Method for processing a wafer

Abstract

To provide a wafer processing method capable of suppressing cracking of an edge-trimmed wafer when grinding the wafer and generation of dust in the step after the grinding.SOLUTION: Prior to a grinding step of grinding a wafer, energy is supplied locally to a cutting surface of an outer peripheral region of a wafer formed in a trimming step. Accordingly, at least a portion of a damaged layer formed in the outer peripheral region of the wafer by the trimming step can be removed or repaired. As a result, it is possible to suppress the cracking of the wafer originating from the outer peripheral region when grinding the edge-trimmed wafer and the generation of dust in the post-grinding step.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a method for processing a wafer by grinding and thinning a wafer having a chamfered outer peripheral region.

Background Art

[0002] Chips of devices such as IC (Integrated Circuit) and LSI (Large Scale Integration) are essential components in various electronic devices such as mobile phones and personal computers. Such chips are manufactured, for example, by forming a large number of devices on the surface of a wafer made of a semiconductor material and then dividing the wafer into regions each including an individual device.

[0003] Cracks are likely to occur in the outer peripheral region of a wafer where stress is concentrated, which is used for manufacturing chips. Therefore, in the chip manufacturing process, it is common for the outer peripheral region to be chamfered prior to various processes. Further, in the chip manufacturing process, for the purpose of miniaturizing the manufactured chips, etc., the back surface side of the wafer is often ground to thin the wafer prior to dividing the wafer.

[0004] However, when the back surface side of a wafer having a chamfered outer peripheral region is ground to thin the wafer, the back surface side of the outer peripheral region becomes a shape like a knife edge. And stress concentrates in this portion and cracks are likely to occur. Therefore, in the chip manufacturing process, after edge trimming is performed to cut and remove a part of the surface side of the outer peripheral region of the wafer, the back surface side of the wafer may be ground to remove the remaining portion of this outer peripheral region (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] On the outer peripheral region of the wafer, a cut surface is formed by edge trimming. When edge trimming is performed, cutting marks (periodic unevenness) are formed on this cut surface, and chips (cutting chips) generated by cutting the wafer adhere to the cut surface so as to be embedded in the wafer, and a damage layer may be formed on the wafer.

[0007] Such a damage layer may be a starting point for cracking of the wafer when the wafer is ground after edge trimming, and may also be a source of dust (cutting chips) in the process after this grinding. In view of this point, an object of the present invention is to provide a wafer processing method capable of suppressing cracking of the wafer when grinding a wafer subjected to edge trimming and generation of dust in the process after this grinding.

Means for Solving the Problems

[0008] According to the present invention, there is provided a wafer processing method for grinding and thinning a wafer having a chamfered outer peripheral region, the method including: a trimming step of cutting a cutting blade into the chamfered outer peripheral region from one surface side of the wafer to cut the chamfered outer peripheral region in a ring shape and removing at least a part of the chamfered outer peripheral region; and a cut surface treatment step of locally supplying energy to the cut surface of the outer peripheral region formed in the trimming step after the trimming step is performed. After performing the cutting surface treatment step, a grinding step of grinding the other surface side of the wafer to thin the wafer, A wafer processing method including these steps is provided.

Effects of the Invention

[0009] In the present invention, before the grinding step of grinding the wafer, energy is locally supplied to the cut surface of the outer peripheral region of the wafer formed in the trimming step. As a result, at least a part of the damaged layer formed in the outer peripheral region of the wafer by the trimming step can be removed or repaired. As a result, it is possible to suppress cracking of the wafer starting from the outer peripheral region when grinding the wafer subjected to edge trimming and generation of dust in the steps after this grinding.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

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Figure 4

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Figure 11

Figure 12

MODE FOR CARRYING OUT THE INVENTION

[0011] Embodiments 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, and FIG. 1(B) is a cross-sectional view schematically showing an example of the wafer. The wafer 11 shown in FIGS. 1(A) and 1(B) is made of a semiconductor material such as silicon (Si), for example.

[0012] The surface (one surface) 11a side of this wafer 11 is partitioned into a plurality of regions by a plurality of division planned lines intersecting each other, and a device 13 such as an IC, LSI, semiconductor memory, or CMOS (Complementary Metal Oxide Semiconductor) image sensor is formed in each region.

[0013] Furthermore, the wafer 11 may have openings (through holes extending from the front surface 11a to the back surface (the other surface) 11c) or grooves for wiring such as through-silicon vias (TSVs). Also, the outer peripheral region of the wafer 11 is chamfered. That is, the side surface 11b of the wafer 11 is curved so as to bulge outward.

[0014] Note that there are no restrictions 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), etc.). Similarly, there are no restrictions on the type, quantity, shape, structure, size, and arrangement, etc. of the device 13.

[0015] Also, the wafer 11 may be integrated with a ring frame via a dicing tape to facilitate its handling. For example, the back surface (the other surface) 11c of the wafer 11 may be adhered to the central region of a disk-shaped dicing tape having a diameter longer than that of the wafer 11, and a ring frame having an inner diameter longer than the diameter of the wafer 11 may be adhered to the outer peripheral region of the dicing tape.

