Processing method

Abstract

To provide a processing method that reduces the risk of causing peel-off of a sheet from a wafer during planarization of the sheet.SOLUTION: A processing method includes: a stepped portion forming step 1001 of annularly removing a part of a wafer along an outer periphery of a surface of the wafer to form a stepped portion on the outer periphery of the wafer; a sheet placement step 1002 of placing a sheet covering the stepped portion and the surface of the wafer on the surface of the wafer such that the inside of the sheet is higher than an outer peripheral edge thereof after performing the stepped portion forming step 1001; and a sheet planarizing step 1003 of planarizing an upper surface of the sheet excluding the outer peripheral edge of the sheet by grinding or cutting with a bite after performing the sheet placement step 1002.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a processing method.

Background Art

[0002] When back-grinding a wafer in the manufacturing process of a semiconductor device, a sheet such as a pressure-sensitive tape or a UV-curable tape is attached to the surface of the workpiece, and the workpiece is held by a holding table of a grinding device via the sheet and the back surface is ground.

[0003] When a tape is attached to a wafer having protruded electrodes called bumps formed on its surface, the surface of the tape may be uneven following the bumps. If the surface of the wafer is held by a holding table via the tape in this state, there is a problem that the height of the back surface of the wafer varies and it cannot be thinned to a uniform thickness. Therefore, as disclosed in the above publication, a method has been proposed in which after the tape is attached to the wafer, the upper surface of the tape is cut with a tool to flatten it (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the method disclosed in Patent Document 1 and the like, when a tape having a low fixing force to the wafer is cut with a tool for flattening, there has been a problem that it peels off during cutting.

[0006] On the other hand, a tape having a low fixing force to the wafer is desired to be used because it has an advantage that it can be easily peeled off from the wafer.

[0007] An object of the present invention is to provide a processing method for reducing the risk of the sheet peeling off from the wafer during flattening of the sheet.

Means for Solving the Problems

[0008] In order to solve the above-described problems and achieve the object, a processing method of the present invention is a processing method including: a step of forming a stepped portion by removing a part of the wafer in a circular shape along the outer periphery of the surface of the wafer to form a stepped portion on the outer periphery of the wafer; a step of disposing a sheet covering the stepped portion and the surface of the wafer on the surface of the wafer after performing the stepped portion forming step so as to be higher inside than the outer peripheral edge of the sheet; and a step of flattening the upper surface of the sheet excluding the outer peripheral edge of the sheet by grinding or bite cutting after performing the sheet disposing step. , in the step of forming a stepped portion, a part of the wafer is removed in an annular shape by a predetermined depth exceeding the thickness of the sheet from the surface, characterized in that 。

[0009] In the processing method, after performing the sheet flattening step, a holding step of holding the wafer by a holding table via the sheet and a processing step of performing processing on the wafer held by the holding table may be provided.

[0010] In the processing method, the stepped portion may include a flat surface along the surface and a side surface extending from the flat surface to the surface.

[0011] In the processing method, the stepped portion may include an inclined surface inclined from the surface of the wafer toward the outer peripheral edge.

[0012] In the processing method, the stepped portion may be an annular groove formed on the outer periphery of the surface of the wafer. In the step of disposing the sheet, the sheet is in close contact with the inner surface and the bottom surface of the annular groove which is the stepped portion, After performing the sheet disposing step and before performing the sheet flattening step, at least from the center in the width direction of the bottom surface of the annular groove Remove the outer peripheral sheet and the outer peripheral edge of the sheet is adhered to the bottom surface of the annular groove even after removing the outer peripheral side. The processing method may further include an outer peripheral sheet removing step.

Effects of the Invention

[0013] The present invention has an effect of being able to reduce the risk that the sheet peels off from the wafer during the flattening of the sheet.

Brief Description of the Drawings

[0014]

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DETAILED DESCRIPTION OF THE INVENTION

[0015] The embodiments for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the content described in the following embodiments. Further, the constituent elements described below include those that can be easily assumed by those skilled in the art and substantially the same ones. Furthermore, the configurations described below can be combined as appropriate. Also, various omissions, substitutions, or changes in the configuration can be made without departing from the gist of the present invention.

[0016] [Embodiment 1] The processing method according to Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a workpiece to be processed by the processing method according to Embodiment 1. FIG. 2 is a plan view showing an enlarged view of the device of the workpiece shown in part II in FIG. 1. FIG. 3 is a flowchart showing the flow of the processing method according to Embodiment 1.

[0017] The processing method according to Embodiment 1 is a processing method for the wafer 1 shown in FIG. 1. The wafer 1 to be processed by the processing method according to Embodiment 1 is a disk-shaped semiconductor wafer, an optical device wafer, etc. having silicon (Si), sapphire (Al2O3), gallium arsenide (GaAs), silicon carbide (SiC), etc. as the substrate 2.

[0018] As shown in FIG. 1, the wafer 1 includes a device region 3 and an outer peripheral surplus region 4 on the surface 5. In the device region 3, devices 7 are formed in each region partitioned by a plurality of division planned lines 6 intersecting each other on the surface 5. As shown in FIG. 2, each device 7 has a plurality of bumps 8 protruding from the surface 5 and connected to the electrodes of each device 7. Since the wafer 1 has the bumps 8 where the devices 7 protrude from the surface 5, irregularities are formed on the surface 5. The bump 8 is made of a conductive metal.

[0019] The device 7 is, for example, an integrated circuit such as an IC (Integrated Circuit) or an LSI (Large Scale Integration), an image sensor such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor), etc. The outer peripheral surplus region 4 surrounds the device region 3 over the entire circumference and is a region where no device such as the device 7 is formed.

[0020] Also, the front surface 5 of the wafer 1 and the back surface 9 on the back side of the front surface 5 are each flat and parallel to each other. The wafer 1 has a chamfered portion 11 at the outer peripheral edge 10. The chamfered portion 11 is formed from the front surface 5 to the back surface 9 and is formed in an arc shape in cross section such that the center in the thickness direction is located on the outermost peripheral side.

[0021] In Embodiment 1, the back surface 9 side of the wafer 1 is ground and thinned to the finished thickness, and is divided into individual devices 7 along the planned division line 6.

