Grinding device

Abstract

To remove slurry adhering to an outer periphery of a holding surface while suppressing deterioration in uniformity of a height of the holding surface.SOLUTION: A polishing device includes: a chuck table having a holding surface capable of sucking and holding a wafer; a rotation mechanism for rotating the chuck table around a prescribed rotation axis; a polishing unit having a spindle, and attached with a polishing pad for polishing the wafer sucked and held on the holding surface in the lower end part of the spindle; a slurry supply unit for supplying slurry to at least one of the wafer sucked and held on the holding surface and the polishing pad; and a cleaning unit for cleaning the holding surface. The cleaning unit has a cleaning grindstone coming in contact with the holding surface and removing slurry adhering to the holding surface, and a positioning unit for positioning the cleaning grindstone in a cleaning position where the cleaning grindstone contacts the holding surface, and a retreat position where the cleaning grindstone is separated from the holding surface. A hardness of the cleaning grindstone is lower than a hardness of the holding surface.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a polishing apparatus for polishing a wafer. [Background technology]

[0002] 2. Description of the Related Art In a process for manufacturing semiconductor devices from wafers made of semiconductors such as silicon, chemical mechanical polishing (CMP) is widely used for processing one surface of the wafer to be substantially flat (see, for example, Patent Document 1).

[0003] Chemical mechanical polishing of a wafer is usually performed using a polishing apparatus. The polishing apparatus is equipped with a disk-shaped chuck table including a holding surface for holding the wafer by suction. A rotary drive source such as a motor is provided below the chuck table. When the rotary drive source is operated, the chuck table rotates around a predetermined rotation axis.

[0004] A polishing unit is disposed above the chuck table. The polishing unit includes a spindle. A disk-shaped polishing pad is attached to the lower end of the spindle via a disk-shaped mount. A slurry supply passage is formed in the spindle, and a through hole is formed in the center of each of the mount and the polishing pad so as to overlap with the slurry supply passage.

[0005] When polishing a wafer, first, one side of the wafer is exposed upward while the other side of the wafer is held by suction on the chuck table. Then, the chuck table and the spindle are rotated in a predetermined direction, and the polishing pad is brought into contact with the one side of the wafer while supplying slurry to the polishing pad. The slurry supplied to the wafer reaches the outer periphery of the holding surface by centrifugal force. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2011-206881 A Summary of the Invention [Problem to be solved by the invention]

[0007] The adhesion of the slurry to the outer periphery of the holding surface causes unevenness in height on the outer periphery of the holding surface, which causes a problem of reduced flatness on the outer periphery of the wafer when the next wafer is polished.

[0008] It is difficult to remove the slurry that has adhered to the outer periphery of the holding surface by washing with cleaning water atomized using compressed air (so-called two-fluid washing). Ta It is contemplated that the slurry may be removed using a leveling stone.

[0009] However, since the leveling stone is usually harder than the holding surface, the use of the leveling stone not only removes the slurry but also polishes the holding surface, resulting in a problem of reduced uniformity in the height of the holding surface.

[0010] The present invention has been made in consideration of these problems, and aims to remove slurry adhering to the outer periphery of a holding surface while suppressing a decrease in the uniformity of the height of the holding surface. [Means for solving the problem]

[0011] According to one aspect of the present invention, a polishing apparatus includes a chuck table having a holding surface capable of suction-holding a wafer, a rotation mechanism for rotating the chuck table around a predetermined rotation axis, a polishing unit having a spindle and a polishing pad for polishing the wafer held by suction on the holding surface attached to a lower end of the spindle, a slurry supply unit for supplying slurry to at least one of the wafer and the polishing pad held by suction on the holding surface, and a cleaning unit for cleaning the holding surface, the cleaning unit having a cleaning grindstone that comes into contact with the holding surface to remove the slurry adhering to the holding surface, and a positioning unit that positions the cleaning grindstone at a cleaning position where the cleaning grindstone comes into contact with the holding surface and a retracted position where the cleaning grindstone is separated from the holding surface, and the hardness of the cleaning grindstone is lower than the hardness of the holding surface. The spindle is disposed along a first axis direction, and the position of the cleaning stone is fixed within a plane defined by a second axis direction and a third axis direction each perpendicular to the first axis direction. A polishing apparatus is provided.

