Bonded wafer processing method

Abstract

To provide a processing method for a bonded wafer capable of preventing dimples from being formed on a rear face of a wafer and / or this wafer from being damaged when cutting the wafer in a state where a bonded wafer is held by sucking the rear face of a support wafer and subsequently polishing the rear face side of the wafer in a similar state.SOLUTION: A processing method for a bonded wafer includes: a cutting step of cutting a wafer in a state where the bonded wafer is held by sucking a rear face of a support wafer; and a washing step of washing the rear face of the support wafer between the former cutting step and a cutting step of cutting the rear face side of the wafer in a similar state. Thus, cutting dust deposited on the rear face of the support wafer can be washed away in the washing step prior to the latter cutting step. As a result, dimples can be prevented from being formed on the rear face of the wafer and / or the wafer can be prevented from being damaged in the cutting steps.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for processing a bonded wafer including a wafer having a plurality of devices formed on its front surface and a chamfered portion on its outer periphery, and a support wafer having a surface to be bonded to the front surface of the wafer. [Background technology]

[0002] Chips for devices such as integrated circuits (ICs) are essential components in various electronic devices such as mobile phones and personal computers. Such chips are manufactured, for example, by grinding a wafer having multiple devices formed on its front surface to a desired thickness, and then cutting through the wafer along the boundaries of the multiple devices.

[0003] Wafers are prone to cracking at their outer edges. Therefore, in the chip manufacturing process, the outer edges of wafers are often chamfered, i.e., a chamfer is formed on the outer edges of the wafer, prior to various processes. However, when the backside of a wafer with a chamfered outer edge is ground, the backside of the outer edge becomes shaped like a knife edge.

[0004] Stress is concentrated in this area, making it prone to cracks. For this reason, in the chip manufacturing process, the wafer is cut to remove part of the front side of the chamfer formed on the outer periphery of the wafer, and then the back side of the wafer is ground to remove the remaining part of the chamfer (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-173961 Summary of the Invention [Problem to be solved by the invention]

[0006] In the chip manufacturing process, a wafer is sometimes bonded to another wafer using an adhesive to form a bonded wafer, and then this bonded wafer is divided to manufacture chips. For example, in order to miniaturize the chips to be manufactured, multiple wafers (hereinafter also referred to as "device wafers") each having multiple devices formed on their front surface may be bonded to a support wafer using an adhesive.

[0007] Specifically, first, the front surface of a support wafer and the front surface of a device wafer are bonded together with an adhesive to form a bonded wafer. Next, while the bonded wafer is held by suctioning the back surface of the support wafer, the device wafer is cut to remove the chamfered portion formed on the outer periphery of the device wafer and the adhesive adhering to the chamfered portion. Next, the back surface of the device wafer is ground.

[0008] Next, the backside of the ground device wafer is bonded to the frontside of another device wafer via an adhesive to form a bonded wafer including the two stacked device wafers. Next, while the bonded wafer is held by suctioning the backside of the support wafer, the other device wafer is cut to remove the chamfered portion formed on the outer periphery of the other device wafer and the adhesive adhering to the chamfered portion. Next, the backside of the other device wafer is ground.

[0009] By repeating the same process as necessary, a bonded wafer including three or more stacked device wafers can be formed. When forming a bonded wafer in this manner, the adhesive adhering to the chamfered portion formed on the outer periphery of the device wafer is removed, and then the backside of the device wafer is ground. This prevents the adhesive from being pulled out during grinding, which would otherwise damage the bonded wafer.

[0010] However, when the device wafer is cut while the bonded wafer is held by suctioning the back surface of the support wafer, cutting debris generated by this cutting may be drawn into the back surface side of the support wafer and adhere to the back surface of the support wafer. If the back surface side of the device wafer is ground while cutting debris is adhered to the back surface of the support wafer, dimples may be formed on the back surface of the device wafer and / or the device wafer may be damaged.

