Method of processing laminated wafer

Abstract

To provide a method of processing a laminated wafer suitable for processing the laminated wafer so as not to generate chips from a part in the vicinity of a side surface of the wafer included in the laminated wafer.SOLUTION: A processing method of a laminated wafer including a first wafer having a chamfered outer circumferential edge and a second wafer bonded to the first wafer via a bonding layer includes a cutting step of cutting the outer circumferential edge of the first wafer such that a diameter of a front surface of the first wafer is smaller than a diameter of a back surface of the first wafer and a side surface of the first wafer is curved, and a processing step of processing (for example, wet etching or chemical mechanical polishing) the side surface side of the first wafer after the cutting step.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for processing a stacked wafer including a first wafer having a chamfered outer peripheral edge and a second wafer bonded to the first wafer via a bonding layer. [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 one side until the other side reaches a desired thickness, and then dividing the wafer along the boundaries between the multiple devices.

[0003] When manufacturing chips from wafers, cracks are likely to occur at the outer edge of the wafer. Therefore, in this case, the outer edge of the wafer is often chamfered prior to various processes. However, when the other side of a wafer with a chamfered outer edge is ground, only one side of the original outer edge remains, resulting in a knife-edge-like shape of the outer edge of the wafer after grinding.

[0004] If the outer peripheral edge of the wafer has a knife-edge shape, stress is likely to concentrate on this outer peripheral edge, causing cracks. Therefore, in the chip manufacturing process, the wafer is sometimes subjected to edge trimming (e.g., cutting to remove one side of the chamfered outer peripheral edge) before the other side of the wafer is ground (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 stacked wafer is formed in which one wafer is bonded to another wafer via a bonding layer, and then the stacked wafer is divided to manufacture chips. For example, in order to miniaturize the manufactured chips, multiple wafers each having multiple devices formed on one side (hereinafter, each wafer will also be referred to as a "device wafer") may be bonded to a support wafer via a bonding layer.

[0007] Specifically, first, one side of a support wafer and one side of a device wafer are bonded via a bonding layer to form a stacked wafer. Next, while holding the stacked wafer so that the other side of the device wafer is exposed, the device wafer is cut to remove the outer peripheral edge of the device wafer. Next, the other side of the device wafer is ground.

[0008] Next, the other side of the ground device wafer is bonded to one side of another device wafer via a bonding layer to form a stacked wafer including two stacked device wafers. Next, while holding the stacked wafers so that the other side of the other device wafer is exposed, the other device wafer is cut to remove the outer peripheral edge of the other device wafer. Next, the other side of the other device wafer is ground.

[0009] Thereafter, by repeating the same process as necessary, a stacked wafer including three or more stacked device wafers can be formed. When a stacked wafer is formed in this manner, the portions near the side surfaces of the device wafers may be damaged during cutting to remove the outer peripheral edges.

[0010] If the portion of the device wafer near the side is damaged, that portion may crumble and become scrap in subsequent processes. Furthermore, this scrap may scatter and adhere to the stacked wafers. In this case, there is a risk that the quality of the chips manufactured by dividing the stacked wafers may deteriorate.

[0011] Therefore, after the device wafer is cut to remove the outer peripheral edge, it is preferable to process the device wafer so as to remove the damaged portion near the side surface, for example, by etching using an etching solution (wet etching) or polishing using a soft polishing pad (e.g., chemical mechanical polishing (CMP)).

[0012] However, the side surface of the device wafer cut to remove the outer peripheral edge is generally cylindrical. When wet etching is performed on such a device wafer, the etching solution may remain near the bonding layer. In this case, the etching solution may penetrate between one side of the device wafer and the bonding layer, causing damage to the device.

[0013] Furthermore, even if chemical mechanical polishing is performed on such a device wafer, the polishing pad may not be able to elastically deform so as to contact the entire side surface of the device wafer, and in this case, one side of the side surface of the device wafer may not be polished, and the damaged portion may not be completely removed.

[0014] In view of these points, an object of the present invention is to provide a method for processing laminated wafers that is suitable for processing laminated wafers so as not to generate debris from portions of the wafers near the side surfaces of the laminated wafers. [Means for solving the problem]

[0015] According to the present invention, there is provided a method for processing laminated wafers, which includes a first wafer having a chamfered outer circumferential edge and a second wafer bonded to the first wafer via a bonding layer, the method comprising: a first holding step of holding the laminated wafers on a first holding surface of a first chuck table that is rotatable around a first line that passes through the center of the first holding surface and is perpendicular to the first holding surface as a rotation axis, so that a surface of the first wafer is exposed and the center of the surface is located on the first line; and after the first holding step, adjusting the relative positions of the first chuck table and the spindle so that a cutting edge of an annular cutting blade attached to a tip of a spindle that is rotatable around a second line that is parallel to the first holding surface as a rotation axis and the outer circumferential edge of the first wafer overlaps in a direction parallel to the first line, and so that the first line and the second line are not located on the same plane. a cutting step, after the position adjusting step, of rotating the spindle and bringing the first chuck table and the spindle closer together in the direction until the cutting tip is closer to the first holding surface than to the outer circumferential edge of the first wafer, thereby rotating the first chuck table at least once in that state, thereby cutting the outer circumferential edge of the first wafer so that the diameter of the front surface of the first wafer becomes smaller than the diameter of the back surface and the side surface is curved; a second holding step, after the cutting step, of holding the stacked wafers on the second holding surface of a second chuck table that is rotatable about a rotation axis of a third straight line passing through the center of the second holding surface so that the front surface and the side surface of the first wafer are exposed; and a processing step, after the second holding step, of processing the side surface of the first wafer.

[0016] Furthermore, the laminated wafer processing method of the present invention preferably further comprises a grinding step of grinding the front surface side of the first wafer after the cutting step and before the processing step, or after the processing step. Furthermore, the laminated wafer processing method of the present invention preferably further comprises a film formation step of forming a thin film on the front surface and side surfaces of the first wafer after the processing step. In addition, wet etching or chemical mechanical polishing is preferably performed in the processing step. [Effects of the Invention]

[0017] In the present invention, the outer peripheral edge of the first wafer is cut so that the diameter of the front surface is smaller than the diameter of the back surface and the chamfered side surface is curved, and then the side surface of the first wafer is processed.

