Method of manufacturing device chip

Abstract

To provide a device chip manufacturing method capable of suppressing the occurrence of warpage of a workpiece when a modified layer is formed.SOLUTION: A modified layer forming step S10 of forming a modified layer 16 inside the workpiece 10 by applying a laser beam having a transmission wavelength to the workpiece 10 along each division line L, and a dividing step S10 of dividing the workpiece 10 along each division line L by applying an external force to the workpiece 10 after performing the modified layer forming step S40, in the modified layer forming step S10, a laser beam is applied to the workpiece 10 along each division line L to thereby form a modified layer 16 inside the workpiece 10 except a predetermined area extending from the outer circumference of the workpiece 10 where the devices 13 are not formed.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a device chip. [Background technology]

[0002] As a method for dividing a plate-shaped workpiece such as a semiconductor wafer into device chips, a method is known in which a laser beam that is transparent to the workpiece is irradiated into the inside of the workpiece to form a modified layer, and then an external force is applied starting from the modified layer to divide the workpiece, thereby manufacturing device chips (e.g., Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3408805 Summary of the Invention [Problem to be solved by the invention]

[0004] When a modified layer is formed using a laser beam, the mechanical strength of the surrounding area around the modified layer may decrease, causing the workpiece to expand. In particular, as device chip sizes decrease due to recent trends toward miniaturization, the density of the modified layer increases, making the stress balance in the workpiece more likely to be disrupted. Such a disruption in stress balance can cause the workpiece to warp, potentially leading to problems such as making it impossible to position the focal point of the laser beam appropriately within the workpiece or releasing the suction hold on the workpiece, making it impossible to continue processing.

[0005] The present invention provides a method for manufacturing a device chip that can suppress the occurrence of warpage in a workpiece when a modified layer is formed. [Means for solving the problem]

[0006] One aspect of the present invention is A method of manufacturing device chips, comprising: dividing a workpiece, in which a plurality of devices are formed in an area partitioned by a plurality of intersecting planned dividing lines, along the planned dividing lines to manufacture device chips, a modified layer forming step of forming a modified layer inside the workpiece by irradiating the workpiece with a laser beam having a wavelength that can pass through the workpiece along the planned dividing line; a dividing step of dividing the workpiece along the planned dividing lines by applying an external force to the workpiece after the modified layer forming step is performed, The modified layer forming step includes: The modified layer is formed by irradiating the laser beam along the intended dividing line, leaving an area within a predetermined range from the outer edge of the workpiece where the device is not formed as an unprocessed area. [Effects of the Invention]

[0007] According to the present invention, when a modified layer is formed, warping of the workpiece can be suppressed. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view showing an example of a laser processing device 1. As shown in FIG. [Figure 2] FIG. 2 is a perspective view showing an example of the workpiece 10. As shown in FIG. [Figure 3] FIG. 3 is a flowchart showing an example of a process of a manufacturing method for a device chip. [Figure 4] FIG. 4 is a diagram illustrating an example of the workpiece 10 including the unmachined region 10b. [Figure 5] FIG. 5 is a diagram illustrating an example of processing by the laser irradiation unit 30 in the modified layer forming step S10. [Figure 6] FIG. 6 is a diagram illustrating an example of the shape of the boundary portion 10d. [Figure 7] FIG. 7 is a diagram for explaining another example of the shape of the boundary portion 10d. [Figure 8] FIG. 8 is a diagram illustrating an example of the annular modified layer forming step S20 and the auxiliary modified layer forming step S30. [Figure 9] FIG. 9 is a diagram for explaining an example of the division step S40. [Figure 10] FIG. 10 is a diagram for explaining another embodiment. [Figure 11] FIG. 11 is a flowchart showing another example of the process of the manufacturing method of the device chip. [Figure 12] FIG. 12 is a diagram for explaining a second example of the processing order of the workpiece 10 in the modified layer forming step S10. [Figure 13] FIG. 13 is a diagram for explaining a third example of the processing order of the workpiece 10 in the modified layer forming step S10. [Figure 14] FIG. 14 is a diagram for explaining a third example of the processing order of the workpiece 10 in the modified layer forming step S10, and is an example following FIG. [Figure 15] FIG. 15 is a diagram for explaining a fourth example of the processing order of the workpiece 10 in the modified layer forming step S10.

[0009] [Figure 16] FIG. 16 is a diagram for explaining a fourth example of the processing order of the workpiece 10 in the modified layer forming step S10, and is an example following FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a method for manufacturing a device chip according to an embodiment of the present invention will be described with reference to the drawings.

[0011] First, before describing the details of the device chip manufacturing method, the configuration of the laser processing apparatus 1 used for manufacturing the device chip will be described. In the following description, the X-axis direction is one direction on a horizontal plane. The Y-axis direction is a direction on a horizontal plane that is perpendicular to the X-axis direction. The Z-axis direction is a direction that is perpendicular to the X-axis and Y-axis directions.

[0012] 1 is a perspective view showing an example of a laser processing apparatus 1 according to an embodiment. The laser processing apparatus 1 processes a workpiece 10, which is an object to be processed, by irradiating the workpiece 10 with a laser beam. The processing of the workpiece 10 by the laser processing apparatus 1 is, for example, a modified layer forming process in which a modified layer is formed inside the workpiece 10 by the laser beam. Here, the workpiece 10 will be described.

[0013] (Workpiece) The workpiece 10 is, for example, a substantially disk-shaped wafer or optical device wafer made of a material such as Si (silicon), SiC (silicon carbide), GaN (gallium nitride), GaAs (gallium arsenide), or other semiconductor. The workpiece 10 may also be a variety of plate-shaped processing materials, such as a plate-shaped inorganic material substrate made of ceramics, glass, or sapphire, or a plate-shaped ductile material such as metal or resin. The workpiece 10 may also be a package substrate containing multiple device chips sealed with a molded resin or the like. FIG. 2 shows a wafer as an example of the workpiece 10.

[0014] As shown in FIG. 2, a surface 11 of a workpiece 10 has a plurality of intersecting streets 12 defined as division lines L, and a plurality of regions defined by the division lines L are formed in a grid pattern. Devices 13, such as ICs (Integrated Circuits), LSIs (Large Scale Integrated circuits), and MEMS (Micro Electro Mechanical Systems), are formed in each of the regions defined by the division lines L. The division lines L include division lines Lx extending in the X-axis direction and division lines Ly extending in the Y-axis direction and intersecting the X-axis direction. In the example shown in FIG. 2, two of the division lines Lx and two of the division lines Ly are representatively indicated by dashed lines. Furthermore, in the embodiment shown in FIG. 2, since each device chip formed by dividing the workpiece along the division lines Lx and Ly has a rectangular shape, the number of division lines Ly on the longer side is greater than the number of division lines Lx on the shorter side. In the embodiment, the device chip is rectangular in shape, for example, but may be square in shape or the like.

[0015] In the embodiments, when a planned division line extending in the X-axis direction is indicated, it is marked with the symbol "Lx", when a planned division line extending in the Y-axis direction is indicated, it is marked with the symbol "Ly", and when there is no need to distinguish between a planned division line extending in the X-axis direction and a planned division line extending in the Y-axis direction, it is simply marked with the symbol "L".

[0016] Furthermore, the workpiece 10 is transported and processed while being integrated with an annular frame 14 and tape 15 attached so as to cover the opening of the annular frame 14. The frame 14 is an annular plate member formed of, for example, metal or resin, and has an opening larger than the outer diameter of the workpiece 10. The tape 15 is expandable and in the form of a sheet with an outer diameter larger than the opening of the frame 14. The tape 15 is attached to the back side of the frame 14 so as to cover the opening of the frame 14. The workpiece 10 is positioned at a predetermined position in the opening of the frame 14, and is fixed to the frame 14 and tape 15 by attaching the back side to the tape 15.

[0017] 1, the following describes the configuration of the laser processing apparatus 1. The laser processing apparatus 1 includes a holding table 20, a laser irradiation unit 30, a moving unit 40, an imaging unit 50, and a control unit 100 as main components.

[0018] (holding table) The holding table 20 holds the workpiece 10 on a holding surface 21. The holding surface 21 is a disk-shaped surface made of porous ceramic or the like. In this embodiment, the holding surface 21 is a flat surface parallel to the horizontal direction. The holding surface 21 is connected to a vacuum suction source, for example, via a vacuum suction path (not shown). The holding table 20 holds the workpiece 10 placed on the holding surface 21 by suction. A plurality of clamps 22 are arranged around the holding table 20 to clamp the annular frame 14 that supports the workpiece 10.

