Polishing apparatus

Abstract

To provide a polishing apparatus capable of polishing a peripheral portion of a substrate without bending the substrate, even when a polishing load is increased.SOLUTION: A polishing apparatus comprises: a holding stage 4 that has a diameter smaller than a diameter of a substrate W and holds a central portion of the substrate W; a rotation mechanism M1 that rotates the holding stage 4; a support stage 70 that is positioned outside the holding stage 4 and capable of supporting a back surface of the substrate W that faces a top edge portion of the substrate W; a lifting mechanism 72 that vertically moves the support stage 70; and a protection mechanism 71 that prevents relative sliding between the substrate W held by the holding stage 4 and the support stage 70.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a polishing apparatus for polishing the peripheral edge of a substrate. [Background technology]

[0002] In recent years, management of the surface condition of substrates such as wafers has been attracting attention from the perspective of improving yield in semiconductor device manufacturing. During the semiconductor device manufacturing process, various materials are deposited on silicon substrates. This can lead to the formation of unwanted films and surface roughness around the substrate's periphery. In recent years, a method of transporting a substrate by holding only its periphery with an arm has become common. Under these circumstances, unwanted films remaining on the periphery peel off during various processes and adhere to devices formed on the substrate, reducing yield.

[0003] Therefore, in order to remove the unnecessary film formed on the peripheral edge of the substrate, the peripheral edge of the substrate is polished using a polishing device. This type of polishing device polishes the peripheral edge of the substrate by bringing a polishing tool such as a polishing tape into sliding contact with the peripheral edge of the substrate. More specifically, the substrate is held by a substrate holder (substrate holding device) and rotated, while the polishing head presses the polishing tool against the peripheral edge of the substrate to polish the peripheral edge of the substrate.

[0004] Some polishing apparatuses have a tilt mechanism that allows a polishing head that holds a polishing tool to move (tilt) relative to a substrate held and rotated by a substrate holder. The tilt mechanism allows polishing not only the bevel portion, which is the outermost peripheral surface of the substrate, but also the top edge portion, which is a flat portion located radially inward from the bevel portion, and the bottom edge portion, which is a flat portion located opposite the top edge portion and radially inward from the bevel portion. The top edge portion is included in the flat surface of the substrate on which a device is formed (i.e., the upper surface of the substrate), and the bottom edge portion is included in the flat surface of the substrate held by the substrate holder (i.e., the lower surface of the substrate). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-87136 Summary of the Invention [Problem to be solved by the invention]

[0006] In order to polish the bottom edge of a substrate with a tilt mechanism, the polishing tool must press the substrate from below. Therefore, the substrate holder cannot support at least the bottom edge of the substrate. In contrast, when polishing the top edge of the substrate with a polishing tool, the polishing tool must press the substrate from above.

[0007] In recent years, there has been an increasing need for removing various unnecessary films, such as an increase in the amount of unnecessary film removed and the need to remove hard films, etc. In connection with this, there has also been an increasing demand for improving the polishing rate in removing unnecessary films from the peripheral edge of a substrate.

[0008] The polishing rate can be improved by increasing the rotation speed of the substrate holder that holds the substrate. However, research by the inventors has revealed that the polishing rate decreases when the rotation speed of the substrate holder exceeds a certain speed, and there is a limit to how much the increase in the rotation speed of the substrate holder can meet the needs of users of the polishing apparatus.

[0009] When the polishing tool is a polishing tape, the polishing rate can be improved by increasing the size of the abrasive grains attached to the polishing tape. However, increasing the size of the abrasive grains may not satisfy users of the polishing device in terms of the finish of the polished substrate (i.e., the surface roughness of the polished surface).

[0010] The removal rate can also be improved by increasing the force pressing the polishing tool against the substrate (hereinafter, sometimes referred to as the "polishing load"). However, because the substrate holder cannot support the bottom edge of the substrate, applying an excessive polishing load to the substrate when polishing the top edge with the polishing tool can cause the substrate to bend. This bending of the substrate can lead to damage to devices formed on the substrate or to the substrate itself.

[0011] SUMMARY OF THE INVENTION The present invention provides a polishing apparatus that can polish the peripheral edge of a substrate without bending the substrate even when the polishing load is increased. [Means for solving the problem]

[0012] In one aspect, a polishing apparatus is provided that has at least one polishing head and presses a polishing tool held by the polishing head against a peripheral portion of a substrate, including the top edge portion, to polish the peripheral portion, the polishing apparatus comprising: a holding stage having a diameter smaller than the diameter of the substrate and holding the center portion of the substrate; a rotation mechanism for rotating the holding stage; a support stage positioned outside the holding stage and capable of supporting the back surface of the substrate facing the top edge portion; a lifting mechanism for moving the support stage up and down; and a protection mechanism for preventing relative sliding between the substrate held by the holding stage and the support stage.

