Substrate grinding method

Abstract

This invention relates to a substrate polishing method for polishing substrates such as wafers. The substrate polishing method involves simultaneously rotating the substrate (W) around its axis while making the substrate (W) and polishing head (10C) move in a circular motion relative to each other, and feeding a polishing strip (2B) along its long side. The polishing head (10C) then pushes the polishing strip (2B) onto the surface to be polished (5a) to polish a central region including the center (O1) of the substrate (W) and an outer region adjacent to the central region. The polishing process of the central region and the outer region includes at least two polishing processes performed under different polishing conditions. These at least two polishing processes include: a low polishing rate process performed under polishing conditions where the polishing rate of the central region is lower than that of the outer region; and a high polishing rate process performed under polishing conditions where the polishing rate of the central region is higher than that of the outer region.

Description

Technical Field

[0001] This invention relates to a substrate grinding method for grinding substrates such as wafers. Prior Technology

[0002] In recent years, components such as memory circuits, logic circuits, and image sensors (e.g., CMOS sensors) have become increasingly highly integrated. During the fabrication of these components, foreign matter such as microparticles or dust can adhere to them. This foreign matter can cause short circuits in wiring or malfunctions in the circuitry. Therefore, to improve component reliability, the substrate on which the components are formed must be cleaned to remove foreign matter.

[0003] On the back side of the substrate (non-component side), there may also be foreign matter such as microparticles or dust as described above, or excess film formed unintentionally during the film deposition process. If foreign matter or excess film as described above adheres to the back side of the substrate, the substrate separates from the stage reference plane of the exposure apparatus, and the substrate surface tilts relative to the stage reference plane, resulting in patterning shift or focal distance shift. To prevent the problems described above, the foreign matter or excess film adhering to the back side of the substrate must be removed.

[0004] Therefore, a substrate polishing apparatus is used to polish the back side of the substrate by pressing a polishing head against a polishing strip. Recently, there has been an increasing demand for apparatuses that can more efficiently polish the entire surface of a substrate. Therefore, a substrate polishing apparatus is proposed that polishes the back side of the substrate while making the polishing head rotate in a circular motion relative to the substrate, and that ensures the relative speed between the pressing member of the polishing head and the substrate.

[0005] Figure 18 is a top view of a conventional substrate polishing apparatus in which the back side of the substrate W is polished by an polishing strip 502 while the substrate W is rotated in a circular motion. Figure 19 is a side view of the conventional substrate polishing apparatus shown in Figure 18. The substrate holding part 510 of the substrate polishing apparatus includes: a plurality of rollers 500 and a plurality of eccentric shafts 507 respectively fixed to the plurality of rollers 500.

[0006] As shown in Figure 19, the eccentric shaft 507 has a first shaft portion 507a and a second shaft portion 507b, which are eccentric by a distance e. A 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 driven by the motor 509, the roller 500 performs a circular motion with radius e around the axis of the second shaft portion 507b, and the roller 500 itself also rotates around its axis. In this way, the substrate holding portion 510 causes the substrate W to perform a circular motion with radius e while simultaneously rotating the substrate W around its axis O1.

[0007] The abrasive strip 502 is disposed on the back side of the substrate W. The abrasive strip 502 is subjected to a predetermined tension while traveling in the direction indicated by arrow Z. A plurality of pressing members 505A-505D are arranged along the diameter direction of the substrate W, and these pressing members 505A-505D push the abrasive strip 502 against the back side of the substrate W, thereby abrading the back side of the substrate W. The conventional substrate abrasive apparatus described above, by causing the pressing members 505A-505D to move in a circular motion relative to the substrate W, can also abrade the central portion of the substrate W, which would not be sufficiently abrasive if only the rotation of the substrate W were used. Therefore, the entire back side of the substrate W can be abraded efficiently. [Previous Technical Documents] [Patent Literature]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2019-77003 Summary of the Invention

[0009] [The problem that the invention aims to solve]

[0010] However, when the pressing members 505A-505D are moving in a circular motion relative to the substrate W while grinding the back surface of the substrate W, the central region CR, which includes the center O1 of the substrate W as shown in FIG. 18, is continuously pressed by the pressing member 505C for a relatively longer period of time compared to other regions. Therefore, compared to the regions other than the central region CR, the central region CR of the substrate W is over-ground. As a result, the substrate grinding apparatus is unable to uniformly grind the back surface of the substrate W.

[0011] Therefore, the present invention provides a substrate polishing method that can polish the entire surface of the substrate with a uniform polishing rate. [Methods for solving problems]

[0012] In one embodiment, a substrate polishing method is provided, which is a substrate polishing method for polishing the polished surface of a substrate. The method includes: while making the substrate and polishing head move in a circular motion relative to each other, while making the substrate rotate around its axis, while feeding an polishing strip in the long side direction, and while pushing the polishing strip onto the polished surface by the polishing head, so as to polish a central region including the center of the substrate and an outer region adjacent to the central region. The process of polishing the central region and the outer region includes at least two polishing processes performed under different polishing conditions. The at least two polishing processes include: a low polishing rate process performed under polishing conditions where the polishing rate of the central region is lower than that of the outer region; and a high polishing rate process performed under polishing conditions where the polishing rate of the central region is higher than that of the outer region.

