Removal method

Abstract

To shorten the time required for removing an annular concave portion, and prevent re-adhesion between an adhesive tape and a part of the annular concave portion that has once been peeled off.SOLUTION: A wafer unit includes a disk-shaped wafer in which a circular concave portion and an annular convex portion surrounding the circular concave portion, each of the concave portions being formed on a back surface side, are divided at the boundary between the circular concave portion and the annular convex portion, an adhesive tape stuck to the back surface side of the wafer, and an annular frame stuck to an outer peripheral portion of the adhesive tape. A method for removing the annular convex portion from the wafer unit includes a removal claw inserting step of inserting a plurality of removal claws spaced apart from one another along a peripheral direction of the wafer into the boundary between the adhesive tape and the annular convex portion, and an annular convex portion removing step of removing the annular convex portion from the adhesive tape by moving the plurality of removal claws in a predetermined direction in which the annular convex portion separates from the adhesive tape while rotating the plurality of removal claws along the outer periphery of the wafer.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for removing annular convex portions from a disk-shaped wafer in which a circular recess and an annular convex portion surrounding the circular recess are formed on the back surface side and are divided at the boundary between the circular recess and the annular convex portion. [Background technology]

[0002] In a manufacturing process for semiconductor devices, for example, first, a plurality of division lines are set in a grid pattern on the surface of a disk-shaped semiconductor wafer, and devices such as ICs (Integrated Circuits) are formed in each area partitioned by the plurality of division lines.

[0003] The semiconductor wafer is then cut along each of the planned division lines to divide the semiconductor wafer into a plurality of semiconductor device chips. However, in recent years, in order to meet the demand for lighter and smaller semiconductor device chips, the back side of the semiconductor wafer is ground to thin the wafer to a predetermined thickness before cutting the semiconductor wafer.

[0004] However, if the entire back surface side is uniformly ground, it becomes difficult to handle the ground semiconductor wafer, such as by transporting it, and there is a risk that the semiconductor wafer may be damaged during transportation. Therefore, in order to maintain a certain degree of strength of the ground semiconductor wafer, a grinding method has been proposed in which a reinforcing annular protrusion is left on the outer periphery of the back surface side after grinding (see, for example, Patent Document 1).

[0005] Specifically, grinding is performed on a circular area on the back side that corresponds in the thickness direction of the semiconductor wafer to a device area on the front side on which a plurality of devices are formed, but grinding is not performed outside this circular area, thereby forming a circular recess and an annular protrusion surrounding the circular recess on the back side of the semiconductor wafer.

[0006] This makes it easier to transport the semiconductor wafer with the back surface thinned compared to when no annular protrusion is formed. However, before dividing the semiconductor wafer into a plurality of device chips, the annular protrusion needs to be removed. The annular protrusion is separated from the circular recess by cutting, for example, and then removed by a dedicated removal device (see, for example, Patent Document 2).

[0007] To remove the annular convex portion, first, the central portion of an adhesive tape having an outer diameter larger than the diameter of the semiconductor wafer is adhered to the circular concave portion and the annular convex portion located on the back side, and the outer periphery of the adhesive tape is adhered to one surface of a metal annular frame to form a wafer unit.

[0008] The boundary between the circular recess and the annular protrusion is cut to separate the annular protrusion from the semiconductor wafer, and after reducing the adhesive strength of the adhesive tape in the area corresponding to the annular protrusion, the annular protrusion is lifted up by the above-mentioned removal device.

[0009] The removal device described in Patent Document 2 has a cylindrical base and a guide table extending in all four directions from the bottom of the base. The guide table, which is substantially cross-shaped when viewed from above, is provided with a disk-shaped removal claw at each tip.

[0010] When the annular protrusion is lifted by the removal device, first, each removal claw is inserted between the annular protrusion and the adhesive tape, and then the removal claws are rotated along the circumferential direction of the wafer, and then the removal claws are raised to remove the annular protrusion from the adhesive tape. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] JP 2007-173487 A [Patent Document 2] JP 2014-170822 A Summary of the Invention [Problem to be solved by the invention]

[0012] However, since the first operation of rotating and moving the multiple removal claws while they are inserted is followed by the second operation of lifting the multiple removal claws, each operation requires its own time.

