Processing method of workpiece

Abstract

To provide a method for processing a workpiece that can correct the deviation of a processing position in multi-channel cut.SOLUTION: A method for processing a workpiece includes: a first processing groove forming step 1 of irradiating the workpiece with a laser beam along a first scheduled division line to form a first processing groove and picking up an image of the first processing groove to form a first image; a first alignment step 2; a second processing groove forming step 3 of irradiating the workpiece with a laser beam along a second scheduled division line to form a second processing groove; a second alignment step 4; a second image forming step 5 of picking up an image of the first processing groove to form a second image; a deviation amount calculation step 6 of calculating the amount of deviation in an indexing feeding direction of the first processing groove between the first image and the second image; and a third processing groove forming step 7 of correcting a position irradiated with the laser beam based on the deviation amount and irradiating the workpiece with a laser beam along the first scheduled division line to form a third processing groove overlapping the first processing groove.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method for processing a workpiece. Background Art

[0002] As a method of dividing a workpiece such as a semiconductor wafer into individual chips, methods have been proposed in which a laser beam is irradiated along planned dividing lines set on the workpiece to form processed grooves, and then the workpiece is fractured and divided along the processed grooves, or the workpiece is divided by etching with plasma, for example (see Patent Documents 1 and 2). Prior Art Literature Patent Documents

[0003] Patent Document 1 Japanese Unexamined Patent Publication No. 10-305420 Patent Document 2 Japanese Unexamined Patent Publication No. 2018-190857 Summary of the Invention Problem to be Solved by the Invention

[0004] In processing by laser beam irradiation as described above, debris is generated during processing and may adhere so as to bulge along both sides of the processed groove in some cases. In such a case, at an intersection of planned dividing lines, when one planned dividing line is processed, a bulge (backfill) that blocks the other planned dividing line is formed on the other planned dividing line. If such backfill remains on the planned dividing line, it causes the problem that chips adhere to each other without being divided, which is so-called double dies, or the backfill acts as a mask for plasma etching, resulting in undivided chips.

[0005] Therefore, a so-called multi-channel cut is commonly performed, in which, after machining one planned division line (CH1; first channel), the chuck table holding the workpiece is rotated to machine the other planned division line (CH2; second channel), and then the chuck table is rotated again to machine the first planned division line (CH3; third channel), thereby removing the backfill formed on the first planned division line during the machining of the other planned division line. However, a problem with multi-channel cuts is that, due to temperature changes in the rotation axis of the chuck table during machining, a discrepancy occurs between the machining position when CH1 is machined and the machining position when CH3 is machined.

[0006] This invention has been made in view of the above problems, and its purpose is to provide a method for processing a workpiece that can correct misalignment in processing position during multi-channel cutting. [Means for solving the problem]

[0007] To solve the above-mentioned problems and achieve the objective, the present invention provides a method for processing a workpiece, wherein a workpiece has a plurality of first division lines extending along a first direction and a plurality of second division lines extending along a second direction intersecting the first direction, and the workpiece is processed by irradiating the workpiece with a laser beam of a wavelength absorbed by the workpiece, the method comprising: a first processing groove formation step in which one end of the first division lines is positioned at an irradiation position where the laser beam is focused and irradiated, and the first processing groove is formed by irradiating the laser beam while relatively feeding the first division lines and the focal point of the laser beam along the first direction, and the first processing groove is imaged to form a first image; a first alignment step in which, after performing the first processing groove formation step, one end of the second division lines is positioned at an irradiation position where the laser beam is focused and irradiated; and after performing the first alignment step, the second division lines and the focal point of the laser beam are relatively along the second direction The device is characterized by comprising: a second processing groove forming step of forming a second processing groove by irradiating the laser beam while feeding the workpiece; a second alignment step of positioning one end of the first planned division line at an irradiation position where the laser beam is focused and irradiated, after performing the second processing groove forming step; a second image forming step of forming a second image by imaging the first processing groove formed in the first planned division line in the first processing groove forming step, after performing the second alignment step; a deviation amount calculation step of calculating the deviation amount between the position of the first processing groove in the indexing feed direction in the first image and the position of the first processing groove in the indexing feed direction in the second image; and a third processing groove forming step of correcting the position of the irradiation position where the laser beam is focused and irradiated based on the deviation amount calculated in the deviation amount calculation step, and forming a third processing groove that overlaps with the first processing groove by irradiating the laser beam while relatively feeding the first planned division line and the focal point of the laser beam along the first direction.

[0008] In the workpiece processing method of the present invention, in the second image forming step, the first processing groove may be imaged by an imaging unit positioned to capture an area forward of the focusing point of the laser beam in the processing feed direction and which moves relative to the focusing point of the laser beam in the processing feed direction, thereby forming the second image, and the third processing groove forming step may be performed while the second image forming step is being carried out.

