Polishing apparatus

Abstract

To prevent polishing in a state where a polishing pad is chipped.SOLUTION: A polishing apparatus (1) includes a chuck table (12) for holding a wafer (W), and a polishing mechanism (40) for polishing the wafer held on the chuck table with a polishing surface (56) of a polishing pad (52) by rotating the polishing pad. The polishing apparatus includes a displacement measuring mechanism (70) configured to measure a displacement of the polishing pad in a direction perpendicular to the polishing surface, a table moving mechanism (20) configured to horizontally move the polishing pad and the displacement measuring mechanism relative to each other, and a displacement map generator (86) configured to generate a displacement map (M1) of the entire polishing surface by using the displacement measured by the displacement measuring mechanism while the polishing pad is horizontally moved by the table moving mechanism. the displacement map generated by the displacement map generator is compared with a preset displacement map (M0). And a quality determination part (87) for determining the quality of the polishing pad from the difference.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a polishing apparatus that forms a gettering layer by rotating a polishing pad on the backside of a wafer. Patent Document 2 discloses a polishing apparatus with a grinding wheel that has four or five segmented polishing pads arranged circumferentially around a wheel base. The segmented polishing pads in Patent Document 2 are arranged in the shape of cherry blossom petals.

[0003] Patent Document 3 discloses a polishing apparatus equipped with a dressing mechanism that dresses the polishing surface of a polishing pad. The dressing mechanism includes a dressing board fixed to the upper end of a support part erected from a base. The dressing board is fed from the center of the polishing pad outward while being brought into contact with the polishing surface of the rotating polishing pad, thereby dressing the entire polishing surface with the dressing board. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-067964 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-093018 [Patent Document 3] Japanese Patent Application Publication No. 2018-008339 Summary of the Invention [Problem to be solved by the invention]

[0005] In a configuration in which multiple segment polishing pads are arranged side by side, as in Patent Document 2, chipping can occur at the corners of the segment polishing pad when the segment polishing pad comes into contact with the wafer or the dress board. If a segment polishing pad with such chipping is used to perform polishing to form a gettering layer on the backside of a wafer, the gettering layer cannot be formed, which is a problem.

[0006] The present invention has been made in view of the above points, and one of its objects is to provide a polishing apparatus that can prevent polishing in a state where a chip has occurred in the polishing pad. [Means for solving the problem]

[0007] A polishing apparatus according to one embodiment of the present invention comprises a chuck table for holding a wafer, and a polishing mechanism for rotating a polishing pad to polish the wafer held on the chuck table using the polishing surface of the polishing pad, and further comprises a displacement measurement mechanism for measuring displacement perpendicular to the polishing surface of the polishing pad, a horizontal movement mechanism for relatively moving the polishing pad and the displacement measurement mechanism in a horizontal direction, a displacement map generation unit for generating a displacement map of the entire polishing surface using displacement measured by the displacement measurement mechanism after horizontal movement by the horizontal movement mechanism, and a quality judgment unit for comparing the displacement map generated by the displacement map generation unit with a predetermined displacement map and judging the quality of the polishing pad from the difference. [Effects of the Invention]

[0008] According to the present invention, since the quality of the polishing pad is judged by generating and comparing a displacement map, it is possible to prevent polishing when a chip has occurred in the polishing pad, thereby preventing the occurrence of a situation in which an unpolished portion is formed on the wafer during polishing with the polishing pad. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view showing an example of a polishing apparatus according to an embodiment; [Figure 2]2A and 2B are diagrams showing the polishing mechanism and the chuck table and their surroundings as viewed from the X-axis direction. [Figure 3] FIG. 2 is a view of the grinding wheel from below. [Figure 4] FIG. 2 is a view of the polishing mechanism and the chuck table and their surroundings as viewed from the X-axis direction. [Figure 5] 5A and 5B are diagrams showing examples of displacement maps. [Figure 6] FIG. 10 is a flow chart showing the flow of checking a segment polishing pad. [Figure 7] 10A and 10B are explanatory diagrams of a displacement measuring mechanism according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a polishing apparatus according to the present embodiment will be described with reference to the accompanying drawings. Note that the polishing apparatus according to the present embodiment is not limited to the configuration shown below and can be modified as appropriate. For the sake of convenience, some components are omitted in the following drawings.

