Method of dividing a workpiece

Abstract

To suppress a workpiece from warping after laser light irradiation when dividing the workpiece.SOLUTION: A method of dividing a workpiece comprises: a support member formation step of fixing a support member (15, 55 and 56) to a first surface (11, 51) of the workpiece (10, 50); a heat shrinkage step of heating and shrinking the support member and applying force (Fb, Fe) causing the workpiece to warp convexly in a direction from the first surface toward a second surface (12, 52); a laser light irradiation step of irradiating the workpiece with a laser beam to form a crack extending to a modified layer and the first surface, and then applying force (Fc, Ff) making the workpiece warp convexly from the second surface toward the first surface because of the crack; and a grinding step of grinding the workpiece from the second surface and dividing it into a plurality of chips (14, 54), wherein the force making the workpiece warp in the heat shrinkage step and the force making the workpiece warp in the laser light beam irradiation step are cancelled by each other so as to suppress the workpiece from warping after the laser light beam irradiation step.SELECTED DRAWING: Figure 3

Description

Technical Field

[0004] , ,

[0001] The present invention relates to a method for dividing a workpiece.

Background Art

[0002] As a method for dividing a workpiece such as a wafer into a plurality of chips, an SDBG (Stealth Dicing Before Grinding) process that combines laser processing and grinding is known. In the SDBG process, a laser beam having a wavelength that is transmissive to the workpiece is irradiated along the planned division line of the workpiece to form a modified layer having a lower intensity than the surrounding area at a position having a predetermined depth in the workpiece. Subsequently, by grinding the back surface of the workpiece, the workpiece is thinned to the finish thickness, and the workpiece is divided into individual device chips. The usefulness of the SDBG process is high when chipping is likely to occur when dividing a relatively thick workpiece by cutting with a cutting blade.

[0003] In the SDBG process, there is a type of processing in which a crack (BHC: Backside Half Cut) extending from the modified layer toward the surface side of the workpiece is formed in the laser beam irradiation step, and in the laser beam irradiation step, no crack is formed in the workpiece, and then in the subsequent grinding step, a crack is formed in the workpiece by the grinding pressure to divide it.

[0004] When cracks are formed in a workpiece during the laser beam irradiation step, the surface of the workpiece expands in area compared to the back side due to the gaps created by the cracks, causing the workpiece to warp with a convex shape on the surface and a concave shape on the back. In particular, the smaller the individual chips on the workpiece, the greater the cumulative amount of gaps formed by cracks between the chips, resulting in greater warping of the workpiece. For example, when the chip size (length of one side of the chip) is 0.25 mm or less, warping of the workpiece due to the accumulation of cracks tends to become a problem. When the workpiece warps significantly, problems arise such as difficulty in transporting the workpiece, difficulty in holding the workpiece on the chuck table of the grinding machine, damage to the workpiece due to grinding while it is warped, and the workpiece not being ground with a uniform amount of material removed.

[0005] In laser cutting processes that do not create cracks in the workpiece during the laser irradiation step, there is a risk of undivided areas or meandering cut lines occurring when the chip is small. Therefore, in order to reliably divide small chips with high precision, cracks are often created in the workpiece during the laser irradiation step, and countermeasures are needed to prevent warping of the workpiece caused by cracks after the laser irradiation step.

[0006] To suppress warping of the workpiece, a method has been proposed in which, in addition to forming cracks from the modified layer toward the surface side of the workpiece along some or all of the planned cutting lines, cracks are also formed from the modified layer toward the back side of the workpiece (forming a full cut line) (for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2017-084923 [Overview of the project] [Problems that the invention aims to solve]

[0008] In the processing method described in Patent Document 1, modified layers are formed at multiple locations (positions closer to the surface and positions closer to the back) in the thickness direction of the workpiece, and cracks are extended from the modified layer closer to the surface toward the surface of the workpiece, and from the modified layer closer to the back toward the back of the workpiece. In order to reliably suppress warping of the workpiece, if cracks are formed on both the surface and back of the workpiece at many planned division lines, the operation and control during the laser beam irradiation step become complex and time-consuming.

[0009] Furthermore, in the SDBG process, protective tape is often applied to the surface of the workpiece while the back surface is ground. If cracks are formed on both the front and back surfaces of the workpiece along all planned division lines during the laser irradiation step, the cracks may cause the workpiece to expand beyond the tape, resulting in significant warping and potentially making it difficult to transport the workpiece.

[0010] This invention has been made in view of the above, and aims to provide a method for dividing a workpiece that can efficiently suppress warping of the workpiece after irradiation with a laser beam. [Means for solving the problem]

[0011] One aspect of the present invention is a method for dividing a workpiece into a plurality of chips along a planned division line, comprising: a support member forming step of fixing a support member to a first surface of the workpiece; a thermal shrinkage step of heating and shrinking the support member and applying a force that causes the workpiece to bend in a convex shape from the first surface toward a second surface opposite the first surface; and after performing the thermal shrinkage step, irradiating the workpiece with a laser beam from the second surface to form a modified layer inside the workpiece and cracks extending from the modified layer toward the first surface, and The process includes a laser beam irradiation step in which the first surface of the workpiece is expanded by a rack, and a force is applied to the workpiece causing it to bend in a convex shape from the second surface toward the first surface; and a grinding step in which the workpiece is ground from the second surface toward the first surface after the laser beam irradiation step, thereby dividing it into a plurality of chips, wherein the force applied to the workpiece in the heat shrinkage step causing it to bend in a convex shape from the first surface toward the second surface and the force generated on the workpiece in the laser beam irradiation step causing it to bend in a convex shape toward the first surface cancel each other out. Set it to do so The invention is characterized by suppressing warping of the workpiece after the laser beam irradiation step.

