Polishing method and polishing tool

Abstract

To suppress a recess from being formed in the vicinity of a center of a surface to be polished.SOLUTION: In a polishing method, a polishing device which is provided with a chuck table that can rotate while holding a wafer and a polishing unit having a spindle mounted with a polishing tool is used to polish the wafer. The polishing tool has a discoid base, and an annular polishing layer fixed to one surface of the base and including an opening part positioned at a central part in a diameter direction of the base and having a predetermined diameter, where a maximum width of an effective polishing region of the polishing layer in a radial direction of the base is smaller than a radius of the wafer and the radius of the wafer is smaller than the diameter of the opening part. The polishing method includes a holding step of holding the wafer with a holding surface, and a polishing step of polishing the wafer, while positioning the wafer and the polishing tool so that a portion of an outer peripheral edge of the wafer protrudes from an outer periphery of the polishing layer and a center of the wafer is positioned at the opening part of the polishing layer.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a polishing method for polishing a wafer and a polishing tool used when polishing a wafer.

Background Art

[0002] Electronic devices such as mobile phones and personal computers are equipped with semiconductor device chips. A semiconductor device chip is manufactured, for example, by processing a semiconductor wafer in which a plurality of division planned lines are set in a grid pattern on the surface and devices such as ICs (Integrated Circuits) and LSIs (Large Scale Integration) are formed in each region partitioned by the plurality of division planned lines.

[0003] Specifically, after grinding and thinning the back side of the semiconductor wafer, the semiconductor wafer is cut along each division planned line to manufacture semiconductor device chips. A grinding device is used for grinding the semiconductor wafer. For example, by sequentially performing rough grinding and finish grinding on the back side of the semiconductor wafer, the semiconductor wafer is thinned to a predetermined thickness (see, for example, Patent Document 1).

[0004] However, grinding marks (i.e., saw marks) are formed on the ground surface by grinding. When the semiconductor wafer is divided into semiconductor device chips with grinding marks remaining on the ground surface, the flexural strength of the semiconductor device chips is reduced compared to the case without grinding marks.

[0005] Therefore, after grinding, CMP (Chemical Mechanical Polishing) for polishing the back side of the semiconductor wafer to remove saw marks is performed (see, for example, Patent Document 2). The polishing device used in CMP has a disk-shaped chuck table.

[0006] The chuck table has a holding surface for sucking and holding a semiconductor wafer. Above the chuck table, a polishing unit having a columnar spindle is arranged. The spindle is arranged substantially parallel to the vertical direction.

[0007] At the lower end of the spindle, for example, a disk-shaped polishing wheel is attached via a wheel mount (see Patent Document 3). The polishing wheel has a wheel base in which a hole penetrating from the central portion of the upper surface to the central portion of the lower surface is formed.

[0008] On one surface of the wheel base, a plurality of segment polishing pads are annularly arranged around this hole. Each segment polishing pad has a polishing region with a width that is smaller than the diameter of the wafer held by the chuck table and larger than the radius of this wafer in the radial direction of the wheel base.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0010] However, when the wafer is polished using this polishing wheel, the vicinity of the center of the polished surface of the wafer may be excessively polished, resulting in a dent in the vicinity of the center of the wafer.

[0011] The present invention has been made in view of such problems, and an object thereof is to suppress the occurrence of a dent in the vicinity of the center of the polished surface of the wafer.

Means for Solving the Problems

[0012] According to one aspect of the present invention, there is provided a polishing method for polishing a wafer using a polishing apparatus including a chuck table rotatable while holding the wafer and a polishing unit having a spindle to which a polishing tool for polishing the wafer held on the holding surface of the chuck table is attached. The polishing tool has a disk-shaped base and an annular polishing layer fixed to one surface of the base and including an opening located at the central portion in the diameter direction of the base and having a predetermined diameter. The maximum width of the effective polishing region of the polishing layer in the radial direction of the base is smaller than the radius of the wafer, and the radius of the wafer is smaller than the diameter of the opening. The polishing method includes a holding step of holding the wafer on the holding surface, and a polishing step of polishing the wafer while rotating the polishing tool around the spindle with a part of the outer peripheral edge of the wafer protruding from the outer periphery of the polishing layer and the center of the wafer positioned in the opening of the polishing layer. The maximum width of the effective polishing area is larger than the radius of the opening of the polishing layer and smaller than the diameter of the opening of the polishing layer A polishing method is provided.