[0018] For example, when wet etching is performed in the processing step, the etching solution flows down the side surface of the first wafer and easily falls off the stacked wafers, making it difficult for the etching solution to remain near the bonding layer. Also, when chemical mechanical polishing is performed in the processing step, the polishing pad can be brought into contact with the entire side surface of the first wafer without significantly deforming the polishing pad, making it easier to polish the side surface of the first wafer.

[0019] Therefore, in the present invention, compared to, for example, cutting the outer peripheral edge of the first wafer, which is chamfered so that the side of the first wafer is cylindrical, and then processing the side of the first wafer, the stacked wafers can be processed preferably so as not to generate debris in the area near the side of the first wafer. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1(A) is a top view that schematically shows an example of a wafer, and FIG. 1(B) is a front view that schematically shows this wafer. [Figure 2]FIG. 2(A) is a front view showing a schematic diagram of bonding one side of a wafer to one side of a support wafer, and FIG. 2(B) is a front view showing a schematic diagram of a stacked wafer formed by this bonding. [Figure 3] FIG. 3 is a flow chart schematically illustrating an example of a method for processing laminated wafers. [Figure 4] FIG. 4 is a perspective view schematically illustrating an example of a cutting device capable of performing the edge trimming step included in the laminated wafer processing method. [Figure 5] FIG. 5 is a plan view schematically showing components of a cutting unit that are exposed and not housed in a housing included in the cutting device. [Figure 6] FIG. 6 is a flow chart that schematically illustrates an example of an edge trimming step performed in the cutting device. [Figure 7] FIG. 7(A) is a plan view that schematically shows the state of the holding step included in the edge trimming step, and FIG. 7(B) is a partial front view that schematically shows the state of this holding step. [Figure 8] FIG. 8(A) is a plan view that schematically shows the state of the position adjusting step included in the edge trimming step, and FIG. 8(B) is a front view that schematically shows the state of this position adjusting step. [Figure 9] FIG. 9(A) is a front view that schematically shows the state of the cutting step included in the edge trimming step, and FIG. 9(B) is a side view that schematically shows the state of this cutting step. [Figure 10] FIG. 10(A) is a plan view schematically showing the laminated wafers after the cutting step, and FIG. 10(B) is a front view schematically showing the laminated wafers after the cutting step. [Figure 11] FIG. 11 is a flow chart schematically illustrating an example of a damaged portion removing step included in a laminated wafer processing method performed in an etching apparatus. [Figure 12]FIG. 12(A) is a front view showing a schematic diagram of a holding step included in a damaged portion removal step performed in an etching apparatus, and FIG. 12(B) is a front view showing a schematic diagram of a wet etching step included in this damaged portion removal step. [Figure 13] FIG. 13 is a flow chart schematically illustrating an example of a damaged portion removing step performed in a polishing apparatus. [Figure 14] Figure 14(A) is a partial cross-sectional front view showing a schematic diagram of a holding step included in a damaged portion removal step performed in a polishing apparatus, and Figure 14(B) is a partial cross-sectional front view showing a schematic diagram of a chemical mechanical polishing step included in this damaged portion removal step. [Figure 15] FIG. 15 is a flowchart schematically showing another example of a method for processing laminated wafers. [Figure 16] 16(A) and 16(B) are each a front view schematically showing the state of the grinding step included in the laminated wafer processing method shown in FIG. [Figure 17] FIG. 17 is a diagram schematically showing the film forming step included in the laminated wafer processing method shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0021] An embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1(A) is a top view schematically showing an example of a wafer (first wafer), and Fig. 1(B) is a front view schematically showing the wafer shown in Fig. 1(A). The wafer 11 shown in Fig. 1(A) and Fig. 1(B) has one surface 11a and another surface 11b that are generally parallel, and is made of, for example, silicon (Si).

[0022] A plurality of devices 13 are provided on one surface 11a of this wafer 11. Each device 13 includes, for example, a semiconductor element for constituting an IC, a semiconductor memory, or a CMOS (Complementary Metal Oxide Semiconductor) image sensor. The plurality of devices 13 are arranged in a matrix. That is, the boundaries between the plurality of devices 13 extend in a lattice pattern.

[0023] Furthermore, the wafer 11 may have recesses formed therein in which wiring such as through-silicon vias (TSVs (Through-Silicon Vias)) is provided. The outer peripheral edge of the wafer 11 is chamfered. In other words, the side surface 11c of the wafer 11 is curved so as to be convex outward.

[0024] There are no limitations on the material, shape, structure, size, etc. of the wafer 11. The wafer 11 may be made of a semiconductor 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 multiple devices 13.

[0025] Fig. 2(A) is a front view schematically showing how one surface 11a of the wafer 11 is bonded to one surface of a support wafer (second wafer), and Fig. 2(B) is a front view schematically showing the stacked wafers formed by this bonding. Note that the support wafer 15 shown in Figs. 2(A) and 2(B) has, for example, the same shape as the wafer 11. Furthermore, similar to the wafer 11, multiple devices may be provided on the one surface 15a of the support wafer 15.

[0026] During this bonding, first, a bonding layer 17 containing an acrylic adhesive or an epoxy adhesive is provided on one surface 15a of the support wafer 15. The bonding layer 17 is provided, for example, in a disk shape that is concentric with the support wafer 15 in a plan view and has a radius smaller than that of the support wafer 15.

[0027] Next, while the other surface 15b of the support wafer 15 is supported, one surface 11a of the wafer 11 is pressed against one surface 15a of the support wafer 15 via the bonding layer 17. This forms a stacked wafer 19 including the wafer 11 and the support wafer 15 bonded to the wafer 11 via the bonding layer 17.