[0022] The processing method according to Embodiment 1 is a processing method for processing a single wafer 1, and as shown in FIG. 3, includes a step 1001 of forming a stepped portion, a step 1002 of disposing a sheet, a step 1003 of flattening the sheet, a step 1004 of holding, and a step 1005 of processing.

[0023] (Step of forming a stepped portion) FIG. 4 is a cross-sectional view schematically showing the step of forming a stepped portion of the processing method shown in FIG. 3. FIG. 5 is a cross-sectional view of the main part of the wafer after the step of forming a stepped portion of the processing method shown in FIG. 3. The step 1001 of forming a stepped portion is a step of removing a part of the wafer 1 in an annular shape along the outer peripheral edge 10 which is the outer periphery of the front surface 5 of the wafer 1, and forming a stepped portion 20 in the outer peripheral surplus region 4 of the wafer 1.

[0024] In the step 1001 of forming the stepped portion, the cutting device 30 opens the on-off valve 33 and is sucked from the suction source 34, thereby sucking and holding the back surface 9 side of the wafer 1 on the holding surface 32 of the chuck table 31. In the step 1001 of forming the stepped portion, the cutting device 30 rotates the cutting blade 36 around the axis by the spindle 35, and the lower end of the cutting edge 361 of the cutting blade 36 is arranged along the outer peripheral edge 10 of the wafer 1 and in the processing feed direction of the chuck table 31, and at a position below the surface 5 of the wafer 1.

[0025] In the step 1001 of forming the stepped portion, the cutting device 30 performs processing feed in the direction of approaching the chuck table 31 to the cutting blade 36. As shown in FIG. 4, the cutting edge 361 of the cutting blade 36 is cut into a position including the outer peripheral edge 10 of the outer peripheral surplus region 4 from the surface 5 side of the wafer 1. The chuck table 31 is rotated around the axis, and the chamfered portion 11, which is a part of the substrate 2 of the wafer 1, is removed annularly from the surface 5 side. In the step 1001 of forming the stepped portion, the cutting device 30 cuts the cutting blade 36 into a position including the outer peripheral edge 10 of the outer peripheral surplus region 4 from the surface 5 side of the wafer 1, removes the chamfered portion 11 by a predetermined depth 202 from the surface 5 side, and forms the stepped portion 20 shown in FIG. 5 at a position including the outer peripheral edge 10 of the outer peripheral surplus region 4.

[0026] In Embodiment 1, as shown in FIG. 5, the stepped portion 20 includes a flat surface 21 that is continuous with the outer peripheral edge 10 of the wafer 1 and extends along the surface 5 of the substrate 2, and an inner peripheral side of the outer peripheral edge 10 of the wafer 1 and a side surface 22 that intersects (orthogonal in Embodiment 1) the surface 5 from the inner edge of the flat surface 21 toward the surface 5. In this way, the stepped portion 20 is formed by the flat surface 21 along the surface 5 of the substrate 2 and the side surface 22 from the flat surface 21 to the surface 5. In Embodiment 1, the flat surface 21 does not have to be parallel to the surface 5 as long as it is flat along the surface 5 of the substrate 2, but in the present invention, it may be parallel to the surface 5 of the substrate 2. That is, the term "along" described in this specification means being parallel and intersecting so that the angle formed by each other is as close to zero degrees as possible. The flat surface 21 and the side surface 22 are formed over the entire circumference of the wafer 1 along the outer peripheral edge 10, and the stepped portion 20 is formed over the entire circumference of the outer peripheral edge 10 of the wafer 1 and is formed in an annular shape.

[0027] Thus, in Embodiment 1, in the stepped portion forming step 1001, the cutting device 30 moves the cutting blade 36 with the lower end of the cutting edge 361 positioned below the surface 5 relative to the wafer 1 in the horizontal direction and cuts into the wafer 1, and rotates the wafer 1 around the axis by the chuck table 31 to form the stepped portion 20 on the surface 5 side, and performs edge trimming to remove the outer peripheral edge 10 of the wafer 1. However, in the present invention, in the stepped portion forming step 1001, the cutting device 30 lowers the cutting blade 36 positioned above the chamfered portion 11 of the wafer 1, so that the cutting edge 361 cuts into a position including the outer peripheral edge 10 of the outer peripheral surplus region 4 of the wafer 1, and the wafer 1 is rotated around the axis by the chuck table 31, and edge trimming for forming the stepped portion 20 on the surface 5 side may be performed by a so-called chopper cut.

[0028] (Sheet Arrangement Step) FIG. 6 is a cross-sectional view of a wafer after the sheet disposition step of the processing method shown in FIG. 3. The sheet disposition step 1002 is a step of disposing, on the surface 5 of the wafer 1, a step portion 20 and a sheet 23 covering the surface 5 of the wafer 1 after performing the step portion formation step 1001, so that the inner peripheral side is higher than the outer peripheral edge 231 of the sheet 23.

[0029] In the first embodiment, the sheet 23 that adheres to the surface 5 of the wafer 1 is composed only of a base material 24 made of a synthetic resin having thermocompression bonding properties, non-adhesive properties, and airtightness. In the first embodiment, the base material 24 constituting the sheet 23 is made of, for example, a polyolefin-based synthetic resin. Since the sheet 23 used in the processing method according to the first embodiment is composed only of the base material 24, it has a lower adhesive force than the adhesive layer of a UV-curable sheet that cures when irradiated with ultraviolet rays.

[0030] The sheet 23 is formed in a circular planar shape that is slightly larger than the planar shape of the wafer 1. Since the sheet 23 used in the processing method of the first embodiment is composed only of a base material 24 made of a synthetic resin having thermocompression bonding properties, non-adhesive properties, and airtightness, an adhesive layer is not formed in the region corresponding to the device region 3 of the wafer 1. The region corresponding to the device region 3 of the wafer 1 is the region of the surface of the sheet 23 that overlaps the device region 3 of the wafer 1.