[0011] First, the overall configuration of a polishing apparatus will be described with reference to Figure 1. Figure 1 is a perspective view showing an example of a polishing apparatus according to an embodiment. The X-axis, Y-axis, and Z-axis directions shown in Figure 1 are perpendicular to one another. The X-axis and Y-axis directions are approximately horizontal, and the Z-axis direction is an up-down direction (vertical direction). In addition, in the following figures, the front side in the X-axis direction will be referred to as the +X side, the back side as the -X side, the right side in the Y-axis direction as the +Y side, the left side as the -Y side, and the upper side in the Z-axis direction as the +Z side and the lower side as the -Z side.

[0012] 1, the polishing apparatus 1 is configured to polish a wafer W held on a chuck table 12 with a polishing pad 52 of a polishing mechanism 40 to form a gettering layer. More specifically, the polishing apparatus 1 forms a gettering layer by polishing, in which minute distortions (irregularities) are formed on the back surface W2 of the wafer W from which grinding marks and the like have been removed. The formation of the gettering layer can prevent impurities such as copper contained inside the wafer W from floating to the front surface side and causing current leakage.

[0013] For example, the wafer W is made of a silicon wafer, and a plurality of streets are formed in a grid pattern on the front surface W1, with devices (not shown) such as ICs and LSIs formed in areas partitioned by the streets. When the back surface W2 of the wafer W is polished to form a gettering layer, a tape T is attached to the front surface W1 of the wafer W as a protective member to protect the devices formed on the front surface W1 of the wafer W. The wafer W is held on a chuck table 12 (described later) with the back surface W2, which is the surface to be polished, facing up.

[0014] 1, a rectangular opening extending in the Y-axis direction is formed on the upper surface of a base 10 of the polishing apparatus 1. This opening is covered by a bellows-shaped cover 14 that is movable in the Y-axis direction together with a chuck table 12.

[0015] The chuck table 12 is provided with a circular porous plate 15. The porous plate 15 is made of a porous material such as ceramics, and has fine pores formed throughout. The upper surface of the porous plate 15 constitutes a holding surface 16. The holding surface 16 holds the wafer W by suction using a suction source 17 (see FIG. 2A).

[0016] A table moving mechanism 20 constituting a horizontal moving mechanism that moves the chuck table 12 in the Y-axis direction is provided below the cover 14. The table moving mechanism 20 includes a pair of guide rails 21 extending in the Y-axis direction and a ball screw 22, and a moving platform 23 is supported so as to be movable along the guide rails 21. The ball screw 22 is threadedly engaged with a threaded portion (not shown) of the moving platform 23, and when the ball screw 22 is rotated by operation of a Y-axis motor 24, the moving platform 23 moves in the Y-axis direction. An encoder 25 is provided on the Y-axis motor 24, and the positions of the chuck table 12 and the wafer W held on the chuck table 12 in the Y-axis direction can be measured based on the values ​​detected by the encoder 25.

[0017] In addition, a table rotation mechanism 30 that rotates the chuck table 12 is provided below the cover 14. The table rotation mechanism 30 includes a base 31 supported on the movable table 23, and a table rotation shaft 32 rotatably supported inside the base 31 via a bearing (not shown). A load sensor 38 is disposed between the movable table 23 and the base 31.

[0018] In addition, the table rotation mechanism 30 has an endless belt 36 wound around a driven pulley 33 provided on the outer surface of the table rotation shaft 32 and a drive pulley 35 rotated by a motor 34. When the drive pulley 35 is rotated by operation of the motor 34, the rotation is transmitted to the driven pulley 33 via the endless belt 36, and the table rotation shaft 32 and the chuck table 12 are rotated around a central axis parallel to the Z-axis direction.

[0019] Next, we will explain the polishing mechanism 40 and polishing feed mechanism 60, which constitute the processing unit. A column 18 erected on the rear side (-X side) of the base 10 is provided with the polishing feed mechanism 60, which moves the polishing mechanism 40 up and down in the Z-axis direction.

[0020] The polishing feed mechanism 60 includes a pair of guide rails 61 arranged on the front side (+X side) of the column 18 and extending in the Z-axis direction, a lifting table 62 installed so as to be movable in the Z-axis direction relative to the pair of guide rails 61, and a ball screw 63 extending in the Z-axis direction and threaded into a screw-type portion (not shown) of the lifting table 62.