[0016] FIG. 2 is a flowchart schematically showing an example of a method for processing the wafer 11. In this method, first, the chamfered outer peripheral region of the wafer 11 is cut annularly (trimming step: S1). FIG. 3(A) is a partial cross-sectional side view schematically showing the state of performing the trimming step (S1) on the wafer 11.

[0017] Specifically, FIG. 3(A) is a partial cross-sectional side view schematically showing the state of cutting the outer peripheral region of the wafer 11 in a cutting apparatus. Note that the X1-axis direction (front-back direction) and the Y1-axis direction (left-right direction) shown in FIG. 3(A) are perpendicular to each other on a horizontal plane, and the Z1-axis direction (up-down direction) is a direction (vertical direction) perpendicular to the X1-axis direction and the Y1-axis direction.

[0018] The cutting device 2 shown in Fig. 3(A) has a cylindrical θ table 4. On the upper part of this θ table 4, a disc-shaped chuck table 6 on which the wafer 11 is placed is provided. Further, the θ table 4 is connected to a rotational drive source (not shown) such as a motor. When this rotational drive source is operated, the θ table 4 and the chuck table 6 rotate about a straight line along the Z1-axis direction passing through the center of the chuck table 6 as the rotation axis.

[0019] The chuck table 6 has a frame body 6a made of stainless steel or the like. This frame body 6a has a disc-shaped bottom wall and an annular side wall provided upward from the peripheral edge of this bottom wall. That is, a recess defined by the bottom wall and the side wall is formed in the upper part of the frame body 6a.

[0020] A disc-shaped porous plate (not shown) made of porous ceramics and having substantially the same diameter as the inner diameter of the recess is fixed in this recess. This porous plate is connected to a suction source (not shown) such as a vacuum pump via a flow path formed in the frame body 6a. When this suction source is operated, the space near the upper surface of the porous plate (the holding surface of the chuck table 6) becomes a negative pressure.

[0021] Therefore, by operating the suction source with the wafer 11 placed on the holding surface of the chuck table 6, the wafer 11 can be sucked and held on the chuck table 6. Further, the θ table 4 and the chuck table 6 are connected to an X1-axis direction movement mechanism (not shown). When this X1-axis direction movement mechanism is operated, the θ table 4 and the chuck table 6 move along the X1-axis direction.

[0022] Above the chuck table 6, a cutting unit 8 is provided. The cutting unit 8 is connected to a Y1-axis direction movement mechanism (not shown) and a Z1-axis direction movement mechanism (not shown). When this Y1-axis direction movement mechanism is operated, the cutting unit 8 moves along the Y1-axis direction. Also, when this Z1-axis direction movement mechanism is operated, the cutting unit 8 moves along the Z1-axis direction.

[0023] The cutting unit 8 has a columnar spindle 10 extending in the Y1-axis direction. A cutting blade 12 having an annular cutting edge is attached to one end (tip end) of the spindle 10. The cutting blade 12 is, for example, a hub-type cutting blade configured by integrating an annular base made of metal or the like and an annular cutting edge along the outer peripheral edge of the base.

[0024] The cutting edge of the hub-type cutting blade is constituted by an electroformed grinding wheel in which abrasive grains made of diamond or cubic boron nitride (cBN) are fixed by a binder such as nickel. Also, as the cutting blade 12, a washer-type cutting blade constituted by an annular cutting edge in which abrasive grains are fixed by a binder made of metal, ceramics, resin, or the like may be used.

[0025] Also, the other end (base end) of the spindle is connected to a rotational drive source (not shown) such as a motor. When this rotational drive source operates, the cutting blade 12 rotates together with the spindle 10 with a straight line along the Y1-axis direction as the rotation axis. Further, in the vicinity of this cutting blade 12, a nozzle (not shown) for supplying a liquid (cutting water) to the region of the wafer 11 to be cut is provided.

[0026] In this cutting apparatus 2, for example, the trimming step (S1) is performed in the following order. First, the X1-axis direction movement mechanism moves the chuck table 6 along the X1-axis direction so as to position the chuck table 6 at a position where it is separated from the cutting blade 12 and the wafer 11 can be carried onto the holding surface of the chuck table 6.

[0027] Next, after the wafer 11 is carried onto the holding surface of the chuck table 6 with the surface 11a facing upward, the suction source is operated so that the back surface 11c side of the wafer 11 is sucked and held by the chuck table 6. Next, the Y1-axis direction moving mechanism moves the cutting unit 8 along the Y1-axis direction so that a part of the outer peripheral region of the wafer 11 located in the Y1-axis direction as viewed from the center of the wafer 11 is arranged in the X1-axis direction as viewed from the cutting blade 12.

[0028] Next, the Z1-axis direction moving mechanism lowers the cutting unit 8 so that the lowermost end of the cutting blade 12 is positioned at a position lower than the surface 11a of the wafer 11 and higher than the back surface 11c.

[0029] Next, the rotation drive source connected to the other end of the spindle 10 rotates the cutting blade 12 together with the spindle 10. Next, while supplying liquid (cutting water) from a nozzle provided near the cutting blade 12 to the vicinity of the lowermost end of the cutting blade 12, the cutting blade 12 is cut into the wafer 11.

