Diamond wafer dividing method and chip manufacturing method

Abstract

To provide a diamond wafer dividing method capable of appropriately dividing a diamond wafer in comparison with a conventional method.SOLUTION: The present invention relates to a diamond wafer dividing method used for dividing a diamond wafer having a surface along a {100} plane along with predetermined dividing lines in a <110> direction. The diamond wafer dividing method includes: a first modified layer forming step of forming a first modified layer in a linear first region along with the predetermined dividing lines inside of the diamond wafer; a second modified layer forming step of forming a second modified layer in a linear second region deviated from the first region in a width direction and a thickness direction with respect to the surface; and a dividing step of dividing the diamond wafer along with the predetermined dividing lines by applying a force to the diamond wafer in which the first modified layer and the second modified layer are formed.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a method for dividing a diamond wafer and a method for manufacturing chips using the same. [Background technology]

[0002] Device chips equipped with devices such as electronic circuits are essential components of electronic devices such as mobile phones and personal computers. Device chips are obtained by dividing the front surface of a wafer made of a material such as silicon (Si) or silicon carbide (SiC) into multiple regions along planned division lines called streets, forming devices in each region, and then dividing the wafer along these planned division lines.

[0003] When dividing a wafer into small pieces such as device chips, for example, a cutting device with a circular tool called a cutting blade attached to a spindle is used. The cutting blade is rotated at high speed and cuts into the wafer along the planned division lines while supplying a liquid such as pure water, thereby cutting the wafer and dividing it into multiple small pieces (see, for example, Patent Document 1).

[0004] In recent years, diamond has been attracting attention due to its superior dielectric strength and thermal conductivity compared to materials such as silicon and silicon carbide. For example, if a device is formed using a diamond wafer made of single crystal diamond, it becomes easier to realize a device with higher performance than when a wafer made of materials such as silicon or silicon carbide is used.

[0005] However, because diamond has an extremely high Mohs hardness, the above-mentioned method of cutting with a cutting blade does not necessarily allow for proper division of the diamond wafer. Specifically, for example, as the processing progresses, the cutting blade rapidly wears and thins, changing the size of the pieces cut out from the diamond wafer. In addition, the life of the cutting blade becomes extremely short, which is a problem in that it requires a great deal of cost to divide the diamond wafer.

[0006] Therefore, a method has been studied in which the inside of a diamond wafer is modified along a planned dividing line with a laser beam, and then a force is applied to divide the diamond wafer starting from the region that has become brittle due to the modification (hereinafter referred to as the modified layer) (see, for example, Patent Document 2). This method does not use tools such as cutting blades for mechanically processing the diamond wafer, and therefore does not cause various problems caused by tool wear. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 3-198363 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-192370 Summary of the Invention [Problem to be solved by the invention]

[0008] When dividing a thick wafer by the above-mentioned method of forming a modified layer, a plurality of modified layers are generally stacked in the thickness direction (depth direction). However, even if such a plurality of modified layers stacked in the thickness direction are formed on a diamond wafer, it is not always possible to divide the diamond wafer appropriately.

[0009] Therefore, an object of the present invention is to provide a method for dividing a diamond wafer that can divide a diamond wafer more appropriately than conventional methods, and a method for manufacturing chips using the same. [Means for solving the problem]

[0010] According to one aspect of the present invention, a diamond wafer having a surface along a {100} plane is <110> The present invention provides a method for dividing a diamond wafer along a planned dividing line extending in a direction, the method comprising: a first modified layer forming step of irradiating a linear first region inside the diamond wafer along the planned dividing line with a laser beam of a wavelength that passes through the diamond wafer so as to focus the laser beam, thereby forming a first modified layer in the first region; a second modified layer forming step of irradiating a linear second region inside the diamond wafer that is shifted from the first region in both the width direction parallel to the surface and perpendicular to the first region and the thickness direction perpendicular to the surface with a laser beam of a wavelength that passes through the diamond wafer so as to focus the laser beam, thereby forming a second modified layer in the second region; and a dividing step of applying a force to the diamond wafer on which the first modified layer and the second modified layer have been formed, thereby dividing the diamond wafer along the planned dividing line.

[0011] Preferably, the method further includes, before the dividing step, a third modified layer forming step of forming a third modified layer in a linear third region inside the diamond wafer, the third region being shifted from the first region in the thickness direction and shifted from the second region in the width direction and the thickness direction, by irradiating the third region with a laser beam of a wavelength that is transmitted through the diamond wafer in a focused manner.