[0021] A motor 64 is connected to one end of the ball screw 63. In the polishing feed mechanism 60, the ball screw 63 is rotated by the driving force of the motor 64, causing the lifting table 62 and the polishing mechanism 40 to move up and down in the Z-axis direction. An encoder 65 is provided to the motor 64, and the height position (position in the Z-axis direction) of the polishing mechanism 40 moving up and down can be measured based on the value detected by the encoder 65.

[0022] The polishing mechanism 40 further includes a holder 41 attached to the +X side surface of the lift table 62, and a spindle unit 42 supported by the holder 41. The spindle unit 42 includes a spindle housing 44 disposed within the holder 41, and a spindle 45 that rotates around the Z-axis direction as its central axis by the driving force of a spindle motor (not shown). The spindle motor is provided with an encoder, and the rotation angle of the spindle 45 around the Z-axis can be measured from the value detected by the encoder.

[0023] A mount 47 is connected to the tip (lower end) of the spindle 45, and a grinding wheel 50 is attached to the mount 47. Therefore, when the spindle 45 rotates, the grinding wheel 50 rotates about the Z-axis direction as its central axis. The grinding wheel 50 includes a wheel base 51 made of metal and a grinding pad 52 provided on the underside of the wheel base 51. The grinding wheel 50 including the grinding pad 52 will be described later.

[0024] 2A and 2B are views of the polishing mechanism and the configuration around the chuck table as viewed from the X-axis direction, with Fig. 2A being an explanatory diagram of the wafer being polished, and Fig. 2B being an explanatory diagram of the polishing pad displacement being measured. As shown in Fig. 2A, a supply path 48 is formed at the center of the spindle 45 and the mount 47. An air supply source (not shown) is connected to the supply path 48, and air is supplied from the air supply source through the supply path 48, causing air to flow between the polishing pad 52 and the wafer W just before they come into contact.

[0025] The polishing apparatus 1 further includes a displacement measuring mechanism 70 and a dressing unit 80. The displacement measuring mechanism 70 and the dressing unit 80 are disposed on the upper surface of a base member 73 provided on the +Y side of the movable table 23. More specifically, the displacement measuring mechanism 70 and the dressing unit 80 are supported so as to be movable in the Z-axis direction via a cylinder 74 serving as a vertical movement mechanism disposed on the upper surface of the base member 73. Therefore, by driving the cylinder 74, the displacement measuring mechanism 70 and the dressing unit 80 can move toward or away from the polishing pad 52 of the polishing wheel 50 located above.

[0026] The displacement measuring mechanism 70 is a displacement measuring device equipped with a light-projecting unit that projects measurement light toward the polishing pad 52 of the polishing wheel 50 and a light-receiving unit that receives the reflected light of the measurement light. In the displacement measuring mechanism 70, the light-projecting unit projects light, which is reflected by the polishing surface 56 (lower surface) of the polishing pad 52 (described later), and the light-receiving unit receives the reflected light. The displacement measuring mechanism 70 measures the distance from the displacement measuring mechanism 70 to the polishing surface 56 using triangulation along the optical path from the light-projecting unit to the polishing surface 56 and back to the light-receiving unit. Based on the measured distance, the displacement measuring mechanism 70 measures and outputs the displacement in the direction perpendicular to the polishing surface 56 (the amount of displacement of the polishing surface 56 in the Z-axis direction relative to a predetermined horizontal plane).

[0027] The dressing section 80 is composed of a support member 81 standing on the base member 73 and a dressing board 82 fixed to the upper end of the support member 81. The dressing board 82 is disposed above the upper surface of the displacement measuring mechanism 70 via the support member 81.

[0028] 3 is a view of the polishing wheel as seen from below. A central hole 53 communicating with the supply path 48 (see FIG. 2A) is formed in the wheel base 51 of the polishing wheel 50. The polishing pad 52 of the polishing wheel 50 is composed of a plurality of (five in this embodiment) segment polishing pads 55 attached to the underside of the wheel base 51. Each segment polishing pad 55 is arranged along a horizontal plane parallel to the paper surface of FIG. 3 with the polishing wheel 50 attached to the mount 47 (see FIG. 2A). The underside of each segment polishing pad 55 serves as a polishing surface 56 for polishing the wafer W.