[0031] In the first embodiment, in the sheet disposition step 1002, the sheet 23 is overlapped on the surface 5 of the wafer 1, the pressure between the wafer 1 and the sheet 23 is reduced while heating the wafer 1 and the sheet 23, and the sheet 23 is pressed toward the surface 5 of the wafer 1. In the sheet disposition step 1002, since the wafer 1 and the sheet 23 are heated and the sheet 23 is pressed toward the surface 5 of the wafer 1, the sheet 23 enters between the adjacent bumps 8 and, as shown in FIG. 6, adheres to the surface 5 of the device region 3 of the wafer 1 and the surface of the bumps 8 without gaps, and also adheres to the flat surface 21 and the side surface 22 of the step portion 20 of the outer peripheral surplus region 4 without gaps.

[0032] Note that after the sheet placement step 1002, the sheet 23 is in close contact with the surface 5 of the substrate 2 and the surface of the bumps 8 in the device region 3 of the wafer 1 without any gaps, and is also in close contact with the flat surface 21 and the side surface 22 of the step portion 20 in the outer peripheral surplus region 4 of the wafer 1 without any gaps. Therefore, the sheet 23 is adhered to the wafer 1 in a state where the inner peripheral side of the sheet 23 is higher than the outer peripheral edge 231 of the sheet 23. That is, after the sheet placement step 1002, when the wafer 1 is arranged such that the back surface 9 is on the lower side and the surface 5 is on the upper side, the sheet 23 is adhered to the wafer 1 in a state where the inner peripheral side of the side surface 22 of the step portion 20, that is, the inner peripheral side of the step portion 20 is higher than the outer peripheral side of the side surface 22 of the step portion 20. Further, after the sheet placement step 1002, the outer peripheral edge 231 of the sheet 23 is located on the outer edge of the flat surface 21 of the step portion 20, that is, on the outer peripheral edge 10 of the wafer 1.

[0033] In the sheet placement step 1002, since the sheet 23 is in close contact with the surface 5 of the wafer 1 and the surface of the bumps 8 without any gaps, although omitted in FIG. 6, irregularities following the bumps 8 are formed on the upper surface 232 of the sheet 23.

[0034] (Sheet flattening step) FIG. 7 is a cross-sectional view schematically showing the sheet flattening step of the processing method shown in FIG. 3. FIG. 8 is a cross-sectional view schematically showing cutting water or the like sprayed onto the lower end of the cutting tool in the sheet flattening step of the processing method shown in FIG. 3. The sheet flattening step 1003 is a step of performing byte cutting on the upper surface 232 of the sheet 23 excluding the outer peripheral edge 231 of the sheet 23 after the sheet placement step 1002 to flatten it.

[0035] In the sheet flattening step 1003, the bite cutting device 40 opens the on-off valve 43 and is suctioned from the suction source 44, thereby suction-holding the back surface 9 side of the wafer 1 on the holding surface 42 of the chuck table 41. In the sheet flattening step 1003, the bite cutting device 40 positions the lower end of the bite tool 47 below the lowest position of the upper surface 232 of the sheet 23 in close contact with the surface 5 of the wafer 1 and above all the bumps 8 of the wafer 1.

[0036] In the sheet flattening step 1003, as shown in FIG. 7, the bite cutting device 40 drives a motor (not shown) to rotate the spindle 45 and the bite wheel 46 around an axis parallel to the vertical direction, and moves the chuck table 41 horizontally while rotating it around an axis parallel to the vertical direction, so that the chuck table 41 passes below the bite wheel 46. At this time, as shown in FIG. 8, the bite cutting device 40 sprays cutting water 48 from a cutting water supply nozzle (not shown) onto the lower end of the bite tool 47 of the bite wheel 46. The cutting water 48 sprayed onto the lower end of the bite tool 47 is sprayed onto the lower end of the bite tool 47 from the outer peripheral side to the inner peripheral side of the wafer 1 held on the chuck table 41.

[0037] In the sheet flattening step 1003, the bite cutting device 40 inserts the bite tool 47 into the upper surface 232 of the sheet 23 in close contact with the surface 5 of the wafer 1 excluding the outer peripheral edge 231 in close contact with the step portion 20, and performs turning cutting on the upper surface 232 of the sheet 23 excluding the outer peripheral edge 231 in close contact with the step portion 20. In the sheet flattening step 1003, the bite cutting device 40 flattens the upper surface 232 of the sheet 23 in close contact with the surface 5 of the wafer 1 excluding the outer peripheral edge 231 in close contact with the step portion 20.

[0038] That is, in the sheet flattening step 1003, the bite cutting device 40 bite cuts and flattens the inner circumferential side of the upper surface 232 of the sheet 23 that is closer to the inner circumference than the step portion 20, and does not bite cut the region of the step portion 20 including the outer peripheral edge 231 of the sheet 23 that is in close contact with the flat surface 21 in particular. Further, in the sheet flattening step 1003, the cutting water 48 sprayed from the cutting water supply nozzle of the bite cutting device 40 to the lower end of the bite tool 47 is also sprayed onto the side surface 22 of the step portion 20 of the wafer 1, the outer peripheral edge 231 of the sheet 23 in close contact with the flat surface 21, and the outer peripheral edge 10 of the wafer 1, as shown in FIG. 8.

[0039] (Holding Step) FIG. 9 is a cross-sectional view schematically showing the holding step of the processing method shown in FIG. 3. The holding step 1004 is a step of holding the wafer 1 on the holding table 51 of the processing device 50 via the sheet 23 after the sheet flattening step 1003 is performed. In the holding step 1004, as shown in FIG. 9, the processing device 50 opens the on-off valve 53 and is sucked from the suction source 54, so that the surface 5 side of the wafer 1 is sucked and held on the holding surface 52 of the holding table 51 via the sheet 23. In Embodiment 11, the processing device 50 is a grinding device that grinds the back surface 9 of the wafer 1.

[0040] (Processing Step) FIG. 10 is a side view schematically showing a partial cross-section of the processing step of the processing method shown in FIG. 3. The processing step 1005 is a step in which the processing device 50 performs processing on the wafer 1 held on the holding table 51. In Embodiment 1, in the processing step 1005, as shown in FIG. 10, the processing device 50 rotates the holding table 51 around an axis parallel to the vertical direction and rotates the grinding wheel 56 of the grinding unit 55 around an axis parallel to the vertical direction, and brings the grinding abrasive 57 of the grinding wheel 56 into contact with the back surface 9 of the wafer 1 to perform grinding, which is the processing, on the back surface 9. In the processing step 1005, when the processing device 100 grinds and thins the wafer 1 to the finish thickness, the processing method ends.