[0013] In addition, although the adhesive strength of the adhesive tape has already decreased to a certain extent, when the tape is rotated with the removal claw inserted, there is a problem that part of the annular convex portion that was once peeled off from the adhesive tape by the removal claw may re-adhere to the adhesive tape after the removal claw moves.

[0014] The present invention has been made in consideration of these problems, and aims to shorten the time required to remove the annular convex portion and to prevent the adhesive tape from re-adhering to a part of the annular convex portion that has once been peeled off. [Means for solving the problem]

[0015] According to one aspect of the present invention, there is provided a method for removing annular convex portions from a wafer unit having a disk-shaped wafer in which a circular recess and an annular convex portion surrounding the circular recess are formed on a back surface side of the wafer and are separated at a boundary between the circular recess and the annular convex portion, an adhesive tape affixed to the back surface side of the wafer, and an annular frame affixed to an outer periphery of the adhesive tape, the method comprising: a holding step of suction-holding the back surface side of the wafer via the adhesive tape side with a holding surface of a chuck table having an outer diameter smaller than a diameter of the circular recess; a removal claw insertion step of inserting a plurality of removal claws, the removal claws being disposed apart from one another along a circumferential direction of the wafer, into the boundary between the adhesive tape and the annular convex portion after the holding step; and an annular convexity removal step of removing the annular convex portion from the adhesive tape while rotating the plurality of removal claws along the outer periphery of the wafer, the removal claws being moved in a predetermined direction in which the annular convex portion moves away from the adhesive tape after the removal claw insertion step.

[0016] Preferably, the annular protrusion removal step further includes a removal claw retraction step of moving the multiple removal claws in the predetermined direction while rotating the multiple removal claws along the outer periphery of the wafer, and moving the multiple removal claws toward the center of the back surface of the wafer.

[0017] Also, preferably, the annular protrusion removal step further includes a speed reducing step of monitoring the gauge pressure of the chuck table and, if the magnitude of the gauge pressure becomes smaller than a predetermined value, reducing the speed at which the multiple removal claws are moved in the predetermined direction.

[0018] Also, preferably, the removal method further includes a lowering step of lowering the annular frame below the annular protrusion after the holding step and before the removal claw inserting step.

[0019] Also, preferably, the plurality of removal claws include three removal claws, and the three removal claws are used in the removal claw inserting step and the annular protrusion removing step. Effect of the Invention

[0020] In a removal method according to one aspect of the present invention, in a removal claw insertion step, multiple removal claws are inserted into the boundary between the adhesive tape and the annular convex portion, and then, in an annular convex portion removal step, the multiple removal claws are moved in a predetermined direction in which the annular convex portion moves away from the adhesive tape while rotating along the outer periphery of the wafer.

[0021] In this way, the operation of rotating and moving the multiple removal claws around the wafer and the operation of moving the multiple removal claws in a predetermined direction are performed in combination, thereby reducing the time required to remove the annular convex portion from the adhesive tape compared to when each operation is performed individually.

[0022] In addition, since the annular projection is moved in a predetermined direction away from the adhesive tape as the removal claw rotates, the annular projection does not re-adhere to the adhesive tape. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1(A) is a perspective view of the front side of the wafer, and FIG. 1(B) is a perspective view of the back side of the wafer. [Diagram 2] FIG. 1 is a flow diagram of a removal method. [Diagram 3] FIG. [Figure 4] FIG. 2 illustrates a pull-down step. [Diagram 5] FIG. 13 is a top view showing the removal claw insertion step. [Figure 6] 6 is a partially sectional side view of the annular protrusion removing arm and the like as viewed along the AA section of FIG. 5. [Figure 7] FIG. 13 is a top view showing the annular protrusion removing step. [Figure 8] FIG. 11 is a perspective view showing an annular protrusion removing step. [Figure 9] FIG. 6 is a flow diagram of a removal method according to a second embodiment. [Figure 10] FIG. 13 is a top view showing the removal claw retracting step. [Figure 11] FIG. 11 is a flow diagram of a removal method according to a third embodiment. [Figure 12] 13 is a partial cross-sectional side view of the annular protrusion removal arm, etc., when a speed reduction step is performed. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] An embodiment according to one aspect of the present invention will be described with reference to the accompanying drawings. First, a wafer 11 to be processed will be described. Fig. 1(A) is a perspective view of a front surface 11a side of a disk-shaped wafer 11, and Fig. 1(B) is a perspective view of a back surface 11b side of the wafer 11.