[0029] Each segmented polishing pad 55 is formed by fixing fine abrasive grains together with a binder such as varnish in a polishing cloth such as a nonwoven fabric, and the abrasive grains are made of silica, cerium oxide, etc. with a particle size of 0.01 μm to 10.0 μm. Alternatively, the segmented polishing pad 55 may be formed by fixing silica or cerium oxide with urethane foam.

[0030] The circumferential width of each segmented polishing pad 55 increases from the rotation center toward the center in the radial direction and decreases from the center toward the periphery, giving the segmented polishing pads 55 a cherry blossom petal shape. The segmented polishing pads 55 are arranged so that the spacing between adjacent segmented polishing pads 55 decreases from the rotation center toward the center in the radial direction, and then they abut against each other at the center and then increase toward the periphery.

[0031] A plurality of segmented polishing pads 55 arranged on the wheel base 51 of the polishing wheel 50 are arranged in a ring shape to have a polishing area width smaller than the diameter and larger than the radius of the wafer W held on the chuck table 12. The polishing mechanism 40 rotates the ring-shaped segmented polishing pad 55 by the spindle 45, and polishes the back surface W2 of the wafer W held by suction on the holding surface 16 of the chuck table 12.

[0032] The polishing apparatus 1 is provided with a control unit 85 that controls all parts of the apparatus (see FIG. 1). The control unit 85 is configured with a processor that executes various processes, as well as a memory that stores various parameters, programs, etc. The control unit 85 controls various operations, such as polishing the back surface W2 of the wafer W and measuring the height and displacement of the polishing surface 56 of the segment polishing pad 55, in accordance with the control program stored in the memory.

[0033] Here, the control unit 85 is provided with a displacement map generation unit 86 and a quality determination unit 87. The displacement map generation unit 86 acquires the displacement in the direction perpendicular to the polishing surface 56 measured by the displacement measurement mechanism 70 as a measurement value, and generates a displacement map of the entire polishing surface 56 of each segment polishing pad 55 (polishing pad 52) using the measurement value.

[0034] 5A and 5B are diagrams showing examples of displacement maps. FIG. 5A shows an example of a displacement map M0 generated by the displacement map generator 86 in an unused state before polishing. The displacement map M0 is generated based on measurements of an unused polishing pad 52, and therefore represents images and data in which five segment polishing pads 55 have the same shape and are arranged at equal angles in the circumferential direction. FIG. 5B shows an example of a displacement map M1 generated by the displacement map generator 86 after polishing the wafer W. The displacement map M1 represents images and data in which the five segment polishing pads 55 are no longer uniform in shape due to chipping or other defects occurring on the outer edges of the pads.

[0035] The quality determination unit 87, for example, sets the displacement map M0 generated by the displacement map generation unit 86 as described above as the preset displacement map M0, and sets the displacement map M1 as the judgment target displacement map M1. The quality determination unit 87 then compares the preset displacement map M0 with the judgment target displacement map M1 generated by the displacement map generation unit 86 after polishing, and determines the quality of the segmented polishing pad 55 from the difference between the preset displacement map M0 and the judgment target displacement map M1 generated by the displacement map generation unit 86 after polishing. For example, the quality determination unit 87 calculates the difference in the area of ​​the segmented polishing pad 55 that is painted white between the preset displacement map M0 of FIG. 5A and the displacement map M1 of FIG. 5B. If the difference is equal to or less than a predetermined threshold, the quality determination unit 87 determines the segmented polishing pad 55 as good, and if the difference is greater than the threshold, the quality determination unit 87 determines the segmented polishing pad 55 as bad.

[0036] In the following description of the operation of each part of the polishing apparatus 1, unless a control entity is specified, it is assumed that the operation is controlled by a control signal sent from the control unit 85.

[0037] Next, a method for polishing a wafer W using the polishing apparatus 1 of the above embodiment will be described. When polishing the back surface W2 of a wafer W in the polishing apparatus 1, the wafer W is placed on the holding surface 16 of the chuck table 12 with tape T attached to the front surface W1 of the wafer W. Thereafter, the holding surface 16 is connected to the suction source 17, and the front surface W1 side of the wafer W is sucked and held by the chuck table 12 via the tape T, with the back surface W2 of the wafer W facing upward and exposed.

