Inspection method for laser processing device and laser processing method

Abstract

To prevent a buffer layer from being fractured insufficiently due to processing performance of a laser processing device, in performing laser processing to a work-piece.SOLUTION: An inspection method for a laser processing device comprises: a laser processing step of performing laser processing to a predetermined area of a substrate for inspecting, by scanning the predetermined area with a pulse-shape laser beam using a laser beam scanning unit of a laser processing device, after making a holding table of the laser processing device remain still with the substrate for inspecting held by the holding table; a photographing step of photographing a plurality of processing traces formed on the predetermined area, after the lase processing step; and a determining step of determining whether an abnormality occurs on the laser beam scanning unit or not, on the basis of an image photographed in the photographing step.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an inspection method for a laser processing apparatus that inspects whether or not there is an abnormality in a laser beam scanning unit for scanning a laser beam, and a laser processing method that performs laser processing on a workpiece after the inspection. [Background technology]

[0002] In the manufacturing process of optical devices such as LEDs (Light Emitting Diodes) and LDs (Laser Diodes), a processing method called Laser Lift-Off (LLO) is often used to transfer multiple optical devices formed on an epitaxy substrate such as a sapphire substrate via a buffer layer to a transfer substrate.

[0003] In the laser lift-off method, first, each optical device is bonded to a transfer substrate via a metal bonding layer, and then a laser beam is irradiated to the buffer layer through the epitaxy substrate to destroy the buffer layer. Next, the epitaxy substrate is peeled off, and each optical device is transferred to the transfer substrate.

[0004] A laser processing device is known as a processing device for destroying a buffer layer (see, for example, Patent Document 1). This laser processing device includes a laser beam scanning unit that can move the focused spot of a laser beam within a predetermined plane.

[0005] However, due to dirt on the mirrors, lenses, etc. that make up the laser beam scanning unit, deterioration of the mirrors, lenses, etc., malfunction of the motors that operate the mirrors, etc., the size and shape of the focused spot, the spacing between multiple focused spots, etc. change depending on the irradiation position of the laser beam, and therefore the buffer layer may not be sufficiently destroyed.

[0006] Of course, the problem of the buffer layer not being sufficiently destroyed can be solved by replacing the laser beam scanning unit itself with a new one that is free of dirt, deterioration, malfunctions, etc. (i.e., has no problems with processing performance); however, this would increase the cost of laser processing. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2013-179237 A Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, even if there are some problems with the processing performance of the laser beam scanning unit, there is a demand to continue using the laser beam scanning unit.

[0009] The present invention has been made in consideration of these problems, and aims to prevent insufficient destruction of a buffer layer due to the processing performance of a laser processing device when performing laser processing on a workpiece. [Means for solving the problem]

[0010] According to one aspect of the present invention, there is provided an inspection method for a laser processing apparatus, comprising: a laser processing step of holding an inspection substrate on a holding table of the laser processing apparatus while the holding table is stationary, and then scanning a predetermined area of ​​the inspection substrate with a pulsed laser beam using a laser beam scanning unit of the laser processing apparatus to perform laser processing on the predetermined area; an imaging step of imaging a plurality of processing marks formed in the predetermined area after the laser processing step; and a judgment step of judging whether or not there is an abnormality in the laser beam scanning unit based on the image obtained in the imaging step.

[0011] Preferably, in the determination step, it is determined whether or not there is an abnormality in the laser beam scanning unit based on at least one characteristic amount of the spacing, size, and shape of a plurality of processing marks formed on the inspection board.

[0012] Preferably, the judgment step includes a storage step in which a controller of the laser processing apparatus links and stores the image obtained in the imaging step with coordinates corresponding to the image, and an abnormal area identification step in which, based on the image and the coordinates stored in the storage step, an abnormal area is identified on the inspection board where scanning of the laser beam by the laser beam scanning unit has become abnormal.

[0013] Preferably, the inspection method for a laser processing apparatus further includes a notification step in which, if it is determined in the judgment step that there is an abnormality in the laser beam scanning unit, the controller of the laser processing apparatus notifies an operator of the existence of an abnormality using at least one of a display, an indicator light, and a speaker.

[0014] According to another aspect of the present invention, there is provided a laser processing method for performing laser processing on a workpiece using a laser processing device, the method including: a preliminary processing step of performing laser processing on a predetermined area of ​​the inspection substrate by scanning the predetermined area of ​​the inspection substrate with a pulsed laser beam using a laser beam scanning unit of the laser processing device while the holding table of the laser processing device is stationary in a state in which the holding table holds the inspection substrate; an imaging step of imaging a plurality of processing marks formed in the predetermined area after the preliminary processing step; a storage step of storing an image obtained in the imaging step in association with coordinates corresponding to the image; and The laser processing method includes an abnormal area identifying step of identifying an abnormal area on the inspection board where scanning of the laser beam by the laser beam scanning unit has become abnormal based on the image and the coordinates stored in the memory step, and a main processing step of performing laser processing on the workpiece by scanning the workpiece with the laser beam using the laser beam scanning unit after the abnormal area identifying step, wherein, in the main processing step, when performing laser processing on the abnormal area identified in the abnormal area identifying step, processing conditions different from processing conditions applied to normal areas other than the abnormal area are applied. Effect of the Invention

[0015] In a method for inspecting a laser processing device according to one embodiment of the present invention, after a laser processing process is performed on a test substrate using a laser beam scanning unit, an image of a plurality of processing marks formed in a specified area of ​​the test substrate is captured (image capturing process).

[0016] Then, based on the image obtained in the imaging step, it is determined whether or not there is an abnormality in the laser beam scanning unit (determination step). Therefore, an abnormality in the laser beam scanning unit can be detected before laser processing is performed on the workpiece.

