Laser processing device and laser processing method

Abstract

The laser processing device includes a support unit, a light source, a spatial light modulator, a focusing unit, and a control unit. The control unit controls the spatial light modulator in such a manner that the laser is branched into a plurality of processing lights including 0-order light, and a plurality of focusing points of the plurality of processing lights are located at different positions in the Z direction and the X direction, respectively, and controls at least one of the support unit and the focusing unit in such a manner that the X direction coincides with the extension direction of the line and the plurality of focusing points move relatively along the line. The control unit controls the spatial light modulator in such a manner that the focusing point of the 0-order light is located on one side relative to the focusing point of the non-modulated light of the laser in the X direction.

Description

Technical Field

[0001] The present disclosure relates to a laser processing device and a laser processing method. Background Art

[0002] As a laser processing device for irradiating a target with laser light to form a modified region on the target, there is known a device that modulates the laser light so that the laser light is branched into a plurality of processing lights and the plurality of processing lights are focused on different locations (for example, see Patent Documents 1 and 2).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2015-223620

[0006] Patent Document 2: Japanese Patent Application Publication No. 2015-226012 Summary of the invention

[0007] The technical problem that the invention is intended to solve

[0008] The laser processing apparatus described above is extremely effective in shortening the processing time because it is capable of forming a plurality of rows of modified regions using a plurality of processing lights.

[0009] An object of the present disclosure is to provide a laser processing device and a laser processing method that can obtain high processing quality in processing in which laser light is branched into a plurality of processing lights.

[0010] Technical means for solving technical problems

[0011] A laser processing device according to one embodiment of the present disclosure is a laser processing device for forming a modified region on an object by irradiating a laser beam to the object, and comprises: a support portion for supporting an object having a first surface and a second surface on the opposite side of the first surface in such a manner that the second surface is orthogonal to a Z direction; a light source for emitting laser beams; a spatial light modulator for modulating the laser beams emitted from the light source; a focusing portion for focusing the laser beams modulated by the spatial light modulator on the object from the second surface side; and a control portion for controlling the spatial light modulator in such a manner that the laser beam is branched into a plurality of processing lights including 0-order light, and a plurality of light-converging points of the plurality of processing lights are located at different positions in each of the Z direction and the X direction perpendicular to the Z direction, and for controlling at least one of the support portion and the light-converging portion in such a manner that the X direction coincides with an extension direction of a line extending along the second surface and the plurality of light-converging points move relatively along the line, and the control portion controls the spatial light modulator in such a manner that the light-converging point of the 0-order light is located on one side relative to the light-converging point of the non-modulated light of the laser beam in the X direction.

[0012] In the laser processing device, the focal point of one of the plurality of processing lights, namely, the 0th order light, is located on one side relative to the focal point of the non-modulated light in the X direction. Thus, it is possible to suppress the non-modulated light in the laser that is not modulated by the spatial light modulator from affecting the focal state of the 0th order light (for example, the non-modulated light interferes with the 0th order light). Therefore, according to the laser processing device, in the processing of branching the laser into a plurality of processing lights, high processing quality can be obtained.

[0013] In the laser processing device of one embodiment of the present disclosure, the control unit may control the spatial light modulator in such a manner that the focal point of the 0-order light is located in front of the focal point of the non-modulated light in the relative moving direction of the laser. Thus, in the X direction, when the focal point of the 0-order light is located on one side relative to the focal point of the non-modulated light, a higher processing quality can be obtained.

[0014] In the laser processing device of one embodiment of the present disclosure, the control unit may control the spatial light modulator in such a manner that the plurality of light-converging points have a positional relationship that the closer they are to the front side in the relative movement direction of the laser light, the closer they are to the first surface side in the Z direction. This can prevent the light-converging points of the plurality of processing lights from being blocked in the already formed modified region.

[0015] In the laser processing device of one embodiment of the present disclosure, the control unit may control the spatial light modulator so that the processing light branched to the front side in the relative moving direction of the laser light has the largest output among the plurality of processing lights. Thus, when a crack extending over a plurality of columns of modified regions is formed in the object, the crack can be greatly extended toward the first surface side.

[0016] A laser processing method according to one embodiment of the present disclosure is a laser processing method for forming a modified region in an object by irradiating a laser onto the object, and comprises: a first step of preparing an object having a first surface and a second surface on the opposite side of the first surface; and a second step of modulating the laser light using a spatial light modulator in a state where the object is supported in a manner such that the second surface is orthogonal to the Z direction, and focusing the modulated laser light from the second surface side onto the object, wherein in the second step, the spatial light modulator is controlled in a manner such that the laser light is branched into a plurality of processing lights including 0th-order light, and a plurality of light-converging points of the plurality of processing lights are located at different positions in each of the Z direction and the X direction perpendicular to the Z direction, and the spatial light modulator is controlled in a manner such that the light-converging point of the 0th-order light is located on one side relative to the light-converging point of the non-modulated light of the laser light in the X direction, and the plurality of light-converging points are relatively moved along the line in a state where the X direction is consistent with the extension direction of the line extending along the second surface.

[0017] Therefore, according to this laser processing method, for the same reason as the above-mentioned laser processing apparatus, high processing quality can be obtained in processing in which laser light is branched into a plurality of processing lights.

[0018] Effects of the Invention

[0019] Based on the present disclosure, it is possible to provide a laser processing device and a laser processing method that can obtain high processing quality in processing in which laser light is branched into a plurality of processing lights. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a structural diagram of a laser processing device according to one embodiment.

[0021] Figure 2 yes Figure 1 A cross-sectional view of a portion of a spatial light modulator is shown.

[0022] Figure 3 This is a top view of a wafer which is an object of one embodiment.

[0023] Figure 4 yes Figure 3 A cross-sectional view of a portion of a wafer is shown.

[0024] Figure 5 This is a cross-sectional view of a wafer for explaining a three-point branching laser processing method.

[0025] Figure 6 This is a schematic diagram for explaining the two-point branching laser processing method.

[0026] Figure 7 This is an image of a cross section of a silicon substrate processed by a two-point branching laser.

[0027] Figure 8 This is a schematic diagram for explaining the three-point branching laser processing method.

[0028] Fig. 9 This is an image of a cross-section of a silicon substrate processed by a three-point branching laser.

[0029] Fig.10 This is a schematic diagram for explaining the laser processing method of X-direction offset.

[0030] Fig.11 This is a diagram showing the experimental results of the laser processing method regarding the X-direction deviation.

[0031] Fig.12 This is a schematic diagram for explaining the laser processing method for Y-direction offset.

[0032] Fig.13It is a figure which shows the experimental result of the laser processing method regarding the Y direction deviation.

[0033] Fig.14 This is a schematic diagram for explaining the laser processing method of Z-direction offset.

[0034] Fig.15 This is a diagram showing the experimental results of the laser processing method regarding the Z-direction deviation.

[0035] Fig.16 The diagram shows experimental results regarding a laser processing method that combines a Z-direction offset with a Y-direction offset and a laser processing method that combines a Z-direction offset with an X-direction offset.

[0036] Fig.17 This is a flowchart for explaining the laser processing method of X-direction offset.

[0037] Fig.18 It is a diagram showing a display example of an input receiving unit and a table example of a storage unit in the laser processing method regarding an X-direction offset.

[0038] Fig.19 This is a diagram for explaining the laser processing method of X-direction offset.

[0039] Fig. 20 This is a flowchart for explaining the laser processing method with Y-direction offset.

[0040] Fig.21 It is a diagram showing a display example of an input receiving unit and a table example of a storage unit in the laser processing method regarding a Y-direction offset.

[0041] Fig. 22 This is a diagram for explaining the optical axis adjustment in the laser processing method for Y-direction deviation.

[0042] Fig.23 It is a diagram for explaining the laser processing method of Y-direction offset.

[0043] Fig.24 This is a diagram for explaining the optical axis adjustment in the laser processing method for Y-direction deviation.

[0044] Fig.25 This is a flowchart for explaining the laser processing method with Z-direction offset.

[0045] Fig.26 It is a diagram showing a display example of an input receiving unit and a table example of a storage unit in the laser processing method regarding a Z-direction offset.

[0046] Fig. 27 This is a diagram for explaining the laser processing method of Z-direction offset. DETAILED DESCRIPTION

[0047] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings, etc. In addition, in each figure, the same reference numerals are sometimes given to the same or corresponding parts, and repeated descriptions are omitted.

[0048] [Structure of laser processing device]

[0049] like Figure 1 As shown, the laser processing device 1 includes: a support part 2, a light source 3, an optical axis adjustment part 4, a spatial light modulator 5, a focusing part 6, an optical axis monitor part 7, a visual camera part (camera part) 8, an infrared camera part 9, and a control part 10. The laser processing device 1 is a device for forming a modified region 12 on the object 11 by irradiating the object 11 with laser light L. In the following description, three directions orthogonal to each other are respectively referred to as the X direction, the Y direction, and the Z direction. In this embodiment, the X direction is the first horizontal direction, the Y direction is the second horizontal direction perpendicular to the first horizontal direction, and the Z direction is the vertical direction.

