Processing method and processing device of wafer

Abstract

To provide a processing device of a wafer capable of completely removing a chamfered portion from a first wafer in a joined wafer that comprises the first wafer and a second wafer joined together.SOLUTION: A processing device 34 of a wafer includes: a spinner table 36 holding a portion on an inner side than a modified layer 30 in a first wafer 4; rotating means 38 rotating the spinner table 36 to generate centrifugal force at a chamfered portion 18; and external force applying means 40 applying external force to the chamfered portion 18 when the rotational speed of the spinner table 36 reaches a predetermined value. The external force applying means 40 stimulates the chamfered portion 18, and the chamfered portion 18 is scattered and removed by the centrifugal force.SELECTED DRAWING: Figure 12

Description

[Technical Field]

[0001] The present invention relates to a method for processing a bonded wafer in which a first wafer and a second wafer are bonded together, and a wafer processing apparatus for processing a bonded wafer in which a modified layer is formed in a ring shape along the chamfered portion of the first wafer. [Background technology]

[0002] Wafers have device regions formed on their surface, with multiple devices such as ICs and LSIs separated by planned dividing lines.The back surface is ground to thin the wafer to the desired thickness, and then the wafer is divided into individual device chips using a cutting machine and a laser processing machine.Each of the divided device chips is used in electrical equipment such as mobile phones and personal computers.

[0003] Because a chamfer is formed on the outer periphery of a wafer, when the backside of the wafer is ground to thin it, the chamfer becomes a sharp knife-edge. This requires operators to be extra careful when handling the wafer. Furthermore, when the chamfer becomes a sharp knife-edge, cracks tend to form from the outer periphery of the wafer to the inside, increasing the risk of device damage. The above-mentioned problem can occur not only with a single wafer, but also with a bonded wafer consisting of two stacked wafers.

[0004] Therefore, the present applicant has proposed a technology in which, before grinding the back surface of the wafer, the focal point of a laser beam having a wavelength that is transparent to the wafer is positioned inside the chamfered portion, and the laser beam is irradiated onto the wafer, forming a ring-shaped modified layer inside the wafer and removing the chamfered portion (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-88187 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the case of bonded wafers, the chamfered portion may not be completely removed and may remain slightly, which may cause problems such as the remaining portion falling off in later processes and becoming a source of contamination, or causing chipping of device chips when the wafer is divided into individual device chips.

[0007] An object of the present invention is to provide a wafer processing method and processing apparatus that can completely remove a chamfered portion from a first wafer in a bonded wafer formed by bonding a first wafer and a second wafer. [Means for solving the problem]

[0008] According to the present invention, there is provided the following wafer processing method that solves the above-mentioned problems. "A processing method for a bonded wafer obtained by bonding a first wafer and a second wafer, the first wafer having an effective area including a device area in which a plurality of devices are partitioned by planned division lines and an outer peripheral excess area in which a chamfered portion surrounding the effective area is formed, a modified layer forming step of irradiating the first wafer with a laser beam having a wavelength that is transparent to the first wafer, with the focal point positioned within the outer peripheral excess region, to form a ring-shaped modified layer along the chamfered portion; a centrifugal force generating step of holding the first wafer side on a spinner table and rotating the first wafer to generate centrifugal force on the chamfered portion of the first wafer; and a chamfer removing step in which the centrifugal force generated in the chamfer of the first wafer exceeds the resistance of the modified layer, causing the chamfer to be scattered and removed by the centrifugal force.

[0009] Preferably, the method includes a grinding step of holding the second wafer side on a chuck table and grinding the surface of the first wafer from which the chamfered portion has been removed to form the desired thickness.

[0010] Furthermore, according to the present invention, there is provided the following wafer processing apparatus that solves the above-mentioned problems: "A wafer processing device for processing a bonded wafer in which a first wafer and a second wafer are bonded together, the first wafer having an effective area including a device area in which a plurality of devices are partitioned by planned division lines and an outer peripheral excess area in which a chamfered portion surrounding the effective area is formed, the device irradiating the first wafer with a laser beam having a wavelength that is transparent to the first wafer and a focal point of the laser beam being positioned inside the outer peripheral excess area, to form a ring-shaped modified layer along the chamfered portion of the first wafer, a spinner table that holds a portion of the first wafer inside the modified layer; a rotating means for rotating the spinner table to generate centrifugal force on the chamfered portion; an external force applying means for applying an external force to the chamfered portion when the rotation speed of the spinner table reaches a predetermined value; The external force applying means applies a stimulus to the chamfered portion, and the chamfered portion is scattered and removed by centrifugal force.

