Polishing device and polishing method

Abstract

The present invention relates to a polishing device for polishing a substrate such as a wafer. This polishing device (1) comprises: a substrate holding device (5) that holds a substrate (W) and performs a circular motion / rotation operation of the substrate (W); and a polishing head (50A) that presses a polishing tool (3A) against a flat surface part (2a) of the substrate (W). The substrate holding device (5) comprises: a holding stage (10) that holds the substrate (W); a stage circular motion mechanism (12) that circularly moves the holding stage (10) such that the holding stage (10) moves along a circumference having a prescribed radius (R1); and a stage rotation mechanism (14) that rotates the holding stage (10) about the axis (CP) thereof. The dimension of a substrate pressing surface (PS1) of the polishing tool (3A) in the radial direction of the holding stage (10) is equal to or less than the radius of the substrate (W).

Description

Polishing apparatus and polishing method

[0001] The present invention relates to a polishing apparatus and a polishing method for polishing a substrate such as a wafer.

[0002] The manufacturing process for silicon-on-insulator (SOI) substrates, through silicon vias (TSVs), and power devices (semiconductor elements for power applications) involves a process called backgrinding, in which the backside of a substrate such as a wafer is ground to thin the substrate. This backgrinding process uses a grinding tool called a backgrinder to grind the backside of the substrate until the substrate is, for example, 300 μm or less in thickness. Specifically, the backside of the substrate is pressed against a rotating backgrinder, and the backside of the substrate is ground until the substrate reaches the desired thickness.

[0003] JP 2018-134710 A

[0004] The uniformity of the thickness within the substrate surface after back-grinding can affect the processing accuracy in subsequent processes, etc. However, thickness variations of the order of several hundred nanometers to several micrometers can occur within the substrate surface after back-grinding.

[0005] Therefore, the present invention provides a polishing apparatus and a polishing method that can locally polish a substrate to improve the thickness uniformity within the substrate surface.

[0006] In one aspect, a polishing apparatus for polishing a flat portion of a substrate is provided, comprising: a substrate holding device that holds the substrate and performs a circular rotation operation to rotate the substrate while moving it in a circular motion; and a polishing head that presses a polishing tool against the flat portion of the substrate, wherein the substrate holding device comprises a holding stage that holds the substrate; a stage circular motion mechanism connected to the holding stage and that causes the holding stage to move in a circular motion so that the holding stage moves on a circumference having a predetermined radius; and a stage rotation mechanism connected to the holding stage via the stage circular motion mechanism and that rotates the holding stage around its axis, wherein the substrate pressing surface of the polishing tool has a dimension in the radial direction of the holding stage that is less than the radius of the substrate.

[0007] In one aspect, the period of the circular motion of the holding stage is shorter than the time it takes for the holding stage to rotate once around the axis. In one aspect, the stage circular motion mechanism includes a plurality of eccentric shafts connected to the holding stage and an eccentric shaft rotation device that rotates the plurality of eccentric shafts, each of the plurality of eccentric shafts having a first shaft portion rotatably connected to the holding stage and a second shaft portion eccentric from the first shaft portion by the predetermined radius and connected to the eccentric shaft rotation device, and the stage rotation mechanism includes a table base to which the second shaft portions of each of the plurality of eccentric shafts are rotatably connected, and a table base rotation device that rotates the table base. In one aspect, the polishing apparatus further includes an operation control unit that controls the operation of the polishing head, and the operation control unit is configured to generate thickness distribution data of the substrate, determine a polishing target area of ​​the flat portion of the substrate based on the thickness distribution data, and cause the polishing head to press the polishing tool against the polishing target area with a pressing force that is greater than the pressing force against other areas. In one aspect, the polishing apparatus further includes a polishing head moving mechanism that moves the polishing head in a radial direction of the holding stage, and the operation control unit is configured to cause the polishing head moving mechanism to move the polishing head in the radial direction of the holding stage to a position corresponding to the region to be polished.In one aspect, the polishing apparatus further includes a thickness measuring device that measures a thickness of the substrate, and the operation control unit is electrically connected to the thickness measuring device and configured to generate the thickness distribution data based on the thickness measured by the thickness measuring device and the measurement position of the thickness.

[0008] In one aspect, the polishing apparatus further includes an operation control unit that controls the circular rotation operation of the substrate holding device to include a forward rotation operation that rotates the holding stage about the axis in the same direction as the circular motion of the holding stage and a reverse rotation operation that rotates the holding stage about the axis in the opposite direction to the circular motion of the holding stage.In one aspect, the polishing apparatus further includes a polishing head moving mechanism that moves the polishing head in the radial direction of the holding stage, and an operation control unit that controls the operation of the polishing head and the polishing head moving mechanism to include a first polishing operation that shifts the polishing head from a reference position radially outward of the substrate by a first offset amount and causes the polishing head to press the polishing tool against the flat surface of the substrate, and a second polishing operation that shifts the polishing head from the reference position radially inward of the substrate by a second offset amount and causes the polishing head to press the polishing tool against the flat surface of the substrate. In one aspect, the polishing head is a plurality of polishing heads arranged along a radial direction of the holding stage, and the polishing apparatus further includes an operation control unit configured to individually control the pressing force of each of the plurality of polishing heads against the flat surface of the substrate. In one aspect, the polishing tool is a polishing tape having abrasive grains on its surface or a grinding stone.

[0009] In one aspect, a polishing method for polishing a flat portion of a substrate includes holding the substrate on a holding stage, rotating the holding stage around its axis while circularly moving the holding stage so that the holding stage moves on a circumference having a predetermined radius, and pressing a polishing tool against the flat portion of the substrate with a polishing head during the circular rotation, wherein the substrate pressing surface of the polishing tool has a dimension in the radial direction of the holding stage that is equal to or less than the radius of the substrate. In one aspect, a period of the circular motion of the holding stage is shorter than the time it takes for the holding stage to rotate once around the axis. In one aspect, the polishing method further includes generating thickness distribution data for the substrate and determining a polishing target area of ​​the flat portion of the substrate based on the thickness distribution data, wherein the pressing force of the polishing head against the polishing target area is greater than the pressing force of the polishing head against other areas. In one aspect, the polishing method further includes moving the polishing head to a position corresponding to the area to be polished in a radial direction of the holding stage before pressing the polishing tool against the flat surface portion of the substrate with the polishing head. In one aspect, the polishing method further includes measuring a thickness of the substrate with a thickness measuring device, and generating the thickness distribution data based on the thickness measured by the thickness measuring device and the measurement position of the thickness.