[0013] In one embodiment, the parameters of the aforementioned grinding conditions include at least one of the following: the strip pressing pressure generated by the aforementioned grinding head, the strip tension of the aforementioned grinding strip, the position of the guide roller that guides the aforementioned grinding strip adjacent to the aforementioned grinding head, the outer diameter of the aforementioned guide roller, the length of the pressing member of the aforementioned grinding head that presses the aforementioned grinding strip against the aforementioned substrate, the angle at which the aforementioned pressing member is inclined downward toward the center of the aforementioned substrate, and the hardness of the aforementioned pressing member. In one state, the strip pressing pressure in the grinding conditions of the aforementioned high grinding rate process is greater than the strip pressing pressure in the grinding conditions of the aforementioned low grinding rate process.

[0014] In one state, the strip tension of the aforementioned grinding strip in the grinding conditions of the aforementioned high grinding rate process is less than the strip tension of the aforementioned grinding strip in the grinding conditions of the aforementioned low grinding rate process. In one state, the position of the aforementioned guide roller in the grinding conditions of the aforementioned high grinding rate process is higher than the position of the aforementioned guide roller in the grinding conditions of the aforementioned low grinding rate process. In one state, the angle at which the pressing member is tilted downward toward the center of the substrate in the grinding conditions of the aforementioned high grinding rate process is smaller than the angle at which the pressing member is tilted downward toward the center of the substrate in the grinding conditions of the aforementioned low grinding rate process. [Effects of the Invention]

[0015] The substrate polishing method includes at least two polishing steps, namely: a low polishing rate step with a low polishing rate in the central region of the substrate, and a high polishing rate step with a high polishing rate in the central region of the substrate. Therefore, there is no situation where the central region of the substrate is over-polished, and the entire surface to be polished can be polished with a uniform polishing rate. Simple Explanation of the Diagram

[0016] Figure 1 is a side view of one embodiment of the substrate polishing apparatus. Figure 2 is a top view of the substrate polishing apparatus shown in Figure 1. Figure 3 is a schematic diagram showing one embodiment of the guide roller position adjustment mechanism. Figure 4 is a side view showing one embodiment of the grinding head. Figure 5 is a top view of the grinding head shown in Figure 4. Figure 6 is a graph showing the relationship between the position of the substrate from the center and the polishing rate during a low polishing rate process. Figure 7 is a graph showing the relationship between the position of the substrate from the center and the polishing rate during a high polishing rate process. Figure 8 illustrates the change in the abrasion rate in the central region due to different strip pressing pressures. Figure 9 illustrates the change in the grinding rate of the central region due to different belt tensions. Figure 10 illustrates the variation in the grinding rate in the central region due to the different positions of the guide rollers positioned adjacent to the grinding head. Figure 11 illustrates the variation in the grinding rate in the central region due to different angles of the pressing component of the grinding head. Figure 12 illustrates the variation in the grinding rate in the central region due to the different outer diameters of the guide rollers positioned adjacent to the grinding heads. Figure 13 illustrates the variation in the grinding rate in the central region due to the different lengths of the pressing components of the grinding head. Figure 14 is a graph showing the relationship between the position from the center of the substrate and the polishing rate in a polishing process that includes both low-polishing-rate and high-polishing-rate processes. Figure 15 is a flowchart of one embodiment of the polishing process of the display substrate. Figure 16 is a diagram showing an example of the parameters of the grinding conditions in low-grinding-rate processes and high-grinding-rate processes. Figure 17 is a side view of another embodiment of the substrate polishing apparatus. Figure 18 is a top view of a conventional substrate polishing apparatus. Figure 19 is a side view of the conventional substrate polishing apparatus shown in Figure 18. Implementation

[0017] The embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a side view showing one embodiment of the substrate polishing apparatus, and Figure 2 is a top view of the substrate polishing apparatus shown in Figure 1. The substrate polishing apparatus shown in Figures 1 and 2 includes: a substrate holding part 20 that holds and rotates a substrate W; a plurality of polishing heads 10A to 10D that polishing strips 2A and 2B contact the first surface 5a of the substrate W held in the substrate holding part 20 to polish the first surface 5a of the substrate W; a polishing strip supply mechanism 30A that feeds the polishing strip 2A in the direction of its long side; and a polishing strip supply mechanism 30B that feeds the polishing strip 2B in the direction of its long side.

[0018] In this embodiment, the first surface 5a of the substrate W is the back surface of the substrate W where no element is formed or no element is planned to be formed, i.e., the non-element surface. The second surface 5b of the substrate W, which is opposite to the first surface 5a, is the surface where an element is formed or a element is planned to be formed, i.e., the element surface. In this embodiment, the substrate W is horizontally supported on the substrate holding portion 20 with the first surface 5a, which is the surface to be polished, facing downwards.

[0019] The substrate holding section 20 includes: a plurality of rollers 25 that can contact the periphery of the substrate W; a plurality of motors 29 that rotate the plurality of rollers 25; and a plurality of eccentric shafts 27 that connect the plurality of rollers 25 and the plurality of motors 29. In this embodiment, four rollers are provided, but five or more rollers may also be provided.

