Single crystal silicon wafer and method for dividing same

Abstract

To suppress a yield of a chip of an optical device manufactured from a single crystal silicon wafer of which a perpendicular of its front surface is along a crystal orientation [100].SOLUTION: A plurality of regions in each of which an optical device is formed on a front surface side of a single crystal silicon wafer having a perpendicular of a front surface along a crystal orientation [100], is divided by a plurality of first division schedule lines and a plurality of second division schedule lines in polygonal lines crossed to the plurality of first division schedule lines in a plan view. Each of the plurality of second division schedule lines contains: a first part that is extended along a third direction in non-parallel to both of a first direction and a second direction vertical to the first direction (that is vertical to a crystal orientation [011], that is, to a direction parallel to a crystal surface (011)) in a space between a pair of adjacent first division schedule lines; and a second part that is extended along a fourth direction in non-parallel to all of the first to third directions.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a single crystal silicon wafer in which optical devices are formed in each of a plurality of regions on the front surface side and in which a perpendicular line to the front surface is aligned along a

[0100] crystal orientation, and a method for dividing the same. [Background technology]

[0002] Single crystal silicon is used in the manufacture of various devices. For example, single crystal silicon is used not only in semiconductor devices that process electrical signals by utilizing the semiconductor properties of silicon, but also in the manufacture of optical devices that process light directly without converting it into an electrical signal. Such optical devices include optical elements such as optical waveguides that are composed of a silicon core and a silicon dioxide cladding.

[0003] Chips for these devices are manufactured, for example, by dividing a single crystal silicon wafer (hereinafter, simply referred to as a wafer) on which multiple devices are formed on the front surface into regions each including an individual device. Such division of the wafer is performed, for example, by using a laser beam (see, for example, Patent Document 1).

[0004] Specifically, a modified layer and cracks arising from the modified layer are formed inside the wafer along the boundaries of the area where devices are to be formed by irradiating the wafer with a laser beam having a wavelength (e.g., 1064 nm). Then, by applying an external force to the wafer, the cracks starting from the modified layer are propagated further. As a result, the wafer can be divided along the boundaries of the area where devices are to be formed to manufacture device chips. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2002-192370 A Summary of the Invention [Problem to be solved by the invention]

[0006] Single crystal silicon is easily cleaved along the {111} or {110} crystal planes expressed in Miller indices. For example, when the perpendicular to the surface of the wafer is aligned along the Miller indices, <100> When the crystal plane is aligned along the {110} plane, the wafer is likely to be cleaved along a crystal plane perpendicular to the surface of the wafer, among equivalent specific crystal planes contained in the {110} crystal plane.

[0007] The crystal orientation parallel to the perpendicular line of the surface of the wafer is determined when the wafer is cut from a single crystal silicon ingot. <100> Wafers with their surface perpendicular to the crystal orientation

[0100] , which is one of the equivalent specific crystal orientations included in, are produced by slicing the wafer from a single crystal silicon ingot along a plane perpendicular to the crystal orientation

[0100] , i.e., along the crystal plane (100).

[0008] When the perpendicular line to the surface of the wafer is along the crystal orientation

[0100] , the wafer is likely to be cleaved along the following equivalent crystal planes contained in the crystal plane {110}:

[0009]

number

[0010] In short, the wafer is likely to be cleaved along the (011) crystal plane and a plane perpendicular thereto.

[0011] Therefore, when a wafer is used to manufacture chips for semiconductor devices, the boundaries of the regions in which the semiconductor devices are formed (the shapes of the chips) are generally set to be square or rectangular with each side aligned with the (011) crystal plane or a plane perpendicular thereto.

[0011] On the other hand, the optical waveguide included in the optical device is generally provided to be curved. In order to efficiently use the wafer, the chip of the optical device is manufactured in a shape corresponding to the shape of the optical waveguide. FIG. 5 is a plan view showing the chip of the optical device manufactured using the wafer. Note that FIG. 5 also shows the crystal orientation of the single crystal silicon used to manufacture the chip.