[0050] The support part 2 supports the object 11 so that the surface 11a of the object 11 is perpendicular to the Z direction by, for example, adsorbing a thin film (not shown) attached to the object 11. The support part 2 can move in each of the X direction and the Y direction, and can rotate about an axis parallel to the Z direction as a center line.

[0051] The light source 3 emits laser light L by, for example, a pulse oscillation method. The laser light L is transparent to the object 11 .

[0052] The optical axis adjusting unit 4 adjusts the optical axis of the laser light L emitted from the light source 3. In the present embodiment, the optical axis adjusting unit 4 changes the traveling direction of the laser light L emitted from the light source 3 to be along the Z direction while adjusting the optical axis of the laser light L. The optical axis adjusting unit 4 is composed of, for example, a plurality of reflective mirrors that can adjust the position and angle.

[0053] The spatial light modulator 5 is disposed in the housing H. The spatial light modulator 5 modulates the laser light L emitted from the light source 3. In the present embodiment, the laser light L traveling downward along the Z direction from the optical axis adjustment unit 4 is incident on the housing H, and the laser light L incident on the housing H is horizontally reflected by the reflector M1 in a manner that forms an angle with respect to the Y direction, and the laser light L reflected by the reflector M1 is incident on the spatial light modulator 5. In this way, the spatial light modulator 5 modulates the incident laser light L while reflecting it horizontally along the Y direction.

[0054] The focusing section 6 is mounted on the bottom wall of the frame H. The focusing section 6 focuses the laser light L modulated by the spatial light modulator 5 from the surface 11a side along the Z direction to the object 11 supported by the support section 2. In the present embodiment, the laser light L horizontally reflected along the Y direction by the spatial light modulator 5 is reflected downward along the Z direction by the beam splitter M2, and the laser light L reflected by the beam splitter M2 enters the focusing section 6. The focusing section 6 focuses the laser light L thus incident on the object 11. In the present embodiment, the focusing section 6 is configured by mounting a focusing lens unit 61 on the bottom wall of the frame H via a driving mechanism 62. The driving mechanism 62 moves the focusing lens unit 61 along the Z direction by a driving force of, for example, a piezoelectric element.

[0055] Furthermore, an imaging optical system (not shown) is arranged between the spatial light modulator 5 and the focusing section 6 in the housing H. The imaging optical system is a bilateral telecentric optical system in which the reflection surface of the spatial light modulator 5 and the incident pupil plane of the focusing section 6 are in an imaging relationship. Thus, the image of the laser light L on the reflection surface of the spatial light modulator 5 (the image of the laser light L modulated by the spatial light modulator 5) is transferred (imaged) to the incident pupil plane of the focusing section 6.

[0056] A pair of distance measuring sensors S1 and S2 are arranged on the bottom wall of the housing H so as to be located on both sides of the condenser lens unit 61 in the X direction. Each of the distance measuring sensors S1 and S2 emits distance measuring light (e.g., laser light) to the surface 11a of the object 11, and detects the distance measuring light reflected by the surface 11a, thereby acquiring displacement data of the surface 11a.

[0057] The optical axis monitoring unit 7 is disposed in the housing H. The optical axis monitoring unit 7 detects a portion of the laser light L transmitted through the beam splitter M2 (for example, 0.5 to 5% of the laser light L incident on the beam splitter M2). The detection result of the optical axis monitoring unit 7 indicates, for example, the relationship between the optical axis of the laser light L incident on the condensing lens unit 61 and the optical axis of the condensing lens unit 61.

[0058] The visual camera unit 8 is disposed in the frame H. The visual camera unit 8 emits visible light V, and obtains an image of the object 11 passing through the visible light V as an image. In the present embodiment, the visible light V emitted from the visual camera unit 8 is irradiated onto the surface 11a of the object 11 via the spectroscope M2 and the focusing unit 6, and the visible light V reflected by the surface 11a is detected by the visual camera unit 8 via the focusing unit 6 and the spectroscope M2.

[0059] The infrared imaging unit 9 is attached to the side wall of the housing H. The infrared imaging unit 9 emits infrared light and acquires an image of the object 11 passing through the infrared light as an image. In this embodiment, the housing H and the infrared imaging unit 9 are integrally movable in the Z direction.

[0060] The control unit 10 controls the operation of each part of the laser processing device 1. The control unit 10 has: a processing unit 101, a storage unit 102, and an input receiving unit 103. The processing unit 101 is configured as a computer device including a processor, a memory, a storage, and a communication device. In the processing unit 101, the processor executes software (program) loaded in the memory, etc., controls the reading and writing of data in the memory and the storage, and the communication through the communication device. The storage unit 102 is, for example, a hard disk, etc., which stores various data. The input receiving unit 103 is an interface unit that receives input of various data from the operator. In this embodiment, the input receiving unit 103 constitutes a GUI (Graphical User Interface).

[0061] In the laser processing device 1 configured as above, if the laser light L is focused inside the object 11, the laser light L is absorbed in the portion corresponding to the focusing point C of the laser light L, and a modified region 12 is formed inside the object 11. The modified region 12 is a region in which the density, refractive index, mechanical strength, other physical properties, etc. are formed to be different from the surrounding non-modified regions. As the modified region 12, there are, for example, a melt processing region, a crack region, an insulation breakdown region, a refractive index change region, etc. The modified region 12 has a characteristic that cracks easily extend from the modified region 12 toward the incident side of the laser light L and the opposite side thereof. Such characteristics of the modified region 12 are used for cutting the object 11.

[0062] As an example, the operation of the laser processing apparatus 1 will be described regarding a case where the reformed region 12 is formed inside the object 11 along the line 15 for cutting the object 11 .

[0063] First, in the laser processing device 1, the support part 2 is rotated with the axis parallel to the Z direction as the center line so that the line 15 set on the object 11 becomes parallel to the X direction. Next, the laser processing device 1 moves the support part 2 in each of the X direction and the Y direction based on the image obtained by the infrared camera 9 (for example, the image of the functional element layer of the object 11) so that the focal point C of the laser L is located on the line 15 when viewed from the Z direction. Hereinafter, such [positioning of the focusing part 6 with respect to the processing start position on the line 15] is referred to as [alignment].

[0064] Next, the laser processing device 1 moves the frame H (i.e., the focusing unit 6) in the Z direction based on the image (e.g., the image of the surface 11a of the object 11) obtained by the visual camera unit 8 so that the focusing point C of the laser light L is located on the surface 11a. Hereinafter, such [positioning of the focusing unit 6 relative to the surface 11a] is referred to as [height setting]. Next, the laser processing device 1 moves the frame H (i.e., the focusing unit 6) in the Z direction based on this position so that the focusing point C of the laser light L is located at a predetermined depth from the surface 11a.

[0065] Next, the laser processing device 1 emits the laser light L from the light source 3, and moves the support unit 2 along the X direction so that the focal point C of the laser light L moves relatively along the line 15. Hereinafter, the [relative movement direction of the laser light L with respect to the object 11] is referred to as the [relative movement direction A of the laser light L]. At this time, the laser processing device 1 operates the driving mechanism 62 of the focusing unit 6 so that the focal point C of the laser light L is located at a predetermined depth from the surface 11a based on the displacement data of the surface 11a obtained by the distance measuring sensor located on the front side of the pair of distance measuring sensors S1 and S2 in the relative movement direction A of the laser light L.

[0066] Based on the above method, a row of modified regions 12 is formed along the line 15 and at a certain depth from the surface 11a of the object 11. If the laser L is emitted from the light source 3 by pulse oscillation, a plurality of modified points 12s are formed in a row along the X direction. One modified point 12s is formed by irradiation with one pulse of laser L. One row of modified regions 12 is a collection of a plurality of modified points 12s arranged in a row. Adjacent modified points 12s may be connected to each other or separated from each other depending on the pulse pitch of the laser L (the relative moving speed of the focal point C relative to the object 11 divided by the repetition frequency of the laser L).

[0067] [Structure of spatial light modulator]

[0068] The spatial light modulator 5 of this embodiment is, for example, a reflective liquid crystal (LCOS: Liquid Crystal on Silicon) spatial light modulator (SLM: Spatial Light Modulator). Figure 2 As shown, the spatial light modulator 5 is constructed by sequentially stacking a drive circuit layer 52 , a pixel electrode layer 53 , a reflective film 54 , an alignment film 55 , a liquid crystal layer 56 , an alignment film 57 , a transparent conductive film 58 and a transparent substrate 59 on a semiconductor substrate 51 .

[0069] The semiconductor substrate 51 is, for example, a silicon substrate. The driving circuit layer 52 forms an active matrix circuit on the semiconductor substrate 51. The pixel electrode layer 53 includes a plurality of pixel electrodes 53a arranged in a matrix along the surface of the semiconductor substrate 51. Each pixel electrode 53a is formed of a metal material such as aluminum. A voltage is applied to each pixel electrode 53a through the driving circuit layer 52.