[0028] 3 is a flowchart schematically showing an example of a laminated wafer processing method for processing laminated wafers 19. In this method, first, the outer peripheral edge of wafer 11 is cut so that the diameter of other surface 11b of wafer 11 is smaller than the diameter of one surface 11a and the side surface 11c is curved (edge ​​trimming step S1).

[0029] Fig. 4 is a perspective view schematically showing an example of a cutting device capable of performing the edge trimming step S1. Note that the direction indicated by the arrow X (X direction) and the direction indicated by the arrow Y (Y direction) shown in Fig. 4 are directions perpendicular to each other on a horizontal plane. Furthermore, the direction indicated by the arrow Z (Z direction) is a direction (vertical direction) perpendicular to both the X direction and the Y direction.

[0030] 4 includes a base 4 that supports each component. A recess 4a extending along the X direction is formed on the top surface of the base 4. Inside the recess 4a, a flat table cover 6 and a bellows-like dustproof and drip-proof cover 8 that expands and contracts as the table cover 6 moves are provided.

[0031] A chuck table (first chuck table) 10 is provided above the table cover 6. The chuck table 10 has a disk-shaped frame 10a made of ceramics or the like. The frame 10a has a disk-shaped bottom wall and a cylindrical side wall extending from the outer periphery of the bottom wall. A disk-shaped porous plate 10b made of, for example, porous ceramics is fixed in a recess defined by the bottom wall and the side wall of the frame 10a.

[0032] The porous plate 10b has a diameter approximately equal to the inner diameter of the sidewall of the frame body 10a. Furthermore, the porous plate 10b communicates with a suction source (not shown), such as an ejector, provided inside the recess 4a via a flow path or the like formed in the bottom wall of the frame body 10a. The upper surfaces of the sidewalls of the frame body 10a and the upper surface of the porous plate 10b are parallel to the X and Y directions, respectively, and function as a holding surface (first holding surface) of the chuck table 10 when holding the stacked wafers 19.

[0033] Specifically, when the stacked wafers 19 are carried into the cutting device 2, they are placed on the chuck table 10 with the other surface 11b of the wafer 11 facing upward. Then, when a suction source communicating with the porous plate 10b is operated in this state, a suction force acts on the stacked wafers 19. As a result, the stacked wafers 19 are held on the holding surface of the chuck table 10.

[0034] The chuck table 10 is also connected to an X-direction movement mechanism (not shown) provided inside the recess 4a. This X-direction movement mechanism includes, for example, a ball screw and a motor for rotating the screw shaft of the ball screw. When this X-direction movement mechanism is operated, the chuck table 10 moves in the X direction or the opposite direction. Furthermore, in conjunction with this movement, the table cover 6 moves in the X direction or the opposite direction, and the dust-proof and drip-proof cover 8 expands and contracts.

[0035] The chuck table 10 is also connected to a rotational drive source (not shown) provided inside the recess 4a. This rotational drive source includes, for example, a shaft, a pulley connected to the shaft, and a motor for rotating the pulley. When the rotational drive source is operated, the chuck table 10 rotates around a rotation axis that is a straight line (first straight line) that passes through the center of the holding surface of the chuck table 10 and that runs along the Z direction.

[0036] A support structure 14 is provided in an area near the recess 4a on the upper surface of the base 4. This support structure 14 has an upright portion 14a that stands upright from the upper surface of the base 4, and an arm portion 14b that extends in the opposite direction to the Y direction from an upper portion of the upright portion 14a so as to cross over the recess 4a. A Y-direction movement mechanism 16 is provided on one side of the arm portion 14b.

[0037] The Y-direction movement mechanism 16 is fixed to one surface of the arm portion 14b and has a pair of guide rails 18 extending along the Y direction. A moving plate 20 is connected to the front surface of the pair of guide rails 18 in a manner that allows it to slide along the pair of guide rails 18.

[0038] A screw shaft 22 extending along the Y direction is disposed between the pair of guide rails 18. A motor (not shown) for rotating the screw shaft 22 is connected to one end of the screw shaft 22. A nut (not shown) that accommodates a large number of balls that roll on the surface of the rotating screw shaft 22 is provided on the surface of the screw shaft 22, on which a spiral groove is formed, thereby constituting a ball screw.

[0039] That is, when the screw shaft 22 rotates, a large number of balls circulate inside the nut, causing the nut to move in the Y direction or the opposite direction. The nut is fixed to the rear surface side of the moving plate 20. Therefore, when the screw shaft 22 is rotated by a motor connected to one end of the screw shaft 22, the moving plate 20 moves together with the nut in the Y direction or the opposite direction.

[0040] A Z-direction movement mechanism 24 is provided on the surface side of the movable plate 20. This Z-direction movement mechanism 24 is fixed to the surface of the movable plate 20 and has a pair of guide rails 26 extending along the Z direction. A movable plate 28 is connected to the surface side of the pair of guide rails 26 in a manner that allows it to slide along the pair of guide rails 26.

[0041] A screw shaft 30 extending along the Z direction is disposed between the pair of guide rails 26. A motor 32 for rotating the screw shaft 30 is connected to the upper end of the screw shaft 30. A nut (not shown) that houses a large number of balls that roll on the surface of the rotating screw shaft 30 is provided on the surface of the screw shaft 30 on which a spiral groove is formed, thereby forming a ball screw.

[0042] That is, when the screw shaft 30 rotates, a large number of balls circulate inside the nut, causing the nut to move in the Z direction or the opposite direction. The nut is fixed to the back side of the moving plate 28. Therefore, when the screw shaft 30 is rotated by the motor 32, the moving plate 28 moves together with the nut in the Z direction or the opposite direction.

[0043] A cylindrical housing 34 is fixed to the lower part of the moving plate 28. A cutting unit 36 ​​is partially housed in the housing 34. Some components of the cutting unit 36 ​​are not housed in the housing 34, but are exposed on the chuck table 10 side.

