Substrate grinding method

Abstract

To provide a substrate polishing device which can polish a whole surface to be polished of a substrate at uniformed polishing rate.SOLUTION: A method for polishing a substrate includes rotating about the axis while moving the substrate W and a polishing head 10C in a relative circular motion, pressing, with the polishing head 10C, a polishing tape 2B against a surface 5a to be polished while feeding the polishing tape 2B in a longitudinal direction, and polishing a center region including a center O1 of the substrate W and an outer region adjacent to the center region. The step of polishing the center region and the outer region includes at least two polishing steps that are performed under different polishing conditions. The at least two polishing steps include a low polishing rate step that is performed under polishing conditions where a polishing rate of the center region is lower than that of the outer region, and a high polishing rate step that is performed under polishing conditions where the polishing rate of the center region is higher than that of the outer region.SELECTED DRAWING: Figure 15

Description

[Technical Field]

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

[0002] In recent years, devices such as memory circuits, logic circuits, and image sensors (e.g., CMOS sensors) have become increasingly highly integrated. During the processes used to fabricate these devices, foreign particles such as particles and dust can adhere to the devices. Foreign particles adhering to devices can cause short circuits between wiring and circuit malfunctions. Therefore, in order to improve device reliability, it is necessary to clean the substrates on which the devices are formed and remove any foreign particles on the substrate.

[0003] The back surface (non-device surface) of the substrate can also become contaminated with foreign matter such as the fine particles and dust particles mentioned above, as well as excess film unintentionally formed during the film formation process. If such foreign matter or excess film adheres to the back surface of the substrate, the substrate will move away from the stage reference surface of the exposure tool, causing the substrate surface to tilt relative to the stage reference surface, resulting in patterning misalignment and focal length deviation. To prevent such problems, it is necessary to remove the foreign matter and excess film adhered to the back surface of the substrate.

[0004] Therefore, a substrate polishing apparatus is used that polishes the back surface of a substrate by pressing a polishing head against a polishing tape against the back surface of the substrate. Recently, there has been an increasing demand for an apparatus that can polish the entire front surface of a substrate more efficiently. Therefore, a substrate polishing apparatus has been proposed that polishes the back surface of the substrate while causing the polishing head and the substrate to move circularly relative to each other, thereby ensuring the relative speed between the pressing member of the polishing head and the substrate.

[0005] Fig. 18 is a top view of a conventional substrate polishing apparatus that polishes the back surface of a substrate W with a polishing tape 502 while moving the substrate W in a circular motion, and Fig. 19 is a side view of the conventional substrate polishing apparatus shown in Fig. 18. A substrate holding unit 510 of the substrate polishing apparatus has a plurality of rollers 500 and a plurality of eccentric shafts 507 fixed to the plurality of rollers 500, respectively.

[0006] 19, the eccentric shaft 507 has a first shaft portion 507a and a second shaft portion 507b that are eccentric by a distance e. The roller 500 is fixed to one end of the second shaft portion 507b, and the first shaft portion 507a is connected to a motor 509. When the motor 509 is driven, the roller 500 performs a circular motion with a radius e around the axis of the second shaft portion 507b, and the roller 500 itself rotates around that axis. As a result, the substrate holder 510 rotates the substrate W around its axis O1 while causing the substrate W to perform a circular motion with a radius e.

[0007] The polishing tape 502 is placed on the backside of the substrate W. A predetermined tension is applied to the polishing tape 502 as it advances in the direction indicated by arrow Z. A plurality of pressing members 505A-505D are arranged in the diameter direction of the substrate W, and these pressing members 505A-505D press the polishing tape 502 against the backside of the substrate W, thereby polishing the backside of the substrate W. In such a conventional substrate polishing apparatus, the pressing members 505A-505D and the substrate W are caused to perform a circular motion relative to each other, thereby polishing the central part of the substrate W, which could not be polished by rotation of the substrate W alone. Therefore, the entire backside of the substrate W can be polished efficiently. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2019-77003 Summary of the Invention [Problem to be solved by the invention]

[0009] However, when the back surface of the substrate W is polished while the pressing members 505A-505D and the substrate W are circularly moved relative to each other, the central region CR including the center O1 of the substrate W shown in FIG. 18 continues to be pressed by the pressing member 505C for a relatively longer time than the other regions. Therefore, the central region CR of the substrate W may be over-polished compared to the regions other than the central region CR. As a result, the substrate polishing apparatus may not be able to uniformly polish the back surface of the substrate W.

