Laser processing device and laser processing method

Abstract

A laser processing device comprises a carrier unit, a laser light source, a spatial light modulator, and a condenser unit. A modulation pattern, displayed on a display unit of the spatial light modulator, includes a branching pattern for splitting laser light into first branched laser light components to form a first groove and second branched laser light components to form a second groove. The distance between the position of the focusing point of the first branched laser light and the position of the focusing point of the second branched laser light, lying side by side in one direction along the line, is greater than the distance between the position of the focusing point of the first branched laser light and the position of the focusing point of the second branched laser light in the latitude direction of the first and second grooves.

Description

Technical area

[0001] One aspect of the present invention relates to a laser processing apparatus and a laser processing method. State of the art

[0002] When cutting an object along the line, for example, groove processing can be performed to remove the surface layer of the object along the line (see, for example, Patent Literatures 1 and 2). In such groove processing, a groove is formed in the object along the line by irradiating the object with laser light. Citation listPatent literature Patent Literature 1: Japanese Unexamined Patent Publication No. 2007-173475 Patent Literature 2: Unexamined Japanese Patent Publication No. 2017-011040 Summary of the inventionTechnical problem

[0003] In the techniques described above, for example, to improve the tactile speed (work efficiency), at least one first groove and one second groove may be formed in the object along the line by splitting the laser light emitted onto the object into a plurality of branched laser light components. However, in this case, the focusing points (processing points) of the respective branched laser light components may interfere with each other, which may lead to the problem that the first groove and the second groove cannot be satisfactorily formed.

[0004] Therefore, it is an object of the present invention to satisfactorily form a first groove and a second groove in an object along the line with a laser processing apparatus and a laser processing method for branching laser light and irradiating the object with the branched laser light components. Solution to the problem

[0005] A laser processing apparatus according to one aspect of the present invention is a laser processing apparatus for forming a groove in an object along a line by irradiating the object with laser light along the line, and comprises: a support unit configured to support the object; a laser light source configured to emit the laser light; a spatial light modulator including a display unit onto which the laser light emitted from the laser light source is incident and which modulates the laser light according to a modulation pattern displayed on the display unit; and a condenser unit configured to condense the laser light modulated by the spatial light modulator onto the object supported by the support unit.The modulation pattern includes a branching pattern for branching the laser light into at least one or more first branched laser light components to form a first groove and one or more second branched laser light components to form a second groove. A distance between a position of a focusing point of the first branched laser light and a position of a focusing point of the second branched laser light adjacent to each other in a direction along the line is greater than a distance between a position of a focusing point of the first branched laser light and a position of a focusing point of the second branched laser light in a width direction of the first groove and the second groove.

[0006] In this laser processing apparatus, the distance between the position of the focusing point of the first branched laser light (hereinafter also referred to as the "first processing position") and the position of the focusing point of the second branched laser light (hereinafter also referred to as the "second processing position") adjacent to each other in the along-line direction is greater than the distance between the first processing position and the second processing position in the width direction. For this reason, since it is possible to separate the first processing point and the second processing point from each other until mutual interference is less likely (e.g., interference between focusing points and influence of processing in a heat-affected state; see below), each of the first groove and the second groove can be reliably formed as an independent groove in the object.Therefore, it is possible to satisfactorily form the first groove and the second groove in the object along the line.

[0007] In the laser processing apparatus according to one aspect of the present invention, the second groove may overlap an end portion of the first groove in the width direction of the first groove. In this case, a compound groove including the first groove and the second groove may be formed in the object. Such a compound groove can effectively induce a crack extending from, for example, a modified region inside the object.

[0008] In the laser processing apparatus according to one aspect of the present invention, the branching pattern can branch the laser light into one or more third branched laser light components to form a third groove in addition to the first branched laser light and the second branched laser light, the third groove overlapping an end portion of the second groove in the width direction of the second groove. In this case, it is possible to form a wide compound groove.

[0009] In the laser processing apparatus according to one aspect of the present invention, the distance between the position of the focusing point of the first branched laser light and the position of the focusing point of the second branched laser light, adjacent to each other in the direction along the line, can be greater than a pulse interval of the laser light. In this case, since the occurrence of a situation in which the distance between the first processing position and the second processing position is too short and, accordingly, their mutual interference becomes significant, is suppressed, it is possible to satisfactorily form the first groove and the second groove in the object.

[0010] In the laser processing apparatus according to one aspect of the present invention, the distance between the positions of the focusing points of the plurality of first branched laser light components in the direction along the line can be greater than the pulse interval of the laser light. In this case, since it is possible to suppress the occurrence of a situation where the distance between a plurality of first processing positions is too short and, accordingly, their influence on each other becomes significant, it is possible to satisfactorily form the first groove in the object.

[0011] In the laser processing apparatus according to one aspect of the present invention, a distance between the positions of the focusing points of the plurality of first branched laser light components in the direction along the line may be smaller than the distance between the position of the focusing point of the first branched laser light and the position of the focusing point of the second branched laser light adjacent to each other in the direction along the line. In this case, the distance between the plurality of first processing positions can be set to a range where they influence each other, so that a HAZ (heat-affected zone) can be suppressed.

[0012] In the laser processing apparatus according to one aspect of the present invention, the distance between the positions of the focusing points of the plurality of second branched laser light components in the direction along the line can be greater than the pulse interval of the laser light. In this case, since it is possible to suppress the occurrence of a situation where the distance between a plurality of second processing positions is too short and, accordingly, their influence on each other becomes significant, it is possible to satisfactorily form the second groove in the object.

[0013] In the laser processing apparatus according to one aspect of the present invention, a distance between the positions of the focusing points of the plurality of second branched laser light components in the direction along the line may be smaller than the distance between the position of the focusing point of the first branched laser light and the position of the focusing point of the second branched laser light adjacent to each other in the direction along the line. In this case, the distance between the plurality of second processing positions can be set to a range where they influence each other, so that the HAZ can be suppressed.

[0014] In the laser processing apparatus according to one aspect of the present invention, the branching pattern can split the laser light into two first branched laser light components and two second branched laser light components. Since the energy at each focusing point can be reduced, it is possible to suppress the HAZ in this case.

[0015] In the laser processing apparatus according to one aspect of the present invention, the branching pattern can split the laser light into three first branched laser light components and three second branched laser light components. In this case, the energy at each focusing point can be further reduced, thus enabling further suppression of the HAZ.

[0016] In the laser processing apparatus according to one aspect of the present invention, the branching pattern can branch the laser light so that the focusing points are aligned in a one-dimensional array along the line. Therefore, it is possible to form a narrow compound groove in the object.

[0017] A laser machining method according to one aspect of the present invention is a laser machining method for forming a groove in an object along a line by irradiating the object with laser light along the line, and comprising a step of emitting the laser light, making the emitted laser light incident on a display unit of a spatial light modulator, modulating the laser light according to a modulation pattern displayed on the display unit, and condensing the modulated laser light onto the object. The modulation pattern includes a branching pattern for branching the laser light into at least one or more first branched laser light components for forming a first groove and one or more second branched laser light components for forming a second groove.A distance between a position of a focusing point of the first branched laser light and a position of a focusing point of the second branched laser light adjacent to each other in a direction along the line is larger than a distance between a position of a focusing point of the first branched laser light and a position of a focusing point of the second branched laser light in a width direction of the first groove and the second groove.

[0018] Also, with this laser processing method, it is possible to satisfactorily form the first groove and the second groove in the object along the line. Advantageous effects of the invention