[0019] The holding table 20 is rotated around an axis parallel to the Z-axis direction by a rotation unit 23. The rotation unit 23 is supported by an X-axis direction moving plate 24, and is moved together with the holding table 20 in the X-axis direction by a processing feed unit 41 of a moving unit 40, which will be described later, via the X-axis direction moving plate 24. Furthermore, the rotation unit 23 and the holding table 20 are moved in the Y-axis direction by an indexing feed unit 42 of the moving unit 40, which will be described later, via a Y-axis direction moving plate 25.

[0020] (Laser irradiation unit) The laser irradiation unit 30 is a unit that irradiates a laser beam onto the workpiece 10 held on the holding surface 21 of the holding table 20. The laser irradiation unit 30 has an oscillator that can oscillate a pulsed laser beam of a predetermined wavelength that is transparent or absorbent to the workpiece 10 and the tape 15, and in an embodiment in which a modified layer is formed, oscillates a transparent laser beam. Specifically, the laser irradiation unit 30 irradiates the laser beam along the planned dividing line L on the workpiece 10 to form a modified layer 16 (see, for example, FIG. 5 ) inside the workpiece 10.

[0021] The laser irradiation unit 30 also includes a condenser 31 that irradiates the laser beam at a desired position inside the workpiece 10. The condenser 31 is a focusing lens that focuses the laser beam on the workpiece 10 held on the holding table 20 and irradiates the workpiece 10. The focal point of the laser beam focused by the condenser 31 is positioned inside the workpiece 10. Note that in the embodiment, as an example, the front surface 11 side of the workpiece 10 is held by the holding table 20 and the laser beam is irradiated from the back surface side, but the front surface 11 side of the workpiece may also be held by the holding table 20 and the laser beam may be irradiated from the back surface side.

[0022] The laser irradiation unit 30 then irradiates the laser beam along the planned dividing line L while moving the focal point of the laser beam and the workpiece 10 relative to each other, thereby forming a modified layer 16 along the planned dividing line L.

[0023] (Mobile unit) The moving unit 40 is a unit that moves the focal point of the laser beam in the laser irradiation unit 30 and the imaging unit 50 relative to the workpiece 10 held on the holding table 20. The moving unit 40 includes a processing feed unit 41 and an indexing feed unit 42.

[0024] The processing feed unit 41 is a unit that relatively moves the holding table 20 and the focal point of the laser irradiation unit 30 in the X-axis direction, which is the processing feed direction. The processing feed unit 41 is installed on the device body 2 of the laser processing device 1, supports the X-axis moving plate 24 so that it can move freely in the X-axis direction, and moves the holding table 20 in the X-axis direction via the X-axis moving plate 24, for example.

[0025] The indexing feed unit 42 is a unit that moves the holding table 20 and the focal point of the laser irradiation unit 30 relatively in the Y-axis direction, which is the indexing feed direction. The indexing feed unit 42 is installed on the device body 2 of the laser processing device 1, supports the Y-axis moving plate 25 so that it can move freely in the Y-axis direction, and moves the holding table 20 in the Y-axis direction via, for example, the Y-axis moving plate 25 and the X-axis moving plate 24.

[0026] The processing feed unit 41 includes a ball screw 41a, a pulse motor 41b, and a guide rail 41c. Similarly, the indexing feed unit 42 includes a ball screw 42a, a pulse motor 42b, and a guide rail 42c. The ball screws 41a, 42a are rotatable about their respective axes. The pulse motors 41b, 42b rotate the ball screws 41a, 42a about their respective axes. The guide rail 41c of the processing feed unit 41 supports the X-axis moving plate 24 so that it can move in the X-axis direction. The guide rail 41c of the processing feed unit 41 is fixed to the Y-axis moving plate 25. The guide rail 42c of the indexing feed unit 42 supports the Y-axis moving plate 25 so that it can move in the Y-axis direction. The guide rail 42c of the indexing feed unit 42 is fixed to the apparatus main body 2.

[0027] (imaging unit) The imaging unit 50 is provided to face the workpiece 10 held on the holding table 20 in the Z-axis direction, and images the workpiece 10. For example, it images each planned dividing line L, each street 12, etc. of the wafer, which is the workpiece 10. The imaging unit 50 is fixed, for example, adjacent to the condenser 31 of the laser irradiation unit 30, and is moved by the moving unit 40 integrally with the laser irradiation unit 30 relative to the workpiece 10 held on the holding table 20.

[0028] The imaging unit 50 includes a microscope section and an imaging section (not shown), and the imaging section captures an image of the workpiece 10 captured by the microscope section. The imaging element may be, for example, a charge-coupled device (CCD) imaging element or a complementary metal oxide semiconductor (CMOS) imaging element. The imaging unit 50 acquires an image for aligning the workpiece 10 with the laser irradiation unit 30, and outputs the image data to the control unit 100. The imaging unit 50 may be, for example, an infrared ray (IR) camera that uses infrared rays that pass through the workpiece 10.

[0029] In addition, although not shown, the laser processing apparatus 1 is also equipped with a display unit including a display screen that displays images captured by the imaging unit 50, a setting screen for processing conditions, the status of processing operations, etc., and an input unit that accepts various operations from an operator, etc.

[0030] (control unit) The control unit 100 controls each of the above-mentioned components of the laser processing apparatus 1, causing the laser processing apparatus 1 to perform various processes on the workpiece 10. The control unit 100 is a computer including a control unit 110 that performs various calculations, a memory unit having a storage medium, and an input / output interface (not shown) that controls the input and output of data to and from the control unit 100. The control unit 110 includes a microprocessor such as a CPU (Central Processing Unit). The memory unit has memories such as an HDD (Hard Disk Drive), ROM (Read Only Memory), or RAM (Random Access Memory). The control unit 110 performs various calculations based on predetermined programs stored in the memory unit. The control unit 110 outputs various control signals to each of the above-mentioned components via the input / output interface according to the calculation results, thereby controlling the laser processing apparatus 1.

[0031] The control unit 110 executes various programs stored in the memory unit. As described above, the laser processing apparatus 1 forms modified layers 16 along the streets 12 of the workpiece 10 when manufacturing device chips. Here, the modified layers 16 will be described. The modified layers 16 refer to areas where the density, refractive index, mechanical strength, or other physical properties are different from those of the surrounding area. The modified layers 16 are, for example, crack areas, dielectric breakdown areas, refractive index change areas, or a mixture of these areas. In other words, the areas where the modified layers 16 are formed have lower mechanical strength and other properties than other areas of the workpiece 10.

[0032] The workpiece 10 may expand in the area where the modified layer 16 is formed. In particular, as the size of device chips decreases due to recent trends such as miniaturization of devices, the density of the modified layer 16 formed increases, making it easier for the stress balance in the workpiece 10 to be disrupted. Such a disruption of the stress balance may cause warping of the workpiece 10, which may result in problems such as making it impossible to position the focal point of the laser beam at an appropriate position inside the workpiece 10 or releasing the suction hold of the workpiece 10, making it impossible to continue processing. Therefore, in the embodiment, a program is executed to reduce the possibility of warping of the workpiece 10 and causing problems such as making it impossible to continue processing. Specific processing details will be described in the device chip manufacturing method.

[0033] (Device Chip Manufacturing Method) Next, a method for manufacturing a device chip according to an embodiment will be described. Fig. 3 is a flowchart showing an example of the method for manufacturing the device chip. The method for manufacturing the device chip includes, as processing steps, a modified layer forming step S10, an annular modified layer forming step S20, an auxiliary modified layer forming step S30, and a dividing step S40. The dividing step S40 includes a grinding step S41. The processing of each of these steps is executed by the control unit 110.

[0034] In the device chip manufacturing method of the embodiment, before executing the modified layer formation step S10, the control unit 110 transports the workpiece 10 onto the holding table 20 using a transport unit or the like not shown, and holds the workpiece 10 on the holding surface 21 of the holding table 20.