[0011] The external force application means is a lever having a force point, a fulcrum, and a point of action, the fulcrum being formed on the outer periphery of the spinner table, the force point being formed by a weight, and a claw being formed at the point of action that applies a stimulus to the chamfered portion, so that when the centrifugal force generated by the rotation of the spinner table moves the weight to the outer periphery and the rotation speed reaches a predetermined value, the claw at the point of action applies a stimulus to the chamfered portion, causing the chamfered portion to be scattered and removed by the centrifugal force.

[0012] A spring that resists centrifugal force is provided on the weight, and when the rotation speed of the spinner table reaches a predetermined value, the weight overcomes the resistance of the spring and moves to the outer periphery, causing the claw at the point of action to stimulate the chamfered portion, causing the chamfered portion to be scattered and removed by centrifugal force.

[0013] Preferably, the weight is provided with a magnet that resists centrifugal force, and when the rotation speed of the spinner table reaches a predetermined value, the weight overcomes the resistance of the magnet and moves to the outer periphery, causing the claws at the point of action to stimulate the chamfered portion, causing the chamfered portion to be scattered and removed by centrifugal force.

[0014] The external force applying means may include a nozzle that sprays a fluid onto the chamfered portion, and when the rotation speed of the spinner table reaches a predetermined value, the fluid sprayed from the nozzle stimulates the chamfered portion, causing the chamfered portion to be scattered and removed by centrifugal force.

[0015] The predetermined rotation speed of the spinner table may be 3000 rpm. [Effects of the Invention]

[0016] The wafer processing method of the present invention includes: A processing method for a bonded wafer obtained by bonding a first wafer and a second wafer, the first wafer having an effective area including a device area in which a plurality of devices are partitioned by planned division lines, and an outer peripheral excess area in which a chamfered portion is formed surrounding the effective area, comprising: a modified layer forming step of irradiating the first wafer with a laser beam having a wavelength that is transparent to the first wafer, with the focal point positioned within the outer peripheral excess region, to form a ring-shaped modified layer along the chamfered portion; a centrifugal force generating step of holding the first wafer side on a spinner table and rotating the first wafer to generate centrifugal force on the chamfered portion of the first wafer; and a chamfer removal step in which the centrifugal force generated in the chamfer of the first wafer exceeds the resistance of the modified layer, scattering and removing the chamfer by centrifugal force, thereby enabling the chamfer to be completely removed from the first wafer. This eliminates problems such as the remaining portion falling off in a subsequent process and becoming a source of contamination, or causing chipping of device chips when the first wafer is divided into individual device chips. Furthermore, because the first wafer on which the modified layer has been formed is held on the spinner table, the second wafer prevents the chamfer of the first wafer from scattering upward.

[0017] The wafer processing apparatus of the present invention comprises: A wafer processing device for processing a bonded wafer in which a first wafer and a second wafer are bonded together, the first wafer having an effective area including a device area in which a plurality of devices are partitioned by planned division lines and an outer peripheral excess area in which a chamfered portion surrounding the effective area is formed, the device irradiating the first wafer with a laser beam having a wavelength that is transparent to the first wafer and positioning the focal point of the laser beam within the outer peripheral excess area, and forming a ring-shaped modified layer along the chamfered portion of the first wafer, a spinner table that holds a portion of the first wafer inside the modified layer; a rotating means for rotating the spinner table to generate centrifugal force on the chamfered portion; an external force applying means for applying an external force to the chamfered portion when the rotation speed of the spinner table reaches a predetermined value; The external force applying means applies a stimulus to the chamfered portion, scattering and removing it by centrifugal force, thereby enabling the chamfered portion to be completely removed from the first wafer. This eliminates problems such as the remaining portion falling off in a subsequent process and becoming a source of contamination, or causing chipping of device chips when the first wafer is divided into individual device chips. Furthermore, because the spinner table holds the first wafer on which the modified layer has been formed, the second wafer prevents the chamfered portion of the first wafer from scattering upward. [Brief explanation of the drawings]

