Processing method of bonding wafer

Abstract

To provide a processing method of a bonding wafer, capable of effectively removing a bevelling part of a bonding wafer.SOLUTION: A processing method of a bonding wafer obtained by bonding a first wafer and a second wafer having an effective region and an outer peripheral residual region surrounding the effective region and having a bevelling part, comprises: a bonding surface cutting step of cutting a bonding surface in the outer peripheral residual region so as to position a cutting blade to an outer periphery of the bonding wafer; a bevelling part processing step of executing a processing for forming an original point for removing the bevelling part at a boundary part of the effective region and the outer peripheral residual region of the first wafer after / before the bonding surface cutting step; a holding step of holding the bonding wafer so that a second wafer side is positioned to a rotatable chuck table composing a grinding device; and a grinding step of rotating the chuck table so that a grinding wheel onto which a grinding abrasive wheel is distributed in an annular shape is positioned to the first wafer of the bonding wafer held by the chuck table to rotate the chuck table, and grinding the first wafer by rotating the grinding wheel.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a method for processing a bonded wafer in which a first wafer having an effective region and an outer peripheral surplus region surrounding the effective region and having a chamfered portion is bonded and joined to a second wafer.

Background Art

[0002] A wafer on which a plurality of devices such as ICs and LSIs are partitioned by a dicing line and formed on the surface is ground on the back surface to a predetermined thickness and then diced by a dicing device into individual device chips and used in electrical devices such as mobile phones and personal computers.

[0003] A grinding device includes a chuck table for holding a wafer, grinding means rotatably provided with a grinding wheel having a grinding stone for grinding the wafer held on the chuck table arranged in an annular shape, feeding means for feeding the grinding means, and measuring means for measuring the thickness of the wafer, and is configured to be able to process the wafer to a desired thickness.

[0004] However, a chamfered portion is formed on the outer periphery of the wafer. When the back surface of the wafer is ground and thinned, the chamfered portion becomes a sharp knife edge, cracks occur from the outer periphery and progress to the region where the device is formed, damaging the device, and there is also a problem that an operator may touch the chamfered portion and get injured.

[0005] Therefore, a technique for removing the chamfered portion has been proposed by the applicant before grinding the back surface of the wafer (see Patent Document 1). Also, in the case of a bonded wafer in which two wafers are bonded and joined, it has also been proposed to remove the chamfered portion of one of the wafers whose back surface is to be ground (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

[0007] By the way, in the case of the above-mentioned bonded wafer, at least the outer peripheral surplus region of one wafer and the outer peripheral surplus region of the other wafer are firmly bonded by a predetermined bonding method. Therefore, in order to remove the chamfer formed on the outer periphery of the outer peripheral surplus region, the condensing point of the laser beam having a wavelength that is transmissive to the wafer is positioned at the boundary between the outer peripheral surplus region and the effective region where the device is formed and irradiated, and a modification layer serving as a starting point for removing the chamfer is formed in a ring shape. Or, even if a machining process is performed in which a cutting blade is positioned at the boundary portion to form a cutting groove serving as a starting point for division in a ring shape, there is a problem that the chamfer is not effectively removed. Note that such a problem is not limited to the bonded wafer in which a plurality of devices are partitioned by division planned lines in the effective region and wafers formed on the surface are bonded to each other as described above, but a region closer to the center where no device is formed is an effective region used as a product. The same problem can occur in a bonded wafer in which wafers having an outer peripheral surplus region surrounding the effective region are bonded to each other.