[0019] According to one aspect of the present invention, it is possible to satisfactorily form the first groove and the second groove in the object along the line by using the laser processing apparatus and the laser processing method for branching laser light and irradiating the object with branched laser light components. Brief description of the drawings Fig. 1 is a configuration diagram of a laser processing apparatus for forming a modified region within a wafer. Fig. 2 is a configuration diagram of a laser processing apparatus for performing groove processing. Fig. 3 is a plan view of a wafer to be processed. Fig. 4 is a cross-sectional view of a portion of the Fig. 3 shown wafer. Fig. 5 is a plan view of a part of the Fig. 3 shown street. Fig. 6 is a diagram showing an example of a case where the position of each focusing point of the first branched laser light and the position of each focusing point of the second branched laser light are viewed from a Z direction. Fig. 7(a) is a cross-sectional view of a wafer for explaining a laser processing method according to an embodiment. Fig. Figure 7(b) is a cross-sectional view of the wafer, which is a continuation of Fig. 7(a) shows. Fig. Figure 7(c) is a cross-sectional view of the wafer, which is a continuation of Fig. 7(b) shows. Fig. Figure 8(a) is a cross-sectional view of the wafer, which is a continuation of Fig. 7(c) shows. Fig. Figure 8(b) is a cross-sectional view of the wafer, which is a continuation of Fig. 8(a) shows. Fig. Figure 8(c) is a cross-sectional view of the wafer, which is a continuation of Fig. 8(b) shows. Fig. Figure 9(a) is a cross-sectional view of the wafer, which is a continuation of Fig. 8(c) shows. Fig. 9(b) is a cross-sectional view of the wafer, which is a continuation of Fig. 9(a) shows. Fig. 10 is an enlarged cross-sectional view of a portion of the wafer in Fig. 9(b). Fig. 11(a) is a cross-sectional view corresponding to Fig. 10 of a wafer according to a modification example. Fig. 11(b) is a cross-sectional view corresponding to Fig. 10 of a wafer according to another modification example. Fig. 11(c) is a cross-sectional view corresponding to Fig. 10 of a wafer according to another modification example. Fig. 12 is a cross-sectional view of the wafer, which is a continuation of Fig. 9(b) shows. Fig. 13 is a cross-sectional view corresponding to Fig. 10 of a wafer according to a conventional example. Fig. 14 is a diagram showing another example of the case where the position of each focusing point of the first branched laser light and the position of each focusing point of the second branched laser light are viewed from the Z direction. Fig. 15(a) is a diagram showing an example of a case where the position of each focusing point of the first branched laser light, the position of each focusing point of the second branched laser light, and the position of each focusing point of the third branched laser light are viewed from the Z direction. Fig. 15(b) is a cross-sectional view of a wafer showing a compound groove according to a modification example. Fig. 16(a) is a cross-sectional view of a wafer showing a compound groove according to a modification example. Fig. 16(b) is a cross-sectional view of a wafer showing a compound groove according to a modification example. Fig. 16(c) is a cross-sectional view of a wafer showing a compound groove according to a modification example. Fig. 17(a) is a cross-sectional view of a wafer showing a compound groove according to a modification example. Fig. 17(b) is a cross-sectional view of a wafer showing a compound groove according to a modification example. Fig. 17(c) is a cross-sectional view of a wafer showing a compound groove according to a modification example. Fig. Figure 18 is a graph showing test results for evaluating the deviation of a crack in the formation of a composite groove. Fig. 19(a) is a cross-sectional view of a wafer showing another example of a method for forming a compound groove. Fig. 19(b) is a cross-sectional view of the wafer, which is a continuation of Fig. 19(a) shows. Fig. 20(a) is a cross-sectional view of a wafer showing another example of the method for forming a compound groove. Fig. 20(b) is a cross-sectional view of the wafer, which is a continuation of Fig. 20(a) shows. Fig. 21 is a flowchart showing an example of laser processing including a step for correcting the formation position of a modified area. Fig. 22 is a perspective view showing a laser processing apparatus in which a groove processing optical system and a modified region forming optical system are mounted. Fig. 23(a) is a cross-sectional view of a wafer for explaining a laser processing method according to a modification example. Fig. 23(b) is a cross-sectional view of the wafer, which is a continuation of Fig. 23(a) shows. Fig. 23(c) is a cross-sectional view of the wafer, which is a continuation of Fig. 23(b) shows. Fig. Figure 24(a) is a cross-sectional view of the wafer, which is a continuation of Fig. 23(c) shows. Fig. 24(b) is a cross-sectional view of the wafer, which is a continuation of Fig. 24(a) shows. Fig. Figure 24(c) is a cross-sectional view of the wafer, which is a continuation of Fig. 24(b) shows. Fig. 25 is a cross-sectional view of the wafer, which is a continuation of Fig. 24(c) shows. Description of the embodiments

[0020] Hereinafter, an embodiment according to one aspect of the present invention will be described in detail with reference to the diagrams. Like or equivalent parts in the diagrams are designated by like reference numerals, and repeated descriptions thereof will be omitted.

[0021] In the present embodiment, a modified region is formed within a wafer (object). For example, a laser processing apparatus 100 shown in Fig. 1, can be used as a device for forming a modified region within a wafer. As shown in Fig. 1, 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 condenser unit 106, an optical axis monitoring 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 is an apparatus for forming a modified region 11 on a wafer 20 by irradiating the wafer 20 with laser light L0. In the following description, three directions perpendicular to each other are referred to as the X direction, the Y direction, and the Z direction. For example, the X direction is a first horizontal direction, the Y direction is a second horizontal direction perpendicular to the first horizontal direction, and the Z direction is a vertical direction.

[0022] The carrier unit 102 supports the wafer 20, for example, by adsorbing the wafer 20. The carrier unit 102 is movable in both the X and Y directions. The carrier unit 102 is rotatable about a rotation axis in the Z direction. The light source 103 emits the laser light L0, for example, using a pulse oscillation method. The laser light L0 is transparent to the wafer 20. The optical axis adjustment unit 104 adjusts the optical axis of the laser light L0 emitted by the light source 103. The optical axis adjustment unit 104 is formed, for example, by a plurality of reflecting mirrors whose positions and angles can be adjusted.

[0023] The spatial light modulator 105 is arranged in a 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 liquid crystal on silicon (LCOS) spatial light modulator (SLM). In the spatial light modulator 105, the laser light L0 can be modulated by appropriately setting a modulation pattern displayed on its display unit (liquid crystal layer). In the present embodiment, the laser light L0, which has traveled downward along the Z direction from the optical axis adjustment unit 104, enters the laser processing head H, is reflected by a mirror MM1, and is incident on the spatial light modulator 105. The spatial light modulator 105 modulates the thus incident laser light L0 while reflecting the laser light L0.

[0024] The condenser unit 106 is attached to the bottom wall of the laser processing head H. The condenser unit 106 condenses the laser light L0 modulated by the spatial light modulator 105 onto the wafer 20 supported by the support unit 102. In the present embodiment, the laser light L0 reflected by the spatial light modulator 105 is reflected by a dichroic mirror MM2 to be incident on the condenser unit 106. The condenser unit 106 condenses the laser light L0 thus incident on the wafer 20. The condenser unit 106 is formed by attaching a condenser lens unit 161 to the bottom wall of the laser processing head H through a drive mechanism 162. The drive mechanism 162 moves the condenser lens unit 161 along the Z direction, for example, by the driving force of a piezoelectric element.

[0025] Furthermore, in the laser processing head H, an imaging optical system (not shown) is arranged between the spatial light modulator 105 and the condenser unit 106. The imaging optical system forms a double-sided telecentric optical system in which the reflecting surface of the spatial light modulator 105 and the entrance pupil plane of the condenser unit 106 are in an imaging relationship. Therefore, the image of the laser light L0 on the reflecting surface of the spatial light modulator 105 (image of the laser light L0 modulated by the spatial light modulator 105) is transferred (formed) onto the entrance pupil plane of the condenser unit 106. A pair of distance sensors S1 and S2 are mounted on the bottom wall of the laser processing head H so as to be located on both sides of the condenser lens unit 161 in the X direction.Each of the distance sensors S1 and S2 detects displacement data of the laser light incident surface by emitting light for distance measurement (e.g., laser light) onto the laser light incident surface of the wafer 20 and detecting the light reflected from the laser light incident surface for distance measurement.

[0026] The optical axis monitoring unit 107 is arranged inside the laser processing head H. The optical axis monitoring unit 107 detects a portion of the laser light L0 transmitted through the dichroic mirror MM2. The detection result of the optical axis monitoring unit 107 indicates, for example, a relationship between the optical axis of the laser light L0 incident on the condenser lens unit 161 and the optical axis of the condenser lens unit 161. The visual imaging unit 108A emits visible light V0 and captures an image of the wafer 20 through the visible light V0 as an image. The visual imaging unit 108A is arranged inside the laser processing head H. The infrared imaging unit 108B emits infrared light and captures an image of the wafer 20 through the infrared light as an infrared image. The infrared imaging unit 108B is mounted on the side wall of the laser processing head H.

[0027] The movement mechanism 109 includes a mechanism that moves at least one of the laser processing head H and the support unit 102 in the X direction, the Y direction, and the Z direction. The movement mechanism 109 drives at least the laser processing head H and / or the support unit 102 with the driving force of a known driving device, such as a motor, so that the focusing point C of the laser light L0 moves in the X direction, the Y direction, and the Z direction. The movement mechanism 109 includes a mechanism that rotates the support unit 102. The movement mechanism 109 rotationally drives the support unit 102 with the driving force of a known driving device, such as a motor.

[0028] The management unit 150 includes a control unit 151, a user interface 152, and a storage unit 153. The control unit 151 controls the operation of the individual units of the laser processing device 100. The control unit 151 is configured as a computer device including a processor, a storage space, a memory, a communication device, and the like. In the control unit 151, the processor executes software (program) read into the memory or the like to control the reading and writing of data in the memory and the storage and communication through the communication device. The user interface 152 displays and outputs various types of data. The user interface 152 is a graphical user interface (GUI) with a graphics-based operating system.