[0044] Fig. 5 is a plan view schematically showing the components of the cutting unit 36 ​​that are exposed and not housed in the housing 34. The components of the cutting unit 36 ​​shown in Fig. 5 are concentric structures centered on a line along the Y direction. Therefore, Fig. 5 can also be expressed as a front view schematically showing the components of the cutting unit 36 ​​that are exposed and not housed in the housing 34.

[0045] The cutting unit 36 ​​has a spindle 38 that extends along the Y direction and has a tip end that protrudes from the housing 34. The spindle 38 is supported by the housing 34 in a manner that allows it to rotate about a straight line (second straight line) parallel to the Y direction as a rotation axis. A cutting blade 40 is attached to the tip end of the spindle 38.

[0046] The cutting blade 40 has an annular cutting edge 40a that includes a binder made of metal, ceramic, resin, or the like, and abrasive grains made of diamond or the like dispersed in the binder. The base end of the spindle 38 is connected to a rotational drive source (not shown), such as a motor, that is housed in the housing 34. When the rotational drive source is operated, the cutting blade 40 rotates together with the spindle 38 around a straight line (second straight line) along the Y direction as the rotation axis.

[0047] 6 is a flowchart schematically illustrating an example of the edge trimming step S1 performed by the cutting device 2. In this edge trimming step S1, first, the stacked wafers 19 are held on the holding surface of the chuck table 10 so that the other side 11b of the wafer 11 is exposed and the center of the other side 11b is positioned on a straight line that serves as the rotation axis of the chuck table 10 (holding step S11).

[0048] 7(A) is a plan view schematically showing the state of the holding step S11, and FIG. 7(B) is a front view schematically showing the state of the holding step. In this holding step S11, first, the stacked wafers 19 are placed on the chuck table 10 so that the other surface 11b of the wafer 11 faces upward and the center of the wafer 11 is positioned on the straight line L1 that serves as the rotation axis of the chuck table 10.

[0049] Next, the suction source communicating with the porous plate 10b of the chuck table 10 is operated, which applies a suction force to the stacked wafers 19. As a result, the stacked wafers 19 are held on the holding surface of the chuck table 10 with the other surface 11b of each wafer 11 exposed.

[0050] After the holding step S11, the relative positions of the chuck table 10 and the spindle 38 are adjusted so that the cutting tip of the cutting blade 40 (specifically, the lower end of the cutting edge 40a) and the outer peripheral edge of the wafer 11 overlap in the Z direction and the straight lines that serve as the rotation axes of both are not positioned on the same plane (position adjustment step S12).

[0051] 8(A) is a plan view that schematically shows the state of the position adjusting step S12, and Fig. 8(B) is a front view that schematically shows the state of the position adjusting step S12. In this position adjusting step S12, for example, in a plan view, the relative positions of the chuck table 10 and the spindle 38 are adjusted so that the angle θ formed by the line segment connecting the straight line L1 that serves as the rotation axis of the chuck table 10 and the tip of the cutting blade 40 and the straight line L2 that serves as the rotation axis of the spindle 38 is between 3° and 20°.

[0052] Specifically, first, the position of the spindle 38 in the Z direction is adjusted so that the cutting edge of the cutting blade 40 is positioned above the other surface 11b of the wafer 11. Next, the position of the chuck table 10 in the X direction is adjusted so that the line L1 is positioned slightly deviated from the line L2 in a plan view. Next, the position of the spindle 38 in the Y direction is adjusted so that the cutting edge of the cutting blade 40 overlaps with the outer peripheral edge of the wafer 11 in a plan view.

[0053] The order of adjusting the position of the chuck table 10 in the X direction and the position of the spindle 38 in the Y and Z directions in the position adjusting step S12 can be changed as appropriate as long as the adjustment is performed so that the cutting blade 40 does not come into contact with the wafer 11. Alternatively, these position adjustments may be performed in parallel.

[0054] After the position adjustment step S12, the spindle 38 is rotated and the chuck table 10 is rotated at least once while the chuck table 10 and the spindle 38 are brought closer together in the Z direction until the tip of the cutting blade 40 is closer to the holding surface of the chuck table 10 than the outer peripheral edge of the wafer 11 (cutting step S13).

[0055] Fig. 9(A) is a plan view schematically showing the state of cutting step S13, and Fig. 9(B) is a front view schematically showing the state of cutting step S13. Also, Fig. 10(A) is a plan view schematically showing the laminated wafers 19 after cutting step S13, and Fig. 10(B) is a front view schematically showing the laminated wafers 19 after cutting step S13.

[0056] In this cutting step S13, first, the cutting blade 40 is rotated together with the spindle 38. Next, while the spindle 38 is still rotating, the spindle 38 is lowered until the cutting edge of the cutting blade 40 is positioned below one surface 11a of the wafer 11 (for example, below one surface 15a of the support wafer 15) and above the holding surface of the chuck table 10.

[0057] As a result, the cutting blade 40 cuts into the stacked wafers 19 so as to penetrate the outer peripheral edges of the wafers 11 (see FIGS. 9(A) and 9(B)). Next, the chuck table 10 is rotated at least once while the spindle 38 is still rotating. As a result, the stacked wafers 19 are cut so as to remove the outer peripheral edges of the wafers 11.

[0058] In this cutting step S13, the portion of the cutting blade 40 that is positioned in a direction parallel to the straight line L2 when viewed from the straight line L1 bites deeper into the wafer 11 than the portion 40b near the cutting tip. Therefore, after the cutting step S13, the diameter of the other surface 11b of the wafer 11 becomes smaller than the diameter of the one surface 11a, and the side surface 11c has a curved shape (see FIGS. 10(A) and 10(B)).

[0059] Furthermore, the cutting of the outer peripheral edge of the wafer 11 in the cutting step S13 may damage a portion of the wafer 11 near the side surface 11c. Therefore, in the laminated wafer processing method shown in Fig. 3, after the cutting step S13, i.e., after the edge trimming step S1, the portion near the side surface 11c that has been damaged in the cutting of the outer peripheral edge of the wafer 11 is removed (damaged portion removing step S2).

