Wafer processing method

Abstract

To provide a wafer processing method that can appropriately remove a chamfered portion of a first wafer when processing the first wafer in a joined wafer formed by joining the first wafer and a second wafer.SOLUTION: A wafer processing method that processes a first wafer 10A in a bonded wafer W formed by bonding a first wafer 10A and a second wafer 10B includes a modified layer formation step of positioning a laser beam LB at a focal point inside adjacent to a chamfered portion 17A formed on the outer periphery of the first wafer 10A and irradiated to form ring-shaped modified layers 100, 102, 104, and a chamfer removal step of removing the chamfered portion 17A of the first wafer 10A starting from the modified layers 100, 102, 104, and includes a chamfer removal promotion step of supplying fluids L, L1 that weaken the bonding force to the interface 20 of the chamfered portion where the first wafer 10A and the second wafer 10B are bonded, and allowing the fluids to penetrate to an area where the chamfered portion can be removed prior to the chamfer removal step.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a method for processing a wafer by processing a first wafer in a bonded wafer obtained by bonding a first wafer and a second wafer.

Background Art

[0002] A wafer on which a plurality of devices such as ICs and LSIs are partitioned by a dicing planned line and formed on the surface is ground on the back surface to a predetermined thickness, and then divided into individual device chips by a dicing device or a laser processing device, and is used for electric devices such as mobile phones and personal computers.

[0003] In addition, a chamfered portion is formed on the outer periphery of the wafer. When the back surface of the wafer is ground, the chamfered portion becomes a sharp knife edge, and cracks occur from the knife edge and reach the inside, damaging the devices formed in the region closer to the center, or causing problems such as the operator being injured by the chamfered portion that has become a knife edge. Therefore, a technique for removing the chamfered portion of the wafer has been proposed (see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the technique of bonding a first wafer and a second wafer to form a bonded wafer and then processing the first wafer in order to improve the functions of the devices, there is a problem that it is relatively difficult to remove the chamfered portion from the first wafer.

[0006] That is, (1) Wafers bonded by siloxane bonds or the like have a strong bonding force. Even if a laser beam having a wavelength that is transmissive to the first wafer is irradiated with the focal point positioned inside adjacent to the chamfered portion to form a modified layer inside the first wafer, it is difficult to remove only the chamfered portion by itself. (2) When attempting to remove the chamfered portion of the first wafer by forming a modified layer as shown in (1) with a high adhesion state between the first wafer and the second wafer, the influence of the laser beam when forming the modified layer reaches the second wafer, and there is a risk of damaging the second wafer. (3) Even when removing the chamfered portion from the first wafer using a cutting blade, it is difficult to completely remove it without damaging the second wafer. There is such a problem.

[0007] The present invention has been made to solve the problems shown in (1) to (3) above, and its main technical problem is to provide a wafer processing method capable of appropriately removing the chamfered portion of the first wafer when processing the first wafer in a bonded wafer in which the first wafer and the second wafer are bonded.

Means for Solving the Problem

[0008] To solve the above main technical problem, according to the present invention, there is provided a wafer processing method for processing the first wafer in a bonded wafer in which the first wafer and the second wafer are bonded, including a modified layer forming step of positioning and irradiating the focal point of a laser beam inside adjacent to the chamfered portion formed on the outer periphery of the first wafer to form a ring-shaped modified layer, and a chamfered portion removing step of removing the chamfered portion of the first wafer starting from the modified layer, and before the chamfered portion removing step, a chamfered portion removing promotion step of supplying a fluid that weakens the bonding force to the interface of the chamfered portion where the first wafer and the second wafer are bonded and immersing it to a region where the chamfered portion can be removed.

[0009] The method includes an external force applying step of applying an external force to the interface. In the chamfer removing acceleration step, it is preferable to weaken the bonding force of the interface in combination with the external force. In the modified layer forming step, the method includes a first step of irradiating with a laser beam with the focusing point positioned near the interface to form a relatively deep first modified layer in which cracks reach the interface, and a second step of forming a relatively shallow second modified layer adjacent to the first modified layer on the outside or inside that does not reach the interface. The external force applying step of applying an external force for deflecting the chamfer from the interface starting from the first modified layer may be performed.

[0010] In the modified layer forming step, a radially extending modified layer may be formed from the ring-shaped modified layer toward the outside. The chamfer removing acceleration step may be performed before, after, or simultaneously with the modified layer forming step. After the chamfer removing step, a grinding step of grinding and thinning the upper surface of the first wafer may be included.

[0011] The first wafer and the second wafer are joined by a Si-O-Si siloxane bond. The fluid for weakening the bonding force includes any one of water, water vapor, and mist. In the chamfer removing acceleration step, it is preferable that the Si-O-Si bond changes to a Si-OH-OH-Si bond to weaken the bonding force of the interface.