[0013] Preferably, in the polishing step, the polishing tool and the wafer are relatively moved along the diameter direction of the polishing tool passing through the center of one surface of the wafer.

[0014] According to another aspect of the present invention, there is provided a polishing tool used when polishing a wafer. The polishing tool includes a disk-shaped base and an annular polishing layer fixed to one surface of the base and including an opening located at the central portion in the diameter direction of the base and having a predetermined diameter. The maximum width of the effective polishing region of the polishing layer in the radial direction of the base is Larger than the radius of the opening and smaller than the diameter of the opening.

Effect of the Invention

[0015] In the polishing method according to one aspect of the present invention, a polishing tool is used which has a disk-shaped base and an annular polishing layer fixed to one surface of the base and including an opening located at the central portion in the diameter direction of the base and having a predetermined diameter, wherein the maximum width of the effective polishing region of the polishing layer in the radial direction of the base is smaller than the radius of the wafer, and the radius of the wafer is smaller than the diameter of the opening.

[0016] In the polishing step, the wafer is polished in a state where the wafer and the polishing tool are positioned such that a part of the outer peripheral edge of the wafer protrudes from the outer periphery of the polishing layer and the center of the wafer is positioned in the opening of the polishing layer. Therefore, generation of dents in the vicinity of the center of the surface to be polished can be suppressed.

[0017] The polishing tool according to another aspect of the present invention includes a disk-shaped base and an annular polishing layer fixed to one surface of the base and including an opening located at the central portion in the diameter direction of the base and having a predetermined diameter. In the polishing tool, the maximum width of the effective polishing region of the polishing layer in the radial direction of the base is smaller than the diameter of the opening. Therefore, when polishing a wafer having a radius smaller than the diameter of the opening, generation of dents in the vicinity of the center of the surface to be polished can be suppressed.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 6

Figure 7

Figure 8

DETAILED DESCRIPTION OF THE INVENTION

[0019] An embodiment according to an aspect of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a perspective view of the polishing apparatus 2. The X-axis direction, Y-axis direction, and Z-axis direction (vertical direction, polishing feed direction) shown in FIG. 1 are orthogonal to each other.

[0020] The polishing apparatus 2 has a base 4 that supports components. An opening 4a having a long portion in the Y-axis direction is formed in the upper part of the base 4. A disk-shaped chuck table 6 is disposed in the opening 4a.

[0021] The chuck table 6 has a metal frame and a porous plate formed of porous ceramics. The upper surface 8a of the frame 1 and the upper surface 8a of the porous plate 2 are flush with each other and constitute a substantially flat holding surface 6a.

[0022] A predetermined flow path (not shown) is formed in the frame, and a suction source (not shown) such as an ejector is connected to this flow path. The negative pressure generated by the suction source is transmitted to the upper surface 8a of the porous plate through a predetermined flow path. 2 is transmitted.

[0023] On the holding surface 6a, the surface 11a side of the wafer 11 (see FIG. 4) having substantially the same diameter as the upper surface 8a of the porous plate 2 is sucked and held. The diameter of the wafer 11 in the present embodiment is equal to or larger than the diameter of the upper surface 8a of the porous plate 2 and less than the outer diameter of the upper surface 8a of the frame 1 is less than.

[0024] The wafer 11 is a disk-shaped semiconductor wafer made of silicon or the like, and a plurality of planned division lines (not shown) are set in a lattice pattern on the surface 11a side. Devices (not shown) such as ICs and LSIs are formed in each region partitioned by each planned division line.

[0025] During polishing, since the surface 11a side faces the holding surface 6a and the back surface 11b side is exposed upward, in order to reduce damage to the device, a resin protection tape 13 having substantially the same diameter as the wafer 11 is attached to the surface 11a side to form a wafer unit 15 (see FIG. 4).

[0026] A rotary drive source (not shown) such as a motor is provided below the chuck table 6, and the output shaft of the rotary drive source is connected to the lower surface side of the chuck table 6. The chuck table 6 is rotatable around this output shaft.

[0027] The rotary drive source is supported by a Y-axis moving plate (not shown). The Y-axis moving plate is slidably attached to a pair of guide rails (not shown) arranged substantially parallel to the Y-axis direction. A nut portion (not shown) is provided on the lower surface side of the Y-axis moving plate.

