Method for manufacturing a wafer, method for manufacturing a chip, wafer, and method for aligning a laser beam

Abstract

To provide a manufacturing method of a wafer, allowing proper adjustment of an irradiation position of a laser beam while suppressing lowering of strength of a chip.SOLUTION: A manufacturing method of a wafer includes: a preparation step of preparing a wafer that includes a substrate and a stacked body disposed on a front surface side of the substrate and that has a device region and an outer circumferential surplus region surrounding the device region, the device region having a plurality of devices disposed in a plurality of regions divided by a plurality of planned dividing lines arranged to intersect each other; and a laser processed groove forming step of forming laser processed grooves along the planned dividing lines through executing irradiation with a first laser beam with a wavelength having absorbability with respect to the stacked body, along the planned dividing lines from the side of the stacked body of the wafer. An irradiation condition of the first laser beam is set to cause melting of the stacked body to occur more readily in the outer circumferential surplus region than in the device region.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a wafer, a method for manufacturing the wafer, a method for manufacturing a chip by dividing the wafer into chips, and a method for aligning a laser beam used for processing the wafer.

Background Art

[0002] In the manufacture of chips incorporated in various electronic devices such as mobile phones and personal computers, wafers in which devices are formed in a plurality of regions partitioned by a plurality of division planned lines (streets) intersecting each other are used. By dividing this wafer along the division planned line, a plurality of chips (device chips) each having a device are obtained.

[0003] For dividing a wafer, a cutting device that cuts a workpiece with an annular cutting blade is used. On the other hand, in recent years, the development of a process for dividing a wafer by laser processing has also been promoted. For laser processing of a wafer, a laser processing apparatus including a chuck table for holding the workpiece and a laser irradiation unit for irradiating the workpiece with a laser beam is used.

[0004] For example, while condensing a laser beam having a wavelength that is transmissive to the wafer inside the wafer, by scanning the laser beam along the division planned line, a modified layer is formed along the division planned line inside the wafer. The region where the modified layer of the wafer is formed becomes more brittle than other regions. Therefore, when an external force is applied to the wafer in which the modified layer is formed, the modified layer functions as a division starting point and the wafer is divided along the division planned line.

[0005] The wafer used in the manufacture of device chips includes a substrate made of a semiconductor material such as silicon, and a laminate formed on the surface side of the substrate. The laminate has a structure in which various thin films such as a conductive film that functions as an electrode and an insulating film that functions as an interlayer insulating film (for example, a low dielectric constant insulating film (Low-k film)) are laminated. By forming the laminate on the surface side of the substrate, semiconductor devices, TEG (Test Element Group) for inspecting semiconductor devices, etc. are constituted.

[0006] Note that if the laminate remains on the planned division line when the wafer is divided, it may prevent the wafer from being divided. Therefore, before dividing the wafer, a process may be performed in which the laminate is preliminarily cut along the planned division line by laser processing (see Patent Document 1). As a result, the wafer can be easily divided appropriately, and it is possible to prevent the thin films contained in the laminate from peeling off and damaging the device when the wafer is divided.

[0007] The division of the laminate is performed by irradiating the laminate with a laser beam to form a groove (laser processing groove) having a depth reaching the substrate. At this time, not only the laminate but also the surface side of the substrate may be irradiated with the laser beam, and processing marks may be formed on the substrate. In this case, processing marks may remain on the device chips obtained by dividing the wafer, and the flexural strength (bending strength) of the device chips may decrease.

[0008] Therefore, a method has been proposed in which a laser processing groove having a depth that does not reach the substrate is formed in the laminate so that the laminate is not completely divided, and the laser processing groove is used as a starting point for dividing the laminate (see Patent Document 2). By using this method, it is possible to avoid forming processing marks on the substrate and prevent a decrease in the flexural strength of the device chips.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

[0010] After the laser processing groove is formed in the laminate as described above, a modified layer is formed inside the substrate by irradiation with a laser beam, and the wafer is divided. When forming the modified layer, the laser beam is irradiated from the back side of the substrate so that the irradiation of the laser beam is not inhibited by the laminate formed on the front side of the substrate. Therefore, the substrate is arranged such that the front side (laminate side) faces the holding surface of the chuck table and the back side is exposed upward.

[0011] In addition, in order to appropriately divide the wafer, it is required to form a modified layer at a position overlapping the laser processing groove formed in the laminate. Therefore, before irradiating the substrate with the laser beam, alignment between the substrate and the laser beam is performed so that the laser beam is scanned along the laser processing groove.

[0012] Generally, when the front side (laminate side) of the substrate is held by a chuck table, the substrate is imaged from the back side by an infrared camera, and the laser processing groove formed in the laminate through the substrate is observed. Then, based on the position of the laser processing groove, the position of the chuck table is adjusted. However, when a laser processing groove having a depth that does not reach the substrate is formed as described above, a part (remaining portion) of the laminate remains between the substrate and the laser processing groove, and the imaging of the laser processing groove is hindered by the remaining portion. As a result, the laser processing groove cannot be observed, and it becomes difficult to perform alignment.

[0013] The present invention has been made in view of such problems, and an object thereof is to provide a wafer capable of appropriately adjusting the irradiation position of a laser beam while suppressing a decrease in the strength of a chip, a method for manufacturing the wafer, a method for manufacturing a chip by dividing the wafer to manufacture a chip, or a method for aligning a laser beam used for processing the wafer.

Means for Solving the Problems

[0014] According to one aspect of the present invention, a preparation step of preparing a wafer including a substrate and a laminate provided on the surface side of the substrate, and a device region in which a plurality of devices are provided in a plurality of regions partitioned by a plurality of division planned lines arranged to intersect each other, and an outer peripheral surplus region surrounding the device region, and a laser processing groove forming step of irradiating a first laser beam having a wavelength that is absorbable by the laminate from the laminate side of the wafer along the division planned line to form a laser processing groove along the division planned line, wherein the irradiation conditions of the first laser beam are set such that melting of the laminate is more likely to occur in the outer peripheral surplus region than in the device region The overlap rate of the first laser beam irradiated on the outer peripheral surplus region is larger than the overlap rate of the first laser beam irradiated on the device region. A method for manufacturing a wafer is provided.

[0015] Preferably, the energy density of the first laser beam irradiated to the outer peripheral surplus region is larger than the energy density of the first laser beam irradiated to the device region. Also preferably, the peak power of the first laser beam irradiated to the outer peripheral surplus region is larger than the peak power of the first laser beam irradiated to the device region 。

[0016] Also, according to another aspect of the present invention, a wafer is provided which includes a substrate and a laminate provided on the surface side of the substrate, and has a device region in which a plurality of devices are provided in a plurality of regions partitioned by a plurality of planned division lines arranged to intersect each other, and an outer peripheral surplus region surrounding the device region. A preparation step of preparing a wafer, and a laser processing groove forming step of irradiating a first laser beam having a wavelength absorbable by the laminate from the laminate side of the wafer along the planned division line to form a laser processing groove along the planned division line, wherein the laser processing groove formed in the outer peripheral surplus region is deeper than the laser processing groove formed in the device region. In the device region, laser processing grooves having a depth that does not reach the substrate are formed, and in the outer peripheral surplus region, laser processing grooves having a depth that reaches the substrate are formed. A method for manufacturing a wafer is provided.

[0017] Also, according to another aspect of the present invention, a wafer including a substrate and a laminate provided on the surface side of the substrate, and having a plurality of devices provided in a plurality of regions partitioned by a plurality of division planned lines arranged to intersect each other. A preparation step of preparing a wafer including a device region and an outer peripheral surplus region surrounding the device region; irradiating a first laser beam having a wavelength that is absorbent to the laminate from the laminate side of the wafer along the division planned line to form a laser processing groove along the division planned line; a laser processing groove forming step; after performing the laser processing groove forming step, positioning the condensing position of a second laser beam having a wavelength that is transmissive to the substrate inside the substrate and irradiating the second laser beam from the back surface side of the substrate along the division planned line to form a modified layer along the division planned line; a modified layer forming step; after performing the modified layer forming step, applying an external force to the wafer to divide the wafer along the division planned line; a dividing step; The irradiation conditions of the first laser beam are set so that melting of the laminate is more likely to occur in the outer peripheral surplus region than in the device region, and the overlap rate of the first laser beam irradiated on the outer peripheral surplus region is larger than the overlap rate of the first laser beam irradiated on the device region. A method for manufacturing a chip is provided.