[0030] Specifically, until the lowermost end of the cutting blade 12 reaches a part of the outer peripheral region of the wafer 11 located in the Y1-axis direction as viewed from the center of the wafer 11, the X1-axis direction moving mechanism moves the chuck table 6 along the X1-axis direction. Next, while the cutting blade 12 is rotating, the rotation drive source connected to the θ table 4 is operated to rotate the chuck table 6 at least once.

[0031] Thereby, the outer peripheral region of the wafer 11 is cut in a ring shape. FIG. 3(B) is a cross-sectional view schematically showing the wafer 11 after the trimming step (S1) is performed. By this trimming step (S1), a part of the chamfered outer peripheral region of the wafer 11 on the surface 11a side is removed.

[0032] At this time, a damage layer 11d is formed in the vicinity of the cut surface of the outer peripheral region of the wafer 11 formed in the trimming step (S1). This damage layer 11d is a layer in which cutting marks (periodic unevenness) are formed on its surface (cut surface) and / or cutting chips generated in the trimming step (S1) adhere to the cut surface so as to be embedded in the wafer.

[0033] In the method shown in FIG. 2, after the trimming step (S1) is performed, a laser beam is irradiated onto the cut surface of the outer peripheral region of the wafer 11 (cut surface treatment step: S2). FIG. 4(A) is a partial cross-sectional side view schematically showing a state in which the cut surface treatment step (S2) is performed on the wafer 11.

[0034] Specifically, FIG. 4(A) is a partial cross-sectional side view schematically showing a state in which a laser beam L is irradiated onto the cut surface (the surface of the damage layer 11d) of the outer peripheral region of the wafer 11 in a laser processing apparatus. Note that the X2-axis direction (front-rear direction) and the Y2-axis direction (left-right direction) shown in FIG. 4(A) are directions perpendicular to each other on a horizontal plane, and the Z2-axis direction (vertical direction) is a direction perpendicular to the X2-axis direction and the Y2-axis direction (vertical direction).

[0035] The laser processing apparatus 14 shown in FIG. 4(A) has a cylindrical θ table 16. A disk-shaped chuck table 18 on which the wafer 11 is placed is provided on the upper part of this θ table 16.

[0036] Further, the θ table 16 is connected to a rotational drive source (not shown) such as a motor. When this rotational drive source is operated, the θ table 16 and the chuck table 18 rotate about a straight line along the Z2-axis direction passing through the center of the chuck table 18 as a rotation axis.

[0037] The chuck table 18 has a frame body 18a made of stainless steel or the like. This frame body 18a has a disk-shaped bottom wall and an annular side wall provided upward from the peripheral edge of this bottom wall. That is, a recess defined by the bottom wall and the side wall is formed in the upper part of the frame body 18a.

[0038] A disk-shaped porous plate (not shown) made of porous ceramics and having substantially the same diameter as the inner diameter of the concave portion is fixed to this concave portion. This porous plate is connected to a suction source (not shown) such as a vacuum pump through a flow path formed in the frame body 18a.

[0039] When this suction source is operated, the space near the upper surface of the porous plate (the holding surface of the chuck table 18) becomes a negative pressure. Therefore, by operating the suction source with the wafer 11 placed on the holding surface of the chuck table 18, the wafer 11 can be sucked and held on the chuck table 18.

[0040] A laser beam irradiation unit (not shown) is provided on the side of the chuck table 18. This laser beam irradiation unit has Nd:YAG or the like as a laser medium, and irradiates a laser beam L having a wavelength absorbed by the wafer (for example, 355 nm) along a direction perpendicular to the Z2-axis direction.

[0041] Further, the laser beam irradiation unit is connected to a Z2-axis direction movement mechanism (not shown). When this Z2-axis direction movement mechanism is operated, the laser beam irradiation unit moves along the Z2-axis direction.

[0042] In this laser processing apparatus 14, for example, the cutting surface treatment step (S2) is performed in the following order. First, after the wafer 11 is carried into the holding surface of the chuck table 18 with the surface 11a facing upward, the suction source is operated so that the back surface 11c side of the wafer 11 is sucked and held by the chuck table 18.

[0043] Next, the Z2-axis direction movement mechanism adjusts the position of the laser beam irradiation unit so that the cutting surface (the surface of the damaged layer 11d) in the outer peripheral region of the wafer 11 formed in the trimming step (S1) is positioned in the irradiation direction of the laser beam L as viewed from the laser beam irradiation unit.

[0044] Next, while rotating the chuck table 18, the laser beam irradiation unit irradiates the laser beam L. Further, the irradiation of the laser beam L may be performed while the Z2-axis direction movement mechanism moves the position of the laser beam irradiation unit. Thereby, for example, laser ablation occurs in the damaged layer 11d irradiated with the laser beam L.

[0045] As a result, at least a part of the damaged layer 11d is removed. FIG. 4(B) is a cross-sectional view schematically showing the wafer 11 after the cutting surface treatment step (S2) is performed. By this cutting surface treatment step (S2), for example, a portion of the damaged layer 11d extending along the thickness direction (Z2-axis direction) of the wafer 11 is removed.

[0046] Alternatively, the irradiation of the laser beam L may be performed while varying the incident angle (irradiation direction of the laser beam L) of the laser beam L to the damaged layer 11d. Thereby, for example, the entire damaged layer 11d can be removed.

