Laser processing methods

Abstract

The laser processing method comprises: a step of irradiating a workpiece with laser light and forming a first groove on the workpiece along a cutting line; a step of irradiating the workpiece with laser light and forming a second groove on the workpiece along the cutting line, wherein the ends of the first groove overlap with those of the first groove in the width direction; a step of forming a composite groove including the first and second grooves on the workpiece, and then irradiating the workpiece with laser light to form a modified region inside the workpiece along the cutting line, and causing cracks to extend from the modified region.

Description

Technical Field

[0001] One aspect of the present invention relates to a laser processing method. Prior Technology

[0002] When cutting an object along a cutting line, there are cases where grooving is performed to remove the surface layer of the object along the cutting line (see, for example, Patent Documents 1 and 2). Such grooving is performed by irradiating the object with laser light, thereby forming a groove in the object along the cutting line. [Previous Technical Documents] [Patent Literature]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2007-173475 [Patent Document 2] Japanese Patent Application Publication No. 2017-011040 Summary of the Invention

[0004] (The problem that the invention aims to solve) In the aforementioned techniques, after forming a groove, laser light is irradiated onto the object to form a modified region within the object along a cutting line. Cracks then extend from this modified region, thereby cutting the object along the cutting line. In this case, to improve the yield of the cut object (e.g., wafer yield), it is desirable to narrow the width of the groove formed in the object. However, if the groove width is narrowed, the cracks are prone to extend and deviate from the groove, potentially leading to a significant deviation from the cutting line and a deterioration in cutting quality.

[0005] Therefore, one aspect of the present invention aims to provide a laser processing method that can narrow the width of the groove formed on the object while suppressing the deviation of cracks extending from the modified region. (Methods used to solve problems)

[0006] One aspect of the laser processing method of the present invention comprises: The process of shining a laser beam onto the object and forming the first groove on the object along the cutting line; The process of irradiating an object with laser light and forming a second groove on the object along the cutting line, the ends of which overlap with the first groove in the width direction; After forming a composite groove including the first groove and the second groove on the object, laser light is irradiated onto the object to form a modified region inside the object along the cutting line, and cracks extend from the modified region.

[0007] In this laser processing method, a composite groove is formed on the workpiece, comprising a first groove and a second groove whose ends overlap. This prevents the width of the groove formed on the workpiece from expanding, while simultaneously inducing crack propagation towards the two grooves. Compared to forming a single groove, this improves the crack induction effect and prevents crack propagation from deviating from the groove. In other words, it narrows the width of the groove formed on the workpiece while suppressing the deviation of cracks extending from the modified region.

[0008] One embodiment of the laser processing method of the present invention may further include: after forming the modified region, and with the cracked end reaching the inner surface of the first groove or the inner surface of the second groove, a process of cutting the object along a cutting line by expanding the adhesive tape attached to the object. In this case, the object can be cut with high precision along the cutting line.

[0009] In one embodiment of the laser processing method of the present invention, the object is a substrate and a functional element layer on the substrate, and the composite trench can be configured on the functional element layer side of the object, with the bottom of the first trench and the bottom of the second trench both reaching the substrate. In this case, the crack induction effect caused by the first trench and the second trench can be further improved.

[0010] In one embodiment of the laser processing method of the present invention, the object is a substrate and a functional element layer on the substrate, and the composite trench is located on the functional element layer side of the object, with the bottom of the first trench and the bottom of the second trench not reaching the substrate. In this case, the depth of the first trench and the second trench can be reduced.

[0011] In one embodiment of the laser processing method of the present invention, the object is a substrate and a functional element layer on the substrate, and the composite trench is located on the functional element layer of the object, with either the bottom of the first trench or the bottom of the second trench reaching the substrate. In this case, the crack-inducing effect caused by the first trench and the second trench can be further improved.

[0012] One embodiment of the laser processing method of the present invention may also include a step of forming a protective film on the functional element layer before forming the composite trench. In this case, the functional element layer can be effectively protected by the protective film.

[0013] In one embodiment of the laser processing method of the present invention, the composite groove can also present a W-shape in a cross-sectional view orthogonal to the cutting line. In this case, the aforementioned effect of narrowing the width of the groove formed on the object and suppressing the deviation of cracks extending from the modified region is significant.

[0014] One embodiment of the laser processing method of the present invention may also include a process of thinning the workpiece by grinding before forming the composite groove. In this case, the workpiece can be thinned by grinding before the composite groove is formed.

[0015] One embodiment of the laser processing method of the present invention may also include a process of thinning the object by grinding after forming the modified region. In this case, the object can be thinned by grinding after the formation of the composite groove.

[0016] In one embodiment of the laser processing method of the present invention, the cutting lines are multiple times set on the object, and the process of forming the modified region may also include: when the deviation of the formation position of the modified region from the center position of the composite groove in the width direction of the composite groove is greater than half the width of the composite groove, the process of correcting the formation position of the modified region to be consistent with the center position. In this case, the width of the composite groove can be used to correct the formation position of the modified region. [The effects of the invention]

[0017] According to one embodiment of the present invention, a laser processing method can be provided that can narrow the width of the groove formed on the object while suppressing the deviation of cracks extending from the modified region. Simple Explanation of the Diagram

[0018] [Figure 1] is a schematic diagram of a laser processing apparatus that forms a modified region inside a wafer. [Figure 2] is a schematic diagram of the laser processing apparatus for performing grooving. [Figure 3] is a plan view of the wafer that will be processed. [Figure 4] is a cross-sectional view of a portion of the wafer shown in Figure 3. [Figure 5] is a plan view of a portion of the cutting channel shown in Figure 3. [Figure 6] is an example of the positions of the focusing points of the first branch laser beam and the second branch laser beam when viewed from the Z direction. [Figure 7](a) is a cross-sectional view of a wafer used to illustrate a laser processing method of one embodiment, (b) is a cross-sectional view of a subsequent wafer of Figure 7(a), and (c) is a cross-sectional view of a subsequent wafer of Figure 7(b). [Figure 8](a) is a cross-sectional view of the subsequent wafer in Figure 7(c), (b) is a cross-sectional view of the subsequent wafer in Figure 8(a), and (c) is a cross-sectional view of the subsequent wafer in Figure 8(b). [Figure 9](a) is a cross-sectional view of the subsequent wafer in Figure 8(c), and (b) is a cross-sectional view of the subsequent wafer in Figure 9(a). [Figure 10] is a cross-sectional view of a portion of the wafer shown in Figure 9(b). [Fig. 11](a) is a cross-sectional view of the wafer of the modified example corresponding to Fig. 10,(b) is a cross-sectional view of the wafer of another modified example corresponding to Fig. 10,(c) is a cross-sectional view of the wafer of yet another modified example corresponding to Fig. 10. [Figure 12] is a cross-sectional view of the subsequent wafer in Figure 9(b). [Figure 13] is a cross-sectional view of a conventional wafer corresponding to Figure 10. [Figure 14] shows other examples of the positions of the focusing points of the first branch laser beam and the second branch laser beam when viewed from the Z direction. [Fig. 15](a) is an example of the positions of the focal points of the first branch laser beam, the second branch laser beam, and the third branch laser beam when viewed from the Z direction. (b) is a cross-sectional view of the wafer of the composite trench in the modified example. [Fig. 16](a) is a cross-sectional view of the wafer of the modified example of the composite trench,(b) is a cross-sectional view of the wafer of the modified example of the composite trench,(c) is a cross-sectional view of the wafer of the modified example of the composite trench. [Fig. 17](a) is a cross-sectional view of the wafer showing the composite trench of the modified example, and (b) is a cross-sectional view of the wafer showing the composite trench of the modified example. [Figure 18] is a graph showing the test results of evaluating the deviation of cracks when forming composite grooves. [Fig. 19](a) is a cross-sectional view of a wafer showing another example of the method of forming a composite trench, and (b) is a cross-sectional view of a subsequent wafer of Fig. 19(a). [Figure 20](a) is a cross-sectional view of a wafer showing a further example of the method for forming a composite trench, and (b) is a cross-sectional view of a subsequent wafer showing Figure 20(a). [Figure 21] is a flowchart illustrating an example of laser processing that includes the formation location of the modified region. [Figure 22] is a perspective view of a laser processing apparatus equipped with an optical system for grooving and an optical system for forming modified regions. [Fig. 23](a) is a cross-sectional view of a wafer used to illustrate the modified laser processing method, (b) is a cross-sectional view of a subsequent wafer of Fig. 23(a), and (c) is a cross-sectional view of a subsequent wafer of Fig. 23(b). [Figure 24](a) is a cross-sectional view of the subsequent wafer in Figure 23(c), (b) is a cross-sectional view of the subsequent wafer in Figure 24(a), and (c) is a cross-sectional view of the subsequent wafer in Figure 24(b). [Figure 25] is a cross-sectional view of the subsequent wafer of Figure 24(c). Implementation

[0019] Hereinafter, embodiments of one aspect of the present invention will be described in detail with reference to the drawings. Identical or equivalent parts in the drawings are indicated by the same reference numerals, and repeated descriptions are omitted.