[0010] Therefore, the present invention provides a substrate polishing method that can polish the entire surface of a substrate to be polished at a uniform polishing rate. [Means for solving the problem]

[0011] In one aspect, there is provided a substrate polishing method for polishing a surface of a substrate, the method comprising: , a first polishing head and a second polishing head While rotating the substrate around its axis while rotating the polishing head in a circular motion relative to the polishing tape, and feeding the polishing tape in its longitudinal direction, The first a polishing head pressing the polishing tape against the surface to be polished to polish a central region including the center of the substrate and an outer region adjacent to the central region; While feeding the polishing tape in its longitudinal direction, the second polishing head presses the polishing tape against the surface to be polished to polish the area other than the central area and the outer area of ​​the substrate, and the first polishing head The step of polishing the central region and the outer region includes at least two polishing steps carried out under different polishing conditions, and the at least two polishing steps include a low polishing rate step carried out under polishing conditions such that the polishing rate of the central region is lower than the polishing rate of the outer region, and a high polishing rate step carried out under polishing conditions such that the polishing rate of the central region is higher than the polishing rate of the outer region. When the polishing of the central region and the outer region by the first polishing head is changed between the low polishing rate step and the high polishing rate step, the polishing of the region other than the central region and the outer region by the second polishing head is continued without changing the polishing conditions. SUMMARY OF THE INVENTION A method for polishing a substrate is provided.

[0012] In one aspect, The low polishing rate step and the high polishing rate step are changed. The parameters of the polishing conditions are No. 1 The tape pressing force generated by the polishing head, the tape tension of the polishing tape, No. 1 The position of a guide roller that is disposed adjacent to the polishing head and that guides the polishing tape, the outer diameter of the guide roller, and the No. 1 The polishing head includes at least one of the length of the pressing member, the angle at which the pressing member slopes downward toward the center of the substrate, and the hardness of the pressing member. In one embodiment, the tape pressing force under the polishing conditions in the high polishing rate step is greater than the tape pressing force under the polishing conditions in the low polishing rate step.

[0013] In one embodiment, the tape tension of the polishing tape under the polishing conditions in the high polishing rate step is smaller than the tape tension of the polishing tape under the polishing conditions in the low polishing rate step. In one embodiment, the position of the guide roller under the polishing conditions of the high polishing rate step is higher than the position of the guide roller under the polishing conditions of the low polishing rate step. In one aspect, the angle at which the pressing member inclines downward toward the center of the substrate under the polishing conditions of the high polishing rate step is smaller than the angle at which the pressing member inclines downward toward the center of the substrate under the polishing conditions of the low polishing rate step. [Effects of the Invention]

[0014] The substrate polishing method includes at least two polishing steps, including a low polishing rate step in which the polishing rate in the central region of the substrate is low and a high polishing rate step in which the polishing rate in the central region of the substrate is high. Therefore, the entire surface to be polished can be polished at a uniform polishing rate without over-polishing the central region of the substrate. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a side view showing an embodiment of a substrate polishing apparatus. [Figure 2] FIG. 2 is a top view of the substrate polishing apparatus shown in FIG. [Figure 3] 10A and 10B are schematic diagrams illustrating an embodiment of a guide roller position adjustment mechanism. [Figure 4] FIG. 1 is a perspective view showing an embodiment of a polishing head. [Figure 5] FIG. 5 is a top view of the polishing head shown in FIG. [Figure 6] 1 is a graph showing the relationship between the position from the center of the substrate and the polishing rate in a low polishing rate process. [Figure 7] 1 is a graph showing the relationship between the position on the substrate and the polishing rate in a high polishing rate process. [Figure 8] 10A and 10B are diagrams illustrating changes in the polishing rate of the central region due to differences in the tape pressing force. [Figure 9] FIG. 10 is a diagram illustrating a change in the polishing rate of the central region due to differences in tape tension. [Figure 10] 10A and 10B are diagrams illustrating changes in the polishing rate in the central region due to differences in the positions of guide rollers arranged adjacent to the polishing head. [Figure 11] 10A and 10B are diagrams illustrating changes in the polishing rate in the central region due to differences in the angle of the pressing member of the polishing head. [Figure 12] 10A and 10B are diagrams illustrating changes in the polishing rate in the central region due to differences in the outer diameter of a guide roller disposed adjacent to the polishing head. [Figure 13] 10A and 10B are diagrams illustrating changes in the polishing rate in the central region due to differences in the length of the pressing member of the polishing head. [Figure 14] 1 is a graph showing the relationship between the position from the center of the substrate and the polishing rate in a polishing process including a low polishing rate process and a high polishing rate process. [Figure 15] 1 is a flow chart illustrating one embodiment of a process for polishing a substrate. [Figure 16] FIG. 10 is a diagram showing an example of parameters of polishing conditions in a low polishing rate process and a high polishing rate process. [Figure 17] FIG. 10 is a side view showing another embodiment of the substrate polishing apparatus. [Figure 18] FIG. 1 is a top view of a conventional substrate polishing apparatus. [Figure 19] FIG. 19 is a side view of the conventional substrate polishing apparatus shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a side view showing one embodiment of a substrate polishing apparatus, and Fig. 2 is a top view of the substrate polishing apparatus shown in Fig. 1. The substrate polishing apparatus shown in Fig. 1 and Fig. 2 includes a substrate holding unit 20 that holds and rotates a substrate W, a plurality of polishing heads 10A to 10D that polish the first surface 5a of the substrate W by bringing polishing tapes 2A and 2B into contact with the first surface 5a of the substrate W held by the substrate holding unit 20, a polishing tape supply mechanism 30A that feeds the polishing tape 2A in its longitudinal direction, and a polishing tape supply mechanism 30B that feeds the polishing tape 2B in its longitudinal direction.