[0047] Note that in the cutting surface treatment step (S2), the damaged layer 11d may not be removed. That is, in the cutting surface treatment step (S2), it is sufficient to be able to repair the damaged layer 11d in order to suppress cracking of the wafer 11 when grinding the wafer 11 and generation of dust in the subsequent steps after this grinding.

[0048] For example, in the cutting surface treatment step (S2), the laser beam L may be irradiated to the damaged layer 11d so that the damaged layer 11d slightly melts and then immediately solidifies. Thereby, the surface (cutting surface) of the damaged layer 11d can be smoothed, and dust (cutting chips) adhering to the cutting surface can be fixed so as to be embedded in the wafer 11.

[0049] Furthermore, the irradiation of the laser beam L for repairing the damage layer 11d may be performed while the Z2-axis direction moving mechanism moves the position of the laser beam irradiation unit, or may be performed while varying the incident angle of the laser beam L to the damage layer 11d. Thus, in order to remove or repair the damage layer 11d, for example, it is preferable that the output of the laser beam L is set to 1 W to 30 W.

[0050] In the method shown in FIG. 2, after the cutting surface treatment step (S2) is performed, the wafer 11 is bonded to another support wafer (bonding step: S3). FIG. 5 is a cross-sectional view schematically showing an example of the wafer 11 (bonded wafer) bonded to the support wafer.

[0051] In the bonding step (S3), for example, the bonded wafer 17 is formed by bonding the surface 11a side of the wafer 11 to the surface 15a side of the support wafer 15 via an adhesive. This support wafer 15 has a diameter substantially equal to that of the wafer 11 and is made of a semiconductor material such as silicon, for example.

[0052] Also, the support wafer 15 may be a bare wafer or a wafer on which some device is formed. For example, when a BSI (Back Side Illumination) type CMOS image sensor is manufactured using this bonded wafer 17, a circuit for pixels of the image sensor may be formed on the support wafer 15. Further, the outer peripheral region of the support wafer 15 is chamfered.

[0053] In the method shown in FIG. 2, after the bonding step (S3) is performed, the bonded wafer 17 is ground to be thinned to the finished thickness (grinding step: S4). FIG. 6(A) is a partial cross-sectional side view schematically showing a state in which the grinding step (S4) is performed on the bonded wafer 17.

[0054] Specifically, FIG. 6(A) is a partial cross-sectional side view schematically showing a state of grinding the back surface 11c side of the wafer 11 in the grinding apparatus. The X3-axis direction (front-rear direction) and the Y3-axis direction (left-right direction) shown in FIG. 6(A) are directions perpendicular to each other on a horizontal plane, and the Z3-axis direction (vertical direction) is a direction perpendicular to the X3-axis direction and the Y3-axis direction (vertical direction).

[0055] The grinding apparatus 20 shown in FIG. 6(A) has a disk-shaped chuck table 22. This chuck table 22 has a frame 24 made of ceramics or the like. This frame 24 has a disk-shaped bottom wall and an annular side wall provided upward from the peripheral portion of this bottom wall. That is, a recess defined by the bottom wall and the side wall is formed in the upper part of the frame 24.

[0056] A disk-shaped porous plate 26 made of porous ceramics and having a diameter approximately equal to the inner diameter of the recess is fixed in this recess. The lower surface of this porous plate 26 is generally flat, and its upper surface has a shape in which the central portion slightly protrudes compared to the outer peripheral portion, that is, a shape corresponding to the side surface of a cone.

[0057] Further, the porous plate 26 is connected to a suction source (not shown) such as a vacuum pump via a flow path formed in the frame 24. When this suction source is operated, the space near the upper surface of the porous plate 26 (the holding surface of the chuck table 22) becomes a negative pressure.

[0058] Therefore, by operating the suction source with the wafer 11 placed on the holding surface of the chuck table 22, the bonded wafer 17 can be sucked and held on the chuck table 22. Further, the upper part of a columnar spindle 28 is connected to the lower part of the chuck table 22. Note that the chuck table 22 is detachable from the spindle 28.

[0059] The lower part of this spindle 28 is connected to a rotational drive source (not shown) such as a motor. When this rotational drive source is operated, the chuck table 22 rotates about a rotation axis 30 passing through the center of the holding surface of the chuck table 22. That is, the chuck table 22 rotates along the circumferential direction of its holding surface.

[0060] Below the chuck table 22, an annular bearing 32 for supporting the chuck table 22 is provided. Below the bearing 32, an annular support plate 34 is fixed. And the bearing 32 supports the chuck table 22 in a manner that the chuck table 22 can rotate with respect to the support plate 34. Below the support plate 34, an annular table base 36 is provided.

[0061] The spindle 28 is located in openings provided at the centers of the bearing 32, the support plate 34, and the table base 36, respectively. On the lower surface side of the table base 36, three support mechanisms (a fixed support mechanism 38a, a first movable support mechanism 38b, and a second movable support mechanism 38c) are provided so as to be separated from each other along the circumferential direction of the lower surface of the table base 36. In this specification, these three support mechanisms are collectively referred to as an inclination adjustment unit 38.

[0062] The table base 36 is supported by the fixed support mechanism 38a, the first movable support mechanism 38b, and the second movable support mechanism 38c. The fixed support mechanism 38a has a column (fixed shaft) of a predetermined length. The upper part of this column supports an upper support body fixed to the lower surface of the table base 36, and the lower part of this column is fixed to a support base.