[0012] Preferably, in the second modified layer forming step, the distance in the width direction between the first region and the second region is 5 μm or more and 50 μm or less, and preferably, in the second modified layer forming step, the angle between the surface and a plane passing through the first region and the second region is 27° or more and 72° or less.

[0013] According to another aspect of the present invention, there is provided a chip manufacturing method for manufacturing a plurality of chips by dividing a diamond wafer using the above-described diamond wafer dividing method. [Effects of the Invention]

[0014] In a method for dividing a diamond wafer according to one aspect of the present invention, a diamond wafer having a surface along a {100} plane is divided into <110> When dividing the diamond wafer along a dividing line extending in the direction, a first modified layer is formed in a linear first region along the dividing line inside the diamond wafer, and a second modified layer is formed in a linear second region inside the diamond wafer displaced from the first region in the width direction and thickness direction, so that cleavage progresses more easily along the {111} plane inclined relative to the surface than when a plurality of modified layers are stacked in the thickness direction of the diamond wafer. Thus, according to the method for dividing a diamond wafer according to one aspect of the present invention, the diamond wafer can be divided more appropriately than conventional methods. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a perspective view schematically showing a diamond wafer. [Figure 2] FIG. 2 is a diagram showing a schematic diagram of the crystal structure of diamond. [Figure 3] FIG. 3 is a perspective view schematically showing a frame unit including a diamond wafer. [Figure 4] FIG. 4 is a cross-sectional view schematically showing how a modified layer is formed inside a diamond wafer. [Figure 5] FIG. 5 is a cross-sectional view schematically showing a region inside the diamond wafer where the laser beam is focused. [Figure 6] FIG. 6 is a cross-sectional view schematically showing a state in which a first modified layer has been formed on a diamond wafer. [Figure 7] FIG. 7 is a cross-sectional view schematically showing a state in which a second modified layer has been formed on a diamond wafer. [Figure 8]FIG. 8 is a cross-sectional view schematically showing a state in which a third modified layer has been formed on a diamond wafer. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a perspective view showing a diamond wafer 11 to be divided by the diamond wafer dividing method of this embodiment, and Fig. 2 is a diagram showing the structure of a diamond crystal. As shown in Fig. 1, the diamond wafer 11 is formed in a disk shape from substantially single-crystal diamond, and has a circular front surface 11a and a circular back surface 11b opposite to the front surface 11a.

[0017] The orientation of the diamond crystal constituting the diamond wafer 11 is adjusted so that the (001) plane (for example, crystal plane A in FIG. 2) is roughly parallel to the front surface 11a and back surface 11b. However, it is sufficient that the front surface 11a and back surface 11b are roughly parallel to a crystal plane equivalent to the (001) plane. In other words, the front surface 11a and back surface 11b are aligned with the {100} plane of the diamond crystal.

[0018] The surface 11a of the diamond wafer 11 is divided into a plurality of small regions by a plurality of first planned division lines (first streets) 13a extending along the

[0110] direction (for example, direction B in Figure 2) and second planned division lines (second streets) 13b extending in a direction generally perpendicular to the first planned division lines 13a, and each small region is provided with a device 15 such as a power device or an IC (Integrated Circuit).

[0019] That is, the direction in which the second division line 13b extends is equivalent to the

[0110] direction, and both the first division line 13a and the second division line 13b extend in the direction <110> The first division lines 13a and the second division lines 13b each extend in the direction perpendicular to the sheet W. Both the first division lines 13a and the second division lines 13b have a predetermined width.

[0020] This diamond wafer 11 has the property of easily cleaving along a crystal plane equivalent to the (111) plane (for example, crystal plane C in FIG. 2). In other words, the diamond wafer 11 is easily broken along the {111} plane. In this embodiment, since the surface 11a is roughly parallel to the (001) plane, the diamond wafer 11 is easily broken along a plane tilted relative to this surface 11a.

[0021] Therefore, simply stacking a plurality of modified layers in the thickness direction of the diamond wafer 11 does not result in a problem where the first dividing line 13a or the second dividing line 13b (i.e., <110> In some cases, it may not be possible to properly divide the diamond wafer 11 along a plane parallel to the cutting direction.