[0018] Also, according to another aspect of the present invention, a wafer is provided which includes a substrate and a laminate provided on the surface side of the substrate, and has a device region in which a plurality of devices are provided in a plurality of regions partitioned by a plurality of planned division lines arranged to intersect each other, and an outer peripheral surplus region surrounding the device region. A preparation step of preparing a wafer, and a laser processing groove forming step of irradiating a first laser beam having a wavelength absorbable by the laminate from the laminate side of the wafer along the planned division line to form a laser processing groove along the planned division line. After performing the laser processing groove forming step, observing the laser processing grooves formed in the outer peripheral surplus region from the back surface side of the substrate, and adjusting the positional relationship between the wafer and the second laser beam so that the second laser beam is irradiated on a region overlapping the laser processing grooves; an alignment step; the alignment step After performing the above steps, the condensing position of a second laser beam having a wavelength transmissive to the substrate is positioned inside the substrate, and the second laser beam is irradiated from the back side of the substrate along the planned division line to form a modified layer along the planned division line. After performing the modified layer forming step, an external force is applied to the wafer to divide the wafer along the planned division line. A method for manufacturing a chip is provided, wherein the irradiation conditions of the first laser beam are set such that melting of the laminate is more likely to occur in the outer peripheral surplus region than in the device region. The A method for manufacturing a chip is provided, wherein the irradiation conditions of the first laser beam are set such that melting of the laminate is more likely to occur in the outer peripheral surplus region than in the device region.

[0019] Preferably, the energy density of the first laser beam irradiated on the outer peripheral surplus region is greater than the energy density of the first laser beam irradiated on the device region. Also preferably, the peak power of the first laser beam irradiated on the outer peripheral surplus region is greater than the peak power of the first laser beam irradiated on the device region 。

[0020] According to another aspect of the present invention, there is provided a preparation step of preparing a wafer including a substrate and a laminate provided on the surface side of the substrate, the wafer including a device region in which a plurality of devices are provided in a plurality of regions partitioned by a plurality of division planned lines arranged to intersect each other, and an outer peripheral surplus region surrounding the device region; a laser processing groove forming step of irradiating a first laser beam having a wavelength absorbable by the laminate from the laminate side of the wafer along the division planned line to form a laser processing groove along the division planned line; a modified layer forming step of positioning a condensing position of a second laser beam having a wavelength transmissive to the substrate inside the substrate after the laser processing groove forming step and irradiating the second laser beam from the back side of the substrate along the division planned line to form a modified layer along the division planned line; and a dividing step of applying an external force to the wafer after the modified layer forming step to divide the wafer along the division planned line, wherein the laser processing groove formed in the outer peripheral surplus region is deeper than the laser processing groove formed in the device region In the device region, laser processing grooves having a depth that does not reach the substrate are formed, and in the outer peripheral surplus region, laser processing grooves having a depth that reaches the substrate are formed. A method for manufacturing a chip is provided

[0021] According to another aspect of the present invention, there is provided a method for manufacturing a chip, comprising: a preparation step of preparing a wafer including a substrate and a laminate provided on the front surface side of the substrate, the wafer having a device region in which a plurality of devices are provided in a plurality of regions defined by a plurality of planned division lines arranged to intersect each other, and an outer peripheral surplus region surrounding the device region; a laser processing groove forming step of irradiating a first laser beam having a wavelength that is absorbable by the laminate onto the laminate side of the wafer along the planned division lines to form laser processing grooves along the planned division lines; an alignment step of observing the laser processing grooves formed in the outer peripheral surplus region from the back surface side of the substrate after the laser processing groove forming step and adjusting the positional relationship between the wafer and the second laser beam so that the second laser beam is irradiated onto a region overlapping the laser processing grooves; a modified layer forming step of positioning the condensing position of the second laser beam having a wavelength that is transmissive to the substrate inside the substrate and irradiating the second laser beam from the back surface side of the substrate along the planned division lines to form a modified layer along the planned division lines; and a dividing step of applying an external force to the wafer to divide the wafer along the planned division lines. The laser processing grooves formed in the outer peripheral surplus region are deeper than the laser processing grooves formed in the device region.

[0022] Also, according to another aspect of the present invention, there is provided a wafer including a substrate and a laminate provided on the surface side of the substrate, the wafer comprising a device region in which a plurality of devices are provided in a plurality of regions partitioned by a plurality of division planned lines arranged in a lattice pattern, and an outer peripheral surplus region surrounding the device region, wherein the laminate is provided with grooves along the division planned lines, and the grooves provided in the outer peripheral surplus region are deeper than the grooves provided in the device region. In the device region, grooves having a depth that does not reach the substrate are provided, and in the outer peripheral surplus region, grooves having a depth that reaches the substrate are provided. A wafer is provided.

[0024] Also, according to another aspect of the present invention, there is provided a method of aligning a laser beam, including a step of preparing a grooved wafer including a substrate and a laminate provided on the surface side of the substrate, the grooved wafer comprising a device region in which a plurality of devices are provided in a plurality of regions partitioned by a plurality of division planned lines arranged to intersect each other, and an outer peripheral surplus region surrounding the device region, and the laminate being provided with grooves along the division planned lines, and a step of observing the grooves formed in the outer peripheral surplus region from the back surface side of the substrate and adjusting the positional relationship between the wafer and the laser beam so that the laser beam is irradiated onto a region overlapping the grooves, wherein the grooves provided in the outer peripheral surplus region are deeper than the grooves provided in the device region.

[0025] Preferably, the device region is provided with grooves having a depth that does not reach the substrate, and the outer peripheral surplus region is provided with grooves having a depth that reaches the substrate.

Advantages of the Invention

[0026] According to one aspect of the present invention, laser processing grooves having a depth that does not reach the substrate are formed in the device region of the wafer. As a result, it is possible to form laser processing grooves that function as a starting point for dividing the laminate while avoiding the remaining processing marks on the substrate and the reduction in the flexural strength of the chip. Further, laser processing grooves deeper than the laser processing grooves formed in the device region are formed in the outer peripheral surplus region of the wafer. As a result, the laser processing grooves in the outer peripheral surplus region are easily observable from the back side of the substrate, and the alignment between the wafer and the second laser beam based on the position of the laser processing grooves becomes easy. As a result, it is possible to appropriately adjust the irradiation position of the second laser beam while suppressing the reduction in the strength of the chip.

Brief Description of the Drawings

[0027]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 7

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0028] Hereinafter, embodiments according to an aspect of the present invention will be described with reference to the accompanying drawings. First, a configuration example of a wafer that can be used in a method for manufacturing a wafer and a method for manufacturing a chip according to the present embodiment will be described. FIG. 1(A) is a perspective view showing a wafer 11.

[0029] The wafer 11 includes a disk-shaped substrate 13. For example, the substrate 13 is made of a semiconductor material such as silicon and has a front surface (first surface) 13a and a back surface (second surface) 13b that are substantially parallel to each other. However, there are no restrictions on the material, shape, structure, size, etc. of the substrate 13. For example, the substrate 13 may be a substrate made of a semiconductor other than silicon (GaAs, SiC, InP, GaN, etc.), sapphire, glass, ceramics, resin, metal, etc. Note that the back surface 13b of the substrate 13 corresponds to the back surface (second surface) 11b of the wafer 11.

[0030] On the surface 13a side of the substrate 13, a laminate 15 including a plurality of laminated thin films is provided. The laminate 15 includes various thin films such as a conductive film that functions as an electrode and an insulating film that functions as an interlayer insulating film (for example, a low dielectric constant insulating film (Low-k film)), and is formed over the entire surface 13a side of the substrate 13. Note that the surface (upper surface) of the laminate 15 corresponds to the surface (first surface) 11a of the wafer 11.