[0063] Each of the first movable support mechanism 38b and the second movable support mechanism 38c has a column (movable shaft) 40 having a male thread formed at its tip. The tip (upper part) of the column 40 is rotatably connected to an upper support body 42 fixed to the lower surface of the table base 36. More specifically, the upper support body 42 is a metal columnar member such as a rod having a female thread, and the male thread of the column 40 is rotatably connected to the female thread of the upper support body 42.

[0064] An annular bearing 44 having a predetermined outer diameter is fixed to the outer periphery of the columns 40 of the first movable support mechanism 38b and the second movable support mechanism 38c. A part of the bearing 44 is supported by a stepped support plate 46. That is, the first movable support mechanism 38b and the second movable support mechanism 38c are supported by the support plate 46.

[0065] A motor 48 for rotating the column 40 is connected to the lower part of the column 40. By operating the motor 48 to rotate the column 40 in one direction, the upper support 42 rises. Also, by operating the motor 48 to rotate the column 40 in the other direction, the upper support 42 descends. In this way, by raising and lowering the upper support 42 of the first movable support mechanism 38b and the second movable support mechanism 38c, the inclination of the table base 36 (that is, the chuck table 22) is adjusted.

[0066] Furthermore, the chuck table 22 is connected to a horizontal movement mechanism (not shown). When this horizontal movement mechanism is operated, the chuck table 22 moves in a direction perpendicular to the Z3-axis direction.

[0067] Above the chuck table 22, a grinding unit 50 is provided. The grinding unit 50 is connected to a Z3-axis direction movement mechanism (not shown). When this Z3-axis direction movement mechanism is operated, the grinding unit 50 moves along the Z3-axis direction. Also, the grinding unit 50 has a columnar spindle 52 extending in the Z3-axis direction.

[0068] The upper surface of a disc-shaped wheel mount 54 made of stainless steel or the like is fixed to the lower end portion (tip portion) of this spindle 52. An annular grinding wheel 56 having substantially the same diameter as the wheel mount 54 is detachably mounted on the lower part of the wheel mount 54.

[0069] The grinding wheel 56 has an annular wheel base 58. The wheel base 58 is made of, for example, stainless steel or the like, and on the lower surface side thereof, a plurality of grinding wheels 60 are discretely arranged along the circumferential direction of the lower surface. The lower surfaces of the plurality of grinding wheels 60 are arranged at substantially the same height in the Z3-axis direction.

[0070] Also, the upper end portion (base end portion) of the spindle 52 is connected to a rotational drive source (not shown) such as a motor. When this rotational drive source operates, the grinding wheel 56 rotates together with the spindle 52 with a straight line along the Z3-axis direction passing through the center of the spindle 52 as the rotation axis. Further, in the vicinity of this grinding wheel 56, a nozzle (not shown) for supplying a liquid (grinding water) to the region of the wafer 11 to be cut is provided.

[0071] In this grinding apparatus 20, for example, the grinding step (S4) is performed in the following order. First, the horizontal movement mechanism moves the chuck table 22 so as to position the chuck table 22 at a position where it is separated from the grinding wheel 56 and the bonded wafer 17 can be carried onto the holding surface of the chuck table 22.

[0072] Next, after the bonded wafer 17 is carried onto the holding surface of the chuck table 22 with the back surface 11c of the wafer 11 facing upward, the suction source is operated so that the support wafer 15 is sucked and held by the chuck table 22.

[0073] Next, the inclination of the chuck table 22 is adjusted. Specifically, the inclination adjustment unit 38 adjusts the inclination of the chuck table 22 so that the line segment connecting the highest point among the points on the outer periphery of the holding surface of the chuck table 22 and the center of the holding surface is perpendicular to the Z3-axis direction. That is, the inclination adjustment unit 38 adjusts the inclination of the chuck table 22 so that this line segment is parallel to the lower surfaces of the plurality of grinding wheels 60. When this line segment is perpendicular to the Z3-axis direction in advance, the adjustment of the inclination of the chuck table 22 is omitted.

[0074] Next, in a plan view, the horizontal movement mechanism moves the chuck table 22 so that the trajectories of the plurality of grinding wheels 60 when the grinding wheel 56 is rotated overlap with one end and the other end of the above-described line segment. Next, a rotation drive source connected to the upper end of the spindle 52 rotates the grinding wheel 56 together with the spindle 52, and a rotation drive source connected to the lower part of the spindle 28 rotates the chuck table 22 together with the spindle 28.

[0075] Next, while supplying a liquid (grinding water) from a nozzle provided in the vicinity of the grinding wheel 56 to the back surface 11c of the wafer 11, the Z3-axis direction movement mechanism lowers the grinding unit 50 so that the lower surfaces of the plurality of grinding wheels 60 are brought into contact with the back surface 11c of the wafer 11. As a result, a part of the back surface 11c side of the wafer 11 is ground and removed. Further, while the grinding wheel 56 and the chuck table 22 are kept rotating, the Z3-axis direction movement mechanism lowers the grinding unit 50 until the bonded wafer 17 is thinned to the finish thickness.