[0022] In this embodiment, a disk-shaped diamond wafer 11 made substantially of single-crystal diamond is exemplified, but there are no limitations on the shape, structure, size, etc. of the diamond wafer 11. Similarly, there are no limitations on the type, number, shape, structure, size, arrangement, etc. of the devices 15.

[0023] When dividing the diamond wafer 11 configured in this manner along the first dividing lines 13a and the second dividing lines 13b, for example, a frame unit including the diamond wafer 11 is formed (frame unit forming step). Fig. 3 is a perspective view schematically showing a frame unit 21 including the diamond wafer 11.

[0024] Specifically, a tape 23 large enough to cover the entire surface 11a of the diamond wafer 11 is attached to the surface 11a side of the diamond wafer 11. An annular frame 25 surrounding the diamond wafer 11 is fixed to the peripheral edge of the tape 23. This allows the formation of a frame unit 21 in which the diamond wafer 11 and the annular frame 25 surrounding the diamond wafer 11 are integrated via the tape 23. Forming such a frame unit 21 makes it easier to handle the diamond wafer 11.

[0025] After the frame unit 21 is formed, modified layers that serve as starting points when dividing the diamond wafer 11 are formed inside the diamond wafer 11. Figure 4 is a cross-sectional view that schematically shows how modified layers 17 are formed inside the diamond wafer 11. In this embodiment, for example, a laser processing device 2 shown in Figure 4 is used to form a plurality of modified layers 17 inside the diamond wafer 11.

[0026] This laser processing device 2 is equipped with a chuck table 4 used to hold a diamond wafer 11. The chuck table 4 includes a disk-shaped frame 6 made of a metal such as stainless steel, and a holding plate 8 made of a porous disk-shaped material such as ceramics and placed in a recess 6a that opens to the top surface of the frame 6.

[0027] The upper surface of the holding plate 8 functions as a holding surface 8a that holds the diamond wafer 11. The recess 6a of the frame 6 is connected to a suction source (not shown) such as a vacuum pump via a flow path 6b or the like provided inside the frame 6. The flow path 6b or the like is provided with a valve (not shown) that can control the flow of fluid. Therefore, if the valve is opened while the suction source is operating, the negative pressure generated by the suction source acts on the holding surface 8a of the holding plate 8.

[0028] A plurality of clamp mechanisms 10 used to secure the frame 25 are provided around the periphery of the frame 6. A rotational drive source (not shown), such as a motor, is connected to the lower part of the frame 6, and the chuck table 4 can rotate, for example, around a rotation axis that is approximately perpendicular to the holding surface 8a. The frame 6 is also supported by a movement mechanism (not shown), and the chuck table 4 can move, for example, in a direction approximately parallel to the holding surface 8a (horizontal direction).

[0029] A laser irradiation head 12 is disposed above the chuck table 4. The laser irradiation head 12 focuses a laser beam 12a generated by a laser oscillator (not shown) at a predetermined position. The laser oscillator contains a laser medium such as Nd:YAG, and is configured to generate a pulsed laser beam 12a having a wavelength that can pass through the diamond wafer 11.

[0030] When forming the modified layer 17 inside the diamond wafer 11, first, the diamond wafer 11 is held by the chuck table 4 of the laser processing device 2 (holding step). Specifically, the frame unit 21 is placed on the chuck table 4 so that the tape 23 attached to the front surface 11a of the diamond wafer 11 is brought into contact with the holding surface 8a of the chuck table 4. Thereafter, a negative pressure is applied to the holding surface 8a, and the tape 23 is sucked by the holding surface 8a.

[0031] After the tape 23 is sucked by the holding surface 8a, the frame 25 is gripped by the clamping mechanism 10 provided around the chuck table 4. The clamping mechanism 10 may grip the frame 25 simultaneously with or before the tape 23 is brought into contact with the holding surface 8a. As a result, the diamond wafer 11 is held on the chuck table 4 so that the back surface 11b side is exposed upward.

[0032] After the diamond wafer 11 is held on the chuck table 4, a laser beam 12a having a wavelength that can pass through the diamond wafer 11 is irradiated so as to be focused on each of a plurality of regions inside the diamond wafer 11, thereby forming a plurality of modified layers 17. Figure 5 is a cross-sectional view that schematically shows a plurality of regions inside the diamond wafer 11 where the laser beam 12a is focused. Note that Figure 5 shows a cross section perpendicular to the first planned dividing line 13a.