[0070] The reflective film 54 is, for example, a dielectric multilayer film. The orientation film 55 is provided on the surface of the liquid crystal layer 56 on the reflective film 54 side, and the orientation film 57 is provided on the surface of the liquid crystal layer 56 on the opposite side to the reflective film 54. Each of the orientation films 55 and 57 is made of a polymer material such as polyimide, and a rubbing treatment is applied to the contact surface of each of the orientation films 55 and 57 that contacts the liquid crystal layer 56. The orientation films 55 and 57 align the liquid crystal molecules 56a contained in the liquid crystal layer 56 in a certain direction.

[0071] The transparent conductive film 58 is provided on the surface of the transparent substrate 59 on the side of the alignment film 57, and faces the pixel electrode layer 53 via the liquid crystal layer 56. The transparent substrate 59 is, for example, a glass substrate. The transparent conductive film 58 is formed of a light-transmitting and conductive material such as ITO. The transparent substrate 59 and the transparent conductive film 58 allow the laser light L to pass through.

[0072] In the spatial light modulator 5 constructed as described above, if a signal indicating a modulation pattern is input from the control unit 10 to the drive circuit layer 52, a voltage according to the signal is applied to each pixel electrode 53a, and an electric field is formed between each pixel electrode 53a and the transparent conductive film 58. When the electric field is formed, the arrangement direction of the liquid crystal molecules 216a is changed in each region corresponding to each pixel electrode 53a in the liquid crystal layer 56, and the refractive index is changed in each region corresponding to each pixel electrode 53a. This state is a state in which the modulation pattern is displayed on the liquid crystal layer 56.

[0073] In a state where the modulation pattern is displayed on the liquid crystal layer 56, if the laser light L is incident on the liquid crystal layer 56 from the outside via the transparent substrate 59 and the transparent conductive film 58, and is reflected by the reflective film 54, and is emitted to the outside from the liquid crystal layer 56 via the transparent conductive film 58 and the transparent substrate 59, the laser light L is modulated according to the modulation pattern displayed on the liquid crystal layer 56. In this way, the modulation pattern displayed on the liquid crystal layer 56 is appropriately set by the spatial light modulator 5, so that the laser light L can be modulated (for example, the intensity, amplitude, phase, polarization, etc. of the laser light L is modulated).

[0074] [Structure of the object]

[0075] like Figure 3 and Figure 4As shown, the object 11 of the present embodiment is a wafer 20. The wafer 20 has a first surface 20a and a second surface 20b opposite to the first surface 20a. The wafer 20 is formed by stacking a functional element layer 22 on a semiconductor substrate 21.

[0076] The semiconductor substrate 21 is, for example, a silicon substrate. The semiconductor substrate 21 has a first surface 21a and a second surface 21b on the opposite side of the first surface 21a. The second surface 21b is the second surface 20b of the wafer 20. The semiconductor substrate 21 is provided with a notch 21c showing the crystal orientation. In addition, the semiconductor substrate 21 may also be provided with an orientation flat instead of the notch 21c.

[0077] The functional element layer 22 is provided on the first surface 21a of the semiconductor substrate 21. The functional element layer 22 includes a plurality of functional elements 22a arranged in a matrix along the first surface 21a of the semiconductor substrate 21. Each functional element 22a is, for example, a light receiving element such as a light emitting diode, a light emitting element such as a laser diode, a circuit element such as a memory, etc. Each functional element 22a may be three-dimensionally configured by stacking a plurality of layers.

[0078] The wafer 20 is cut into each functional element 22a along a plurality of lines 15. The plurality of lines 15 extend in a grid pattern along the second surface 21b of the wafer 20 so as to pass between each of the plurality of functional elements 22a when viewed from the thickness direction of the wafer 20 (more specifically, extend to pass through the center of the street area 23 between adjacent functional elements 22a). Each line 15 is an imaginary line set on the wafer 20 by the laser processing device 1. In addition, each line 15 may also be a line actually drawn to the wafer 20.

[0079] [Operation of laser processing device and laser processing method]

[0080] like Figure 5 As shown, in the laser processing device 1, the wafer 20 is supported by the support unit 2 in such a manner that the second surface 20b of the wafer 20 is orthogonal to the Z direction. In addition, the spatial light modulator 5 is controlled by the control unit 10 so that a predetermined modulation pattern (for example, a modulation pattern including a diffraction pattern) is displayed on the liquid crystal layer 56 of the spatial light modulator 5. In this state, the laser light L is emitted from the light source 3, and the laser light L is focused on the wafer 20 from the second surface 20b side by the focusing unit 6. That is, the laser light L is modulated by the spatial light modulator 5, and the modulated laser light L is focused on the wafer 20 from the second surface 20b side by the focusing unit 6.

[0081] Thus, the laser light L is branched (diffracted) into a plurality of processing lights L1, L2, and L3 including 0-order light, and a plurality of light-converging points C1, C2, and C3 of the plurality of processing lights L1, L2, and L3 are located at different positions in the Z direction and the X direction, respectively. In the present embodiment, the processing light L2 is 0-order light. The light-converging point C1 of the processing light L1 is located closer to the front side of the relative moving direction A of the laser light L than the light-converging point C2 of the processing light L2 of 0-order light, and the light-converging point C3 of the processing light L3 is located closer to the rear side of the relative moving direction A of the laser light L than the light-converging point C2 of the processing light L2 of 0-order light. As an example, the processing light L1 is +1-order light, and the processing light L3 is -1-order light.

[0082] In the present embodiment, the laser light L is modulated by the spatial light modulator 5 so that the plurality of light-converging points C1, C2, and C3 have a positional relationship that the closer to the front side of the relative moving direction A of the laser light L, the closer to the first surface 20a side of the wafer 20 in the Z direction. That is, the laser light L is modulated by the spatial light modulator 5 so that the light-converging point C2 is located on the first surface 20a side of the wafer 20 in the Z direction relative to the light-converging point C3, and the light-converging point C1 is located on the first surface 20a side of the wafer 20 in the Z direction relative to the light-converging point C2. Furthermore, in the present embodiment, the laser light L is modulated by the spatial light modulator 5 so that among the plurality of processing lights L1, L2, and L3, the processing light L1 branched to the frontmost side of the relative moving direction A of the laser light L has the largest output (energy, intensity). Furthermore, even if there is a processing light having an output equal to that of processing light L1 among the plurality of processing lights L1 , L2 , and L3 , the case where the output of other processing lights is smaller than that of processing light L1 is included in the case where processing light L1 has the maximum output.

[0083] In a state where the laser light L is branched into a plurality of processing lights L1, L2, and L3 including 0-order light, the support part 2 is controlled by the control part 10 so that the X direction coincides with the extension direction of the line 15 and the plurality of light-converging points C1, C2, and C3 move relatively along the line 15. Thus, three rows of modified regions 12 are formed along one line 15. The distances from the second surface 20b of the wafer 20 to the modified regions 12 are different from each other, and the depths of the modified regions 12 are formed to match the depths of the light-converging points C1, C2, and C3.

[0084] Here, the influence caused by the non-modulated light of the laser light L is described. The non-modulated light of the laser light L refers to the light that is emitted from the spatial light modulator 5 without being modulated by the spatial light modulator 5 among the laser light L incident on the spatial light modulator 5. For example, the light reflected by the outer surface of the transparent substrate 59 (the surface on the opposite side of the transparent conductive film 58) among the laser light L incident on the spatial light modulator 5 becomes the non-modulated light.

[0085] like Figure 6As shown, when the laser light L is branched into two processing lights L1 and L2 by diffraction, and the processing light L1 is +1-order light and the processing light L2 is -1-order light, the two light-converging points C1 and C2 of the two processing lights L1 and L2 are separated from the light-converging point C0 of the non-modulated light. Therefore, the two processing lights L1 and L2 are less susceptible to the influence of the non-modulated light, and as a result, the two rows of modified regions 12 are easily formed in a desired state.

[0086] Figure 7 Is implemented as Figure 6 The image of the cross section of a silicon substrate obtained by the two-point branch laser processing method is shown. Figure 7 In the example shown, on the surface of the silicon substrate opposite to the incident side of the laser L (eg Figure 7 No black stripes appear in the region of the lower surface of the silicon substrate shown in FIG. 1 and the region between adjacent modified regions 12. This indicates that the cracks have fully extended from the two rows of modified regions 12 to the surface of the silicon substrate on the opposite side of the incident side of the laser L.

[0087] In contrast, Figure 8 As shown, when the laser light L is branched into three processing lights L1, L2, and L3 by diffraction, the processing light L1 is +1-order light, the processing light L2 is 0-order light, and the processing light L3 is -1-order light. Although the two focal points C1 and C3 of the two processing lights L1 and L3 are separated from the focal point C0 of the non-modulated light, the focal point C2 of the processing light L2 is close to the focal point C0 of the non-modulated light. The focal point C2 of the processing light L2 is mainly separated from the focal point C0 of the non-modulated light by the correction amount corresponding to the spherical aberration correction. Therefore, the processing light L2 becomes easily affected by the non-modulated light, and as a result, it becomes difficult to form the three rows of modified regions 12 in a desired state.