[0012] In the laser beam irradiation step, some of the lines to be divided may form cracks from the modified layer on both the first and second surfaces of the workpiece, thereby reducing the force that causes the workpiece to bend in a convex shape from the second surface toward the first surface. [Effects of the Invention]

[0013] According to the workpiece division method of the present invention, by utilizing the thermal shrinkage of the support member, the force that bends the workpiece in the thermal shrinkage step and the force that bends the workpiece in the laser beam irradiation step can be canceled out, thereby efficiently suppressing the bending of the workpiece after laser beam irradiation. [Brief explanation of the drawing]

[0014] [Figure 1] This is a perspective view showing the workpiece. [Figure 2] This figure shows the support member formation step of the first embodiment. [Figure 3] It is a diagram showing the heat shrinkage step of the first embodiment. [Figure 4] It is a diagram showing the laser beam irradiation step of the first embodiment. [Figure 5] It is a diagram showing the grinding step of the first embodiment. [Figure 6] It is a diagram showing a workpiece of a comparative example in which the laser beam irradiation step is performed without performing the heat shrinkage step. [Figure 7] It is a diagram showing a modified example of the laser beam irradiation step. [Figure 8] It is a diagram showing the support member formation step (first support member attachment step) and the heat shrinkage step of the second embodiment. [Figure 9] It is a diagram showing the support member formation step (resin coating step) of the second embodiment. [Figure 10] It is a diagram showing the support member formation step (surplus region removal step) of the second embodiment. [Figure 11] It is a diagram showing the laser beam irradiation step of the second embodiment. [Figure 12] It is a diagram showing the grinding step of the second embodiment. [Figure 13] It is a perspective view of a laser processing apparatus. [Figure 14] It is a perspective view of a grinding apparatus.

Mode for Carrying Out the Invention

[0015] Hereinafter, with reference to the accompanying drawings, a method for dividing a workpiece according to the present embodiment will be described. The first embodiment and its modified examples will be mainly described with reference to FIGS. 1 to 7, and the second embodiment will be mainly described with reference to FIGS. 8 to 12. FIG. 13 shows a laser processing apparatus used in the laser beam irradiation step of each embodiment, and FIG. 14 shows a grinding apparatus used in the grinding step of each embodiment.

[0016] A first embodiment of a method for dividing a workpiece will be described. Figure 1 shows a workpiece 10 that is divided by the division method of the first embodiment. The workpiece 10 is a disc-shaped semiconductor wafer made of, for example, silicon, and has a first surface, which is a front surface 11, and a second surface, which is a back surface 12 opposite to the first surface. On the front surface 11 side of the workpiece 10, chips 14, which are electronic devices, are formed in multiple regions demarcated by a grid of division lines 13. In other words, the workpiece 10 has multiple chips 14 demarcated by division lines 13.

[0017] Furthermore, the workpiece to which this invention is applied is not limited to semiconductor wafers; it can be applied to any workpiece that is ground and divided after laser irradiation. For example, the workpiece may be an inorganic material substrate such as ceramic, glass, or sapphire, or it may be a package substrate for a semiconductor product.

[0018] [Support member formation step] In the support member formation step shown in Figure 2, a support member 15 is formed to cover the surface 11 of the workpiece 10. The support member 15 has a base layer 151 and an adhesive layer 152. The base layer 151 is made of a thermoplastic resin such as polyolefin, polyethylene, or polyethylene terephthalate (PET) formed into a sheet, and has flexibility and non-adhesive properties. The adhesive layer 152 is laminated on the base layer 151 and has flexibility and adhesive properties. When the adhesive layer 152 is heated to a predetermined temperature, it softens and its adhesiveness increases. When the base layer 151 is heated to a predetermined temperature, it undergoes thermal shrinkage. The temperature at which thermal shrinkage of the base layer 151 occurs is higher than the temperature at which softening of the adhesive layer 152 occurs.

[0019] The support member 15 is fixed to the surface 11 of the workpiece 10 by attaching the adhesive layer 152 to the surface 11. In order to soften the adhesive layer 152 during attachment and improve the degree of adhesion to the workpiece 10, the support member 15 may be heated to a predetermined temperature range (for example, about 60°C to 80°C).

[0020] [Heat shrink step] In the heat shrinkage step shown in Figure 3, the support member 15 is heated to cause thermal shrinkage. For example, the workpiece 10 with the support member 15 fixed to the surface 11 is transported to the heating device 20. The heating device 20 has a heater 22, which is a heat source, inside the housing 21, and the heater 22 can heat the heating surface 23, which is the upper surface of the housing 21. The workpiece 10 that has been transported to the heating device 20 is placed on the heating surface 23 with the support member 15 facing downwards. This brings the base material layer 151 of the support member 15 into contact with the heating surface 23. When the heating surface 23 is heated by the heater 22, heat is transferred from the heating surface 23 to the support member 15, and the temperature of the support member 15 rises.

[0021] In the heat shrinkage step, the support member 15 is heated to a temperature at which thermal shrinkage occurs in the base layer 151. The temperature at which thermal shrinkage occurs in the base layer 151 is higher than the temperature at which the adhesive layer 152 is softened in the support member formation step to improve adhesion. As an example, in the heat shrinkage step, the support member 15 is heated to 100°C or higher for about 10 minutes.

[0022] In the heating device 20 shown in Figure 3, heat is applied from below to the support member 15 placed on the heating surface 23 by the heater 22. However, the heating method is not limited to this, and other heating methods may be used. For example, the support member 15 may be heated by infrared irradiation or hot air. When using infrared irradiation or hot air, the support member 15 can be supported so that it is exposed facing upward, and infrared irradiation or hot air blowing can be applied to the support member 15 from above.

[0023] As shown in Figure 3, when the support member 15 is heated by the heating device 20 to a temperature range in which thermal shrinkage occurs in the base material layer 151, a force Fa in the shrinkage (diameter reduction) direction is generated in the support member 15. When a force Fa in the shrinkage direction is generated in the support member 15, a force Fb is applied to the workpiece 10, causing it to bend into a convex shape from the surface 11 to the back surface 12. In other words, the force Fb acts as a force that bends the workpiece 10 so that when viewed from the surface 11 side, the surface 11 becomes concave, and when viewed from the back surface 12 side, the back surface 12 becomes convex. However, at this point, the modified layer 101 and cracks 102 described later have not yet formed on the workpiece 10, so it has high strength, and the workpiece 10 has not been thinned by grinding and has a predetermined thickness, so the workpiece 10 maintains its original shape against the force Fb, and the bending of the workpiece 10 is suppressed. In other words, during the heat shrinkage step, parameters such as the degree of heat shrinkage of the support member 15 are set to prevent warping of the workpiece 10.