[0035] In the modified layer forming step S10, the control unit 110 forms a modified layer 16 inside the workpiece 10 by irradiating the workpiece 10 with a laser beam having a wavelength that transmits through the workpiece 10 along each of the planned division lines L. As described above, forming the modified layer 16 with a laser beam may cause the workpiece 10 to warp from the end side of the workpiece 10. Therefore, in this embodiment, as shown in FIG. 4, for example, an unprocessed region 10b where no processing is performed is set in an area of ​​the end of the workpiece 10 where no device 13 is formed. In other words, a configuration is provided in which the end of the workpiece 10 is not processed uniformly and is maintained in a suction-held state.

[0036] Specifically, as shown in FIG. 4, an area within a predetermined range from the outer peripheral edge 10a of the workpiece 10 where no devices 13 are formed is set as an unprocessed area 10b. FIG. 4(a) shows a top view of the workpiece 10 in which the unprocessed area 10b is provided and a modified layer 16 is formed along the planned division lines L, and FIG. 4(b) shows a cross-sectional view of the workpiece 10. In the example shown in FIG. 4, the unprocessed area 10b has an annular shape. In this way, the unprocessed area 10b is provided, and the control unit 110 executes a modified layer forming step S10 in which the unprocessed area 10b is left and the modified layer 16 is formed by irradiating the laser beam along the planned division lines L.

[0037] FIG. 5 is a diagram illustrating an example of the processing in the modified layer forming step S10. The control unit 110, for example, moves the holding table 20 in the Y-axis direction using the moving unit 40, while the laser irradiation unit 30 forms a modified layer 16 inside the workpiece 10. That is, in this example, the Y-axis direction is the processing feed direction and the X-axis direction is the indexing feed direction. However, as described above, the X-axis direction may be the processing feed direction and the Y-axis direction may be the indexing feed direction. This processing is performed sequentially, for example, from the planned division line Ly on one end to the planned division line Ly on the other end, leaving the unprocessed region 10b. Similarly, processing is performed sequentially from the planned division line Lx on one end to the planned division line Lx on the other end, leaving the unprocessed region 10b.

[0038] The example in which processing is performed in order from the planned division line L on one end side to the planned division line L on the other end side is a first example of the processing order for the workpiece 10. In addition, in Fig. 4(a), reference numeral 10c indicates a processing region in which a device 13 is formed, and multiple solid lines on the processing region 10c indicate processing lines when a modified layer 16 is formed. Since the modified layer 16 is formed inside the workpiece 10, it is usually impossible to determine whether or not the modified layer 16 has been processed unless cracks or the like have occurred, but in the example shown in Fig. 4(a), it is illustrated for the convenience of explaining that the modified layer 16 has been processed.

[0039] On the other hand, in the example shown in FIG. 4, the shape of the unprocessed area 10b, i.e., the shape of the boundary portion 10d which is the boundary between the unprocessed area 10b and the processed area 10c, is formed in a circular ring shape whose length in the X-axis direction and the length in the Y-axis direction are the same, but the shape of this boundary portion 10d is not limited to a circular ring shape.

[0040] For example, as shown in Figures 6 and 7, the shape of boundary 10d may be an ellipse or an oval. That is, when an imaginary circle is drawn with center P of workpiece 10 as the center, boundary 10d may have a ring shape that is deformed such that the length in the X-axis direction and the length in the Y-axis direction are different from the imaginary circle. Figure 6 shows an example of an ellipse or an oval shape in which the length in the Y-axis direction is longer than the X-axis direction. Figure 7 shows an example of an ellipse or an oval shape in which the length in the X-axis direction is longer than the Y-axis direction.

[0041] In the embodiment, since the workpiece itself is circular, the workpiece 10 may be considered a virtual circle. In this case, in the examples shown in Figures 6 and 7, at least one of the lengths in the X-axis direction and the Y-axis direction of the ring shape of the boundary portion 10d is approximately equal to the diameter of the workpiece 10. In the example shown in Figure 6, the length in the Y-axis direction is approximately the same as the diameter of the workpiece 10, and in the example shown in Figure 7, the length in the X-axis direction is approximately the same as the diameter of the workpiece 10. In other words, in the X-axis and Y-axis directions, the lengths of the longer sides of the ring shape are approximately equal to the diameter of the workpiece 10, and the lengths of the shorter sides of the ring shape are shorter than the diameter of the workpiece 10.

[0042] Furthermore, when focusing on the shape of the unprocessed region 10b, it can be said that the unprocessed region 10b configured in this manner is configured so that the areas of the unprocessed regions 10b located at both ends in the X-axis direction are different from the areas of the unprocessed regions 10b located at both ends in the Y-axis direction. For example, in the example shown in FIG. 6, the unprocessed regions 10b at both ends in the X-axis direction are larger than the unprocessed regions 10b at both ends in the Y-axis direction. Conversely, in the example shown in FIG. 7, the unprocessed regions 10b at both ends in the Y-axis direction are larger than the unprocessed regions 10b at both ends in the X-axis direction. In other words, when the shape of the boundary 10d is annular as shown in FIG. 4, the areas of the unprocessed regions 10b at both ends in the X-axis direction and the unprocessed regions 10b at both ends in the Y-axis direction are the same. However, when the shape of the boundary 10d is elliptical or oval as shown in the examples of FIGS. 6 and 7, the areas of the unprocessed regions 10b at both ends in the X-axis direction and the Y-axis direction are different.

[0043] The size of the unprocessed region 10b may be determined taking into consideration warpage, deformation, and the like of the workpiece 10 that may occur due to the formation of the modified layer 16. If the size and area of ​​the unprocessed region 10b can be made smaller by forming the unprocessed region 10b in an elliptical shape compared to when the unprocessed region 10b is in an annular shape, it may be easier to divide the workpiece 10 in the dividing step S40 described later. This is because the area in which the modified layer 16 is formed increases.

[0044] Furthermore, as described above, the sizes of the unmachined areas 10b at both ends in the X-axis direction and the unmachined areas 10b at both ends in the Y-axis direction are different in the examples of Figures 6 and 7. Which example to use may be determined depending on, for example, whether warping of the workpiece 10 is more likely to occur at the ends in the X-axis direction or in the Y-axis direction.

[0045] For example, as shown in FIGS. 6 and 7 , when the number of processed lines in the Y-axis direction is greater than the number of processed lines in the X-axis direction, the workpiece 10 may be more likely to warp at both ends in the X-axis direction due to factors such as a higher density of processed lines in the central region of the workpiece 10. In such cases, it is preferable to provide unprocessed regions 10b as shown in FIG. 6 , in which the unprocessed regions 10b at both ends in the X-axis direction are relatively large. On the other hand, even when the number of processed lines in the Y-axis direction is greater than the number of processed lines in the X-axis direction, the workpiece 10 may be more likely to warp at both ends in the Y-axis direction due to factors such as a higher density of processed lines in the Y-axis direction, in which the number of processed lines is greater. In such cases, it is preferable to provide unprocessed regions 10b as shown in FIG. 7, in which the unprocessed regions 10b at both ends in the Y-axis direction are relatively large. Note that which end of the workpiece 10 is more likely to warp may vary depending on factors such as the number of processed lines, and this tendency may be obtained in advance, for example, by experimentation. In either case, it is preferable to set the unprocessed area 10b to be relatively large on the end side where warping is likely to occur of the workpiece 10. This is because when the unprocessed area 10b on the end side where warping is likely to occur of the workpiece 10 is large, the suction holding of the workpiece 10 is maintained in the unprocessed area 10b, and the possibility of warping of the workpiece 10 can be reduced.

[0046] Next, the annular modified layer forming step S20 will be described. When the unmachined region 10b is provided as described above, the workpiece 10 is divided into the unmachined region 10b and the machined region 10c at the boundary 10d during the process of dividing the workpiece 10 into chips. Therefore, as an example of a means for assisting this division, the control unit 110 executes the annular modified layer forming step S20, which forms an annular modified layer 16 at the boundary 10d. As described above, the shape of the boundary 10d can include a circular ring shape, an elliptical shape, an oval shape, and the like. Therefore, in this annular modified layer forming step S20, an annular modified layer 16a (hereinafter referred to as "annular modified layer 16a") is formed, which is a modified layer corresponding to such an annular shape.