[0009] In the workpiece processing method of the present invention, in the third processing groove forming step, if the amount of deviation calculated in the deviation amount calculation step exceeds a preset threshold, the position in the indexing feed direction of the irradiation position where the laser beam is focused and irradiated may be corrected. [Effects of the Invention]

[0010] This invention can correct machining position deviations in multi-channel cutting. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a perspective view showing an example of a workpiece 10 to be processed by the workpiece processing method according to the embodiment. [Figure 2] Figure 2 is a perspective view showing an example of the configuration of a laser processing apparatus that implements the workpiece processing method according to the embodiment. [Figure 3] Figure 3 is a flowchart showing the flow of the workpiece processing method according to the embodiment. [Figure 4] Figure 4 is a side view showing a partial cross-section of one state of the first groove formation step shown in Figure 3. [Figure 5] Figure 5 is a plan view showing the workpiece before the first alignment step shown in Figure 3. [Figure 6] Figure 6 is a plan view showing the workpiece after the first alignment step shown in Figure 3. [Figure 7] Figure 7 is a side view showing a partial cross-section of one state of the second groove formation step shown in Figure 3. [Figure 8]FIG. 8 is a plan view showing a workpiece before the second alignment step shown in FIG. 3. [Figure 9] FIG. 9 is a plan view showing the workpiece after the second alignment step shown in FIG. 3. [Figure 10] FIG. 10 is a side view, partially in cross-section, showing one state of the second image forming step shown in FIG. 3. [Figure 11] FIG. 11 is an explanatory diagram for explaining the displacement amount calculating step shown in FIG. 3. [Figure 12] FIG. 12 is a side view, partially in cross-section, showing one state of the third processed groove forming step shown in FIG. 3. [Figure 13] FIG. 13 is a captured image obtained by capturing the workpiece during the third processed groove forming step shown in FIG. 3. [Figure 14] FIG. 14 is a captured image obtained by capturing a workpiece during a third processed groove forming step in a comparative example. DESCRIPTION OF EMBODIMENTS

[0012] Modes (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following embodiments. The components described below include those that can be easily conceived by a person skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. Various omissions, substitutions, or changes to the configuration can be made without departing from the scope of the gist of the present invention.

[0013] [Embodiment] A method for processing a workpiece 10 according to an embodiment of the present invention will be described with reference to the drawings. First, a configuration example of the workpiece 10 to be processed and a laser processing apparatus 100 used for processing will be described. FIG. 1 is a perspective view showing an example of the workpiece 10 to be processed in the method for processing the workpiece 10 according to the embodiment. FIG. 2 is a perspective view showing a configuration example of the laser processing apparatus 100 that implements the method for processing the workpiece 10 according to the embodiment.

[0014] The workpiece 10 shown in FIG. 1 is a wafer such as a disk-shaped semiconductor device wafer or optical device wafer having a substrate 11 made of silicon (Si), sapphire (Al₂O₃), gallium arsenide (GaAs), silicon carbide (SiC), lithium tantalate (LiTaO₃), or the like.

[0015] In the workpiece 10, a first planned dividing lines 13 and a second planned dividing lines 14 are set on a surface 12. The first planned dividing lines 13 extend along a first direction 21, and a plurality of first planned dividing lines 13 are arranged side by side in a second direction 22 intersecting the first direction 21. The second planned dividing lines 14 extend along the second direction 22, and a plurality of second planned dividing lines 14 are arranged side by side in the first direction 21. In the embodiment, the first direction 21 and the second direction 22 are orthogonal to each other.

[0016] The workpiece 10 includes devices 15 formed in regions partitioned by the first planned dividing lines 13 and the second planned dividing lines 14 set in a grid pattern. The devices 15 are, for example, integrated circuits such as IC (Integrated Circuit) or LSI (Large Scale Integration), image sensors such as CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor), or MEMS (Micro Electro Mechanical Systems), or the like.

[0017] The workpiece 10 is conveyed and processed while being supported by, for example, the annular frame 30 and a tape 31 shown in FIG. 2. The frame 30 is an annular plate member formed of metal or resin and having an opening larger than the outer diameter of the workpiece 10. The tape 31 is in a sheet shape having an outer diameter larger than that of the opening of the frame 30, and is attached to the back side of the frame 30 so as to cover the opening of the frame 30. The tape 31 may be configured to include, for example, a base material layer made of a stretchable synthetic resin, and an adhesive layer laminated on the base material layer and made of a stretchable and adhesive synthetic resin, or may be made of a thermoplastic resin without having an adhesive layer.

[0018] The workpiece 10 is positioned at a predetermined location in the opening of the frame 30 and fixed to the frame 30 and tape 31 by adhering its front surface 12 or back surface 16 to the tape 31. The workpiece 10 is divided into individual devices 15 along a plurality of first division lines 13 and a plurality of second division lines 14, and then fragmented into device chips 17. In this embodiment, the device chip 17 is square in shape, but it may also be rectangular. In this embodiment, the workpiece 10 is disc-shaped, but it does not have to be disc-shaped in this invention.

