NL2026427B1

NL2026427B1 - Laser machining apparatus

Info

Publication number: NL2026427B1
Application number: NL2026427A
Authority: NL
Inventors: Hayashi Hirokazu; Shimoda Ayuka
Original assignee: Tokyo Seimitsu Co Ltd
Priority date: 2019-09-10
Filing date: 2020-09-08
Publication date: 2021-10-13
Also published as: JP7198999B2; JP2022031317A; NL2026427A; TW202116460A

Abstract

Provided is a laser machining apparatus that can reduce tact time required for laser machining of the wafer. The laser machining apparatus includes: a first laser light source configured to emit a laser light with a condition corresponding to the edge cutting; a second laser light source configured to emit a laser light with a condition corresponding to the hollowing; a first light forming element configured to form two first laser lights from the laser light emitted from the first laser light source; a second light forming element configured to form second laser light from the laser light emitted from the second laser light source; a first condenser lens; two second condenser lenses arranged in a row with the first condenser lens interposed therebetween; and a connecting optical system configured to guide the two first laser lights emitted from the first light forming element to the first condenser lens and guide the second laser light emitted from the second light forming element selectively to the two second condenser lenses.

Description

LASER MACHINING APPARATUS

BACKGROUND OF THE INVENTION Field of the Invention

[0001] The present invention relates to a laser machining apparatus for performing laser machining of wafers.

Description of the Related Art

[0002] In the field of manufacturing semiconductor devices in recent years, waters (semiconductor wafers) are known to have a plurality of devices formed in a laminated body. Such a laminated body is formed by laminating an insulation layer having low- dielectric constant (low-k layer) made of a glassy material and a functional layer having circuits thereon, on a surface of a substrate made of silicon or the like. On the wafer, the plurality of devices are partitioned to form a grid pattern with streets, and individual devices are manufactured by dividing (dicing) the wafer along the streets.

[0003] Known examples of the method of dicing the wafer into the plurality of devices (chips) include a method of using a blade rotating at a high speed, and a method of forming laser machining regions in the wafer along the streets and applying an external force along the streets whose strength are reduced by the formation of the laser machining regions. However, when the wafer includes the low-k layer applied thereon, it is difficult to cut the insulation layer and the substrate simultaneously with the blade in the former method because the low-k layer and the wafer are made of different materials. With the latter method, it is difficult to divide the wafer into the individual devices with a desirable quality when the low-k layer is present on the streets.

[0004] Accordingly, Japanese Patent Application Laid-Open No. 2009-182019 discloses a laser machining apparatus which performs: edge cutting for forming two lines of edge cutting grooves (isolating grooves) along streets of a wafer (see U.S. Patent No. 5922224); and hollowing for forming a hollow groove (dividing groove) between the two lines of edge cutting grooves. The laser machining apparatus includes a first laser beam irradiating unit for edge cutting and a second laser beam irradiating unit for hollowing, both moving along a feed direction of machining parallel to the streets of the wafer (see Fig. 15 in Japanese Patent Application Laid-Open No. 2009-182019). The first laser beam irradiating unit and the second laser beam irradiating unit are then moved toward one direction side (for example, an outward direction side) of the feed direction of machining relative to the wafer to simultaneously (parallelly) form the two lines of edge cutting grooves and a hollow groove along an identical street, so that the low-k layer or the like is removed.

[0005] Japanese Patent Application Laid-Open No. 58-143553 discloses a laser machining apparatus which performs: first groove machining for forming a first groove (fusing site) along a street of a wafer and second groove machining for forming a second groove (fusing site) at the bottom of the first groove. The laser machining apparatus includes: a first laser beam head unit for the first groove machining; and a second laser beam head unit for the second groove machining along the feed direction of machining parallel to the streets of the wafer. The first laser beam head unit and the second laser beam head unit are then moved relative to the wafer toward one direction side (for example, the outward direction side) of the feed direction of machining to simultaneously form the first groove and the second groove along the same street.

[0006] Japanese Patent Application Laid-Open No. 2016-208035 discloses a laser machining apparatus which moves a chuck configured to hold a wafer and a laser optical system disposed at a position facing the wafer relatively to each other, and forms a pair of trenches (two first grooves) parallel to each other along a dicing street and a furrow (second groove) which is a recess formed between the pair of trenches. The laser optical system disclosed by Japanese Patent Application Laid-Open No. 2016-208035 includes: a laser light emitting system configured to emit laser beams (two first laser lights) corresponding to machining of the pair of trenches and a laser beam (second laser light) corresponding to machining of the furrow; and a condensing optical system configured to condense each laser beam on the wafer. The condensing optical system allows the laser beams corresponding to machining of the pair of trenches to precede the laser beam corresponding to machining of the furrow, irrespective of a machining direction (outward direction and return direction) of the laser optical system (condensing optical system) with respect to the wafer. [Cited References]

[0007] Patent Literature 1: Japanese Patent Application Laid-Open No. 2009-182019 Patent Literature 2: U.S. Patent No. 5922224 Patent Literature 3: Japanese Patent Application Laid-Open No. 58-143553 Patent Literature 4: Japanese Patent Application Laid-Open No. 2016-208035

SUMMARY OF THE INVENTION

[0008] As described in Japanese Patent Application Laid-Open No. 2009-182019, in order to form the two lines of edge cutting grooves and the hollow groove along the street, it is necessary to form the two lines of edge cutting grooves prior to the hollow groove. Therefore, in the laser machining apparatus according to the Japanese Patent Application Laid-Open No. 2009-182019, the two lines of edge cutting grooves and the hollow groove can be simultaneously formed along the same street (identical street) only when the first laser beam irradiating unit and the second laser beam irradiating unit are moved relative to the wafer toward the one direction side (for example, the outward direction side) of the feed direction of machining. Therefore, with the laser machining apparatus disclosed in Japanese Patent Application Laid-Open No. 2009-182019, when these beam irradiating units are moved relative to the wafer toward the other direction side (for example, the return direction side) of the feed direction of machining, two lines of edge cutting grooves and a hollow groove cannot be simultaneously formed along the same street. Consequently, time required for machining one wafer (tact time) may increase.

[0009] Accordingly, when the beam irradiating units are moved relative to the wafer toward the other direction side of the feed direction of machining in the laser machining apparatus disclosed in Japanese Patent Application Laid-Open No. 2009-182019, it is conceivable to perform edge cutting with the second laser beam irradiating unit and perform hollowing with the first laser beam irradiating unit. However, since the optical system for edge cutting is different from the optical system for hollowing, the optical system of each of the beam irradiating units becomes very complicated when each beam irradiating unit is configured to support both of the edge cutting and the hollowing.

[0010] With the laser machining apparatus disclosed in Japanese Patent Application Laid- Open No. 58-143553 as well, when the laser beam head units are moved relative to the wafer toward the other direction side (for example, the return direction side) of the feed direction of machining, the first groove and the second groove cannot be simultaneously formed along an identical street.

[0011] Further, in the laser machining apparatus of Japanese Patent Application Laid-Open No. 2016-208035, because the edge cutting precedes the hollowing irrespective of the machining direction (outward direction and return direction), the laser machining apparatus of Japanese Patent Application Laid-Open No. 2016-208035 can make the tact time shorter than in the laser machining apparatuses of Japanese Patent Application Laid-Open No. 2009- 182019, U.S. Patent No. 5922224 and Japanese Patent Application Laid-Open No. 58-

143553. However, in the laser machining apparatus of Japanese Patent Application Laid- Open No. 2016-208035, the edge cutting and the hollowing are performed using laser lights emitted from one common laser light source. In this case, the edge cutting and the hollowing are different from each other in a suitable condition of laser light (wavelength, pulse width, repeating frequency, and the like). Therefore, in a case where the condition of the laser light is deviated from the condition suitable for one of the edge cutting and the hollowing, it is required to reduce a machining speed for the one of the edge cutting and the hollowing. In addition, it is required to reduce a machining speed for the other of the edge cutting and the hollowing, correspondingly. Thus, also in the laser machining apparatus disclosed in Japanese Patent Application Laid-Open No. 2016-208035, there 1s a limit on reduction of the tact time required for the laser machining on a wafer.

[0012] In view of such circumstances, the present invention aims to provide a laser machining apparatus which can reduce tact time required for laser machining of wafers.

[0013] In order to achieve the object of the present invention, in a laser machining apparatus which moves a table configured to hold a wafer thereon and a laser optical system disposed at a position opposing the table relative to each other in a feed direction of machining along a street of the wafer while irradiating the wafer with laser lights from the laser optical system, to perform, for each street, edge cutting for forming two first grooves parallel to each other along the street and hollowing for forming a second groove between the two first grooves, the laser optical system includes: a first laser light source configured to emit a laser light with a condition corresponding to the edge cutting; a second laser light source configured to emit a laser light with a condition corresponding to the hollowing; a first light forming element configured to form two first laser lights from the laser light emitted from the first laser light source; a second light forming element configured to form second laser light from the laser light emitted from the second laser light source; a first condenser lens; two second condenser lenses arranged in a row along the feed direction of machining together with the first condenser lens with the first condenser lens interposed therebetween; and a connecting optical system configured to guide the two first laser lights emitted from the first light forming element to the first condenser lens and guide the second laser light emitted from the second light forming element selectively to the two second condenser lenses. In a case where the laser optical system is moved relative to the table toward an outward direction side of the feed direction of machining, the connecting optical system guides the second laser light to one of the two second condenser lenses which is located on a return direction side of the feed direction of machining, relative to the first condenser lens, and in a case where the laser optical system is moved relative to the table toward the return direction side, the connecting optical system guides the second laser light to another of the two second condenser lenses which is located on the outward direction side relative to the first condenser lens.

[0014] The laser machining apparatus can improve a machining peed of a wafer (reduce tact time).

[0015] In order to achieve the object of the present invention, in a laser machining apparatus which moves a table configured to hold a wafer thereon and a laser optical system disposed at a position opposing the table relative to each other in a feed direction of machining along a street of the wafer while irradiating the wafer with laser lights from the laser optical system, to perform, for each street, edge cutting for forming two first grooves parallel to each other along the street and hollowing for forming a second groove between 5 the two first grooves, the laser optical system includes: a first laser light source configured to emit a laser light with a condition corresponding to the edge cutting; a second laser light source configured to emit a laser light with a condition corresponding to the hollowing; a first light forming element configured to form two first laser lights from the laser light emitted from the first laser light source; a second light forming element configured to form second laser light from the laser light emitted from the second laser light source; two first condenser lenses arranged in a row along the feed direction of machining; a second condenser lens arranged between the two first condenser lenses; and a connecting optical system configured to guide the two first laser lights emitted from the first light forming element selectively to the two first condenser lenses and guide the second laser light emitted from the second light forming element to the second condenser lens. In a case where the laser optical system is moved relative to the table toward an outward direction side of the feed direction of machining, the connecting optical system guides the two first laser lights to one of the two first condenser lenses which is located on the outward direction side relative to the second condenser lens, and in a case where the laser optical system is moved relative to the table toward a return direction side of the feed direction of machining, the connecting optical system guides the two first laser lights to another of the two first condenser lenses which is located on the return direction side relative to the second condenser lens.

[0016] The laser machining apparatus can improve a machining peed of a wafer (reduce tact time).

[0017] The laser machining apparatus according to another mode of the present invention, includes: a first moving mechanism configured to move the first condenser lens in a first perpendicular direction which is parallel to the table and perpendicular to the feed direction of machining; and a second moving mechanism configured to move the second condenser lens relative to the table in the first perpendicular direction. Thus, it is possible to allow the each machining point move (trace) on an optimum movement track, irrespective of the motion accuracy along the feed axis (X-direction) of machining during laser machining.

[0018] In the laser machining apparatus according to another mode of the present invention, the first moving mechanism can move the first condenser lens relative to the table in the first perpendicular direction and a second perpendicular direction which is perpendicular to the table, and the second moving mechanism can move the second condenser lens relative to the table in the first perpendicular direction and the second perpendicular direction. Thus, it is possible to allow the each machining point move (trace) on an optimum movement track, irrespective of the motion accuracy along the feed axis (X- direction) of machining during laser machining.

[0019] The laser machining apparatus according to another mode of the present invention, further includes: a first moving mechanism configured to move the first condenser lens in a first perpendicular direction which is parallel to the table and perpendicular to the feed direction of machining; and a second moving mechanism configured to integrally move the two second condenser lenses relative to the table in the first perpendicular direction.

[0020] In the laser machining apparatus according to another mode of the present invention, the first moving mechanism can move the first condenser lens relative to the table in the first perpendicular direction and a second perpendicular direction which is perpendicular to the table, and the second moving mechanism can integrally move the two second condenser lenses relative to the table in the first perpendicular direction and the second perpendicular direction.

[0021] The laser machining apparatus according to another mode of the present invention further includes: a first moving mechanism configured to integrally move the two first condenser lenses in a first perpendicular direction which is parallel to the table and perpendicular to the feed direction of machining; and a second moving mechanism configured to move the second condenser lens relative to the table in the first perpendicular direction.

[0022] In the laser machining apparatus according to another mode of the present invention, the first moving mechanism can integrally move the two first condenser lenses relative to the table in the first perpendicular direction and a second perpendicular direction which is perpendicular to the table, and the second moving mechanism can move the second condenser lens relative to the table in the first perpendicular direction and the second perpendicular direction.

[0023] In the laser machining apparatus according to another mode of the present invention, the first moving mechanism moves the table in the first perpendicular direction.

[0024] In the laser machining apparatus according to another mode of the present invention, the second moving mechanism moves the table in the first perpendicular direction.

[0025] In the laser machining apparatus according to another mode of the present invention, the first moving mechanism moves the table in the first perpendicular direction and the second perpendicular direction.

[0026] In the laser machining apparatus according to another mode of the present invention, the second moving mechanism moves the table in the first perpendicular direction and the second perpendicular direction.

