Laser processing device and laser processing method

Abstract

To provide a laser processing device and a laser processing method that can more reliably determine whether a structure such as a metal pattern has been removed from a dividing line.SOLUTION: A laser processing device includes a second processing point imaging device 51A that images a processing point P2A of second laser light L2 during laser processing, a light intensity acquisition unit that acquires a second light intensity at the processing point P2A from second image data D2A captured by the second processing point imaging device 51A, a reference light intensity memory unit that stores a first reference light intensity that indicates that the laser processing at the processing point P2A is in a completed state, and a determination unit that compares the second light intensity with the first reference light intensity to determine whether the processing point P2A is in a completed state.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a laser processing apparatus and a laser processing method for removing a structure such as a metal pattern provided on a parting line. [Background technology]

[0002] Wafers containing various devices such as semiconductor devices and electronic components are divided into individual chips by dividing them along grid-like dividing lines. Known methods for dividing such wafers include dividing them using a high-speed rotating blade, and dividing them by irradiating the inside of the wafer with a laser to form a modified layer and then applying an external force using an expander or the like.

[0003] Incidentally, a wafer may have a low-dielectric-constant insulating film (low-k film) made of a glassy material laminated on a base material such as silicon carbide. Also, a predetermined metal pattern may be formed on the wafer along the dividing line. If such structures such as low-dielectric-constant insulating films or metal patterns remain on the dividing line, processing defects are likely to occur when dividing the wafer using the above-mentioned method. Therefore, Patent Document 1 discloses a laser processing device that performs laser processing (laser ablation processing) to remove structures by irradiating laser light along the dividing line. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-120820 Summary of the Invention [Problem to be solved by the invention]

[0005] In the laser processing device of Patent Document 1, the position of the plasma is identified by capturing an image of the plasma generated at the processing point of the laser light during laser processing, and the processing position of the laser processing is corrected based on the positional relationship between the identified plasma position and the intended processing position. However, with the laser processing device of Patent Document 1, it is difficult to estimate whether or not a structure remains on the parting line. [Means for solving the problem]

[0006] A laser processing apparatus that solves the above problem includes a work table that supports a wafer having a dividing line and a laser head that irradiates a laser beam, and performs laser processing to remove structures on the surface of the dividing line by irradiating the laser beam from the laser head while the work table and the laser head are moved relative to each other along the dividing line. The laser processing apparatus includes a processing point imaging device that images a processing point of the laser beam during laser processing, a light amount acquisition unit that acquires the light amount at the processing point from the image captured by the processing point imaging device, a reference light amount storage unit that stores a reference light amount that indicates that laser processing at the processing point is complete, and a determination unit that compares the light amount with the reference light amount to determine whether the processing point is in the complete state.

[0007] A laser processing method that solves the above problem removes structures on the surface of the dividing line by irradiating the laser beam from the laser head while moving a work table that supports a wafer having a dividing line and a laser head that irradiates the laser beam relative to the dividing line. The laser processing method includes the steps of: capturing an image of a processing point of the laser beam during laser processing; acquiring the light intensity at the processing point from the captured image; and comparing the light intensity with a reference light intensity that indicates that laser processing at the processing point is complete to determine whether the processing point is in the completed state. [Effects of the Invention]

[0008] According to the present invention, it is possible to more reliably determine whether or not a structure has been removed from a dividing line. [Brief explanation of the drawings]

[0009] [Figure 1] In the first embodiment, FIG. 1(a) is a plan view that schematically shows a wafer to be processed, and FIG. 1(b) is an enlarged view of the vicinity of the parting line on the wafer. [Figure 2] FIG. 2 is a diagram showing a schematic configuration of an embodiment of the laser processing device in the first embodiment. [Figure 3] FIG. 3 is a perspective view that schematically shows the edge cutting process and the hollowing process in the forward process in the first embodiment. [Figure 4] FIG. 4 is a diagram showing a schematic diagram of the optical system of the laser head involved in forward processing and the irradiation position of the laser light on the wafer in the first embodiment. [Figure 5] FIG. 5 is a diagram showing a schematic diagram of the optical system of the laser head involved in the backward machining and the irradiation position of the laser light on the wafer in the first embodiment. [Figure 6] FIG. 6 is a block diagram showing the electrical configuration of the laser processing device in the first embodiment. [Figure 7] FIG. 7 is a diagram schematically showing an example of an image based on second image data captured during forward processing using five second laser beams aligned in the X direction in each embodiment. [Figure 8] FIG. 8 is a flowchart showing an embodiment of the laser processing method in the first embodiment. [Figure 9] FIG. 9 is a flowchart showing an example of a procedure for the determination process in the first embodiment. [Figure 10] FIG. 10 is a diagram schematically showing another example of an image based on second image data captured during forward processing using five second laser beams aligned in the X direction in the second embodiment. [Figure 11]FIG. 11 is a diagram schematically showing another example of an image based on second image data captured during forward processing using five second laser beams aligned in the X direction in the second embodiment. [Figure 12] In the second embodiment, FIGS. 12(a) and 12(b) are diagrams showing an example of the position at which the step of adjusting the laser processing conditions is incorporated into one embodiment of the laser processing method. [Figure 13] FIG. 13 is a diagram schematically showing a part of the optical system of the laser head in the modified example. DETAILED DESCRIPTION OF THE INVENTION

[0010] (First embodiment) A first embodiment of a laser processing apparatus and a laser processing method will be described with reference to FIGS.

[0011] As shown in Figure 1(a), a wafer 10 is divided into individual chips by being divided along grid-like dividing lines 11. The wafer 10 is composed of a laminate in which a low-k film and a functional film that forms a circuit are laminated on a base material such as silicon. The surface on which the low-k film and functional film are laminated is called the device surface 10a, and the surface opposite the device surface 10a is called the back surface 10b (see Figure 2).