[0008] The present invention has been made in view of the above facts, and its main technical problem is that a first wafer having an effective region and an outer peripheral surplus region surrounding the effective region and having a chamfer, and a second wafer are bonded and bonded. An object of the present invention is to provide a method for processing a bonded wafer that can effectively remove the chamfer of the bonded wafer. [Means for Solving the Problems]

[0009] In order to solve the above-described main technical problem, according to the present invention, there is provided a method for processing a bonded wafer in which a first wafer having an effective area and an outer peripheral surplus area surrounding the effective area and having a chamfered portion is bonded to a second wafer, the method including: a joint surface cutting step of positioning a cutting blade on the outer periphery of the bonded wafer and cutting the joint surface in the outer peripheral surplus area; a chamfered portion processing step of performing a process for forming a starting point for removing the chamfered portion at a boundary between the effective area and the outer peripheral surplus area of the first wafer before or after the joint surface cutting step; a holding step of positioning the second wafer side on a rotatable chuck table constituting a grinding device and holding the bonded wafer; and a grinding step of positioning a grinding wheel having an annularly disposed grinding stone on the first wafer of the bonded wafer held by the chuck table, rotating the chuck table, and rotating the grinding wheel to grind the first wafer.

[0010] After performing the joint surface cutting step and the chamfered portion processing step, it is preferable to include a chamfered portion removing step of removing the chamfered portion of the first wafer. Further, in the grinding step, the chamfered portion may be removed when the first wafer is ground with the grinding wheel. Furthermore, the cutting blade used in the joint surface cutting step is preferably either a wire saw or a cutting blade.

[0011] The process performed in the chamfered portion processing step may be a process of irradiating a condensing point of a laser beam having a wavelength that is transmissive to the first wafer and positioning the condensing point inside the boundary between the effective area and the outer peripheral surplus area of the first wafer to form a modified layer serving as a starting point for cutting. Alternatively, the process performed in the chamfered portion processing step may be a process of positioning a cutting blade at the boundary between the effective area and the outer peripheral surplus area of the first wafer to form a cutting groove reaching the joint surface.

Advantages of the Invention

[0012] The processing method of the bonded wafer of the present invention is a processing method of a bonded wafer in which a first wafer having an effective region and an outer peripheral surplus region surrounding the effective region and having a chamfered portion is bonded to a second wafer. The method includes a bonding surface cutting step of positioning a cutting blade on the outer periphery of the bonded wafer and cutting the bonding surface in the outer peripheral surplus region, and a chamfered portion processing step of performing a process of forming a starting point for removing the chamfered portion at the boundary between the effective region and the outer peripheral surplus region of the first wafer before or after the bonding surface cutting step. The method also includes a holding step of positioning the second wafer side on a rotatable chuck table constituting a grinding device to hold the bonded wafer, and a grinding step of positioning a grinding wheel having an annularly arranged grinding stone on the first wafer of the bonded wafer held by the chuck table, rotating the chuck table, and rotating the grinding wheel to grind the first wafer. Therefore, the chamfered portion of the bonded wafer in which the first wafer having the effective region and the outer peripheral surplus region surrounding the effective region and having the chamfered portion is bonded to the second wafer can be effectively removed.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

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

[0015] The workpiece to be processed by the processing method of the present embodiment is, for example, the bonded wafer W shown in FIGS. 1(a) and 1(b). The bonded wafer W has a diameter of, for example, 300 mm, and is a wafer in which the surface 10a of the first wafer 10 and the surface 12a of the second wafer 12 are bonded together. The first wafer 10 is, for example, a silicon wafer, and as shown in the figure, a plurality of devices D are partitioned by a dicing line L and formed on the surface 10a. The first wafer 10 includes an effective region 10A from the center where the plurality of devices D described above are formed and an outer peripheral surplus region 10B surrounding the effective region 10A. At the outer peripheral end of the outer peripheral surplus region 10B, as can be understood from FIG. 1(b), an annular chamfering portion 10C formed in a curved surface shape is formed. Further, a notch 10d indicating the crystal orientation of the first wafer 10 is formed on the outer periphery of the outer peripheral surplus region 10B. In addition, in FIG. 1(a), an annular dividing line 16 (shown by a two-dot chain line) for distinguishing the effective region 10A and the outer peripheral surplus region 10B is described, but the dividing line 16 is described for convenience of explanation and is not actually attached to the surface 10a of the first wafer 10.