[0020] This embodiment forms a modified region inside a wafer (object). As an apparatus for forming a modified region inside a wafer, a laser processing apparatus 100 as shown in FIG1 can be used, for example. As shown in FIG1, the laser processing apparatus 100 includes a support unit 102, a light source 103, an optical axis adjustment unit 104, a spatial light modulator 105, a light collection unit 106, an optical axis monitor unit 107, a visual imaging unit 108A, an infrared imaging unit 108B, a moving mechanism 109, and a management unit 150. The laser processing apparatus 100 forms a modified region 11 on the wafer 20 by irradiating the wafer 20 with laser light L0. In the following description, the three mutually orthogonal directions are referred to as the X direction, Y direction, and Z direction. For example, 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.

[0021] The support portion 102 supports the wafer 20, for example, by adsorbing it. The support portion 102 is movable along both the X and Y directions. The support portion 102 is rotatable about a rotation axis along the Z direction. The light source 103 emits laser light L0, for example, using a pulse oscillation method. The laser light L0 is transmissive to the wafer 20. The optical axis adjustment portion 104 adjusts the optical axis of the laser light L0 emitted from the light source 103. The optical axis adjustment portion 104 is, for example, constructed using a plurality of mirrors whose position and angle can be adjusted.

[0022] A spatial light modulator 105 is disposed within the laser processing head H. The spatial light modulator 105 modulates the laser light L0 emitted from the light source 103. The spatial light modulator 105 is a spatial light modulator (SLM) for reflective liquid crystal on silicon (LCOS). In the spatial light modulator 105, the laser light L0 can be modulated by appropriately setting the modulation pattern displayed on its display section (liquid crystal layer). In this embodiment, the laser light L0 traveling downwards along the Z-direction from the optical axis adjustment section 104 is incident into the laser processing head H, reflected by the reflector MM1, and incident into the spatial light modulator 105. The spatial light modulator 105 modulates the incident laser light L0 while reflecting it.

[0023] The light-collecting section 106 is mounted on the bottom wall of the laser processing head H. The light-collecting section 106 collects the laser light L0, modulated by the spatial light modulator 105, onto the wafer 20 supported by the support section 102. In this embodiment, the laser light L0 reflected by the spatial light modulator 105 is reflected by the beam splitter MM2 and enters the light-collecting section 106. The light-collecting section 106 collects the incoming laser light L0 onto the wafer 20. The light-collecting section 106 is constructed by mounting a light-collecting lens unit 161 on the bottom wall of the laser processing head H via a drive mechanism 162. The drive mechanism 162 moves the light-collecting lens unit 161 along the Z-direction, for example, by the driving force of a piezoelectric element.

[0024] Additionally, within the laser processing head H, an imaging optical system (not shown) is disposed between the spatial light modulator 105 and the light collecting section 106. This imaging optical system is a telecentric optical system on either side of the reflecting surface of the spatial light modulator 105 and the entrance pupil surface of the light collecting section 106, positioned in an imaging relationship. In this way, the image of the laser light L0 on the reflecting surface of the spatial light modulator 105 (the image of the laser light L0 modulated by the spatial light modulator 105) is imaged (imaged) onto the entrance pupil surface of the light collecting section 106. On the bottom wall of the laser processing head H, a pair of range sensors S1 and S2 are mounted on either side of the light collecting lens unit 161 in the X direction. Each ranging sensor S1, S2 emits ranging light (e.g., laser light) to the laser light incident surface of wafer 20, detects the ranging light reflected from the laser light incident surface, and thereby obtains displacement data of the laser light incident surface.

[0025] An optical axis monitor 107 is disposed within the laser processing head H. The optical axis monitor 107 detects a portion of the laser light L0 transmitted through the beam splitter MM2. The detection result of the optical axis monitor 107 displays, for example, the relationship between the optical axis of the laser light L0 incident on the light-collecting lens unit 161 and the optical axis of the light-collecting lens unit 161. A visible image camera 108A emits visible light V0 and acquires an image of the wafer 20 caused by the visible light V0 as a photograph. The visible image camera 108A is disposed within the laser processing head H. An infrared image camera 108B emits infrared light and acquires an image of the wafer 20 caused by the infrared light as an infrared photograph. The infrared image camera 108B is mounted on the sidewall of the laser processing head H.

[0026] The moving mechanism 109 includes a mechanism for moving at least one of the laser processing head H and the support portion 102 in the X, Y, and Z directions. The moving mechanism 109 drives at least one of the laser processing head H and the support portion 102 by means of a driving force from a known drive device such as a motor, such that the focusing point C of the laser light L0 can move in the X, Y, and Z directions. The moving mechanism 109 also includes a mechanism for rotating the support portion 102. The moving mechanism 109 drives the support portion 102 to rotate by means of a driving force from a known drive device such as a motor.

[0027] The management unit 150 comprises a control unit 151, a user interface 152, and a memory unit 153. The control unit 151 controls the operation of various parts of the laser processing apparatus 100. The control unit 151 is configured as a computer device including a processor, memory, storage, and communication devices. In the control unit 151, the processor executes software (programs) loaded into the memory, controlling the reading and writing of data in the memory and storage, as well as communication via the communication devices. The user interface 152 is used for displaying and inputting various data. The user interface 152 is a GUI (Graphical User Interface) that constitutes a graphics-based operating system.

[0028] User interface 152 includes at least one of the following: a touch panel, keyboard, mouse, microphone, tablet terminal device, monitor, etc. User interface 152 can accept various types of input, such as touch input, keyboard input, mouse operation, and voice input. User interface 152 can display various information on its display screen. User interface 152 is equivalent to an input receiving unit that accepts input and a display unit that can display a setting screen based on the accepted input. Memory unit 153 is, for example, a hard drive, that stores various types of data.

[0029] The laser processing apparatus 100 configured as described above, when laser light L0 is focused inside the wafer 20, is absorbed at a point (at least a portion of the focusing area) C corresponding to the laser light L0, forming a modified region 11 inside the wafer 20. The modified region 11 is a region whose density, refractive index, mechanical strength, and other physical properties differ from the surrounding unmodified region. The modified region 11 may include, for example, a melt-processed region, a cracked region, an insulation-damaged region, or a region with a change in refractive index. The modified region 11 comprises a plurality of modified points 11s and cracks extending from the plurality of modified points 11s.

[0030] As an example, the operation of the laser processing apparatus 100 when forming a modified region 11 inside the wafer 20 along the cutting line 15 used to cut the wafer 20 is explained.

[0031] First, the laser processing apparatus 100 rotates the support 102 such that the cutting line 15 of the wafer 20 is parallel to the X-direction. The laser processing apparatus 100 moves the support 102 along both the X and Y directions based on an image (e.g., an image of the functional element layer on the wafer 20) obtained by the infrared camera 108B, such that the focal point C of the laser light L0, when viewed from the Z-direction, is located on the cutting line 15. The laser processing apparatus 100 moves the laser processing head H (i.e., the light-collecting part 106) along the Z-direction (height set) based on an image (e.g., an image of the laser light incident surface of the wafer 20) obtained by the visual camera 108A, such that the focal point C of the laser light L0 is located on the laser light incident surface. The laser processing apparatus 100 uses this position as a reference and moves the laser processing head H along the Z direction in such a way that the focusing point C of the laser light L0 will be located at a predetermined depth from the incident surface of the laser light.

