a first laser light source 22A corresponding to edge cutting processing and a second laser light source 22B corresponding to core cutting processing, a decrease in the processing speed of each of the edge cutting processing and core cutting processing is prevented, as in the above-mentioned fourth embodiment, and therefore the takt time can be further reduced.

[0196] <Variation 2> Fig. 35 is an explanatory diagram for explaining edge cutting and hollow cutting by the laser optical system 24 that is moved relatively to the outgoing direction side X1 with respect to the wafer 12 in Modification 2 of the ninth embodiment. Fig. 36 is an explanatory diagram for explaining edge cutting and hollow cutting by the laser optical system 24 that is moved relatively to the return direction side X2 with respect to the wafer 12 in Modification 2 of the ninth embodiment.

[0197] 35 and 36, Modification 2 of the ninth embodiment has a function of being able to continue laser processing of the wafer 12 even if a malfunction occurs in either the first laser light source 22A or the second laser light source 22B in Modification 1. Specifically, Modification 2 of the ninth embodiment is provided with bypass optical systems 72 and 74, similar to the fifth embodiment (see FIGS. 18 and 19). Note that parts that are the same in function or configuration as those in the fifth embodiment are given the same reference numerals, and descriptions thereof will be omitted.

[0198] In this way, in variant example 2 of the ninth embodiment, by providing bypass optical systems 72 and 74, as in the fourth embodiment described above, laser processing of the wafer 12 can be continued even if a malfunction occurs in either the first laser light source 22A or the second laser light source 22B.

[0199] <Other> In the ninth embodiment, as in the second embodiment (see Figures 8 to 11), the width of the two edge-cutting grooves 18 may be adjusted by the first rotation mechanism 44, and the width of the second laser light L2 may be adjusted by the second rotation mechanism 46.

[0200] Furthermore, in the ninth embodiment, as in the third embodiment (see FIG. 12), the Y-direction positions of the two spots of the first laser light L1 and the second laser light L2 may be adjustable using mirrors 37, 39B and moving mechanisms 48, 49B, etc.

[0201] Furthermore, the ninth embodiment (including modifications 1 and 2) may be appropriately combined with the configurations of the seventh and eighth embodiments.

[0202] [Tenth embodiment] 37 is an explanatory diagram for explaining edge cutting and hollow cutting by the laser optical system 24 of the laser processing apparatus 10 of the tenth embodiment. In the ninth embodiment, the edge cutting using the first condenser lens 38 and hollow cutting using the second condenser lens 40, and the edge cutting using the second condenser lens 40 and hollow cutting using the first condenser lens 38 are switched depending on the relative movement direction of the laser optical system 24 with respect to the wafer 12. In contrast, in the tenth embodiment, the edge cutting is performed in the same manner as in the ninth embodiment, and hollow cutting is also performed using both the first condenser lens 38 and the second condenser lens 40.

[0203] The laser optical system 24 of the 10th embodiment has basically the same configuration as the laser processing apparatus 10 of the 9th embodiment, except for the fact that the function of the λ / 2 plate 208 is slightly different. Therefore, parts that are the same in function or configuration as those of the 9th embodiment are given the same symbols and their explanations are omitted.

[0204] The λ / 2 plate 208 of the tenth embodiment is set to a half-rotation state rotated 22.5 degrees from the reference angle state by the above-mentioned control device 30. In the half-rotation state, when the second laser light L2 (P-polarized) is incident from the second light formation element 34, the λ / 2 plate 208 rotates the polarization direction of the second laser light L2 by 45 degrees.

[0205] The polarizing beam splitter 210 of the tenth embodiment transmits the P-polarized component of the second laser light L2 that has passed through the half-rotated λ / 2 plate 208 and emits it toward the polarizing beam splitter 212, while reflecting the S-polarized component toward the mirror 220. In this way, the second laser light L2 is split into two by the polarizing beam splitter 210. The second laser light L2 (P-polarized) that has passed through the polarizing beam splitter 210 passes through the polarizing beam splitter 212 and the λ / 2 plate 214 and is guided to the second focusing lens 40.