[0017] In this embodiment, the first surface 5a of the substrate W is the back surface of the substrate W on which no devices have been formed or are not planned to be formed, i.e., the non-device surface. The second surface 5b of the substrate W opposite the first surface 5a is the surface on which devices have been formed or are planned to be formed, i.e., the device surface. In this embodiment, the substrate W is supported horizontally by the substrate holder 20 with the first surface 5a, which is the surface to be polished, facing downward.

[0018] The substrate holder 20 includes a plurality of rollers 25 that can come into contact with the peripheral edge of the substrate W, a plurality of motors 29 that rotate the rollers 25, and a plurality of eccentric shafts 27 that connect the rollers 25 to the motors 29. In this embodiment, four rollers are provided, but five or more rollers may be provided.

[0019] Each of the multiple eccentric shafts 27 has a first shaft portion 27a and a second shaft portion 27b that extend parallel to each other. The second shaft portion 27b is eccentric from the first shaft portion 27a by a distance e1. The multiple rollers 25 are fixed to one end of the multiple second shaft portions 27b, respectively. The axes of the multiple rollers 25 coincide with the axes of the multiple second shaft portions 27b, respectively. The motors 29 are connected to one end of the first shaft portion 27a, respectively.

[0020] When the multiple motors 29 are driven, the multiple eccentric shafts 27 are rotated around their first shaft portions 27a. When the multiple eccentric shafts 27 rotate, the rollers 25 perform a circular motion with a radius e1 around the axis of the first shaft portions 27a. When the rollers 25 rotate once around the axis of the first shaft portions 27a, the rollers 25 rotate once around the axis of the rollers 25. In this specification, circular motion is defined as the motion of an object moving on a circular orbit.

[0021] The substrate holder 20 rotates the substrate W held by the rollers 25 about its axis (center) O1 while making a circular motion of radius e1 due to such movement of the rollers 25. Therefore, the substrate W and the polishing heads 10A to 10D make a circular motion relative to each other.

[0022] Polishing heads 10A and 10B are supported by support member 18A, and polishing heads 10C and 10D are supported by support member 18B. The polishing heads 10A to 10D are arranged below the substrate W held by substrate holder 20. These polishing heads 10A to 10D are arranged in the diameter direction of the substrate W. In this embodiment, four polishing heads 10A to 10D are provided, but the number of polishing heads is not limited to this embodiment. In another embodiment, a single polishing head may be provided.

[0023] The polishing tape supply mechanisms 30A and 30B have the same configuration, so the following will describe only the polishing tape supply mechanism 30A. The polishing tape supply mechanism 30A is equipped with a tape supply reel 31 to which one end of the polishing tape 2A is connected, a tape take-up reel 32 to which the other end of the polishing tape 2A is connected, and a plurality of guide rollers 33 that guide the polishing tape 2A in the traveling direction. The tape supply reel 31 and the tape take-up reel 32 are connected to reel motors 36 and 37, respectively.

[0024] By rotating the tape take-up reel 32 in the direction indicated by the arrow, the polishing tape 2A is fed from the tape supply reel 31 to the polishing heads 10A and 10B and then to the tape take-up reel 32. The polishing tape 2A is supplied above the polishing heads 10A and 10B so that the polishing surface of the polishing tape 2A faces the first surface 5a of the substrate W. The reel motor 36 applies a predetermined torque to the tape supply reel 31, thereby applying tension to the polishing tape 2A. The reel motor 37 is controlled to feed the polishing tape 2A at a constant speed. The feeding speed of the polishing tape 2A can be changed by changing the rotational speed of the tape take-up reel 32.

[0025] In one embodiment, the substrate polishing apparatus may include a tape feeding device that feeds the polishing tape 2A in its longitudinal direction, separate from the tape supply reel 31, the tape take-up reel 32, and the reel motors 36 and 37. In other embodiments, the positions of the tape supply reel 31 and the tape take-up reel 32 may be reversed.

[0026] The substrate polishing apparatus further includes a guide roller position adjustment mechanism 40 that moves the guide roller 33 up and down. FIG. 3 is a schematic diagram showing one embodiment of the guide roller position adjustment mechanism 40. The guide roller position adjustment mechanism 40 has an actuator 45 and a movable shaft 43. The movable shaft 43 extends in the vertical direction, with one end connected to the guide roller 33 and the other end connected to the actuator 45. The actuator 45 is configured to move the movable shaft 43 up and down, thereby moving the guide roller 33 up and down in the direction indicated by the arrow. Examples of the actuator 45 include a piston cylinder device equipped with a piston that moves the movable shaft 43 up and down, and a combination of a servo motor and a gear.

[0027] The guide roller position adjustment mechanism 40 is connected to each of the multiple guide rollers 33. In one embodiment, the guide roller position adjustment mechanism 40 may be connected only to the guide rollers 33 adjacent to the polishing heads 10A to 10D. Note that the specific configuration of the guide roller position adjustment mechanism 40 is not limited to the embodiment shown in FIG. 3, as long as it can move the guide rollers 33 up and down. In other embodiments, the guide roller position adjustment mechanism 40 may not have the actuator 45, but may include a guide member that supports the guide rollers 33 and a fixing member that fixes the position of the guide rollers 33 relative to the guide member. In still other embodiments, the substrate polishing apparatus may not include the guide roller position adjustment mechanism 40.