[0019] The laser processing apparatus 100 shown in Figure 2 is a device that processes a workpiece 10 by irradiating it with a laser beam 122. As shown in the figure, the laser processing apparatus 100 comprises a holding table 110, a laser beam irradiation unit 120, an imaging unit 130, a moving unit 140, a display unit 150, and a control unit 160. In the following description, the X-axis direction is a single direction in the horizontal plane. The Y-axis direction is a direction perpendicular to the X-axis direction in the horizontal plane. The Z-axis direction is a direction perpendicular to both the X-axis and Y-axis directions. In the embodiment of the laser processing apparatus 100, the processing feed direction is the X-axis direction, the indexing feed direction is the Y-axis direction, and the focusing point position adjustment direction is the Z-axis direction.

[0020] The holding table 110 holds the workpiece 10 on its holding surface 111. The holding surface 111 is a disc shape formed from porous ceramic or the like. In this embodiment, the holding surface 111 is a plane parallel to the horizontal direction. The holding surface 111 is connected to a vacuum suction source, for example, via a vacuum suction path. The holding table 110 holds the workpiece 10 placed on the holding surface 111 by suction. Multiple clamping parts 112 are arranged around the holding table 110 to clamp the frame 30 that supports the workpiece 10.

[0021] The holding table 110 is rotated by the rotating unit 113 around an axis parallel to the Z-axis direction. The rotating unit 113 is supported by the X-axis direction moving plate 114. The rotating unit 113 and the holding table 110 are moved in the X-axis direction by the machining feed unit 141 of the moving unit 140 via the X-axis direction moving plate 114. The rotating unit 113 and the holding table 110 are moved in the Y-axis direction by the indexing feed unit 142 of the moving unit 140 via the X-axis direction moving plate 114, the machining feed unit 141, and the Y-axis direction moving plate 115.

[0022] The laser beam irradiation unit 120 is a unit that irradiates a workpiece 10 held on a holding table 110 with a pulsed laser beam 122 having a predetermined wavelength for processing the workpiece 10. In this embodiment, a portion of the laser beam irradiation unit 120, including the irradiation head 121, is supported at the tip of a support beam 103, the base end of which is attached to an upright wall 102 erected from the main body 101 of the apparatus.

[0023] The laser beam irradiation unit 120 includes, for example, an oscillator that emits a laser beam 122, a focuser that focuses the laser beam 122 emitted from the oscillator onto the processing point, and various optical components that guide the laser beam 122 from the oscillator to the focuser. The focuser is located inside the irradiation head 121. The focal point 123 of the laser beam 122 that is focused by the focuser and irradiated from the irradiation head 121 is movable relative to the holding table 110 in the Z-axis direction, which is the focal point position adjustment direction, by, for example, a focal point position adjustment unit (not shown).

[0024] The imaging unit 130 images the workpiece 10 held on the holding table 110. The imaging unit 130 includes a CCD camera or an infrared camera. The imaging unit 130, for example, images the workpiece 10 to capture an image for performing alignment, which involves positioning the workpiece 10 with the laser beam irradiation unit 120. The imaging unit 130 outputs the captured image 50 (see, for example, Figure 4, and Figures 10 to 14, etc.) to the control unit 160. The captured image 50 has reference lines 51 that indicate the centers of the imaging area in two directions (X-axis direction and Y-axis direction). The imaging unit 130 includes a first imaging unit 131 and a second imaging unit 132.

[0025] The first imaging unit 131 is fixed adjacent to one side of the irradiation head 121 of the laser beam irradiation unit 120 in the processing feed direction. The first imaging unit 131 is positioned to image a region in the processing feed direction ahead of the focal point 123 of the laser beam 122 irradiated from the laser beam irradiation unit 120. The first imaging unit 131 moves relative to the processing feed direction together with the focal point 123 of the laser beam 122. When the processing feed direction is the direction in which the irradiation head 121 moves toward the first imaging unit 131, the first imaging unit 131 can image a region in front of the focal point 123 in the processing feed direction. When the processing feed direction is the direction in which the irradiation head 121 moves toward the first imaging unit 131, the first imaging unit 131 can image a region behind the focal point 123 in the processing feed direction.

[0026] The second imaging unit 132 is fixed adjacent to the other side of the irradiation head 121 of the laser beam irradiation unit 120 in the processing feed direction. The second imaging unit 132 is positioned to be able to image the area on the other side of the focusing point 123 of the laser beam 122 irradiated from the laser beam irradiation unit 120 in the processing feed direction. The second imaging unit 132 moves relative to the focusing point 123 of the laser beam 122 in the processing feed direction. When the first imaging unit 131 is being processed in a direction that allows imaging of the area in front of the focusing point 123 in the processing feed direction, the second imaging unit 132 is able to image the area behind the focusing point 123 in the processing feed direction. When the first imaging unit 131 is being processed in a direction that allows imaging of the area behind the focusing point 123 in the processing feed direction, the second imaging unit 132 is able to image the area in front of the focusing point 123 in the processing feed direction.

