Processing device

Abstract

To provide a processing device which can easily align a center of a lower wafer with a rotation center of a chuck table even when centers of two wafers forming a bonded wafer are slightly misaligned.SOLUTION: A processing device includes: a chuck table 34 which may rotate suctioning and holding a bonded wafer; processing means which processes a chamfer part of an upper wafer of the bonded wafer held by the chuck table 34; and center positioning means 35 each of which moves in a center direction O1 of the chuck table 34 at an outer periphery of the bonded wafer placed on the chuck table 34 to align the rotation center O1 of the chuck table 34 with a center of the upper wafer or a lower wafer of the bonded wafer. The center positioning means 35 includes claws which are respectively placed in a first position where the claw contacts with an outer periphery of the lower wafer placed on the chuck table 34 to align the center of the lower wafer with the rotation center O1 of the chuck table 34 and a second position where the claw contacts with an outer periphery of the upper wafer to align the center of the upper wafer with the rotation center of the chuck table 34.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a processing device that processes a chamfered portion of a bonded wafer formed by bonding two wafers together. [Background technology]

[0002] A wafer has a plurality of devices such as ICs and LSIs formed on its surface, separated by planned dividing lines. The back surface is ground by a grinding machine to form the wafer to a predetermined thickness, and then the wafer is divided into individual device chips by a dicing machine for use in electrical devices such as mobile phones and personal computers.

[0003] The grinding device is configured to include a chuck table for holding a wafer, a grinding means having a rotatable grinding wheel with a ring-shaped arrangement of grinding stones for grinding the wafer held on the chuck table, a feeding means for feeding the grinding means for grinding, and a measuring means for measuring the thickness of the wafer, and can process the wafer to the desired thickness.

[0004] However, a chamfer is formed on the outer periphery of the wafer, and when the front side of the wafer is held on a chuck table and the back side of the wafer is ground to thin it, the chamfer becomes a sharp knife edge, causing cracks to form from the outer periphery and progress to the area where the devices are formed, damaging the devices and injuring the operator.

[0005] Therefore, the present applicant has proposed a technique for removing the chamfered portion before grinding the back surface of the wafer (see Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-96295 Summary of the Invention [Problem to be solved by the invention]

[0007] When the workpiece is a bonded wafer formed by bonding two wafers together, the centers of the two wafers may be slightly misaligned, and when processing the upper wafer, the center of rotation of the chuck table may be aligned with the center of the upper wafer held on the chuck table, or the center of rotation of the chuck table may be aligned with the center of the lower wafer held on the chuck table, as necessary. While it is relatively easy to align the center of the upper wafer held on the chuck table with the center of rotation of the chuck table, a problem arises in that it is difficult to accurately align the center of the lower wafer with the center of rotation of the chuck table.

[0008] The present invention has been made in consideration of the above-mentioned facts, and its main technical object is to provide a processing apparatus that can easily align the center of the lower wafer with the center of rotation of the chuck table even when the centers of the two wafers that make up the bonded wafer are slightly misaligned. [Means for solving the problem]

[0009] In order to solve the above-mentioned main technical problem, according to the present invention, there is provided a processing apparatus for processing a chamfered portion of a bonded wafer formed by bonding two wafers together, the processing apparatus including: a rotatable chuck table that suction-holds the bonded wafer; processing means that processes the chamfered portion of an upper wafer of the bonded wafers held on the chuck table; and centering means that moves the outer periphery of the bonded wafer placed on the chuck table toward the center of the chuck table to align the center of rotation of the chuck table with the center of either the upper or lower wafer of the bonded wafers, the centering means having claws that are positionable at a first position in which the outer periphery of the lower wafer placed on the chuck table is brought into contact with the center of rotation of the chuck table to align the center of the lower wafer with the center of rotation of the chuck table, and a second position in which the outer periphery of the upper wafer is brought into contact with the outer periphery of the upper wafer to align the center of rotation of the chuck table.