[0012] Preferably, the positioning unit includes an elastic member for pressing the cleaning stone against the holding surface. Also, preferably, the positioning unit positions the cleaning stone at the cleaning position when cleaning the holding surface, and brings the cleaning stone into contact with a part of the outer periphery of the holding surface.

[0013] Preferably, the holding surface is made of ceramics, and the hardness of the cleaning stone is 680 HV or less in Vickers hardness. Also, preferably, the cleaning stone is a PVA stone having abrasive grains and a binder for fixing the abrasive grains. Also, preferably, the cleaning stone contains the abrasive grains made of cerium oxide. Effect of the Invention

[0014] A polishing apparatus according to one aspect of the present invention includes a cleaning unit. The cleaning unit includes a cleaning stone having a hardness lower than that of the holding surface, and a positioning unit that positions the cleaning stone at a cleaning position and a retreated position. By rotating the chuck table with the cleaning stone in contact with the outer periphery of the holding surface, the slurry adhering to the outer periphery of the holding surface can be removed by the cleaning stone.

[0015] Moreover, since the hardness of the cleaning grindstone is lower than that of the holding surface, the cleaning grindstone can remove the slurry without polishing the holding surface itself, which prevents the uniformity of the height of the holding surface from decreasing compared to polishing the holding surface with a polishing tool such as a leveling stone. [Brief description of the drawings]

[0016] [Figure 1] FIG. 2 is a perspective view of a main part of the polishing apparatus. [Diagram 2] FIG. 2 is a partial cross-sectional side view of the cleaning whetstone holder. [Diagram 3] FIG. 13 is a diagram showing a state in which a cleaning whetstone is brought into contact with a holding surface. [Figure 4] FIG. 4(A) is a graph showing the thickness of the outer periphery of a wafer when multiple wafers are polished by applying two-fluid cleaning to the outer periphery of the holding surface in a cleaning process, and FIG. 4(B) is a graph showing the thickness of the outer periphery of a wafer when multiple wafers are polished by cleaning the outer periphery of the holding surface using a cleaning unit in a cleaning process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] An embodiment according to one aspect of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a perspective view of a main part of a polishing apparatus 2. Note that the X-axis direction, the Y-axis direction, and the Z-axis direction shown in Fig. 1 are mutually orthogonal. For example, the Z-axis direction is a vertical direction, and the XY plane is a horizontal plane.

[0018] The polishing apparatus 2 in this embodiment is part of a single processing apparatus (polishing / grinding apparatus) equipped with a rough grinding apparatus and a finish grinding apparatus, but the polishing apparatus 2 may also be a processing apparatus that performs polishing without grinding.

[0019] The polishing apparatus 2 has a disk-shaped chuck table 4. The chuck table 4 has a disk-shaped frame 6 made of non-porous ceramics. The frame 6 in this embodiment is made of non-porous alumina and has a Vickers hardness of 1597HV.

[0020] A disk-shaped recess (not shown) is formed in the frame 6, and a disk-shaped porous plate 8 made of porous ceramics is fixed in this recess. The porous plate 8 in this embodiment is made of porous alumina and has a Vickers hardness of 681 HV.

[0021] In this embodiment, the upper surface 8a of the porous plate 8 has a convex shape with the center protruding slightly compared to the outer periphery. The upper surface 6a of the frame 6 and the upper surface 8a of the porous plate 8 are substantially flush with each other and form the holding surface 4a. Note that, in the case where the polishing device 2 is a processing device that performs polishing without grinding, the upper surface 8a of the porous plate 8 may be substantially flat.

[0022] A predetermined flow path is formed in the frame 6. One end of the predetermined flow path is connected to a suction source (not shown) such as an ejector, and the other end of the predetermined flow path is exposed to the recess. Negative pressure generated by the suction source is transmitted to the upper surface 8a of the porous plate 8 via the predetermined flow path.