[0027] Of the first imaging unit 131 and the second imaging unit 132, the imaging unit 130, which is capable of imaging the area behind the processing feed beyond the focusing point 123, images the first processing groove 40, described later, formed by the laser beam 122 irradiated from the laser beam irradiation unit 120, to form a first image 52 (see Figures 4 and 11, etc.). The first imaging unit 131 or the second imaging unit 132 images the already formed first processing groove 40 before the third processing groove 43, described later, is formed by the laser beam 122 irradiated from the laser beam irradiation unit 120, to form a second image 53 (see Figures 10 and 11, etc.).

[0028] The moving unit 140 is a unit that moves the holding table 110 and the focal point 123 (see Figure 4, etc.) of the laser beam 122 emitted from the laser beam irradiation unit 120 relative to each other. The moving unit 140 includes a machining feed unit 141 and an indexing feed unit 142.

[0029] The processing feed unit 141 is a unit that moves the holding table 110 and the focal point 123 (see Figure 4, etc.) of the laser beam 122 irradiated from the laser beam irradiation unit 120 relative to each other in the X-axis direction, which is the processing feed direction. In the embodiment, the processing feed unit 141 moves the holding table 110 in the X-axis direction. In the embodiment, the processing feed unit 141 is installed on the main body 101 of the laser processing apparatus 100. The processing feed unit 141 supports the X-axis direction moving plate 114 so as to be movable in the X-axis direction.

[0030] The indexing feed unit 142 is a unit that moves the holding table 110 and the focal point 123 (see Figure 4, etc.) of the laser beam 122 irradiated from the laser beam irradiation unit 120 relatively in the Y-axis direction, which is the indexing feed direction. In the embodiment, the indexing feed unit 142 moves the holding table 110 in the Y-axis direction. In the embodiment, the indexing feed unit 142 is installed on the main body 101 of the laser processing apparatus 100. The indexing feed unit 142 supports the Y-axis direction moving plate 115 so as to be movable in the Y-axis direction.

[0031] The machining feed unit 141 and the indexing feed unit 142 each include, for example, a well-known ball screw, a well-known pulse motor, and a well-known guide rail. The ball screw is rotatably mounted around its axis. The pulse motor rotates the ball screw around its axis. The guide rail of the machining feed unit 141 is fixed to the Y-axis moving plate 115 and supports the X-axis moving plate 114 so as to be movable in the X-axis direction. The guide rail of the indexing feed unit 142 is fixed to the apparatus body 101 and supports the Y-axis moving plate 115 so as to be movable in the Y-axis direction.

[0032] The display unit 150 is a display unit composed of a liquid crystal display device or the like. The display unit 150 displays, for example, the setting screen for processing conditions, the state of the workpiece 10 captured by the imaging unit 130, the state of processing operations, etc., on its display surface. If the display surface of the display unit 150 includes a touch panel, the display unit 150 may also include an input unit. The input unit can accept various operations from the operator, such as registering processing content information. The input unit may also be an external input device such as a keyboard. The information and images displayed on the display surface of the display unit 150 can be switched by operations from the input unit, etc. The display unit 150 may also include a notification device. The notification device emits at least one of sound and light to notify the operator of the laser processing device 100 of predetermined notification information. The notification device may also be an external notification device such as a speaker or a light-emitting device.

[0033] The control unit 160 controls each of the above-mentioned components of the laser processing apparatus 100 to cause the laser processing apparatus 100 to perform processing operations on the workpiece 10. The control unit 160 is a computer that includes an arithmetic processing unit as an arithmetic means, a memory device as a storage means, and an input / output interface device as a communication means. The arithmetic processing unit includes, for example, a microprocessor such as a CPU (Central Processing Unit). The memory device has memory such as ROM (Read Only Memory) or RAM (Random Access Memory). The arithmetic processing unit performs various calculations based on a predetermined program stored in the memory device. The arithmetic processing unit outputs various control signals to each of the above-mentioned components via the input / output interface device according to the calculation results, thereby controlling the laser processing apparatus 100.

[0034] Figure 3 is a flowchart showing the flow of a machining method for a workpiece 10 according to the embodiment. The machining method for the workpiece 10 is a method for forming machining grooves (first machining groove 40, second machining groove 42, and third machining groove 43) along a first division line 13 and a second division line 14. As shown in Figure 3, the machining method for the workpiece 10 includes a first machining groove formation step 1, a first alignment step 2, a second machining groove formation step 3, a second alignment step 4, a second image formation step 5, a deviation amount calculation step 6, and a third machining groove formation step 7.

[0035] (First machining groove formation step 1) Figure 4 is a side view showing a partial cross-section of one state of the first machining groove formation step 1 shown in Figure 3. The first machining groove formation step 1 is a step in which a first machining groove 40 is formed by irradiating a laser beam 122 along the first division line 13, and a first image 52 is formed by imaging the first machining groove 40. The laser beam 122 is a laser beam with a wavelength that is absorbed by the workpiece 10.