Advantages of the Invention

[0012] The wafer processing method of the present invention is a wafer processing method for performing processing on a first wafer in a bonded wafer obtained by bonding a first wafer and a second wafer. The method includes a modified layer forming step of positioning a condensing point of a laser beam inside adjacent to a chamfered portion formed on the outer periphery of the first wafer and irradiating the laser beam to form a ring-shaped modified layer, and a chamfered portion removing step of removing the chamfered portion of the first wafer starting from the modified layer. Before the chamfered portion removing step, the method further includes a chamfered portion removing promotion step of supplying a fluid that weakens the bonding force to the interface of the chamfered portion where the first wafer and the second wafer are bonded and immersing the fluid into a region where the chamfered portion can be removed. Therefore, when processing the first wafer in the bonded wafer obtained by bonding the first wafer and the second wafer, the chamfered portion of the first wafer can be appropriately removed.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments of a wafer processing method configured based on the present invention will be described in detail with reference to the accompanying drawings.

[0015] FIG. 1 shows a bonded wafer W as an example of a workpiece to be processed in the present embodiment. The bonded wafer W is a wafer in which a first wafer 10A and a second wafer 10B are bonded together. The first wafer 10A is, for example, a silicon (Si) wafer having a diameter of 300 mm and a thickness of 300 μm, and a plurality of devices 12A are formed on a surface 10Aa partitioned by a dicing line 14A. The first wafer 10A has a front surface 10Aa and a back surface 10Ab, and includes an effective region 16A near the center where the devices 12A used as products are formed, and an outer peripheral surplus region 18A surrounding the effective region 16A where a chamfered portion 17A is formed on the outer periphery. The second wafer 10B also has the same configuration as the first wafer 10A, and a chamfered portion 17B is formed on the outer periphery. Although not shown, it is a silicon wafer having an effective region in which a plurality of devices are partitioned and formed by dicing lines on a surface 10Ba facing the lower surface side in the figure. In the present embodiment, the first wafer 10A and the second wafer 10B of the bonded wafer W are, for example, bonded by bonding the front surface 10Aa of the first wafer 10A and the front surface 10Ba of the second wafer 10B to form an interface 20 by a siloxane bond and integrated. The siloxane bond is a Si - O - Si bond in which silicon (Si) and oxygen (O) are alternately bonded, and since the first wafer 10A and the second wafer 10B are bonded by heat treatment, a strong bonding state is maintained even at high temperatures.

[0016] When implementing the wafer processing method of the present embodiment for the first wafer 10A of the bonded wafer W described above, a modified layer forming step of positioning a condensing point of a laser beam inside adjacent to the chamfered portion 17A formed on the outer periphery of the first wafer 10A and irradiating it to form a ring-shaped modified layer, and a chamfered portion removal promoting step of supplying a fluid that weakens the bonding force to the interface 20 near the chamfered portion 17A and the chamfered portion 17B where the first wafer 10A and the second wafer 10B are bonded and immersing it to a region where the chamfered portion 17A of the first wafer 10A can be removed are carried out.

[0017] FIG. 2 shows a laser processing apparatus 1 configured to be capable of performing the modified layer forming step and the chamfer removal promotion step of the present embodiment.

[0018] The laser processing apparatus 1 is disposed on a base 2, and includes a holding means 3 for holding the above-described bonding wafer W, a moving means 4 for moving the holding means 3, an alignment means 6 for imaging the bonding wafer W held by the holding means 3 and performing an alignment process, a laser beam irradiation means 7 for irradiating a laser beam toward the bonding wafer W held by the holding means 3, a frame body 5 including a vertical wall portion 5a erected on the side of the moving means 4 and a horizontal wall portion 5b extending in the horizontal direction from the upper end portion of the vertical wall portion 5a, and a fluid supply means 8.

[0019] As shown in FIG. 2, the holding means 3 includes a rectangular X-axis direction movable plate 31 mounted on the base 2 so as to be movable in the X-axis direction, a rectangular Y-axis direction movable plate 32 disposed on the X-axis direction movable plate 31 so as to be movable in the Y-axis direction, a cylindrical support column 33 fixed to the upper surface of the Y-axis direction movable plate 32, and a chuck table 34 disposed at the upper end of the support column 33. The chuck table 34 is configured to be rotatable by a rotation driving means (not shown) housed in the support column 33, and the upper surface of the chuck table 34 is constituted by an adsorption chuck 35 formed of a porous material having air permeability. The adsorption chuck 35 is connected to a suction means (not shown) by a flow path passing through the support column 33. By operating the suction means, a negative pressure is generated on the upper surface of the adsorption chuck 35, and the bonding wafer W can be sucked and held.