[0024] In the example above, the heat shrinking step is performed after the support member formation step, but the heat shrinking step may be performed simultaneously with the support member formation step. For example, the support member 15 is set on the heating surface 23 of the heating device 20 so that the adhesive layer 152 is exposed facing upward, and the support member 15 is heated by the heater 22. Next, the workpiece 10 is brought close to the support member 15 from above, and its surface 11 is pressed against the adhesive layer 152. This fixes the support member 15 to the surface 11 of the workpiece 10, and at the same time the base material layer 151 can be heat-shrinked. Alternatively, the support member 15 may be pressed against a preheated workpiece 10, and the support member formation step and the heat shrinking step may be performed simultaneously.

[0025] [Laser beam irradiation step] Once the heat shrinkage step is complete, the workpiece 10 is transported to the laser processing device 30, where the laser beam irradiation step shown in Figure 4 is performed. Since no warping occurs in the workpiece 10 during the heat shrinkage step, it is easy to transport the workpiece 10 to the laser processing device 30.

[0026] As shown in Figure 13, the laser processing apparatus 30 includes a chuck table 31 for holding the workpiece 10, a laser irradiation unit 32 for irradiating the workpiece 10 on the chuck table 31 with a laser beam L (Figure 4), and an imaging unit 33 for imaging the workpiece 10 on the chuck table 31. The vertical direction in the laser processing apparatus 30 is defined as the Z-axis direction. The X-axis direction and Y-axis direction in the laser processing apparatus 30 are both perpendicular to the Z-axis direction (horizontal direction), and the X-axis direction and Y-axis direction are perpendicular to each other.

[0027] The chuck table 31 is supported on the base 34 of the laser processing device 30 so as to be able to move horizontally. Specifically, the chuck table 31 is moved in the X-axis direction by the first moving mechanism 35, and the chuck table 31 is moved in the Y-axis direction by the second moving mechanism 36.

[0028] The first moving mechanism 35 includes a pair of guide rails 351 mounted on a base 34 and extending in the X-axis direction, a ball screw 353 extending in the X-axis direction from a motor 352, and a first moving platform 354 supported so as to be movable in the X-axis direction via the pair of guide rails 351. The ball screw 353 is screwed into a threaded portion (not shown) provided on the first moving platform 354, and when the motor 352 is driven and the ball screw 353 rotates, power is transmitted from the ball screw 353 to the first moving platform 354, causing the first moving platform 354 to move in the X-axis direction.

[0029] The second moving mechanism 36 includes a pair of guide rails 361 provided on the first moving table 354 and extending in the Y-axis direction, a ball screw 363 extending in the Y-axis direction from a motor 362, and a second moving table 364 supported so as to be movable in the Y-axis direction via the pair of guide rails 361. The ball screw 363 is screwed into a threaded portion (not shown) provided on the second moving table 364, and when the motor 362 is driven and the ball screw 363 rotates, power is transmitted from the ball screw 363 to the second moving table 364, causing the second moving table 364 to move in the Y-axis direction. A chuck table 31 is supported on the second moving table 364.

[0030] The chuck table 31 has an upward-facing holding surface 311 on which the workpiece 10 is placed. The holding surface 311 is formed of a porous material that communicates with a suction source (not shown), and a suction force can be applied to the holding surface 311 by operating the suction source.

[0031] As shown in Figure 4, the laser irradiation unit 32 focuses the laser beam L emitted from the laser light source 321 with a light condenser 322 and irradiates it downward in the Z-axis direction. The laser beam L is, for example, a pulsed laser beam that is penetrating to the material of the workpiece 10.

[0032] The laser beam irradiation step is performed by the control unit 37 of the laser processing apparatus 30, which controls each part according to the control program. The workpiece 10 is held with the support member 15 (surface 11) facing downwards, and the base material layer 151 is placed on the holding surface 311 of the chuck table 31. In other words, the workpiece 10 is held with its back surface 12 facing upwards. Once the workpiece 10 is placed on the holding surface 311, the control unit 37 activates a suction source communicating with the holding surface 311 to hold the workpiece 10 in place by suction.

[0033] Next, the control unit 37 uses the imaging unit 33 to detect the division lines 13 of the workpiece 10 and aligns the laser beam irradiation position so that the laser beam L is irradiated along the division lines 13. Specifically, the first moving mechanism 35 and the second moving mechanism 36 adjust the position of the chuck table 31 in the X-axis and Y-axis directions so that one end of a predetermined division line 13 among the multiple division lines 13 is positioned directly below the concentrator 322 of the laser irradiation unit 32. Then, the focusing point of the laser beam L irradiated from the laser irradiation unit 32 is aligned to a predetermined position inside the thickness of the workpiece 10.

[0034] Next, the control unit 37 irradiates the workpiece 10 with a laser beam L from the laser irradiation unit 32 at a focal point while moving the chuck table 31 in the feed direction at a predetermined feed speed. The laser beam L is irradiated from the back surface 12 and incident on the workpiece 10. When machining along a division line 13 extending in the X-axis direction, the feed direction is the X-axis direction, and the chuck table 31 is moved in the X-axis direction by the first moving mechanism 35. When machining along a division line 13 extending in the Y-axis direction, the feed direction is the Y-axis direction, and the chuck table 31 is moved in the Y-axis direction by the second moving mechanism 36. When the irradiation position of the laser beam L from the laser irradiation unit 32 reaches the other end of the division line 13, the control unit 37 stops the irradiation of the laser beam L from the laser irradiation unit 32 and stops the movement of the chuck table 31 in the feed direction.

[0035] As a result, a modified layer 101 is formed inside the workpiece 10 along the planned division line 13. Modification means that the density, refractive index, mechanical strength, and other physical properties inside the workpiece 10 become different from the surrounding area due to irradiation with the laser beam L. As a result of the modification, the modified layer 101 becomes a region with lower strength than the surrounding area.