[0017] When an abnormality in the laser beam scanning unit is detected, the influence of the abnormality in the laser beam scanning unit can be mitigated by, for example, changing the processing conditions, and therefore, when performing laser processing on the workpiece, it is possible to prevent insufficient destruction of the buffer layer due to the processing performance of the laser processing device. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a flow diagram of a laser processing method. [Diagram 2] FIG. 2 is a perspective view of the laser processing device. [Diagram 3] FIG. 3(A) is a side view showing an outline of the galvano scanner, and FIG. 3(B) is a plan view showing an outline of the galvano scanner. [Figure 4] FIG. 4(A) is a diagram showing an outline of an example of a movement path of a focal point in a laser processing process, and FIG. 4(B) is a diagram showing an outline of another example of a movement path of a focal point in a laser processing process. [Diagram 5] FIG. [Figure 6] FIG. 13 is a schematic diagram showing an example of a machining result during normal operation. [Figure 7] 11A and 11B are schematic diagrams showing an example of a processing result including a case where an abnormal operation occurs; [Figure 8] FIG. [Figure 9] FIG. [Figure 10] 1A to 1C are diagrams showing a main processing step in which laser processing is performed on a workpiece. [Figure 11] FIG. 11A is a diagram showing an outline of an example of a movement path of a light-focusing point according to a modified example, and FIG. 11B is a diagram showing an outline of another example of a movement path of a light-focusing point according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] An embodiment according to one aspect of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a flow diagram of a laser processing method for performing laser processing on a workpiece 21 (see Fig. 10) using a laser processing device 2 (see Fig. 2).

[0020] The laser processing method of this embodiment includes (i) an inspection method for the laser processing apparatus 2, which includes a laser processing step (preliminary processing step) S10, an imaging step S20, a judgment step S30, and a notification step S40 for an inspection substrate 11 (see Figure 3 (A)), and (ii) a main processing step S50 in which laser processing is performed on the workpiece 21 via a processing condition change step S42.

[0021] First, the laser processing device 2 used in each process will be described with reference to Fig. 2 to Fig. 4(B). Fig. 2 is a perspective view of the laser processing device 2. The X-axis direction (processing feed direction), Y-axis direction (indexing feed direction), and Z-axis direction (up-down direction, vertical direction) shown in Fig. 2 are mutually orthogonal.

[0022] The laser processing device 2 has a base 4 that supports or houses each of the components. A movement mechanism 6 is provided on the upper surface of the base 4. The movement mechanism 6 has a pair of Y-axis guide rails 8 fixed to the upper surface of the base 4. The pair of Y-axis guide rails 8 are arranged along the Y-axis direction.

[0023] A Y-axis direction moving plate 10 is attached to the upper part of the pair of Y-axis direction guide rails 8 so as to be slidable along the pair of Y-axis direction guide rails 8. A nut portion (not shown) is fixed to the lower part of the Y-axis direction moving plate 10, and a screw shaft 12 is rotatably connected to the nut portion by using a plurality of balls (not shown).

[0024] The screw shaft 12 is disposed along the Y-axis direction between a pair of Y-axis guide rails 8. A drive source 14 such as a pulse motor for rotating the screw shaft 12 is connected to one end of the screw shaft 12.

[0025] When the driving source 14 is operated, the Y-axis direction moving plate 10 moves along the Y-axis direction. The pair of Y-axis direction guide rails 8, the Y-axis direction moving plate 10, the screw shaft 12, the nut portion, the driving source 14, etc. constitute a Y-axis direction moving mechanism.

[0026] A Y-axis linear scale (not shown) with its longitudinal direction aligned along the Y-axis direction is provided near the Y-axis guide rail 8. A read head (not shown) that optically reads the markings of the Y-axis linear scale is provided on the lower surface of the Y-axis moving plate 10. The Y-axis linear scale and the read head constitute a Y-axis linear encoder.

[0027] A pair of X-axis guide rails 16 arranged along the X-axis direction are fixed to the upper part of the Y-axis moving plate 10. An X-axis moving plate 18 is slidably attached to the upper part of the pair of X-axis guide rails 16.

[0028] A nut portion (not shown) is fixed to the lower portion of the X-axis direction moving plate 18, and a screw shaft 20 is rotatably connected to the nut portion by using a plurality of balls (not shown). The screw shaft 20 is disposed along the X-axis direction between a pair of X-axis direction guide rails 16.

[0029] A driving source 22 such as a pulse motor for rotating the screw shaft 20 is connected to one end of the screw shaft 20. When the driving source 22 is operated, the X-axis direction moving plate 18 moves along the X-axis direction.

[0030] The pair of X-axis guide rails 16, the X-axis moving plate 18, the screw shaft 20, the nut portion, the drive source 22, etc. constitute an X-axis moving mechanism. An X-axis linear scale (not shown) is provided near the X-axis guide rails 16, with its longitudinal direction aligned along the X-axis direction.

[0031] A read head (not shown) that optically reads the markings of the X-axis linear scale is provided on the lower surface of the X-axis moving plate 18. The X-axis linear scale and the read head constitute an X-axis linear encoder.

[0032] A cylindrical table base 24 is provided on the upper part of the X-axis direction moving plate 18. The table base 24 has a rotation drive source (not shown) such as a motor. A disk-shaped chuck table (holding table) 26 is disposed on the upper part of the table base 24. The chuck table 26 can be rotated around a predetermined rotation axis parallel to the Z-axis direction by the rotation drive source.

[0033] The chuck table 26 has a disk-shaped frame made of non-porous metal. A disk-shaped recess is formed in the center of the frame and is exposed on the upper surface of the frame. A disk-shaped porous plate made of ceramics is fixed in the recess.

[0034] A flow path is formed in the frame so as to connect to the recess. A suction source (not shown) such as a vacuum pump is connected to this flow path. Negative pressure generated by the suction source is transmitted to the upper surface of the porous plate via the flow path.

[0035] The annular upper surface of the frame and the circular upper surface of the porous plate are substantially flush with each other, and function as a substantially flat holding surface 26a for suction-holding the testing substrate 11, the workpiece 21, etc. The holding surface 26a is disposed substantially parallel to the XY plane.

[0036] A plurality of clamp units 26b (four in this embodiment) are provided at approximately equal intervals on the outer periphery of the chuck table 26 along the circumferential direction of the chuck table 26. Each clamp unit 26b clamps a ring frame 15 (or a ring frame 35) described later.

[0037] A support structure 30 is provided on a predetermined region of the base 4 located behind (one side in the Y-axis direction) the movement mechanism 6. A Z-axis direction movement mechanism 32 is provided on one side surface of the support structure 30 along the YZ plane.