[0020] Each of the plurality of eccentric shafts 27 has a first shaft portion 27a and a second shaft portion 27b extending in parallel. The second shaft portion 27b is eccentrically positioned from the first shaft portion 27a by a distance e1. A plurality of rollers 25 are each fixed to one end of the plurality of second shaft portions 27b. The axis of each of the plurality of rollers 25 is aligned with the axis of each of the plurality of second shaft portions 27b. A motor 29 is connected to one end of the first shaft portion 27a.

[0021] If driven by multiple motors 29, multiple eccentric shafts 27 rotate around their first shaft portion 27a. When the multiple eccentric shafts 27 rotate, the roller 25 performs a circular motion with radius e1 around the axis of the first shaft portion 27a. When the roller 25 rotates around the axis of the first shaft portion 27a, the roller 25 rotates around its own axis. In this specification, circular motion is defined as the motion of an object moving on a circular track.

[0022] The substrate holding section 20 uses the movement of the roller 25 as shown above to cause the substrate W held on the roller 25 to move in a circular motion with a radius e1 while rotating around its axis (center) O1. Therefore, the substrate W and the polishing heads 10A~10D move in a circular motion relative to each other.

[0023] Grinding heads 10A and 10B are supported by support member 18A, and grinding heads 10C and 10D are supported by support member 18B. The plurality of grinding heads 10A to 10D are disposed on the underside of the substrate W held in the substrate holding portion 20. These grinding heads 10A to 10D are arranged in the diameter direction of the substrate W. In this embodiment, four grinding heads 10A to 10D are provided; however, the number of grinding heads is not limited to this embodiment. In one embodiment, a single grinding head may also be provided.

[0024] The grinding strip supply mechanisms 30A and 30B have the same configuration, therefore, the grinding strip supply mechanism 30A will be described below. The grinding strip supply mechanism 30A includes: a strip unwinding reel 31 connected to one end of the grinding strip 2A, a strip winding reel 32 connected to the other end of the grinding strip 2A, and a plurality of guide rollers 33 guiding the travel direction of the grinding strip 2A. The strip unwinding reel 31 and the strip winding reel 32 are respectively connected to the reel motors 36 and 37.

[0025] The grinding strip 2A is fed from the strip unwinding reel 31 to the strip rewinding reel 32 via the grinding heads 10A and 10B by rotating the strip reel 32 in the direction indicated by the arrow. The grinding strip 2A is supplied to the top of the grinding heads 10A and 10B with the grinding surface of the grinding strip 2A facing the first surface 5a of the substrate W. The reel motor 36 applies tension to the grinding strip 2A by supplying a predetermined torque to the strip unwinding reel 31. The reel motor 37 controls the conveying of the grinding strip 2A at a constant speed. The conveying speed of the grinding strip 2A can be changed by varying the rotational speed of the strip rewinding reel 32.

[0026] In one embodiment, the substrate polishing apparatus may also differ from the strip unwinding reel 31, the strip winding reel 32, and the reel motors 36 and 37, and may additionally include a strip conveying device for conveying the polishing strip 2A along its long side. In other embodiments, the positions of the strip unwinding reel 31 and the strip winding reel 32 may also be reversed.

[0027] The substrate polishing apparatus further includes a guide roller position adjustment mechanism 40 for moving the guide roller 33 up and down. Figure 3 is a schematic diagram showing one embodiment of the guide roller position adjustment mechanism 40. The guide roller position adjustment mechanism 40 includes 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, causing the guide roller 33 to move up and down in the direction indicated by the arrow. Examples of actuators 45 include a piston cylinder device with a piston that moves the movable shaft 43 up and down, or a combination of a servo motor and gears.

[0028] The guide roller position adjustment mechanism 40 is connected to each of the plurality of guide rollers 33. In one embodiment, the guide roller position adjustment mechanism 40 may also be connected only to the guide rollers 33 adjacent to the grinding heads 10A to 10D. The specific configuration of the guide roller position adjustment mechanism 40 is not limited to the embodiment shown in FIG3, as long as the guide rollers 33 can move up and down. In other embodiments, the guide roller position adjustment mechanism 40 may not have an actuator 45, but may have: a guide member supporting the guide rollers 33; and a fixing member fixing the relative position of the guide rollers 33 to the guide member. In other still embodiments, the substrate grinding apparatus may not have the guide roller position adjustment mechanism 40.

[0029] Figure 4 is a side view showing one embodiment of the polishing head 10A, and Figure 5 is a top view of the polishing head 10A shown in Figure 4. Polishing heads 10A to 10D have essentially the same configuration, so polishing head 10A will be described below. Polishing head 10A is disposed below the substrate W and the polishing strip 2A, and is configured to press the polishing strip 2A against the back side of the substrate W from its back side.

[0030] The grinding head 10A includes: a pressing member 12 for pressing the grinding strip 2A against the substrate W; a pressing member holder 13 for holding the pressing member 12; a grinding head actuator 15 for applying pressing force to the pressing member 12; a grinding head housing 16 connected to the support member 18A; and a tilting mechanism 17 for tilting the pressing member holder 13.