[0028] Fig. 4 is a side view showing one embodiment of the polishing head 10A, and Fig. 5 is a top view of the polishing head 10A shown in Fig. 4. Since the polishing heads 10A to 10D basically have the same configuration, only the polishing head 10A will be described below. The polishing head 10A is disposed below the substrate W and the polishing tape 2A so as to press the polishing tape 2A against the back surface of the substrate W from the back side.

[0029] The polishing head 10A includes a pressing member 12 for pressing the polishing tape 2A against the substrate W, a pressing member holder 13 for holding the pressing member 12, a polishing head actuator 15 for applying a pressing force to the pressing member 12, a polishing head housing 16 connected to the support member 18A, and a tilt mechanism 17 for tilting the pressing member holder 13.

[0030] The pressing member 12 is a blade having a linearly extending shape, and has a pressing surface 12a for pressing the polishing tape 2A against the substrate W. The pressing member 12 is fixed to a pressing member holder 13. The pressing member 12 is inclined obliquely with respect to the direction of travel of the polishing tape 2A indicated by the arrow Z. The pressing member 12 is made of an elastic material. Examples of materials that can be used to form the pressing member 12 include rubbers such as fluororubber, silicone rubber, and ethylene propylene diene rubber. The cross section of the pressing member 12 has a circular shape.

[0031] However, the pressing member 12 is not limited to this embodiment and may have other shapes or be made of other materials. In one embodiment, the pressing member 12 may be disposed perpendicular to the traveling direction of the polishing tape 2A. In other embodiments, the pressing member 12 may have two blades or may be a blade with a curved shape.

[0032] The polishing head actuator 15 is disposed in the polishing head housing 16 and is connected to the pressing member holder 13 by a connecting member (not shown). The polishing head actuator 15 is configured to move the pressing member holder 13 and the pressing member 12 in the pressing direction indicated by the arrow CL, thereby generating a tape pressing force that presses the polishing tape 2A against the substrate W.

[0033] The tilt mechanism 17 is fixed to the pressing member holder 13. The tilt mechanism 17 has a support shaft 17a, and can rotate the pressing member holder 13 by a predetermined angle around the axis of the support shaft 17a using a motor (not shown). This allows the tilt mechanism 17 to tilt the pressing member holder 13 and the pressing member 12 with respect to the pressing direction indicated by the arrow CL. Furthermore, the tilt mechanism 17 is configured to maintain the tilted angles of the pressing member holder 13 and the pressing member 12. Examples of the motor include a servo motor or a stepping motor. Note that the specific configuration of the tilt mechanism 17 is not limited to the embodiment shown in FIG. 4 , as long as it can tilt the pressing member 12 with respect to the pressing direction indicated by the arrow CL. In other embodiments, the tilt mechanism 17 may not have a motor for tilting the pressing member 12, but may instead include a support member that rotatably supports the pressing member 12 and a fixing member that fixes the angle of the pressing member 12 relative to the support member. In still other embodiments, the substrate polishing apparatus may not include the tilt mechanism 17 .

[0034] The substrate polishing apparatus is electrically connected to an operation control unit 50 that controls the operation of each component of the substrate polishing apparatus. The motor 29 of the substrate holding unit 20, the polishing head actuator 15 of the polishing heads 10A to 10D, the tilt mechanism 17, the polishing tape supply mechanisms 30A and 30B, and the actuator 45 of the guide roller position adjustment mechanism 40 are electrically connected to the operation control unit 50. The operations of the substrate holding unit 20, the polishing heads 10A to 10D, the polishing tape supply mechanisms 30A and 30B, and the guide roller position adjustment mechanism 40 are controlled by the operation control unit 50.

[0035] The operation control unit 50 includes at least one computer. The operation control unit 50 includes a storage device 50a that stores a program, and an arithmetic unit 50b that executes calculations in accordance with the program. The storage device 50a includes a main storage device (e.g., random access memory) accessible by the arithmetic unit 50b, and an auxiliary storage device (e.g., a hard disk drive or solid state drive) that stores the program. The arithmetic unit 50b 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 50a. However, the specific configuration of the operation control unit 50 is not limited to these examples.

[0036] The substrate W is polished as follows. The substrate holding unit 20 holds the peripheral edge of the substrate W with a plurality of rollers 25 and rotates a plurality of eccentric shafts 27 to cause the rollers 25 to perform circular motion. The substrate holding unit 20 rotates the substrate W about its axis O1, while causing the substrate W and the polishing heads 10A to 10D to perform circular motion relative to each other. While the polishing tape supply mechanisms 30A and 30B feed the polishing tapes 2A and 2B to the polishing heads 10A to 10D, the pressing members 12 of the polishing heads 10A to 10D press the polishing tapes 2A and 2B against the first surface 5a of the substrate W to polish the first surface 5a of the substrate W.