[0206] On the other hand, the second laser light L2 (S-polarized light) reflected by the polarizing beam splitter 210 is reflected by the mirror 220 and enters the polarizing beam splitter 202. The second laser light L2 (S-polarized light) is then reflected by the polarizing beam splitter 202 toward the λ / 2 plate 204, converted to P-polarized light by this λ / 2 plate 204, and then transmitted through the polarizing beam splitter 206 and guided to the first condenser lens 38. As a result, the second laser light L2 is condensed onto street C (return path) by both the first condenser lens 38 and the second condenser lens 40.

[0207] Due to the relative movement of the laser optical system 24 toward the return direction side X2, the second condenser lens 40 performs edge cutting and hollow cutting along the street C (return direction) in advance, thereby forming two edge cutting grooves 18 and hollow cutting groove 19 in advance, and then the first condenser lens 38 performs hollow cutting, thereby forming another hollow cutting groove 19 on top of the previous hollow cutting groove 19. This makes it possible to improve the overlap rate of spots of the second laser light L2 that are adjacent to each other in the processing feed direction.

[0208] When the laser optical system 24 is moved relatively in the outward direction X1, the second laser light L2 (S-polarized light) reflected by the polarizing beam splitter 202 needs to be converted to P-polarized light before it enters the polarizing beam splitter 206. In this case, for example, a λ / 2 plate (in a rotated state) is temporarily placed only on the optical path of the second laser light L2 between the polarizing beam splitter 202 and the polarizing beam splitter 206. As a result, the relative movement of the laser optical system 24 in the outward direction X1 causes the first condenser lens 38 to perform edge cutting and hollow cutting along the street C (outward path), and then the second condenser lens 40 performs hollow cutting.

[0209] As described above, in the tenth embodiment, it is possible to perform pseudo three-point simultaneous processing, including edge cutting and hollowing processing by one of the first condenser lens 38 and the second condenser lens 40, and hollowing processing by the other of the first condenser lens 38 and the second condenser lens 40, depending on the relative movement direction of the laser optical system 24 with respect to the wafer 12. As a result, it is possible to improve the overlap rate of the spot of the second laser light L2 on the street C.

[0210] Note that, when the overlap rate of the spots of the two first laser beams L1 on the street C is improved, the λ / 2 plate 204 is set to a half-rotation state instead of setting the λ / 2 plate 208 to a half-rotation state. As a result, the λ / 2 plate 204 splits the two first laser beams L1 (P polarized) incident from the polarizing beam splitter 202 into P polarized light and S polarized light, and outputs them toward the polarizing beam splitter 206. As a result, the P polarized light of the two first laser beams L1 is guided to the first condenser lens 38, and the S polarized light is guided to the polarizing beam splitter 212 (second condenser lens 40).

[0211] Therefore, it is possible to perform pseudo three-point simultaneous processing including edge cutting processing by one of the first condenser lens 38 and the second condenser lens 40, and edge cutting processing and hollowing processing by the other of the first condenser lens 38 and the second condenser lens 40, depending on the relative movement direction of the laser optical system 24 with respect to the wafer 12. As a result, it is possible to improve the overlap rate of the spots of the two first laser beams L1 on the street C.

[0212] <Modification> In the tenth embodiment, similarly to the ninth embodiment (including the first and second modifications), the configurations of the second to eighth embodiments may be combined as appropriate.

[0213] [Eleventh embodiment] Fig. 38 is an explanatory diagram for explaining edge cutting and hollow cutting by the laser optical system 24 of the laser processing apparatus 10 of the eleventh embodiment, which is moved relatively in the forward direction side X1 with respect to the wafer 12. Fig. 39 is an enlarged view of the area within the dotted circle K1 in Fig. 38. Fig. 40 is an explanatory diagram for explaining edge cutting and hollow cutting by the laser optical system 24 of the laser processing apparatus 10 of the eleventh embodiment, which is moved relatively in the backward direction side X2 with respect to the wafer 12. Fig. 41 is an enlarged view of the area within the dotted circle K2 in Fig. 40.