[0010] Preferably, the jaws are arranged in three numbers to sandwich the bonded wafer toward the center of rotation of the chuck table, and include an advancing / retracting unit that advances and retracts the jaws toward the center of rotation and a selecting unit that selectively positions the jaws at the first position and the second position. The jaws may also include three first jaws positioned at the first position to sandwich the bonded wafer toward the center of rotation of the chuck table, three second jaws positioned at the second position to sandwich the bonded wafer toward the center of rotation of the chuck table, and an advancing / retracting unit that selectively advances and retracts the first jaws and the second jaws toward the center of rotation. A position adjusting unit may also be provided to position the second jaws at the second position. [Effects of the Invention]

[0011] The processing apparatus of the present invention processes the chamfered portion of a bonded wafer formed by bonding two wafers together, and includes a rotatable chuck table that suction-holds the bonded wafer, processing means that processes the chamfered portion of the upper wafer of the bonded wafer held on the chuck table, and centering means that moves the outer periphery of the bonded wafer placed on the chuck table toward the center of the chuck table to align the center of rotation of the chuck table with the center of either the upper or lower wafer of the bonded wafers. The centering means has claws that are positioned at a first position where they contact the outer periphery of the lower wafer placed on the chuck table to align the center of the lower wafer with the center of rotation of the chuck table, and a second position where they contact the outer periphery of the upper wafer to align the center of the upper wafer with the center of rotation of the chuck table. Therefore, even if the centers of the upper and lower wafers are slightly misaligned, the center of the lower wafer can easily be aligned with the center of rotation of the chuck table. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is an overall perspective view of a processing device according to an embodiment of the present invention; [Figure 2]2(a) is a perspective view showing a bonded wafer processed by the processing apparatus shown in FIG. 1, and FIG. 2(b) is a cross-sectional view taken along the line AA of the bonded wafer shown in FIG. [Figure 3] 2 is an enlarged perspective view showing a support column including a chuck table disposed in the processing apparatus shown in FIG. 1 and a center positioning mechanism disposed in the support column. FIG. [Figure 4] FIG. 1(a) is a perspective view showing a mode in which a first claw is brought into contact with the outer periphery of a lower wafer placed on a chuck table to be positioned at a first position where the center of the lower wafer coincides with the center of rotation of the chuck table; FIG. 1(b) is a side view showing a cross section of the chuck table in the mode shown in FIG. 1(a) and also showing the bonded wafers placed on the chuck table from the side. [Figure 5] FIG. 1(a) is a perspective view showing a mode in which the second claws are positioned at a second position in which they come into contact with the outer periphery of an upper wafer placed on a chuck table to align the center of the upper wafer with the center of rotation of the chuck table; FIG. 1(b) is a side view showing a cross section of the chuck table in the mode shown in FIG. 1(a) and a bonded wafer placed on the chuck table as viewed from the side. [Figure 6] 1A is a perspective view showing how laser processing is performed on the chamfered portion of the bonded wafer, and FIG. 1B is a partially enlarged cross-sectional view showing a modified layer formed by the laser processing shown in FIG. 1A. [Figure 7] 1A is a perspective view showing how a chamfered portion of a bonded wafer is cut, and FIG. 1B is a partially enlarged cross-sectional view showing a cut surface formed by the cutting shown in FIG. 1A. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a processing apparatus configured based on the present invention will be described in detail with reference to the accompanying drawings.

[0014] 1 shows a laser processing apparatus 1 as an example of a processing apparatus configured based on the present invention. The illustrated laser processing apparatus 1 is a processing apparatus for processing a bonded wafer W formed by bonding two wafers together, and includes a rotatable chuck table 34 that suction-holds the bonded wafer W, a processing means 6 that processes the chamfered portion of the upper wafer of the bonded wafer W held on the chuck table 34, and a centering means 35 that moves the outer periphery of the bonded wafer W placed on the chuck table 34 toward the center of the chuck table 34 to align the center of rotation of the chuck table 34 with the center of either the upper wafer or the lower wafer of the bonded wafer W.

[0015] A specific example of a bonded wafer W processed by the laser processing apparatus 1 of this embodiment will be described with reference to Fig. 2. As shown in Fig. 2(a), the bonded wafer W is formed, for example, by bonding a first wafer 10 and a second wafer 12. As shown in the figure, the first wafer 10 has a plurality of devices D formed on its surface 10a, which are partitioned by planned division lines L. The surface 10a of the wafer 10 is formed with a central effective area 10A including a device region in which the plurality of devices D are formed, and a peripheral excess area 10B having a chamfered portion 10C formed on its outer periphery surrounding the effective area 10A. A notch 10D indicating the crystal orientation is also formed on the outer periphery. In addition, in Figure 2(a), a circular dividing line 16 (shown by a two-dot chain line) is shown dividing the effective area 10A and the peripheral excess area 10B, but this dividing line 16 is shown for convenience of explanation and is not actually applied to the surface 10a of the first wafer 10.