[0029] The user interface 152 includes, for example, at least one of a touch panel, a keyboard, a mouse, a microphone, a tablet terminal, a monitor, and the like. The user interface 152 can receive various inputs, for example, through touch input, keyboard input, mouse operation, and voice input. The user interface 152 can display various types of information on its screen. The user interface 152 corresponds to an input receiving unit that receives an input and a display unit that can display an adjustment screen based on the received input. The storage unit 153 is, for example, a hard disk and stores various types of data.

[0030] In the laser processing apparatus 100 configured as described above, when the laser light L0 is condensed inside the wafer 20, the laser light L is absorbed in a portion corresponding to the focusing point (at least a part of the focusing region) C of the laser light L0, and the modified region 11 is formed inside the wafer 20. The modified region 11 is a region whose density, refractive index, mechanical strength, and other physical properties differ from those of the surrounding unmodified region. Examples of the modified region 11 include a melt treatment region, a crack region, a dielectric breakdown region, and a refractive index change region. The modified region 11 includes a plurality of modified points 11s and cracks extending from the plurality of modified points 11s.

[0031] As an example, the operation of the laser processing apparatus 100 in forming the modified region 11 within the wafer 20 along a line 15 for cutting the wafer 20 will be described.

[0032] First, the laser processing apparatus 100 rotates the carrier unit 102 so that the line 15 drawn on the wafer 20 is parallel to the X direction. The laser processing apparatus 100 moves the carrier unit 102 along the X direction and the Y direction based on the image (e.g., an image of the functional element layer included in the wafer 20) acquired by the infrared imaging unit 108B, so that the focusing point C of the laser light L0 is located on the line 15 when viewed from the Z direction. The laser processing apparatus 100 moves the laser processing head H (ie, the condenser unit 106) along the Z direction based on the image (eg, an image of the laser light incident surface of the wafer 20) acquired by the visual imaging unit 108A so that the focusing point C of the laser light L0 is located on the laser light incident surface (height set).With the position as a reference, the laser processing apparatus 100 moves the laser processing head H along the Z direction so that the focusing point C of the laser light L0 is located at a predetermined depth from the laser light incident surface.

[0033] Subsequently, the laser processing apparatus 100 emits the laser light L0 from the light source 103 and moves the carrier unit 102 along the X direction so that the focusing point C of the laser light L0 moves relatively along the line 15. At this time, the laser processing apparatus 100 actuates the drive mechanism 162 of the condenser unit 106 based on the displacement data of the laser light incident surface detected by one of the pair of distance sensors S1 and S2 located on the front side in the machining progress direction of the laser light L0, so that the focusing point C of the laser light L0 is located at a predetermined depth from the laser light incident surface.

[0034] As a result of the above, a row of modified regions 11 is formed along line 15 and at a fixed depth from the laser light incident surface of the wafer 20. When the laser light L0 is emitted from the light source 103 using a pulse oscillation method, a plurality of modified spots 11s are formed aligned in a row along the X direction. A modified spot 11s is formed by emitting a single pulse of laser light L0. The modified regions 11 in a row are a set of multiple modified spots 11s arranged in a row. The adjacent modified spots 11s may be connected to each other or separated from each other depending on the pulse pitch of the laser light L0 (a value obtained by dividing the relative moving speed of the focusing spot C with respect to the wafer 20 by the repetition frequency of the laser light L0).

[0035] In the present embodiment, groove processing is performed to form a groove in the wafer 20 along the line 15 by emitting laser light onto the road along the line 15 so that the surface layer of the road on the wafer 20 is removed. For example, a laser processing apparatus 1 shown in Fig. 2, can be used as a device for performing the groove machining.

[0036] As in Fig. 2, the laser processing apparatus 1 includes a carrier unit 2, an irradiation unit 3, an imaging unit 4, and a control unit 5. The carrier unit 2 supports the wafer 20. The carrier unit 2 holds the wafer 20 such that the surface of the wafer 20 including the street faces the irradiation unit 3 and the imaging unit 4, for example, by adsorption of the wafer 20. The carrier unit 2 can move, for example, along the X direction and the Y direction and rotate about an axis parallel to the Z direction as a center line.

[0037] The irradiation unit 3 irradiates the street of the wafer 20 carried by the carrier unit 2 with the laser light L. The irradiation unit 3 includes a laser light source 31, a shaping optical system 32, a dichroic mirror 33, and a condenser unit 34. The laser light source 31 emits the laser light L. The shaping optical system 32 adjusts the laser light L emitted by the laser light source 31. The shaping optical system 32 includes a spatial light modulator 132 that modulates the phase of the laser light L.

[0038] The spatial light modulator 132 has a display unit 132A onto which the laser light L emitted from the laser light source 31 is incident. The spatial light modulator 132 modulates the laser light L according to a modulation pattern displayed on the display unit 132A. The shaping optical system 32 may include an imaging optical system forming a double-sided telecentric optical system in which the modulation surface of the spatial light modulator and the entrance pupil plane of the condenser unit 34 are in an imaging relationship. The shaping optical system 32 may further include an attenuator for adjusting the power of the laser light L and a beam expander for increasing the diameter of the laser light L.

[0039] The dichroic mirror 33 reflects the laser light L emitted by the shaping optical system 32 and makes the reflected laser light L incident on the condenser unit 34. The condenser unit 34 condenses the laser light L reflected by the dichroic mirror 33 (the laser light L modulated by the spatial light modulator 132) onto the wafer 20 supported by the carrier unit 2.

[0040] The irradiation unit 3 further includes a light source 35, a half mirror 36, and an imaging element 37. The light source 35 emits the visible light V1. The half mirror 36 reflects the visible light V1 emitted by the light source 35 and makes the reflected visible light V1 incident on the condenser unit 34. The dichroic mirror 33 transmits the visible light V1 between the half mirror 36 and the condenser unit 34. The condenser unit 34 condenses the visible light V1 reflected by the half mirror 36 onto the street of the wafer 20 carried by the carrier unit 2. The imaging element 37 detects the visible light V1 reflected from the street of the wafer 20 and transmitted through the condenser unit 34, the dichroic mirror 33, and the half mirror 36.In the laser processing apparatus 1, the control unit 5 moves the condenser unit 34 along the Z direction based on the detection result of the imaging element 37, for example, so that the focusing point of the laser light L is located on the road of the wafer 20.

[0041] The imaging unit 4 acquires image data from the street of the wafer 20 supported by the carrier unit 2. The imaging unit 4 is an internal observation camera for observing the interior of the wafer 20 on which the modified region 11 has been formed by the laser processing apparatus 100. The imaging unit 4 irradiates infrared light onto the wafer 20 and captures an image of the wafer 20 using the infrared light as image data. An InGaAs camera can be used as the imaging unit 4.

[0042] The control unit 5 controls the operation of each unit of the laser processing device 1. The control unit 5 includes a processing unit 51, a storage unit 52, and an input receiving unit 53. The processing unit 51 is a computer device including a processor, a memory, a storage space, a communication device, and the like. In the processing unit 51, the processor executes software (program) read into the memory or the like to control the reading and writing of data in the memory and the storage and communication through the communication device. The storage unit 52 is, for example, a hard disk and stores various types of data. The input receiving unit 53 is an interface unit that receives input of various types of data from the operator.The input receiving unit 53 is, for example, at least one of a keyboard, a mouse, or a graphical user interface (GUI).

[0043] The laser processing apparatus 1 performs groove processing. During groove processing, the control unit 5 controls the irradiation unit 3 so that the laser light L is emitted along the line 15 to each street of the wafer 20 supported by the carrier unit 2, and the control unit 5 controls the carrier unit 2 so that the laser light L moves relatively along the line 15 (details will be described later).

[0044] As in the Fig. 3 and Fig. 4, the wafer 20 includes 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 front surface 21a and a back surface 21b. The semiconductor substrate 21 is, for example, a silicon substrate. A notch 21c indicating crystal orientation is provided in the semiconductor substrate 21. Instead of the notch 21c, an orientation surface may also be provided in the semiconductor substrate 21. The functional element layer 22 is formed on the front surface 21a of the semiconductor substrate 21. The functional element layer 22 includes a plurality of functional elements 22a. The plurality of functional elements 22a are arranged in a two-dimensional manner along the front surface 21a of the semiconductor substrate 21.Each functional element 22a is, for example, a light-receiving element such as a photodiode, a light-emitting element such as a laser diode, or a circuit element such as a memory. Each functional element 22a can be formed in a three-dimensional manner by stacking multiple layers.