[0032] Next, the laser processing apparatus 100 moves the support 102 in the X direction by emitting laser light L0 from the light source 103 and moving the laser light L0's focusing point C relative to the cutting line 15. At this time, the laser processing apparatus 100 actuates the drive mechanism 162 of the focusing unit 106 in such a way that the focusing point C of the laser light L0 is located at a predetermined depth from the laser light's incident surface, based on the displacement data of the laser light incident surface obtained by the one of the pair of range sensors S1 and S2 located in front of the laser light L0's processing travel direction.

[0033] As described above, a row of modified regions 11 is formed along the cutting line 15 at a certain depth from the laser incident surface of the wafer 20. If laser light L0 is emitted from the light source 103 using a pulse oscillation method, a plurality of modified points 11s will be formed into a row along the X direction. A single modified point 11s is formed by irradiation with a single pulse of laser light L0. A row of modified regions 11 is a collection of a plurality of modified points 11s arranged in a row. Adjacent modified points 11s may be connected or separated depending on the pulse spacing of the laser light L0 (the value obtained by dividing the relative movement speed of the light-collecting point C with respect to the wafer 20 by the repetition frequency of the laser light L0).

[0034] In this embodiment, the process involves irradiating the dicing track with laser light along the dicing line 15 in such a way that the surface layer of the dicing track on the wafer 20 is removed, thereby forming a groove on the wafer 20 along the dicing line 15. As an apparatus for performing the grooving process, a laser processing apparatus 1 as shown in FIG2 can be used, for example.

[0035] As shown in Figure 2, the laser processing apparatus 1 includes a support unit 2, an irradiation unit 3, an imaging unit 4, and a control unit 5. The support unit 2 supports the wafer 20. The support unit 2 holds the wafer 20, for example, by adsorbing it, such that the surface of the wafer 20, including the dicing channels, faces the irradiation unit 3 and the imaging unit 4. For example, the support unit 2 can move along both the X and Y directions and can rotate about an axis parallel to the Z direction.

[0036] The irradiation unit 3 irradiates the laser light L onto the dicing groove of the wafer 20 supported by the support unit 2. The irradiation unit 3 includes a laser light source 31, a shaping optics system 32, a beam splitter 33, and a light collecting unit 34. The laser light source 31 emits the laser light L. The shaping optics system 32 adjusts the laser light L emitted from the laser light source 31. The shaping optics system 32 includes a spatial light modulator 132 that modulates the phase of the laser light L.

[0037] The spatial light modulator 132 is a display unit 132A into which the laser light L emitted from the laser light source 31 enters. The spatial light modulator 132 modulates the laser light L according to a modulation pattern that causes it to be displayed on the display unit 132A. The shaping optical system 32 may also include an imaging optical system constituting a telecentric optical system on both sides, which forms an imaging relationship between the modulation surface of the spatial light modulator and the entrance pupil surface of the light collecting part 34. The shaping optical system 32 may also further include an attenuator to adjust the output of the laser light L and a beam expander to increase the diameter of the laser light L.

[0038] The spectroscope 33 reflects the laser light L ejected from the plastic optics system 32 so that it is injected into the light collector 34 . The light collector 34 is a cutting channel that collects the reflected laser light L (laser light L modulated by the spatial light modulator 132 ) by means of the spectroscope 33 to the wafer 20 supported by the support part 2 .

[0039] The irradiation portion 3 is further comprised of a light source 35 , a semi-reflective mirror 36 and a camera element 37 . Light source 35 emits visible light V1. The semi-reflective mirror 36 reflects the visible light V1 ejected from the light source 35 into the light collector 34 . The spectroscope 33 transmits visible light V1 between the semi-reflective mirror 36 and the light collector 34 . The light collector 34 is a cutting channel that collects the reflected visible light V1 by means of a semi-reflective mirror 36 to the wafer 20 supported by the support part 2 . The camera element 37 is the detection of visible light V1 that is reflected through the light collector 34 , the spectroscope 33 , and the semireflector 36 through the cutting channel of the wafer 20 . In the laser processing device 1 , the control unit 5 moves the light collector 34 along the Z direction according to the detection results of the camera element 37 , for example, in such a way that the light collector point of the laser light L will be located in the cutting channel of the wafer 20 .

[0040] The camera part 4 obtains the image data of the cutting channel of the wafer 20 supported by the support part 2 . The camera unit 4 is an internal observation camera observing the interior of the wafer 20 formed by the laser processing device 100 to form the reforming region 11 . The camera section 4 is for wafer 20 emitted infrared light and obtains an image of wafer 20 caused by infrared light as portrait data. The camera section 4 is available with InGaAs cameras.

[0041] The control unit 5 controls the movements of each part of the laser processing device 1 . The control portion 5 is comprising the processing portion 51 , the memory portion 52 , and the input acceptance portion 53 . The processing unit 51 is a computer device comprising a processor, memory, memory, and communication devices. In the processing unit 51, the processor implements software (programs) that are written to memory, etc., to control the reading and writing of data from memory and storage and the communication of communication devices. The memory part 52 such as a hard drive, etc., memorizes various data. The input acceptance section 53 is the interface section that accepts the input of various data from the operator. Input Acceptance Section 53 is at least one of keyboard, mouse, GUI (Graphical User Interface), as an example.

[0042] The laser processing apparatus 1 performs grooving processing. During grooving processing, the control unit 5 controls the irradiation unit 3 so that the laser light L irradiates each dicing track of the wafer 20 supported by the support unit 2 along the cutting line 15. The control unit 5 controls the support unit 2 so that the laser light L moves relative to each other along the cutting line 15 (details will be described later).

[0043] As shown in Figures 3 and 4, the wafer 20 has a semiconductor substrate (substrate) 21 and a functional element layer 22. The thickness of the wafer 20 is, for example, 775 μm. The semiconductor substrate 21 has a surface 21a and a back surface 21b. The semiconductor substrate 21 is, for example, a silicon substrate. A notch 21c is provided on the semiconductor substrate 21 to indicate the crystal orientation. An orientation flat may also be provided on the semiconductor substrate 21 instead of the notch 21c. The functional element layer 22 is formed on the surface 21a of the semiconductor substrate 21. The functional element layer 22 contains a plurality of functional elements 22a. The plurality of functional elements 22a are arranged in two dimensions along the 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 also be three-dimensionally constructed by stacking a plurality of layers.

[0044] A plurality of dices 23 are formed on wafer 20. The plurality of dices 23 are areas exposed to the outside between adjacent functional elements 22a. That is, the plurality of functional elements 22a are arranged to be adjacent to each other with respect to the dices 23. For example, the plurality of dices 23 extend in a lattice-like manner through the adjacent functional elements 22a for the plurality of functional elements 22a arranged in a matrix. As shown in FIG. 5, an insulating film 24 and a plurality of metal structures 25, 26 are formed on the surface of the dices 23. The insulating film 24 is, for example, a Low-k film. Each metal structure 25, 26 is, for example, a metal pad. The metal structures 25 and 26 are, for example, different from each other in terms of thickness, area, and material.

[0045] As shown in Figures 3 and 4, a plurality of dicing lines 15 are provided on the wafer 20. The wafer 20 is pre-defined to be cut along each of the plurality of dicing lines 15 according to each functional element 22a (i.e., to wafer-scale each functional element 22a). When viewed in the thickness direction of the wafer 20, each dicing line 15 passes through each dicing track 23. For example, when viewed in the thickness direction of the wafer 20, each dicing line 15 extends through the center of each dicing track 23. Each dicing line 15 is a hypothetical dicing line set on the wafer 20 by the laser processing apparatus 1,100. Each dicing line 15 can also be an actual dicing line drawn on the wafer 20.