[0016] The second wafer 12 bonded to the above-described first wafer 10 has substantially the same configuration as the first wafer 10 and is provided with a notch 12d indicating the crystal orientation similar to that of the first wafer 10 (explanation of the other details is omitted). As can be understood from FIG. 1(b) in addition to FIG. 1(a), the first wafer 10 is inverted, and the surface 10a of the first wafer 10 and the surface 12a of the second wafer 12 are bonded together with the crystal orientations aligned with reference to the notch 10d and the notch 12d, and are bonded by an appropriate bonding method (for example, room temperature bonding, siloxane bonding, etc.) to form a bonding surface 20 and form a bonded wafer W.

[0017] The bonded wafer W processed by the processing method of the present embodiment is not limited to the above-described bonded wafer W. For example, it may be formed by bonding a first wafer 10 in which a plurality of devices D as described above are not formed in the effective region 10A to a second wafer 12. In that case, the effective region 10A of the first wafer corresponds to, for example, the region where the devices D of the second wafer 12 are formed, and is the region where the bonded wafer W processed by the processing method of the bonded wafer of the present embodiment is individually divided and finally used as a product. In the following description, the case where the bonded wafer W shown in FIG. 1 is processed by the processing method of the bonded wafer of the present embodiment will be described.

[0018] (Bonding surface cutting step) Prepare the above-described bonded wafer W, and perform a bonding surface cutting step of positioning a cutting blade on the outer periphery of the bonded wafer W and cutting the bonding surface 20 in the outer peripheral surplus region 10B. The method of performing the bonding surface cutting step is not particularly limited, but for example, it can be performed by Examples 1 and 2 described below. The present invention also includes the case where a chamfering portion processing step described later is performed before performing the bonding surface cutting step described below, and is not limited to performing the bonding surface cutting step first.

[0019] (Example 1) When performing the bonding surface cutting process according to Example 1, the above-described bonded wafer W is transported to, for example, the first cutting device 30 (only a part is shown) shown in FIG. 2. The first cutting device 30 is configured to include at least a first cutting means 31 and a wafer holding means 32. The first cutting means 31 includes, for example, a wire saw 31a having a diameter of 0.12 mm obtained by electrodepositing diamond abrasive grains of particle size #2000 on a metal wire having a diameter of 0.1 mm with nickel plating as a cutting edge, and a rotary feed driving means 33 for rotating and feeding the wire saw 31a, and a driven feed means 35 for driving the wire saw 31a in a driven feed manner. The rotary feed driving means 33 includes an electric motor 33a, a rotary shaft 33b rotated by the electric motor 33a, and a driving roller 33c disposed at the upper end of the rotary shaft 33b. The driven feed means 35 includes a driven roller 35a and a support shaft 35b rotatably supporting the driven roller 35a. The wire saw 31a is wound around the driving roller 33c and the driven roller 35a, and is adjusted to a desired tension by a tensioner (not shown).

[0020] The wafer holding means 32 includes a chuck table 32a for holding the wafer, a rotary shaft 32b supporting the chuck table 32a, and an electric motor 32c for rotationally driving the rotary shaft 32b. The chuck table 32a is connected to a suction means (not shown), and by operating the suction means, a negative pressure is generated on the holding surface (not shown) of the chuck table 32a to suck and hold the wafer. Although not shown, the wafer holding means 32 includes a machining feed means for moving it toward the wire saw 31a (in the direction indicated by the arrow R5 in the figure).

[0021] The above-described first cutting device 30 has a configuration generally as described above, and an embodiment of Example 1 of the bonding surface cutting process performed using the first cutting device 30 will be described below.

[0022] If the bonded wafer W is transported to the first cutting device 30, as shown in Fig. 2(a), the bonded wafer W is placed on the chuck table 32a and the above-described suction means is operated to suck and hold it. At this time, the height adjusting means of the wafer holding means 32 (not shown) is operated to position the height of the bonding surface 20 of the bonded wafer W to coincide with the height of the wire saw 31a described above.