[0027] The present invention can reduce tact time required for laser machining on the wafer, with a simple configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Fig. 1 is a schematic drawing of a laser machining apparatus according to a first embodiment; Fig. 2 is a plan view of a wafer to be machined by the laser machining apparatus; Fig. 3 is an explanatory drawing for explaining laser machining along odd- numbered streets; Fig. 4 is an explanatory drawing for explaining laser machining along even- numbered streets; Fig. 5 is an explanatory drawing for explaining edge cutting and hollowing performed by a laser optical system moved toward an outward direction side relative to the wafer; Fig. 6 is an explanatory drawing for explaining edge cutting and hollowing performed by the laser optical system moved toward a return direction side relative to the wafer; Fig. 7 is a flowchart of laser machining process for each street of the wafer by the laser machining apparatus according to the first embodiment; Fig. 8 is an explanatory drawing illustrating a distance adjustment of two lines of edge cutting grooves in a Y-direction by a first rotating mechanism; Fig. 9 is an explanatory drawing illustrating the distance adjustment of the two lines of edge cutting grooves in the Y-direction by the first rotating mechanism; Fig. 10 is an explanatory drawing illustrating a width adjustment of a hollow groove in the Y-direction by a second rotating mechanism; Fig. 11 is an explanatory drawing illustrating the width adjustment of the hollow groove in the Y-direction by the second rotating mechanism; Fig. 12 is a schematic drawing of a laser machining apparatus according to a third embodiment; Fig. 13 1s an explanatory drawing for explaining edge cutting and hollowing performed by a laser optical system moved toward the outward direction side relative to the wafer in a fourth embodiment;

Fig. 14 1s an explanatory drawing for explaining edge cutting and hollowing performed by the laser optical system moved toward the return direction side relative to the wafer in the fourth embodiment;

Fig. 15 is an explanatory drawing illustrating Specific Example | of a connection switching element according to a fourth embodiment;

Fig. 16 is an explanatory drawing for explaining Specific Example 2 of the connection switching element according to the fourth embodiment;

Fig. 17 is an explanatory drawing for explaining Specific Example 3 of the connection switching element according to the fourth embodiment;

Fig. 18 is an explanatory drawing for explaining edge cutting and hollowing performed by the laser optical system moved toward the outward direction side relative to the wafer in a fifth embodiment;

Fig. 19 is an explanatory drawing for explaining edge cutting and hollowing performed by the laser optical system 24 moved toward the return direction side relative to the wafer in the fifth embodiment;

Fig. 20 is an explanatory drawing for explaining edge cutting and hollowing performed by the laser optical system moved toward the outward direction side relative to the wafer in a sixth embodiment;

Fig. 21 is an explanatory drawing for explaining edge cutting and hollowing performed by the laser optical system 24 moved toward the return direction side relative to the wafer in the sixth embodiment;

Fig. 22 is an explanatory drawing for explaining a problem that occurs when an intensity distribution of a second laser light has a Gaussian shape;

Fig. 23 is an explanatory drawing illustrating an example of an ideal intensity distribution of the second laser light;

Fig. 24 is an explanatory drawing illustrating an example of an actual intensity distribution of the second laser light;

Fig. 25 is an explanatory drawing illustrating an example of an intensity distribution (E) of the second laser light, in which reference sign XXVA shows an example of an intensity distribution (E) in the Y-direction and reference sign XXVB shows an example of the intensity distribution (E) in the X-direction;

Fig. 26 is an explanatory drawing illustrating an example of the intensity distribution of a second laser light L2 on an XY plane according to a seventh embodiment;

Fig. 27 is a schematic drawing illustrating a laser optical system of a laser machining apparatus according to an eighth embodiment;

Fig. 28 is an explanatory drawing for explaining effects of the laser machining apparatus according to the eighth embodiment;

Fig. 29 is an explanatory drawing for explaining edge cutting and hollowing performed by a laser optical system of a laser machining apparatus according to a ninth embodiment moved toward the outward direction side relative to the wafer;

Fig. 30 is an explanatory drawing for explaining edge cutting and hollowing performed by the laser optical system of the laser machining apparatus according to the ninth embodiment moved toward the return direction side relative to the wafer;

Fig. 31 is an explanatory drawing for explaining a function of a connecting optical system when the laser optical system is moved toward the outward direction side by a relative movement mechanism relative to the wafer;

Fig. 32 is an explanatory drawing for explaining a function of the connecting optical system when the laser optical system is moved toward the return direction side by the relative movement mechanism relative to the wafer;

Fig. 33 is an explanatory drawing for explaining edge cutting and hollowing performed by a laser optical system moved toward the outward direction side relative to the wafer in Modified Example 1 of the ninth embodiment;

Fig. 34 is an explanatory drawing for explaining edge cutting and hollowing performed by the laser optical system moved toward the return direction side relative to the wafer in Modified Example 1 of the ninth embodiment;

Fig. 35 is an explanatory drawing for explaining edge cutting and hollowing performed by a laser optical system moved toward the outward direction side relative to the wafer in Modified Example 2 of the ninth embodiment;

Fig. 36 is an explanatory drawing for explaining edge cutting and hollowing performed by the laser optical system moved toward the return direction side relative to the wafer in Modified Example 2 of the ninth embodiment;

Fig. 37 is an explanatory drawing for explaining edge cutting and hollowing performed by a laser optical system of the laser machining apparatus according to a tenth embodiment;

Fig. 38 is an explanatory drawing for explaining edge cutting and hollowing performed by a laser optical system of a laser machining apparatus according to an eleventh embodiment moved toward the outward direction side relative to the wafer;

Fig. 39 1s an enlarged drawing in a dotted circle K1 in Fig. 38;

Fig. 40 1s an explanatory drawing for explaining edge cutting and hollowing performed by the laser optical system of the laser machining apparatus according to the eleventh embodiment moved toward the return direction side relative to the wafer; Fig. 41 is an enlarged drawing in a dotted circle K2 in Fig. 40; Fig. 42 1s an explanatory drawing for explaining a modified example of the eleventh embodiment; and Fig. 43 1s an explanatory drawing for explaining a modified example of the third embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] <General Configuration of Laser Machining Apparatus according to First Embodiment> Fig. 1 1s a schematic drawing of a laser machining apparatus 10 according to a first embodiment. As illustrated in Fig. 1, the laser machining apparatus 10 applies laser machining (ablation groove machining) on a wafer 12 as a pre-process before dividing (dicing) the wafer 12 into a plurality of chips 14 (see Fig. 2). Note that X, Y, and Z directions in the drawings are perpendicular to each other, the X-direction and the Y- direction correspond to the horizontal direction, and the Z-direction corresponds to the vertical direction. The X-direction in this specification corresponds to a feed direction of machining of the present invention.

[0030] Fig. 2 is a plan view of the wafer 12 to be machined by the laser machining apparatus 10. Asillustrated in Fig. 2, the wafer 12 is a laminated body formed by laminating a low-k layer and a functional layer having a circuit formed thereon on a surface of a substrate made of silicon or the like. The wafer 12 is partitioned into a plurality of regions by a plurality of streets C (planned dividing lines) arrayed into a grid pattern. In each of these divided regions, a device 16 that constitutes a chip 14 is provided.

[0031] The laser machining apparatus 10 removes the low-k layer or the like on the substrate by performing laser machining (ablation process for grooving) on the wafer 12 along the streets C for each of the streets C as indicated by parenthesized numerals (1) to (4), ... in the drawing.

[0032] At this time, the laser machining apparatus 10 switches the direction of relative movement in which a laser optical system 24, which will be described later, 1s moved relative to the wafer 12 in the X-direction alternately for each of the streets C in order to reduce a tact time required for laser machining of the wafer 12.

[0033] For example, in order to perform laser machining along the odd-numbered streets C indicated by the parenthesized numerals (1), (3), and so forth in the drawing, the laser optical system 24, which will be described later, is moved toward an outward direction side X1 (see Fig. 5), which is one direction side in the X-direction, relative to the wafer 12.

Likewise, in order to perform laser machining along the even-numbered streets C indicated by the parenthesized numerals (2), (4), and so forth in the drawing, the laser optical system 24 is moved toward a return direction side X2 (see Fig. 6), which is the other direction side of the X-direction relative to the wafer 12.

[0034] Fig. 3 is an explanatory drawing for explaining laser machining along the odd- numbered streets C. Fig. 4 is an explanatory drawing for explaining laser machining along the even-numbered streets C.

[0035] As illustrated in Fig. 3 and Fig. 4, in the present embodiment, as laser machining, edge cutting and hollowing are executed simultaneously (in parallel). Edge cutting is laser machining to be performed by using two first laser lights L1 for forming two lines of edge cutting grooves 18 (ablation grooves corresponding to the two first grooves of the present invention) parallel to each other along the street C. Hollowing is laser machining to be performed by using one second laser light L2 having a diameter larger than diameters of the two first laser lights L1 for forming a hollow groove 19 (an ablation groove corresponding to the second groove of the present invention) between the two lines of edge cutting grooves 18 formed by edge cutting. Note that the two lines of edge cutting grooves 18 and the hollow groove 19, which are ablation grooves, are known in the related art, and thus further detailed description will be omitted (see Japanese Patent Application Laid-Open No. 2009-182019).

[0036] In this manner, in the laser machining apparatus 10 of the present embodiment, edge cutting 1s always performed prior to hollowing in both cases of moving the laser optical system 24, which will be described later, toward the outward direction side X1 (see Fig. 5) and toward the return direction side X2 (see Fig. 6) relative to the wafer 12.

[0037] Returning back to Fig. 1, the laser machining apparatus 10 includes a table 20, a laser light source 22, the 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. In addition, the table 20 is moved in the X- direction, which is a feed direction of machining parallel to the street C to be machined by the relative movement mechanism 28 and is rotated around a center axis (axis of rotation) of the table 20, which is parallel to the Z-direction under the control of the control device 30.

[0039] The laser light source 22 constitutes the laser optical system of the present invention in cooperation with the laser optical system 24, which will be described later. The laser light source 22 constantly emits laser light L under the conditions (wavelength, pulse width, repeating frequency, and the like) suitable for both edge cutting and hollowing. 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 laser unit), which will be described in detail later, bifurcates the laser light L from the laser light source 22 and forms two first laser lights L1 for edge cutting and one second laser light L2 for hollowing. The laser optical system 24 then emits (radiates) the two first laser lights L1 from the first condenser lens 38 toward the street C. The laser optical system 24 emits (radiates) the second laser light L2 selectively from the two second condenser lenses 40A, 40B toward the street C under the control of the control device 30.

[0041] The laser optical system 24 is also moved in the Y-direction and the Z-direction by the 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 takes an image of an alignment reference (illustration is omitted) formed on the wafer 12 before performing edge cutting and hollowing on the wafer 12. The microscope 26 also takes an image of the two lines of edge cutting grooves 18 and the hollow groove 19 formed along the street C by edge cutting and hollowing. The image (image data) taken by the microscope 26 is output to the control device 30 and is displayed on a monitor, not illustrated, by the control device 30.

[0043] The relative movement mechanism 28 includes an XYZ actuator, a motor, and the like, not illustrated, to cause a movement in the X-direction and a rotation around the axis of rotation of the table 20 and a movement of the laser optical system 24 in the Y-direction and the Z-direction under the control of the control device 30. Accordingly, the relative movement mechanism 28 may 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 the laser optical system 24 in the YZ directions, it is also applicable to move the laser optical system 24 in the Z-direction and the table 20 in the XY directions, for example. The method of relative movement is not specifically limited as long as the laser optical system 24 can be moved in respective directions (including rotation) relative to the table 20 (wafer 12).

[0044] By driving the relative movement mechanism 28, it is possible to repeatedly perform: positioning (alignment) of the laser optical system 24 with respect to a machining start position, which corresponds to one end of the street C to be machined; and the relative movement of the laser optical system 24 in the X-direction along the street C (outward direction side XI (see Fig. 5) or the return direction side X2 (see Fig. 6). In addition, by driving the relative movement mechanism 28 and rotating the table 20 by 90°, the respective streets C of the wafer 12 along the Y-direction may be made parallel to the X-direction, which is the feed direction of machining.

[0045] The control device 30 includes a computing device such as a personal computer and includes a computing circuit including various types of processors, memory, and the like.

The various types of processors include a central processing unit (CPU), a graphics processing unit (GPU), an application specific integrated circuit (ASIC), and programable logic devices (for example, a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), and field programmable gate arrays (FPGA)). Note that various functions of the control device 30 may be implemented in one processor or may be implemented in a plurality of processors of the same type or different types.

[0046] The control device 30 integrally controls operations of the laser light source 22, the laser optical system 24, the microscope 26, and the relative movement mechanism 28.

[0047] <Laser Optical System> Fig. 5 is an explanatory drawing for explaining edge cutting and hollowing performed by a laser optical system 24 which is moved toward the outward direction side X1 relative to the wafer 12. Fig. 6 is an explanatory drawing for explaining edge cutting and hollowing performed by the laser optical system 24 which is moved toward a return direction side X2 relative to the wafer 12. Hereinafter, the odd-numbered streets C to be machined by the laser optical system 24 moved toward the outward direction side X1 relative to the wafer 12 are referred to as "outward paths" as needed, and the even-numbered streets C to be machined by the laser optical system 24 moved toward the return direction side X2 relative to the wafer 12 are referred to as "return paths" as needed.

[0048] As illustrated in Fig. 5 and Fig. 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, the first condenser lens 38, the two second condenser lenses 40A, 40B, a first high-speed shutter 47A and a second high-speed shutter 47B, and a high-speed shutter drive mechanism 47C. Note that the branching element 31, the first light forming element 32, the second light forming element 34, and the safety shutter 100 constitute the laser light emitting system of the present invention in cooperation with the laser light source 22. In addition, the connection switching element 36, the first condenser lens 38, the two second condenser lenses 40A, 40B, the first high-speed shutter 47A, the second high-speed shutter 47B, and the high-speed shutter drive mechanism 47C constitute the condensing optical system of the present invention.

[0049] The safety shutter drive mechanism 102 is an actuator configured to insert and remove the safety shutter 100 into and from an optical path between the laser light source 22 and the branching element 31 under the control of the control device 30. The safety shutter drive mechanism 102 inserts the safety shutter 100 into the optical path to stop emission of the two first laser lights L1 and the second laser light L2 from the laser optical system 24 except during laser machining. The safety shutter drive mechanism 102 also causes the safety shutter 100 to retract from the optical path during laser machining to enable emission of the two first laser lights L1 and the second laser light L2 from the laser optical system 24.

[0050] For example, a half mirror or the like may be used as the branching element 31.

The branching element 31 bifurcates the laser light L emitted from the laser light source 22, and allows one of the bifurcated laser lights L to be emitted to the first light forming element 32 and allows the other one of the laser light L to be emitted to the second light forming element 34. Note that the branching ratio of the "bifurcating" in this specification is not limited to 50:50 and may be changed as needed.

[0051] For example, a diffractive optical element (DOE) is used as the first light forming element 32. The first light forming element 32 is configured to form the two first laser lights L1 for edge cutting from the laser light L entering from the branching element 31, and allow the two first laser lights L1 to be emitted toward the first condenser lens 38. Accordingly, the two first laser lights L1 are condensed (collected) on the street C (outward path and return path) by the first condenser lens 38, and two spots (also referred to as condensing points, or machining points) are formed on the street C. The two spots are separated from each other in the Y-direction. Not that, although illustration is omitted, the optical path for the two first laser lights L1 proceeding from the first light forming element 32 to the first condenser lens 38 (including various types of optical elements provided on the optical path) constitutes a part of the connecting optical system of the present invention.

[0052] For example, a diffractive optical element, a mask, and the like are used as the second light forming element 34. The second light forming element 34 forms the second laser light L2 for hollowing from the laser light L entering from the branching element 31. The second laser light L2 forms one spot (see Fig. 10 and Fig. 11) having a rectangular shape (other shapes such as circle shapes are also possible) between the two lines of edge cutting grooves 18 on the wafer 12. The width of the spot in the Y-direction is adjusted so as to match the interval between the two lines of edge cutting grooves 18. The second light forming element 34 then allows the second laser light L2 to be emitted to the connection switching element 36.

[0053] The connection switching element 36 constitutes the connecting optical system of the present invention in cooperation with the branching element 31 already described, and the like. For example, a known optical switch or various types of optical elements (A/2 plate 52 and a polarizing beam splitter 54, a half mirror 58 and shutters 62A, 62B, mirrors 066A, 66B, and the like) illustrated in Fig. 15 to Fig. 17, which will be described later, may be used as the connection switching element 36. The connection switching element 36 guides the second laser light L2 emitted from the second light forming element 34 selectively to the second condenser lenses 40A, 40B under the control of the control device

30.

[0054] The first condenser lens 38 and the second condenser lenses 40A, 40B are arranged in a row along the X-direction (feed direction of machining). The first condenser lens 38 is disposed between the second condenser lens 40A and the second condenser lens 40B. The second condenser lens 40A is disposed on the return direction side X2 with respect to the first condenser lens 38. The second condenser lens 40B is disposed on the outward direction side X1 with respect to the first condenser lens 38.