[0010] In one aspect, the circular rotation operation includes a forward rotation operation in which the holding stage is rotated about the axis in the same direction as the circular motion of the holding stage, and a reverse rotation operation in which the holding stage is rotated about the axis in the opposite direction to the circular motion of the holding stage. In one aspect, pressing the polishing tool against the flat surface of the substrate with the polishing head during the circular rotation operation includes performing a first polishing operation in which the polishing head is pressed against the flat surface of the substrate with the polishing head in a state where the polishing head is shifted from a reference position by a first offset amount toward the outside in the radial direction of the substrate during the circular rotation operation, and a second polishing operation in which the polishing head is pressed against the flat surface of the substrate with the polishing head in a state where the polishing head is shifted from the reference position by a second offset amount toward the inside in the radial direction of the substrate during the circular rotation operation. In one embodiment, pressing the polishing tool against the flat surface of the substrate with the polishing head comprises pressing a plurality of polishing tools against the flat surface of the substrate with a plurality of polishing heads arranged along a radial direction of the holding stage, respectively, and includes individually controlling the pressing force of each of the plurality of polishing heads against the flat surface of the substrate. In one embodiment, the polishing tool is a polishing tape having abrasive grains on its surface or a grinding stone.

[0011] By pressing a substrate pressing surface, which has a diameter smaller than that of the substrate, against the substrate, the region of the substrate to be polished can be locally polished. As a result, the thickness uniformity within the surface of the substrate can be improved. Furthermore, by circularly moving the holding stage and rotating the holding stage, the small-diameter substrate pressing surface can be efficiently brought into contact with the substrate on the holding stage, thereby improving polishing efficiency.

[0012] 4 is a side view showing an embodiment of a polishing apparatus; FIG. 5 is a top view of the polishing apparatus shown in FIG. 1; FIG. 6 is a top view showing an embodiment of an eccentric shaft rotation device; FIG. 7 is a front view showing an embodiment of a polishing head; FIG. 8 is a side view of the polishing head as seen from the arrow A in FIG. 4; FIG. 9 is a bottom view of the polishing head as seen from the arrow B in FIG. 4; FIG. 10 is a schematic view showing how the polishing head presses a polishing tape against a first surface of a substrate; FIG. 11 is a diagram explaining a trajectory when the substrate pressing surface of the polishing tape moves relative to the substrate due to the circular rotation operation of the holding stage; FIG. 12 is a flowchart showing an embodiment of a method for polishing a substrate; FIG. 13 is a schematic view explaining a forward rotation operation, which is one type of circular rotation operation of the holding stage; FIG. 14 is a schematic view explaining a reverse rotation operation, which is one type of circular rotation operation of the holding stage; FIG. 15 is a graph showing an example of changes in the relationship between the radial position of the substrate and the polishing rate depending on the type of circular rotation operation of the holding stage; FIG. 16 is a schematic view explaining another embodiment of a method for polishing a substrate; FIG. 17 is a graph showing an example of the relationship between the radial position of the substrate and the polishing rate when the substrate is polished at a reference position and when the substrate is polished including a first polishing operation and a second polishing operation. FIG. 10 is a schematic view showing another embodiment of the grinding tool.

[0013] Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side view showing one embodiment of a polishing apparatus 1, and FIG. 2 is a top view of the polishing apparatus 1 shown in FIG. 1. The polishing apparatus 1 is an apparatus for polishing a planar portion of a substrate W, such as a wafer. The substrate W has a first surface 2a, which is a non-device surface, and a second surface 2b, which is a device surface. The first surface 2a, which is the non-device surface, is the back surface of the substrate W on which no devices are formed or on which no devices are planned to be formed. The second surface 2b, which is the device surface, is the surface opposite to the first surface 2a and on which devices are formed or are planned to be formed. The planar portion of the substrate W is the first surface 2a or the second surface 2b. In this embodiment, the surface to be polished of the substrate W is the first surface 2a. In another embodiment, the surface to be polished of the substrate W may be the second surface 2b of the substrate W.

[0014] The polishing apparatus 1 shown in Figures 1 and 2 includes a substrate holding device 5 that holds a substrate W and performs a circular rotation operation to rotate the substrate W while causing it to move in a circular motion, and a polishing head assembly 8 that presses polishing tapes 3A, 3B, and 3C, which are examples of polishing tools, against a first surface 2a of the substrate W held by the substrate holding device 5 to polish the first surface 2a of the substrate W. The substrate holding device 5 includes a holding stage 10 that holds the substrate W by vacuum suction, a stage circular motion mechanism 12 that causes the holding stage 10 to move in a circular motion, and a stage rotation mechanism 14 that rotates the holding stage 10 about its axis CP. In this embodiment, the substrate W is supported horizontally on the holding stage 10 with the first surface 2a, which is the surface to be polished, facing upward. The axis passing through the center of the substrate W coincides with the axis CP of the holding stage 10.

[0015] The stage circular motion mechanism 12 includes a plurality of eccentric shafts 16 (four in this embodiment) connected to the holding stage 10, and an eccentric shaft rotation device 20 that rotates the plurality of eccentric shafts 16. Although the stage circular motion mechanism 12 of this embodiment includes four eccentric shafts 16, the number of eccentric shafts 16 is not limited to this embodiment. Each of the plurality of eccentric shafts 16 includes a first shaft portion 16a rotatably connected to the holding stage 10, a second shaft portion 16b that is eccentric from the first shaft portion 16a by a predetermined radius R1 and connected to the eccentric shaft rotation device 20, and an intermediate shaft portion 16c that connects the first shaft portion 16a and the second shaft portion 16b.

[0016] The first shaft portion 16a and the second shaft portion 16b of each of the multiple eccentric shafts 16 extend parallel to each other. One end of the first shaft portion 16a is rotatably connected to the holding stage 10 via a bearing 18. The other end of the first shaft portion 16a is fixed to the upper surface of the intermediate shaft portion 16c. One end of the second shaft portion 16b is fixed to the lower surface of the intermediate shaft portion 16c. The first shaft portion 16a, the intermediate shaft portion 16c, and the second shaft portion 16b may be separate structures or may be an integrated structure.

[0017] The stage circular motion mechanism 12 includes a plurality of counterweights 17 fixed to the other ends of the plurality of second shaft portions 16 b, respectively. The weight of the counterweights 17 is determined by the centrifugal force acting on the counterweights 17, which cancels out the centrifugal force generated in the radial direction from the second shaft portion 16 b toward the first shaft portion 16 a when the eccentric shaft 16 rotates around the second shaft portion 16 b.

[0018] 3 is a top view showing one embodiment of the eccentric shaft rotation device 20. The eccentric shaft rotation device 20 includes a plurality of (four in this embodiment) planetary gears 22 respectively connected to a plurality of second shaft portions 16b, a sun gear 23 meshing with the plurality of planetary gears 22, a drive shaft 25 connected to the sun gear 23, a pulley 27 attached to the drive shaft 25, a motor 30, a pulley 28 attached to a rotation shaft 30a of the motor 30, and a belt 29 wound around these pulleys 27, 28. The plurality of planetary gears 22 are arranged around the sun gear 23. The rotation shaft 30a of the motor 30 extends parallel to the drive shaft 25.

[0019] When the motor 30 is driven, the drive shaft 25 and the sun gear 23 rotate via the pulleys 27, 28 and the belt 29. When the sun gear 23 rotates, the plurality of planetary gears 22 rotate in response to the rotation of the sun gear 23. This rotation of the plurality of planetary gears 22 causes the plurality of eccentric shafts 16 to rotate about the plurality of second shaft portions 16b, and the holding stage 10 connected to the plurality of eccentric shafts 16 and the substrate W on the holding stage 10 perform circular motion so as to move on a circumference having a radius R1. This circular motion is translational circular motion.