[0041] In Embodiment 1, the holding step 1004 and the processing step 1005 are performed by the grinding device which is the processing device 50, and the processing device 50 grinds the wafer 1. However, in the present invention, the processing device 50 is not limited to the grinding device. In the present invention, the holding step 1004 and the processing step 1005 may be performed by various processing devices such as a polishing device that polishes (corresponding to processing) the wafer 1, a laser processing device that forms a modified layer inside the substrate 2 by irradiating the wafer 1 with a laser beam having a wavelength that is transmissive to the wafer 1 from the back surface 9 side (corresponding to processing), a cutting device that performs cutting (corresponding to processing) by cutting a cutting blade into the wafer 1 from the back surface 9 side, and a laser processing device that performs laser processing (corresponding to processing) by irradiating the wafer 1 with a laser beam having a wavelength that is absorptive to the wafer 1 from the back surface 9 side to ablate the wafer 1. That is, in the present invention, the processing device 50 may perform various processes such as polishing, laser processing, and cutting on the wafer 1.

[0042] As described above, the processing method according to Embodiment 1 removes a chamfered portion 11 which is a part of the wafer 1 annularly from the surface 5 side along the outer peripheral edge 10 of the surface 5 of the wafer 1 before performing the sheet flattening step 1003 to form a stepped portion 20 in the outer peripheral surplus region 4. Then, in the sheet disposing step 1002 of the processing method according to Embodiment 1, by disposing the sheet 23 that covers the stepped portion 20 and the surface 5 of the wafer 1, the sheet 23 is adhered to the wafer 1 in a state where the inner peripheral side of the sheet 23 is higher than the outer peripheral edge 231, that is, the inner peripheral side of the side surface 22 of the stepped portion 20 is higher than the outer peripheral side of the side surface 22 of the stepped portion 20, that is, the inner peripheral side of the stepped portion 20.

[0043] For this purpose, in the sheet flattening step 1003 of the processing method according to Embodiment 1, the area excluding the outer peripheral edge 231 of the sheet 23 is subjected to turning cutting with the tool bit 47. That is, the inner peripheral side of the upper surface 232 of the sheet 23, which is closer to the inner circumference than the step portion 20, is cut with the tool bit to be flattened, and the area of the step portion 20 including the outer peripheral edge 231 of the sheet 23, which is in close contact with the flat surface 21 in particular, is not cut with the tool bit. Therefore, when the tool bit 47 abuts on the outer peripheral edge 231 of the sheet 23 and the tool bit 47 moves to the inner peripheral side of the wafer 1, peeling of the sheet 23 is induced. However, in the processing method according to Embodiment 1, the tool bit 47 does not contact the outer peripheral edge 231 of the sheet 23, the upper surface 232 of the sheet 23 can be cut with the tool bit, and peeling of the sheet 23 is not induced.

[0044] As a result, the processing method according to Embodiment 1 has the effect of reducing the possibility that the sheet 23 peels off from the wafer 1 during the flattening of the sheet 23. That is, the processing method according to Embodiment 1 has the effect of reducing the possibility that the sheet 23 peels off from the wafer 1 during the flattening of the sheet 23, even if the sheet 23 has a lower adhesive force than the UV-curable sheet without an adhesive layer, because the tool bit 47 does not abut on the outer peripheral edge 231 of the sheet 23.

[0045] 〔Modification Example 1〕 The processing method according to Modification Example 1 of Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 11 is a cross-sectional view of a main part of the wafer after the step portion forming step of the processing method according to Modification Example 1 of Embodiment 1. In addition, in FIG. 11, the same parts as those in Embodiment 1 are denoted by the same reference numerals, and the description thereof is omitted.

[0046] The processing method according to Modification Example 1 of Embodiment 1 is the same as that of Embodiment 1 except that the step portion forming step 1001 is different from that of Embodiment 1. In the step portion forming step 1001 of the processing method according to Modification Example 1, edge trimming is performed twice by varying the cutting depth at which the cutting blade 36 is cut into the wafer 1, and a step portion 20-1 including two flat surfaces 21-1 and 21-2 and two side surfaces 22-1 and 22-2 is formed on the surface 5 side of the outer peripheral surplus region 4 of the wafer 1.

[0047] In the step 1001 of forming the stepped portion of the processing method according to the first modification, the cutting edge 361 of the cutting blade 36 is inserted into a position including the outer peripheral edge 10 of the outer peripheral surplus region 4 of the surface 5 of the wafer 1 to form a first flat surface 21-1 continuous with the outer peripheral edge 10 and along the surface 5, and a first side surface 22-1 continuous with the inner edge of the first flat surface 21-1 and extending toward the surface 5 side. In the step 1001 of forming the stepped portion of the processing method according to the first modification, the cutting edge 361 of the cutting blade 36 is inserted into a position including the first side surface 22-1 of the outer peripheral surplus region 4 of the surface 5 of the wafer 1 to form a second flat surface 21-2 along the surface 5 continuous with the first side surface 22-1 and a second side surface 22-2 extending from the second flat surface 21-2 to the surface 5.

[0048] In the step 1001 of forming the stepped portion of the processing method according to the first modification, the height of the lower end of the cutting edge 361 of the cutting blade 36 when forming the second flat surface 21-2 and the second side surface 22-2 is made higher than the height of the lower end of the cutting edge 361 of the cutting blade 36 when forming the first flat surface 21-1 and the first side surface 22-1, that is, the cutting depth of the cutting blade 36 when forming the second flat surface 21-2 and the second side surface 22-2 is made shallower than the cutting depth of the cutting blade 36 when forming the first flat surface 21-1 and the first side surface 22-1. Further, in the step 1001 of forming the stepped portion of the processing method according to the first modification, the lower end of the cutting edge 361 of the cutting blade 36 when forming the second flat surface 21-2 and the second side surface 22-2 is positioned closer to the inner peripheral side of the wafer 1 than the lower end of the cutting edge 361 of the cutting blade 36 when forming the first flat surface 21-1 and the first side surface 22-1, and the second flat surface 22-2 is formed closer to the surface 5 of the wafer 1 and on the inner peripheral side of the wafer 1 than the first flat surface 22-1.