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

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

[0057] Specifically, as illustrated in Fig. 5, when the laser optical system 24 is moved toward the outward direction side X1 relative to the wafer 12 by the relative movement mechanism 28, the connection switching element 36 guides the second laser light L2 emitted from the second light forming element 34 to the second condenser lens 40A. Accordingly, the second laser light L2 is condensed on the street C (outward path) by the second condenser lens 40A. Consequently, the two lines of edge cutting grooves 18 are firstly formed by executing edge cutting along the street C (outward path) by the relative movement of the laser optical system 24 toward the outward direction side X1, and then the hollow groove 19 is formed between the two lines of edge cutting grooves 18 by subsequently executing hollowing.

[0058] As illustrated in Fig. 6, when the laser optical system 24 is moved toward the return direction side X2 relative to the wafer 12 by the relative movement mechanism 28, the connection switching element 36 guides the second laser light L2 emitted from the second light forming element 34 to the second condenser lens 40B. Accordingly, the second laser light L2 is condensed on the street C (return path) by the second condenser lens 40B. Consequently, the two lines of edge cutting grooves 18 are firstly formed by executing edge cutting along the street C (return path) by the relative movement of the laser optical system 24 toward the return direction side X2, and then, the hollow groove 19 is formed between the two lines of edge cutting grooves 18 by subsequently executing hollowing.

[0059] The first high-speed shutter 47A is provided between the branching element 31 and the first light forming element 32 so as to be freely inserted into and retracted from the optical path of the laser light L (the optical path between the first light forming element 32 and the first condenser lens 38 is also applicable). The first high-speed shutter 47A, when being inserted into the optical path between the branching element 31 and the first light forming element 32, intercepts the laser light L entering from the branching element 31 into the first light forming element 32 to stop 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 freely inserted into and retracted from the optical path of the laser light L between the branching element 31 and the second light forming element 34 (the optical path between the second light forming element 34 and the connection switching element 36 is also applicable). The second high-speed shutter 47B, when being inserted into the optical path between the branching element 31 and the second light forming element 34, intercepts the laser light L entering from the branching element 31 into the second light forming element 34 to stop 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 configured to insert and retract the first high-speed shutter 47A and the second high-speed shutter 47B into and from the respective optical paths described above, 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 and inserts the first high-speed shutter 47A into the optical path of the laser light L other than during edge cutting. Likewise, the high-speed shutter drive mechanism 47C retracts the second high-speed shutter 47B from the optical path of the laser light L during hollowing and inserts the second high-speed shutter 47B into the optical path of the laser light L other than during hollowing.

[0062] Fig. 7 is a flowchart of laser machining process (a method of controlling the laser machining apparatus 10) for each street C of the wafer 12 by the laser machining apparatus according to the first embodiment having the configuration described above. Note that it 1s assumed that the first high-speed shutter 47A, the second high-speed shutter 47B, and the safety shutter 100 are each inserted into the optical path of the laser light L in the initial state. In addition, it is assumed that emission of the laser light L from the laser light source 22 is started in response to activation of the laser machining apparatus 10.

10 [0063] As illustrated in Fig. 7, when the wafer 12 to be laser machined is held on the table 20, the control device 30 drives the safety shutter drive mechanism 102 first to cause the safety shutter 100 to retract from the optical path of the laser light L (Step SO).

Accordingly, the laser optical system 24 is brought to a state where the two first laser lights L1 and the second laser light L2 can be emitted. Note that at this time point, the first high- speed shutter 47A and the second high-speed shutter 47B are each inserted in the optical path of the laser light L, and thus the two first laser lights L1 and the second laser light L2 are not emitted from the laser optical system 24.

[0064] Subsequently, after the control device 30 drives the relative movement mechanism 28 to move the microscope 26 relative to the wafer 12 to a position which allows imaging of the alignment reference (illustration is omitted) of the wafer 12, imaging of the alignment reference by the microscope 26 is executed. The control device 30 then performs alignment detection for detecting the positions of the respective streets C in the wafer 12 based on the image of the alignment reference taken by the microscope 26. Subsequently, the control device 30 drives the relative movement mechanism 28 to align the position of the optical axis of the first condenser lens 38 of the laser optical system 24 with the machining start position of the first street C (outward path) (Step S1).

[0065] The control device 30 drives the connection switching element 36 to switch the lens that allows the second laser light L2 to be emitted to the second condenser lens 40A (Step S2). Note that the order of Step SO to Step S3 may be changed as needed or these steps may be executed in parallel.

[0066] When Step S2 1s completed, the control device 30 drives the high-speed shutter drive mechanism 47C to cause the first high-speed shutter 47A to retract from the optical path of the laser light L (Step S3). Accordingly, two first laser lights L1 are emitted from the first condenser lens 38 via the branching element 31 and the first light forming element

32 so that the two first laser lights L1 can be condensed on the machining start position on the street C (outward path).

[0067] Subsequently, the control device 30 drives the relative movement mechanism 28 to move the laser optical system 24 toward the outward direction side X1 relative to the wafer 12 (Step S4). Then, when the optical axis of the second condenser lens 40A reaches the machining start position of the street C (outward path), the control device 30 drives the high- speed shutter drive mechanism 47C to cause the second high-speed shutter 47B to retract from the optical path of the laser light L (Step S5). Accordingly, 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 condensed on the above-described machining start position. By shifting the timing of starting hollowing, an outside of the wafer 12 is prevented from being laser machined (hollowed).

[0068] When the relative movement of the laser optical system 24 toward the outward direction side X1 continues, spots of the two first laser lights L1 and a spot of the second laser light L2 move toward the outward direction side X1 along the street C (outward path) as illustrated in Fig. 3 and Fig. 5. Consequently, formation of the two lines of edge cutting grooves 18 by edge cutting and formation of the hollow groove 19 by hollowing are executed simultaneously along the street C (outward path) while keeping an interval (space) therebetween.

[0069] Then, at a timing when the spots of the two first laser lights L1 emitted from the first condenser lens 38 reaches the machining end position of the street C (outward path), the control device 30 drives the high-speed shutter drive mechanism 47C to cause the first high- speed shutter 47A to be inserted into the optical path of the laser light L (Steps S6, S7).

Further, at a timing when the spot of the second laser light L2 emitted from the second condenser lens 40A reaches the machining end position described above, the control device drives the high-speed shutter drive mechanism 47C to cause the second high-speed shutter 47B to be inserted into the optical path of the laser light L and stops the driving of the relative movement mechanism 28 (Step S8). Accordingly, laser machining for the first 30 street C (outward path) is completed. Note that when the outside of the wafer 12 may be subjected to laser machined (edge cutting), the timing of insertion of the first high-speed shutter 47A into the optical path of the laser light L may be synchronized with the timing when the second high-speed shutter 47B is inserted into the optical path of the laser light L.

[0070] When the laser machining of the first street C (outward path) is completed, the control device 30 drives the relative movement mechanism 28 to align the position of the optical axis of the first condenser lens 38 with the machining start position of the second street C (return path) (Yes in Step S9, Step S10).

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

[0072] When Step S11 is completed, the control device 30 drives the high-speed shutter drive mechanism 47C to cause the first high-speed shutter 47A to retract from the optical path of the laser light L (Step S12). Accordingly, two first laser lights L1 are emitted from the first condenser lens 38 via the branching element 31 and the first light forming element 32 so that the two first laser lights L1 are condensed on the machining start position on the street C (return path).

[0073] Subsequently, the control device 30 drives the relative movement mechanism 28 to move the laser optical system 24 toward the return direction side X2 relative to the wafer 12 (Step S13). Then, when the optical axis of the second condenser lens 40B reaches the machining start position of the street C (return path), the control device 30 drives the high- speed shutter drive mechanism 47C to cause the second high-speed shutter 47B to retract from the optical path of the laser light L (Step S14). Accordingly, 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 condensed on a position shifted from the above-described machining start position toward the outward direction side X1. By shifting the timing of starting hollowing, an outside of the wafer 12 1s prevented from being laser machined (hollowed).

[0074] When the relative movement of the laser optical system 24 toward the return direction side X2 continues, spots of the two first laser lights L1 and a spot of the second laser light L2 move toward the return direction side X2 along the street C (return path) as illustrated in Fig. 4 and Fig. 6. Consequently, formation of the two lines of edge cutting grooves 18 by edge cutting and formation of the hollow groove 19 by hollowing are executed simultaneously along the street C (return path) while keeping an interval (space) therebetween.

[0075] Then, at a timing when the spots of the two first laser lights L1 emitted from the first condenser lens 38 reaches the machining end position of the street C (return path), the control device 30 drives the high-speed shutter drive mechanism 47C to cause the first high- speed shutter 47A to be inserted into the optical path of the laser light L (Steps S15, S16). In addition, at a timing when the spot of the second laser light L2 emitted from the second condenser lens 40B reaches the machining end position, the control device 30 drives the high-speed shutter drive mechanism 47C to cause the second high-speed shutter 47B to be inserted into the optical path of the laser light L and stops the driving of the relative movement mechanism 28 (Step S17). Accordingly, laser machining for the second street C (return path) is completed. Note that the timing of insertion of the first high-speed shutter 47A into the optical path of the laser light L may be synchronized with the timing when the second high-speed shutter 47B is inserted into the optical path of the laser light L as described above.

[0076] Hereinafter, in the same manner, the laser machining (edge cutting and hollowing) are repeatedly executed along all the streets C extending in parallel to the X-direction (Yes in Step S9, Yes in Step S18). Subsequently, the control device 30 drives the relative movement mechanism 28 and rotate the table 20 by 90°, whereby the remaining respective streets C on the wafer 12 parallel to the Y-direction may be brought into an orientation parallel to the X-direction. The control device 30 then executes a series of steps described above repeatedly. Accordingly, the laser machining is executed along each of the streets C having a grid pattern.

[0077] When the laser machining on all the streets C having a grid pattern is completed (No in Step S9, No in Step S18), the wafer 12 is fed to the post process and is divided into a plurality of chips 14 (devices 16) therein. Note that although the flowchart shows an example under the fastest conditions in which formation of the two lines of edge cutting grooves 18 and formation of the hollow groove 19 are completed by one laser machining operation in one direction (outward path: X1 direction, return path; X2 direction) for each street C (outward path and return path), the present invention is not limited thereto. For example, at least one of edge cutting and hollowing may be executed a plurality of times for each street C (outward path and return path), considering the machining depth of each of the two lines of edge cutting grooves 18 and the hollow groove 19.

[0078] <Effects of First Embodiment> As described thus far, the laser machining apparatus 10 according to the first embodiment is capable of performing hollowing by selectively using the second condenser lenses 40A, 40B according to the direction of relative movement of the laser optical system 24 relative to the wafer 12. Accordingly, edge cutting and hollowing can be performed simultaneously along an identical street irrespective of the outward path or the return path of the street C. Therefore, since the laser machining for two streets C (outward path and return path) is completed by one reciprocation (one round trip) of the laser optical system 24 inthe X-direction, the tact time required for laser machining of the wafer 12 can be reduced.

In addition, switching between hollowing with the second condenser lens 40A and hollowing with the second condenser lens 40B can be performed only by operating the connection switching element 36 according to the direction of relative movement of the laser optical system 24, whereby complication of the laser optical system 24 (optical system) is prevented. Consequently, reduction of tact time required for laser machining of the wafer 12 is achieved with a simple configuration.

[0079] <Second Embodiment> Next, the laser machining apparatus 10 according to a second embodiment will be described below. The laser machining apparatus 10 according to the second embodiment has a function of adjusting a distance between the two lines of edge cutting grooves 18 in the Y-direction and the width of the hollow groove 19 in the Y-direction. Note that the laser machining apparatus 10 according to the second embodiment has basically the same configuration as the laser machining apparatus 10 according to the first embodiment described above except that a first rotating mechanism 44 (see Fig. 8 and Fig. 9) and a second rotating mechanism 46 (see Fig. 10 and Fig. 11), which will be described later, are provided. Therefore, those having the same function or configuration as the first embodiment described above are designated by the same reference signs and description thereof will be omitted.

[0080] Fig. 8 and Fig. 9 are explanatory drawings illustrating a distance adjustment of the two lines of edge cutting grooves 18 in the Y-direction by the first rotating mechanism 44. As illustrated in Fig. 8 and Fig. 9, the first rotating mechanism 44 includes a motor and a drive transmission mechanism, for example. The first rotating mechanism 44 1s configured to rotate the first light forming element 32 around an axis centered on an optical axis of the first light forming element 32 under the control of the control device 30. Accordingly, when the wafer 12 is viewed from above side in the Z-direction, spots of the two first laser lights L1 condensed on the street C by the first condenser lens 38 can be rotated around the optical axis of the first condenser lens 38. Consequently, because the distance between spots of the two first laser lights L1 condensed on the street C in the Y-direction can be increased or decreased, it is possible to adjust the distance between the two lines of edge cutting grooves 18 in the Y-direction.

[0081] Fig. 10 and Fis. 11 are explanatory drawings illustrating a width adjustment of the hollow groove 19 in the Y-direction by the second rotating mechanism 46. As illustrated in Fig. 10 and Fig. 11, the second rotating mechanism 46 includes a motor and a drive transmission mechanism, for example in the same manner as the first rotating mechanism

44. The second rotating mechanism 46 is configured to rotate the second light forming element 34 in a direction around an axis centered on an optical axis of the second light forming element 34 under the control of the control device 30. Accordingly, when the wafer 12 is viewed from above side in the Z-direction, a spot of the second laser light L2 condensed on the street C by the second condenser lens 40A or 40B can be rotated around the optical axis of the second condenser lens 40A or 40B. The spot of the second laser light L2 formed on the street C here has a rectangular shape, that is, a non-circular shape. Therefore, by rotating the rectangular-shaped spot, the width of the hollow groove 19 formed on the street C in the Y-direction can be adjusted, that is, can be increased or decreased, for example. Note that the shape of the spot of the second laser light L2 is not limited to the rectangular shape as long as it is a non-circular shape.

[0082] The control device 30 drives each of the first rotating mechanism 44 and the second rotating mechanism 46 based on an adjustment instruction input by the operator into an operating unit, not illustrated, to rotate the first light forming element 32 and the second light forming element 34 respectively, thereby adjusting the distance of the two lines of edge cutting grooves 18 and the width of the hollow groove 19.

[0083] <Third Embodiment> Fig. 12 is a schematic drawing of the laser machining apparatus 10 according to a third embodiment. In the laser machining apparatus 10 according to each of the above embodiments, the edge cutting and the hollowing are performed along the street C of the wafer. In this case, three kinds of machining points including the machining points for the edge cutting (spots of the two first laser lights L1 condensed on the street C by the first condenser lens 38) and two kinds of machining points for the hollowing (spots of the second laser light L2 condensed on the street C by the second condenser lenses 40A, 40B) are independent from each other, in the laser machining apparatus 10 of each embodiment.

Therefore, there is an interval of several tens of mm (millimeters) between the three kinds of machining points. Thus, in a case where the position of the first condenser lens 38 and the positions of the second condenser lenses 40A, 40B are fixed in the laser optical system 24 as in each of the above embodiments, there is a problem that the machining points of the two lines of edge cutting grooves 18 and the machining point of the hollow groove 19 are deviated from each other (deviated from the optimum machining point) in the horizontal direction (Y-direction) and the vertical direction (Z-direction), depending on motion accuracy (precision) of the feed axis (X-direction) of machining during the laser machining.