[0036] In the first groove forming step 1, the back surface 16 of the workpiece 10 is first held on the holding surface 111 of the holding table 110 via the tape 31. Next, the frame 30 supporting the workpiece 10 is clamped by the clamp portion 112. Then, a negative pressure is activated by a vacuum suction source connected to the holding surface 111 via a vacuum suction path to hold the workpiece 10 placed on the holding surface 111 by suction.

[0037] In the first groove formation step 1, the holding table 110 is then moved to the processing position by the moving unit 140. Next, the first planned division line 13 is detected by imaging the workpiece 10 with the imaging unit 130. Once the first planned division line 13 is detected, the holding table 110 is rotated around the Z axis by the rotating unit 113 to align the first direction 21 along which the first planned division line 13 of the workpiece 10 follows with the processing feed direction (X axis direction) of the laser processing device 100. The moving unit 140 also performs alignment to position one end 13-1 (see Figure 5) of the first planned division line 13 at the irradiation position (focusing point 123) where the laser beam 122 is focused and irradiated.

[0038] In the first machining groove formation step 1, the machining feed unit 141 then irradiates the workpiece 10 from the surface 12 side with the laser beam 122 while relatively feeding the first division line 13 and the focal point 123 of the laser beam 122 along the first direction 21. This forms the first machining groove 40 along the first division line 13. Simultaneously in the first machining groove formation step 1, the surface 12 of the workpiece 10 is continuously or intermittently imaged by the imaging unit 130 (Figure 4 shows the state where the first imaging unit 131 is positioned behind the machining feed direction), which is one of the first imaging unit 131 and the second imaging unit 132 and capable of imaging the area behind the focal point 123.

[0039] In the state shown in Figure 4, the first imaging unit 131 is positioned behind the irradiation head 121 of the laser beam irradiation unit 120 in the processing feed direction, and therefore follows the focusing point 123 of the laser beam 122 in the processing feed direction. Accordingly, the first imaging unit 131 images a predetermined area including the first division line 13 after the first processing groove 40 has been formed by irradiation with the laser beam 122, and forms a first image 52. The formed first image 52 is output to the control unit 160.

[0040] After forming the first machining groove 40 on one of the first division lines 13, the indexing feed unit 142 moves the focusing point 123 relative to the indexing feed direction (Y-axis direction), i.e., the second direction 22, and similarly forms the first machining groove 40 on the adjacent first division line 13. Note that the front and back directions are reversed between the forward and return paths of the machining feed, so when the second imaging unit 132 is positioned behind in the machining feed direction, the second imaging unit 132 forms the first image 52 and outputs it to the control unit 160. When the first machining groove 40 has been formed along all of the first division lines 13 and the irradiation position (focusing point 123) where the laser beam 122 is focused and irradiated reaches the other end 13-2 (see Figure 5) of the last first division line 13, the first machining groove formation step 1 is completed. Note that the first image 52 may be captured only on the first first division line 13, or it may be captured every few lines.

[0041] (First alignment step 2) Figure 5 is a plan view showing the workpiece 10 before the first alignment step 2 shown in Figure 3. Figure 6 is a plan view showing the workpiece 10 after the first alignment step 2 shown in Figure 3. The first alignment step 2 is performed after the first machining groove forming step 1 is carried out. The first alignment step 2 is a step in which one end 14-1 of the second division line 14 is positioned at the irradiation position (focusing point 123) where the laser beam 122 is focused and irradiated.

[0042] In the first alignment step 2, the rotating unit 113 rotates the holding table 110 around the Z axis to align the second direction 22 along which the second division line 14 of the workpiece 10 follows with the processing feed direction (X axis direction) of the laser processing device 100. In this embodiment, the holding table 110 is rotated 90 degrees in the direction of the arrow shown in Figure 5. The moving unit 140 also positions one end 14-1 of the second division line 14 at the irradiation position (focusing point 123, see Figure 6) where the laser beam 122 is focused and irradiated.

[0043] (Second processing groove formation step 3) Figure 7 is a side view showing a partial cross-section of one state of the second machining groove formation step 3 shown in Figure 3. The second machining groove formation step 3 is performed after the first alignment step 2 is carried out. The second machining groove formation step 3 is a step in which a second machining groove 42 is formed by irradiating a laser beam 122 along the second division line 14.

[0044] In the second machining groove formation step 3, the machining feed unit 141 moves the second division line 14 and the focusing point 123 of the laser beam 122 relative to each other along the second direction 22, while irradiating the workpiece 10 from the surface 12 side with the laser beam 122. This forms the second machining groove 42 along the second division line 14.

[0045] During this process, debris and burrs generated by laser processing are formed on both sides of the second processing groove 42 in the width direction. Such debris and burrs also adhere to and form on the first processing groove 40 at the intersection where the first planned division line 13 and the second planned division line 14 intersect perpendicularly (backfilling).