[0088] Fig. 9 Is implemented as Figure 8 The image of the cross section of a silicon substrate obtained by the three-point branch laser processing method is shown. Fig. 9 In the example shown, on the surface of the silicon substrate opposite to the incident side of the laser L (eg Fig. 9 Black stripes appear in the region of the modified regions 12 (the lower surface of the silicon substrate shown in FIG. 1 ) and the region between adjacent modified regions 12. This indicates that the cracks have not sufficiently extended from the three rows of modified regions 12 to the surface of the silicon substrate on the opposite side of the incident side of the laser light L (particularly, the cracks have not reached the surface of the silicon substrate on the opposite side of the incident side of the laser light L).

[0089] Based on the above findings, in the laser processing apparatus 1 , at least one of the laser processing method of X-direction offset, the laser processing method of Y-direction offset, and the laser processing method of Z-direction offset is implemented.

[0090] Laser processing methods that are offset in the X direction, such as Fig.10 As shown, the spatial light modulator 5 is controlled by the control unit 10 so that the focal point C2 of the processing light L2 of the 0-order light is located on one side (i.e., the front side or the rear side of the relative moving direction A of the laser light L) with respect to the focal point C0 of the non-modulated light in the X direction. In the present embodiment, the spatial light modulator 5 is controlled by the control unit 10 so that the focal point C1 of the processing light L1 is located on the front side of the relative moving direction A of the laser light L with respect to the focal point C10, the focal point C2 of the processing light L2 is located on the front side of the relative moving direction A of the laser light L with respect to the focal point C20, and the focal point C3 of the processing light L3 is located on the front side of the relative moving direction A of the laser light L with respect to the focal point C30. In addition, each of the focal points C10, C20, and C30 is equivalent to the focal points of each of the processing lights L1, L2, and L3 when no X-direction offset is performed in the modulation of the laser light L.

[0091] Fig.11 This is a diagram showing the experimental results of the laser processing method regarding the X-direction offset. Fig.11 , [Offset] represents [the distance between the focal point C0 of the non-modulated light and the focal point C2 of the processing light L2 of the 0-order light] in the X direction, [-] represents the offset toward the front side of the relative moving direction A of the laser L, and [+] represents the offset toward the rear side of the relative moving direction A of the laser L. In this experiment, the offset in the X direction was changed, and three rows of modified regions 12 were formed on a silicon substrate having an electrical resistivity of more than 1Ω·cm, a crystal orientation of (100), and a thickness of 775μm under the following conditions.

[0092] Wavelength of laser L: 1099nm

[0093] Laser L pulse width: 700ns

[0094] Laser L repetition frequency: 70kHz

[0095] Relative moving speed of laser L relative to silicon substrate: 500 mm / s

[0096] Output of each processing light L1, L2, L3: 2.0W

[0097] Depth of the modified region 12 formed by the processing light L1: 694 μm

[0098] Depth of the modified region 12 formed by the processing light L2: 630 μm

[0099] Depth of the modified region 12 formed by the processing light L3: 566 μm

[0100] Distance between the focal points C1 and C2 in the X direction: 55 μm

[0101] Distance between the focal points C2 and C3 in the X direction: 55 μm

[0102] The results of this experiment are Fig.11 The [cross-sectional photograph (image of the cut surface of the silicon substrate)] and [results] are shown. Regarding the [cross-sectional photograph], the surface of the silicon substrate opposite to the incident side of the laser L from the three rows of modified regions 12 ( Fig.11 The evaluation was conducted from the perspective of whether the crack was sufficiently extended, and the case where the crack was extended was regarded as [C], the case where the crack was sufficiently extended was regarded as [B], and the case where the crack was more fully extended was regarded as [A]. In this experiment, it was found that it is preferable to make the focal point C2 of the processing light L2 as the 0-order light be located on the front side of the relative movement direction A of the laser light L relative to the focal point C0 of the non-modulated light, and it is preferable to make the offset in the X direction in this case be 2 μm or more.

[0103] In the laser processing method with Y-direction offset, such as Fig.12 As shown, the spatial light modulator 5 is controlled by the control unit 10 so that in the Y direction, the focal point C2 of the processing light L2 of the 0-order light is located on one side relative to the focal point C0 of the non-modulated light. In the present embodiment, the spatial light modulator 5 is controlled by the control unit 10 so that: in the Y direction, the focal point C1 of the processing light L1 is located on one side relative to the focal point C10; and in the Y direction, the focal point C2 of the processing light L2 is located on one side relative to the focal point C20; and in the Y direction, the focal point C3 of the processing light L3 is located on one side relative to the focal point C30 (that is, in the Y direction, the multiple focal points C1, C2, C3 of the multiple processing lights L1, L2, L3 are located on one side (the same side) relative to the focal point C0 of the non-modulated light. In addition, each focal point C10, C20, C30 is equivalent to the focal point of each processing light L1, L2, L3 when the Y direction offset is not performed in the modulation of the laser L.

[0104] Fig.13 This is a diagram showing the experimental results of the laser processing method regarding the Y-direction offset. Fig.13 , [Offset] is [the distance between the focal point C0 of the non-modulated light and the focal point C2 of the processing light L2 of the 0th order light] in the Y direction. In this experiment, the offset in the Y direction is changed, and three rows of modified regions 12 are formed on a silicon substrate with a resistivity of more than 1Ω·cm, a crystal orientation of (100), and a thickness of 775μm under the same conditions as the laser processing method with an X-direction offset.

[0105] The results of this experiment are Fig.13The [cross-sectional photograph (image of the cut surface of the silicon substrate)] and [results] are shown. The [cross-sectional photograph] was evaluated from the above-mentioned viewpoints, and the case where the crack was extended was regarded as [C], the case where the crack was fully extended was regarded as [B], and the case where the crack was more fully extended was regarded as [A]. In this experiment, it was found that the offset in the Y direction was preferably set to 4 μm or more.

[0106] In the laser processing method with Z-direction offset, such as Fig.14 As shown, the spatial light modulator 5 is controlled by the control unit 10 so that in the Z direction, the focal point C2 of the processing light L2 of the 0-order light is located on the opposite side of the focal point C0 of the non-modulated light (i.e., the [exit side of the processing light L2] in the Z direction) relative to the ideal focal point IC of the 0-order light. Alternatively, the spatial light modulator 5 is controlled by the control unit 10 so that in the Z direction, the focal point C2 of the processing light L2 of the 0-order light is located on the opposite side of the ideal focal point IC of the 0-order light (i.e., the [incident side of the processing light L2] in the Z direction) relative to the focal point C0 of the non-modulated light. The ideal focal point IC of the 0-order light refers to the focal point of the 0-order light when it is assumed that there is no spherical aberration and the 0-order light is focused on 1 point in the object, and as an example, it is roughly consistent with the focal point C20. In the present embodiment, the spatial light modulator 5 is controlled by the control unit 10 so that in the Z direction, the focal point C1 of the processing light L1 is located on the exit side of the processing light L1 relative to the focal point C10, and in the Z direction, the focal point C2 of the processing light L2 is located on the exit side of the processing light L2 relative to the focal point C20, and in the Z direction, the focal point C3 of the processing light L3 is located on the exit side of the processing light L3 relative to the focal point C30. In addition, each of the focal points C10, C20, and C30 is equivalent to the focal point of each processing light L1, L2, and L3 when no Z-direction offset is performed in the modulation of the laser light L.

[0107] Fig.15 This is a diagram showing the experimental results of the laser processing method regarding the Z-direction offset. Fig.15 In the figure, [Offset] refers to [the distance between the ideal focal point IC of the 0-order light and the focal point C2 of the processing light L2 of the 0-order light] in the Z direction, [-] indicates the offset in the Z direction toward [the incident side of the processing light L2], and [+] indicates the offset in the Z direction toward [the exit side of the processing light L2]. Fig.15 , [distance] is [the distance between the focal point C0 of the non-modulated light and the focal point C2 of the processing light L2 of the 0th order light] in the Z direction. In this experiment, the offset in the Z direction is changed, and three rows of modified regions 12 are formed on a silicon substrate with a resistivity of more than 1Ω·cm, a crystal orientation of (100), and a thickness of 775μm under the same conditions as the laser processing method with an offset in the X direction.

[0108] The results of this experiment, such as Fig.15The [cross-sectional photograph (image of the cut surface of the silicon substrate)] and [results] are shown. The [cross-sectional photograph] was evaluated from the above-mentioned viewpoints, and the case where the crack was extended was regarded as [C], the case where the crack was fully extended was regarded as [B], and the case where the crack was more fully extended was regarded as [A]. In this experiment, it can be seen that it is preferable to make the focal point C2 of the processing light L2 of the 0-order light be located on the [opposite side of the incident side of the processing light L2] relative to the ideal focal point IC of the 0-order light, and it is preferable to set the offset in the Z direction in this case to 20μm or more.