[0025] The wafer 11 in this example is made of a semiconductor material such as silicon. However, the wafer 11 is not limited to silicon, and may be made of a compound semiconductor such as silicon carbide (SiC) or gallium nitride (GaN), or may be made of other materials.

[0026] 1A, a plurality of division lines 13 are set in a lattice pattern on the front surface 11a of the wafer 11. In each of the regions partitioned by the plurality of division lines 13, a device 15 such as an IC (Integrated Circuit) is formed.

[0027] In the radial direction of the wafer 11, an annular peripheral surplus region 19 exists outside the device region 17 in which the multiple devices 15 are formed. The peripheral surplus region 19 is a substantially flat region in which no devices 15 are formed. Note that a notch 21 indicating the crystal orientation is formed on the outer periphery of the wafer 11.

[0028] 1(B), a circular region corresponding to the device region 17 on the back surface 11b of the wafer 11 is thinned by grinding to form a circular recess 23 on the back surface 11b. The thickness of the wafer 11 at the circular recess 23 is, for example, about 50 μm.

[0029] An annular protrusion 25 is formed outside the circular recess 23 so as to surround the periphery of the circular recess 23. The annular protrusion 25 is a region that remains without being ground when the circular recess 23 is formed. The thickness of the wafer 11 at the annular protrusion 25 is, for example, about 700 μm. The annular protrusion 25 has a width of, for example, about 2.1 mm in the radial direction of the wafer 11.

[0030] The annular protrusion 25 functions as a reinforcing part for the wafer 11 having the circular recess 23. By providing the annular protrusion 25, the wafer 11 can be more easily transported without being damaged, compared to a case in which the back surface 11b side is uniformly thinned without providing the annular protrusion 25.

[0031] After forming the circular recess 23 and the annular protrusion 25 on the back surface 11b, a circular adhesive tape 27 (see FIG. 3) is attached to the back surface 11b of the wafer 11. The adhesive tape 27 has a laminated structure including an adhesive layer (glue layer) made of an adhesive resin such as an ultraviolet curing resin, and a sheet-like base layer made of a resin.

[0032] As shown in FIG. 3, the adhesive tape 27 has an outer diameter larger than the diameter of the wafer 11, and the bottom surface of the circular recess 23, the side surface of the circular recess 23 (i.e., the inner side surface of the annular protrusion 25), and the annular protrusion 25 are each adhered to the central portion of the adhesive tape 27.

[0033] Furthermore, one surface of an annular frame 29 made of metal is attached to the outer periphery of the adhesive tape 27. In this manner, as shown in Fig. 3, a wafer unit 31 is formed in which the wafer 11 is supported on the annular frame 29 via the adhesive tape 27.

[0034] Continuing to refer to FIG. 3, after the wafer unit 31 is formed, a cutting device or laser processing device (neither shown) is used to form an annular through groove 33 at the boundary between the circular recess 23 and the annular protrusion 25, completely dividing the circular recess 23 and the annular protrusion 25 in the thickness direction of the wafer 11.

[0035] For example, a cutting blade (not shown) is cut into the peripheral excess area 19 corresponding to the circular recess 23, and a circle cut is performed on the wafer 11, thereby forming an annular through groove 33 approximately concentric with the wafer 11.

[0036] After the annular through groove 33 is formed, a predetermined process is performed to reduce the adhesive strength between the annular protrusion 25 and the adhesive tape 27. For example, when the adhesive layer of the adhesive tape 27 is formed of an ultraviolet curing resin, the adhesive strength is reduced by irradiating the annular region of the adhesive tape 27 corresponding to the annular protrusion 25 with ultraviolet light.

[0037] In this manner, a wafer unit 31 is prepared in which the thin portion corresponding to the circular recess 23 is relatively strongly adhered to the adhesive tape 27, while the thick portion corresponding to the annular protrusion 25 is relatively weakly adhered to the adhesive tape 27.