[0031] Wafer 11 is partitioned into a plurality of rectangular regions by a plurality of division planned lines (streets) 17 arranged in a lattice pattern so as to intersect each other. And in each of the plurality of regions partitioned by the division planned line 17, devices 19 such as IC (Integrated Circuit), LSI (Large Scale Integration), and MEMS (Micro Electro Mechanical Systems) devices are formed. However, there are no restrictions on the type, quantity, shape, structure, size, arrangement, etc. of the devices 19.

[0032] Wafer 11 includes a substantially circular device region 21 in which a plurality of devices 19 are formed, and an outer peripheral surplus region 23 surrounding the device region 21. The outer peripheral surplus region 23 corresponds to an annular region having a predetermined width (for example, about 2 mm) including the outer peripheral edges of the substrate 13 and the laminate 15. In FIG. 1(A), the boundary between the device region 21 and the outer peripheral surplus region 23 is shown by a broken line.

[0033] FIG. 1(B) is a cross-sectional view showing a part of the wafer 11. A plurality of regions surrounded by the division planned line 17 in the laminate 15 respectively constitute the devices 19. For example, a semiconductor element is constituted by the surface 13a side of the substrate 13 and a thin film included in the laminate 15. Also, a part of the thin film included in the laminate 15 is formed on the division planned line 17. The region of the laminate 15 located on the division planned line 17 may constitute, for example, a TEG or the like used for inspection of the device 19.

[0034] By dividing the wafer 11 along the division planned line 17, a plurality of chips (device chips) each including the device 19 are manufactured. For example, the wafer 11 is divided by laser processing using a laser processing apparatus. Hereinafter, a specific example of a chip manufacturing method for manufacturing chips by dividing the wafer 11 will be described.

[0035] First, prepare the wafer 11 (preparation step). As described above, the wafer 11 includes a substrate 13 and a laminate 15 provided on the surface 13a side of the substrate 13. Further, the wafer 11 includes a device region 21 and an outer peripheral surplus region 23 (see FIGS. 1(A) and 1(B)).

[0036] The wafer 11 is supported by an annular frame. FIG. 2 is a perspective view showing the wafer 11 supported by the annular frame 27. A circular tape 25 having a diameter larger than that of the substrate 13 is attached to the back surface 13b side of the substrate 13. For example, the tape 25 includes a film-shaped base material formed in a circular shape and an adhesive layer (paste layer) provided on the base material. The base material is made of a resin such as polyolefin, polyvinyl chloride, or polyethylene terephthalate. The adhesive layer is made of an epoxy-based, acrylic-based, or rubber-based adhesive or the like. The adhesive layer may be an ultraviolet curable resin that cures by irradiation with ultraviolet rays.

[0037] The outer peripheral portion of the tape 25 is attached to an annular frame 27 made of a metal such as SUS (stainless steel). A circular opening 27a penetrating the frame 27 in the thickness direction is provided at the central portion of the frame 27. The diameter of the opening 27a is larger than the diameter of the substrate 13. With the substrate 13 disposed inside the opening 27a, the central portion of the tape 25 is attached to the back surface 13b side of the substrate 13, and the outer peripheral portion of the tape 25 is attached to the frame 27, so that the wafer 11 is supported by the frame 27 via the tape 25.

[0038] Next, a laser beam (first laser beam) having an absorbable wavelength with respect to the laminate 15 is irradiated from the laminate 15 side of the wafer 11 along the division planned line 17 to form a groove (laser processing groove) along the division planned line 17 (laser processing groove forming step). In the present embodiment, the wafer 11 is subjected to first laser processing using a laser processing apparatus to form a laser processing groove.

[0039] FIG. 3 is a partial cross-sectional front view showing the laser processing apparatus 2. In FIG. 3, the X-axis direction (processing feed direction, first horizontal direction) and the Y-axis direction (indexing feed direction, second horizontal direction) are perpendicular to each other. Also, the Z-axis direction (vertical direction, up and down direction, height direction) is perpendicular to the X-axis direction and the Y-axis direction.

[0040] The laser processing apparatus 2 includes a chuck table (holding table) 4 that holds the wafer 11. The upper surface of the chuck table 4 is a circular flat surface generally parallel to the horizontal direction (XY plane direction), and constitutes a holding surface 4a for holding the wafer 11. The holding surface 4a is connected to a suction source (not shown) such as an ejector via a flow path (not shown), a valve (not shown), etc. formed inside the chuck table 4.

[0041] A ball screw type moving mechanism (not shown) for moving the chuck table 4 along the X-axis direction is connected to the chuck table 4. Also, a rotational drive source (not shown) such as a motor for rotating the chuck table 4 around a rotation axis substantially perpendicular to the holding surface 4a is connected to the chuck table 4. Further, a plurality of clamps 6 for gripping and fixing the frame 27 are provided around the chuck table 4.

[0042] The laser processing apparatus 2 also includes a laser irradiation unit 8 that irradiates a laser beam. The laser irradiation unit 8 includes a laser oscillator (not shown) such as a YAG laser, a YVO4 laser, a YLF laser, etc., and a head 10 disposed above the chuck table 4. The head 10 incorporates an optical system for guiding the pulsed laser beam emitted from the laser oscillator to the wafer 11, and the optical system includes optical elements such as a condenser lens for condensing the laser beam. The wafer 11 is processed by the laser beam (first laser beam) 12 irradiated from the laser irradiation unit 8.

[0043] In the laser processing groove formation step, first, the wafer 11 is held by the chuck table 4. Specifically, the wafer 11 is placed on the chuck table 4 such that the back surface 11b side (the back surface 13b side of the substrate 13, the tape 25 side) faces the holding surface 4a and the front surface 11a side (the laminate 15 side) is exposed upward. Also, the frame 27 is fixed by a plurality of clamps 6. In this state, when the suction force (negative pressure) of the suction source is applied to the holding surface 4a, the wafer 11 is suction-held by the chuck table 4 via the tape 25.

[0044] Next, the chuck table 4 is rotated to align the length direction of the division planned line 17 (see FIG. 1(A) etc.) with the processing feed direction (X-axis direction). Also, the position in the indexing feed direction (Y-axis direction) of the chuck table 4 is adjusted so that the position in the Y-axis direction of the region irradiated with the laser beam 12 (the irradiated region) coincides with the region inside both ends in the width direction of the division planned line 17 (for example, the center in the width direction of the division planned line 17). Further, the position of the head 10 and the arrangement of the optical system are adjusted so that the condensing position of the laser beam 12 is positioned at the same height position (the position in the Z-axis direction) as the surface or inside of the laminate 15.

[0045] Then, while irradiating the laser beam 12 from the laser irradiation unit 8, the chuck table 4 is moved along the processing feed direction (X-axis direction). As a result, the chuck table 4 and the laser beam 12 relatively move at a predetermined speed (processing feed speed) along the processing feed direction (X-axis direction), and the laser beam 12 is irradiated from the front surface 11a side (the laminate 15 side) of the wafer 11 along the division planned line 17.

[0046] Note that the irradiation conditions of the laser beam 12 are set such that ablation processing is performed on the laminate 15. Specifically, the wavelength of the laser beam 12 is set such that at least a part of the laser beam 12 is absorbed by the laminate 15. That is, the laser beam 12 is a laser beam having a wavelength that is absorbable by the laminate 15. Further, the irradiation conditions of the other laser beam 12 are also set such that ablation processing is appropriately performed on the laminate 15.

[0047] When the laminate 15 is irradiated with the laser beam 12 along the planned division line 17, the region of the laminate 15 irradiated with the laser beam 12 is removed by ablation processing. As a result, a laser processing groove 29 is formed along the planned division line 17 in the laminate 15.

[0048] Here, in the laser processing groove forming step, the irradiation conditions of the laser beam 12 are set such that melting of the laminate 15 is likely to occur in the outer peripheral surplus region 23 rather than in the device region 21. That is, the irradiation conditions (first irradiation conditions) of the laser beam 12 irradiated to the outer peripheral surplus region 23 are different from the irradiation conditions (second irradiation conditions) of the laser beam 12 irradiated to the device region 21. And the first irradiation conditions are set to conditions where melting of the laminate 15 is more likely to occur and the laser processing groove 29 is more likely to be formed than the second irradiation conditions.