[0020] The configuration of the eccentric shaft rotating device 20 is not limited to the above embodiment. For example, the eccentric shaft rotating device 20 may have a plurality of gears instead of the pulleys 27 and 28 and the belt 29.

[0021] 1 , the stage rotation mechanism 14 includes a table base 32 to which the second shaft portions 16b of the multiple eccentric shafts 16 are rotatably connected via bearings 33, a base ring 34 connected to the table base 32 via bearings 35, and a table base rotation device 37 that rotates the table base 32. The multiple eccentric shafts 16 are rotatably supported by the bearings 33 held in the table base 32. The table base 32 is rotatably supported by the bearings 35. The base ring 34 is fixed to a base plate 36.

[0022] The table base rotating device 37 includes a connecting member 38 connected to the table base 32, a pulley 39 attached to the connecting member 38, a motor 42, a pulley 40 attached to a rotating shaft 42a of the motor 42, and a belt 41 looped around these pulleys 39 and 40. The rotating shaft 42a of the motor 42 extends parallel to the rotation axis of the connecting member 38.

[0023] When the motor 42 is driven, the connecting member 38 and the table base 32 rotate via the pulleys 39, 40 and the belt 41. When the table base 32 rotates, the holding stage 10 and the substrate W on the holding stage 10 rotate about their axis CP via the multiple eccentric shafts 16 connected to the table base 32.

[0024] The configuration of the table base rotating device 37 is not limited to the above embodiment. For example, the table base rotating device 37 may have a plurality of gears instead of the pulleys 39 and 40 and the belt 41.

[0025] In this embodiment, the substrate holding device 5 causes the stage circular motion mechanism 12 to cause the holding stage 10 to perform circular motion (translational circular motion) so that the holding stage 10 moves on a circumference having a radius R1, while the stage rotation mechanism 14 rotates the holding stage 10 about its axis CP. In this specification, the operation of rotating the holding stage 10 about its axis CP while causing the holding stage 10 to perform circular motion using the substrate holding device 5 is defined as a circular rotation operation.

[0026] The rotation speed of the multiple eccentric shafts 16 by the eccentric shaft rotation device 20 and the rotation speed of the table base 32 by the table base rotation device 37 can be controlled separately. The period of the circular motion of the holding stage 10 is shorter than the time it takes for the holding stage 10 to make one rotation about the axis CP. In other words, the time it takes for the stage circular motion mechanism 12 (more specifically, the eccentric shaft rotation device 20) of the substrate holding device 5 to make one rotation of the multiple eccentric shafts 16 is shorter than the time it takes for the stage rotation mechanism 14 (more specifically, the table base rotation device 37) to make one rotation of the table base 32.

[0027] The polishing head assembly 8 includes multiple (three in this embodiment) polishing heads 50A, 50B, and 50C, and polishing tape supply mechanisms 60A, 60B, and 60C that supply polishing tapes 3A, 3B, and 3C to the polishing heads 50A, 50B, and 50C, respectively. The polishing tape supply mechanisms 60A, 60B, and 60C individually feed the polishing tape 3A to the polishing head 50A, the polishing tape 3B to the polishing head 50B, and the polishing tape 3C to the polishing head 50C. The multiple polishing heads 50A, 50B, and 50C are disposed above the holding stage 10 of the substrate holding device 5. The polishing heads 50A, 50B, and 50C are disposed at different distances from the axis CP of the holding stage 10. In this embodiment, as shown in FIG. 1 , the polishing heads 50A, 50B, and 50C are arranged along the radial direction of the holding stage 10.

[0028] In one embodiment, the polishing head assembly 8 may include a single polishing head, or may include two, four, or more polishing heads. The four or more polishing heads may be arranged along the radial direction of the holding stage 10, or may be arranged radially around the axis CP of the holding stage 10.

[0029] The polishing heads 50A, 50B, and 50C and the polishing tape supply mechanisms 60A, 60B, and 60C basically have the same configuration, so the following will describe the polishing head 50A and the polishing tape supply mechanism 60A. Fig. 4 is a front view showing one embodiment of the polishing head 50A, Fig. 5 is a side view of the polishing head 50A as seen from the arrow A in Fig. 4, and Fig. 6 is a bottom view of the polishing head 50A as seen from the arrow B in Fig. 4.

[0030] As shown in FIG. 5 , the polishing head 50A includes a pressing member 52 that presses the polishing tape 3A against the polishing target surface (first surface 2 a) of the substrate W, and a pressing actuator 54 that applies a pressing force to the pressing member 52 against the polishing target surface (first surface 2 a) of the substrate W. An example of the pressing actuator 54 is an air cylinder. As shown in FIG. 6 , the pressing member 52 in this embodiment has a circular shape. The shape of the pressing member 52 is not limited to this embodiment and may be other shapes, such as an annular shape or a rectangular shape. In one embodiment, the shapes and sizes of the pressing members 52 of the polishing heads 50A, 50B, and 50C may be different.

[0031] The polishing tape supply mechanism 60A is configured to feed the polishing tape 3A in its longitudinal direction. The polishing tape supply mechanism 60A includes a tape supply reel 64 to which one end of the polishing tape 3A is connected, a tape take-up reel 65 to which the other end of the polishing tape 3A is connected, and a brake mechanism 67 that applies a predetermined tension to the polishing tape 3A. The tape supply reel 64, the tape take-up reel 65, and the brake mechanism 67 are disposed inside the outer wall 61.

[0032] The tape take-up reel 65 is connected to a reel motor 69 housed in a motor casing 62. The reel motor 69 is controlled to feed the polishing tape 3A at a constant speed. When the reel motor 69 is driven, the polishing tape 3A is fed from the tape feed reel 64 to the tape take-up reel 65 via the polishing head 50A. The brake mechanism 67 has a brake reel 67a and a support roller 67b. The polishing tape 3A is sandwiched between the brake reel 67a and the support roller 67b. The brake mechanism 67 can apply tension to the polishing tape 3A by applying rotational resistance to the brake reel 67a. The polishing tape 3A is supplied to the polishing head 50A so that the polishing surface of the polishing tape 3A faces the first surface 2a of the substrate W.

[0033] The polishing head 50A is equipped with tape stoppers 56 that limit the widthwise position of the polishing tape 3A. The tape stoppers 56 are disposed upstream and downstream of the pressing member 52 in the traveling direction of the polishing tape 3A, and are disposed on both sides of the polishing tape 3A in the widthwise direction of the polishing tape 3A. The tape stoppers 56 guide the widthwise position of the polishing tape 3A so that the polishing tape 3A is positioned directly below the pressing member 52.

[0034] In this embodiment, polishing tape supply mechanisms 60A to 60C are provided individually to supply polishing tapes 3A to 3C to polishing heads 50A to 50C, respectively. However, in one embodiment, a single polishing tape supply mechanism is provided for polishing heads 50A to 50C, and the feeding operation of polishing tapes 3A to 3C to polishing heads 50A to 50C may be performed collectively by the single polishing tape supply mechanism.