[0028] A ball screw (not shown) arranged substantially parallel to the Y-axis direction is rotatably connected to the nut portion. A drive source (not shown) such as a pulse motor is connected to one end of the ball screw.

[0029] The Y-axis moving plate, the pair of guide rails, the ball screw, the drive source, etc. constitute a Y-axis direction moving mechanism for moving the chuck table 6 and the rotary drive source in the Y-axis direction. As shown in FIG. 1, a rectangular table base 10 is provided between the chuck table 6 and the rotary drive source.

[0030] On both sides of the table base 10 in the Y-axis direction, bellows-shaped telescopic covers 12 are provided. The table base 10 moves between the loading / unloading area A on the front side (one side in the Y-axis direction) and the polishing area B on the rear side (the other side in the Y-axis direction) together with the chuck table 6.

[0031] Behind the polishing device 2, a prismatic column part 14 is provided. On the front side surface of the column part 14, a pair of guide rails 16 arranged along the Z-axis direction are fixed. A Z-axis moving plate 18 is slidably attached to the pair of guide rails 16.

[0032] On the rear side surface of the Z-axis moving plate 18, a nut part (not shown) is provided, and a ball screw 20 arranged substantially parallel to the Z-axis direction is rotatably connected to the nut part. A drive source 22 such as a pulse motor is connected to the upper end of the ball screw 20.

[0033] The pair of guide rails 16, the Z-axis moving plate 18, the ball screw 20, the drive source 22, etc. constitute a Z-axis direction moving mechanism 24. On the front side surface of the Z-axis moving plate 18, a support part 26 for fixing the polishing unit 28 is provided.

[0034] The polishing unit 28 has a cylindrical spindle housing 30 whose height direction is arranged substantially parallel to the Z-axis direction. A part of a cylindrical spindle 32 is rotatably accommodated in the spindle housing 30.

[0035] A motor 34 is provided at the upper end of the spindle 32. The lower end of the spindle 32 protrudes below the spindle housing 30, and the upper surface side of a disk-shaped mount 36 is fixed to the lower end of the spindle 32.

[0036] A disk-shaped polishing tool 40 is attached to the lower surface side of the mount 36 using a fixture 38 such as a screw. Here, referring to FIG. 4, the polishing tool 40 will be described. The polishing tool 40 has a disk-shaped base 42. The upper surface 42a of the base 42 is fixed to the lower surface of the mount 36.

[0037] A plurality of segment polishing pads 44 are fixed to the lower surface (one surface) 42b of the base 42. The segment polishing pad 44 has, for example, a polishing cloth such as a non-woven fabric, abrasive grains provided in the polishing cloth, and a binder such as a varnish for fixing the abrasive grains in the polishing cloth.

[0038] The abrasive grains are formed of diamond, cerium oxide, silicon oxide, etc., and have a size of about 0.01 μm to 10.0 μm, for example. Note that the segment polishing pad 44 may have a foamed plastic such as foamed urethane and abrasive grains fixed in the foamed plastic.

[0039] The plurality of segment polishing pads 44 are annularly arranged in the circumferential direction 42e (see FIG. 2) of the base 42 and constitute a polishing layer 46. A circular opening 46a is formed in the lowermost surface of the polishing layer 46. The opening 46a has a predetermined diameter and is arranged concentrically with the base 42 at the central portion in the diameter direction of the base 42.

[0040] Immediately above the opening 46a, a cylindrical opening 42c formed in the central portion in the diameter direction of the base 42, a cylindrical opening 36a formed in the central portion in the diameter direction of the mount 36, and a cylindrical opening 32a formed in the central portion in the diameter direction of the spindle 32 are concentrically arranged.

[0041] The openings 32a, 36a, and 42c function as supply paths through which an alkaline slurry is supplied when wet polishing is performed. Further, the openings 32a, etc. function as wiring ducts in which a temperature sensor and lead wires for measuring the temperature of the wafer 11 are arranged when dry polishing is performed.

[0042] Here, referring to FIG. 2, the configuration of the segment polishing pad 44 will be described. FIG. 2 is a bottom view of the polishing tool 40. In the first embodiment, five segment polishing pads 44 are arranged in a substantially rotationally symmetric manner around the center 42d of the bottom surface 42b of the base 42. Each segment polishing pad 44 has a shape similar to a cherry blossom petal or a teardrop.