[0038] Next, a description will be given of a method for removing the annular convex portion 25 from the wafer unit 31. Fig. 2 is a flow diagram of a first embodiment of the method for removing the annular convex portion 25. Each step will be described below according to the flow diagram of Fig. 2.

[0039] First, the back surface 11b side of the wafer 11 is suction-held by the chuck table 4 of the annular protrusion removing device 2 via the adhesive tape 27 (holding step S10). Fig. 3 is a diagram showing the holding step S10. Here, the chuck table 4 will be described.

[0040] The chuck table 4 has a frame 6 made of metal. The frame 6 has a cylindrical shape with a bottom and a diameter sufficiently larger than its height. A plurality of flow paths 6a are formed radially on the bottom surface of the recess of the frame 6.

[0041] Further, a central flow passage 6b is formed in the frame 6 so as to penetrate through the center of the bottom surface of the recess of the frame 6. One end of the central flow passage 6b is connected to the multiple flow passages 6a, and the other end of the central flow passage 6b is connected to a suction source 8 such as a vacuum pump or an ejector.

[0042] A circular porous plate 10 made of porous ceramics is fixed in the recess of the frame 6. When the suction source 8 is operated, negative pressure is generated on the upper surface of the porous plate 10. The upper surface of the frame 6 and the upper surface of the porous plate 10 are flush with each other, forming a substantially flat holding surface 4a.

[0043] The holding surface 4a of the chuck table 4 has an outer diameter 4b that is smaller than the diameter 23a of the circular recess 23. Therefore, when the back surface 11b side of the wafer 11 is suction-held by the holding surface 4a, the upper part of the chuck table 4 is accommodated in the circular recess 23.

[0044] The chuck table 4 is supported by a cylindrical support portion 12. A predetermined flow path 12a that connects the central flow path 6b and the suction source 8 is formed in the support portion 12. A pressure gauge 14 for measuring the negative pressure (gauge pressure) of the porous plate 10 is provided in the flow path 12a.

[0045] While the wafer 11 is held on the holding surface 4a, the negative pressure acting on the porous plate 10 is monitored by a pressure gauge 14. A plurality of clamp units 4c are provided on the outer periphery of the chuck table 4 at approximately equal intervals along the circumferential direction of the frame 6.

[0046] Each clamp unit 4c clamps the annular frame 29 of the wafer unit 31 placed on the chuck table 4. Each clamp unit 4c is configured to be movable downward relative to the chuck table 4 by a driving device (not shown) such as an air actuator.

[0047] In the holding step S10, first, the wafer 11 is placed on the chuck table 4 so that the front surface 11a faces upward and the upper part of the chuck table 4 is accommodated in the circular recess 23. Thereafter, the back surface 11b side corresponding to the circular recess 23 is suction-held by the holding surface 4a via the adhesive tape 27, and further, the annular frame 29 is clamped by each clamp unit 4c.

[0048] After the holding step S10, each clamp unit 4c is pulled downward, thereby pulling the annular frame 29 below the annular protrusion 25 (pulling step S20). Fig. 4 is a diagram showing the pulling step S20.

[0049] In the lowering step S20, by lowering the annular frame 29 below the annular protrusion 25, there is an advantage that the removal claws 38 described below can be easily inserted into the boundary between the adhesive tape 27 and the annular protrusion 25.

[0050] After the pulling down step S20, a plurality of removal claws 38 (see FIG. 5) of the annular protrusion removal arm 20 are inserted into the boundary between the adhesive tape 27 and the annular protrusion 25 (removal claw insertion step S30). FIG 5 is a top view showing the removal claw insertion step S30, and FIG 6 is a partial cross-sectional side view of the annular protrusion removal arm 20 etc. as seen along the AA section in FIG 5.

[0051] First, the configuration of the annular protrusion removal arm 20 will be described. The annular protrusion removal arm 20 has cylindrical arms 22 arranged approximately parallel to the height direction. The arms 22 can be moved in the height direction and horizontal direction by, for example, a ball screw type height direction movement mechanism 42 (see FIG. 12) and a horizontal direction movement mechanism (not shown), respectively.