[0023] Using this negative pressure, the wafer 11 placed on the holding surface 4a is sucked and held on the holding surface 4a. The wafer 11 is made of, for example, silicon (Si), but there are no limitations on the material, shape, structure, size, etc., of the wafer 11.

[0024] For example, the wafer 11 may be formed of a semiconductor material other than silicon, such as gallium nitride (GaN), silicon carbide (SiC), etc. A resin protective tape 13 having approximately the same diameter as the wafer 11 is attached to the front surface 11a of the wafer 11 in order to reduce damage to the front surface 11a side.

[0025] A ring-shaped rotating table 10a is fixed to the lower part of the chuck table 4. A plurality of movable members (not shown), such as air cylinders and screw-type movable shafts, are provided on the upper part of the rotating table 10a along the circumferential direction of the rotating table 10a.

[0026] Each of the multiple movable members supports the chuck table 4, and the inclination of the chuck table 4 is adjusted by the extension and contraction of the movable members. For example, the inclination of the chuck table 4 is adjusted so that a part of the holding surface 4a becomes approximately horizontal with respect to the XY plane. The part of the holding surface 4a that is approximately horizontal with respect to the XY plane is covered with a polishing pad 20, which will be described later.

[0027] The rotating base 10a is supported by a fixed base 10b in a rotatable manner. A driven gear 10c is formed on the outer circumferential side of the rotating base 10a, and a driving gear 10e connected to a motor 10d is engaged with the driven gear 10c.

[0028] When the driving gear 10e is rotated, the chuck table 4 rotates around a predetermined rotation axis 10f at about 10 rpm to 300 rpm. The rotating base 10a, the fixed base 10b, the driven gear 10c, the motor 10d, the driving gear 10e, etc. constitute a rotation mechanism 10 that rotates the chuck table 4.

[0029] A polishing unit 12 is disposed above the chuck table 4. The polishing unit 12 has a cylindrical spindle housing 14. A part of a columnar spindle 16 is rotatably housed in the spindle housing 14.

[0030] The spindle 16 is disposed along the Z-axis direction, and a rotation drive source (not shown), such as a motor, is provided at the upper end of the spindle 16. The lower end of the spindle 16 protrudes downward beyond the spindle housing 14.

[0031] A disc-shaped polishing pad 20 is attached to the lower end of the spindle 16 via a disc-shaped mount 18. The polishing pad 20 includes a disc-shaped base. A pad portion that comes into contact with the wafer 11 is fixed to one surface of the base.

[0032] The pad portion of this embodiment does not have fixed abrasive grains and is made of a predetermined material, such as a foamed hard material such as foamed hard polyurethane, or a nonwoven fabric made of polyester impregnated with urethane.

[0033] The mount 18 and the polishing pad 20 have approximately the same diameter, and through holes 18a, 20a are formed so as to pass through the center of each circle. A flow path 16a for a slurry 22a formed in the spindle 16 is connected to each of the through holes 18a, 20a.

[0034] The slurry 22a is, for example, an alkaline aqueous solution containing abrasive grains made of silica (silicon oxide, SiO2), but the material of the abrasive grains may be GC (green carbon), diamond, alumina (aluminum oxide, Al2O3), ceria (cerium oxide, CeO2), cBN (cubic boron nitride), silicon carbide (SiC), etc. Also, an acidic aqueous solution may be used instead of the alkaline aqueous solution.

[0035] The slurry 22a is supplied to the through holes 18a and 20a from the slurry supply unit 22 through the flow path 16a. The slurry supply unit 22 includes a storage tank (not shown) in which the slurry 22a is stored, and a pump (not shown) for supplying the slurry 22a from the storage tank to the flow path 16a.

[0036] A holding member 24 is fixed to the outer periphery of the spindle housing 14. The holding member 24 is fixed to a Z-axis moving plate 26. The Z-axis moving plate 26 is slidably attached to a pair of guide rails 28 arranged substantially parallel to the Z-axis direction.

[0037] A ball screw 30 is disposed between the pair of guide rails 28 and substantially parallel to the Z-axis direction. The ball screw 30 is rotatably connected to a nut portion (not shown) provided on the Z-axis moving plate 26. A pulse motor 32 is connected to the upper end portion of the ball screw 30.