[0018] [Figure 1] (a) A perspective view of the bonded wafer, (b) A partial cross-sectional view of the wafer shown in (a). [Figure 2] FIG. 2 is a schematic diagram showing a state in which a bonded wafer is held on a chuck table of a laser processing apparatus. [Figure 3] FIG. 4 is a schematic diagram showing a state in which a modified layer is being formed. [Figure 4](a) Partial cross-sectional view of a bonded wafer on which a Type 1 modified layer is formed, (b) Partial cross-sectional view of a bonded wafer on which a Type 2 modified layer is formed, (c) Partial cross-sectional view of a bonded wafer on which a Type 3 modified layer is formed, (d) Partial cross-sectional view of a bonded wafer on which a Type 4 modified layer is formed. [Figure 5] FIG. 10 is a plan view of a wafer on which a ring-shaped modified layer and a radial modified layer are formed. [Figure 6] 1 is a perspective view of a wafer processing apparatus according to the present invention; [Figure 7] FIG. 7 is a schematic diagram of the external force application means shown in FIG. 6. [Figure 8] FIG. 8 is a schematic diagram showing a first modified example of the external force application means shown in FIG. 7. [Figure 9] FIG. 8 is a schematic diagram showing a second modified example of the external force application means shown in FIG. 7. [Figure 10] 10A and 10B are schematic diagrams showing other forms of external force application means. [Figure 11] 7 is a schematic diagram showing a state in which a bonded wafer is held on a spinner table of the wafer processing apparatus shown in FIG. 6. [Figure 12] FIG. 4 is a schematic diagram showing a state in which a chamfered portion is being removed from a first wafer. [Figure 13] FIG. 10 is a perspective view of the bonded wafers with the chamfer removed from the first wafer. [Figure 14] Schematic diagram showing a grinding process. DETAILED DESCRIPTION OF THE INVENTION

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a wafer processing method and processing apparatus according to the present invention will now be described with reference to the drawings.

[0020] (Bonded wafer 2) 1(a) and 1(b) show a disk-shaped bonded wafer 2 that can be processed by the method and apparatus of the present invention. The bonded wafer 2 is made by stacking and integrating a first wafer 4 and a second wafer 6.

[0021] The first and second wafers 4 and 6 may be formed from an appropriate semiconductor material such as silicon. The first and second wafers 4 and 6 each have, for example, a diameter of 300 mm and a thickness of 300 μm. As shown in FIG. 1( a), the surface 6 a of the second wafer 6 has an effective area 12 including a device region in which a plurality of devices 8, such as ICs and LSIs, are partitioned by lattice-shaped division lines 10, and a peripheral surplus area 14 surrounding the effective area 12. For convenience, FIG. 1( a) shows a ring-shaped boundary 16 between the effective area 12 and the peripheral surplus area 14 with a two-dot chain line, but in reality, no line indicating the boundary 16 exists. Although not shown, the surface 4 a of the first wafer 4 has the same configuration as the surface 6 a of the second wafer 6. Furthermore, the first and second wafers 4 and 6 each have a curved chamfered portion 18 formed on their outer peripheries, as well as a notch 20 indicating the crystal orientation.

[0022] When forming the bonded wafer 2, the effective region 12 of the first wafer 4 and the effective region 12 of the second wafer 6 are bonded together. At this time, the notch 20 of the first wafer 4 and the notch 20 of the second wafer 6 are aligned, and the first and second wafers 4, 6 are bonded together with the same crystal orientation. After the first and second wafers 4, 6 are bonded together, they are preferably heat-treated to bond them together by siloxane bonding.

[0023] (Modified layer forming process) In this embodiment, first, a modified layer formation process is carried out in which the focal point of a laser beam having a wavelength that is transparent to the first wafer 4 is positioned inside the peripheral excess region 14, and the laser beam is irradiated onto the first wafer 4 to form a ring-shaped modified layer along the chamfered portion 18.

[0024] The modified layer forming step can be carried out using, for example, a laser processing device 22 shown in Figures 2 and 3. The laser processing device 22 includes a chuck table 24 that suction-holds the wafer, an oscillator (not shown) that oscillates a pulsed laser beam LB having a wavelength that is transparent to the first wafer 4, and a condenser 26 (see Figure 3) that condenses the laser beam LB oscillated by the oscillator and irradiates the first wafer 4 with the laser beam LB.