[0033] 5, in this embodiment, three regions for focusing the laser beam 12a are set for each first planned dividing line 13a. The first region 11c is a linear region located a predetermined distance from the surface 11a of the diamond wafer 11, and is set along the length of the target first planned dividing line 13a.

[0034] The second region 11d is a linear region shifted from the first region 11c in a width direction (width direction of the first planned dividing lines 13a) parallel to the surface 11a and perpendicular to the first region 11c, and in a thickness direction (thickness direction of the diamond wafer 11) perpendicular to the surface 11a. The second region 11d is also set along the length direction of the target first planned dividing lines 13a.

[0035] The third region 11e is a linear region that is offset from the first region 11c in the thickness direction and offset from the first region 11c in both the width direction and the thickness direction. However, the third region 11e may also be offset from the first region 11c in the width direction. In other words, the third region 11e does not have to be offset from the first region 11c only in the thickness direction.

[0036] The third region 11e is also set along the length direction of the target first planned division line 13a. That is, the first region 11c, the second region 11d, and the third region 11e are generally parallel to one another. Furthermore, the lengths of the first region 11c, the second region 11d, and the third region 11e are all approximately the same as the length of the target first planned division line 13a.

[0037] The distance d (shift distance, interval) in the width direction between the first region 11c and the second region 11d is preferably set to 5 μm or more and 50 μm or less, typically 28 μm. The angle θ1 formed between a plane passing through the first region 11c and the second region 11d and the front surface 11a (or the back surface 11b) is preferably set to 27° or more and 72° or less, typically 54° to 55°.

[0038] The same applies to the relationship between the second region 11d and the third region 11e. That is, the distance d (shift distance, interval) in the width direction between the second region 11d and the third region 11e is preferably set to 5 μm or more and 50 μm or less, typically 28 μm. Furthermore, the angle θ2 formed between a plane passing through the second region 11d and the third region 11e and the front surface 11a (or the back surface 11b) is preferably set to 27° or more and 72° or less, typically 54° to 55°.

[0039] By setting the first region 11c, the second region 11d, and the third region 11e to satisfy these conditions, cracks can be easily propagated along the {111} plane, for example, between the modified layer 17 formed in the first region 11c and the modified layer 17 formed in the second region 11d, and between the modified layer 17 formed in the second region 11d and the modified layer 17 formed in the third region 11e. As a result, the diamond wafer 11 can be appropriately divided along the target first planned division lines 13a.

[0040] An example of a procedure for forming a plurality of modified layers 17 along the first planned dividing lines 13a of the diamond wafer 11 will be described below. First, the laser beam 12a is irradiated so as to be focused onto the first region 11c described above, thereby forming the modified layer 17 in the first region 11c (first modified layer forming step).

[0041] Specifically, for example, the angle around the rotation axis of the chuck table 4 is adjusted so that the target first planned division line 13a is roughly parallel to the direction of movement of the chuck table 4. Then, the chuck table 4 is moved to align the position of the laser irradiation head 12 above the extension line of the target first region 11c.

[0042] 4, the chuck table 4 is moved in a direction substantially parallel to the first planned division line 13a while irradiating the laser beam 12a from the laser irradiation head 12. Here, the position of the focal point where the laser beam 12a is focused is adjusted so as to overlap with the above-mentioned first region 11c.

[0043] There are no particular limitations on other conditions, but it is advisable to set the power of the laser beam 12a, for example, to 0.2 W to 2 W, typically 0.8 W, the repetition frequency of the laser beam 12a, for example, to 20 KHz to 200 KHz, typically 50 KHz, and the movement speed of the chuck table 4, for example, to 100 mm / s to 800 mm / s, typically 400 mm / s.

[0044] This causes multiphoton absorption near the focal point of the laser beam 12a, and a modified layer 17 can be formed in the linear first region 11c inside the diamond wafer 11. Figure 6 is a cross-sectional view schematically showing the first modified layer 17a formed in the diamond wafer 11. Note that Figure 6 also shows a cross section perpendicular to the first planned dividing line 13a.

[0045] After the first modified layer 17a is formed in the first region 11c, the modified layer 17 is formed in the second region 11d in the same manner (second modified layer forming step). Specifically, the chuck table 4 is moved to align the laser irradiation head 12 with a position above an extension line of the target second region 11d.