[0011] In view of this, an object of the present invention is to provide a method for processing a bonded wafer that can prevent dimples from being formed on the back surface of the device wafer and / or damage to the device wafer when the back surface of the device wafer is ground in a similar state after cutting the device wafer while holding the bonded wafer by suctioning the back surface of the support wafer. [Means for solving the problem]

[0012] According to the present invention, there is provided a method for processing a bonded wafer including a wafer having a plurality of devices formed on a front surface side and a chamfered portion on an outer periphery thereof, and a support wafer having a front surface to be bonded to the front surface of the wafer, the method comprising the steps of: cutting the wafer so as to remove the chamfered portion of the wafer while holding the bonded wafer by suctioning the back surface of the support wafer; and, after the cutting step, a first cleaning step of cleaning the back surface of the wafer; and after the first cleaning step, holding the bonded wafer by suctioning the back surface of the wafer. Cleaning the back surface of the support wafer. No. 2 A washing step and No. 2 After the cleaning step, the back surface of the support wafer is sucked to hold the bonded wafer. Applicable and a grinding step of grinding the backside of the bonded wafer. [Effects of the Invention]

[0013] The present invention includes a cleaning step for cleaning the back surface of the support wafer between a cutting step in which the wafer is cut while holding the bonded wafer by suctioning the back surface of the support wafer, and a grinding step in which the back surface of the wafer is ground in the same state.

[0014] Therefore, in the present invention, cutting debris adhering to the backside of the support wafer can be washed away in the cleaning step prior to the grinding step, and as a result, in the present invention, it is possible to prevent dimples from being formed on the backside of the device wafer and / or damage to the device wafer in the grinding step. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1(A) is a top view that schematically shows an example of a wafer, and FIG. 1(B) is a cross-sectional view that schematically shows an example of a wafer. [Figure 2] FIG. 2 is a flow chart that schematically shows an example of a method for processing a bonded wafer. [Figure 3] FIG. 3(A) is a cross-sectional view that schematically shows an example of a bonded wafer, and FIG. 3(B) is a partially cross-sectional side view that schematically shows the cutting step. [Figure 4] FIG. 4(A) is a partial cross-sectional side view schematically showing the state of the wafer cleaning step, and FIG. 4(B) is a partial cross-sectional side view schematically showing the state of the support wafer cleaning step. [Figure 5] FIG. 5(A) is a partial cross-sectional side view that schematically shows the state of the grinding step, and FIG. 5(B) is a cross-sectional view that schematically shows the bonded wafer after the grinding step is completed. [Figure 6] FIG. 6 is a flowchart schematically showing another example of the method for processing a bonded wafer. [Figure 7] FIG. 7(A) is a cross-sectional view schematically showing another example of a bonded wafer, and FIG. 7(B) is a cross-sectional view schematically showing the bonded wafer after the second grinding step is completed. DETAILED DESCRIPTION OF THE INVENTION

[0016] An embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1(A) is a top view showing an example of a wafer, and Fig. 1(B) is a cross-sectional view showing an example of the wafer. The wafer 11 shown in Figs. 1(A) and 1(B) is made of, for example, silicon (Si).

[0017] A plurality of devices 13 are formed on the front surface 11a of the wafer 11. Each of the plurality of devices 13 includes, for example, an element for constituting an IC, a semiconductor memory, or a CMOS (Complementary Metal Oxide Semiconductor) image sensor. The boundaries of the plurality of devices 13 extend, for example, in a grid pattern.

[0018] Furthermore, the wafer 11 may have openings (through holes extending from the front surface 11a to the back surface 11c) or grooves in which wiring such as through-silicon vias (TSVs (Through-Silicon Vias)) is provided. The outer peripheral edge of the wafer 11 is chamfered, that is, a chamfered portion is formed on the outer peripheral edge of the wafer 11. In other words, the side surface 11b of the wafer 11 is curved so as to be convex outward.

[0019] There are no limitations on the material, shape, structure, size, etc. of the wafer 11. The wafer 11 may be made of, for example, a semiconductor material other than silicon (e.g., silicon carbide (SiC) or gallium nitride (GaN)). Similarly, there are no limitations on the type, number, shape, structure, size, arrangement, etc. of the devices 13.

[0020] Fig. 2 is a flow chart that schematically shows an example of a method for processing a bonded wafer including the wafer 11. Also, Fig. 3(A) is a cross-sectional view that schematically shows an example of this bonded wafer.