[0046] After forming a second machining groove 42 on one of the second division lines 14, the indexing feed unit 142 moves the focusing point 123 relative to the indexing feed direction (Y-axis direction), i.e., the first direction 21, and similarly forms a second machining groove 42 on the adjacent second division line 14. When the second machining grooves 42 have been formed along all of the second division lines 14 and the irradiation position (focusing point 123) where the laser beam 122 is focused and irradiated reaches the other end 14-2 (see Figure 8) of the last second division line 14, the second machining groove formation step 3 is completed.

[0047] (Second alignment step 4) Figure 8 is a plan view showing the workpiece 10 before the second alignment step 4 shown in Figure 3. Figure 9 is a plan view showing the workpiece 10 after the second alignment step 4 shown in Figure 3. The second alignment step 4 is performed after the second machining groove forming step 3 is carried out. The second alignment step 4 is a step in which one end 13-1 of the first division line 13 is positioned at the irradiation position (focusing point 123) where the laser beam 122 is focused and irradiated.

[0048] In the second alignment step 4, the rotating unit 113 rotates the holding table 110 around the Z axis to align the first direction 21 along which the first division line 13 of the workpiece 10 follows with the processing feed direction (X axis direction) of the laser processing device 100. In this embodiment, the holding table 110 is rotated 90 degrees in the direction of the arrow shown in Figure 8. The moving unit 140 also positions one end 13-1 of the first division line 13 at the irradiation position (focusing point 123) where the laser beam 122 is focused and irradiated.

[0049] In this process, the temperature of the axis of the continuously operating moving unit 140 rises due to the processing in the first processing groove formation step 1 and the second processing groove formation step 3, which may cause a temperature change in the rotation axis of the rotation unit 113 that rotates the holding table 110 around the Z axis. In the second alignment step 4, the positional relationship between the workpiece 10 and the various parts of the laser processing device 100 is returned to the state in the first processing groove formation step 1. However, due to temperature changes in the rotation axis, the irradiation position (focusing point 123) where the laser beam 122 is focused and irradiated may shift from the center 41 of the first processing groove 40 (see Figure 11).

[0050] (Second image formation step 5) Figure 10 is a side view showing a partial cross-section of one state of the second image formation step 5 shown in Figure 3. The second image formation step 5 is performed after the second alignment step 4 is performed. The second image formation step 5 is a step in which the first machining groove 40 formed in the first division line 13 in the first machining groove formation step 1 is imaged to form the second image 53.

[0051] In the second image formation step 5, the machining feed unit 141 machine-feeds the first division line 13 and the imaging unit 130 relative to each other along the first direction 21, while the imaging unit 130 (second imaging unit 132 in the example shown in Figure 10) continuously or intermittently images the surface 12 of the workpiece 10. In the second image formation step 5, either the first imaging unit 131 or the second imaging unit 132 may be used. The imaging unit 130 images a predetermined area including the first division line 13 where the first machining groove 40 was formed in the first machining groove formation step 1, and forms a second image 53. In the second image formation step 5, the second image 53 is formed at the same position as the first image 52. The formed second image 53 is output to the control unit 160.

[0052] (Step 6 for calculating the amount of deviation) Figure 11 is an explanatory diagram illustrating the deviation amount calculation step 6 shown in Figure 3. The deviation amount calculation step 6 is a step in which the deviation amount 54 is calculated between the position of the first machining groove 40 in the indexing feed direction in the first image 52 and the position of the first machining groove 40 in the indexing feed direction in the second image 53.

[0053] In the first processing groove formation step 1, the focusing point 123 of the laser beam 122 is aligned with the first planned division line 13, and the imaging unit 130 is fixed relative to the irradiation head 121. Therefore, as shown in Figure 11, the first processing groove 40 is formed such that its center 41 in the width direction aligns with the reference line 51 of the first image 52.

[0054] On the other hand, if, in the second alignment step 4, the irradiation position (focusing point 123) where the laser beam 122 is focused and irradiated is misaligned from the center 41 of the first processing groove 40 (see Figure 11), then in the second image forming step 5, the reference line 51 of the second image 53 produced by the imaging unit 130, which is fixed relative to the irradiation head 121, will be misaligned from the center 41 of the first processing groove 40.

[0055] In step 6 of the deviation amount calculation, for example, the control unit 160 first detects the position of the first machining groove 40 from the second image 53 using known image processing and edge detection. The control unit 160 obtains the coordinates of the center 41 in the width direction (indexing feed direction) of the detected first machining groove 40, and obtains the distance between the obtained center 41 and the reference line 51 as the deviation amount 54. In the above explanation, it was assumed that the center 41 of the first machining groove 40 coincides with the reference line 51 in the first image 52, but there may be cases where there is a deviation between the center 41 of the first machining groove 40 (especially the first machining groove 40 of the first division line 13 that was machined later) and the reference line 51 in the first image 52. In this case, the position of the first machining groove 40 may also be detected from the first image 52 using known image processing and edge detection, and the difference between the position in the first image 52 and the position in the second image 53 may be obtained as the deviation amount.

