JP2012232316A - Laser processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser processing device that can irradiate a laser beam to an appropriate position from the undersurface of a wafer even if a deviation occurs in a position relationship over time between an imaging means for detecting a processing position and a focal point of the laser beam.SOLUTION: A position deviation between an upper surface imaging means 70 and a lower surface imaging means 71 is recognized by providing the upper surface imaging means 70 and the lower surface imaging means 71 on a laser processing device 1, by forming a position deviation detection mark for detecting the deviation between the reference position when an image is taken by the upper surface imaging means 70 on a transparent holding plate 20 provided with a holding means 2 which holds a workpiece and the reference position when an image is taken by the lower surface imaging means 71, and by detecting the position deviation detection mark from both the upper surface imaging means 70 and the lower surface imaging means 71. Accordingly, even though the undersurface of the workpiece is exposed upward and a division schedule line is formed on the surface, the amount of the position deviation can be offset to perform laser processing from the undersurface side.

Description

  The present invention relates to a laser processing apparatus for processing a workpiece by laser irradiation.

  Wafers formed on the surface by dividing devices such as IC, LSI, etc. by dividing lines are divided into individual devices by cutting along the dividing lines using a cutting machine, laser processing apparatus, etc. Used for electronic devices.

  In the case of dividing a wafer using a laser processing device, when laser light is irradiated from the front surface of the wafer, debris adheres to the surface, so laser light is irradiated from the back side of the wafer along the planned dividing line. A technique for dividing the device into individual devices has been proposed by the present applicant and has been filed as a patent (see Patent Document 1).

  In this technique, since the division line formed on the front side cannot be directly detected from the back side of the wafer, the chuck table for holding the wafer is formed of a transparent member and the image pickup means is disposed below the chuck table. Accordingly, the surface side of the wafer is held on the chuck table, and the division line formed on the surface side is imaged and detected from below.

  The lens of the imaging means is formed with a reference line for alignment between the condensing point of the laser beam and the planned division line, and the reference line and the laser irradiation head are located on the same straight line. Since the positional relationship is set in advance, the laser light can be condensed on the planned division line by performing laser irradiation in a state where the reference line and the planned division line are in a predetermined positional relationship. .

JP 2011-18850 A

  However, due to the thermal expansion of the device, there may be a positional shift over time between the reference line set on the image of the imaging means and the laser irradiation head. Since the laser irradiation is performed at the position, there is a problem that the device is damaged or the quality of the device is deteriorated.

  The present invention has been considered in view of such a problem, and even when a predetermined positional relationship between the imaging means and the condensing point of the laser beam changes with time, it can be appropriately applied from the back surface of the wafer. It is an object to be able to irradiate a laser beam at any position.

  The present invention includes a holding unit that holds a workpiece supported by a frame via a tape, a laser irradiation unit that performs processing by irradiating the workpiece held by the holding unit with a laser beam, and a holding unit that holds the workpiece. The laser processing apparatus includes at least a detection mechanism that images and detects a region to be processed of the processed workpiece, and the holding means includes a holding plate and a frame formed of a transparent member that holds the workpiece. At least a frame support unit that supports the upper surface imaging unit that images the upper surface of the workpiece held by the holding plate, and a lower surface imaging unit that images the lower surface of the workpiece held by the holding plate. And a positional deviation detection mark for detecting a deviation between the reference position at the time of imaging by the upper surface imaging means and the reference position at the time of imaging by the lower surface imaging means is formed on the holding plate. And butterflies.

  The laser processing apparatus according to the present invention includes an upper surface imaging unit and a lower surface imaging unit for imaging the upper surface and the lower surface of the workpiece, respectively, and a holding plate made of a transparent member provided in the holding unit for holding the workpiece. Since a misalignment detection mark for detecting a deviation between the reference position at the time of imaging by the upper surface imaging means and the reference position at the time of imaging by the lower surface imaging means is formed, both the upper surface imaging means and the lower surface imaging means A misalignment detection mark can be detected. Therefore, since the positional deviation between the upper surface imaging means and the lower surface imaging means can be recognized by imaging the position deviation detection mark from the upper surface imaging means and the lower surface imaging means, the back surface of the workpiece is directed upward. Even when the line to be divided is formed on the front surface, laser processing can be performed from the back surface side by correcting the misalignment. In addition, it is possible to confirm whether or not the groove is formed at an appropriate position by imaging the groove formed by processing from the upper surface imaging means. By correcting the amount of deviation at the time of processing, laser irradiation can be performed at an appropriate position, and damage to the device and deterioration of quality can be prevented.