[0046] In this embodiment, the modulation pattern of the display unit 132A displayed on the spatial light modulator 132 includes a splitting pattern in which the laser light L is split into a plurality (in this case, two) of first-branch laser light for forming a first groove and a plurality (in this case, two) of second-branch laser light for forming a second groove. As shown in FIG6, in this embodiment, after the focusing points SA1 and SA2 of the two first-branch laser lights are arranged from one side of the cut-off line 15 to the other side along the X direction of the cut-off line 15, the focusing points SB1 and SB2 of the two second-branch laser lights are arranged. In the Y direction, corresponding to the width direction of the formed groove, the positions of the focusing points SA1 and SA2 of the first-branch laser lights are equal to each other. In the Y direction, the positions of the focusing points SB1 and SB2 of the second-branch laser lights are equal to each other.

[0047] The positions of the focusing points SA1 and SA2 of the first branch laser beam are also referred to as the first processing points, and the positions of the focusing points SB1 and SB2 of the second branch laser beam are also referred to as the second processing points. In the X direction, the distance between the positions of the adjacent focusing points SA2 of the first branch laser beam and SB1 of the second branch laser beam is defined as the interval d23. In other words, the interval d23 is the distance in the X direction between the adjacent first and second processing points. In the Y direction, corresponding to the width direction of the formed groove, the distance between the positions of the focusing points SA1 and SA2 of the first branch laser beam and SB1 and SB2 of the second branch laser beam is defined as the interval Y1.

[0048] The interval d23 is larger than the interval Y1. The interval d23 is larger than the pulse spacing of the laser light L. The interval d23 is, for example, 20 μm or more. In the X direction along the cut line 15, the interval d12 between the positions of the focusing points SA1, SA2 of the plurality of first branch laser lights is larger than the pulse spacing of the laser light L. The interval d12 is smaller than the interval d23. In the X direction, the interval d34 between the positions of the focusing points SB1, SB2 of the plurality of second branch laser lights is larger than the pulse spacing of the laser light L. The interval d34 is smaller than the interval d23. The branching pattern is such that the focusing points SA1, SA2, SB1, SB2 are arranged in a one-dimensional array (including approximate one-dimensional array, substantially one-dimensional array, and generally one-dimensional array, hereinafter the same) along the cut line 15, thus branching the laser light L.

[0049] As shown in Figure 8(b), the first groove M1 formed by the first branched laser beam LA and the second groove M2 formed by the second branched laser beam LB constitute a composite groove MH. In a cross-sectional view orthogonal to the cut line 15, the composite groove MH is a W-shaped groove (W-groove). In a cross-sectional view orthogonal to the cut line 15, the composite groove MH is a groove with two valley portions and one mountain portion on its bottom side. In a cross-sectional view orthogonal to the cut line 15, both the first groove M1 and the second groove M2 are V-shaped grooves (V-grooves). The second groove M2 overlaps with the first groove M1 in the Y direction. In other words, the first groove M1 and the second groove M2 extend in the X direction while overlapping in the Y direction. The first groove M1 and the second groove M2 are designed so that their peripheral parts contact each other. The first groove M1 and the second groove M2 are grooves of the same depth and width.

[0050] The composite trench MH is located on the functional element layer 22 side of wafer 20, with the bottoms of the first trench M1 and the second trench M2 reaching the semiconductor substrate 21. The bottoms of the first trench M1 and the second trench M2 reach the functional element layer 22 side of the semiconductor substrate 21. The overlapping ends of the first trench M1 and the second trench M2 (the bottom portion of the composite trench MH) reach the semiconductor substrate 21 side of the functional element layer 22. The trench width at the widest opening side of the composite trench MH is, for example, set to 12 μm. The trench width can be appropriately input via the input receiving unit 53 (see Figure 2). The trench width is narrower than the width of the dicing track 23.

[0051] Furthermore, intervals d12 and d34 can be equal or different. For example, when the pulse pitch is 0.5 μm, interval d12 is 10 μm, interval d23 is 20 μm, interval d34 is 10 μm, and interval Y1 can also be 5 μm. Interval Y1 is a cross-sectional view of the composite trench MH, which can form a W-shaped interval or be smaller than the slot width.

[0052] Next, the laser processing method using the laser processing apparatus 100 and the laser processing apparatus 1 will be described with reference to Figures 7 to 11.

[0053] First, as shown in Figure 7(a), a wafer 20 is prepared. A grinding tape 28 is attached to the surface of the wafer 20 on the side of the functional element layer 22. As shown in Figure 7(b), the back side 21b of the semiconductor substrate 21 of the wafer 20 is ground in a grinding apparatus until the wafer 20 is thinned to the desired thickness (grinding process). As shown in Figure 7(c), the grinding tape 28 is removed, and a protective film 29 is applied to the surface of the wafer 20 on the side of the functional element layer 22 to protect the functional element layer 22 (functional element 22a).

[0054] Next, as shown in FIG8(a), in the laser processing apparatus 1, after the wafer 20 is held in place by the support part 2, a grooving process is performed on the wafer 20. During the grooving process, the control part 5 controls the irradiation part 3 so that the laser light L irradiates the dicing track 23 of the wafer 20 along the cutting line 15, and the control part 5 controls the support part 2 so that the laser light L moves relative to the cutting line 15. Thereby, as shown in FIG8(b), the surface layer of the dicing track 23 of the wafer 20 is removed, forming a composite trench MH including the first trench M1 and the second trench M2.

[0055] Specifically, during the grooving process, a laser beam L is emitted and directed to the display section 132A of the spatial light modulator 132 (see Figure 2). Based on the modulation pattern displayed on the display section 132A, the laser beam L is split into a first-branch laser beam LA and a second-branch laser beam LB. The first-branch laser beam LA and the second-branch laser beam LB are then focused onto the wafer 20. During the grooving process, for example, in the Z direction, the light-collecting section 34 (see Figure 2) is moved or modulated by the spatial light modulator 132 in such a way that the first-branch laser beam LA and the second-branch laser beam LB are focused onto the surface of the functional element layer 22. The first groove M1 is formed by focusing the light of the first-branch laser beam LA, and the second groove M2 is formed by focusing the light of the second-branch laser beam LB.

[0056] As described above, the modulation pattern includes a branching pattern. The branching pattern can be appropriately generated in the control unit 5 based on the slot width input via the input receiving unit 53 (see Figure 2). For example, the branching pattern can be automatically generated by the control unit 5 using various well-known methods, so that the focusing points SA1, SA2, SB1, SB2 of the first branching laser light LA ​​and the second branching laser light LB are positioned in a one-dimensional array as shown in Figure 6, thereby realizing the composite groove MH of the slot width.

[0057] The processing conditions for forming the composite groove MH are not limited and can be set according to various well-known perspectives. The processing conditions for forming the composite groove MH can be appropriately input via the input receiving unit 53. The processing conditions for forming the composite groove MH can also be set as follows, for example. An example of the following conditions is that a burst pulse is not used, but a burst pulse can also be used, for example, to suppress film peeling (the same applies below). Wavelength of laser light L: 515nm Laser pulse width L: 600 fs The pulse spacing of the laser beam L is 0.5 μm. Processing energy (total energy of all collecting points): 4.0 μJ Number of scans: 1 pass The bottom of the composite trench MH is located 3 μm away from the surface 21a of the semiconductor substrate 21.

[0058] Next, as shown in FIG8(c), the wafer 20 is removed from the support 2, and the protective film 29 is removed, for example, using a solution. As shown in FIG9(a), a transparent dicing tape (tape) DC with a ring frame RF is attached to the back side 21b of the semiconductor substrate 21 of the wafer 20. The transparent dicing tape DC is also known as an expanded film.

[0059] Next, as shown in FIG9(b), in the laser processing apparatus 100, laser light L0 is irradiated onto the wafer 20 along the cutting line 15, thereby forming a modified region 11 inside the wafer 20 along the cutting line 15. Here, with the transparent dicing tape DC attached to the back surface 21b of the semiconductor substrate 21, the wafer 20 is held in place by the support portion 102, and the laser light L0 is aligned with the interior of the semiconductor substrate 21 by the transparent dicing tape DC, with the back surface 21b as the laser light incident surface, and the laser light L0 is irradiated onto the wafer 20.