[0109] Fig.16 The figure shows the experimental results of the laser processing method of the combination of Z-direction offset and Y-direction offset, and the laser processing method of the combination of Z-direction offset and X-direction offset. Fig.16 In the figure, the value of [Z direction offset] represents the offset in the Z direction (i.e., the distance between the ideal focal point IC of the 0-order light and the focal point C2 of the processing light L2 of the 0-order light in the Z direction), and [+] represents the offset in the Z direction toward the [exit side of the processing light L2]. The value of [Y direction offset] is the offset in the Y direction (i.e., the distance between the focal point C0 of the non-modulated light and the focal point C2 of the processing light L2 of the 0-order light in the Y direction). The value of [X direction offset] is the offset in the X direction (i.e., the distance between the focal point C0 of the non-modulated light and the focal point C2 of the processing light L2 of the 0-order light in the X direction), [-] represents the offset toward the front side of the relative movement direction A of the laser L, and [+] represents the offset toward the rear side of the relative movement direction A of the laser L.

[0110] Thus, the laser processing method can be implemented by combining the Z-direction offset and the Y-direction offset, or the laser processing method can be implemented by combining the Z-direction offset and the X-direction offset. In addition, the laser processing method can be implemented by combining the X-direction offset and the Y-direction offset, or the laser processing method can be implemented by combining the X-direction offset, the Y-direction offset, and the Z-direction offset.

[0111] [Operation of laser processing device and laser processing method with X-direction offset]

[0112] While referring to Fig.17 The X-direction offset laser processing method performed by the laser processing apparatus 1 will be described in more detail with reference to the flowchart shown in FIG.

[0113] First, prepare the wafer 20 (such as Fig.17 Specifically, Figure 5 As shown, the wafer 20 is supported by the support portion 2 so that the second surface 20 b of the wafer 20 is perpendicular to the Z direction.

[0114] Next, the data is input into the laser processing device 1 (such as Fig.17 Specifically, as shown in S12. Fig.18 As shown in (a) of FIG. 1 , various data input by the operator are received by the input receiving unit 103 (see FIG. 1 ) of the control unit 10. Figure 1 ) is accepted. Fig.18 In (a), [SD1] represents processing light L1, [SD2] represents processing light L2, and [SD3] represents processing light L3. The operator can input [Number of branches] and [Offset direction] as well as numerical values ​​of each processing light L1, L2, and L3.

[0115] In this example, [3] is input in [Number of branches], and [X direction] is input in [Offset direction]. That is, a laser processing method with X-direction offset is selected in a state where the laser L is branched into three processing lights L1, L2, and L3. In the numerical values ​​of each processing light L1, L2, and L3, [ZH] represents the amount of fall when each focal point C1, C2, and C3 falls from the second surface 20b of the wafer 20 (in this example, Z1, Z2, and Z3). [1] input in [BP] represents the type of combination of various beam parameters, and [Benchmark] input in [Spherical aberration] represents the correction amount of spherical aberration of each processing light L1, L2, and L3.

[0116] Furthermore, in the input receiving unit 103, the input of the [output] of each processing light L1, L2, L3 may be limited in such a manner that the processing light L1 that is branched in the frontmost side of the relative moving direction A of the laser light L has the largest output among the plurality of processing lights L1, L2, L3. Furthermore, in the input receiving unit 103, [spherical aberration] and [BP] may be input for each processing light L1, L2, L3, respectively. Furthermore, in the input receiving unit 103, the formation depth of the modified region 12 (i.e., a value corresponding to the distance from the second surface 20b to each modified region 12) by each processing light L1, L2, L3 may be input instead of [ZH] or together with [ZH].

[0117] As data in the case where the laser processing method of X-direction offset is selected in a state where the laser light L is branched into three processing lights L1, L2, and L3, the storage unit 102 (see Figure 1 )like Fig.18 As shown in (b), data of [reference SD], [X-direction branch amount] and [X-direction offset] are stored.

[0118] [Reference SD] indicates the reference when falling into each focal point C1, C2, and C3 from the second surface 20b of the wafer 20, and [SD2] input to [Reference SD] indicates that the focal point C2 of the processing light L2 is the reference (the focal point C1 of the processing light L1 or the focal point C3 of the processing light L3 may also be the reference). [X-direction branching amount] indicates [the distance between the focal point C1 of the processing light L1 and the focal point C3 of the processing light L3] in the X direction (in this example, X10). In this case, as an example, [the distance between the focal point C1 of the processing light L1 and the focal point C2 of the processing light L2] in the X direction becomes X10 / 2, and [the distance between the focal point C2 of the processing light L2 and the focal point C3 of the processing light L3] in the X direction becomes X10 / 2. [X-direction offset] indicates an offset in the X direction (X1 in this example), that is, [the distance between the focal point C0 of the non-modulated light and the focal point C2 of the processing light L2 which is 0-order light] in the X direction.

[0119] Next, the laser processing device 1 is aligned (eg Fig.17 Thus, when viewed from the Z direction, the focal point C of the laser L is located on the line 15. Next, the laser processing device 1 performs a height setting (such as Fig.17 As shown in S14). Thus, Fig.19 As shown on the left side of , the focal point C of the laser light L is located on the laser incident surface (ie, the second surface 20 b of the wafer 20 ).

[0120] Then, if Fig.19 As shown on the right side of the figure, the focusing lens unit 61 (refer to Figure 1 ) only falls by an amount Z2. As a result, the multiple focal points C1, C2, and C3 of the multiple processing lights L1, L2, and L3 are positioned relative to the wafer 20 so that the [distance between the laser incident surface and the focal point C2 of the processing light L2] in the Z direction becomes Z2' (a value equivalent to the value obtained by multiplying Z2 by the refractive index of the wafer 20), and the [distance between the focal point C0 of the non-modulated light and the focal point C2 of the processing light L2] in the X direction becomes X1.

[0121] Thus, in the laser processing device 1, the control unit 10 controls the support unit 2 and the frame H (i.e., the focusing unit 6) based on the image obtained by the visual camera unit 8 before emitting the laser L from the light source 3, so that the focusing point C2 of the processing light L2 of the 0th-order light is located at a specified depth from the second surface 20b of the wafer 20.

[0122] Next, laser light L is emitted from the light source 3 and passes through the spatial light modulator 5 (see Figure 1 ) modulates the laser light L, and the modulated laser light L (ie, a plurality of processing lights L1, L2, L3) is focused on the wafer 20 from the second surface 20b side (refer to Figure 5 )(like Fig.17 S15, the second step shown in FIG. 1 ). Specifically, the control unit 10 controls the spatial light modulator 5 so that the laser light L is branched into a plurality of processing lights L1, L2, and L3 including 0-order light, and the plurality of light-converging points C1, C2, and C3 of the plurality of processing lights L1, L2, and L3 are located at different positions in the Z direction and the X direction, respectively. Further, the control unit 10 controls the spatial light modulator 5 so that in the X direction, the light-converging point C2 of the processing light L2 of the 0-order light is located on one side relative to the light-converging point C0 of the non-modulated light. In addition, in a state where the X direction is aligned with the extension direction of the line 15, the plurality of light-converging points C1, C2, and C3 move relatively along the line 15.

[0123] As described above, in the laser processing device 1, in the X direction, the focal point C2 of the processing light L2 of the 0th order light is located on one side relative to the focal point C0 of the non-modulated light. As a result, it is possible to suppress the non-modulated light in the laser L that is not modulated by the spatial light modulator 5 from affecting the focusing state of the processing light L2 of the 0th order light (for example, the non-modulated light interferes with the processing light L2 of the 0th order light). Therefore, according to the laser processing device 1 (and the laser processing method with an X-direction offset), in the processing of branching the laser L into a plurality of processing lights L1, L2, and L3, high processing quality can be obtained.

[0124] In addition, in the laser processing device 1, the spatial light modulator 5 is controlled by the control unit 10 so that the focal point C2 of the processing light L2 of the 0th order light is located on the front side of the relative moving direction A of the laser L relative to the focal point C0 of the non-modulated light. Thus, in the X direction, when the focal point C2 of the processing light L2 of the 0th order light is located on one side relative to the focal point C0 of the non-modulated light, a higher processing quality can be obtained.

[0125] In addition, in the laser processing device 1, the spatial light modulator 5 is controlled by the control unit 10 so that the plurality of light-converging points C1, C2, and C3 of the plurality of processing lights L1, L2, and L3 have a positional relationship that they are located closer to the first surface 20a side of the wafer 20 in the Z direction as they are closer to the front side in the relative moving direction A of the laser light L. Thus, it is possible to suppress the light-converging of each of the plurality of processing lights L1, L2, and L3 from being blocked on the already formed modified region 12.

[0126] In addition, in the laser processing device 1, the spatial light modulator 5 is controlled by the control unit 10 so that the processing light branched at the front side of the relative moving direction A of the laser light L among the plurality of processing lights L1, L2, and L3 has the largest output. Thus, when cracks extending over a plurality of rows of modified regions 12 are formed on the wafer 20, the cracks can be extended significantly toward the first surface 20a side of the wafer 20.