[0012] The chip 1 of the optical device shown in FIG. 5 is manufactured using a single crystal silicon wafer whose surface perpendicular line is aligned along the crystal orientation

[0100] . The surface of the optical device chip 1 includes a first side 1a extending along a first direction parallel to the crystal orientation

[0011] , a second side 1b extending along a second direction perpendicular to the first direction and having one end overlapping with one end of the first side 1a, a third side 1c extending along a third direction non-parallel to both the first and second directions and having one end overlapping with the other end of the second side 1b, a fourth side 1d extending along the second direction and having one end overlapping with the other end of the third side 1c, a fifth side 1e extending along a fourth direction non-parallel to any of the first to third directions and having one end overlapping with the other end of the fourth side 1d, and a fifth side 1e extending along the second direction and having one end overlapping with the other end of the fifth side 1d. a sixth side 1f extending along the first direction and having one end overlapping with the other end of the sixth side 1f; a seventh side 1g extending along the second direction and having one end overlapping with the other end of the seventh side 1g; a ninth side 1i extending along the fourth direction and having one end overlapping with the other end of the eighth side 1h; a ninth side 1i extending along the second direction and having one end overlapping with the other end of the ninth side 1i; a tenth side 1j extending along the second direction and having one end overlapping with the other end of the ninth side 1i; an eleventh side 1k extending along the third direction and having one end overlapping with the other end of the tenth side 1j; and a twelfth side 1l extending along the second direction and having one end overlapping with the other end of the eleventh side 1k and the other end overlapping with the other end of the first side 1a.

[0013] Here, when the wafer is divided to manufacture optical device chips 1 by the method utilizing the laser beam described above, the wafer is likely to be divided along the first side 1a and seventh side 1g which are parallel to the crystal orientation

[0011] , i.e., perpendicular to the crystal plane (011), and the second side 1b, fourth side 1d, sixth side 1f, eighth side 1h, tenth side 1j and twelfth side 1l which are perpendicular to the crystal orientation

[0011] , i.e., parallel to the crystal plane (011).

[0014] In this case, however, cracks occurring along the second side 1b and the sixth side 1f tend to propagate in the linear region 3 between them, which is perpendicular to the crystal orientation

[0011] , i.e., parallel to the crystal plane (011). In this case, there is a risk of a decrease in yield when optical device chips 1 are manufactured from the wafer.

[0015] In view of this, an object of the present invention is to suppress a decrease in the yield of optical device chips manufactured from a single crystal silicon wafer having a surface perpendicular to the crystal orientation

[0100] . [Means for solving the problem]

[0016] According to one aspect of the present invention, there is provided a monocrystalline silicon wafer having a surface side with optical devices formed in each of a plurality of regions, the surface being perpendicular to the crystal orientation

[0100] , the plurality of regions being partitioned in a plan view by a plurality of first division lines extending linearly along a first direction parallel to the crystal orientation

[0011] , and a plurality of second division lines extending in a broken line shape so as to intersect with the plurality of first division lines, each of the plurality of second division lines being a plurality of first division lines. a first portion extending from a first point on one of a pair of adjacent first dividing lines among the first dividing lines along a third direction non-parallel to both the first direction and a second direction perpendicular to the first direction to a second point between the pair of first dividing lines, and a second portion extending from the second point along a fourth direction non-parallel to any of the first direction to the third direction to a third point on the other of the pair of first dividing lines.

[0017] According to another aspect of the present invention, there is provided a method for dividing the above-mentioned single crystal silicon wafer along the plurality of first planned division lines and the plurality of second planned division lines which partition the single crystal silicon wafer into the plurality of regions, the method comprising: a modified layer forming step of irradiating the single crystal silicon wafer along the plurality of first planned division lines and the plurality of second planned division lines with a laser beam having a wavelength which transmits through the single crystal silicon wafer to form a modified layer inside the single crystal silicon wafer; and a dividing step of applying an external force to the single crystal silicon wafer after the modified layer forming step to extend cracks originating from the modified layer, thereby dividing the single crystal silicon wafer along the plurality of first planned division lines and the plurality of second planned division lines. Effect of the Invention

[0018] In the present invention, a plurality of regions in which optical devices are formed on the front surface side of a single crystal silicon wafer, the normal to which is aligned along the crystal orientation

[0100] , are partitioned in a plan view by a plurality of first planned division lines and a plurality of second planned division lines in the form of broken lines intersecting the plurality of first planned division lines.