[0038] When the ball screw 30 is rotated by the pulse motor 32, the Z-axis moving plate 26 moves along the Z-axis direction. The holding member 24, the Z-axis moving plate 26, the pair of guide rails 28, the ball screw 30, the pulse motor 32, etc. constitute a Z-axis moving unit 34 that adjusts the height position of the polishing unit 12.

[0039] The Z-axis movement unit 34 is fixed to a moving block 2a that is movable in the X-axis direction by a ball screw type X-axis movement mechanism (not shown). A support column 2b fixed to a base (not shown) is provided on one side in the X-axis direction of the moving block 2a.

[0040] A cleaning unit 40 for cleaning the holding surface 4a is provided on the support column 2b. The cleaning unit 40 is disposed above the chuck table 4. The cleaning unit 40 has a positioning unit .

[0041] The positioning unit 42 has a pair of guide rails 44 whose positions are fixed relative to the support column 2b. A Z-axis moving plate 46 is slidably attached to the pair of guide rails 44.

[0042] A nut portion (not shown) is provided on the Z-axis moving plate 46. A ball screw 48, which is disposed between the pair of guide rails 44 and approximately parallel to the Z-axis direction, is rotatably connected to the nut portion.

[0043] A pulse motor 50 is connected to the upper end of the ball screw 48. When the ball screw 48 is rotated by the pulse motor 50, the Z-axis moving plate 46 moves along the Z-axis direction. A cleaning grindstone holder 52 is fixed to the front surface of the Z-axis moving plate 46 (one side in the Y-axis direction).

[0044] A cleaning stone 54 having a rectangular parallelepiped shape (e.g., length 24 mm, width 46 mm, height 28 mm) and a hardness lower than that of the holding surface 4a is fixed to the cleaning stone holder 52. The cleaning stone 54 has a Vickers hardness of 680 HV or less, for example.

[0045] The cleaning grindstone 54 of this embodiment is a PVA grindstone in which cerium oxide abrasive grains (#3000, which indicates the grain size of the abrasive grains) are fixed using PVA (polyvinyl alcohol) as a binder. The PVA grindstone has elasticity due to the pores continuously formed in the binder, and has a Vickers hardness of, for example, 34HV.

[0046] However, the cleaning grindstone 54 is not limited to the PVA grindstone, and may be a rubber grindstone in which abrasive grains such as ceria, silica, alumina, etc. are fixed by vulcanized rubber, as long as the Vickers hardness is 680 HV or less.

[0047] In this manner, by contacting the holding surface 4a with a cleaning grindstone 54 that is sufficiently softer than the holding surface 4a, the slurry 22a adhering to the outer periphery of the holding surface 4a can be removed without changing the uniformity of the height of the holding surface 4a.

[0048] However, even if the Vickers hardness is 680HV or less, sponges such as urethane sponges available for household use are too soft to remove the slurry 22a. Therefore, the Vickers hardness of the cleaning grindstone 54 is set to 10HV or more, and more preferably 20HV or more. HV It is more preferable that the hardness is 30HV or more.

[0049] Even if the Vickers hardness is 680 HV or less, in order to reduce the amount of polishing of the holding surface 4a as much as possible, the Vickers hardness of the cleaning grindstone 54 is preferably 600 HV or less, more preferably 300 HV or less, and even more preferably 100 HV or less.

[0050] Here, the structure of the cleaning stone holder 52 will be described in more detail with reference to Fig. 2. Fig. 2 is a partially sectional side view of the cleaning stone holder 52. The cleaning stone holder 52 has a bracket 56 that is L-shaped in side view.

[0051] The bracket 56 has a first straight portion fixed to the front surface side of the Z-axis moving plate 46 by a bolt 58. A second straight portion is provided at one end of the first straight portion in a manner perpendicular to the first straight portion. In the bracket 56 fixed to the Z-axis moving plate 46, an upper plate 60 is fixed to the lower surface of the second straight portion by a bolt (not shown).

