Workpiece processing method and laser processing device

Abstract

To provide a processing method for a work piece and a laser processing device, by which a work piece with a dicing tape stuck thereto can be processed with a laser beam having high processability with respect to a dicing tape while an adverse effect on a post-process is restricted.SOLUTION: A processing method for a plate-like work piece includes: a sheet sticking step 1 of sticking a heat press sheet to a work piece by laying the heat press sheet on one surface of the work piece and heat pressing the sheet; a laser beam emission step 2 of performing a process by emitting a laser beam with an absorbable wavelength, to the work piece from the other surface of the work piece and along a dividing line set on the work piece; and a sheet joining step 3 of pressing the heat press sheet while re-heating and softening the heat press sheet, thereby joining the sheet so as to close a dividing groove or through-hole in the heat press sheet processed and formed together with the work piece in the laser beam emission step.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for processing a workpiece and a laser processing apparatus. [Background technology]

[0002] A known method for dividing a workpiece such as a semiconductor wafer into chips involves irradiating the workpiece with a laser beam along streets (planned dividing lines) set on the workpiece to ablate it. In this type of processing, the workpiece is typically held on a chuck table with the workpiece attached to dicing tape to improve handling, and the laser beam is then irradiated onto the workpiece on the chuck table.

[0003] During this process, the laser beam also irradiates the dicing tape that exists on the extension of the streets set on the workpiece. However, when processing the workpiece using a short-pulse laser with high peak power or a mid-infrared laser that is highly effective at processing resins, the dicing tape may also be processed, resulting in holes or splitting. This can cause problems, such as the dicing tape welding to the chuck table, contaminating the chuck table, and making it difficult to remove the wafer. To address this problem, a processing method can be considered in which the laser irradiation is stopped inside the wafer to prevent the laser beam from irradiating the dicing tape (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-253140 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the method of Patent Document 1 leaves a small unprocessed portion on the outer periphery of the wafer, which causes issues in subsequent processes, such as wafer fragments scattering during expansion and adverse effects during blade dicing.

[0006] The present invention has been made in consideration of these problems, and its purpose is to provide a method and a laser processing device for processing a workpiece to which dicing tape has been attached, which can process the workpiece with a laser beam that has high processability for the dicing tape while suppressing adverse effects on subsequent processes. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, the method for processing a workpiece of the present invention is a method for processing a plate-shaped workpiece, and is characterized by including: a sheet attachment step in which a thermo-compression sheet is laid on one side of the workpiece and heated and thermo-compressed to attach the thermo-compression sheet to the workpiece; a laser beam irradiation step in which a laser beam of a wavelength that is absorbed by the workpiece is irradiated from the other side of the workpiece along a planned division line set on the workpiece to process the workpiece; and a sheet joining step in which the thermo-compression sheet is heated again to soften it and pressed, thereby joining the thermo-compression sheet so as to close the division grooves or through holes in the thermo-compression sheet that were processed and formed together with the workpiece in the laser beam irradiation step.

[0008] In addition, the laser processing apparatus of the present invention is a laser processing apparatus for processing a plate-shaped workpiece, and is characterized by comprising: a holding table having a holding surface for holding the workpiece having a thermo-compression sheet attached to one side; and a laser beam irradiation unit for concentrating and irradiating a laser beam having a wavelength that is absorbed by the workpiece held on the holding table, and further comprising: a heating unit for heating and softening the thermo-compression sheet attached to the workpiece, and a pressing unit for pressing the thermo-compression sheet heated by the heating unit to bond it so as to close the dividing grooves or through holes in the thermo-compression sheet that have been processed and formed together with the workpiece by the laser boom irradiation unit.