[0013] In one aspect, the rotation mechanism comprises a stage shaft connected to the holding stage and an actuator that rotates the stage shaft, and the protection mechanism includes a connecting arm that connects the support stage to the stage shaft. In one embodiment, the rotation mechanism includes a first motor that rotates the holding stage, and the protection mechanism includes a second motor that rotates the support stage in synchronization with the first motor. In one embodiment, the protection mechanism includes at least one roller provided on a support surface of the support stage that faces the back surface of the substrate. In one embodiment, the protection mechanism is a fluid ejection mechanism that ejects fluid having a pressure corresponding to the polishing load with which the polishing tool is pressed against the top edge portion of the substrate.

[0014] In one embodiment, the support stage has a ring shape. In one embodiment, the support stage has a support surface for supporting a portion of the back surface of the substrate that faces the polishing head. [Effects of the Invention]

[0015] The support stage can support the polishing load when polishing the top edge of the substrate. Therefore, even if a large polishing load is applied to the top edge of the substrate, the substrate does not bend, and devices formed on the substrate and the substrate itself are not damaged. As a result, the polishing load during polishing of the top edge, i.e., the polishing rate of the top edge, can be freely controlled. Furthermore, the protection mechanism prevents relative sliding between the substrate held by the holding stage and the support stage. As a result, the back surface of the substrate is not damaged when polishing the top edge. [Brief explanation of the drawings]

[0016] [Figure 1] 1(a) and 1(b) are enlarged cross-sectional views showing the peripheral edge of a wafer. [Figure 2] FIG. 2 is a plan view schematically showing a polishing apparatus according to an embodiment. [Figure 3] FIG. 3 is a vertical cross-sectional view schematically showing the polishing apparatus shown in FIG. [Figure 4] FIG. 4 is an enlarged view of the polishing head. [Figure 5] FIG. 5 is a diagram showing how the polishing head is polishing the bevel portion of the wafer. [Figure 6] FIG. 6 is a diagram showing the state in which the polishing head is polishing the top edge E1 of the wafer. [Figure 7] FIG. 7 is a diagram showing the polishing head assembly polishing the bottom edge of the wafer. [Figure 8] FIG. 8 is a top view of a support stage according to one embodiment. [Figure 9] FIG. 9 is a schematic diagram showing the support stage moved to the support position by the lifting actuator. [Figure 10] FIG. 10 is a schematic diagram showing the support stage moved to the retracted position by the lifting actuator. [Figure 11] FIG. 11 is a vertical cross-sectional view schematically showing a polishing apparatus according to another embodiment. [Figure 12] FIG. 12(a) is a top view schematically showing a support stage of a polishing apparatus according to yet another embodiment, and FIG. 12(b) is a cross-sectional view taken along line AA in FIG. 12(a). [Figure 13] FIG. 13 is a side view schematically showing a support stage of a polishing apparatus according to yet another embodiment. [Figure 14] FIG. 14 is a vertical cross-sectional view schematically showing a support stage of a polishing apparatus according to still another embodiment. [Figure 15] 15 is a top view schematically showing the support stage of the polishing apparatus shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The polishing apparatus according to the embodiment described below is an apparatus that polishes the peripheral edge of a wafer, which is an example of a substrate, by bringing a polishing tool into sliding contact with the peripheral edge of the wafer. In the embodiment described below, a polishing tape is used as the polishing tool. However, the polishing tool is not limited to this example as long as the polishing tool can polish the peripheral edge of the substrate. For example, the polishing tool may be a grindstone.

[0018] 1(a) and 1(b) are enlarged cross-sectional views showing the peripheral edge of a wafer. More specifically, FIG. 1(a) is a cross-sectional view of a so-called straight wafer, and FIG. 1(b) is a cross-sectional view of a so-called round wafer. In the wafer W of FIG. 1(a), the bevel portion is the outermost peripheral surface (indicated by symbol B) of the wafer W, which is composed of an upper inclined portion (upper bevel portion) P, a lower inclined portion (lower bevel portion) Q, and a side portion (apex) R. In the wafer W of FIG. 1(b), the bevel portion is the portion (indicated by symbol B) having a curved cross section that constitutes the outermost peripheral surface of the wafer W. The top edge portion E1 is a flat portion E1 located radially inward from the bevel portion B. The bottom edge portion is a flat portion E2 located opposite the top edge portion E1 and radially inward from the bevel portion B. The top edge portion E1 may include a region in which a device is formed. The top edge portion E1 and the bottom edge portion E2 are sometimes collectively referred to as near-edge portions. In this specification, the peripheral edge of the wafer W is defined as a region including a bevel portion located at the outermost periphery of the wafer W, and a top edge portion E1 and a bottom edge portion located radially inward of this bevel portion.

[0019] Fig. 2 is a plan view schematically showing a polishing apparatus according to one embodiment. Fig. 3 is a longitudinal cross-sectional view schematically showing the polishing apparatus shown in Fig. 2. As shown in Figs. 2 and 3, this polishing apparatus includes a substrate holder 3 that horizontally holds and rotates a wafer (substrate) W, which is an object to be polished, polishing head assemblies 1A, 1B, 1C, and 1D that press a polishing tape 23 against the peripheral edge of the wafer W to polish the peripheral edge of the wafer W, and a control device 11 configured to control the operation of the polishing apparatus.