[0021] 2, first, the front surface 11a of the wafer 11 and the front surface 15a of the support wafer 15 are bonded together to form a bonded wafer 17 (bonding step: S1). In this bonding step (S1), for example, the front surface 11a of the wafer 11 is pressed against the front surface 15a of the support wafer 15 on which an adhesive 19 is provided, thereby forming the bonded wafer 17 (see FIG. 3(A)).

[0022] The support wafer 15 has a diameter approximately equal to that of the wafer 11 and is made of a semiconductor material such as silicon. The support wafer 15 may be a bare wafer or a wafer on which some kind of device is formed.

[0023] For example, when a BSI (Back Side Illumination) type CMOS image sensor is manufactured using this bonded wafer 17, a pixel circuit of the image sensor may be formed on the front surface 15a side of the support wafer 15. The adhesive 19 is, for example, an acrylic adhesive or an epoxy adhesive.

[0024] Next, the back surface 15b of the support wafer 15 is sucked to hold the bonded wafer 17, and the wafer 11 is cut to remove the chamfered portion of the wafer 11 (cutting step: S2). Fig. 3(B) is a partial cross-sectional side view schematically showing the cutting step (S2) performed in the cutting device.

[0025] The cutting device 2 shown in Fig. 3(B) has a cylindrical θ table 4. A disk-shaped chuck table 6 is provided on top of the θ table 4. The θ table 4 is connected to a rotational drive source (not shown) such as a motor. When the rotational drive source is operated, the θ table 4 and the chuck table 6 rotate around a rotation axis that passes through the center of the chuck table 6 and is aligned in the vertical direction.

[0026] The chuck table 6 has a frame 6a made of a metal material such as stainless steel. The frame 6a has a disk-shaped bottom wall and an annular side wall extending upward from the periphery of the bottom wall. A disk-shaped porous plate (not shown) made of porous ceramics and having a diameter approximately the same as the inner diameter of the recess is fixed in a recess defined by the bottom wall and side wall of the frame 6a.

[0027] The porous plate of the chuck table 6 is connected to a suction source (not shown), such as an ejector, through a flow path formed in the frame 6a. When this suction source is operated, a negative pressure is created in the space near the upper surface of the porous plate (the holding surface of the chuck table 6). Therefore, when the suction source is operated with the back surface 15b of the support wafer 15 in contact with the holding surface of the chuck table 6, the back surface 15b of the support wafer 15 is sucked, and the bonded wafer 17 is held by the chuck table 6.

[0028] Furthermore, the θ table 4 and the chuck table 6 are connected to a first horizontal movement mechanism (not shown). When this first horizontal movement mechanism is operated, the θ table 4 and the chuck table 6 move in a direction (first horizontal direction) perpendicular to the vertical direction.

[0029] In addition, a cutting unit 8 is provided above the chuck table 6. The cutting unit 8 is connected to a second horizontal movement mechanism and a vertical movement mechanism. When the second horizontal movement mechanism is operated, the cutting unit 8 moves along a direction (second horizontal direction) perpendicular to both the vertical axis direction and the first horizontal direction. When the vertical movement mechanism is operated, the cutting unit 8 moves along the vertical direction, i.e., the cutting unit 8 moves up and down.

[0030] The cutting unit 8 has a cylindrical spindle 10 extending along the second horizontal direction. A cutting blade 12 having an annular cutting edge is attached to one end of the spindle 10. The width (length along the second horizontal direction) of the cutting edge included in the cutting blade 12 is wider than the width of the chamfer formed on the outer periphery of the wafer 11.

[0031] The cutting blade 12 is, for example, a hub-type cutting blade. A hub-type cutting blade is composed of an annular base made of metal or the like and an annular cutting edge along the outer periphery of the base. The cutting edge is composed of an electroformed grinding stone in which abrasive grains made of diamond or cubic boron nitride (cBN) or the like are fixed with a binder such as nickel.

[0032] Alternatively, the cutting blade 12 may be a washer-type cutting blade. A washer-type cutting blade is configured with an annular cutting edge to which abrasive grains are fixed by a binder made of, for example, metal, ceramic, or resin.

[0033] The other end of the spindle is connected to a rotary drive source (not shown) such as a motor. When this rotary drive source operates, the spindle 10 and the cutting blade 12 rotate around a rotation axis that passes through the center of the spindle 10 and is aligned in the second horizontal direction.

