Laser processing equipment

Abstract

To monitor the condition of a laser beam with which a workpiece is irradiated.SOLUTION: A laser processing device that processes a workpiece with a laser includes a chuck table that holds the workpiece, a laser beam irradiation unit that irradiates the workpiece held on the chuck table with a laser beam, an imaging unit that forms an image by capturing the light generated by irradiating the workpiece with the laser beam, and a control unit, and the laser beam irradiation unit includes a laser oscillator and a condensing lens that condenses the laser beam emitted from the laser oscillator and irradiates the workpiece with the laser beam, and the control unit includes a determination unit that determines the state of the laser beam with which the workpiece is irradiated on the basis of the shape of the light that appears in the captured image.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a laser processing apparatus for laser processing a workpiece such as a semiconductor wafer. [Background technology]

[0002] In the manufacturing process of device chips used in electronic devices such as mobile phones and personal computers, first, a number of mutually intersecting division lines (streets) are set on the surface of a wafer made of a material such as a semiconductor. Then, devices such as ICs (Integrated Circuits) and LSIs (Large-scale Integrations) are formed in each area defined by the division lines. After that, the wafer is divided along the division lines to form individual device chips.

[0003] The division of the wafer is carried out, for example, by a laser processing device capable of laser processing the wafer by irradiating the wafer with a laser beam. The laser processing device includes a chuck table for holding a workpiece such as a wafer, and a laser beam irradiation unit for irradiating the workpiece held by the chuck table with a laser beam to laser process the workpiece.

[0004] The laser beam irradiation unit focuses a laser beam having a wavelength that is absorbed by the workpiece (a wavelength that is absorbed by the workpiece) on the upper surface of the workpiece, and ablates the workpiece (see Patent Document 1). If the output of the laser beam changes during laser processing, processing defects may occur. For this reason, the output of the laser beam is periodically monitored by a power meter in the laser processing device (see Patent Document 2).

[0005] However, to measure the output of the laser beam, it is necessary to either block the optical path with a power meter or interrupt the laser processing and irradiate the power meter with the laser beam. In either case, the laser processing of the workpiece cannot be performed while the output of the laser beam is being measured, which causes a problem of a decrease in the processing efficiency of the workpiece in the laser processing device. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2003-320466 A [Patent Document 2] JP 2009-291818 A Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, for example, a mirror that can transmit a part of the laser beam may be installed in the optical path of the laser beam inside the laser beam irradiation unit. For example, a part of the laser beam emitted from a laser oscillator is irradiated onto a workpiece to perform laser processing, and another part of the laser beam is irradiated onto a power meter to monitor the output of the laser beam. In this case, the laser processing of the workpiece and the monitoring of the output of the laser beam can be performed simultaneously, thereby improving the processing efficiency of the workpiece.

[0008] However, when a problem occurs outside the laser beam irradiation unit, such as when dirt adheres to the outer surface of the focusing lens at the end of the optical path of the laser beam irradiation unit and the laser beam does not irradiate the workpiece as planned, this method cannot detect the problem. In other words, there is a problem with the laser processing apparatus in that it is necessary to monitor the state of the laser beam that is actually irradiated to the workpiece so that problems outside the laser beam irradiation unit can be detected in addition to problems inside the laser beam irradiation unit.

[0009] SUMMARY OF THE PRESENT INVETION The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a laser processing apparatus capable of monitoring the state of a laser beam irradiated onto a workpiece. [Means for solving the problem]

[0010] According to one aspect of the present invention, a chuck table for holding a workpiece and a laser beam for irradiating the workpiece held on the chuck table are provided. Then, laser processing of the workpiece is performed. a laser beam irradiation unit for irradiating the workpiece with the laser beam to generate a laser beam; Plasma-induced The laser beam irradiation unit includes an imaging unit that images light to form an image, and a control unit. The laser beam irradiation unit includes a laser oscillator and a condenser lens that condenses the laser beam emitted from the laser oscillator and irradiates the workpiece with the laser beam. The control unit includes a determination unit that determines the state of the laser beam irradiated to the workpiece based on the shape of the light shown in the image. The determination unit evaluates the output of the laser beam based on the magnitude of the light reflected in the captured image, and the control unit adjusts the output of the laser beam by referring to a result of the evaluation of the output of the laser beam performed by the determination unit when the laser processing of the workpiece is being performed by the laser beam irradiation unit. The present invention provides a laser processing apparatus characterized by the above.

[0011] Preferably, the control unit detects a temperature generated when the laser beam is irradiated to the workpiece under a predetermined condition. Plasma-induced The device further includes a memory unit that pre-stores a reference image captured by capturing light, and a comparison unit that compares the reference image stored in the memory unit with the captured image, and the judgment unit makes a judgment based on a result of the comparison between the reference image and the captured image by the comparison unit.

[0012] Preferably, the laser beam irradiation unit has an attenuator disposed between the laser oscillator and the condenser lens for adjusting the output of the laser beam emitted from the laser oscillator. , applicable The control unit is , applicable The attenuator is controlled to adjust the power of the laser beam.

[0013] In addition, preferably, the laser beam irradiation unit further includes a dichroic mirror which transmits the laser beam emitted from the laser oscillator and guides it to the collecting lens, and which reflects wavelengths other than the wavelength of the laser beam, and the light imaged by the imaging unit is generated when the laser beam propagated through the collecting lens and the dichroic mirror is irradiated onto the workpiece, transmits through the collecting lens, is reflected by the dichroic mirror, and reaches the imaging unit.