[0052] A center portion of a disk-shaped base plate 24 is rotatably connected to a lower end portion of the arm portion 22. A rotation drive source (not shown) such as a motor is built into the arm portion 22. The rotation drive source rotates the base plate 24 in a predetermined direction.

[0053] A plurality of removal claw units 26 are provided on the upper part of the base plate 24. Each removal claw unit 26 has a linear motion mechanism 28. The linear motion mechanism 28 includes a ball screw mechanism (not shown) that moves the advancing and retracting rod 30 forward and backward.

[0054] The advancing / retracting rod 30 includes a nut portion (not shown) slidably connected to a guide portion of the linear motion mechanism 28. The nut portion is rotatably connected to a ball screw (not shown) of the linear motion mechanism 28. By advancing and retracting the nut portion by the linear motion mechanism 28, the advancing / retracting rod 30 advances and retreats along its longitudinal direction.

[0055] In this embodiment, three advancing / retracting rods 30 are provided. The orientations and positions of the three advancing / retracting rods 30 are determined so that a triangle 30a (shown by a dashed line in FIG. 5) defined by the extension lines of each advancing / retracting rod 30 is a substantially equilateral triangle.

[0056] One longitudinal end (base end) of a rectangular parallelepiped moving block 32 is fixed to the tip of the advancing / retracting rod 30. The advancing / retracting rod 30 is fixed to the moving block 32 so that the longitudinal direction of the advancing / retracting rod 30 and the longitudinal direction of the moving block 32 are perpendicular to each other in a horizontal plane.

[0057] A cylindrical rotating shaft rod 34 is fixed to the other end (tip) of the moving block 32 so as to extend vertically downward. A removal claw 38 is rotatably connected to the lower end of the rotating shaft rod 34 via a bearing 36.

[0058] The removal claws 38 each have a disk-shaped upper claw 38a and a disk-shaped lower claw 38b, and a cylindrical connecting portion 38c that connects the centers of the upper claw 38a and the lower claw 38b. The upper claw 38a and the lower claw 38b are fixed via the connecting portion 38c.

[0059] In this embodiment, three removal claws 38 are arranged at approximately equal intervals apart from each other along the circumferential direction of the base plate 24, and three lower claws 38b are used to peel the annular convex portion 25 from the adhesive tape 27 and support the peeled annular convex portion 25 at three points.

[0060] In the removal claw insertion step S30, first, the base plate 24 is placed above the wafer 11. Then, the base plate 24 is lowered with the removal claws 38 protruding outward so that the removal claws 38 are positioned outside the wafer 11.

[0061] The arm 22 is lowered until the lower claw 38b of the removal claw 38 is positioned at the boundary between the adhesive tape 27 and the annular protrusion 25, and then the lowering is stopped. Next, as shown in Figures 5 and 6, the removal claw 38 is moved toward the inside of the base plate 24. At this time, the lower claw 38b is moved inward from the outer periphery of the wafer 11 by, for example, 1.6 mm.

[0062] In the removal claw insertion step S30, the three removal claws 38 are inserted into the boundary between the adhesive tape 27 and the annular convex portion 25 with the three removal claws 38 positioned approximately evenly spaced apart from one another along the circumferential direction of the wafer 11.

[0063] After the removal claw insertion step S30, the base plate 24 is rotated around the arm portion 22 as a rotation axis, causing the three removal claws 38 to rotate along the outer periphery of the wafer 11, while the arm portion 22 and the base plate 24 are raised, moving the multiple removal claws 38 upward (in a specified direction) (annular protrusion removal step S40).

[0064] The rotation speed of the removal claws 38 is, for example, 10° / s, and each removal claw 38 is rotated 140° over 14 seconds. The lifting speed of the removal claws 38 is, for example, 0.14 mm / s.

[0065] Fig. 7 is a top view showing the annular convex portion removing step S40, and Fig. 8 is a perspective view showing the annular convex portion removing step S40. The annular convex portion 25 is separated from the adhesive tape 27, whereby the annular convex portion 25 is removed from the adhesive tape 27 (wafer unit 31).

[0066] In this embodiment, the operation of rotating the multiple removal claws 38 around the wafer 11 and the operation of moving the multiple removal claws 38 upward are performed in combination, so that the time required to remove the annular convex portion 25 from the adhesive tape 27 can be shortened compared to when each operation is performed individually.