[0060] Laser light L0 is transparent to both the transparent cutting tape DC and the semiconductor substrate 21. If laser light L0 is focused inside the semiconductor substrate 21, the laser light L0 will be absorbed at the point corresponding to the focusing point of laser light L0, forming a modified region 11 inside the semiconductor substrate 21, and cracks 9 will extend from the modified region 11. The processing conditions for forming the modified region 11 are not particularly limited and can be set according to various well-known insights. The processing conditions for forming the modified region 11 can be appropriately input via the user interface 152 (see Figure 1). The processing conditions for forming the modified region 11 can also be set, for example, as follows. The wavelength of laser light L0 is 1099 nm. Laser pulse width L0: 700 nmsec The pulse spacing of laser L0 is 6.5 μm. Processing energy: 22μJ Number of scans: 8 passes

[0061] The crack 9 extending from the modified region 11 to the functional element layer 22 is induced to form two grooves, the first groove M1 and the second groove M2, towards the composite groove MH, with its end reaching the inner surface of either the first groove M1 or the second groove M2. For example, in the example shown in FIG10, where there is no substantial deviation of the modified region 11 from the cut line 15 in the Y direction, the induced crack 9 reaches the inner surface of the second groove M2 side of the first groove M1. Or, as in the example shown in FIG11(a), when there is a deviation of the modified region 11 from the cut line 15 in the Y direction, the induced crack 9 can also reach the bottom of the first groove M1. Or, as in the example shown in FIG11(b), when there is a deviation of the modified region 11 from the cut line 15 in the Y direction, the induced crack 9 can also reach the inner surface of the first groove M1 on the side opposite to the second groove side. Alternatively, as in the example shown in Figure 11(c), when the modified region 11 deviates from the cut line 15 in the Y direction, the induced crack 9 can also reach the inner surface of the second groove M2 side of the first groove M1.

[0062] Next, as shown in FIG12, in the expansion device (not shown), by expanding the attached transparent dicing tape DC, cracks are extended along the cutting lines 15 from the modified region 11 formed inside the semiconductor substrate 21 in the thickness direction of the wafer 20, and the wafer 20 is cut by the cutting lines 15. In this way, the wafer 20 is wafered according to each functional element 22a, and a plurality of wafers T1 are obtained.

[0063] In the above, for example, instead of the transparent cutting tape DC, a protective tape can be attached to the functional element layer 22 side. After the modified region 11 is formed by irradiating the back side 21b of the semiconductor substrate 21 with laser light L0, the transparent cutting tape DC is attached to the back side 21b side of the semiconductor substrate 21. After peeling off the protective tape on the functional element layer 22 side, the transparent cutting tape DC is expanded and divided. Alternatively, for example, a reinforcing material can be used. Laser processing (grooving and formation of the modified region 11) can be performed with a protective film attached. Then, the protective film is removed, the transparent cutting tape DC is attached, and the transparent cutting tape DC is expanded and divided.

[0064] However, as shown in Figure 13, when a single V-groove M0 is formed on wafer 20 along the cleaving line 15, cracks 9 originating from the modified region 11 formed in the inner direction of the V-groove M0 in the wafer 20 can easily extend and deviate from the V-groove M0. Therefore, these cracks 9 will deviate significantly from the cleaving line 15. In this case, the cleaving quality of wafer 20 will deteriorate. The likelihood of cleaving quality deterioration, tearing, and residual cracks will increase.

[0065] In this embodiment, a composite trench MH is formed on wafer 20, comprising a first trench M1 and a second trench M2 whose ends overlap. This prevents the trench width from widening while simultaneously inducing the extension of crack 9 towards the two first trenches M1 and M2. Compared to a single V-groove M0, this improves the induction effect on crack 9 and suppresses its deviation. In other words, the trench width can be narrowed while suppressing the deviation of crack 9 extending from the modified region 11. The deviation of crack 9 can be contained within the trench width. Improved dicing quality is possible, and all wafer dicing can be reliably achieved. The width of the dicing track 23 can be narrowed.

[0066] This embodiment further includes: after forming the modified region 11, when the end of the crack 9 reaches the inner surface of the first groove M1 or the inner surface of the second groove M2, the transparent dicing tape DC attached to the wafer 20 is expanded, thereby cutting the wafer 20 along the dicing line 15. In this case, the wafer 20 can be cut with high precision along the dicing line 15.

[0067] In this embodiment, wafer 20 has a semiconductor substrate 21 and a functional element layer 22. A composite trench MH is formed on the functional element layer 22 side of wafer 20, with both the bottom of the first trench M1 and the bottom of the second trench M2 reaching the semiconductor substrate 21. This further enhances the attraction effect of the first trench M1 and the second trench M2 on the cracks 9 caused by them.

[0068] This embodiment includes a process of forming a protective film 29 on the functional element layer 22 before forming the composite trench MH. In this case, the functional element layer 22 can be effectively protected by the protective film 29. In this embodiment, in a cross-sectional view orthogonal to the cut line 15, the composite trench MH presents a W-shape. In this case, the aforementioned effect of narrowing the trench width and suppressing the deviation of the crack 9 becomes more significant. This embodiment also includes a process of thinning the wafer 20 by grinding before forming the composite trench MH. In this case, the wafer 20 can be thinned by grinding before the formation of the composite trench MH.

[0069] In this embodiment of the laser processing apparatus 1 and laser processing method, the distance d23 between adjacent first and second processing points (the positions of the focusing points SA2 of the first branch laser beam and SB1 of the second branch laser beam) in the X direction is larger than the distance Y1 between the first and second processing positions in the Y direction. This allows the first and second processing points to be separated until their mutual influence is minimal. Such influence includes, for example, interference with previous processing points and processing under conditions of residual heat effects. Furthermore, the first and second processing points can be separated until this influence substantially disappears. As a result, the first trench M1 and the second trench M2 can be reliably formed as independent trenches on the wafer 20. The bottoms of the first trench M1 and the second trench M2 can be clearly formed. Therefore, in the laser processing apparatus 1 and laser processing method that splits the laser light L into multiple split laser lights and irradiates the wafer 20, the first trench M1 and the second trench M2 can be well formed on the wafer 20 along the cutting line 15.

[0070] In this embodiment, the second trench M2 overlaps with the first trench M1 in the width direction. A composite trench MH comprising the first trench M1 and the second trench M2 can be formed on the wafer 20. Such a composite trench MH can effectively induce cracks 9 extending, for example, from the modified region 11 formed inside the wafer 20.

[0071] In this embodiment, the spacing d23 in the X direction is larger than the pulse spacing of the laser light L. This can suppress the significant mutual interference between the first processing position and the second processing position due to excessively narrow spacing, and can ensure the proper formation of the first trench M1 and the second trench M2 on the wafer 20.

[0072] In this embodiment, the interval d12 between the multiple first processing positions in the X direction is larger than the pulse spacing of the laser light L. In this case, the significant mutual interference between the multiple first processing positions due to excessively narrow interval d12 can be suppressed, and the first groove M1 can be formed well.

[0073] In this embodiment, in the X direction, the interval d12 between the plurality of first processing positions is smaller than the interval d23. In this case, the interval between the plurality of first processing positions can be set within the range of mutual influence, so that the HAZ (Heat-Affected Zone) that occurs around the formed first groove M1 can be suppressed.

[0074] In this embodiment, the interval d34 between the multiple second processing positions in the X direction is larger than the pulse spacing of the laser light L. In this case, the significant interference between the multiple second processing positions due to excessively narrow intervals can be suppressed, and the second groove M2 can be formed well.

[0075] In this embodiment, the interval d34 between the plurality of second processing positions in the X direction is smaller than the interval d23. In this case, the interval between the plurality of second processing positions can be set within the range of mutual influence, so that HAZ such as thermal effects occurring around the formed second groove M2 can be suppressed.

[0076] In this embodiment, the branching pattern splits the laser beam L into two first-branch laser beams LA and two second-branch laser beams LB. This reduces the energy at each focusing point SA1, SA2, SB1, SB2, and suppresses HAZ.

[0077] In this embodiment, the branching pattern involves splitting the laser beam L into individual focusing points SA1, SA2, SB1, and SB2 arranged in a one-dimensional array along the cutting line 15. This allows for the formation of a narrow composite trench MH on the wafer 20, and also improves the flexural strength of the wafer 20.