[0016] The second wafer 12 to be bonded to the first wafer 10 described above has a similar configuration to the first wafer 10, and as shown in FIG. 2(a), a plurality of devices D are formed on the surface 12a, separated by planned division lines L. A chamfered portion 12c is formed on the outer periphery, and a notch 12d indicating the crystal orientation is also formed. The first wafer 10 and the second wafer 12 are, for example, silicon wafers having a diameter of 300 mm and a thickness of 700 μm.

[0017] The bonded wafer W is formed by inverting the first wafer 10 as shown in the figure, with the back surface 10b facing upward and the front surface 10a facing downward, aligning the front surface 10a of the first wafer 10 with the front surface 12a of the second wafer 12 based on the notches 10D and 12d, and bonding them together by an appropriate bonding method. Note that the bonding method for bonding the first wafer 10 and the second wafer 12 is not particularly limited, but for example, the insulating film on the surface may be made hydrophilic by a surface activation treatment, and the front surface 10a of the first wafer 10 and the front surface 12a of the second wafer 12 may be bonded by pressure bonding to form a siloxane bond on the bonding surfaces, or by bonding using an appropriate adhesive.

[0018] When forming the above-described bonded wafer W, the center of the first wafer 10 and the center of the second wafer 12 may not perfectly coincide with each other, and may be bonded with a slight misalignment. In the bonded wafer W of this embodiment, as can be seen from FIG. 2(b), which shows the cross section AA of FIG. 2(a), there is a slight misalignment of up to about 50 μm in the diameter direction between the first wafer 10 and the second wafer 12. In the following description, it is assumed that processing is performed on a bonded wafer W including such a slight misalignment.

[0019] 1, the laser processing apparatus 1 will be described in more detail. The laser processing apparatus 1 is provided with: a holding means 3 disposed on a base 2 and including the chuck table 34 and the centering means 35 of the present invention; a moving means 4 for moving the holding means 3; a frame 5 consisting of a vertical wall 5a erected on the side of the moving means 4 and a horizontal wall 5b extending horizontally from the upper end of the vertical wall 5a; an imaging means 7 for imaging the bonded wafer W held on the chuck table 34 of the holding means 3 and detecting the position to be processed by the processing means 6; and a control means and a display means (not shown).

[0020] The processing means 6 is a laser beam application means that applies a laser beam having a wavelength that is transparent to the first wafer 10, and an optical system that constitutes the processing means 6 and an imaging means 7 are housed inside the horizontal wall portion 5b of the frame 5. A condenser 61 that constitutes part of the processing means 6 and applies a laser beam toward the bonded wafer W is disposed on the lower surface side of the tip of the horizontal wall portion 5b. The imaging means 7 is disposed on the lower surface side of the tip of the horizontal wall portion 5b at a position adjacent to the condenser 61 in the X-axis direction indicated by the arrow X in the figure.

[0021] The holding means 3 includes a rectangular X-axis movable plate 31 mounted on the base 2 so as to be movable in the X-axis direction, a rectangular Y-axis movable plate 32 mounted on the X-axis movable plate 31 so as to be movable in the Y-axis direction, and a substantially cylindrical support column 33 fixed to the upper surface of the Y-axis movable plate 32. A chuck table 34 for holding the bonded wafer W is formed on the upper end of the support column 33. The chuck table 34 is configured to be rotatable by a rotation drive means (not shown) housed in the support column 33. A circular suction chuck 34a made of a porous material with air permeability and having an XY plane defined by the X and Y coordinates as its holding surface is disposed on the upper surface of the chuck table 34. The suction chuck 34a is connected to a suction means (not shown) through a flow path passing through the support column 33. Activating the suction means generates a negative pressure on the suction chuck 34a.

[0022] The moving means 4 includes X-axis moving means 41 that moves in the X-axis direction and Y-axis moving means 44 that moves the holding means 3 in the Y-axis direction. The X-axis moving means 41 converts the rotational motion of a motor 42 into linear motion via a ball screw 43 and transmits the linear motion to the X-axis movable plate 31, moving the X-axis movable plate 31 in the X-axis direction along a pair of guide rails 2a, 2a arranged on the base 2 along the X-axis direction. The Y-axis moving means 44 converts the rotational motion of a motor 45 into linear motion via a ball screw 46 and transmits the linear motion to the Y-axis movable plate 32, moving the Y-axis movable plate 32 in the Y-axis direction along a pair of guide rails 31a, 31a arranged on the X-axis movable plate 31 along the Y-axis direction.

