Processing method of wafer

Abstract

To provide a processing method of a wafer, capable of reducing a damage generated by formation of a modified layer.SOLUTION: A processing method of a wafer, comprises: a modified-layer formation step 102 of irradiating a first laser beam along a division--planned line from a front surface of the wafer to form a division starting point including a modified layer inside the wafer, and a cracking extending from the modified layer; a support sheet fixing step 101 of, prior to the modified-layer formation step 102, fixing a support sheet to a back surface of the wafer; a chip interval expansion step 103 of expanding the support sheet to expand an interval of chips divided along the division starting point; and a repair step 104 of, after the chip interval expansion step 103, irradiating a second layer beam to a side surface of each chip, so as to repair at least a part of the modified layer generated by the modified layer formation step 102.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a wafer processing method. [Background technology]

[0002] There is a processing method in which a wafer is divided into a plurality of chips starting from a modified layer formed inside the wafer (see, for example, 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] However, the processing method described in Patent Document 1 has a problem in that if damage caused by the modified layer remains on the side surface of the chip, the strength of the chip decreases.

[0005] An object of the present invention is to provide a wafer processing method capable of reducing damage caused by the formation of a modified layer. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the wafer processing method of the present invention is a wafer processing method for manufacturing a plurality of chips by dividing a wafer having a plurality of planned dividing lines formed thereon along the planned dividing lines, and is characterized by comprising a modified layer forming step of irradiating a first laser beam along the planned dividing lines from one side of the wafer to form a dividing starting point including a modified layer inside the wafer and a crack extending from the modified layer, a support sheet fixing step of fixing a support sheet to either side of the wafer before or after the modified layer forming step, a chip spacing expanding step of expanding the support sheet to increase the spacing between chips divided along the dividing starting points, and a repair step of irradiating a side of the chip with a second laser beam after the chip spacing expanding step to melt the chip, and repairing at least a portion of the damage caused by the modified layer forming step.

[0007] In the wafer processing method, the repairing step may include melting at least the region where the modified layer is formed.

[0008] In the wafer processing method, the wavelength of the second laser beam used in the repair step may be in the range of 500 nm or more and less than 1100 nm. Effect of the Invention

[0009] The present invention has an effect of reducing damage caused by the formation of a modified layer. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view that illustrates a wafer to be processed by the wafer processing method according to the first embodiment. [Diagram 2] FIG. 2 is a flowchart showing the flow of the wafer processing method according to the first embodiment. [Diagram 3] FIG. 3 is a perspective view that illustrates the wafer after the support sheet fixing step of the wafer processing method illustrated in FIG. [Figure 4]FIG. 4 is a perspective view that illustrates a schematic configuration example of a laser processing apparatus that performs the modified layer forming step of the wafer processing method shown in FIG. [Diagram 5] FIG. 5 is a cross-sectional view that illustrates a modified layer forming step in the wafer processing method illustrated in FIG. [Figure 6] FIG. 6 is a cross-sectional view that illustrates a chip spacing expansion step in the wafer processing method illustrated in FIG. [Figure 7] FIG. 7 is a cross-sectional view that illustrates a repair step of the wafer processing method illustrated in FIG. [Figure 8] FIG. 8 is a cross-sectional view that illustrates a schematic view of a main part of a wafer after a repair step in the wafer processing method illustrated in FIG. [Figure 9] FIG. 9 is a side view, partially in section, typically showing a second laser processing apparatus used in a repair step of a wafer processing method according to a modified example of the first embodiment. [Figure 10] FIG. 10 is a plan view diagrammatically showing a main part of the second laser processing apparatus shown in FIG. [Figure 11] FIG. 11 is a cross-sectional view illustrating a typical repair step of a wafer processing method according to a modified example of the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The form (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiment. Furthermore, the components described below include those that a person skilled in the art can easily imagine and those that are substantially the same. Furthermore, the configurations described below can be appropriately combined. Furthermore, various omissions, substitutions, or modifications of the configurations can be made without departing from the gist of the present invention.

[0012] [Embodiment 1] The wafer processing method according to the first embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a perspective view showing a wafer to be processed by the wafer processing method according to the first embodiment. Fig. 2 is a flow chart showing the flow of the wafer processing method according to the first embodiment.

