Laser processing apparatus

Abstract

To cause a slit center to coincide with a sectional center of a laser beam.SOLUTION: A first control unit 52 adjusts a position in a W-axis direction of a slit 72 so that an output of a laser beam 200 is maximized. Accordingly, a center 73 of the slit 72 coincides with a sectional center 201 of the laser beam 200, and an end of the laser beam 200 is symmetrically intercepted by the slit 72. As a result thereof, an energy distribution of the laser beam 200 is symmetrical in the W-axis direction. Thus, split grooves with a prescribed depth and an appropriate shape can be formed on a wafer.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a laser processing apparatus.

Background Art

[0002] As disclosed in Patent Documents 1 and 2, a laser processing apparatus performs ablation processing in which a laser beam is irradiated onto a wafer to form a dividing groove extending in the X-axis direction on the surface of the wafer. Then, by performing a dividing process of dividing the wafer along the formed dividing groove, a fragmented chip is manufactured.

[0003] The width of this dividing groove is narrowed in order to produce many chips. Therefore, a slit having a narrow width corresponding to the formed dividing groove width is used. By irradiating the wafer with a laser beam whose width has been narrowed by passing through the narrow slit, a narrow dividing groove is formed.

[0004] In order to use such a slit, as disclosed in Patent Document 1, a plate (mask plate) in which the slit is formed is adopted. Also, as disclosed in Patent Document 2, a slit is formed by the interval between two plates.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, due to the aging deterioration of the laser oscillator, the optical axis of the laser beam may shift in the width direction of the slit. That is, the center of the slit and the cross-sectional center of the laser beam may not coincide. In this case, the splitting groove may not reach the predetermined depth due to insufficient power of the laser beam required for forming the splitting groove.

[0007] Therefore, an object of the present invention is to make the center of the slit coincide with the cross-sectional center of the laser beam in a laser processing apparatus.

Means for Solving the Problem

[0008] The laser processing apparatus (this laser processing apparatus) of the present invention is a laser processing apparatus that irradiates the upper surface of a wafer held by a chuck table with a laser beam to form a splitting groove in the wafer, and includes a laser oscillator that oscillates a laser beam, a slit that narrows the width of the laser beam oscillated from the laser oscillator to a width corresponding to the splitting groove in order to form a splitting groove having a predetermined width, a slit moving mechanism that moves the slit in a direction corresponding to the width direction of the splitting groove, and an adjustment unit that makes the center of the slit coincide with the cross-sectional center of the laser beam passing through the slit in the moving direction of the slit. A mirror that reflects the laser beam oscillated from the laser oscillator and irradiates the wafer held on the chuck table with the laser beam, and a camera that is disposed on the back side of the mirror and images the transmitted laser beam that is the laser beam oscillated from the laser oscillator and passed through the mirror. The adjustment unit includes a center recognition unit that recognizes the cross-section center of the transmitted laser beam based on the brightness and darkness of the pixels of the captured image obtained by imaging with the camera, and based on the cross-section center of the transmitted laser beam recognized by the center recognition unit, in the moving direction of the slit, a second control unit that controls the slit movement mechanism so that the cross-section center of the laser beam coincides with the center of the slit. It is provided with. This laser processing apparatus may be provided with a power meter that measures the output of the laser beam passing through the slit. The adjustment unit measures the output of the laser beam with the power meter while moving the slit in a direction corresponding to the width direction of the splitting groove by the slit moving mechanism, and determines that the center of the slit coincides with the cross-sectional center of the laser beam when the measured output is maximum, and may be provided with a first control unit that stops the movement of the slit.

Effect of the Invention

[0009] In this laser processing apparatus, the first control unit of the adjustment unit adjusts the position of the slit so that the output power of the laser beam is maximized, or the second control unit adjusts the position of the slit based on the center of the cross-section of the transmitted laser beam, thereby aligning the center of the cross-section of the laser beam with the center of the slit. As a result, it is possible to suppress the shortage of the power of the laser beam, so that a dividing groove having a predetermined depth can be formed in the wafer.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

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Figure 10

Embodiments for Carrying Out the Invention

[0011] The laser processing apparatus 10 shown in FIG. 1 is an apparatus for irradiating a laser beam onto the upper surface of a wafer 100 held by a chuck table 43 to form a dividing groove in the wafer 100.