[0025] 2, a circular suction chuck 28 is disposed on the upper end of the chuck table 24. The suction chuck 28 is formed from a porous material such as porous ceramics, and is connected to a suction means (not shown). The chuck table 24 is rotated by a motor (not shown) in the direction indicated by arrow R1 in FIG. 3.

[0026] In the modified layer forming step, first, the bonded wafer 2 is suction-held on the upper surface of the chuck table 24. At this time, the bonded wafer 2 is placed on the upper surface of the chuck table 24 with the center of rotation of the chuck table 24 aligned with the center of the bonded wafer 2. At this time, the first wafer 4 from which the chamfered portion 18 is to be removed is positioned on top. Then, a suction force is generated on the upper surface of the suction chuck 28 by the suction means, and the second wafer 6 side is suction-held on the upper surface of the suction chuck 28.

[0027] Once the bonded wafer 2 is suction-held on the chuck table 24, a processing line to be irradiated with the laser beam LB is set. At this time, the first wafer 4 is imaged from above using an imaging means (not shown) of the laser processing device 22, and the outer periphery and center position of the first wafer 4 are detected based on the image of the first wafer 4 captured by the imaging means. Next, based on the detected outer periphery and center position of the first wafer 4, a ring-shaped line located within the outer periphery excess region 14 and radially inward of the chamfered portion 18 of the first wafer 4 is set as the processing line. For example, if the chamfered portion 18 is formed in a ring-shaped region 0.5 mm wide from the outer periphery of the first wafer 4, a ring-shaped line located 3 mm radially inward from the outer periphery of the first wafer 4 is set as the processing line.

[0028] After setting the line to be processed along which the laser beam LB is to be irradiated, the focal point of the laser beam LB is positioned at a required position on the line to be processed. At this time, the height of the back surface 4b of the first wafer 4 is detected by a height detection means (not shown) of the laser processing device 22. Then, using the detected height of the back surface 4b as a reference, the focal point of the laser beam LB is positioned at a required position on the line to be processed inside the first wafer 4 (inside the outer peripheral excess region 14).

[0029] Once the focal point of the laser beam LB has been positioned at the required position, the first wafer 4 is irradiated with the laser beam LB having a wavelength that is transparent to the first wafer 4, thereby forming a ring-shaped modified layer along the chamfered portion 18. That is, by irradiating the first wafer 4 with the laser beam LB while rotating the chuck table 24 in the direction indicated by the arrow R1 in Figure 3, a ring-shaped modified layer 30 is formed along the entire circumference of the ring-shaped intended processing line.

[0030] After one ring-shaped modified layer 30 (one circumference) has been formed, the height position of the focal point of the laser beam LB is changed to a shallower position, and the laser beam LB is irradiated onto the first wafer 4 in the same manner as above. By repeating this process of changing the height position of the focal point and irradiating the laser beam LB, multiple ring-shaped modified layers 30 are formed at intervals in the vertical direction, as shown in Figure 4(a) (Type 1).

[0031] Furthermore, as shown in Figure 4(b), by repeatedly changing the height position and radial position of the focal point of the laser beam LB and irradiating the laser beam LB, multiple ring-shaped modified layers 30 may be formed at intervals in the vertical and radial directions (Type 2).

[0032] Alternatively, as shown in Figure 4(c), multiple ring-shaped modified layers 30 may be formed at intervals in the vertical direction, and multiple ring-shaped modified layers 30 may be formed at intervals in the radial direction on the surface 4a side (bonding surface side) of the first wafer 4 (Type 3).

[0033] Alternatively, as shown in Figure 4(d), multiple ring-shaped modified layers 30 may be formed at intervals in the vertical direction, and multiple ring-shaped modified layers 30 may be formed at intervals in the radial direction on the back surface 4b side (exposed surface side) of the first wafer 4 (Type 4).

[0034] In any of the above types 1 to 4, after forming the ring-shaped modified layer 30 along the chamfered portion 18, modified layers 32 extending radially from the ring-shaped modified layer 30 may be formed as shown in Fig. 5. That is, a plurality of linear modified layers 32 (three in the illustrated embodiment) extending radially from the ring-shaped modified layer 30 to the outer circumferential edge of the first wafer 4 may be formed at equal intervals in the circumferential direction inside the first wafer 4. By forming such radial modified layers 32, the chamfered portion 18 can be finely divided and effectively removed in the chamfered portion removing step described below.