[0038] The Z-axis direction moving mechanism 32 is fixed to one side of the support structure 30 and has a pair of Z-axis direction guide rails 34 arranged along the Z-axis direction. A Z-axis direction moving plate 36 is slidably attached to the front surface side of the pair of Z-axis direction guide rails 34.

[0039] A nut portion (not shown) is fixed to the rear surface side of the Z-axis direction moving plate 36. A screw shaft (not shown) is rotatably connected to the nut portion (not shown) by using a plurality of balls (not shown). The screw shaft is disposed between a pair of Z-axis direction guide rails 34 along the Z-axis direction.

[0040] A driving source 38 such as a pulse motor for rotating the screw shaft is connected to the upper end of the screw shaft. When the driving source 38 is operated, the Z-axis direction moving plate 36 moves along the Z-axis direction. A support 40 is fixed to the front surface side of the Z-axis direction moving plate 36.

[0041] The support 40 supports a part of the laser beam irradiation unit 42. The laser beam irradiation unit 42 has a cylindrical housing 44 whose longitudinal portion is disposed along the Y-axis direction, and a part of the housing 44 is supported by the support 40.

[0042] A laser oscillator 46 (see FIG. 3(A)) is provided in an optical box (not shown) placed on the base 4. The laser oscillator 46 generates a pulsed laser beam L having a predetermined wavelength (for example, 266 nm).

[0043] The laser oscillator 46 is, for example, a Nd:YAG crystal or a Nd:YVO 4It includes a laser medium such as a crystal, an excitation light source such as a lamp that irradiates the laser medium with excitation light, and a switch such as a Q switch that controls the timing at which the laser beam L is emitted (none of which are shown).

[0044] A laser beam scanning unit 48 is fixed to the tip of the housing 44. The laser beam scanning unit 48 has a galvano scanner 50 for scanning with a laser beam L within a predetermined plane disposed approximately parallel to the XY plane.

[0045] Fig. 3(A) is a side view showing an overview of the galvano-scanner 50, and Fig. 3(B) is a plan view showing an overview of the galvano-scanner 50. The galvano-scanner 50 has a first mirror 50a that moves the light-focusing point along the X-axis direction, and a second mirror 50b that moves the light-focusing point along the Y-axis direction.

[0046] The first mirror 50a has a rotation axis arranged along the Z-axis direction, and the reflecting surface of the first mirror 50a is configured to be rotatable within a predetermined angle range on the XY plane. The second mirror 50b has a rotation axis arranged along the X-axis direction, and the reflecting surface of the second mirror 50b is configured to be rotatable within a predetermined angle range on the YZ plane.

[0047] The laser beam L reflected by the galvano scanner 50 is irradiated substantially perpendicularly to the holding surface 26a by passing through an fθ lens (i.e., a telecentric fθ lens) 52. The focal point of the laser beam L irradiated onto the holding surface 26a via the fθ lens 52 usually has substantially the same diameter regardless of the position in the XY plane.

[0048] The laser beam scanning unit 48 moves the focal point of the laser beam L along the XY plane. The laser beam scanning unit 48 repeats a series of steps, for example, moving the focal point in one direction along the X-axis direction, then moving it a predetermined distance along the Y-axis direction, then moving it in the other direction along the X-axis direction, and then moving it again a predetermined distance along the Y-axis direction (see FIG. 4(A)).

[0049] Also, for example, the laser beam scanning unit 48 moves the focal point of the laser beam L in a spiral shape (i.e., so as to approach the center of rotation as it rotates) (see FIG. 4(B)). Note that the galvano scanner 50 may move the focal point so as to move away from the center of rotation as it rotates.

[0050] Incidentally, a plurality of polygon mirrors (not shown) may be used instead of the galvano scanner 50, and a piezo scanner (not shown) may be used as the laser beam scanning unit 48. In addition, any two of the galvano scanner 50, the polygon mirror, and the piezo scanner may be combined. Furthermore, a polygon mirror and an acousto-optic deflector (AOD) may be combined.

[0051] 2, a microscope camera unit 54 is fixed to the side surface of the tip of the housing 44 in a manner that allows it to face the holding surface 26a. The microscope camera unit 54 has an objective lens and an imaging element such as a CCD (Charge-Coupled Device) image sensor or a CMOS (Complementary Metal-Oxide-Semiconductor) image sensor.

[0052] The microscope camera unit 54 in this embodiment is an area sensor camera capable of capturing an image of a planar area of ​​a predetermined size, but may be a line sensor camera capable of capturing an image of a linear area of ​​a predetermined length. Moreover, the microscope camera unit 54 may be equipped with both an area sensor camera and a line sensor camera.

[0053] The microscope camera unit 54 is provided with a light source such as an LED for illuminating an object to be imaged. The housing 44, the laser beam scanning unit 48, the microscope camera unit 54, etc. can be moved integrally along the Z-axis direction by the Z-axis direction moving mechanism 32.

[0054] An exterior panel that covers the above-mentioned components is provided on the base 4. In Fig. 1, the exterior panel is indicated by a dashed line. A touch panel 56 is provided on the front side of the exterior panel. The touch panel 56 is a display such as a liquid crystal display or an OLED (Organic Light Emitting Diode) display that functions as an input device and a display device.

[0055] For example, an operator can input processing conditions to the laser processing device 2 via the touch panel 56, and can also view a GUI (Graphical User Interface), the input processing conditions, images obtained by the microscope camera unit 54, etc. via the touch panel 56.

[0056] A display device that does not have the function of an input device may be provided instead of the touch panel 56. In this case, however, an input device (such as a keyboard, mouse, trackball, touchpad, or digitizer) for the operator to input instructions is provided separately.

[0057] A cylindrical indicator light 58 is provided on the top surface of the exterior panel. The indicator light 58 has a base 58a in which a speaker (not shown) is built in. The speaker may be provided in the laser processing device 2 separately from the indicator light 58.

[0058] Light-emitting unit 58b capable of emitting light in different colors is provided on base 58a. Light-emitting unit 58b has multiple light-emitting regions arranged to overlap in the Z-axis direction. Each of the multiple light-emitting regions includes an LED and a light-diffusing lens provided to surround the LED, and can light up or flash in different predetermined colors such as red, yellow, blue, and green.