[0014] In addition, preferably, the determination unit can determine the presence or absence of an abnormality in the optical system of the laser beam based on the presence or absence of an abnormal deformation of the shape of the light reflected in the captured image. Cut . Effect of the Invention

[0015] A laser processing apparatus according to one aspect of the present invention includes an imaging unit that captures light generated when a laser beam is irradiated onto a workpiece to form an image. The shape of the light generated at the workpiece reflects the state of the laser beam. Therefore, a determination section of a control unit can determine the state of the laser beam based on the shape of the light shown in the captured image. The determination section can detect an abnormality whether the abnormality occurs inside or outside the laser beam irradiation unit. When an abnormality is detected, there is no need to stop laser processing.

[0016] Therefore, according to one aspect of the present invention, there is provided a laser processing apparatus capable of monitoring the state of a laser beam irradiated onto a workpiece. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a perspective view showing an example of a workpiece; [Diagram 2] FIG. 1 is a perspective view showing a schematic diagram of a laser processing apparatus. [Diagram 3] FIG. 2 is a side view illustrating a schematic diagram of an optical system of a laser beam irradiation unit. [Figure 4]FIG. 2 is a plan view showing a schematic diagram of a trajectory of a laser beam irradiated on a workpiece. [Diagram 5] 5(A) to 5(D) are plan views each showing a schematic image obtained by capturing an image of light emitted by a laser beam irradiated onto a workpiece. [Figure 6] 6(A) to 6(C) are plan views each showing a schematic image obtained by capturing an image of light emitted by a laser beam irradiated onto a workpiece. [Figure 7] 1A to 1C are plan views each showing a schematic diagram of an evaluation procedure for light reflected in a captured image. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] A laser processing device according to an embodiment of the present invention will be described with reference to the accompanying drawings. First, a workpiece to be processed by the laser processing device according to this embodiment will be described. The workpiece is, for example, a disk-shaped wafer made of Si (silicon), SiC (silicon carbide), GaN (gallium nitride), GaAs (gallium arsenide), or other semiconductor material.

[0019] Alternatively, the workpiece is a substantially disk-shaped substrate made of a material such as sapphire, glass, or quartz. The glass is, for example, alkali glass, non-alkali glass, soda-lime glass, lead glass, borosilicate glass, or quartz glass. The workpiece may be a package substrate, a ceramic substrate, or the like. In the following, an example will be described in which the workpiece is a disk-shaped wafer, but the workpiece is not limited to this. FIG. 1 is a perspective view showing a frame unit 11 including a workpiece 1.

[0020] The surface 1a of the workpiece 1 is partitioned by a plurality of planned division lines 3 arranged in a grid pattern. Devices 5 such as ICs and LSIs are formed in each area partitioned by the planned division lines 3 on the surface 1a of the workpiece 1. The laser processing apparatus according to this embodiment laser processes the workpiece 1 along the planned division lines 3, forms division grooves in the workpiece 1, and divides the workpiece 1 into individual device chips.

[0021] A workpiece 1 such as a wafer is carried into a laser processing device while being supported by a frame 7 via a dicing tape 9. That is, before the workpiece 1 is carried into the laser processing device, the workpiece 1, the frame 7, and the dicing tape 9 are integrated to form a frame unit 11. The frame unit 11 includes an annular frame 7 having an opening 7a, a dicing tape 9 disposed on the frame 7 so as to close the opening 7a, and the workpiece 1 attached to the dicing tape 9 inside the opening 7a.

[0022] The individual device chips formed by dividing the workpiece 1 are supported on a dicing tape 9. Thereafter, the dicing tape 9 is expanded to widen the spaces between the device chips, making it easier to pick up the device chips.

[0023] The frame 7 is formed of a material such as metal, and has an opening 7a with a diameter larger than that of the workpiece 1. When forming the frame unit 11, the workpiece 1 is positioned within the opening 7a of the frame 7 and accommodated in the opening 7a.

[0024] The dicing tape 9 has a diameter larger than the opening 7a of the frame 7. The dicing tape 9 includes a base layer and an adhesive layer formed on the base layer. The dicing tape 9 is attached to the frame 7 and the back surface 1b of the workpiece 1 by the adhesive force exerted by the adhesive layer. When the dicing tape 9 is attached to the back surface 1b side of the workpiece 1, the front surface 1a side of the workpiece 1 is exposed upward. The dicing tape 9 may be attached to the front surface 1a of the workpiece 1, in which case the back surface 1b of the workpiece 1 is exposed upward.

[0025] Next, a description will be given of a laser processing apparatus according to this embodiment that laser processes a workpiece 1 such as a wafer contained in the frame unit 11. Fig. 2 is a perspective view that shows a schematic view of the laser processing apparatus 2 according to this embodiment.

[0026] The laser processing device 2 includes a base 4 that supports each of the components. A chuck table 28 that holds the workpiece 1 is provided on the upper surface of the base 4. A laser beam irradiation unit 32 that irradiates the workpiece 1 held on the chuck table 28 with a laser beam is provided above the chuck table 28.

[0027] In addition, on the upper surface of the base 4, there are provided a Y-axis direction moving unit 6 which moves the chuck table 28 and the laser beam irradiation unit 32 relatively in the Y-axis direction, and an X-axis direction moving unit 16 which moves them in the X-axis direction perpendicular to the Y-axis direction.