[0009] In the laser processing apparatus, the pressing unit may be provided so as to face the holding surface of the holding table, and may press at least the outer periphery of the workpiece against the thermocompression sheet. [Effects of the Invention]

[0010] The present invention makes it possible to process a workpiece having a dicing tape attached thereto using a laser beam that has high processability for the dicing tape while suppressing adverse effects on subsequent processes. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a flowchart showing the flow of a method for processing a workpiece according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing an example of the sheet attaching step shown in FIG. [Figure 3] FIG. 3 is a perspective view showing the workpiece after the sheet application step shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view showing another example of the sheet attaching step shown in FIG. [Figure 5] FIG. 5 is a perspective view showing an example of the laser beam irradiation step shown in FIG. [Figure 6]FIG. 6 is a cross-sectional view showing a state before processing by the laser beam irradiation step shown in FIG. [Figure 7] FIG. 7 is a cross-sectional view showing a state after processing by the laser beam irradiation step shown in FIG. [Figure 8] FIG. 8 is a perspective view illustrating an example of the sheet joining step shown in FIG. [Figure 9] FIG. 9 is a cross-sectional view showing one state of the sheet joining step shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[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 to the contents described in the following embodiments. Furthermore, the components described below include those that can be easily imagined by a person skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the configuration can be made within the scope of the gist of the present invention.

[0013] [Embodiment] A method for processing a workpiece 10 and a laser processing apparatus 40 according to an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a flow chart showing the flow of the method for processing a workpiece 10 according to the embodiment. The method for processing a workpiece 10 according to the embodiment includes a sheet attaching step 1, a laser beam irradiation step 2, and a sheet joining step 3.

[0014] The sheet joining step 1 of the embodiment is performed by a sheet joining unit 30, 30-1 shown in Fig. 2 or Fig. 4. The laser beam irradiation step 2 and the sheet joining step 3 of the embodiment are performed by a laser processing apparatus 40 shown in Figs. 5 to 9. The laser processing apparatus 40 includes a holding table 50, a heating unit 60, a laser beam irradiation unit 70, an imaging unit 80, and a pressing unit 90. The sheet joining units 30, 30-1 may be mounted on the laser processing apparatus 40.

[0015] (Sheet application step 1) Fig. 2 is a cross-sectional view showing an example of sheet attachment step 1 shown in Fig. 1. Fig. 3 is a perspective view showing workpiece 10 after sheet attachment step 1 shown in Fig. 1. Sheet attachment step 1 is a step in which a thermocompression sheet 20 is laid on one surface of workpiece 10 and heated to thermocompress the sheet 20 to attach it to workpiece 10.

[0016] The workpiece 10 is plate-shaped. The workpiece 10 in this embodiment is, for example, a disk-shaped semiconductor wafer or a wafer such as an optical device wafer, with silicon (Si), sapphire (Al2O3), gallium arsenide (GaAs), silicon carbide (SiC), or the like as the substrate 11. As shown in Fig. 3, the workpiece 10 has a plurality of planned division lines 13 set in a grid pattern on the surface 12 of the substrate 11, and devices 14 formed in each region defined by the planned division lines 13.

[0017] The device 14 is, for example, an integrated circuit such as an IC (Integrated Circuit) or an LSI (Large Scale Integration), an image sensor such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor), or a MEMS (Micro Electro Mechanical Systems). The workpiece 10 may have unevenness on the surface 12 side, for example, by mounting a plurality of bumps that are convex portions protruding from the surface of the device 14, and the unevenness may be absorbed by thermocompression bonding a thermocompression sheet 20 to the surface 12 side.

[0018] The back surface 15 of the workpiece 10, which is located on the opposite side to the front surface 12 on which the devices 14 are formed, is ground to a finish thickness by, for example, a grinding device. After being thinned, the workpiece 10 is divided along the division lines 13 by cutting or the like to be separated into individual device chips. Note that although the device chips are square in shape in FIG. 3, they may also be rectangular in shape.