[0059] The operations of the moving mechanism 6 , the Z-axis direction moving mechanism 32 , the laser beam irradiation unit 42 , the microscope camera unit 54 , the touch panel 56 , the indicator lamp 58 , etc. are controlled by a controller 60 .

[0060] 2, for convenience of explanation, the controller 60 is shown outside the laser processing device 2, but in reality, the controller 60 is disposed inside the base 4 or inside the exterior panel. The controller 60 is configured by a computer including, for example, a processor 60a represented by a CPU (Central Processing Unit) and a memory 60b.

[0061] The memory 60b includes a main storage device such as a dynamic random access memory (DRAM) and an auxiliary storage device such as a flash memory, a hard disk drive, a solid state drive, etc. The auxiliary storage device stores software including a predetermined program.

[0062] The functions of the controller 60 are realized by operating the processor 60a etc. in accordance with this software. The controller 60 includes a function of performing image processing on the image obtained by the microscope camera unit 54, in addition to a function of controlling the operation of the laser processing device 2.

[0063] Next, a description will be given of the inspection substrate 11 to be subjected to laser processing in the inspection method of the laser processing apparatus 2 from the laser processing step S10 to the notification step S40. The inspection substrate 11 is a disk-shaped wafer made of single crystal silicon.

[0064] The inspection substrate 11 is a dummy wafer used for inspecting whether or not there is an abnormality in the laser beam scanning unit 48, and has approximately the same diameter as the workpiece 21. However, it is sufficient that the inspection substrate 11 has the same shape and size as the workpiece 21.

[0065] Both the test substrate 11 and the workpiece 21 usually have a disk shape, but may have a rectangular plate shape or other shapes. However, the thickness of the test substrate 11 and the workpiece 21 may be different.

[0066] The inspection board 11 satisfies the requirements stipulated in, for example, SEMI M18 or SEMI M24 of the SEMI (Semiconductor Equipment and Materials International) standard. Note that, although the above-mentioned optical device is not formed on the inspection board 11, an optical device is formed on the workpiece 21.

[0067] When laser processing is performed on the testing board 11, a testing board unit 17 is formed by integrating the testing board 11, the tape 13, and the ring frame 15 as shown in Fig. 3(A). Specifically, first, the testing board 11 is placed in the opening of the ring frame 15.

[0068] Next, a circular tape 13 is attached to one surface of the ring frame 15 and one surface 11b of the testing board 11 to form a testing board unit 17. In the testing board unit 17, the testing board 11 is supported by the metal ring frame 15 via the resin tape 13.

[0069] Next, the steps from the laser processing step S10 to the notification step S40 will be described. In the laser processing step S10, first, the inspection board unit 17 is placed on the chuck table 26. Next, the ring frame 15 is clamped by each clamp unit 26b, and the inspection board 11 is suction-held by the holding surface 26a via the tape 13.

[0070] In this state, the chuck table 26 is made stationary directly below the laser beam scanning unit 48. Then, the laser beam scanning unit 48 is used to scan the other surface 11a of the inspection board 11 with a laser beam L, thereby performing laser processing on substantially the entirety (i.e., a predetermined region) of the other surface 11a of the inspection board 11 (laser processing step S10).

[0071] For example, by irradiating the inspection board 11 with a laser beam L corresponding to a predetermined number of pulses, one processing mark 19 (see FIG. 6) is formed on the other surface 11a of the inspection board 11. By scanning the other surface 11a with the pulsed laser beam L, multiple processing marks 19 are formed on the other surface 11a.

[0072] In this embodiment, performing laser processing on the entire other surface 11a of the testing substrate 11 does not mean forming a plurality of processing marks 19 evenly over the entire other surface 11a without any gaps.

[0073] In this embodiment, the shape of the focused spot is circular or elliptical or similar, and multiple processing marks 19 are formed by scanning a plane arranged approximately parallel to the XY plane with a pulsed laser beam L using a laser beam scanning unit 48, so that unprocessed areas always exist near adjacent processing marks 19.

[0074] In other words, the multiple processing marks 19 are not formed evenly across the entire other surface 11a without any gaps. There are areas on the other surface 11a where the multiple processing marks 19 are not in contact with each other and do not overlap each other.

[0075] If there is no problem with the processing performance of the laser beam scanning unit 48, when laser processing is performed on the entire other surface 11a of the inspection board 11, the distance between two adjacent processing marks 19 in the scanning direction of the laser beam L will be approximately constant, or the overlap rate of these two processing marks 19 (i.e., the ratio of the area of ​​the overlapping portion of the two processing marks 19 to the area of ​​one processing mark 19) will be approximately constant.

[0076] In addition, within the plane where the laser beam L is scanned, the spacing (or overlap rate) between two adjacent processing marks 19 in a direction perpendicular to the scanning direction of the laser beam L is determined appropriately based on the processing conditions, but is usually set to be the same as the spacing (or overlap rate) between two processing marks 19 in the scanning direction.

[0077] Fig. 4(A) is a diagram showing an outline of an example of a movement path of the focal point of the laser beam L in the laser processing step S10. Of course, in reality, the laser beam L is scanned so that the interval between adjacent movement loci in a direction perpendicular to the movement locus of the focal point becomes closer than that shown in Fig. 4(A).

[0078] 4A, when the focal point is moved back and forth, the moving speed of the focal point is constant regardless of the position on the other surface 11a. An example of processing conditions in the laser processing step S10 is shown below.

[0079] Wavelength: 266nm Average power: 0.1W to 2W Pulse energy: 0.5μJ to 10μJ Repetition rate: 50kHz to 200kHz Spot diameter: 10μm to 50μm Defocus amount: 0.5mm to 2mm above (from the other surface 11a) Scanning speed: 50mm / s to 100mm / s

[0080] In the example shown in FIG. 4(A), the focal point is moved from the outer edge to the outer edge of the other surface 11a so as to traverse the other surface 11a by moving in one direction or the other along the horizontal direction of the other surface 11a, and the focal point is moved stepwise along the vertical direction from one end of the other surface 11a to the other end.

[0081] In the laser processing step S10, the scanning speed is adjusted so that the distance between the geometric centers of the light-focusing points in the scanning direction is approximately constant. The conditions such as the absorptance of the laser beam L by the inspection substrate 11 are approximately constant regardless of the location on the other surface 11a.