[0036] Once the modified layer 101 has formed along one planned division line 13, the control unit 37 uses the first moving mechanism 35 and the second moving mechanism 36 to change the positional relationship between the chuck table 31 and the laser irradiation unit 32, so that one end of the next planned division line 13 to be processed is positioned directly below the concentrator 322 of the laser irradiation unit 32. Then, in the same manner as above, the laser beam L is irradiated onto the focal point in the workpiece 10, and the workpiece 10 is fed through the machine to form the modified layer 101 along the next planned division line 13. In this way, the modified layer 101 is formed along all of the grid-like planned division lines 13.

[0037] The laser processing apparatus 30 described above is merely an example and is not limited to this configuration. For example, the chuck table 31 may be rotatable around the Z-axis. In this configuration, once the modified layer 101 has been formed along all the parallel division lines 13, the chuck table 31 can be rotated 90° to form the modified layer 101 along all the remaining unprocessed parallel division lines 13.

[0038] As shown in Figure 4, after the laser irradiation step, cracks 102 are formed in the workpiece 10 from each modified layer 101 toward the surface 11. In the laser irradiation step, the direction in which cracks are formed can be controlled by appropriately setting the focal point position of the laser beam L in the thickness direction of the workpiece 10. For example, if the modified layer 101 is formed in the thickness of the workpiece 10 closer to the surface 11, cracks 102 will mainly be formed toward the surface 11 that is close to the modified layer 101.

[0039] When a crack 102 is formed on the surface 11 side, the area of ​​the surface 11 side becomes larger than that of the back surface 12 side by the amount of the gap created by the crack 102 (the surface 11 side expands), and a force Fc acts on the workpiece 10, causing it to bend in a convex shape from the back surface 12 toward the surface 11. In other words, the force Fc acts as a force that bends the workpiece 10 so that the surface 11 becomes convex when viewed from the surface 11 side, and the back surface 12 becomes concave when viewed from the back surface 12 side.

[0040] Figure 6 shows a comparative example in which the laser beam irradiation step is performed without the heat shrinkage step described above. Since the heat shrinkage step is not performed, no force Fa (Figure 3) in the shrinkage direction acts on the support member 15, and no force Fb (Figure 3) is applied to the workpiece 10 in the direction that causes the back surface 12 to bend into a convex shape (the front surface 11 to bend into a concave shape). Therefore, when a crack 102 is formed only on the front surface 11 side of the workpiece 10, and a force Fc acts on the workpiece 10 in the direction that causes the front surface 11 to bend into a convex shape (the back surface 12 to bend into a concave shape), the workpiece 10 will bend in accordance with this force Fc. When viewed from the front surface 11 side, the bent workpiece 10 has a convex shape where the center protrudes more than the outer circumference, and when viewed from the back surface 12 side, it has a concave shape where the center is recessed more than the outer circumference.

[0041] In contrast, when the aforementioned heat shrinkage step is performed, a force Fa (Figure 3) in the shrinkage direction acts on the support member 15 covering the surface 11, and consequently, a force Fb (Figure 3) is applied to the workpiece 10, causing it to bend in a convex shape from the surface 11 towards the back surface 12. This suppresses the widening of the gap at the location of the crack 102 on the surface 11 side. As a result, the workpiece 10 does not become warped as shown in Figure 6, but maintains the flat shape shown in Figure 4.

[0042] The magnitudes of forces Fa and Fb are set so as to suppress warping of the workpiece 10 when cracks 102 are formed along all planned division lines 13 of the workpiece 10 during the laser beam irradiation step. The magnitudes of forces Fa and Fb can be set by the degree of heating in the heat shrinkage step, the selection of the material of the base layer 151 in the support member 15 (selection of the heat shrinkage rate of the base layer 151), etc.

[0043] [Grinding step] Once the laser beam irradiation step is complete, the support member 15 is transported from the laser processing device 30 to the grinding device 40, and the grinding step shown in Figure 5 is performed.

[0044] As shown in Figure 14, the grinding device 40 includes a chuck table 41 for holding the workpiece 10 and a grinding mechanism 42 for performing grinding on the workpiece 10 on the chuck table 41.

[0045] The chuck table 41 has an upward-facing holding surface 411 on which the workpiece 10 is placed. The holding surface 411 is formed of a porous material that communicates with a suction source (not shown), and a suction force can be applied to the holding surface 411 by activating the suction source. The chuck table 41 is rotated around the center of the holding surface 411 by a table rotation mechanism (not shown).

[0046] The grinding mechanism 42 rotatably supports the spindle 44 with respect to the spindle housing 43. The spindle 44 rotates around an axis oriented vertically, driven by the spindle motor 45. A mount 46 is connected to the lower end of the spindle 44, and a grinding wheel 47 is mounted on the mount 46. Multiple grinding wheels 48 are arranged in an annular pattern on the lower surface of the grinding wheel 47. The grinding mechanism 42 is moved vertically by a lifting mechanism (not shown).

[0047] The grinding step is performed by the control unit 49 of the grinding apparatus 40, which controls each part according to the control program. As shown in Figure 5, the workpiece 10 is held with the support member 15 (surface 11) facing downwards, and the base material layer 151 is placed on the holding surface 411 of the chuck table 41. In other words, the workpiece 10 is held with its back surface 12 facing upwards. Once the workpiece 10 is placed on the holding surface 411, the control unit 49 activates a suction source communicating with the holding surface 411 to hold the workpiece 10 in place by suction.

[0048] Next, the control unit 37 causes the grinding mechanism 42 to grind the back surface 12 of the workpiece 10, which is held by suction on the holding surface 411 of the chuck table 41. During grinding, the lifting mechanism lowers the grinding mechanism 42 to bring the grinding wheel 48 into contact with the back surface 12 of the workpiece 10, the spindle 44 rotates the grinding wheel 47 (rotation indicated by arrow Ra in Figure 14), and the table rotation mechanism rotates the chuck table 41 around the center of the holding surface 411 (rotation indicated by arrow Rb in Figure 14), grinding the back surface 12 while pressing the workpiece 10 with the grinding wheel 48. Since the surface 11 of the workpiece 10 is covered by the support member 15, grinding is performed while protecting the chip 14 from grinding pressure.