[0019] The thermocompression sheet 20 is a thermoplastic resin formed into a sheet shape. The thermocompression sheet 20 is flexible, non-adhesive, and thermoplastic, and does not have an adhesive layer. In the embodiment, the thermocompression sheet 20 is made of a resin that is transparent or translucent to visible light. In the embodiment, the thermocompression sheet 20 is a sheet of a polymer synthesized using an alkene as a monomer, and is made of, for example, polyethylene, polypropylene, polystyrene, or the like as a thermoplastic resin.

[0020] In the sheet attachment step 1 of the embodiment, a thermocompression sheet 20 is thermocompression-bonded to the back surface 15 of the workpiece 10 and one surface of an annular frame 21, thereby integrating the workpiece 10 and the frame 21 via the thermocompression sheet 20. The frame 21 is formed in an annular shape with an opening 22 larger than the outer diameter of the workpiece 10 in a plan view. The frame 21 is capable of accommodating the workpiece 10 inside the opening 22. The frame 21 is made of a material such as metal or resin. Note that, although the embodiment will be described assuming that the thermocompression sheet 20 is thermocompression-bonded to the back surface 15 of the workpiece 10, in the present invention, the thermocompression sheet 20 may also be thermocompression-bonded to the front surface 12.

[0021] The sheet application step 1 of the embodiment is performed by a sheet application unit 30 shown in Fig. 2. The sheet application unit 30 has a holding table 31, a heating unit 34, and a pressure roller 35. The holding table 31 is a so-called heat table that has a heat source for the heating unit 34 inside.

[0022] The holding table 31 includes recesses 32, 33 formed on its upper surface. In a plan view, the recess 32 has a circular shape that follows the outer shape of the workpiece 10. The recess 32 holds and positions the front surface 12 of the workpiece 10 on its upper surface. The recess 33 is formed outside the recess 32 in a plan view and has a ring shape that follows the outer shape of the frame 21. The recess 33 holds and positions one surface of the frame 21 on its upper surface.

[0023] The heating unit 34 has a heat source provided inside the holder 31 and heats the workpiece 10 and frame 21 placed in the recesses 32, 33. The pressure roller 35 is cylindrical with an axis extending horizontally and can roll while rotating around its axis from one end of the holder 31 to the other. By rolling, the pressure roller 35 presses the thermocompression sheet 20 against the workpiece 10 and frame 21 supported by the holder 31, thereby bonding them together.

[0024] 2, first, a flat, disk-shaped thermocompression sheet 20 is prepared, the planar shape of which is larger than the opening 22 of the frame 21. Next, the heat source of the heating unit 34 is activated to heat the holder 31 to a predetermined temperature.

[0025] Next, with the back surface 15 of the workpiece 10 facing upward, the workpiece 10 is positioned in the recess 32 of the holder 31, and the frame 21 is positioned in the recess 33. In this way, with the workpiece 10 housed and positioned within the opening 22 of the frame 21, the workpiece 10 is heated from the front surface 12 side, and the frame 21 is heated from the bottom surface side.

[0026] Next, the pressure roller 35 is placed on one end of the holder 31 with the thermocompression sheet 20 interposed therebetween. The pressure roller 35 is then rolled from one end of the holder 31 to the other in the direction shown by the arrow in FIG. 2 on the back surface 15 side of the workpiece 10. As a result, the pressure roller 35 presses the thermocompression sheet 20 in a direction that spreads it toward the back surface 15 side of the workpiece 10, thereby thermocompression bonding the thermocompression sheet 20 to the workpiece 10 and the frame 21.

[0027] 2, thermocompression bonding is performed by pressing the thermocompression sheet 20 with the pressure roller 35 while heating the front surface 12 of the workpiece 10 and the underside of the frame 21 with the holding table 31 having the heat source of the heating unit 34 inside. As a result, the thermocompression sheet 20 is pressed against the back surface 15 of the workpiece 10 and the upper surface of the frame 21, and the workpiece 10 and the frame 21 are integrated via the thermocompression sheet 20.