[0034] When cutting the wafer 11 in the cutting device 2 to remove the chamfered portion of the wafer 11, first, the bonded wafer 17 is carried into the holding surface of the chuck table 6 so that the center of the back surface 15b of the support wafer 15 coincides with the center of the holding surface of the chuck table 6. Next, the suction source communicating with the porous plate of the chuck table 6 is operated so that the bonded wafer 17 is held by the chuck table 6.

[0035] Next, the position of the chuck table 6 in the first horizontal direction and / or the position of the cutting unit 8 in the second horizontal direction is adjusted so that the cutting blade 12 is positioned directly above the chamfered portion formed on the outer peripheral edge of the wafer 11. Next, while rotating the spindle 10, the cutting unit 8 is lowered until the lower end of the cutting blade 12 reaches a position lower than the surface 11a of the wafer 11 and higher than the surface 15a of the support wafer 15.

[0036] Next, while the spindle 10 is still rotating, the rotary drive source connected to the θ table 4 is operated so as to rotate the chuck table 6 at least once (see FIG. 3(B)). This removes the chamfer formed on the outer periphery of the wafer 11 and the adhesive 19 adhering to the chamfer. This completes the cutting step (S2).

[0037] Furthermore, cutting debris is generated in this cutting step (S2). These cutting debris not only adhere to the back surface 11c of the wafer 11, but may also be sucked from the chuck table 6 side and adhere to the back surface 15b of the support wafer 15. Therefore, in the method shown in Fig. 2, both surfaces of the bonded wafer 17 are cleaned after the cutting step (S2).

[0038] Specifically, the back surface 11c of the wafer 11 is cleaned (first cleaning step: S3), and then the back surface 15b of the support wafer 15 is cleaned (second cleaning step: S4). Fig. 4(A) is a partial cross-sectional side view schematically showing the first cleaning step (S3) performed in the cleaning apparatus, and Fig. 4(B) is a partial cross-sectional side view schematically showing the second cleaning step (S4) performed in the cleaning apparatus.

[0039] 4(A) and 4(B) has a cylindrical spindle 16. A disk-shaped chuck table 18 is provided on top of the spindle 16. The spindle 16 is connected to a rotational drive source (not shown) such as a motor. When the rotational drive source is operated, the spindle 16 and the chuck table 18 rotate around a rotation axis that passes through the center of the chuck table 18 and is aligned in the vertical direction.

[0040] The chuck table 18 has a frame 18a made of a metal material such as stainless steel. The frame 18a has a disk-shaped bottom wall and an annular side wall extending upward from the periphery of the bottom wall. A disk-shaped porous plate (not shown) made of porous ceramics and having a diameter approximately the same as the inner diameter of the recess is fixed in a recess defined by the bottom wall and side wall of the frame 18a.

[0041] The porous plate of the chuck table 18 is connected to a suction source (not shown), such as an ejector, through a flow path formed in the frame 18a. When this suction source is operated, a negative pressure is created in the space near the upper surface of the porous plate (the holding surface of the chuck table 18). Therefore, when the suction source is operated with the back surface 15b of the support wafer 15 in contact with the holding surface of the chuck table 18, the back surface 15b of the support wafer 15 is sucked, and the bonded wafer 17 is held by the chuck table 18.

[0042] Furthermore, a nozzle unit 20 is provided above the chuck table 18. The nozzle unit 20 is located outside the chuck table 18 and has a cylindrical shaft portion (not shown) extending along the vertical direction. A rotation drive source (not shown), such as a motor, for rotating the shaft portion is connected to the lower end of the shaft portion.

[0043] A cylindrical arm 20a is connected to the upper end of the shaft, extending from the upper end of the shaft in a direction parallel to the holding surface of the chuck table 18. A cleaning nozzle 20b facing downward is provided at the tip of the arm 20a (the end of the arm 20a not connected to the shaft). Furthermore, the cleaning nozzle 20b is connected to a cleaning fluid supply source (not shown) via the arm 20a and the shaft.

[0044] Therefore, when cleaning fluid is supplied from a fluid supply source to the cleaning nozzle 20b while the cleaning nozzle 20b is positioned above the chuck table 18, the cleaning fluid is supplied from the cleaning nozzle 20b toward the holding surface of the chuck table 18. This fluid includes water. Alternatively, this fluid may be a mixture of water and air.