[0076] As a result, the chamfered portion remaining on the back surface 11c side of the outer peripheral region of the wafer 11 is removed. FIG. 6(B) is a cross-sectional view schematically showing the bonded wafer 17 after the grinding step (S4) is performed. By this grinding step (S4), for example, the chamfered portion remaining on the back surface 11c side of the outer peripheral region of the wafer 11 and the portion of the damage layer 11d extending along the plane direction of the wafer 11 are removed.

[0077] In the method shown in FIG. 2, before the grinding step (S4) of grinding the wafer 11, a laser beam L is irradiated onto the cutting surface (the surface of the damage layer 11d) of the outer peripheral region of the wafer 11 formed in the trimming step (S1). Thereby, a part of the damage layer 11d formed in the outer peripheral region of the wafer 11 by the trimming step (S1) can be removed or repaired. As a result, cracking of the wafer 11 starting from the outer peripheral region in the grinding step (S4) and generation of dust in the steps after the grinding step (S4) can be suppressed.

[0078] Note that the method described above is one aspect of the present invention, and the present invention is not limited to the method described above. For example, in the wafer processing method of the present invention, a bonding step may be performed prior to the trimming step and the cutting surface treatment step. FIG. 7 is a flowchart schematically showing an example of such a wafer processing method.

[0079] In this method, first, the wafer 11 is bonded to another support wafer 15 (bonding step: S11). FIG. 8 is a cross-sectional view schematically showing an example of the wafer 11 (bonded wafer 17) bonded to the support wafer 15. Since this bonding step (S11) is carried out in the same manner as the above-described bonding step (S3), the above description is incorporated herein by reference.

[0080] In the method shown in FIG. 7, after the bonding step (S11) is performed, the chamfered outer peripheral region of the bonded wafer 17 (wafer 11 and support wafer 15) is cut annularly (trimming step: S12). FIG. 9(A) is a partial cross-sectional side view schematically showing the state of performing the trimming step (S12) on the bonded wafer 17. Note that the description of the cutting device 2 used in the trimming step (S12) is incorporated herein by reference.

[0081] This trimming step (S12) is performed, for example, in the following order. First, the X1-axis direction moving mechanism moves the chuck table 6 along the X1-axis direction so that the chuck table 6 is positioned at a position separated from the cutting blade 12 and capable of loading the wafer 11 onto the holding surface of the chuck table 6.

[0082] Next, after the bonded wafer 17 is carried into the holding surface of the chuck table 6 with the back surface 11c of the wafer 11 facing upward, the suction source is operated so that the back surface 15b side of the support wafer 15 is sucked and held by the chuck table 6. Next, the Y1-axis direction moving mechanism moves the cutting unit 8 along the Y1-axis direction so that a part of the outer peripheral region of the bonded wafer 17 located in the Y1-axis direction as viewed from the center of the wafer 11 is arranged in the X1-axis direction as viewed from the cutting blade 12.

[0083] Next, the Z1-axis direction moving mechanism lowers the cutting unit 8 so that the lowermost end of the cutting blade 12 is positioned at a position lower than the front surface 15a of the support wafer 15 and higher than the back surface 15b.

[0084] Next, the rotation drive source connected to the other end of the spindle 10 rotates the cutting blade 12 together with the spindle 10. Next, while supplying liquid (cutting water) from a nozzle provided in the vicinity of the cutting blade 12 to the vicinity of the lowermost end of the cutting blade 12, the cutting blade 12 is cut into the wafer 11.

[0085] Specifically, until the lowermost end of the cutting blade 12 reaches a part of the outer peripheral region of the bonded wafer 17 located in the Y1-axis direction as viewed from the center of the bonded wafer 17, the X1-axis direction moving mechanism moves the chuck table 6 along the X1-axis direction. Next, while the cutting blade 12 is rotating, the rotation drive source connected to the θ table 4 is operated to rotate the chuck table 6 at least once.

[0086] As a result, the outer peripheral region of the bonded wafer 17 is cut in an annular shape. FIG. 9(B) is a cross-sectional view schematically showing the bonded wafer 17 after the trimming step (S2) is performed. By this trimming step (S2), all of the chamfered outer peripheral region of the wafer 11 and a part of the surface 15a side of the chamfered outer peripheral region of the support wafer 15 are removed.

[0087] At this time, a damage layer 11d is formed near the cut surface in the outer peripheral region of the wafer 11 formed in the trimming step (S2), and a damage layer 15c is formed near the cut surface in the outer peripheral region of the support wafer 15.

[0088] In the method shown in FIG. 7, after the trimming step (S2) is performed, a laser beam is irradiated onto the cut surface in the outer peripheral region of the bonded wafer 17 (wafer 11 and support wafer 15) (cut surface treatment step: S13). FIG. 10(A) is a partial cross-sectional side view schematically showing a state in which the cut surface treatment step (S13) is performed on the bonded wafer 17. Regarding the laser processing apparatus 14 used in the cut surface treatment step (S13), the above description is incorporated herein by reference.

[0089] This cut surface treatment step (S13) is performed, for example, in the following order. First, after the bonded wafer 17 is carried onto the holding surface of the chuck table 18 so that the back surface 11c of the wafer 11 faces upward, a suction source is operated so that the back surface 15b side of the support wafer 15 is sucked and held by the chuck table 18.