[0046] Thereafter, the chuck table 4 is moved in a direction substantially parallel to the first planned division line 13a while irradiating the laser beam 12a from the laser irradiation head 12. The position of the focal point of the laser beam 12a is adjusted so as to overlap with the second region 11d described above. Other conditions may be the same as those for forming the first modified layer 17a, for example.

[0047] This causes multiphoton absorption near the focal point of the laser beam 12a, and a modified layer 17 can be formed in the linear second region 11d inside the diamond wafer 11. Figure 7 is a cross-sectional view schematically showing the second modified layer 17b formed in the diamond wafer 11. Note that Figure 7 also shows a cross section perpendicular to the first planned dividing line 13a.

[0048] When the first modified layer 17a and the second modified layer 17b are formed so as to satisfy the positional relationship described above, stress acting from both the first modified layer 17a and the second modified layer 17b makes it easier for cracks 19 along the {111} plane to propagate between the first modified layer 17a and the second modified layer 17b, as shown in Fig. 7. This allows the diamond wafer 11 to be appropriately divided along the target first planned division lines 13a.

[0049] After forming the second modified layer 17b in the second region 11d, the modified layer 17 is formed in the third region 11e in the same procedure (third modified layer forming step). Specifically, the chuck table 4 is moved to align the position of the laser irradiation head 12 above the extension line of the target third region 11e.

[0050] Thereafter, the chuck table 4 is moved in a direction substantially parallel to the first planned division line 13a while irradiating the laser beam 12a from the laser irradiation head 12. The position of the focal point of the laser beam 12a is adjusted so as to overlap with the third region 11e. Other conditions may be the same as those for forming the first modified layer 17a, for example.

[0051] This causes multiphoton absorption near the focal point of the laser beam 12a, and a modified layer 17 can be formed in a linear third region 11e inside the diamond wafer 11. Figure 8 is a cross-sectional view schematically showing the third modified layer 17c formed in the diamond wafer 11. Note that Figure 8 also shows a cross section perpendicular to the first planned dividing line 13a.

[0052] When the second modified layer 17b and the third modified layer 17c are formed so as to satisfy the positional relationship described above, stress acting from both the second modified layer 17b and the third modified layer 17c makes it easier for cracks 19 along the {111} plane to propagate between the second modified layer 17b and the third modified layer 17c, as shown in Fig. 8. This allows the diamond wafer 11 to be appropriately divided along the target first planned division lines 13a.

[0053] Here, the procedure for forming the first modified layer 17a, the second modified layer 17b, and the third modified layer 17c has been described, focusing on the target first planned division line 13a. However, the first modified layer 17a, the second modified layer 17b, and the third modified layer 17c are also formed on the other first planned division lines 13a and second planned division lines 13b using a similar procedure.

[0054] However, there is no particular limitation on the order in which the first modified layer 17a, the second modified layer 17b, and the third modified layer 17c are formed. For example, the first modified layer 17a can be formed along all of the first and second division lines 13a, 13b, then the second modified layer 17b can be formed along all of the first and second division lines 13a, 13b, and then the third modified layer 17c can be formed along all of the first and second division lines 13a, 13b.

[0055] In other words, the present invention is not limited to a configuration in which the first modified layer 17a, the second modified layer 17b, and the third modified layer 17c are formed along one first planned division line 13a or one second planned division line 13b, and then the first modified layer 17a, the second modified layer 17b, and the third modified layer 17c are formed along another first planned division line 13a or another second planned division line 13b.

[0056] After the first modified layer 17a, the second modified layer 17b, and the third modified layer 17c are formed along all of the first planned dividing lines 13a and the second planned dividing lines 13b of the diamond wafer 11, respectively, force is applied to the diamond wafer 11 to divide the diamond wafer 11 into a plurality of chips along the first planned dividing lines 13a and the second planned dividing lines 13b (dividing step).

[0057] In this embodiment, the first modified layer 17a, the second modified layer 17b, and the third modified layer 17c are formed so as to satisfy the positional relationship described above. Therefore, by applying an appropriate force to the diamond wafer 11, the diamond wafer 11 can be divided along the first planned dividing lines 13a and the second planned dividing lines 13b to form a plurality of chips.

[0058] There is no particular limitation on the method for applying force to the diamond wafer 11. For example, the force can be applied by expanding the tape 23 or by pressing a blade-shaped member against the diamond wafer 11.