[0012] As shown in Figure 1(b), wafer 10 has devices 14 provided in each region defined by dividing lines 11. Also, metal patterns 17 made of a metal material such as copper are formed in some regions of dividing lines 11. Wafer 10 is subjected to laser ablation processing by irradiating a laser along dividing lines 11 to remove structures such as the low-k film and metal patterns 17 on the surface and expose the underlying material.

[0013] In the following description, the planar directions in which the device surface 10a and back surface 10b of the wafer 10 extend are referred to as the XY direction, one direction in the XY direction is referred to as the X direction, and the direction perpendicular to the X direction in the XY direction is referred to as the Y direction. The X direction is the direction in which the parting lines to be processed in each process extend. Regarding the X direction, the direction indicated by the arrow in the figure may be referred to as the +X direction, and the direction opposite to the +X direction as the -X direction. The direction perpendicular to the XY direction is referred to as the Z direction. The Z direction is the thickness direction of the wafer 10.

[0014] (Laser processing equipment) 2, the laser ablation processing is performed by a laser processing apparatus 20. The laser processing apparatus 20 has a work table 21, a laser head 22, a relative movement mechanism 23, an alignment imaging device 24, and a control device 25.

[0015] The work table 21 supports the back surface 10b of the wafer 10 via a dicing tape (not shown). The work table 21 is configured to be movable in the X direction and rotatable around the Z direction as a rotation axis by a relative movement mechanism 23. The movement speed of the work table 21 in the X direction is called the laser processing speed.

[0016] The laser head 22 is configured to be movable in the Y and Z directions by a relative movement mechanism 23. The laser head 22 has a first laser light source 31, a second laser light source 32, a first condenser lens 33, and a pair of second condenser lenses 34A and 34B. The laser head 22 irradiates the device surface 10a of the wafer 10 with a first laser light L1 formed by the first laser light source 31 and the first condenser lens 33. The laser head 22 selectively irradiates the device surface 10a of the wafer 10 with second laser light L2A and L2B formed by the second laser light source 32 and the second condenser lenses 34A and 34B.

[0017] The irradiation positions of the laser beams L1, L2A, and L2B in the X and Y directions are adjusted by the relative movement of the work table 21 and the laser head 22. The irradiation positions of the laser beams L1, L2A, and L2B in the Z direction are adjusted by the movement of the laser head 22 in the Z direction or the movement of the condenser lenses 33, 34A, and 34B in the Z direction.

[0018] The alignment imaging device 24 is attached to the laser head 22. The alignment imaging device 24 captures an image of an alignment mark provided on the wafer 10. The alignment imaging device 24 outputs image data indicating the captured image to the control device 25.

[0019] The control device 25 controls various control objects such as the relative movement mechanism 23 and the alignment imaging device 24, thereby controlling the overall operation of the laser processing device 20. The laser processing device 20 performs forward and backward laser ablation processing.

[0020] The forward path processing is laser ablation processing in which the processing direction, which is the direction in which the first laser beam L1 and the second laser beam L2A advance at the parting line 11, is the −X direction. In the forward path processing, the first laser beam L1 and the second laser beam L2A are irradiated onto the wafer 10 while the work table 21 is moved in the +X direction.

[0021] The return path processing is laser ablation processing in which the processing direction, which is the direction in which the first laser beam L1 and the second laser beam L2B advance at the parting line 11, is the +X direction. In the return path processing, the first laser beam L1 and the second laser beam L2B are irradiated onto the wafer 10 while the work table 21 is moved in the −X direction.

[0022] (About laser ablation processing) Laser ablation processing (hereinafter simply referred to as laser processing) performed by laser processing apparatus 20 will be briefly described with reference to Fig. 3. Here, laser ablation processing will be described using forward path processing as an example.

[0023] As shown in FIG. 3, the laser processing apparatus 20 performs laser processing, which includes edge cutting and hollow cutting, in parallel. In the edge cutting, the laser processing apparatus 20 forms a pair of edge cutting grooves 18 parallel to the X direction using a pair of first laser beams L1. In the hollow cutting, the laser processing apparatus 20 forms a hollow cut groove 19 between the pair of edge cutting grooves 18 using multiple second laser beams L2A aligned in the X direction. By forming this hollow cut groove 19, structures such as the low-k film and the metal pattern 17 are removed. Note that, although FIG. 3 shows the hollow cutting using two second laser beams L2A, the hollow cutting may be performed using three or more second laser beams L2A. In this embodiment, the laser processing apparatus 20 performs the hollow cutting using five second laser beams L2A.

[0024] (laser head) The laser head 22 will be described in more detail with reference to Figures 4 and 5. Figure 4 is a diagram schematically showing the configuration of the laser head 22 during forward processing. Figure 5 is a diagram schematically showing the configuration of the laser head 22 during backward processing. Note that the description will basically be given with reference to Figure 4, but will also be given with reference to Figure 5 depending on the situation.

[0025] As shown in FIG. 4, the laser head 22 includes the above-mentioned laser light sources 31, 32 and focusing lenses 33, 34A, 34B, as well as a first light forming element 35, a beam splitter 36, a second light forming element 37, a beam splitter 38, a branching optical element 39, a connection switching element 40, and a beam splitter 41A.

[0026] The first laser light source 31 emits laser light L11 used for edge cutting processing to the first light forming element 35. The output (wavelength, pulse width, repetition frequency, etc.) of the laser light L11 is set to an output suitable for edge cutting processing. For example, the wavelength of the laser light L11 is set to 355 nm.

[0027] The first light forming element 35 is configured by, for example, a diffractive optical element (DOE). The first light forming element 35 forms a pair of first laser beams L1 used for edge cutting processing from the laser beam L11. The first light forming element 35 emits the pair of first laser beams L1 to the beam splitter 36.

[0028] The beam splitter 36 reflects the pair of first laser beams L1 toward the first condenser lens 33. The first condenser lens 33 condenses each of the pair of first laser beams L1 onto the division line 11 of the processing object. As a result, a pair of processing points P1 spaced apart in the Y direction are formed on the division line 11. The distance between the pair of processing points P1 in the Y direction can be adjusted by rotating the first light forming element 35 around the optical axis of the laser beam L11.