[0047] Fig. 8 shows an example of the workpiece 10 when the annular modified layer forming step S20 is performed on the workpiece 10, where Fig. 8(a) shows a top view of the workpiece 10 on which the annular modified layer 16a is formed, and Fig. 8(b) shows a cross-sectional view of the workpiece 10. In the example shown in Fig. 8(a), the annular modified layer 16a is indicated by a dashed line.

[0048] In relation to the modified layer forming step S10 described above, the annular modified layer forming step S20 can be performed on the boundary portion 10d first, and then the modified layer forming step S10 can be performed on the processing region 10c. However, in this embodiment, it is preferable to perform the annular modified layer forming step S20 after performing the modified layer forming step S10. The boundary portion 10d is the end of the processing region 10c, and can essentially be said to be the end of the workpiece 10. Therefore, if a modified layer is first formed on the boundary portion 10d by the annular modified layer forming step S20, the workpiece 10 will warp at the boundary portion 10d, which may reduce the suction holding force of the workpiece 10 at the boundary portion 10d and cause problems such as an inability to continue processing.

[0049] Furthermore, in the process of dividing the workpiece 10 into chips, the control unit 110 may further execute an auxiliary modified layer forming step S30 in which a predetermined modified layer is formed in the unprocessed region 10b as an example of a means for assisting the division. The predetermined modified layer is, for example, an auxiliary modified layer 16b formed in an appropriate shape, such as a radial or lattice shape, in the unprocessed region 10b. FIG. 8 shows the auxiliary modified layer 16b formed radially in addition to the above-mentioned annular modified layer 16a. Note that in the example shown in FIG. 8, seven radial auxiliary modified layers 16b are formed, but the number may be set arbitrarily by an operator or the like. For example, the number may be determined based on the ease of dividing the workpiece 10, etc., based on the material of the workpiece 10.

[0050] Next, the dividing step S40 will be described. In the dividing step S40, the control unit 110 grinds the workpiece 10 to thin the workpiece 10, and divides the workpiece 10 into individual device chips starting from the modified layer 16 formed inside the planned division line L. The method of dividing the workpiece 10 into individual device chips may be various methods, such as dividing the workpiece 10 by applying an external force to the workpiece 10 using a grinding device, or dividing the workpiece 10 by expanding the tape 15 and applying an external force in the radial direction. In the embodiment, as an example, a grinding step S41 is performed in which the grinding device 200 is used to divide the workpiece 10 into individual device chips.

[0051] 9 is a diagram schematically illustrating the grinding step S41, in which (a) of Fig. 9 illustrates the state of the workpiece 10 before grinding, and (b) of Fig. 9 illustrates the state of the workpiece 10 after grinding. In the grinding step S41, the workpiece 10 is ground from the back surface side to expose the modified layer 16 on the back surface side, thereby dividing the workpiece 10 into individual device chips.

[0052] Here, the grinding apparatus 200 will be described. The grinding apparatus 200 includes a chuck table 210 having a holding surface 210a that suction-holds the workpiece 10 to be ground, and a grinding unit 220 that grinds the workpiece 10 suction-held on the chuck table 210. The workpiece 10 is suction-held on the holding surface 210a by a suction-holding source (not shown). The chuck table 210 is connected to a rotational drive source such as a motor, and can rotate around a rotation axis perpendicular to the holding surface 210a by operating the rotational drive source.

[0053] The grinding unit 220 provided above the chuck table 210 includes a spindle 221 that is substantially perpendicular to the holding surface 210a of the chuck table 210, and a rotation drive source (not shown) such as a motor that rotates the spindle 221. A disk-shaped wheel mount 222 is fixed to the lower end of the spindle 221, and a grinding wheel 223 is fixed to the lower end of the wheel mount 222.

[0054] The grinding wheel 223 has an annular base 224 made of a metal material such as stainless steel or aluminum, and a plurality of grinding stones 225 arranged in a ring shape on the underside of the base 224. The grinding stones 225 include a binder made of, for example, ceramic, resin, or a metal material, and numerous abrasive grains such as diamond dispersed and fixed in the binder.

[0055] In the grinding device 200 configured in this manner, the control unit 110 rotates the chuck table 210 and also rotates the grinding wheel 223 via the spindle 221. Then, the control unit 110 lowers the grinding unit 220 and brings the lower surface of the grinding wheel 225 into contact with the workpiece 10 held by suction on the chuck table 210, thereby starting grinding of the workpiece 10.

[0056] As the grinding of the workpiece 10 progresses, the thickness of the workpiece 10 gradually decreases, as shown in FIG. 9(b). Then, when at least a portion of the modified layer 16 formed on the workpiece 10 is removed and the modified layer 16 is exposed on the back side of the workpiece 10, the workpiece 10 is divided using the modified layer 16 as a starting point. This separates the multiple devices 13 formed on the workpiece 10, producing multiple device chips. While the example in FIG. 9(b) shows a state in which some of the modified layer 16 remains, it is preferable to continue grinding until all of the modified layer 16 is removed. This is because if the modified layer 16 remains on the manufactured device chip, defects such as cracking of the device chip may occur, starting from the remaining modified layer 16.

[0057] Furthermore, by grinding the workpiece 10 in this manner, the workpiece 10 is similarly divided into a processed region 10c and an unprocessed region 10b, starting from the annular modified layer 16a and the auxiliary modified layer 16b.

[0058] In addition, in the example shown in Figure 9, the workpiece 10 is divided by the grinding device 200, but division by the grinding device 200 and division by expanding the tape 15 and applying an external force may be performed in combination.

[0059] As described above, in the embodiment, the region within a predetermined range from the outer circumferential edge 10a of the workpiece 10 where the devices 13 are not formed is left as the unprocessed region 10b, and the laser beam is irradiated along the intended division line L. In other words, the unprocessed region 10b is provided on the outer periphery of the workpiece 10, and the region inside the unprocessed region 10b is processed as the processed region 10c. As a result, the unprocessed region 10b is not processed, so the end of the workpiece 10 included in the unprocessed region 10b can be maintained in a suction-held state, and as a result, the possibility of the workpiece 10 being warped can be further reduced.

[0060] In the embodiment, the shape of the boundary 10d, which is the boundary between the unprocessed region 10b where the devices 13 are not formed and the processed region where the devices 13 are formed, is a ring shape, such as an ellipse or an oval, which is a virtual circle centered at the center of the workpiece 10 such that the length in the X-axis direction and the length in the Y-axis direction are different. In particular, in the embodiment, at least one of the lengths in the X-axis direction and the Y-axis direction is approximately equal to the diameter of the workpiece 10. For example, in the example shown in FIG. 6 above, the ellipse shape has a length in the Y-axis direction that is approximately equal to the diameter of the workpiece 10. In the example shown in FIG. 7 , the ellipse shape has a length in the X-axis direction that is approximately equal to the diameter of the workpiece 10. In other words, the unprocessed region 10b located at both ends in the X-axis direction and the unprocessed region 10b located at both ends in the Y-axis direction have different areas. This may enable the size of the unprocessed region 10b to be smaller than when the shape of the boundary 10d is a ring shape in which the length in the X-axis direction and the length in the Y-axis direction are the same. If the unprocessed region 10b can be made smaller, the area in which the modified layer 16 can be formed becomes larger, making it easier to divide the workpiece 10 and enabling more device chips to be manufactured.

[0061] In the embodiment, an annular modified layer 16a is formed at the boundary 10d between the unprocessed region 10b and the processed region 10c, which can assist in dividing the workpiece 10 into device chips starting from the annular modified layer 16a.

[0062] In the embodiment, an auxiliary modified layer 16b is formed in the unprocessed region 10b, for example, radially, which can assist in dividing the workpiece 10 into device chips starting from the auxiliary modified layer 16b.

[0063] In addition, in the embodiment, when dividing the workpiece 10, the workpiece 10 is divided using a grinding device 200. That is, by grinding the workpiece 10 using the grinding device 200, the workpiece 10 is thinned and the modified layer 16 is exposed. Then, the workpiece 10 is divided into individual device chips starting from the modified layer 16. At this time, it is preferable to perform grinding so that the modified layer 16 is completely removed. In this way, thinning the workpiece 10 by grinding makes it easier to divide the workpiece 10 into chips, and removing all of the modified layer of the thinned workpiece 10 can prevent problems such as cracking of the device chips after division.