[0045] A plurality of streets 23 are formed on the wafer 20. The plurality of streets 23 are regions that are open to the outside between the adjacent functional elements 22a. That is, the plurality of functional elements 22a are arranged next to one another, with the street 23 in between. For example, the plurality of streets 23 extend in a grid pattern so that they run between the adjacent functional elements 22a for the plurality of functional elements 22a arranged in a matrix. As shown in Fig. As shown in Figure 5, an insulating film 24 and a plurality of metal structures 25 and 26 are formed on the surface layer of the road 23. The insulating film 24 is, for example, a low-k film. Each of the metal structures 25 and 26 is, for example, a metal pad. The metal structure 25 and the metal structure 26 differ, for example, in at least one of thickness, area, and material.

[0046] As in the Fig. 3 and Fig. 4, a plurality of lines 15 are provided on the wafer 20. The wafer 20 is to be systematically cut into the functional elements 22a (i.e., fabricated into chips corresponding to the respective functional elements 22a) along each of the plurality of lines 15. Each line 15 passes through each street 23 when viewed from the thickness direction of the wafer 20. For example, each line 15 is such that, when viewed from the thickness direction of the wafer 20, it passes through the center of each street 23. Each line 15 is a virtual line set on the wafer 20 by the laser processing devices 1 and 100. Each line 15 may be a line actually drawn on the wafer 20.

[0047] In the present embodiment, the modulation pattern displayed on the display unit 132A of the spatial light modulator 132 includes a branching pattern for branching the laser light L into a plurality (here, two) of first branched laser light components to form a first groove and a plurality (here, two) of second branched laser light components to form a second groove. As shown in Fig. As shown in Figure 6, in the present embodiment, the focusing points SA1 and SA2 of the two first branched laser light components are aligned, and then the focusing points SB1 and SB2 of the two second branched laser light components are aligned from one side of the line 15 to the other side in the X direction along the line 15. In the Y direction, which corresponds to the width direction of a groove to be formed, the positions of the focusing points SA1 and SA2 of the first branched laser light components are the same. In the Y direction, the positions of the focusing points SB1 and SB2 of the second branched laser light components are the same.

[0048] Each position of the focusing points SA1 and SA2 of the first branched laser light components is also referred to as a first processing point, and each position of the focusing points SB1 and SB2 of the second branched laser light components is also referred to as a second processing point. In the X direction, the distance between the position of the focusing point SA2 of the first branched laser light and the position of the focusing point SB1 of the second branched laser light, which are adjacent to each other, is defined as a distance d23. In other words, the distance d23 is a distance in the X direction between the first processing point and the second processing point, which are adjacent to each other.In the Y direction, which corresponds to the width direction of the groove to be formed, the distance between the positions of the focusing points SA1 and SA2 of the first branched laser light components and the positions of the focusing points SB1 and SB2 of the second branched laser light components is defined as distance Y1.

[0049] The distance d23 is greater than the distance Y1. The distance d23 is greater than the pulse pitch of the laser light L. The distance d23 is, for example, 20 µm or more. The distance d12 between the positions of the focusing points SA1 and SA2 of a plurality of first branched laser light components in the X direction along the line 15 is greater than the pulse pitch of the laser light L. The distance d12 is smaller than the distance d23. The distance d34 between the positions of the focusing points SB1 and SB2 of a plurality of second branched laser light components in the X direction is greater than the pulse pitch of the laser light L. The distance d34 is smaller than the distance d23.The branching pattern branches the laser light L so that the focusing points SA1, SA2, SB1 and SB2 are aligned in a one-dimensional array (including an approximately one-dimensional array, a substantially one-dimensional array and an approximately one-dimensional array, as described below) along the line 15.

[0050] As in Fig. As shown in Figure 8(b), a first groove M1 formed by the first branched laser light LA ​​and a second groove M2 formed by the second branched laser light LB form a compound groove MH. The compound groove MH is a W-shaped groove (W-groove) in a cross-sectional view perpendicular to line 15. The compound groove MH is a groove having a shape including two valley portions and a peak portion on the bottom in a cross-sectional view perpendicular to line 15. Both the first groove M1 and the second groove M2 are V-shaped grooves (V-groove) in a cross-sectional view perpendicular to line 15. The second groove M2 overlaps an end portion of 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 their end portions in the Y direction overlap each other.The first groove M1 and the second groove M2 are provided such that their circumferential edges are in contact with each other. The first groove M1 and the second groove M2 are grooves of equal depth and width.

[0051] The compound groove MH is provided on the functional element layer 22 side of the wafer 20 so that both the bottom of the first groove M1 and the bottom of the second groove M2 reach the semiconductor substrate 21. The bottom of the first groove M1 and the bottom of the second groove M2 reach the functional element layer 22 side of the semiconductor substrate 21. The overlapping end portions of the first groove M1 and the second groove M2 (a peak portion on the bottom of the compound groove MH) reach the functional element layer 22 side of the semiconductor substrate 21. The groove width, which is the groove width of the compound groove MH at its most open side, is, for example, 12 μm. The groove width can be input via the input receiving unit 53 (see Fig. 2) must be entered. The groove width is smaller than the width of the road 23.

[0052] Furthermore, the pitch d12 and the pitch d34 can be the same or different. For example, if the pulse pitch is 0.5 µm, the pitch d12 can be 10 µm, the pitch d23 can be 20 µm, the pitch d34 can be 10 µm, and the pitch Y1 can be 5 µm. The pitch Y1 is a distance that allows the compound groove MH to have a W-shape in cross-section and can be smaller than the groove width.

[0053] Next, a laser processing method using the laser processing apparatus 100 and the laser processing apparatus 1 will be described with reference to FIG. Fig. 7 to 11.

[0054] First, as in Fig. 7(a), the wafer 20 is prepared. A grinding belt 28 is applied to the surface of the wafer 20 on the side of the functional element layer 22. As shown in Fig. As shown in Fig. 7(b), the back surface 21b of the semiconductor substrate 21 of the wafer 20 is ground with a grinder to thin the wafer 20 to a desired thickness (grinding step). As shown in Fig. As shown in Fig. 7(c), the grinding tape 28 is removed, and a protective film 29 for protecting the functional element layer 22 (functional element 22a) is applied to the surface of the wafer 20 on the side of the functional element layer 22.

[0055] Then, as in Fig. 8(a), in the laser processing apparatus 1, after the wafer 20 has been adsorbed and supported by the carrier unit 2, groove processing is performed on the wafer 20. During the groove processing, the control unit 5 controls the irradiation unit 3 so that the laser light L is emitted onto the street 23 of the wafer 20 along the line 15, and the control unit 5 controls the carrier unit 2 so that the laser light L moves relatively along the line 15. As a result, as shown in Fig. 8(b), the surface layer of the street 23 on the wafer 20 is removed to form the compound groove MH including the first groove M1 and the second groove M2.

[0056] In particular, during the groove processing, the laser light L is emitted, the emitted laser light L is displayed on the display unit 132A (see Fig. 2) of the spatial light modulator 132 (see Fig. 2) is brought into contact, the laser light L is split into the first branched laser light LA ​​and the second branched laser light LB by the modulation pattern displayed on the display unit 132A, and the first branched laser light LA ​​and the second branched laser light LB are condensed on the wafer 20. During the groove processing, the condenser unit 34 (see Fig. 2) is moved or modulated by the spatial light modulator 132 so that the first branched laser light LA ​​and the second branched laser light LB are condensed on the surface of the functional element layer 22, for example, in the Z direction. The first groove M1 is formed by condensing the first branched laser light LA, and the second groove M2 is formed by condensing the second branched laser light LB.

[0057] As described above, the modulation pattern includes a branching pattern. The branching pattern can be appropriately generated by the control unit 5 based on the groove width input via the input receiving unit 53 (see Fig. 2). For example, the branching pattern can be automatically generated by the control unit 5 using various known methods, so that the focusing points SA1, SA2, SB1 and SB2 of the first branched laser light LA ​​and the second branched laser light LB are arranged in a one-dimensional array, which in Fig. 6 to realize the composite groove MH with the groove width.

[0058] The processing conditions for forming the compound groove MH are not particularly limited and can be determined based on various known techniques. The processing conditions for forming the compound groove MH can be appropriately input via the input receiving unit 53. The processing conditions for forming the compound groove MH can be, for example, the following conditions. In the following example of conditions, no shock pulses are used. However, shock pulses can be used, for example, to suppress film peeling (see also below). Wavelength of laser light L: 515 nm Pulse width of the laser light L: 600 fs Pulse distance of the laser light L: 0.5 µm Processing energy (total energy of each focusing point): 4.0 µJ Number of scans: 1 pass Position of the bottom of the compound groove MH: 3 µm from the front surface 21a of the semiconductor substrate 21

[0059] Then, as in Fig. 8(c), the wafer 20 is removed from the carrier unit 2, and the protective film 29 is removed, for example, using a chemical solution. As shown in Fig. As shown in Figure 9(a), a transparent dicing tape DC provided with a ring frame RF is attached to the backside 21b of the semiconductor substrate 21 of the wafer 20. The transparent dicing tape DC is also referred to as an expanding film.