[0127] [Operation of laser processing device and laser processing method with Y-direction offset]

[0128] While referring to Fig. 20 The Y-direction offset laser processing method performed by the laser processing apparatus 1 will be described in more detail with reference to the flowchart shown.

[0129] First, prepare the wafer 20 (such as Fig. 20 Specifically, Figure 5 As shown, the wafer 20 is supported by the support portion 2 so that the second surface 20 b of the wafer 20 is perpendicular to the Z direction.

[0130] Next, the data is input into the laser processing device 1 (such as Fig. 20 Specifically, as shown in S22, Fig.21 As shown in (a) of FIG. 1 , various data input by the operator are received by the input receiving unit 103 (see FIG. 1 ) of the control unit 10. Figure 1 ) is accepted. Fig.21 In (a), [SD1] represents processing light L1, [SD2] represents processing light L2, and [SD3] represents processing light L3. The operator can input [Number of branches] and [Offset direction] as well as numerical values ​​of each processing light L1, L2, and L3.

[0131] In this example, [3] is input in [Number of branches], and [Y direction] is input in [Offset direction]. That is, a laser processing method with Y-direction offset is selected in a state where the laser L is branched into three processing lights L1, L2, and L3. In the numerical values ​​of each processing light L1, L2, and L3, [ZH] represents the amount of fall when each focal point C1, C2, and C3 falls from the second surface 20b of the wafer 20 (in this example, Z1, Z2, and Z3). [1] input in [BP] represents the type of combination of various beam parameters, and [Benchmark] input in [Spherical aberration] represents the correction amount of spherical aberration of each processing light L1, L2, and L3.

[0132] Furthermore, in the input receiving unit 103, the input of the [output] of each processing light L1, L2, L3 may be limited in such a manner that the processing light L1 that is branched in the frontmost side of the relative moving direction A of the laser light L has the largest output among the plurality of processing lights L1, L2, L3. Furthermore, in the input receiving unit 103, [spherical aberration] and [BP] may be input for each processing light L1, L2, L3, respectively. Furthermore, in the input receiving unit 103, the formation depth of the modified region 12 (i.e., a value corresponding to the distance from the second surface 20b to each modified region 12) by each processing light L1, L2, L3 may be input instead of [ZH] or together with [ZH].

[0133] As data in the case where the laser processing method of Y-direction offset is selected in a state where the laser light L is branched into three processing lights L1, L2, and L3, the storage unit 102 (see Figure 1 )like Fig.21 As shown in (b), data of [reference SD], [X-direction branch amount] and [Y-direction offset] are stored.

[0134] [Reference SD] indicates the reference when falling into each focal point C1, C2, and C3 from the second surface 20b of the wafer 20, and [SD2] input to [Reference SD] indicates that the focal point C2 of the processing light L2 is the reference (the focal point C1 of the processing light L1 or the focal point C3 of the processing light L3 may also be the reference). [X-direction branching amount] indicates [the distance between the focal point C1 of the processing light L1 and the focal point C3 of the processing light L3] in the X direction (in this example, X10). In this case, as an example, [the distance between the focal point C1 of the processing light L1 and the focal point C2 of the processing light L2] in the X direction becomes X10 / 2, and [the distance between the focal point C2 of the processing light L2 and the focal point C3 of the processing light L3] in the X direction becomes X10 / 2. [Y direction offset] indicates the offset in the Y direction (in this example, Y1), that is, [the distance between the focal point C0 of the non-modulated light and the focal point C2 of the processing light L2 which is the 0th-order light] in the Y direction.

[0135] Next, the laser processing device 1 is subjected to optical axis adjustment (such as Fig. 20 Specifically, as described below. In the case where the optical axis of the laser light L passing through the focusing section 6 coincides with the optical axis of the focusing section 6 (refer to S23). Figure 1 ),like Fig. 22 As shown in (a), when the line 15 is aligned with the center of the image (e.g., the image of the second surface 20b of the wafer 20) obtained by the visual camera unit 8, the focal point C0 of the non-modulated light is located on the line 15, and the multiple focal points C1, C2, and C3 of the multiple processing lights L1, L2, and L3 are located on one side relative to the line 15. In the laser processing device 1, for this state, Fig. 22 As shown in (b), the optical axis adjustment unit 4 (see Figure 1 ) so that multiple focal points C1, C2, and C3 are located on line 15.

[0136] Thus, in the laser processing device 1, the control unit 10 controls the optical axis adjustment unit 4 based on the image obtained by the visual camera unit 8 before the laser light L is emitted from the light source 3, so that the focal point C2 of the processing light L2 of the 0-order light is located on the line 15. In addition, such optical axis adjustment can also be implemented in advance in the laser processing device 1.

[0137] Next, the laser processing device 1 is aligned (eg Fig. 20Thus, when viewed from the Z direction, the focal point C of the laser L is located on the line 15. Next, the laser processing device 1 performs a height setting (such as Fig. 20 As shown in S25). Thus, Fig.23 As shown on the left side of , the focal point C of the laser light L is located on the laser incident surface (ie, the second surface 20 b of the wafer 20 ).

[0138] Then, if Fig.23 As shown on the right side of the figure, the focusing lens unit 61 (refer to Figure 1 ) only falls by an amount Z2. As a result, the multiple focal points C1, C2, and C3 of the multiple processing lights L1, L2, and L3 are positioned relative to the wafer 20 so that the [distance between the laser incident surface and the focal point C2 of the processing light L2] in the Z direction becomes Z2' (a value equivalent to the value obtained by multiplying Z2 by the refractive index of the wafer 20), and the [distance between the focal point C0 of the non-modulated light and the focal point C2 of the processing light L2] in the Y direction becomes Y1.

[0139] Thus, in the laser processing device 1, before emitting the laser L from the light source 3, the control unit 10 controls the support unit 2 and the frame H (i.e., the focusing unit 6) based on the image obtained by the visual camera unit 8, so that the focusing point C2 of the processing light L2 of the 0th-order light is located at a specified depth from the second surface 20b of the wafer 20.

[0140] Next, laser light L is emitted from the light source 3 and passes through the spatial light modulator 5 (see Figure 1 ) modulates the laser light L, and the modulated laser light L (ie, a plurality of processing lights L1, L2, L3) is focused on the wafer 20 from the second surface 20b side (refer to Figure 5 )(like Fig. 20 S26, the second step shown in FIG. 1 ). Specifically, the control unit 10 controls the spatial light modulator 5 so that the laser light L is branched into a plurality of processing lights L1, L2, and L3 including 0-order light, and the plurality of light-converging points C1, C2, and C3 of the plurality of processing lights L1, L2, and L3 are located at different positions in the Z direction and the X direction, respectively. Further, the control unit 10 controls the spatial light modulator 5 so that in the Y direction, the light-converging point C2 of the processing light L2 of the 0-order light is located on one side relative to the light-converging point C0 of the non-modulated light. In addition, in a state where the X direction is aligned with the extension direction of the line 15, the plurality of light-converging points C1, C2, and C3 move relatively along the line 15.

[0141] In addition, the optical axis adjustment can also be used, for example, to implement alignment (such as Fig. 20 After S24 shown in FIG. 1 , the following method is used. When the optical axis of the laser light L passing through the focusing section 6 coincides with the optical axis of the focusing section 6 (refer to FIG. 1 ). Figure 1 ),like Fig.24 As shown in (a), when the line 15 is aligned with the center of the image (e.g., the image of the second surface 20b of the wafer 20) obtained by the visual camera unit 8, the focal point C0 of the non-modulated light is located on the line 15, and the multiple focal points C1, C2, and C3 of the multiple processing lights L1, L2, and L3 are located on one side of the line 15. In the laser processing device 1, for this state, it is also possible to Fig.24 As shown in (b), the control unit 10 controls the support unit 2 (refer to Figure 1 ) so that the plurality of light-converging points C1, C2, and C3 are located on the line 15. In this case, the optical axis adjustment unit 4 is not used.

[0142] Thus, in the laser processing device 1 , the control unit 10 may control the support unit 2 based on the image obtained by the visual camera unit 8 before the laser light L is emitted from the light source 3 so that the focal point C2 of the 0th-order processing light L2 is located on the line 15 .

[0143] As described above, in the laser processing device 1, in the Y direction, the focal point C2 of the processing light L2 of the 0th order light is located on one side relative to the focal point C0 of the non-modulated light. As a result, it is possible to suppress the non-modulated light in the laser L that is not modulated by the spatial light modulator 5 from affecting the focusing state of the processing light L2 of the 0th order light (for example, the non-modulated light interferes with the processing light L2 of the 0th order light). Therefore, according to the laser processing device 1 (and the laser processing method with Y-direction offset), in the processing of branching the laser L into a plurality of processing lights L1, L2, and L3, high processing quality can be obtained.