[0028] The Y-axis movement unit 6 is provided with a pair of Y-axis guide rails 8 aligned along the Y-axis direction on the upper surface of the base 4. A Y-axis movement table 10 is slidably attached to the pair of Y-axis guide rails 8. A nut portion (not shown) is provided on the rear surface side of the Y-axis movement table 10, and a Y-axis ball screw 12 that is generally parallel to the Y-axis guide rails 8 is screwed into this nut portion.

[0029] A Y-axis pulse motor 14 is connected to one end of the Y-axis ball screw 12. When the Y-axis ball screw 12 is rotated by the Y-axis pulse motor 14, the Y-axis moving table 10 moves in the Y-axis direction along the Y-axis guide rail 8.

[0030] The X-axis movement unit 16 is provided with a pair of X-axis guide rails 18 aligned along the X-axis direction on the upper surface of the Y-axis movement table 10. An X-axis movement table 20 is slidably attached to the pair of X-axis guide rails 18. A nut portion (not shown) is provided on the rear surface side of the X-axis movement table 20, and an X-axis ball screw 22 roughly parallel to the X-axis guide rails 18 is screwed into this nut portion.

[0031] An X-axis pulse motor 24 is connected to one end of the X-axis ball screw 22. By rotating the X-axis ball screw 22 by the X-axis pulse motor 24, the X-axis moving table 20 moves in the X-axis direction along the X-axis guide rail 18. On the upper surface of the X-axis moving table 20, a power meter 26 capable of measuring the output of the irradiated laser beam and a chuck table 28 for holding the workpiece 1 are provided.

[0032] The chuck table 28 includes a porous member exposed on its upper surface, a suction passage having one end connected to the porous member, and a suction source connected to the other end of the suction passage. When the suction source is operated, the workpiece 1 placed on the chuck table 28 is sucked and held. That is, the upper surface of the chuck table 28 becomes a holding surface 28a. In addition, a plurality of clamps 28b for holding the frame 7 of the frame unit 11 including the workpiece 1 are provided around the periphery of the chuck table 28.

[0033] A laser beam irradiation unit 32 is provided above the chuck table 28, which performs laser processing on the workpiece 1 suction-held by the chuck table 28. The laser beam irradiation unit 32 focuses a laser beam having a wavelength absorbable by the workpiece 1 (a laser beam having a wavelength that can be absorbed by the workpiece 1) inside the workpiece 1 held by the chuck table 28, and performs laser processing (ablation processing) on ​​the workpiece 1.

[0034] A focal point is positioned on the surface 1a of the workpiece 1 at a position overlapping the planned dividing line 3, and the chuck table 28 and the laser beam irradiating unit 32 are moved relatively in a direction parallel to the holding surface 28a while the laser beam is being focused on the focal point. Then, the laser beam is irradiated onto the workpiece 1 along the planned dividing line 3, and dividing grooves are formed in the workpiece 1 along the planned dividing line 3, and the workpiece 1 is divided.

[0035] A Z-axis direction moving unit 34 that supports the laser beam irradiation unit 32 so as to be movable in the Z-axis direction perpendicular to the X-axis direction and the Y-axis direction is provided on the rear side of the base 4. The Z-axis direction moving unit 34 is, for example, a ball screw type moving mechanism configured similarly to the Y-axis direction moving unit 6 and the X-axis direction moving unit 16, and moves the lifting body 36 up and down along the Z-axis direction.

[0036] An arm 38 extending above the chuck table 28 is connected to the lifting body 36. A laser beam irradiation unit 32 is fixed to the tip of the arm 38. A camera 40 for capturing an image of the upper surface (surface 1a) of the workpiece 1 held on the chuck table 28 is provided at a position adjacent to the laser beam irradiation unit 32 at the tip of the arm 38.

[0037] The camera 40 includes an image sensor such as a CCD (Charge-Coupled Device) sensor or a CMOS (Complementary Metal-Oxide-Semiconductor) sensor, and can form a captured image by capturing light that reaches the camera 40. The position of the planned dividing line 3 of the workpiece 1 is identified based on the captured image obtained by capturing an image of the top surface of the workpiece 1 with the camera 40. The camera 40 can also be used to check the result of processing by the laser beam irradiation unit 32.

[0038] Furthermore, the laser processing apparatus 2 includes a control unit 42 that controls each component of the laser processing apparatus 2. The control unit 42 is configured by a computer including a processing device such as a CPU (Central Processing Unit), a main storage device such as a DRAM (Dynamic Random Access Memory), and an auxiliary storage device such as a flash memory. By operating the processing device and the like according to software stored in the auxiliary storage device, the control unit 42 functions as a concrete means in which the software and the processing device (hardware resources) work together.

[0039] When machining the workpiece 1 along the planned dividing lines 3, the control unit 42 controls the Y-axis direction moving unit 6 and the X-axis direction moving unit 16 to move the chuck table 28 in a direction parallel to the holding surface 28a relative to the laser beam irradiation unit 32. In other words, the control unit 42 moves the focal point of the laser beam along the planned dividing lines 3 relative to the workpiece 1.

[0040] Then, the control unit 42 causes the laser beam application unit 32 to apply the laser beam to the workpiece 1 while relatively moving the focal point of the laser beam, thereby laser processing the workpiece 1 along the intended division lines 3.