[0043] The width of the segment polishing pad 44 in the circumferential direction 42e of the bottom surface 42b expands from the center 42d to a predetermined position toward the outside in the radial direction 42f of the bottom surface 42b, and contracts from the predetermined position to the outer peripheral end.

[0044] On a circle concentric with the center 42d and passing through the first position 42p in the radial direction 42f (see double-headed arrow 42g), one segment polishing pad 44 is in contact with two adjacent segment polishing pads 44 in the circumferential direction 42e. 1

[0045] In each segment polishing pad 44, an annular thin portion 44a is formed inside the second position 42p located more inward (i.e., on the center 42d side) than the first position 42p in the radial direction 42f. In FIG. 2, for convenience, the thin portion 44a is hatched. 1 2

[0046] A circle concentric with the center 42d and passing through the second position 42p corresponds to the outer shape of the opening 46a formed in the polishing layer 46. The thin portion 44a gradually becomes thinner from the second position 42p toward the center 42d. Note that the inner end of the thin portion 44a is located outside the opening 42c of the base 42. 2 2

[0047] The thin portion 44a does not contact the wafer 11 when polishing the wafer 11 with the polishing tool 40. Therefore, the region of the segment polishing pad 44 outside the thin portion 44a becomes the effective polishing region 44b that contributes to the polishing of the wafer 11.

[0048] ​​​​​The effective polishing area 44b of the present embodiment has a feature that the maximum width 44c in the radial direction 42f is smaller than the diameter 46a of the opening 46a of the polishing layer 46 (i.e., the maximum width 44c < the diameter 46a 1 ). 1 )

[0049] Here, returning to FIG. 1, other components of the polishing apparatus 2 will be described. The polishing apparatus 2 includes a control unit 48 that controls operations of a polishing unit 28, a Y-axis direction moving mechanism, a rotation drive source, and the like.

[0050] The control unit 48 is configured by a computer including, for example, a processor (processing device) represented by a CPU (Central Processing Unit), a main storage device such as a DRAM (Dynamic Random Access Memory), and an auxiliary storage device such as a flash memory.

[0051] The auxiliary storage device stores software including a predetermined program. By operating the processing device and the like according to this software, the functions of the control unit 48 are realized.

[0052] Next, referring to FIGS. 3 to 6, a polishing method for polishing the wafer 11 using the polishing apparatus 2 according to the first embodiment will be described. FIG. 3 is a flowchart of the polishing method using the polishing apparatus 2. Note that the diameter of the wafer 11 polished in the present embodiment is 300 mm (12 inches).

[0053] First, as shown in FIG. 4, the surface 11a side of the wafer unit 15 is sucked and held by the holding surface 6a via the protective tape 13 (holding step S10). After the holding step S10, a polishing step S20 for polishing the back surface (one surface) 11b side exposed upward is performed.

[0054] FIG. 4 is a diagram showing a state in which the wafer 11 is polished. In the polishing step S20, first, the chuck table 6 is rotated in a predetermined direction at a first rotational speed (for example, 100 rpm), and the spindle 32 is rotated in a predetermined direction at a second rotational speed (for example, 1600 rpm).

[0055] While rotating both the chuck table 6 and the spindle 32, and further applying a predetermined load (for example, 300 N) to the wafer 11 by the Z-axis direction moving mechanism 24, the back surface 11b side is polished for a predetermined time (for example, 100 seconds).

[0056] In particular, in the first embodiment, while rotating the polishing tool 40, the back surface 11b side is polished in a state where the wafer 11 and the polishing tool 40 are positioned such that the center 11c of the back surface 11b of the wafer 11 is located in the opening 46a.

[0057] FIG. 5(A) is a schematic bottom view showing the positional relationship between the polishing tool 40 and the wafer 11 in the first embodiment. In FIG. 5(A), the polishing layer 46 is shown simplified in an annular region. However, the diameter 46a of the opening 46a of the polishing layer 46 1 and the maximum width 44c of the effective polishing region 44b correspond to FIG. 2 (that is, the maximum width 44c < diameter 46a 1 ).