[0029] The second laser light source 32 emits laser light L21 used for hollow cutting to the second light forming element 37. The output (wavelength, pulse width, repetition frequency, etc.) of the laser light L21 is set to an output suitable for hollow cutting. For example, the wavelength of the laser light L21 is set to 355 nm.

[0030] The second light forming element 37 is composed of, for example, a diffractive optical element and a mask. The second light forming element 37 forms the second laser light L2 used for hollowing out from the laser light L21. The second laser light L2 forms a processing spot of a predetermined shape, such as a rectangular, elliptical, or oval shape, between a pair of edge-cutting grooves 18 on the wafer 10. The width of the processing spot in the Y direction is adjusted by rotating the second light forming element 37 around the optical axis of the laser light L21. Specifically, the width of the processing spot in the Y direction is adjusted to match the distance between the pair of edge-cutting grooves 18 in the Y direction. The second light forming element 37 emits the second laser light L2 to the beam splitter 38. The beam splitter 38 reflects the second laser light L2 toward the branching optical element 39.

[0031] The branching optical element 39 branches the second laser light L2. The branching optical element 39 is configured by appropriately combining various optical components such as a diffractive optical element, a refractive optical element, and a prism. The branching optical element 39 outputs each of the branched second laser light L2 to the connection switching element 40. The branching optical element 39 of this embodiment branches the second laser light L2 into five beams.

[0032] The connection switching element 40 guides the split second laser light L2 to either the beam splitter 41A or the second focusing lens 34B. For example, the connection switching element 40 is configured with an optical switch. Alternatively, for example, the connection switching element 40 is configured by appropriately combining various optical components such as a λ / 2 plate, a polarizing beam splitter, a half mirror (beam splitter), and a shutter.

[0033] When forward processing is performed, the connection switching element 40 guides the second laser light L2 to the beam splitter 41A. The beam splitter 41A reflects each second laser light L2 from the connection switching element 40 toward the second condenser lens 34A. The second condenser lens 34A is disposed in the +X direction relative to the first condenser lens 33. The second condenser lens 34A condenses each second laser light L2 onto the dividing line 11 of the processing target on the +X direction side of the first laser light L1.

[0034] 5, when backward processing is performed, the connection switching element 40 guides the second laser beam L2 to the second condenser lens 34B. The second condenser lens 34B is disposed on the −X direction side of the first condenser lens 33. The second condenser lens 34B condenses each second laser beam L2 onto the dividing line 11 of the processing target on the −X direction side of the first laser beam L1.

[0035] The laser head 22 also includes an illumination light source 45 and beam splitters 46, 47A, and 47B. The laser head 22 also includes a first imaging lens 48 and a first processing point imaging device 49. The laser head 22 also includes second imaging lenses 50A and 50B and second processing point imaging devices 51A and 51B.

[0036] The illumination light source 45 emits illumination light L3 toward the beam splitters 46, 47A, and 47B. It is preferable that the illumination light L3 be light in a wavelength range (approximately 430 nm) close to the wavelength range (approximately 355 nm) of the laser beams L11 and L21 in order to suppress the effects of aberration in the first condenser lens 33 and the second condenser lenses 34A and 34B. Note that the illumination light source 45 stops emitting illumination light L3 during laser processing.

[0037] The illumination light L3 emitted from the illumination light source 45 toward the beam splitter 46 is incident on the first condenser lens 33 through the beam splitter 46. The first condenser lens 33 condenses the illumination light L3 onto the surface of the wafer 10. As a result, the portion irradiated with the first laser light L1 is illuminated by the illumination light L3.

[0038] Illumination light L3 emitted from illumination light source 45 toward beam splitter 47A enters second condenser lens 34A through beam splitter 41A. Second condenser lens 34A condenses illumination light L3 onto the surface of wafer 10. As a result, the area irradiated with second laser light L2 emitted from second condenser lens 34A is illuminated by illumination light L3.

[0039] Illumination light L3 emitted from illumination light source 45 toward beam splitter 47B is incident on second condenser lens 34B via beam splitter 38, branching optical element 39, and connection switching element 40. Second condenser lens 34B condenses illumination light L3 onto the surface of wafer 10. As a result, the area irradiated with second laser light L2 emitted from second condenser lens 34B is illuminated by illumination light L3.

[0040] In laser head 22, a first optical path 51 is formed by an optical path from first laser light source 31 to first condenser lens 33 and an optical path from illumination light source 45 to first condenser lens 33. During laser processing, first optical path 51 guides first laser light L1 to first condenser lens 33. Also, during laser processing, first plasma light PL1 generated for each pair of processing points P1 enters first optical path 51 from first condenser lens 33.

[0041] First plasma light PL1 is light based on plasma generated at a pair of processing points P1 by laser processing. First plasma light PL1 enters beam splitter 46 via beam splitter 36. Beam splitter 46 reflects first plasma light PL1 to first branched optical path 53 branching from first optical path 51.

[0042] First imaging lens 48 and first processing-point imaging device 49 are disposed on first branched optical path 53. First imaging lens 48 images first plasma light PL1 from beam splitter 46 onto first processing-point imaging device 49. First processing-point imaging device 49 images first plasma light PL1 imaged by first imaging lens 48. First processing-point imaging device 49 outputs first image data D1 obtained by imaging first plasma light PL1 to control device 25.

[0043] In the laser head 22, the optical path from the second laser light source 32 to the second condenser lens 34A and the optical path from the illumination light source 45 to the second condenser lens 34A form a second optical path 52A.

[0044] During laser processing, second optical path 52A guides second laser beam L2 to second condenser lens 34A. Second plasma light PL2A generated at each processing point P2A enters second optical path 52A from second condenser lens 34A.