[0049] For example, in the first irradiation conditions and the second irradiation conditions, the energy density and the overlap ratio of the laser beam 12 are set to different values. Let the average output of the laser beam 12 be P (W), the repetition frequency of the laser beam 12 be F (kHz), and the irradiation area (area at the condensing position) of the laser beam 12 be S (cm 2 ). Then, the pulse energy E (mJ) and the energy density I (mJ / cm 2 ) of the laser beam 12 are represented by formulas (1) and (2), respectively.

[0050]

Equation

[0051] [Number]

[0052] Also, when the processing feed rate during the irradiation of the laser beam 12 is V (mm / s) and the spot diameter of the laser beam (diameter at the focusing position) is d (mm), the overlap ratio OL (%) of the laser beam 12 is expressed by Equation (3).

[0053] [Number]

[0054] And the irradiation conditions (first irradiation conditions) of the laser beam 12 irradiated to the outer peripheral surplus region 23 are set as follows, for example. Wavelength: 355 nm Average output: 2 W Repetition frequency: 200 kHz Processing feed rate: 400 mm / s

[0055] Also, the irradiation conditions (second irradiation conditions) of the laser beam 12 irradiated to the device region 21 are set as follows, for example. Wavelength: 355 nm Average output: 1 W Repetition frequency: 200 kHz Processing feed rate: 400 mm / s

[0056] When the first irradiation conditions and the second irradiation conditions are set as described above, the average output of the laser beam 12 irradiated to the outer peripheral surplus region 23 becomes larger than the average output of the laser beam 12 irradiated to the device region 21. As a result, the energy density of the laser beam 12 irradiated to the outer peripheral surplus region 23 becomes larger than the energy density of the laser beam 12 irradiated to the device region 21. Consequently, melting of the laminate 15 is more likely to occur in the outer peripheral surplus region 23 than in the device region 21.

[0057] Note that the method for setting the first irradiation condition and the second irradiation condition is not limited to the above. For example, only the peak power of the laser beam 12 may be made different between the first irradiation condition and the second irradiation condition. The peak power of the laser beam 12 corresponds to the value obtained by dividing the pulse energy of the laser beam 12 by the pulse width of the laser beam 12, and affects the melting of the laminate 15.

[0058] When the peak power of the first irradiation condition is set to a value larger than the peak power of the second irradiation condition, the peak power of the laser beam 12 irradiated to the outer peripheral surplus region 23 becomes larger than the peak power of the laser beam 12 irradiated to the device region 21. In this case, even if the energy density of the laser beam 12 is equal between the first irradiation condition and the second irradiation condition, melting of the laminate 15 is likely to occur in the outer peripheral surplus region 23 rather than in the device region 21.

[0059] Also, only the processing feed rate may be made different between the first irradiation condition and the second irradiation condition. In this case, the processing feed rate of the first irradiation condition is set to a value smaller than the processing feed rate of the second irradiation condition. That is, the processing feed rate when the laser beam 12 is irradiated to the outer peripheral surplus region 23 becomes smaller than the processing feed rate when the laser beam 12 is irradiated to the device region 21. Thereby, the overlap rate of the laser beam 12 irradiated to the outer peripheral surplus region 23 becomes larger than the overlap rate of the laser beam 12 irradiated to the device region 21. As a result, melting of the laminate 15 is likely to occur in the outer peripheral surplus region 23 rather than in the device region 21.

[0060] Also, by setting different values for other parameters (spot diameter, irradiation area, repetition frequency, etc.) of the laser beam 12 between the first irradiation condition and the second irradiation condition, melting of the laminate 15 may be more likely to occur in the outer peripheral surplus region 23 than in the device region 21. Furthermore, two or more parameters may be set to different values between the first irradiation condition and the second irradiation condition.

[0061] When the machining feed of the chuck table 4 is performed, the laser beam 12 is irradiated in sequence to one end of the outer peripheral surplus region 23, the device region 21, and the other end of the outer peripheral surplus region 23. And at the timing when the laser beam 12 shifts from the state of being irradiated to one end of the outer peripheral surplus region 23 to the state of being irradiated to the device region 21, the irradiation condition of the laser beam 12 switches from the first irradiation condition to the second irradiation condition. Also, at the timing when the laser beam 12 shifts from the state of being irradiated to the device region 21 to the state of being irradiated to the other end of the outer peripheral surplus region 23, the irradiation condition of the laser beam 12 switches from the second irradiation condition to the first irradiation condition.

[0062] Figure 4(A) is a cross-sectional view showing a part of the wafer 11 when the laser beam 12 is irradiated to one end of the outer peripheral surplus region 23. First, in a state where the irradiation condition of the laser beam 12 is set to the first irradiation condition, the laser beam 12 is irradiated to one end of the outer peripheral surplus region 23. As a result, in the laminate 15, a laser processing groove 29 (laser processing groove 29a) having a depth reaching the surface 13a of the substrate 13 is formed along the division planned line 17.

[0063] And when the region irradiated with the laser beam 12 reaches the boundary between the outer peripheral surplus region 23 and the device region 21, the irradiation condition of the laser beam 12 switches from the first irradiation condition to the second irradiation condition. After that, in a state where the irradiation condition of the laser beam 12 is set to the second irradiation condition, the laser beam 12 is irradiated to the device region 21.

[0064] Figure 4(B) is a cross-sectional view showing a part of the wafer 11 when the laser beam 12 is irradiated to the device region 21. As described above, the second irradiation condition is the irradiation condition of the laser beam 12 in which melting of the laminate 15 is less likely to occur than in the first irradiation condition. Therefore, when the laser beam 12 is irradiated to the device region 21 under the second irradiation condition, a laser processing groove 29 (laser processing groove 29b) having a depth not reaching the surface 13a of the substrate 13 is formed along the division planned line 17 in the laminate 15.

[0065] When the area irradiated with the laser beam 12 reaches the boundary between the device area 21 and the outer peripheral surplus area 23, the irradiation condition of the laser beam 12 switches from the second irradiation condition to the first irradiation condition. Thereafter, with the irradiation condition of the laser beam 12 set to the first irradiation condition, the laser beam 12 is irradiated to the other end of the outer peripheral surplus area 23.

[0066] Figure 4(C) is a cross-sectional view showing a part of the wafer 11 when the laser beam 12 is irradiated to the other end of the outer peripheral surplus area 23. When the laser beam 12 is irradiated to the other end of the outer peripheral surplus area 23 under the first irradiation condition, a laser processing groove 29 (laser processing groove 29a) having a depth reaching the surface 13a of the substrate 13 is formed along the division planned line 17 in the laminate 15.

[0067] Thereafter, the same procedure is repeated, and the laser beam 12 is irradiated along other division planned lines 17. As a result, in the outer peripheral surplus area 23 of the wafer 11, laser processing grooves 29a for dividing the laminate 15 are formed along the division planned lines 17. On the other hand, in the device area 21 of the wafer 11, laser processing grooves 29b that do not divide the laminate 15 are formed in a lattice pattern along the division planned lines 17.

[0068] Note that the laser beam 12 can also be irradiated a plurality of times along each division planned line 17. For example, the laser beam 12 may be irradiated so as to reciprocate along each division planned line 17. In this case, in the forward path (or the return path), the laser beam 12 is irradiated to the outer peripheral surplus area 23 under the first irradiation condition, and in the return path (or the forward path), the laser beam 12 is irradiated to the device area 21 under the second irradiation condition.