[0060] In the damaged portion removing step S2, for example, wet etching or chemical mechanical polishing is performed. Fig. 11 is a flow chart schematically showing an example of the damaged portion removing step S2 performed in an etching apparatus. In the damaged portion removing step S2, the stacked wafers are held on the holding surface of the chuck table (second chuck table) so that the other side of the wafer is exposed (holding step S21).

[0061] Fig. 12(A) is a front view schematically showing the holding step S21. The etching apparatus 52 shown in Fig. 12(A) includes a chuck table (second chuck table) 54 having a structure similar to that of the chuck table 10 of the cutting apparatus 2. That is, the chuck table 54 has a circular holding surface (second holding surface), and a porous plate (not shown) is exposed on this holding surface.

[0062] Furthermore, this porous plate is connected to a suction source (not shown), such as an ejector, via a flow path formed inside the chuck table 54. When this suction source is operated, a suction force acts on the space near the holding surface of the chuck table 54. Therefore, for example, when the suction source is operated with the stacked wafers 19 placed on the chuck table 54, the stacked wafers 19 are held on the holding surface of the chuck table 54.

[0063] A rotary drive source (not shown), such as a motor, is connected to the chuck table 54. When the rotary drive source is operated, the chuck table 54 rotates about a straight line (third straight line) L3 that passes through the center of the holding surface and is perpendicular to the holding surface as the rotation axis. Furthermore, the chuck table 54 may be connected to a horizontal movement mechanism (not shown) for moving the chuck table 54 in the horizontal direction.

[0064] An etching liquid supply nozzle 56 is provided above the chuck table 54. This etching liquid supply nozzle 56 supplies etching liquid E directly downward from its tip. The etching liquid E contains, for example, hydrofluoric acid. Furthermore, the etching liquid supply nozzle 56 is movable in the horizontal direction. For example, the etching liquid supply nozzle 56 is movable so as to rotate around its base end.

[0065] In the etching apparatus 52, the damaged portion removal step S2 is performed, for example, in the following order: Specifically, first, the stacked wafers 19 are placed on the chuck table 54 so that the other surface 11b of the wafer 11 faces upward and the center of the wafer 19 is positioned on the straight line L3 that serves as the rotation axis of the chuck table 54.

[0066] Next, the suction source communicating with the porous plate of the chuck table 54 is operated. This causes a suction force to act on the stacked wafers 19. As a result, the stacked wafers 19 are held on the holding surface of the chuck table 54 with the other surfaces 11b of the wafers 11 exposed. This completes the holding step S21.

[0067] After the holding step S21, the side surface 11c of the wafer 11 is wet-etched (wet etching step (processing step) S22). FIG. 12(B) is a front view schematically showing the wet etching step S22. In this wet etching step S22, first, the chuck table 54 and the etching solution supply nozzle 56 are moved relative to each other so that the side surface 11c of the wafer 11 is positioned directly below the tip of the etching solution supply nozzle 56.

[0068] Next, the chuck table 54 is rotated while the etching solution E is supplied from the tip of the etching solution supply nozzle 56 toward the side surface 11c of the wafer 11. As a result, the side surface 11c of the wafer 11 is etched by the etching solution E, and the portion near the side surface 11c that was damaged in association with cutting the outer peripheral edge of the wafer 11 is removed.

[0069] In the wet etching step S22, a region near the outer periphery of the other surface 11b of the wafer 11 may be etched with the etching liquid E. Similarly, in the wet etching step S22, the side surface of the support wafer 15 may be etched with the etching liquid E. Furthermore, in the wet etching step S22, the entire area of ​​the other surface 11b of the wafer 11 may be etched with the etching liquid E.

[0070] In addition, in the damaged portion removing step S2, chemical mechanical polishing may be performed instead of or in addition to wet etching. Fig. 13 is a flow chart schematically showing an example of the damaged portion removing step S2 performed in the polishing apparatus. In this damaged portion removing step S2, the stacked wafers 19 are held on the holding surface of the chuck table (second chuck table) so that the other surface 11b of the wafer 11 is exposed (holding step S21').

[0071] Fig. 14(A) is a partial cross-sectional front view schematically showing the holding step S21'. The polishing apparatus 62 shown in Fig. 14(A) includes a chuck table (second chuck table) 64 having a structure similar to that of the chuck table 10 of the cutting apparatus 2. That is, the chuck table 64 has a circular holding surface (second holding surface), and a porous plate (not shown) is exposed on this holding surface.

[0072] Furthermore, this porous plate is connected to a suction source (not shown), such as an ejector, via a flow path formed inside the chuck table 64. When this suction source is operated, a suction force acts on the space near the holding surface of the chuck table 64. Therefore, for example, when the suction source is operated with the stacked wafers 19 placed on the chuck table 64, the stacked wafers 19 are held on the holding surface of the chuck table 64.

[0073] A rotary drive source (not shown), such as a motor, is connected to the chuck table 64. When the rotary drive source is operated, the chuck table 64 rotates about a straight line (third straight line) L3' that passes through the center of the holding surface and is perpendicular to the holding surface as the rotation axis. Furthermore, the chuck table 64 may be connected to a horizontal movement mechanism (not shown) for moving the chuck table 64 in the horizontal direction.

[0074] A polishing unit 66 is provided above the chuck table 64 for chemically and mechanically polishing the other surface 11b and the side surface 11c of the wafer 11. The polishing unit 66 has a spindle 68 extending in the vertical direction. A rotation drive source (not shown) such as a motor and a vertical movement mechanism (not shown) including a ball screw, a motor, etc. are connected to the upper end of the spindle 68.

[0075] When the rotational drive source is operated, the spindle 68 rotates around a vertical line L4 as its rotation axis. When the vertical movement mechanism is operated, the spindle 68 moves vertically. A disk-shaped mount 70 is fixed to the lower end of the spindle 68. A disk-shaped polishing pad 72 is attached to the underside of the mount 70.