[0023] Next, the electric motor 33a of the first cutting means 31 is operated, and the drive roller 33c is rotated in the direction indicated by the arrow R1, whereby the wire saw 31a is rotationally fed in the direction indicated by the arrow R2. As a result, the driven roller 35a rotates in the direction indicated by R3, and the wire saw 31a is rotationally fed at a predetermined linear speed, for example, 600 m / min. At this time, the wire saw 31a is adjusted to a predetermined wire tension (for example, 25 N) by a tensoner (not shown). At the same time, the electric motor 32c of the wafer holding means 32 is operated to rotate the bonded wafer W in the direction indicated by the arrow R4. Then, the above-described machining feed means is operated, and as understood from Fig. 2(b) in addition to Fig. 2(a), the bonded wafer W held by the wafer holding means 32 is machined and fed in the direction indicated by the arrow R5. At the same time, 90% concentrated diethylene glycol as a cleaning and coolant is supplied (not shown) to the cutting portion by the wire saw 31a while the wire saw 31a is cut into the bonding surface 20 of the bonded wafer W. The cutting feed speed at this time is, for example, 0.4 mm / min. Then, it is cut and fed horizontally by a predetermined depth (depth) along the bonding surface 20, for example, 2 mm, and as shown in Fig. 2(c), the bonding surface 20 in the outer peripheral surplus region 10B is horizontally cut to form an annular cutting groove 100. Thus, the bonding surface cutting step carried out according to the first embodiment is completed.

[0024] (Embodiment 2) Fig. 3(a) shows a second cutting device 30' in which a second cutting means 36 is disposed instead of the first cutting means 31 in the above-described first cutting device 30, and the bonding surface cutting step of the present invention can be carried out in the mode of Embodiment 2 described below.

[0025] The wafer holding means 32 shown in Fig. 3(a) has the same configuration as that disposed in the above-described first cutting device 30, and a detailed description thereof will be omitted. The second cutting means 36 includes, as shown in the figure, a disk-shaped cutting blade 36a as a cutting edge, a rotating shaft 36b disposed at the upper end of the cutting blade 36a, and an electric motor 36a that rotationally drives the cutting blade 36a together with the rotating shaft 36b. The thickness of the cutting blade 36a is set to a thickness (0.12 mm) corresponding to the width of the cutting groove 100 formed by the wire saw 31a in the above-described Example 1.

[0026] When performing the bonding surface cutting process according to the second embodiment, if the bonded wafer W is transported to the second cutting device 30', it is placed on the chuck table 32a shown in Fig. 3(a), and the above-described suction means is operated to suck and hold it. At this time, the height adjustment means of the wafer holding means 32 (not shown) is operated to position the height of the bonding surface 20 of the bonded wafer W to coincide with the height of the above-described cutting blade 36a.

[0027] Next, the electric motor 36c of the second cutting means 36 is operated to rotate the cutting blade 36a in the direction indicated by the arrow R6. At the same time, the electric motor 32c of the wafer holding means 32 is operated to rotate the bonded wafer W in the direction indicated by the arrow R4. Then, the above-described machining feed means is operated to feed the wafer holding means 32 holding the bonded wafer W in the direction indicated by the arrow R5 for machining feed, and the cutting blade 36a is cut into the bonding surface 20 of the bonded wafer W from the side. The machining feed speed at this time is, for example, 0.4 mm / min. Then, in order to reach a predetermined depth (depth) in the horizontal direction along the bonding surface 20, more specifically, it is fed in by 2 mm of cut, and as shown in Fig. 3(b), the bonding surface 20 in the outer peripheral surplus region 10B is horizontally cut. As a result, a cutting groove 100 similar to the cutting groove 100 formed in Example 1 is formed on the entire circumference of the bonded wafer W. Thus, the bonding surface cutting process performed according to the second embodiment is completed.