[0037] 18 and 19, in this embodiment, to prevent the central region including the center O1 of the substrate W from being over-polished compared to the regions other than the central region, the polishing process by polishing head 10C, one of the multiple polishing heads 10A to 10D, which polishes the region including the center O1 of the substrate W, includes at least two polishing processes performed under different polishing conditions. Polishing head 10C polishes the central region within the first surface 5a including the center O1 of the substrate W and an outer region adjacent to the central region. The at least two polishing processes by polishing head 10C include a low-polishing rate process performed under polishing conditions such that the polishing rate in the central region is lower than the polishing rate in the outer regions, and a high-polishing rate process performed under polishing conditions such that the polishing rate in the central region is higher than the polishing rate in the outer regions.

[0038] FIG. 6 is a graph showing the relationship between the position from the center O1 of the substrate W and the polishing rate in the low polishing rate process, and FIG. 7 is a graph showing the relationship between the position from the center O1 of the substrate W and the polishing rate in the high polishing rate process. FIGS. 6 and 7 are graphs obtained when the polishing head 10C presses the polishing tape 2B against the first surface 5a of the substrate W to polish it. The position from the center O1 of the substrate W represents the position from the center O1 of the substrate W on a line that passes through the center O1 of the substrate W and follows the direction of travel of the polishing tape 2B. In other words, the position from the center O1 of the substrate W represents the position in the radial direction of the substrate W. A negative value for the position from the center O1 of the substrate W indicates a position upstream of the center O1 of the substrate W in the direction of travel of the polishing tape 2B, and a positive value for the position from the center O1 of the substrate W indicates a position downstream of the center O1 of the substrate W in the direction of travel of the polishing tape 2B.

[0039] In this embodiment, the central region is a region whose distance from the center O1 of the substrate W is from 0 to X1, and the outer region is a region whose distance from the center O1 of the substrate W is from X1 to X2. The outer region is located radially outward of the substrate W from the central region. As shown in FIG. 6, in the low polishing rate step, the polishing rate in the central region is lower than the polishing rate in the outer region. As shown in FIG. 7, in the high polishing rate step, the polishing rate in the central region is higher than the polishing rate in the outer region.

[0040] These polishing rates can be adjusted by parameters of the polishing conditions, which include at least one of the tape pressing force generated by the polishing head 10C, the tape tension of the polishing tape 2B, the position of the guide roller 33 disposed adjacent to the polishing head 10C, the angle of the pressing member 12 of the polishing head 10C that slopes downward toward the center O1 of the substrate W, the outer diameter of the guide roller 33 disposed adjacent to the polishing head 10C, the length of the pressing member 12 of the polishing head 10C, and the hardness of the pressing member 12 of the polishing head 10C.

[0041] 8 is a diagram illustrating the change in the polishing rate of the central region due to differences in tape pressure. The tape pressure generated by the polishing head 10C can be adjusted by the polishing head actuator 15 shown in FIG. 4. When the tape pressure F2 is greater than the tape pressure F1, the polishing rate of the central region when the substrate W is polished with the tape pressure F2 is higher than the polishing rate of the central region when the substrate W is polished with the tape pressure F1. Therefore, the tape pressure under the polishing conditions of the high polishing rate step is greater than the tape pressure under the polishing conditions of the low polishing rate step.

[0042] 9 is a diagram illustrating the change in the polishing rate of the central region due to differences in tape tension. The tape tension can be adjusted by the torque applied to the tape unwinding reel 31 by the reel motor 36 shown in FIG. 1. When the tape tension T2 is smaller than the tape tension T1, the polishing rate of the central region when the substrate W is polished with the tape tension T2 is higher than the polishing rate of the central region when the substrate W is polished with the tape tension T1. Therefore, the tape tension under the polishing conditions for the high polishing rate step is smaller than the tape tension under the polishing conditions for the low polishing rate step.

[0043] 10 is a diagram illustrating the change in the polishing rate of the central region depending on the position of the guide roller 33 disposed adjacent to the polishing head 10C. The position of the guide roller 33 disposed adjacent to the polishing head 10C can be adjusted by the guide roller position adjustment mechanism 40 shown in FIG. 3. When height H2 is higher than height H1, the polishing rate of the central region when the substrate W is polished at height H2 of the guide roller 33 is higher than the polishing rate of the central region when the substrate W is polished at height H1 of the guide roller 33. Therefore, the position of the guide roller 33 disposed adjacent to the polishing head 10C under the polishing conditions for the high polishing rate step is higher than the position of the guide roller 33 under the polishing conditions for the low polishing rate step.

[0044] 11 is a diagram illustrating the change in the polishing rate of the central region due to differences in the angle of the pressing member 12 of the polishing head 10C. The angle of the pressing member 12 of the polishing head 10C is the angle of the pressing surface 12a of the pressing member 12 with respect to the first surface 5a of the substrate W. The angle of the pressing member 12 of the polishing head 10C can be adjusted by the tilt mechanism 17 shown in FIG. 4. When the angle α2 (angle α2 is 0 degrees in FIG. 11) at which the pressing member 12 of the polishing head 10C is tilted downward toward the center O1 of the substrate W is smaller than angle α1, the polishing rate of the central region when the substrate W is polished at angle α2 is higher than the polishing rate of the central region when the substrate W is polished at angle α1. Therefore, the angle at which the pressing member 12 of the polishing head 10C tilts downward toward the center O1 of the substrate W under the polishing conditions of the high polishing rate process is smaller than the angle at which the pressing member 12 of the polishing head 10C tilts downward toward the center O1 of the substrate W under the polishing conditions of the low polishing rate process.