[0049] During grinding, the thickness of the workpiece 10 is measured using a thickness measuring device (not shown in the diagram). When it is detected that the workpiece 10 has been ground to a preset finish thickness, the control unit 49 stops the rotation of the grinding wheel 47 and the chuck table 41, raises the grinding mechanism 42 using the lifting mechanism to separate the grinding wheel 48 from the workpiece 10 on the chuck table 41, and ends the grinding process.

[0050] In the grinding step, the workpiece 10, which has been thinned, is divided into individual chips 14 along the cracks 102, with the modified layer 101 as the dividing point, by the grinding pressure of the grinding wheel 47 acting on the workpiece 10 via the grinding wheel 48. Because cracks 102 are formed not only in the modified layer 101 but also extending from the modified layer 101 toward the surface 11, the occurrence of undivided areas in the workpiece 10 and the occurrence of meandering of the cut line are suppressed, enabling highly accurate division.

[0051] Since the support member 15 is attached to the surface 11 of the workpiece 10, after division, the individual chips 14 do not fall off and generally maintain their positional relationship with the original workpiece 10. The divided workpiece 10 is removed from the grinding machine 40, the support member 15 is removed and the workpiece is separated into multiple chips 14, completing the series of division processes.

[0052] Incidentally, the workpiece 10 that has undergone the laser beam irradiation step (Figure 4) in the laser processing device 30 is transported from the laser processing device 30 to the grinding device 40, where it is placed on the holding surface 411 of the chuck table 41 and held in the grinding device 40. When transporting the workpiece 10, a transport pad that holds the workpiece 10 by suction force is used. In this case, if the workpiece 10 has a curved shape, it becomes difficult to hold it with the transport pad, or a transport pad with a special structure that can hold a curved workpiece 10 is required.

[0053] Furthermore, if the workpiece 10 has a warped shape, when the workpiece 10 is placed on the holding surface 411 of the chuck table 41 of the grinding device 40, a part of the workpiece 10 may lift off the holding surface 411, and even if suction force is applied to the holding surface 411, the workpiece 10 may not be properly held in place by suction. For example, if the workpiece 10 has a warp where the surface 11 is convex and the back surface 12 is concave, as shown in Figure 6, the outer circumference of the back surface 12 of the workpiece 10 placed on the holding surface 411 will be warped upward. If the workpiece 10 is ground using the grinding wheel 48 of the grinding mechanism 42 in this state, the lifted portion on the outer circumference of the workpiece 10 may be damaged, or the amount of grinding may become uneven in the radial direction of the workpiece 10, resulting in unsatisfactory processing results.

[0054] Therefore, after the laser irradiation step, it is necessary to suppress the occurrence of warping caused by the modified layer 101 and cracks 102 in the workpiece 10. As shown in Figure 6, the warping that occurs in the workpiece 10 during the laser irradiation step is caused by a force Fc that causes it to warp in a convex shape from the back surface 12 toward the front surface 11. In this embodiment, a heat shrinkage step is performed before the laser irradiation step to apply a force Fb (Figure 3) to the workpiece 10 that causes it to warp in a convex shape from the front surface 11 toward the back surface 12.

[0055] In other words, by performing a heat shrinkage step and applying a force Fa in the direction that causes the support member 15 to shrink, the force Fb applied to the workpiece 10 during the heat shrinkage step and the force Fc applied to the workpiece 10 during the laser beam irradiation step cancel each other out, thereby mitigating the warping of the workpiece 10 after the laser beam irradiation step.

[0056] In this way, by utilizing the thermal contraction of the support member 15 to suppress warping of the workpiece 10, the process transitions from the laser beam irradiation step to the grinding step, making it easier to transport the workpiece 10, and allowing the entire workpiece 10 to be held tightly against the holding surface 411 of the chuck table 41 without lifting. Therefore, the transport mechanism for transporting the workpiece 10 after the laser beam irradiation step can be made inexpensive and simple. In addition, the accuracy of the grinding process of the workpiece 10 by the grinding device 40 can be improved, resulting in superior processing results.

[0057] The suppression of warping of the workpiece 10 by utilizing the shrinkage of the support member 15 is effective when the support member 15 is heated to a predetermined temperature in the heat shrinkage step. This has the advantage of being relatively low-cost and efficient, as it does not require complex control of the laser processing device 30 in the subsequent laser beam irradiation step. In particular, if heating is performed in the support member formation step to increase the degree of adhesion of the support member 15 to the workpiece 10, the heating device used for that step can also be used in the heat shrinkage step, thus eliminating the need for additional equipment installation and further reducing costs.

[0058] Furthermore, since the warping suppression effect is obtained in the area where the support member 15 covers the surface 11, warping can be mitigated evenly throughout the entire workpiece 10.

[0059] In the heat shrinkage step, the support member 15 is heated to a temperature higher than the temperature at which the adhesive layer 152 softens, causing the base layer 151 to shrink and generating a force Fa in the shrinkage direction. By utilizing the shrinkage of the base layer 151, which is thicker than the adhesive layer 152, the warping of the workpiece 10 and the warping of the support member 15 can be efficiently canceled out, thereby enhancing the effect of suppressing the warping of the workpiece 10.

[0060] In this embodiment, the workpiece 10 and support member 15 are transported together from the laser beam irradiation step to the grinding step. In contrast, the workpiece may also be transported supported by an annular frame or the like. If the workpiece is supported by a frame, the rigidity of the frame can suppress the warping of the workpiece during transport. However, there are types of processing equipment (such as grinding equipment) that do not support the use of frames, and in such cases, the workpiece is transported without a frame. Therefore, the method of this embodiment, which can suppress the warping of the workpiece 10 using only the support member 15 without using a frame, is particularly useful.

[0061] However, even when a frame is attached during the transport of the workpiece, the workpiece is removed from the frame during the grinding step. Therefore, from the standpoint of suppressing warping of the workpiece during the grinding step, the method of this embodiment, which suppresses warping of the workpiece 10 using only the support member 15, is effective regardless of whether a frame is used during transport.