[0045] Second plasma light PL2A is light based on plasma generated at processing point P2A by laser processing. Second plasma light PL2A passes through beam splitter 41A and enters beam splitter 47A. Beam splitter 47A reflects second plasma light PL2A to second branched optical path 54A branching from second optical path 52A.

[0046] Second imaging lens 50A and second processing-point imaging device 51A are disposed on second branched optical path 54A. Second imaging lens 50A images second plasma light PL2A from beam splitter 47A onto second processing-point imaging device 51A. Second processing-point imaging device 51A images the second plasma light PL2A imaged by second imaging lens 50A. Second processing-point imaging device 51A outputs second image data D2A obtained by imaging the second plasma light PL2A to control device 25.

[0047] In the laser head 22, the optical path from the second laser light source 32 to the second condenser lens 34B and the optical path from the illumination light source 45 to the second condenser lens 34B form a second branched optical path 54B.

[0048] 5, during laser processing, second branched optical path 54B guides second laser beam L2 to second condenser lens 34B. Second plasma light PL2B generated at each processing point P2B enters second optical path 52B from second condenser lens 34B.

[0049] Second plasma light PL2B is light based on plasma generated at processing point P2B by laser processing. Second plasma light PL2B passes through connection switching element 40, branching optical element 39, and beam splitter 38, and enters beam splitter 47B. Beam splitter 47B reflects second plasma light PL2B to second branched optical path 54B, which branches from second optical path 52B.

[0050] Second imaging lens 50B and second processing-point imaging device 51B are disposed on second branched optical path 54B. Second imaging lens 50B images second plasma light PL2B from beam splitter 47B onto second processing-point imaging device 51B. Second processing-point imaging device 51B images the second plasma light PL2B imaged by second imaging lens 50B. Second processing-point imaging device 51B outputs second image data D2B obtained by imaging the second plasma light PL2B to control device 25.

[0051] (Control device) The controller 25 can be realized, for example, by circuitry, i.e., one or more dedicated hardware circuits such as ASICs, one or more processing circuits operating according to a computer program (software), or a combination of both. The processing circuitry includes a CPU and memory (such as ROM and RAM) that stores programs executed by the CPU. Memory, i.e., computer-readable media, includes any available media that can be accessed by a general-purpose or special-purpose computer.

[0052] As shown in Figure 6, the control device 25 is electrically connected to the relative movement mechanism 23, the alignment imaging device 24, the first laser light source 31, the second laser light source 32, the connection switching element 40, the illumination light source 45, the first processing point imaging device 49, and the second processing point imaging devices 51A and 51B.

[0053] In addition, an input unit 55 and an output unit 56 are electrically connected to the control device 25. The input unit 55 receives various pieces of information input to the laser processing device 20. The input unit 55 is composed of, for example, a mouse, a keyboard, a touch panel, an input interface, etc. For example, an operator inputs laser processing conditions through the input unit 55. Specifically, the operator inputs the output of the laser beams L11 and L21, the laser processing speed, etc. as the laser processing conditions. Also, for example, the operator instructs the laser processing device 20 to start laser processing, etc. through the input unit 55. The output unit 56 is composed of, for example, a monitor that displays various pieces of information.

[0054] The control device 25 has, as functional units that function by executing various programs, an alignment detection unit 61, a laser processing control unit 62, an imaging control unit 63, a light amount acquisition unit 64, and a judgment unit 65. The control device 25 also has, as storage units that store various types of information, a reference light amount storage unit 66 and a judgment result storage unit 67.

[0055] The alignment detection unit 61 executes an alignment detection process to detect the position of each dividing line 11 on the wafer 10. For example, in the alignment detection process, the alignment detection unit 61 controls the relative movement mechanism 23 to adjust the position of the alignment imager 24 relative to the alignment marks provided on the wafer 10. Next, the alignment detection unit 61 photographs the alignment marks using the alignment imager 24 and obtains image data representing the photographed image. Then, the alignment detection unit 61 detects the position of each dividing line 11 by performing image processing on the image data.

[0056] The laser processing control unit 62 performs laser processing along each division line 11. The laser processing control unit 62 holds the laser processing conditions and the position of each division line 11 based on the alignment detection process. The laser processing control unit 62 performs laser processing based on the laser processing conditions, the position of each division line 11, and various information. In laser processing, the laser processing control unit 62 controls the relative movement mechanism 23, the first laser light source 31, the second laser light source 32, and the connection switching element 40.

[0057] The imaging control unit 63 controls the first processing point imaging device 49 and the second processing point imaging devices 51A and 51B to obtain image data of the processing points P1, P2A and P2B. Specifically, in forward processing, the imaging control unit 63 repeatedly captures the first plasma light PL1 with a short exposure time by the first processing-point imaging device 49 and the second plasma light PL2A with a short exposure time by the second processing-point imaging device 51A at a predetermined imaging cycle. As a result, the imaging control unit 63 repeatedly acquires first image data D1 in which a pair of processing points P1 are captured and second image data D2A in which each processing point P2A is captured.

[0058] Furthermore, in the return path processing, the imaging control unit 63 repeatedly captures the first plasma light PL1 with a short exposure time by the first processing-point imaging device 49 and the second plasma light PL2B with a short exposure time by the second processing-point imaging device 51B at a predetermined imaging cycle. As a result, the imaging control unit 63 repeatedly acquires first image data D1 in which the pair of processing points P1 are captured and second image data D2B in which each processing point P2B is captured.

[0059] The light amount acquiring unit 64 acquires the light amount of each of the processing points P1, P2A, and P2B based on the image data acquired by the imaging control unit 63. The light amount acquiring unit 64 acquires the first light amount at the processing point P1 by performing image processing or image analysis on the first image data D1.

[0060] The light amount acquisition unit 64 acquires the second light amount at the processing point P2A by performing image processing and image analysis on the second image data D2A during forward processing. In the backward machining, the light amount acquisition unit 64 acquires the second light amount at the machining point P2B by image processing and image analysis of the second image data D2B.