[0013] (Wafer) The wafer processing method according to the embodiment is a method for processing a wafer 1 shown in Fig. 1. The wafer 1 to be processed by the wafer processing method according to the embodiment is a disk-shaped semiconductor wafer, an optical device wafer, or the like, with a substrate 2 made of silicon (Si), gallium arsenide (GaAs), silicon carbide (SiC), sapphire, or the like.

[0014] The wafer 1 has devices 5 formed in each of the regions defined by a plurality of planned division lines 4 on the surface 3. The devices 5 are, for example, integrated circuits such as ICs (Integrated Circuits) or LSIs (Large Scale Integration), image sensors such as CCDs (Charge Coupled Devices) or CMOSs ​​(Complementary Metal Oxide Semiconductors), optical elements such as LEDs (Light-Emitting Diodes), MEMS (Micro Electro Mechanical Systems), or semiconductor memories (semiconductor storage devices).

[0015] The wafer 1 is divided into individual chips 10 along the planned division lines 4. Each chip 10 includes a part of the substrate 2 and a device 5.

[0016] (Wafer processing method) The wafer processing method according to the first embodiment is a method of manufacturing a plurality of chips 10 by dividing a wafer 1, on which a plurality of planned division lines 4 are formed, along the planned division lines 4. As shown in Fig. 2, the wafer processing method according to the first embodiment includes a support sheet fixing step 101, a modified layer forming step 102, a chip spacing expanding step 103, and a repairing step 104.

[0017] (Support sheet fixing step) Fig. 3 is a perspective view showing a wafer after a support sheet fixing step of the wafer processing method shown in Fig. 2. The support sheet fixing step 101 is a step of fixing a support sheet 11 to either the front surface 3 or the back surface 6 behind the front surface 3 of the wafer 1 before or after the modified layer forming step 102.

[0018] In the first embodiment, in the support sheet fixing step 101, as shown in Fig. 3, the center of the support sheet 11, which is a disk-shaped support sheet with a diameter larger than the outer diameter of the wafer 1 and has an annular frame 12 attached to its outer edge, is attached to the back surface 6 of the wafer 1, thereby supporting the wafer 1 within the opening of the annular frame 12. The support sheet 11 may be an adhesive tape having a base material made of a non-adhesive and flexible resin and a glue layer made of an adhesive and flexible resin laminated on the base material, in which the glue layer is attached to the annular frame 12 and the wafer 1, or may be a so-called glueless tape made of only a base material made of a non-adhesive thermoplastic resin and heat-pressed to the annular frame 12 and the wafer 1.

[0019] (Modified layer formation step) Fig. 4 is a perspective view showing a schematic configuration example of a laser processing device for performing the modified layer forming step of the wafer processing method shown in Fig. 2. Fig. 5 is a cross-sectional view showing the modified layer forming step of the wafer processing method shown in Fig. 2. The modified layer forming step 102 is a step of irradiating a first laser beam 41 along a planned division line 4 from a front surface 3, which is one surface of the wafer 1, to form a modified layer 7 (shown in Fig. 5) inside the wafer 1 and a division starting point 9 (shown in Fig. 5) including a crack 8 (shown in Fig. 5) extending from the modified layer 7.

[0020] The modified layer 7 means a region in which the density, refractive index, mechanical strength, and other physical properties are different from those of the surrounding area, and examples of such regions include a melting process region, a crack region, a dielectric breakdown region, a refractive index change region, and a region in which these regions are mixed, etc. The mechanical strength of the division starting point 9 is lower than that of other parts of the substrate 2.

[0021] The modified layer forming step 102 of the wafer processing method according to the first embodiment is performed by a laser processing apparatus 20 shown in Fig. 4. The laser processing apparatus 20 shown in Fig. 4 is a processing apparatus that performs laser processing on the wafer 1 by setting a focal point 411 of a pulsed first laser beam 41 (shown in Fig. 5) having a wavelength that is transparent to the substrate 2 constituting the wafer 1 inside the substrate 2 and irradiating the first laser beam 41 from the front surface 3 of the wafer 1 along the intended dividing lines 4. As shown in Fig. 4, the laser processing apparatus 20 has a holding table 30 that holds the wafer 1, a laser beam application unit 40, a moving unit 50, an imaging unit 43, and a control unit 45.

[0022] The holding table 30 holds the wafer 1 on a holding surface 31 parallel to the horizontal direction. The holding surface 31 is disk-shaped and made of porous ceramics or the like, and is connected to a vacuum suction source (not shown) via a suction path (not shown). The holding table 30 suction-holds the wafer 1 placed on the holding surface 31 by being sucked by the vacuum suction source. A plurality of clamps 32 are arranged around the holding table 30 to clamp the annular frame 12 that supports the wafer 1 in the opening.