[0049] Also, after the sheet arrangement step 1002 according to the first modification, the sheet 23 is in close contact with the surface 5 of the substrate 2 in the device region 3 of the wafer 1 and the surface 5 of the bumps 8 without any gaps, and is in close contact with the flat surfaces 21-1, 21-2 and the side surfaces 22-1, 22-2 of the step portion 20 in the outer peripheral surplus region 4 of the wafer 1 without any gaps. After the sheet arrangement step 1002 according to the first modification, the outer peripheral edge 231 of the sheet 23 is located on the outer edge of the second flat surface 21-2 of the step portion 20-1, that is, on the outer peripheral edge 10 of the wafer 1.

[0050] Before performing the sheet flattening step 1003, the processing method according to the first modification annularly removes a chamfered portion 11, which is a part of the wafer 1, from the surface 5 side along the outer peripheral edge 10 of the surface 5 of the wafer 1 to form a step portion 20-1. In the sheet arrangement step 1002, a sheet 23 covering the step portion 20 and the surface 5 of the wafer 1 is arranged. As a result, in the sheet flattening step 1003 of the processing method according to the first modification, the bite tool 47 does not contact the outer peripheral edge 231 of the sheet 23, and peeling of the sheet 23 is not induced. Therefore, similar to the first embodiment, it is possible to reduce the risk that the sheet 23 peels off from the wafer 1 during the flattening of the sheet 23.

[0051] 〔Second Modification〕 The processing method according to the second modification of the first embodiment of the present invention will be described with reference to the drawings. FIG. 12 is a cross-sectional view schematically showing the step portion forming step of the processing method according to the second modification of the first embodiment. FIG. 13 is a cross-sectional view of the main part of the wafer after the step portion forming step of the processing method according to the second modification of the first embodiment. In addition, the same reference numerals are given to the same parts as those in the first embodiment in FIGS. 12 and 13, and the description thereof will be omitted.

[0052] The processing method according to Modification Example 2 of Embodiment 1 is the same as that of Embodiment 1 except that the step formation step 1001 is different from that of Embodiment 1. In the step formation step 1001 of the processing method according to Modification Example 2, as shown in FIG. 12, a so-called bevel blade cutting blade 37 in which the outer diameter at the center in the thickness direction of the cutting edge 371 is larger than the outer diameter at the end in the thickness direction and the cross-sectional shape of the outer edge of the cutting edge 371 is formed in a mountain shape is cut into a position including the outer peripheral edge 10 of the outer peripheral surplus region 4 of the surface 5 of the wafer 1, and the chamfered portion 11 which is a part of the wafer 1 is removed from the surface 5 side.

[0053] In the step formation step 1001 of the processing method according to Modification Example 2, as shown in FIG. 13, the cutting device 30 forms a stepped portion 20-2 including an inclined surface 25 that gradually thins the wafer 1 toward the outer peripheral edge 10 while being inclined with respect to both the surface 5 and the thickness direction of the wafer 1 from the surface 5 of the substrate 2 of the wafer 1 toward the outer peripheral edge 10 in the outer peripheral surplus region 4 on the surface 5 side of the outer peripheral surplus region 4 of the wafer 1. Note that the stepped portion 20-2 formed in the step formation step 1001 of the processing method according to Modification Example 2 does not include the flat surface 21 and the side surface 22.

[0054] Before performing the sheet flattening step 1003, the processing method according to Modification Example 2 annularly removes the chamfered portion 11 which is a part of the wafer 1 from the surface 5 side along the outer peripheral edge 10 of the surface 5 of the wafer 1 to form the stepped portion 20-2, and in the sheet disposition step 1002, the sheet 23 covering the stepped portion 20-2 and the surface 5 of the wafer 1 is disposed. As a result, since the stepped portion 20-2 of the processing method according to Modification Example 2 includes the inclined surface 25, in the sheet flattening step 1003, the bite tool 47 does not contact the outer peripheral edge 231 of the sheet 23, and the peeling of the sheet 23 is not induced. Therefore, similar to Embodiment 1, there is an effect that the possibility of the sheet 23 peeling from the wafer 1 during the flattening of the sheet 23 can be reduced.

[0055] 〔Embodiment 2〕 The processing method according to Embodiment 2 of the present invention will be described with reference to the drawings. FIG. 14 is a flowchart showing the flow of the processing method according to Embodiment 2. FIG. 15 is a cross-sectional view schematically showing the step of forming a stepped portion of the processing method shown in FIG. 14. FIG. 16 is a cross-sectional view of a main part of the wafer after the step of forming a stepped portion of the processing method shown in FIG. 14. FIG. 17 is a cross-sectional view of the wafer after the step of disposing a sheet of the processing method shown in FIG. 14. FIG. 18 is a partial cross-sectional view of the wafer schematically showing the step of removing an outer peripheral sheet of the processing method shown in FIG. 14. FIG. 19 is a partial cross-sectional view of the wafer after the step of removing an outer peripheral sheet of the processing method shown in FIG. 14. FIG. 20 is a cross-sectional view schematically showing the step of flattening the sheet of the processing method shown in FIG. 14. FIG. 21 is a cross-sectional view schematically showing cutting water or the like sprayed onto the lower end of a cutting tool in the step of flattening the sheet of the processing method shown in FIG. 14. FIG. 22 is a side view schematically showing a part of the processing step of the processing method shown in FIG. 14 in a partial cross-section. Note that the same reference numerals are given to the same parts as in Embodiment 1 in FIGS. 14, 15, 16, 17, 18, 19, 20, 21, and 22, and the description thereof will be omitted.

[0056] The processing method according to Embodiment 2 is a processing method for processing a single wafer 1. As shown in FIG. 14, the processing method includes a stepped portion forming step 1001-2, a sheet disposing step 1002, an outer peripheral sheet removing step 1010, a sheet flattening step 1003, a holding step 1004, and a processing step 1005.