[0028] It is preferable that the thermocompression sheet 20 is heated to a temperature equal to or higher than the softening point and equal to or lower than the melting point when thermocompression-bonded by the pressure roller 35. In the sheet-bonding step 1 of the embodiment, the pressure roller 35 may be a heat roller equipped with an internal heat source, and may press the thermocompression sheet 20 from both sides while heating it together with the holding table 31. The surface of the pressure roller 35 may be coated with a fluororesin.

[0029] Fig. 4 is a cross-sectional view showing another example of the sheet applying step 1 shown in Fig. 1. Compared to the sheet applying unit 30 shown in Fig. 2, the sheet applying unit 30-1 shown in Fig. 4 has a pressure plate 36 and a heating unit 37 instead of the pressure roller 35.

[0030] The presser plate 36 has a flat lower surface facing the recesses 32, 33 of the holder 31 and is provided so as to be movable up and down to approach and move away from the holder 31. The heating unit 37 has a heat source provided inside the presser plate 36 and heats the thermocompression sheet 20 pressed by the presser plate 36. When the heating unit 37 is operating, the presser plate 36 presses the thermocompression sheet 20 placed on the workpiece 10 and frame 21 supported by the holder 31 against the workpiece 10 and frame 21 to bond them together.

[0031] 4, first, a flat, disk-shaped thermocompression sheet 20 is prepared, the planar shape of which is larger than the opening 22 of the frame 21. Next, with the pressure plate 36 spaced apart from the holder 31, the heat source of the heating unit 34 is activated to heat the holder 31 to a predetermined temperature, and the heat source of the heating unit 37 is activated to heat the pressure plate 36 to a predetermined temperature.

[0032] Next, with the back surface 15 of the workpiece 10 facing upward, the workpiece 10 is positioned in the recess 32 of the holder 31, and the frame 21 is positioned in the recess 33. In this manner, with the workpiece 10 housed and positioned within the opening 22 of the frame 21, the workpiece 10 is heated from the front surface 12 side and the frame 21 is heated from the bottom side. Furthermore, a thermocompression sheet 20 is placed so as to cover the back surface 15 side of the workpiece 10 and the top surface side of the frame 21. As a result, the thermocompression sheet 20 is heated via the workpiece 10 and the frame 21.

[0033] Next, the pressure plate 36 is lowered to press the thermocompression sheet 20. As a result, the pressure plate 36 presses the thermocompression sheet 20 in a direction that spreads it toward the rear surface 15 of the workpiece 10, thereby thermocompression bonding the thermocompression sheet 20 to the workpiece 10 and the frame 21.

[0034] 4 , the back surface 15 of the workpiece 10 and the underside of the frame 21 are heated by the holder 31 having a heat source inside the heating unit 34, and the top surface of the thermocompression sheet 20 is heated by the pressure plate 36 having a heat source inside the heating unit 37. That is, thermocompression bonding is performed by pressing the thermocompression sheet 20 with the pressure plate 36 while heating from both sides. As a result, the bottom surface of the thermocompression sheet 20 is pressure-bonded to the back surface 15 of the workpiece 10 and the top surface of the frame 21, and the workpiece 10 and the frame 21 are integrated via the thermocompression sheet 20.

[0035] After the thermocompression sheet 20 has been thermocompressed, the workpiece 10 supported by the frame 21 via the thermocompression sheet 20 is carried out. In a production line in which a plurality of workpieces 10 are processed one after another, the heat source of the heating unit 34 is not stopped, and thermocompression bonding to the thermocompression sheet 20 is carried out one after another to the workpieces 10 and the frames 21. The thermocompression sheet 20 is cooled by being carried out from the support table 31 in the production line.