[0082] Therefore, if there is no abnormality in the processing performance of the laser processing device 2, when the interval between the geometric centers of the light focusing points is made approximately constant, the interval between the geometric centers of the multiple processing marks 19 will also be approximately constant in the scanning direction.

[0083] For example, as long as the motor (actuator) that constitutes the galvano scanner 50 operates normally and there is no adhesion on the first mirror 50a, the second mirror 50b, and the fθ lens 52 and there is no significant deterioration thereon, if the spacing between the geometric centers of the focusing points is approximately constant, then the spacing between the geometric centers of the multiple processing marks 19 will also be approximately constant in the scanning direction.

[0084] Fig. 4(B) is a diagram showing an outline of another example of the movement path of the focal point in the laser processing step S10. Of course, in reality, the laser beam L is scanned so that the intervals between adjacent movement loci are closer than those shown in Fig. 4(B).

[0085] In the laser processing step S10, the interval between the geometric centers of the focal points is made substantially constant, so that when the focal points are moved in a spiral shape as shown in Fig. 4(B), the moving speed of the focal points is slowed as they move toward the center of the other surface 11a. For example, the focal points start moving from a point on the outer periphery of the other surface 11a, approach the center of rotation as they rotate, and finally reach the center of rotation.

[0086] Conversely, the light collecting point may start moving from the center of rotation, move away from the center of rotation as it rotates, and finally reach a point on the outer periphery. In this case, the moving speed of the light collecting point is increased as it moves away from the center of rotation.

[0087] After the laser processing step S10, the entire other surface 11a of the inspection board 11 (i.e., a predetermined area) is imaged to image all of the processing marks 19 (a plurality of processing marks 19) formed on the other surface 11a (imaging step S20). Fig. 5 is a diagram showing the imaging step S20. In the imaging step S20, for example, a microscope camera unit 54 having an area sensor camera is used.

[0088] After imaging a partial area of ​​the other surface 11a with the microscope camera unit 54, the chuck table 26 is moved a predetermined distance along the X-axis direction so that the first imaging area and the second imaging area captured by the microscope camera unit 54 overlap slightly in the X-axis direction.

[0089] Then, after the second imaging is performed to obtain images of the partial regions, the chuck table 26 is moved a predetermined distance along the X-axis direction, and then the third imaging is performed. In this manner, after a group of images of a first strip-shaped region whose longitudinal portion is along the X-axis direction is obtained by imaging a plurality of partial regions, the chuck table 26 is moved a predetermined distance along the Y-axis direction.

[0090] Then, in the same manner as when the first strip-shaped area was obtained, the chuck table 26 is moved stepwise along the X-axis direction while capturing images of portions of the other surface 11a at each stationary position of the chuck table 26, thereby obtaining a group of images of a second strip-shaped area whose longitudinal portion runs along the X-axis direction.

[0091] The first strip region and the second strip region slightly overlap in the Y-axis direction. In this way, after acquiring a group of multiple images, the images can be stitched together by image processing to obtain an entire image of the other surface 11a.

[0092] Of course, a microscope camera unit 54 having a line sensor camera may be used instead of the area sensor camera. Fig. 6 is a schematic diagram showing an example of a processing result when the laser processing device 2 is operating normally.

[0093] In FIG. 6, images 11c of a plurality of partial regions of the entire image are 1 Image 11c from 4 Image 11c is shown enlarged. 1 Image 11c from 4 Each of the above has only a normal region 11e where normal laser processing has been performed.

[0094] As shown in FIG. 6, adjacent processing marks 19 do not overlap each other, but by forming multiple processing marks 19 so that adjacent processing marks 19 are in contact with each other or slightly separated, the shape of each individual processing mark 19 can be grasped.

[0095] This has the advantage that image processing such as pattern recognition for the processing marks 19 is simplified compared to when adjacent processing marks 19 are formed so as to overlap each other.

[0096] FIG. 7 is a schematic diagram showing an example of a processing result including a case where an abnormal operation of the laser processing device 2 occurs. In FIG. 7, an abnormal area 11d 1 From anomalous region 11d 3 Corresponding image 11c 1 Image 11c from 3 and an image 11c having only normal regions 11e 4 and are shown enlarged.

[0097] Image 11c 1 In the example, a motor malfunction causes the focal point to move at a scanning speed different from a predetermined setting value, resulting in an abnormal region 11d in which multiple processing marks 19 overlap in the scanning direction. 1 In other words, abnormal region 11d 1 reflects the abnormal operation of the laser beam scanning unit 48.

[0098] Such a motor malfunction occurs in a localized area on the movement locus of the focal point. On the other hand, the operation of the laser beam scanning unit 48 is normal in areas other than the localized area on the movement locus of the focal point.

[0099] Also, image 11c 2 In the example shown in FIG. 1, the energy density of the laser beam L is reduced due to an attachment present on the path of the laser beam L in the fθ lens 52, and the size of the processing mark 19 is reduced in the abnormal region 11d. 2 In other words, abnormal region 11d 2 reflects the abnormal operation of the laser beam scanning unit 48.

[0100] Image 11c 3 In the abnormal region 11d, the shape of the focal point of the laser beam L is distorted from a predetermined shape (for example, a perfect circle) due to the influence of adhesions or deterioration of the mirror and / or the fθ lens 52, and as a result, the shape of the processing mark 19 is different from the predetermined shape (for example, an ellipse). 3 exists.

[0101] In other words, abnormal region 11d 3 reflects abnormal operation of the laser beam scanning unit 48. Such a decrease in energy density at the focal point occurs in a localized area on the movement trajectory of the focal point. In other words, the operation of the laser processing device 2 is normal in areas other than this localized area on the movement trajectory of the focal point.

[0102] In this way, abnormal operation of the laser beam scanning unit 48 means, for example, that the actuator of the galvano scanner 50 is operating abnormally, such as the focal point moving at a scanning speed different from a predetermined set value, or that there is a factor on the optical path of the laser beam L at the mirror and / or fθ lens 52 that reduces the energy density of the focal point.

[0103] In contrast, image 11c 4 In the image 11c, the abnormal operation of the laser processing device 2 is not reflected. 4 When performing laser processing on the range contained in the laser beam scanning unit 48, the operation of the laser beam scanning unit 48 is normal.