[0041] In the laser processing apparatus 2, one or both of the Y-axis direction moving unit 6 and the X-axis direction moving unit 16 may move the laser beam irradiation unit 32 instead of the chuck table 28. In addition, when a mechanism for adjusting the height of the focal point by raising and lowering the focusing lens is provided inside the laser beam irradiation unit 32, the laser processing apparatus 2 does not need to include the Z-axis direction moving unit 34.

[0042] The laser processing apparatus 2 also includes a display unit 44 that can display various information such as operating status and warning information. The display unit 44 is, for example, a liquid crystal display. The laser processing apparatus 2 may also include a touch panel that functions as an input interface for an operator to input various commands. The display unit 44 may also be, for example, a display with a touch panel.

[0043] Next, the laser beam irradiation unit 32 will be described in detail. Fig. 3 is a side view showing a schematic diagram of the optical system of the laser beam irradiation unit 32. Fig. 3 also includes a cross-sectional view of some of the components. In addition, various housings and the like are omitted in Fig. 3. Furthermore, the arrangement of the components of the laser beam irradiation unit 32 may be changed as appropriate.

[0044] The laser beam irradiation unit 32 includes a laser oscillator 46 that emits a laser beam 48. The laser oscillator 46 includes a medium such as Nd;YAG or Nd;YVO4, and can emit the laser beam 48 with a wavelength that is absorbed by the workpiece 1.

[0045] The laser beam irradiation unit 32 further includes an output adjustment unit (attenuator) 50 that adjusts the output of the laser beam 48 emitted from the laser oscillator 46. The output adjustment unit 50 includes a half-wave plate 54 rotatably supported by a hollow motor 52, and a beam splitter 56 that reflects the S-polarized component of the laser beam 48 and transmits the P-polarized component. The output adjustment unit 50 further includes a beam damper 58 that absorbs the S-polarized component of the laser beam 48 reflected by the beam splitter 56.

[0046] The laser beam 48 that reaches the output adjustment unit 50 travels inside the hollow motor 52 and passes through the half-wave plate 54. At this time, the laser beam 48 is optically rotated, and the ratio of the P-polarized component and the S-polarized component of the laser beam 48 that reaches the beam splitter 56 changes. The output adjustment unit 50 adjusts the amount of the P-polarized component of the laser beam 48 that reaches the beam splitter 56 by rotating the half-wave plate 54 with the hollow motor 52.

[0047] Therefore, the output adjustment unit 50 can adjust the amount of the component of the laser beam 48 that transmits through the beam splitter 56 by rotating the half-wave plate, that is, can adjust the output of the laser beam 48 emitted from the output adjustment unit 50. However, the configuration of the output adjustment unit 50 is not limited to this.

[0048] The laser beam irradiation unit 32 includes a mask 60 having a transmission window of a predetermined shape and configured to shape the laser beam 48, the output of which has been adjusted by the output adjustment unit 50, into a predetermined shape. However, in the laser beam irradiation unit 32, the shape of the laser beam 48 may be shaped by other methods.

[0049] Furthermore, the laser beam irradiation unit 32 includes a mirror 62 that reflects the laser beam 48 shaped by the mask 60 toward the chuck table 28, and a condenser lens 64 that condenses the laser beam 48 reflected by the mirror 62 onto the upper surface of the workpiece 1 held by the chuck table 28. The condenser lens 64 has a condensing point positioned on the surface 1a of the workpiece 1 held by the chuck table 28. The height of the condensing point may be adjusted by the Z-axis direction moving unit 34 or by another method.

[0050] When laser processing the workpiece 1 with the laser processing device 2, first, the frame unit 11 is held by the chuck table 28, and the surface 1a of the workpiece 1 is observed by the camera 40 to detect the position and extension direction of the planned division line 3. After that, the chuck table 28 is rotated around an axis perpendicular to the holding surface 28a, and the direction of the planned division line 3 is aligned with the X-axis or Y-axis direction.

[0051] Next, the Y-axis direction moving unit 6 and the X-axis direction moving unit 16 are operated to position one end of one of the planned division lines 3 below the laser beam irradiation unit 32. Thereafter, the laser oscillator 46 is operated to focus the laser beam 48 on the surface 1a of the workpiece 1, while the Y-axis direction moving unit 6 or the X-axis direction moving unit 16 is operated to feed the workpiece 1 for processing. Then, the workpiece 1 is laser processed (ablation processed) along the planned division line 3, and a division groove along the planned division line 3 is formed in the workpiece 1.

[0052] After the workpiece 1 has been laser-machined along one planned dividing line 3, the Y-axis direction moving unit 6 or the X-axis direction moving unit 16 is operated to index and feed the workpiece 1, and similarly laser-machine the workpiece 1 along the next planned dividing line 3. In this way, the workpieces 1 are laser-machined one after another along the planned dividing lines 3 that run in one direction.

[0053] Thereafter, the chuck table 28 is rotated, or the roles of the Y-axis direction moving unit 6 and the X-axis direction moving unit 16 are switched, and the workpiece 1 is laser-machined in the same manner along the division lines 3 that extend in the other directions. When the workpiece 1 is laser-machined in this manner along all the division lines 3, the workpiece 1 is divided by the division grooves to form individual chips.