[0023] FIG. 3 shows the centering means 35 of this embodiment together with the support column 33 constituting part of the holding means 3. The centering means 35 of this embodiment is a means for moving the outer periphery of the bonded wafer W placed on the chuck table 34 toward the center to align the rotation center O1 of the chuck table 34 with the center of the upper or lower wafer of the bonded wafer W. The centering means 35 of this embodiment is composed of three centering mechanisms 35a, and some of the centering mechanisms 35a are housed in a centering mechanism housing portion 350 formed on the outer periphery of the support column 33. For convenience of explanation, FIG. 3 shows a perspective view of the centering mechanism housing portion 350 with a portion cut away to show the internal space 350a, and an enlarged view of the centering mechanism 35a housed in the internal space 350a, extracted to the left in FIG. 3.

[0024] The centering mechanism 35a constituting the illustrated centering means 35 includes a first claw 352a positioned at a first position where it contacts the outer periphery of the lower wafer of the bonded wafer W placed on the chuck table 34 to align the center of the lower wafer with the rotation center O1 of the chuck table 34, and a second claw 353a positioned at a second position where it contacts the outer periphery of the upper wafer of the bonded wafer W placed on the chuck table 34 to align the center of the upper wafer with the rotation center O1 of the chuck table 34.

[0025] The first claws 352a and the second claws 353a are arranged in threes at intervals of 120° so as to sandwich the bonded wafer W placed on the chuck table 34 toward the rotation center O1 of the chuck table 34, and are equipped with an advancing / retreating section 35A that moves the first claws 352a and the second claws 353a forward and backward in the direction toward the rotation center O1 of the chuck table 34, and a selecting section 35B that selectively positions the first claws 352a or the second claws 353a constituting the claws of the present invention at the first position or the second position.

[0026] The illustrated advancing / retreating unit 35A includes a first pulse motor 351, a hollow first rotating shaft 352 that is rotated forward or backward in the direction indicated by arrow R1 by the first pulse motor 351, a second rotating shaft 353 that is inserted into the hollow interior of the first rotating shaft 352 and protrudes from the upper and lower ends of the first rotating shaft 352, a circular first connecting plate 354 that is disposed at the lower end of the second rotating shaft 353 and has a flat lower surface, a spring 355 that is disposed between the upper surface of the first connecting plate 354 and the lower end of the first rotating shaft 352, and a rotary connecting unit 356 that includes an elongated hole 352b formed below the first rotating shaft 352, that penetrates the hollow interior of the first rotating shaft 352 and runs along the longitudinal direction (up and down direction), and an engaging pin 353b formed on the second rotating shaft 353 that engages with the elongated hole 352b and protrudes outward.

[0027] The first claw 352a is disposed on the upper end of the first rotating shaft 352, and the second claw 353a is disposed on the upper end of the second rotating shaft 353. As can be seen from Fig. 3, the second rotating shaft 353 can move up and down within the elongated hole 352b that constitutes the rotational coupling part 356 within a range in which the engagement pin 353b of the second rotating shaft 353 moves, and the rotational coupling part 356 restricts the second rotating shaft 353 from rotating relative to the first rotating shaft 352. This allows the second rotating shaft 353 to rotate by rotating the first rotating shaft 352 forward or backward in the direction indicated by arrow R1.

[0028] The selection unit 35B includes a second pulse motor 357 that rotates a third rotation shaft 357a having a male thread formed on its side, a circular regulating plate 358 having a rectangular opening 358a in its center, a lifting rod 357b having a rectangular cross section that is inserted into the rectangular opening 358a and threadedly engages with the third rotation shaft 357a from below so that it moves up and down as the third rotation shaft 357a rotates, and a second connecting plate 357c that is formed at the upper end of the lifting rod 357b and has a flat upper surface. The lower surface of the first connecting plate 354 of the advance / retreat unit 35A and the upper surface of the second connecting plate 357c of the selection unit 35B are in slidable contact with each other via flat surfaces and are not fixed to each other.