[0061] The second light amount is a value indicating the brightness at the processing points P2A and P2B. For example, the second light amount may be a value indicating the brightness, such as luminous energy, luminance, the total value of RGB values, or a value derived from a combination of these.

[0062] The determination unit 65 determines the processing state at the processing points P2A and P2B based on the second light intensity and the reference light intensity stored in the reference light intensity storage unit 66. A first reference light intensity is stored in the reference light intensity storage unit 66. The first reference light intensity is a light intensity that indicates that processing is complete.

[0063] The determination unit 65 determines that a processing point is in a completed state when the second light amount at the processing point is equal to or less than the first reference light amount, and determines that a processing point is in an incomplete state when the second light amount at the processing point is greater than the first reference light amount.

[0064] The first reference light amount is a light amount set based on a test processing performed in advance. For example, the first reference light amount is a light amount obtained by performing laser processing on a test piece in which a metal pattern 17 identical to or similar to that of the wafer 10 is formed on a base material in which a low-k film is laminated, like the wafer 10. Also, for example, the first reference light amount is a light amount obtained by performing test laser processing on the parting line 11 of the wafer 10.

[0065] FIG. 7 shows an example of an image based on second image data D2A captured during forward processing using five second laser beams L2A aligned in the X direction. As shown in FIG. 7, image 70 captures processing points P22, P23, P24, and P25 following processing point P21, the leftmost processing point preceding the processing point in the processing direction (-X direction). In image 70, areas corresponding to processing points P21, P22, P23, P24, and P25 are defined relative to reference position RP. These areas are set by an operator via input unit 55. Light amount acquisition unit 64 acquires the light amount of the area corresponding to processing point P25 as the second light amount. Processing point P25 is the processing point located at the end of the processing direction (-X direction). Note that image 70 shown in FIG. 7 is an image captured when hollowing is performed properly, i.e., when the light amount gradually decreases from processing point P21 until the light amount at processing point P25 becomes equal to or less than the first reference light amount.

[0066] The determination unit 65 determines the processing state for each position on the dividing line 11 of the processing target based on the second light amount corresponding to the processing point P25. Specifically, when the determination unit 65 determines that the processing point P25 is in a completed state, the determination unit 65 associates the position on the dividing line 11 corresponding to the processing point P25 with the completed state and stores the association in the determination result storage unit 67. When the determination unit 65 determines that the processing point P25 is in an incomplete state, the determination unit 65 associates the position on the dividing line 11 corresponding to the processing point P25 with the incomplete state and stores the association in the determination result storage unit 67. The position on the dividing line 11 associated with the incomplete state is the incomplete position. The information stored by the determination unit 65 in the determination result storage unit 67 is referred to as determination result information. Note that in the image based on the second image data D2B obtained during the return path processing, the processing points P21, P22, P23, P24, and P25 are lined up in order from the right.

[0067] (Laser processing method) An example of a laser processing method using the laser processing device 20 will be described with reference to FIGS.

[0068] 8, in one example of the laser processing method, first, a reference light amount is acquired (step S101). In this step, the first reference light amount is stored in the reference light amount storage unit 66.

[0069] Next, alignment detection (step S102) is performed. In this step, the alignment detection unit 61 of the control device 25 executes the above-mentioned alignment detection process. As a result, the control device 25 detects the position of each dividing line 11 on the wafer 10.

[0070] Next, alignment (step S103) is performed. In this step, the laser processing control section 62 of the control device 25 aligns the laser head 22 with the parting line 11 to be processed.

[0071] Specifically, the laser processing control unit 62 rotates the work table 21 about the Z direction as the rotation axis so that the parting line 11 to be processed extends in the X direction. When performing forward processing, the laser processing control unit 62 moves the work table 21 in the X and Y directions so that the laser head 22 is positioned above the end of the parting line 11 in the +X direction. When performing backward processing, the laser processing control unit 62 moves the work table 21 in the X and Y directions so that the laser head 22 is positioned above the end of the parting line 11 in the -X direction.

[0072] Next, setting of the second condenser lens is performed (step S104). In this step, the laser processing control unit 62 sets the lens that emits the second laser light L2 by driving the connection switching element 40. Specifically, when performing forward path processing, the laser processing control unit 62 sets the lens that emits the second laser light L2 to the second condenser lens 34A. When performing backward path processing, the laser processing control unit 62 sets the lens that emits the second laser light L2 to the second condenser lens 34B.

[0073] When step S104 is completed, the laser processing control unit 62 starts laser processing by driving the first laser light source 31 and the second laser light source 32 (step S105). When laser processing starts, the laser processing control unit 62 drives the relative movement mechanism 23 to move the work table 21 in the X direction, thereby performing relative movement between the work table 21 and the laser head 22 (step S106). Specifically, when performing forward processing, the laser processing control unit 62 moves the work table 21 in the +X direction until the laser head 22 is positioned above the end of the parting line 11 in the -X direction. When performing backward processing, the laser processing control unit 62 moves the work table 21 in the -X direction until the laser head 22 is positioned above the end of the parting line 11 in the +X direction.

[0074] Furthermore, when laser processing is started, a determination process is performed in parallel with step S106 (step S107). 9, in the determination process, first, image data of an image of a processing point is acquired (step S107-1). In this step, when forward processing is being performed, the imaging control unit 63 of the control device 25 acquires second image data D2A by driving the second processing point imaging device 51A. When backward processing is being performed, the imaging control unit 63 acquires second image data D2B by driving the second processing point imaging device 51B.

[0075] Next, the light amount is acquired (step S107-2). In this step, the light amount acquisition unit 64 of the control device 25 acquires the second light amount based on the second image data D2A or D2B.

[0076] Next, the machining state is determined (step S107-3). In this step, the determination unit 65 of the control device 25 determines the machining state by comparing the second light amount with the first reference light amount. Then, the determination unit 65 associates the position on the division line 11 corresponding to the machining point P25 with the determination result and stores the association result in the determination result storage unit 67 (step S107-4).