[0023] The holding table 30 is rotated by the rotary movement unit 53 of the moving unit 50 about an axis parallel to the Z-axis direction which is perpendicular to the holding surface 31 and parallel to the vertical direction. The holding table 30 is moved together with the rotary movement unit 53 in the X-axis direction (corresponding to the processing proceeding direction) parallel to the horizontal direction by the X-axis movement unit 51 of the moving unit 50, and is moved in the Y-axis direction which is parallel to the horizontal direction and perpendicular to the X-axis direction by the Y-axis movement unit 52. The holding table 30 is moved by the moving unit 50 between the processing region below the laser beam application unit 40 and a carry-in / out region away from below the laser beam application unit 40 where the wafer 1 is carried in and out.

[0024] The moving unit 50 relatively moves the holding table 30 and the focal point 411 of the first laser beam 41 irradiated by the laser beam application unit 40 in the X-axis direction, the Y-axis direction, the Z-axis direction, and around an axis parallel to the Z-axis direction. The X-axis direction and the Y-axis direction are perpendicular to each other and parallel to the holding surface 31 (i.e., the horizontal direction). The Z-axis direction is perpendicular to both the X-axis direction and the Y-axis direction.

[0025] The moving unit 50 includes an X-axis moving unit 51 which is a processing feed unit that moves the holding table 30 in the X-axis direction, a Y-axis moving unit 52 which is an indexing feed unit that moves the holding table 30 in the Y-axis direction, a rotational moving unit 53 which rotates the holding table 30 around an axis parallel to the Z-axis direction, and a Z-axis moving unit 54 which moves the focal point 411 of the first laser beam 41 of the laser beam application unit 40 in the Z-axis direction.

[0026] The Y-axis moving unit 52 is an indexing feed unit that relatively moves the holding table 30 and the focal point 411 of the first laser beam 41 of the laser beam application unit 40 in the Y-axis direction. In the first embodiment, the Y-axis moving unit 52 is installed on the apparatus body 21 of the laser processing apparatus 20. The Y-axis moving unit 52 supports the moving plate 24 that supports the X-axis moving unit 51 so as to be freely movable in the Y-axis direction.

[0027] The X-axis moving unit 51 is a processing feed unit that relatively moves the holding table 30 and the focal point 211 of the first laser beam 41 of the laser beam application unit 40 in the X-axis direction. The X-axis moving unit 51 is installed on the moving plate 24. The X-axis moving unit 51 supports the second moving plate 25, which supports the rotational moving unit 53 that rotates the holding table 30 around an axis parallel to the Z-axis direction, so as to be movable in the X-axis direction. The second moving plate 25 supports the rotational moving unit 53 and the holding table 30. The rotational moving unit 53 supports the holding table 30.

[0028] The Z-axis moving unit 54 is a feed unit that relatively moves the holding table 30 and the focal point 211 of the first laser beam 41 of the laser beam application unit 40 in the Z-axis direction. The Z-axis moving unit 54 is installed on an erect wall 22 erected from the apparatus body 21. The Z-axis moving unit 54 supports a support column 23 having a part including a condenser lens etc. of the laser beam application unit 40, which will be described later, at its tip, so as to be movable in the Z-axis direction.

[0029] The X-axis moving unit 51 includes a known ball screw that is rotatable about its axis and moves the second moving plate 25 in the X-axis direction when rotated about its axis, a known pulse motor that rotates the ball screw about its axis, and a known guide rail that supports the second moving plate 25 movably in the X-axis direction. The Y-axis moving unit 52 includes a known ball screw that is rotatable about its axis and moves the moving plate 24 in the Y-axis direction when rotated about its axis, a known pulse motor that rotates the ball screw about its axis, and a known guide rail that supports the moving plate 24 movably in the Y-axis direction. The Z-axis moving unit 54 includes a known ball screw that is rotatable about its axis and moves the support column 23 in the Z-axis direction when rotated about its axis, a known pulse motor that rotates the ball screw about its axis, and a known guide rail that supports the support column 23 movably in the Z-axis direction. The rotation moving unit 53 includes a motor that rotates the holding table 30 about its axis, etc.