[0054] In order to uniformly laser process a plurality of workpieces 1 using the laser processing device 2, it is necessary to irradiate the laser beam 48 under uniform conditions to each workpiece 1. However, while laser processing of the workpieces 1 is being performed, the state of the laser beam 48 may change.

[0055] For example, the operation of the laser oscillator 46 may become unstable, causing a pointing shift or a change in the energy distribution of the laser beam 48. Also, the output of the laser beam 48 may change, causing the laser beam 48 to not irradiate the workpiece 1 with the required output, or to irradiate the workpiece 1 with excessive output. In these cases, processing defects may occur.

[0056] Therefore, it is conceivable to periodically monitor the output of the laser beam 48 with the power meter 26. However, in order to measure the output of the laser beam 48, it is necessary to interrupt the laser processing of the workpiece 1 and irradiate the power meter 26 with the laser beam 48. In other words, since the laser processing of the workpiece 1 cannot be performed while the output of the laser beam 48 is being measured, there is a problem that the processing efficiency of the workpiece 1 in the laser processing device 2 decreases.

[0057] Furthermore, inside the output adjustment unit 50, minute dust particles generated when the hollow motor 52 rotates the half-wave plate 54 and grease used in the hollow motor 52 may fly up and some of these may enter the optical path. Also, the position of the mask 60 may change in a plane perpendicular to the optical path, and the laser beam 48 may not be shaped appropriately by the mask 60.

[0058] Another possibility is that debris generated when the workpiece 1 is laser processed by the laser beam 48 adheres to the outer surface of the focusing lens 64, preventing the laser beam 48 from being properly irradiated onto the workpiece 1.

[0059] In these cases, the laser beam 48 may be partially blocked or scattered by the foreign matter, causing a change in the shape of the laser beam 48. In other words, an abnormality may occur in the optical system, and the laser beam 48 may not be properly focused on the workpiece 1, resulting in the workpiece 1 not being properly laser-processed.

[0060] In this way, due to various factors, the laser beam 48 may not be irradiated to the workpiece 1 in a predetermined state, and the workpiece 1 may not be properly processed. Therefore, the laser processing device 2 according to this embodiment captures an image of the light generated by the laser beam 48 irradiated to the workpiece 1, and monitors the state of the laser beam 48 from the shape of the light reflected in the captured image.

[0061] Since the state of the laser beam 48 is reflected in the position and shape of the light captured in the captured image, the state of the laser beam 48 can be determined from the shape of the light, etc. Here, when the light is captured and determination is performed, it is not necessary to interrupt the laser processing of the workpiece 1. Below, the laser processing apparatus 2 according to this embodiment will be described, focusing on the configuration that contributes to monitoring the state of the laser beam 48.

[0062] When the workpiece 1 is irradiated with the laser beam 48, a portion of the workpiece 1 turns into plasma, generating light 66. The light 66 generated at the workpiece 1 reaches the condenser lens 64 and proceeds into the laser beam irradiation unit 32. The laser processing device 2 according to this embodiment includes a mechanism for capturing an image of this light 66.

[0063] More specifically, the laser beam irradiation unit 32 includes a dichroic mirror 68 between the mirror 62 and the condenser lens 64. The dichroic mirror 68 transmits the laser beam 48 emitted from the laser oscillator 46 and guides it to the condenser lens 64, and reflects light of wavelengths other than that of the laser beam 48. The dichroic mirror 68 reflects light 66 generated from the workpiece 1 by the laser beam 48 to an imaging unit 70, which will be described next.

[0064] That is, light 66 is generated when the laser beam 48 propagated through the focusing lens 64 and the dichroic mirror 68 is irradiated onto the workpiece 1, passes through the focusing lens 64, is reflected by the dichroic mirror 68, and reaches the imaging unit 70.

[0065] The imaging unit 70 captures an image of light 66 generated when the workpiece 1 is irradiated with the laser beam 48. The imaging unit 70 includes a mirror 74 that reflects the light reflected by the dichroic mirror 68 to an imaging element 72. The imaging element 72 is, for example, a CCD sensor or a CMOS sensor. The imaging unit 70 is connected to the control unit 42, and sends a captured image showing the light 66 obtained by imaging to the control unit 42.

[0066] Furthermore, the imaging unit 70 may be capable of irradiating illumination light onto the surface 1a of the workpiece 1. For example, the imaging unit 70 may further include a half mirror 80 provided between the dichroic mirror 68 and the mirror 74, and an illumination light source 78. The illumination light source 78 is, for example, a xenon flash lamp.

[0067] Illumination light 76 emitted from an illumination light source 78 is reflected by a half mirror 80 toward a dichroic mirror 68, and is then reflected by the dichroic mirror 68 and irradiated onto the surface 1a of the workpiece 1 through a condenser lens 64. When the illumination light 76 is irradiated onto the surface 1a of the workpiece 1, the surface 1a of the workpiece 1 appears together with the light 66 in the captured image acquired by the imaging unit 70. In this case, the irradiated area of ​​the surface 1a of the workpiece 1 with the laser beam 48 can be confirmed, making it possible to determine whether the irradiation position of the laser beam 48 is appropriate.

[0068] The captured images may be acquired repeatedly and continuously while the laser processing of the workpiece 1 is being performed. In this case, when a change occurs in the state of the laser beam 48, the change can be detected immediately, but an excessive load is placed on the control unit 42 that determines the state of the laser beam 48. If a sudden change in the state of the laser beam 48 is not expected, it is sufficient to acquire captured images at predetermined intervals.