[0019] Here, the first division lines extend linearly along a first direction parallel to the crystal orientation

[0011] , i.e., perpendicular to the crystal plane (011). Therefore, it is easy to divide the wafer along the first division lines, and the extension of cracks from each of the first division lines to the inside of the regions where optical devices are formed is suppressed.

[0020] In addition, each of the multiple second planned division lines includes, between an adjacent pair of first planned division lines, a first portion extending along a third direction that is non-parallel to both the first direction and a second direction perpendicular to the first direction (perpendicular to the crystal orientation

[0011] , i.e., a direction parallel to the crystal plane (011)), and a second portion extending along a fourth direction that is non-parallel to any of the first direction to the third direction.

[0021] That is, each of the second division lines does not include a portion extending along the first direction and the second direction between a pair of adjacent first division lines. Therefore, in the present invention, the extension of cracks from each of the second division lines to the inside of the regions where optical devices are formed is suppressed. This makes it possible to suppress a decrease in the yield of optical device chips manufactured from a wafer. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a plan view diagrammatically illustrating an example of a single crystal silicon wafer. [Diagram 2] FIG. 2 is a flowchart showing an example of a method for dividing a single crystal silicon wafer. [Diagram 3] FIG. 3 is a partial cross-sectional side view that illustrates the modified layer forming step. [Figure 4] 4(A) and 4(B) are partial cross-sectional side views that typically show the state of the dividing step. [Diagram 5] FIG. 5 is a plan view showing a chip of a conventional optical device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] An embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a plan view showing a schematic diagram of an example of a single crystal silicon wafer used in the manufacture of chips for optical devices. In Fig. 1, the crystal orientation of the single crystal silicon is also shown.

[0024] 1, the perpendicular line to the surface 11a of the wafer 11 is aligned along the crystal orientation

[0100] . Also, an orientation flat 13 is formed in the outer peripheral region of the wafer 11, which is located along the crystal orientation

[0011] when viewed from the center of the surface 11a of the wafer 11.

[0025] When viewed in a plane, this wafer 11 is divided into a plurality of regions 19 by a plurality of first planned dividing lines 15 extending linearly along a first direction parallel to the crystal orientation

[0011] , and a plurality of second planned dividing lines 17 extending in a zigzag manner so as to intersect with the plurality of first planned dividing lines 15.

[0026] Specifically, each of the multiple second planned division lines 17 extends through a first point A on one of an adjacent pair of first planned division lines 15, a second point B between this pair of first planned division lines 15, and a third point C on the other of the pair of first planned division lines 15.

[0027] The first portion 17a of each of the second division lines 17, which extends linearly from the first point A to the second point B, is aligned along a third direction that is non-parallel to both the first direction and the second direction perpendicular to the first direction. The acute angle (e.g., θ1 shown in FIG. 1) between the first portion 17a and the first division lines 15 is, for example, 15° or more and 75° or less.

[0028] Further, the second portions 17b of the second division lines 17 extending linearly from the second point B to the third point C are aligned along a fourth direction that is not parallel to any of the first to third directions. The acute angle (e.g., θ2 shown in FIG. 1) between the second portions 17b and the first division lines 15 is, for example, 15° or more and 75° or less.

[0029] The first portion 17a and the second portion 17b are arranged symmetrically with respect to a straight line that passes through the second point B and is parallel to the first planned division line 15. That is, θ1 and θ2 shown in Fig. 1 are equal. Therefore, each of the multiple regions 19 has a shape in which an isosceles triangular portion with one side of a rectangle as its base is removed from the rectangle, and the isosceles triangular portion is attached to the outside of the side opposite to the one side.