[0035] 7 is a schematic diagram showing the polishing head 50A pressing the polishing tape 3A against the first surface 2a of the substrate W. As shown in FIG. 7, when the pressing actuator 54 of the polishing head 50A presses the pressing member 52 toward the first surface 2a of the substrate W, the polishing surface of the polishing tape 3A is pressed against the first surface 2a of the substrate W by the pressing member 52. The polishing tape 3A has abrasive grains on its surface (polishing surface). The polishing head 50A polishes the first surface 2a of the substrate W by pressing the polishing tape 3A against the first surface 2a of the substrate W from the back side of the polishing tape 3A with the pressing member 52.

[0036] The substrate pressing surface PS1 of the polishing tape 3A has a dimension in the radial direction of the holding stage 10 (the radial direction of the substrate W on the holding stage 10) that is equal to or less than the radius of the substrate W. The dimension of the substrate pressing surface PS1 of the polishing tape 3A is a dimension that allows localized polishing of the surface to be polished of the substrate W (the first surface 2a in this embodiment). In one embodiment, the dimension of the substrate pressing surface PS1 of the polishing tape 3A is 10 mm. In this embodiment, the shape of the substrate pressing surface PS1 of the polishing tape 3A corresponds to the shape of the pressing member 52 of the polishing head 50A.

[0037] Similarly, in the polishing head 50B, when the pressing actuator 54 of the polishing head 50B presses the pressing member 52 toward the first surface 2a of the substrate W, the polishing surface of the polishing tape 3B is pressed against the first surface 2a of the substrate W by the pressing member 52. The polishing tape 3B has abrasive grains on its front surface (polishing surface). The polishing head 50B polishes the first surface 2a of the substrate W by pressing the polishing tape 3B against the first surface 2a of the substrate W from the back side of the polishing tape 3B with the pressing member 52.

[0038] The substrate pressing surface PS2 of the polishing tape 3B has a dimension in the radial direction of the holding stage 10 (the radial direction of the substrate W on the holding stage 10) that is equal to or less than the radius of the substrate W. The dimension of the substrate pressing surface PS2 of the polishing tape 3B is a dimension that allows localized polishing of the surface to be polished of the substrate W (first surface 2a in this embodiment). In one embodiment, the dimension of the substrate pressing surface PS2 of the polishing tape 3B is 10 mm. In this embodiment, the shape of the substrate pressing surface PS2 of the polishing tape 3B corresponds to the shape of the pressing member 52 of the polishing head 50B.

[0039] Similarly, in the polishing head 50C, when the pressing actuator 54 of the polishing head 50C presses the pressing member 52 toward the first surface 2a of the substrate W, the polishing surface of the polishing tape 3C is pressed against the first surface 2a of the substrate W by the pressing member 52. The polishing tape 3C has abrasive grains on its front surface (polishing surface). The polishing head 50C polishes the first surface 2a of the substrate W by pressing the polishing tape 3C against the first surface 2a of the substrate W from the back side of the polishing tape 3C with the pressing member 52.

[0040] The substrate pressing surface PS3 of the polishing tape 3C has a dimension in the radial direction of the holding stage 10 (the radial direction of the substrate W on the holding stage 10) that is equal to or less than the radius of the substrate W. The dimension of the substrate pressing surface PS3 of the polishing tape 3C is a dimension that allows localized polishing of the surface to be polished of the substrate W (the first surface 2a in this embodiment). In one embodiment, the dimension of the substrate pressing surface PS3 of the polishing tape 3C is 10 mm. In this embodiment, the shape of the substrate pressing surface PS3 of the polishing tape 3C corresponds to the shape of the pressing member 52 of the polishing head 50C.

[0041] Due to the circular rotation of the holding stage 10 by the substrate holding device 5 described above, the substrate pressing surfaces PS1 to PS3 of the polishing tapes 3A to 3C move relatively to the substrate W on the holding stage 10 on a circumference centered on the axis CP of the holding stage 10 while moving circularly relative to the substrate W on the holding stage 10. Figure 8 is a diagram illustrating the trajectories of the substrate pressing surfaces PS1 to PS3 of the polishing tapes 3A to 3C when moving relative to the substrate W due to the circular rotation of the holding stage 10. The substrate pressing surface PS1 of the polishing tape 3A moves relatively to the substrate W on a circumference of radius R2 centered on the axis CP of the holding stage 10 while moving circularly relative to the substrate W so as to move on a circumference having radius R1. The radius R2 is the distance from the axis CP of the holding stage 10 to the substrate pressing surface PS1 of the polishing tape 3A (i.e., the pressing member 52 of the polishing head 50A).

[0042] The substrate pressing surface PS2 of the polishing tape 3B moves relative to the substrate W on a circumference of radius R3 centered on the axis CP of the holding stage 10, while circularly moving relative to the substrate W so as to move on a circumference of radius R1. Radius R3 is the distance from the axis CP of the holding stage 10 to the substrate pressing surface PS2 of the polishing tape 3B (i.e., the pressing member 52 of the polishing head 50B). The substrate pressing surface PS3 of the polishing tape 3C moves relative to the substrate W on a circumference of radius R4 centered on the axis CP of the holding stage 10, while circularly moving relative to the substrate W so as to move on a circumference of radius R1. Radius R4 is the distance from the axis CP of the holding stage 10 to the substrate pressing surface PS3 of the polishing tape 3C (i.e., the pressing member 52 of the polishing head 50C).

[0043] The substrate pressing surfaces PS1 to PS3 perform circular motion relative to the substrate W in the same direction as the direction of the circular motion of the holding stage 10. The substrate pressing surfaces PS1 to PS3 move relative to the substrate W on a circumference centered on the axis CP in a direction opposite to the direction of rotation of the holding stage 10 about the axis CP. As described above, the period of the circular motion of the holding stage 10 is shorter than the time it takes for the holding stage 10 to rotate once about the axis CP. Therefore, as shown in Figure 8, the trajectories of the substrate pressing surfaces PS1 to PS3 relative to the substrate W are trajectories that go around circles having radii R2, R3, and R4, respectively, in a spiral manner on a plane.

[0044] In one embodiment, the radius R1 is the same as the radius of the substrate pressing surfaces PS1 to PS3, while in other embodiments, the radius R1 may be smaller than the radius of the substrate pressing surfaces PS1 to PS3 or may be larger than the radius of the substrate pressing surfaces PS1 to PS3.

[0045] 1 and 2, the polishing apparatus 1 further includes a polishing head moving mechanism 70 that moves the polishing heads 50A to 50C in the radial direction of the holding stage 10. The polishing head moving mechanism 70 of this embodiment moves the polishing head assembly 8 (i.e., the polishing heads 50A to 50C and the polishing tape supply mechanisms 60A to 60C) in the radial direction of the holding stage 10. The polishing heads 50A to 50C are connected to the polishing head moving mechanism 70. The polishing head moving mechanism 70 moves the polishing heads 50A to 50C and the polishing tape supply mechanisms 60A to 60C along guide rails 75 toward the radially inward or radially outward direction of the holding stage 10.