[0038] Next, the table moving mechanism 20 moves the chuck table 12 below the polishing mechanism 40, and the table rotating mechanism 30 rotates the chuck table 12. Then, the spindle 45 and polishing pad 52 in the polishing mechanism 40 are rotated, and the polishing feed mechanism 60 feeds the polishing mechanism 40 in a direction (-Z-axis direction) approaching the holding surface 16 of the chuck table 12. As a result, the polishing surface 56 of the segment polishing pad 55 of the rotating polishing pad 52 comes into contact with the back surface W2 of the wafer W, thereby polishing the wafer. At this time, the displacement measuring mechanism 70 and the dressing unit 80 are lowered via the cylinder 74. More specifically, the upper surface of the dress board 82 of the dressing unit 80 is positioned below the holding surface 16 of the chuck table 12, so that the polishing surface 56 does not come into contact with the dress board 82.

[0039] Next, we will explain how to measure the displacement of the polishing surface 56 of the segment polishing pad 55 of the polishing pad 52 when a new, unused polishing wheel 50 is attached (replaced) in the polishing mechanism 40 or each time a wafer W is polished. Fig. 4 is a view of the polishing mechanism and the configuration around the chuck table as seen from the X-axis direction, and is an explanatory diagram showing the displacement of the polishing surface being measured.

[0040] 4, in this measurement, the polishing surface 56 of the polishing pad 52 is positioned above the holding surface 16 of the chuck table 12 by the polishing feed mechanism 60. Thereafter, the cylinder 74 is driven to raise the displacement measuring mechanism 70, bringing the displacement measuring mechanism 70 closer to the polishing surface 56. Next, the table moving mechanism 20 moves the chuck table 12 in the Y-axis direction, and the displacement measuring mechanism 70 is moved inward from the inner periphery of the segment polishing pad 55.

[0041] From this state, the displacement map generating unit 86 controls the spindle motor (not shown) of the polishing mechanism 40 to rotate the polishing pad 52. The displacement map generating unit 86 also controls the driving of the Y-axis motor 24 of the table moving mechanism 20 to move the displacement measuring mechanism 70 in the Y-axis direction from the center of the polishing wheel 50 toward the outside. In other words, the table moving mechanism 20 moves the polishing pad 52 and the displacement measuring mechanism 70 relatively in the horizontal direction.

[0042] As a result, the five segmented polishing pads 55 and the displacement measurement mechanism 70 are moved relative to each other along a spiral trajectory as viewed from the Z-axis direction, and the displacement measurement mechanism 70 passes below the entire polishing surfaces 56 of the five segmented polishing pads 55. During this relative movement, the displacement measurement mechanism 70 measures displacements perpendicular to the polishing surfaces 56 at predetermined measurement intervals and outputs the results to the displacement map generation unit 86. Furthermore, the number of pulses from an encoder (not shown) built into the spindle motor and an encoder 25 (see FIG. 1) built into the Y-axis motor 24 are output to the displacement map generation unit 86. The displacement map generation unit 86 uses the number of pulses acquired from each encoder 25 and the measurement values ​​of the displacement measurement mechanism 70 to generate a displacement map of the entire polishing surfaces 56 of each segmented polishing pad 55, and outputs the map to the pass / fail judgment unit 87.

[0043] Here, the quality determination unit 87 designates the displacement map generated for an unused grinding wheel 50 from among the displacement maps generated by the displacement map generation unit 86 as a preset displacement map M0 (see FIG. 5A). Also, the displacement map generated for a grinding wheel 50 whose quality is to be determined after grinding processing as a determination target displacement map M1 (see FIG. 5B). The quality determination unit 87 compares the preset displacement map M0 with the determination target displacement map M1, and determines the quality of the segment polishing pad 55 from the difference between them.

[0044] The pass / fail judgment unit 87 can make various comparisons and judgments for each displacement map M0, M1 to judge pass / fail. For example, as described above, the pass / fail judgment unit 87 may calculate the difference in the area of ​​the segment polishing pad 55 in each displacement map M0, M1, and judge the pad to be pass if the difference is equal to or smaller than a predetermined threshold, or judge the pad to be fail if the difference is greater than the threshold.

[0045] Alternatively, the displacement map generating unit 86 may calculate the coordinate values ​​of the outer edge of the segment polishing pad 55 in each displacement map M0, M1, and the pass / fail determining unit 87 may compare the displacement (difference) of the coordinate values ​​in each displacement map M0, M1 with a predetermined threshold value to determine pass / fail. Furthermore, the displacement map generating unit 86 may calculate the surface roughness of the polishing surface 56 in each displacement map M0, M1, and the pass / fail determining unit 87 may compare the difference in surface roughness calculated by the displacement map generating unit 86 with a predetermined threshold value to determine pass / fail.