[0045] 12 is a diagram illustrating the change in the polishing rate in the central region due to differences in the outer diameter of guide roller 33 disposed adjacent to polishing head 10C. When the axes of guide rollers 33 are in the same position and outer diameter D2 of guide roller 33 is larger than outer diameter D1 of guide roller 33, the polishing rate in the central region when substrate W is polished with outer diameter D2 is higher than the polishing rate in the central region when substrate W is polished with outer diameter D1. Therefore, the outer diameter of guide roller 33 disposed adjacent to polishing head 10C under polishing conditions for the high polishing rate step is larger than the outer diameter of guide roller 33 under polishing conditions for the low polishing rate step.

[0046] 13 is a diagram illustrating the change in the polishing rate of the central region due to differences in the length of the pressing member 12 of the polishing head 10C. When the length L2 is longer than the length L1 in the direction toward the center O1 of the substrate W, the polishing rate of the central region when the pressing member 12 of the polishing head 10C polishes the substrate W at the length L2 is higher than the polishing rate of the central region when the pressing member 12 of the polishing head 10C polishes the substrate W at the length L2. Therefore, the length of the pressing member 12 of the polishing head 10C under the polishing conditions for the high polishing rate step is longer in the direction toward the center O1 of the substrate W than the length of the pressing member 12 of the polishing head 10C under the polishing conditions for the low polishing rate step. The length of the pressing member 12 of the polishing head 10C is the length along the longitudinal direction of the polishing tape 2B.

[0047] Furthermore, the polishing rate of the central region also varies depending on the hardness of the pressing member 12 of the polishing head 10C. The hardness of the pressing member 12 can be adjusted by the material that makes up the pressing member 12. The polishing rate of the central region when the hardness of the pressing member 12 of the polishing head 10C is low is higher than the polishing rate of the central region when the hardness of the pressing member 12 of the polishing head 10C is high. Therefore, the hardness of the pressing member 12 of the polishing head 10C under the polishing conditions for the high polishing rate step is lower than the hardness of the pressing member 12 of the polishing head 10C under the polishing conditions for the low polishing rate step.

[0048] 14 is a graph showing the relationship between the position from the center O1 of the substrate W and the polishing rate in a polishing process including a low polishing rate process and a high polishing rate process. The process of polishing the central region and the outer region using the polishing head 10C includes at least two polishing processes, including a low polishing rate process and a high polishing rate process, so that the central region and the outer region have a uniform polishing rate, as shown in FIG. 14. The polishing conditions in each polishing process using the polishing head 10C are determined based on data on the polishing results of past substrates. More specifically, the parameters of the polishing conditions in the low polishing rate process and the high polishing rate process are determined based on data on the polishing results of past substrates in which each parameter of the polishing conditions described above was changed.

[0049] FIG. 15 is a flowchart showing an embodiment of a process for polishing a substrate W. In step 1, the polishing conditions for the low polishing rate step and the high polishing rate step by the polishing head 10C are determined based on data on the results of polishing substrates in the past. In step 2, the substrate holder 20 rotates the substrate W about its axis O1 while causing the substrate W and the polishing heads 10A to 10D to perform a circular motion relative to each other.

[0050] In step 3, the substrate W is polished by using the polishing heads 10A and 10B to press the polishing tape 2A against the first surface 5a of the substrate W. Furthermore, the substrate W is polished by using the polishing heads 10C and 10D to press the polishing tape 2B against the first surface 5a of the substrate W. In the polishing by the polishing head 10C, a low polishing rate process is performed under the determined polishing conditions.

[0051] In step 4, while polishing of the substrate W by the polishing heads 10A, 10B, and 10D continues, polishing by the polishing head 10C performs a high polishing rate process under the determined polishing conditions. That is, the polishing conditions for polishing by the polishing head 10C are changed from a low polishing rate process to a high polishing rate process. This makes the polishing rates in the central region and outer regions of the substrate W uniform, and allows the entire first surface 5a of the substrate W to be polished at a uniform polishing rate. In step 5, polishing of the substrate W by the polishing heads 10A to 10D is completed.

[0052] In this embodiment, polishing by the polishing head 10C involves a low polishing rate step followed by a high polishing rate step, but the polishing steps by the polishing head 10C are not limited to this embodiment. In one embodiment, polishing by the polishing head 10C may involve a high polishing rate step followed by a low polishing rate step. In other embodiments, polishing by the polishing head 10C may include three or more polishing steps. For example, polishing by the polishing head 10C may involve two low polishing rate steps performed under different polishing conditions followed by one high polishing rate step.