[0028] (Chamfering Process) The processing method of the bonded wafer of the present invention performs a chamfering portion processing step of performing processing to form a starting point for removing the chamfering portion 10C at the boundary between the effective region 10A and the outer peripheral surplus region 10B of the first wafer 10 before or after the above-described bonding surface cutting step. The chamfering portion processing step can be performed, for example, by Examples 3 and 4 described below. In the following description, an example in which the chamfering portion processing step is performed after the above-described bonding surface cutting step to form the cutting groove 100 in the bonding surface 20 will be described. However, the chamfering portion processing step described below may be performed before the above-described bonding surface cutting step.

[0029] (Example 3) FIG. 4(a) shows a laser processing apparatus 40 (only a part is shown) configured to be able to perform the chamfering portion processing step of the present invention. The laser processing apparatus 40 includes a chuck table 41 and a laser beam irradiation means 42. The chuck table 41 includes an X-axis feed means for relatively processing and feeding the chuck table 41 and the laser beam irradiation means 42 in the X-axis direction, a Y-axis feed means for relatively processing and feeding the chuck table 41 and the laser beam irradiation means 42 in the Y-axis direction orthogonal to the X-axis direction, and a rotation drive means for rotating the chuck table 41 (all are not shown). The laser beam irradiation means 42 includes a condenser 43, and condenses and irradiates a laser beam LB having a wavelength that is transmissive to the first wafer 10A of the bonded wafer W held on the chuck table 4.

[0030] To perform the chamfering process, the bonded wafer W is transported to the illustrated laser processing apparatus 40. The bonded wafer W transported to the laser processing apparatus 40 is placed on the chuck table 41 with the back surface 10b side of the first wafer 10 facing upward as shown in FIG. 4(a), and is sucked and held by operating suction means (not shown). The bonded wafer W held on the chuck table 41 is aligned using alignment means (not shown) disposed in the laser processing apparatus 40, and the laser beam irradiation position set at the boundary between the effective region 10A and the outer peripheral surplus region 10B of the first wafer 10 is detected. The laser beam irradiation position is the position where a modified layer serving as a starting point for removing the chamfering portion 10C is formed, and is preferably set on the above-described cutting groove 100. In the present embodiment, it is set 2 mm inward from the outer peripheral end corresponding to the depth (depth) of the cutting groove 100 from the outer peripheral end where the chamfering portion 10C is formed. If the laser beam irradiation position is detected as described above, the bonded wafer W is moved by the above-described X-axis feed means and Y-axis feed means, and the detected laser beam irradiation position is positioned directly below the condenser 43 of the laser beam irradiation means 42.

[0031] Next, the condensing point of the laser beam LB irradiated from the condenser 43 of the laser beam irradiation means 42 is positioned inside the laser beam irradiation position set at the boundary portion and irradiated, and the above-described rotational drive means is operated to rotate the chuck table 41 in the direction indicated by the arrow R7 in FIG. 4(a), thereby forming a modified layer 110 that serves as a starting point when removing the chamfering portion 10C. This modified layer 110 is preferably formed in a plurality of layers as shown in FIG. 4(b) by changing the depth position at which the condensing point is positioned and irradiating in the vertical direction.

[0032] The laser processing conditions for forming the above-described modified layer 110 are set as follows, for example. Wavelength: 1099 nm Repetition frequency: 80 kHz Average output: 2.0 W Processing feed rate: 450 mm / s

[0033] The chamfering portion machining step may be carried out according to Example 4 described below.

[0034] (Example 4) Fig. 5(a) shows a cutting device 50 (only a part is shown) configured to be able to carry out the chamfering portion machining step of the present invention. The cutting device 50 is configured to include at least a chuck table 51 and a cutting means 52. A suction means (not shown) is connected to the chuck table 51 so that a negative pressure can be generated on the holding surface on which the bonded wafer W is placed. The cutting means 52 includes a rotary shaft housing 53, a rotary shaft 54 rotatably held by the rotary shaft housing 53, and a cutting blade 55 fixed to the tip of the rotary shaft 54. An electric motor (not shown) for rotationally driving the rotary shaft 54 is disposed on the rear end side of the rotary shaft housing 53. The cutting device 50 is provided with a machining feed means (not shown) for relatively moving the chuck table 51 and the cutting means 52 for machining feed.