[0020] 2 and 3 show a state in which the substrate holder 3 is holding a wafer W. The substrate holder 3 includes a dish-shaped holding stage 4 that holds the backside of the wafer W by vacuum suction, a hollow shaft (stage shaft) 5 connected to the center of the holding stage 4, and a holding stage actuator M1 (rotation mechanism) that rotates the hollow shaft 5. In this embodiment, the holding stage actuator M1 is a motor. The wafer W is placed on the holding stage 4 by a transfer unit (not shown) so that the center of the wafer W coincides with the axis of the hollow shaft 5.

[0021] The hollow shaft 5 is supported by a ball spline bearing (linear bearing) 6 so that it can move up and down. A groove is formed in the upper surface of the holding stage 4, and this groove is connected to a communication passage 7 that extends through the hollow shaft 5. The communication passage 7 is connected to a vacuum line 9 via a rotary joint 8 attached to the lower end of the hollow shaft 5. The communication passage 7 is also connected to a nitrogen gas supply line 10 for removing the processed wafer W from the holding stage 4. By switching between the vacuum line 9 and the nitrogen gas supply line 10, the wafer W is vacuum-adsorbed to the upper surface of the holding stage 4 and then removed.

[0022] The hollow shaft 5 is rotated by the holding stage actuator M1 via a pulley p1 connected to the hollow shaft 5, a pulley p2 attached to the rotating shaft of a motor M1, and a belt b1 looped around these pulleys p1 and p2. The ball spline bearing 6 is a bearing that allows the hollow shaft 5 to move freely in its longitudinal direction. The ball spline bearing 6 is fixed to a cylindrical casing 12. Therefore, in this embodiment, the hollow shaft 5 is configured to be able to move linearly up and down relative to the casing 12, and the hollow shaft 5 and the casing 12 rotate together. The hollow shaft 5 is connected to an air cylinder (elevating mechanism) 15, which allows the hollow shaft 5 and the holding stage 4 to rise and fall.

[0023] A radial bearing 18 is interposed between the casing 12 and a cylindrical casing 14 arranged concentrically outside the casing 12, and the casing 12 is rotatably supported by the bearing 18. With this configuration, the substrate holder 3 can rotate the wafer W about its central axis Cr and raise and lower the wafer W along the central axis Cr.

[0024] The polishing apparatus includes at least one polishing head assembly for polishing the peripheral edge of the wafer W. There is no limit to the number of polishing head assemblies as long as they are capable of polishing the peripheral edge of the wafer W. In this embodiment, as shown in FIG. 3, four polishing head assemblies (polishing units) 1A, 1B, 1C, and 1D are arranged radially outward of the wafer W held by the substrate holder 3.

[0025] In this embodiment, tape supply and recovery mechanisms 2A, 2B, 2C, and 2D are provided radially outward of the polishing head assemblies 1A, 1B, 1C, and 1D, respectively. The polishing head assemblies 1A, 1B, 1C, and 1D are separated from the tape supply and recovery mechanisms 2A, 2B, 2C, and 2D by a partition wall 20. The internal space of the partition wall 20 forms a polishing chamber 21, and the four polishing head assemblies 1A, 1B, 1C, and 1D and the holding stage 4 are disposed within the polishing chamber 21. Meanwhile, the polishing tape supply and recovery mechanisms 2A, 2B, 2C, and 2D are disposed outside the partition wall 20 (i.e., outside the polishing chamber 21). The polishing head assemblies 1A, 1B, 1C, and 1D have the same configuration, and the tape supply and recovery mechanisms 2A, 2B, 2C, and 2D also have the same configuration. The polishing head assembly 1A and the tape supply and recovery mechanism 2A will be described below.

[0026] The tape supply and recovery mechanism 2A includes a supply reel 24 that supplies the polishing tape 23 to the polishing head assembly 1A, and a recovery reel 25 that recovers the polishing tape 23 that has been used to polish the wafer W. The supply reel 24 is disposed above the recovery reel 25. A motor M2 is connected to each of the supply reel 24 and recovery reel 25 via a coupling 27 (only the coupling 27 and motor M2 connected to the supply reel 24 are shown in FIG. 2). Each motor M2 applies a constant torque in a predetermined rotational direction, enabling a predetermined tension to be applied to the polishing tape 23.

[0027] The polishing tape 23 is a long, strip-shaped polishing tool, one side of which constitutes the polishing surface. The polishing tape 23 has a base tape made of, for example, a PET sheet, and a polishing layer formed on the base tape. The polishing layer is composed of a binder (e.g., resin) that covers one surface of the base tape and abrasive grains held in the binder, and the surface of the polishing layer constitutes the polishing surface.