[0077] This determination process is repeated for each imaging period of the second processing point imaging devices 51A, 51B until the outward processing or the return processing for the dividing line 11 to be processed is completed. As a result, the determination result information is stored in the determination result storage unit 67.

[0078] 8, when the relative movement between the work table 21 and the laser head 22 is completed, the laser processing control unit 62 determines whether or not laser processing of the parting line 11 of the processing target is completed (step S108). In this step, the laser processing control unit 62 determines whether or not processing is completed by referring to the determination result storage unit 67. Specifically, the laser processing control unit 62 determines that processing is not completed when an incomplete position is stored in the determination result storage unit 67 for the immediately preceding laser processing.

[0079] If the processing is not completed (step S108: NO), the laser processing control unit 62 performs re-processing by executing steps S104 to S108 again. In this re-processing, if there is an incomplete position in the forward path processing, the laser processing control unit 62 performs return path processing on the same dividing line 11. Furthermore, if there is an incomplete position in the return path processing, the laser processing control unit 62 performs forward path processing on the same dividing line 11. Furthermore, the laser processing control unit 62 starts laser processing without driving the first laser light source 31 and the second laser light source 32, and drives the second laser light source 32 so that the second laser light is irradiated only around the incomplete position.

[0080] On the other hand, if processing is complete (step S108: YES), the laser processing control unit 62 determines whether or not there is a dividing line 11 to be processed next on the wafer 10. If there is a dividing line 11 to be processed next (step S109: YES), the laser processing control unit 62 executes steps S103 to S108 for the dividing line 11 to be processed next. If there is no dividing line 11 to be processed next (step S109: NO), the laser processing control unit 62 ends the laser processing.

[0081] The operation and effects of the first embodiment will be described. (1-1) The laser processing apparatus 20 includes second processing point imaging devices 51A, 51B that image processing points P2A, P2B of the second laser light L2A, L2B during laser processing, a light intensity acquisition unit 64 that acquires a second light intensity at the processing points P2A, P2B from second image data D2A, D2B captured by the second processing point imaging devices 51A, 51B, a reference light intensity memory unit 66 that stores a first reference light intensity indicating that the laser processing at the processing points P2A, P2B is in a completed state, and a judgment unit 65 that compares the second light intensity with the first reference light intensity to judge whether the processing points P2A, P2B are in a completed state.

[0082] Here, at processing points P2A and P2B, the more structures remain on parting line 11, particularly the more metal patterns 17 there are, the more intense the plasma generated. Therefore, the brighter the second plasma lights PL2A and PL2B become as the number of structures remaining on parting line 11 increases.

[0083] According to the above-described configuration, whether or not laser processing has been completed at each position on the parting line 11 of the processing target is determined based on the result of comparing the second light intensity with the first reference light intensity. As a result, it is possible to more reliably determine whether or not structures such as the metal pattern 17 on the parting line 11 have been removed.

[0084] (1-2) The laser processing device 20 includes a determination result storage unit 67 that stores incomplete positions, which are positions on the division line 11 and are positions of the processing points P2A and P2B that are determined by the determination unit 65 to be in an incomplete state.

[0085] According to this configuration, the parting line 11 to be processed can be reprocessed based on the incomplete position stored in the determination result storage unit 67. As a result, structures such as the metal pattern 17 on the parting line 11 can be removed more reliably.

[0086] (1-3) The laser processing device 20 is configured to automatically perform reprocessing based on the incomplete position of the immediately preceding laser processing stored in the determination result storage unit 67. This makes it possible to more reliably remove structures such as the metal pattern 17 from each division line 11 when the laser processing of each division line 11 is completed.

[0087] (Second embodiment) A second embodiment of the laser processing apparatus and laser processing method will be described with reference to Figures 7 and 10 to 12. The laser processing apparatus and laser processing method of the second embodiment have the same main configuration as the laser processing apparatus and laser processing method of the first embodiment. Therefore, in the second embodiment, only the parts that are different from the first embodiment will be described in detail, and the parts that are the same as those in the first embodiment will be denoted by the same reference numerals and will not be described in detail again.

[0088] The determination unit 65 determines the processing state at each of the processing points P21 to P25 shown in Fig. 7 based on the first reference light amount and the second reference light amount stored in the reference light amount storage unit 66. The second reference light amount is a light amount greater than the first reference light amount and is a light amount for distinguishing the processing state. The second reference light amount is a light amount set based on test processing performed in advance.

[0089] When the second light amount is greater than the first reference light amount and greater than the second reference light amount, the determining unit 65 determines that the processing state is in the initial processing state. The initial processing state is a processing state in which there are many structures, such as the metal pattern 17, to be removed at the processing point.

[0090] When the second light amount is greater than the first reference light amount and equal to or less than the second reference light amount, the determining unit 65 determines that the processing state is in a later processing state. The later processing state is a processing state in which there are few structures, such as the metal pattern 17, to be removed at the processing point.

[0091] The determination unit 65 stores information relating the position on the dividing line 11 corresponding to the processing point P25 and the determination results of the processing states at the processing points P21 to P25 as determination result information in the determination result storage unit 67. In other words, this determination result information is information including the transition of the processing states at the processing points P21 to P25.

[0092] 10 and 11 show other examples of images based on second image data D2A captured during forward path processing using five second laser beams L2A aligned in the X direction. 10, an image 75 shows an image in which all of the processing points P21 to P25 are determined to be in the initial processing state. That is, the image 75 shows a case in which the output of the laser beam L21 emitted by the second laser light source 32 is small or the laser processing speed is high.

[0093] 11, an image 76 shows an image in which the processing point P21 is determined to be in the initial processing state and the processing points P22 to P25 are determined to be in the completed state. That is, the image 76 shows a case in which the output of the laser beam L21 is high or the laser processing speed is slow.