[0104] In this embodiment, the normal operation of the laser beam scanning unit 48 means, for example, that the motor constituting the galvano scanner 50 operates normally and that there are substantially no factors in the mirror and the fθ lens 52 that reduce the energy density at the focal point.

[0105] In one example, when the laser beam scanning unit 48 is operating normally, the abnormal region 11d 1 As shown in the figure, the processing marks 19 do not overlap, and the abnormal area 11d 2 As shown in FIG. 1, the size of the processing mark 19 is not smaller than the other processing marks 19 in the surrounding area, and the abnormal area 11d 3 As shown, the shape of the processing mark 19 becomes the same as the other processing marks 19 around it.

[0106] After the imaging step S20, the process proceeds to a storage step S32 that constitutes the determination step S30. Fig. 8 is a diagram showing the storage step S32 in the determination step S30. In the storage step S32, the controller 60 associates each image 11c obtained in the imaging step S20 with the coordinates corresponding to each image 11c and stores them.

[0107] The coordinates corresponding to the image 11c are calculated by the controller 60, for example, with the center 26c of the holding surface 26a, which corresponds to the intersection of the rotation axis of the chuck table 26 and the holding surface 26a, as the origin. Note that in the example shown in Fig. 8, the radial center of the testing substrate 11 and the center 26c of the holding surface 26a coincide in the XY plane, but they do not have to coincide completely.

[0108] The position of the radial center of the testing board 11 can be identified by imaging three different points on the outer periphery of the testing board 11. Therefore, if the radial center of the testing board 11 is misaligned with the center 26c, the coordinates of the image 11c relative to the center 26c can be corrected based on this misalignment.

[0109] The controller 60 uses the above-mentioned X-axis and Y-axis linear encoders to grasp the initial position and the amount of movement of the chuck table 26 by the movement mechanism 6. For example, the controller 60 1 The coordinates of a representative position (for example, the central position 11f) of the imaging area when acquiring the image 11c are grasped as the coordinates corresponding to the image 11c.

[0110] The coordinates corresponding to the image 11c have the center 26c of the holding surface 26a as the origin, but may be calculated based on a predetermined position of the testing board 11. This predetermined position may be a notch of the testing board 11, or may be the center of the other surface 11a of the testing board 11 calculated from an image of the testing board 11 after imaging the testing board 11.

[0111] The controller 60 stores the image 11c and the coordinates corresponding to the image 11c in association with each other. In the case of a line sensor camera, the controller 60 may store one entire image in association with the coordinates of a representative position (e.g., a central position) of the entire image, or may store an image in which a plurality of lines are grouped together in association with the coordinates of a representative position (e.g., a central position) of the image.

[0112] After the storage step S32, the controller 60 detects an abnormal area 11d where the scanning of the laser beam L by the laser beam scanning unit 48 has become abnormal on the inspection board 11 based on each image 11c stored in the memory 60b in the storage step S32 and the coordinates corresponding to each image 11c. 1 etc. are identified (abnormal region identifying step S34).

[0113] In this case, the distance between two adjacent processing marks 19 (or the overlap rate between two adjacent processing marks 19), the size of the processing marks 19, and the shape of the processing marks 19 each become features used when identifying an abnormal area.

[0114] The controller 60 pre-stores, for example, a threshold value indicating the acceptable range of the spacing between two adjacent processing marks 19 (or the overlap rate of two adjacent processing marks 19), the acceptable range of the size of the processing marks 19, and the degree of deviation from the ideal shape.

[0115] In the abnormal area identification process S34, the controller 60 determines, through image processing in each image 11c, whether the spacing between adjacent processing marks 19 is within an acceptable range, whether the size of each processing mark 19 is within an acceptable range, and whether the degree of deviation from the ideal shape is less than a threshold value.

[0116] In the abnormal region identifying step S34, the controller 60 identifies, for example, the abnormal region 11d 1 The length of the range of the corresponding area in the X-axis and Y-axis directions is determined by image processing, with the center position 11f as the reference position.

[0117] Since the unit length (e.g., 1 pixel) in each image 11c is predetermined to correspond to a predetermined length (e.g., 1 μm), the controller 60 can identify, in each image 11c, the range of XY coordinates where abnormal regions 11d 1 , 11d 2 , 11d 3 etc. exist by image processing.

[0118] After the abnormal region identification step S34, the controller 60 determines whether there is an abnormality in the laser beam scanning unit 48 based on at least one feature amount of the intervals (refer to image 11c 1 ), sizes (refer to image 11c 2 ), and shapes (refer to image 11c 3 ) of the plurality of processing marks 19 formed on the inspection substrate 11.

[0119] In this way, in the determination step S30 including S32, S34, and S36, the controller 60 determines whether there are abnormal regions 11d 1 etc. in each image 11c (i.e., whether there is an abnormality in the laser beam scanning unit 48) based on the plurality of images 11c obtained in the imaging step S20. Therefore, before performing laser processing on the workpiece 21, an abnormality in the laser beam scanning unit 48 can be detected.

[0120] When the controller 60 determines that there is an abnormality in the laser beam scanning unit 48 in the abnormal region identification step S34 (YES in S36), it notifies the operator that there is an abnormality by using at least one of the touch panel 56, the indicator lamp 58, and the speaker (refer to the base 58a) (notification step S40).

[0121] FIG. 9 is a diagram showing the notification step S40. In the processing condition change step S42 after the notification step S40, the operator changes the processing conditions in the subsequent main processing step S50.

[0122] For example, the operator can set the processing conditions in the subsequent main processing step S50 for the abnormal region 11d where a plurality of processing marks 19 overlap in the scanning direction 1Then, the processing conditions are set in the controller 60 via the touch panel 56 so that the scanning speed is slower than that in the normal region 11e where normal laser processing has been performed.

[0123] Also, for example, the operator may select an abnormal region 11d where the size of the processing mark 19 is reduced. 2 Then, processing conditions are set in the controller 60 via the touch panel 56 so that the energy density of the laser beam L is higher than that in the normal region 11e.

[0124] Furthermore, for example, the operator may determine whether the shape of the processing mark 19 is different from the predetermined shape in the abnormal region 11d. 3 Then, by changing the irradiation position of the laser beam L in the XY plane and increasing the energy density of the laser beam L, processing conditions are set in the controller 60 via the touch panel 56 so that processing similar to that of the normal region 11e can be performed.