[0031] The pressing member 12 is a blade, which has a shape extending in a straight line. The pressing member 12 has a pressing surface 12a for pressing the abrasive strip 2A against the substrate W. The pressing member 12 is fixed to the pressing member holder 13. The pressing member 12 is inclined at an angle to the direction of travel of the abrasive strip 2A, as indicated by arrow Z. The pressing member 12 is formed of an elastic material. Examples of materials constituting the pressing member 12 include: fluororubber, silicone rubber, ethylene propylene diene rubber, etc. The cross-section of the pressing member 12 has a circular shape.

[0032] 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 also be arranged perpendicular to the traveling direction of the grinding strip 2A. In other embodiments, the pressing member 12 may have two blades or may have blades with a curved shape.

[0033] The grinding head actuator 15 is disposed within the grinding head housing 16 and is connected to the pressing member holder 13 by a connecting member (not shown). The grinding head actuator 15 is configured to move the pressing member holder 13 and the pressing member 12 in the pressing direction indicated by arrow CL, thereby generating a force that pushes the grinding strip 2A against the substrate W, i.e., the strip pressing force.

[0034] The tilting mechanism 17 is fixed to the pressing member holder 13. The tilting mechanism 17 has a support shaft 17a, which, via a motor (not shown), allows the pressing member holder 13 to rotate at a predetermined angle around the axis of the support shaft 17a. Thus, the tilting mechanism 17 is configured to tilt the pressing member holder 13 and the pressing member 12 relative to the pressing direction indicated by arrow CL. Furthermore, the tilting mechanism 17 is configured to maintain the angle of the tilted pressing member holder 13 and the pressing member 12. Examples of motors include servo motors and stepper motors. The specific configuration of the tilting mechanism 17 is not limited to the embodiment shown in FIG. 4, as long as the pressing member 12 can be tilted relative to the pressing direction indicated by arrow CL. In other embodiments, the tilting mechanism 17 does not have a motor for tilting the pressing member 12, but instead includes: a support member that rotatably supports the pressing member 12; and a fixing member that fixes the relative angle between the pressing member 12 and the support member. In other embodiments, the substrate polishing apparatus may not have a tilting mechanism 17.

[0035] The substrate polishing apparatus is electrically connected to the motion control unit 50, which 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-10D, the tilting mechanism 17, the polishing strip supply mechanisms 30A and 30B, and the actuator 45 of the guide roller position adjustment mechanism 40 are all electrically connected to the motion control unit 50. The operation of the substrate holding unit 20, the polishing heads 10A-10D, the polishing strip supply mechanisms 30A and 30B, and the guide roller position adjustment mechanism 40 is controlled by the motion control unit 50.

[0036] The motion control unit 50 includes at least one computer. The motion control unit 50 includes a memory device 50a storing programs and a processing unit 50b executing calculations according to the programs. The memory device 50a includes a main memory (e.g., random access memory) accessible by the processing unit 50b and an auxiliary memory device (e.g., a hard disk drive or solid-state drive) storing programs. The processing unit 50b includes a CPU (central processing unit) or GPU (graphics processing unit) that performs calculations according to commands contained in the programs stored in the memory device 50a. However, the specific configuration of the motion control unit 50 is not limited to these examples.

[0037] The substrate W is polished as shown below. The substrate holding part 20 holds the periphery of the substrate W with a plurality of rollers 25, and rotates a plurality of eccentric shafts 27, thereby causing the plurality of rollers 25 to move in a circular motion. The substrate holding part 20 rotates the substrate W around its axis O1 while making the substrate W move in a circular motion relative to the polishing heads 10A-10D. Polishing strips 2A and 2B are fed to the polishing heads 10A-10D by polishing strip supply mechanisms 30A and 30B, and the pressing members 12 of the polishing heads 10A-10D push the polishing strips 2A and 2B against the first surface 5a of the substrate W to polish the first surface 5a of the substrate W.

[0038] As described with reference to Figures 18 and 19, in order to prevent the central region of the center O1 of the substrate W from being over-polished compared to the regions outside the central region, in this embodiment, among the plurality of polishing heads 10A to 10D, the polishing process performed by polishing head 10C, which polishes the region containing 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 of the center O1 of the substrate W, and the outer region adjacent to the central region. The at least two polishing processes performed by polishing head 10C include: a low polishing rate process performed under polishing conditions where the polishing rate of the central region is lower than that of the outer region; and a high polishing rate process performed under polishing conditions where the polishing rate of the central region is higher than that of the outer region.

[0039] Figure 6 is a graph showing the relationship between the position of the substrate W's center O1 and the polishing rate in a low polishing rate process, and Figure 7 is a graph showing the relationship between the position of the substrate W's center O1 and the polishing rate in a high polishing rate process. Figures 6 and 7 are obtained when the polishing head 10C pushes the polishing strip 2B to polish the first surface 5a of the substrate W. The position of the substrate W's center O1 represents the position of the substrate W's center O1 along a straight line passing through the center O1 of the substrate W and along the traveling direction of the polishing strip 2B. That is, the position of the substrate W's center O1 represents the radial position of the substrate W. A negative value of the position of the substrate W's center O1 indicates a position upstream of the center O1 of the substrate W in the traveling direction of the polishing strip 2B, while a positive value indicates a position downstream of the center O1 of the substrate W in the traveling direction of the polishing strip 2B.