[0020] The moving means 4 includes an X-axis moving means 43 that moves the holding means 3 in the X-axis direction and a Y-axis moving means 46 that moves the holding means 3 in the Y-axis direction orthogonal to the X-axis direction. The X-axis moving means 43 converts the rotational motion of the motor 41 into linear motion via a ball screw 42 and transmits it to the X-axis movable plate 31, and moves the X-axis movable plate 31 in the X-axis direction along a pair of guide rails 2A, 2A disposed along the X-axis direction on the base 2. The Y-axis moving means 46 converts the rotational motion of the motor 44 into linear motion via a ball screw 45 and transmits it to the Y-axis movable plate 32, and moves the Y-axis movable plate 32 along a pair of guide rails 31a, 31a disposed along the Y-axis direction on the X-axis movable plate 31.

[0021] Inside the horizontal wall portion 5b of the frame body 5, an optical system constituting the above-described laser beam irradiation means 7 is accommodated. On the lower surface side of the tip of the horizontal wall portion 5b, a condenser 71 is disposed which constitutes a part of the laser beam irradiation means 7 and condenses a laser beam having a wavelength that is at least transmissive to the first wafer 10A described above and irradiates the bonding wafer W. Alignment means 6 is disposed at a position adjacent to the condenser 71 in the X-axis direction. The alignment means 6 is an imaging means that images the bonding wafer W held by the holding means 3 and detects the position and orientation of the bonding wafer W, the processing position where the laser beam should be irradiated, and the like.

[0022] The fluid supply means 8 of the present embodiment is disposed on the Y-axis movable plate 32 and is disposed adjacent to the chuck table 34. The fluid supply means 8 is provided with a nozzle 8a at its upper end and is connected to a fluid supply source (not shown) that supplies the fluid L to the nozzle 8a. The fluid supply means 8 is configured to be movable in the vertical direction indicated by the arrow R0 and in the direction toward the center of the chuck table 34 indicated by the arrow R1 by a driving means (not shown), and can position the nozzle 8a at a desired position and eject the fluid L from the tip of the nozzle 8a.

[0023] In addition to the above-described configuration, the laser processing apparatus 1 is provided with control means for controlling each operating unit, display means, etc. (not shown). The control means is constituted by a computer and includes a central processing unit (CPU) that performs arithmetic processing according to a control program, a read-only memory (ROM) that stores the control program and the like, a readable and writable random access memory (RAM) for temporarily storing the detected detection values, arithmetic results, etc., an input interface, and an output interface (illustrations of details are omitted). The above-described moving means 4, alignment means 6, laser beam irradiation means 7, display means (not shown), etc. are connected to the control means.

[0024] The laser processing apparatus 1 of the present embodiment generally has the configuration as described above, and the modified layer forming step and the chamfer removal promotion step, which are carried out before the chamfer removal step (to be described later) in the method for processing a wafer of the present invention, will be described.

[0025] (Modified layer forming step, Chamfer removal promotion step) The modified layer forming step can be carried out using the above-described laser processing apparatus 1, and the chamfer removal promotion step can be carried out before, after, or simultaneously with the modified layer forming step. In the present embodiment, an example in which the chamfer removal promotion step is carried out before the modified layer forming step will be described. Since the above-described fluid supply means 8 is provided in the laser processing apparatus 1, the chamfer removal promotion step can be carried out by the laser processing apparatus 1.

[0026] If the bonded wafer W described with reference to FIG. 1 is prepared, the bonded wafer W is transported to the laser processing apparatus 1 described with reference to FIG. 2, and as shown in FIG. 3, the back surface 10Ab side of the first wafer 10A is oriented upward and the second wafer 10B side is oriented downward, and it is placed on the suction chuck 35 that constitutes the holding surface of the chuck table 34. In the present embodiment, in order to prevent the fluid L supplied in this chamfering portion removal promotion step from being sucked by the negative pressure generated in the suction chuck 35 of the chuck table 34, a protective tape T is adhered to the back surface 10Ba side of the second wafer 10B. The illustrated protective tape T is formed with dimensions slightly larger than those of the suction chuck 35 so as to be able to cover at least the entire suction chuck 35. Note that if the suction of the fluid from the chuck table 34 is not a problem, the protective tape T may be omitted.

[0027] If the bonded wafer W is placed on the chuck table 34, the suction means (not shown) is operated to perform suction holding. Next, the fluid supply means 8 is moved in the directions indicated by the arrows R0 and R1 shown in FIG. 1, and as shown in FIG. 4, the tip of the nozzle 8a is positioned at the height of the interface 20 where the first wafer 10A and the second wafer 10B are bonded and at a position close to the side of the interface 20.