[0030] An optical device is formed on the front surface 11a side of each of the multiple regions 19. The optical device includes an optical element such as an optical waveguide having a core made of silicon and a clad made of silicon dioxide. The optical waveguide is curved along the second planned dividing lines 17 that extend in a broken line shape.

[0031] 2 is a flow chart showing an example of a method for dividing the wafer 11. In this method, first, a modified layer is formed inside the wafer 11 (modified layer forming step: S1). This modified layer is formed, for example, by irradiating the wafer 11 with a laser beam having a wavelength that is transmitted through the wafer 11 along a plurality of first division lines and a plurality of second division lines.

[0032] 3 is a partially sectional side view showing the modified layer forming step (S1) in a schematic manner. Prior to the modified layer forming step (S1), the wafer 11 is integrated with a first annular frame 23 via a disk-shaped first protective tape 21 attached to the front surface 11a of the wafer 11. The inner diameter of the first annular frame 23 is longer than the diameter of the wafer 11, and the outer peripheral region of the first protective tape 21 is attached to one surface of the frame.

[0033] The central region of the first protective tape 21 is attached to the surface 11a of the wafer 11. The first protective tape 21 is, for example, a resin film having a glue layer (adhesive layer) provided on a base layer made of resin. The base layer is made of, for example, a polyolefin resin, and the adhesive layer is made of, for example, an ultraviolet-curable resin.

[0034] In addition, in the modified layer forming step (S1), the wafer 11 may not be integrated with the first annular frame 23 via the first protective tape 21, and the surface 11a of the wafer 11 may be attached to a protective tape of approximately the same diameter.

[0035] In the modified layer forming step (S1), a laser processing device 2 shown in Fig. 3 is used. This laser processing device 2 is equipped with a disk-shaped chuck table 4 having a holding surface 4a that suction-holds the front surface 11a side of the wafer 11. This chuck table 4 has a disk-shaped frame and a disk-shaped porous plate (not shown) having a smaller diameter than the frame.

[0036] A negative pressure from a suction source such as an ejector is applied to this porous plate through a flow path (not shown) formed in the frame. The chuck table 4 is configured to be rotatable around a predetermined rotation axis. The rotation of the chuck table 4 is performed by a rotation drive source (not shown) that rotates a base member on which the chuck table 4 is placed.

[0037] Furthermore, the chuck table 4 is configured to be movable along a first horizontal direction 6 and a second horizontal direction that are perpendicular to each other on a horizontal plane. For example, the movement of the chuck table 4 along the first horizontal direction 6 is performed by a ball screw type first horizontal direction movement mechanism, and the movement along the second horizontal direction is performed by a ball screw type second horizontal direction movement mechanism.

[0038] A plurality of clamp mechanisms 8 are provided at approximately equal intervals on the sides of the chuck table 4 along the circumferential direction of the chuck table 4. In addition, a head portion 12 of a laser beam irradiation unit 10 is provided above the holding surface 4a of the chuck table 4.

[0039] The laser beam irradiation unit 10 includes a laser oscillator (not shown) and a head unit 12 equipped with a condenser lens (not shown). A laser beam L having a wavelength that is transmitted through the wafer 11 is irradiated from the head unit 12 toward the holding surface 4a.

[0040] In the modified layer forming step (S1), first, the front surface 11a side of the wafer 11 is suction-held by the holding surface 4a, and the first annular frame 23 is clamped by each clamp mechanism 8. At this time, the back surface 11b of the wafer 11 is exposed upward.

[0041] Then, the chuck table 4 is rotated as appropriate so that the multiple first planned division lines 15 become parallel to the first horizontal direction 6. Next, the chuck table 4 is moved as appropriate along the second horizontal direction so that the laser beam L is irradiated onto one of the first planned division lines 15. Next, the chuck table 4 is moved along the first horizontal direction 6 while irradiating the laser beam L onto the wafer 11 so that the focal point F is positioned inside the wafer 11.