[0029] The first pulse motor 351, the second pulse motor 357, and the regulating plate 358 that constitute the centering mechanism 35a are fixed at predetermined positions in the internal space 350a of the centering mechanism housing 350. Therefore, by operating the second pulse motor 357 to rotate the third rotating shaft 357a forward or backward in the direction indicated by arrow R2, the lifting rod 357b, whose rotation is regulated by the regulating plate 358, can be raised and lowered in the direction indicated by arrow R3. That is, by operating the second pulse motor 357, the third rotating shaft 357a, which is threaded into a female threaded hole formed inside the lifting rod 357b, rotates to raise and lower the lifting rod 357b in the direction indicated by arrow R3. This raises and lowers the second rotating shaft 353 in the direction indicated by arrow R4 via the second connecting plate 357c and the first connecting plate 354. As a result, the vertical position of the second claw 353a formed on the upper end of the second rotating shaft 353 can be adjusted to a desired height. The selection unit 35B configured in this manner functions as a position adjustment unit that causes the second claw 353a to correspond to a second position that coincides with the outer periphery of the upper wafer of the bonded wafers W placed on the chuck table 34.

[0030] In the centering mechanism 35 a in the above-described embodiment, the height of the first rotating shaft 352 does not change, and the height of the first claws 352 a formed on the upper end of the first rotating shaft 352 is set in advance to correspond to the height of a first position that is to be aligned with the outer periphery of the lower wafer of the bonded wafers W placed on the chuck table 34.

[0031] As shown in FIG. 3, three center positioning mechanisms 35a constituting the center positioning means 35 of this embodiment are arranged on the outer periphery of the support 33, and the first pulse motor 351 and the second pulse motor 357 of each center positioning mechanism 35a are controlled by a control means (not shown) so that they operate in the same manner.

[0032] The laser processing apparatus 1 of this embodiment has roughly the configuration as described above, and the functions and effects of the laser processing apparatus 1 of this embodiment will be described below.

[0033] First, the bonded wafer W is carried into the laser processing apparatus 1 by a conveying means not shown, and is placed on the chuck table 34 with the second wafer 12 facing downward and the first wafer 10 facing upward, as shown in Fig. 4(a). Here, when the center O2 of the second wafer 12 constituting the lower wafer of the bonded wafer W is to be aligned with the rotation center (O1) of the chuck table 34, the suction means is not operated, negative pressure is not generated in the internal passage 34b of the chuck table 34 shown in Fig. 4(b), and the bonded wafer W is not held by suction on the suction chuck 34a. In this state, the first pulse motor 351 of the advancing / retracting unit 35A is operated to constitute the center positioning means 35. 4(a) and 4(b), the first jaws 352a formed on the upper ends of the first rotary shafts 352 and positioned at first positions are advanced in the direction indicated by the arrow R5 in the figure, so that the first jaws 352a come into contact with the chamfered portion 12c on the outer periphery of the second wafer 12, which is the lower wafer, and the three first jaws 352a clamp the second wafer 12 toward the rotation center O1 of the chuck table 34. This causes the center O2 of the second wafer 12 and the rotation center O1 of the chuck table 34 to coincide with each other. After aligning the center O2 of the second wafer 12 with the rotation center O1 of the chuck table 34 in this manner, the advancing / retreating section 35A is operated to move the first claws 352a and the second claws 353a to a retracted position (the state shown in FIG. 3) away from the chuck table 34, and then the suction means is operated to suction-hold the bonded wafer W onto the chuck table 34.

[0034] According to the above-described embodiment, even if the center of the first wafer 10 constituting the upper wafer and the center of the second wafer 12 constituting the lower wafer are slightly misaligned, the center O2 of the second wafer 12 constituting the lower wafer can be easily aligned with the rotation center O1 of the chuck table 34.

[0035] Furthermore, in the bonded wafers W placed on the chuck table 34, when the center O3 of the first wafer 10 constituting the upper wafer of the bonded wafers W is to be aligned with the rotation center O1 of the chuck table 34, the second pulse motor 357 of the selection unit 35B, which functions as the position adjustment unit of the present invention, is operated to lift the second rotating shaft 353. At this time, the number of pulses when operating the second pulse motor 357 is calculated from the thickness (700 μm) of the first wafer 10 and the thickness (700 μm) of the second wafer 12, and the second claws 353 formed on the upper end of the second rotating shaft 353 are accurately positioned at a second position that coincides with the outer periphery of the first wafer 10 constituting the upper wafer.