[0062] Figure 7 shows a modified example of the laser beam irradiation step. In this modified example, in some of the multiple planned division lines 13 of the workpiece 10, cracks 102 extending from the modified layer 101 towards the surface 11 are formed, as well as cracks 104 extending from the modified layer 103 towards the back surface 12. In other words, in some of the planned division lines 13, the workpiece 10 is fully cut by cracks 102 and 104 extending to both the surface 11 and the back surface 12.

[0063] As described above, in the laser beam irradiation step, the direction in which cracks are formed can be controlled by appropriately setting the focal point position of the laser beam L in the thickness direction of the workpiece 10. As shown in Figure 7, by forming a modified layer 101 at a position closer to the surface 11 of the workpiece 10's thickness, cracks 102 are formed from the modified layer 101 toward the surface 11, and by forming a modified layer 103 at a position closer to the back surface 12 of the workpiece 10's thickness, cracks 104 are formed from the modified layer 103 toward the back surface 12.

[0064] When a gap is created by the crack 104, the area on the back surface 12 side increases (the back surface 12 side expands), and a force acts on the workpiece 10 that causes it to warp in a convex shape from the surface 11 to the back surface 12. Since this force is similar to the force Fb shown in Figure 3, it has the effect of weakening the force Fc (Figure 4) that causes the workpiece 10 to warp due to the crack 102. Therefore, in the modified example shown in Figure 7, the warping suppression effect due to the thermal contraction of the support member 15 and the warping suppression effect due to the formation of the crack 104 work synergistically, resulting in a higher effect of suppressing the warping of the workpiece 10 caused by the formation of the crack 102.

[0065] Furthermore, in the modified example shown in Figure 7, unlike forming cracks 104 along all planned division lines 13, cracks 104 are formed only on some of the planned division lines 13 to assist in the warping suppression effect using the support member 15, thereby minimizing the increase in processing time and effort in the laser beam irradiation step. The number of planned division lines 13 in which cracks 104 are formed (crack formation frequency) can be arbitrarily selected, and the warping suppression effect of the workpiece 10 can be controlled by appropriately mixing the planned division lines 13 in which cracks 104 are formed.

[0066] In the above embodiment, the method is applied to a support member 15 having a base layer 151 and an adhesive layer 152 laminated together, but it can also be applied to a different support member. For example, the support member may be a sheet made of a thermoplastic resin without an adhesive layer. In this case, the material of the support member is preferably polyolefin, polyethylene, polypropylene, or polystyrene, and in the support member formation step, the support member is attached to the workpiece by heat compression. In the heat shrinking step, the support member is heated to a temperature higher than the temperature at which it is heat-pressed to the workpiece, causing the support member to shrink. Therefore, the temperature for heat shrinking in the heat shrinking step is higher than the temperature for attachment in the support member formation step, and in terms of the technical feature of setting a specific heating state for heat shrinking, it has commonalities with the above embodiment using a support member 15 with an adhesive layer 152. In this modified example, the workpiece may be pressed against a preheated support member, and the support member formation step and the heat shrinking step may be performed simultaneously. Alternatively, the support member may be pressed against a preheated workpiece, and the support member formation step and the heat shrinking step may be performed simultaneously.

[0067] Furthermore, the support member does not necessarily have to be in sheet form from the beginning; it is also possible to supply powder or liquid to the first surface of the workpiece and form it into a sheet that covers the first surface of the workpiece by means of thermocompression bonding, pressing, spin coating, etc.

[0068] Next, a second embodiment of the method for dividing the workpiece will be described. Note that components common to the first embodiment may be denoted by the same reference numerals and their descriptions may be omitted.

[0069] As shown in Figure 8, the workpiece 50 of the second embodiment has one surface 51 which is the first surface and the other surface 52 which is the second surface opposite to the first surface. Although detailed illustrations are omitted, the workpiece 50 has chips 54 (Figure 12) formed in multiple regions demarcated by multiple grid-like division lines, similar to the workpiece 10 described above. In addition, multiple bumps 53, which are metal protrusions, are formed on one surface 51 of the workpiece 50.

[0070] [Support member formation step, heat shrinkage step] In the support member formation step, a support member with a multi-layer structure is formed to cover one surface 51 of the workpiece 50. The support member formation step includes the first support member attachment step shown in Figure 8, the resin coating step shown in Figure 9, and the excess area removal step shown in Figure 10. A heat shrinkage step is also performed together with the first support member attachment step.

[0071] In the first support member attachment step shown in Figure 8, a sheet made of a thermoplastic resin such as polyolefin or polyethylene is brought into close contact with one surface 51 of the workpiece 50 to form the first support member 55 so as to cover the bump 53. When attaching the first support member 55 to the workpiece 50, the first support member 55 is heated by a heater 61 in a reduced-pressure space inside a vacuum chamber provided by the support member forming apparatus 60 and heat-pressed.

[0072] When heating the first support member 55 with the heater 61, the first support member 55 is heated to a temperature higher than the temperature required to heat-press the first support member 55 onto the workpiece 50, causing thermal shrinkage of the first support member 55. In other words, the thermal shrinkage step for the first support member 55 is performed immediately following the first support member attachment step.

[0073] As shown in Figure 8, when the first support member 55 is heated to a temperature range where thermal shrinkage occurs, a force Fd in the shrinkage (diameter reduction) direction is generated. When a force Fd in the shrinkage direction is generated in the first support member 55, a force Fe is applied to the workpiece 50, causing it to bend in a convex shape from one surface 51 to the other surface 52. In other words, the force Fe acts as a force that bends the workpiece 50 so that when viewed from the side of the one surface 51, the one surface 51 becomes concave, and when viewed from the side of the other surface 52, the other surface 52 becomes convex. However, at this point, the workpiece 50 has not yet formed the modified layer 501 or cracks 502 described later, and has high strength. Furthermore, the workpiece 50 has not been thinned by grinding and has a predetermined thickness, so the workpiece 50 maintains its original shape against the force Fe, and the bending of the workpiece 50 is suppressed.

[0074] Next, the resin coating step shown in Figure 9 is performed. The resin coating step is performed on the support member forming stage 62 of the support member forming apparatus 60. The support member forming stage 62 is made of a translucent material such as glass and has an upward-facing holding surface 621. An ultraviolet irradiation section 63 is provided below the support member forming stage 62, and ultraviolet UV light can be irradiated from the ultraviolet irradiation section 63 toward the holding surface 621.