[0069] 4 is a plan view showing a schematic diagram of a trajectory 13 of a spot irradiated with a laser beam 48 on the workpiece 1. As described above, the laser beam 48 is successively focused on the surface 1a of the workpiece 1 along the planned division line 3, so that the irradiated spot on the surface 1a moves along the planned division line 3. Then, for example, when the irradiated spot approaches a specific imaging position 15, the imaging unit 70 is operated to image the surface 1a of the workpiece 1, and the captured image is obtained. In this case, the load on the control unit 42 is reduced.

[0070] The state of the laser beam 48 based on the captured image formed by the imaging unit 70 is determined by the control unit 42 of the laser processing device 2. The control unit 42 has a determination section 42a that determines the state of the laser beam 48 irradiated to the workpiece 1 based on the shape of the light 66 shown in the captured image.

[0071] Next, a method of determining the state of the laser beam 48 performed by the determining unit 42a will be described. Figures 5(A) to 5(D) are plan views each showing a schematic representation of captured images 17a, 17b, 17c, and 17d of light generated when the laser beam 48 is irradiated to the workpiece 1 with different outputs. As shown in each figure, the captured images 17a, 17b, 17c, and 17d show light 19a, 19b, 19c, and 19d generated when the laser beam 48 is irradiated to the workpiece 1, respectively.

[0072] A laser beam 48 emitted from a laser oscillator 46 is shaped into a predetermined shape by a mask 60 and irradiated onto the workpiece 1. The cross-sectional shape of the laser beam 48 (shape in a plane perpendicular to the direction of travel) is shaped into, for example, an ellipse close to a rectangle. The irradiated area of ​​the laser beam 48 on the surface 1a of the workpiece 1 is set to an ellipse whose minor axis is aligned with the extension direction (processing feed direction) of the planned division lines 3 and whose major axis is aligned with the width direction of the planned division lines 3.

[0073] When the laser beam 48 is irradiated onto the workpiece 1 in this state, light 66 is generated in a shape that reflects the shape of the irradiated area, and the shapes of the lights 19a, 19b, 19c, and 19d reflected in each captured image 17a, 17b, 17c, and 17d also become elliptical.

[0074] The output of the laser beam 48 irradiated to the workpiece 1 when the captured image 17b shown in Fig. 5(B) is captured is greater than the output of the laser beam 48 irradiated to the workpiece 1 when the captured image 17a shown in Fig. 5(A) is captured. The output of the laser beam 48 irradiated to the workpiece 1 when the captured image 17c shown in Fig. 5(C) is captured is even greater, and the output of the laser beam 48 irradiated to the workpiece 1 when the captured image 17d shown in Fig. 5(D) is captured is even greater.

[0075] The size of each light 19a, 19b, 19c, 19d reflected in each captured image 17a, 17b, 17c, 17d is determined by the output of the laser beam 48 that contributed to its generation, and the larger the output, the larger the size of the light. Therefore, the output of the laser beam 48 can be evaluated from the size of the light generated by irradiating the workpiece 1 with the laser beam and reflected in the captured image. The determination section 42a of the control unit 42 can evaluate the output of the laser beam 48 from the captured image acquired by the imaging unit 70.

[0076] The output of the laser beam 48 can be adjusted by an output adjustment unit (attenuator) 50. Therefore, the control unit 42 may refer to the result of the evaluation of the output of the laser beam 48 performed by the judgment unit 42a and control the output adjustment unit (attenuator) 50 to adjust the output of the laser beam 48. In this case, the laser processing device 2 can monitor the output of the laser beam 48 even while the workpiece 1 is being laser processed, and can immediately correct the output when the output deviates from a predetermined value beyond a tolerable amount.

[0077] Furthermore, the determination section 42a of the control unit 42 may determine a state other than the output of the laser beam 48. For example, the presence or absence of an abnormality in the optical system may be determined as the state of the laser beam 48. Figures 6(A) to 6(C) are plan views that typically show captured images 17e, 17f, and 17g obtained by the imaging unit 70 when an abnormality such as the inclusion of a foreign object occurs in the optical system.

[0078] 6(A) to 6(C), when an abnormality occurs in the optical system of the laser beam 48, the laser beam 48 is irradiated to the workpiece 1 with a distorted cross-sectional shape. Accordingly, a distorted light 66 is generated on the surface 1a of the workpiece 1. Therefore, the captured images 17e, 17f, and 17g show the abnormally deformed light 19e, 19f, and 19g.

[0079] Therefore, the presence or absence of an abnormality in the optical system can be determined based on the presence or absence of abnormal deformation in the shape of the light 66 generated when the laser beam 48 is irradiated onto the workpiece 1 and captured in the captured image. The determination section 42a of the control unit 42 can determine the presence or absence of an abnormality in the optical system of the laser beam 48 based on the presence or absence of abnormal deformation in the shape of the light captured in the captured image.

[0080] For example, it is possible to provide a power meter for monitoring the state of the laser beam 48 inside the laser beam irradiation unit 32. In this case, even if an abnormality occurs outside the laser beam irradiation unit 32, such as a foreign object being mixed in the traveling path of the laser beam 48, the abnormality of the laser beam 48 cannot be detected by the power meter.