[0012] The laser processing apparatus 10 includes a rectangular parallelepiped base 11, a standing wall portion 13 erected at one end of the base 11, and an adjustment unit 51 that controls each member of the laser processing apparatus 10.

[0013] On the upper surface of the base 11, a chuck table moving mechanism 14 for moving the chuck table 43 is provided. The chuck table moving mechanism 14 processes and feeds the chuck table 43 in the X-axis direction and indexes and feeds it in the Y-axis direction orthogonal to the X-axis direction.

[0014] The chuck table moving mechanism 14 includes a chuck table portion 40 having the chuck table 43, a Y-axis moving mechanism 20 that moves the chuck table 43 in the Y-axis direction, which is the index feed direction, and an X-axis moving mechanism 30 that moves the chuck table 43 in the X-axis direction, which is the processing feed direction. The chuck table 43 has a holding surface 44 for holding the wafer 100.

[0015] The Y-axis moving mechanism 20 moves the chuck table 43 in the Y-axis direction, which is parallel to the holding surface 44 and orthogonal to the X-axis direction, with respect to the laser processing mechanism 12.

[0016] The Y-axis moving mechanism 20 includes a pair of guide rails 23 extending in the Y-axis direction, a Y-axis table 24 placed on the guide rails 23, a ball screw 25 extending parallel to the guide rails 23, and a drive motor 26 that rotates the ball screw 25.

[0017] The pair of guide rails 23 are arranged on the upper surface of the base 11 in parallel in the Y-axis direction. The Y-axis table 24 is slidably installed on the pair of guide rails 23 along these guide rails 23. The X-axis moving mechanism 30 and the chuck table portion 40 are placed on the Y-axis table 24.

[0018] The ball screw 25 is screwed into a nut portion (not shown) provided on the Y-axis table 24. The drive motor 26 is connected to one end of the ball screw 25 and rotationally drives the ball screw 25. When the ball screw 25 is rotationally driven, the Y-axis table 24, the X-axis moving mechanism 30, and the chuck table portion 40 move in the Y-axis direction along the guide rail 23.

[0019] The X-axis moving mechanism 30 moves the chuck table 43 in the X-axis direction parallel to the holding surface 44 with respect to the laser processing mechanism 12.

[0020] The X-axis moving mechanism 30 includes a pair of guide rails 31 extending in the X-axis direction, an X-axis table 32 placed on the guide rails 31, a ball screw 33 extending parallel to the guide rails 31, and a drive motor 35 for rotating the ball screw 33.

[0021] The pair of guide rails 31 are arranged on the upper surface of the Y-axis table 24 in parallel with the X-axis direction. The X-axis table 32 is slidably installed on the pair of guide rails 31 along these guide rails 31. The chuck table portion 40 and the power meter 80 are placed on the X-axis table 32.

[0022] The ball screw 33 is screwed into a nut portion (not shown) provided on the X-axis table 32. The drive motor 35 is connected to one end of the ball screw 33 and rotationally drives the ball screw 33. When the ball screw 33 is rotationally driven, the X-axis table 32 and the chuck table portion 40 move in the processing feed direction (X-axis direction) along the guide rails 31.

[0023] The chuck table portion 40 is used to hold the wafer 100 as an example of the workpiece to be processed. As shown in FIG. 1, the wafer 100 is held by the chuck table portion 40 as a workpiece set 110 including the ring frame 111, the adhesive tape 113, and the wafer 100.

[0024] The chuck table unit 40 has a chuck table 43 for holding the wafer 100, a clamp unit 45 provided around the chuck table 43, and a θ table 47 for supporting the chuck table 43. The θ table 47 is rotatably provided on the upper surface of the X-axis table 32 within the XY plane.

[0025] The chuck table 43 is a member for holding the wafer 100. The chuck table 43 is formed in a disc shape and is provided on the θ table 47.