[0058] In the first embodiment, since the maximum width 44c is 125 mm and the radius of the wafer 11 is 150 mm, the maximum width 44c is smaller than the radius of the wafer 11. Further, since the diameter 46a 1 is 200 mm, the radius of the wafer 11 is smaller than the diameter 46a 1 (that is, the maximum width 44c < the radius of the wafer 11 < the diameter 46a 1 ). The outer diameter of each of the base 42 and the polishing layer 46 is 450 mm.

[0059] FIG. 5(B) is a schematic cross-sectional view of the wafer 11 and the polishing layer 46 showing the wafer 11 polished in a state of being disposed at the front position. The wafer 11 shown in FIG. 5(B) corresponds to the position of the wafer 11 indicated by the solid line in FIG. 5(A).

[0060] In this embodiment, polishing is performed such that the center 11c of the back surface 11b is exposed to the opening 46a. When the wafer 11 is in the forward position, the central axis of rotation of the wafer 11 is located slightly inside the end of the opening 46a.

[0061] Also, when the wafer 11 is in the forward position, the center 11c of the back surface 11b is exposed to the opening 46a, and the front end portion (a part of the outer peripheral edge) 11d of the wafer 11 is not covered by the polishing layer 46 and protrudes from the outer periphery of the polishing layer 46.

[0062] FIG. 5(C) is a schematic cross-sectional view of the wafer 11 and the polishing layer 46 showing the wafer 11 polished in a state of being disposed at the rear position. The wafer 11 shown in FIG. 5(C) corresponds to the position of the wafer 11 indicated by the broken line in FIG. 5(A).

[0063] Even when the wafer 11 is in the rear position, the center 11c of the back surface 11b is exposed to the opening 46a, and the front end portion 11d of the wafer 11 is not covered by the polishing layer 46 and slightly protrudes from the outer periphery of the polishing layer 46.

[0064] In the polishing step S20, the wafer 11 and the polishing tool 40 are relatively moved along the diameter direction 42h of the base 42 passing through the center 11c of the back surface 11b so that the wafer 11 reciprocates between the forward position (FIG. 5(B)) and the rear position (FIG. 5(C)).

[0065] For example, the Y-axis direction moving mechanism is operated to move the chuck table 6 along the Y-axis direction at a speed of 0.1 mm / s to 0.2 mm / s while polishing the wafer 11. In this example where the maximum width 44c is 125 mm, the radius of the wafer 11 is 150 mm, and the diameter 46a 1 is 200 mm, it is reciprocated with an amplitude of less than 25 mm.

[0066] Therefore, with the center 11c always positioned at the opening 46a, the back surface 11b side can be polished. Accordingly, excessive polishing in the vicinity of the center 11c of the wafer 11 can be prevented, and the occurrence of dents in the vicinity of the center 11c can be suppressed.

[0067] Incidentally, when the front end 11d on the front side of the wafer 11 does not protrude from the outer periphery of the polishing layer 46 (i.e., the outer periphery of the polishing layer 46 protrudes from the front end 11d on the front side of the wafer 11), the polishing layer 46 protrudes slightly below the back surface 11b, and a step is formed in the polishing layer 46. As a result, there are problems such as an abnormal load on the polishing layer 46 and an acceleration of the deterioration of the polishing layer 46.

[0068] On the other hand, in the present embodiment, even when the wafer 11 is disposed at a rear position (see FIG. 5(C)), since the front end 11d on the front side of the wafer 11 always protrudes from the outer periphery of the polishing layer 46, a step is not formed in the polishing layer 46. Therefore, an abnormal load and an acceleration of deterioration can be prevented.

[0069] FIG. 6 is a graph showing the experimental results of measuring the removal amount of the wafer 11 when the wafer 11 is polished by the polishing method according to the first embodiment. The horizontal axis represents the measurement position (mm) of the wafer 11 with the center 11c as the origin, and the vertical axis represents the removal amount (μm).

[0070] In this experiment, using the polishing apparatus 2 to which the polishing tool 40 was attached, the back surface 11b sides of three wafers 11 each having a diameter of 300 mm (12 inches) were sequentially polished. However, no devices were formed on the front surface 11a side of each wafer 11.