[0046] Next, a method for dressing the polishing surface 56 of the segmented polishing pad 55 using the dressing portion 80 will be described.

[0047] To dress the polishing surface 56, first, the cylinder 74 is driven to raise the dressing unit 80 so that the upper surface of the dressing board 82 is positioned above the polishing surface 56 and above the holding surface 16 of the chuck table 12. Next, the table moving mechanism 20 moves the chuck table 12 in the Y-axis direction, and the dressing unit 80 is moved below the center of the polishing wheel 50.

[0048] Thereafter, the polishing mechanism 40 is fed downward (in the -Z-axis direction) by a predetermined feed amount by the polishing feed mechanism 60 until the polishing surface 56 of each segmented polishing pad 55 is positioned below the upper surface of the dressing board 82. At this time, the dressing board 82 is positioned in the central region of the polishing pad 52 where each segmented polishing pad 55 is not formed. In this state, while rotating the polishing wheel 50, the dressing board 82 is fed from the center of the polishing pad 52, which is in the +Y-axis direction, outward. As a result, the dressing board 82 comes into contact with the polishing surface 56 of each rotating segmented polishing pad 55, and the entire polishing surface 56 of each rotating segmented polishing pad 55 is dressed by the dressing board 82.

[0049] Next, an example of the flow of checking each segment polishing pad 55, which is performed after polishing wafers W in any order and before polishing the next wafer W, when polishing multiple wafers W with the polishing apparatus 1 of this embodiment will be described with reference to the flow chart of Fig. 6. Fig. 6 is a flow chart showing the flow of checking the segment polishing pads.

[0050] Here, it is assumed that the above-described preset displacement map M0 (see FIG. 5A) has been generated and stored for each segmented polishing pad 55 to be checked. After polishing the back surface W2 of the wafer W, in step S01 of FIG. 5, the displacement of the polishing surface 56 of the segmented polishing pad 55 is measured via the displacement measurement mechanism 70 or the like as described above. Based on the measurement results of step S01, in step S02, the displacement map generator 86 generates the judgment target displacement map M1 (see FIG. 5B) as described above.

[0051] After step S02 is performed, in step S03, the displacement map M0 preset in the quality judgment unit 87 as described above is compared with the judgment target displacement map M1, and the difference is used to judge the quality of the segment polishing pad 55. If the quality judgment result is that the segment polishing pad 55 is good (S03: Yes), the process proceeds to step S04, where the polishing process of the next wafer W is started.

[0052] If the result of the pass / fail judgment in step S03 is that the polishing wheel 50 is determined to be defective (S03: No), in step S05, the polishing surface 56 of the segment polishing pad 55 is dressed using the dressing unit 80 as described above. After performing step S05, in step S06, the control unit 85 adds "1" to the number of dressings N for each polishing wheel 50.

[0053] In step S07, the control unit 85 compares the number of dressing times N, which was increased in step S06, with the preset designated number of dressing times C. If the number of dressing times N is equal to or less than the designated number of dressing times C (designated number of dressing times C≧number of dressing times N, S07: Yes), the process returns to step S01. By returning to step S01, the displacement of the polishing surface 56 of the dressed segmented polishing pad 55 is measured again, a judgment target displacement map M1 is generated, and the quality judgment unit 87 judges whether the polishing surface 56 is good or bad (steps S01 to S03).

[0054] In the comparison in step S07, if the dressing count N is greater than the designated count C (designated count C<dressing count N, S07: No), polishing will be impossible even with the dressed segmented polishing pad 55. Therefore, in step S08, the control unit 85 notifies an operator or the like via a display device or output device (not shown) to replace the polishing wheel 50 with a new one without proceeding to polishing the next wafer W. This makes it possible to prevent portions of the wafer W from being left unpolished due to a defective segmented polishing pad 55 measured by the displacement measuring mechanism 70.