[0081] In contrast to this, in the laser processing device 2 according to this embodiment, the state of the laser beam 48 is monitored based on the light 66 that is generated when the laser beam 48 is actually irradiated onto the workpiece 1. Therefore, even if a foreign object is present on the traveling path of the laser beam 48 outside the laser beam irradiation unit 32, it is possible to detect an abnormality in the laser beam 48.

[0082] The determination unit 42a may determine whether or not there is an abnormality in the laser beam 48 by comparing the captured image obtained by the imaging unit 70 with a reference image prepared in advance. In this case, the control unit 42 includes a storage unit 42b that stores in advance one or more reference images captured by capturing light generated when the workpiece 1 is irradiated with the laser beam 48 under predetermined conditions, as shown in FIG.

[0083] Furthermore, the control unit 42 further includes a comparison section 42c that compares the reference image stored in the storage section 42b with the captured image. The judgment section 42a then performs judgment based on the result of the comparison between the reference image and the captured image by the comparison section 42c. For example, the captured image obtained by irradiating the workpiece 1 with a laser beam 48 in a predetermined state and capturing the light 66 generated by the workpiece 1 with the imaging unit 70 is registered as a reference image in the storage section 42b.

[0084] In particular, it is preferable to irradiate the workpiece 1 with the laser beam 48 at a plurality of predetermined outputs, and have the imaging unit 70 capture each of the captured images of the light 66 generated at the workpiece 1, and store them in the memory unit 42b for each output of the laser beam 48. In this case, the comparison unit 42c can perform the comparison by using a reference image corresponding to the output set for the laser beam 48.

[0085] The comparison unit 42c processes, for example, a captured image showing light 66 generated on the workpiece 1 when the laser beam 48 is irradiated thereon, extracts the contour of the area showing the light 66, and specifies the shape of the area. The comparison unit 42c also selects a reference image corresponding to the output of the laser beam 48 irradiated to the workpiece 1, reads it from the storage unit 42b, and similarly specifies the shape of the light shown in the selected reference image.

[0086] Thereafter, the comparison unit 42c compares the captured image captured by the imaging unit 70 with the reference image, and calculates the degree of match between the areas capturing the light generated by the workpiece 1. Then, the determination unit 42a determines that there is no abnormality in the state of the laser beam 48 when the two match by a predetermined threshold or more, and determines that there is an abnormality in the state of the laser beam 48 when the degree of match between the two falls below the threshold.

[0087] However, the method of judgment by the judgment unit 42a based on the result of the comparison by the comparison unit 42c is not limited to this. Furthermore, the judgment performed by the judgment unit 42a is not limited to the method of comparing the captured image captured by the imaging unit 70 with the reference image. Next, other methods of judgment performed by the judgment unit 42a will be described.

[0088] Fig. 7 is a plan view showing a schematic diagram of a captured image 17h obtained when the light 66 generated by irradiating the workpiece 1 with the laser beam 48 is captured by the imaging unit 70. As shown in Fig. 7, the shape of the light 19h shown in the captured image 17h is a distorted elliptical shape, unlike the light 19a, 19b, 19c, and 19d shown in Figs. 4(A) to 4(D). The method for evaluating the shape of the light 19h is as follows.

[0089] In the captured image 17h, a center line 21 is set that passes through the center of the portion of the surface 1a of the workpiece 1 that is irradiated with the laser beam 48 and crosses the light 19h along the minor axis direction (horizontal direction in FIG. 7). The width of the light 19h is measured at points equidistant from the center line 21 along the major axis direction (vertical direction in FIG. 7), and the difference between the respective widths of the measured light 19h is calculated. Then, this difference in width is evaluated. For example, when the length of the light 19h in the vertical direction is 35 μm to 60 μm, the width of the light 19h may be measured at intervals of about 5 μm to 10 μm from the center line 21.

[0090] For example, width 23a of light 19h at a position above center line 21 and close to center line 21, width 25a of light 19h at a position slightly away from center line 21, and width 27a of light 19h at a position further away from center line 21 are measured. In addition, width 23b of light 19h at a position corresponding to the measurement position of width 23a, width 25b of light 19h at a position corresponding to the measurement position of width 25a, and width 27b of light 19h at a position corresponding to the measurement position of width 27a are measured below center line 21 of light 19h.

[0091] Then, the difference between widths 23a and 23b, the difference between widths 25a and 25b, and the difference between widths 27a and 27b are calculated as the differences in the widths of light 19h at points equidistant above and below center line 21. Then, it is determined whether each difference value exceeds a predetermined threshold value.

[0092] In the laser processing device 2, the shape of the transmission window of the mask 60 and the arrangement of each optical component are determined so that the irradiated area of ​​the laser beam 48 on the surface 1a of the workpiece 1 has a predetermined elliptical shape. Therefore, the predetermined threshold value is preferably set based on the width of the planned irradiated area of ​​the laser beam 48 on the surface 1a of the workpiece 1.

[0093] For example, the threshold value may be set to 15% to 25% of the width of the elliptical region to be irradiated at the center line along the minor axis of the elliptical region to be irradiated, and preferably set to about 20%. For example, when the width of the elliptical region to be irradiated at the center line along the minor axis is 10 μm, the threshold value may be set to 2 μm.

[0094] The determination unit 42a determines that there is no abnormality in the state of the laser beam 48 when all of the differences in the width of the light 19h at points equidistant above and below the center line 21 are below 2 μm. On the other hand, when any of the differences is 2 μm or more, the determination unit 42a determines that there is an abnormality in the state of the laser beam 48.