[0028] Next, a fluid L that weakens the bonding force of the interface 20 is supplied from the tip of the nozzle 8a to the interface 20, and the chuck table 34 is rotated. As described above, the interface 20 of the present embodiment is bonded by a siloxane bond (Si—O—Si bond). By supplying the above-described fluid L (for example, pure water) from the side to the interface 20, water molecules gradually penetrate into the interface 20 from the outer periphery, and the penetrated region changes to a Si—OH—OH—Si bond. As a result, the bonding force of the interface 20 is weakened, and a bonding force reduction region 21 is formed in a ring shape on the outer peripheral side of the interface 20. Note that the fluid L supplied from the nozzle 8a is not limited to being supplied in a liquid state, and may be in a vapor or mist state.

[0029] In this embodiment, by injecting the fluid L from the nozzle 8a of the fluid supply means 8 at high pressure, the water pressure of the fluid L acts as an external force that warps the chamfered portion 17A of the first wafer 10A away from the chamfered portion 17B of the second wafer 10B. That is, the fluid supply means 8 also functions as an external force applying means for applying an external force that weakens the bonding force at the interface 20, and an external force applying step for weakening the bonding force at the interface 20 by this external force is carried out simultaneously with the chamfered portion removal promoting step. By doing so, the change in the bonding at the interface 20 described above and the external force applied by the fluid L combine to reduce the adhesion in the illustrated bonding force reduction region 21, and a minute gap can be formed in the bonding force reduction region 21. Note that the bonding force reduction region 21 is set so as not to reach the effective region 16A, and by setting appropriate values for the amount of the fluid L supplied, the injection pressure of the fluid L, the rotational speed of the chuck table 34, etc., the width of the bonding force reduction region 21 formed on the outer periphery of the interface 20 is adjusted.

[0030] As described above, if the chamfered portion removal promoting step is carried out, the modification layer forming step described below is carried out. In the modification layer forming step, alignment is carried out on the bonded wafer W sucked and held by the chuck table 34 using the alignment means 6 provided in the laser processing apparatus 1. By this alignment, the position of the outer peripheral end portion where the chamfered portion 17A of the first wafer 10A is formed and the center position of the first wafer 10A are detected, and the height of the upper surface of the back surface 10Ab of the first wafer 10A is detected. Inside the first wafer 10A adjacent to the chamfered portion 17A formed on the outer periphery, the processing position (for example, a position at a radius of 147 mm from the center point of the first wafer 10A) where the condensing point of the laser beam LB should be positioned and irradiated is detected.

[0031] The modification layer forming step carried out in the present invention can be carried out, for example, including the first step and the second step described below.

[0032] (First step) Based on the position information of the processing position detected by the above alignment, the chuck table 34 is moved to position the processing position set on the first wafer 10A of the bonding wafer W directly below the condenser 71 of the laser beam irradiation means 7 as shown in FIG. 5. Next, in addition to FIG. 5, as understood from FIG. 6(a), the condensing point of the laser beam LB is positioned and irradiated inside the processing position on the first wafer 10A from the back surface 10Ab side of the first wafer 10A, and the chuck table 34 is rotated in the direction indicated by the arrow R2 to form a ring-shaped first modified layer 100 along the entire circumference along the inside of the chamfered portion 17A of the first wafer 10A.

[0033] The first modified layer 100 formed by the first step of this embodiment is preferably formed of a plurality of layers in the vertical direction as shown in FIG. 6(a). For example, the first modified layer 100 shown in FIG. 6(a) is composed of four modified layers in the vertical direction. When forming the first modified layer 100 including such a plurality of layers, first, the condensing point of the laser beam LB is positioned and irradiated at a position set at the deepest part (for example, a depth of 180 μm from the back surface 10Ab) close to the interface 20 inside the chamfered portion 17A of the first wafer 10A adjacent to the inner side, and the chuck table 34 is rotated to form a first ring-shaped modified layer along the chamfered portion 17A. Then, while rotating the chuck table 34, the condensing point is directed toward the back surface 10Ab side (upward) three times, and for example, the depth from the back surface 10Ab is increased to 170 μm → 160 μm → 150 μm to form a total of four ring-shaped modified layers along the chamfered portion 17A. By positioning and irradiating the condensing point of the laser beam LB in the vicinity of the interface 20 in this way and forming a relatively deep first modified layer, cracks are formed at a relatively deep position on the surface 10Aa side of the first wafer 10A along the first modified layer 100, that is, reaching the interface 20. Note that the first modified layer 100 shown in FIG. 6 is conceptually shown for convenience of explanation, and the depth positions of the respective layers do not conform to the actual dimensions. Thus, the first step is completed. Note that the first modified layer 100 formed by the first step is not limited to being formed of four layers, and is appropriately set according to the wavelength, output, thickness of the first wafer 10A, material constituting the first wafer 10A, etc. of the laser beam LB irradiated by the laser beam irradiation means 7.