[0052] A through hole 60a is formed in the upper plate 60, and a cylindrical shaft portion 62 is slidably inserted into this through hole 60a. A disk-shaped head portion 62a having a diameter larger than that of the through hole 60a is fixed to the upper end portion of the shaft portion 62.

[0053] Since the head 62a is disposed above the upper plate 60, the shaft portion 62 is supported by the upper plate 60. A disk-shaped support portion 62b having a larger diameter than the shaft portion 62 is fixed to the vicinity of the lower end of the shaft portion 62.

[0054] A metallic compression coil spring (elastic member) 64 is provided on the outer periphery of the shaft portion 62 between an upper surface 62c of the support portion 62b and a lower surface 60b of the upper plate 60. In this embodiment, the compression coil spring 64 is used, but other types of springs, rubber, etc. may be used as long as they can exert a restoring force.

[0055] A lower plate 66 is fixed to the lower surface of the support portion 62b. An upper end portion of a first plate portion 68a is fixed to one side in the Y-axis direction of the lower plate 66. A second plate portion 68b is fixed via a plurality of bolts 70 to the other side in the Y-axis direction of the first plate portion 68a.

[0056] The first plate portion 68a and the second plate portion 68b sandwich the above-mentioned cleaning grindstone 54 in the Y-axis direction. The cleaning grindstone 54 is fixed by the lower plate 66, the first plate portion 68a, and the second plate portion 68b in such a manner that its upper portion contacts the lower surface of the lower plate 66 and its lower portion protrudes downward beyond the first plate portion 68a and the second plate portion 68b.

[0057] The position of the cleaning grindstone 54 in the XY plane corresponds to one location on the outer periphery of the holding surface 4a. The positioning unit 42 moves the cleaning grindstone 54 along the Z-axis direction, whereby the cleaning grindstone 54 is positioned at a cleaning position (see FIG. 3) in contact with the holding surface 4a and at a retracted position (see FIG. 1) away from the holding surface 4a.

[0058] 1, a nozzle 72 for supplying cleaning water such as pure water to the contact area between the cleaning stone 54 and the holding surface 4a is provided at the bottom of the cleaning stone holder 52. A cleaning water supply unit (not shown) having a tank, a pump, etc. is connected to the nozzle 72 via a predetermined flow path.

[0059] The operation of the cleaning unit 40 including the nozzle 72 is controlled by a control unit (not shown). The control unit also controls the operations of the rotation mechanism 10, the rotation drive source provided in the spindle housing 14, the slurry supply unit 22, the Z-axis movement unit 34, etc.

[0060] The control unit 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.

[0061] The auxiliary storage device stores software including a predetermined program. The functions of the control unit are realized by operating the processing device and the like in accordance with this software. Next, polishing the wafer 11, removing the slurry 22a adhering to the outer periphery of the holding surface 4a, and the like will be described with reference to Figs. 2 and 3.

[0062] First, the polishing unit 12 is retracted from directly above the holding surface 4a by the movable block 2a, and the cleaning grindstone 54 is moved to a retracted position. Then, the wafer 11 is transported to the holding surface 4a by a transport unit (not shown) so that the back surface 11b of the wafer 11 is exposed upward (transportation process).

[0063] After the transport step, the front surface 11a side of the wafer 11 is suction-held by the holding surface 4a (holding step). After the holding step, the polishing unit 12 is moved by the moving block 2a so that a part of the polishing unit 12 covers the holding surface 4a.

[0064] Thereafter, the chuck table 4 and the polishing pad 20 are rotated in a predetermined direction and the polishing unit 12 is lowered at a predetermined polishing feed rate, while the slurry supply unit 22 supplies a slurry 22a to at least one of the wafer 11 and the polishing pad 20.

[0065] In this manner, the back surface 11b of the wafer 11 is polished by the polishing pad 20 while the wafer 11 is pressed with a predetermined pressure (polishing step). The wafer 11, which has been thinned to a predetermined thickness by the polishing step, is carried out from the holding surface 4a by a transport unit (not shown) (carrying out step).