[0084] Accordingly, the laser machining apparatus 10 of the third embodiment has a function of adjusting the machining points for the edge cutting and two kinds of machining points for the hollowing in the Y-direction and the Z-direction individually. The laser machining apparatus 10 according to the third embodiment has basically the same configuration as the laser machining apparatus 10 according to each embodiment described above except that three mirrors 37, 39A, 39B, and three moving mechanisms 48, 49A, 49B are provided. Therefore, those having the same function or configuration as each embodiment described above are designated by the same reference signs and description thereof will be omitted.

[0085] The mirror 37 (first reflecting element) is disposed above the first condenser lens 38 in the Z-direction and is configured to reflect the two first laser lights L1 emitted from the laser light source 22 and entering via the branching element 31 and the first light forming element 32 toward the first condenser lens 38.

[0086] The mirrors 39A, 39B correspond to second reflecting elements according to the present invention. The mirror 39A is disposed above the second condenser lens 40A in the Z-direction and is configured to reflect the second laser light L2 emitted from the laser light source 22 and entering via the connection switching element 36 or the like toward the second condenser lens 40A. Likewise, the mirror 39B is disposed above the second condenser lens 40B in the Z-direction and is configured to reflect the second laser light L2 emitted from the laser light source 22 and entering via the connection switching element 36 or the like toward the second condenser lens 40B.

[0087] The moving mechanism 48 corresponds to the first moving mechanism of the present invention, and moving mechanisms 49A, 49B correspond to the second moving mechanism of the present invention. As the moving mechanisms 48, 49A, 49B, linear actuators known in the public can be used, for example. The moving mechanism 48 moves the mirror 37 and the first condenser lens 38 integrally in the Y -direction (corresponding to the first perpendicular direction of the present invention) under the control of the control device 30. In addition, the moving mechanism 48 moves the first condenser lens 38 in the Z-direction (corresponding to the second perpendicular direction of the present invention). The moving mechanism 49A moves the mirror 39A and the second condenser lens 40A integrally in the Y-direction under the control of the control device 30. In addition, the moving mechanism 49A moves the second condenser lens 40A in the Z-direction.

Likewise, the moving mechanism 49B moves the mirror 39B and the second condenser lens 40B integrally in the Y-direction under the control of the control device 30. In addition, the moving mechanism 49B moves the second condenser lens 40B in the Z-direction.

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

[0089] In this manner, in the third embodiment, each pair of 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. Consequently, it is possible to achieve the function of adjusting the positions of the spots of the two first laser lights L1 formed on the street C and the position of the spot of the second laser lights L2 of each of the second condenser lenses 40A, 40B in the Y - direction and the Z-direction individually. Accordingly, it is possible to adjust the positions (adjust parallelism) of the respective spots in the Y-direction and the Z-direction, for example by the manufacturer of the laser machining apparatus 10.

[0090] Further, it is possible to allow the machining points (spots) for the edge cutting to trace the street C and allow the machining points (spots) for the hollowing to trace the center of the two lines of edge cutting grooves 18, based on the image of the street C, the two lines of edge cutting grooves 18 (spots of the two first laser lights L1) and the hollow groove 19 (spots of the second laser light L2) taken by the microscope 26 during laser machining of the wafer 12. In addition, based on the above-described image, it is possible to adjust displacement amount in the Z-direction (displacement amount of condensing position) of the spots of the two lines of the first laser lights L1 and the spots of the second laser light L2 with respect to the front surface of the water 12 (street C).

[0091] Here, in this case, it may be possible to provide a camera which can simultaneously image the machining grooves (two lines of edge cutting grooves 18, hollow groove 18) and spots, for each lens of the first condenser lens 38 and the second condenser lenses 40A, 40B.

[0092] As described above, according to the third embodiment, it is possible to individually adjust positions of three kinds of the machining points including the machining points for the edge cutting and the two kinds of machining points for the hollowing, in the Y-direction and the Z-direction. Therefore, it is possible to allow each kind of the machining points to move (trace) on an optimum movement track, irrespective of the motion accuracy along the feed axis (X-direction) of machining during laser machining.

[0093] In the above described third embodiment, the laser machining apparatus can individually adjust positions of the three kinds of machining points including the machining points for the edge cutting and two kinds of machining points for the hollowing, in the Y - direction and the Z-direction. However, the laser machining apparatus may be configured such that positions can be adjusted in only one of the Y-direction and Z-direction.

[0094] In the third embodiment, positions of the three kinds of machining points including the machining points for the edge cutting and the two kinds of machining points for hollowing can be individually adjusted in the Y-direction and the Y-direction by moving mechanisms 48, 49A, 49B. However, the positions of the machining points for the edge cutting may be adjusted by the moving mechanism 48 and the positions of the two kinds of machining points for the hollowing may be adjusted by the relative movement mechanism

28. That is, the table 20 may be moved in at least one of the Y-direction and the Z- direction by the relative movement mechanism 28 so as to adjust the positions of the two kinds of machining points for the hollowing.

[0095] Contrary, the positions of the machining points for the edge cutting may be adjusted by moving the table 20 with the movement mechanism 28, and the positions of the two kinds of machining points for the hollowing may be adjusted by moving mechanisms 94A, 94B.

[0096] Fig. 43 is an explanatory diagram for explaining a modified example of the third embodiment. Note that the first laser light source 22A and the second laser light source 22B, in Fig. 43 will be explained in the fourth embodiment. In the above-described third embodiment, the lase machining apparatus 10 is configured such that positions of the two kinds of machining points for the hollowing can be individually adjusted in the Y -direction and the Z-direction by the moving mechanisms 49A, 49B. On the other hand, as shown in reference signs 1000A and 1000B in Fig. 43, the second condenser lenses 40A, 40B and the mirrors 39A, 39B and the like may be provided on one common frame (illustration is omitted) so that the positions of the two kinds of machining points for the hollowing can be integrally adjusted in at least one of the Y-direction and the Z-direction by one single moving mechanism 49. Because the machining is not simultaneously performed at the two kinds of machining points for the hollowing, there is no problem even when the positions of the two kinds of machining points for the hollowing are integrally moved.

[0097] Further, in Fig. 43, the table 20 may be moved by the relative movement mechanism 28 so as to adjust positions of the machining points for the edge cutting. Still further, the table 20 may be moved by the relative movement mechanism 28 so as to adjust positons of the two kinds of machining points for the hollowing.

[0098] <Fourth Embodiment> Next, the laser machining apparatus 10 according to a fourth embodiment will be described below. While in the laser machining apparatus 10 according to each embodiment described above, the two first laser lights L1 for edge cutting and the second laser light L2 for hollowing are formed from the laser light L emitted from the common laser light source 22, the conditions (wavelength, pulse width, and repeating frequency, and the like) of the suitable laser light L are different between edge cutting and hollowing. Therefore, if the condition of the laser light L is deviated from the condition suitable for one of edge cutting and hollowing, the machining speed for the one of edge cutting and hollowing needs to be lowered, and in addition, the machining speed of the other one also needs to be lowered correspondingly.

[0099] That ís, in a case where the edge cutting and the hollowing are performed using one laser light source 22, although a machining speed for the edge cutting is improved, a machining speed for the hollowing cannot be improved depending on a condition of the laser light. In such a case, it is required to perform machining at a speed for the hollowing which cannot be improved. Further, there may be a reverse case depending on a condition of the laser light. Therefore, in each case, the upper limit of the machining speed is determined by the lower one of a machining speed for the edge cutting and a machining speed for the hollowing. Because there are conditions of laser light respectively suitable for the edge cutting in which two lines of edge cutting grooves 18 (isolation grooves) are formed along the street C of the wafer 12 and the hollowing in which a hollow groove 19 (cut-off groove) is formed between the two lines of edge cutting grooves 18, in terms of a machining speed and a finishing precision, it is difficult to satisfy conditions suitable for both of the edge cutting and hollowing using one laser light source 22.

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

[0101] Fig. 13 is an explanatory drawing for explaining edge cutting and hollowing performed by a laser optical system 24 moved toward the outward direction side X1 relative to the wafer 12 in the fourth embodiment. Fig. 14 is an explanatory drawing for explaining edge cutting and hollowing performed by the laser optical system 24 moved toward the return direction side X2 relative to the wafer 12 in the fourth embodiment.

[0102] As illustrated in Fig. 13 and Fig. 14, the laser machining apparatus 10 according to the fourth embodiment has basically the same configuration as the laser machining apparatus 10 according to each embodiment described above except that 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 are provided instead of the laser light source 22 and the branching element 31. Therefore, those having the same function or configuration as each embodiment described above are designated by the same reference signs and description thereof will be omitted.

[0103] The first laser light source 22 A constantly emits a laser light LA to the first light forming element 32 under the conditions (wavelength, pulse width, repeating frequency, and the like) suitable for edge cutting. Accordingly, formation of the two first laser lights L1 by the first light forming element 32 and condensation of the two first laser lights L1 on the street C by the first condenser lens 38 are performed in the same manner as each embodiment described above.

[0104] The second laser light source 22B constantly emits a laser light LB to the second light forming element 34 under the conditions (wavelength, pulse width, repeating frequency, and the like) suitable for hollowing. Accordingly, formation of the second laser light L2 by the second light forming element 34, switching of the second condenser lenses 40A, 40B by the connection switching element 36, condensation of the second laser light L2 on the street C (outward path) by the second condenser lens 40A, and condensation of the second laser light L2 on the street C (return path) by the second condenser lens 40B are performed in the same manner as each embodiment described above.

[0105] The first safety shutter 100A is provided so as to be freely inserted into and retracted from the optical path of the laser light LA between the first laser light source 22A and the first light forming element 32. Likewise, the second safety shutter 100B is provided so as to be freely inserted into and retracted from 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 configured to cause the first safety shutter 100A to be inserted into and retract from the optical path of the laser light LA, and to cause the second safety shutter 100B to be inserted into and retract from the optical path of the laser light LB under the control of the control device 30. The safety shutter drive mechanism 102A inserts the first safety shutter 100A into the optical path of the laser light LA except during edge cutting machining, in order to stop emission of the two first laser lights L1 from the laser optical system 24. Likewise, the safety shutter drive mechanism 102A retracts the first safety shutter 100A from the optical path of the laser light LA during edge cutting machining, in order to allow the two first laser lights L1 to be emitted from the laser optical system 24.

[0107] Likewise, the safety shutter drive mechanism 102A inserts the second safety shutter 100B into the optical path of the laser light LB except during hollowing, in order to stop emission of the second laser lights L2 from the laser optical system 24. In addition, the safety shutter drive mechanism 102A retracts the second safety shutter 100B from the optical path of the laser light LB during hollowing, in order to allow the second laser light L2 to be emitted from the laser optical system 24.

[0108] A flow of the laser machining process for each of the streets C by the laser machining apparatus 10 according to the fourth embodiment is basically the same as the flow of the laser machining process of the first embodiment illustrated in Fig. 7 described above. However, in the Step SO 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 light LA, and retract the second safety shutter 100B from the optical path of the laser light LB.

[0109] As described thus far, in the fourth embodiment, the first laser light source 22A for edge cutting and the second laser light source 22B for hollowing are separately provided.

Therefore, it is possible to prevent decline in processing speeds of edge cutting and hollowing respectively. Consequently, the tact time described above can be further reduced. Furthermore, processing qualities of edge cutting and hollowing can be each optimized.

[0110] Further, laser lights LA, LB having wavelengths different from each other are used in the edge cutting and the hollowing, and the conditions of machining at the wavelengths are optimized so as to improve the machining speeds. Accordingly, the laser machining apparatus 10 which uses the first laser light source 22 A and the second laser light source 22B according to the fourth embodiment can perform machining at higher speed than the laser machining apparatus 10 which uses one single laser light source 22 as in the first embodiment.

[0111] In the fourth embodiment descried above as well, in the same manner as the third embodiment described above, the positions of machining points for the edge cutting and the positions of the two kinds of machining points for the hollowing may be individually adjusted in the Y-direction and the Z-direction so as to achieve the same advantageous effect with the third embodiment. Further, instead of individually adjusting positions of the three kinds of machining points including the machining points for the edge cutting and the two kinds of machining points for the hollowing in the Y -direction and the Z-direction, the laser machining apparatus 10 may be configured so that the positions can be adjusted in either one ofthe Y-direction and the Z-direction.

[0112] <Specific Example of Connection Switching Element of Fourth Embodiment> Next, specific examples 1 to 3 of the connection switching element 36 according to the fourth embodiment will be described below. Note that the configuration other than the connection switching element 36 is basically the same as the laser machining apparatus 10 of the fourth embodiment (and the first embodiment to the third embodiment). Therefore, those having the same function or configuration as each embodiment described above are designated by the same reference signs and description thereof will be omitted. The specific examples 1 to 3 are also applicable to the connection switching element 36 according to the first embodiment to the third embodiment described above.

[0113] <<Specific Example 1 of Connection Switching Element 36>>

Fig. 15 1s an explanatory drawing illustrating Specific Example 1 of the connection switching element 36 according to the fourth embodiment. As illustrated in Fig. 15, the connection switching element 36 of Specific Example 1 includes a 3/2 plate 52 and a plate rotating mechanism 53 and a polarizing beam splitter 54.

[0114] The X2 plate 52 rotates the polarization direction of the second laser light L2 (linear polarization) emitted from the second light forming element 34, and then allows the second laser light L2 to be emitted toward the polarizing beam splitter 54.

[0115] The plate rotating mechanism 53 adjusts the polarization direction of the second laser light L2 by rotating the A/2 plate 52 around an optical axis thereof under the control of the control device 30. Accordingly, when the laser optical system 24 is moved toward the outward direction side X1 relative to the wafer 12 by the relative movement mechanism 28, the plate rotating mechanism 53 adjusts the rotation angle of the A/2 plate 52 so that the second laser light L2 has S-polarization. Likewise, when the laser optical system 24 is moved toward the return direction side X2 relative to the wafer 12 by the relative movement mechanism 28, the plate rotating mechanism 53 adjusts the rotation angle of the A/2 plate 52 so that the second laser light L2 has P-polarization.

[0116] The polarizing beam splitter 54 reflects S-polarized light toward the second condenser lens 40A and transmits (allows to pass therethrough) P-polarized light so as to emit the P-polarized light as-is toward the second condenser lens 40B. Accordingly, hollowing can be performed by selectively using the second condenser lenses 40A, 40B according to the direction of relative movement (the outward direction side X1 or the return direction side X2) of the laser optical system 24 relative to the wafer 12.

[0117] <<Specific Example 2 of Connection Switching Element 36>> Fig. 16 1s an explanatory drawing illustrating Specific Example 2 of the connection switching element 36 according to the fourth embodiment. As illustrated in Fig. 16, the connection switching element 36 of Specific Example 2 includes the half mirror 58, a mirror 60, shutters 62A, 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 at a position opposing the second condenser lens 40A. The half mirror 58 bifurcates the second laser light L2 entering from the second light forming element 34, reflects one of the bifurcated second laser lights L2 toward the second condenser lens 40A, and transmits (allows to pass therethrough) the other one of the bifurcated second laser lights L2 so as to be emitted toward the mirror 60.

[0119] The mirror 60 is disposed on the optical path of the second laser light L2 transmitted through the half mirror 58 at a position opposing the second condenser lens 40B.