[0071] Graph C 1 、Graph C 2 、Graph C 3 are the polishing results of the first, second, and third wafers 11, respectively. The processing conditions were as follows. Rotation speed of the chuck table: 300 rpm Rotation speed of the spindle: 1500 rpm Polishing load: 300 N Reciprocating movement in the Y-axis direction: 0.1 mm / s to 0.2 mm / s Polishing time: 150 s Supply of slurry: None (dry polishing)

[0072] Graph C 1 from C 3 In each of them, the difference between the maximum value and the minimum value of the polished amount was calculated, and further, the average of each difference was calculated, and it was 0.364 μm. That is, a relatively high flatness was achieved. Further, as shown in FIG. 6, no dent was formed in the vicinity of the center 11c (that is, in the vicinity of the origin).

[0073] Next, a comparative example will be described. FIG. 7(A) is a schematic bottom view showing the positional relationship between the polishing tool 60 and the wafer 11 in the comparative example. The polishing tool 60 corresponds to the polishing tool 40 according to the first embodiment and has a polishing layer 66 with the same outer diameter (450 mm) as the polishing layer 46.

[0074] However, the diameter 66a of the opening 66a of the polishing layer 66 1 is smaller than the above-mentioned diameter 46a 1 The diameter 66a in the comparative example 1 is 150 mm, and the maximum width 64c of the effective polishing region is also 150 mm.

[0075] In FIG. 7(A), the wafer 11 shown by the solid line shows the case where the front end 11d on the front side of the wafer 11 is overlapped with the front end of the polishing layer 66. At this time, the center 11c of the back surface 11b is located at the end of the opening 66a.

[0076] On the other hand, the two wafers 11 shown by the broken line in FIG. 7(A) show the wafer 11 at the front position (FIG. 7(B)) and the wafer 11 at the rear position (FIG. 7(C)).

[0077] FIG. 7(B) is a schematic cross-sectional view of the wafer 11 and the polishing layer 66 showing the wafer 11 polished in the state of being arranged at the front position. FIG. 7(C) is a schematic cross-sectional view of the wafer 11 and the polishing layer 66 showing the wafer 11 polished in the state of being arranged at the rear position.

[0078] When polishing a wafer 11 with a diameter of 300 mm (12 inches) using this polishing tool 60, if polishing is performed while relatively moving the polishing tool 60 and the wafer 11 in the Y-axis direction, as shown in FIG. 7(B), the contact time between the effective polishing region and the vicinity of the center 11c becomes long, and a dent occurs in the vicinity of the center 11c (see the region surrounded by the broken line in FIG. 7(B)).

[0079] Furthermore, as shown in FIG. 7(C), since the outer periphery of the polishing layer 66 protrudes from the front end portion 11d of the wafer 11, a step is formed in the polishing layer 66. Therefore, an abnormal load is applied to the polishing layer 66, and the deterioration of the polishing layer 66 is promoted (see the region surrounded by the broken line in FIG. 7(C)).

[0080] On the other hand, as described above, in the first embodiment, with the wafer 11 and the polishing tool 40 positioned such that the center 11c of the back surface 11b of the wafer 11 is located in the opening 46a, the back surface 11b side is polished. Therefore, excessive polishing in the vicinity of the center 11c of the wafer 11 can be prevented, and the occurrence of dents in the vicinity of the center 11c can be suppressed.

[0081] Furthermore, in the first embodiment, since the front end portion 11d of the wafer 11 protrudes from the outer periphery of the polishing layer 46 and the back surface 11b side is polished, no step is formed in the polishing layer 46, and an abnormal load can be prevented from being applied to the polishing layer 46 and the promotion of deterioration can be prevented.

[0082] Next, a second embodiment will be described. FIG. 8 is a bottom view of a polishing tool 50 according to the second embodiment. The polishing tool 50 corresponds to the polishing tool 40 and has a base 52 corresponding to the base 42 and a polishing layer 56 corresponding to the polishing layer 46.

[0083] However, the base 52 is a disk shape without the opening 42c in the base 42, and the center 52d is exposed without being covered by the polishing layer 56 on the lower surface (one surface) 52b to which the polishing layer 56 is fixed.

[0084] Further, the polishing layer 56 does not have a plurality of segment polishing pads 44 and is constituted by an integral annular polishing pad. This point is different from the first embodiment, but other points are the same as those of the first embodiment.