[0036] Then, without operating the suction means, without generating a negative pressure in the internal passage 34b of the chuck table 34 shown in FIG. 5(b), and without holding the bonded wafer W by suction on the suction chuck 34a, the first pulse motor 351 of the advancing / retreating unit 35A is operated to reverse the first rotating shaft 352 of each center positioning mechanism 35a and rotate the second rotating shaft 353, as shown in FIG. 5(a). 5(a) and 5(b), the second claws 353a formed on the upper end of the second rotating shaft 353 are advanced in the direction indicated by the arrow R6 in the drawings, and the second claws 353a come into contact with the chamfered portion 10C on the outer periphery of the first wafer 10, which is the upper wafer, and the three second claws 353a grip the first wafer 10 toward the rotation center O1 of the chuck table 34, thereby aligning the center O3 of the first wafer 10 with the rotation center O1 of the chuck table 34. Once the center O3 of the first wafer 10 and the rotation center O1 of the chuck table 34 are aligned in this manner, the first claws 352a and the second claws 353a move to a retracted position (the state shown in FIG. 3) away from the chuck table 34, and the suction means is activated to suction-hold the bonded wafer W on the chuck table 34.

[0037] According to the above-described embodiment, even if the center of the first wafer 10 constituting the upper wafer and the center of the second wafer 12 constituting the lower wafer are slightly misaligned, the center O3 of the upper wafer (first wafer 10) can be easily aligned with the rotation center O1 of the chuck table 34.

[0038] As described above, after the center O2 of the lower wafer (second wafer 12) is aligned with the rotation center O1 of the chuck table 34, or the center O3 of the upper wafer (first wafer 10) is aligned with the rotation center O1 of the chuck table 34, laser processing is performed on the chamfered portion 10C of the first wafer 10 using the processing means 6 of the laser processing device 1.

[0039] More specifically, first, the image of the bonded wafer W held by suction on the chuck table 34 is taken using the imaging means 7 arranged in the laser processing apparatus 1, and the outer periphery where the chamfered portion 10C of the first wafer 10 constituting the bonded wafer W is formed is detected. Information on the detected outer periphery position is stored in a control means (not shown).

[0040] Based on the positional information of the outer periphery (chamfered portion 10C) detected by the imaging means 7, the moving means 4 is operated to position the condenser 61 of the processing means 6 at a target processing position near the chamfered portion 10C formed in the outer periphery excess region 10B of the first wafer 10, as shown in FIG. 6(a). For convenience of explanation, the center positioning mechanism 35a is omitted from FIG. 6(a). Then, as shown in FIG. 6(b), a focal point of a laser beam LB having a wavelength that is transparent to the first wafer 10 is positioned and irradiated inside the chamfered portion 10C of the bonded wafer W, and the rotation drive means for rotating the chuck table 34 is operated to rotate the bonded wafer W in the direction indicated by arrow R7, thereby forming an annular modified layer 100 in the chamfered portion 10C of the bonded wafer W. In the embodiment shown in FIG. 6(b), multiple modified layers 100 are formed in the vertical direction by changing the depth at which the focal point is positioned.

[0041] After the above-described laser processing is performed, the bonded wafer W is transferred to a grinding device (not shown), where grinding is performed on the back surface 10b of the first wafer 10 of the bonded wafer W, thereby thinning the first wafer 10 to a desired thickness. As described above, the annular modified layer 100 is formed on the chamfered portion 10C of the first wafer 10, and by performing grinding on the back surface 10b of the first wafer 10 using the grinding device as described above, an external force is applied to the modified layer 100, causing a crack to extend in the vertical direction, and the chamfered portion 10C is removed from the first wafer 10.

[0042] As described above, before performing laser processing on the bonded wafer W, if the center O2 of the second wafer 12 constituting the lower wafer is aligned with the rotation center O1 of the chuck table 34 and the bonded wafer W is held by suction on the chuck table 34, the modified layer 100 is formed at a position equidistant (for example, 149.5 mm) from the center O2 of the second wafer 12 constituting the lower wafer, and the chamfered portion 10C of the first wafer 10 is removed starting from the modified layer 100, so that the peripheral excess region including the chamfered portion 12c of the second wafer 12 bonded to the first wafer 10 is exposed with a uniform width.