[0045] When cleaning the back surface 11c of the wafer 11 in the cleaning device 14, first, the bonded wafer 17 is loaded onto the holding surface of the chuck table 18 so that the center of the back surface 15b of the support wafer 15 coincides with the center of the holding surface of the chuck table 18. Note that, if necessary, prior to loading of the bonded wafer 17, the rotary drive source connected to the lower end of the shaft of the nozzle unit 20 may be operated to rotate the shaft so as to move the cleaning nozzle 20b away from the chuck table 18.

[0046] Next, a suction source communicating with the porous plate of the chuck table 18 is operated so that the bonded wafer 17 is held by the chuck table 18. Next, a rotation drive source connected to the lower end of the shaft of the nozzle unit 20 is operated so that the cleaning nozzle 20b is positioned at a desired position above the bonded wafer 17.

[0047] Next, a cleaning fluid is supplied from the cleaning nozzle 20b toward the back surface 11c of the wafer 11 while operating the rotation drive source connected to the spindle 16 to rotate the spindle 16 and the chuck table 18 (see FIG. 4(A)). This completes the first cleaning step (S3), and allows cutting debris adhering to the back surface 11c of the wafer 11 to be removed.

[0048] Next, the operation of the suction source communicating with the porous plate of the chuck table 18 is stopped. Next, the bonded wafer 17 is inverted so that the center of the back surface 11c of the wafer 11 coincides with the center of the holding surface of the chuck table 18. Note that, if necessary, prior to inverting the bonded wafer 17, the rotary drive source connected to the lower end of the shaft of the nozzle unit 20 may be operated to rotate the shaft so as to move the cleaning nozzle 20b away from the chuck table 18.

[0049] Next, a suction source communicating with the porous plate of the chuck table 18 is operated so that the bonded wafer 17 is held by the chuck table 18. Next, a rotation drive source connected to the lower end of the shaft of the nozzle unit 20 is operated so that the cleaning nozzle 20b is positioned at a desired position above the bonded wafer 17.

[0050] Next, a cleaning fluid is supplied from the cleaning nozzle 20b toward the back surface 15b of the support wafer 15 (see FIG. 4(B)) while operating the rotation drive source connected to the spindle 16 to rotate the spindle 16 and the chuck table 18. This completes the second cleaning step (S4), and allows cutting debris adhering to the back surface 15b of the support wafer 15 to be removed.

[0051] In the second cleaning step (S4), the back surface 15b of the support wafer 15 is cleaned while the back surface 11c of the wafer 11 is being sucked, which may result in scratches on the back surface 11c of the wafer 11 and / or adhesion of foreign matter such as cutting chips. However, these do not pose a problem because the back surface 11c side of the wafer 11 is ground in the grinding step (S5) described below.

[0052] Next, the back surface 11c side of the wafer 11 is ground while holding the bonded wafer 17 by sucking the back surface 15b of the support wafer 15 (grinding step: S5). Fig. 5(A) is a partial cross-sectional side view schematically showing the grinding step (S5) performed in the grinding device.

[0053] 5(A) has a disk-shaped chuck table 24. The chuck table 24 has a frame 24a made of ceramics or the like. The frame 24a has a disk-shaped bottom wall and an annular side wall extending upward from the periphery of the bottom wall.

[0054] A disk-shaped porous plate 24b made of porous ceramics and having a diameter roughly the same as the inner diameter of the recess is fixed in the recess defined by the bottom wall and side walls of the frame 24a. The lower surface of this porous plate 24b is roughly flat, and the upper surface has a shape in which the center protrudes slightly compared to the outer periphery, i.e., a shape corresponding to the side of a cone.

[0055] Furthermore, the porous plate 24b is connected to a suction source (not shown) such as an ejector through a flow path formed in the frame 24a. When this suction source is operated, a negative pressure is created in the space near the upper surface of the porous plate 24b (the holding surface of the chuck table 24). Therefore, when the suction source is operated with the back surface 15b of the support wafer 15 in contact with the holding surface of the chuck table 24, the back surface 15b of the support wafer 15 is sucked, and the bonded wafer 17 is held by the chuck table 24.