[0125] After the processing condition change step S42, the process proceeds to the main processing step S50. 1 , 11d 2 , 11d 3 By setting different processing conditions from the processing conditions applied to the normal region 11e other than the abnormal region 11d, in the main processing step S50, the changed processing conditions are 1 , 11d 2 , 11d 3 is applied locally in the region corresponding to

[0126] Incidentally, if the controller 60 determines in the abnormal area identifying step S34 that there is no abnormality in the laser beam scanning unit 48 (NO in S36), after the abnormal area identifying step S34, the process proceeds to the main processing step S50 without going through the processing condition changing step S42.

[0127] Fig. 10 is a diagram showing a main processing step S50 in which laser processing is performed on a workpiece 21 using the laser processing device 2. Note that in Fig. 10, hatching of the workpiece 21 is omitted for ease of viewing the drawing.

[0128] First, a description will be given of the workpiece 21. The workpiece 21 to be subjected to laser lift-off has an epitaxy substrate 23, a buffer layer 25, an optical device layer 27, a bonding layer 29, and a transfer substrate 31.

[0129] A buffer layer 25 including a plurality of island-shaped buffer regions is provided on one surface of the epitaxy substrate 23. Each buffer region is formed by dividing the buffer layer 25 into a lattice shape in a plan view.

[0130] The buffer region has a function of reducing the degree of lattice mismatch between the epitaxy substrate 23 and the optical device, for example. The material of the buffer region is determined according to the optical device, and may be, for example, a semiconductor material such as gallium nitride (GaN) or aluminum gallium nitride (AlGaN).

[0131] The optical device layer 27 is provided in contact with the buffer layer 25, and includes a plurality of island-shaped optical devices. One optical device is formed at a position corresponding to one buffer region. Each optical device has approximately the same thickness.

[0132] The optical device is, for example, a micro LED. The optical device has a first electrode serving as an anode and a second electrode serving as a cathode (both not shown). The optical device also includes a compound semiconductor formed by combining a group III element and a group V element.

[0133] Compound semiconductors that make up optical devices include the above-mentioned GaN, gallium phosphide (GaP), indium gallium phosphide (GaInP), indium gallium arsenide (GaInAs), indium gallium arsenide phosphide (InGaAsP), indium phosphide (InP), indium nitride (InN), indium arsenide (InAs), aluminum nitride (AlN), and aluminum gallium arsenide (AlGaAs).

[0134] The optical device layer 27 is fixed to the transfer substrate 31 via a bonding layer 29. The bonding layer 29 is made of an alloy such as silver-tin (AgSn) or gold-tin (AuSn), a pure metal such as gold (Au), platinum (Pt), chromium (Cr), indium (In), or palladium (Pd), or an organic material such as a resin.

[0135] The transfer substrate 31 is a silicon (Si) single crystal substrate having substantially the same rectangular plate shape as the epitaxy substrate 23. However, the transfer substrate 31 may be a copper (Cu) substrate, a molybdenum (Mo) substrate, or the like having the same shape.

[0136] In this manner, the optical device layer 27 is sandwiched and fixed between the epitaxy substrate 23 and the transfer substrate 31, thereby forming the workpiece 21. In this processing step S50, the buffer layer 25 is destroyed by the laser beam L, thereby weakening the fixation between the epitaxy substrate 23 and the optical device layer 27, and forming the optical device layer 27 fixed to the transfer substrate 31 via the bonding layer 29.

[0137] 10, when performing this processing step S50, first, a workpiece unit 37 in which the workpiece 21 is supported by the ring frame 35 via the tape 33 is placed on the chuck table 26. At this time, the epitaxy substrate 23 is exposed upward, and the transfer substrate 31 faces the holding surface 26a via the tape 33.

[0138] Next, the workpiece 21 is suction-held by the holding surface 26a via the tape 33, and the ring frame 35 is clamped by the clamp unit 26b. In this state, the chuck table 26 is made stationary immediately below the laser beam scanning unit 48.

[0139] Then, the laser beam scanning unit 48 is used to scan the buffer layer 25 arranged approximately parallel to the XY plane with the laser beam L, thereby irradiating the entire buffer layer 25 with the laser beam L. In this way, the buffer layer 25 is laser processed.

[0140] In this embodiment, when an abnormality is detected in the laser beam scanning unit 48, the processing conditions are changed to mitigate the effect of the abnormality in the laser beam scanning unit 48 in the main processing step S50. Therefore, when performing laser processing on the workpiece 21, it is possible to prevent the buffer layer 25 from being insufficiently destroyed due to the processing performance of the laser processing device 2.

[0141] (Modification) Next, a modification will be described with reference to Fig. 11(A) and Fig. 11(B). In the laser processing step S10 of the above embodiment, the laser processing is performed on the entire other surface 11a of the testing substrate 11, but the laser processing may be performed on only a part of the other surface 11a.

[0142] As shown in Fig. 11(A) and Fig. 11(B), the inspection board 11 of the modified example has a rectangular plate shape, and laser processing is performed only on a circular area in the center of the other surface 11a of the rectangle. Fig. 11(A) is a diagram showing an outline of an example of a movement path of the focal point in the laser processing step S10 according to the modified example, and Fig. 11(B) is a diagram showing an outline of another example of the same movement path.

[0143] In short, the irradiation range in the laser processing step S10 is adjusted so that the irradiation range of the laser beam L in the laser processing step S10 and the irradiation range of the laser beam L in the main processing step S50 are identical in three respects: (1) shape, (2) area, and (3) the relative positional relationship of the irradiated range to the outer shape.

[0144] In addition, the structures, methods, etc. according to the above-described embodiments may be modified as appropriate without departing from the scope of the present invention. For example, the abnormal region identifying step S34 and the abnormal region 11d 1 The determination S36 as to whether or not there is an abnormality may be performed by an operator instead of the controller 60. Specifically, the operator identifies an abnormal area and registers the coordinates of the abnormal area while viewing the image 11c.

[0145] In addition, in the above-mentioned imaging process S20, multiple images 11c are acquired using an area sensor camera or a line sensor camera, but depending on the performance of the microscope camera unit 54, the size of the processing mark 19, etc., the entire non-irradiated area of ​​the laser beam L may be imaged at once to obtain a single image 11c.