[0026] On the upper surface of the chuck table 43, a holding surface 44 made of a porous material is formed. By being communicated with a suction source (not shown), the holding surface 44 can suck and hold the wafer 100 in the workpiece set 110.

[0027] Four clamp units 45 are provided around the chuck table 43. The four clamp units 45 are driven by an air actuator (not shown) to sandwich and fix the ring frame 111 around the wafer 100 held on the chuck table 43 from four directions.

[0028] The vertical wall portion 13 of the laser processing apparatus 10 is erected behind the chuck table moving mechanism 14. A laser processing mechanism 12 is provided on the front surface of the vertical wall portion 13.

[0029] The laser processing mechanism 12 performs ablation processing on the wafer 100 held on the chuck table 43 by irradiating a laser beam. Specifically, the laser processing mechanism 12 forms split grooves along the split planned lines on the wafer 100 by irradiating a laser beam on the upper surface of the wafer 100.

[0030] The laser processing mechanism 12 has a processing head 18 for irradiating the wafer 100 with a laser beam, and an arm portion 17 for supporting the processing head 18.

[0031] The arm portion 17 protrudes from the vertical wall portion 13 in the direction of the chuck table moving mechanism 14. The processing head 18 is supported at the tip of the arm portion 17 so as to face the chuck table 43 of the chuck table portion 40 in the chuck table moving mechanism 14 or the power meter 80.

[0032] Inside the arm portion 17 and the processing head 18, an optical system of the laser processing mechanism 12 is provided.

[0033] As shown in FIGS. 1 and 2, the laser processing mechanism 12 includes, inside the arm portion 17, a laser oscillator 61 that oscillates a laser beam 200, a beam expander 62 for adjusting the laser beam oscillated from the laser oscillator 61 into parallel light, and an energy distribution corrector 63 for correcting the energy distribution of the laser beam 200.

[0034] Also, as shown in FIG. 2, the laser processing mechanism 12 has, inside the processing head 18, a mirror 65 that reflects the laser beam 200 and a condenser (condensing lens) 66 that condenses and outputs the laser beam 200.

[0035] The mirror 65 is used, for example, to reflect the laser beam 200 oscillated from the laser oscillator 61 and irradiate the wafer 100 held on the holding surface 44 (see FIG. 1) of the chuck table 43 with the laser beam 200. The mirror 65 is configured to transmit a part of the incident laser beam 200. Furthermore, the laser processing mechanism 12 includes a camera 67 on the back side of the mirror 65 on the side surface of the processing head 18.

[0036] The laser oscillator 61 is, for example, a solid-state laser light source. The laser oscillator 61 oscillates a laser beam 200 in the -Y direction within the arm portion 17. The energy distribution of the laser beam 200 can be approximated by a Gaussian distribution. Therefore, the energy of the laser beam 200 has a distribution as shown by the arrow 300 in the cross-section in the W-axis direction.

[0037] Here, the W-axis direction is perpendicular to the optical axis direction (propagation direction) of the laser beam 200 and is also perpendicular to the X-axis direction (the direction perpendicular to the plane of the paper in FIG. 2), which is the machining feed direction. Therefore, the W-axis direction coincides with the Z-axis direction within the arm portion 17 and coincides with the Y-axis direction within the machining head 18. Note that this W-axis direction corresponds to the width direction of the dividing groove formed in the wafer 100.

[0038] The energy distribution modifier 63 is disposed between the laser oscillator 61 and the mirror 65. The energy distribution modifier 63 corrects the energy distribution of the laser beam 200 in the W-axis direction by blocking a part of the laser beam 200.

[0039] The laser beam 200 that has passed through the energy distribution modifier 63 is reflected in the -Z direction by the mirror 65 within the machining head 18 and is guided to the condenser 66. The condenser 66 condenses the laser beam 200 and irradiates it in the -Z direction toward the outside of the machining head 18.

[0040] The laser beam 200 condensed by the condenser 66 is irradiated onto the wafer 100 on the chuck table 43 when machining the wafer 100 shown in FIG. 1. On the other hand, when correcting the energy distribution of the laser beam 200, as shown in FIG. 2, the laser beam 200 is irradiated onto the power meter 80.