[0056] Furthermore, the upper part of a cylindrical spindle 26 is connected to the lower part of the chuck table 24. The chuck table 24 is detachable from the spindle 26. The lower part of the spindle 26 is connected to a rotational drive source (not shown) such as a motor. When the rotational drive source is operated, the spindle 26 and the chuck table 24 rotate around a rotation axis that passes through the center of the holding surface of the chuck table 24 and is aligned with the direction in which the spindle 26 extends.

[0057] An annular bearing 28 that supports the chuck table 24 is provided below the chuck table 24. An annular support plate 30 is fixed below the bearing 28. The bearing 28 supports the chuck table 24 in a manner that allows the chuck table 24 to rotate relative to the support plate 30. An annular table base 32 is provided below the support plate 30.

[0058] The spindle 26 is located in an opening provided in the center of each of the bearing 28, the support plate 30, and the table base 32. In addition, three support mechanisms (a fixed support mechanism 34a, a first movable support mechanism 34b, and a second movable support mechanism 34c) are provided on the underside of the table base 32 so as to be spaced apart from one another along the circumferential direction of the underside of the table base 32. In this specification, these three support mechanisms are collectively referred to as the tilt adjustment unit 34.

[0059] The table base 32 is supported by a fixed support mechanism 34a, a first movable support mechanism 34b, and a second movable support mechanism 34c. The fixed support mechanism 34a has a pillar (fixed shaft) of a predetermined length. The upper part of this pillar supports an upper support member fixed to the underside of the table base 32, and the lower part of this pillar is fixed to the support base.

[0060] Each of the first movable support mechanism 34b and the second movable support mechanism 34c has a support (movable shaft) 36 with a male thread formed at its tip. The tip (upper part) of this support 36 is rotatably connected to an upper support body 38 fixed to the underside of the table base 32. Specifically, the upper support body 38 is a metal columnar member such as a rod having a female thread, and the male thread of the support 36 is rotatably engaged with the female thread of the upper support body 38.

[0061] An annular bearing 40 having a predetermined diameter is provided at the base end (lower part) of the support pillar 36 of the first movable support mechanism 34b and the second movable support mechanism 34c. A part of this bearing 40 is supported by a stepped support plate 42. The first movable support mechanism 34b and the second movable support mechanism 34c are each supported by the support plate 42.

[0062] A motor 44 that rotates the support column 36 is connected to the bottom of the support column 36. When the motor 44 is operated to loosen the support column 36 that is screwed into the upper support body 38, the upper support body 38 rises. When the motor 44 is operated to tighten the support column 36 that is screwed into the upper support body 38, the upper support body 38 descends.

[0063] Therefore, in the grinding device 22, the tilt of the table base 32 (i.e., the chuck table 24) can be adjusted by raising and lowering the upper support 38 using each of the first movable support mechanism 34b and the second movable support mechanism 34c.

[0064] Furthermore, the chuck table 24 is connected to a horizontal movement mechanism (not shown). When this horizontal movement mechanism is operated, the chuck table 24 moves in a direction perpendicular to the vertical direction (horizontal direction).

[0065] A grinding unit 46 is provided above the chuck table 24. The grinding unit 46 is connected to a vertical movement mechanism (not shown). When the vertical movement mechanism is operated, the grinding unit 46 moves in the vertical direction. The grinding unit 46 also has a cylindrical spindle 48 that extends in the vertical direction.

[0066] The upper surface of a disk-shaped wheel mount 50 made of stainless steel or the like is fixed to the tip (lower end) of the spindle 48. In addition, an annular grinding wheel 52 having roughly the same diameter as the wheel mount 50 is removably attached to the lower part of the wheel mount 50.

[0067] The grinding wheel 52 has an annular wheel base 54. This wheel base 54 is made of, for example, stainless steel, and has a plurality of grinding stones 56 arranged at approximately equal intervals on the underside of the wheel base 54 along the circumferential direction.

[0068] The base end (upper end) of the spindle 48 is connected to a rotary drive source (not shown) such as a motor. When this rotary drive source operates, the spindle 48, wheel mount 50, and grinding wheel 52 rotate around a rotation axis that passes through the center of the spindle 48 and is aligned vertically.