[0046] In this embodiment, a single polishing head moving mechanism 70 is provided for the polishing heads 50A to 50C and the polishing tape supply mechanisms 60A to 60C, but in one embodiment, multiple polishing head moving mechanisms are provided for the polishing heads 50A to 50C and the polishing tape supply mechanisms 60A to 60C, and the multiple polishing head moving mechanisms may be configured to individually move the combination of polishing head 50A and polishing tape supply mechanism 60A, the combination of polishing head 50B and polishing tape supply mechanism 60B, and the combination of polishing head 50C and polishing tape supply mechanism 60C.

[0047] The polishing apparatus 1 further includes a thickness measuring device 80 that measures the thickness of the substrate W, and a thickness measuring device moving mechanism 85 that moves the thickness measuring device 80 in the radial direction of the holding stage 10. The thickness measuring device 80 of this embodiment is an optical thickness measuring device configured to guide light to the first surface 2 a of the substrate W and determine the thickness of the substrate W based on the light reflected from the substrate W. The specific configuration of the thickness measuring device 80 is not limited to this embodiment as long as it can measure the thickness of the substrate W. The thickness measuring device 80 is connected to the thickness measuring device moving mechanism 85. The thickness measuring device moving mechanism 85 is configured to move the thickness measuring device 80 along the guide rails 75 toward the radially inward or radially outward of the holding stage 10.

[0048] In one embodiment, the polishing apparatus 1 does not need to include the thickness measuring device 80 and the thickness measuring device moving mechanism 85 .

[0049] The polishing apparatus 1 further includes an operation control unit 100 that controls the operation of each component of the polishing apparatus 1. Specifically, the stage circular motion mechanism 12 (more specifically, the eccentric shaft rotation device 20) and stage rotation mechanism 14 (more specifically, the table base rotation device 37) of the substrate holding device 5, the polishing heads 50A-50C, the polishing tape supply mechanisms 60A-60C, the polishing head moving mechanism 70, the thickness measurement device 80, and the thickness measurement device moving mechanism 85 are electrically connected to the operation control unit 100. The operation of the stage circular motion mechanism 12 (more specifically, the eccentric shaft rotation device 20) and stage rotation mechanism 14 (more specifically, the table base rotation device 37) of the substrate holding device 5, the polishing heads 50A-50C, the polishing tape supply mechanisms 60A-60C, the polishing head moving mechanism 70, and the thickness measurement device moving mechanism 85 is controlled by the operation control unit 100. The thickness of the substrate W measured by the thickness measurement device 80 is sent to the operation control unit 100.

[0050] The operation control unit 100 includes at least one computer. The operation control unit 100 includes a storage device 100a that stores a program and an arithmetic unit 100b that executes calculations in accordance with the program. The storage device 100a includes a main storage device (e.g., random access memory) accessible by the arithmetic unit 100b and an auxiliary storage device (e.g., a hard disk drive or solid state drive) that stores the program. The arithmetic unit 100b includes a CPU (central processing unit) or a GPU (graphics processing module) that executes calculations in accordance with instructions included in the program stored in the storage device 100a. However, the specific configuration of the operation control unit 100 is not limited to these examples.

[0051] The operation control unit 100 is configured to generate thickness distribution data of the substrate W and to determine a region to be polished on the first surface 2 a of the substrate W based on the thickness distribution data of the substrate W. In this embodiment, the operation control unit 100 is configured to generate the thickness distribution data based on the thickness of the substrate W measured by the thickness measurement device 80 and the measurement position of the thickness of the substrate W. The thickness measurement device 80 measures the entire thickness of the substrate W while being moved in the radial direction of the holding stage 10 (i.e., the radial direction of the substrate W) by the thickness measurement device moving mechanism 85 during the circular rotation of the holding stage 10 by the substrate holding device 5. The operation control unit 100 generates the thickness distribution data based on the thickness of the substrate W measured by the thickness measurement device 80 and the measurement position of the thickness of the substrate W.

[0052] In one embodiment, the operation control unit 100 may generate thickness distribution data for the substrate W based on the thickness of the substrate W measured by a thickness measuring device provided outside the polishing apparatus 1 and the measurement position of the thickness of the substrate W.

[0053] The operation control unit 100 determines a region to be polished on the first surface 2 a of the substrate W based on the thickness distribution data of the substrate W. In one embodiment, the operation control unit 100 determines a region of the substrate W where the thickness is greater than a predetermined target thickness as the region to be polished on the first surface 2 a of the substrate W. Position information of the determined region to be polished is stored in the storage device 100 a.

[0054] The operation control unit 100 is configured to individually control the operation of the pressure actuators 54 of the polishing heads 50A to 50C. This allows the pressing force of each of the polishing heads 50A to 50C to be individually controlled. The operation control unit 100 causes the polishing heads 50A to 50C to press the polishing tapes 3A to 3C against the area to be polished with a pressing force greater than the pressing force against other areas. In one embodiment, the pressing force of the polishing heads 50A to 50C against other areas may be zero. In other words, the polishing heads 50A to 50C may locally polish only the area to be polished.

[0055] The operation control unit 100 controls the timing at which the polishing heads 50A to 50C press the polishing tapes 3A to 3C against the polishing target area based on position information of the polishing target area of ​​the substrate W and rotation angle information obtained from rotary encoders (not shown) attached to the stage circular motion mechanism 12 and the stage rotation mechanism 14.

[0056] In one embodiment, the operation control unit 100 is configured to cause the polishing head moving mechanism 70 to move the polishing heads 50A-50C to positions corresponding to the regions to be polished in the radial direction of the holding stage 10 (i.e., the radial direction of the substrate W). Specifically, the operation control unit 100 determines the polishing head (e.g., polishing head 50A) that will polish the regions to be polished, and issues a command to the polishing head moving mechanism 70 to move the polishing heads 50A-50C so that the determined polishing head is positioned at a position corresponding to the regions to be polished in the radial direction of the holding stage 10 (i.e., the radial direction of the substrate W). The polishing head that polishes the regions to be polished may be a single polishing head or multiple polishing heads.

[0057] In one embodiment, the thickness measurement device 80 may measure the thickness of the substrate W while the substrate W is being polished, and the operation control device 100 may generate thickness distribution data based on the thickness of the substrate W measured by the thickness measurement device 80 while the substrate W is being polished and the measurement position of the thickness of the substrate W. The operation control device 100 may determine the region to be polished based on the thickness distribution data generated while polishing the substrate W. In one embodiment, the operation control device 100 may terminate polishing of the substrate W when the thickness of the region to be polished reaches a predetermined target thickness.

[0058] 9 is a flowchart showing one embodiment of a method for polishing a substrate W. In this embodiment, the polishing apparatus 1 locally polishes only the region to be polished of the substrate W. In step S101, the operation control unit 100 issues a command to the stage circular motion mechanism 12 of the substrate holding device 5 to circularly move the holding stage 10 so that the holding stage 10 moves on a circumference having a radius R1, while issuing a command to the stage rotation mechanism 14 to rotate the holding stage 10 about its axis CP. This starts the circular rotation operation of the holding stage 10 and the substrate W by the substrate holding device 5.