[0069] FIG. 5(A) is a cross-sectional view showing a part of the outer peripheral surplus region 23 of the wafer 11, and FIG. 5(B) is a cross-sectional view showing a part of the device region 21 of the wafer 11. When the wafer 11 is irradiated with the laser beam 12 under the above conditions, the laser processing groove 29a formed in the outer peripheral surplus region 23 becomes deeper than the laser processing groove 29b formed in the device region 21. Then, on the division planned line 17 of the outer peripheral surplus region 23, the laminate 15 is removed and the surface 13a side of the substrate 13 is exposed. On the other hand, on the division planned line 17 of the device region 21, a part of the laminate 15 remains between the substrate 13 and the laser processing groove 29a, and the surface 13a side of the substrate 13 is not exposed.

[0070] Note that the laser processing groove 29a does not necessarily have to be formed deeper (so as to reach the substrate 13) than the laser processing groove 29b in the entire outer peripheral surplus region 23. That is, the laser processing groove 29a may be formed such that at least a part thereof is deeper (so as to reach the substrate 13) than the laser processing groove 29b. On the other hand, the laser processing groove 29b is preferably formed so as not to reach the substrate 13 in the entire device region 21.

[0071] For example, before the irradiation region of the laser beam 12 reaches the boundary between one end of the outer peripheral surplus region 23 and the device region 21, the irradiation conditions of the laser beam 12 may be switched from the first irradiation conditions to the second irradiation conditions. Also, after the irradiation region of the laser beam 12 reaches the boundary between the device region 21 and the other end of the outer peripheral surplus region 23, the irradiation conditions of the laser beam 12 may be switched from the second irradiation conditions to the first irradiation conditions. In this case, a part of the laser processing groove 29a is formed to have the same depth as the laser processing groove 29b.

[0072] Also, the laser processing groove 29a formed in the outer peripheral surplus region 23 may be formed only in a part of the region on the division planned line 17. For example, in the outer peripheral surplus region 23, a plurality of dot-shaped laser processing grooves 29a may be formed along the division planned line 17. In this case, the regions where the laser processing groove 29a exists and the regions where it does not exist are alternately arranged along the division planned line 17.

[0073] Further, the laser processing grooves 29a formed in the outer peripheral surplus region 23 do not necessarily have to be formed along all the planned division lines 17. For example, one laser processing groove 29a may be formed for every predetermined number (two or more) of planned division lines 17.

[0074] Furthermore, instead of irradiating the outer peripheral surplus region 23 with the laser beam 12, an annular cutting blade may be cut in. In this case, a cutting groove is formed instead of the laser processing groove 29a. Then, the cutting groove formed in the outer peripheral surplus region 23 and the laser processing groove 29b formed in the device region 21 are connected. Note that the region where the cutting groove is formed, the depth, shape, number, etc. of the cutting groove can be set in the same manner as the laser processing groove 29a. Also, the formation of the cutting groove may be carried out at any timing before or after the formation of the laser processing groove 29b.

[0075] By performing the above preparation step and the laser processing groove formation step, a wafer 11 (grooved wafer) provided with grooves (laser processing grooves 29) along the planned division lines 17 is obtained in the laminate 15 (grooved wafer preparation step). That is, the grooved wafer preparation step corresponds to a method for manufacturing a grooved wafer.

[0076] Next, second laser processing is performed on the substrate 13. For example, by irradiating the substrate 13 with a laser beam 16 (see FIG. 7), a modified layer 35 (see FIG. 7) that functions as a starting point for division (a trigger for division) is formed inside the substrate 13. Hereinafter, the case where the laser processing apparatus 2 is used for processing the substrate 13 will be described, but other laser processing apparatuses may be used for laser processing of the substrate 13.

[0077] When performing laser processing on the substrate 13, first, the positional relationship between the wafer 11 and the laser beam 16 is adjusted (alignment step). FIG. 6(A) is a partial cross-sectional front view showing the laser processing apparatus 2 in the alignment step. Hereinafter, a specific example of the alignment method of the laser beam 16 will be described.

[0078] The laser processing apparatus 2 includes an imaging unit 14 provided above the chuck table 4, and the imaging unit 14 is used to align the wafer 11 and the laser beam 16. For example, the imaging unit 14 is an infrared camera including an imaging element that receives infrared rays and converts them into electrical signals.

[0079] In the alignment step, first, the tape 25 (see FIG. 2) is peeled off from the wafer 11 (grooved wafer) in which the laser processing groove 29 is provided in the laminate 15, and then the wafer 11 is supported by the annular frame 33 via the tape 31. Note that the structures and materials of the tape 31 and the frame 33 are the same as those of the tape 25 and the frame 27 (see FIG. 2, etc.), respectively. Then, the central portion of the tape 31 is attached to the surface 11a side (laminate 15 side) of the wafer 11, and the outer peripheral portion of the tape 31 is attached to the frame 33. However, the support of the wafer 11 by the frame 33 can also be omitted. In this case, it is not necessary to attach the tape 25 to the frame 27.

[0080] Next, the wafer 11 is held by the chuck table 4. Specifically, the wafer 11 is placed on the chuck table 4 such that the surface 11a side (laminate 15 side, tape 31 side) faces the holding surface 4a and the back surface 11b side (back surface 13b side of the substrate 13) is exposed upward. Also, the frame 33 is fixed by a plurality of clamps 6. In this state, when the suction force (negative pressure) of the suction source is applied to the holding surface 4a, the wafer 11 is suction-held by the chuck table 4 via the tape 31.

[0081] Next, the laser processing groove 29 formed in the outer peripheral surplus region 23 is observed from the back surface 13b side of the substrate 13. Specifically, first, the positional relationship between the chuck table 4 and the imaging unit 14 is adjusted so that the imaging unit 14 is positioned directly above the outer peripheral surplus region 23 of the wafer 11. Then, the outer peripheral surplus region 23 of the wafer 11 is imaged by the imaging unit 14.

[0082] FIG. 6(B) is a cross-sectional view showing the wafer 11 imaged by the imaging unit 14. In the outer peripheral surplus region 23, laser processing grooves 29a reaching the substrate 13 are formed in the laminate 15, and the substrate 13 is partially exposed inside the laser processing grooves 29a. Therefore, the light (infrared ray) transmittance is different between the region where the laser processing grooves 29a exist and the region where they do not exist in the outer peripheral surplus region 23. As a result, an image corresponding to the contour of the laser processing grooves 29a is represented in the image acquired by the imaging unit 14.

[0083] Thus, when the laser processing grooves 29a are formed to reach the substrate 13, the laser processing grooves 29a can be clearly observed from the back surface 13b side of the substrate 13. Thereby, even in a state where the surface 11a side (laminate 15 side) of the wafer 11 is covered with the holding surface 4a of the chuck table 4, the position of the laser processing grooves 29a can be accurately grasped.

[0084] Note that FIG. 6(B) illustrates a state where the laser processing grooves 29a are formed to reach the substrate 13, but the depth of the laser processing grooves 29a may be less than the thickness of the laminate 15. That is, a part (remaining portion) of the laminate 15 may slightly remain between the front surface 13a of the substrate 13 and the laser processing grooves 29a.

[0085] If the remaining portion is sufficiently thin, light (infrared ray) passes through the remaining portion, and the contour of the laser processing grooves 29a is faintly represented in the image acquired by the imaging unit 14. In this case, even if the laser processing grooves 29a do not reach the substrate 13, the position of the laser processing grooves 29a can be confirmed.

[0086] In order to clearly display the contour of the laser processing grooves 29a in the image acquired by the imaging unit 14, the thickness of the remaining portion is preferably 1 / 5 or less of the thickness of the laminate 15, and more preferably 1 / 10 or less. More specifically, the thickness of the remaining portion is preferably 2 μm or less, and more preferably 1 μm or less.

[0087] Next, the positional relationship between the wafer 11 and the laser beam 16 (see FIG. 7) is adjusted. Note that the laser beam 16 is the laser beam that irradiates the wafer 11 in the modification layer formation step described later.

[0088] Specifically, first, based on the image acquired by the imaging unit 14, the position of the laser processing groove 29a is specified. Then, the positional relationship between the wafer 11 and the laser beam 16 is adjusted so that the laser beam 16 is irradiated onto the region overlapping the laser processing groove 29 in the modification layer formation step described later.