[0042] As a result, a modified layer 11c is formed inside the wafer 11 along one of the first planned dividing lines 15. The irradiation conditions of the laser beam L at this time are set, for example, as follows. Laser beam wavelength: 1064nm Average power output: 1W Pulse repetition frequency: 100kHz Machining feed speed: 800mm / s Number of passes: 1

[0043] The number of passes means the number of times the laser beam L is irradiated along one first planned dividing line 15. However, the number of passes may be two or more, and two or more modified layers 11c may be formed at multiple positions having different depths from the front surface 11a of the wafer 11. For example, it is preferable to set the number of passes to three, and form three modified layers 11c inside the wafer 11.

[0044] When the modified layer 11c is formed inside the wafer 11 along one of the first dividing lines 15, the chuck table 4 is moved in the second horizontal direction by the distance between the pair of adjacent first dividing lines 15. Then, a modified layer 11c is similarly formed inside the wafer 11 along the other first dividing line 15 adjacent to the one of the first dividing lines 15.

[0045] When modified layers 11c are formed inside the wafer 11 along all of the multiple first planned dividing lines 15, the chuck table 4 is rotated 90 degrees so that the straight line passing through the first point A and the third point C shown in Fig. 1 becomes parallel to the first horizontal direction 6. Next, while irradiating the wafer 11 with the laser beam L so that the focusing point F is positioned inside the wafer 11, the chuck table 4 is moved along the first horizontal direction 6 and the second horizontal direction so that the laser beam L is irradiated onto the wafer 11 along one of the second planned dividing lines 17.

[0046] As a result, modified layers 11c are formed inside the wafer 11 along one of the second planned dividing lines 17. The irradiation conditions of the laser beam L at this time are the same as those when the laser beam L is irradiated along the first planned dividing lines 15. Moreover, modified layers 11c are similarly formed inside the wafer 11 along the remaining second planned dividing lines 17.

[0047] The method of forming the modified layer 11c inside the wafer 11 along the second dividing lines 17 is not limited to the above-mentioned method. For example, the modified layer 11c may be formed inside the wafer 11 along the first portion 17a of each of the second dividing lines 17, and then the modified layer 11c may be formed inside the wafer 11 along the second portion 17b of each of the second dividing lines 17.

[0048] In this case, first, the chuck table 4 is rotated, for example, by 15° to 75° so that a first portion 17a (a straight line passing through a first point A and a second point B shown in FIG. 1) of the plurality of second planned dividing lines 17 becomes parallel to the first horizontal direction 6. Next, while irradiating the wafer 11 with the laser beam L so that a focal point F is positioned inside the wafer 11, the chuck table 4 is moved along the first horizontal direction 6 so that the laser beam L is irradiated onto the wafer 11 along one first portion 17a of one second planned dividing line 17.

[0049] Then, when irradiation of the wafer 11 with the laser beam L along this one first portion 17a is completed, irradiation of the laser beam L is stopped. Next, the chuck table 4 is moved along the first horizontal direction 6 to a position where the laser beam L can be irradiated along the one first portion 17a of the other second planned dividing line 17 adjacent to this one first portion 17a. At this time, the chuck table 4 may be moved along the second horizontal direction if necessary.

[0050] Next, while again irradiating the wafer 11 with the laser beam L, the chuck table 4 is moved in the first horizontal direction 6 so that the laser beam L is irradiated onto the wafer 11 along one of the first portions 17a of the other second planned dividing lines 17. Then, by repeating the same irradiation of the laser beam L and the movement of the chuck table 4, a modified layer 11c is formed inside the wafer 11 along the first portions 17a of the multiple second planned dividing lines 17.

[0051] Next, the chuck table 4 is rotated so that the second portions 17b (a straight line passing through the second point B and the third point C shown in FIG. 1 ) of the multiple second planned dividing lines 17 become parallel to the first horizontal direction 6. Next, while the laser beam L is irradiated onto the wafer 11 so that the focal point F is positioned inside the wafer 11, the chuck table 4 is moved along the first horizontal direction 6 so that the laser beam L is irradiated onto the wafer 11 along one second portion 17b of one second planned dividing line 17.