[0040] In this embodiment, the central region is the area at a distance of 0 to X1 from the center O1 of the substrate W, and the outer region is the area at a distance of X1 to X2 from the center O1 of the substrate W. The outer region is located radially outward from the substrate W, closer to the central region than the central region. As shown in Figure 6, in the low polishing rate process, the polishing rate of the central region is lower than that of the outer region. As shown in Figure 7, in the high polishing rate process, the polishing rate of the central region is higher than that of the outer region.

[0041] The grinding rate can be adjusted by parameters of the grinding conditions. The parameters of the grinding conditions include at least one of the following: the strip pressing force generated by the grinding head 10C, the strip tension of the grinding strip 2B, the position of the guide roller 33 adjacent to the grinding head 10C, the downward tilt angle of the pressing member 12 of the grinding head 10C toward the center O1 of the substrate W, the outer diameter of the guide roller 33 adjacent to the grinding head 10C, the length of the pressing member 12 of the grinding head 10C, and the hardness of the pressing member 12 of the grinding head 10C.

[0042] Figure 8 illustrates the change in the polishing rate of the central region due to different strip pressing pressures. The strip pressing pressure generated by the polishing head 10C can be adjusted by the polishing head actuator 15 shown in Figure 4. If the strip pressing pressure F2 is greater than the strip pressing pressure F1, the polishing rate of the central region when polishing the substrate W with the strip pressing pressure F2 is higher than the polishing rate of the central region when polishing the substrate W with the strip pressing pressure F1. Therefore, the strip pressing pressure in the polishing conditions of the high polishing rate process is greater than the strip pressing pressure in the polishing conditions of the low polishing rate process.

[0043] Figure 9 illustrates the variation in the polishing rate of the central region due to differences in strip tension. Strip tension can be adjusted by the torque supplied to the strip unwinding reel 31 via the reel motor 36 shown in Figure 1. If the strip tension T2 is less than the strip tension T1, the polishing rate of the central region when polishing the substrate W with strip tension T2 is higher than that when polishing the substrate W with strip tension T1. Therefore, the strip tension in the polishing conditions of a high polishing rate process is less than the strip tension in the polishing conditions of a low polishing rate process.

[0044] Figure 10 illustrates the variation in the grinding rate of the central region due to different positions of the guide rollers 33 adjacent to the grinding head 10C. The position of the guide rollers 33 adjacent to the grinding head 10C can be adjusted by the guide roller position adjustment mechanism 40 shown in Figure 3. If the height H2 is higher than the height H1, the grinding rate of the central region when the guide rollers 33 are positioned at height H2 and grinding the substrate W is higher than the grinding rate of the central region when the guide rollers 33 are positioned at height H1 and grinding the substrate W. Therefore, the position of the guide rollers 33 adjacent to the grinding head 10C in the grinding conditions of the high grinding rate process is higher than the position of the guide rollers 33 in the grinding conditions of the low grinding rate process.

[0045] Figure 11 illustrates the variation in the grinding rate of the central region due to different angles of the pressing member 12 of the grinding head 10C. The angle of the pressing member 12 of the grinding head 10C is the angle between the pressing surface 12a of the pressing member 12 and the first surface 5a of the substrate W. The angle of the pressing member 12 of the grinding head 10C can be adjusted by the tilting mechanism 17 shown in Figure 4. If the angle α2 (0 degrees in Figure 11) of the pressing member 12 of the grinding head 10C tilting downward toward the center O1 of the substrate W is less than the angle α1, the grinding rate of the central region when grinding the substrate W at angle α2 is higher than the grinding rate of the central region when grinding the substrate W at angle α1. Therefore, in the grinding conditions of the high grinding rate process, the angle of the pressing member 12 of the grinding head 10C tilting downward toward the center O1 of the substrate W is less than the angle of the pressing member 12 of the grinding head 10C tilting downward toward the center O1 of the substrate W in the grinding conditions of the low grinding rate process.

[0046] Figure 12 illustrates the variation in the grinding rate of the central region due to the different outer diameters of the guide rollers 33 arranged adjacent to the grinding head 10C. If the axes of the guide rollers 33 are located at the same position, and the outer diameter D2 of the guide rollers 33 is greater than the outer diameter D1 of the guide rollers 33, the grinding rate of the central region when grinding the substrate W with the outer diameter D2 is higher than the grinding rate of the central region when grinding the substrate W with the outer diameter D1. Therefore, in the grinding conditions of the high grinding rate process, the outer diameter of the guide rollers 33 arranged adjacent to the grinding head 10C is greater than the outer diameter of the guide rollers 33 in the grinding conditions of the low grinding rate process.