[0028] The polishing tape 23 is set in the polishing tape supply mechanism 2A while being wound around a supply reel 24. The sides of the polishing tape 23 are supported by a reel plate to prevent the tape from becoming unwound. One end of the polishing tape 23 is attached to a recovery reel 25, and the recovery reel 25 recovers the polishing tape 23 by taking it up after it has been supplied to the polishing head assembly 1A.

[0029] The polishing head assembly 1A includes a polishing head 30 for bringing the polishing tape 23 supplied from the polishing tape supply mechanism 2A into contact with the peripheral edge of the wafer W. The polishing tape 23 is supplied to the polishing head 30 so that the polishing surface of the polishing tape 23 faces the wafer W.

[0030] The polishing tape supply and recovery mechanism 2A has a plurality of guide rollers 31, 32, 33, and 34, and the polishing tape 23 supplied to the polishing head assembly 1A and recovered from the polishing head assembly 1A is guided by these guide rollers 31, 32, 33, and 34. The polishing tape 23 is supplied from the supply reel 24 to the polishing head 30 through an opening 20a provided in the partition wall 20, and used polishing tape 23 is recovered on the recovery reel 25 through the opening 20a.

[0031] Although not shown, an upper supply nozzle is disposed above the wafer W, supplying a polishing liquid toward the wafer W held by the substrate holder 3. A lower supply nozzle may also be provided, supplying a polishing liquid toward the boundary between the back surface of the wafer W and the holding stage 4 of the substrate holder 3 (the outer periphery of the holding stage 4). The polishing liquid may be, for example, pure water. The polishing apparatus may also be provided with a cleaning nozzle that cleans the polishing head 30 after the polishing process of the wafer W. After the wafer W is raised by the substrate holder 3 after the polishing process, cleaning water can be sprayed from the cleaning nozzle toward the polishing head 30, thereby cleaning the polishing head 30 after the polishing process.

[0032] 3 shows a state in which the hollow shaft 5 is lowered and the holding stage 4 is at the polishing position. After the polishing process, the air cylinder 15 raises the wafer W together with the holding stage 4 and hollow shaft 5 to the transfer position, and the wafer W is released from the holding stage 4 at this transfer position.

[0033] 2, the polishing head 30 is fixed to one end of an arm 60, which is rotatable about a rotation axis Ct parallel to a tangent to the wafer W. The other end of the arm 60 is connected to a motor M4 via pulleys p3 and p4 and a belt b2. When the motor M4 rotates clockwise and counterclockwise by a predetermined angle, the arm 60 rotates about the axis Ct by a predetermined angle. In this embodiment, the motor M4, the arm 60, the pulleys p3 and p4, and the belt b2 form a tilt mechanism that tilts the polishing head 30.

[0034] The tilt mechanism is mounted on a movable table 61. As shown in FIG. 3, the movable table 61 is movably connected to a base plate 65 via guides 62 and rails 63. The rails 63 extend linearly along the radial direction of the wafer W held by the substrate holder 3, and the movable table 61 is capable of linear movement along the radial direction of the wafer W. A connecting plate 66 that penetrates the base plate 65 is attached to the movable table 61, and a linear actuator 67 is connected to the connecting plate 66 via a joint 68. The linear actuator 67 is fixed directly or indirectly to the base plate 65.

[0035] The linear actuator 67 may be an air cylinder or a combination of a positioning motor and a ball screw. The linear actuator 67, the rails 63, and the guides 62 form a movement mechanism that moves the polishing head 30 linearly in the radial direction of the wafer W. That is, the movement mechanism operates along the rails 63 to move the polishing head 30 toward and away from the wafer W. On the other hand, the tape supply and recovery mechanism 2A is fixed to a base plate 65.

[0036] FIG. 4 is an enlarged view of the polishing head 30. As shown in FIG. 4, the polishing head 30 includes a pressing mechanism 41 that presses the polishing surface of the polishing tape 23 against the wafer W with a predetermined force. The polishing head 30 also includes a tape feed mechanism 42 that feeds the polishing tape 23 from the supply reel 24 to the recovery reel 25. The polishing tape feed mechanism 42 includes a tape feed roller 42a that feeds the polishing tape 23, a nip roller 42b that presses the polishing tape 23 against the tape feed roller 42a, and a tape feed motor M3 that rotates the tape feed roller 42a. The nip roller 42b is supported by a mechanism (not shown) so as to generate a force in the direction indicated by the arrow NF in FIG. 4 (the direction toward the tape feed roller 42a), and is configured to press the tape feed roller 42a.

[0037] The polishing tape 23 is sandwiched between the tape feed roller 42a and the nip roller 42b. When the tape feed roller 42a is rotated in the direction shown by the arrow in Figure 4, the tape feed roller 42a rotates, and the polishing tape 23 can be fed from the supply reel 24 to the recovery reel 25 via the polishing head 30. The nip roller 42b is configured to be able to rotate about its own axis, and is rotated by the feeding of the polishing tape 23. The polishing head 30 has multiple guide rollers 43, 44, 45, 46, 47, 48, and 49, which guide the polishing tape 23 so that it advances in a direction perpendicular to the tangent direction of the wafer W.