It is a perspective view which shows an example of a laser processing apparatus. It is a disassembled perspective view which shows an example of a structure of a holding means. It is explanatory drawing which shows the relationship between a collector and the reference line of an upper surface imaging means and a lower surface imaging means. It is sectional drawing which shows schematically the relationship between an upper surface imaging means and a lower surface imaging means, and a holding means. (A) is explanatory drawing which shows position shift with the reference line of a lower surface imaging means, and the position shift detection mark formed in the holding | maintenance board, (B) corrects the said position shift, and is a reference line of a lower surface image pickup means. FIG. 4C is an explanatory diagram showing a state in which the position detection mark formed on the holding plate and the position detection mark formed on the holding plate are matched with each other. FIG. It is explanatory drawing which shows position shift. It is a perspective view which shows an example of a to-be-processed object. It is a disassembled perspective view which shows the state which hold | maintains a to-be-processed object to a holding means. It is explanatory drawing which shows the state which imaged the division | segmentation planned line by the lower surface imaging means. It is explanatory drawing which shows the position shift with the reference line of an ablation groove | channel and an upper surface imaging means. It is a perspective view which shows the to-be-processed object in which the ablation groove | channel was formed in the back surface.

1 Configuration of Laser Processing Apparatus A laser processing apparatus 1 shown in FIG. 1 is an apparatus that performs laser processing on a workpiece held by a holding means 2 by a laser irradiation means 3.

  The workpiece W held by the holding means 2 is stuck to the tape T, a ring-shaped frame F is stuck to the peripheral edge of the tape T, and the workpiece W is supported by the frame F via the tape T. Is done. Corresponding to this, the holding means 2 includes a holding plate 20 that holds the workpiece and a frame support portion 21 that supports the frame F around the holding plate 20. The holding plate 20 is formed of a transparent member such as quartz glass.

  The holding means 2 is fed by the machining feed means 4 and can move in the X-axis direction. The processing feed means 4 is provided on the base 10 and rotates a ball screw 40 extending in the X-axis direction, a pair of guide rails 41 arranged in parallel to the ball screw 40, and the ball screw 40 in both forward and reverse directions. A motor 42 to be moved and a movable plate 43 having a nut (not shown) screwed to the ball screw 40 and having a lower portion slidably contacting the guide rail 41 are driven by the ball screw 40 being driven by the motor 42. The movable plate 43 is guided by the guide rail 41 and processed and fed in the X-axis direction.

  The movable plate 43 includes index feeding means 5 for indexing and feeding the holding means 2 in the Y-axis direction. The index feeding means 5 is screwed into the ball screw 50 extending in the Y-axis direction, a pair of guide rails 51 arranged in parallel to the ball screw 50, a motor 52 for rotating the ball screw 50 in both forward and reverse directions, and the ball screw 50. The movable plate 53 is configured to be guided by the guide rail 51 when the ball screw 50 is rotated by being driven by the motor 52. It is configured to be indexed and fed in the direction.

  The processing feed means 4 and the index feed means 5 are controlled by the control means 8. The control means 8 includes a CPU, a memory and the like, and controls the operations of the machining feed means 4 and the index feed means 5 by sending pulse signals to the motor 42 and the motor 52, and the X-axis direction of the holding means 2 and The movement distance in the Y-axis direction can be accurately recognized and stored in the memory.

  A holding means support portion 6 that supports the holding means 2 from below is provided above the movable plate 53. The holding means support portion 6 includes a wall portion 60 standing from the movable plate 53 and a horizontal plate 61 extending in the Y-axis direction from the upper end of the wall portion 60. An opening 62 that opens toward the column 11 that is erected is formed.