[0085] Specifically, the maximum width 54c of the effective polishing region 54b in the radial direction 52f of the base 52 is smaller than the diameter 56a of the opening 56a of the polishing layer 56 (i.e., the maximum width 54c < the diameter 56a 1 ). 1 )

[0086] For example, when the radius of the wafer 11 is 150 mm, the maximum width 54c in the radial direction 53f is 125 mm, and the diameter 56a 1 is 200 mm (i.e., the maximum width 54c < the radius of the wafer 11 < the diameter 56a 1 ).

[0087] Also in the second embodiment, excessive polishing in the vicinity of the center 11c of the wafer 11 can be prevented, and the occurrence of dents in the vicinity of the center 11c can be suppressed. Further, by polishing the back surface 11b so that the front end portion 11d of the wafer 11 protrudes from the outer periphery of the polishing layer 56, no step is formed in the polishing layer 56, so that abnormal loading on the polishing layer 46 and acceleration of deterioration can be prevented.

[0088] In addition, the structures, methods, etc. according to the above embodiments can be appropriately modified and implemented without departing from the scope of the object of the present invention.

Explanation of Reference Numerals

[0089] 2: Polishing apparatus, 4: Base, 4a: Opening, 6: Chuck table, 6a: Holding surface 8a 1 , 8a 2 : Upper surface, 10: Table base, 12: Telescopic cover, 14: Column portion 11: Wafer, 11a: Surface, 11b: Back surface (one side), 11c: Center 11d: End portion (a part of the outer periphery), 13: Protective tape, 15: Wafer unit 16: Guide rail, 18: Z-axis moving plate, 20: Ball screw, 22: Drive source 24: Z-axis direction moving mechanism, 26: Support part, 28: Polishing unit 30: Spindle housing, 32: Spindle, 32a: Opening 34: Motor, 36: Mount, 36a: Opening, 38: Fixture, 40: Polishing tool 42: Base, 42a: Upper surface, 42b: Lower surface (one side), 42c: Opening, 42d: Center 42e: Circumferential direction, 42f: Radial direction, 42g: Double arrow, 42h: Diameter direction 42p 1 : First position, 42p 2 : Second position 44: Segment polishing pad, 44a: Thin part, 44b: Effective polishing area, 44c: Maximum width 46: Polishing layer, 46a: Opening part, 46a 1 : Diameter 48: Control unit 50: Polishing tool, 52: Base, 52b: Lower surface (one side), 52d: Center, 52f: Radial direction 54b: Effective polishing area, 54c: Maximum width 56: Polishing layer, 56a: Opening part, 56a 1 : Diameter 60: Polishing tool, 64c: Maximum width 66: Polishing layer, 66a: Opening part, 66a 1 : Diameter A: Loading and unloading area, B: Polishing area, C 1 、C 2 、C 3 : Graph

Claims

1. A polishing method for polishing a wafer using a polishing apparatus including a chuck table rotatable while holding the wafer, and a polishing unit having a spindle to which a polishing tool for polishing the wafer held on a holding surface of the chuck table is attached, comprising: The polishing tool has a disk-shaped base, and an annular polishing layer fixed to one surface of the base and including an opening located at a central portion in the diameter direction of the base and having a predetermined diameter. The maximum width of the effective polishing region of the polishing layer in the radial direction of the base is smaller than the radius of the wafer, and the radius of the wafer is smaller than the diameter of the opening. The polishing method includes: A holding step of holding the wafer on the holding surface; A polishing step of polishing the wafer while rotating the polishing tool around the spindle in a state where the wafer and the polishing tool are positioned such that a part of the outer peripheral edge of the wafer protrudes from the outer periphery of the polishing layer and the center of the wafer is located in the opening of the polishing layer. The polishing method is characterized in that the maximum width of the effective polishing region is larger than the radius of the opening of the polishing layer and smaller than the diameter of the opening of the polishing layer.

2. The polishing method according to claim 1, wherein in the polishing step, the polishing tool and the wafer are relatively moved along the diameter direction of the polishing tool passing through the center of one surface of the wafer.

3. A polishing tool used when polishing a wafer, The polishing tool includes: A disk-shaped base; An annular polishing layer fixed to one surface of the base and including an opening located at a central portion in the diameter direction of the base and having a predetermined diameter. The polishing tool is characterized in that the maximum width of the effective polishing region of the polishing layer in the radial direction of the base is larger than the radius of the opening and smaller than the diameter of the opening. ​

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