[0041] Here, the configuration of the energy distribution corrector 63 will be described. The energy distribution corrector 63 corrects the energy distribution in the W-axis direction of the laser beam 200 into a Gaussian distribution with a flat skirt portion as indicated by the arrow 301. Thereby, the width (length in the W-axis direction) of the laser beam 200 is set.

[0042] As shown in FIG. 2, the energy distribution corrector 63 includes a slit plate 70 having a slit 72 disposed on the optical axis of the laser beam 200, and a slit moving mechanism 71 that moves the slit plate 70 in the W-axis direction.

[0043] As shown in FIGS. 2 and 3, the slit plate 70 is disposed within the arm portion 17 so as to be parallel to the ZX plane, which is a plane perpendicular to the optical axis of the laser beam 200 within the arm portion 17.

[0044] The slit 72 formed in the slit plate 70 is used to narrow the width of the laser beam 200 oscillated from the laser oscillator 61 to a width corresponding to the divided groove in order to form a divided groove of a predetermined width in the wafer 100. As shown in FIG. 3, the slit 72 has a rectangular shape and is defined by a first width HX in the X-axis direction and a second width HW in the W-axis direction corresponding to the divided groove.

[0045] The slit moving mechanism 71 moves the slit plate 70 having the slit 72 in the W-axis direction (Z-axis direction), which is the direction corresponding to the width direction of the divided groove formed in the wafer 100. Thereby, the slit moving mechanism 71 can align the center 73 of the slit 72 with the cross-sectional center 201 of the laser beam 200 passing through the slit 72 in the moving direction of the slit 72. This cross-sectional center 201 is the center of the cross-section in the ZX plane of the laser beam 200 incident on the slit 72 and corresponds to the apex (center of the optical axis) of the Gaussian distribution in the laser beam 200.

[0046] The power meter 80 shown in FIGS. 1 and 2 is disposed downstream of the condenser 66 in the traveling direction of the laser beam 200. The power meter 80 receives the irradiation of the laser beam 200 condensed by the condenser 66. Thereby, the power meter 80 measures the output (energy amount) of the laser beam 200 that has passed through the slit 72.

[0047] The adjustment unit 51 controls each member of the laser processing apparatus 10 to perform ablation processing on the wafer 100.

[0048] Further, the adjustment unit 51 controls the slit movement mechanism 71 shown in FIG. 2 to perform energy distribution correction of the laser beam 200 in order to adjust the shape of the dividing groove formed in the wafer 100 by ablation processing.

[0049] That is, the adjustment unit 51 controls the slit movement mechanism 71 to move the slit plate 70 having the slit 72 in the W-axis direction (Z-axis direction), so that in the moving direction of the slit 72, the center of the slit 72 and the cross-sectional center 201 of the laser beam 200 passing through the slit 72 are made to coincide.

[0050] When the center of the slit 72 coincides with the cross-sectional center 201 of the laser beam 200, the energy distribution of the laser beam 200 transmitted through the slit 72 vertically cuts the tail portion of the Gaussian distribution and has only the power necessary for forming the dividing groove. Thereby, the shape of the dividing groove formed in the wafer 100 can be made into an appropriate shape having a predetermined depth.

[0051] The operation of the energy distribution correction of the laser beam 200 by the adjustment unit 51 will be described below.

[0052] As shown in Fig. 2, the adjustment unit 51 includes a first control unit 52. While moving the slit 72 in the W-axis direction by the slit movement mechanism 71, the first control unit 52 measures the output of the laser beam 200 by the power meter 80, and when the measured output is maximum, determines that the center 73 of the slit 72 and the cross-sectional center 201 of the laser beam 200 coincide in the W-axis direction, and stops the movement of the slit 72.