[0053] 15, when changing the polishing by the polishing head 10C from a low polishing rate process to a high polishing rate process, it is necessary to change the parameters of the polishing conditions that can be changed during polishing of the substrate W. Therefore, the parameters of the polishing conditions that can be changed during polishing of the substrate W include at least one of the parameters of the polishing conditions described above: the tape pressing force generated by the polishing head 10C, the tape tension of the polishing tape 2B, the position of the guide roller 33 arranged adjacent to the polishing head 10C, and the angle of inclination of the pressing member 12 of the polishing head 10C downward toward the center O1 of the substrate W.

[0054] FIG. 16 is a diagram showing an example of parameters of polishing conditions in the low polishing rate process and the high polishing rate process. The polishing conditions in the low polishing rate process are: the angle at which the pressing member 12 of the polishing head 10C tilts downward toward the center O1 of the substrate W is angle α; and the tape pressing force generated by the polishing head 10C is tape pressing force F1. The polishing conditions in the high polishing rate process are: the angle at which the pressing member 12 of the polishing head 10C tilts downward toward the center O1 of the substrate W is angle α; and the tape pressing force generated by the polishing head 10C is tape pressing force F2, which is greater than the tape pressing force F1. The parameters of the polishing conditions other than the tape pressing force are the same as those in the low polishing rate process. In this example, the low polishing rate process is performed for polishing time Y1, and then the high polishing rate process is performed for polishing time Y2.

[0055] 16, the low polishing rate step is performed by setting the angle of inclination of the pressing member 12 of the polishing head 10C downward toward the center O1 of the substrate W to angle α. Furthermore, the high polishing rate step is performed by changing the tape pressing force generated by the polishing head 10C to tape pressing force F2, which is greater than tape pressing force F1. As a result, the polishing rates in the central region and the outer region of the substrate W become uniform, and the entire first surface 5a of the substrate W can be polished at a uniform polishing rate.

[0056] For example, the polishing time Y1 of the low polishing rate step and the polishing time Y2 of the high polishing rate step are determined to be appropriate times by polishing a test substrate. Alternatively, the polishing profile of the substrate W may be measured at predetermined time intervals during the high polishing rate step, and the high polishing rate step may be terminated when an appropriate polishing profile is obtained.

[0057] The parameters of the polishing conditions in the low polishing rate process and the high polishing rate process shown in Figure 16 are just examples, and the parameters of the polishing conditions in the low polishing rate process and the high polishing rate process may be other parameters such as the tape tension of the polishing tape 2B or the position of the guide roller 33 arranged adjacent to the polishing head 10C, or may be a combination of multiple parameters including other parameters.

[0058] Figure 17 is a side view showing another embodiment of the substrate polishing apparatus. The configuration of the substrate polishing apparatus of this embodiment, which is not specifically described, is the same as the configuration of the substrate polishing apparatus described with reference to Figures 1 to 5, and therefore a duplicated description will be omitted. The substrate polishing apparatus of this embodiment differs from the embodiment described with reference to Figures 1 to 5 in the configuration of the substrate holding unit 60, and further includes a table circular motion mechanism 70 that causes circular motion of the polishing heads 10A to 10D and the polishing tape supply mechanisms 30A and 30B.

[0059] The substrate holding unit 60 includes a plurality of rollers 65 that can come into contact with the peripheral edge of the substrate W, and a roller rotation device (not shown) for rotating the plurality of rollers 65 at the same speed. The substrate W is held horizontally by the substrate holding unit 60 with its first surface 5a facing downward. In this embodiment, four rollers 65 are provided, but five or more rollers may be provided.

[0060] The polishing heads 10A-10D are disposed below the substrate W held by the substrate holder 60. The table circular motion mechanism 70 is disposed below the polishing heads 10A-10D and the polishing tape supply mechanisms 30A and 30B. The support member 18A that supports the polishing heads 10A and 10B, the support member 18B that supports the polishing heads 10C and 10D, and the polishing tape supply mechanisms 30A and 30B are connected to the table circular motion mechanism 70.

[0061] The table circular motion mechanism 70 includes a table motor 72, a crankshaft 74 fixed to the table motor 72, a table 81, a base 82, and multiple eccentric joints 75. The table motor 72 is disposed below the base 82 and fixed to the underside of the base 82. The crankshaft 74 extends upward through the base 82. The table 81 is coupled to the multiple eccentric joints 75 and the crankshaft 74. The base 82 is connected to the multiple eccentric joints 75. The table 81 is coupled to the base 82 via the multiple eccentric joints 75 and the crankshaft 74. Although only two eccentric joints 75 are shown in FIG. 17 , the table circular motion mechanism 70 includes at least two eccentric joints 75.

[0062] The tip of the crankshaft 74 is eccentric by a distance e2 from the axis of the table motor 72. Therefore, when the table motor 72 is driven, the table 81 performs a circular motion with a radius e2. Because the table 81 is supported by multiple eccentric joints 75, the table 81 itself does not rotate while performing the circular motion. The amount of eccentricity of the multiple eccentric joints 75 is the same as the amount of eccentricity of the table 81. The polishing heads 10A to 10D and the polishing tape supply mechanisms 30A and 30B are fixed to the table 81.

[0063] When the table circular movement mechanism 70 is operated, the polishing heads 10A to 10D and the polishing tape supply mechanisms 30A, 30B are caused to circularly move together, so that the substrate W held by the substrate holding part 60 and the polishing heads 10A to 10D are caused to circularly move relative to each other.