[0078] Even if the position of the unmodified region 11 in the Y direction deviates from the position of the cut line 15, when a single V-groove M0 is formed, the serpentine cracks 9 extending from the modified region 11 may result in poor condition. In this embodiment, since a composite groove MH is formed as a W-groove, this poor condition can be suppressed.

[0079] Furthermore, in this embodiment, the branching pattern can also split the laser light L into three first-branch laser lights LA for forming the first groove M1 and three second-branch laser lights LB for forming the second groove M2. In this case, for example, as shown in FIG14, from one side of the cut line 15 to the other side, along the X direction of the cut line 15, the focusing points SA1, SA2, SA3 of the three first-branch laser lights are arranged, and the focusing points SB1, SB2, SB3 of the three second-branch laser lights are arranged. In the Y direction, corresponding to the width direction of the formed groove, the positions of the focusing points SA1, SA2, SA3 of the first-branch laser lights are equal to each other. In the Y direction, the positions of the focusing points SB1, SB2, SB3 of the second-branch laser lights are equal to each other. With such a branching pattern, the energy at each focusing point SA1, SA2, SA3, SB1, SB2, SB3 can be further reduced, and HAZ can be further suppressed.

[0080] In this embodiment, the branching pattern of the display unit 132A displayed on the spatial light modulator 132 can be such that the laser light L can be branched into one or more (in this case, two) first branched laser light LA ​​for forming the first groove M1, one or more (in this case, two) second branched laser light LB for forming the second groove M2, and one or more (in this case, two) third branched laser light for forming the third groove M3. In this case, for example, as shown in FIG15(a), from one side of the cut-off line 15 to the other side, along the X direction of the cut-off line 15, the light-collecting points SA1, SA2 of the two first branched laser lights are arranged, the light-collecting points SB1, SB2 of the two second branched laser lights are arranged, and then the light-collecting points SC1, SC2 of the two third branched laser lights are arranged. In the Y direction, corresponding to the width of the formed groove, the positions of the focusing points SC1 and SC2 of the third branch laser beam are equal.

[0081] In the X direction, the distance between the position of the focusing point SB2 of the adjacent second-branch laser beam and the position of the focusing point SC1 of the third-branch laser beam is defined as interval d45. Interval d45 is equal to interval d23. In the Y direction, the distance between the positions of the focusing points SB1, SB2 of the second-branch laser beam and the positions of the focusing points SC1, SC2 of the third-branch laser beam is defined as interval Y2. Interval Y2 is equal to interval Y1. Interval d45 is larger than interval Y1. Interval d45 is larger than the pulse spacing of laser beam L. In the X direction along the cut-off line 15, the interval d56 between the positions of the focusing points SC1, SC2 of the plurality of third-branch laser beams is larger than the pulse spacing of laser beam L. Interval d56 is smaller than interval d23. The branching pattern is such that the focusing points SA1, SA2, SB1, SB2, SC1, SC2 are arranged in a one-dimensional array along the cut-off line 15 to branch the laser beam L. As shown in Figure 15(b), this situation can form a wide composite trench MH1.

[0082] The first groove M1 formed by the first branched laser beam LA, the second groove M2 formed by the second branched laser beam LB, and the third groove M3 formed by the third branched laser beam constitute a composite groove MH1. In a cross-sectional view orthogonal to the cut line 15, the composite groove MH1 is a groove with three valley portions and two mountain portions on its bottom side. In a cross-sectional view orthogonal to the cut line 15, each of the first groove M1, the second groove M2, and the third groove M3 is a V-groove. The second groove M2 overlaps with the first groove M1 in the Y direction. In other words, the first groove M1 and the second groove M2 extend in the X direction while overlapping in the Y direction. The first groove M1 and the second groove M2 are designed to have their peripheral parts in contact. The third groove M3 overlaps with the second groove M2 in the Y direction. In other words, the ends of the second groove M2 and the third groove M3 in the Y direction extend towards the X direction. The second groove M2 and the third groove M3 are designed so that their peripheral parts will contact each other. The first groove M1, the second groove M2, and the third groove M3 are grooves of the same depth and width.

[0083] The composite trench MH1 is located on the functional element layer 22 side of wafer 20, and the bottoms of the first trench M1, the second trench M2, and the third trench M3 all extend to the semiconductor substrate 21. The bottoms of the first trench M1 and the second trench M2 extend to the functional element layer 22 side of the semiconductor substrate 21. The repeated ends of the first trench M1, the second trench M2, and the third trench M3 (the two bottom portions of the composite trench MH1) extend to the semiconductor substrate 21 side of the functional element layer 22.

[0084] Incidentally, in this embodiment, as shown in FIG16(a), a composite trench MH2 may also be provided on the functional element layer 22 side of the wafer 20. The composite trench MH2 is a W-shaped trench formed by a first trench M1 and a second trench M2. The ends of the second trench M2 overlap with the first trench M1 in the Y direction. The composite trench MH2 is configured such that the bottom of the first trench M1 and the bottom of the second trench M2 both reach the semiconductor substrate 21. The overlapping ends of the first trench M1 and the second trench M2 (the bottom portion of the composite trench MH2) reach the surface side of the functional element layer 22. The bottoms of the first trench M1 and the second trench M2 of the composite trench MH2 are separated in the Y direction from those of the composite trench MH (see FIG8(b)). Such a composite trench MH2 also has the same effect as the composite trench MH.

[0085] In this embodiment, as shown in FIG16(b), a composite trench MH3 may also be provided on the functional element layer 22 side of the wafer 20. The composite trench MH3 is a W-shaped trench formed by a first trench M1 and a second trench M2. The second trench M2 overlaps with the first trench M1 in the Y direction. The first trench M1 is a trench with a deeper depth than the second trench M2. The composite trench MH3 is configured such that the bottom of the first trench M1 reaches the semiconductor substrate 21, while the bottom of the second trench M2 does not reach the semiconductor substrate 21. That is, either the bottom of the first trench M1 or the bottom of the second trench M2 reaches the semiconductor substrate 21. The overlapping ends in the first trench M1 and the second trench M2 (the bottom portion of the composite trench MH3) extend to the semiconductor substrate 21 side of the functional element layer 22. The same effect as the composite trench MH can be achieved in such a composite trench MH3. It can further enhance the attraction effect of cracks 9 caused by groove M1 and groove M2.

[0086] In this embodiment, as shown in FIG16(c), a composite trench MH4 may also be provided on the functional element layer 22 side of the wafer 20. The composite trench MH4 is a W-shaped trench formed by a first trench M1 and a second trench M2. The second trench M2 overlaps with the first trench M1 in the Y direction. The first trench M1 is a trench with a deeper depth than the second trench M2. The composite trench MH4 is configured such that the bottom of the first trench M1 reaches the semiconductor substrate 21, while the bottom of the second trench M2 does not reach the semiconductor substrate 21. That is, either the bottom of the first trench M1 or the bottom of the second trench M2 reaches the semiconductor substrate 21. The overlapping ends of the first trench M1 and the second trench M2 (the bottom portion of the composite trench MH4) extend to the surface side of the functional element layer 22. The bottoms of the first trench M1 and the second trench M2 of the composite trench MH4 are separated in the Y direction from those of the composite trench MH3 (see FIG16(b)). The same effect as the composite groove MH4 is achieved in this composite groove. It can further enhance the attraction effect of cracks 9 caused by the first groove M1 and the second groove M2.

[0087] In this embodiment, as shown in FIG17(a), a composite trench MH5 may also be provided on the functional element layer 22 side of the wafer 20. The composite trench MH5 is a W-shaped trench formed by a first trench M1 and a second trench M2. The second trench M2 overlaps with the first trench M1 in the Y direction. The first trench M1 and the second trench M2 are trenches of the same depth and width. The composite trench MH2 is designed such that neither the bottom of the first trench M1 nor the bottom of the second trench M2 reaches the semiconductor substrate 21. The same effect as the composite trench MH can be achieved in such a composite trench MH5. The depth of the first trench M1 and the second trench M2 can be reduced.