[0060] Then, as in Fig. As shown in Fig. 9(b), in the laser processing apparatus 100, the wafer 20 is irradiated with the laser light L0 along the line 15, thereby forming the modified region 11 within the wafer 20 along the line 15. Here, the wafer 20 is adsorbed and supported by the carrier unit 102 with the transparent dicing tape DC attached to the back surface 21b of the semiconductor substrate 21, and then the focusing point of the laser light L0 within the semiconductor substrate 21 is aligned by the transparent dicing tape DC, so that the wafer 20 is irradiated with the laser light L0 with the back surface 21b as the laser light incident surface.

[0061] The laser light L0 is transparent to the transparent dicing tape DC and the semiconductor substrate 21. When the laser light L0 is condensed within the semiconductor substrate 21, the laser light L0 is absorbed in a region corresponding to the focusing point of the laser light L0, and accordingly, the modified region 11 is formed within the semiconductor substrate 21, and a crack 9 extends from the modified region 11. The processing conditions for forming the modified region 11 are not particularly limited and can be determined based on various known techniques. The processing conditions for forming the modified region 11 can be set via the user interface 152 (see Fig. 1). The processing conditions for forming the modified area 11 can be, for example, the following conditions. Wavelength of laser light L0: 1099 nm Pulse width of the laser light L0: 700 ns Pulse spacing of the laser light L0: 6.5 µm Processing energy: 22 µJ Number of scans: 8 passes

[0062] The crack 9 extending from the modified region 11 toward the side of the functional element layer 22 is caused to extend toward two grooves of the first groove M1 and the second groove M2 of the composite groove MH, and its end reaches the inner surface of the first groove M1 or the inner surface of the second groove M2. In the Fig. For example, in the example shown in Figure 10, there is substantially no deviation of the modified region 11 from the line 15 in the Y direction, and in this case, the induced crack 9 reaches the inner surface of the first groove M1 on the side of the second groove M2. Alternatively, for example, the induced crack 9 may reach the bottom of the first groove M1 when the modified region 11 deviates from the line 15 in the Y direction, as in the example shown in Fig. 11(a). Alternatively, for example, the induced crack 9 may reach the inner surface of the first groove M1 on a side opposite to the second groove side when the modified region 11 deviates from the line 15 in the Y direction, as in the example shown in Fig. 11(b). Alternatively, for example, the induced crack 9 may reach the inner surface of the first groove M1 on the side of the second groove M2 when the modified region 11 deviates from the line 15 in the Y direction, as in the example shown in Fig. Example shown in Figure 11(c).

[0063] Then, as in Fig. 12, by expanding the attached transparent dicing tape DC with an expander (not shown), the crack is expanded in the thickness direction of the wafer 20 from the modified region 11 formed within the semiconductor substrate 21 along each line 15, thereby cutting the wafer 20 along the line 15. As a result, the wafer 20 is processed into chips corresponding to the respective functional elements 22a, and a plurality of chips T1 are obtained.

[0064] For example, in the above example, instead of the transparent dicing tape DC, a protective tape may be attached to the functional element layer 22 side, and the laser light L0 may be emitted from the back surface 21b of the semiconductor substrate 21 to form the modified region 11. Then, the transparent dicing tape DC may be attached to the back surface 21b of the semiconductor substrate 21, and the protective tape on the functional element layer 22 side may be peeled off, and then the transparent dicing tape DC may be expanded and divided. When using a base material, for example, laser processing (groove processing and formation of the modified region 11) may be performed with a protective film attached. Then, the protective film may be removed, the transparent dicing tape DC may be attached, and the transparent dicing tape DC may be expanded and divided.

[0065] As in Fig. Incidentally, as shown in FIG. 13, when a single V-groove M0 is formed in the wafer 20 along the line 15, the crack 9 from the modified region 11, which is formed further inside than the V-groove M0 in the Z direction, tends to extend to deviate from the V-groove M0. For this reason, the crack 9 deviates significantly from the line 15. In this case, the cutting quality deteriorates when cutting the wafer 20. This increases the likelihood of deterioration of the separation quality, the occurrence of cracking, and residual cracks.

[0066] In this regard, in the present embodiment, the compound groove MH including the first groove M1 and the second groove M2 whose end portions overlap with each other is formed in the wafer 20. Since the crack 9 is caused to extend toward two grooves of the first groove M1 and the second groove M2 while suppressing the increase in the groove width, the effect of crack inducing 9 can be increased compared to a case where the single V-groove M0 is formed. As a result, it is possible to prevent the crack 9 from extending in a deviated manner. That is, it is possible to suppress the deviation of the crack 9 extending from the modified region 11 while reducing the groove width. The deviation of the crack 9 can be kept within the groove width. Since it is possible to improve the division quality, all chips can be reliably divided.The width of road 23 can be reduced.

[0067] The present embodiment further includes a step of cutting the wafer 20 along the line 15 by expanding the transparent dicing tape DC attached to the wafer 20, the end of the crack 9 reaching the inner surface of the first groove M1 or the inner surface of the second groove M2 after the modified region 11 is formed. In this case, it is possible to cut the wafer 20 accurately along the line 15.

[0068] In the present embodiment, the wafer 20 includes the semiconductor substrate 21 and the functional element layer 22. The compound groove MH is provided on the functional element layer 22 side of the wafer 20, so that both the bottom of the first groove M1 and the bottom of the second groove M2 reach the semiconductor substrate 21. In this case, it is possible to further enhance the effect of the crack induction 9 by the first groove M1 and the second groove M2.

[0069] The present embodiment includes a step of forming the protective film 29 on the functional element layer 22 before forming the compound groove MH. In this case, the functional element layer 22 can be effectively protected by the protective film 29. In the present embodiment, the compound groove MH has a W shape in a cross-sectional view perpendicular to the line 15. In this case, the above-described effect of suppressing the deviation of the crack 9 while reducing the groove width becomes apparent. The present embodiment includes a step of grinding the wafer 20 to make the wafer 20 thin before forming the compound groove MH. In this case, the wafer 20 can be made thin by grinding before forming the compound groove MH.

[0070] Here, in the laser processing apparatus 1 and the laser processing method according to the present embodiment, the distance d23 between the first processing point and the second processing point, which are adjacent to each other (the position of the focusing point SA2 of the first branched laser light and the position of the focusing point SB1 of the second branched laser light), in the X direction is larger than the distance Y1 between the first processing position and the second processing position in the Y direction. This makes it possible to separate the first processing point and the second processing point from each other until the first processing point and the second processing point hardly interfere with each other. Examples of the interference include the interference from the previous processing point and the interference from processing in a heat-affected state.Furthermore, it is possible to separate the first processing point and the second processing point from each other until the influence substantially disappears. As a result, the first groove M1 and the second groove M2 can each be reliably formed as independent grooves in the wafer 20. The first groove M1 and the second groove M2 can be solidly formed so that their bottoms are clearly defined. Therefore, with the laser processing apparatus 1 and the laser processing method for branching the laser light L into a plurality of branched laser light components and irradiating the wafer 20 with the branched laser light components, it is possible to satisfactorily form the first groove M1 and the second groove M2 in the wafer 20 along the line 15.

[0071] In the present embodiment, the second groove M2 overlaps the end portion of the first groove M1 in the width direction of the first groove M1. The compound groove MH including the first groove M1 and the second groove M2 can be formed in the wafer 20. Such a compound groove MH can effectively induce the crack 9 extending from the modified region 11 formed, for example, inside the wafer 20.

[0072] In the present embodiment, the distance d23 in the X direction is larger than the pulse pitch of the laser light L. In this case, since the occurrence of a situation in which the distance between the first processing position and the second processing position is too short and accordingly their mutual interference becomes significant is suppressed, it is possible to satisfactorily form the first groove M1 and the second groove M2 in the wafer 20.

[0073] In the present embodiment, the distance d12 between a plurality of first machining positions in the X direction is larger than the pulse pitch of the laser light L. In this case, since it is possible to suppress the occurrence of a situation in which the distance d12 between the plurality of first machining positions is too short and accordingly their influence on each other becomes significant, it is possible to satisfactorily form the first groove M1.

[0074] In the present embodiment, the distance d12 between the plurality of first machining positions in the X direction is smaller than the distance d23. In this case, the distance between the plurality of first machining positions can be set to a range where they interfere with each other, so that a HAZ (heat-affected zone) generated around the formed first groove M1 can be suppressed.