[0064] (Other embodiments) Next, another embodiment will be described. In the above-described embodiment, as an example of the processing of the modified layer forming step S10, a configuration has been described in which processing is performed sequentially from the planned division line L on one end side toward the planned division line L on the other end side, leaving the unprocessed region 10b. On the other hand, considering that warping of the workpiece 10 is likely to occur at the end of the workpiece 10, the control unit 110 may perform processing in the processing of the modified layer forming step S10 from the planned division line L located closer to the center toward the planned division line L located on the end side.

[0065] For example, as shown in FIG. 10 , the workpiece 10 is divided into two regions in the X-axis direction by a center line CLy extending in the Y-axis direction. Similarly, the workpiece 10 is divided into two regions in the Y-axis direction by a center line CLx extending in the X-axis direction. Then, in each of the two divided regions in the X-axis direction, processing is performed from the division line Ly located near the center toward the division line Ly located at the end. Similarly, in each of the two divided regions in the Y-axis direction, processing is performed from the division line Lx located near the center toward the division line Lx located at the end. Specifically, the control unit 110 executes the device chip manufacturing method shown in the flowchart of FIG. 11 . The flowchart shown in FIG. 11 differs from the flowchart shown in FIG. 3 in that the modified layer forming step 10 includes a first modified layer forming step S11, a second modified layer forming step S12, a third modified layer forming step S13, and a fourth modified layer forming step S14. Therefore, the following mainly describes the first modified layer forming step S11, the second modified layer forming step S12, the third modified layer forming step S13, and the fourth modified layer forming step S14. The other processes are the same as those in the above-described embodiment, and therefore, the description thereof will be omitted here.

[0066] In Fig. 10, for convenience of drawing, only a few lines are drawn from each of the planned division lines Lx and Ly, which are indicated by dashed lines. Furthermore, the unprocessed region 10b is not shown in Fig. 10 and Figs. 12 to 16, which will be described later. Each step of forming the modified layer 16 will now be described in detail.

[0067] In the first modified layer forming step S11, the control unit 110 irradiates a laser beam along a first planned division line to form the modified layer 16. Here, the first planned division line may be either a planned division line Lx extending in the X-axis direction or a planned division line Ly extending in the Y-axis direction, but in this embodiment, it is the planned division line Ly.

[0068] The control unit 110 captures an image of any one of the multiple streets 12 formed in the Y-axis direction, and uses the captured image to align, in the Y-axis direction, for example, the street 12 on the workpiece 10 with the focal point of the laser beam in the laser irradiation unit 30. Then, the control unit 110 irradiates the laser beam along the planned division line Ly formed along the center of the street 12, and performs a processing process to form a modified layer 16 inside the workpiece 10.

[0069] For example, as shown in FIG. 12(a), the workpiece 10 is divided into two regions in the X-axis direction by a center line CLy in the Y-axis direction. In this state, in one region (e.g., the region on the left side of FIG. 12(a)) including the division line Ly at one end of the workpiece 10, processing is performed sequentially from the division line Ly located near the center toward the division line Ly at the one end. In FIG. 12(a), multiple arrows shown with solid lines indicate processing lines when processing is performed along the division line Ly. That is, in the first modified layer forming step S11, the control unit 110 performs processing in one region in the X-axis direction including the division line Ly at one end of the workpiece 10 in the X-axis direction, from the division line Ly located near the center toward the division line Ly at the one end.

[0070] In the second modified layer formation step S12, the control unit 110 forms a modified layer 16 inside the workpiece 10 by irradiating a laser beam along the planned division line Ly in the other of the two regions obtained by dividing the workpiece 10 in the X-axis direction.

[0071] Specifically, as shown in FIG. 12(b), in the other region including the planned division line Ly at the other end of the workpiece 10 (for example, the region on the right side of FIG. 12(b)), processing is performed sequentially from the planned division line Ly located closer to the center toward the planned division line Ly at the other end. In FIG. 12(b), the multiple arrows shown by solid lines indicate processing lines when processing along the planned division line Ly in the second modified layer forming step S12. Note that the multiple arrows shown by dashed lines indicate processing lines already processed in the first modified layer forming step S11. That is, in the second modified layer forming step S12, the control unit 110 performs processing in the other region in the X-axis direction including the planned division line Ly at the other end of the workpiece 10 in the X-axis direction, from the planned division line Ly located closer to the center toward the planned division line Ly at the other end.

[0072] In the third modified layer forming step S13, the control unit 110 forms a modified layer 16 inside the workpiece 10 by irradiating the laser beam along the second planned dividing line. Here, the second planned dividing line is the planned dividing line Lx.

[0073] The control unit 110 rotates the holding table 20 to align the streets 12 in the X-axis direction with the focal point of the laser beam, and irradiates the laser beam onto the planned division lines Lx formed along the centers of the streets 12, thereby performing a processing process to form a modified layer 16 inside the workpiece 10. Note that in the examples shown in Figure 12(c) and Figure 12(d) described below, for convenience of explanation, the workpiece 10 held on the holding table 20 is not rotated and is shown in the same orientation as in Figures 12(a) and 12(b).

[0074] For example, as shown in FIG. 12(c), the workpiece 10 is divided into two regions in the Y-axis direction by a center line CLx in the X-axis direction. In this state, in one region (e.g., the upper region in FIG. 12(c)) including the division line Lx at one end of the workpiece 10, machining is performed sequentially from the division line Lx located near the center toward the division line Lx at the one end. In FIG. 12(c), multiple arrows shown by solid lines indicate machining lines when machining along the division line Lx in the third modified layer forming step S13. Note that multiple arrows shown by dashed lines indicate machining lines already machined in the first modified layer forming step S11 and the second modified layer forming step S12. That is, in the third modified layer forming step S13, the control unit 110 performs machining in one region in the Y-axis direction including the division line Lx at one end of the workpiece 10 in the Y-axis direction, from the division line Lx located near the center toward the division line Lx at the one end.

[0075] In the fourth modified layer formation step S14, the control unit 110 forms a modified layer 16 inside the workpiece 10 by irradiating a laser beam along the planned division line Lx in the other of the two regions obtained by dividing the workpiece 10 in the Y-axis direction.

[0076] Specifically, as shown in FIG. 12(d), in the other region (e.g., the lower region in FIG. 12(d)) including the division line Lx at the other end of the workpiece 10, machining is performed sequentially from the division line Lx located closer to the center toward the division line Lx at the other end. In FIG. 12(d), the multiple arrows shown by solid lines indicate the machining lines when machining along the division line Lx in the fourth modified layer forming step S14. Note that the multiple arrows shown by dashed lines indicate the machining lines already machined in the first modified layer forming step S11, the second modified layer forming step S12, and the third modified layer forming step S13. That is, in the fourth modified layer forming step S14, the control unit 110 performs machining in the other region in the Y-axis direction including the division line Lx at the other end of the workpiece 10 in the Y-axis direction, starting from the division line Lx located closer to the center toward the division line Lx at the other end. The example shown in FIG. 12 is a second example of the machining sequence for the workpiece 10.

[0077] Thus, in this other embodiment, processing is performed from the planned division line L near the center of the workpiece 10 toward the planned division line L at one end, and similarly, processing is performed from the planned division line L near the center of the workpiece toward the planned division line L at the other end. That is, in the process of forming the modified layer 16, the end of the workpiece 10 is maintained in a suction-held state until processing is performed along each planned division line Lx and planned division line Ly located at the end. As a result, the end of the workpiece 10 is processed sequentially from the planned division line L near the center to the planned division line L at the end while being held by suction, making the workpiece 10 less likely to warp overall. That is, as is conventionally known, if processing is performed sequentially from one end of the workpiece 10 to the other, the stress balance in the workpiece 10 may be disrupted, potentially causing the end of the workpiece 10 to warp. However, by starting processing from the planned division line L located near the center as in this embodiment, such warping can be suppressed.

[0078] Furthermore, by suppressing warping of the workpiece 10, the possibility of problems occurring, such as the laser beam focal point not being able to be positioned at an appropriate position inside the workpiece 10, or the suction hold of the workpiece 10 being released, making it impossible to continue processing, can be reduced.

[0079] In another embodiment, the above-described first modified layer forming step S11, second modified layer forming step S12, third modified layer forming step S13, and fourth modified layer forming step S14 are performed. As a result, for each of the planned division line Ly extending in the Y-axis direction and the planned division line Lx extending in the X-axis direction, processing can be performed from the planned division line L located closer to the center toward the planned division line L located closer to the end, which reduces the possibility of warping of the end of the workpiece 10 in either direction, and ultimately prevents warping of the workpiece as a whole.