[0056] (Third machining groove formation step 7) Figure 12 is a side view showing a partial cross-section of one state of the third groove formation step 7 shown in Figure 3. Figure 13 is an image 50 of the workpiece 10 taken during the third groove formation step 7 shown in Figure 3. The third groove formation step 7 is a step in which a third groove 43 is formed by irradiating a laser beam 122 along the first division line 13. Figure 14 is an image 50 of the workpiece 10 taken during the third groove formation step 7 in a comparative example.

[0057] In this case, in the third machining groove formation step 7, the position of the focusing position (focusing point 123) where the laser beam 122 is focused and irradiated is corrected in the indexing feed direction (Y-axis direction) based on the amount of deviation 54 calculated in the deviation amount calculation step 6. In the third machining groove formation step 7, if the amount of deviation 54 calculated in the deviation amount calculation step 6 exceeds a preset threshold, the position of the focusing position (focusing point 123) where the laser beam 122 is focused and irradiated is corrected in the indexing feed direction (Y-axis direction). The threshold is stored in advance in the memory of the control unit 160, for example.

[0058] In the third machining groove formation step 7, the position in the indexing feed direction is corrected first. Specifically, the indexing feed unit 142 moves the holding table 110 in the indexing feed direction (Y-axis direction) and in a direction that eliminates the misalignment by an amount of misalignment 54. For example, in the second image 53, if the Y coordinate of the center 41 of the first machining groove 40 is y, the holding table 110 is moved by -y.

[0059] In the third machining groove formation step 7, the machining feed unit 141 then irradiates the workpiece 10 from the surface 12 side with the laser beam 122 while relatively feeding the first division line 13 and the focusing point 123 of the laser beam 122 along the first direction 21. As a result, as shown in Figure 13, a third machining groove 43 is formed that overlaps with the first machining groove 40 along the first division line 13. In the second machining groove formation step 3, debris and burrs attached to the first machining groove 40 at the intersection where the first division line 13 and the second division line 14 intersect are removed when forming the third machining groove 43.

[0060] Furthermore, if the third machining groove 43 is formed without correcting the position in the indexing feed direction, as shown in the comparative example in Figure 14, the third machining groove 43 will be formed at a position shifted in the indexing feed direction relative to the first machining groove 40 by the amount of the shift 54.

[0061] After forming a third machining groove 43 on one of the first division lines 13, the indexing feed unit 142 moves the focusing point 123 relative to the indexing feed direction (Y-axis direction), i.e., the second direction 22, to similarly form a third machining groove 43 that overlaps with the first machining groove 40 on the adjacent first division line 13. Once all the third machining grooves 43 that overlap with the first machining groove 40 have been formed along the first division lines 13, the third machining groove formation step 7 is completed.

[0062] If a misalignment between the first machining groove 40 and the third machining groove 43 on the first division line 13 to be machined first is acceptable, the third machining groove formation step 7 may be performed while the second image formation step 5 is being carried out. That is, the machining feed unit 141 machined the first division line 13 and the focal point 123 of the laser beam 122 relatively along the first direction 21, while irradiating with the laser beam 122, and at the same time, the first imaging unit 131 or the second imaging unit 132, which is positioned in front of the focal point 123 of the laser beam 122 in the machining feed direction, formed a second image 53.

[0063] The control unit 160 acquires a second image 53 from a first imaging unit 131 or a second imaging unit 132 positioned in front of the focusing point 123 in the processing feed direction. For example, before finishing forming the third processing groove 43 on the first planned division line 13, it calculates the amount of deviation 54 and corrects the irradiation position of the laser beam 122 based on the amount of deviation 54 before starting to form the third processing groove 43 on the second planned division line 13. Performing the third processing groove formation step 7 while performing the second image formation step 5 improves throughput compared to completing the second image formation step 5 before starting the third processing groove formation step 7.

[0064] For example, the second imaging unit 132 may form a second image 53 by imaging a predetermined region including the (n+1)th first division line 13 while processing the nth first division line 13. In this case, after performing the second image forming step 5 on the nth first division line 13, the third processing groove forming step 7 is performed on the nth first division line 13 while the second image forming step 5 is being performed on the (n+1)th first division line 13. In this case, the imaging unit 130 that captures the second image 53 is positioned to capture a predetermined region including the (n+1)th first division line 13 while processing the nth first division line 13.

[0065] Furthermore, if a misalignment between the first machined groove 40 and the third machined groove 43 at the nth first planned division line 13 is acceptable, the second image forming step 5 may not be performed on the nth first planned division line 13. Instead, while the second image forming step 5 is being performed on the (n+1)th first planned division line 13, the third machined groove forming step 7 may be performed on the nth first planned division line 13.

[0066] As described above, in the method for processing the workpiece 10 in the embodiment, before processing the third processing groove 43, the position of the first processing groove 40 is imaged and detected, and the irradiation position of the laser beam 122 is corrected so that the third processing groove 43 overlaps the first processing groove 40. This corrects the processing position deviation in multi-channel cutting, and thus has the effect of suppressing processing defects such as undivided parts.