The mirror 60 reflects the second laser light L2 transmitted through the half mirror 58 toward the second condenser lens 40B.

[0120] The shutter 62A is provided so as to be freely inserted into and retracted from the optical path of the second laser light L2 between the half mirror 58 and the second condenser lens 40A. Accordingly, 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 intercepted by the shutter 62A. 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 enters the second condenser lens 40A.

[0121] The shutter 62B is provided so as to be freely inserted into and retracted from the optical path of the second laser light L2 between the mirror 60 and the second condenser lens 40B. Accordingly, when the shutter 62B is inserted into the optical path of the second laser light L2, the second laser light L2 reflected by the mirror 60 is intercepted by the shutter 62B. Further, 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 enters the second condenser lens 40B.

[0122] The shutter drive mechanism 64 is a known actuator configured to insert and retract (open and close) the shutters 62A, 62B on the optical path of the second laser light L2 under the control of the control device 30. When the laser optical system 24 is moved toward the outward direction side X1 relative to the wafer 12 by the relative movement mechanism 28, 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] In contrast, when the laser optical system 24 is moved toward the return direction side X2 relative to the wafer 12 by the relative movement mechanism 28, the shutter drive mechanism 64 inserts the shutter 62A into the optical path of the second laser light L2 and retracts the shutter 62B from the optical path of the second laser light L2. Accordingly, hollowing may be performed by selectively using the two second condenser lenses 40A, 40B according to the direction of relative movement (the outward direction side X1 or the return direction side X2) of the laser optical system 24 relative to the wafer 12.

[0124] <<Specific Example 3 of Connection Switching Element 36>> Fig. 17 is an explanatory drawing for explaining Specific Example 3 of the connection switching element 36 according to the fourth embodiment; As illustrated in Fig. 17, the connection switching element 36 of Specific Example 3 includes a mirror 66A, a mirror 66B, and a mirror drive mechanism 68.

[0125] The mirror 66A is provided so as to be freely inserted into and retracted from the optical path of the second laser light L2 emitted from the second light forming element 34 at a position opposing the second condenser lens 40A. When the mirror 66A is inserted into the optical path of the second laser light L2, the second laser light L2 entering from the second light forming element 34 is reflected 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 enters the mirror 66B.

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

[0127] The mirror drive mechanism 68 is a known actuator configured to insert and retract the mirror 66A into and from the optical path of the second laser light L2 under the control of the control device 30. When the laser optical system 24 is moved toward the outward direction side X1 relative to the wafer 12 by the relative movement mechanism 28, the mirror drive mechanism 68 inserts the mirror 66A into the optical path of the second laser light L2. Accordingly, the entire part 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] In contrast, when the laser optical system 24 is moved toward the return direction side X2 relative to the wafer 12 by the relative movement mechanism 28, the mirror drive mechanism 68 retracts the mirror 66A from the optical path of the second laser light L2. Accordingly, the entire part 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.

Consequently, hollowing can be performed by selectively using the two second condenser lenses 40A, 40B according to the direction of relative movement (the outward direction side X1 or the return direction side X2) of the laser optical system 24 relative to the wafer 12.

[0129] <Fifth Embodiment> Next, the laser machining apparatus 10 according to a fifth embodiment will be described below. The laser machining apparatus 10 according to the fourth embodiment described above includes two types of light sources, namely, the first laser light source 22A and the second laser light source 22B. However, if one of the first laser light source 22A and the second laser light source 22B malfunctions, laser machining cannot be performed on the water 12. Therefore, the laser machining apparatus 10 according to the fifth embodiment has a function capable of continuing laser machining of the wafer 12 even when one of the first laser light source 22A and the second laser light source 22B malfunctions.

[0130] Fig. 18 is an explanatory drawing for explaining edge cutting and hollowing by the laser optical system 24 moved toward the outward direction side X1 relative to the wafer 12 in the fifth embodiment. Fig. 19 is an explanatory drawing for explaining edge cutting and hollowing by the laser optical system 24 moved toward the return direction side X2 relative to the wafer 12 in the fifth embodiment. Note that Fig. 18 and Fig. 19 illustrate a case where the second laser light source 22B malfunctions.

[0131] As illustrated in Fig. 18 and Fig. 19, the laser machining apparatus 10 according to the fifth embodiment has basically the same configuration as the laser machining apparatus 10 according to the fourth embodiment described above (including Specific Examples 1 to 3) except that bypass optical systems 72, 74 are provided. Therefore, those having the same function or configuration as the fourth embodiment described above are designated by the same reference signs and description thereof will be omitted.

[0132] The bypass optical system 72 includes 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. When the second laser light source 22B does not malfunction, the bypass optical system 72 allows the entire laser light LA emitted from the first laser light source 22A to be emitted toward the first light forming element 32 under the control of the control device 30. Note that the presence or absence of malfunction in the second laser light source 22B may be determined by monitoring an operation of the second laser light source 22B and the light amount or the like of the laser light LB.

[0133] In contrast, when the second laser light source 22B malfunctions, the bypass optical system 72 bifurcates the laser light LA emitted from the first laser light source 22A, allows one of the bifurcated laser lights LA to be emitted toward the first light forming element 32, and allows the other one of the bifurcated laser lights LA to be emitted toward the second light forming element 34 under the control of the control device 30. Accordingly, the second laser light L2 is formed from the laser light LA by the second light forming element

34. The second laser light, via the connection switching element 36, is selectively emitted from the second condenser lenses 40A, 40B L2 according to the direction of relative movement of the laser optical system 24 in the same manner as the fourth embodiment described above.

[0134] The bypass optical system 74 includes one or more optical elements in the same manner as 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.

When the first laser light source 22A does not malfunction, the bypass optical system 74 allows the entire laser light LB emitted from the second laser light source 22B to be emitted toward the second light forming element 34 under the control of the control device 30.

Note that the presence or absence of malfunction in the first laser light source 22A may also be determined by monitoring an operation of the first laser light source 22A and the light amount or the like of the laser light LA.

[0135] In contrast, when the first laser light source 22A malfunctions, the bypass optical system 74 bifurcates the laser light LB emitted from the second laser light source 22B, allows one of the bifurcated laser lights LB to be emitted toward the second light forming element 34, and allows the other one of the bifurcated laser lights LB to be emitted toward the first light forming element 32 under the control of the control device 30. Accordingly, the two first laser lights L1 are formed from the laser light LB by the first light forming element 32. The two first laser lights L1 is emitted from the first condenser lens 38 in the same manner as the fourth embodiment described above.

[0136] As described thus far, in the laser machining apparatus 10 according to the fifth embodiment, the bypass optical systems 72, 74 are provided so that laser machining of the wafer 12 can be continued even when one of the first laser light source 22A and the second laser light source 22B malfunctions. Consequently, downtime of the laser machining apparatus 10 can be reduced.

[0137] <Sixth Embodiment> Next, the laser machining apparatus 10 according to a sixth embodiment will be described below. While the laser machining apparatus 10 according to each embodiment described above includes the single first condenser lens 38 for edge cutting and the second condenser lenses 40A, 40B for hollowing with the first condenser lens 38 interposed therebetween, the first condenser lens 38 and the second condenser lenses 40A, 40B may be replaced.

[0138] Fig. 20 is an explanatory drawing for explaining edge cutting and hollowing by the laser optical system 24 moved toward the outward direction side X1 relative to the wafer 12 in a sixth embodiment. Fig. 21 is an explanatory drawing for explaining edge cutting and hollowing by the laser optical system 24 moved toward the return direction side X2 relative to the wafer 12 in the sixth embodiment.

[0139] As illustrated in Fig. 20 and Fig. 21, in the laser machining apparatus 10 according to the sixth embodiment, a single second condenser lens 40 for hollowing is provided instead of the first condenser lens 38. In addition, two first condenser lenses 38A, 38B for edge cutting are provided instead of the second condenser lenses 40A, 40B. Further, positions of the first light forming element 32 and the second light forming element 34 are exchanged. Note that as other configurations are basically the same as the laser machining apparatus 10 according to the first embodiment to the third embodiment described above, specific description 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 (feed direction of machining). The second condenser lens 40 is disposed between the two first condenser lenses 38A and 38B. The first condenser lens 38A is disposed on the outward direction side X1 with respect to the second condenser lens 40. The first condenser lens 38B is disposed on the return direction side X2 with respect to the second condenser lens 40.

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

[0142] When the relative movement mechanism 28 moves the laser optical system 24 in one direction side of the outward direction side X1 and the return direction side X2 relative to the wafer 12, the connection switching element 36 according to the sixth embodiment guides the two first laser lights L1 emitted from the first light forming element 32 to one of the two first condenser lenses 38 A, 38B positioned on the one direction side described above relative to the second condenser lens 40.

[0143] Specifically, as illustrated in Fig. 20, when the laser optical system 24 is moved toward the outward direction side X1 relative to the wafer 12 by the relative movement mechanism 28, the connection switching element 36 guides the two first laser lights L1 emitted from the first light forming element 32 to the first condenser lens 38 A under the control of the control device 30. Accordingly, the two first laser lights L1 are condensed on the street C (outward path) by the first condenser lens 38 A. Likewise, the second laser light L2 is condensed by the second condenser lens 40. Consequently, edge cutting and hollowing are executed along the street C (outward path) by the relative movement of the laser optical system 24 toward the outward direction side X1.

[0144] As illustrated in Fig. 21, when the laser optical system 24 is moved toward the return direction side X2 relative to the wafer 12 by the relative movement mechanism 28, the connection switching element 36 guides the two first laser lights L1 emitted from the first light forming element 32 to the first condenser lens 38B under the control of the control device 30. Accordingly, the two first laser lights L1 is condensed on the street C (return path) by the first condenser lens 38B. Likewise, the second laser light L2 is condensed by the second condenser lens 40. Consequently, edge cutting and hollowing are executed along the street C (return path) by the relative movement of the laser optical system 24 toward the return direction side X2.

[0145] Note that the positions of the first condenser lens 38 and the second condenser lenses 40A, 40B may be exchanged, and the positions of the first light forming element 32 and the second light forming element 34 may be exchanged also in the fourth embodiment (including Specific Examples 1 to 3) and the fifth embodiment described above, in the same manner as the sixth embodiment.

[0146] Further, positions of the two kinds of machining points for the edge cutting may be adjusted by moving the table 20 using the relative movement mechanism 28. Further, the position of the machining point for the hollowing may be adjusted by moving the table 20 using the relative movement mechanism 28. Moreover, as a modified example of the embodiment illustrated in Fig. 43 above, the first condenser lenses 38A, 38B and the like may be provided on one common frame (illustration is omitted) so that the positions of the two kinds of machining points for the edge cutting can be integrally adjusted by one single moving mechanism 48 in at least one of the Y-direction and the Z-direction.

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

[0148] As illustrated in reference sign XXIIA in Fig. 22, the intensity distribution of the laser light L emitted from the laser light source 22 has a Gaussian shape. Therefore, when hollowing is executed with the second laser light L2 having the Gaussian shape, the cross- sectional shape of the hollow groove 19 (illustration of the two lines of edge cutting grooves 18 is omitted) also has the Gaussian shape as illustrated in the reference sign XXIIB. In this case, in a cutting step for cutting the wafer 12 by a blade 110 that rotates at a high speed after laser machining along the hollow groove 19 (Street C), partial abrasion may occur on the blade 110 depending on the positional relationship between the blade 110 and the hollow groove 19. Therefore, it is required to form the bottom of the hollow groove 19 so as to be flat (including substantially flat).

[0149] As illustrated in Fig. 23, in order to form the flat bottom of the hollow groove 19, one possible approach is a method of forming the intensity distribution of the second laser light L2 into an isotropic top-hat shape by using, for example, a DOE and a refracting beam shaper. However, the optical element such as the DOE and the refracting beam shaper as described above is designed on the assumption that the laser light L (beam) has an ideal real circle (cross-sectional shape). The cross-sectional shape of the actual laser light L is not a real circle and has an oval shape caused by individual differences of the laser light source 22 or the like (a state in which a spread angle has an anisotropic nature). In this case, as illustrated in Fig. 24, the intensity distribution (E) of the second laser light L2 has a shape different from the top-hat shape, and thus formation of the flat bottom of the hollow groove 19 is difficult.

[0150] In addition, in a case where the spread angle of the Laser light L has an anisotropic nature as described above, astigmatism is generated, and thus the Z-positions to form the top-hat shape are different in the X-direction and Y-direction. In addition, when hollowing is executed by using the second laser light L2 having the intensity distribution (E) as illustrated in Fig. 23, the cross-sectional shape of the hollow groove 19 has a shape obtained by integrating the spots of the second laser light L2 according to an overlapping rate in the feed direction of machining (X-direction). Consequently, it is difficult to estimate the cross-sectional shape of the hollow groove 19 from the shape of the spot of the second laser light L2 itself.

[0151] Accordingly, in the laser machining apparatus 10 according to the seventh embodiment, the intensity distribution (E) of the second laser light L2 is adjusted by the second light forming element 34 so that the intensity distribution (E) of the second laser light L2 has a stable top-hat shape and the cross-sectional shape of the hollow groove 19 can be estimated easily. Note that the laser machining apparatus 10 according to the seventh embodiment has basically the same configuration as the laser machining apparatus 10 according to each embodiment described above except that the function of the second light forming element 34 is different. Therefore, those having the same function or configuration as each embodiment described above are designated by the same reference signs and description thereof will be omitted.

[0152] In Fig. 25, reference sign XXVA designates an explanatory drawing illustrating an example of an intensity distribution (E) of the second laser light L2 in the Y-direction according to the seventh embodiment, and reference sign XXVB designates an example of the intensity distribution (E) of the second laser light L2 in an X-direction according to the seventh embodiment. Fig. 26 is an explanatory drawing illustrating an example of the intensity distribution of the second laser light L2 on an XY plane according to the seventh embodiment.

[0153] As illustrated in Fig. 25 and Fig. 26, the second laser light L2 formed by the second light forming element 34 according to the seventh embodiment has an intensity distribution with a top-hat shape in a first direction (Y-direction which is perpendicular to the feed direction of machining), and an intensity distribution with the Gaussian shape in a second direction (X-direction parallel to the feed direction of machining), for example. In this case, the Y-direction corresponds to the first direction of the present invention and the X- direction corresponds to the second direction of the present invention. As the second light forming element 34, an optical element such as a DOE and a refracting beam shaper may be used (a plurality of types of the optical elements may be combined).

[0154] In this manner, in adjustment for formation of the second laser light L2 with the top-hat shape, formation of the second laser light L2 having the intensity distribution with the top-hat shape only in one direction (in the Y-direction, here) has less difficulty than the formation of the second laser light L2 having an intensity distribution with the top-hat shape in a plurality of directions as illustrated in Fig. 23. Consequently, the second laser light L2 can be formed into a stable top-hat shape, and thus the bottom of the hollow groove 19 can be formed flat.

[0155] In addition, by forming the intensity distribution of the second laser light L2 in the X-direction (feed direction of machining) into a Gaussian shape, a profile shape of the spot of the second laser light L2 in the Y-direction (that is, an inverted top-hat shape) can be reflected directly to a machined shape of the hollow groove 19. Consequently, it is easy to estimate the machined shape of the hollow groove 19 from the shape of the spot of the second laser light L2 itself.