[0036] (Laser beam irradiation step 2) Fig. 5 is a perspective view showing an example of laser beam irradiation step 2 shown in Fig. 1. Fig. 6 is a cross-sectional view showing a state before processing by laser beam irradiation step 2 shown in Fig. 1. Fig. 7 is a cross-sectional view showing a state after processing by laser beam irradiation step 2 shown in Fig. 1. Laser beam irradiation step 2 is a step of processing by irradiating a laser beam 71 having a wavelength that is absorbed by the workpiece 10 from the other side of the workpiece 10 along the planned dividing line 13 set on the workpiece 10.

[0037] In the laser beam irradiation step 2 of the embodiment, the laser beam irradiation unit 70 irradiates the workpiece 10, whose back surface 15 is held on the holding table 50 of the laser processing device 40, with a laser beam 71 from the front surface 12 side of the workpiece 10.

[0038] The holding table 50 holds the workpiece 10 on a holding surface 51. In the embodiment, the holding table 50 holds the back surface 15 of the workpiece 10, which has a thermocompression sheet 20 attached to one surface (back surface 15), via the thermocompression sheet 20. The holding surface 51 has a disk shape made of porous ceramic or the like. In the embodiment, the holding surface 51 is a flat surface parallel to the horizontal direction.

[0039] The holding surface 51 is connected to a vacuum suction source 53 via a vacuum suction path 52. A solenoid valve 54 is provided between the vacuum suction path 52 and the vacuum suction source 53. The holding table 50 holds the back surface 15 of the workpiece 10 placed on the holding surface 51 by suction via a thermocompression sheet 20. A plurality of clamps 55 are arranged around the holding table 50 to clamp a frame 21 that supports the workpiece 10.

[0040] The holding table 50 is rotated around a vertical axis by a rotation unit 56. The holding table 50 can be moved relative to the laser beam irradiation unit 70 by a movement unit (not shown). The holding table 50 can also be moved relative to a pressing unit 90 (described below) by a movement unit (not shown). In the following description, the X-axis direction is one direction in a horizontal plane. The Y-axis direction is a direction perpendicular to the X-axis direction in a horizontal plane. In the embodiment, the X-axis direction is the processing feed direction, and the Y-axis direction is the indexing feed direction.

[0041] The holding table 50 includes a heat source for the heating unit 60 therein. The heating unit 60 heats the holding surface 51 of the holding table 50 to a predetermined temperature. The heating unit 60 heats and softens the thermocompression sheet 20 attached to the workpiece 10 placed on the holding surface 51.

[0042] The laser beam irradiation unit 70 is a unit that condenses and irradiates a laser beam 71 having a wavelength that is absorbed by the workpiece 10, onto the workpiece 10 held on the holding table 50. The laser beam irradiation unit 70 includes, for example, a laser oscillator that emits the laser beam 71, a condenser 72, and various optical components that are provided on the optical path of the laser beam 71 between the laser oscillator and the condenser 72. The condenser 72 condenses the laser beam 71, which is emitted from the laser oscillator and propagated through the various optical components, onto the workpiece 10 held on the holding surface 51 of the holding table 50, and irradiates the workpiece 10.

[0043] In this embodiment, an imaging unit 80 is fixedly provided adjacent to the condenser 72 of the laser beam irradiation unit 70. The imaging unit 80 images the workpiece 10 held on the holding table 50. The imaging unit 80 includes a CCD camera or an infrared camera that images the workpiece 10 held on the holding table 50. The imaging unit 80 images the workpiece 10 to obtain an image for performing alignment between the workpiece 10 and the laser beam irradiation unit 70, and outputs the obtained image to a control unit of the laser processing apparatus 40.

[0044] In the laser beam irradiation step 2, first, the back surface 15 of the workpiece 10 is suction-held to the holding surface 51 of the holding table 50 via the thermocompression sheet 20. Next, the holding table 50 is moved to the processing position by a moving unit (not shown). Next, the workpiece 10 is imaged by the imaging unit 80, and the planned division line 13 is detected. Once the planned division line 13 has been detected, alignment is performed to align the planned division line 13 of the workpiece 10 with the irradiation portion of the laser beam irradiation unit 70.