[0088] In this embodiment, as shown in FIG17(b), a composite trench MH6 may also be provided on the functional element layer 22 side of the wafer 20. The composite trench MH6 is a W-shaped trench formed by a first trench M1 and a second trench M2. The second trench M2 overlaps with the first trench M1 in the Y direction. The first trench M1 and the second trench M2 are trenches of the same depth and width. The composite trench MH6 is designed such that neither the bottom of the first trench M1 nor the bottom of the second trench M2 reaches the semiconductor substrate 21. The overlapping ends of the first trench M1 and the second trench M2 (the bottom portion of the composite trench MH6) extend to the surface side of the functional element layer 22. The bottoms of the first trench M1 and the second trench M2 of the composite trench MH6 are separated in the Y direction from those of the composite trench MH5 (see FIG17(a)). The same effect as the composite trench MH6 can be achieved in such a composite trench MH6. It can further enhance the attraction effect of cracks 9 caused by groove M1 and groove M2.

[0089] Figure 18 is a graph showing the test results of evaluating the deviation of the crack 9 during the formation of the composite trench MH. In the figure, the excavation amount is the amount of material entering the semiconductor substrate 21 from the surface 21a of the semiconductor substrate 21 at the bottom position of the composite trench MH. The shift amount is the amount of deviation in the width direction of the composite trench MH corresponding to the deviation of the formed modified region 11 from the center of the composite trench MH. "0" means that the end of the crack 9 is induced to reach the inner surface of the first trench M1 or the inner surface of the second trench M2. "Deviation" means that the crack 9 deviates from the composite trench MH, and the end of the crack 9 does not reach the inner surface of the first trench M1 or the inner surface of the second trench M2. In the test shown in the figure, the trench width is 12 μm. As shown in Figure 18, it can be seen that according to the composite trench MH, even if the formed modified region 11 deviates from the composite trench MH in the width direction, as long as it is within a certain range, the effect of inducing the crack 9 can be achieved. Furthermore, it can be seen that the greater the excavation volume, the more effectively the attraction effect of crack 9 can be exerted in terms of movement volume.

[0090] In this embodiment, the grooving process displays a branching pattern on the display section 132A of the spatial light modulator 132. The first groove M1 and the second groove M2 are simultaneously formed by splitting the laser light L into a first branched laser light LA ​​and a second branched laser light LB, but this is not a limitation. The grooving process can simply include: irradiating the wafer 20 with laser light L to form the first groove M1 on the wafer 20 along the dicing line 15, and irradiating the wafer 20 with laser light L to form the second groove M2 on the wafer 20 along the dicing line 15.

[0091] For example, as shown in FIG19(a), the laser light L is focused onto the functional element layer 22 via the light-collecting part 34, thereby removing the surface layer on the functional element layer 22 side of the wafer 20 to form the first trench M1. Then, as shown in FIG19(b), at least one of the light-collecting part 34 and the support part 2 (refer to FIG2) can be moved by a predetermined amount in the Y direction (the width direction of the first trench M1), and the laser light L is focused onto the functional element layer 22 via the light-collecting part 34, thereby removing the surface layer on the functional element layer 22 side of the wafer 20 to form the second trench M2.

[0092] Furthermore, as shown in Figure 20(a), the laser light L is focused onto the functional element layer 22 via the light-collecting section 34, thereby removing the surface layer on the functional element layer 22 side of the wafer 20 to form the first trench M1. Then, a shift pattern in which the light-collecting point of the laser light L is offset by a predetermined amount in the Y direction (the width direction of the first trench M1) can also be displayed on the display section 132A of the spatial light modulator 132, as shown in Figure 20(b), where the laser light L is focused onto the functional element layer 22 via the light-collecting section 34, removing the surface layer on the functional element layer 22 side of the wafer 20 to form the second trench M2.

[0093] In this embodiment, the process of forming the modified region 11 may also include: when the deviation of the formation position of the modified region 11 from the center position of the composite trench MH (hereinafter also referred to as "width deviation") is greater than half the width of the trench, the process of correcting the formation position of the modified region 11 to be consistent with the center position. For example, the process shown in FIG21 may also be included as an example.

[0094] In the process of forming the modified region 11, firstly, in the Y direction corresponding to the width direction of the composite groove MH, the formation position of the modified region 11 (the predetermined formation position of the modified region 11) is aligned with the center position of the composite groove MH at the reference processing position (step S11). The center position of the composite groove MH can be determined, for example, by an image captured by the infrared camera 108B (see Figure 1). Next, the modified region 11 is formed along the cutting line 15 as described above (step S12).

[0095] When the formation of the modified region 11 along the entire cutting line 15 extending in the X direction is completed (step S13, YES), the process ends, and the laser processing is considered complete, moving to the next process. On the other hand, when the formation of the modified region 11 along the entire cutting line 15 extending in the X direction is not completed (step S13, NO), the formation position of the modified region 11 is moved only a predetermined distance in the Y direction (corresponding to the distance between two adjacent cutting lines 15), and at least one of the laser processing head H and the support portion 102 (see Figure 1) is moved in the Y direction (step S14).

[0096] Determine whether the width deviation of the modified region 11 is greater than half the slot width (1 / 2 value) (step S15). The width deviation of the modified region 11 can be determined, for example, from an image captured by the infrared camera 108B (see Figure 1). If YES in step S15, the formation position of the modified region 11 in the Y direction is corrected (step S16). In step S16, at least one of the laser processing head H and the support 102 (see Figure 1) is adjusted in the Y direction so that the formation position of the modified region 11 coincides with the center position of the composite groove MH. If NO in step S15 or after step S16, return to the processing of step S12. According to the laser processing method of the above general variation, the formation position of the modified region 11 can be corrected using the slot width.

[0097] [Variation Example] One aspect of the present invention is not limited to the embodiments described above.

[0098] In the above embodiment, the laser processing apparatus 1 for grooving and the laser processing apparatus 100 for forming the modified region 11 inside the wafer 20 are separate devices, but they are not limited to this. For example, the grooving apparatus and the modified region 11 forming apparatus can be integrated by connecting them with a transfer arm. Alternatively, as shown in FIG22, the laser processing apparatus 200 can have a common platform 202, and carry an optical system 210A corresponding to the grooving apparatus and an optical system 210B corresponding to the modified region 11 forming apparatus, as an example. In addition, such a laser processing apparatus 200 includes a moving mechanism 205 for moving the platform (support) 202 and a moving mechanism 206 for moving the optical systems 210A and 210B.

[0099] The laser processing method using the laser processing apparatus 100 and the laser processing apparatus 1 is not limited to the method described above; alternative methods may also be used. Specifically, first, as shown in FIG23(a), a wafer 20 is prepared. A protective film 29 is coated on the surface of the functional element layer 22 side of the wafer 20. Next, as shown in FIG23(b), in the laser processing apparatus 1, after the wafer 20 is held in place by the support portion 2, a grooving process is performed on the wafer 20. During the grooving process, the control portion 5 controls the irradiation portion 3 so that the laser light L is irradiated along the cutting line 15 onto the dicing groove 23 of the wafer 20, and the control portion 5 controls the support portion 2 so that the laser light L moves relative to the cutting line 15. In this way, the surface layer of the dicing groove 23 of the wafer 20 is removed, forming a composite groove MH.

[0100] Next, as shown in FIG23(c), the wafer 20 is removed from the support 2, and the protective film 29 is removed, for example, using a chemical solution. As shown in FIG24(a), a grinding tape 28 is attached to the surface of the wafer 20 on the side of the functional element layer 22. In the laser processing apparatus 100, laser light L0 is irradiated onto the wafer 20 along the cutting line 15, thereby forming a modified region 11 inside the wafer 20 along the cutting line 15. Here, after the wafer 20 is held in place by the support 102, the spot of the laser light L0 is aligned with the interior of the semiconductor substrate 21, and the position of the spot in the Z direction is changed to repeatedly scan the wafer 20 with laser light L0 from the back side 21b. In this way, a plurality of modified regions 11 are formed in the Z direction inside the semiconductor substrate 21, and cracks 9 extend from the modified regions 11.