[0035] When the bonded wafer W is transported to the above-described cutting device 50 to carry out the chamfering portion machining step, the back surface 10b side of the first wafer 10 of the bonded wafer W is directed upward, placed on the holding surface of the chuck table 51, and the above-described suction means is operated to suck and hold. The bonded wafer W held by the chuck table 51 is aligned using an alignment means (not shown) disposed in the cutting device 50, and a cutting planned position set at the boundary between the effective region 10A and the outer peripheral surplus region 10B of the first wafer 10 is detected. The cutting planned position is a position for forming an annular cutting groove that serves as a starting point for removing the chamfering portion 10C, is set in the outer peripheral surplus region 10B inside the chamfering portion 10C of the first wafer 10, and is preferably set on the above-described cutting groove 100.

[0036] If the above alignment is performed, the moving means (not shown) is actuated to position the cutting blade 55 rotated in the direction indicated by arrow R9 at the planned cutting position set at the above-described boundary portion, and cut-in feed is performed from the back surface 10b side of the first wafer 10. At the same time, the chuck table 51 is rotated in the direction indicated by arrow R8 to form a cutting groove 120. The cutting groove 120 is formed to a depth reaching the bonding surface 20 of the bonded wafer W at a position 2 mm inside from the outer peripheral end portion where the chamfered portion 10C is formed. In the present Example 4, the bonding surface cutting step has been previously performed to form the cutting groove 100, and the cutting groove 120 is formed so as to reach the cutting groove 100. As a result, the chamfered portion 10C is completely separated from the bonded wafer W.

[0037] (Holding Step and Grinding Step) As described above, if the bonding surface cutting step and the chamfered portion machining step are performed, the bonded wafer W is transported to, for example, a grinding apparatus 1 as shown in FIG. 6 in order to perform the holding step and the grinding step described later.

[0038] The grinding apparatus 1 includes at least a chuck table 3 for holding the above-described bonded wafer W, a grinding means 4 for grinding the back surface 10b of the first wafer 10 of the bonded wafer W held by the chuck table 3, and a feed means 5 for feeding the grinding means 4 in the Z-axis direction (vertical direction).

[0039] As understood from FIG. 6, the chuck table 3 includes a holding surface 3a for sucking and holding the bonded wafer W and a frame body 3b that supports and surrounds the holding surface 3a. The holding surface 3a is formed of a porous member having air permeability, and a suction means (not shown) is connected to the frame body 3b. By operating the suction means, a negative pressure is generated on the holding surface 3a, and the bonded wafer W can be sucked and held.

[0040] The chuck table 3 is configured to be rotatable by a rotation driving means (not shown) and is moved by an X-axis moving means (not shown) housed inside the apparatus housing 2 to an arbitrary position in the X-axis direction, for example, a loading / unloading position for loading and unloading the bonding wafer W on the front side in the drawing, and a grinding position where grinding is performed directly below the grinding means 4.

[0041] The grinding means 4 includes at least a rotating shaft 4a, a grinding wheel 4b disposed at the lower end of the rotating shaft 4a, a plurality of grinding wheels 4c annularly disposed on the lower surface of the grinding wheel 4b, an electric motor 4d for rotating the rotating shaft 4a, a support portion 4e for supporting the grinding means 4, and a Z-axis moving base 4f supported by the vertical wall portion 2a of the apparatus housing 2 so as to be movable up and down in the Z-axis direction together with the support portion 4e. The feeding means 5 converts the rotational motion of the pulse motor 5a into a linear motion via a ball screw 5b rotated by the pulse motor 5a and transmits it to the Z-axis moving base 4f, enabling the grinding means 4 to be moved to an arbitrary position in the Z-axis direction (vertical direction).