[0053] Specifically, the first control unit 52 controls the slit movement mechanism 71 to continuously move the slit 72 of the slit plate 70 little by little in the W-axis direction, for example, in the -W direction and the +W direction respectively, while measuring the output of the laser beam 200 by the power meter 80. Then, when the output of the laser beam 200 measured by the power meter 80 becomes maximum, the first control unit 52 stops the position of the slit 72 in the W-axis direction. That is, the first control unit 52 adjusts the position of the slit 72 in the W-axis direction so that the output of the laser beam 200 becomes maximum.

[0054] For example, as shown in Fig. 3, the center 73 of the slit 72 and the cross-sectional center 201 of the laser beam 200 may be slightly displaced in the W-axis direction (Z-axis direction).

[0055] In this case, the end of the laser beam 200 is asymmetrically (distortedly) blocked by the slit 72. As a result, as shown in Fig. 4, the energy distribution (density) of the laser beam 200 becomes asymmetric in the W-axis direction. If a dividing groove is formed in the wafer 100 in this state, there is a possibility that the dividing groove may not reach a predetermined depth due to insufficient power of the laser beam 200 required for forming the dividing groove. Furthermore, there may also occur processing defects (shape defects) such as a depth difference in the dividing groove in the W-axis direction (Y-axis direction) and unevenness on the bottom surface of the groove.

[0056] In addition, in the case of a process in which a Low-k film is formed on the planned division line and the Low-k film is divided by laser processing, there may be processing defects such as the Low-k film not being divided or one side of the divided Low-k film being curled up.

[0057] Therefore, in the present embodiment, as described above, the first control unit 52 adjusts the position of the slit 72 in the W-axis direction so that the energy amount of the laser beam 200 becomes maximum. By this adjustment, in the examples shown in FIGS. 3 and 5, the slit plate 70 having the slit 72 is lowered in the -W direction as indicated by the arrow 250 in FIG. 5.

[0058] As a result, in the W-axis direction, the center 73 of the slit 72 and the cross-sectional center 201 of the laser beam 200 coincide with each other, and the end portion of the laser beam 200 is symmetrically blocked by the slit 72. As a result, as shown in FIG. 6, the energy distribution (density) of the laser beam 200 becomes symmetric in the W-axis direction, and the power shortage of the laser beam 200 can be eliminated. Thereby, a division groove having a predetermined depth and an appropriate shape can be formed in the wafer 100.

[0059] In addition, in the present embodiment, the W-axis direction in which the slit plate 70 is moved by the slit moving mechanism 71 is the Z-axis direction orthogonal to the X-axis direction. Therefore, it is possible to suppress the deviation in the X-axis direction between the center 73 of the slit and the cross-sectional center 201 of the laser beam 200 as the slit plate 70 moves.

[0060] As shown in FIG. 2, a part of the laser beam 200 that has passed through the energy distribution corrector 63 passes through the mirror 65 and is incident on the camera 67 disposed on the back side of the mirror 65. The camera 67 images the incident laser beam 200. That is, the camera 67 images the transmitted laser beam 210, which is the laser beam that has been oscillated from the laser oscillator 61 and passed through the mirror 65.

[0061] In this embodiment, the adjustment unit 51 may correct the energy distribution of the laser beam 200 based on the image captured by the camera 67. The operation of correcting the energy distribution in this case will be described below.

[0062] As shown in FIG. 2, the adjustment unit 51 includes a center recognition unit 53 and a second control unit 54. The center recognition unit 53 recognizes the cross-sectional center of the transmitted laser beam 210 based on the brightness and darkness of the pixels of the captured image obtained by imaging with the camera 67.

[0063] Based on the cross-sectional center of the transmitted laser beam 210 recognized by the center recognition unit 53, the second control unit 54 controls the slit movement mechanism 71 so that the cross-sectional center 201 of the laser beam 200 coincides with the center 73 of the slit 72 in the W-axis direction, which is the movement direction of the slit 72.

[0064] FIGS. 7 and 8 show examples of captured images obtained by imaging with the camera 67. These figures also show the center 73 of the slit 72 and the cross-sectional center 211 of the transmitted laser beam 210.