[0080] On the other hand, warpage at the end of the workpiece 10 may be further reduced if the order of processing along the planned dividing lines L located on the end side is relatively later than the order of processing along the planned dividing lines L located closer to the center. Therefore, the control unit 110 may process the modified layer forming step S10 as in the third example in Figures 13 and 14 or the fourth example in Figures 15 and 16.

[0081] The examples of Figures 13 and 14 are examples in which processing is performed on all planned division lines L by repeatedly performing processing to form a predetermined number of modified layers 16 along one of the planned division lines L in the X-axis direction and the Y-axis direction (for example, planned division line Ly), and then repeatedly performing processing to form a predetermined number of modified layers 16 along the other planned division line L (for example, planned division line Lx).

[0082] Specifically, as shown in FIG. 13A, in one region (e.g., the left region of FIG. 13A) including the planned dividing line Ly located at one end of the workpiece 10, the control unit 110 performs the processing in the first modified layer forming step S11 for an arbitrary number of lines set by, for example, an operator, from the planned dividing line Ly located near the center toward the planned dividing line Ly at the one end. Here, the arbitrary number refers to a number that does not reach the planned dividing line Ly at the one end of the one region. For example, in the example shown in FIG. 13, since processing is ultimately performed along eight planned dividing lines Ly in the one region, the arbitrary number is set to a number at least less than eight. This arbitrary number is determined, for example, taking into consideration warpage and deformation of the workpiece 10 caused by forming the modified layer 16. For example, the arbitrary number may be determined in advance by an experiment or the like to obtain the degree of deformation, such as warpage, of the workpiece 10 due to the formation of the modified layer 16. Furthermore, since the degree of deformation such as warpage of the workpiece 10 may differ depending on the material of the workpiece 10, any number of lines to be processed in the first modified layer forming step S11 may be determined depending on the material of the workpiece 10. In the embodiment, in the first modified layer forming step S11, as an example, processing is performed along four planned division lines Ly.

[0083] In this way, at the stage of FIG. 13(a), processing is not performed up to the planned dividing line Ly on one end side of one region, thereby suppressing warping at the end of the workpiece 10.

[0084] Next, as shown in Fig. 13(b), the control unit 110 executes processing in a second modified layer forming step S12 for an arbitrary number of lines from the intended dividing line Ly located near the center toward the intended dividing line Ly on the other end side in the other region (for example, the region on the right side of Fig. 13(b)) including the intended dividing line Ly on the other end side of the workpiece 10. Note that the arbitrary number of lines processed in the second modified layer forming step S12 may be the same as or different from that in the first modified layer forming step S11, as long as the number does not reach the intended dividing line Ly on the other end side.

[0085] Next, as shown in (c) of Figure 13, the control unit 110 again performs processing on the remaining planned dividing lines Ly in one region in the X-axis direction of the workpiece 10 using the first modified layer formation step S11, from the planned dividing line Ly located closer to the center among the remaining planned dividing lines Ly toward the planned dividing line Ly on one end side.

[0086] Next, as shown in (d) of Figure 13, the control unit 110 again performs processing on the remaining planned dividing lines Ly in the other region in the X-axis direction of the workpiece 10 using the second modified layer formation step S12, from the planned dividing line Ly located closer to the center among the remaining planned dividing lines Ly toward the planned dividing line Ly on the other end side.

[0087] 13, in each of the regions in the X-axis direction of the workpiece 10, the entire division line Ly is processed alternately in multiple iterations, starting from the central division line Ly toward the division lines Ly at one end and the other end. In the example shown in FIG. 13, the first modified layer forming step S11 and the second modified layer forming step S12 are each performed twice alternately to process the entire division line Ly. However, the number of iterations is not limited as long as it is performed multiple times. For example, as described above, the number of times the processing is performed may be determined depending on the warpage of the workpiece 10, the material of the workpiece 10, and other factors, such as the required accuracy of the warpage of the workpiece 10. The accuracy of the warpage of the workpiece 10 is assumed to be high enough to prevent the workpiece 10 from warping.

[0088] After the processing for the planned division line Ly is completed, the control unit 110 performs the same processing for the planned division line Lx.

[0089] Specifically, as shown in Fig. 14(e), the control unit 110 executes the processing by the third modified layer forming step S13 for an arbitrary number of lines in one region (for example, the upper region in Fig. 14(e)) including the planned dividing line Lx at one end of the workpiece 10, from the planned dividing line Lx located near the center toward the planned dividing line Lx at one end. Here, the arbitrary number may be any number that does not reach the planned dividing line Lx at one end of one region, as described above.

[0090] In this way, at the stage of (e) of FIG. 14, processing is not performed up to the planned dividing line Lx on one end side of one region, thereby suppressing warping at the end of the workpiece 10.

[0091] Next, as shown in Fig. 14(f), the control unit 110 executes processing in a fourth modified layer forming step S14 for an arbitrary number of lines from the planned dividing line Lx located closer to the center toward the planned dividing line Lx on the other end side in the other region (for example, the lower region in Fig. 14(f)) including the planned dividing line Lx on the other end side of the workpiece 10. Note that the arbitrary number of lines to be processed in the fourth modified layer forming step S14 may be any number as long as it does not reach the planned dividing line Lx on the other end side.

[0092] Next, as shown in (g) of Figure 14, the control unit 110 again performs processing on the remaining planned dividing lines Lx in one region in the Y-axis direction of the workpiece 10 using the third modified layer formation step S13, from the planned dividing lines Lx located closer to the center among the remaining planned dividing lines Lx toward the planned dividing lines Lx on one end side.

[0093] Next, as shown in (h) of Figure 14, the control unit 110 again performs processing of the remaining planned dividing lines Lx in the other region in the Y-axis direction of the workpiece 10 using the fourth modified layer formation step S14, from the planned dividing line Lx located closer to the center among the remaining planned dividing lines Lx toward the planned dividing line Lx on the other end side.

[0094] 14, all of the planned division lines Lx are processed alternately in multiple steps in each of one region and the other region in the Y-axis direction of the workpiece 10, from the planned division line Lx located near the center toward the planned division lines Lx on one end side and the other end side. Note that in the example shown in Fig. 14, the third modified layer forming step S13 and the fourth modified layer forming step S14 are each performed alternately twice to process all of the planned division lines Lx, but as with the processing of the planned division line Ly, the number of times is not limited as long as it is multiple times.

[0095] 13 and 14, the first modified layer forming step S11 and the second modified layer forming step S12 are repeatedly performed along the planned division line Ly for a predetermined number of lines, thereby processing all of the planned division line Ly, and the third modified layer forming step S13 and the fourth modified layer forming step S14 are repeatedly performed along the planned division line Lx for a predetermined number of lines, thereby processing all of the planned division line Lx. This allows the end of the workpiece 10 to remain unprocessed for a longer period of time, compared to, for example, processing all of a region in one direction without processing a predetermined number of lines at a time, and then processing other regions sequentially using a similar method, thereby further reducing the possibility of warping of the workpiece 10.

[0096] On the other hand, in the examples shown in Figures 13 and 14, processing was performed on all planned division lines Lx after processing on all planned division lines Ly was completed, but for example, processing on planned division lines Lx may be started before processing on all planned division lines Ly is completed.

[0097] 15 and 16 are diagrams (fourth example) for explaining one example of the processing. In the example shown in Fig. 15, the control unit 110 sequentially performs a first modified layer forming step S11 in Fig. 15(a), a second modified layer forming step S12 in Fig. 15(b), a third modified layer forming step S13 in Fig. 15(c), and a fourth modified layer forming step S14 in Fig. 15(d), as shown in Fig. 15(a) to Fig. 15(d). Then, the same processing is repeated again, sequentially, as shown in Fig. 16(e) to Fig. 16(h), as shown in Fig. 16(e) to Fig. 16(h).