[0069] When grinding the back surface 11c side of the wafer 11 in the grinding device 22, first, the horizontal movement mechanism moves the chuck table 24 so as to move it away from the grinding wheel 52 and position the chuck table 24 at a position where the bonded wafer 17 can be carried onto the holding surface of the chuck table 24.

[0070] Next, the bonded wafer 17 is carried onto the holding surface of the chuck table 24 so that the center of the back surface 15b of the support wafer 15 coincides with the center of the holding surface of the chuck table 24. Next, the suction source communicating with the porous plate 24b is operated so that the bonded wafer 17 is held by the chuck table 24.

[0071] Next, the tilt of the chuck table 24 is adjusted. Specifically, the tilt adjustment unit 34 adjusts the tilt of the chuck table 24 so that the line segment connecting the highest point on the periphery of the holding surface of the chuck table 24 and the center of the holding surface is perpendicular to the vertical direction.

[0072] Next, the horizontal movement mechanism moves the chuck table 24 so that the trajectory of the multiple grinding stones 56 when the grinding wheel 52 is rotated overlaps one end and the other end of the line segment in a plan view. Next, the rotary drive source connected to the base end of the spindle 48 is operated to rotate the grinding wheel 52, and the rotary drive source connected to the lower part of the spindle 26 is operated to rotate the chuck table 24.

[0073] Next, while rotating the grinding wheel 52 and the chuck table 24, the vertical movement mechanism lowers the grinding unit 46 so that the lower surfaces of the multiple grinding wheels 56 come into contact with the back surface 11c of the wafer 11. As a result, the back surface 11c side of the wafer 11 is ground by the multiple grinding wheels 56.

[0074] This grinding continues until the bonded wafer 17 reaches the desired thickness. That is, the vertical movement mechanism lowers the grinding unit 46 until the bonded wafer 17 reaches the desired thickness. This completes the grinding step (S5).

[0075] 5(B) is a cross-sectional view schematically showing the bonded wafer 17 after the grinding step (S5) is completed. This grinding step (S5) is performed after removing the adhesive 19 adhering to the chamfered portion formed on the outer periphery of the wafer 11. This prevents the adhesive 19 from being drawn out during the grinding, which would otherwise damage the bonded wafer 17.

[0076] The processing method for the bonded wafer shown in FIG. 2 includes a cutting step (S2) in which the wafer 11 is cut while holding the bonded wafer 17 by suctioning the back surface 15b of the support wafer 15, and a grinding step (S5) in which the back surface 11c side of the wafer 11 is ground in the same state, and a second cleaning step (S4) in which the back surface 15b of the support wafer 15 is cleaned.

[0077] Therefore, in this method, it is possible to wash away cutting debris adhering to the back surface 15b of the support wafer 15 in the second cleaning step (S4) prior to the grinding step (S5). As a result, in this method, it is possible to prevent dimples from being formed on the back surface 11c of the wafer 11 and / or damage to the wafer 11 in the grinding step (S5).

[0078] Fig. 6 is a flowchart schematically showing an example of a method for processing a bonded wafer including a wafer (second wafer) other than wafer 11. Specifically, Fig. 6 is a flowchart schematically showing an example of a method for processing a bonded wafer including two stacked wafers (wafer 11 and second wafer). Also, Fig. 7(A) is a cross-sectional view schematically showing an example of such a bonded wafer.

[0079] 6, first, the front surface 21a of the second wafer 21 is bonded to the back surface 11c of the bonded and ground wafer 11 to form a bonded wafer 23 (second bonding step: S6). In this second bonding step (S1), for example, the front surface 21a of the second wafer 21 is pressed against the back surface 11c of the wafer 11 on which an adhesive 25 is provided, thereby forming the bonded wafer 23 (see FIG. 7(A)).

[0080] The second wafer 21 has the same structure as the wafer 11 before being bonded to the support wafer 15. Furthermore, the front surface 21a of the second wafer 21 may have formed thereon devices that are connected to devices formed on the front surface 11a of the wafer 11, or may have formed thereon devices that are independent from the devices formed on the front surface 11a of the wafer 11. The adhesive 25 is, for example, an acrylic adhesive or an epoxy adhesive.