[0064] The roller rotation device of the substrate holding unit 60 and the table motor 72 of the table circular motion mechanism 70 are electrically connected to the operation control unit 50. The operations of the substrate holding unit 60 and the table circular motion mechanism 70 are controlled by the operation control unit 50.

[0065] The substrate W is polished as follows. The substrate holder 60 rotates the substrate W by holding the peripheral edge of the substrate W with a plurality of rollers 65. The table circular motion mechanism 70 causes the polishing heads 10A to 10D and the polishing tape supply mechanisms 30A and 30B to perform circular motion together, thereby causing the substrate W and the polishing heads 10A to 10D to perform circular motion relative to each other. While the polishing tape supply mechanisms 30A and 30B feed the polishing tapes 2A and 2B to the polishing heads 10A to 10D, the pressing members 12 of the polishing heads 10A to 10D press the polishing tapes 2A and 2B against the first surface 5a of the substrate W to polish the first surface 5a of the substrate W.

[0066] Of the multiple polishing heads 10A-10D of the substrate polishing apparatus shown in Figure 17, the polishing process performed by polishing head 10C, which polishes the region including the center O1 of the substrate W, includes at least two polishing processes performed under different polishing conditions, similar to the embodiment described with reference to Figures 6 to 16. More specifically, the at least two polishing processes performed by polishing head 10C include at least two polishing processes including a low polishing rate process and a high polishing rate process so that the central region and the outer region have a uniform polishing rate. The polishing process of this embodiment is the same as the polishing process described with reference to Figures 6 to 16, so a duplicated description will be omitted.

[0067] 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]

[0068] 2A, 2B Polishing Tape 5a First Side 5b Second Side 10A, 10B, 10C, 10D Polishing head 12 Pressing member 13 Pressing member holder 15 Polishing head actuator 16 Polishing head housing 17 Tilt mechanism 17a Support shaft 18A, 18B Support member 20 Board holding part 25 Roller 27 Eccentric shaft 27a 1st shaft part 27b 2nd shaft part 29 Motor 30A, 30B Polishing tape supply mechanism 31 Tape unwinding reel 32 Tape take-up reel 33 Guide roller 36,37 Reel motor 40 Guide roller position adjustment mechanism 43 Movable axis 45 Actuator 50 Operation control section 50a storage device 50b Arithmetic unit 60 Board holding part 65 Roller 70 Table circular motion mechanism 72 Table Motor 74 crankshaft 75 Eccentric joint 81 Table 82 Foundation

Claims

1. A substrate polishing method for polishing a surface of a substrate, comprising: rotating the substrate around its axis while causing the substrate, the first polishing head, and the second polishing head to perform a circular motion relative to each other; While feeding the polishing tape in its longitudinal direction, the polishing tape is pressed against the surface to be polished by the first polishing head, thereby polishing a central region including the center of the substrate and an outer region adjacent to the central region; While feeding the polishing tape in its longitudinal direction, the second polishing head presses the polishing tape against the surface to be polished, thereby polishing an area other than the central area and the outer area of ​​the substrate; the step of polishing the central region and the outer region by the first polishing head includes at least two polishing steps performed under different polishing conditions; The at least two polishing steps include: a low polishing rate step carried out under polishing conditions in which the polishing rate in the central region is lower than the polishing rate in the outer region; a high polishing rate step carried out under polishing conditions in which the polishing rate in the central region is higher than the polishing rate in the outer region; A substrate polishing method, wherein when polishing of the central region and the outer region by the first polishing head is changed between the low polishing rate process and the high polishing rate process, polishing of the region other than the central region and the outer region by the second polishing head is continued without changing the polishing conditions.

2. A substrate polishing method as described in claim 1, wherein the parameters of the polishing conditions that are changed between the low polishing rate process and the high polishing rate process include at least one of the tape pressing force generated by the first polishing head, the tape tension of the polishing tape, the position of a guide roller that guides the polishing tape and is arranged adjacent to the first polishing head, the outer diameter of the guide roller, the length of the pressing member of the first polishing head that presses the polishing tape against the substrate, the angle at which the pressing member inclines downward toward the center of the substrate, and the hardness of the pressing member.

3. 3. The substrate polishing method according to claim 2, wherein the tape pressing force under the polishing conditions in the high polishing rate step is greater than the tape pressing force under the polishing conditions in the low polishing rate step.

4. 3. The substrate polishing method according to claim 2, wherein the tape tension of the polishing tape under the polishing conditions in the high polishing rate step is smaller than the tape tension of the polishing tape under the polishing conditions in the low polishing rate step.

5. 3. The substrate polishing method according to claim 2, wherein a position of the guide roller under polishing conditions in the high polishing rate step is higher than a position of the guide roller under polishing conditions in the low polishing rate step.

6. 3. The substrate polishing method according to claim 2, wherein an angle of the pressing member inclining downward toward the center of the substrate under polishing conditions in the high polishing rate step is smaller than an angle of the pressing member inclining downward toward the center of the substrate under polishing conditions in the low polishing rate step.

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