[0098] That is, the control unit 110 performs the first modified layer forming step S11 and the second modified layer forming step S12 for a predetermined number of lines along the planned division line Ly, and then performs the third modified layer forming step S13 and the fourth modified layer forming step S14 for a predetermined number of lines along the planned division line Lx. The first modified layer forming step S11 and the second modified layer forming step S12 along the planned division line Ly, and the third modified layer forming step S13 and the fourth modified layer forming step S14 along the planned division line Lx are repeatedly performed, thereby processing all of the planned division lines Ly and all of the planned division lines Lx. The specific processes of the first modified layer forming step S11, the second modified layer forming step S12, the third modified layer forming step S13, and the fourth modified layer forming step S14 are as described above, and therefore will not be described here.

[0099] As described with reference to Figures 15 and 16, after the first modified layer forming step S11 and the second modified layer forming step S12 are performed for a predetermined number of lines along the division line Ly, the third modified layer forming step S13 and the fourth modified layer forming step S14 are performed for a predetermined number of lines along the division line Lx. The first modified layer forming step S11 and the second modified layer forming step S12 along the division line Ly and the third modified layer forming step S13 and the fourth modified layer forming step S14 along the division line Lx are then repeatedly performed, thereby processing all of the division lines Ly and all of the division lines Lx. This repeatedly processes a predetermined number of lines in both the X-axis and Y-axis directions from the division line L located closer to the center toward the division line L located closer to the end. This means that the processing gradually progresses toward the end in both the X-axis and Y-axis directions, further reducing the possibility of warping of the workpiece 10.

[0100] Although the embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such embodiments. It is clear that a person skilled in the art can conceive of various modifications and alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components of the above-described embodiments may be combined in any manner without departing from the spirit of the invention.

[0101] For example, in the above embodiment, the region at the end of the workpiece 10 where the devices 13 are not formed is described as the unmachined region 10b, but this unmachined region 10b does not have to be provided in all regions where the devices 13 are not formed. That is, even regions where the devices 13 are not formed may be machined to a predetermined extent. Furthermore, for example, the unmachined region 10b may be set in the street 12 in the region where the devices 13 are formed, near the end or outer periphery of the workpiece 10. In other words, the unmachined region 10b may be provided in any appropriate location as long as it can reduce the possibility of the workpiece 10 warping.

[0102] In the above-described embodiment, the division line Ly extending in the Y-axis direction is processed first, followed by the division line Lx extending in the X-axis direction, but the order may be reversed. That is, the division line Lx may be processed first, followed by the division line Ly.

[0103] Furthermore, the processing order in the modified layer forming step S10 may be changed as appropriate as long as the processing can be performed from the planned division line L located closer to the center toward the planned division line L located at the end. For example, in addition to the above example, the processing may be performed alternately on the planned division line Ly extending in the Y-axis direction and the planned division line Lx extending in the X-axis direction by repeatedly performing the processing in the order of the first modified layer forming step S11, the third modified layer forming step S13, the second modified layer forming step S12, and the fourth modified layer forming step S14.

[0104] In the above embodiment, the reference for dividing the X-axis into two regions is the center line CLy in the Y-axis direction, but the reference is not limited to the center line CLy and may be a central region having a predetermined width. Similarly, the reference for dividing the Y-axis into two regions is the center line CLx in the X-axis direction, but the reference is not limited to the center line CLx and may be a central region having a predetermined width.

[0105] Furthermore, the unprocessed region 10b is not limited to a ring shape, but may be rectangular or the like.

[0106] The manufacturing method described in the above-described embodiment can be realized by executing a prepared control program on a computer. The control program is recorded on a computer-readable storage medium and executed by being read from the storage medium. The control program may be provided in a form stored on a non-transitory storage medium such as a flash memory, or may be provided via a network such as the Internet. The computer that executes the control program may be included in a processing device, or may be included in an electronic device such as a smartphone, tablet, or personal computer that can communicate with the processing device, or may be included in a server device that can communicate with these processing devices and electronic devices.

[0107] This specification describes at least the following items. Note that the components in parentheses correspond to those in the above-described embodiment, but are not limited to these.

[0108] (1) A method for manufacturing device chips, comprising: dividing a workpiece (workpiece 10) having a plurality of devices (devices 13) formed in an area defined by a plurality of intersecting planned division lines (planned division lines L) along the planned division lines to manufacture device chips; A modified layer forming step (modified layer forming step S10) of forming a modified layer (modified layer 16) inside the workpiece by irradiating a laser beam having a wavelength that transmits the workpiece along the planned dividing line; a dividing step (dividing step S40) of dividing the workpiece along the planned dividing lines by applying an external force to the workpiece after the modified layer forming step is performed, The modified layer forming step includes: The modified layer is formed by irradiating the laser beam along the planned dividing line, leaving an area in which the device is not formed within a predetermined range from the outer periphery of the workpiece as an unprocessed area (unprocessed area 10b). A method for manufacturing a device chip.

[0109] According to (1), for example, the unprocessed area is not processed, so the suction holding state of the end of the workpiece included in the unprocessed area can be maintained, and as a result, the possibility of the workpiece warping can be reduced.

[0110] (2) A method for manufacturing the device chip according to (1), the planned division lines include a first planned division line (planned division line Ly) extending in a first direction (Y-axis direction) and a second planned division line (planned division line Lx) extending in a second direction (X-axis direction) intersecting the first direction, The shape of the boundary portion (boundary portion 10d) which is the boundary between the unprocessed region and the processed region (processed region 10c) in which the device is formed is a ring shape which is deformed so that the length in the first direction and the length in the second direction are different with respect to a virtual circle centered on the center (center P) of the workpiece. A method for manufacturing a device chip.

[0111] According to (2), the shape of the boundary portion is a ring shape (e.g., an ellipse) that is deformed so that the length in the first direction is different from the length in the second direction, and this may enable the size of the unprocessed area to be reduced compared to when the shape of the boundary portion is a circular ring. If the size of the unprocessed area can be reduced, it becomes easier to divide the workpiece and it becomes possible to manufacture more device chips.

[0112] (3) A method for manufacturing the device chip according to (2), At least one of the length in the first direction and the length in the second direction is approximately equal to the diameter of the workpiece. A method for manufacturing a device chip.

[0113] According to (3), by making at least one of the lengths of the boundary in one direction and the length in the second direction substantially equal to the diameter of the workpiece, the size of the unprocessed area can be reduced compared to when the length is shorter than the diameter of the workpiece in both directions. If the size of the unprocessed area can be reduced, it becomes easier to divide the workpiece and it becomes possible to manufacture more device chips.

[0114] (4) A method for manufacturing a device chip according to (2) or (3), The first division line has a larger number of processed lines than the second division line, The boundary portion has a ring shape whose length in the first direction is longer than its length in the second direction. A method for manufacturing a device chip.

[0115] According to (4), the shape of the boundary portion is a ring shape (such as an ellipse) whose length in the first direction is longer than its length in the second direction, which may, for example, make it possible to reduce the unprocessed area.

[0116] (5) A method for manufacturing a device chip according to (2) or (3), The first division line has a larger number of processed lines than the second division line, The boundary portion has a ring shape whose length in the second direction is longer than its length in the first direction. A method for manufacturing a device chip.

[0117] According to (5), the shape of the boundary portion is a ring shape (such as an ellipse) whose length in the second direction is longer than its length in the first direction, which may, for example, make it possible to reduce the unprocessed area.

[0118] (6) A method for manufacturing a device chip according to (2) or (3), The method further includes, before the dividing step, forming the modified layer at the boundary portion, an annular modified layer forming step (annular modified layer forming step S20). A method for manufacturing a device chip.

[0119] According to (6), for example, in the process of dividing a workpiece into device chips, division can be assisted starting from the annular modified layer.

[0120] (7) A method for manufacturing a device chip according to (1) or (2), Before the dividing step, further includes an auxiliary modified layer forming step (auxiliary modified layer forming step S30) of forming a predetermined modified layer in the unprocessed region; A method for manufacturing a device chip.

[0121] According to (7), for example, in the process of dividing a workpiece into device chips, it is possible to assist division starting from a predetermined modified layer formed in an unprocessed region.

[0122] (8) A method for manufacturing the device chip according to (7), The predetermined modified layer is A modified layer formed radially relative to the unprocessed region. A method for manufacturing a device chip.

[0123] According to (8), for example, in the process of dividing a workpiece into device chips, it is possible to assist division starting from the radial modified layer formed in the unprocessed region.