[0034] (Second step) If the first modified layer 100 is formed by the above-described first step, a second step of forming a second modified layer at a relatively shallow position that does not reach the interface 20 of the bonding wafer W is performed outside or inside the first modified layer 100. In the second step of the present embodiment, as shown in FIG. 6(b), the condensing point of the laser beam LB is positioned and irradiated at a position adjacent to the outside of the uppermost modified layer (depth of 150 μm from the back surface 10Ab) and the lower modified layer (depth of 160 μm from the back surface 10Ab) in the first modified layer 100, and the chuck table 34 is rotated to form ring-shaped second modified layers 102 and 104. As shown in the figure, the second modified layers 102 and 104 are preferably formed of a plurality of modified layers (three in the illustrated embodiment) having different diameters formed at the same depth.

[0035] In the above-described modified layer forming step, in addition to forming the first modified layer 100 by the first step, second modified layers 102 and 104 are formed at a relatively shallow depth position adjacent to the first modified layer 100 and not reaching the interface 20 by the second step. As a result, stress is applied to the first modified layer 100, and an external force can be applied in the direction indicated by arrow R3 that warps the chamfered portion 17A from the interface 20 starting from the first modified layer 100, and an external force applying step is performed simultaneously with the modified layer forming step. As a result, the bonding force in the bonding force reduction region 21 formed at the interface 20 can be more reliably reduced, and the crack formed along the first modified layer 100 can be further extended.

[0036] Thus, the modified layer forming step is completed. In the above-described embodiment, the second modified layers 102 and 104 are formed outside adjacent to the first modified layer 100, but the present invention is not limited to this, and they may be formed inside adjacent to the first modified layer 100. Similar to the case of forming them outside as described above, an external force can be applied in the direction indicated by arrow R3 that warps the chamfered portion 17A from the interface 20 starting from the first modified layer 100.

[0037] In addition, when forming the second modified layer in the second step, it is not limited to forming three ring-shaped modified layers as described above, and it may be two or less, or four or more.

[0038] The laser processing conditions when performing the above-described modified layer forming step are set as follows, for example. Wavelength: 1099 nm Repetition frequency: 80 kHz Average output: 2.0 W Processing feed rate: 450 mm / s Or Wavelength: 1342 nm Repetition frequency: 90 kHz Average output: 1.9 W Processing feed rate: 400 mm / s

[0039] In the above-described modified layer forming step, for example, as shown in FIG. 7, a radial modified layer 110 extending in the direction of the outer peripheral end where the chamfered portion 17A is formed may be formed from the region where the first modified layer 100 or the second modified layers 102 and 104 are formed. The illustrated modified layer 110 is a modified layer that functions to more finely divide the chamfered portion 17A when removing the ring-shaped chamfered portion 17A, and is formed by irradiating a laser beam LB under the same laser processing conditions as when forming the first modified layer 100 described above, and is formed at a plurality of locations (four locations in the illustrated embodiment) at equal intervals on the outer periphery of the first wafer 10A. By forming this modified layer 110, when removing the chamfered portion 17A from the first wafer 10A in the chamfered portion removing step described later, the chamfered portion 17A is finely divided, and the removal of the chamfered portion 17A is favorably realized.

[0040] (Chamfered Portion Removing Step) After performing the chamfer removal promotion step and the modification layer formation step described above, starting from the above-described modification layer (first modification layer 100), as shown in FIG. 8, a chamfer removal step of removing the chamfer 17A formed on the outer periphery of the first wafer 10A is performed. In the present embodiment, as described above, the modification layer formation step and the chamfer removal promotion step are performed in advance, and the bonding strength of the interface 20 between the chamfer 17A of the first wafer 10A and the chamfer 17B of the second wafer 10B is weakened, and a bonding strength reduction region 21 is formed. Further, since a crack is also formed along the first modification layer 100, it is possible to easily remove the outer peripheral surplus region 18A including the chamfer 17A starting from the first modification layer 100. The method of performing the chamfer removal step is not particularly limited. For example, air or water flow is jetted from the nozzle 8a of the fluid supply means 8 positioned on the side of the chuck table 34 toward the interface 20 to remove the chamfer 17A from the first wafer 10A, and the wafer processing method of the present invention can be completed. When the above-described radial modification layer 110 is formed on the first wafer 10A, in the chamfer removal step, the chamfer 17A is removed as a plurality of fragments.