[0042] Grinding water P is supplied from a grinding water supply source (not shown) to the upper end portion 4a' of the rotating shaft 4a and is supplied to the wafer 10 held by the chuck table 3 and the grinding wheel 4c for grinding the wafer 10 via the inside of the rotating shaft 4a. The grinding apparatus 1 includes a control means (not shown), and each of the above-described operating portions is controlled by a control signal instructed from the control means.

[0043] The grinding apparatus 1 has a configuration generally as described above, and the holding process and the grinding process performed using the illustrated grinding apparatus 1 will be described below.

[0044] When performing the holding process, first, operate the above-described X-axis moving means to move the chuck table 3 to the loading / unloading position on the front side in FIG. 6. Next, position and hold the second wafer 12 side of the bonding wafer W on the chuck table 3. Specifically, place the second wafer 12 side of the bonding wafer W downward and the back surface 10b of the first wafer 10 upward on the chuck table 3, and by operating a suction means (not shown), generate a negative pressure on the holding surface 3a of the chuck table 3 to suck and hold the bonding wafer W on the chuck table 3. Here, when the chamfering process is performed in the form of Example 3 described above, as shown on the left side of FIG. 7(a), the bonding wafer W in a state where the chamfered portion 10C of the first wafer 10 remains in the outer peripheral surplus region 10B is held on the chuck table 3. On the other hand, when the chamfering process is performed in the form of Example 4 described above, since the chamfered portion 10C is separated from the first wafer 10 by the cutting groove 120, before performing the holding process, it is possible for the operator to easily remove the chamfered portion 10C (chamfered portion removal process). Therefore, in that case, as shown on the right side of FIG. 7, the bonding wafer W' including the first wafer 10' in a state where the chamfered portion 10C is removed and a new outer peripheral end portion 10e is exposed is placed on the chuck table 3. In the following description, in the above-described holding process, the description will continue assuming that the bonding wafer W in which the chamfering process is performed in the form shown in Example 3 is held.

[0045] As described above, if the holding process is carried out, while rotating the rotating shaft 4a of the grinding means 4 in the direction indicated by the arrow R10 in FIG. 7(b) at, for example, 6000 rpm, the chuck table 3 is rotated in the direction indicated by the arrow R11 at, for example, 300 rpm. Then, the grinding water P is introduced from the upper end portion 4a' (see FIG. 6) of the rotating shaft 4a by the above-described grinding water supply means and supplied onto the back surface 10b of the first wafer 10 of the bonded wafer W. While supplying the grinding water P, the above-described feeding means 5 is operated, and as shown in FIG. 7(b), the grinding wheel 4c is brought into contact with the back surface 10b of the first wafer 10, and the grinding wheel 4b is fed downward in the direction indicated by the arrow R12 at a grinding feed rate of, for example, 1.0 μm / second. At this time, grinding can be advanced while measuring the thickness of the bonded wafer W with a contact type or non-contact measuring gauge (not shown), and the back surface 10b of the first wafer 10 is ground by a predetermined amount. At this time, the bonded wafer W is thinned, and an external force associated with the grinding process is applied to the bonded wafer W. As shown in FIG. 7(c), starting from the modified layer 110 formed in the above-described chamfering portion processing step, the chamfering portion 10C of the first wafer 10 is separated from the first wafer 10 and removed. As a result, a bonded wafer W' including the first wafer 10' in a state where the chamfering portion 10C is removed and a new outer peripheral end portion 10e is exposed is formed. When the first wafer 10 is thinned and the bonded wafer W reaches a desired thickness, the operation of the grinding means 4 is stopped, and after undergoing cleaning, drying treatment, etc. (description omitted), the grinding process for grinding the back surface 10b of the first wafer 10 is completed.

[0046] As described above, when the chamfering portion processing step is carried out in the form shown in Example 3, when the back surface 10b of the first wafer 10 is ground with the grinding wheel 4c in the above-described grinding process, an external force is applied to the first wafer 10. As a result, starting from the modified layer 110, the chamfering portion 10C is separated and removed, so that the grinding process substantially also serves as a chamfering portion removing process.