[0038] The pressing mechanism 41 includes a pressing member 50 disposed on the rear surface of the polishing tape 23 and an air cylinder (drive mechanism) 52 that moves the pressing member 50 toward the peripheral edge of the wafer W. The force that presses the polishing tape 23 against the wafer W is adjusted by controlling the pressure of the gas (e.g., air) supplied to the air cylinder 52. The tilt mechanism, pressing mechanism 41, and tape feed mechanism 42 disposed in each of the polishing head assemblies 1A, 1B, 1C, and 1D disposed around the wafer W are configured to be able to operate independently. Furthermore, the movement mechanisms that move each polishing head assembly are configured to be able to operate independently.

[0039] FIG. 5 is a diagram showing the polishing head 30 polishing the bevel portion of the wafer W. When polishing the bevel portion of the wafer W, as shown in FIG. 5, the tilt angle of the polishing head 30 is continuously changed by the tilt mechanism described above, and the polishing tape 23 is pressed against the bevel portion of the wafer W by the pressure pad 64. During polishing, the polishing tape 23 is fed at a predetermined speed by the tape feed mechanism 42. Furthermore, the polishing head 30 can polish the top edge portion E1 and bottom edge portion of the wafer W. That is, as shown in FIG. 6, the polishing head 30 can be tilted upward, and the protrusion 51a can press the polishing tape 23 against the top edge portion E1 of the wafer W, thereby polishing the top edge portion E1. Furthermore, as shown in FIG. 7, the polishing head 30 can be tilted downward, and the protrusion 51b can press the polishing tape 23 against the bottom edge portion of the wafer W, thereby polishing the bottom edge portion.

[0040] Returning to Figures 2 and 3, the substrate holding unit 3 of the polishing apparatus is located horizontally outboard of the holding stage 4, and further includes a support stage 70 that can support the back surface of the wafer W facing the top edge portion E1 (see Figures 1(a) and 1(b)) when polishing the top edge portion E1, an elevator device 72 that moves the support stage 70 up and down, and a connecting arm 71 that connects the elevator device 72 to the hollow shaft 5.

[0041] FIG. 8 is a top view of the support stage 70 shown in FIGS. 2 and 3. In FIG. 8, the support stage 70 and the holding stage 4 are hatched to facilitate understanding of the invention. As shown in FIG. 8, the support stage 70 is located radially outward from the dish-shaped holding stage 4. The support stage 70 shown in FIG. 8 has a ring shape and is arranged concentrically with the holding stage 4. The support stage 70 is configured to be able to hold the entire back surface of the peripheral edge of the wafer W, including the bottom edge E2 (see FIGS. 1(a) and 1(b)) of the wafer W held by the holding stage 4.

[0042] The lifting device 72 is a device that moves the support stage 70 between a support position where the support stage 70 contacts the backside of the wafer W when the polishing head 30 polishes the top edge portion E1 using the polishing tape 23, and a retracted position where the support stage 70 is separated from the backside of the wafer W. In this embodiment, the lifting device 72 includes a lifting actuator 73 that is a motor or a cylinder, and a guide rail 74 that connects the support stage 70 to the lifting actuator 73 and guides the movement of the support stage 70. The lifting actuator 73 is connected to a control device 11, which is configured to be able to control the operation of the lifting actuator 73. The control device 11 drives the lifting actuator 73, thereby moving the support stage 70 linearly up and down along the guide rail 74.

[0043] Fig. 9 is a schematic diagram showing the support stage 70 moved to the support position by the lift actuator 73, and Fig. 10 is a schematic diagram showing the support stage 70 moved to the retracted position by the lift actuator 73. As shown in Fig. 10, when polishing the bevel portion B (see Figs. 1(a) and 1(b)) of the wafer W, the support stage 70 is moved to the retracted position so as not to interfere with the movement of the polishing head 30. On the other hand, as shown in Fig. 9, when polishing the top edge portion E1 of the wafer W, the support stage 70 is moved to the support position and supports the back surface of the wafer W to which a polishing load is applied from above.

[0044] When the top edge E1 of the wafer W is polished, the wafer W rotates together with the holding stage 4. Therefore, if relative sliding between the wafer W held by the holding stage 4 and the support stage 70 is not prevented, the back surface of the wafer W will be damaged. In this embodiment, the support stage 70 is connected to the holding stage 4 via the connecting arm 71 and the hollow shaft 5, so the support stage 70 can rotate at the same rotational speed as the holding stage 4. As a result, relative sliding between the wafer W held by the holding stage 4 and the support stage 70 is prevented, and the back surface of the wafer W will not be damaged. In this embodiment, the connecting arm 71 constitutes a protection mechanism that prevents relative sliding between the wafer W held by the holding stage 4 and the support stage 70.