[0090] Next, the Z2-axis direction movement mechanism adjusts the position of the laser beam irradiation unit so that the cut surface (the surfaces of the damage layer 11d and the damage layer 15c) in the outer peripheral region of the bonded wafer 17 formed in the trimming step (S12) is positioned in the irradiation direction of the laser beam L as viewed from the laser beam irradiation unit.

[0091] Next, while rotating the chuck table 18, the laser beam irradiation unit irradiates the laser beam L. Further, the irradiation of the laser beam L may be performed while the Z2-axis direction movement mechanism moves the position of the laser beam irradiation unit. Thereby, for example, laser ablation occurs in the damage layer 11d and the damage layer 15c irradiated with the laser beam L.

[0092] Furthermore, the irradiation of the laser beam L is performed while varying the incident angle of the laser beam L (the irradiation direction of the laser beam L) on the damage layer 11d and the damage layer 15c. As a result, for example, all of the damage layer 11d and the damage layer 15c can be removed.

[0093] As a result, all of the damage layer 11d and the damage layer 15c are removed. FIG. 10(B) is a cross-sectional view schematically showing the bonded wafer 17 after the cutting surface treatment step (S13) is performed. By this cutting surface treatment step (S3), for example, all of the damage layer 11d and the damage layer 15c are removed.

[0094] Note that in the cutting surface treatment step (S13), the damage layer 11d and the damage layer 15c may not be removed. That is, in the cutting surface treatment step (S3), in order to suppress cracking of the wafer 11 when grinding the wafer 11 and generation of dust in the subsequent steps after this grinding, it is sufficient if the damage layer 11d and the damage layer 15c can be repaired.

[0095] For example, in the cutting surface treatment step (S13), the laser beam L may be irradiated onto the damage layer 11d and the damage layer 15c so that the damage layer 11d and the damage layer 15c slightly melt and then immediately solidify. Thereby, the surface (cutting surface) of the damage layer 11d and the damage layer 15c can be smoothed, and dust (cutting chips) adhering to the cutting surface can be fixed so as to be embedded in the wafer 11 and the support wafer 15.

[0096] Furthermore, similar to the cutting surface treatment step (S2), in order to remove or repair the damage layer 11d, for example, it is preferable that the output of the laser beam L in the cutting surface treatment step (S13) be 1 W to 30 W.

[0097] In the method shown in FIG. 7, after the cutting surface treatment step (S13) is performed, the bonded wafer is ground to be thinned to the finish thickness (grinding step: S14). Since this grinding step (S14) is performed in the same manner as the above-described grinding step (S4), the above description is incorporated herein by reference.

[0098] Also in the wafer processing method shown in FIG. 7, similar to the wafer processing method shown in FIG. 2, cracking of the wafer 11 starting from the outer peripheral region in the grinding step (S14) and generation of dust in the steps after the grinding step (S14) can be suppressed.

[0099] Further, in the wafer processing method of the present invention, the bonding step may not be performed. That is, in the wafer processing method of the present invention, all of the trimming step, the cutting surface treatment step, and the grinding step may be performed using a single wafer. FIG. 11 is a flowchart schematically showing an example of such a wafer processing method.

[0100] In this method, first, the chamfered outer peripheral region of the wafer 11 is cut in a ring shape (trimming step: S21). Since this trimming step (S21) is performed in the same manner as the above-described trimming step (S1), the above description is incorporated herein by reference.

[0101] In the method shown in FIG. 11, after the trimming step (S21) is performed, a laser beam is irradiated onto the cut surface of the outer peripheral region of the wafer 11 (cutting surface treatment step: S22). Since this cutting surface treatment step (S22) is performed in the same manner as the above-described cutting surface treatment step (S2), the above description is incorporated herein by reference.

[0102] In the method shown in FIG. 11, after the cutting surface treatment step (S22) is performed, the wafer 11 is ground to be thinned to the finish thickness (grinding step: S23). FIG. 12(A) is a partial cross-sectional side view schematically showing the state of performing the grinding step (S23) on the wafer 11. Note that for the grinding device 20 used in the grinding step (S23), the above description is incorporated by reference.

[0103] This grinding step (S23) is performed, for example, in the following order. First, the horizontal movement mechanism moves the chuck table 22 so that the chuck table 22 is positioned at a position separated from the grinding wheel 56 and where the wafer 11 can be carried onto the holding surface of the chuck table 22.

[0104] Next, a film-shaped protective member (not shown) having substantially the same diameter as the wafer 11 is attached to the surface 11a of the wafer 11. This protective member is made of, for example, resin and protects the device 13 by alleviating the impact applied to the surface 11a side when grinding the back surface 11c side of the wafer 11.

[0105] Next, after the wafer 11 is carried onto the holding surface of the chuck table 22 with the back surface 11c facing upward, the suction source is operated so that the surface 11a side of the wafer 11 is sucked and held by the chuck table 22.

[0106] Next, the inclination of the chuck table 22 is adjusted. Specifically, the inclination adjustment unit 38 adjusts the inclination of the chuck table 22 so that a line segment connecting the highest point among the points on the outer periphery of the holding surface of the chuck table 22 and the center of the holding surface is perpendicular to the Z3-axis direction. That is, the inclination adjustment unit 38 adjusts the inclination of the chuck table 22 so that this line segment is parallel to the lower surfaces of the plurality of grinding wheels 60. Note that when this line segment is perpendicular to the Z3-axis direction in advance, the adjustment of the inclination of the chuck table 22 is omitted.