[0156] Note that although the first direction in the present invention corresponds to the Y- direction and the second direction of the present invention corresponds to the X-direction in Fig. 25 and Fig. 26. However, the first direction and the second direction may be set to arbitrary directions in the XY plane (horizontal plane) by rotating the second light forming element 34 by the second rotating mechanism 46 according to the second embodiment described above (see Fig. 10 and Fig. 11). In other words, when the directions parallel to the table 20 (perpendicular to the travelling direction of the second laser light L2 emitted from the second light forming element 34) and perpendicular to each other are defined as the first direction and the second direction, the second light forming element 34 forms the second laser light L2 having an intensity distribution with the top-hat shape in the first direction and an intensity distribution with the Gaussian shape in the second direction.

[0157] Although the second light forming element 34 forms the second laser light L2 having an intensity distribution with a top-hat shape only in one direction in the seventh embodiment, the first light forming element 32 may also form the two first laser lights L1 each having the intensity distribution with the top-hat shape only in one direction. In addition, the invention of the seventh embodiment may be applied to various types of laser machining of the wafer 12, other than edge cutting and hollowing.

[0158] <Eighth Embodiment> Fig. 27 is a schematic drawing illustrating a laser optical system 24 of a laser machining apparatus 10 according to an eighth embodiment. In the respective embodiments described above, edge cutting is performed by using one of the first condenser lenses 38, 38A, 38B, and hollowing is performed by using one of the second condenser lenses 40, 40A, 40B. In contrast, the laser machining apparatus 10 according to the eighth embodiment performs edge cutting by using a first condenser lens group 120 and performs hollowing by using one of second condenser lens groups 122A, 122B as illustrated in Fig.

27.

[0159] The laser machining apparatus 10 according to the eighth embodiment has basically the same configuration as the laser machining apparatus 10 of each embodiment described above (here, the sixth embodiment is excluded) except that the first condenser lens group 120 and the second condenser lens groups 122A, 122B are provided. Therefore, those having the same function or configuration as each embodiment described above are designated by the same reference signs and description thereof will be omitted. Note that the first condenser lens group 120 and the second condenser lens groups 122A, 122B constitute the condensing optical system in cooperation with the above-described connection switching element 36 and the like.

[0160] The first condenser lens group 120 is provided instead of the first condenser lens 38 in each embodiment described above. 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 lights L1 entering from the first light forming element 32 into three and emits the three branches of the two first laser lights L1respectively toward the three first condenser lenses 38. The three first condenser lenses 38 are arranged in a row along the X-direction (feed direction of machining). Each of the three first condenser lenses 38 condenses the two first laser lights L1 entering from the branching element 124 simultaneously on the streets C (outward path and return path).

[0162] The second condenser lens group 122A is provided instead of the second condenser lens 40A of each embodiment described above. The second condenser lens group 120A is provided with a branching element 126A and three second condenser lenses 40A.

[0163] The branching element 126A branches the second laser light L2 entering from the second light forming element 34 into three and emits the three branches of the second laser light L2 respectively toward the three second condenser lenses 40A. The three second condenser lenses 40A are arranged in a row along the X-direction (feed direction of machining). The three second condenser lenses 40A condense the respective second laser lights L2 entering from the branching element 126A simultaneously on the streets C (outward path).

[0164] The second condenser lens group 122B is provided instead of the second condenser lens 40B of each embodiment described above. The second condenser lens group 120B is provided with a branching element 126B and three second condenser lenses 40B.

[0165] The branching element 126B branches the second laser light L2 entering from the second light forming element 34 into three and emits the three branches of the second laser light L2 respectively toward the three second condenser lenses 40B. The three second condenser lenses 40B are arranged in a row along the X-direction (feed direction of machining). The three second condenser lenses 40B condense the respective second laser lights L2 entering from the branching element 126B simultaneously on the streets C (return path).

[0166] Fig. 28 is an explanatory drawing for explaining effects of the laser machining apparatus 10 according to the eighth embodiment. Note that reference sign XXVIIIA in Fig. 28 illustrates movement of the spots SP of the respective laser lights (two first laser lights L1, second laser light L.2) condensed on the street C during edge cutting and hollowing by the laser machining apparatus 10 of each embodiment described above. Likewise, reference sign XXVIIIB in Fig. 28 illustrates movement of the spots SP1 to SP3 of the respective laser lights condensed on the street C during edge cutting and hollowing by the laser machining apparatus 10 of the eighth embodiment.

[0167] As illustrated in reference sign XXVIIIA in Fig. 28, the spots SP of the two first laser lights L1 and the spot SP of the second laser light L2 formed on the street C (outward path and return path) by the laser optical system 24 move along the street C by the relative movement of the laser optical system 24 toward the outward direction side X1 or the return direction side X2 during edge cutting and hollowing. In this case, when the moving speed of the relative movement of the laser optical system 24 is increased, the distance between the spots SP along the feed direction of machining increases, and then the bottom surfaces of the machined grooves (the two lines of edge cutting grooves 18 and the hollow groove 19) may have unevenness (irregularity). Therefore, in the respective embodiments described above, the moving speed of the relative movement of the laser optical system 24 needs to be limited so as to make the spots SP adjacent to each other in the feed direction of machining partly overlap.

[0168] In contrast, in the laser machining apparatus 10 according to the eighth embodiment, a plurality of the first condenser lenses 38, a plurality of the second condenser lenses 40A and a plurality of the second condenser lenses 40B are respectively arranged along the feed direction of machining, whereby the two first laser lights L1 and the second laser light L2 may be condensed simultaneously on a plurality of spots of the street C (outward path and return path) respectively as illustrated in reference sign XXVIIIB in Fig.

28. Therefore, in the eighth embodiment, three spots SP1, SP2, SP3 of the two first laser lights L1 and three spots SP1, SP2, SP3 of the second laser light L2 formed on the street C (outward path and return path) move along the street C by the relative movement of the laser optical system 24 toward the outward direction side X1 or the return direction side X2.

[0169] In this manner, in the eighth embodiment, even when the moving speed of the relative movement of the laser optical system 24 is increased, the spots SPI, SP2, SP3 adjacent to each other can be partly overlapped in the feed direction of machining due to the increased number of spots for each laser machining. Accordingly, the machining groove having a stable shape can be formed. Consequently, in the eighth embodiment, the tact time required for laser machining of the wafer 12 can be reduced more than each embodiment described above.

[0170] Here, three first condenser lens 38, three second condenser lens 40A, and three second condenser lens 40B are arranged along the feed direction of machining in the eighth embodiment, the number of arrangement may be two or four or more. Further, in the same manner as the sixth embodiment described above (see Fig. 21 and Fig. 22), the first condenser lens group 120 and the second condenser lens groups 122A, 122B may be exchanged.

[0171] <Ninth Embodiment> Fig. 29 is an explanatory drawing for explaining edge cutting and hollowing performed by a laser optical system 24 of a laser machining apparatus 10 according to a ninth embodiment moved toward the outward direction side X1 relative to the wafer 12. Fig. 30 is an explanatory drawing for explaining edge cutting and hollowing performed by the laser optical system 24 of the laser machining apparatus 10 according to the ninth embodiment moved toward the return direction side X2 relative to the wafer 12.

[0172] In the respective embodiments described above, laser machining is performed by selectively using three kinds of condenser lenses including the first condenser lens 38 (or first condenser lenses 38 A, 38B) and the second condenser lenses 40A, 40B (or second condenser lens 40) according to the direction of relative movement of the laser optical system 24 relative to the wafer 12. In contrast, as illustrated in Fig. 29 and Fig. 30, in the ninth embodiment, laser machining is performed by using the first condenser lens 38 and the second condenser lens 40 (corresponding to two condenser lenses of the present invention). Then, in the ninth embodiment, it is possible to switch between edge cutting by the first condenser lens 38 and hollowing by the second condenser lens 40, and edge cutting by the second condenser lens 40 and hollowing by the first condenser lens 38, according to the direction of relative movement of the laser optical system 24 relative to the wafer 12.

[0173] The laser optical system 24 of the ninth embodiment basically has the same configuration as the laser machining apparatus 10 according to the first embodiment described above except that the first condenser lens 38 and second condenser lens 40 are provided instead of the first condenser lens 38 and the second condenser lenses 40A, 40B, and the connecting optical system 200 is provided instead of the connection switching element 36. Therefore, those having the same function or configuration as the first embodiment described above are designated by the same reference signs and description thereof will be omitted.

[0174] The first condenser lenses 38 and the second condenser lens 40 are arranged in a row along the X-direction (feed direction of machining). The first condenser lens 38 is disposed on the outward direction side X1 with respect to the second condenser lens 40. The first condenser lens 38 condenses the two first laser lights L1 or the second laser light L2 entering from the connecting optical system 200, which will be described later, on the street C. Likewise, the second condenser lens 40 condenses the two first laser lights L1 or the second laser light L2 entering from the connecting optical system 200 on the street C.

[0175] The connecting optical system 200 guides the two first laser lights L1 emitted from the first light forming element 32 to the first condenser lens 38 and guides the second laser light L2 emitted from the second light forming element 34 to the second condenser lens 40 when the relative movement mechanism 28 moves the laser optical system 24 toward the outward direction side X1 relative to the wafer 12 (see Fig. 29). In contrast, the connecting optical system 200 guides the two first laser lights L1 emitted from the first light forming element 32 to the second condenser lens 40 and guides the second laser light L2 emitted from the second light forming element 34 to the first condenser lens 38 when the relative movement mechanism 28 moves the laser optical system 24 toward the return direction side X2 relative to the wafer 12 (see Fig. 30).

[0176] Fig. 31 is an explanatory drawing for explaining a function of the connecting optical system 200 when the laser optical system 24 is moved toward the outward direction side XI by a relative movement mechanism 28 relative to the wafer 12. Fig. 32 1s an explanatory drawing for explaining the function of the connecting optical system 200 when the laser optical system 24 is moved toward the return direction side X2 by a relative movement mechanism 28 relative to the wafer 12.

[0177] Note that in Fig. 31 and Fig. 32, reference sign PP1 indicates that the two first laser lights L1 are the P-polarized light, reference sign SP1 indicates the two first laser lights L1 are S-polarized light, reference sign PP2 indicates that the second laser light L2 is P- polarized light, and reference sign SP2 indicates that the second laser light L2 is the S- polarized light. Further, in the present embodiment, description will be given assuming that the two first laser lights L1 emitted from the first light forming element 32 and the second laser light L2 emitted from the second light forming element 34 are each the P- polarized light.

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

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

[0180] The respective polarizing beam splitters 202, 206, 210, 212 allow the P-polarized light to pass therethrough and reflect the S-polarized light.

[0181] The A/2 plates 204, 208, 214 can be switched between a reference state in which the P-polarized light and the S-polarized light can pass therethrough without changing the polarization state and a rotated state in which the axis of the optical system is rotated from the reference state by 45°. The 2/2 plates 204, 208, 214 convert the P-polarized light entering thereto into the S-polarized light, and the S-polarized light entering thereto into the P-polarized light, in the rotated state.

[0182] The mirrors 220 guide the S-polarized light reflected by the polarizing beam splitter 210 to the polarizing beam splitter 202. The mirrors 222 guide the S-polarized light reflected by the polarizing beam splitter 206 to the polarizing beam splitter 212. Note that the mirrors 220 may be omitted when the polarizing beam splitters 202, 210 are positioned so as to face each other in the X-direction. The mirrors 222 may be omitted when the polarizing beam splitters 206, 212 are positioned so as to face each other in the X-direction.

[0183] Asillustrated in Fig. 31, the control device 30 (see Fig. 1) of the ninth embodiment sets the respective A/2 plates 204, 208, 214 to the reference state, when performing laser machining of the street C (outward path), that is, when the relative movement mechanism 28 moves the laser optical system 24 toward the outward direction side X1 relative to the wafer

12.

[0184] The two first laser lights L1 (P-polarized light) emitted from the first light forming element 32 pass through the polarizing beam splitter 202, the A/2 plate 204, and the polarizing beam splitter 206 in sequence and are guided to the first condenser lens 38.

Consequently, the two first laser lights L1 are condensed on the 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 passes through the A/2 plate 208, the polarizing beam splitters 210, 212, and the A/2 plate 214 in sequence, and is guided to the second condenser lens 40. Consequently, the second laser light L2 is condensed on the street C (outward path) by the second condenser lens 40.

[0186] In the same manner as each embodiment described above, edge cutting is executed first, and subsequently, hollowing is executed along the street C (outward path) by the relative movement of the laser optical system 24 toward the outward direction side XI.

Note that the timing of emitting the two first laser lights L1 and the second laser light L2 and stopping the emission of them during laser machining of the street C (outward path) is the same as the first embodiment described above, and thus, specific description will be omitted here (the same applies also to a tenth embodiment and an eleventh embodiment described below).

[0187] Asillustrated in Fig. 32, when performing laser machining of the street C (return path), that is, when the relative movement mechanism 28 moves the laser optical system 24 toward the return direction side X2 relative to the wafer 12, the control device 30 of the ninth embodiment sets the A/2 plates 204, 208, 214 to the rotated states, respectively.

[0188] The two first laser lights L1 (P-polarized light) which are emitted from the first light forming element 32 pass through the polarizing beam splitter 202, and then, are converted into the S-polarized light by the A/2 plate 204 . The two first laser lights L.1 converted into the S-polarized light are reflected toward the mirrors 222 by the polarizing beam splitter 206 and further reflected by the mirror 222 so as to enter the polarizing beam splitter 212. The two first laser lights L1 (S-polarized light) entering the polarizing beam splitter 212 are reflected by the polarizing beam splitter 212 toward the A/2 plate 214, and are converted into the P-polarized light by the A/2 plate 214, and then are guided to the second condenser lens 40. Consequently, the two first laser lights L1 are condensed on the 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 the S-polarized light by the 2/2 plate 208, and then is reflected by the polarizing beam splitter 210 toward the mirror 220, and is further reflected by the mirror 220 so as to enter the polarizing beam splitter 202. The second laser light L2 (S- polarized light) entering the polarizing beam splitter 202 (S-polarized light) is reflected by the polarizing beam splitter 202 toward the 2/2 plate 204, is converted into the P-polarized light by the 2/2 plate 204, and then passes through the polarizing beam splitter 206 and is guided to the first condenser lens 38. Consequently, the second laser light L2 is condensed on the street C (return path) by the first condenser lens 38.

[0190] In the same manner as each embodiment described above, edge cutting is executed first and subsequently, hollowing is executed along the street C (return path) by the relative movement of the laser optical system 24 toward the return direction side X2. Note that the timing of emitting the two first laser lights L1 and the second laser light L2 and stopping the emission of them during laser machining of the street C (return path) is the same as the first embodiment described above, and thus, specific description will be omitted here (the same applies also to a tenth embodiment and an eleventh embodiment described below).

[0191] Note that although the A/2 plate 214 is provided so that the polarization state of the two first laser lights L1 for edge cutting of the street C (outward path) becomes P polarization which is the same as the polarization state when performing edge cutting of the street C (return path) in the ninth embodiment, the A/2 plate 214 may be omitted if it is not necessary to align the polarization state to the same P-polarization.

[0192] As described thus far, according to the ninth embodiment, it is possible to switch between edge cutting by using the first condenser lens 38 and hollowing by using the second condenser lens 40, and edge cutting by using the second condenser lens 40 and hollowing by using the first condenser lens 38, according to the direction of relative movement of the laser optical system 24 relative to the wafer 12. Consequently, the same effects as in each embodiment described above can be obtained.