[0081] Next, the second wafer 21 is cut so as to remove the chamfered portion of the second wafer 21 while holding the bonded wafer 23 by sucking the back surface 15b of the support wafer 15 (second cutting step: S7). Note that the second cutting step (S7) is performed, for example, in the same manner as the above-mentioned cutting step (S2). Therefore, details of the second cutting step (S7) will be omitted.

[0082] Furthermore, cutting waste is generated in this second cutting step (S7). These cutting waste may adhere not only to the back surface 21b of the second wafer 21 but also to the back surface 15b of the support wafer 15. Therefore, in the method shown in Fig. 6, both surfaces of the bonded wafer 17 are cleaned after the second cutting step (S7).

[0083] Specifically, the back surface 21b of the second wafer 21 is cleaned (third cleaning step: S8), and then the back surface 15b of the support wafer 15 is cleaned (fourth cleaning step: S9). The third cleaning step (S8) and the fourth cleaning step (S9) are performed, for example, in the same manner as the first cleaning step (S3) and the second cleaning step (S4) described above. Therefore, details of the third cleaning step (S8) and the fourth cleaning step (S9) will be omitted.

[0084] Next, the back surface 15b of the support wafer 15 is sucked to hold the bonded wafer 23, and the back surface 21b of the second wafer 21 is ground (second grinding step: S10). The second grinding step (S10) is performed, for example, in the same manner as the grinding step (S5) described above. Therefore, details of the second grinding step (S10) will be omitted.

[0085] 7(B) is a cross-sectional view schematically showing the bonded wafer 23 after the second grinding step (S10) is completed. This second grinding step (S10) is performed after removing the adhesive 25 adhering to the chamfered portion formed on the outer periphery of the second wafer 21. This prevents the adhesive 25 from being drawn out during this grinding, which would otherwise damage the bonded wafer 23.

[0086] Furthermore, in the processing method of a bonded wafer shown in Figure 6, similar to the processing method of a bonded wafer shown in Figure 2, it is possible to prevent dimples from being formed on the back surface 21b of the second wafer 21 and / or damage to the second wafer 21 in the second grinding step (S10).

[0087] In addition, in the present invention, it is also possible to form a bonded wafer including three or more stacked wafers by repeating the method shown in Fig. 6. In addition, the structures and methods according to the above-described embodiments can be appropriately modified and implemented without departing from the scope of the object of the present invention. [Explanation of symbols]

[0088] 2:Cutting device 4: θ table 6: Chuck table (6a: frame) 8: Cutting unit 10:Spindle 11: Wafer (11a: front surface, 11b: side surface, 11c: back surface) 12: Cutting blade 13: Device 14: Cleaning equipment 15: Support wafer (15a: front surface, 15b: back surface) 16: Spindle 17: Bonded wafer 18: Chuck table (18a: Frame) 19: Adhesive 20: Nozzle unit (20a: arm, 20b: nozzle) 21: Second wafer (21a: front surface, 21b: back surface) 22: Grinding equipment 23: Bonded wafer 24: chuck table (24a: frame, 24b: porous plate) 25: Adhesive 26: Spindle 28: Bearing 30: Support plate 32: Table base 34: Tilt adjustment unit (34a: Fixed support mechanism, 34b: First movable support mechanism, 34c: Second movable support mechanism) 36: Post 38: Upper support 40: Bearing 42: Support plate 44: Motor 46: Grinding unit 48: Spindle 50: Wheel mount 52: Grinding wheel 54: Wheel base 56: Grinding wheel

Claims

[Claim 1] A processing method for a bonded wafer including a wafer having a plurality of devices formed on a front surface side and a chamfered portion on an outer periphery, and a support wafer having a surface to be bonded to the front surface of the wafer, the method comprising: a cutting step of cutting the wafer so as to remove the chamfered portion of the wafer while holding the bonded wafer by sucking the back surface of the support wafer; a first cleaning step of cleaning the back surface of the wafer after the cutting step; a second cleaning step of cleaning the back surface of the support wafer while holding the bonded wafer by sucking the back surface side of the wafer after the first cleaning step; a grinding step of grinding the back surface side of the wafer while holding the bonded wafer by suctioning the back surface of the support wafer after the second cleaning step; A method for processing a bonded wafer, comprising:

Images