[0047] According to the present embodiment, together with the joint surface cutting step, by the form shown in the above-described Example 3, a chamfering portion processing step of forming a modified layer 110 serving as a starting point for removing the chamfering portion 10C inside the boundary portion between the effective region 10A and the outer peripheral surplus region 10B of the first wafer 10 is performed, and then, since the above-described holding step and grinding step are performed, the chamfering portion 10C can be effectively removed.

[0048] Also, when, together with the joint surface cutting step, a chamfering portion processing step of positioning a cutting blade 55 at the boundary portion between the effective region 10A and the outer peripheral surplus region 10B of the first wafer 10 and forming a cutting groove 120 reaching the joint surface 20 is performed according to the form shown in the above-described Example 4, before performing the holding step and the grinding step, since the chamfering portion 10C is easily separated from the first wafer 10, the chamfering portion 10C can be effectively removed.

Explanation of Reference Numerals

[0049] 1: Grinding device 2: Device housing 3: Chuck table 4: Grinding means 4a: Rotation axis 4b: Grinding wheel 4c: Grinding stone 4d: Electric motor 4e: Support portion 5: Feeding means 10: First wafer 10a: Surface 10b: Back surface 10d: Notch 10A: Effective region 10B: Outer peripheral surplus region 10C: Chamfering portion 12: Second wafer 12a: Surface 12b: Back surface 12d: Notch 16: Division line 20: Bonding surface 30: First cutting device 31: First cutting means 31a: Wire saw 32: Wafer holding means 32a: Chuck table 32b: Rotation axis 32c: Electric motor 33: Rotary feed driving means 33a: Electric motor 33b: Rotation axis 33c: Driving roller 35: Driven feed means 35a: Driven roller 35b: Support shaft 40: Laser processing device 41: Chuck table 42: Laser beam irradiation means 43: Condenser 50: Cutting device 51: Chuck table 52: Cutting means 53: Rotation axis housing 54: Rotation axis 55: Cutting blade 100: Cutting groove 110: Modified layer 120: Cutting groove D: Device L: Scribing line P: Grinding water W, W’: Bonded wafer

Claims

1. A method for processing a bonded wafer in which a first wafer having an effective area and an outer peripheral surplus area surrounding the effective area and having a chamfered portion is bonded and joined to a second wafer, comprising: a bonding surface cutting step of positioning a cutting blade on the outer periphery of the bonded wafer and cutting the bonding surface in the outer peripheral surplus area; a chamfered portion processing step of performing a process of forming a starting point for removing the chamfered portion at the boundary between the effective area and the outer peripheral surplus area of the first wafer before or after the bonding surface cutting step; a holding step of positioning the second wafer side on a rotatable chuck table constituting a grinding device and holding the bonded wafer; a grinding step of positioning a grinding wheel having an annularly arranged grinding stone on the first wafer of the bonded wafer held by the chuck table, rotating the chuck table, and rotating the grinding wheel to grind the first wafer; A method for processing a bonded wafer, which includes the above steps.

2. The method for processing a bonded wafer according to claim 1, further including a chamfered portion removing step of removing the chamfered portion of the first wafer after performing the bonding surface cutting step and the chamfered portion processing step.

3. The method for processing a bonded wafer according to claim 1, wherein in the grinding step, the chamfered portion is removed when the first wafer is ground with the grinding wheel.

4. The method for processing a bonded wafer according to claim 1, wherein the cutting blade used in the bonding surface cutting step is either a wire saw or a cutting blade.

5. The process performed in the chamfered portion processing step is to position the focus point of a laser beam having a wavelength that is transmissive to the first wafer inside the boundary between the effective area and the outer peripheral surplus area of the first wafer and irradiate it to form a modified layer serving as a starting point for cutting. The method for processing a bonded wafer according to claim 1.

6. The process performed in the chamfered portion processing step is to position a cutting blade at the boundary between the effective area and the outer peripheral surplus area of the first wafer to form a cutting groove reaching the bonding surface. The method for processing a bonded wafer according to claim 1.

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