[0075] In the present embodiment, the distance d34 between a plurality of second machining positions in the X direction is larger than the pulse pitch of the laser light L. In this case, since it is possible to suppress the occurrence of a situation in which the distance between the plurality of second machining positions is too short and accordingly their influence on each other becomes significant, it is possible to satisfactorily form the second groove M2.

[0076] In the present embodiment, the distance d34 between the plurality of second machining positions in the X direction is smaller than the distance d23. In this case, the distance between the plurality of second machining positions can be set to a range where they interfere with each other, so that the HAZ generated around the formed second groove M2 can be suppressed.

[0077] In the present embodiment, the branching pattern branches the laser light L into two first branched laser light components LA and two second branched laser light components LB. Since the energy at each of the focusing points SA1, SA2, SB1, and SB2 can be reduced, the HAZ can be suppressed in this case.

[0078] In the present embodiment, the branching pattern branches the laser light L such that the focusing points SA1, SA2, SB1, and SB2 are aligned in a one-dimensional array along the line 15. Therefore, it is possible to form the narrow compound groove MH in the wafer 20. Furthermore, the bending strength of the wafer 20 can be improved.

[0079] Even if there is no deviation in the position of the modified region 11 from the position of the line 15 in the Y direction, a problem may occur in the formation of a single V-groove M0 due to the meandering of the crack 9 extending from the modified region 11. In this regard, the problem can be suppressed in the present embodiment because the compound groove MH is formed as a W-groove.

[0080] Furthermore, in the present embodiment, the branching pattern may divide the laser light L into three first branched laser light components LA forming the first groove M1 and three second branched laser light components LB forming the second groove M2. In this case, for example, as shown in Fig. 14, in the X direction along line 15 from one side of line 15 to the other side, the focusing points SA1, SA2, and SA3 of the three first branched laser light components are aligned, and then the focusing points SB1, SB2, and SB3 of the three second branched laser light components are aligned. In the Y direction, which corresponds to the width direction of a groove to be formed, the positions of the focusing points SA1, SA2, and SA3 of the first branched laser light components are the same. In the Y direction, the positions of the focusing points SB1, SB2, and SB3 of the second branched laser light components are the same. Since the energy at each of the focusing points SA1, SA2, SA3, SB1, SB2, and SB3 can be further reduced, the HAZ can be further suppressed according to such a branching pattern.

[0081] In the present embodiment, the branching pattern displayed on the display unit 132A of the spatial light modulator 132 can branch the laser light L into one or more (here, two) first branched laser light components LA for forming the first groove M1, one or more (here, two) second branched laser light components LB for forming the second groove M2, and one or more (here, two) third branched laser light components for forming the third groove M3. In this case, for example, as shown in Fig. As shown in Figure 15(a), in the X direction along line 15 from one side of line 15 to the other, the focusing points SA1 and SA2 of the first two branched laser light components are aligned, the focusing points SB1 and SB2 of the second two branched laser light components are aligned, and then the focusing points SC1 and SC2 of the third two branched laser light components are aligned. In the Y direction, which corresponds to the width direction of a groove to be formed, the positions of the focusing points SC1 and SC2 of the third branched laser light components are the same.

[0082] In the X direction, the distance between the position of the focusing point SB2 of the second branched laser light and the position of the focusing point SC1 of the third branched laser light, which are adjacent to each other, is defined as a distance d45. The distance d45 is equal to the distance d23. In the Y direction, the distance between each of the positions of the focusing points SB1 and SB2 of the second branched laser light components and each of the positions of the focusing points SC1 and SC2 of the third branched laser light components is defined as a distance Y2. The distance Y2 is equal to the distance Y1. The distance d45 is greater than the distance Y1. The distance d45 is greater than the pulse pitch of the laser light L. The distance d56 between the positions of the focusing points SC1 and SC2 of a plurality of third branched laser light components in the X direction along the line 15 is greater than the pulse pitch of the laser light L. The distance d56 is smaller than the distance d23.The branching pattern branches the laser light L such that the focusing points SA1, SA2, SB1, SB2, SC1, and SC2 are aligned in a one-dimensional array along line 15. In this case, as shown in . Fig. 15(b), a wide compound groove MH1 can be formed.

[0083] The first groove M1 formed by the first branched laser light LA, the second groove M2 formed by the second branched laser light LB, and the third groove M3 formed by the third branched laser light constitute the compound groove MH1. The compound groove MH1 is a groove with a shape that has three valley portions and two peak portions on the bottom in a cross-sectional view perpendicular to line 15. Each of the first groove M1, the second groove M2, and the third groove M3 is a V-groove in a cross-sectional view perpendicular to line 15. The second groove M2 overlaps an end portion of 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 their end portions in the Y direction overlap each other. The first groove M1 and the second groove M2 are provided so that their circumferential edges are in contact with each other.A Y-direction end portion of the third groove M3 overlaps a Y-direction end portion of the second groove M2. In other words, the second groove M2 and the third groove M3 extend in the X direction, while their Y-direction end portions overlap each other. The second groove M2 and the third groove M3 are provided so that their circumferential edges are in contact with each other. The first groove M1, the second groove M2, and the third groove M3 are grooves with the same depth and width.

[0084] The compound groove MH1 is provided on the functional element layer 22 side of the wafer 20, so that the bottom of the first groove M1, the bottom of the second groove M2, and the bottom of the third groove M3 all reach the semiconductor substrate 21. The bottom of the first groove M1 and the bottom of the second groove M2 reach the functional element layer 22 side of the semiconductor substrate 21. The overlapping end portions of the first groove M1, the second groove M2, and the third groove M3 (two peak portions on the bottom side of the compound groove MH1) reach the semiconductor substrate 21 side of the functional element layer 22.

[0085] Incidentally, in the present embodiment, as shown in Fig. 16(a), a compound groove MH2 may be provided on the functional element layer 22 side of the wafer 20. The compound groove MH2 is a W-groove formed by the first groove M1 and the second groove M2. The second groove M2 overlaps an end portion of the first groove M1 in the Y direction. The compound groove MH2 is provided so that both the bottom of the first groove M1 and the bottom of the second groove M2 reach the semiconductor substrate 21. The overlapping end portions of the first groove M1 and the second groove M2 (a peak portion on the bottom of the compound groove MH) reach the semiconductor substrate 21 side of the functional element layer 22. The bottoms of the first groove M1 and the second groove M2 of the compound groove MH2 are separated from each other in the Y direction compared to the compound groove MH (see Fig. 8(b)). Even with such a composite groove MH2, the same effect as with the composite groove MH is achieved.

[0086] In the present embodiment, as shown in Fig. 16(b), a compound groove MH3 may be provided on the functional element layer 22 side of the wafer 20. The compound groove MH3 is a W-groove formed by the first groove M1 and the second groove M2. The second groove M2 overlaps an end portion of the first groove M1 in the Y direction. The first groove M1 is a deeper groove than the second groove M2. The compound groove MH3 is provided so that the bottom of the first groove M1 reaches the semiconductor substrate 21 and the bottom of the second groove M2 does not reach the semiconductor substrate 21. That is, either the bottom of the first groove M1 or the bottom of the second groove M2 is provided to reach the semiconductor substrate 21. The overlapping end portions of the first groove M1 and the second groove M2 (a mountain portion on the bottom of the compound groove MH3) reach the semiconductor substrate 21 on the side of the functional element layer 22.

[0087] Even with such a composite groove MH3, the same effect as with the composite groove MH is achieved. It is possible to further enhance the crack induction effect 9 by the first groove M1 and the second groove M2.

[0088] In the present embodiment, as shown in Fig. 16(c), a compound groove MH4 may be provided on the functional element layer 22 side of the wafer 20. The compound groove MH4 is a W-groove formed by the first groove M1 and the second groove M2. The second groove M2 overlaps an end portion of the first groove M1 in the Y direction. The first groove M1 is a deeper groove than the second groove M2. The compound groove MH4 is provided so that the bottom of the first groove M1 reaches the semiconductor substrate 21 and the bottom of the second groove M2 does not reach the semiconductor substrate 21. That is, either the bottom of the first groove M1 or the bottom of the second groove M2 is provided to reach the semiconductor substrate 21. The overlapping end portions of the first groove M1 and the second groove M2 (a mountain portion on the bottom of the composite groove MH4) reach the surface side of the functional element layer 22.The bottoms of the first groove M1 and the second groove M2 of the composite groove MH4 are separated from each other in the Y direction compared to the composite groove MH3 (see . Fig. 16(b)). Even with such a composite groove MH4, the same effect as with the composite groove MH is achieved. It is possible to further enhance the crack induction effect 9 by the first groove M1 and the second groove M2.