[0057] The stepped portion forming step 1001-2 in the processing direction according to Embodiment 2 is a step of removing a part of the wafer 1 in an annular shape along the outer peripheral edge 10 which is the outer periphery of the surface 5 of the wafer 1, and forming an annular groove 20-3 which is a stepped portion in the outer peripheral surplus region 4 of the wafer 1.

[0058] In the step 1001-2 of forming the stepped portion, the cutting device 30 sucks and holds the back surface 9 side of the wafer 1 on the holding surface 32 of the chuck table 31 in the same manner as in the first embodiment. In the step 1001-1 of forming the stepped portion, the cutting device 30 rotates the cutting blade 36 around the axis by the spindle 35, and positions the lower end of the cutting edge 361 of the cutting blade 36 above the outer peripheral surplus region 4 of the wafer 1 held by the chuck table 31 and closer to the inner circumference than the outer peripheral edge 10.

[0059] In the step 1001-1 of forming the stepped portion, when the cutting device 30 lowers the cutting blade 36 and cuts the cutting edge 361 into a position closer to the inner circumference and closer to the outer peripheral edge 10 of the outer peripheral surplus region 4 of the wafer 1, and the lower end of the cutting edge 361 cuts into the center in the thickness direction of the wafer 1, the lowering of the cutting blade 36 is stopped, and the wafer 1 is rotated around the axis by the chuck table 31. By means of a so-called chopper cut, the outer peripheral surplus region 4, which is a part of the substrate 2 of the wafer 1, is removed annularly from the surface 5 side. In the step 1001-1 of forming the stepped portion, the cutting device 30 cuts the cutting edge 361 of the cutting blade 36 into a position closer to the inner circumference and closer to the outer peripheral edge 10 of the outer peripheral surplus region 4 from the surface 5 side of the wafer 1, and as shown in FIG. 16, an annular groove 20-3 with a predetermined depth 202 is formed over the entire circumference as the stepped portion 20 from the surface 5 side.

[0060] Thus, the stepped portion 20 formed in the step 1001-1 of the processing method according to the second embodiment is an annular groove 20-3 formed in the outer peripheral surplus region 4 of the surface 5 of the wafer 1. In the second embodiment, the inner surface 26 and the bottom surface 27 of the annular groove 20-3 are formed at positions coaxial with the wafer 1, and the bottom surface 27 is along the surface 5 of the wafer 1 (in the first embodiment, it is parallel to the surface 5).

[0061] In Embodiment 2, in the sheet disposing step 1002, similar to Embodiment 1, the sheet 23 is overlaid on the surface 5 of the wafer 1, and while heating the wafer 1 and the sheet 23, the pressure between the wafer 1 and the sheet 23 is reduced, and the sheet 23 is pressed toward the surface 5 of the wafer 1. In Embodiment 2, in the sheet disposing step 1002, as shown in FIG. 17, the sheet 23 is in close contact with the surface 5 of the device region 3 of the wafer 1 and the surface of the bump 8 without any gap, and is in close contact with the inner surface 26 and the bottom surface 27 of the annular groove 20-3 which is the stepped portion 20 of the outer peripheral surplus region 4 without any gap, and is in close contact with the surface 5 side of the chamfered portion 11 without any gap.

[0062] The outer peripheral sheet removing step 1010 of the processing method according to Embodiment 2 is a step of removing at least the sheet 23 on the outer peripheral side of the annular groove 20-3 after the sheet disposing step 1002 is performed and before the sheet flattening step 1003 is performed. In the outer peripheral sheet removing step 1010 of the processing method according to Embodiment 2, the cutting device 30 sucks and holds the back surface 9 side of the wafer 1 on the holding surface 32 of the chuck table 31, and the cutting blade 381 is rotated around the axis by the spindle 35 with a cutting blade 38 thinner than the cutting blade 361 and the width of the annular groove 20-3, and the lower end of the cutting blade 381 of the cutting blade 38 is positioned above the bottom surface 27 of the annular groove 20-3 of the wafer 1 held by the chuck table 31.

[0063] In the outer peripheral sheet removing step 1010, the cutting device 30 lowers the cutting blade 38 and, as shown in FIG. 18, inserts the cutting edge 381 into the center in the width direction of the annular groove 20-3 of the sheet 23 in close contact with the bottom surface 27. When the lower end of the cutting edge 381 cuts into the lower surface of the sheet 23, the lowering of the cutting blade 38 is stopped, and the wafer 1 is rotated around the axis by the chuck table 31. By means of a so-called chopper cut, the sheet 23 in close contact with the bottom surface 27 of the annular groove 20-3 is cut over the entire circumference to form a dividing groove 233 in the sheet 23. In the outer peripheral sheet removing step 1010, when the cutting device 30 cuts the sheet 23 in close contact with the bottom surface 27 of the annular groove 20-3 over the entire circumference with the cutting blade 38, the cutting blade 36 is retracted from the wafer 1, and as shown in FIG. 19, the outer peripheral side of the sheet 23 beyond the dividing groove 233 is removed. Thus, in Embodiment 2, in the outer peripheral sheet removing step 1010, at least the sheet 23 on the outer peripheral side of the center in the width direction of the bottom surface 27 of the annular groove 20-3 is removed.

[0064] In the sheet flattening step 1003 of the processing method according to Embodiment 2, as shown in FIG. 20, similar to Embodiment 1, the tool bit 47 is inserted into the upper surface of the sheet 23, and the tool bit cutting device 40 performs tool bit cutting on the inner peripheral side of the upper surface 232 of the sheet 23, which is the stepped portion 20, i.e., the annular groove 20-3, to flatten it, and does not perform tool bit cutting on the region of the annular groove 20-3 of the sheet 23 that is particularly in close contact with the bottom surface 27. Also, in the sheet flattening step 1003, the cutting water 48 sprayed from the cutting water supply nozzle of the tool bit cutting device 40 to the lower end of the tool bit 47 is sprayed onto the side surface 22 of the stepped portion 20 of the wafer 1, as shown in FIG. 21, but is not sprayed onto the outer peripheral edge 231 of the sheet 23 in close contact with the bottom surface 27.