[0095] The predetermined threshold value may be set based on the width of the center line along the minor axis direction of the light reflected in the reference image described above, or may be set based on the width of the center line 21 of the light 19h reflected in the captured image 17h.

[0096] When it is determined by this method that there is an abnormality in the state of the laser beam 48, one possible cause of the abnormality is a misalignment of the mask 60. Therefore, a possible countermeasure would be to check the adjustment screws that movably fix the mask 60 and readjust the position of the mask 60.

[0097] The control unit 42 may, for example, notify the user or manager of the laser processing device 2 of the result of the judgment by the judging section 42a by displaying the result of the judgment on the display unit 44. Furthermore, when it is detected that the state of the laser beam 48 is in a state where the occurrence of a processing defect is inevitable as a result of judging the state of the laser beam 48, the control unit 42 may immediately interrupt the processing of the workpiece 1.

[0098] As described above, in the laser processing device according to this embodiment, when laser processing the workpiece 1 with the laser beam 48, the state of the laser beam 48 is judged by utilizing light caused by plasma or the like generated in the workpiece 1. Therefore, it is not necessary to stop the laser processing of the workpiece 1 to judge the state of the laser beam 48.

[0099] The present invention is not limited to the above embodiment, and can be modified in various ways. For example, in the above embodiment, the storage unit 42b of the control unit 42 may store and accumulate not only a reference image used for comparison with the captured image captured by the imaging unit 70, but also the captured image. In this case, when an abnormality occurs in the state of the laser beam 48 or when a processing defect occurs in the workpiece 1, the captured image stored in the storage unit 42b can be used to identify the cause of the abnormality.

[0100] In addition, the structures, methods, etc. according to the above-described embodiments can be modified as appropriate without departing from the scope of the object of the present invention. [Explanation of symbols]

[0101] 1 Workpiece 1a surface 1b back side 3. Planned division line 5 Devices 7 Frame 7a aperture 9 Dicing Tape 11 Frame unit 13 Trajectory 15 Imaging position 17a, 17b, 17c, 17d, 17e, 17f, 17g, 17h Images 19a,19b,19c,19d,19e,19f,19g,19h light 21 Center line 23a,23b,25a,25b,27a,27b width 2 Laser processing equipment 4 Foundation 6,16 Mobile Units 8,18 Guide rail 10,20 Moving table 12,22 Ball screw 14,24 Pulse motor 26 Power Meter 28 Chuck Table 28a Holding surface 28b Clamp 32 Laser beam irradiation unit 34 Z-axis direction movement unit 36 Lifting body 38 Arm 40 Camera 42 Control Unit 42a Judgment part 42b Storage section 42c Comparison section 44 Display unit 46 Laser Oscillator 48 Laser Beam 50 Output adjustment unit (attenuator) 52 Hollow Motor 54 Half-wave plate 56 Beam splitter 58 Beam Dumper 60 Mask 62 Mirror 64 Condenser Lens 66 light 68 Dichroic Mirror 70 Imaging unit 72 Image sensor 74 Mirror 76 Illumination 78 Lighting source 80 Half Mirror

Claims

1. A chuck table for holding the workpiece; a laser beam irradiation unit that irradiates a laser beam onto a workpiece held on the chuck table to perform laser processing of the workpiece; an imaging unit that captures light resulting from plasma generated when the workpiece is irradiated with the laser beam and forms an image; a control unit; The laser beam irradiation unit includes: A laser oscillator; a condenser lens for condensing the laser beam emitted from the laser oscillator and irradiating the laser beam on the workpiece; The control unit has a determination unit that determines a state of the laser beam irradiated to the workpiece based on the shape of the light reflected in the captured image, The determination unit evaluates the output of the laser beam based on the magnitude of the light reflected in the captured image, The control unit adjusts the output of the laser beam by referring to the result of evaluation of the output of the laser beam performed by the judgment unit when the laser processing of the workpiece is being performed by the laser beam irradiation unit.

2. The control unit a storage unit that stores in advance a reference image obtained by capturing light resulting from plasma generated when the workpiece is irradiated with the laser beam under predetermined conditions; a comparison unit that compares the reference image stored in the storage unit with the captured image, 2. The laser processing apparatus according to claim 1, wherein the determination section makes a determination based on a result of a comparison between the reference image and the captured image by the comparison section.

3. the laser beam irradiation unit has an attenuator disposed between the laser oscillator and the condenser lens and configured to adjust the output of the laser beam emitted from the laser oscillator; 3. The laser processing apparatus according to claim 1, wherein the control unit controls the attenuator to adjust the output of the laser beam.

4. the laser beam irradiation unit further includes a dichroic mirror that transmits the laser beam emitted from the laser oscillator and guides it to the condenser lens, and reflects light of wavelengths other than the wavelength of the laser beam; 4. The laser processing apparatus according to claim 1, wherein the light imaged by the imaging unit is generated when the laser beam propagated through the focusing lens and the dichroic mirror is irradiated onto the workpiece, passes through the focusing lens, is reflected by the dichroic mirror, and reaches the imaging unit.

5. 5. The laser processing apparatus according to claim 1, wherein the determining unit can determine the presence or absence of an abnormality in the optical system of the laser beam based on the presence or absence of an abnormal deformation of the shape of the light reflected in the captured image.

Images