[0047] Figure 13 illustrates the variation in the grinding rate of the central region due to the different lengths of the pressing member 12 of the grinding head 10C. If, compared to length L1, length L2 is longer in the direction toward the center O1 of the substrate W, the grinding rate of the central region when the pressing member 12 of the grinding head 10C grinds the substrate W with length L2 is higher than the grinding rate of the central region when grinding the substrate W with length L1. Therefore, compared to the length of the pressing member 12 of the grinding head 10C in the grinding conditions of the low grinding rate process, the length of the pressing member 12 of the grinding head 10C in the grinding conditions of the high grinding rate process is longer in the direction toward the center O1 of the substrate W. The length of the pressing member 12 of the grinding head 10C is the length along the long side direction of the grinding strip 2B.

[0048] Furthermore, the grinding rate of the central region varies depending on the hardness of the pressing member 12 of the grinding head 10C. The hardness of the pressing member 12 can be adjusted by the material constituting the pressing member 12. The grinding rate of the central region when the hardness of the pressing member 12 of the grinding head 10C is low is higher than the grinding rate of the central region when the hardness of the pressing member 12 of the grinding head 10C is high. Therefore, the hardness of the pressing member 12 of the grinding head 10C in the grinding conditions of the high grinding rate process is lower than the hardness of the pressing member 12 of the grinding head 10C in the grinding conditions of the low grinding rate process.

[0049] Figure 14 is a graph showing the relationship between the position of the center O1 of the substrate W and the polishing rate in a polishing process that includes both low-polishing-rate and high-polishing-rate processes. As shown in Figure 14, the polishing process using polishing head 10C to polish the central and outer regions involves at least two polishing processes, including a low-polishing-rate process and a high-polishing-rate process, with the central and outer regions having a uniform polishing rate. The polishing conditions in each polishing process performed by polishing head 10C are determined based on data from past substrate polishing results. More specifically, the parameters of the polishing conditions in the low-polishing-rate and high-polishing-rate processes are determined based on data from past substrate polishing results that cause changes in the parameters of the aforementioned polishing conditions.

[0050] Figure 15 is a flowchart of one embodiment of the polishing process of the display substrate W. In step 1, based on data from past substrate polishing results, the polishing conditions for the low polishing rate process and the high polishing rate process performed by the polishing head 10C are determined. In step 2, the substrate holding part 20 moves the substrate W in a circular motion relative to the grinding heads 10A~10D while rotating the substrate W around its axis O1.

[0051] In step 3, the polishing strip 2A is pressed onto the first surface 5a of the substrate W using polishing heads 10A and 10B, thereby polishing the substrate W. Similarly, the polishing strip 2B is pressed onto the first surface 5a of the substrate W using polishing heads 10C and 10D, thereby polishing the substrate W. The polishing performed by polishing head 10C is a low-polishing-rate process executed under predetermined polishing conditions.

[0052] In step 4, while continuing to polish the substrate W using polishing heads 10A, 10B, and 10D, polishing is also performed using polishing head 10C. The polishing performed by polishing head 10C is a high-polish rate process executed under predetermined polishing conditions. That is, the polishing performed by polishing head 10C changes the polishing conditions from a low-polish rate process to a high-polish rate process. This ensures that the polishing rate of the central and outer regions of the substrate W becomes uniform, allowing for uniform polishing of the entire first surface 5a of the substrate W. In step 5, the grinding of the substrate W by the grinding heads 10A to 10D is completed.

[0053] In this embodiment, the grinding performed by the grinding head 10C is a high-grinding-rate process performed after a low-grinding-rate process. However, the grinding process performed by the grinding head 10C is not limited to this embodiment. In one embodiment, the grinding performed by the grinding head 10C can also be a low-grinding-rate process performed after a high-grinding-rate process. In other embodiments, the grinding process performed by the grinding head 10C can include three or more grinding processes. For example, the grinding performed by the grinding head 10C can also be a high-grinding-rate process performed after two low-grinding-rate processes performed under different grinding conditions.

[0054] In step 4 of Figure 15, when changing the grinding process performed by the grinding head 10C from a low grinding rate process to a high grinding rate process, it is necessary to change the parameters of the grinding conditions that can be changed in the grinding of the substrate W. Therefore, the parameters of the grinding conditions that are changed in the grinding of the substrate W are at least one of the following parameters: the strip pressing pressure generated by the grinding head 10C, the strip tension of the grinding strip 2B, the position of the guide roller 33 adjacent to the grinding head 10C, and the angle at which the pressing member 12 of the grinding head 10C is inclined downward toward the center O1 of the substrate W.

[0055] Figure 16 is a diagram showing an example of the parameters of the polishing conditions in the low polishing rate process and the high polishing rate process. In the low polishing rate process, the polishing conditions are: the pressing member 12 of the polishing head 10C is tilted downwards at the center O1 of the substrate W at an angle α; and the strip pressing pressure generated by the polishing head 10C is the strip pressing pressure F1. In the high polishing rate process, the polishing conditions are: the pressing member 12 of the polishing head 10C is tilted downwards at the center O1 of the substrate W at an angle α; and the strip pressing pressure generated by the polishing head 10C is the strip pressing pressure F2, which is greater than the strip pressing pressure F1. The parameters of the polishing conditions other than the strip pressing pressure are the same as in the low polishing rate process. In this example, after performing the low polishing rate process for polishing time Y1, the high polishing rate process is performed for polishing time Y2.