[0076] The polishing pad 72 includes a disc-shaped pad base 72a having approximately the same diameter as the mount 70, and a disc-shaped polishing layer 72b fixed to the underside of the pad base 72a and having approximately the same diameter as the mount 70. The polishing layer 72b is, for example, a fixed abrasive layer having abrasive grains dispersed therein. For example, the polishing layer 72b is produced by impregnating a polyester nonwoven fabric with a urethane solution in which abrasive grains having an average grain size of 0.4 μm to 0.6 μm are dispersed, followed by drying.

[0077] The abrasive grains dispersed inside the polishing layer 72b are made of materials such as SiC, cBN, diamond, or metal oxide particles, etc. The metal oxide particles may be made of silica (SiO2), ceria (CeO2), zirconia (ZrO2), or alumina (Al2O3).

[0078] The polishing layer 72b is flexible and elastically deforms in response to pressure applied during polishing. For example, the polishing layer 72b elastically deforms in response to pressure applied when polishing the other surface 11b of the wafer 11 so that the wafer 11 is embedded in the polishing layer 72b, i.e., so that the polishing layer 72b comes into contact with the entire side surface 11c of the wafer 11.

[0079] In this case, polishing is performed on the side surface 11c as well as the other surface 11b of the wafer 11. Furthermore, the radial centers of the spindle 68, the mount 70, and the pad base 72a and polishing layer 72b of the polishing pad 72 are generally aligned, and a cylindrical through-hole 74 is formed to pass through these centers.

[0080] Additionally, the through-hole 74 is connected to a slurry supply source (not shown). This slurry supply source includes a slurry storage tank, a liquid supply pump, and the like. When the liquid supply pump is operated, a slurry (not shown) containing various chemical components is supplied from the storage tank to the holding surface of the chuck table 64 via the through-hole 74. The slurry may or may not contain abrasive grains.

[0081] In the polishing apparatus 62, the damaged portion removing step S2 is performed, for example, in the following order: First, the stacked wafers 19 are placed on the chuck table 64 so that the other surface 11b of the wafer 11 faces upward and the center of the wafer 19 is positioned on the straight line L3' that serves as the rotation axis of the chuck table 64.

[0082] Next, the suction source communicating with the porous plate of the chuck table 64 is operated. This causes a suction force to act on the stacked wafers 19. As a result, the stacked wafers 19 are held on the holding surface of the chuck table 64 with the other surfaces 11b of the wafers 11 exposed. This completes the holding step S21'.

[0083] After the holding step S21', the other surface 11b and the side surface 11c of the wafer 11 are chemically mechanically polished (chemical mechanical polishing step (processing step) S23). FIG. 14(B) is a partial cross-sectional front view schematically showing the chemical mechanical polishing step S23. In this chemical mechanical polishing step S23, first, both the chuck table 64 and the spindle 68 are rotated, and slurry is supplied to the other surface 11b of the wafer 11 through the through-hole 74.

[0084] Then, while rotating these and supplying the slurry, the spindle 68 is lowered until the polishing layer 72b elastically deforms so as to bury the wafer 11 in the polishing layer 72b, that is, so as to bring the polishing layer 72b into contact with the entire other surface 11b and side surface 11c of the wafer 11. As a result, the other surface 11b and side surface 11c of the wafer 11 are chemically mechanically polished, and the portion near the side surface 11c that was damaged due to cutting of the outer peripheral edge of the wafer 11 is removed.

[0085] In the processing method for the laminated wafer shown in FIG. 3, the outer peripheral edge of the wafer 11 is cut so that the diameter of the other surface 11b of the wafer 11 is smaller than the diameter of the one surface 11a and the side surface 11c is curved, and then the side surface 11c of the wafer 11 is processed (for example, by wet etching or chemical mechanical polishing).

[0086] For example, when wet etching is performed in the damaged portion removal step S2, the etching solution E flows down the side surface 11c of the wafer 11 and tends to drop from the stacked wafer 19, making it difficult for the etching solution E to remain near the bonding layer 17. When chemical mechanical polishing is performed in the damaged portion removal step S2, the polishing pad 72 can be brought into contact with the entire side surface 11c of the wafer 11 without significantly deforming the polishing pad 72, making it easier to polish the side surface 11c of the wafer 11.

[0087] Therefore, in this method, the laminated wafer 19 can be processed more suitably so as not to generate debris in the area near the side 11c of the wafer 11, compared to, for example, cutting the outer peripheral edge that is chamfered so that the side of the wafer 11 becomes cylindrical and then processing the side of the wafer 11.

[0088] The above-described content is one aspect of the present invention, and the present invention is not limited to the above-described content. For example, in the laminated wafer processing method of the present invention, the edge trimming step S1 may be performed in a cutting device other than the cutting device 2.

[0089] Specifically, the edge trimming step S1 may be performed in a cutting device provided with an X-direction movement mechanism for moving the cutting unit 36 ​​in the X direction or the opposite direction, instead of or in addition to the X-direction movement mechanism provided in the recess 4a formed in the upper surface of the base 4. Similarly, the edge trimming step S1 may be performed in a cutting device provided with a Y-direction movement mechanism for moving the chuck table 10 in the Y direction or the opposite direction and / or a Z-direction movement mechanism for moving the chuck table 10 in the Z direction or the opposite direction, instead of or in addition to the Y-direction movement mechanism 16 and / or the Z-direction movement mechanism 24.

[0090] The laminated wafer processing method of the present invention may also include steps other than those described above. Fig. 15 is a flowchart schematically showing an example of a laminated wafer processing method including steps other than those described above.

[0091] Specifically, in the laminated wafer processing method shown in Fig. 15, the other surface 11b of the wafer 11 is ground (grinding step S3) after the edge trimming step S1 and before the damaged portion removing step S2. Fig. 16(A) and Fig. 16(B) are front views each showing a schematic view of the grinding step S3.

[0092] 16(A) and 16(B) includes a chuck table 84 having a structure similar to that of the chuck table 10 of the cutting device 2. That is, the chuck table 84 has a circular holding surface, and a porous plate (not shown) is exposed on this holding surface. Note that the shape of the holding surface of the chuck table 84 is not limited to a circular shape, and may be a shape corresponding to the side surface of a cone.