[0043] Furthermore, before laser processing is performed on the bonded wafer W, if the center O3 of the first wafer 10 constituting the upper wafer is aligned with the rotation center O1 of the chuck table 34 and the bonded wafer W is held by suction on the chuck table 34, the modified layer 100 is formed at a position equidistant (for example, 149.5 mm) from the center O3 of the first wafer 10 constituting the upper wafer, and when the chamfered portion 10C is removed starting from the modified layer 100, the outer periphery of the first wafer 10 including the chamfered portion 10C is removed with an equal width.

[0044] Before performing laser processing on the bonded wafer W, whether to align the center O2 of the second wafer 12 constituting the lower wafer with the center of rotation O1 of the chuck table 34 and hold the bonded wafer W by suction on the chuck table 34, or to align the center O3 of the first wafer 10 constituting the upper wafer with the center of rotation O1 of the chuck table 34 and hold the bonded wafer W by suction on the chuck table 34 is determined appropriately depending on the types of the first wafer 10 and second wafer 12 constituting the bonded wafer W, the specifications of the device D, etc.

[0045] Although the above-described embodiment illustrates an example in which the present invention is applied to the laser processing apparatus 1, the present invention is not limited thereto. For example, the present invention may be applied to a cutting apparatus 8 (only a portion of which is shown) as shown in FIG. 7 . The cutting apparatus 8 includes a cutting means 80 disposed as a processing means for processing the chamfered portion of the bonded wafer W, a chuck table 82 for suction-holding the bonded wafer W, and an alignment means (not shown). The cutting apparatus 8 also includes a support (not shown) on the upper end of which the chuck table 82 is disposed, and a centering means (not shown) configured according to the present invention disposed on the support. The support and the centering means have the same configuration as the support 33 and the centering means 35 of the laser processing apparatus 1 described with reference to FIG. 3 , and therefore detailed description thereof will be omitted. The cutting means 80 includes a rotary shaft housing 81 that rotatably supports a rotary shaft 84, a cutting blade 83 fixed to the tip of the rotary shaft 84, and an electric motor (not shown) disposed in the rotary shaft housing 81 and for rotating the rotary shaft 84. The cutting means 80 is a means for removing the chamfered portion 10C of the first wafer 10 constituting the upper wafer of the bonded wafer W held by suction on the chuck table 82.

[0046] The above-described cutting device 8 is equipped with the same support columns and centering means as the laser processing device 1 described above, and therefore, before the second wafer 12 of the bonded wafers W is placed facing downward on the chuck table 82 and held by suction, the centering means configured according to the present invention can be used to align the center of the second wafer 12 constituting the lower wafer with the center of rotation of the chuck table 82 or the center of the first wafer 10 constituting the upper wafer with the center of rotation of the chuck table 82. Once the centering means has positioned the center of the first wafer 10 or second wafer 12 constituting the bonded wafer W at the rotation center position of the chuck table 82, negative pressure is generated on the holding surface of the chuck table 82 to hold the bonded wafer W by suction.

[0047] Then, the cutting blade 83 is rotated in the direction indicated by the arrow R8 in FIG. 8, and the chuck table 82 is rotated in the direction indicated by the arrow R9, and the cutting means 80 is fed in the direction indicated by the arrow R10 through the thickness (700 μm) of the first wafer 10 to perform cutting on the chamfered portion 10C of the first wafer 10, and the chamfered portion 10C is removed to form a cut surface 10d as shown in FIG. 7(b).

[0048] Even in this case, if the center O2 of the second wafer 12 constituting the lower wafer is aligned with the rotation center O1 of the chuck table 34 and the bonded wafer W is held by suction on the chuck table 34 before cutting the bonded wafer W, the chamfered portion 10C of the first wafer 10 is removed at a position equidistant (for example, 149.5 mm) from the center O2 of the second wafer 12 constituting the lower wafer. Therefore, after the chamfered portion 10C is removed, the outer periphery including the chamfered portion 12c of the second wafer 12 bonded to the first wafer 10 is exposed with a uniform width.