[0065] In the sheet flattening step 1003 of the processing method according to Embodiment 2, similar to Embodiment 1, the processing device 50 sucks and holds the surface 5 side of the wafer 1 through the sheet 23 on the holding surface 52 of the holding table 51.

[0066] In the machining step 1005 of the machining method according to Embodiment 2, as in Embodiment 1, the machining apparatus 50 performs grinding, which is machining, on the back surface 9 of the wafer 1 as shown in FIG. 22.

[0067] The machining method according to Embodiment 2 forms an annular groove 20-3, which is a stepped portion, from the surface 5 side in the outer peripheral surplus region 4 of the wafer 1 along the outer peripheral edge 10 of the surface 5 of the wafer 1 before performing the sheet flattening step 1003, and disposes a sheet 23 covering the annular groove 20-3 and the surface 5 of the wafer 1 in the sheet disposition step 1002. Further, the machining method according to Embodiment 2 removes the sheet 23 on the outer peripheral side of the center in the width direction of the bottom surface 27 of the annular groove 20-3 in the outer peripheral sheet removal step 1010.

[0068] As a result, in the machining method according to Embodiment 2, since the outer peripheral edge 231 of the sheet 23 adheres to the bottom surface 27 of the annular groove 20-3, in the sheet flattening step 1003, the cutting tool 47 does not contact the outer peripheral edge 231 of the sheet 23, and peeling of the sheet 23 is not induced. Thus, similar to Embodiment 1, there is an effect that the possibility of the sheet 23 peeling from the wafer 1 during flattening of the sheet 23 can be reduced.

[0069] Further, in the machining method according to Embodiment 2, since the cutting fluid 48 is not sprayed onto the outer peripheral edge 231 of the sheet 23 in close contact with the bottom surface 27 in the sheet flattening step 1003, peeling of the sheet 23 is not induced.

[0070] [Modification Example] The machining method according to the modification examples of Embodiment 1 and Embodiment 2 of the present invention will be described with reference to the drawings. FIG. 23 is a side view schematically showing a part of a cross section of the sheet flattening step of the machining method according to the modification examples of Embodiment 1 and Embodiment 2. FIG. 24 is a partial cross-sectional view of a modification example of the sheet of the machining method according to Embodiment 1 and Embodiment 2. Note that the same reference numerals are given to the same parts as those in Embodiment 1 and the like, and the description thereof is omitted.

[0071] In the sheet flattening step 1003 of the processing method according to the modification example, similar to the holding step 1004, the processing apparatus 50 sucks and holds the back surface 9 side of the wafer 1 on the holding surface 52 of the holding table 51. In the sheet flattening step 1003 of the processing method according to the modification example, similar to the processing step 1005, the processing apparatus 50 rotates the grinding wheel 56 of the grinding unit 55 around the axis while rotating the holding table 51 around the axis as shown in FIG. 23, and brings the grinding abrasive 57 of the grinding wheel 56 into contact with the upper surface 232 of the sheet 23, and grinds the upper surface 232 of the sheet 23 to flatten the upper surface 232 of the sheet 23.

[0072] In the processing method according to the modification example shown in FIG. 23, before performing the sheet flattening step 1003, a step portion 20 is formed along the outer peripheral edge 10 of the surface 5 of the wafer 1, and in the sheet disposing step 1002, the step portion 20 and the sheet 23 covering the surface 5 of the wafer 1 are disposed. As a result, in the sheet flattening step 1003 of the processing method according to the modification example, the cutting tool 47 does not contact the outer peripheral edge 231 of the sheet 23, and peeling of the sheet 23 is not induced. Therefore, similar to Embodiment 1 and the like, it is possible to reduce the risk that the sheet 23 peels off from the wafer 1 during flattening of the sheet 23.

[0073] Although FIG. 23 shows an example in which the step portion 20 is formed on the wafer 1, in the present invention, the step portions 20-1, 20-2 or the annular groove 20-3 may be formed on the wafer 1.

[0074] Further, in the processing method of the present invention, as shown in FIG. 24, the sheet 23-1 includes a base material 24 and an adhesive layer 28 laminated on the base material 24 and having an adhesive force, and the adhesive layer 28 is a so-called non-UV type adhesive layer having a lower adhesive force than that of a UV-curable adhesive layer that cures when irradiated with ultraviolet rays. Thus, it is desirable that the sheets 23 and 23-1 used in the processing method of the present invention have a lower adhesive force than the adhesive layer of a UV-curable sheet that cures when irradiated with ultraviolet rays.

[0075] Next, the inventors of the present invention confirmed the effects of the present invention. The results are shown in Table 1 below. Note that FIG. 25 is a cross-sectional view showing a part of the wafer to which the sheet of Comparative Example 1 is attached. FIG. 26 is a cross-sectional view showing a part of the wafer to which the sheet of Comparative Example 2 is attached. FIG. 27 is a cross-sectional view showing a part of the wafer to which the sheet of Comparative Example 3 is attached.

[0076]

Table 1

[0077] Table 1 shows the results of checking whether or not the sheet 23 peeled off from the wafer 1 when the upper surface 232 of the sheet 23 of each of Comparative Example 1, Comparative Example 2, Comparative Example 3, Invention Product 1, Invention Product 2, Invention Product 3, and Invention Product 4 was bite-cut with the bite tool 47. Further, Table 1 also shows the results of checking whether or not the sheet 23 peeled off from the wafer 1 when the cutting depth of the bite tool 47 into the upper surface 232 of the sheet 23 was set to 10 μm, 20 μm, 30 μm, 40 μm, and 50 μm in each of Comparative Example 1, Comparative Example 2, Comparative Example 3, Invention Product 1, Invention Product 2, Invention Product 3, and Invention Product 4. In Table 1, those with peeling are indicated by crosses, and those without peeling are indicated by circles.