[0093] Furthermore, this porous plate is connected to a suction source (not shown), such as an ejector, via a flow path formed inside the chuck table 84. When this suction source is operated, a suction force acts on the space near the holding surface of the chuck table 84. Therefore, for example, when the suction source is operated with the stacked wafers 19 placed on the chuck table 84, the stacked wafers 19 are held on the holding surface of the chuck table 84.

[0094] A rotary drive source (not shown), such as a motor, is connected to the chuck table 84. When the rotary drive source is operated, the chuck table 84 rotates around a straight line L5 passing through the center of the holding surface as the rotation axis. Furthermore, the chuck table 84 may be connected to a horizontal movement mechanism (not shown) for moving the chuck table 84 in the horizontal direction.

[0095] A grinding unit 86 for grinding the other surface 11b of the wafer 11 is provided above the chuck table 84. The grinding unit 86 has a spindle 88 extending in the vertical direction. The upper end of the spindle 88 is connected to a rotation drive source (not shown) such as a motor, and a vertical movement mechanism (not shown) including a ball screw, a motor, etc.

[0096] When the rotation drive source is operated, the spindle 88 rotates around a vertical line L6 as its rotation axis. When the vertical movement mechanism is operated, the spindle 88 moves vertically. A disk-shaped mount 90 is fixed to the lower end of the spindle 88. A grinding wheel 92 is attached to the underside of the mount 90.

[0097] The grinding wheel 92 includes a disk-shaped wheel base 92a having inner and outer diameters roughly equal to those of the mount 90, and a plurality of rectangular parallelepiped grinding stones 92b fixed to the underside of the wheel base 92a. Each grinding stone 92b includes abrasive grains made of, for example, diamond or cBN (cubic boron nitride), and a binder that holds the abrasive grains. Examples of the binder include a metal bond, a resin bond, or a vitrified bond.

[0098] Furthermore, a grinding fluid supply nozzle (not shown) is disposed near the grinding wheel 92 for supplying a grinding fluid (not shown) containing water toward the holding surface of the chuck table 84. Alternatively, instead of or in addition to this grinding fluid supply nozzle, a flow path for supplying the grinding fluid may be formed in the grinding wheel 92, and the grinding fluid may be supplied to the holding surface of the chuck table 84 via this flow path.

[0099] In the grinding device 82, the grinding step S3 is performed, for example, in the following order: First, the stacked wafers 19 are placed on the chuck table 84 so that the other surface 11b of the wafer 11 faces upward and the center of the wafer 19 is positioned on the straight line L5 that serves as the rotation axis of the chuck table 84.

[0100] Next, the suction source communicating with the porous plate of the chuck table 84 is operated, thereby applying a suction force to the stacked wafers 19. As a result, the stacked wafers 19 are held on the holding surface of the chuck table 84 with the other surfaces 11b of the wafers 11 exposed (see FIG. 16(A)).

[0101] Next, both the chuck table 84 and the spindle 88 are rotated, and grinding fluid is supplied to the other side 11b of the wafer 11 through the grinding fluid supply nozzle and / or a flow path formed in the grinding wheel 92. Then, while these are being rotated and the grinding fluid is being supplied, the spindle 88 is lowered so that the multiple grinding wheels 92b come into contact with the other side 11b of the wafer 11. This causes the other side 11b of the wafer 11 to be ground (see FIG. 16(B)).

[0102] The grinding step S3 can flatten the other surface 11b of the wafer 11. Therefore, by performing the grinding step S3 prior to the damaged portion removal step S2 in which chemical mechanical polishing is performed, wear of the polishing layer 72b of the polishing pad 72 in the damaged portion removal step S2 can be suppressed.

[0103] 15, after the damaged portion removing step S2, a thin film is formed on the other surface 11b and the side surface 11c of the wafer 11 (film forming step S4). The thin film functions as, for example, a protective film for protecting the multiple devices 13 formed on the one surface 11a of the wafer 11.

[0104] Fig. 17 is a diagram showing a film formation step S4. The film formation apparatus 102 shown in Fig. 17 includes a chamber 104 made of a conductive material and grounded. The chamber 104 is provided with a loading / unloading opening 104a for loading and unloading the stacked wafers 19.

[0105] The loading / unloading port 104a is provided with a gate valve 106 that can isolate or connect the internal space of the chamber 104 to the external space. The chamber 104 also has an exhaust port 104b formed therein for exhausting the internal space.

[0106] The exhaust port 104b communicates with an exhaust device 110 such as a vacuum pump via a pipe 108. A support member 112 is provided on the inner surface of the chamber 104, and the support member 112 supports a table 114.

[0107] An electrostatic chuck (not shown) is provided above the table 114. A disk-shaped electrode 114a located below the electrostatic chuck is provided inside the table 114. The electrode 114a is connected to a high-frequency power supply 118 via a matching box 116.

[0108] A disk-shaped opening is formed in chamber 104 at a position facing the upper surface of table 114, and a gas ejection head 122 is provided in this opening and supported by chamber 104 via bearings 120. Gas ejection head 122 is made of a conductive material, and is connected to a high-frequency power supply 126 via a matching box 124.

[0109] A gas diffusion space 122a exists inside the gas injection head 122. A plurality of gas discharge ports 122b are formed in an inner portion (for example, a lower portion) of the gas injection head 122, connecting the gas diffusion space 122a with the internal space of the chamber 104. Two gas supply ports 122c and 122d are formed in an outer portion (for example, an upper portion) of the gas injection head 122 for supplying a predetermined gas to the gas diffusion space 122a.

[0110] Furthermore, the gas supply port 122c is in communication with a gas supply source 130a, which supplies, for example, a fluorocarbon gas such as C4F8 and / or a fluorosulfur gas such as SF6, via a pipe 128a, etc. Furthermore, the gas supply port 122d is in communication with a gas supply source 130b, which supplies, for example, an inert gas such as Ar and O2 gas, via a pipe 128b, etc.