[0030] The laser processing apparatus 20 also includes an X-axis position detection unit (not shown) for detecting the position of the holding table 30 in the X-axis direction, a Y-axis position detection unit (not shown) for detecting the position of the holding table 30 in the Y-axis direction, and a Z-axis position detection unit (not shown) for detecting the position of the focusing lens of the laser beam application unit 40 in the Z-axis direction. Each position detection unit outputs the detection result to the control unit 45. In the first embodiment, the position of the holding table 30 of the laser processing apparatus 20 in the X-axis direction, the Y-axis direction, and the position of the focusing lens of the laser beam application unit 40 in the Z-axis direction are determined by the distances in the X-axis direction, the Y-axis direction, and the Z-axis direction from a predetermined reference position (not shown), etc.

[0031] The laser beam application unit 40 is a laser beam application means for condensing a pulsed first laser beam 41 with a condenser lens and applying it to the wafer 1 held on the holding surface 31 of the holding table 30. In the first embodiment, a part of the laser beam application unit 40 is disposed at the tip of a support column 23 supported by a Z-axis moving unit 54 installed on an erect wall 22 erected from the apparatus body 21, as shown in FIG.

[0032] The laser beam application unit 40 irradiates the wafer 1 held on the holding table 30 with a first laser beam 41 having a wavelength through which the substrate 2 of the wafer 1 is transparent, thereby performing laser processing on the wafer 1. In the first embodiment, the wavelength of the first laser beam 41 is in the infrared region (e.g., 1064 nm).

[0033] The imaging unit 43 captures an image of the wafer 1 held on the holding table 30. The imaging unit 43 includes an imaging element such as a CCD (Charge Coupled Device) imaging element or a CMOS (Complementary MOS) imaging element that captures an image of an object facing the objective lens in the Z-axis direction. In the first embodiment, the imaging unit 43 is disposed at the tip of the support column 23 as shown in FIG. 1, and the objective lens is disposed at a position aligned with the condenser lens of the laser beam application unit 40 along the X-axis direction.

[0034] The imaging unit 43 acquires an image captured by the imaging element, and outputs the acquired image to the control unit 45. The imaging unit 43 also acquires an image of the wafer 1 held on the holding surface 31 of the holding table 30, and acquires an image for performing alignment between the wafer 1 and the laser beam application unit 40.

[0035] The control unit 45 controls each of the above-mentioned components of the laser processing apparatus 20, and causes the laser processing apparatus 20 to perform processing operations on the wafer 1. The control unit 45 is a computer having an arithmetic processing device having a microprocessor such as a CPU (central processing unit), a storage device having a memory such as a ROM (read only memory) or a RAM (random access memory), and an input / output interface device. The arithmetic processing device of the control unit 45 performs arithmetic processing according to a computer program stored in the storage device, and outputs control signals for controlling the laser processing apparatus 20 to the above-mentioned components of the laser processing apparatus 20 via the input / output interface device, thereby realizing the functions of the control unit 45.

[0036] The laser processing device 20 also includes a display unit, which is a display means configured with a liquid crystal display device or the like for displaying the status of the processing operation, images, etc., and an input unit, which is an input means used when an operator inputs processing conditions, etc. The display unit and the input unit are connected to the control unit. In the first embodiment, the input unit is configured with a touch panel provided on the display unit.

[0037] In the first embodiment, in the modified layer forming step 102, the control unit 45 of the laser processing device 20 receives and registers the processing conditions and the like input by the operator, and the wafer 1 is placed on the holding surface 31 of the holding table 30 positioned in the carry-in / out area. In the first embodiment, in the modified layer forming step 102, when the control unit 45 of the laser processing device 20 receives an instruction to start the processing operation from the operator, the wafer 1 is sucked and held on the holding surface 31 of the holding table 30 via the support sheet 11, and the annular frame 12 is clamped by the clamping portion 32.

[0038] In the first embodiment, in the modified layer forming step 102, the control unit 45 of the laser processing device 20 controls the moving unit 50 to move the holding table 30 to the processing area, and the imaging unit 43 captures an image of the wafer 1 held on the holding table 30 to perform alignment. In the first embodiment, in the modified layer forming step, the laser processing device 20 sets the focal point 411 of the first laser beam 41 inside the substrate 2 based on the processing conditions, and irradiates the planned dividing lines 4 of the wafer 1 with the pulsed first laser beam 41 from the front surface 3 side of the substrate 2 while moving the holding table 30 and the laser beam application unit 40 relatively along the planned dividing lines 4 by the moving unit 50, as shown in FIG. 5, to form the modified layer 7 and the cracks 8 extending from the modified layer 7 inside the substrate 2 of the wafer 1, and form the dividing starting points 9 along all the planned dividing lines 4 inside the wafer 1.