[0214] In each of the above embodiments, the edge cutting and hollowing are performed using a plurality of various lenses while the laser optical system 24 is moved relative to the wafer 12 in the forward direction side X1 and the backward direction side X2. In contrast, in the eleventh embodiment, the edge cutting and hollowing are performed using only one first condenser lens 38 while the laser optical system 24 is moved relative to the wafer 12 in the forward direction side X1 and the backward direction side X2.

[0215] 38 to 41, the laser optical system 24 of the eleventh embodiment is equipped with a first condenser lens 38 and a connecting optical system 200A, and has basically the same configuration as the laser processing apparatus 10 of each of the above-described embodiments, except that the first light forming element 32 generates two first laser beams L1 (S-polarized) and the second light forming element 34 generates a second laser beam L2 (P-polarized). For this reason, components that are the same in function or configuration as those of the above-described embodiments are given the same reference numerals, and their description will be omitted.

[0216] The first focusing lens 38 of the eleventh embodiment focuses two beams of first laser light L1 and second laser light L2 incident from a connecting optical system 200A (described later) onto the street C. Note that in Figures 39 and 41, the symbol OP indicates the optical axis of the first focusing lens 38, the symbol SPA indicates the spots of the two beams of first laser light L1, and the symbol SPB indicates the spot of the second laser light L2.

[0217] The connection optical system 200A guides the two first laser beams L1 emitted from the first light forming element 32 and the second laser beam L2 emitted from the second light forming element 34 to the first condenser lens 38. At this time, when the relative movement mechanism 28 moves the laser optical system 24 in the forward direction side X1 relative to the wafer 12, the connection optical system 200A shifts the spots SPA of the two first laser beams L1 relative to the spots SPB of the second laser beam L2 in the forward direction side X1. Conversely, when the relative movement mechanism 28 moves the laser optical system 24 in the backward direction side X2 relative to the wafer 12, the connection optical system 200A shifts the spots SPA of the two first laser beams L1 relative to the spots SPB of the second laser beam L2 in the backward direction side X2.

[0218] The connecting optical system 200A includes a shift element 230, a mirror 232, and a polarizing beam splitter 234.

[0219] The shift element 230 and the mirror 232 are disposed on the optical path from the first light shaping element 32 to the polarizing beam splitter 234 .

[0220] The shift element 230 is configured with, for example, a plurality of prisms (shift prisms) or a plurality of mirrors, and shifts the two first laser beams L1 incident from the first light forming element 32 in the X direction, and then emits the two first laser beams L1 toward a mirror 232 located below in the Z direction. The shift element 230 can be rotated about the Z axis to arbitrarily adjust the shift direction of the two first laser beams L1. When the shift element 230 is set to a first angular position in the direction about the Z axis, it shifts the two first laser beams L1 toward the outgoing direction side X1, and when the shift element 230 is set to a second angular position rotated 180 degrees from the first angular position, it shifts the two first laser beams L1 toward the return direction side X2.

[0221] The mirror 232 guides the two first laser beams L 1 incident from the shift element 230 to the polarizing beam splitter 234 .

[0222] The polarizing beam splitter 234 is disposed on the optical path from the second light forming element 34 to the first condenser lens 38. This polarizing beam splitter 234 reflects the two first laser beams L1 (S-polarized) incident from the mirror 232 toward the first condenser lens 38, and transmits the second laser beam L2 (P-polarized) incident from the second light forming element 34 to emit it to the first condenser lens 38. As a result, the two first laser beams L1 and second laser beam L2 are condensed onto the street C by the first condenser lens 38.

[0223] 38 and 39, the control device 30 of the eleventh embodiment sets the shift element 230 to the first angle position when performing laser processing of street C (outward path), i.e., when the relative movement mechanism 28 moves the laser optical system 24 relatively to the wafer 12 in the forward path direction X1. As a result, on street C (outward path), the spots SPA of the two first laser beams L1 are shifted toward the forward path direction X1 relative to the spots SPB of the second laser beam L2. As a result, as in the above-described embodiments, the relative movement of the laser optical system 24 in the forward path direction X1 causes edge cutting processing to be performed first along street C (outward path), followed by hollowing processing.