[0144] In addition, in the laser processing apparatus 1, before the laser light L is emitted from the light source 3, the control unit 10 controls the optical axis adjustment unit 4 based on the image of the wafer 20 obtained by the visual camera unit 8 so that the focal point C2 of the processing light L2 of the 0th order light is located on the line 15. Alternatively, in the laser processing apparatus 1, before the laser light L is emitted from the light source 3, the control unit 10 controls the support unit 2 based on the image of the wafer 20 obtained by the visual camera unit 8 so that the focal point C2 of the processing light L2 of the 0th order light is located on the line 15. In addition, in either case, before the laser light L is emitted from the light source 3, the control unit 10 controls the support unit 2 and the frame H (that is, the focusing unit 6) based on the image of the wafer 20 obtained by the visual camera unit 8 so that the focal point C2 of the processing light L2 of the 0th order light is located at a predetermined depth from the second surface 20b of the wafer 20. As a result, the focal point C2 of the 0th-order processing light L2 can be easily and reliably located on the line 15 .

[0145] In the laser processing device 1, the control unit 10 controls the spatial light modulator 5 so that the plurality of light-converging points C1, C2, and C3 of the plurality of processing lights L1, L2, and L3 are located on one side relative to the light-converging point C0 of the non-modulated light in the Y direction. Thus, the plurality of light-converging points C1, C2, and C3 can be arranged along the line 15.

[0146] In addition, in the laser processing device 1, the spatial light modulator 5 is controlled by the control unit 10 so that the plurality of light-converging points C1, C2, and C3 of the plurality of processing lights L1, L2, and L3 have a positional relationship that they are located closer to the first surface 20a side of the wafer 20 in the Z direction as they are closer to the front side in the relative moving direction A of the laser light L. Thus, it is possible to suppress the light-converging of each of the plurality of processing lights L1, L2, and L3 from being blocked on the already formed modified region 12.

[0147] In addition, in the laser processing device 1, the spatial light modulator 5 is controlled by the control unit 10 so that the processing light branched at the front side of the relative moving direction A of the laser light L among the plurality of processing lights L1, L2, and L3 has the largest output. Thus, when cracks extending over a plurality of rows of modified regions 12 are formed on the wafer 20, the cracks can be extended significantly toward the first surface 20a side of the wafer 20.

[0148] [Operation of laser processing device and laser processing method with Z-direction offset]

[0149] While referring to Fig.25 The flowchart shown in the figure will be used to explain in more detail the laser processing method of the Z-direction offset performed by the laser processing device 1.

[0150] First, prepare the wafer 20 (such as Fig.25 Specifically, Figure 5 As shown, the wafer 20 is supported by the support portion 2 so that the second surface 20 b of the wafer 20 is perpendicular to the Z direction.

[0151] Next, the data is input into the laser processing device 1 (such as Fig.25 Specifically, as shown in S32, Fig.26 As shown in (a) of FIG. 1 , various data input by the operator are received by the input receiving unit 103 (see FIG. 1 ) of the control unit 10. Figure 1 ) is accepted. Fig.26 In (a), [SD1] represents processing light L1, [SD2] represents processing light L2, and [SD3] represents processing light L3. The operator can input [Number of branches] and [Offset direction] as well as numerical values ​​of each processing light L1, L2, and L3.

[0152] In this example, [3] is input in [Number of branches], and [Z direction] is input in [Offset direction]. That is, a laser processing method with Z-direction offset is selected in a state where the laser L is branched into three processing lights L1, L2, and L3. In the numerical values ​​of each processing light L1, L2, and L3, [ZH] represents the amount of fall when each focal point C1, C2, and C3 falls from the second surface 20b of the wafer 20 (in this example, Z1, Z2, and Z3). [1] input in [BP] represents the type of combination of various beam parameters, and [Benchmark] input in [Spherical aberration] represents the correction amount of spherical aberration of each processing light L1, L2, and L3.

[0153] Furthermore, in the input receiving unit 103, the input of the [output] of each processing light L1, L2, L3 may be limited in such a manner that the processing light L1 that is branched in the frontmost side of the relative moving direction A of the laser light L has the largest output among the plurality of processing lights L1, L2, L3. Furthermore, in the input receiving unit 103, [spherical aberration] and [BP] may be input for each processing light L1, L2, L3, respectively. Furthermore, in the input receiving unit 103, the formation depth of the modified region 12 (i.e., a value corresponding to the distance from the second surface 20b to each modified region 12) by each processing light L1, L2, L3 may be input instead of [ZH] or together with [ZH].

[0154] As data in the case where the laser processing method of the Z-direction offset is selected in a state where the laser light L is branched into three processing lights L1, L2, and L3, the storage unit 102 (see Figure 1 )like Fig.26 As shown in (b), data of [reference SD], [X-direction branch amount] and [Z-direction offset] are stored.

[0155] [Reference SD] indicates the reference when falling into each focal point C1, C2, and C3 from the second surface 20b of the wafer 20, and [SD2] input to [Reference SD] indicates that the focal point C2 of the processing light L2 is the reference (the focal point C1 of the processing light L1 or the focal point C3 of the processing light L3 may also be the reference). [X-direction branching amount] indicates [the distance between the focal point C1 of the processing light L1 and the focal point C3 of the processing light L3] in the X direction (in this example, X10). In this case, as an example, [the distance between the focal point C1 of the processing light L1 and the focal point C2 of the processing light L2] in the X direction becomes X10 / 2, and [the distance between the focal point C2 of the processing light L2 and the focal point C3 of the processing light L3] in the X direction becomes X10 / 2. [Z-direction offset] indicates the offset in the Z direction (Z4 in this example), that is, [the distance between the ideal focal point IC of the 0-order light and the focal point C2 of the processing light L2 of the 0-order light] in the Z direction.

[0156] Next, the laser processing device 1 is aligned (eg Fig.25 Thus, when viewed from the Z direction, the focal point C of the laser L is located on the line 15. Next, the laser processing device 1 performs a height setting (such as Fig.25 As shown in S34). Thus, Fig. 27 As shown on the left side of , the focal point C of the laser light L is located on the laser incident surface (ie, the second surface 20 b of the wafer 20 ).

[0157] Then, if Fig. 27 As shown on the right side of the figure, the focusing lens unit 61 (refer to Figure 1 ) only drops an amount of [Z2-Z4]. As a result, the multiple focal points C1, C2, and C3 of the multiple processing lights L1, L2, and L3 are positioned relative to the wafer 20 so that the [distance between the laser incident surface and the focal point C2 of the processing light L2] in the Z direction becomes Z2' (a value equivalent to the value obtained by multiplying Z2 by the refractive index of the wafer 20), and the [distance between the ideal focal point IC of the 0-order light and the focal point C2 of the processing light L2 of the 0-order light] in the Z direction becomes Z4' (a value equivalent to the value obtained by multiplying Z4 by the refractive index of the wafer 20).

[0158] Thus, in the laser processing device 1, the control unit 10 controls the support unit 2 and the frame H (i.e., the focusing unit 6) based on the image obtained by the visual camera unit 8 before emitting the laser L from the light source 3, so that the focusing point C2 of the processing light L2 of the 0th-order light is located at a specified depth from the second surface 20b of the wafer 20.

[0159] Next, laser light L is emitted from the light source 3 and passes through the spatial light modulator 5 (see Figure 1 ) modulates the laser light L, and the modulated laser light L (ie, a plurality of processing lights L1, L2, L3) is focused on the wafer 20 from the second surface 20b side (refer to Figure 5 )(like Fig.25 S35, the second step shown in FIG. 1 ). Specifically, the control unit 10 controls the spatial light modulator 5 so that the laser light L is branched into a plurality of processing lights L1, L2, and L3 including 0-order light, and the plurality of focal points C1, C2, and C3 of the plurality of processing lights L1, L2, and L3 are located at different positions in the Z direction and the X direction, respectively. Further, the control unit 10 controls the spatial light modulator 5 so that in the Z direction, the focal point C2 of the processing light L2 of the 0-order light is located on the opposite side of the focal point C0 of the non-modulated light relative to the ideal focal point IC of the 0-order light. In addition, in a state where the X direction is aligned with the extension direction of the line 15, the plurality of focal points C1, C2, and C3 move relatively along the line 15.

[0160] As described above, in the laser processing device 1, the input receiving unit 103 receives the input of [ZH], and the storage unit 102 stores [Z-direction offset]. Here, [ZH] is the first data on the formation position of the modified region 12 by each processing light L1, L2, and L3, and [Z-direction offset] is the second data on [the distance between the ideal focal point IC of the 0-order light and the focal point C2 of the processing light L2 of the 0-order light] in the Z direction. In addition, in the laser processing device 1, the control unit 10 controls the support unit 2 and the frame H (that is, the focusing unit 6) based on the first data [ZH] and the second data [Z-direction offset] so that the focal point C2 of the processing light L2 of the 0-order light is located at a predetermined depth from the second surface 20b of the wafer 20. In addition, in the laser processing device 1, the input receiving unit 103 can also receive the input of the second data [Z-direction offset]. In the laser processing apparatus 1 , the input receiving unit 103 may receive the input of the formation depth of the modified region 12 by each of the processing lights L1 , L2 , and L3 as the first data, instead of or together with [ZH].