[0078] In Comparative Example 1 of Table 1, as shown in FIG. 25, the sheet 23 was adhered to the entire flat surface 5 of the wafer 1 in the same manner as in the sheet arrangement step 1002 without forming the stepped portions 20, 20-1, 20-2 or the annular groove 20-3. In Comparative Example 2 of Table 1, as shown in FIG. 26, the sheet 23 was adhered to the entire flat surface 5 of the wafer 1 and the entire chamfered portion 11 in the same manner as in the sheet arrangement step 1002 without forming the stepped portions 20, 20-1, 20-2 or the annular groove 20-3. In Comparative Example 3 of Table 1, as shown in FIG. 27, the annular groove 20-3 was formed, and the sheet 23 was adhered to the entire flat surface 5 of the wafer 1, the inner surface 26 and the bottom surface 27 of the annular groove 20-3 in the same manner as in the sheet arrangement step 1002.

[0079] Product 1 of the present invention in Table 1 successively carried out the step 1001-2 of forming a stepped portion, the step 1002 of disposing a sheet, and the step 1010 of removing the outer peripheral sheet according to Embodiment 2.

[0080] Product 2 of the present invention in Table 1 successively carried out the step 1001 of forming a stepped portion and the step 1002 of disposing a sheet according to the processing method according to Embodiment 1, and formed a stepped portion 20 in which the width 201 (shown in FIG. 5) of the flat surface 21 was 3.0 mm and the depth 202 (shown in FIG. 5) of the side surface 22 was 0.2 mm.

[0081] Product 3 of the present invention in Table 1 successively carried out the step 1001 of forming a stepped portion and the step 1002 of disposing a sheet according to the processing method according to Embodiment 1, and formed a stepped portion 20 in which the width 201 of the flat surface 21 was 0.6 mm and the depth 202 of the side surface 22 was 0.2 mm.

[0082] Product 4 of the present invention in Table 1 successively carried out the step 1001 of forming a stepped portion and the step 1002 of disposing a sheet according to the processing method according to Modification 1 of Embodiment 1, and the combined width 201-1 (shown in FIG. 11) of the first flat surface 21-1 and the second flat surface 21-2 was 0.6 mm, and a stepped portion 20-1 in which the combined depth 202-1 (shown in FIG. 11) of the first side surface 22-1 and the second side surface 22-2 was 0.4 mm was formed.

[0083] According to Table 1, in Comparative Example 1, the sheet 23 peeled off when the cutting depth was 10 μm, in Comparative Example 2, the sheet 23 peeled off when the cutting depth was 20 μm, and in Comparative Example 3, the sheet 23 peeled off when the cutting depth was 30 μm.

[0084] For Comparative Example 1, Comparative Example 2, and Comparative Example 3 as described above, for Invention Product 1, Invention Product 2, Invention Product 3, and Invention Product 4, peeling of the sheet 23 could be suppressed when the cutting depth was 10 μm, 20 μm, 30 μm, 40 μm, and 50 μm, respectively. Therefore, according to Table 1, in the step 1001 of forming the stepped portion, by forming the stepped portions 20, 20-1 and performing the sheet arranging step 1002, it became clear that peeling of the sheet 23 could be suppressed during the sheet flattening step 1003, that is, during the flattening of the sheet 23. Also, in the step 1001-2 of forming the stepped portion, by forming the annular groove 20-3 and sequentially performing the sheet arranging step 1002 and the outer peripheral sheet removing step 1010, it became clear that peeling of the sheet 23 could be suppressed during the sheet flattening step 1003, that is, during the flattening of the sheet 23.

[0085] Note that the present invention is not limited to the above-described embodiments. That is, various modifications can be made and implemented without departing from the gist of the present invention. In the above-described embodiments and the like, the holding step 1004 and the processing step 1005 were performed, but the processing method of the present invention does not necessarily require performing the holding step 1004 and the processing step 1005.

Explanation of Reference Numerals

[0086] 1 Wafer 5 Surface 10 Outer Periphery (Outer Peripheral Edge) 20, 20-1, 20-2 Stepped Portion 20-3 Annular Groove (Stepped Portion) 21 Flat Surface 21-1 First Flat Surface (Flat Surface) 21-2 Second Flat Surface (Flat Surface) 22 Side Surface 22-1 First Side Surface (Side Surface) 22-2 Second Side Surface (Side Surface) 23, 23-1 Sheet 25 Inclined Surface 231 Outer Peripheral Edge 232 Upper Surface 1001, 1001-2 Stepped Portion Forming Step 1002 Sheet Arrangement Step 1003 Sheet Flattening Step 1004 Holding Step 1005 Processing Step 1010 Outer Periphery Sheet Removal Step

Claims

1. A processing method, comprising: a step of forming a stepped portion by removing a part of the wafer in an annular shape along the outer periphery of the surface of the wafer to form a stepped portion on the outer periphery of the wafer; after performing the stepped portion forming step, a step of disposing a sheet covering the stepped portion and the surface of the wafer on the surface of the wafer so that the inside is higher than the outer peripheral edge of the sheet; after performing the sheet disposing step, a step of grinding or facing the upper surface of the sheet except the outer peripheral edge of the sheet to flatten it; and in the stepped portion forming step, removing a part of the wafer in an annular shape by a predetermined depth exceeding the thickness of the sheet from the surface; A processing method characterized by the above.

2. After performing the sheet flattening step, a holding step of holding the wafer with a holding table via the sheet; A processing method according to claim 1, further comprising a processing step of processing the wafer held by the holding table.

3. The processing method according to claim 1 or claim 2, wherein the stepped portion includes a flat surface along the surface and a side surface extending from the flat surface to the surface.

4. The processing method according to claim 1 or claim 2, wherein the stepped portion includes an inclined surface inclined from the surface of the wafer toward the outer peripheral edge.

5. The stepped portion is an annular groove formed on the outer periphery of the surface of the wafer, in the sheet disposing step, the sheet is in close contact with the inner surface and the bottom surface of the annular groove that is the stepped portion, after performing the sheet disposing step and before performing the sheet flattening step, further comprising an outer peripheral sheet removing step of removing at least the sheet on the outer peripheral side of the center in the width direction of the bottom surface of the annular groove and ensuring that the outer peripheral edge of the sheet remains adhered to the bottom surface of the annular groove after removing the outer peripheral side; a processing method according to claim 1 or claim 2.

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