[0066] After the unloading step, the slurry 22a supplied in the polishing step moves due to centrifugal force or the like, so that the slurry 22a adheres to the outer periphery of the holding surface 4a (see FIG. 3). The slurry 22a adheres mainly to the upper surface 6a of the frame 6 that is not covered by the wafer 11, but may also adhere to the outer periphery of the upper surface 8a due to negative pressure or the like generated on the upper surface 8a of the porous plate 8.

[0067] In this embodiment, the slurry 22a attached to the outer periphery of the holding surface 4a is removed (cleaning step) using the cleaning unit 40. During cleaning, the chuck table 4 is rotated at a predetermined speed while cleaning water is supplied to the outer periphery of the holding surface 4a from the nozzle 72 at a predetermined flow rate (for example, 2 (l / min)).

[0068] Next, the positioning unit 42 lowers the cleaning grindstone 54, moving it to the cleaning position. In this manner, the lower surface 54a comes into contact with a part of the upper surface 6a of the frame 6 and a part of the upper surface 8a of the porous plate 8 (see FIG. 3). FIG. 3 is a diagram showing the state in which the cleaning grindstone 54 is in contact with the holding surface 4a.

[0069] At this time, the position of the cleaning stone holder 52 in the Z-axis direction is adjusted so that the lower surface 54a (see FIG. 2) of the cleaning stone 54 is lower than the holding surface 4a by, for example, 6 mm. In this manner, the cleaning stone 54 is pressed against the holding surface 4a with a constant pressure by the restoring force of the compression coil spring 64.

[0070] In the cleaning process, the slurry 22a is scraped off by the cleaning grindstone 54, and the scraped off slurry 22a is dropped off the holding surface 4a by using cleaning water that flows radially outward of the holding surface 4a by centrifugal force. In this manner, the slurry 22a adhering to the outer periphery of the holding surface 4a can be almost entirely removed.

[0071] In this embodiment, the hardness of the cleaning grindstone 54 is lower than that of the holding surface 4a, so the cleaning grindstone 54 can remove the slurry 22a without changing the uniformity of the height of the holding surface 4a. Therefore, the decrease in the uniformity of the height of the holding surface 4a can be suppressed compared to the case where the holding surface 4a is polished with a polishing tool such as a leveling stone.

[0072] After the cleaning process, the process returns to the loading process and polishes the second wafer 11. In this manner, polishing of the wafer 11 and cleaning of the holding surface 4a are performed alternately. Next, the results of an experiment in which a plurality of wafers 11 are polished one by one by the polishing apparatus 2 will be described.

[0073] FIG. 4(A) is a graph showing the thickness of the outer periphery of the wafer 11 when multiple wafers 11 are polished by performing two-fluid cleaning on the outer periphery of the holding surface 4a in the cleaning process (i.e., cleaning the holding surface 4a with cleaning water atomized using compressed air).

[0074] In contrast, FIG. 4(B) is a graph showing the thickness of the outer periphery of the wafer 11 when the outer periphery of the holding surface 4a is cleaned and multiple wafers 11 are polished using the above-mentioned cleaning unit 40 in the cleaning process.

[0075] 4(A) and 4(B), the horizontal axis indicates the radial position (mm) of the wafer 11, and the vertical axis indicates the thickness (μm) of the wafer 11. Furthermore, a white circle indicates the first wafer 11, a dotted circle indicates the 50th wafer 11, and a black circle indicates the 100th wafer 11.

[0076] In the experiment shown in FIG. 4(A), after the first wafer 11 was polished, a two-fluid Washing Then, the second wafer 11 was polished. Thereafter, the outer periphery of the holding surface 4a was subjected to two-fluid cleaning, and the third wafer 11 was polished. In this manner, 100 wafers 11 were polished.

[0077] 4(B), after the first wafer 11 was polished, the outer periphery of the holding surface 4a was cleaned with the cleaning grindstone 54, and then, after the second wafer 11 was polished, the outer periphery of the holding surface 4a was cleaned with the cleaning grindstone 54. In this manner, 100 wafers 11 were polished.