[0111] In the film formation step S4, for example, the film formation step S4 is performed in the following order: Specifically, first, with the gate valve 106 connecting the internal space of the chamber 104 with the external space, the stacked wafers 19 are loaded onto the table 114 so that the other surface 11b and the side surface 11c of the wafer 11 are exposed.

[0112] Next, the stacked wafers 19 are held by the electrostatic chuck of the table 114. Next, the internal space of the chamber 104 is evacuated to a vacuum state by the exhaust device 110. Next, anisotropic chemical vapor deposition (CVD) is carried out.

[0113] Specifically, while a gas containing CF is supplied from gas supply source 130a to the internal space of chamber 104 and a gas containing Ar is supplied from gas supply source 130b, high frequency power is supplied from high frequency power supply 118 to electrode 114a provided inside table 114, and high frequency power is supplied from high frequency power supply 126 to gas ejection head 122. As a result, CF radicals are deposited on the other surface 11b and side surface 11c of wafer 11, and a film containing carbon fluoride is formed.

[0114] In the film formation step S4, anisotropic chemical vapor deposition is performed on the curved side surface 11c of the wafer 11. In this case, a desired film is more easily formed on the side surface 11c of the wafer 11 than when anisotropic chemical vapor deposition is performed on the cylindrical side surface of the wafer 11.

[0115] The laminated wafer processing method of the present invention may be one in which the grinding step S3 or the film-forming step S4 is omitted from the laminated wafer processing method shown in Fig. 15. Also, the laminated wafer processing method of the present invention may be one in which the grinding step S3 is performed after the damaged portion removal step S2 and before the film-forming step S4, instead of or in addition to the timing after the edge trimming step S1 and before the damaged portion removal step S2. Also, the laminated wafer processing method of the present invention may be one in which the chemical mechanical polishing step S23 and the grinding step S3 are performed with the laminated wafers 19 held on the holding surface of the same chuck table.

[0116] In addition, the structures and methods according to the above-described embodiments can be modified as appropriate without departing from the scope of the present invention. [Explanation of symbols]

[0117] 2:Cutting device 4: Base (4a: recess) 6: Table cover 8: Dustproof and water-resistant cover 10: chuck table (10a: frame, 10b: porous plate) 11: Wafer (first wafer) (11a: One side (back side), 11b: Other side (front side), 11c: Side) 13: Device 14: Support structure (14a: standing part, 14b: arm part) 15: Support wafer (second wafer) (15a: One side, 15b: Other side) 16:Y direction movement mechanism 17: Bonding layer 18: Guide rail 19: Stacked wafer 20: Moving plate 22: Screw shaft 24:Z direction movement mechanism 26: Guide rail 28: Moving plate 30:Screw shaft 32: Motor 34: Housing 36: Cutting unit 38: Spindle 40: Cutting blade (40a: cutting edge, 40b: part near the cutting tip) 42: Imaging unit 52: Etching equipment 54: Chuck table 56: Etching solution supply nozzle 62: Polishing equipment 64: Chuck table 66: Polishing unit 68: Spindle 70: Mount 72: Polishing pad (72a: pad base, 72b: polishing layer) 82: Grinding equipment 84: Chuck table 86: Grinding unit 88: Spindle 90: Mount 92: Grinding wheel (92a: wheel base, 92b: grinding wheel 92b) 102: Film deposition equipment 104: Chamber (104a: loading / unloading port, 104b: exhaust port) 106: Gate valve 108: Piping 110: Exhaust system 112: Support member 114: table (114a: electrode) 116: Matching box 118: High frequency power supply 120: Bearing 122: gas ejection head (122a: gas diffusion space, 122b: gas outlet 122) (122c, 122d: gas supply port) 124: Matching box 126: High frequency power supply 128a, 128b: Piping 130a, 130b: Gas supply source

Claims

1. A method for processing a laminated wafer, the method including: processing a laminated wafer including a first wafer having a chamfered outer peripheral edge portion; and a second wafer bonded to the first wafer via a bonding layer, the method comprising: a first holding step of holding the stacked wafers on a first holding surface of a first chuck table that is rotatable about a first line that passes through the center of the first holding surface and is perpendicular to the first holding surface as a rotation axis, so that a surface of the first wafer is exposed and the center of the surface is positioned on the first line; a position adjusting step of adjusting the relative positions of the first chuck table and the spindle after the first holding step so that the cutting edge of an annular cutting blade attached to the tip of a spindle rotatable around a second straight line parallel to the first holding surface as a rotation axis and the outer peripheral edge of the first wafer overlap in a direction parallel to the first straight line, and so that the first straight line and the second straight line are not positioned on the same plane; a cutting step after the position adjusting step, in which the spindle is rotated and the first chuck table and the spindle are brought closer to each other in the direction until the cutting tip is closer to the first holding surface than the outer peripheral edge of the first wafer, and the first chuck table is rotated at least once while the spindle is rotated in the direction until the cutting tip is closer to the first holding surface than the outer peripheral edge of the first wafer, thereby cutting the outer peripheral edge of the first wafer so that the diameter of the front surface of the first wafer is smaller than the diameter of the back surface of the first wafer and the side surface is curved; a second holding step of holding the stacked wafers on a second holding surface of a second chuck table that is rotatable around a third line passing through the center of the second holding surface as a rotation axis, so that the front surface and the side surface of the first wafer are exposed, after the cutting step; a processing step of processing the side surface of the first wafer after the second holding step; A laminated wafer processing method comprising:

2. 2. The method for processing laminated wafers according to claim 1, further comprising a grinding step of grinding the front surface side of the first wafer after the cutting step and before the processing step, or after the processing step.

3. 2. The method for processing laminated wafers according to claim 1, further comprising, after the processing step, a film-forming step of forming a thin film on the front surface and the side surface of the first wafer.

4. 4. The laminated wafer processing method according to claim 1, wherein the processing step includes wet etching or chemical mechanical polishing.

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