[0089] In the present embodiment, as shown in Fig. 17(a), a compound groove MH5 may be provided on the functional element layer 22 side of the wafer 20. The compound groove MH5 is a W-groove formed by the first groove M1 and the second groove M2. The second groove M2 overlaps an end portion of the first groove M1 in the Y direction. The first groove M1 and the second groove M2 are grooves with the same depth and width. The compound groove MH5 is provided so that both the bottom of the first groove M1 and the bottom of the second groove M2 do not reach the semiconductor substrate 21. Even with such a compound groove MH5, the same effect as that of the compound groove MH is achieved. It is possible to reduce the depth of the first groove M1 and the second groove M2.

[0090] In the present embodiment, as shown in Fig. As shown in Figure 17(b), a compound groove MH6 may be provided on the functional element layer 22 side of the wafer 20. The compound groove MH6 is a W-groove formed by the first groove M1 and the second groove M2. The second groove M2 overlaps an end portion of the first groove M1 in the Y direction. The first groove M1 and the second groove M2 are grooves with the same depth and width. The compound groove MH6 is provided so that both the bottom of the first groove M1 and the bottom of the second groove M2 do not reach the semiconductor substrate 21. The overlapping end portions of the first groove M1 and the second groove M2 (a mountain portion on the bottom of the composite groove MH6) reach the surface side of the functional element layer 22. The bottoms of the first groove M1 and the second groove M2 of the composite groove MH6 are separated from each other in the Y direction compared to the composite groove MH5 (see Fig. 17(a)). Even with such a composite groove MH6, the same effect as with the composite groove MH is achieved. It is possible to further enhance the crack induction effect 9 by the first groove M1 and the second groove M2.

[0091] Fig. Figure 18 is a graph showing the test results for evaluating the deviation of the crack 9 when the compound groove MH is formed. In the graph, the amount of excavation is the position of the bottom of the compound groove MH and the amount of penetration into the semiconductor substrate 21 from the front surface 21a of the semiconductor substrate 21. The amount of displacement corresponds to the amount of deviation between the formed modified region 11 and the center of the compound groove MH in the width direction of the compound groove MH. "○" means that the end of the crack 9 is caused to reach the inner surface of the first groove M1 or the inner surface of the second groove M2. "Deviation" means that the crack 9 deviates from the compound groove MH and 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 the test shown in the graph, the groove width is 12 μm. As shown in Fig. As shown in Figure 18, it can be seen from the composite groove MH that even if the formed modified region 11 deviates from the composite groove MH in the width direction, the crack induction effect 9 can be achieved as long as the amount of deviation is within a predetermined range. Furthermore, it can be seen that the greater the amount of excavation, the more effectively the crack induction effect 9 can be achieved in terms of the amount of displacement.

[0092] In the groove processing of the present embodiment, the first groove M1 and the second groove M2 are simultaneously formed by the first branched laser light LA ​​and the second branched laser light LB, which are formed by branching the laser light L with the branching pattern displayed on the display unit 132A of the spatial light modulator 132. However, the present invention is not limited to this. The groove processing may include a step of forming the first groove M1 in the wafer 20 along the line 15 by irradiating the wafer 20 with the laser light L, and a step of forming the second groove M2 in the wafer 20 along the line 15 by irradiating the wafer 20 with the laser light L.

[0093] For example, as in Fig. 19(a), the surface layer of the wafer 20 on the side of the functional element layer 22 is removed by condensing the laser light L onto the functional element layer 22 by the condenser unit 34, thereby forming the first groove M1. Thereafter, as shown in Fig. 19(b), the surface layer of the wafer 20 on the side of the functional element layer 22 can be removed by removing at least one of the condenser unit 34 and the carrier unit 2 (see Fig. 2) is moved by a predetermined amount in the Y direction (width direction of the first groove M1) and the laser light L is condensed by the condenser unit 34 onto the functional element layer 22, thereby forming the second groove M2.

[0094] In addition, for example, as in Fig. As shown in Figure 20(a), the surface layer of the wafer 20 on the side of the functional element layer 22 is removed by condensing the laser light L onto the functional element layer 22 through the condenser unit 34, thereby forming the first groove M1. Thereafter, the surface layer of the wafer 20 on the side of the functional element layer 22 can be removed by displaying a shift pattern on the display unit 132A of the spatial light modulator 132 to shift the focusing point of the laser light L by a predetermined amount in the Y direction (width direction of the first groove M1), and the laser light L is condensed onto the functional element layer 22 by the condenser unit 34, as shown in Figure 20(a). Fig. 20(b), thereby forming the second groove M2.

[0095] In the present embodiment, the step of forming the modified region 11 may include a step of correcting the formation position of the modified region 11 to coincide with the center position when the amount of deviation (hereinafter referred to as "width direction deviation amount") of the formation position of the modified region 11 from the center position of the composite groove MH in the width direction of the composite groove MH is greater than half the groove width. For example, the following, in Fig. 21 steps shown are included.

[0096] In the step of forming the modified region 11, first, in the Y direction, which corresponds to the width direction of the compound groove MH, the formation position of the modified region 11 (position where the modified region 11 is to be formed) is aligned with the center position of the compound groove MH, which is a reference processing position (step S11). The center position of the compound groove MH can be verified, for example, from an image captured by the infrared imaging unit 108B (see Fig. 1). Subsequently, the modified region 11 is formed along the line 15 as described above (step S12).

[0097] When the formation of the modified region 11 along the entire line 15 extending in the X direction is completed (YES in step S13), it is determined that the laser processing is completed, and the processing is terminated, and the process proceeds to the next step. On the other hand, when the formation of the modified region 11 along the entire line 15 extending in the X direction is not completed (NO in step S13), the formation position of the modified region 11 is moved by a predetermined distance (distance corresponding to the distance between the two lines 15 adjacent to each other) in the Y direction, and at least one of the laser processing head H and the carrier unit 102 (see Fig. 1) is moved in the Y direction (step S14).

[0098] It is determined whether the amount of deviation in the width direction of the modified region 11 is greater than half the value (1 / 2 value) of the groove width (step S15). The amount of deviation in the width direction of the modified region 11 can be checked, for example, based on an image captured by the infrared imaging unit 108B (see Fig. 1). If YES in the above step S15, the formation position of the modified area 11 in the Y direction is corrected (step S16). In the above step S16, the position of at least one of the laser processing head H and the carrier unit 102 (see Fig. 1) in the Y direction so that the formation position of the modified region 11 coincides with the center position of the compound groove MH in the Y direction. If NO in step S15 above or after step S16 above, the process returns to the processing of step S12. According to the laser processing method according to the above modification example, it is possible to correct the formation position of the modified region 11 by using the groove width. [Modification examples]

[0099] One aspect of the present invention is not limited to the embodiment described above.

[0100] In the above-described embodiment, the laser processing device 1 for performing the groove processing and the laser processing device 100 for forming the modified region 11 within the wafer 20 are separate devices, but the present invention is not limited thereto. For example, a device for groove processing and a device for forming the modified region 11 may be integrated by connecting them with a transfer arm. For example, as in the embodiment shown in Fig. 22, a table 202 may be used jointly to mount an optical system 210A corresponding to a processing device for groove processing and an optical system 210B corresponding to a processing device for forming the modified region 11. Furthermore, such a laser processing device 200 includes a moving mechanism 205 for moving the table (support unit) 202 and a moving mechanism 206 for moving the optical systems 210A and 210B.

[0101] The laser processing method using the laser processing device 100 and the laser processing device 1 is not limited to the method described above and may be, for example, the following method. That is, first, as shown in Fig. 23(a), the wafer 20 is prepared. The protective film 29 is applied to the surface of the wafer 20 on the side of the functional element layer 22. Subsequently, the wafer 20 is, as shown in Fig. 23(b), adsorbed in the laser processing apparatus 1 and supported by the carrier unit 2, and then the groove processing is performed on the wafer 20. During the groove processing, the control unit 5 controls the irradiation unit 3 so that the street 23 of the wafer 20 is irradiated with the laser light L along the line 15, and the control unit 5 controls the carrier unit 2 so that the laser light L moves relatively along the line 15. As a result, the surface layer of the street 23 on the wafer 20 is removed to form the compound groove MH.

[0102] Then, as in Fig. 23(c), the wafer 20 is removed from the carrier unit 2 and the protective film 29 is removed, for example, with a chemical solution. As shown in Fig. As shown in Figure 24(a), the abrasive 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, the modified region 11 is formed inside the wafer 20 along the line 15 by irradiating the wafer 20 with the laser light L0 along the line 15. Here, after the wafer 20 is adsorbed and supported by the carrier unit 102, a scan in which the wafer 20 is irradiated with the laser light L0 from the back surface 21b, aligned with the focusing point of the laser light L0 within the semiconductor substrate 21, is repeated several times by changing the position of the focusing point in the Z direction. As a result, a plurality of rows of modified regions 11 are formed in the Z direction within the semiconductor substrate 21, and the cracks 9 extend from the modified regions 11.