[0075] The control unit 64 of the support member forming apparatus 60 operates a sheet supply mechanism (not shown) to place the second support member 56 on the holding surface 621 of the support member forming stage 62. The second support member 56 is held in place on the holding surface 621 by a suction mechanism (not shown) to maintain its flatness.

[0076] The second support member 56 is a sheet made of a thermoplastic resin such as polyolefin or polyethylene terephthalate. When placed on the holding surface 621, the area of ​​the second support member 56 is larger than the area of ​​the workpiece 50. An annular ring frame 58 may be attached to the outer circumference of the second support member 56.

[0077] Next, the control unit 64 drops liquid resin 57 onto the second support member 56 from a resin supply nozzle (not shown) positioned above the support member forming stage 62. The amount of liquid resin 57 supplied from the resin supply nozzle can be adjusted by a dispenser (not shown).

[0078] The support member forming apparatus 60 includes a holding section 65 for holding the workpiece 50 and a lifting mechanism 66 for moving the holding section 65 up and down. The holding section 65 holds the other side 52 of the workpiece 50 from above by suction, with the first support member 55 facing downwards. From a state where the workpiece 50 held by the holding section 65 is positioned above the support member forming stage 62, the control unit 64 lowers the holding section 65 using the lifting mechanism 66. As a result, the first support member 55 comes into contact with the liquid resin 57 supplied onto the second support member 56, and the liquid resin 57 is spread out by the downward force of the workpiece 50.

[0079] When it is determined that the liquid resin 57 has been sufficiently spread, the control unit 64 controls the lifting mechanism 66 to stop the descent of the workpiece 50. At this stage, the multiple bumps 53 protruding from one surface 51 of the workpiece 50 are embedded in the liquid resin 57, and one surface 51 is supported in a flat state without any irregularities caused by the bumps 53. By covering one surface 51 with the first support member 55 in advance before forming the layer of liquid resin 57, it is possible to prevent the liquid resin 57 from getting into the gaps between the multiple bumps 53 and becoming difficult to remove in later processes.

[0080] Next, the control unit 64 controls the ultraviolet irradiation unit 63 to irradiate the liquid resin 57 with ultraviolet UV light of sufficient intensity toward the holding surface 621. The ultraviolet UV light emitted from the ultraviolet irradiation unit 63 passes through the light-transmitting support member forming stage 62 and the second support member 56 to reach the liquid resin 57, curing the liquid resin 57, which is an ultraviolet-curable resin. When it is determined that the liquid resin 57 has sufficiently cured, the control unit 64 terminates the irradiation of ultraviolet UV light from the ultraviolet irradiation unit 63.

[0081] Through the resin coating step described above, the multiple bumps 53 protruding from one surface 51 of the workpiece 50 are covered by the first support member 55 and the cured liquid resin 57, and the liquid resin 57 is further supported by the second support member 56, forming a support member with a flat shape in which the irregularities caused by the bumps 53 are not exposed.

[0082] Next, the excess area removal step shown in Figure 10 is performed. In the excess area removal step, the workpiece 50 is transported from the support member forming stage 62 to the sheet cutting table 67. The transport mechanism (not shown) that transports the workpiece 50 to the sheet cutting table 67 holds the ring frame 58 (Figure 9) while transporting it. The workpiece 50 is placed on the sheet cutting table 67, and the sheet cutter 68 is used to cut the excess area of ​​the first support member 55, the second support member 56, and the liquid resin 57 (the area that extends beyond the outer shape of the workpiece 50) along the outer shape of the workpiece 50.

[0083] The support member formation step is completed after the first support member attachment step, the resin coating step, and the excess area removal step described above. Along with the first support member attachment step, a heat shrinkage step is performed to heat shrink the first support member 55, so a force Fe (Figure 8) is applied to the workpiece 50, causing it to bend in a convex shape from one surface 51 to the other surface 52.

[0084] The heat shrinking step for heat shrinking the first support member 55 can be performed separately from the first support member attachment step. For example, a heating device having a heating surface may be provided in addition to the heater 61 shown in Figure 8, and the first support member 55, which is attached to the workpiece 50, may be placed on the heating surface of the heating device and heated. When heat shrinking the first support member 55, in addition to using the heater 61, the first support member 55 may also be heated by infrared irradiation or hot air.

[0085] Furthermore, in addition to the first support member 55, the second support member 56 may also be subjected to a heat shrinkage step to cause thermal shrinkage. The second support member 56 can be thermally shrunk, for example, using the heating device 20 shown in Figure 3. The workpiece 50 is transported to the heating device 20, the second support member 56 is placed on the heating surface 23 with the second support member 56 facing downwards, and heated by the heater 22, causing the second support member 56 to thermally shrink. When the second support member 56 thermally shrinks, a force Fe (Figure 8) in the same direction as when the first support member 55 thermally shrinks can be applied to the workpiece 50 via the liquid resin 57.

[0086] When thermally shrinking the second support member 56, in addition to using the heating device 20, the second support member 56 may also be heated by infrared irradiation or hot air.

[0087] Instead of the UV-curing liquid resin 57, a thermosetting liquid resin can also be used. In this case, it is possible to perform a heat shrinkage step in which the second support member 56 is heat-shrunk at the same time as the liquid resin is heated and cured.

[0088] [Laser beam irradiation step] Once the support member formation step and the heat shrinkage step are completed, the workpiece 50 is transported to the laser processing apparatus 30 and the laser beam irradiation step shown in Figure 11 is performed. The laser beam irradiation step performed in the laser processing apparatus 30 is the same as that of the first practical embodiment described earlier, so it will be explained briefly.