[0101] Next, as shown in FIG24(b), in a grinding apparatus, the back side 21b of the semiconductor substrate 21 of the wafer 20 is ground until the wafer 20 is thinned to the desired thickness after the modified region 11 is removed. As shown in FIG24(c), a transparent dicing tape DC with a ring frame RF is attached to the back side 21b of the semiconductor substrate 21 of the wafer 20. Then, as shown in FIG25, in an expansion apparatus (not shown), the attached transparent dicing tape DC is expanded to extend the cracks 9 along each cutting line 15 in the thickness direction of the wafer 20, and the wafer 20 is cut along the cutting line 15. In this way, the wafer 20 is wafered according to each functional element 22a, and a plurality of wafers T1 are obtained. In this modified laser processing method, the wafer 20 can be thinned by grinding after the formation of the composite trench MH.

[0102] In the above embodiments and modifications, the imaging unit 4 may also be a camera capable of acquiring image data of the dicing traces of the wafer 20 using visible light. In the above embodiments and modifications, by capturing an image of at least the surface layer of the dicing trace 23 after cutting, or by using an infrared-transparent image, information is generated to control the irradiation conditions (laser ON / OFF control, laser power) of the laser light L in each region of the dicing trace 23, and the grooving process can be controlled based on this information. In the above embodiments and modifications, the surface layer of the dicing trace 23 can also be removed by scanning a plurality of laser light Ls on the dicing trace 23. In the above embodiments and modifications, by having the laser light L0 move relatively along each cutting line 15, it is possible to control only the support 102, only the laser processing head H, or both the support 102 and the laser processing head H. In the above-described embodiments and variations, the laser light L moves relative to each cutting path 23, so that only the support part 2 can be controlled, only the irradiation part 3 can be controlled, or both the support part 2 and the irradiation part 3 can be controlled.

[0103] In the above embodiments and variations, the energy of each focusing point of the plurality of branched laser beams split into multiple branched laser beams L can be equal, or the intensity can be varied by changing the splitting ratio. In the above embodiments and variations, in the Y direction, the focusing points SA1, SA2, and SA3 of the first branched laser beam are positioned identically, but can also be moved within a range narrower than the interval Y1 in the Y direction at least once. In the Y direction, the focusing points SB1, SB2, and SB3 of the second branched laser beam are positioned identically, but can also be moved within a range narrower than the interval Y1 in the Y direction at least once. In the Y direction, the focusing points SC1 and SC2 of the third branched laser beam are positioned identically, but can also be moved within a range narrower than either the interval Y1 or the interval Y2 in the Y direction. The interval Y1 can be equal to or different from the interval Y2.

[0104] In the above embodiments and modifications, the bottoms of the first trench M1 and the second trench M2 can both be located on the surface 21a of the semiconductor substrate 21. In the above embodiments and modifications, the number of branches that branch the laser light L in a branching pattern is not limited, as long as it is multiple. In the above embodiments and modifications, during the formation of the modified region 11, the end of the crack 9 can also reach the inner surface of the first trench M1 or the inner surface of the second trench M2. In processes following the formation of the modified region 11, the end of the crack 9 can also reach the inner surface of the first trench M1 or the inner surface of the second trench M2. In the above embodiments and variations, the phrase "the end of the crack 9 reaches the inner surface of the first groove M1 or the inner surface of the second groove M2" means, for example, if the subsequent process is carried out for the purpose of wafer 20 waferization, it also includes the case where the end of the crack 9 does not reach the inner surface of the first groove M1 or the inner surface of the second groove M2 in part of the cutting line 15.

[0105] 1: Laser processing equipment 2,102: Support section 9: Cracks 11: Modified Area 15: Cut the thread 20: Wafer (object) 21: Semiconductor substrate (substrate) 22: Functional Component Layer 29: Protective film 31: Laser light source 34,106: Light collecting part 100: Laser processing equipment 105,132: Spatial light modulator 132A: Display Unit 200: Laser processing equipment 202: Platform (Support Department) d12: Interval d23: Interval d34: Interval d45: Interval d56: Interval DC: Transparent Cutting Tape L: Laser light L0: Laser light LA: First Divergence Laser LB: Second branch laser beam M1: First ditch (ditch) M2: Second ditch (ditch) M3: Third ditch (ditch) MH, MH1, MH2, MH3, MH4, MH5, MH6: Composite trench SA1, SA2, SA3: Focusing points of the first branching laser beam SB1, SB2, SB3: Focusing points of the second branch laser beam SC1, SC2: Focusing points of the third branch laser beam Y1, Y2: Interval

Claims

1. A laser processing method, characterized by comprising: irradiating a workpiece with laser light and forming a first groove on the workpiece along a cutting line; irradiating the workpiece with laser light and forming a second groove on the workpiece along the cutting line, wherein the ends of the first groove overlap with the first groove in the width direction; and after forming a composite groove including the first groove and the second groove on the workpiece, irradiating the workpiece with laser light and forming a modified region inside the workpiece along the cutting line, and causing cracks to extend from the modified region, wherein the workpiece has a substrate and a functional element layer on the substrate, and the composite groove is located on the functional element layer of the workpiece, wherein either the bottom of the first groove or the bottom of the second groove reaches the substrate.

2. The laser processing method as described in claim 1, wherein, Furthermore, it has the following process: after forming the aforementioned modified area, when the aforementioned cracked end reaches the inner surface of the aforementioned first groove or the inner surface of the aforementioned second groove, the aforementioned object is cut along the aforementioned cutting line by expanding the tape attached to the aforementioned object.

3. The laser processing method as described in claim 1, wherein, The aforementioned object is a substrate and a functional element layer on the aforementioned substrate. The aforementioned composite trench is located on the side of the aforementioned functional element layer of the aforementioned object, and both the bottom of the aforementioned first trench and the bottom of the aforementioned second trench reach the aforementioned substrate.

4. The laser processing method as described in claim 2, wherein, The aforementioned object is a substrate and a functional element layer on the aforementioned substrate. The aforementioned composite trench is located on the side of the aforementioned functional element layer of the aforementioned object, and both the bottom of the aforementioned first trench and the bottom of the aforementioned second trench reach the aforementioned substrate.

5. The laser processing method as described in claim 1, wherein, The aforementioned object is a substrate and a functional element layer on the aforementioned substrate. The aforementioned composite trench is located on the side of the aforementioned functional element layer of the aforementioned object, and both the bottom of the aforementioned first trench and the bottom of the aforementioned second trench do not reach the aforementioned substrate.

6. The laser processing method as described in claim 2, wherein, The aforementioned object is a substrate and a functional element layer on the aforementioned substrate. The aforementioned composite trench is located on the side of the aforementioned functional element layer of the aforementioned object, and both the bottom of the aforementioned first trench and the bottom of the aforementioned second trench do not reach the aforementioned substrate.

7. The laser processing method described in any of claims 1 to 6, wherein, It includes the step of forming a protective film on the aforementioned functional element layer before forming the aforementioned composite trench.

8. The laser processing method described in any of claims 1 to 6, wherein, In a cross-sectional view orthogonal to the aforementioned cut line, the aforementioned composite trench presents a W-shape.

9. The laser processing method described in any of claims 1 to 6, wherein, It includes a process of grinding and thinning the object before forming the aforementioned composite groove.

10. The laser processing method described in any of claims 1 to 6, wherein, It has the following steps: after forming the aforementioned modified region, grinding and thinning the aforementioned object.

11. The laser processing method described in any of claims 1 to 6, wherein, The aforementioned cutting lines are set multiple times on the aforementioned object. The process of forming the aforementioned modified region includes: when the deviation of the formation position of the aforementioned modified region from the center position of the aforementioned composite groove in the width direction of the aforementioned composite groove is greater than half the width of the aforementioned composite groove, the process of correcting the formation position of the aforementioned modified region to be consistent with the center position.

12. A laser processing method, characterized by comprising: irradiating a workpiece with laser light and forming a first groove on the workpiece along a cutting line; irradiating the workpiece with laser light and forming a second groove on the workpiece along the cutting line, wherein the ends of the first groove overlap with the first groove in the width direction; and after forming a composite groove including the first groove and the second groove on the workpiece, irradiating the workpiece with laser light and forming a modified region inside the workpiece along the cutting line, and causing cracks to extend from the modified region, wherein the cutting line is multiple times set on the workpiece, and the step of forming the modified region includes: when the deviation of the formation position of the modified region from the center position of the composite groove in the width direction is greater than half the width of the composite groove, correcting the formation position of the modified region to be consistent with the center position.

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