[0035] Such a modified layer forming step can be carried out, for example, under the following processing conditions: Note that the defocus described below is the amount of movement of the condenser 26 when the condenser 26 is moved toward the bonded wafer 2 from a state in which the focal point of the laser beam LB is positioned on the back surface 4b (exposed surface) of the first wafer 4. Laser beam wavelength: 1099nm Repetition frequency: 80kHz Average output: 2W Defocus: 180μm, 170μm, 160μm, 150μm Feed speed: 450mm / s

[0036] (Centrifugal force generation process) After the modified layer forming step is performed, a centrifugal force generating step is performed in which the first wafer 4 side is held on a spinner table and rotated to generate centrifugal force on the chamfered portion 18 of the first wafer 4 .

[0037] (Wafer processing equipment 34) The centrifugal force generating step can be performed using, for example, a wafer processing device 34 shown in Fig. 6. The wafer processing device 34 includes a spinner table 36 that holds a portion of the first wafer 4 that is inside the modified layer 30, a rotation means 38 that rotates the spinner table 36 to generate centrifugal force in the chamfered portion 18, and an external force applying means 40 that applies an external force to the chamfered portion 18 when the rotation speed of the spinner table 36 reaches a predetermined value.

[0038] (Spinner Table 36) The spinner table 36 includes a circular suction chuck 42 with an exposed top surface and a frame member 44 that surrounds the suction chuck 42. The suction chuck 42 is made of a porous material such as porous ceramics and is connected to a suction means (not shown). The diameter of the suction chuck 42 is smaller than the diameter of the ring-shaped modified layer 30 formed on the first wafer 4. In the spinner table 36, the suction means generates a suction force on the top surface of the suction chuck 42, thereby suction-holding the portion of the first wafer 4 that is inside the ring-shaped modified layer 30. As shown in FIG. 7, the top surface 44a of the frame member 44 extends radially outward, sloping downward.

[0039] (Rotation means 38) 6, the rotation means 38 includes a motor 46 having a rotation shaft 46a connected to the lower center of the spinner table 36, and the motor 46 rotates the spinner table 36 about an axis extending in the vertical direction. The motor 46 also has an elevating means 48, which may be an actuator such as an air cylinder, attached to its outer periphery. The elevating means 48 raises and lowers the spinner table 36 together with the motor 46.

[0040] (External force applying means 40) 6 and 7, external force application means 40 can be configured as a lever having a force point 50, a fulcrum 52, and a point of action 54. As shown in Fig. 6, a plurality of levers (three in the illustrated embodiment) serving as external force application means 40 are provided at intervals in the circumferential direction on the outer periphery of frame member 44 of spinner table 36.

[0041] The external force application means 40 of this embodiment has a main shaft 56 extending in the vertical direction. As shown in FIG. 7 , a fulcrum 52 protrudes from the middle of the main shaft 56 radially inward of the spinner table 36, and the fulcrum 52 is connected to the frame member 44 of the spinner table 36 by a pin 58. That is, the fulcrum 52 is formed on the outer periphery of the spinner table 36. A force point 50 is formed by a weight extending from the lower part of the main shaft 56 radially outward of the spinner table 36. The point of action 54 extends from the upper part of the main shaft 56 radially inward of the spinner table 36. A claw 54a is formed at the tip of the point of action 54 to apply a force to the chamfered portion 18 of the first wafer 4. The claw 54a is formed in a triangular shape that narrows radially inward of the spinner table 36 when viewed from above.

[0042] When the spinner table 36 is not rotating, the external force application means 40 is located at the position shown by the solid line in Fig. 7. On the other hand, when the spinner table 36 is rotating, the centrifugal force generated by the rotation of the spinner table 36 moves the weight at the force point 50 to the outer periphery (the radially outer side of the spinner table 36). When the rotation speed of the spinner table 36 reaches a predetermined value (e.g., 3000 rpm), the external force application means 40 swings in the direction shown by the arrow R2 toward the position shown by the two-dot chain line in Fig. 7, and the claw 54a of the action point 54 applies a stimulus to the chamfered portion 18 of the first wafer 4.

[0043] External force application means 40 is not limited to the form shown in Fig. 7 , and for example, as shown in Fig. 8 , a spring 60 that resists the centrifugal force associated with the rotation of spinner table 36 may be disposed on the weight at force point 50. Alternatively, as shown in Fig. 9 , a magnet 62 that resists the centrifugal force associated with the rotation of spinner table 36 may be disposed on the weight at force point 50. That is, a first magnet 62a may be disposed on the weight at force point 50, and a second magnet 62b that is attracted to first magnet 62a may be disposed on frame member 44 of spinner table 36.