[0059] In step S102, the thickness measurement device 80 measures the thickness of the substrate W while being moved in the radial direction of the holding stage 10 (i.e., the radial direction of the substrate W) during the circular rotation of the holding stage 10 and the substrate W. While the thickness measurement device 80 is measuring the thickness of the substrate W, the operation control unit 100 issues a command to the thickness measurement device moving mechanism 85 to move the thickness measurement device 80 in the radial direction of the holding stage 10 (i.e., the radial direction of the substrate W) and cause the thickness measurement device 80 to measure the entire thickness of the substrate W. The thickness of the substrate W measured by the thickness measurement device 80 is sent to the operation control unit 100. In step S103, the operation control unit 100 generates thickness distribution data based on the thickness of the substrate W measured by the thickness measurement device 80 and the measurement position of the thickness of the substrate W.

[0060] In step S104, the operation control unit 100 determines a region to be polished on the first side 2a of the substrate W based on the thickness distribution data of the substrate W. In one embodiment, the operation control unit 100 determines a region of the first side 2a of the substrate W where the thickness of the substrate W is greater than a predetermined target thickness as the region to be polished. In step S105, the operation control unit 100 determines a polishing head to polish the region to be polished. The polishing head to polish the region to be polished may be a single polishing head or multiple polishing heads. In this embodiment, the polishing head to polish the region to be polished is polishing head 50A.

[0061] In step S106, the operation control unit 100 issues a command to the polishing head moving mechanism 70 to move the polishing head 50A to a position corresponding to the region to be polished in the radial direction of the holding stage 10 (i.e., the radial direction of the substrate W). More specifically, the operation control unit 100 issues a command to the polishing head moving mechanism 70 to move the polishing heads 50A-50C so that the polishing head 50A is positioned in the radial direction of the holding stage 10 (i.e., the radial direction of the substrate W) at a position corresponding to the region to be polished. In step S107, the operation control unit 100 issues a command to the polishing tape supply mechanism 60A corresponding to the polishing head 50A that polishes the region to be polished, to supply the polishing tape 3A to the polishing head 50A.

[0062] In step S108, the operation control unit 100 issues a command to the pressing actuator 54 of the polishing head 50A to press the polishing tape 3A against the area to be polished of the substrate W with the polishing head 50A. The polishing head 50A presses the polishing tape 3A against the area to be polished with a pressing force greater than the pressing force against other areas. In this embodiment, the pressing force against other areas is zero. That is, when the polishing head 50A is positioned over the area to be polished of the substrate W, the pressing actuator 54 of the polishing head 50A presses the polishing tape 3A against the area to be polished of the substrate W with the polishing head 50A.

[0063] In one embodiment, when the area to be polished of the substrate W is larger than the polishing range of the polishing head 50A, the operation control unit 100 polishes a portion of the area to be polished of the substrate W, and then issues a command to the pressing actuator 54 of the polishing head 50A to move the polishing head 50A in a direction away from the first surface 2a of the substrate W and temporarily separate the polishing tape 3A from the substrate W. Thereafter, the operation control unit 100 issues a command to the polishing head moving mechanism 70 to move the polishing head 50A in the radial direction of the holding stage 10 (i.e., the radial direction of the substrate W) to a position corresponding to the unpolished portion of the area to be polished. Furthermore, the operation control unit 100 issues a command to the pressing actuator 54 of the polishing head 50A to press the polishing tape 3A with the polishing head 50A against the unpolished portion of the area to be polished of the substrate W.

[0064] In one embodiment, the operation control unit 100 may issue a command to the polishing head moving mechanism 70 to polish the area to be polished of the substrate W while moving the polishing head 50A in the radial direction of the holding stage 10 (i.e., the radial direction of the substrate W).

[0065] In step S109, the operation control unit 100 executes a polishing completion operation for the polishing target region of the substrate W. Specifically, the operation control unit 100 issues a command to the pressing actuator 54 of the polishing head 50A to move the polishing head 50A in a direction away from the first surface 2a of the substrate W and separate the polishing tape 3A from the substrate W. Next, the operation control unit 100 issues a command to the polishing tape supply mechanism 60A to stop supplying the polishing tape 3A to the polishing head 50A. Furthermore, the operation control unit 100 issues a command to the stage circular motion mechanism 12 and the stage rotation mechanism 14 of the substrate holding device 5 to stop the circular rotation of the holding stage 10.

[0066] According to this embodiment, the region to be polished of the substrate W can be locally polished by pressing the substrate pressing surface PS1, which has a smaller diameter than the substrate W, against the first surface 2a of the substrate W. As a result, it is possible to improve the thickness uniformity within the surface of the substrate W. Furthermore, by performing a circular motion of the holding stage 10 and a circular rotation operation of rotating the holding stage 10, the small-diameter substrate pressing surface PS1 can be efficiently brought into contact with the substrate W on the holding stage 10, thereby improving the polishing efficiency.

[0067] In one embodiment, the operation control unit 100 may use multiple polishing heads 50A-50C and control the operation of the polishing heads 50A-50C so that the pressing force of the polishing heads against the region to be polished is greater than the pressing force of the polishing heads against other regions, thereby polishing the entire substrate W. In this case, the polishing head moving mechanism 70 moves the polishing heads 50A-50C in the radial direction of the holding stage 10 (i.e., the radial direction of the substrate W) to polish the entire first surface 2a of the substrate W. The movement of the polishing heads 50A-50C by the polishing head moving mechanism 70 may be performed while the substrate W is being polished, or may be performed while the polishing heads 50A-50C are temporarily stopped from pressing the polishing tapes 3A-3C against the substrate W.

[0068] The circular rotation operation of the holding stage 10 by the substrate holding device 5 includes two types: a forward rotation operation in which the holding stage 10 is rotated around its axis CP in the same direction as the direction of the circular motion of the holding stage 10, as shown in Figure 10, and a reverse rotation operation in which the holding stage 10 is rotated around its axis CP in the opposite direction to the direction of the circular motion of the holding stage 10, as shown in Figure 11.

[0069] 12 is a graph showing an example of the change in the relationship between the radial position of the substrate W and the polishing rate depending on the type of circular rotational motion of the holding stage 10. Fig. 12 shows a graph obtained when a polishing tape (e.g., polishing tape 3A) is pressed against the first surface 2a of the substrate W by a single polishing head (e.g., polishing head 50A). The dotted line in Fig. 12 is a graph obtained when the substrate W is polished during a forward rotation operation in which the holding stage 10 is rotated about its axis CP in the same direction as the direction of the circular motion of the holding stage 10, as shown in Fig. 10. The dashed-dotted line in Fig. 12 is a graph obtained when the substrate W is polished during a reverse rotation operation in which the holding stage 10 is rotated about its axis CP in the opposite direction to the direction of the circular motion of the holding stage 10, as shown in Fig. 11.