[0193] <Modified Example of Ninth Embodiment> <<Modified Example 1>> Fig. 33 1s an explanatory drawing for explaining edge cutting and hollowing performed by a laser optical system 24 moved toward the outward direction side X1 relative to the wafer 12 in Modified Example 1 in the ninth embodiment. Fig. 34 is an explanatory drawing for explaining edge cutting and hollowing performed by the laser optical system 24 moved toward the return direction side X2 relative to the wafer 12 in Modified Example 1 of the ninth embodiment.

[0194] In the ninth embodiment described above, the two first laser lights L1 for edge cutting and the second laser light L2 for hollowing are formed from the laser light L emitted from the laser light source 22. In contrast, as illustrated in Fig. 33 and Fig. 34, Modified Example 1 of the ninth embodiment, the first laser light source 22A for edge cutting and the second laser light source 22B for hollowing are provided separately in the same manner as the fourth embodiment described above (see Fig. 13 and Fig. 14). Note that those having the same function or configuration as the fourth embodiment described above are designated by the same reference signs and description thereof will be omitted.

[0195] In this manner, in Modified Example 1 of the ninth embodiment as well, by providing the first laser light source 22A for edge cutting and the second laser light source 22B for hollowing separately, decline in processing speeds of edge cutting and hollowing is prevented respectively in the same manner as the fourth embodiment described above, so that more reduction in tact time can be achieved.

[0196] <<Modified Example 2>> Fig. 35 is an explanatory drawing for explaining edge cutting and hollowing performed by a laser optical system 24 moved toward the outward direction side X1 relative to the wafer 12 in Modified Example 2 in the ninth embodiment. Fig. 36 is an explanatory drawing for explaining edge cutting and hollowing performed by the laser optical system 24 moved toward the return direction side X2 relative to the wafer 12 in Modified Example 2 of the ninth embodiment.

[0197] As illustrated in Fig. 35 and Fig. 36, Modified Example 2 of the ninth embodiment provides a function of enabling to continue laser machining of the wafer 12 even when one of the first laser light source 22A and the second laser light source 22B malfunctions in Modified Example 1 described above. Specifically, in Modified Example 2 of the ninth embodiment, the bypass optical systems 72, 74 are provided as in the fifth embodiment described above (see Fig. 18 and Fig. 19). Note that those having the same function or configuration as the fifth embodiment described above are designated by the same reference signs and description thereof will be omitted.

[0198] In this manner, in Modified Example 2 of the ninth embodiment, the bypass optical systems 72, 74 are provided so that laser machining of the wafer 12 can be continued even when one of the first laser light source 22A and the second laser light source 22B malfunctions in the same manner as the fourth embodiment described above.

[0199] <<Others>> In the ninth embodiment descried above as well, in the same manner as the second embodiment described above (see Fig. 8 to Fig. 11), the width between the two lines of edge cutting grooves 18 may be adjusted by the first rotating mechanism 44 or the width of the second laser light L2 may be adjusted by the second rotating mechanism 46.

[0200] In the ninth embodiment described above as well, in the same manner as the third embodiment described above (see Fig. 12), positions of the spots of the two first laser lights L1 and the position of the spot of the second laser light L2 in the Y-direction may be made adjustable by using the mirrors 37, 39B, the moving mechanisms 48, 49B, and the like.

[0201] In addition, configurations of the seventh embodiment and the eighth embodiment described above may be, as needed, combined with the ninth embodiment described above (including Modified Examples 1 and 2).

[0202] <Tenth Embodiment> Fig. 37 1s an explanatory drawing for explaining edge cutting and hollowing performed by a laser optical system 24 of the laser machining apparatus 10 according to a tenth embodiment. According to the ninth embodiment described above, it is possible to switch between edge cutting by using the first condenser lens 38 and hollowing by using the second condenser lens 40, and edge cutting by using the second condenser lens 40 and hollowing by using the first condenser lens 38, according to the direction of relative movement of the laser optical system 24 relative to the wafer 12. In contrast, in the tenth embodiment, edge cutting is performed in the same manner as the ninth embodiment described above, and hollowing is performed using both of the first condenser lens 38 and the second condenser lens 40.

[0203] The laser optical system 24 according to the tenth embodiment has basically the same configuration as the laser machining apparatus 10 of the ninth embodiment except that the function of the 3/2 plate 208 is partly different. Therefore, those having the same function and configuration as the ninth embodiment described above are designated by the same reference signs and descriptions thereof are omitted.

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

[0205] The polarizing beam splitter 210 of the tenth embodiment transmits the P-polarized light component of the second laser light L2 transmitted through the M/2 plate 208 in the half rotated state so as to be emitted toward the polarizing beam splitter 212, and reflects the S- polarized light component of the second laser light L2 transmitted through the A/2 plate 208 in the half rotated state, toward the mirrors 220. Accordingly, the second laser light L2 is split into two parts by the polarizing beam splitter 210. The second laser light L2 (P- polarized light) transmitted through the polarizing beam splitter 210 is guided to the second condenser lens 40 through the polarizing beam splitter 212 and the A/2 plate 214.

[0206] In contrast, the second laser light L2 (S-polarized light) reflected by the polarizing beam splitter 210 is reflected by the mirrors 220 and enters the polarizing beam splitter 202. Then, the second laser light L2 (S-polarized light) is reflected by the polarizing beam splitter 202 toward the A/2 plate 204, is converted into the P-polarized light by the A/2 plate 204, and then is guided to the first condenser lens 38 through the polarizing beam splitter 206. Consequently, the second laser light L2 is condensed on the street C (return path) by both of the first condenser lens 38 and the second condenser lens 40.

[0207] Firstly, edge cutting and hollowing are executed by the second condenser lens 40 along the street C (return path) by the relative movement of the laser optical system 24 toward the return direction side X2 so as to firstly form the two lines of edge cutting grooves 18 and the hollow groove 19. Subsequently, hollowing is executed by the first condenser lens 38 so as to form the hollow groove 19 again on the previously formed hollow groove

19. Accordingly, it is possible to improve the overlap rate of the spots of the second laser lights L2 adjacent to each other in the feed direction of machining.

[0208] Note that in order to relatively move the laser optical system 24 toward the outward direction side X1, the second laser light L2 (S-polarized light) reflected by the polarizing beam splitter 202 needs to be converted to the P-polarized light before entering the polarizing beam splitter 206. In this case, for example, the A/2 plate (in the rotated state) is temporarily disposed only on the optical path of the second laser light L2 between the polarizing beam splitter 202 and the polarizing beam splitter 206. Accordingly, edge cutting and hollowing are firstly executed by the first condenser lens 38 along the street C

(outward path) by the relative movement of the laser optical system 24 toward the outward direction side X1, and subsequently, hollowing is executed by the second condenser lens 40.

[0209] As described thus far, in the tenth embodiment, it is possible to execute pseudo three point simultaneous machining including edge cutting and hollowing by one of the first condenser lens 38 and the second condenser lens 40, and hollowing by the other one of the first condenser lens 38 and the second condenser lens 40, according to the direction of relative movement of the laser optical system 24 relative to the wafer 12. Consequently, it is possible to improve the overlap rate of the spots of the second laser light L2 on the street C.

[0210] Here, in order to improve the overlap rate of the spots of the two first laser lights L1 on the street C, the 2/2 plate 204 is set to the half rotated state, instead of setting the A/2 plate 208 to the half rotated state. Accordingly, the A/2 plate 204 splits the two first laser lights L1 (P-polarized light) entering from the polarizing beam splitter 202 respectively into two to obtain the P-polarized lights and the S-polarized lights and emits them toward the polarizing beam splitter 206. Consequently, the P-polarized lights of the two first laser lights L1 are guided to the first condenser lens 38, and the S-polarized lights of the two first laser lights L1 are guided to the polarizing beam splitter 212 (second condenser lens 40).

[0211] Therefore, it is possible to execute pseudo three point simultaneous machining including edge cutting by one of the first condenser lens 38 and the second condenser lens 40, and edge cutting and hollowing by the other one of the first condenser lens 38 and the second condenser lens 40, according to the direction of movement of the laser optical system 24 relative to the wafer 12. Consequently, improvement in overlap rate of the spots of the two first laser lights L1 on the street C can be achieved.

[0212] <<Modified Example>> The configurations of the second embodiment to the eighth embodiment described above may be combined with the configuration of the tenth embodiment, as needed, in the same manner as the ninth embodiment described above (including Modified Examples 1 and 2).

[0213] <Eleventh Embodiment> Fig. 38 is an explanatory drawing for explaining edge cutting and hollowing performed by a laser optical system 24 of a laser machining apparatus 10 according to an eleventh embodiment moved toward the outward direction side X1 relative to the wafer 12. Fig. 39 is an enlarged drawing in a dotted circle K1 in Fig. 38. Fig. 40 is an explanatory drawing for explaining edge cutting and hollowing performed by a laser optical system 24 of the laser machining apparatus 10 according to the eleventh embodiment moved toward the return direction side X2 relative to the wafer 12. Fig. 41 is an enlarged drawing in a dotted circle K2 in Fig. 40.

[0214] In the respective embodiments described above, edge cutting and hollowing are executed by using a plurality of various lenses while moving the laser optical system 24 toward the outward direction side X1 and the return direction side X2 relative to the wafer

12. In contrast, in the eleventh embodiment, edge cutting and hollowing are executed by using only one single first condenser lens 38 while moving the laser optical system 24 toward the outward direction side X1 and the return direction side X2 relative to the wafer

12.

[0215] As illustrated in Fig. 38 to Fig. 41, the laser optical system 24 according to the eleventh embodiment has basically the same configuration as the laser machining apparatus 10 of each embodiment described above except that the first condenser lens 38 and the connecting optical system 200A are provided, and that the first light forming element 32 generates the two first laser lights L1 (S-polarized light) and the second light forming element 34 generates the second laser light L2 (P-polarized light). Therefore, those having the same function or configuration as each embodiment described above are designated by the same reference signs and description thereof will be omitted.

[0216] The first condenser lens 38 of the eleventh embodiment condenses the two first laser lights L1 and the second laser light L2 entering from the connecting optical system 200A, which will be described later, on the street C. Note that reference sign OP in Fig. 39 and Fig. 41 designates an optical axis of the first condenser lens 38, and reference sign SPA designate spots of the two first laser lights L1, and reference sign SPB designates a spot of the second laser light L2.

[0217] The connecting optical system 200A guides the two first laser lights L1 emitted from the first light forming element 32 and the second laser light L2 emitted from the second light forming element 34 to the first condenser lens 38. In this case, when the relative movement mechanism 28 moves the laser optical system 24 toward the outward direction side X1 relative to the wafer 12, the connecting optical system 200A shifts the spots SPA of the two first laser lights Ll toward the outward direction side X1 relative to the spot SPB of the second laser light L2. In contrast, when the relative movement mechanism 28 moves the laser optical system 24 toward the return direction side X2 relative to the wafer 12, the connecting optical system 200A shifts the spots SPA of the two first laser lights L1 toward the return direction side X2 relative to the spot SPB of the second laser light L2.

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

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

[0220] The shift element 230 includes, for example, a plurality of prisms (shift prism), a plurality of mirrors, or the like. The shit element 230 shifts the two first laser lights L1 entering from the first light forming element 32 in the X-direction, and then emits the two first laser lights L1 towards the mirrors 232 positioned downward side in the Z-direction. By rotating the shift element 230 around the Z-axis, the shifting direction of the two first laser lights L1 can be arbitrarily adjusted. The shift element 230 shifts the two first laser lights L1 toward the outward direction side X1 when the shift element 230 is set at the first angular position in the direction around the Z-axis. The shift element 230 shifts the two first laser light L1 toward the return direction side X2 when the shift element 230 is set at a second angular position where the shift element 230 is rotated by 180° from the first angular position.

[0221] The mirrors 232 guide the two first laser lights L1 entering from the shift element 230 to the polarizing beam splitter 234.

[0222] The polarizing beam splitter 234 is disposed on an optical path extending from the second light forming element 34 to the first condenser lens 38. The polarizing beam splitter 234 reflects the two first laser lights L1 (S-polarized light) entering from the mirrors 232 toward the first condenser lens 38, and transmits the second laser light L2 (P-polarized light) entering from the second light forming element 34 to emit transmits the second laser light L2 toward the first condenser lens 38. Accordingly, the two first laser lights L1 and the second laser light L2 are condensed on the street C by the first condenser lens 38.

[0223] As illustrated in Fig. 38 and Fig. 39, the control device 30 of the eleventh embodiment sets the shift element 230 to the first angular position when performing laser machining on the street C (outward path), that is, when the relative movement mechanism 28 moves the laser optical system 24 toward the outward direction side X1 relative to the wafer

12. Accordingly, on the street C (outward path), the spots SPA of the two first laser lights L1 is shifted toward the outward direction side X1 relative to the spot SPB of the second laser light L2. Consequently, in the same manner as each embodiment described above, edge cutting is firstly executed and subsequently, hollowing is executed along the street C (outward path) by the relative movement of the laser optical system 24 toward the outward direction side X1.

[0224] As illustrated in Fig. 40 and 41, the control device 30 of the eleventh embodiment sets the shift element 230 to the second angular position when performing laser machining on the street C (return path), that is, when the relative movement mechanism 28 moves the laser optical system 24 toward the return direction side X2 relative to the wafer 12. Accordingly, on the street C (return path), the spots SPA of the two first laser lights LI is shifted toward the return direction side X2 relative to the spot SPB of the second laser light L2. Consequently, in the same manner as each embodiment described above, edge cutting 1s firstly executed and subsequently, hollowing is executed along the street C (return path) by the relative movement of the laser optical system 24 toward the return direction side X2.

[0225] As described thus far, in the eleventh embodiment, the two first laser lights L1 are shifted toward the feed direction side in the machining direction relative to the second laser light L2 by the shift element 230 so that edge cutting and hollowing of the street C (outward path and return path) can be executed by the single first condenser lens 38. Consequently, the same effects as in each embodiment described above can be obtained.

[0226] <<Modified Example>> In the eleventh embodiment described above, the two first laser lights L1 (spots SPA) are shifted by the shift element 230. However, shifting the second laser light L2 (spot SPB) toward a side opposite to the feed direction side in the machining direction is also applicable.

[0227] Fig. 42 is an explanatory drawing for explaining the modified example of the eleventh embodiment. As illustrated in reference sign XLIIA and reference sign XLIIB in Fig. 42, in the eleventh embodiment descried above as well, it is possible to adjust the width between the two lines of edge cutting grooves 18 by the first rotating mechanism 44, or adjust the width of the second laser light L2 by the second rotating mechanism 46 in the same manner as the second embodiment described above (see Fig. 8 to Fig. 11).

[0228] Configurations of the fourth embodiment, the fifth embodiment, the seventh embodiment, and the eighth embodiment may be combined with the configuration of the eleventh embodiment, as needed in the same manner as other embodiments.

[0229] <<Others>> In the respective embodiments described above, ON and OFF of edge cutting and hollowing are switched by inserting and retracting the respective safety shutters 100, 100A, 100B into and from the optical path. However, ON and OFF of edge cutting and hollowing may be switched by turning the laser light source 22 (first laser light source 22A and second laser light source 22B) ON and OFF.

[0230] <Additional Items> As can be understood from the detailed explanations about the embodiments, the present disclosure covers various technical ideas including inventions shown below.