[0146] In the laser processing step S10 and the main processing step S50, the position of the focal point of the laser beam L in the Z-axis direction is usually constant, but may be appropriately changed so as to be the same depending on the type of laser processing to be performed on the workpiece 21. Furthermore, the scanning speed and energy density of the laser beam L may also be appropriately changed so as to be the same depending on the type of laser processing to be performed on the workpiece 21.

[0147] In the above-mentioned main processing step S50, the abnormal region 11d is removed by scanning the buffer layer 25 with the laser beam L. 1 , 11d 2 , 11d 3 Instead of changing the processing conditions locally in the region corresponding to abnormal region 11d after scanning the entire buffer layer 25 with laser beam L, 1 , 11d 2 , 11d 3It is also possible to locally irradiate the laser beam L in the area corresponding to the laser beam L.

[0148] In this way, even when the laser beam L is irradiated locally, the abnormal region 11d is not irradiated with the laser beam L multiple times. 1 , 11d 2 , 11d 3 In the area corresponding to the normal area 11e, processing conditions different from the processing conditions applied to the normal area 11e are applied.

[0149] Incidentally, in the laser processing step S10, the inspection board unit 17, in which the inspection board 11, the tape 13 and the ring frame 15 are integrated, is held by suction on the holding surface 26a. However, the tape 13 and the ring frame 15 may be omitted, and the inspection board 11 may be directly held by suction on the holding surface 26a with one surface 11b in contact with the holding surface 26a.

[0150] Similarly, in this processing step S50, instead of using a workpiece unit 37 in which the workpiece 21, tape 33 and ring frame 35 are integrated, the tape 33 and ring frame 35 may be omitted, and the workpiece 21 may be directly suction-held by the holding surface 26a in a manner in which the transfer substrate 31 and the holding surface 26a are in contact with each other. [Explanation of symbols]

[0151] 2: Laser processing device, 4: Base, 6: Moving mechanism 8: Y-axis guide rail, 10: Y-axis moving plate 11: Test board, 11a: other side, 11b: one side 11c,11c 1 ,11c 2 ,11c 3 ,11c 4 :image 11d 1 ,11d 2 ,11d 3 :Abnormal area 11e: Normal area, 11f: Center position 12: screw shaft, 14: driving source, 16: X-axis direction guide rail, 18: X-axis direction moving plate 13: Tape, 15: Ring frame, 17: Inspection board unit, 19: Processing marks 20: screw shaft, 22: drive source, 24: table base 21: workpiece, 23: epitaxy substrate, 25: buffer layer 26: Chuck table (holding table) 26a: holding surface, 26b: clamp unit, 26c: center 27: optical device layer, 29: bonding layer, 31: transfer substrate 30: Support structure, 32: Z-axis direction movement mechanism, 34: Z-axis direction guide rail 33: tape, 35: ring frame, 37: workpiece unit 36: Z-axis direction moving plate, 38: driving source, 40: support 42: laser beam irradiation unit, 44: housing, 46: laser oscillator 48: Laser beam scanning unit 50: Galvano scanner, 50a: First mirror, 50b: Second mirror, 52: fθ lens 54: Microscope camera unit, 56: Touch panel 58: indicator light, 58a: base, 58b: light-emitting part 60: controller, 60a: processor, 60b: memory L: Laser beam S10: Laser processing process (preparatory processing process), S20: Imaging process S30: Judgment process, S32: Storage process, S34: Abnormal area identification process, S36: Judgment S40: Notification step, S42: Processing condition change step, S50: Main processing step

Claims

1. A method for inspecting a laser processing device, comprising: a laser processing step of performing laser processing on a predetermined area of ​​the inspection substrate by scanning the predetermined area of ​​the inspection substrate with a pulsed laser beam using a laser beam scanning unit of the laser processing device while the holding table of the laser processing device is stationary in a state where the inspection substrate is held by the holding table; an imaging step of imaging a plurality of processing marks formed in the predetermined area after the laser processing step; a determination step of determining whether or not there is an abnormality in the laser beam scanning unit based on the image obtained in the imaging step; A method for inspecting a laser processing device, comprising:

2. The inspection method for a laser processing apparatus according to claim 1, characterized in that in the judgment step, it is judged whether or not there is an abnormality in the laser beam scanning unit based on at least one characteristic parameter of the spacing, size, and shape of a plurality of processing marks formed on the inspection board.

3. The determination step includes: a storage step in which a controller of the laser processing apparatus associates the image obtained in the imaging step with coordinates corresponding to the image and stores the image; an abnormal area specifying step of specifying an abnormal area where scanning of the laser beam by the laser beam scanning unit has become abnormal on the inspection board based on the image and the coordinates stored in the storing step; 3. The method for inspecting a laser processing device according to claim 1, further comprising:

4. The inspection method for a laser processing apparatus according to claim 1 or 2, further comprising an alarm process in which, if it is determined in the judgment process that there is an abnormality in the laser beam scanning unit, the controller of the laser processing apparatus uses at least one of a display, an indicator light, and a speaker to notify an operator of the abnormality.

5. A laser processing method for performing laser processing on a workpiece using a laser processing device, comprising: a preliminary processing step of performing laser processing on a predetermined area of ​​the inspection substrate by scanning the predetermined area with a pulsed laser beam using a laser beam scanning unit of the laser processing apparatus while the inspection substrate is held on the holding table of the laser processing apparatus and the holding table is stationary in a state where the inspection substrate is held on the holding table; an imaging step of imaging a plurality of processing marks formed in the predetermined area after the preliminary processing step; a storage step of storing the image obtained in the imaging step and the coordinates corresponding to the image in association with each other; an abnormal area specifying step of specifying an abnormal area where scanning of the laser beam by the laser beam scanning unit has become abnormal on the inspection board based on the image and the coordinates stored in the storing step; a main processing step of performing laser processing on the workpiece by scanning the workpiece with the laser beam using the laser beam scanning unit after the abnormal area specifying step; Equipped with This laser processing method is characterized in that, in this processing step, when laser processing is performed on the abnormal area identified in the abnormal area identifying step, processing conditions that are different from the processing conditions applied to normal areas other than the abnormal area are applied.

Images