[0055] According to the above embodiment, the displacement map generator 86 generates a preset displacement map M0 and a judgment target displacement map M1, and the quality judger 87 compares the displacement maps M0 and M1 to judge the quality of the segment polishing pad 55. As a result, if a chip or the like occurs in one of the multiple (five in this embodiment) arranged segment polishing pads 55, it is possible to control the polishing surface 56 to be dressed or to notify an operator or the like to prompt replacement of the polishing wheel 50. This makes it possible to prevent polishing the wafer W with a segment polishing pad 55 that is defective due to a chip or the like, and to avoid a situation in which a gettering layer is not formed on the wafer W.

[0056] The present invention is not limited to the above-described embodiment, and various modifications can be made to the present invention. In the above-described embodiment, the size and shape shown in the accompanying drawings are not limited to these, and can be modified as appropriate within the scope of the effects of the present invention. In addition, the present invention can be modified as appropriate without departing from the scope of the object of the present invention.

[0057] The polishing wheel 50 in the above embodiment is equipped with a polishing pad 52 consisting of five segmented polishing pads 55, but a ring-shaped polishing pad may also be used instead of segments. Even with a ring-shaped polishing pad, chipping may occur in the center of the polishing wheel 50, and it is possible to measure the displacement perpendicular to the polishing surface in the same manner as described above and generate a displacement map.

[0058] Various modifications can be made to the displacement measuring mechanism 70 as long as it can measure displacement in the same manner as in the above embodiment. For example, the displacement measuring mechanism 70 may be a displacement sensor that includes an oscillator that emits ultrasonic vibrations and an oscillator that receives reflected vibrations and measures the displacement of the polishing surface 56.

[0059] 7, the displacement measuring mechanism 90 can be modified to a configuration using a sensor 91 configured with an AE sensor or an acceleration sensor. FIG. 7 is an explanatory diagram of a displacement measuring mechanism according to a modified example. In the modified example of FIG. 7, the displacement measuring mechanism 90 includes, in addition to the sensor 91, a cylindrical dressing pin 92 (dressing portion) that comes into contact with the polishing surface 56 of the polishing pad 52 to dress the polishing surface 56, and a plate 93 on which the dressing pin 92 is erected. The sensor 91 is disposed on the plate 93.

[0060] In the modified example shown in Figure 7, the amplitude (vibration) transmitted to the plate 93 when the polishing pad 52 is dressed by the dressing pin 92 is measured by a sensor 91, and the displacement perpendicular to the polishing surface 56 is measured based on the magnitude (value) of the amplitude. The sensor 91 may be provided inside the dress pin 92. Furthermore, the dress pin 92 is not limited to a cylindrical shape, but may be a polygonal pillar or the like. [Industrial Applicability]

[0061] As described above, the present invention has the effect of preventing polishing when a chip has occurred in the polishing pad, and can avoid the situation where a gettering layer is not formed when forming a gettering layer on a wafer during polishing with a polishing pad. [Explanation of symbols]

[0062] 1: Polishing device 12: Chuck table 20: Table movement mechanism (horizontal movement mechanism) 40: Polishing mechanism 52: Polishing pad 55: Segmented polishing pad 56: Polished surface 70: Displacement measurement mechanism (displacement measuring device) 86: Displacement map generation unit 87: Good / bad judgment section 90: Displacement measurement mechanism 91: Sensor 92: Dress pin (dress part) M0: Displacement map M1: Displacement map W: wafer

Claims

1. A polishing apparatus comprising: a chuck table for holding a wafer; and a polishing mechanism for rotating a polishing pad to polish the wafer held on the chuck table with a polishing surface of the polishing pad, a displacement measuring mechanism for measuring a displacement of the polishing pad in a direction perpendicular to the polishing surface; a horizontal movement mechanism that moves the polishing pad and the displacement measurement mechanism relatively in a horizontal direction; a displacement map generating unit that generates a displacement map of the entire polishing surface using the displacement measured by the displacement measuring mechanism when the horizontal movement mechanism is used; a quality determining section that compares the displacement map generated by the displacement map generating section with a preset displacement map and determines the quality of the polishing pad based on the difference between the two.

2. 2. A polishing apparatus according to claim 1, wherein said displacement measuring mechanism is a displacement measuring device that measures displacement in a direction perpendicular to said polishing surface.

3. 2. A polishing apparatus as described in claim 1, wherein the displacement measuring mechanism comprises a dressing portion that contacts the polishing surface and dresses the polishing surface, and a sensor that measures vibration of the dressing portion when dressing the polishing surface, and the value measured by the sensor is taken as the displacement.

Images