[0231] (Additional Item 1)

A laser machining apparatus which moves a table with a wafer held thereon and a laser optical system disposed at a position opposing the table relative to each other in a feed direction of machining along a street of the wafer while irradiating the wafer with laser lights from the laser optical system, to perform, for each street, edge cutting for forming two first grooves parallel to each other along the street and hollowing for forming a second groove between the two first grooves, wherein the laser optical system comprises: a laser light emitting system configured to emit two first laser lights for edge cutting and a second laser light for hollowing; and a condensing optical system configured to condense the two first laser lights and the second laser light on the street to be machined, wherein in a case where the laser optical system is moved relative to the table toward an outward direction side of the feed direction of machining, the condensing optical system condenses the two first laser lights on the street at a position shifted toward the outward direction side relative to the second laser light, and in a case where the laser optical system is moved relative to the table toward a return direction side of the feed direction of machining, the condensing optical system condenses the two first laser lights on the street at a position shifted toward the return direction side relative to the second laser light.

[0232] (Additional Item 2) The laser machining apparatus according to additional item 1, wherein the condensing optical system comprises: a first condenser lens configured to condense the two first laser lights on the wafer; two second condenser lenses arranged in a row along the feed direction of machining together with the first condenser lens with the first condenser lens interposed therebetween, each of the two second condenser lenses configured to condense the second laser light on the wafer; and a connecting optical system configured to guide the two first laser lights emitted from the laser light emitting system to the first condenser lens and guide the second laser light emitted from the laser light emitting system selectively to the two second condenser lenses, wherein in a case where the laser optical system is moved toward the return direction side relative to the table, the connecting optical system guides the second laser light to one of the two second condenser lenses positioned on the return direction side relative to the first condenser lens, and in a case where the laser optical system is moved toward the outward direction side relative to the table, the connecting optical system guides the second laser light to the other of the second condenser lenses positioned on the outward direction side relative to the first condenser lens.

[0233] (Additional Item 3) The laser machining apparatus according to additional item 1, wherein the condensing optical system comprises: two first condenser lenses arranged in a row along the feed direction of machining, each of the two first condenser lenses configured to condense the two first laser lights on the wafer; a second condenser lens disposed between the two first condenser lenses and configured to condense the second laser light on the wafer; and a connecting optical system configured to guide the two first laser lights emitted from the laser light emitting system selectively to the two first condenser lenses, and guide the second laser light emitted from the laser light emitting system to the second condenser lens, wherein in a case where the laser optical system is moved toward the outward direction side relative to the table, the connecting optical system guides the two first laser lights to one of the two first condenser lenses positioned on the outward direction side relative to the second condenser lens, and in a case where the laser optical system is moved toward the return direction side relative to the table, the connecting optical system guides the two first laser lights to the first condenser lens positioned on the return direction side with respect to the second condenser lens.

[0234] (Additional Item 4) The laser machining apparatus according to additional item 1, wherein the condensing optical system comprises: two condenser lenses arranged in a row along the feed direction of machining; and a connecting optical system configured to guide the two first laser lights and the second laser light emitted from the laser light emitting system to the two condenser lenses, wherein in a case where the laser optical system is moved toward the outward direction side relative to the table, the connecting optical system guides the two first laser lights to one of the two condenser lenses on the outward direction side and guides the second laser light to another of the two condenser lenses on the return direction side, and in a case where the laser optical system is moved toward the return direction side relative to the table, the connecting optical system guides the two first laser lights to the another of the two condenser lenses on the return direction side and guides the second laser light to the one of the two condenser lenses on the outward direction side.

[0235] (Additional Item 5) The laser machining apparatus according to additional item 4, wherein the connecting optical system splits either the two first laser lights or the second laser light into two parts, and guides the two parts to both of the two condenser lenses.

[0236] (Additional Item 6) The laser machining apparatus according to additional item 1, wherein the condensing optical system comprises: a condenser lens; and a connecting optical system configured to guide the two first laser lights and the second laser light emitted from the laser light emitting system to the condenser lens, wherein the connecting optical system includes a shift element configured to: shift the second laser light toward the return direction side relative to the two first laser lights in a case where the laser optical system is moved toward the outward direction side relative to the table; and shift the second laser light toward the outward direction side relative to the two first laser lights in a case where the laser optical system is moved toward the return direction side relative to the table.

[0237] (Additional Item 7) The laser machining apparatus according to additional item 2 or 3, further comprising: a first moving mechanism configured to move the first condenser lens in a perpendicular parallel to the table and perpendicular to the feed direction of machining; and a second moving mechanism configured to move the second condenser lens in the perpendicular direction parallel to the table and perpendicular to the feed direction of machining.

[0238] (Additional Item 8) The laser machining apparatus according to additional item 4 or 5, further comprising a moving mechanism configured to move the condenser lens in a perpendicular direction parallel to the table and perpendicular to the feed direction of machining

[0239] (Additional Item 9)

The laser machining apparatus according to any one of additional items 1 to 8, wherein the laser light emitting system comprises: a laser light source configured to emit a laser light; a branching element configured to bifurcate the laser light emitted from the laser light source; a first light forming element configured to form the two first laser lights from one of laser lights bifurcated by the branching element; and a second light forming element configured to form the second laser light from another of the laser lights bifurcated by the branching element.

[0240] (Additional Item 10) The laser machining apparatus according to any one of additional items 1 to 8, wherein the laser light emitting system comprises: a first laser light source configured to emit a laser light under a condition for the edge cutting; a second laser light source configured to emit a laser light under a condition for the hollowing; a first light forming element configured to form the two first laser lights from the laser light emitted from the first laser light source; and a second light forming element configured to form the second laser light from the laser light emitted from the second laser light source.

[0241] (Additional Item 11) The laser machining apparatus according to additional item 10, further comprising a bypass optical system configured to: bifurcate the laser light emitted from the second laser light source and emit bifurcated laser lights to the first light forming element and the second light forming element in a case where the first laser light source malfunctions; and bifurcate the laser light emitted from the first laser light source and emit bifurcated laser lights to the first light forming element and the second light forming element in a case where the second laser light source malfunctions.

[0242] (Additional Item 12) The laser machining apparatus according to any one of additional items 9 to 11, further comprising a first rotating mechanism configured to rotate the first light forming element around an optical axis of the first light forming element.

[0243] (Additional Item 13) The laser machining apparatus according to any one of additional items 9 to 12, wherein the second light forming element forms the second laser light which forms a non- circular-shaped spot on the wafer, and the laser machining apparatus further comprises a second rotating mechanism configured to rotate the second light forming element around an optical axis of the second light forming element.

[0244] (Additional Item 14) The laser machining apparatus according to any one of additional items 9 to 13, wherein in a case where it is assumed that directions parallel to the table and perpendicular to each other are a first direction and a second direction, the second light forming element forms the second laser light having an intensity distribution having a top-hat shape in the first direction and an intensity distribution having a Gaussian shape in the second direction.

[0245] (Additional Item 15) The laser machining apparatus according to additional item 1, wherein the condensing optical system comprises: a first condenser lens group including a plurality of the first condenser lenses configured to condense the two first laser lights on the wafer, the plurality of the first condenser lenses being arranged along the feed direction of machining; two second condenser lens groups arranged in a row along the feed direction of machining together with the first condenser lens group with the first condenser lens group interposed therebetween, the second condenser lens groups each including a plurality of second condenser lenses configured to condense the second laser light on the wafer, the plurality of second condenser lenses being arranged along the feed direction of machining; and a connecting optical system configured to guide the two first laser lights emitted from the laser light emitting system to the first condenser lens group and guide the second laser light emitted from the laser light emitting system selectively to the two second condenser lens groups, wherein in a case where the laser optical system is moved toward the outward direction side relative to the table, the connecting optical system guides the second laser light to one of the two second condenser lens groups positioned on the return direction side relative to the first condenser lens group, and in a case where the laser optical system is moved toward the return direction side relative to the table, the connecting optical system guides the second laser light to another of the two second condenser lens groups positioned on the outward direction side relative to the first condenser lens group. Reference Signs List

[0246] laser machining apparatus 10 12 wafer 14 chip 16 device 18 edge cutting groove 19 hollow groove table 22 laser light source 22A first laser light source 22B second laser light source 24 laser optical system 20 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 rotating mechanism 46 second rotating mechanism 47A first high-speed shutter 47B second high-speed shutter 47C high-speed shutter drive mechanism

48, 49A, 49B moving mechanism 52 M2 plate 53 plate rotating mechanism 54 polarizing beam splitter 58 half mirror 60 mirror 62A, 62B shutter 64 shutter drive mechanism 66A, 66B 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 branching element 200, 200A connecting optical system 202 polarizing beam splitter 204 M2 plate 206 polarizing beam splitter 208 M2 plate 210, 212 polarizing beam splitter 214 M2 plate 220, 222 mirror 230 shift element 232 mirror 234 polarizing 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 Xl outward direction side X2 return direction side

Claims

MODIFIED CONCLUSIONS

A laser processing apparatus (10) comprising a table (20) configured to hold a wafer (12) thereon and a laser optical system (24) arranged at a position opposite the table from each other in a feed direction ( X1) of processing along a lane (C) of the wafer, wherein the laser optical system (24) is configured to irradiate the wafer with laser light (L1, L2) from the laser optical system and the laser processing apparatus (10) is configured to position the table (20) and the wafer (12) relative to each other along the street during irradiation, to cut edges for each street to form two first grooves (18) parallel to each other along the street and for hollowing to forming a second groove (19) between the two first grooves, the laser optical system (24) comprising: a first laser light source (22, 22A) configured to emit laser light having a state corresponding to cutting the edge; a second laser light source (22, 22B) configured to emit laser light with a state corresponding to the hollowing; a first light-shaping element (32) configured to form two first laser lights (L1) from the laser light emitted from the first laser light source; a second light-shaping element (34) configured to generate second laser light (L2) from the laser light emitted from the second laser light source; a first condenser lens (38); two second condenser lenses (40A, 40B) arranged in a row along the processing feed direction together with the first condenser lens with the first condenser lens interposed therebetween; and a connecting optical system (200) configured to conduct the two first laser lights (L1) emitted from the first light generating element (32) to the first condenser lens (38) and the second laser light (L2) emitted from the second light generating element (34 ) selectively guiding to the two second condenser lenses (40A, 40B), wherein the connecting optical system (200) directs the second laser light (L2) to one (40A) of the two second condenser lenses (40A, 40B) which is in a return direction (X2) is located opposite to the processing feed direction (X1) with respect to the first condenser lens (38) in a case where the laser optical system (24) is moved with respect to the table (20) in a direction corresponding to the processing feed direction (X1), and direct the second laser light (L2) to the other (40B) of the two second condenser lenses (40A, 40B) which is on the outward side in the feed direction (X1) with respect to the e The first condenser lens (38) is in a case where the laser optical system (24) is moved relative to the table (20) in the return direction (X2).

A laser processing apparatus (10) comprising a table (20) configured to hold a wafer (12) thereon and a laser optical system (24) arranged at a position opposite the table from each other in a feed direction ( X1) of processing along a lane (C) of the wafer, wherein the laser optical system (24) is configured to irradiate the wafer with laser light (L1, L2) from the laser optical system and the laser processing apparatus (10) is configured to position the table (20) and the wafer (12) relative to each other along the street during irradiation, to cut edges for each street to form two first grooves (18) parallel to each other along the street and for hollowing to forming a second groove (19) between the two first grooves, the laser optical system comprising:

a first laser light source (22, 22A) configured to emit laser light with a state corresponding to cutting the edge;

a second laser light source (22, 22B) configured to emit laser light with a state corresponding to the hollowing out;

a first light-shaping element (32) configured to form two first laser lights (L1) from the laser light emitted from the first laser light source (22A);

a second light-shaping element (34) configured to generate second laser light (L2) from the laser light emitted from the second laser light source (22B);

two first condenser lenses (38A, 38B) arranged in a row along the processing feed direction (X1);

a second condenser lens (40) disposed between the two first condenser lenses (38A, 38B); and a connecting optical system (200) configured to selectively direct the two first laser lights (L1) emitted from the first light-forming element (32) to the two first condenser lenses (38A, 38B) and the second laser light (L2) emitted from the second light-forming element (34) to the second condenser lens (40), wherein the connecting optical system directs the two first laser lights (L1) to one (38A) of the two first condenser lenses (38A, 38B) which is forward in the feed direction

(X1) relative to the second condenser lens (40) in a case where the laser optical system (24) is advanced relative to the table (20) in the processing feed direction (X1), and the two first laser lights ( L1) leads to another (38B) of the two first condenser lenses (38A, 38B) located on the return side with respect to the second condenser lens in a case where the laser optical system is moved relative to the table in the direction of the return direction (X2), opposite to the machining feed direction (X1).

The laser processing apparatus according to claim 1 or 2, comprising: a first moving mechanism (48) configured to move the first condenser lens (38) in a first perpendicular direction (Y) parallel to the table (20) and perpendicular to the feed direction (X1) of the operation; and a second movement mechanism (49A, 49B) configured to move the second condenser lens (40A, 40B) relative to the table (20) in the first perpendicular direction (Y).

The laser processing apparatus of claim 3, wherein the first movement mechanism (48) is capable of moving the first condenser lens relative to the table (20) in the first perpendicular direction (Y) and in a second perpendicular direction (Z) perpendicular to the table (20), and the second movement mechanism (49A, 49B) can move the second condenser lens (40A, 40B) relative to the table (20) in the first perpendicular direction (Y) and in the second perpendicular direction (Z).

The laser processing apparatus of claim 1, comprising: a first moving mechanism (48) configured to move the first condenser lens (38) in a first perpendicular direction (Y) parallel to the table (20) and perpendicular to the feed direction (X1 ) of the operation; and a second movement mechanism (49) configured to integrally move the two second condenser lenses (40A, 40B) in the first perpendicular direction with respect to the table.

The laser processing apparatus according to claim 5, wherein the first movement mechanism (48) can move the first condenser lens (38) relative to the table (20) in the first perpendicular direction (Y) and in a second perpendicular direction (Z) which is perpendicular. on the table (20), and the second movement mechanism (49) has the two second condenser lenses (40A, 40B) integral with the table (20) in the first perpendicular direction (Y) and in the second perpendicular direction (Z) can move.

The laser processing apparatus of claim 2, comprising: a first movement mechanism (48) configured to integrally move the two first condenser lenses (38A, 38B) in a first perpendicular direction (Y) parallel to the table (20) and perpendicular to the feed direction of the processing; and a second movement mechanism (49) configured to move the second condenser lens (40) in the first perpendicular direction (Y) relative to the table (20).

The laser processing apparatus according to claim 7, wherein the first movement mechanism (48) can move the two first condenser lenses (38A, 38B) integrally with respect to the table (20) in the first perpendicular direction (Y) and a second perpendicular direction (Z). ) which is perpendicular to the table (20), and the second movement mechanism (49) can move the second condenser lens (40) relative to the table (20) in the first perpendicular direction (Y) and the second perpendicular direction (Z). .

The laser processing apparatus according to any one of claims 3 to 8, wherein the first movement mechanism (48) moves the table (20) in the first perpendicular direction (Y).

The laser processing apparatus according to any one of claims 3-9, wherein the second movement mechanism (49) moves the table (20) in the first perpendicular direction (Y).

The laser processing apparatus according to any one of claims 4, 6 and 8, wherein the first movement mechanism (48) moves the table (20) in the first perpendicular direction (Y) and the second perpendicular direction (Z).

The laser processing apparatus according to any one of claims 4, 6, 8 and 11, wherein the second movement mechanism (49) moves the table in the first perpendicular direction (Y) and the second perpendicular direction (Z).