  On the lower surface side of the ceiling portion 12 extending in the Y-axis direction from the upper portion of the column 11, laser irradiation means 3 for irradiating the workpiece with a laser beam and processing, and upper surface imaging means for imaging the upper surface of the workpiece 70. The laser irradiation means 3 includes a condenser 30 that condenses the laser light downward.

  At the distal end portion of the extending portion 13 extending in the Y-axis direction from the lower portion of the column 11, a lower surface imaging means 71 for imaging the lower surface of the workpiece is provided. The upper surface imaging unit 70 and the lower surface imaging unit 71 are opposed to each other in the vertical direction, and the detection mechanism 7 that captures and detects a region to be processed of the workpiece held by the holding unit 2 with these two imaging units. It is composed.

  As shown in FIG. 2, the holding means 2 includes a cylindrical fitting member 22 that is fitted in a through hole 61 a formed in the horizontal plate 61 and protrudes upward, and a through hole 230 that accommodates the fitting member 22. The detachable table 23 is formed inside, and the holding plate 20 is held on the detachable table 23. The inner peripheral side of the fitting member 22 is a cavity that penetrates the horizontal plate 61.

  In the horizontal plate 61, a ring-shaped recess 610 formed concentrically with the fitting member 22 is formed around the fitting member 22, and a suction source 611 is formed on the bottom surface of the recess 610.

  The detachable table 23 is formed with a suction communication hole 231 penetrating in the vertical direction. When the detachable table 23 is fitted to the fitting member 22, the suction source 611 and the suction communication hole 231 are interposed via the recess 610. It becomes the composition which communicates.

  A plurality of frame support portions 21 are provided on the outer peripheral side of the detachable table 23. The frame support portion 21 includes a guide portion 210 extending in the horizontal direction and a fixing portion 211 that moves along the guide portion 210. The fixed portion 211 includes a pressing portion 211a that rotates a predetermined range about a horizontal rotation axis by air injection or the like and presses the frame F.

  A ring-shaped recess 200 is formed on the front surface side of the holding plate 20, and a through hole 201 penetrating the back surface is formed on the bottom surface of the recess 200. When the holding plate 20 is placed on the detachable table 23, the through hole 201 communicates with the suction communication hole 231 of the detachable table 23. Further, when the detachable table 23 is fitted to the fitting member 22, the holding plate 20 is placed and fixed on the detachable table 23 via a bonding agent, and a suction force is applied to the suction source 611, the holding plate A suction force is generated in the 20 recesses 200, and the workpiece can be sucked and held.

  A gear 232 is provided below the outer peripheral surface of the detachable table 23, and a gear 612 is provided on the horizontal plate 611 so as to protrude upward. The gear 612 is connected to the pulse motor 613. When the detachable table 23 is fitted to the fitting member 22 and the gear 612 is rotated by being driven by the pulse motor 613, the detachable table 23 and the holding plate 20 are rotated.

  As shown in FIG. 3, reference lines 70 a and 71 a extending in the X-axis direction are formed in images at the time of imaging acquired by the upper surface imaging unit 70 and the lower surface imaging unit 71, respectively. The reference line 70a and the center of the condenser 30 of the laser irradiation means 3, that is, the condensing point P are in a predetermined positional relationship. The predetermined positional relationship is, for example, that the condensing point P of the condenser 30 is located on the extended line of the reference line 70a as in the example of FIG. 3, or the Y coordinate of the reference line 70a and the condenser 30 are This is a relationship in which the distance between the condensing point P and the Y coordinate is a constant value. In the example of FIG. 3, the reference line 70a and the reference line 71a are in a matched state. However, the positions in the Y direction may not match due to an error.

  As shown in FIG. 2, a misalignment detection mark 202 extending in the X-axis direction is formed on the holding plate 20. The misregistration detection mark 202 indicates whether or not there is a deviation between the reference line 70a that is the reference position at the time of imaging by the upper surface imaging means 70 and the reference line 71a that is the reference position at the time of imaging by the lower surface imaging means 71. This is for detecting and recognizing the deviation when there is a deviation.