[0039] (Tip Spacing Expansion Step) Fig. 6 is a cross-sectional view that typically shows a chip spacing expanding step in the processing method of the wafer shown in Fig. 2. The chip spacing expanding step 103 is a step in which the support sheet 11 is expanded to widen the spacing between the chips 10 that are to be divided along the division starting points 9.

[0040] In the first embodiment, in the chip spacing expansion step 103, the second laser processing device 60 clamps and holds the annular frame 12 supporting the wafer 1 on the inside and the outer edge of the support sheet 11 in the frame clamping portion 61. In the first embodiment, in the chip spacing expansion step 103, the second laser processing device 60 relatively moves the annular frame 12 and the wafer 1 along a direction intersecting (orthogonal in the first embodiment) the front surface 3 of the wafer 1, and a roller member supported on the upper end of the expansion drum presses upward from below between the outer edge of the wafer 1 on the support sheet 11 and the inner edge of the annular frame 12, expanding the support sheet 11 in the planar direction.

[0041] Then, as a result of the expansion of support sheet 11, a radial tensile force acts on support sheet 11. When a radial tensile force acts on support sheet 11 attached to rear surface 6 of wafer 1, because division starting points 9 are formed along planned division lines 4, wafer 1 is divided into individual chips 10 starting from division starting points 9 as shown in Fig. 6, and the intervals between chips 10 are widened.

[0042] (Repair Steps) Fig. 7 is a cross-sectional view that shows a schematic diagram of a repair step in the wafer processing method shown in Fig. 2. Fig. 8 is a cross-sectional view that shows a schematic diagram of a main part of a wafer after the repair step in the wafer processing method shown in Fig. 2. The repair step 104 is a step that, after the chip spacing expansion step 103, irradiates the side surface of the chip 10 with a second laser beam 63 to melt it, thereby repairing at least a part of the modified layer 7 that is the damage caused by the modified layer formation step 102.

[0043] In the first embodiment, in the repair step 104, the second laser processing device 60 sets a focal point 631 on the side surface 13 of each chip 10 as shown in Fig. 7, and irradiates the modified layer 7 exposed on the side surface 13 of each chip 10 with a second laser beam 63 having a wavelength of 300 nm or more and less than 1100 nm from the laser beam application unit 62. Thus, in the first embodiment, the wavelength of the second laser beam 63 used in the repair step 104 is in the range of 500 nm or more and less than 1100 nm.

[0044] Then, the modified layer 7 irradiated with the second laser beam 63 melts once, and the cracks in the modified layer 7 are bonded and the chips are repaired. Also, the modified layer 7 irradiated with the second laser beam 63 melts once and then recrystallizes, and as shown in Fig. 8, a recrystallized region 14 is formed on the side surface 13 of the chip 10, and the side surface 13 is formed flat. Thus, in the repair step 104 in the first embodiment, at least a region including the region where the modified layer 7 is formed is melted once and recrystallized to form the recrystallized region 14, thereby repairing at least a part of the modified layer 7.

[0045] In the first embodiment, in the repair step 104, the second laser processing device 60 irradiates the entire modified layer 7 exposed on the side surface 13 of all the chips 10 with the second laser beam 63 to melt and recrystallize the modified layer 7. Thus, in the repair step 104, the modified layer 7 is locally irradiated with the second laser beam 63 to melt and recrystallize the modified layer 7 so as not to adversely affect the device 5 formed on the wafer 1. Note that in the present invention, in the repair step 104, other means such as plasma or ion beam may be used instead of the second laser beam 63 as long as the modified layer 7 can be locally supplied with energy to be melted, recrystallized, and repaired so as not to adversely affect the device 5 formed on the wafer 1.

[0046] The chips 10 which have been individually separated and have their modified layers 7 repaired are picked up from the support sheet 11.

[0047] In the above-described wafer processing method according to the first embodiment, the side surface 13 of the chip 10 is irradiated with the second laser beam 63 in the repair step 104. As a result, in the wafer processing method according to the first embodiment, the modified layer 7 formed on the wafer 1 in the modified layer forming step 102 is melted and recrystallized, so that at least a part of the damage contained in the modified layer 7 can be removed or repaired.