[0089] More specifically, based on the image acquired by the imaging unit 14, the angle of the chuck table 4 is adjusted so that the length direction of the laser processing groove 29 is aligned with the processing feed direction (X-axis direction). Also, the position of the chuck table 4 in the indexing feed direction (Y-axis direction) is adjusted so that the position in the Y-axis direction of the region irradiated with the laser beam 16 (irradiated region) coincides with the region inside both ends in the width direction of the laser processing groove 29a (for example, the center in the width direction of the laser processing groove 29).

[0090] Next, a laser beam (second laser beam) 16 having a wavelength that is transmissive to the substrate 13 is irradiated from the back surface 13b side of the substrate 13 along the division planned line 17 to form a modification layer along the division planned line 17 (modification layer formation step). FIG. 7 is a partial cross-sectional front view showing the laser processing apparatus 2 in the modification layer formation step.

[0091] In the modified layer formation step, the position of the head 10 and the arrangement of the optical system are adjusted so that the condensing position of the laser beam 16 is positioned at the same height inside the substrate 13 (between the front surface 13a and the back surface 13b). Then, while irradiating the wafer 11 with the laser beam 16 from the laser irradiation unit 8, the chuck table 4 whose position has been adjusted in the alignment step is moved along the processing feed direction (X-axis direction). As a result, the chuck table 4 and the laser beam 16 relatively move at a predetermined speed (processing feed speed) along the processing feed direction (X-axis direction), and the laser beam 16 is irradiated from the back surface 13b side of the substrate 13 along the planned division line 17.

[0092] Note that the irradiation conditions of the laser beam 16 are set so that the region of the substrate 13 irradiated with the laser beam 16 is modified and altered by multi-photon absorption. Specifically, the wavelength of the laser beam 12 is set so that at least a part of the laser beam 16 penetrates the substrate 13. That is, the laser beam 16 is a laser beam having a wavelength that is transmissive with respect to the substrate 13. Also, the irradiation conditions of the other laser beam 16 are set so that the substrate 13 is appropriately modified. Examples of the irradiation conditions of the laser beam 16 capable of modifying the substrate 13 are as follows. Wavelength: 1064 nm Average output: 1 W Repetition frequency: 100 kHz Processing feed speed: 800 mm / s

[0093] When the substrate 13 is irradiated with the laser beam 16, the inside of the substrate 13 is modified and altered by multi-photon absorption, and a modified layer (altered layer) 35 is formed along the planned division line 17 and the laser processing groove 29. Since the laser beam 16 is irradiated from the back surface 13b side of the substrate 13, the irradiation of the laser beam 16 into the substrate 13 is not inhibited by the laminate 15. Thereafter, the laser beam 16 is irradiated along the other planned division lines 17 and the laser processing grooves 29 in the same procedure, and a lattice-shaped modified layer 35 is formed inside the substrate 13.

[0094] FIG. 8(A) is a cross-sectional view showing a part of the outer peripheral surplus region 23 of the wafer 11 on which the modified layer 35 is formed, and FIG. 8(B) is a cross-sectional view showing a part of the device region 21 of the wafer 11 on which the modified layer 35 is formed. The modified layer 35 includes a plurality of modified regions (altered regions) 37 that are modified and altered by multiphoton absorption. The modified regions 37 are formed at the condensing positions of the laser beam 16 (see FIG. 7) and are arranged along the division planned line 17 and the laser processing groove 29. Further, when the modified regions 37 are formed, cracks 39 occur in the modified regions 37 and propagate from the modified regions 37 toward the front surface 13a and the back surface 13b of the substrate 13.

[0095] The region of the substrate 13 where the modified layer 35 and the cracks 39 are formed becomes more brittle than other regions of the substrate 13. Therefore, when an external force is applied to the wafer 11, the substrate 13 is divided along the division planned line 17 and the laser processing groove 29 starting from the modified layer 35 and the cracks 39. That is, the modified layer 35 and the cracks 39 function as a division starting point (a trigger for division).

[0096] Note that depending on the irradiation conditions of the laser beam 16 (see FIG. 7) and the positions of the modified regions 37, the cracks 39 may reach the front surface 13a of the substrate 13. In this case, in the outer peripheral surplus region 23 (see FIG. 8(A)), the cracks 39 are connected to the laser processing groove 29a. Further, in the device region 21 (see FIG. 8(B)), the cracks 39 may also propagate inside the laminate 15 and reach the laser processing groove 29b.

[0097] Also, a plurality of layers of the modified layer 35 may be formed in the thickness direction of the substrate 13. For example, when the substrate 13 is a silicon wafer or the like having a thickness of 200 μm or more, by forming two or more modified layers 35, the substrate 13 can be more easily divided appropriately. When forming a plurality of modified layers 35, while changing the condensing position of the laser beam 16 in the thickness direction of the substrate 13, the laser beam 16 is irradiated a plurality of times along each division planned line 17.

[0098] Next, an external force is applied to the wafer 11 to divide the wafer 11 along the planned division line 17 (division step). In the division step, first, the wafer 11 is thinned by grinding. A grinding device is used for grinding the wafer 11.

[0099] FIG. 9 is a perspective view showing the grinding device 20. The grinding device 20 includes a chuck table (holding table) 22 for holding the wafer 11 and a grinding unit 24 for grinding the wafer 11.

[0100] The upper surface of the chuck table 22 is a flat surface formed along the horizontal direction and constitutes a holding surface 22a for holding the wafer 11. The holding surface 22a is connected to a suction source (not shown) such as an ejector via a flow path (not shown), a valve (not shown), etc. formed inside the chuck table 22.

[0101] A ball screw type moving mechanism (not shown) for moving the chuck table 22 along the horizontal direction is connected to the chuck table 22. Further, a rotation drive source (not shown) such as a motor for rotating the chuck table 22 around a rotation axis substantially perpendicular to the holding surface 22a is connected to the chuck table 22.

[0102] Above the chuck table 22, the grinding unit 24 is arranged. The grinding unit 24 includes a cylindrical spindle 26 arranged along the vertical direction. A disk-shaped mount 28 made of metal or the like is fixed to the tip (lower end) of the spindle 26. Further, a rotation drive source (not shown) such as a motor for rotating the spindle 26 is connected to the base end (upper end) of the spindle 26.

[0103] On the lower surface side of the mount 28, a grinding wheel 30 for grinding the wafer 11 is mounted. The grinding wheel 30 includes an annular base 32 made of a metal such as stainless steel or aluminum and formed to have approximately the same diameter as the mount 28. A plurality of grinding grains 34 are fixed to the lower surface side of the base 32. For example, the plurality of grinding grains 34 are formed in a rectangular parallelepiped shape and are arranged at approximately equal intervals along the outer periphery of the base 32.

[0104] The grinding grains 34 are formed by fixing abrasive grains made of diamond, cBN (cubic Boron Nitride), etc. with a binder such as a metal bond, a resin bond, or a vitrified bond. However, there are no restrictions on the material, shape, structure, size, etc. of the grinding grains 34, and they are appropriately selected according to the material of the substrate 13, etc. Also, the number of the grinding grains 34 can be arbitrarily set.

[0105] The grinding wheel 30 rotates around a rotation axis substantially perpendicular to the holding surface 22a by the power transmitted from a rotation drive source via the spindle 26 and the mount 28. Also, a ball screw type moving mechanism (not shown) for raising and lowering the grinding unit 24 along a direction substantially perpendicular to the holding surface 22a is connected to the grinding unit 24. Further, a grinding fluid supply path (not shown) for supplying a liquid such as pure water (grinding fluid) to the wafer 11 and the grinding grains 34 is provided inside or in the vicinity of the grinding unit 24.

[0106] The back surface 11b (the back surface 13b side of the substrate 13) side of the wafer 11 is ground by the grinding device 20. Specifically, first, a protective sheet 41 made of resin or the like is attached to the surface 11a side (the laminate 15 side) of the wafer 11. Thereby, the laminate 15 is covered and protected by the protective sheet 41.