[0224] 40 and 41 , the control device 30 of the eleventh embodiment sets the shift element 230 to the second angle position when performing laser processing of street C (returning path), i.e., when the relative movement mechanism 28 moves the laser optical system 24 relatively to the wafer 12 in the return direction side X2. As a result, on street C (returning path), the spots SPA of the two first laser beams L1 are shifted toward the return direction side X2 with respect to the spots SPB of the second laser beam L2. As a result, as in the above-described embodiments, the relative movement of the laser optical system 24 toward the return direction side X2 causes edge cutting processing to be performed first along street C (returning path), followed by hollowing processing.

[0225] As described above, in the eleventh embodiment, the shift element 230 shifts the two first laser beams L1 relatively in the processing feed direction with respect to the second laser beam L2, thereby making it possible to perform edge cutting and hollowing of the street C (outward and backward paths) with the single first condenser lens 38. As a result, the same effects as those of the above-described embodiments can be obtained.

[0226] <Modification> In the eleventh embodiment, the two first laser beams L1 (spots SPA) are shifted by the shift element 230, but the second laser beam L2 (spot SPB) may be shifted in the direction opposite to the processing feed direction.

[0227] Fig. 42 is an explanatory diagram for explaining a modified example of the 11th embodiment. As shown by symbols XLIIA and XLIIB in Fig. 42, in the 11th embodiment, similarly to the second embodiment (see Figs. 8 to 11), the width of the two edge-cutting grooves 18 may be adjusted by a first rotation mechanism 44, and the width of the second laser beam L2 may be adjusted by a second rotation mechanism 46.

[0228] Also, in the eleventh embodiment, the configurations of the fourth, fifth, seventh, and eighth embodiments may be combined as appropriate.

[0229] [others] In each of the above embodiments, the edge cutting processing and the hollow cutting processing are switched on and off by inserting and removing each safety shutter 100, 100A, 100B into and from the optical path, but the edge cutting processing and the hollow cutting processing may also be switched on and off by turning the laser light source 22 (first laser light source 22A and second laser light source 22B) on and off.

[0230] [Note] As can be understood from the above detailed description of the embodiments, this specification includes disclosure of various technical ideas including the inventions described below.

[0231] (Additional note 1) a laser processing apparatus for performing, for each street, an edge-cutting process to form two parallel first grooves along the streets and a hollowing process to form a second groove between the two first grooves, by irradiating the wafer with laser light from the laser optical system while moving a table that holds a wafer and a laser optical system that is positioned opposite the table relatively in a processing feed direction along the streets of the wafer, The laser optical system a laser beam emitting system that emits two first laser beams corresponding to the edge cutting process and a second laser beam corresponding to the hollowing process; a focusing optical system that focuses the two first laser beams and the second laser beam on the street of the processing target; Equipped with A laser processing device in which, when the laser optical system is moved relatively in the forward direction of the processing feed direction with respect to the table, the focusing optical system focuses the two first laser beams on the street at a position relatively shifted in the forward direction with respect to the second laser beam, and, when the laser optical system is moved relatively in the backward direction of the processing feed direction with respect to the table, the focusing optical system focuses the two first laser beams on the street at a position relatively shifted in the backward direction with respect to the second laser beam.

[0232] (Additional note 2) The focusing optical system is a first condenser lens that condenses the two first laser beams onto the wafer; two second condenser lenses arranged in a row along the processing feed direction together with the first condenser lens with the first condenser lens sandwiched therebetween, each second condenser lens focusing the second laser light onto the wafer; a connecting optical system that guides the two first laser beams emitted from the laser beam emitting system to the first condenser lens and selectively guides the second laser beams emitted from the laser beam emitting system to two of the second condenser lenses; Equipped with The laser processing apparatus according to appended claim 1, wherein the connecting optical system guides the second laser light to the second focusing lens located on the return path side of the first focusing lens when the laser optical system is moved relative to the table in the forward path direction, and guides the second laser light to the second focusing lens located on the return path side of the first focusing lens when the laser optical system is moved relative to the table in the return path direction.