2 Laser processing method Below, the method of performing a laser processing with respect to a to-be-processed object using the said laser processing apparatus 1 is demonstrated.
(1) Imaging means positional deviation amount recognition step First, with the holding means 2 not holding the work, the holding means 2 is moved in the X-axis direction by driving by the processing feed means 4 shown in FIG. As described above, the holding plate 20 is positioned between the upper surface imaging unit 70 and the lower surface imaging unit 71. At this time, the lower surface imaging means 71 is located in the opening 62.

  First, the lower surface imaging means 71 is used to image the misalignment detection mark 202 formed on the holding plate 20. For example, as shown in FIG. 5A, when there is a positional deviation Y1 between the reference line 71a of the lower surface imaging means 71 and the positional deviation detection mark 202, the indexing means 5 shown in FIG. 2 is moved by Y1 in the Y-axis direction, and as shown in FIG. 5B, the reference line 71a and the misregistration detection mark 202 are matched.

  Next, the upper surface imaging means 70 is used to image the misalignment detection mark 202 formed on the holding plate 20. At this time, as shown in FIG. 5C, if there is a positional deviation Y2 between the reference line 70a and the positional deviation detection mark 202, the control means uses the value of the positional deviation Y2 as the imaging means positional deviation amount. 8 memory. This imaging means position deviation amount Y2 is a deviation amount in the Y-axis direction between the reference line 70a of the upper surface imaging means 70 and the reference line 71a of the lower surface imaging means 71. As described above, since the holding plate 20 is formed of a transparent member, it is possible to detect the misalignment detection mark 202 from both the upper surface imaging unit 70 and the lower surface imaging unit 71, and thereby the reference line 70a and the reference line The amount of deviation from the line 71a can be obtained.

(2) Processing Step After the imaging means positional deviation amount recognition step, the workpiece is laser processed. As shown in FIG. 6, a plurality of devices D are formed on the surface W <b> 1 of the workpiece (workpiece) W by being partitioned by the division planned lines L. As shown in FIG. 7, the work W is turned upside down, and the back surface W <b> 2 is exposed by sticking the front surface W <b> 1 to the tape T so that the work W is supported by the frame F via the tape T. The tape T is a transparent or translucent tape made of, for example, vinyl chloride.

  The workpiece W supported by the frame F via the tape T is sucked and held by the holding plate 20 on the tape T side, and the frame F is held by the frame support portion 21.

  Next, the holding plate 20 and the tape T are transmitted through the lower surface imaging means 71 shown in FIGS. 1 and 4, and the surface W1 of the workpiece W is imaged as shown in FIG. Then, the planned division line L formed on the surface W1 is detected, and the center of the planned division line L and the reference line 71a of the lower surface imaging means 71 are matched. Then, the holding means 2 is processed and fed in the X-axis direction, and the laser beam is irradiated from the condenser 30 so as to be condensed on the division line L of the work W, so that it does not penetrate to the surface along the division line L. Ablation grooves are formed.

(3) Correction Step In the laser processing performed in this manner, the position of the condensing point P of the condenser 30 with respect to the reference line 71a of the lower surface imaging means 71 changes with time due to thermal expansion of the apparatus. Therefore, it is necessary to adjust the position of the holding means 2 in the Y-axis direction in response to the change. Therefore, the formed ablation groove is imaged at an arbitrary timing, and a deviation amount in the Y-axis direction between the ablation groove and the reference line 71a of the lower surface imaging means 71 is obtained.