[0041] In the above embodiment, the chamfer removal promotion step was performed before the modification layer formation step. As a result, a bonding strength reduction region 21 is formed on the outer periphery of the region where the interface 20 on the outer peripheral side of the bonded wafer W is formed, and the adhesion is reduced, and minute gaps can be formed. As a result, even when the condensing point is positioned inside the first wafer 10A and the laser beam LB is irradiated to a relatively deep position in the modification layer formation step, the second wafer 10B is not affected by the laser beam LB and damage to the second wafer 10B is avoided. Furthermore, the chamfer 17A can be surely removed without performing cutting using a cutting blade to remove the chamfer 17A, and there is no problem of damaging the second wafer 10B as in the case of using a cutting blade.

[0042] In the above-described embodiment, it has been described that the chamfered portion removal promotion step is performed and then the modified layer formation step is performed. However, when the modified layer formation step is performed in a form including the first step and the second step described with reference to FIGS. 6(a) and 6(b), it is also effective to perform the chamfered portion removal promotion step of supplying the fluid L that weakens the bonding force toward the interface 20 after the modified layer formation step. That is, before performing the chamfered portion removal promotion step, the modified layer formation step including the above-described first step and second step is performed, and due to the action of the second modified layers 102 and 104 formed in the second step, an external force is generated in a direction that warps the chamfered portion 17A from the interface 20 starting from the first modified layer 100. Then, by performing the above-described chamfered portion removal promotion step, the fluid L that weakens the bonding force is supplied from the outer peripheral side toward the interface 20 where the first wafer 10A and the second wafer 10B are joined. As a result, in combination with the external force generated in a direction that warps the chamfered portion 17A generated by the modified layer formation step from the interface 20, it becomes possible to efficiently weaken the bonding force at the outer periphery of the interface 20.

[0043] The present invention may be configured to perform the chamfered portion removal promotion step simultaneously with the modified layer formation step. In particular, in the above-described laser processing apparatus 1, since the fluid supply means 8 is disposed adjacent to the chuck table 34 of the holding means 3, it is possible to perform the above-described chamfered portion removal promotion step and the modified layer formation step, and it is also possible to apply an external force to the interface 20 by the fluid L supplied from the fluid supply means 8.

[0044] (Modification 1) The chamfer removal promotion step is not limited to the above-described embodiments. For example, FIG. 9(a) shows a modification example 1 of carrying out the chamfer removal promotion step of the present invention using a fluid supply means 60 in which a sponge S containing a fluid L (pure water) is supported by a support base 61. The sponge S holds sufficient fluid L, and the sponge S is pressed from the side of the bonding wafer W suction-held on the chuck table 34 of the holding means 3, and the fluid L that weakens the bonding force of the interface 20 is supplied to the interface 20 of the bonding wafer W. Then, by rotating the chuck table 34, the fluid L is supplied to the entire circumference of the bonding wafer W, and in the same manner as in the above-described embodiment, water molecules are allowed to penetrate into the interface 20, and the region where the water molecules have penetrated is changed from a siloxane bond to a Si-OH-OH-Si bond. Thereby, a bonding force reduction region 21 that can weaken the bonding force of the interface 20 and remove the chamfer portion 17A can be formed in a ring shape in the same manner as the above-described fluid supply means 8. Further, the chamfer removal promotion step using the above-described modification example 1 can also be carried out before, after, or simultaneously with the modified layer formation step.

[0045] (Modification example 2) FIG. 9(b) shows a modification 2 in which a chamfer removal promotion step is carried out using a fluid supply means 80 for supplying steam or a mist of water atomized as a fluid L1. The fluid supply means 80 includes a cover portion 81 that covers at least a part of the outer periphery of the bonding wafer W. The cover portion 81 is provided with a fluid inlet 82 connected to a fluid supply source (not shown) and a fluid outlet 83 connected to a fluid suction means (not shown) that sucks and discharges the fluid L1 from the inside of the cover portion 81. The fluid supply source can be selected, for example, from those that heat pure water to generate steam or those that vibrate pure water by ultrasonic waves to generate a mist. The fluid L1 supplied to the inside of the cover portion 81 by the fluid supply source is supplied to the entire circumference of the bonding wafer W by rotating the chuck table 34. As a result, in the same manner as in the above-described embodiment, water molecules penetrate from the outer periphery of the interface 20, and the region where the water molecules penetrate is changed from a siloxane bond to a Si-OH-OH-Si bond. As a result, a bonding force reduction region 21 that can weaken the bonding force of the interface 20 and remove the chamfer portion 17A can be formed in a ring shape in the same manner as the above-described fluid supply means 8. Then, the fluid L1 supplied to the inside of the cover portion 81 from the fluid outlet 83 is sucked and discharged, and recovered by an appropriate labyrinth mechanism or the like, so that leakage of the mist or steam-like fluid L1 to the outer periphery of the cover portion 81 can be suppressed. The chamfer removal promotion step using the above-described modification 2 can also be carried out before, after, or simultaneously with the modified layer formation step, in the same manner as in modification 1.