[0124] (9) A method for manufacturing the device chip according to (1), the planned division lines include a first planned division line (planned division line Ly) extending in a first direction (Y-axis direction) and a second planned division line (planned division line Lx) extending in a second direction (X-axis direction) intersecting the first direction, The unprocessed regions located at both end sides in the first direction have different areas from the unprocessed regions located at both end sides in the second direction. A method for manufacturing a device chip.

[0125] According to (9), by making the unprocessed areas located at both ends in the first direction different from the unprocessed areas located at both ends in the second direction, it is possible to reduce the size of the unprocessed areas compared to, for example, when the unprocessed areas located at both ends in the first direction and the unprocessed areas located at both ends in the second direction are the same. If the size of the unprocessed areas can be reduced, it becomes easier to divide the workpiece and it becomes possible to manufacture more device chips.

[0126] (10) A method for manufacturing the device chip according to (1), The modified layer forming step includes: A first modified layer forming step (first modified layer forming step S11) in which processing is performed from the planned dividing line located near the center toward the planned dividing line on one end side of the workpiece in one region including the planned dividing line on one end side; A second modified layer forming step (second modified layer forming step S12) in which processing is performed from the planned dividing line located near the center toward the planned dividing line on the other end side of the workpiece in the other region including the planned dividing line on the other end side, A method for manufacturing a device chip.

[0127] According to (10), for example, the end of the workpiece is held by suction and processed sequentially from the planned dividing line closest to the center to the planned dividing line closest to the end, which reduces the overall warpage of the workpiece. As is conventionally known, processing a workpiece sequentially from one end to the other can disrupt the stress balance in the workpiece, potentially causing the end of the workpiece to warp. However, by starting processing from the planned dividing line closest to the center, this warpage can be prevented. Furthermore, by preventing warpage of the workpiece, it is possible to reduce the likelihood of problems, such as the laser beam not being focused properly within the workpiece or the workpiece being released from suction, making it impossible to continue processing.

[0128] (11) A method for manufacturing the device chip according to (10), the planned division lines include a first planned division line (planned division line Ly) extending in a first direction (Y-axis direction) and a second planned division line (planned division line Lx) extending in a second direction (X-axis direction) intersecting the first direction, The modified layer forming step includes: the first modified layer forming step of processing the workpiece in one region in the second direction, including the first planned division line on one end side in the second direction, from the first planned division line located near the center toward the first planned division line on the one end side; the second modified layer forming step of processing the workpiece in another region in the second direction, including the first planned dividing line on the other end side in the second direction, from the first planned dividing line located closer to the center toward the first planned dividing line on the other end side; A third modified layer forming step (third modified layer forming step S13) of processing the workpiece in one region in the first direction including the second planned division line at one end side in the first direction from the second planned division line located near the center toward the second planned division line at the one end side; a fourth modified layer forming step (fourth modified layer forming step S14) of processing the workpiece in the other region in the first direction including the second planned division line on the other end side in the first direction from the second planned division line located near the center toward the second planned division line on the other end side, A method for manufacturing a device chip.

[0129] According to (11), for example, for each of the dividing lines extending in the first direction and the dividing lines extending in the second direction, it is possible to process from the dividing line located closer to the center to the dividing line located closer to the end, and in either direction, it is possible to reduce the possibility of the end of the workpiece warping, and ultimately to suppress warping of the entire workpiece.

[0130] (12) A method for manufacturing the device chip according to (11), The modified layer forming step includes: The first modified layer forming step and the second modified layer forming step are repeatedly performed along the first planned division line by a predetermined number of lines, and after processing all of the first planned division line, the third modified layer forming step and the fourth modified layer forming step are repeatedly performed along the second planned division line by a predetermined number of lines, thereby processing all of the second planned division line; A method for manufacturing a device chip.

[0131] According to (12), for example, compared to when processing a specific number of pieces at a time, and then processing all of the areas in one direction, and then processing other areas sequentially using the same method, the end of the workpiece can be kept unprocessed for a longer period of time, thereby further reducing the possibility of the workpiece warping.

[0132] (13) A method for manufacturing the device chip according to (11), The modified layer forming step includes: After performing the first modified layer forming step and the second modified layer forming step for a predetermined number of lines along the first planned division line, The third modified layer forming step and the fourth modified layer forming step are performed along the second planned division line for a predetermined number of lines, By repeatedly performing the first modified layer forming step and the second modified layer forming step along the first planned division line, and the third modified layer forming step and the fourth modified layer forming step along the second planned division line, all of the first planned division lines and all of the second planned division lines are processed. A method for manufacturing a device chip.

[0133] According to (13), for example, by repeatedly processing a predetermined number of lines in both the first and second directions from the planned dividing line located near the center toward the planned dividing line located toward the end, the processing gradually moves toward the end in both the first and second directions, thereby further reducing the possibility of the workpiece warping.

[0134] (14) A method for manufacturing a device chip according to (1) or (2), The dividing step comprises: a grinding step (grinding step S41) of grinding the workpiece to thin the workpiece and dividing the workpiece into individual device chips starting from the modified layer formed inside the planned dividing line; A method for manufacturing a device chip.

[0135] According to (14), for example, by grinding and thinning the workpiece in the grinding step, the workpiece can be made easier to chip, and by removing all of the modified layer of the thinned workpiece, defects such as cracking of the device chip after chipping can be suppressed. [Explanation of symbols]

[0136] 10 Workpiece 10b Raw area 10c processing area 10d Boundary 13 devices 16 Modified layer L planned division line Ly planned division line (first planned division line) Lx planned division line (second planned division line) P center S10 Modified layer formation step S11 First modified layer formation step S12 Second modified layer formation step S13 Third modified layer formation step S14 Fourth modified layer forming step S20 Annular modified layer formation step S30 Auxiliary modified layer formation step S40 Split Step S41 Grinding Step

Claims

1. A method of manufacturing device chips, comprising: dividing a workpiece, in which a plurality of devices are formed in an area defined by a plurality of intersecting planned dividing lines, along the planned dividing lines to manufacture device chips, a modified layer forming step of forming a modified layer inside the workpiece by irradiating the workpiece with a laser beam having a wavelength that can transmit along the planned dividing line; a dividing step of dividing the workpiece along the planned dividing lines by applying an external force to the workpiece after the modified layer forming step is performed, The modified layer forming step includes: leaving an area within a predetermined range from the outer periphery of the workpiece where the device is not formed as an unprocessed area, and irradiating the laser beam along the planned dividing line to form the modified layer. A method for manufacturing a device chip.

2. 2. A method for manufacturing a device chip according to claim 1, comprising: the predetermined division lines include a first predetermined division line extending in a first direction and a second predetermined division line extending in a second direction intersecting the first direction, a boundary portion between the unprocessed region and the processed region in which the device is formed has a ring shape that is deformed with respect to a virtual circle having a center at the center of the workpiece such that a length in the first direction and a length in the second direction are different from each other; A method for manufacturing a device chip.

3. 3. A method for manufacturing a device chip according to claim 2, comprising: At least one of the length in the first direction and the length in the second direction is approximately equal to the diameter of the workpiece. A method for manufacturing a device chip.

4. 4. A method for manufacturing a device chip according to claim 2 or 3, The first division line has a larger number of processed lines than the second division line, The boundary portion has a ring shape whose length in the first direction is longer than its length in the second direction. A method for manufacturing a device chip.

5. 4. A method for manufacturing a device chip according to claim 2 or 3, The first division line has a larger number of processed lines than the second division line, The boundary portion has a ring shape whose length in the second direction is longer than its length in the first direction. A method for manufacturing a device chip.

6. 4. A method for manufacturing a device chip according to claim 2 or 3, The method further includes, before the dividing step, forming the modified layer at the boundary portion. A method for manufacturing a device chip.

7. 3. A method for manufacturing the device chip according to claim 1 or 2, The method further includes, before the dividing step, forming an auxiliary modified layer in the unprocessed region. A method for manufacturing a device chip.

8. 8. A method for manufacturing a device chip according to claim 7, comprising: The predetermined modified layer is A modified layer formed radially relative to the unprocessed region. A method for manufacturing a device chip.

9. 2. A method for manufacturing a device chip according to claim 1, comprising: the predetermined division lines include a first predetermined division line extending in a first direction and a second predetermined division line extending in a second direction intersecting the first direction, The unprocessed regions located at both end sides in the first direction have different areas from the unprocessed regions located at both end sides in the second direction. A method for manufacturing a device chip.

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