[0045] According to this embodiment, the polishing load applied when polishing the top edge E1 of the wafer W can be supported by the support stage 70. Therefore, even if a large polishing load is applied to the top edge E1 of the wafer W, the wafer W does not bend, and devices formed on the wafer W and the wafer W itself are not damaged. As a result, the polishing load applied during polishing of the top edge E1, i.e., the polishing rate of the top edge E1, can be freely controlled. Furthermore, the protection mechanism prevents relative sliding between the wafer W held by the holding stage 4 and the support stage 70. As a result, the back surface of the wafer W is not damaged when polishing the top edge E1.

[0046] 11 is a vertical cross-sectional view showing a polishing apparatus according to another embodiment. Configurations not specifically described are the same as those in the above-described embodiment, and therefore redundant description will be omitted.

[0047] 11 differs from the above-described embodiments in that it includes a rotary actuator that rotates the support stage 70 in synchronization with the rotation of the holding stage 4. More specifically, the polishing apparatus shown in FIG. 11 differs from the above-described embodiments in that it omits the above-described connecting arm 71 and includes a rotary actuator that rotates the support stage 70.

[0048] 11, a motor 75 serving as a rotary actuator for rotating the support stage 70 is attached to the outer surface of the casing 14. In this embodiment, the motor M1 for rotating the support stage 4 is referred to as the "first motor M1," and the motor 75 for rotating the support stage 70 is referred to as the "second motor 75." The first motor M1 and the second motor 75 are connected to a control device 11, which is configured to be able to independently control the operation of the first motor M1 and the operation of the second motor 75.

[0049] A rotation mount 76 is attached to the second motor 75, and when the control device 11 drives the second motor 75, the rotation mount 76 rotates. The lifting actuator 73 is fixed to the rotation mount 76, and when the second motor 75 is driven, the support stage 70 rotates via the rotation mount 76, the lifting actuator 73, and the guide rails 74.

[0050] In this embodiment, too, the control device 11 controls the operation of the lifting actuator 73, thereby moving the support stage 70 up and down. As a result, the polishing load applied when polishing the top edge E1 of the wafer W can be supported by the support stage 70. Therefore, even if a large polishing load is applied to the top edge E1 of the wafer W, the wafer W will not bend, and neither the device formed on the wafer W nor the wafer W itself will be damaged. Therefore, the polishing load during polishing of the top edge E1, i.e., the polishing rate of the top edge E1, can be freely controlled.

[0051] Furthermore, the control device 11 can synchronize the rotation of the second motor 75 with the rotation of the first motor M1. Therefore, when polishing the top edge portion E1, the support stage 70 can rotate at the same rotational speed as the holding stage 4, preventing damage to the back surface of the wafer W. In this embodiment, the second motor 75 constitutes a protection mechanism that prevents relative sliding between the support stage 70 and the wafer W held by the holding stage 4. In one embodiment, when changing the rotational speed of the holding stage 4, the control device 11 may temporarily separate the polishing head 30 and the support stage 60 from the front and back surfaces of the wafer W. In this case, the control device 11 resumes polishing the top edge portion E1 of the wafer W by bringing the polishing head 30 and the support stage 70 into contact with the front and back surfaces of the wafer W after the rotational speed of the second motor 75 becomes the same as the rotational speed of the first motor M1.

[0052] In this embodiment, the capacity of the first motor M1 that rotates the hollow shaft 5 can be made smaller than the capacity of the first motor M1 in the embodiment shown in Figures 2 and 3. This allows for greater freedom in designing the polishing apparatus, and it is expected that the polishing apparatus can be operated with less energy than in the embodiment shown in Figures 2 and 3.

[0053] Fig. 12(a) is a top view schematically showing a support stage 70 of a polishing apparatus according to yet another embodiment, and Fig. 12(b) is a cross-sectional view taken along line AA in Fig. 12(a). The configuration of this embodiment that is not specifically described is the same as that of the above-described embodiment, and therefore a duplicated description thereof will be omitted.

[0054] 12(a), a support stage 70 of a polishing apparatus has a plurality of rollers 77 arranged on the upper surface of the support stage 70, which is the surface that comes into contact with the wafer W (i.e., the support surface). The rollers 77 are arranged concentrically at equal intervals on the ring-shaped support stage 70. As shown in FIG. 12(b), each roller 77 is rotatably mounted on the upper surface of the support stage 70 via a rotation shaft 78. The rotation shaft 78 extends in the radial direction of the support stage 4.

[0055] The outer circumferential surface of each roller 77 protrudes from the upper surface of the support stage 70, and when the control device 11 moves the support stage 70 to the support position, the back surface of the wafer W comes into contact with the outer circumferential surfaces of the rollers 77, not with the upper surface of the support stage 70. Therefore, even if the back surface of the wafer W, which rotates together with the rotating holding stage 4, shifts (or slides) relative to the support stage 70, the back surface of the wafer W is prevented from being damaged by the rotating rollers 77.