[0107] Next, in a plan view, the horizontal movement mechanism moves the chuck table 22 so that the trajectories of the plurality of grinding wheels 60 when the grinding wheel 56 is rotated overlap with one end and the other end of the above-described line segment. Next, a rotation drive source connected to the upper end of the spindle 52 rotates the grinding wheel 56 together with the spindle 52, and a rotation drive source connected to the lower part of the spindle 28 rotates the chuck table 22 together with the spindle 28.

[0108] Next, while supplying liquid (grinding water) from a nozzle provided near the grinding wheel 56 to the back surface 11c of the wafer 11, the Z3-axis direction movement mechanism lowers the grinding unit 50 so that the lower surfaces of the plurality of grinding wheels 60 contact the back surface 11c of the wafer 11. As a result, a part on the back surface 11c side of the wafer 11 is ground and removed. Further, while the grinding wheel 56 and the chuck table 22 are being rotated, the Z3-axis direction movement mechanism lowers the grinding unit 50 until the wafer 11 is thinned to the finish thickness.

[0109] As a result, the damaged layer 11d remaining together with the chamfered portion remaining on the back surface 11c side of the outer peripheral region of the wafer 11 is removed. FIG. 12(B) is a cross-sectional view schematically showing the wafer 11 after the grinding step (S23) is performed. By this grinding step (S23), for example, a portion of the damaged layer 11d extending along the plane direction of the wafer 11 is removed.

[0110] Also in the wafer processing method shown in FIG. 11, similar to the wafer processing method shown in FIG. 2 or FIG. 7, cracking of the wafer 11 starting from the outer peripheral region in the grinding step (S23) and generation of dust in the steps after the grinding step (S23) can be suppressed.

[0111] Also, in the trimming steps (S1) and (S21) of the above-described method, edge trimming is performed so as to leave a part of the chamfered outer peripheral region of the wafer 11 on the back surface 11c side. However, in the trimming step of the method of the present invention, edge trimming may be performed so as to remove the entire chamfered outer peripheral portion of the wafer 11.

[0112] That is, in the trimming step of the method of the present invention, edge trimming may be performed so that the damage layer 11d is formed only along the thickness direction of the wafer 11. Such edge trimming is performed, for example, by cutting the cutting blade 12 into the wafer 11 with the lowermost end of the cutting blade 12 positioned below the back surface 11c of the wafer 11.

[0113] In this case, it is preferable that a dicing tape is adhered to the back surface 11c side of the wafer 11. That is, it is preferable that the edge trimming of the wafer 11 is performed in a state where the wafer 11 is sucked and held by the chuck table 6 via this dicing tape. Thereby, damage to the chuck table 6 due to contact of the cutting blade 12 with the chuck table 6 can be prevented.

[0114] Also, in the cut surface treatment steps (S2), (S13), and (S22) of the above-described method, a laser beam is irradiated onto the surface of the damage layer 11d (and the damage layer 15c) of the wafer 11. However, in the cut surface treatment step of the method of the present invention, energy may be supplied to the damage layer 11d (and the damage layer 15c) by a method other than laser beam irradiation.

[0115] That is, in the cut surface treatment step of the method of the present invention, any means may be used as long as energy can be locally supplied to the damage layer 11d to remove or repair the damage layer 11d without causing an adverse effect on the device 13. For example, in the cut surface treatment step of the method of the present invention, the laser beam may be replaced with local atmospheric pressure plasma, an ion beam, or the like.

[0116] In addition, the structures, methods, etc. 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 Reference Numerals

[0117] 11: Wafer (11a: Front surface, 11b: Side surface) (11c: Back surface, 11d: Damage layer) 13: Device 15: Support wafer (15a: Front surface, 15b: Back surface) 17: Bonded wafer 2: Cutting device 4: θ table 6: Chuck table (6a: Frame) 8: Cutting unit 10: Spindle 12: Cutting blade 14: Laser processing device 16: θ table 18: Chuck table (18a: Frame) 20: Grinding device 22: Chuck table 24: Frame 26: Porous plate 28: Spindle 30: Rotation shaft 32: Bearing 34: Support plate 36: Table base 38: Tilt adjustment unit (38a: Fixed support mechanism, 38b, 38c: Movable support mechanism) 40: Support column 42: Upper support 44: Bearing 46: Support plate 48: Motor 50: Grinding unit 52: Spindle 54: Wheel mount 56: Grinding wheel 58: Wheel base 60: Grinding wheel

Claims

Claim 1 A method for processing a wafer by grinding and thinning the wafer having a chamfered outer peripheral region, comprising: a trimming step of cutting a cutting blade into the chamfered outer peripheral region from one surface side of the wafer to cut the chamfered outer peripheral region in a ring shape and removing at least a part of the chamfered outer peripheral region; a cutting surface treatment step of locally supplying energy to the cutting surface of the outer peripheral region formed in the trimming step after the trimming step; a grinding step of grinding the other surface side of the wafer to thin the wafer after the cutting surface treatment step; A method for processing a wafer including the above steps.

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