[0107] Then, the wafer 11 is held by the chuck table 22. The wafer 11 is placed on the chuck table 22 such that the surface 11a side (the protective sheet 41 side) faces the holding surface 22a and the back surface 11b side (the back surface 13b side of the substrate 13) is exposed upward. In this state, when a negative pressure of a suction source is applied to the holding surface 22a, the wafer 11 is sucked and held by the chuck table 22 via the protective sheet 41.

[0108] Thereafter, the chuck table 22 is placed below the grinding unit 24. Then, while rotating the chuck table 22 and the grinding wheel 30 in a predetermined direction at a predetermined rotational speed, the grinding wheel 30 is lowered toward the chuck table 22. The lowering speed of the grinding wheel 30 at this time is adjusted so that the grinding wheel 34 presses against the wafer 11 with an appropriate force.

[0109] When the grinding wheel 34 contacts the back surface 13b side of the substrate 13, the back surface 13b side of the substrate 13 is ground and the substrate 13 is thinned. Then, when the crack 39 (see FIGS. 8(A) and 8(B)) that has propagated from the modified layer 35 is exposed on the back surface 13b side of the substrate 13, the wafer 11 is divided along the division planned line 17.

[0110] Note that at the stage when the modified layer 35 is formed on the wafer 11, the crack 39 may not have reached the surface 13a of the substrate 13. In this case, when the grinding wheel 34 is pressed against the wafer 11, an external force is applied to the wafer 11, and the crack 39 propagates toward the surface 13a of the substrate 13. As a result, the crack 39 reaches the laser processing grooves 29a and 29b, and the wafer 11 is divided.

[0111] It is preferable that the grinding of the wafer 11 is continued until the modified layer 35 formed inside the substrate 13 is removed. Thereby, it is possible to avoid the remaining of the modified layer 35 on the wafer 11 after grinding and prevent the decrease in the flexural strength of the chips obtained by dividing the wafer 11.

[0112] As described above, by grinding the wafer 11 and applying an external force to the wafer 11, the wafer 11 can be divided into a plurality of thinned chips. However, even if the grinding wheel 34 is pressed against the wafer 11 during the grinding process, a sufficient external force may not be applied to the wafer 11, and the division of the wafer 11 may be insufficient. In this case, it is preferable to apply an additional external force to the wafer 11 after grinding.

[0113] For example, after the protective sheet 41 is peeled off from the wafer 11, the wafer 11 is supported by an annular frame 45 (see FIG. 10(A)) via a tape 43 (see FIG. 10(A)). The structures and materials of the tape 43 and the frame 45 are the same as those of the tape 25 and the frame 27 (see FIG. 2 etc.), respectively. Then, the central portion of the tape 43 is attached to the back surface 11b side (the back surface 13b side of the substrate 13) of the wafer 11, and the outer peripheral portion of the tape 43 is attached to the frame 45.

[0114] Note that the tape 43 is an expandable tape that can be expanded by the application of an external force. When the tape 43 attached to the wafer 11 is expanded by pulling it radially outward, an external force is applied to the wafer 11. As a result, the wafer 11 is divided along the division planned line 17 and divided into a plurality of chips.

[0115] The expansion of the tape 43 may be performed manually by an operator or may be carried out by a dedicated expansion device. FIG. 10(A) is a partial cross-sectional front view showing the expansion device 40.

[0116] The expansion device 40 has a cylindrical drum 42. A plurality of rollers 44 are provided along the circumferential direction of the drum 42 at the upper end portion of the drum 42. In addition, a plurality of support members 46 are arranged outside the drum 42. An air cylinder (not shown) for moving (raising and lowering) the support members 46 along the vertical direction is connected to the lower end portion of each of the support members 46.

[0117] An annular table 48 is fixed to the upper ends of a plurality of support members 46. A circular opening that penetrates the table 48 in the thickness direction is provided at the center of the table 48. Note that the diameter of the opening of the table 48 is larger than the diameter of the drum 42, and the upper end of the drum 42 can be inserted into the opening of the table 48. A plurality of clamps 50 that grip and fix a frame 45 supporting the wafer 11 are arranged on the outer peripheral portion of the table 48.

[0118] When dividing the wafer 11, first, the support member 46 is moved by an air cylinder (not shown), and the upper end of the roller 44 and the upper surface of the table 48 are arranged at substantially the same height position. Then, the frame 45 is placed on the table 48, and the frame 45 is fixed by a plurality of clamps 50. At this time, the wafer 11 is arranged so as to overlap the region inside the drum 42.

[0119] Next, the support member 46 is lowered by an air cylinder (not shown) to pull down the table 48. As a result, the tape 43 is pulled radially outward while being supported by the roller 44. As a result, the tape 43 is radially expanded.

[0120] FIG. 10(B) is a partial cross-sectional front view showing an expansion device 40 that expands the tape 43. When the tape 43 is expanded, an external force is applied to the wafer 11 to which the tape 43 is attached. As a result, the substrate 13 is divided starting from the crack 39. In addition, in the device region 21 of the wafer 11 (see FIG. 8(B) etc.), laser processing grooves 29b are formed in the laminate 15. When an external force is applied to the wafer 11, the laser processing grooves 29b function as a division starting point, and the laminate 15 is divided along the laser processing grooves 29b.

[0121] When the substrate 13 and the laminate 15 are each divided along the division planned line 17, the wafer 11 is divided into a plurality of chips 47 each including a device 19 (see FIG. 1(A) etc.). Then, the chips 47 are peeled off from the tape 43 and picked up, and mounted on, for example, a predetermined mounting substrate. Note that when the tape 43 is extended, a gap is formed between the chips 47, facilitating the pickup of the chips 47.

[0122] As described above, in this embodiment, before the division of the wafer 11, laser processing grooves 29 are formed along the division planned line 17 by irradiation with the laser beam 12. The irradiation conditions of the laser beam 12 are set such that melting of the laminate 15 is likely to occur in the outer peripheral surplus region 23 rather than in the device region 21.

[0123] According to this embodiment, laser processing grooves 29b having a depth that does not reach the substrate 13 are formed in the device region 21 of the wafer 11. Thereby, while avoiding the occurrence of processing marks remaining on the substrate 13 and a decrease in the flexural strength of the chip 47, laser processing grooves 29b that function as division starting points of the laminate 15 can be formed. Further, laser processing grooves 29a deeper than the laser processing grooves 29b formed in the device region 21 are formed in the outer peripheral surplus region 23 of the wafer 11. Thereby, the laser processing grooves 29a in the outer peripheral surplus region 23 become easier to observe from the back surface 13b side of the substrate 13, and alignment between the wafer 11 and the laser beam 16 based on the position of the laser processing grooves 29a becomes easier. As a result, it becomes possible to appropriately adjust the irradiation position of the laser beam 16 while suppressing a decrease in the strength of the chip 47.

[0124] Note that the structures, methods, etc. according to the above embodiment can be appropriately modified and implemented without departing from the scope of the object of the present invention.

Explanation of Reference Numerals

[0125] 11 Wafer 11a Front surface (first surface) 11b Back surface (second surface) 13 Substrate 13a surface (first surface) 13b back surface (second surface) 15 laminate 17 planned division line (street) 19 device 21 device area 23 outer peripheral surplus area 25 tape 27 frame 27a opening 29, 29a, 29b laser processing grooves 31 tape 33 frame 35 modified layer (altered layer) 37 modified area 39 crack 41 protective sheet 43 tape 45 frame 47 chip 2 laser processing device 4 chuck table (holding table) 4a holding surface 6 clamp 8 laser irradiation unit 10 head 12 laser beam (first laser beam) 14 imaging unit 16 laser beam (second laser beam) 20 grinding device 22 chuck table 22a holding surface 24 grinding unit 26 spindle 28 mount 30 grinding wheel 32 base 34 grinding stone 40 expanding device 42 drum 44 roller 46 support member 48 table 50 clamp

Claims

1. A preparation step of preparing a wafer including a substrate and a laminate provided on the surface side of the substrate, the wafer including a device region in which a plurality of devices are provided in a plurality of regions partitioned by a plurality of division planned lines arranged to intersect each other, and an outer peripheral surplus region surrounding the device region; A laser processing groove forming step of irradiating the laminate with a first laser beam having a wavelength that is absorbable by the laminate from the laminate side of the wafer along the division planned line to form a laser processing groove along the division planned line, including: The irradiation conditions of the first laser beam are set such that melting of the laminate is more likely to occur in the outer peripheral surplus region than in the device region. A method for manufacturing a wafer, characterized in that an overlap rate of the first laser beam irradiated on the outer peripheral surplus region is larger than an overlap rate of the first laser beam irradiated on the device region.