[0056] The plurality of rollers 77 may be provided on the support stage 70 of the polishing apparatus according to the embodiment shown in Figures 2 and 3, or may be provided on the support stage 70 of the polishing apparatus according to the embodiment shown in Figure 11. In the embodiment shown in Figures 2 and 3, when the plurality of rollers 77 are provided on the support stage 70, the protection mechanism is formed by a combination of the connecting arm 71 and the plurality of rollers 77. In the embodiment shown in Figure 11, when the plurality of rollers 77 are provided on the support stage 70, the protection mechanism is formed by a combination of the second motor 75 and the plurality of rollers 77.

[0057] According to this embodiment, even if the wafer W, which is held by the holding stage 4 and rotates together with or in synchronization with the holding stage 4, shifts relative to the support stage 70 during polishing of the top edge portion E1, the rotation of the multiple rollers 77 prevents the rear surface of the wafer W from being damaged. Therefore, the rear surface of the wafer W can be protected more reliably.

[0058] 11, the second motor 75 may be omitted. In this case, the support stage 70 does not rotate synchronously with the holding stage 4. However, the back surface of the wafer W, which rotates together with the holding stage 4, moves on a plurality of rollers 77, and the rotation of the plurality of rollers 77 prevents the back surface of the wafer W from being damaged. In this case, the protection mechanism is formed by the plurality of rollers 77.

[0059] 13 is a side view schematically showing a support stage 70 of a polishing apparatus according to yet another embodiment. The configuration of this embodiment that is not specifically described is the same as that of the above-described embodiment, and therefore, redundant description thereof will be omitted.

[0060] The embodiment shown in Figure 13 differs from the above-described embodiments in that the protection mechanism is a fluid injection mechanism 80 configured to inject fluid at a pressure corresponding to the polishing load with which the polishing tape 23 is pressed against the top edge portion E1 of the wafer W.

[0061] 13 includes a supply line 81 connected to the support stage 70 and supplying fluid to the upper surface (support surface) of the support stage 70, an on-off valve 82 arranged on the supply line 81, and a regulator 83 arranged on the supply line 81 and capable of adjusting the pressure of the fluid flowing through the supply line 81. In this embodiment, the on-off valve 82 is arranged upstream of the regulator 83 in the direction of fluid flow. The on-off valve 82 and the regulator 83 are connected to a control device 11, which is configured to be able to control the operation of the on-off valve 82 and the regulator 83. The supply line 81 is also connected to a fluid supply source (not shown), and when the control device 11 opens the on-off valve 82, the fluid is supplied to the upper surface of the support stage 70.

[0062] The control device 11 controls the operation of the regulator 83 so that the pressure of the fluid supplied to the upper surface of the support stage 70 is equal to the polishing load of the polishing tape 23 applied by the polishing head 30. The fluid supplied to the upper surface of the support stage 70 by the fluid injection mechanism 80 functions as a lubricating fluid that prevents relative sliding between the wafer W held on the holding stage 4 and the support stage 70. Examples of this lubricating fluid include liquids such as pure water, and gases such as nitrogen.

[0063] In this embodiment, the support stage 70 is not rotated. Therefore, the connecting arm 71 shown in FIGS. 2 and 3 or the second motor 75 shown in FIG. 11 is omitted from the polishing apparatus, and the support stage 70 is fixed to a stationary member (for example, the casing 14 or the inner wall of the polishing apparatus) via an elevation actuator 73 and a guide rail 74. In the example shown in FIG. 13, the support stage 70 is fixed to an attachment mount 84 extending from the inner wall of the polishing apparatus via the elevation actuator 73 and the guide rail 74.

[0064] In this embodiment, the control device 11 also controls the operation of the lifting actuator 73 to move the support stage 70 up and down. The polishing load when polishing the top edge E1 of the wafer W can be supported by the fluid supplied to the upper surface of the support stage 70. Therefore, even if a large polishing load is applied to the top edge E1 of the wafer W, the wafer W does not bend, and devices formed on the wafer W and the wafer W itself are not damaged. As a result, the polishing load during polishing of the top edge E1, i.e., the polishing rate of the top edge E1, can be freely controlled. Furthermore, when polishing the top edge E1, the backside of the rotating wafer W slides on the fluid supplied to the upper surface of the support stage 70, preventing the backside of the wafer W from being damaged.

[0065] Fig. 14 is a vertical cross-sectional view schematically showing a support stage 70 of a polishing apparatus according to yet another embodiment, and Fig. 15 is a top view schematically showing the support stage of the polishing apparatus shown in Fig. 14. Configurations of this embodiment that are not specifically described are similar to those of the above-described embodiments, and therefore redundant description will be omitted.

[0066] In the embodiments described so far, the support stage 70 has a ring shape. However, the shape of the support stage 70 is not limited to a ring shape as long as it can support the polishing load applied from the polishing head 30 to the upper surface of the wafer W when polishing the top edge portion E1. For example, the polishing apparatus shown in FIG. 14 has multiple support stages 70A-70D provided corresponding to the number of polishing head assemblies 1A-1D. FIG. 14 depicts only the support stages 70A and 70D corresponding to the polishing head assemblies 1A and 1D. Elevation actuators 73A-73D that move the support stages 70A-70D up and down are connected to the control device 11, and the control device 11 is configured to be able to independently control each of the elevation actuators 73A-73D.