[0065] In these figures, the bright region 91, which is a region of pixels brighter than a preset brightness in the captured image, corresponds to the transmitted laser beam 210. Then, the center recognition unit 53 recognizes the cross-sectional center 211 of the transmitted laser beam 210, for example, according to the shape of the bright region 91. That is, the bright region 91 is an image of a part of a circle that is the cross-section of the transmitted laser beam 210. Therefore, the center recognition unit 53 obtains the position of the center of the circle including the bright region 91 in the captured image and recognizes this position as the position of the cross-sectional center 211 of the transmitted laser beam 210. Also, the center recognition unit 53 recognizes the position of the center 73 of the slit 72 in the W-axis direction as the position of the center of the width in the W-axis direction in the bright region 91.

[0066] In the example shown in FIG. 7, the cross-sectional center 211 of the transmitted laser beam 210 and the center 73 of the slit 72 are slightly displaced in the W-axis direction (Z-axis direction). In this case, as shown in FIG. 3, the cross-sectional center 201 of the laser beam 200 is also displaced from the center 73 of the slit 72 in the W-axis direction, and the end of the laser beam 200 is asymmetrically blocked by the slit 72. As a result, as shown in FIG. 4, the energy distribution (density) of the laser beam 200 becomes asymmetric in the W-axis direction. As described above, the dividing groove does not reach a predetermined depth, and there is a possibility of processing defects occurring.

[0067] Therefore, based on the cross-sectional center 211 of the transmitted laser beam 210, the second control unit 54 controls the slit moving mechanism 71 so that the cross-sectional center 201 of the laser beam 200 and the center 73 of the slit 72 coincide with each other in the W-axis direction, and adjusts the position of the slit plate 70 including the slit 72 in the W-axis direction.

[0068] Specifically, the second control unit 54 grasps the positional relationship between the cross-sectional center 211 of the transmitted laser beam 210 and the center 73 of the slit 72 in the captured image recognized by the center recognition unit 53, and controls the slit moving mechanism 71 so that they coincide with each other in the W-axis direction, and moves the slit 72 of the slit plate 70 in the W-axis direction.

[0069] By this adjustment, as shown in FIG. 8, in the captured image, the center 73 of the slit 72 and the cross-sectional center 211 of the transmitted laser beam 210 coincide with each other in the W-axis direction. As a result, as shown in FIG. 5, the cross-sectional center 201 of the laser beam 200 also coincides with the center 73 of the slit 72 in the W-axis direction, and the end of the laser beam 200 is symmetrically blocked by the slit 72. As a result, as shown in FIG. 6, the energy distribution of the laser beam 200 becomes symmetric in the W-axis direction, and the power shortage of the laser beam 200 can be eliminated. Thereby, a dividing groove having a predetermined depth and an appropriate shape can be formed in the wafer 100.

[0070] Note that since the transmitted laser beam 210 is refracted when passing through the mirror 65 (the degree of refraction is determined for each mirror), there may be a deviation between the cross-section center 201 of the laser beam 200 and the cross-section center 211 of the transmitted laser beam 210. When such a deviation occurs, the second control unit 54 may store in advance the position of the cross-section center 211 of the transmitted laser beam 210 in the imaging picture when the cross-section center 201 of the laser beam 200 coincides with the center 73 of the slit 72. Then, when adjusting the position of the slit 72, the second control unit 54 may move the slit 72 so that the stored position of the cross-section center 211 of the transmitted laser beam 210 coincides with the center 73 of the slit 72 in the W-axis direction in the imaging picture.

[0071] In addition, the energy distribution correction (alignment of the slit 72) of the laser beam 200 using the power meter 80 by the first control unit 52 described above, and the energy distribution correction of the laser beam 200 using the imaging picture of the camera 67 by the center recognition unit 53 and the second control unit 54 may be performed periodically. Thereby, it becomes easy to form a dicing groove having a predetermined depth and an appropriate shape in the wafer 100.

[0072] Also, as described above, the energy distribution of the laser beam 200 can be approximated by a Gaussian distribution as shown in FIG. 9. In this case, the beam diameter can be defined as the beam diameter 601 at 1 / e 2 of the maximum value of the energy in the energy distribution. Also, in this case, the position of the cross-section center 201 of the laser beam 200 required in the present embodiment corresponds to the apex of the Gaussian distribution in the laser beam 200.