[0044] 10 includes a nozzle 64 that sprays fluid F onto the chamfered portion 18 of the first wafer 4, a fluid supply source 66 that supplies fluid F to the nozzle 64, a valve 70 disposed in a pipeline 68 between the fluid supply source 66 and the nozzle 64, and a controller 72 that controls the opening and closing of the valve 70. In the external force applying means 40 shown in FIG. 10, the valve 70 is closed by the controller 72 until the rotation speed of the spinner table 36 reaches a predetermined value. When the rotation speed of the spinner table 36 reaches the predetermined value, the controller 72 opens the valve 70 and supplies fluid F from the fluid supply source 66 to the nozzle 64. The fluid F sprayed from the nozzle 64 applies a stimulus to the chamfered portion 18 of the first wafer 4. The fluid F to be sprayed onto the chamfered portion 18 of the first wafer 4 may be, for example, 1: air, 2: water, or 3: two fluids of air and water.

[0045] As shown in Figure 6, the wafer processing apparatus 34 further includes a cover member 74 that surrounds the periphery of the spinner table 36. The cover member 74 includes a ring-shaped bottom plate 76, an outer peripheral wall 78 that extends upward from the outer peripheral edge of the bottom plate 76, an inner peripheral wall 80 that extends upward from the inner peripheral edge of the bottom plate 76, and a plurality of legs 82 that extend downward at intervals in the circumferential direction from the outer peripheral edge of the lower surface of the bottom plate 76. A circular opening 78a is provided at the upper part of the outer peripheral wall 78. The diameter of the outer peripheral wall 78 gradually decreases toward the top, but the diameter of the opening 78a is slightly larger than the diameter of the frame member 44 of the spinner table 36.

[0046] In the centrifugal force generating step, first, the spinner table 36 is positioned at the upper attachment / detachment position shown in FIG. 11. Next, the bonded wafer 2 is placed on the upper surface of the spinner table 36 with the first wafer 4 on which the modified layer 30 has been formed facing downward. Next, a suction force is generated on the upper surface of the suction chuck 42 by the suction means, and the portion of the first wafer 4 radially inward of the modified layer 30 is suction-held on the upper surface of the suction chuck 42. Next, the spinner table 36 is lowered to the lower removal position shown in FIG. 12. Then, the spinner table 36 is rotated in the direction indicated by arrow R3 in FIG. 12. This allows centrifugal force to be generated at the chamfered portion 18 of the first wafer 4.

[0047] (chamfered portion removal process) Following the centrifugal force generating step, a chamfer removing step is carried out in which the centrifugal force generated in the chamfer 18 of the first wafer 4 exceeds the resistance of the modified layer 30, and the chamfer 18 is scattered and removed by the centrifugal force.

[0048] In the chamfered portion removal process, the rotational speed of the spinner table 36 is gradually increased. When the rotational speed of the spinner table 36 reaches a predetermined value (e.g., 3,000 rpm), an external force is applied to the chamfered portion 18 of the first wafer 4 by the external force application means 40. For example, in the external force application means 40 shown in FIG. 7, when the rotational speed of the spinner table 36 reaches the predetermined value, the external force application means 40 swings to the position indicated by the two-dot chain line in FIG. 7, and the claws 54a of the application point 54 apply a force to the chamfered portion 18 of the first wafer 4. As a result, the chamfered portion 18 of the first wafer 4 is no longer suction-held by the suction chuck 42 of the spinner table 36, and the chamfered portion 18 separates from the first wafer 4 starting from the modified layer 30, and the chamfered portion 18 is scattered by centrifugal force. In this manner, the chamfered portion 18 can be removed from the first wafer 4 (see FIG. 13).

[0049] In the external force application means 40 shown in FIG. 8, when the rotational speed of the spinner table 36 reaches a predetermined value, the weight of the force point 50 moves to the outer periphery (the radially outer side of the spinner table 36) overcoming the resistance of the spring 60. This causes the external force application means 40 to swing in the direction indicated by the arrow R2 toward the position indicated by the two-dot chain line in FIG. 8, and the claw 54a of the action point 54 applies a stimulus to the chamfered portion 18 of the first wafer 4. As a result, the chamfered portion 18 separates from the first wafer 4 starting from the modified layer 30, and the chamfered portion 18 is scattered by centrifugal force. In this way, the chamfered portion 18 can be removed from the first wafer 4.