[0045] In the laser beam irradiation step 2, a pulsed laser beam 71 is then irradiated from the surface 12 side of the workpiece 10, with a focal point 73 positioned on the workpiece 10, while the holding table 50 is moved relative to the laser beam irradiation unit 70. The laser beam 71 has a wavelength that is absorbed by the workpiece 10. Next, the laser beam 71, with the focal point 73 positioned on the workpiece 10, is irradiated along the planned dividing lines 13, thereby forming grooves 16 corresponding to the planned dividing lines 13.

[0046] In this case, in the laser beam irradiation step 2, the laser beam 71 is irradiated along the planned dividing line 13 to a point slightly outside the outer periphery of the workpiece 10 so that no unprocessed portion remains on the outer periphery of the workpiece 10. As a result, the laser beam 71 is also irradiated onto the thermocompression sheet 20 on the extension of the planned dividing line 13, forming dividing grooves 23, and through holes 24 in some of the grooves.

[0047] (Sheet joining step 3) Fig. 8 is a perspective view showing an example of sheet bonding step 3 shown in Fig. 1. Fig. 9 is a cross-sectional view showing one state of sheet bonding step 3 shown in Fig. 1. Sheet bonding step 3 is a step in which thermocompression-bonded sheet 20 is heated again and pressed while being softened.

[0048] In the sheet joining step 3 of the embodiment, the thermocompression-bonded sheet 20, which has been processed together with the workpiece 10 in the laser beam irradiation step 2 and is still held on the holding table 50, is heated and softened by the heating unit 60 and then pressed by the pressing unit 90 of the laser processing device 40.

[0049] The pressing unit 90 is a unit that presses the thermocompression sheet 20 heated by the heating unit 60. The pressing unit 90 has a pressing portion 91 formed of an elastic member. In the pressing unit 90 of this embodiment, the pressing portion 91 is provided so as to be movable in the vertical direction toward and away from the holding table 50. In this embodiment, the pressing portion 91 has a ring shape in plan view with an outer diameter larger than the outer diameter of the workpiece 10 and an inner diameter smaller than the outer diameter of the workpiece 10.

[0050] In the sheet bonding step 3, first, the holding table 50 is moved by a moving unit (not shown) to a position facing the pressing portion 91 of the pressing unit 90. More specifically, the holding table 50 is moved to a position where the outer periphery of the workpiece 10 faces directly below the ring of the pressing portion 91. Next, with the pressing portion 91 separated from the holding table 50, the heat source of the heating unit 60 is activated to heat the holding table 50 to a predetermined temperature. As a result, the thermocompression-bonding sheet 20 is heated from the underside and softened.

[0051] Next, the pressing unit 91 is lowered to press the outer periphery of the workpiece 10 downward. As a result, the thermocompression sheet 20 corresponding to the outer periphery of the workpiece 10 is pressed through the workpiece 10. The thermocompression sheet 20 softened by the heating unit 60 is pressed and spread in the planar direction. The thermocompression sheet 20 spread in the planar direction is spread in a direction that closes the dividing grooves 23 or the through holes 24 that were formed together with the workpiece 10 in the laser beam irradiation step 2, thereby narrowing and closing both edges of the dividing grooves 23 or the peripheries of the through holes 24.

[0052] Thus, in the sheet bonding step 3, the thermocompression-bonded sheet 20 is reheated from below by the holding table 50, which has the heat source of the heating unit 60 inside, while the thermocompression-bonded sheet 20 is pressed by the pressing unit 90. This closes the dividing grooves 23 or through holes 24 formed in the laser beam irradiation step 2, and the entire surface of the thermocompression-bonded sheet 20 is bonded.

[0053] After the thermocompression bonding sheet 20 has been bonded, the pressing unit 91 is raised again, and the workpiece 10 supported by the frame 21 via the thermocompression bonding sheet 20 is carried out.