[0103] Then, as in Fig. 24(b), the back surface 21b of the semiconductor substrate 21 of the wafer 20 was ground with a grinder to make the wafer 20 thin to a desired thickness, removing the modified region 11. As shown in Fig. As shown in Fig. 24(c), the transparent dicing tape DC provided with the ring frame RF is attached to the back surface 21b of the semiconductor substrate 21 of the wafer 20. Then, as shown in Fig.As shown in Figure 25, by expanding the attached transparent dicing tape DC with an expander (not shown), the crack 9 is expanded in the thickness direction of the wafer 20 along each line 15, thereby cutting the wafer 20 along the line 15. As a result, the wafer 20 is diced into chips corresponding to the respective functional elements 22a, and a plurality of chips T1 are obtained. In the laser processing method according to such a modification example, the wafer 20 can be thinned by grinding after forming the compound groove MH.

[0104] In the above-described embodiment and modification example, the imaging unit 4 may include a camera for acquiring image data of the road of the wafer 20 using visible light. In the above-described embodiment and modification example, information for controlling the irradiation conditions (laser ON / OFF control, laser power) of the laser light L in each area of ​​the road 23 can be created using an image of at least the surface layer of the road 23 after cutting and a perspective image using infrared rays, and the groove processing can be controlled based on this information. In the above-described embodiment and modification example, the surface layer of the road 23 can be removed by scanning the road 23 with the laser light L multiple times.In the above-described embodiment and modification example, only the carrier unit 102 can be controlled so that the laser light L0 moves relatively along each line 15, or only the laser processing head H can be controlled so that the laser light L0 moves relatively along each line 15, or both the carrier unit 102 and the laser processing head H can be controlled so that the laser light L0 moves relatively along each line 15. In the above-described embodiment and modification example, only the carrier unit 2 can be controlled so that the laser light L moves relatively along each road 23, or only the irradiation unit 3 can be controlled so that the laser light L moves relatively along each road 23, or both the carrier unit 2 and the irradiation unit 3 can be controlled so that the laser light L moves relatively along each road 23.

[0105] In the above-described embodiment and modification example, the energy at each focusing point of a plurality of branched laser light components obtained by branching the laser light L can be equal, or it can be made stronger or weaker by changing the branching ratio. In the above-described embodiment and modification example, the positions of the focusing points SA1, SA2, and SA3 of the first branched laser light components in the Y direction are equal, but at least one of the positions of the focusing points SA1, SA2, and SA3 of the first branched laser light components in the Y direction can be shifted in the Y direction within a range smaller than the distance Y1.The positions of the Y-direction focusing points SB1, SB2, and SB3 of the second branched laser light components are the same, but at least one of the Y-direction focusing points SB1, SB2, and SB3 of the second branched laser light components can be shifted in the Y direction within a range smaller than the distance Y1. The Y-direction focusing points SC1 and SC2 of the third branched laser light components are the same, but at least one of the Y-direction focusing points SC1 and SC2 of the third branched laser light components can be shifted in the Y direction within a range smaller than the distance Y1 or the distance Y2. The distance Y1 can be the same as or different from the distance Y2.

[0106] In the above-described embodiment and modification example, both the bottom of the first groove M1 and the bottom of the second groove M2 may be arranged on the front surface 21a of the semiconductor substrate 21. In the above-described embodiment and modification example, the number of branches into which the laser light L is branched by the branching pattern is not limited and may be a plurality. In the above-described embodiment and modification example, the end of the crack 9 may reach the inner surface of the first groove M1 or the inner surface of the second groove M2 when the modified region 11 is formed, or the end of the crack 9 may reach the inner surface of the first groove M1 or the inner surface of the second groove M2 in a step after the modified region 11 is formed.For example, in the above-described embodiment and modification example, “the end of the crack 9 reaches the inner surface of the first groove M1 or the inner surface of the second groove M2” 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 a part of the line 15 as long as the processing for the purpose of manufacturing the wafer 20 into chips is performed in a subsequent step. List of reference symbols

[0107] 1: Laser processing device, 2: Support unit, 9: Crack, 11: Modified area, 15: Line, 20: Wafer (object), 21: Semiconductor substrate (substrate), 22: Functional element layer, 29: Protective film, 31: Laser light source, 34: Condenser unit, 100: Laser processing device, 132: Spatial light modulator, 132A: Display unit, 200: Laser processing device, 202: Stage (support unit), d12: Pitch, d23: Pitch, d34: Pitch, d45: Pitch, d56: Pitch, DC: Transparent dicing tape, L: Laser light, L0: Laser light, LA: First branched laser light, LB: Second branched laser light, M1: First groove (groove), M2: Second groove (groove), M3: Third groove (Groove), MH, MH1, MH2, MH3, MH4, MH5, MH6: Compound groove, SA1, SA2, SA3: Focusing point of the first branched laser light, SB1, SB2, SB3: Focusing point of the second branched laser light, SC1, SC2: Focusing point of the third branched laser light, Y1, Y2: Pitch. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2007-173475

[0002] JP 2017-011040

[0002]

Claims

[1] A laser processing apparatus for forming a groove in an object along a line by irradiating the object with laser light along the line, the apparatus comprising: a support unit configured to support the object; a laser light source configured to emit the laser light; a spatial light modulator including a display unit onto which the laser light emitted from the laser light source is incident and configured to modulate the laser light according to a modulation pattern displayed on the display unit; and a condenser unit configured to condense the laser light modulated by the spatial light modulator onto the object supported by the carrier unit, wherein the modulation pattern includes a branching pattern for branching the laser light into at least one or more first branched laser light components to form a first groove and one or more second branched laser light components to form a second groove, and a distance between a position of a focusing point of the first branched laser light and a position of a focusing point of the second branched laser light, which are adjacent to each other in a direction along the line, is greater than a distance between a position of a focusing point of the first branched laser light and a position of a focusing point of the second branched laser light in a width direction of the first groove and the second groove. [2] The laser processing apparatus according to claim 1, wherein the second groove overlaps an end portion of the first groove in the width direction of the first groove. [3] The laser processing apparatus according to claim 2, wherein the branching pattern branches the laser light into one or more third branched laser light components to form a third groove in addition to the first branched laser light and the second branched laser light, the third groove overlapping an end portion of the second groove in the width direction of the second groove. [4] The laser processing apparatus according to any one of claims 1 to 3, wherein the distance between the position of the focusing point of the first branched laser light and the position of the focusing point of the second branched laser light, which are adjacent to each other in the direction along the line, is larger than a pulse pitch of the laser light. [5] The laser processing apparatus according to any one of claims 1 to 4, wherein a distance between the positions of the focusing points of the plurality of first branched laser light components in the direction along the line is larger than a pulse pitch of the laser light. [6] The laser processing apparatus according to any one of claims 1 to 5, wherein a distance between positions of focusing points of the plurality of first branched laser light components in the direction along the line is smaller than the distance between the position of the focusing point of the first branched laser light and the position of the focusing point of the second branched laser light which are adjacent to each other in the direction along the line. [7] The laser processing apparatus according to any one of claims 1 to 6, wherein a distance between the positions of the focusing points of the plurality of second branched laser light components in the direction along the line is larger than a pulse pitch of the laser light. [8] The laser processing apparatus according to any one of claims 1 to 7, wherein a distance between positions of focusing points of the plurality of second branched laser light components in the direction along the line is smaller than the distance between the position of the focusing point of the first branched laser light and the position of the focusing point of the second branched laser light which are adjacent to each other in the direction along the line. [9] The laser processing apparatus according to any one of claims 1 to 8, wherein the branching pattern divides the laser light into the two first branched laser light components and the two second branched laser light components. [10] The laser processing apparatus according to any one of claims 1 to 9, wherein the branching pattern divides the laser light into the three first branched laser light components and the three second branched laser light components. [11] The laser processing apparatus according to any one of claims 1 to 10, wherein the branching pattern branches the laser light so that the focusing points are aligned in a one-dimensional array along the line. [12] A laser machining method for forming a groove in an object along a line by irradiating the object with laser light along the line, the method comprising: a step of emitting the laser light, causing the emitted laser light to impinge on a display unit of a spatial light modulator, modulating the laser light according to a modulation pattern displayed on the display unit, and condensing the modulated laser light onto the object, wherein the modulation pattern includes a branching pattern for branching the laser light into at least one or more first branched laser light components to form a first groove and one or more second branched laser light components to form a second groove, and a distance between a position of a focusing point of the first branched laser light and a position of a focusing point of the second branched laser light, which are adjacent to each other in a direction along the line, is greater than a distance between a position of a focusing point of the first branched laser light and a position of a focusing point of the second branched laser light in a width direction of the first groove and the second groove.

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