[0094] In such a case, it is preferable that the laser processing conditions are adjusted based on the judgment result information. The adjustment of the laser processing conditions may be performed by the laser processing control unit 62. In this case, the laser processing control unit 62 adjusts the output of the laser beam L21 and the laser processing speed based on the amount of change in the second light intensity at the processing points P21 to P25, the difference between the second light intensity and the first reference light intensity at the processing point P25, etc. The laser processing control unit 62 adjusts the laser processing conditions so that the processing point P24 is judged to be in the later processing state and the processing point P25 is judged to be in the completed state.

[0095] As shown in Fig. 12(a), the adjustment of the laser processing conditions (step S110) may be performed in parallel with the relative movement (step S106) and the determination process (step S107). Alternatively, as shown in Fig. 12(b), the adjustment of the laser processing conditions (step S110) may be performed immediately after the completion of the relative movement (step S106) and the determination process (step S107).

[0096] The laser processing conditions may also be adjusted by an operator. In this case, for example, when the laser processing apparatus 20 completes forward or backward processing of the parting line 11 of the processing target, it interrupts laser processing and notifies the operator of the determination result information by outputting determination result information to the output unit 56. The operator adjusts the laser processing conditions by inputting the output power of the laser light L21 and the laser processing speed through the input unit 55 based on the determination result information output to the output unit 56. Then, the operator instructs the laser processing apparatus 20 to resume laser processing through the input unit 55.

[0097] The operation and effects of the second embodiment will be described. (2-1) The reference light intensity storage unit 66 stores a first reference light intensity indicating that processing is complete and a second reference light intensity indicating that laser processing is in progress. The determination unit 65 compares the first and second reference light intensities with the second light intensity to determine the processing state at the processing point P25. This makes it possible to accurately determine the processing state at each position on the parting line 11. As a result, it is possible to adjust the laser processing conditions to conditions that ensure the removal of structures such as the metal pattern 17.

[0098] (2-2) The laser processing device 20 irradiates the wafer 10 with a second laser beam that forms a plurality of processing points P21 to P25 aligned along the dividing line 11. The second processing point imaging devices 51A, 51B capture images of the plurality of processing points P21 to P25 during laser processing. The light amount acquisition unit 64 acquires the light amount at each of the plurality of processing points P21 to P25. The determination unit 65 compares the light amount at each of the plurality of processing points P21 to P25 with the first reference light amount and the second reference light amount to determine the processing state at each of the plurality of processing points.

[0099] The determination unit 65 stores the determination result information including the transition of the processing state at the processing points P21 to P25 in the determination result storage unit 67. This makes it possible to adjust the laser processing conditions so that the transition of the processing state at the processing points P21 to P25 becomes a desired transition.

[0100] (2-3) When the determination unit 65 determines that the machining point P25 located at the rear end in the machining direction among the plurality of machining points P21 to P25 is in an incomplete state, the determination unit 65 stores the position on the division line 11 corresponding to the machining point P25 located at the rear end as an incomplete position in the determination result storage unit 67. As a result, even if the machining state is determined for each of the plurality of machining points P21 to P25, the same effect as that described in (1-2) above can be obtained.

[0101] (Third embodiment) A third embodiment of the laser processing apparatus and the laser processing method will be described. The laser processing apparatus and the laser processing method of the third embodiment have the same main configuration as the laser processing apparatus and the laser processing method of the first embodiment. Therefore, in the second embodiment, parts that are different from the first embodiment will be described in detail, and parts that are the same as those in the first embodiment will be denoted by the same reference numerals and will not be described in detail.

[0102] Here, in order to determine the processing state at each position on the division line 11 with higher accuracy, it is desirable that the second light amount of the processing point located at the rearmost position in the processing direction can be acquired with high accuracy.

[0103] 7, each position on the dividing line 11 is laser-processed in order by processing points P21 to P25 aligned in the X direction, so that the more rearward the processing point is in the processing direction, the more advanced the removal of structures such as the metal pattern 17. Furthermore, when comparing processing points located on the front side and processing points located on the rear side in the processing direction, the amount of light obtained from the processing points located on the rear side is smaller for the same exposure time.

[0104] Based on this, in the third embodiment, the condition for obtaining the second light amount is set according to the position of the processing point in the processing direction. Specifically, for example, for processing points P21 to P24 located on the front side in the processing direction, the light amount acquiring unit 64 acquires the second light amount under first acquisition conditions using predetermined image processing, image analysis, etc. On the other hand, for processing point P25 located at the rear end in the processing direction, the light amount acquiring unit 64 acquires the second light amount under second acquisition conditions using image processing, image analysis, etc. that obtain a light amount higher than that under the first acquisition conditions.

[0105] Further, for example, the imaging control unit 63 controls the second processing point imaging devices 51A and 51B to repeatedly acquire front side second image data obtained with a predetermined exposure time for processing points P21 to P24 located on the front side in the processing direction, while the imaging control unit 63 repeatedly acquires rear end second image data obtained with an exposure time longer than the predetermined exposure time for processing point P25 located at the rear end in the processing direction.

[0106] Then, the light amount acquisition unit 64 acquires the second light amounts of the processing points P21 to P24 using the front second image data as the first acquisition condition, and acquires the second light amount of the processing point P25 using the rear second image data as the second acquisition condition.

[0107] The operation and effects of the third embodiment will be described. (3-1) The light amount acquisition unit 64 acquires the second light amount of the processing point located at the front of the multiple processing points in the processing direction under a first acquisition condition, and acquires the second light amount of the processing point located at the rearmost of the multiple processing points in the processing direction under a second acquisition condition that obtains a light amount greater than that obtained under the first acquisition condition.

[0108] This makes it possible to determine with higher accuracy the processing state at each position on the parting line 11. As a result, it is possible to more reliably determine whether or not structures such as the metal pattern 17 on the parting line 11 have been removed.