[0056] In the example shown in Figure 16, the pressing member 12 of the polishing head 10C is tilted downwards towards the center O1 of the substrate W at an angle α, thereby performing a low polishing rate process. Furthermore, the strip pressing pressure generated by the polishing head 10C is changed to a strip pressing pressure F2, which is greater than the strip pressing pressure F1, thereby performing a high polishing rate process. As a result, the polishing rate of the central and outer regions of the substrate W becomes uniform, allowing for uniform polishing of the entire first surface 5a of the substrate W.

[0057] The grinding time Y1 for the low grinding rate process and the grinding time Y2 for the high grinding rate process are determined by grinding the test substrate, as an example. Alternatively, in the high grinding rate process, the grinding profile of the substrate W can be measured at predetermined intervals, and the high grinding rate process ends when an appropriate grinding profile is obtained.

[0058] The parameters of the grinding conditions in the low grinding rate process and the high grinding rate process shown in Figure 16 are examples. The parameters of the grinding conditions in the low grinding rate process and the high grinding rate process can also be other parameters, such as the belt tension of the grinding belt 2B or the position of the guide roller 33 adjacent to the grinding head 10C, or a combination of multiple parameters including other parameters.

[0059] Figure 17 is a side view showing another embodiment of the substrate polishing apparatus. Unless otherwise specified, the configuration of the substrate polishing apparatus in this embodiment is the same as that described with reference to Figures 1 to 5, and therefore, a repetition of the description is omitted. The substrate polishing apparatus in this embodiment differs from the embodiments described with reference to Figures 1 to 5 in the configuration of the substrate holding part 60, and further includes a platform (table) circular motion mechanism 70 that causes the polishing heads 10A-10D and the polishing strip supply mechanisms 30A and 30B to perform circular motion.

[0060] The substrate holding portion 60 includes: a plurality of rollers 65 that can contact the periphery of the substrate W; and a roller rotating device (not shown) for rotating the plurality of rollers 65 at the same speed. The substrate W is held horizontally in the substrate holding portion 60 with its first surface 5a facing down. In this embodiment, four rollers 65 are provided, but five or more rollers may also be provided.

[0061] A plurality of grinding heads 10A to 10D are disposed on the underside of the substrate W held in the substrate holding portion 60. A platform circular motion mechanism 70 is disposed below the grinding heads 10A to 10D and the grinding strip supply mechanisms 30A and 30B. The support member 18A supporting the grinding heads 10A and 10B, the support member 18B supporting the grinding heads 10C and 10D, and the grinding strip supply mechanisms 30A and 30B are connected to the platform circular motion mechanism 70.

[0062] The platform circular motion mechanism 70 includes: a platform motor 72, a crankshaft 74 fixed to the platform motor 72, a platform 81, a base 82, and multiple eccentric joints 75. The platform motor 72 is disposed on the lower side of the base 82 and fixed to the lower surface of the base 82. The crankshaft 74 extends upward through the base 82. The platform 81 is connected to the multiple eccentric joints 75 and the crankshaft 74. The base 82 is connected to the multiple eccentric joints 75. The platform 81 is connected to the base 82 through the multiple eccentric joints 75 and the crankshaft 74. Figure 17 only depicts two eccentric joints 75, but the platform circular motion mechanism 70 has at least two eccentric joints 75.

[0063] The front end of the crankshaft 74 is offset by a distance e2 from the axis of the platform motor 72. Therefore, when driven by the platform motor 72, the platform 81 performs a circular motion with a radius of e2. The platform 81 is supported by a plurality of eccentric joints 75, so the platform 81 itself does not rotate when it performs circular motion. The eccentricity of the plurality of eccentric joints 75 is the same as the eccentricity of the platform 81. The grinding heads 10A~10D and the grinding strip supply mechanisms 30A and 30B are fixed to the platform 81.

[0064] If the platform circular motion mechanism 70 is activated, the grinding heads 10A-10D and the grinding strip supply mechanisms 30A and 30B move in a circular motion as a whole. Therefore, the substrate W held in the substrate holding part 60 moves in a circular motion relative to the grinding heads 10A-10D.

[0065] The roller rotation device of the substrate holding section 60 and the platform motor 72 of the platform circular motion mechanism 70 are electrically connected to the motion control section 50. The motion of the substrate holding section 60 and the platform circular motion mechanism 70 is controlled by the motion control section 50.

[0066] The substrate W is polished as shown below. The substrate holding part 60 holds the periphery of the substrate W with a plurality of rollers 65, and the substrate W is rotated. The platform circular motion mechanism 70 causes the polishing heads 10A-10D and the polishing strip supply mechanisms 30A and 30B to move in a circular motion as a whole, causing the substrate W to move in a circular motion relative to the polishing heads 10A-10D. While the polishing strip supply mechanisms 30A and 30B feed polishing strips 2A and 2B to the polishing heads 10A-10D, the pressing members 12 of the polishing heads 10A-10D push the polishing strips 2A and 2B against the first surface 5a of the substrate W to polish the first surface 5a of the substrate W.