[0049] Furthermore, before cutting the bonded wafer W, if the center O3 of the first wafer 10 constituting the upper wafer is aligned with the rotation center O1 of the chuck table 34 and the bonded wafer W is held by suction on the chuck table 34, the chamfered portion 10C of the first wafer 10 is removed at a position equidistant (for example, 149.5 mm) from the center O3 of the first wafer 10 constituting the upper wafer. Therefore, the outer periphery of the first wafer 10 including the chamfered portion 10C is removed with a uniform width.

[0050] Although the above-described laser processing apparatus 1 includes three first jaws 352a positioned at the first position toward the rotation center O1 of the chuck table 34 so as to sandwich the bonded wafer W therebetween, and three second jaws 353a positioned at the second position and arranged toward the rotation center O1 of the chuck table 34 so as to sandwich the bonded wafer W therebetween, the present invention is not limited to this. For example, even if the first jaws 352a arranged at the upper end of the first rotating shaft 352 are omitted from the above-described configuration, it is possible to configure a processing apparatus that achieves the effects of the present invention. More specifically, in the center positioning mechanism 35a described with reference to FIG. 3, the selector 35B sets the positionable range of the second jaws 353a arranged at the upper end of the second rotating shaft 353 so as to cover the second wafer 12 constituting the lower wafer and the first wafer 10 constituting the upper wafer. This makes it possible to operate the selection unit 35B in response to an operator's instruction to position the second claw 353a at a first position that matches the outer periphery of the second wafer 12 that constitutes the lower wafer placed on the chuck table 34, or to position it at a second position that matches the outer periphery of the first wafer 10 that constitutes the upper wafer. [Explanation of symbols]

[0051] 1: Laser processing equipment 2: Base 3: Holding means 31:X-axis movable plate 32: Y-axis direction movable plate 33: Prop 34: Chuck table 35: Center positioning means 35a: Center positioning mechanism 35A: Advancement and retreat section 35B: Selection section 350: Center positioning mechanism housing 351: First pulse motor 352: First rotation axis 352a: First Claw 352b: Long hole 353: Second rotation axis 353a: Second Claw 353b: Engagement pin 354: First connecting plate 355: Spring 356: Rotating connection part 357: Second pulse motor 357a: Third axis of rotation 357b: Lifting rod 357c: Second connecting plate 358:Regulation plate 358a: opening 4. Transportation 41:X-axis movement means 44: Y-axis movement means 5: Frame 5a: Vertical wall 5b:Horizontal wall part 6: Processing means 61: Concentrator 7: Imaging means 7 8:Cutting equipment 80:Cutting means 81: Rotating shaft housing 82: Chuck table 83: Cutting blade 10: First wafer 10a: surface 10b: Back side 10d: Cutting surface 10A: Effective area 10B: Surplus outer area 10C: Chamfered part 10D:Notch 12: Second wafer 12a: Surface 12b: Back 12c: Chamfered part 12d: Notch 100: Modified layer

Claims

1. A processing apparatus for processing a chamfered portion of a bonded wafer formed by bonding two wafers, the apparatus includes a rotatable chuck table that holds the bonded wafers by suction, a processing means that processes a chamfered portion of an upper wafer of the bonded wafers held on the chuck table, and a center positioning means that moves the outer periphery of the bonded wafer placed on the chuck table toward the center of the chuck table to align the center of rotation of the chuck table with the center of the upper wafer or the lower wafer of the bonded wafers, The centering means is a processing device having claws that can be positioned at a first position where they contact the outer periphery of the lower wafer placed on the chuck table to align the center of the lower wafer with the center of rotation of the chuck table, and at a second position where they contact the outer periphery of the upper wafer to align the center of the upper wafer with the center of rotation of the chuck table.

2. 2. The processing device according to claim 1, wherein the claws are arranged in three numbers so as to sandwich the bonded wafer toward a rotation center of the chuck table, and the processing device further comprises an advancing / retreating unit which advances and retracts the claws toward the rotation center, and a selecting unit which selectively positions the claws at the first position and the second position.

3. 2. The processing device according to claim 1, wherein the jaws include three first jaws positioned at the first position so as to sandwich the bonded wafer toward the rotation center of the chuck table, three second jaws positioned at the second position and arranged so as to sandwich the bonded wafer toward the rotation center of the chuck table, and an advancing / retracting unit that selectively moves the first jaws and the second jaws toward the rotation center.

4. The processing device according to claim 3 , further comprising a position adjusting unit that causes the second claw to correspond to the second position.

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