[0046] (Modification 3) FIG. 9(c) shows a modification example 3 capable of performing an external force applying step of supplying the fluid L to the interface 20 of the bonded wafer W using the fluid supply means 8 for supplying the fluid L and the horizontal blade 8b, and applying an external force that deflects the chamfered portion 17A from the interface 20 starting from the first modified layer 100. In the illustrated modification example 3, the first modified layer 100 is formed in advance by performing a modified layer forming step (in the illustrated embodiment, the second modified layers 102 and 104 are also formed), and the tip of the horizontal blade 8b is made to enter the interface 20 from the side of the bonded wafer W in the direction indicated by the arrow R4, and the chuck table 34 is rotated to supply the fluid L (pure water) to the upper surface (or lower surface) of the tip of the horizontal blade 8b through the nozzle 8a of the fluid supply means 8. Thereby, by supplying the fluid L that weakens the bonding force to the interface 20, the bonding force of the interface 20 can be weakened to form a ring-shaped bonding force reduction region 21, and an external force applying step of applying an external force that deflects the chamfered portion 17A from the interface 20 in the direction indicated by the arrow R5 starting from the first modified layer 100 can be performed. Note that the chamfered portion removal promotion step performed according to the above-described modification example 3 is not limited to being performed after the modified layer forming step, and may be performed simultaneously with the modified layer forming step or while forming the first modified layer 100.

[0047] (Modification Example 4) FIG. 9(d) shows a modification 4 in which a fluid supply means 90 having a fluid flow path 92 inside and a wedge member 91 capable of supplying a fluid L to the tip is used. In the illustrated modification 4, a first modified layer 100 is formed in advance by performing a modified layer forming step (in the illustrated embodiment, the second modified layers 102 and 104 are also formed). The tip of the wedge member 91 is caused to enter from the side of the bonding wafer W toward the interface 20 in the direction indicated by the arrow R6, and the chuck table 34 is rotated to supply the fluid L to the tip of the wedge member 91 through the fluid flow path 92. Also in this modification 4, similarly to the above modification 3, a reduced bonding force region 21 in which the bonding force of the interface 20 is weakened can be formed in a ring shape by supplying the fluid L that weakens the bonding force to the interface 20, and an external force applying step of warping the chamfered portion 17A from the interface 20 in the direction indicated by the arrow R7 can be performed starting from the first modified layer 100. The chamfered portion removal promotion step performed by the above-described modification 4 is not limited to being performed after the modified layer forming step, and can be performed simultaneously with the modified layer forming step, and can be performed while forming the first modified layer 100.

[0048] (Grinding process) In addition to the above-described modified layer forming step, chamfered portion removing step, and chamfered portion removal promotion step, the present invention may be configured to perform a grinding step of grinding the back surface 10Ab of the first wafer 10A of the bonding wafer W to a desired thickness as necessary.

[0049] The bonding wafer W subjected to the above-described chamfered portion removing step is transported to a grinding apparatus 50 (only a part is shown) shown in FIG. 10. As shown in the figure, the grinding apparatus 50 includes a grinding means 52 for grinding and thinning the bonding wafer W sucked and held on a chuck table 51. The grinding means 52 includes a rotary spindle 52a rotated by a rotation drive mechanism (not shown), a wheel mount 52b attached to the lower end of the rotary spindle 52a, and a grinding wheel 52c attached to the lower surface of the wheel mount 52b. A plurality of grinding wheels 52d are annularly arranged on the lower surface of the grinding wheel 52c.

[0050] If the bonded wafer W is transported to the grinding apparatus 50, as shown in FIG. 10, it is placed on the chuck table 51 with the second wafer 10B side facing downward, and suction means (not shown) is activated to suck and hold it. Next, while rotating the rotary spindle 52a of the grinding means 52 in the direction indicated by the arrow R8 in FIG. 10, for example, at 6000 rpm, the chuck table 51 is rotated in the direction indicated by the arrow R9, for example, at 300 rpm. Then, while supplying grinding water onto the back surface 10Ab of the first wafer 10A by grinding water supply means (not shown), grinding feed means (not shown) is activated to bring the grinding wheel 52d into contact with the back surface 10Ab of the first wafer 10A, and the grinding wheel 52c is fed downward in the direction indicated by the arrow R10 at a grinding feed rate of, for example, 1.0 μm / second. At this time, grinding is advanced while measuring the thickness of the bonded wafer W with a contact or non-contact measuring gauge (not shown), and it can be thinned until it reaches the desired thickness.