[0067] In the plurality of polishing heads 10A to 10D of the substrate polishing apparatus shown in FIG17, the polishing process performed by polishing head 10C, which polishes the region containing the center O1 of the substrate W, is similar to the embodiment described with reference to FIGS. 6 to 16, and includes at least two polishing processes performed under different polishing conditions. More specifically, the at least two polishing processes performed by polishing head 10C are performed with a uniform polishing rate between the central region and the outer region, and include at least two polishing processes, including a low polishing rate process and a high polishing rate process. The polishing process of this embodiment is the same as the polishing process described with reference to FIGS. 6 to 16, so its repeated description is omitted.

[0068] The above-described embodiments are intended to enable those skilled in the art to implement the present invention. Various modifications of the above-described embodiments can naturally be accomplished by those skilled in the art, and the technical concept of the present invention can also be applied to other embodiments. Therefore, the present invention is interpreted within the maximum scope defined by the technical concept as defined in the claims, and is not limited to the described embodiments. [Industry-level availability]

[0069] This invention relates to a substrate polishing method applicable to grinding substrates such as wafers.

[0070] 2A, 2B: Grinding strips 5a: Page 1 5b: Page 2 10A, 10B, 10C, 10D: Grinding heads 12: Pressing component 13: Pressing component retainer 15: Grinding head actuator 16: Grinding head housing 17: Tilting Mechanism 17a: Support shaft 18A, 18B: Supporting components 20: Substrate holding section 25: Roller 27: Eccentric shaft 27a: First shaft section 27b: Second shaft section 29: Motor 30A, 30B: Grinding belt supply mechanism 31: Strip unwinding reel 32: Strip winding reel 33: Guide roller 36, 37: Reel motor 40: Guide roller position adjustment mechanism 43: Movable shaft 45: Actuator 50: Motion Control Department 50a: Memory device 50b: Computing device 60: Substrate holding section 65: Roller 70: Platform Circular Motion Mechanism 72: Platform Motor 74: Crankshaft 75: Eccentric joint 81: Platform 82:Abutment 500: Roller 502: Grinding strip 505A~505D: Pressing components 507: Eccentric Shaft 507a: First shaft section 507b: Second shaft section 509: Motor 510: Substrate holding section e, e1, e2: Distance (radius) O1: Axis (center) CL,Z: Arrow CR: Central Region D1, D2: Outer diameter F1, F2: Strip pressing pressure H1, H2: Height L1, L2: Length T1, T2: Strip tension Y1, Y2: Grinding time W: substrate α, α1, α2: Angles

Claims

1. A substrate polishing method, comprising polishing a surface of a substrate, wherein the substrate is rotated around its axis while simultaneously rotating in a circular motion relative to a first polishing head and a second polishing head, and a polishing strip is fed along its long side while being pressed against the surface to be polished by the first polishing head to polish a central region including the center of the substrate and an outer region adjacent to the central region; and the polishing strip is fed along its long side while being pressed against the surface to be polished by the second polishing head to polish the area of ​​the substrate other than the central region and the outer region, wherein the process 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, wherein the at least two polishing steps include: The low-grinding process is performed under grinding conditions where the grinding rate of the aforementioned central region is lower than that of the aforementioned outer region; and the high-grinding process is performed under grinding conditions where the grinding rate of the aforementioned central region is higher than that of the aforementioned outer region. When the grinding of the aforementioned central region and the aforementioned outer region performed by the aforementioned first grinding head is changed between the aforementioned low-grinding process and the aforementioned high-grinding process, the grinding of the aforementioned regions other than the aforementioned central region and the aforementioned outer region performed by the aforementioned second grinding head continues without changing the grinding conditions.

2. The substrate polishing method as described in claim 1, wherein, The parameters of the grinding conditions in the aforementioned low grinding rate process and the aforementioned high grinding rate process include at least one of the following: the strip pressing pressure generated by the aforementioned first grinding head, the strip tension of the aforementioned grinding strip, the position of the guide roller that guides the aforementioned grinding strip adjacent to the aforementioned first grinding head, the outer diameter of the aforementioned guide roller, the length of the pressing member of the aforementioned first grinding head that presses the aforementioned grinding strip against the aforementioned substrate, the angle at which the aforementioned pressing member is inclined downward toward the center of the aforementioned substrate, and the hardness of the aforementioned pressing member.

3. The substrate polishing method as described in claim 2, wherein, The strip pressing pressure in the grinding conditions of the aforementioned high grinding rate process is greater than the strip pressing pressure in the grinding conditions of the aforementioned low grinding rate process.

4. The substrate polishing method as described in claim 2, wherein, The belt tension of the grinding strip in the grinding conditions of the aforementioned high grinding rate process is less than the belt tension of the grinding strip in the grinding conditions of the aforementioned low grinding rate process.

5. The substrate polishing method as described in claim 2, wherein, The position of the guide roller in the grinding conditions of the aforementioned high grinding rate process is higher than the position of the guide roller in the grinding conditions of the aforementioned low grinding rate process.

6. The substrate polishing method as described in claim 2, wherein, In the aforementioned high-grinding-rate process, the angle at which the aforementioned pressing member is tilted downward toward the center of the aforementioned substrate is smaller than the angle at which the aforementioned pressing member is tilted downward toward the center of the aforementioned substrate in the aforementioned low-grinding-rate process.

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