[0067] In this embodiment, the lifting actuators 73A-73D are attached to the casing 14, which is a stationary member, via installation mounts 84A-84D, respectively. Therefore, the support stages 70A-70D do not rotate together with the holding stage 4 or in synchronization with the holding stage. The control device 11 selects a support stage from the support stages 70A-70D to support the backside of the wafer W, corresponding to the polishing head 30 of the polishing head assembly 1A-1D selected to polish the top edge portion E1 according to the polishing recipe. The selected support stage supports a portion of the backside of the peripheral edge of the wafer W while polishing the top edge portion E1 of the wafer W.

[0068] Each of the support stages 70A-70D has a support surface for supporting a portion of the back surface of the wafer W facing the polishing head 30 of the polishing head assemblies 1A-1D. More specifically, the upper surface (support surface) of each of the support stages 70A-70D has an area equal to or larger than the area of ​​contact between the polishing tape 23 and the upper surface of the wafer W to polish the top edge portion E1 of the wafer W.

[0069] In this embodiment, too, the control device 11 controls the operation of the lifting actuators 73A-73D, thereby moving the support stages 70A-70D up and down in accordance with the polishing head 30 selected to polish the top edge portion E1. As a result, the support stages 70A-70D can support the polishing load when polishing the top edge portion E1 of the wafer W. Therefore, even if a large polishing load is applied to the top edge portion E1 of the wafer W, the wafer W will not bend, and neither the device formed on the wafer W nor the wafer W itself will be damaged. Therefore, the polishing load during polishing of the top edge portion E1, i.e., the polishing rate of the top edge portion E1, can be freely controlled.

[0070] Furthermore, according to this embodiment, the bevel portion B and / or bottom edge portion E2 of the peripheral portion of the wafer W can be polished by a polishing head assembly 1A-1D other than the polishing head assembly 1A-1D selected for polishing the top edge portion E1. For example, while the top edge portion E1 is polished by the polishing head assembly 1A, the bevel portion B may be polished by the polishing head assemblies 1B and 1C, and the bottom edge portion E2 may be polished by the polishing head assembly 1D. In this case, the support stage 70A corresponding to the polishing head assembly 1A is moved to the support position, while the support stages 70B-70D corresponding to the polishing head assemblies 1B-1D are moved to the retracted positions or are kept waiting at the retracted positions. This configuration improves the throughput for polishing the peripheral portion of the wafer W.

[0071] 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. [Explanation of symbols]

[0072] 1A~1D Polishing head assembly 2A~2D Polishing tape supply and recovery mechanism 3 Board holding part 4 Holding stage 5 hollow shaft 6 Ball spline bearing 7 Communication path 9 Vacuum Line 10 Nitrogen gas supply line 11 Control device 30 Polishing Head 41 Pressing mechanism 50 Pressing member 52 Air cylinder 64 Pressure pad 67 Linear Actuator 70 Support Stage 71 Connecting arm 72 Lifting device 73 Lifting Actuator 74 Guide Rail 75 Second motor 76 Rotating Mount 77 Coro 78 Rotational Axis 80 Fluid injection mechanism 81 Supply Line 82 On-off valve 83 Regulator 84 Mount

Claims

1. A polishing apparatus having at least one polishing head, which presses a polishing tool held by the polishing head against a peripheral portion of a substrate, including a top edge portion, to polish the peripheral portion, comprising: a holding stage having a diameter smaller than a diameter of the substrate and configured to hold a center portion of the substrate; a rotation mechanism that rotates the holding stage; a support stage positioned outside the holding stage and capable of supporting a rear surface of the substrate facing the top edge portion; an elevation mechanism that moves the support stage up and down; a protection mechanism for preventing relative sliding between the substrate held by the holding stage and the support stage.

2. The rotation mechanism includes: a stage shaft connected to the holding stage; an actuator that rotates the stage shaft, 2. The polishing apparatus according to claim 1, wherein the protection mechanism includes a connecting arm that connects the support stage to the stage shaft.

3. the rotation mechanism includes a first motor that rotates the holding stage; 2. The polishing apparatus according to claim 1, wherein the protection mechanism includes a second motor that rotates the support stage in synchronization with the first motor.

4. 2. The polishing apparatus according to claim 1, wherein the protection mechanism includes at least one roller provided on a support surface of the support stage facing the back surface of the substrate.

5. 2. The polishing apparatus according to claim 1, wherein the protection mechanism is a fluid injection mechanism that injects fluid having a pressure corresponding to a polishing load with which the polishing tool is pressed against the top edge portion of the substrate.

6. The polishing apparatus according to claim 1 , wherein the support stage has a ring shape.

7. 6. The polishing apparatus according to claim 1, wherein the support stage has a support surface for supporting a part of the rear surface of the substrate that faces the polishing head.

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