[0050] In the external force application means 40 shown in FIG. 9 , when the rotation speed of the spinner table 36 reaches a predetermined value, the weight at the force point 50 moves to the outer periphery (the radially outer side of the spinner table 36) by overcoming the resistance of the magnet 62 (the attractive force of the first magnet 62 a and the second magnet 62 b). This causes the external force application means 40 to swing in the direction indicated by the arrow R2 toward the position indicated by the two-dot chain line in FIG. 9 , and the claw 54 a of the action point 54 applies a stimulus to the chamfered portion 18. As a result, the chamfered portion 18 separates from the first wafer 4 starting from the modified layer 30, and the chamfered portion 18 is scattered by centrifugal force. In this way, the chamfered portion 18 can be removed from the first wafer 4. The external force application means 40 shown in FIG. 9 starts swinging when the rotation speed exceeds a predetermined value, which is advantageous because it can apply a stronger stimulus to the chamfered portion 18 than the embodiments shown in FIGS. 7 and 8 .

[0051] 10, when the rotation speed of the spinner table 36 reaches a predetermined value, the controller 72 opens the valve 70, causing the fluid supply source 66 to supply the fluid F to the nozzle 64. This causes the fluid F to be sprayed from the nozzle 64 onto the chamfered portion 18 of the first wafer 4, and the fluid F stimulates the chamfered portion 18. As a result, the chamfered portion 18 separates from the first wafer 4 starting from the modified layer 30, and the chamfered portion 18 is scattered by centrifugal force. In this way, the chamfered portion 18 can be removed from the first wafer 4.

[0052] Furthermore, in the chamfered portion removing step of this embodiment, the first wafer 4 on which the modified layer 30 is formed is held on the spinner table 36. That is, the first wafer 4 is positioned on the lower side, and the second wafer 6 is positioned on the upper side. Therefore, the second wafer 6 prevents the chamfered portion 18 of the first wafer 4 from scattering upward.

[0053] (Grinding process) After the chamfered portion removal process is performed, the second wafer 6 side is held on a chuck table, and a grinding process is performed in which the surface of the first wafer 4 from which the chamfered portion 18 has been removed is ground to form the desired thickness.

[0054] (Grinding equipment 84) The grinding step can be performed using, for example, a grinding device 84 shown in Fig. 14. The grinding device 84 includes a chuck table 86 that holds the bonded wafer 2 by suction, and grinding means 88 that grinds the bonded wafer 2 held by suction on the chuck table 86. The grinding means 88 includes a spindle 90 that extends in the vertical direction, and a disk-shaped wheel mount 92 fixed to the lower end of the spindle 90. An annular grinding wheel 96 is fastened to the lower surface of the wheel mount 92 by bolts 94. A plurality of grinding stones 98 are fixed to the outer periphery of the lower surface of the grinding wheel 96, and are arranged in an annular shape at intervals in the circumferential direction.

[0055] In the grinding process, first, the back surface 4b of the first wafer 4 faces upward, and the second wafer 6 side is suction-held on the upper surface of the chuck table 86. Next, the chuck table 86 is rotated in the direction indicated by arrow R4 at a predetermined rotational speed (e.g., 300 rpm). The spindle 90 is also rotated in the direction indicated by arrow R5 at a predetermined rotational speed (e.g., 6000 rpm). Next, the spindle 90 is lowered to bring the grinding wheel 98 into contact with the back surface 4b of the first wafer 4, and grinding water is supplied to the portion of the back surface 4b of the first wafer 4 where the grinding wheel 98 is in contact. Thereafter, the spindle 90 is lowered at a predetermined grinding feed rate (e.g., 1.0 μm / s). This allows the back surface 4b of the first wafer 4 to be ground to a desired thickness.