[0070] The graph shown by the solid line in Fig. 12 is a graph obtained when the substrate W is polished by combining a forward rotation operation in which the holding stage 10 is rotated about its axis CP in the same direction as the direction of the circular motion of the holding stage 10, and a reverse rotation operation in which the holding stage 10 is rotated about its axis CP in the opposite direction to the direction of the circular motion of the holding stage 10. As shown in Fig. 12, when the substrate W is polished by combining the forward rotation operation and the reverse rotation operation, the substrate W can be polished at a uniform polishing rate.

[0071] Therefore, in one embodiment, the operation control unit 100 may control the circular rotation operation of the holding stage 10 by the substrate holding device 5 to include a forward rotation operation in which the holding stage 10 rotates around its axis CP in the same direction as the circular motion of the holding stage 10, and a reverse rotation operation in which the holding stage rotates around its axis CP in the opposite direction to the circular motion of the holding stage 10.

[0072] Specifically, the operation control unit 100 issues a command to the stage circular motion mechanism 12 of the substrate holding device 5 to circularly move the holding stage 10 so that it moves on a circumference having a radius R1, while issuing a command to the stage rotation mechanism 14 to rotate the holding stage 10 about its axis CP in the same direction as the circular motion of the holding stage 10 (forward rotation operation). During the forward rotation operation, the operation control unit 100 issues a command to the pressing actuator 54 of the polishing head (e.g., polishing head 50A) corresponding to the region to be polished, causing the polishing head (e.g., polishing head 50A) to press the polishing tape (e.g., polishing tape 3A) against the region to be polished of the substrate W.

[0073] Furthermore, the operation control unit 100 issues a command to the stage rotation mechanism 14 to change the rotation direction so that the holding stage 10 rotates about its axis CP in the direction opposite to the circular motion of the holding stage 10 (reverse operation). The operation control unit 100 continues to issue a command to the pressure actuator 54 of the polishing head (e.g., polishing head 50A) corresponding to the region to be polished during the reverse operation, causing the polishing head (e.g., polishing head 50A) to press the polishing tape (e.g., polishing tape 3A) against the region to be polished on the substrate W. In one embodiment, the polishing time during the forward rotation operation is the same as the polishing time during the reverse rotation operation.

[0074] The order of the forward rotation operation and the reverse rotation operation when polishing the substrate W may be reversed. That is, the substrate W may be polished during the reverse rotation operation, and then polished during the forward rotation operation.

[0075] 13 is a schematic diagram illustrating another embodiment of a method for polishing a substrate W. As shown in FIG. 13 , the method for polishing a substrate W of this embodiment includes a first polishing operation and a second polishing operation, which will be described below. The first polishing operation is an operation in which, during a circular rotation of the holding stage 10 by the substrate holding device 5, the polishing head (e.g., the polishing head 50A) is shifted from the reference position L toward the radially outer side of the substrate W by a first offset amount O1, and the polishing head (e.g., the polishing head 50A) presses a polishing tape (e.g., the polishing tape 3A) against the first surface 2 a of the substrate W. The second polishing operation is an operation in which, during a circular rotation of the holding stage 10 by the substrate holding device 5, the polishing head (e.g., the polishing head 50A) is shifted from the reference position L toward the radially inner side of the substrate W by a second offset amount O2, and the polishing head (e.g., the polishing head 50A) presses a polishing tape (e.g., the polishing tape 3A) against the first surface 2 a of the substrate W. In this embodiment, the second polishing operation is performed after the first polishing operation. In one embodiment, the reference position L is the center position of the area of ​​the substrate W to be polished in the radial direction of the substrate W.

[0076] 14 is a graph showing an example of the relationship between the radial position of the substrate W and the polishing rate when the substrate W is polished at the reference position L and when polishing the substrate W including the first polishing operation and the second polishing operation is performed. Fig. 14 shows a graph when a polishing tape (e.g., polishing tape 3A) is pressed against the first surface 2a of the substrate W by a single polishing head (e.g., polishing head 50A). The graph indicated by the dotted line in Fig. 14 is a graph obtained when the substrate W is polished with the polishing head (e.g., polishing head 50A) positioned at the reference position L.

[0077] The solid line in Fig. 14 is a graph obtained when, as shown in Fig. 13 , a first polishing operation is performed in which the polishing head (e.g., polishing head 50A) is shifted from the reference position L toward the radially outer side of the substrate W by a first offset amount O1 during the circular rotation of the holding stage 10 by the substrate holding device 5, and a polishing tape (e.g., polishing tape 3A) is pressed against the first surface 2a of the substrate W by the polishing head (e.g., polishing head 50A). Then, a second polishing operation is performed in which the polishing head (e.g., polishing head 50A) is shifted from the reference position L toward the radially inner side of the substrate W by a second offset amount O2 during the circular rotation of the holding stage 10 by the substrate holding device 5. As shown in Fig. 14 , the polishing of the substrate W including the first polishing operation and the second polishing operation can polish the substrate W at a uniform polishing rate.

[0078] The order of the first polishing operation and the second polishing operation may be reversed. That is, the first polishing operation may be performed after the second polishing operation. The circular rotation of the holding stage 10 by the substrate holding device 5 in the first polishing operation and the second polishing operation may be performed by combining the forward rotation and the reverse rotation described above.

[0079] In the above-described embodiment, polishing tapes 3A to 3C having abrasive grains on their surfaces are used as an example of a polishing tool. However, a grindstone may be used as another example of a polishing tool. FIG. 15 is a schematic diagram showing another embodiment of a polishing tool. As shown in FIG. 15, a polishing head 50A of this embodiment has a grindstone 90 attached to a pressing member 52. In this embodiment, the polishing tool is the grindstone 90 instead of the polishing tape 3A. When the pressing actuator 54 of the polishing head 50A presses the pressing member 52 toward the first surface 2a of the substrate W, the substrate pressing surface PS1, which is the surface of the grindstone 90, is pressed against the first surface 2a of the substrate W by the pressing member 52. The polishing head 50A polishes the first surface 2a of the substrate W by pressing the grindstone 90 against the first surface 2a of the substrate W.

[0080] The polishing heads 50B and 50C of this embodiment have the same configuration as the polishing head 50A, but the polishing tool is a grindstone 90 attached to the pressing member 52 of each of the polishing heads 50B and 50C, instead of the polishing tapes 3B and 3C.

[0081] The above-described embodiments have been described for the purpose of enabling a person of ordinary skill in the art to practice the present invention. Various modifications of the above-described embodiments would be obvious to a person skilled in the art, and the technical concept of the present invention may be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be interpreted in the broadest scope in accordance with the technical concept defined by the claims.

[0082] The present invention can be used in a polishing apparatus and a polishing method for polishing substrates such as wafers.