[0161] As described above, in the laser processing device 1, in the Z direction, the focal point C2 of the processing light L2 of the 0-order light is located on the opposite side of the focal point C0 of the non-modulated light relative to the ideal focal point IC of the 0-order light. As a result, it is possible to suppress the non-modulated light in the laser L that is not modulated by the spatial light modulator 5 from affecting the focusing state of the processing light L2 of the 0-order light (for example, the non-modulated light interferes with the processing light L2 of the 0-order light). Therefore, according to the laser processing device 1 (and the laser processing method with Z-direction offset), it is possible to obtain high processing quality for processing in which the laser L is branched into a plurality of processing lights L1, L2, and L3. In addition, in the laser processing device 1, it is also possible that the focal point C2 of the processing light L2 of the 0-order light is located on the opposite side of the ideal focal point IC of the 0-order light relative to the focal point C0 of the non-modulated light in the Z direction. In this case, it is also possible to suppress the non-modulated light in the laser L that is not modulated by the spatial light modulator 5 from affecting the focusing state of the processing light L2 of the 0-order light.

[0162] First, in the laser processing device 1, the input receiving unit 103 receives the input of [ZH] (first data on the formation position of the modified region 12 by each processing light L1, L2, L3), and the control unit 10 controls the support unit 2 and the frame H (i.e., the focusing unit 6) based on [ZH] and [Z direction offset] (second data on the distance between the ideal focusing point IC of the 0-order light and the focusing point C2 of the processing light L2 of the 0-order light in the Z direction) so that the focusing point C2 of the processing light L2 of the 0-order light is located at a predetermined depth from the second surface 20b of the wafer 20. In this way, the influence of the non-modulated light on the focusing state of the processing light L2 of the 0-order light can be suppressed, and the modified region 12 can be formed at a desired depth from the second surface 20b of the wafer 20.

[0163] In addition, in the laser processing device 1, the storage unit 102 stores the [Z-direction offset]. Thus, the operator can save time inputting the [Z-direction offset]. Alternatively, the input receiving unit 103 receives the input of the [Z-direction offset]. Thus, the operator can set the [distance between the ideal focal point IC of the 0-order light and the focal point C2 of the processing light L2 of the 0-order light] in the Z direction to a desired value.

[0164] In addition, in the laser processing device 1, the spatial light modulator 5 is controlled by the control unit 10 so that the plurality of light-converging points C1, C2, and C3 of the plurality of processing lights L1, L2, and L3 have a positional relationship that they are located closer to the first surface 20a side of the wafer 20 in the Z direction as they are closer to the front side in the relative moving direction A of the laser light L. Thus, it is possible to suppress the light-converging of each of the plurality of processing lights L1, L2, and L3 from being blocked on the already formed modified region 12.

[0165] In addition, in the laser processing device 1, the spatial light modulator 5 is controlled by the control unit 10 so that the processing light branched at the front side of the relative moving direction A of the laser light L among the plurality of processing lights L1, L2, and L3 has the largest output. Thus, when cracks extending over a plurality of rows of modified regions 12 are formed on the wafer 20, the cracks can be extended significantly toward the first surface 20a side of the wafer 20.

[0166] [Modifications]

[0167] The present disclosure is not limited to the above-mentioned embodiments. For example, in the above-mentioned embodiments, the laser light L is branched into three processing lights L1, L2, and L3 including 0-order light, but the present disclosure is not limited thereto. The laser light L may be branched into two processing lights including 0-order light, or four or more processing lights including 0-order light. In other words, the laser light L may be branched into a plurality of processing lights including 0-order light.

[0168] In addition, in the present disclosure, it is not necessary to modulate the laser light L by the spatial light modulator 5 so that the plurality of light-converging points C1, C2, C3 of the plurality of processing lights L1, L2, L3 have a positional relationship that the closer to the front side of the relative moving direction A of the laser light L, the closer to the first surface 20a side of the wafer 20 in the Z direction. In addition, in the present disclosure, it is not necessary to modulate the laser light L by the spatial light modulator 5 so that the processing light L1 branched at the front side of the relative moving direction A of the laser light L has the largest output among the plurality of processing lights L1, L2, L3. In addition, in the present disclosure, it is not necessary to control the spatial light modulator 5 by the control unit 10 in the laser processing method with an X-direction offset so that the light-converging point C2 of the processing light L2 of the 0-order light is located on the front side of the relative moving direction A of the laser light L relative to the light-converging point C0 of the non-modulated light.

[0169] In addition, in order to adjust or change the positional relationship between the wafer 20 supported by the support part 2 and the focusing part 6 (that is, the positional relationship between the wafer 20 supported by the support part 2 and each focusing point C, C1, C2, C3, etc.), the control part 10 can control at least one of the support part 2 and the focusing part 6 (the movement of at least one of them).

[0170] In addition, the spatial light modulator of the present disclosure is not limited to the reflective liquid crystal spatial light modulator 5. As the spatial light modulator of the present disclosure, for example, a transmissive spatial light modulator may be adopted.

[0171] In addition, if Fig.18 (b) Fig.21 (b) Fig.26 The data shown in (b) (i.e., the data stored in the storage unit 102) can also be input by an operator from the input receiving unit 103. In addition, the optical axis of the laser light L emitted from the light source 3 can also be adjusted by the operator manually adjusting the optical axis adjustment unit 4.

[0172] In addition, each structure of the above-mentioned embodiment is not limited to the above-mentioned materials and shapes, and various materials and shapes can be applied. In addition, each structure of the above-mentioned one embodiment or modification example can be arbitrarily applied to each structure of other embodiments or modification examples.

[0173] Explanation of symbols

[0174] 1...laser processing device; 2...supporting part; 3...light source; 4...optical axis adjusting part; 5...spatial light modulator; 6...focusing part; 8...visible camera part (camera part); 10...control part; 12...modified area; 15...line; 20...wafer (object); 20a...first surface; 20b...second surface; 102...storage part; 103...input receiving part; A...relative moving direction; C, C0, C1, C2, C3...focusing point; IC...ideal focusing point; L...laser; L1, L2, L3...processing light.

Claims

1. A laser processing device, wherein: A laser processing device for forming a modified region in an object by irradiating the object with laser light. The laser processing device comprises: a support portion that supports the object having a first surface and a second surface on the opposite side of the first surface in a manner that the second surface is orthogonal to the Z direction; a light source that emits the laser light; a spatial light modulator for modulating the laser light emitted from the light source; a focusing unit that focuses the laser light modulated by the spatial light modulator onto the object from the second surface side; and a control unit that controls the spatial light modulator in such a manner that the laser beam is branched into a plurality of processing lights including 0-order light, and a plurality of light-converging points of the plurality of processing lights are located at different positions in each of the Z direction and the X direction perpendicular to the Z direction, and controls at least one of the support unit and the light-converging unit in such a manner that the X direction coincides with an extending direction of a line extending along the second surface and the plurality of light-converging points move relatively along the line, The control unit controls the spatial light modulator so that the focal point of the 0th-order light is located on one side with respect to the focal point of the non-modulated light of the laser light in the X direction.

2. The laser processing device according to claim 1, wherein: The control unit controls the spatial light modulator so that the light-converging point of the 0th-order light is located ahead of the light-converging point of the non-modulated light in the relative moving direction of the laser light.

3. The laser processing device according to claim 1 or 2, wherein: The control unit controls the spatial light modulator so that the plurality of light-converging points have a positional relationship in which they are located closer to the first surface side in the Z direction as they are closer to the front side in the relative movement direction of the laser light.

4. The laser processing device according to claim 1 or 2, wherein: The control unit controls the spatial light modulator so that, among the plurality of processing lights, the processing light branched to the frontmost side in the relative moving direction of the laser light has the largest output.

5. The laser processing device according to claim 3, wherein: The control unit controls the spatial light modulator so that, among the plurality of processing lights, the processing light branched to the frontmost side in the relative moving direction of the laser light has the largest output.

6. A laser processing method, wherein: A laser processing method for forming a modified region in an object by irradiating the object with laser light. The laser processing method comprises: A first step of preparing the object having a first surface and a second surface opposite to the first surface; and The second step is to modulate the laser light using a spatial light modulator while the object is supported so that the second surface is perpendicular to the Z direction, and to focus the modulated laser light on the object from the second surface side. In the second step, the spatial light modulator is controlled in such a manner that the laser is branched into a plurality of processing lights including 0-order light, and a plurality of light-converging points of the plurality of processing lights are located at different positions in each of the Z direction and the X direction perpendicular to the Z direction, and the spatial light modulator is controlled in such a manner that the light-converging point of the 0-order light is located on one side with respect to the light-converging point of the non-modulated light of the laser in the X direction, and the plurality of light-converging points are relatively moved along the line extending along the second surface in a state in which the X direction is consistent with an extension direction of the line.

Images