  Since the ablation groove is formed on the back surface W2 of the workpiece W and cannot be recognized from the lower surface imaging means 71, immediately after the laser irradiation to the planned division line L, without moving the holding means 2 in the Y-axis direction, As shown in FIG. 9, the rear surface W <b> 2 of the workpiece W is imaged by the upper surface imaging means 70. Then, for example, a groove position deviation amount Y3 that is a position deviation in the Y-axis direction between the ablation groove G shown in FIG. Remember me. The control means 8 calculates a value of Y4 = (imaging means position deviation amount Y2−groove position deviation amount Y3). This Y4 value is a correction value for the position of the holding means 2 in the Y-axis direction. In the subsequent processing, the holding means 2 is adjusted in the Y-axis direction by this correction value Y4, so that accurate machining is possible. Become. For example, when the image pickup means position deviation amount Y2 = 8 μm and the groove position deviation amount Y3 = 5 μm, the correction value Y4 = (8−5) μm = 3 μm.

  After obtaining the correction value Y4 in this way, the process returns to the machining step, and the lower division imaging means 71 detects the next divisional line L to be machined. As shown in FIG. After matching the line 71a, the holding means 2 is moved in the Y-axis direction by the correction value Y4 to adjust the position of the workpiece W. In this state, the ablation groove that does not penetrate to the surface along the planned division line L by irradiating a laser beam from the condenser 30 and condensing it on the planned division line L of the workpiece W while processing and feeding the holding means 2 Is formed. Since the position of the holding unit 2 is adjusted by the correction value Y4, the ablation groove can be formed by condensing light at the center of the planned division line L.

  After the ablation grooves are formed for one scheduled division line, all the scheduled division lines in the same direction are processed by performing the same laser irradiation while indexing and feeding the holding means 2 in the Y-axis direction. Further, when the same processing is performed after the holding means 2 is rotated 90 degrees, as shown in FIG. 10, ablation grooves G are formed vertically and horizontally in all the planned division lines L. In such a process, the position of the condensing point P in the Y-axis direction with respect to the reference line 71a of the lower surface imaging means 71 changes over time due to the thermal expansion of the apparatus, so the correction process is executed at an appropriate timing. Then, the groove position deviation amount Y3 and the correction value Y4 are obtained each time, and laser irradiation is performed while adjusting the position of the holding means 2 by the correction value Y4, thereby accurately ablating along all the division lines. Grooves can be formed. Therefore, it is possible to prevent the device from being damaged or the quality of the device from being deteriorated. Further, after the ablation grooves are formed on the back surface, the external device can be divided into individual devices by applying an external force to the workpiece W.

1: Laser processing device 2: Holding means 20: Holding plate 200: Concave portion 201: Through hole 202: Position shift detection mark 21: Frame support portion 210: Guide portion 211: Fixing portion 22: Fitting member 23: Removable table 230 : Through hole 231: Suction communication hole 3: Laser irradiation means 30: Condenser 4: Processing feed means 40: Ball screw 41: Guide rail 42: Motor 43: Movable plate 5: Indexing feed means 50: Ball screw 51: Guide rail 52 : Motor 53: Movable plate 6: Holding means support part 60: Wall part 61: Horizontal plate 610: Concave part 611: Suction source 612: Gear 62: Opening part W: Workpiece (workpiece)
W1: Front surface L: Line to be divided D: Device W2: Back surface G: Ablation groove T: Tape F: Frame 7: Detection mechanism 70: Upper surface imaging means 70a: Reference line 71: Lower surface imaging means 71a: Reference line 8: Control means 10: Base 11: Column 12: Ceiling 13: Extension

Claims (1)

A holding means for holding the workpiece supported by the frame via the tape, a laser irradiation means for irradiating the workpiece held by the holding means with a laser beam and processing, and held by the holding means A laser processing apparatus comprising at least a detection mechanism for imaging and detecting a region to be processed of a workpiece,
The holding means includes at least a holding plate formed of a transparent member that holds a workpiece, and a frame support portion that supports the frame,
The detection mechanism includes upper surface imaging means for imaging the upper surface of the workpiece held on the holding plate, and lower surface imaging means for imaging the lower surface of the workpiece held on the holding plate,
A laser processing apparatus in which a displacement detection mark for detecting a displacement between a reference position at the time of imaging by the upper surface imaging means and a reference position at the time of imaging by the lower surface imaging means is formed on the holding plate.

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