[0056] As described above, according to this embodiment, the chamfered portion 18 can be completely removed from the first wafer 4, which eliminates problems such as the remaining portion falling off in a later process and becoming a source of contamination, or causing chipping of device chips when the first wafer 4 is divided into individual device chips. Furthermore, because the first wafer 4 on which the modified layer 30 has been formed is held on the spinner table 36, the second wafer 6 prevents the chamfered portion 18 of the first wafer 4 from scattering upward. [Explanation of symbols]

[0057] 2: Bonded wafer 4: First wafer 4a: Surface of first wafer 4b: Backside of first wafer 6: Second wafer 6a: Surface of second wafer 6b: Backside of second wafer 8: Device 10: Planned division line 12: Effective area 14: Surplus outer area 18: Chamfered part 30: Ring-shaped modified layer 34: Wafer processing equipment 36: Spinner table 38: Rotation means 40: External force applying means 50: Emphasis 52:Fulcrum 54: Point of action 54a: Nail 60: Spring 62: Magnet 62a: First Magnet 62b: Second Magnet 64: Nozzle LB: Laser beam F:Fluid

Claims

1. A processing method for a bonded wafer obtained by bonding a first wafer and a second wafer, the first wafer having an effective area including a device area in which a plurality of devices are partitioned by planned division lines, and an outer peripheral excess area in which a chamfered portion is formed surrounding the effective area, comprising: a modified layer forming step of irradiating the first wafer with a laser beam having a wavelength that is transparent to the first wafer, with the focal point positioned within the outer peripheral excess region, to form a ring-shaped modified layer along the chamfered portion; a centrifugal force generating step of holding the first wafer side on a spinner table and rotating the first wafer to generate centrifugal force on the chamfered portion of the first wafer; a chamfer removing step in which the centrifugal force generated in the chamfer of the first wafer exceeds the resistance of the modified layer, causing the chamfer to be scattered and removed by the centrifugal force.

2. 2. A wafer processing method according to claim 1, further comprising a grinding step of holding the second wafer side on a chuck table and grinding the surface of the first wafer from which the chamfer has been removed to form the first wafer to a desired thickness.

3. A wafer processing device for processing a bonded wafer in which a first wafer and a second wafer are bonded together, the first wafer having an effective area including a device area in which a plurality of devices are partitioned by planned division lines and an outer peripheral excess area in which a chamfered portion surrounding the effective area is formed, the device irradiating the first wafer with a laser beam having a wavelength that is transparent to the first wafer and positioning the focal point of the laser beam within the outer peripheral excess area, and forming a ring-shaped modified layer along the chamfered portion of the first wafer, a spinner table that holds a portion of the first wafer inside the modified layer; a rotating means for rotating the spinner table to generate centrifugal force on the chamfered portion; an external force applying means for applying an external force to the chamfered portion when the rotation speed of the spinner table reaches a predetermined value; The wafer processing device applies a stimulus to the chamfered portion by the external force applying means, and scatters and removes the chamfered portion by centrifugal force.

4. the external force applying means is a lever having a force point, a fulcrum, and a point of action, the fulcrum being formed on the outer periphery of the spinner table, the force point being formed by a weight, and a claw being formed at the point of action for applying a stimulus to a chamfered portion, 4. The wafer processing device according to claim 3, wherein when the centrifugal force generated by the rotation of the spinner table moves the weight to the outer periphery and the rotation speed reaches a predetermined value, the claws at the points of action apply an impulse to the chamfered portion, causing the chamfered portion to be scattered and removed by the centrifugal force.

5. 5. The wafer processing device according to claim 4, wherein the weight is provided with a spring that resists centrifugal force, and when the rotational speed of the spinner table reaches a predetermined value, the weight overcomes the resistance of the spring and moves to the outer periphery, causing the claws at the points of action to apply a stimulus to the chamfered portion, thereby scattering and removing the chamfered portion by centrifugal force.

6. 5. The wafer processing device according to claim 4, wherein a magnet that resists centrifugal force is disposed on the weight, and when the rotation speed of the spinner table reaches a predetermined value, the weight overcomes the resistance of the magnet and moves to the outer periphery, causing the claws at the points of action to apply a stimulus to the chamfered portion, thereby scattering and removing the chamfered portion by centrifugal force.

7. 4. The wafer processing device according to claim 3, wherein the external force applying means includes a nozzle for spraying a fluid onto the chamfered portion, and when the rotation speed of the spinner table reaches a predetermined value, the fluid sprayed from the nozzle stimulates the chamfered portion, scattering and removing the chamfered portion by centrifugal force.

8. 4. The wafer processing apparatus according to claim 3, wherein the predetermined value of the rotation speed of said spinner table is 3000 rpm.

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