[0048] As a result, the wafer processing method according to the first embodiment has the effect of reducing damage caused by the formation of the modified layer 7 and increasing the flexural strength of the chips 10 formed by dividing the wafer 1.

[0049] Furthermore, in the wafer processing method according to embodiment 1, in the repair step 104, a focal point 631 is set on the side surface 13 of the chip 10 and the second laser beam 63 is irradiated, so that energy can be supplied locally to each chip 10, thereby preventing adverse effects on the device 5.

[0050] Furthermore, in the wafer processing method according to embodiment 1, in the repair step 104, a focal point 631 is set on the side surface 13 of the chip 10 and the second laser beam 63 is irradiated thereto, thereby shortening the processing time of the repair step 104 and improving productivity.

[0051] In addition, after ablation, a method called laser cleaning is used in which a laser beam is applied to scrape off the processing debris adhering to the surface of the processed groove. Laser cleaning is efficient because it causes the processing debris adhering to the surface of the processed groove to be absorbed by a laser beam with an ultraviolet wavelength, causing ablation and removal.

[0052] However, the wafer processing method according to the first embodiment not only melts and flattens the side surface 13 of the chip 10 by irradiating the second laser beam 63, but also bonds the cracks that have entered the interior and repairs the modified layer 7. Therefore, the wafer processing method according to the first embodiment does not allow the second laser beam 63 to be absorbed too much, and it is preferable to melt the modified layer 7 to a depth of 0.5 μm or more and 1.5 μm or less, or even 4 μm or less, with the second laser beam 63 having a wavelength longer than that irradiated in laser cleaning, that is, 532 nm or more and less than 1100 nm.

[0053] [Modifications] A wafer processing method according to a modified example of the first embodiment will be described with reference to the drawings. FIG. 9 is a side view, partially in cross section, showing a second laser processing device used in a repair step of the wafer processing method according to a modified example of the first embodiment. FIG. 10 is a plan view showing a main part of the second laser processing device shown in FIG. 9. FIG. 11 is a cross-sectional view showing a repair step of the wafer processing method according to a modified example of the first embodiment. In FIG. 9, FIG. 10, and FIG. 11, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

[0054] 9 and 10, in addition to a laser beam application unit 62 and a frame clamping unit 61 that holds the annular frame 12 and the like, the second laser processing device 60 includes a rotation unit 66 that rotates the frame clamping unit 61 for each wafer 1 about an axis perpendicular to the front surface 3 of the wafer 1, a pressing bar 64 that presses the support sheet 11 attached to the annular frame 12 held by the frame clamping unit 61 to expand the support sheet 11, and a moving unit 65 that moves the pressing bar 64 in the horizontal direction. The pressing bar 64 extends linearly along the horizontal direction, and its upper end is located above the support sheet 11 attached to the annular frame 12 held by the frame clamping unit 61.

[0055] In the modified example, as shown in Figures 9 and 10, the second laser processing device 60 positions a pressing bar 64 below each of the planned division lines 4, expands the support sheet 11 directly below each of the planned division lines 4, and performs a chip spacing expanding step 103 to expose the side surface 13 of the chip 10. In the modified example, as shown in Figure 11, the second laser processing device 60 sets a focusing point 631 on the modified layer 7 exposed on the side surface 13 of the chip 10, and irradiates the second laser beam 63 from the laser beam application unit 62 to perform a repair step 104. Thus, in the modified example, the chip spacing expanding step 103 and the repair step 104 are performed for each of the planned division lines 4.

[0056] In the wafer processing method of the modified example, in the repair step 104, a second laser beam 63 is irradiated onto the side 13 of the chip 10 to melt and recrystallize the modified layer 7, so that at least a portion of the damage contained in the modified layer 7 can be removed or repaired. As in the first embodiment, this has the effect of reducing damage caused by the formation of the modified layer 7 and increasing the flexural strength of the chips 10 formed by dividing the wafer 1.

[0057] Next, the inventors of the present invention confirmed the effect of irradiating the second laser beam 63. In the confirmation, the repair results when the second laser beam 63 of each wavelength was irradiated to the modified layer 7 were visually confirmed and confirmed by a tube performance evaluation. The results are shown in Table 1 below.