[0233] (Additional note 3) The focusing optical system is two first condenser lenses arranged in a row along the processing feed direction, each of which condenses the two first laser beams onto the wafer; a second condenser lens disposed between the two first condenser lenses and configured to condense the second laser light onto the wafer; a connecting optical system that selectively guides the two first laser beams emitted from the laser beam emitting system to the two first condenser lenses and guides the second laser beam emitted from the laser beam emitting system to the second condenser lens; Equipped with The laser processing apparatus described in appended item 1, wherein the connecting optical system guides the two first laser beams to the first focusing lens located on the forward path side of the second focusing lens when the laser optical system is moved relative to the table in the forward path direction, and guides the two first laser beams to the first focusing lens located on the backward path side of the second focusing lens when the laser optical system is moved relative to the table in the backward path direction.

[0234] (Additional note 4) The focusing optical system is two condenser lenses arranged in a row along the processing feed direction; a connecting optical system that guides the two first laser beams and the second laser beam emitted from the laser beam emitting system to the condenser lens; Equipped with The laser processing apparatus according to appended claim 1, wherein the connecting optical system, when the laser optical system is moved relative to the table in the forward direction, guides the two first laser beams to the focusing lens on the forward direction side and guides the second laser beam to the focusing lens on the return direction side, and when the laser optical system is moved relative to the table in the return direction side, guides the two first laser beams to the focusing lens on the return direction side and guides the second laser beam to the focusing lens on the forward direction side.

[0235] (Additional note 5) The laser processing apparatus according to claim 4, wherein the connecting optical system splits one of the two first laser beams and the second laser beam into two and guides the split laser beam to both of the two focusing lenses.

[0236] (Additional note 6) The focusing optical system is A condenser lens; a connecting optical system that guides the two first laser beams and the second laser beam emitted from the laser beam emitting system to the condenser lens; Equipped with The laser processing apparatus according to appended claim 1, wherein the connecting optical system is provided with a shift element that shifts the second laser light relative to the two first laser lights in the return direction when the laser optical system is moved relative to the table in the forward direction, and that shifts the second laser light relative to the two first laser lights in the return direction when the laser optical system is moved relative to the table in the return direction.

[0237] (Additional note 7) a first moving mechanism that moves the first condenser lens in a vertical direction that is parallel to the table and perpendicular to the processing feed direction; a second movement mechanism that moves the second condenser lens in the vertical direction; 4. The laser processing apparatus according to claim 2 or 3, comprising:

[0238] (Additional note 8) 6. The laser processing device according to claim 4 or 5, further comprising a movement mechanism that moves the condenser lens in a vertical direction that is parallel to the table and perpendicular to the processing feed direction.

[0239] (Additional note 9) The laser light emission system a laser light source that emits laser light; a branching element that branches the laser light emitted from the laser light source into two beams; a first light forming element that forms the two first laser beams from one of the laser beams branched into two by the branching element; a second light forming element that forms the second laser light from the other of the laser lights branched into two by the branching element; 9. The laser processing device according to any one of claims 1 to 8, comprising:

[0240] (Additional note 10) The laser light emission system a first laser light source that emits laser light having conditions corresponding to the edge cutting process; a second laser light source that emits laser light under conditions corresponding to the hollowing process; a first light forming element that forms the two first laser beams from the laser beam emitted from the first laser light source; a second light forming element that forms the second laser light from the laser light emitted from the second laser light source; 9. The laser processing device according to any one of claims 1 to 8, comprising:

[0241] (Additional note 11) The laser processing apparatus according to appended claim 10, further comprising a bypass optical system that, when a malfunction occurs in the first laser light source, splits the laser light emitted from the second laser light source into two and outputs them to the first light forming element and the second light forming element, and, when a malfunction occurs in the second laser light source, splits the laser light emitted from the first laser light source into two and outputs them to the first light forming element and the second light forming element.

[0242] (Additional note 12) 12. The laser processing device according to any one of claims 9 to 11, further comprising a first rotation mechanism that rotates the first light forming element in a direction around an axis centered on the optical axis of the first light forming element.