[0052] Then, when irradiation of the wafer 11 with the laser beam L along the one second portion 17b is completed, irradiation of the laser beam L is stopped. Next, the chuck table 4 is moved along the first horizontal direction 6 to a position where irradiation of the laser beam L along the one second portion 17b of the other second planned dividing line 17 adjacent to the one second portion 17b is possible. At this time, the chuck table 4 may be moved along the second horizontal direction if necessary.

[0053] Next, while irradiating the wafer 11 with the laser beam L again, the chuck table 4 is moved in the first horizontal direction 6 so that the laser beam L is irradiated onto the wafer 11 along one of the second portions 17b of the other second planned dividing lines 17. Then, by repeating the same irradiation of the laser beam L and the movement of the chuck table 4, a modified layer 11c is formed inside the wafer 11 along the second portions 17b of the multiple second planned dividing lines 17.

[0054] The modified layer 11c is a region having a lower mechanical strength than a region in which the modified layer 11c is not formed in the wafer 11. Furthermore, when the modified layer 11c is formed inside the wafer 11, cracks 11d are generated that extend from the modified layer 11c toward the front surface 11a side and the back surface 11b side.

[0055] 2, after the modified layer forming step (S1) is performed, an external force is applied to the wafer 11 to divide the wafer 11 (division step: S2). This division is performed, for example, by further extending a crack 11d that originates from a modified layer 11c formed inside the wafer 11 along a plurality of first division lines 15 and a plurality of second division lines 17.

[0056] 4(A) and 4(B) are partial cross-sectional side views showing the state of the dividing step (S2). Here, prior to the modified layer forming step (S1), the disk-shaped first protective tape 21 attached to the front surface 11a of the wafer 11 is peeled off from the wafer 11. Then, prior to the dividing step (S2), the wafer 11 is integrated with the second annular frame 27 via the disk-shaped second protective tape 25 attached to the back surface 11b of the wafer 11.

[0057] The inner diameter of this second annular frame 27 is longer than the diameter of the wafer 11, and the outer circumferential region of the second protective tape 25 is attached to one surface of the second annular frame 27. The central region of the second protective tape 25 is attached to the rear surface 11b of the wafer 11. This second protective tape 25 is a stretchable film, and, like the first protective tape 21, is a resin film in which a glue layer (adhesive layer) is provided on a base layer made of resin.

[0058] In the dividing step (S2), an expansion device shown in Figures 4(A) and 4(B) is used. This expansion device 14 has a cylindrical drum 16. A plurality of rollers 18 are provided on the upper end of the drum 16 along the circumferential direction of the opening of the drum 16. A plurality of (three or more, for example, four) legs 20 are arranged on the outside of the drum 16.

[0059] 4(A) shows two legs 20. An air cylinder (not shown) for vertically moving the leg 20 is provided at the lower end of each of the legs 20. Also, an annular table 22 is provided at the upper end of the legs 20.

[0060] The annular table 22 has a rectangular outer shape and has a circular opening through which the drum 16 can pass. A plurality of clamp mechanisms 24 are arranged on the outer periphery of the annular table 22, each clamping a second annular frame 27 integrated with the wafer 11.

[0061] In the dividing step (S2), first, the upper end of the drum 16 and the upper surface of the annular table 22 are arranged at approximately the same height, and then the back surface 11b side of the wafer 11 is arranged on the drum 16 and the annular table 22. Then, the second annular frame 27 is clamped by a plurality of clamp mechanisms 24 (see FIG. 4(A)).

[0062] Next, the air cylinder is operated to pull down the annular table 22 relative to the drum 16, thereby radially expanding the second protective tape 25 (see FIG. 4(B)). As a result, the second protective tape 25 is expanded, and an external force is also applied to the wafer 11 attached to the second protective tape 25.