[0058] [Table 1]

[0059] In Comparative Example 1 in Table 1, the modified layer 7 was irradiated with the second laser beam 63 having a wavelength of 266 nm. In Comparative Example 2, the modified layer 7 was irradiated with the second laser beam 63 having a wavelength of 355 nm. In Comparative Example 3, the modified layer 7 was irradiated with the second laser beam 63 having a wavelength of 1100 nm.

[0060] In present invention product 1 in Table 1, the modified layer 7 was irradiated with the second laser beam 63 having a wavelength of 514 nm. In present invention product 2, the modified layer 7 was irradiated with the second laser beam 63 having a wavelength of 532 nm. In present invention product 3, the modified layer 7 was irradiated with the second laser beam 63 having a wavelength of 800 nm. In present invention product 4, the modified layer 7 was irradiated with the second laser beam 63 having a wavelength of 1000 nm. In present invention product 5, the modified layer 7 was irradiated with the second laser beam 63 having a wavelength of 1064 nm.

[0061] According to Table 1, the repair results were poor in Comparative Examples 1, 2, and 3. In particular, in Comparative Example 2, the second laser beam 63 was easily absorbed by the surface of the wafer 1, and the melting depth was shallow, so the depth to repair the modified layer 7 including the crack was insufficient. Also, in Comparative Example 3, the second laser beam 63 penetrated the wafer 1, and the internal processing occurred without melting, and the base point of the portion expanded by the internal processing cracked.

[0062] In contrast to Comparative Examples 1, 2, and 3, Invention Products 1, 2, 3, 4, and 5 showed good repair results.

[0063] Therefore, according to Table 1, it is clear that the modified layer 7 can be repaired by irradiating the second laser beam 63 having a wavelength of 500 nm or more and less than 1100 nm in the repair step 104.

[0064] The present invention is not limited to the above-mentioned embodiment. In other words, various modifications can be made without departing from the gist of the present invention. For example, in the present invention, the support sheet fixing step 101 may be performed by attaching the support sheet 11 to the front surface 3 of the wafer 1, or may be performed after the modified layer forming step 102.

[0065] In the above-described embodiment, the wavelengths of the laser beams 41, 63 irradiated in the modified layer forming step 102 and the repairing step 104 are different, so separate laser processing devices 20, 60 are used in the modified layer forming step 102 and the repairing step 104. However, in the present invention, laser beams of the same wavelength may be irradiated in the modified layer forming step 102 and the repairing step 104. In addition, in the present invention, even if the wavelengths of the laser beams 41, 63 irradiated in the modified layer forming step 102 and the repairing step 104 are different, a laser processing device including a laser beam application unit 40 that irradiates a first laser beam 41 and a laser beam application unit 62 that irradiates a second laser beam 63 may be used.

[0066] In addition, in the above-described embodiment, the wafer 1 was not divided into chips 10 after the modified layer formation step 102, but in the present invention, the wafer 1 may be divided into chips 10 after the modified layer formation step 102.

[0067] In the present invention, the first laser beam 41 may be irradiated from the rear surface 6 of the wafer 1 along the intended dividing lines 4 , and a support sheet 11 may be fixed to the front surface 3 of the wafer 1 . [Explanation of symbols]

[0068] 1 wafer 3. Surface (one side) 4. Planned division line 6 Back side 7 Modification layer 8. Crack 9 Division starting point 10 Chips 11 Support sheet 13 Side 41 First Laser Beam 63 Second Laser Beam 101 Support sheet fixing step 102 Modified layer formation step 103 Tip Spacing Expansion Step 104 Repair Steps

Claims

1. A wafer processing method for manufacturing a plurality of chips by dividing a wafer having a plurality of planned dividing lines formed thereon along the planned dividing lines, comprising the steps of: a modified layer forming step of irradiating a first laser beam along a planned dividing line from one side of the wafer to form a dividing starting point including a modified layer and a crack extending from the modified layer inside the wafer; a support sheet fixing step of fixing a support sheet to either side of the wafer before or after the modified layer forming step; a chip spacing expanding step of expanding the support sheet to widen the spacing between the chips separated along the separation starting points; a repair step of irradiating a side surface of the chip with a second laser beam after the chip spacing expanding step to melt the side surface of the chip and repair at least a part of the damage caused by the modified layer forming step; A wafer processing method comprising:

2. 2. The wafer processing method according to claim 1, wherein the repairing step includes melting at least the region where the modified layer is formed.

3. 3. The wafer processing method according to claim 1, wherein the wavelength of the second laser beam used in the repair step is in the range of 500 nm or more and less than 1100 nm.

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