[0243] (Additional note 13) the second light forming element forms the second laser light that forms a non-circular spot on the wafer; a second rotation mechanism that rotates the second light formation element in a direction around an axis centered on the optical axis of the second light formation element; 13. The laser processing device according to any one of claims 9 to 12, comprising:

[0244] (Additional note 14) The laser processing apparatus according to any one of appendix items 9 to 13, wherein, when directions parallel to the table and perpendicular to each other are defined as a first direction and a second direction, the second light forming element forms the second laser light having a top-hat intensity distribution in the first direction and a Gaussian intensity distribution in the second direction.

[0245] (Additional note 15) The focusing optical system is a first condenser lens group including a plurality of first condenser lenses arranged along the processing feed direction to condense the two first laser beams onto the wafer; two sets of second condenser lens groups arranged in a row along the processing feed direction together with the first condenser lens group with the first condenser lens group sandwiched therebetween, wherein a plurality of second condenser lenses that condense the second laser light onto the wafer are arranged for each second condenser lens group along the processing feed direction; a connecting optical system that guides the two first laser beams emitted from the laser beam emitting system to the first condenser lens group and selectively guides the second laser beams emitted from the laser beam emitting system to two sets of the second condenser lens group; Equipped with The laser processing apparatus according to appended claim 1, wherein the connecting optical system guides the second laser light to the second focusing lens group located on the return path side of the first focusing lens group when the laser optical system is moved relative to the table in the forward path direction, and guides the second laser light to the second focusing lens group located on the forward path side of the first focusing lens group when the laser optical system is moved relative to the table in the return path direction. [Explanation of symbols]

[0246] 10...laser processing device, 12...wafer, 14...chip, 16...device, 18...edge cutting groove, 19...core groove, 20...table, 22...laser light source, 22A...first laser light source, 22B...second laser light source, 24...laser optical system, 26...microscope, 28...relative movement mechanism, 30...control device, 31...branching element, 32...first light forming element, 34...second light forming element, 36...connection switching element, 37...mirror, 38, 38A, 38B...first condenser lens , 39A, 39B... mirror, 40, 40A, 40B... second condenser lens, 44... first rotation mechanism, 46... second rotation mechanism, 47A... first high-speed shutter, 47B... second high-speed shutter, 47C... high-speed shutter drive mechanism, 48, 49A, 49B... movement mechanism, 52... λ / 2 plate, 53... plate rotation mechanism, 54... polarizing beam splitter, 58... half mirror, 60... mirror, 62A, 62B... shutter, 64... shutter drive mechanism, 66A, 66B... mirror Mirror, 68...mirror drive mechanism, 72, 74...bypass optical system, 100...safety shutter, 100A...first safety shutter, 100B...second safety shutter, 102, 102A...safety shutter drive mechanism, 110...blade, 120...first condenser lens group, 120A, 120B, 122A, 122B...second condenser lens group, 124, 126A, 126B...splitting element, 200, 200A...connecting optical system, 202...polarized beam splitter, 204... 2 plate, 206...polarized beam splitter, 208...λ / 2 plate, 210, 212...polarized beam splitter, 214...λ / 2 plate, 220, 222...mirror, 230...shift element, 232...mirror, 234...polarized beam splitter, C...street, L...laser light, L1...first laser light, L2...second laser light, LA, LB...laser light, SP, SP1, SP2, SP3, SPA, SPB...spot, X1...forward direction side, X2...return direction side

Claims

[Claim 1] a laser processing apparatus for performing, for each street, an edge-cutting process to form two parallel first grooves along the streets and a hollowing process to form a second groove between the two first grooves, by irradiating the wafer with laser light from the laser optical system while moving a table that holds a wafer and a laser optical system that is positioned opposite the table relatively in a processing feed direction along the streets of the wafer, The laser optical system a laser beam emitting system that emits two first laser beams corresponding to the edge cutting process and a second laser beam corresponding to the hollowing process; a first condenser lens that condenses the two first laser beams onto the street of the processing target; a second condenser lens located on the opposite side of the processing feed direction with respect to the first condenser lens, and configured to condense the second laser light onto the street of the processing target; Equipped with a laser processing apparatus in which the laser light emission system emits the two first laser light and the two second laser light, each having a top-hat intensity distribution in a vertical direction that is parallel to the table and perpendicular to the processing feed direction, and a Gaussian intensity distribution in the processing feed direction.

Images