[0054] As described above, in the embodiment of the method for processing workpiece 10 and the laser processing apparatus 400, a thermoplastic thermocompression sheet 20 is used as a dicing tape for holding workpiece 10. Even if through holes 24 are formed in the thermocompression sheet 20 around the periphery of workpiece 10 or the thermocompression sheet 20 adheres to the holding table 50 when laser beam 71 is irradiated onto workpiece 10, the thermocompression sheet 20 can be rejoined by heating and pressing to return it to its original state. This provides the advantage of being able to process the thermocompression sheet 20, which is a dicing tape, with a laser beam 71 that has high processability, while suppressing contamination of the holding table 50 and adverse effects on subsequent processes.

[0055] The present invention is not limited to the above-described embodiment, and can be implemented in various modifications without departing from the gist of the present invention.

[0056] For example, in the embodiment, the heating unit 60 that heats the thermocompression bonding sheet 20 in the sheet bonding step 3 has a heat source provided inside the holding table 50, but in the present invention, it may also heat the pressing portion 91 of the pressing unit 90. Also, the planar shape of the pressing portion 91 is a ring shape that follows the outer periphery of the workpiece 10 in the embodiment, but it may also be a circular shape with an outer shape larger than the workpiece 10. Also, the pressing portion 91 may be a pressing roller that rolls on the top surface (front surface 12 in the embodiment) of the workpiece 10.

[0057] In the sheet attachment step 1, the thermocompression sheet 20 is prepared in advance by cutting it into a disk shape in the embodiment, but in the present invention, for example, a rectangular thermocompression sheet 20 may be attached to the workpiece 10 and the frame 21 and then cut into a disk shape. In this case, for example, the portion outside the outer periphery of the frame 21 is cut and removed with a cutter or the like. [Explanation of symbols]

[0058] 10 Workpiece 12 Surface 13 Planned division line 15 Back side 16 Machining groove 20 Thermocompression sheet 23 Dividing groove 24 through holes 30, 30-1 Sheet pasting unit 34, 37 Heating unit 35 Pressure roller 36 Pressure plate 40 Laser processing equipment 50 holding table 51 Holding surface 60 Heating Unit 70 Laser beam irradiation unit 71 Laser Beam 90 Pressing unit 91 Pressing part

Claims

1. A method for processing a plate-shaped workpiece, comprising: a sheet attaching step of laying a thermocompression sheet on one surface of the workpiece and attaching the thermocompression sheet to the workpiece by heating and thermocompression bonding; a laser beam irradiation step of irradiating the workpiece from the other surface thereof along a planned dividing line set on the workpiece with a laser beam having a wavelength that is absorbed by the workpiece, thereby performing processing; a sheet joining step in which the thermocompression-bonded sheet is again heated and softened while being pressed to join the workpiece together with the workpiece in the laser beam irradiation step so as to close the dividing grooves or through holes of the thermocompression-bonded sheet formed by processing together with the workpiece in the laser beam irradiation step; A method for processing a workpiece, comprising:

2. A laser processing device for processing a plate-shaped workpiece, a holding table having a holding surface for holding a workpiece having a thermocompression sheet attached to one surface thereof; a laser beam irradiation unit that condenses and irradiates a laser beam having a wavelength that is absorbed by the workpiece held on the holding table; Preparation, a heating unit that heats and softens the thermocompression sheet attached to the workpiece; a pressing unit that presses the thermocompression sheet heated by the heating unit so as to close and bond the dividing grooves or through holes of the thermocompression sheet that are formed by processing the workpiece together with the laser beam irradiation unit; The laser processing device further comprises:

3. The pressing unit comprises: The holding table is provided so as to face the holding surface thereof. At least the outer periphery of the workpiece and the thermocompression sheet are pressed together. The laser processing device according to claim 2.

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