[0073] On the other hand, the energy distribution of the laser beam 200 may collapse so as to have an asymmetric shape as shown in FIG. 10. In this case, the beam diameter may be defined as the aperture diameter 602. The aperture diameter 602 is obtained by calculating a circle that contains a specific percentage (generally 86.5%) of the total energy of the laser beam 200 based on the maximum value of the energy, and is determined as the diameter of this circle. Also, in this case, the position of the cross-section center 201 of the laser beam 200 obtained in the present embodiment corresponds to the center of the aperture diameter 602.

[0074] Further, when the cross-section center 201 of the laser beam 200 is obtained using the camera 67, the adjustment unit 51 can determine whether the shape of the laser beam 200 is an asymmetric shape as shown in FIG. 10 based on the brightness and darkness of the pixels of the captured image obtained by imaging with the camera 67. In this regard, the adjustment unit 51 may be configured to determine whether the shape of the laser beam 200 is asymmetric and notify the operator of the determination result using a notification device (not shown).

Explanation of Reference Numerals

[0075] 10: Laser processing apparatus, 11: Base, 12: Laser processing mechanism, 13: Vertical wall portion, 14: Chuck table moving mechanism, 17: Arm portion, 18: Processing head, 20: Y-axis moving mechanism, 23: Guide rail, 24: Y-axis table, 25: Ball screw, 26: Drive motor, 30: X-axis moving mechanism, 31: Guide rail, 32: X-axis table, 33: Ball screw, 35: Drive motor, 40: Chuck table portion, 43: Chuck table, 44: Holding surface, 45: Clamp portion, 47: θ table, 51: Adjustment unit, 52: First control unit, 53: Center recognition unit, 54: Second control unit, 61: Laser oscillator, 62: Beam expander, 63: Energy distribution corrector, 65: Mirror, 66: Condenser, 67: Camera, 70: Slit plate, 71: Slit moving mechanism, 72: Slit, 73: Center of slit, 80: Power meter, 91: Bright area, 100: Wafer, 110: Workset, 111: Ring frame, 113: Adhesive tape, 200: Laser beam, 201: Cross-section center, 210: Transmitted laser beam, 211: Cross-section center, 601: Beam diameter, 602: Aperture diameter

Claims

1. A laser processing apparatus for irradiating a laser beam onto the upper surface of a wafer held by a chuck table to form a dividing groove in the wafer, comprising: a laser oscillator that oscillates a laser beam; a slit that narrows the width of the laser beam oscillated from the laser oscillator to a width corresponding to the dividing groove in order to form a dividing groove having a predetermined width; a slit moving mechanism that moves the slit in a direction corresponding to the width direction of the dividing groove; an adjusting unit that aligns the center of the slit and the cross-sectional center of the laser beam passing through the slit in the moving direction of the slit; a mirror that reflects the laser beam oscillated from the laser oscillator and irradiates the laser beam onto the wafer held by the chuck table; a camera that is disposed on the back side of the mirror and images a transmitted laser beam that is the laser beam oscillated from the laser oscillator and has passed through the mirror; and comprising: the adjusting unit includes: a center recognition unit that recognizes the cross-sectional center of the transmitted laser beam based on the brightness and darkness of the pixels of the captured image obtained by imaging by the camera; a second control unit that controls the slit moving mechanism so that the cross-sectional center of the laser beam and the center of the slit coincide with each other in the moving direction of the slit based on the cross-sectional center of the transmitted laser beam recognized by the center recognition unit; A laser processing apparatus comprising:

2. comprising a power meter that measures the output of the laser beam that has passed through the slit, the adjusting unit includes: while moving the slit in a direction corresponding to the width direction of the dividing groove by the slit moving mechanism, measuring the output of the laser beam by the power meter, and when the measured output is maximum, determining that the center of the slit and the cross-sectional center of the laser beam coincide with each other, and comprising a first control unit that stops the movement of the slit; The laser processing apparatus according to Claim 1.

Images