[0109] The first to third embodiments can be modified as follows: The first to third embodiments and the following modifications can be combined with each other within the scope of technical compatibility.

[0110] In the first embodiment, reprocessing was automatically performed based on the judgment result information of the immediately preceding laser processing. However, the laser processing device 20 may be configured to output the judgment result information to the output unit 56 without performing reprocessing. With this configuration, the operator can adjust the output power of the laser light L21, the laser processing speed, etc. based on the judgment result information before performing laser processing on another wafer 10 of the same design. As a result, the frequency of reprocessing is reduced, and the cycle time of laser processing on the wafer 10 can be improved.

[0111] In the first embodiment, the re-processing was performed continuously based on the judgment result information of the immediately preceding laser processing for the dividing lines 11 to be processed. However, this is not limited to this, and the laser processing device 20 may perform laser processing on all of the dividing lines 11 and then perform re-processing based on the judgment result information.

[0112] In the second embodiment, the reference light intensity storage unit 66 stores a first reference light intensity and a second reference light intensity as reference light intensities. Alternatively, the reference light intensity storage unit 66 may store a third reference light intensity, which is greater than the first reference light intensity and less than the second reference light intensity, as a light intensity for further distinguishing the processing state. This configuration allows the processing state at each processing point to be determined with higher accuracy.

[0113] 13 , in laser head 22, a first bandpass filter 81 may be provided in first branched optical path 53. First bandpass filter 81 is provided between first imaging lens 48 and first processing-point imaging device 49. First bandpass filter 81 transmits light in the wavelength range of first plasma light PL1, out of the light collected by first imaging lens 48, and outputs the light to first processing-point imaging device 49.

[0114] Furthermore, second bandpass filters 82A and 82B may be provided in second branched optical paths 54A and 54B in laser head 22. Second bandpass filters 82A and 82B are provided between second imaging lenses 50A and 50B and second processing-point imaging devices 51A and 51B. Second bandpass filters 82A and 82B emit light in the wavelength ranges of second plasma lights PL2A and PL2B, which are included in the light reflected by beam splitters 47A and 47B, to second processing-point imaging devices 51A and 51B. [Explanation of symbols]

[0115] 10...wafer, 10a...device surface, 10b...back surface, 11...division line, 14...device, 17...metal pattern, 18...edge cutting groove, 19...core groove, 20...laser processing device, 21...work table, 22...laser head, 23...relative movement mechanism, 24...alignment imaging device, 25...control device, 31...first laser light source, 32...second laser light source, 33...first condenser lens, 34A, 34B...second condenser lens, 35...first light forming element, 36...beam splitter, 37...second light forming element, 38...beam splitter, 39...branching optical element, 40...connection switching element, 41A...beam splitter, 45...illumination light source , 46...beam splitter, 47A, 47B...beam splitter, 48...first imaging lens, 49...first processing point imaging device, 50A, 50B...second imaging lens, 51...first optical path, 51A, 51B...second processing point imaging device, 52A, 52B...second optical path, 53...first branched optical path, 54A, 54B...second branched optical path, 55...input section, 56...output section, 61...alignment detection section, 62...laser processing control section, 63...imaging control section, 64...light intensity acquisition section, 65...judgment section, 66...reference light intensity memory section, 67...judgment result memory section, 70, 75, 76...image, 81...first bandpass filter, 82A, 82B...second bandpass filter.

Claims

1. A laser processing apparatus comprising: a work table that supports a wafer having a dividing line formed thereon; and a laser head that irradiates a laser beam; the laser processing apparatus performs laser processing to remove a structure on a surface of the dividing line by irradiating the laser beam from the laser head while moving the work table and the laser head relatively along the dividing line, a processing point imaging device that images a processing point of the laser light during laser processing; a light amount acquiring unit that acquires the light amount at the processing point from the image captured by the processing point imaging device; a reference light amount storage unit that stores a reference light amount indicating that laser processing at the processing point is complete; a determination unit that compares the light amount with the reference light amount to determine whether the processing point is in the completed state or not. Laser processing equipment.

2. The determination unit stores a position on the division line that corresponds to the machining point determined to be in an incomplete state as an incomplete position in a determination result storage unit. The laser processing device according to claim 1 .

3. the reference light amount storage unit stores a first reference light amount that is the reference light amount and a second reference light amount that indicates that laser processing is in progress, The determination unit compares the first reference light amount and the second reference light amount with the light amount to determine the processing state at the processing point. The laser processing device according to claim 1 .

4. the laser head irradiates the laser light to form a plurality of processing points aligned along the dividing line, The processing point imaging device images the plurality of processing points during the laser processing, the light amount acquisition unit acquires the light amount at each of the plurality of processing points, The determination unit compares the light amount at each of the plurality of processing points with the reference light amount to determine the processing state at each of the plurality of processing points. The laser processing device according to claim 1 .

5. When the determination unit determines that the machining point located at the rear end in the machining direction among the plurality of machining points is in an incomplete state, the determination unit stores a position on the division line corresponding to the machining point located at the rear end as an incomplete position in a determination result storage unit. The laser processing device according to claim 4.

6. The light amount acquisition unit Acquire the light amount of a processing point located on the front side in the processing direction among the plurality of processing points under a first acquisition condition; The light amount of the processing point located at the rear end in the processing direction among the plurality of processing points is acquired under a second acquisition condition that obtains a light amount greater than that of the first acquisition condition. The laser processing device according to claim 4.

7. A laser processing method for removing a structure on a surface of a dividing line by irradiating the laser beam from a laser head while moving a work table supporting a wafer having dividing lines formed thereon and a laser head that irradiates the laser beam relative to each other along the dividing line, the method comprising: a step of capturing an image of a processing point of the laser light during laser processing; acquiring a light amount at the processing point from the captured image; and a step of comparing the light amount with a reference light amount indicating that the laser processing at the processing point is in the completed state to determine whether the processing point is in the completed state. Laser processing method.

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