[0059] As described above, in the method for dividing a diamond wafer according to this embodiment, the diamond wafer 11 having the surface 11a along the {100} plane is divided into <110> When dividing the diamond wafer 11 along the first and second dividing lines 13a and 13b in the width direction, a first modified layer 17a is formed in a linear first region 11c inside the diamond wafer 11, and a second modified layer 17b is formed in a linear second region 11d inside the diamond wafer 11 shifted from the first region 11c in the width direction and thickness direction. This makes it easier for cleavage to progress along the {111} plane inclined relative to the surface 11a compared to when multiple modified layers are stacked in the thickness direction of the diamond wafer 11.

[0060] Therefore, the diamond wafer dividing method according to this embodiment allows the diamond wafer 11 to be divided more appropriately than conventional methods. Furthermore, by using the diamond wafer dividing method according to this embodiment in a chip manufacturing method, the diamond wafer 11 can be divided appropriately to manufacture a plurality of high-quality chips.

[0061] The present invention is not limited to the above-described embodiment and can be practiced with various modifications. For example, in the above-described embodiment, three modified layers 17 (the first modified layer 17a, the second modified layer 17b, and the third modified layer 17c) are formed along each of the first planned division lines 13a and each of the second planned division lines 13b. However, the present invention can be applied to the case where two or more modified layers are formed along each planned division line.

[0062] In particular, when forming four or more modified layers, it is preferable to match the positional relationship between the 2n-1th layer and the 2nth layer (n is an integer of 2 or more) to the positional relationship between the first layer (first modified layer 17a) and the second layer (second modified layer 17b).It is also preferable to match the positional relationship between the 2nth layer and the 2n+1th layer to the positional relationship between the second layer (second modified layer 17b) and the third layer (third modified layer 17c).

[0063] In addition, the structures, methods, etc. according to the above-described embodiments and modifications can be modified as appropriate without departing from the scope of the present invention. [Explanation of symbols]

[0064] 11: Diamond wafer 11a: Surface 11b: Back side 11c: 1st area 11d: 2nd area 11e: 3rd area 13a: First planned division line (First Street) 13b: Second planned division line (Second Street) 15: Device 17: Modified layer 17a: First modified layer 17b: Second modified layer 17c: Third modified layer 19: Crack 21: Frame unit 23: Tape 25: Frame 2: Laser processing equipment 4: Chuck table 6: Frame 6a: Recess 6b: Flow path 8: Holding plate 8a: Holding surface 10: Clamping mechanism 12: Laser irradiation head 12a: Laser beam

Claims

1. A method for dividing a diamond wafer, which is used to divide a diamond wafer having a surface along a {100} plane along a dividing line along a <110> direction, comprising: a first modified layer forming step of irradiating a linear first region along the planned dividing line inside the diamond wafer with a laser beam having a wavelength that is transmitted through the diamond wafer so as to be focused, thereby forming a first modified layer in the first region; a second modified layer forming step of irradiating a linear second region within the diamond wafer, the second region being shifted from the first region in a width direction parallel to the surface and perpendicular to the first region and in a thickness direction perpendicular to the surface, with a laser beam having a wavelength that can be transmitted through the diamond wafer so as to be focused, thereby forming a second modified layer in the second region; a dividing step of dividing the diamond wafer along the planned dividing line by applying force to the diamond wafer on which the first modified layer and the second modified layer have been formed.

2. Prior to the division step, 2. The method for dividing a diamond wafer according to claim 1, further comprising a third modified layer forming step of forming a third modified layer in a linear third region inside the diamond wafer, the third region being shifted from the first region in the thickness direction and shifted from the second region in the width direction and the thickness direction, by irradiating the third region with a laser beam of a wavelength that passes through the diamond wafer in a focused manner.

3. 3. The method for dividing a diamond wafer according to claim 1, wherein in the second modified layer forming step, the distance in the width direction between the first region and the second region is set to 5 μm or more and 50 μm or less.

4. A method for dividing a diamond wafer as described in any one of claims 1 to 3, wherein in the second modified layer formation step, the angle between the surface and a plane passing through the first region and the second region is 27° or more and 72° or less.

5. A method for manufacturing chips, comprising dividing a diamond wafer using the method for dividing a diamond wafer according to any one of claims 1 to 4, thereby manufacturing a plurality of chips.

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