[0067] It should be noted that the present invention is not limited to the embodiments described above. That is, it can be implemented with various modifications without departing from the core principles of the present invention. For example, in order to clearly image the contour of the first machining groove 40, the exposure time during imaging may be increased or the machining feed rate may be increased to average out fine chipping on the captured image 50.

[0068] Furthermore, although the embodiment uses two imaging units 130 arranged in front of and behind the focusing point 123, an imaging unit arranged coaxially with the optical axis of the laser beam 122 may be used, and the second image forming step 5 and the third processing groove forming step 7 may be performed simultaneously. In this case, the first image 52 will show the state where the first processing groove 40 is formed to the left of the processing point and the state where the first processing groove 40 is not formed to the right of the processing point, and the second image 53 will show the state where the third processing groove 43 is formed on top of the first processing groove 40 to the left of the processing point and the state where only the first processing groove 40 is formed to the right of the processing point. Multiple such first images 52 and second images 53 can be acquired, and the left side of the first image 52 and the right side of the second image 53 can be averaged and compared to obtain the amount of displacement 54 and correct the positional displacement.

[0069] Furthermore, in this embodiment, machining was performed from the first machining groove 40 to the third machining groove 43. However, when forming a fourth machining groove along the second planned division line 14, an image 50 of the second machining groove 42 is formed in the second machining groove formation step 3. By imaging the second machining groove 42 before forming the fourth machining groove and correcting the positional misalignment, the machining positional misalignment on the second planned division line 14 side can be corrected. If a fifth machining groove, a sixth machining groove, and so on are to be formed, the first machining groove 40 and the second machining groove 42 are imaged and their positional misalignments corrected before each machining operation.

[0070] Furthermore, when manufacturing the device chip 17 by processing the workpiece 10, after forming processing grooves by laser processing using the above method, the workpiece 10 may be divided by processing such as plasma dicing, or the workpiece 10 may be divided by forming processing grooves that reach the back surface 16 of the workpiece 10 using laser processing. [Explanation of Symbols]

[0071] 10 Workpiece 12 Surface 13. First planned division line 14. Second planned division line 13-1, 14-1 One end 15 devices 21 First Direction 22 Second Direction 40 First machining groove 42 Second machining groove 43 Third machining groove 52 First Image 53 Second image 54. Amount of deviation 100 Laser Processing Equipment 110 Holding Table 120 Laser beam irradiation unit 121 Irradiation head 122 Laser beams 123 Focusing point 130 Imaging Units 131 First Imaging Unit 132 Second Imaging Unit 140 Mobile Units 141 Machining feed unit 142 Indexing feed unit 150 display units 160 control units

Claims

1. A method for processing a workpiece, wherein a workpiece has a plurality of first division lines extending along a first direction and a plurality of second division lines extending along a second direction intersecting the first direction, and the workpiece is processed by irradiating the workpiece with a laser beam of a wavelength absorbed by the workpiece. A first processing groove forming step involves positioning one end of the first planned division line at an irradiation position where the laser beam is focused and irradiated, and irradiating the laser beam while relatively feeding the first planned division line and the focusing point of the laser beam along the first direction to form a first processing groove, and also imaging the first processing groove to form a first image, After performing the first groove forming step, a first alignment step is performed to position one end of the second planned division line at the irradiation position where the laser beam is focused and irradiated. After performing the first alignment step, a second processing groove forming step is performed, in which the second processing groove is formed by irradiating the laser beam while relatively feeding the second planned division line and the focal point of the laser beam along the second direction, After performing the second groove forming step, a second alignment step is performed to position one end of the first planned division line at the irradiation position where the laser beam is focused and irradiated. After performing the second alignment step, a second image forming step is performed, in which the first machining groove formed in the first division line in the first machining groove forming step is imaged to form a second image, A step to calculate the amount of deviation between the position of the first machining groove in the indexing feed direction in the first image and the position of the first machining groove in the indexing feed direction in the second image, A third machining groove forming step is performed by correcting the position in the indexing feed direction of the irradiation position where the laser beam is focused and irradiated based on the amount of deviation calculated in the deviation amount calculation step, and irradiating the laser beam while relatively feeding the first division planned line and the focusing point of the laser beam along the first direction to form a third machining groove that overlaps with the first machining groove, Equipped with A method for processing a workpiece, characterized by the features described above.

2. In the second image forming step, An imaging unit, positioned to capture an area ahead of the focusing point of the laser beam in the processing feed direction and moving relative to the focusing point of the laser beam in the processing feed direction, captures the first processing groove to form the second image. The third groove formation step is performed while the second image formation step is being carried out. A method for processing a workpiece according to claim 1, characterized in that it is a method for processing a workpiece according to claim 1.

3. In the third groove forming step, If the amount of deviation calculated in the deviation amount calculation step exceeds a preset threshold, the position in the indexing feed direction of the irradiation position where the laser beam is focused and irradiated is corrected. A method for processing a workpiece according to claim 1 or 2, characterized in that it is a method for processing a workpiece according to claim 1 or 2.

Images