[0063] That is, a force is applied to the wafer 11 to expand the wafer 11 in the planar direction of the wafer 11. As a result, cracks 11d originating from modified layers 11c formed inside the wafer 11 further extend, and the wafer 11 is divided along the first division lines 15 and the second division lines 17, thereby producing optical device chips 29.

[0064] In the wafer 11, a plurality of regions 19 in which optical devices are to be formed are defined by a plurality of first division lines 15 and a plurality of second division lines 17 in the shape of broken lines intersecting the plurality of first division lines 15.

[0065] Here, the first division lines 15 extend linearly along a first direction parallel to the crystal orientation

[0011] , i.e., perpendicular to the crystal plane (011). Therefore, it is easy to divide the wafer 11 along the first division lines 15, and the extension of the cracks 11d from each of the first division lines 15 to the inside of the regions 19 in which optical devices are formed is suppressed.

[0066] In addition, each of the multiple second planned dividing lines 17 includes, between an adjacent pair of first planned dividing lines 15, a first portion 17a extending along a third direction that is non-parallel to both the first direction and a second direction perpendicular to the first direction (perpendicular to the crystal orientation

[0011] , i.e., a direction parallel to the crystal plane (011)), and a second portion 17b extending along a fourth direction that is non-parallel to any of the first direction to the third direction.

[0067] That is, each of the second dividing lines 17 does not include a portion extending along the first direction and the second direction between a pair of adjacent first dividing lines 15. Therefore, in the wafer 11, the cracks 11d are prevented from extending from each of the second dividing lines 17 toward the inside of the regions 19 in which the optical devices are formed. This makes it possible to prevent a decrease in the yield of the optical device chips manufactured from the wafer 11.

[0068] In addition, the structures and methods according to the above-described embodiments can be modified as appropriate without departing from the scope of the present invention. [Explanation of symbols]

[0069] 1: Chip (1a~1l: sides) 3 :Area 11: Wafer (11a: front surface, 11b: back surface, 11c: modified layer, 11d: crack) 13: Orientation Flat 15: First division line 17: Second planned division line (17a: first part, 17b: second part) 19: Area 21: First protective tape 23: First annular frame 25: Second protective tape 27: Second annular frame 29: Tip 2: Laser processing equipment 4: Chuck table (4a: holding surface) 6 :1st horizontal direction 8: Clamp mechanism 10: Laser beam irradiation unit 12: Head section 14: Expansion device 16: Drums 18: Coro 20: Legs 22: Circular table 24: Clamp mechanism

Claims

1. A single crystal silicon wafer having optical devices formed in each of a plurality of regions on a front surface side, the normal to the front surface being aligned along a crystal orientation [100], The plurality of regions, in a plan view, A plurality of first division lines extending linearly along a first direction parallel to the crystal orientation [011]; a plurality of second division lines extending in a broken line shape so as to intersect with the plurality of first division lines; Each of the plurality of second planned division lines is a first portion extending from a first point on one of a pair of adjacent first division lines among the plurality of first division lines to a second point between the pair of first division lines along a third direction non-parallel to both the first direction and a second direction perpendicular to the first direction; a second portion extending from the second point along a fourth direction non-parallel to any of the first direction to the third direction to a third point on the other of the pair of first dividing lines.

2. A method for dividing a single crystal silicon wafer according to claim 1 along the plurality of first dividing lines and the plurality of second dividing lines which partition the single crystal silicon wafer into the plurality of regions, comprising the steps of: a modified layer forming step of irradiating the single crystal silicon wafer with a laser beam having a wavelength that transmits through the single crystal silicon wafer along the plurality of first division lines and the plurality of second division lines to form a modified layer inside the single crystal silicon wafer; a dividing step of dividing the single crystal silicon wafer along the first dividing lines and the second dividing lines by applying an external force to the single crystal silicon wafer after the modified layer forming step, so as to extend cracks originating from the modified layer; A method for dividing a single crystal silicon wafer, comprising:

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