[0051] If the back surface 10Ab of the first wafer 10A is ground by a predetermined amount to make the bonded wafer W have the desired thickness, the grinding means 52 is stopped and retracted, and the grinding process is completed. If the grinding process is completed, cleaning, drying processes, etc. (details are omitted as appropriate) are carried out.

[0052] The above-described bonded wafer W has been described by taking as an example the bonding of the first wafer 10A and the second wafer 10B by a siloxane bond. However, the bonded wafer W processed according to the present invention is not limited to being bonded by a siloxane bond. For example, the bonded wafer W may be one in which the first wafer 10A and the second wafer 10B are bonded by a SiCN bond by a nitride bond or a TEOS bond in which tetraethyl orthosilicate molecules are changed into an entity having a Si—O—Si bond. Whichever bond it is, the bonding force can be weakened by the above-described fluid L or fluid L1. Further, the present invention can be applied to a bonded wafer W in which O2 plasma treatment or N2 plasma treatment is performed as a pretreatment for the bonding surface forming the interface 20. Furthermore, the fluids L and L1 are not limited to pure water as described above, and a mixed fluid mixed with other fluids containing water molecules can also be applied.

Explanation of Signs

[0053] 1: Laser processing apparatus 2: Base 3: Holding means 31: X-axis movable plate 32: Y-axis movable plate 34: Chuck table 35: Adsorption chuck 4: Moving means 43: X-axis moving means 46: Y-axis moving means 5: Frame 6: Alignment means 7: Laser beam irradiation means 71: Condenser 8: Fluid supply means 8a: Nozzle 8b: Horizontal blade 10A: First wafer 10Aa: Surface 10Ab: Back surface 12A: Device 14A: Scribing line 16A: Active area 17A: Chamfered portion 18A: Outer peripheral surplus region 10B: Second wafer 10Ba: Front surface 10Bb: Back surface 20: Interface 21: Bonding strength reduction region 50: Grinding device 51: Chuck table 52: Grinding means 52a: Rotating spindle 52b: Wheel mount 52c: Grinding wheel 52d: Grinding stone 60: Fluid supply means 61: Support base 80: Fluid supply means 81: Cover part 82: Fluid inlet 83: Fluid outlet 90: Fluid supply means 91: Wedge member 92: Fluid flow path 100: First modified layer 102, 104: Second modified layer L: Fluid (pure water) L1: Fluid (mist or water vapor) S: Sponge

Claims

1. A method for processing a wafer by processing a first wafer in a bonded wafer obtained by bonding a first wafer and a second wafer, comprising: A modified layer forming step of positioning a condensing point of a laser beam inside adjacent to a chamfered portion formed on an outer periphery of the first wafer and irradiating the laser beam to form a ring-shaped modified layer; A chamfered portion removing step of removing the chamfered portion of the first wafer starting from the modified layer; Comprising: Before the chamfered portion removing step, a chamfered portion removing promotion step of supplying a fluid that weakens the bonding force to an interface of the chamfered portion where the first wafer and the second wafer are bonded and immersing the fluid to a region where the chamfered portion can be removed. The wafer processing method is configured to include this step.

2. The wafer processing method according to claim 1, further comprising an external force applying step of applying an external force to the interface, and in the chamfered portion removing promotion step, the bonding force of the interface is weakened in combination with the external force.

3. In the modified layer forming step, A first step of positioning the condensing point of the laser beam near the interface and irradiating the laser beam to form a relatively deep first modified layer where cracks reach the interface; A second step of forming a relatively shallow second modified layer that does not reach the interface outside or inside adjacent to the first modified layer; and including The wafer processing method according to claim 2, wherein the external force applying step of applying an external force that warps the chamfered portion from the interface starting from the first modified layer is performed.

4. The wafer processing method according to claim 1, wherein in the modified layer forming step, a radially modified layer is formed from the ring-shaped modified layer toward the outside.

5. The wafer processing method according to claim 1, wherein the chamfered portion removing promotion step is performed before the modified layer forming step, after the modified layer forming step, or simultaneously with the modified layer forming step.

6. The wafer processing method according to claim 1, further including a grinding step of grinding and thinning the upper surface of the first wafer after the chamfered portion removing step.

7. The first wafer and the second wafer are bonded by a Si—O—Si siloxane bond, and the fluid that weakens the bonding force includes any one of water, water vapor, and mist. The wafer processing method according to claim 1, wherein in the chamfered portion removing promotion step, the Si—O—Si bond changes to a Si—OH—OH—Si bond and the bonding force of the interface is weakened.

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