[0067] In addition, as the removal claw 38 rotates, the annular protrusion 25 is moved in a predetermined direction away from the adhesive tape 27, which has the advantage that the annular protrusion 25 will not re-adhere to the adhesive tape 27.

[0068] Furthermore, the removal claw 38 has an upper claw 38a in addition to a lower claw 38b. The annular protrusion 25 that has been peeled off from the adhesive tape 27 may rise vigorously, but by providing the upper claw 38a, the rise of the annular protrusion 25 can be limited to the range between the upper claw 38a and the lower claw 38b. This makes it possible to prevent the annular protrusion 25 from falling.

[0069] Next, a second embodiment will be described. The annular protrusion removing step S40 of the second embodiment further includes a removal claw retracting step S42 in which the removal claws 38 are moved upward while rotating along the outer periphery of the wafer 11, and the removal claws 38 are moved toward the center of the back surface 11b.

[0070] Fig. 9 is a flow diagram of the removal method according to the second embodiment, and Fig. 10 is a top view showing removal claw retracting step S42 in annular protrusion removing step S40. In removal claw retracting step S42, for example, each removal claw 38 is moved 2 mm toward the center of back surface 11b at a speed of 0.14 mm / s.

[0071] In this way, in the annular protrusion removal step S40, by retracting the multiple removal claws 38 in addition to rotating and raising them, the annular protrusion 25 can be more reliably removed from the adhesive tape 27 than in the absence of retraction.

[0072] Next, a third embodiment will be described. In the annular protrusion removal step S40 of the third embodiment, the control unit 40 of the annular protrusion removal device 2 monitors the gauge pressure of the flow path 12a connected to the porous plate 10 using the pressure gauge 14.

[0073] The control unit 40 monitors the gauge pressure of the chuck table 4 in the annular protrusion removal step S40, and when the magnitude (i.e., absolute value) of the gauge pressure becomes smaller than a predetermined value, it controls the height direction movement mechanism 42 to reduce the rising speed (the speed at which the removal claws 38 are moved in a predetermined direction) (speed reduction step S44).

[0074] The gauge pressure is a pressure based on the air pressure of the indoor environment in which the annular protrusion removal arm 20 is located (e.g., atmospheric pressure), and the gauge pressure of the chuck table 4 is lower than the air pressure of the indoor environment due to the negative pressure from the suction source 8.

[0075] Note that decreasing the ascending speed in the speed decreasing step S44 means decreasing the ascending speed to a speed lower than the current speed, and also includes setting the ascending speed to zero (ie, stopping the ascending speed).

[0076] The control unit 40 is composed of a computer including, for example, a processor (processing device) represented by a CPU (Central Processing Unit), a main memory device such as a DRAM (Dynamic Random Access Memory), an SRAM (Static Random Access Memory), or a ROM (Read Only Memory), and an auxiliary memory device such as a flash memory, a hard disk drive, or a solid state drive.

[0077] The auxiliary storage device stores software including a predetermined program. The functions of the control unit 40 are realized by operating the processing device and the like in accordance with this software.

[0078] FIG. 11 is a flow diagram of the removing method according to the third embodiment, and FIG. 12 is a partial cross-sectional side view of the annular protrusion removing arm 20 etc. when performing the removing claw retracting step S42 and the speed reducing step S44.

[0079] For example, when the wafer 11 is held by suction on the holding surface 4a, the magnitude of the gauge pressure measured by the pressure gauge 14 is −80 kPa. However, for example, when the rising speed is greater than the rotation speed of the multiple removal claws 38, the annular convex portion 25 and the adhesive tape 27 are lifted up, and a gap may be formed between the holding surface 4a and the adhesive tape 27.

[0080] In this case, the air flows in through the gap, and the pressure in flow path 12a becomes higher than before the gap was formed (i.e., the magnitude of the gauge pressure becomes smaller). For example, the pressure in flow path 12a increases to -50 kPa. In other words, the magnitude of the gauge pressure measured by pressure gauge 14 becomes smaller.