[0083] REFERENCE SIGNS LIST 1 Polishing device 2a First surface 2b Second surface 3A, 3B, 3C Polishing tape 5 Substrate holding device 8 Polishing head assembly 10 Holding stage 12 Stage circular motion mechanism 14 Stage rotation mechanism 16 Eccentric shaft 16a First shaft portion 16b Second shaft portion 16c Intermediate shaft portion 17 Counterweight 18 Bearing 20 Eccentric shaft rotation device 22 Planet gear 23 Sun gear 25 Drive shaft 27, 28 Pulley 29 Belt 30 Motor 32 Table base 33 Bearing 34 Base ring 35 Bearing 36 Base plate 37 Table base rotation device 38 Connecting member 39, 40 Pulley 41 Belt 42 Motor 50A, 50B, 50C Polishing head 52 Pressing member 54 Pressing actuator 60A, 60B, 60C Polishing tape supply mechanism 61 Outer wall portion 62 Motor casing 64 Tape supply reel 65 Tape take-up reel 67 Brake mechanism 70 Polishing head moving mechanism 75 Guide rail 80 Thickness measuring device 85 Thickness measuring device moving mechanism 90 Grindstone 100 Operation control unit 100a Storage device 100b Arithmetic unit

Claims

1. A polishing apparatus for polishing a flat surface of a substrate, comprising: a substrate holding device that holds the substrate and performs a circular rotation operation to rotate the substrate while causing it to move in a circular motion; and a polishing head that presses a polishing tool against the flat surface of the substrate, wherein the substrate holding device comprises: a holding stage that holds the substrate; a stage circular motion mechanism that is connected to the holding stage and causes the holding stage to move in a circular motion so that the holding stage moves on a circumference having a predetermined radius; and a stage rotation mechanism that is connected to the holding stage via the stage circular motion mechanism and rotates the holding stage around its axis, wherein the substrate pressing surface of the polishing tool has a dimension in the radial direction of the holding stage that is less than the radius of the substrate.

2. A polishing apparatus according to claim 1, wherein the period of the circular motion of said holding stage is shorter than the time it takes for said holding stage to make one rotation about said axis.

3. A polishing apparatus as described in claim 1, wherein the stage circular motion mechanism comprises a plurality of eccentric shafts connected to the holding stage, and an eccentric shaft rotation device that rotates the plurality of eccentric shafts, each of the plurality of eccentric shafts having a first shaft portion rotatably connected to the holding stage and a second shaft portion eccentric from the first shaft portion by the specified radius and connected to the eccentric shaft rotation device, and the stage rotation mechanism comprises a table base to which the second shaft portions of each of the plurality of eccentric shafts are rotatably connected, and a table base rotation device that rotates the table base.

4. A polishing apparatus as described in claim 1, further comprising an operation control unit that controls the operation of the polishing head, wherein the operation control unit is configured to: generate thickness distribution data for the substrate; determine a region to be polished on the flat surface of the substrate based on the thickness distribution data; and cause the polishing head to press the polishing tool against the region to be polished with a pressing force greater than the pressing force against other regions.

5. A polishing apparatus as described in claim 4, further comprising a polishing head moving mechanism that moves the polishing head along the radial direction of the holding stage, and the operation control unit is configured to cause the polishing head moving mechanism to move the polishing head to a position corresponding to the area to be polished in the radial direction of the holding stage.

6. A polishing apparatus as described in claim 5, further comprising a thickness measuring device for measuring the thickness of the substrate, wherein the operation control unit is electrically connected to the thickness measuring device and configured to generate the thickness distribution data based on the thickness measured by the thickness measuring device and the measurement position of the thickness.

7. A polishing apparatus as described in claim 1, further comprising an operation control unit that controls the circular rotation operation of the substrate holding device to include a forward rotation operation that rotates the holding stage around the axis in the same direction as the circular motion of the holding stage, and a reverse rotation operation that rotates the holding stage around the axis in the opposite direction to the circular motion of the holding stage.

8. A polishing apparatus as described in claim 1, further comprising: a polishing head moving mechanism that moves the polishing head in the radial direction of the holding stage; and an operation control unit that controls the operation of the polishing head and the polishing head moving mechanism to include a first polishing operation in which the polishing head moving mechanism shifts the polishing head from a reference position radially outward of the substrate by a first offset amount and causes the polishing head to press the polishing tool against the flat surface of the substrate, and a second polishing operation in which the polishing head moving mechanism shifts the polishing head from the reference position radially inward of the substrate by a second offset amount and causes the polishing head to press the polishing tool against the flat surface of the substrate.

9. The polishing apparatus according to claim 1, wherein the polishing heads are a plurality of polishing heads arranged along the radial direction of the holding stage, and the polishing apparatus further comprises an operation control unit configured to individually control the pressing force of each of the plurality of polishing heads against the flat surface of the substrate.

10. The polishing device according to claim 1, wherein the polishing tool is a polishing tape having abrasive grains on its surface, or a grinding stone.

11. A polishing method for polishing a flat surface of a substrate, comprising: holding the substrate on a holding stage; rotating the holding stage around its axis while circularly moving the holding stage so that the holding stage moves on a circumference of a circle having a predetermined radius; and pressing a polishing tool against the flat surface of the substrate with a polishing head during the circular rotation, wherein the substrate pressing surface of the polishing tool has a dimension in the radial direction of the holding stage that is less than the radius of the substrate.

12. A polishing method according to claim 11, wherein the period of the circular motion of said holding stage is shorter than the time it takes for said holding stage to make one rotation about said axis.

13. The polishing method according to claim 11, further comprising: generating thickness distribution data for the substrate; and determining a region to be polished on the flat surface of the substrate based on the thickness distribution data; and wherein the pressing force of the polishing head against the region to be polished is greater than the pressing force of the polishing head against other regions.

14. The polishing method according to claim 13, further comprising moving the polishing head in the radial direction of the holding stage to a position corresponding to the area to be polished before pressing the polishing tool against the flat surface of the substrate with the polishing head.

15. The polishing method according to claim 13, further comprising measuring the thickness of the substrate with a thickness measuring device, and generating the thickness distribution data based on the thickness measured by the thickness measuring device and the measurement position of the thickness.

16. A polishing method according to claim 11, wherein the circular rotation motion includes a forward rotation motion that rotates the holding stage around the axis in the same direction as the circular motion of the holding stage, and a reverse rotation motion that rotates the holding stage around the axis in the opposite direction to the circular motion of the holding stage.

17. The polishing method of claim 11, wherein pressing a polishing tool against the flat surface of the substrate with a polishing head during the circular rotation motion includes performing a first polishing operation in which the polishing head presses the polishing tool against the flat surface of the substrate with the polishing head in a state where the polishing head is shifted from a reference position by a first offset amount radially outward of the substrate during the circular rotation motion, and a second polishing operation in which the polishing head presses the polishing tool against the flat surface of the substrate with the polishing head in a state where the polishing head is shifted from the reference position by a second offset amount radially inward of the substrate during the circular rotation motion.

18. The polishing method according to claim 11, wherein pressing the polishing tool against the flat surface of the substrate with the polishing head comprises pressing a plurality of polishing tools against the flat surface of the substrate, respectively, with a plurality of polishing heads arranged along the radial direction of the holding stage, and the method includes individually controlling the pressing force of each of the plurality of polishing heads against the flat surface of the substrate.

19. The polishing method according to claim 11, wherein the polishing tool is a polishing tape having abrasive grains on its surface, or a grinding stone.

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