[0089] A second support member 56 is placed on the holding surface 311 of the chuck table 31 of the laser processing apparatus 30, and while the workpiece 50 is held in place by applying an attractive force to the holding surface 311, a laser beam L is irradiated along all the planned division lines of the workpiece 50 to form a modified layer 501. Cracks 502 are formed in the workpiece 50 from each modified layer 501 toward one surface 51. When cracks 502 are formed, the area of ​​one surface 51 becomes larger than that of the other surface 52, causing it to expand, and a force Ff acts on the workpiece 50, causing it to bend in a convex shape from the other surface 52 toward the one surface 51. In other words, the force Ff acts as a force that bends the workpiece 50 so that when viewed from the side of the one surface 51, the one surface 51 becomes convex, and when viewed from the side of the other surface 52, the other surface 52 becomes concave.

[0090] The heat shrinkage step applies a force Fd (Figure 8) in the shrinkage direction to the first support member 55 and the second support member 56, and consequently, a force Fe (Figure 8) is applied to the workpiece 50, causing it to bend in a convex shape from one surface 51 to the other surface 52. Therefore, the force Fe applied to the workpiece 50 in the heat shrinkage step and the force Ff applied to the workpiece 50 in the laser beam irradiation step cancel each other out, mitigating the bending of the workpiece 50 after the laser beam irradiation step.

[0091] As a variation of the laser beam irradiation step, in addition to the crack 502 extending toward one surface 51, a crack extending toward the other surface 52 may be formed in a portion of the multiple planned division lines of the workpiece 50, resulting in a full-cut structure that extends toward both the one surface 51 and the other surface 52. This provides the same effect as the variation shown in Figure 7 described earlier.

[0092] [Grinding step] Once the laser beam irradiation step is complete, the workpiece 50 is transported to the grinding device 40 and the grinding step shown in Figure 12 is performed. The grinding step performed in the grinding device 40 is the same as that of the first practical embodiment described earlier, so it will be explained briefly.

[0093] The second support member 56 is placed on the holding surface 411 of the chuck table 41 of the grinding device 40, and while the workpiece 50 is held in place by applying a suction force to the holding surface 411, the other surface 52 of the workpiece 50 is ground by the grinding wheel 48 of the grinding mechanism 42. When the workpiece 50 has been thinned to a preset finish thickness, grinding by the grinding wheel 48 is completed.

[0094] The workpiece 50, thinned in the grinding step, is divided into individual chips 54 along the cracks 502, with the modified layer 501 as the dividing point. Because cracks 502 are formed not only in the modified layer 501 but also extending from the modified layer 501 toward one surface 51, the occurrence of undivided areas in the workpiece 50 and the meandering of the cut line are suppressed, enabling highly accurate division.

[0095] The workpiece 50 after division is removed from the grinding device 40, the first support member 55, the second support member 56, and the hardened liquid resin 57 are removed to separate it into multiple chips 54, thus completing the series of division processes.

[0096] As described above, in the second embodiment, when dividing a workpiece 50 having bumps 53 on one surface 51, the support members (first support member 55, second support member 56) fixed to the workpiece 50 are thermally shrunk to fill in the irregularities caused by the bumps 53, thereby suppressing warping of the workpiece 50 after the laser beam irradiation step.

[0097] According to the first embodiment, the second embodiment, and their respective modifications described above, in the SDBG process, which divides a workpiece by combining laser processing and grinding, the thermal contraction of the support member can be used to efficiently suppress the warping of the workpiece after laser irradiation.

[0098] Furthermore, the embodiments of the present invention are not limited to the embodiments and modifications described above, and may be modified, substituted, or altered in various ways without departing from the spirit of the technical idea of ​​the present invention. Moreover, if the technical idea of ​​the present invention can be realized in a different way by advances in the art or by other derived arts, it may be implemented by that method. Accordingly, the claims cover all embodiments that may fall within the scope of the technical idea of ​​the present invention. [Industrial applicability]

[0099] As described above, the workpiece division method of the present invention can efficiently suppress warping of the workpiece after laser beam irradiation, and is particularly useful in processing equipment that transports the workpiece without using frame support after laser beam irradiation. [Explanation of symbols]

[0100] 10: Workpiece 11: Surface (first surface) 12: Reverse side (second side) 13: Planned division line 14: Tip 15: Support member 20: Heating device 30: Laser processing equipment 31: Chuck Table 32: Laser irradiation area 35: 1st movement mechanism 36:Second movement mechanism 40: Grinding equipment 41: Chuck Table 42: Grinding mechanism 47: Grinding Wheel 48: Sharpening stone 50: Workpiece 51: One side (the first side) 52: The other side (the second side) 53: Bump 54: Tip 55: First support member 56: Second support member 57: Liquid resin 60: Support member forming apparatus 61: Heater 62: Support member forming stage 63: UV irradiation area 68: Sheet cutter 101: Modified layer 102: Crack 103: Modified layer 104: Crack 151: Base material layer 152: Adhesive layer 501: Modified layer 502: Crack L: Laser beam UV: Ultraviolet light

Claims

1. A method for dividing a workpiece into multiple chips along a planned division line, A support member forming step in which a support member is fixed to the first surface of the workpiece, A heat shrinkage step in which the support member is heated and shrunk, and a force is applied to the workpiece so that it bends into a convex shape in the direction from the first surface toward the second surface opposite the first surface, After the heat shrinking step is performed, A laser beam irradiation step comprising: irradiating the workpiece with a laser beam from the second surface to form a modified layer inside the workpiece and cracks extending from the modified layer toward the first surface, causing the first surface side of the workpiece to expand due to the cracks, and applying a force that causes the workpiece to bend in a convex shape in the direction from the second surface toward the first surface; After the laser beam irradiation step, The process includes a grinding step of grinding the workpiece from the second surface and dividing it into multiple chips, A method for dividing a workpiece, characterized in that the force applied to the workpiece in the heat shrinkage step, causing it to bend in a convex shape from the first surface toward the second surface, and the force generated on the workpiece in the laser beam irradiation step, causing it to bend in a convex shape from the second surface toward the first surface, cancel each other out, thereby suppressing the warping of the workpiece after the laser beam irradiation step.

2. In the laser beam irradiation step, Some of the planned splitting lines will form cracks from the modified layer on both the first and second surfaces of the workpiece. The method for dividing a workpiece according to claim 1, characterized in that it reduces the force that causes the workpiece to bend in a convex shape in the direction from the second surface toward the first surface.

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