2. The method for manufacturing a wafer according to claim 1, characterized in that an energy density of the first laser beam irradiated on the outer peripheral surplus region is larger than an energy density of the first laser beam irradiated on the device region.

3. The method for manufacturing a wafer according to claim 1 or 2, characterized in that a peak power of the first laser beam irradiated on the outer peripheral surplus region is larger than a peak power of the first laser beam irradiated on the device region.

4. A preparation step of preparing a wafer including a substrate and a laminate provided on the surface side of the substrate, the wafer including a device region in which a plurality of devices are provided in a plurality of regions partitioned by a plurality of division planned lines arranged to intersect each other, and an outer peripheral surplus region surrounding the device region; A laser processing groove forming step of irradiating the laminate with a first laser beam having a wavelength that is absorbable by the laminate from the laminate side of the wafer along the division planned line to form a laser processing groove along the division planned line, including: The laser processing groove formed in the outer peripheral surplus region is deeper than the laser processing groove formed in the device region. In the device region, a laser processing groove having a depth that does not reach the substrate is formed. A method for manufacturing a wafer, characterized in that a laser processing groove having a depth reaching the substrate is formed in the outer peripheral surplus region.

5. A preparation step of preparing a wafer including a substrate and a laminate provided on the surface side of the substrate, the wafer including a device region in which a plurality of devices are provided in a plurality of regions partitioned by a plurality of division planned lines arranged to intersect each other, and an outer peripheral surplus region surrounding the device region; A laser processing groove forming step of irradiating a first laser beam having a wavelength that is absorbable by the laminate from the laminate side of the wafer along the division planned line to form a laser processing groove along the division planned line; After the laser processing groove forming step, a modified layer forming step of positioning a condensing position of a second laser beam having a wavelength that is transmissive to the substrate inside the substrate and irradiating the second laser beam from the back side of the substrate along the division planned line to form a modified layer along the division planned line; After the modified layer forming step, a dividing step of applying an external force to the wafer to divide the wafer along the division planned line. The irradiation conditions of the first laser beam are set so that melting of the laminate is more likely to occur in the outer peripheral surplus region than in the device region. A method for manufacturing a chip, characterized in that an overlap rate of the first laser beam irradiated to the outer peripheral surplus region is larger than an overlap rate of the first laser beam irradiated to the device region.

6. A preparation step of preparing a wafer including a substrate and a laminate provided on the surface side of the substrate, the wafer including a device region in which a plurality of devices are provided in a plurality of regions partitioned by a plurality of division planned lines arranged to intersect each other, and an outer peripheral surplus region surrounding the device region; A laser processing groove forming step of irradiating a first laser beam having a wavelength that is absorbable by the laminate from the laminate side of the wafer along the planned division line to form a laser processing groove along the planned division line; After performing the laser processing groove forming step, observing the laser processing groove formed in the outer peripheral surplus region from the back side of the substrate, and adjusting the positional relationship between the wafer and the second laser beam so that the second laser beam is irradiated to a region overlapping the laser processing groove; an alignment step; After performing the alignment step, positioning the condensing position of the second laser beam having a wavelength that is transmissive through the substrate inside the substrate, and irradiating the second laser beam from the back side of the substrate along the planned division line to form a modified layer along the planned division line; a modified layer forming step; After performing the modified layer forming step, applying an external force to the wafer to divide the wafer along the planned division line; a dividing step, comprising: The irradiation conditions of the first laser beam are set so that melting of the laminate is likely to occur in the outer peripheral surplus region rather than in the device region. A method for manufacturing a chip, characterized in that.

7. The energy density of the first laser beam irradiated to the outer peripheral surplus region is greater than the energy density of the first laser beam irradiated to the device region. The method for manufacturing a chip according to claim 5 or 6, characterized in that.

8. The peak power of the first laser beam irradiated to the outer peripheral surplus region is greater than the peak power of the first laser beam irradiated to the device region. The method for manufacturing a chip according to any one of claims 5 to 7, characterized in that.

9. A preparation step of preparing a wafer including a substrate and a laminate provided on the front side of the substrate, and having a device region in which a plurality of devices are provided in a plurality of regions partitioned by a plurality of planned division lines arranged to intersect each other, and an outer peripheral surplus region surrounding the device region; A laser processing groove forming step of irradiating a first laser beam having a wavelength that is absorbent to the laminate from the laminate side of the wafer along the planned division line to form a laser processing groove along the planned division line; After performing the laser processing groove forming step, a modified layer forming step of positioning the condensing position of a second laser beam having a wavelength that is transmissive to the substrate inside the substrate and irradiating the second laser beam from the back side of the substrate along the planned division line to form a modified layer along the planned division line; After performing the modified layer forming step, a dividing step of applying an external force to the wafer to divide the wafer along the planned division line, including: The laser processing groove formed in the outer peripheral surplus region is deeper than the laser processing groove formed in the device region, In the device region, a laser processing groove having a depth that does not reach the substrate is formed, A method for manufacturing a chip, characterized in that a laser processing groove having a depth reaching the substrate is formed in the outer peripheral surplus region.

10. A preparation step of preparing a wafer including a substrate and a laminate provided on the surface side of the substrate, and having a device region in which a plurality of devices are provided in a plurality of regions partitioned by a plurality of planned division lines arranged to intersect each other, and an outer peripheral surplus region surrounding the device region; A laser processing groove forming step of irradiating a first laser beam having a wavelength that is absorbent to the laminate from the laminate side of the wafer along the planned division line to form a laser processing groove along the planned division line; After performing the laser processing groove forming step, observing the laser processing groove formed in the outer peripheral surplus region from the back side of the substrate, and adjusting the positional relationship between the wafer and the second laser beam so that the second laser beam is irradiated to a region overlapping the laser processing groove; a positioning step; After performing the alignment step, position the focusing position of the second laser beam having a wavelength that is transmissive to the substrate inside the substrate, and irradiate the second laser beam from the back side of the substrate along the planned division line to form a modified layer along the planned division line. A modified layer forming step; After performing the modified layer forming step, apply an external force to the wafer to divide the wafer along the planned division line, including: The laser processing groove formed in the outer peripheral surplus region is deeper than the laser processing groove formed in the device region, and a method for manufacturing a chip is characterized in that.

11. A wafer including a substrate and a laminate provided on the front side of the substrate, having a device region in which a plurality of devices are provided in a plurality of regions partitioned by a plurality of planned division lines arranged in a grid pattern, and an outer peripheral surplus region surrounding the device region, The laminate is provided with a groove along the planned division line, The groove provided in the outer peripheral surplus region is deeper than the groove provided in the device region, The device region is provided with a groove having a depth that does not reach the substrate, The outer peripheral surplus region is provided with a groove having a depth that reaches the substrate, and the wafer is characterized in that.

12. A groove-formed wafer preparation step of preparing a wafer including a substrate and a laminate provided on the front side of the substrate, having a device region in which a plurality of devices are provided in a plurality of regions partitioned by a plurality of planned division lines arranged to intersect each other, and an outer peripheral surplus region surrounding the device region, and the laminate is provided with a groove along the planned division line; An alignment step of observing the groove formed in the outer peripheral surplus region from the back side of the substrate and adjusting the positional relationship between the wafer and the laser beam so that the laser beam is irradiated to a region overlapping the groove; A method for aligning a laser beam, characterized in that the groove provided in the outer peripheral surplus region is deeper than the groove provided in the device region. **Claim 13** In the device region, a groove having a depth that does not reach the substrate is provided. The method for aligning a laser beam according to claim 12, characterized in that a groove having a depth reaching the substrate is provided in the outer peripheral surplus region.

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