[0078] As shown in FIG. 4(A), the two fluids are Washing When the above-mentioned polishing process is performed, the slurry 22a attached to the outer periphery of the holding surface 4a is not sufficiently removed. Therefore, the outer periphery of the wafer 11 is lifted by the remaining slurry 22a, and the polishing amount of the outer periphery of the wafer 11 becomes larger than the polishing amount of the central portion.

[0079] Therefore, the outer periphery of the wafer 11 became thinner than the center of the wafer 11. In particular, as is clear from the 100th wafer 11, the flatness of the wafer 11 deteriorated in the outer periphery of the wafer 11.

[0080] 4(B), when the cleaning process was performed, the flatness of the wafer 11 did not deteriorate even in the 100th wafer 11. In this way, it became clear that the deterioration of the uniformity of the height of the holding surface 4a can be suppressed by removing the slurry 22a adhering to the outer periphery of the holding surface 4a using the cleaning grindstone 54.

[0081] In addition, the structures, methods, etc. 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]

[0082] 2: grinding device, 2a: moving block, 2b: support column 4: chuck table, 4a: holding surface 6: Frame, 6a: Top surface, 8: Porous plate, 8a: Top surface 10: Rotation mechanism, 10a: Rotation table, 10b: Fixed table, 10c: Driven gear 10d: motor, 10e: drive gear, 10f: rotating shaft 11: wafer, 11a: front surface, 11b: back surface, 13: protective tape 12: Polishing unit, 14: Spindle housing 16: spindle, 16a: flow path, 18: mount, 18a: through hole 20: polishing pad, 20a: through hole, 22: slurry supply unit, 22a: slurry 24: Holding member, 26: Z-axis moving plate, 28: Guide rail, 30: Ball screw 32: Pulse motor, 34: Z-axis movement unit 40: cleaning unit, 42: positioning unit 44: Guide rail, 46: Z-axis moving plate, 48: Ball screw, 50: Pulse motor 52: cleaning whetstone holder, 54: cleaning whetstone, 54a: underside 56: bracket, 58: bolt, 60: upper plate, 60a: through hole, 60b: lower surface 62: Shaft, 62a: Head, 62b: Support, 62c: Top surface 64: compression coil spring, 66: lower plate, 68a: first plate portion, 68b: second plate portion 70: Bolt, 72: Nozzle

Claims

1. a chuck table having a holding surface capable of suction-holding a wafer; a rotation mechanism that rotates the chuck table about a predetermined rotation axis; a polishing unit having a spindle, the polishing pad for polishing the wafer held by suction on the holding surface being attached to a lower end of the spindle; a slurry supply unit that supplies a slurry to at least one of the wafer and the polishing pad that are suction-held on the holding surface; a cleaning unit for cleaning the holding surface; Equipped with The cleaning unit comprises: a cleaning grindstone for contacting the holding surface to remove the slurry adhering to the holding surface; a positioning unit for positioning the cleaning stone at a cleaning position where the cleaning stone contacts the holding surface and at a retreated position where the cleaning stone is separated from the holding surface; The hardness of the cleaning stone is lower than the hardness of the holding surface, The spindle is disposed along a first axial direction, A polishing apparatus characterized in that the position of the cleaning whetstone is fixed within a plane defined by second and third axial directions each perpendicular to the first axial direction.

2. 2. The polishing apparatus according to claim 1, wherein the positioning unit includes an elastic member for pressing the cleaning stone against the holding surface.

3. 3. The polishing apparatus according to claim 1, wherein the positioning unit positions the cleaning whetstone at the cleaning position when cleaning the holding surface, and brings the cleaning whetstone into contact with a part of the outer periphery of the holding surface.

4. The holding surface is made of ceramics, 4. A polishing apparatus according to claim 1, wherein the cleaning stone has a Vickers hardness of 680 HV or less.

5. 5. A polishing apparatus according to claim 1, wherein the cleaning abrasive stone is a PVA abrasive stone having abrasive grains and a binder for fixing the abrasive grains.

6. 6. The polishing apparatus according to claim 5, wherein the cleaning stone contains abrasive grains made of cerium oxide.

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