[0081] When the magnitude of the gauge pressure becomes small, the suction holding of the wafer 11 becomes unstable. Therefore, the lifting speed of the multiple removal claws 38 is slowed down or the lifting is temporarily stopped, so that the rotation and retraction of the multiple removal claws 38 is given priority.

[0082] In this way, by performing the speed reduction step S44 according to the magnitude of the gauge pressure, if the adhesive force between the adhesive tape 27 and the annular convex portion 25 is still greater than the suction force between the adhesive tape 27 and the holding surface 4a and the annular convex portion 25 and the adhesive tape 27 are lifted up, the adhesive tape 27 can be preferentially peeled off from the annular convex portion 25 by the removal claw 38.

[0083] Therefore, compared to the case where the magnitude of the gauge pressure is monitored and the speed decreasing step S44 is not performed, the annular convex portion 25 can be more reliably removed from the adhesive tape 27. When the ascending speed is once set to zero, the ascending speed is increased from zero after the removal claw 38 has been rotated and retracted for a predetermined time.

[0084] Incidentally, in the third embodiment, the case where removal claw retracting step S42 and speed reducing step S44 are performed has been described, but the speed reducing step S44 may be performed without performing removal claw retracting step S42.

[0085] In addition, the structures, methods, and the like according to the above-described embodiments can be modified as appropriate without departing from the scope of the object of the present invention. [Explanation of symbols]

[0086] 2: Annular protrusion removal device 4: chuck table, 4a: holding surface, 4b: outer diameter, 4c: clamp unit 6: frame, 6a: flow path, 6b: central flow path, 8: suction source 10: porous plate, 12: support, 12a: flow path, 14: pressure gauge 11: wafer, 11a: front surface, 11b: back surface, 13: planned division line 15: device, 17: device area, 19: peripheral excess area, 21: notch 23: circular recess, 23a: diameter, 25: annular protrusion, 27: adhesive tape, 29: annular frame 31: wafer unit, 33: annular through groove 20: Annular protrusion removal arm, 22: Arm portion, 24: Base plate, 26: Removal claw unit 28: Linear motion mechanism, 30: Retractable rod, 30a: Triangle 32: moving block, 34: rod for rotating shaft 36: bearing, 38: removal claw, 38a: upper claw, 38b: lower claw, 38c: connection part 40: control unit, 42: height direction movement mechanism

Claims

1. A method for removing an annular convex portion from a wafer unit comprising: a disk-shaped wafer in which a circular concave portion and an annular convex portion surrounding the periphery of the circular concave portion are formed on a rear surface side of the wafer and are separated at a boundary between the circular concave portion and the annular convex portion; an adhesive tape attached to the rear surface side of the wafer; and an annular frame attached to an outer periphery of the adhesive tape, the method comprising the steps of: a holding step of suction-holding the back side of the wafer via the adhesive tape on a holding surface of a chuck table having an outer diameter smaller than a diameter of the circular recess; a removal claw insertion step of inserting a plurality of removal claws, the removal claws being spaced apart from one another along a circumferential direction of the wafer, into a boundary between the adhesive tape and the annular convex portion after the holding step; an annular convexity removing step of removing the annular convexity from the adhesive tape by moving the plurality of removal claws in a predetermined direction in which the annular convexity is separated from the adhesive tape while rotating the plurality of removal claws along the outer periphery of the wafer after the removal claw insertion step; A removal method comprising:

2. 2. The method of claim 1, wherein the annular protrusion removing step further includes a removal claw retracting step of moving the multiple removal claws in the predetermined direction while rotating the multiple removal claws along the outer periphery of the wafer, and moving the multiple removal claws toward the center of the back surface of the wafer.

3. 3. The method according to claim 1, wherein the annular protrusion removing step further includes a speed reducing step of monitoring a gauge pressure of the chuck table and, when the magnitude of the gauge pressure becomes smaller than a predetermined value, reducing the speed at which the multiple removal jaws are moved in the predetermined direction.

4. 4. The removal method according to claim 1, further comprising a lowering step of lowering the annular frame below the annular protrusion after the holding step and before the removal claw insertion step.

5. The plurality of removal claws includes three removal claws; 5. The method according to claim 1, wherein the three removal claws are used in the removal claw insertion step and the annular protrusion removal step.

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