Grinding apparatus and grinding method

Abstract

This invention relates to a polishing apparatus and a polishing method. The polishing apparatus includes an action control unit (9) that individually controls the pressure of each of a plurality of pressure chambers. The action control unit (9) controls the pressure in the pressure chamber of the polishing head (1) at a specific position in a manner that reduces the difference between the thickness of the controlled object and the average thickness of the entire substrate.

Description

[Technical Field]

[0001] This invention relates to a grinding apparatus and a grinding method. [Previous Technology]

[0002] Chemical mechanical polishing (CMP) is a commonly known technique in the manufacturing process of semiconductor devices. A polishing apparatus for performing CMP includes: a polishing table that supports the polishing pad; and a polishing head for holding the wafer.

[0003] When using this type of polishing apparatus to polish a wafer, the wafer is held by the polishing head and pressed against the polishing surface of the polishing pad with a specified pressure. At this time, by moving the polishing table and the polishing head relative to each other, the wafer slides into contact with the polishing surface to polish the surface of the wafer.

[0004] Furthermore, the wafer thickness distribution is obtained by detecting the signal corresponding to the wafer thickness using a film thickness detector. The grinding endpoint is determined based on the wafer thickness distribution, or the pressure of a plurality of air bladders arranged concentrically on the grinding head is controlled. The film thickness detector rotates together with the grinding stage, keeping the wafer grinding head rotating as well.

[0005] Therefore, the path of the grinding stage across the film thickness detector on the wafer surface is different for each revolution. As an indicator for controlling the pressure of each gasket, the film thickness measured at different measurement points in each concentric gasket is typically averaged to calculate the representative film thickness value within each gasket. The film thickness distribution of the wafer is calculated based on signals obtained from different measurement points on the circumference, as an averaged value in the circumferential direction. [Prior Art Documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2015 / 163164 [Patent Document 2] Japanese Patent Application Publication No. 2005-11977 [Summary of the Invention]

[0007] (The problem that the invention aims to solve)

[0008] In recent years, the requirements for film thickness uniformity have increased. In a wafer region corresponding to a concentrically arranged gas bladder, the variation in film thickness in the wafer radius direction increases. Therefore, even if the pressure of the gas bladder corresponding to this region is adjusted, it is still impossible to improve the film thickness uniformity to a certain extent.

[0009] In recent years, the requirements for film thickness uniformity have increased. Therefore, it is necessary to further consider factors such as the characteristics of the film deposition apparatus, including the degree of variation in the initial film thickness of the wafer in the circumferential direction, and the degree of variation in the grinding amount generated by grinding in the circumferential direction, in order to manage and control the grinding process (for example, actively grinding the thickest parts of the wafer, or actively grinding areas other than the thinnest parts of the wafer, to improve the uniformity of the film thickness). Furthermore, conventional methods struggle to keep the difference between the maximum and minimum film thickness within the wafer surface within acceptable limits.

[0010] Therefore, the object of the present invention is to provide a polishing apparatus and polishing method that can improve the uniformity of wafer film thickness. (Technical means to solve the problem)

[0011] One embodiment provides a polishing apparatus comprising: a polishing table supporting a polishing pad; a polishing head having a plurality of pressure chambers divided into concentric circles for pressing a substrate against the polishing surface of the polishing pad; a plurality of pressure adjusters connected to the plurality of pressure chambers; a film thickness detector embedded in the polishing table and outputting a signal based on the film thickness of the substrate; and an operation control unit that individually controls the pressure of each of the plurality of pressure chambers via the plurality of pressure adjusters. The operation control unit obtains information about a specific position of the substrate on a portion of its circumference, calculates a controllable film thickness value in a controllable area including the specific position, and an average film thickness value of the entire substrate, and controls the pressure in the pressure chamber of the polishing head corresponding to the specific position by reducing the difference between the controllable film thickness value and the average film thickness value of the entire substrate.

[0012] In one embodiment, the aforementioned motion control unit determines the aforementioned specific position based on the film thickness of the aforementioned substrate measured before polishing. In another embodiment, the aforementioned motion control unit determines the maximum film thickness position (where the maximum film thickness value is obtained) and the minimum film thickness position (where the minimum film thickness value is obtained) based on the film thickness of the aforementioned substrate measured before polishing, and determines at least one of the aforementioned maximum film thickness position and the aforementioned minimum film thickness position as the aforementioned specific position. In yet another embodiment, the aforementioned motion control unit determines the maximum film thickness value and the minimum film thickness value based on the film thickness of the aforementioned substrate measured before polishing, calculates the difference between the average film thickness value of the entire aforementioned substrate and the aforementioned maximum film thickness value, and the difference between the average film thickness value of the entire aforementioned substrate and the aforementioned minimum film thickness value, and determines the position on the aforementioned substrate where the film thickness value with the largest difference is the aforementioned specific position.

[0013] In one embodiment, the aforementioned control object film thickness value is equivalent to at least one of the maximum and minimum film thickness values ​​determined based on the aforementioned substrate film thickness measured before polishing. In another embodiment, the aforementioned control object film thickness value is the average of a plurality of film thickness values ​​in the aforementioned control object region. In yet another embodiment, the aforementioned motion control unit measures the film thickness of the aforementioned control object region, which includes the aforementioned specific location, during polishing based on a signal output from the aforementioned film thickness detector, and controls the pressure in the pressure chamber of the aforementioned polishing head corresponding to the aforementioned specific location based on the aforementioned measured film thickness.

[0014] In one embodiment, the aforementioned motion control unit divides the plurality of pressing areas on the aforementioned substrate into a specific pressing area including the aforementioned control target area and other pressing areas excluding the aforementioned specific pressing area, based on the aforementioned substrate film thickness, and calculates the average film thickness value in the aforementioned other pressing areas to reduce the difference between the average film thickness value of the aforementioned other pressing areas and the average film thickness value of the entire aforementioned substrate, thereby controlling the pressure in the pressure chamber corresponding to the aforementioned other pressing areas. In another embodiment, the aforementioned motion control unit obtains information about a reference position of a portion of a reference substrate different from the aforementioned substrate on the circumference. During the grinding of the aforementioned reference substrate, the aforementioned film thickness detector detects the physical quantity of the film thickness of the area on the aforementioned substrate including the aforementioned reference position, and obtains a plurality of data based on the film thickness of the aforementioned reference substrate based on a plurality of signals sent from the aforementioned film thickness detector, and correlates each of the aforementioned plurality of data with the film thickness of the aforementioned reference substrate at each of the aforementioned plurality of data acquisition times. In one configuration, the aforementioned motion control unit determines the aforementioned reference position based on the film thickness of the aforementioned reference substrate measured before polishing.

[0015] In one embodiment, the motion control unit controls at least one of the rotational speed of the polishing head and the rotational speed of the polishing table by having the film thickness detector pass through the controlled object area. In another embodiment, the motion control unit determines the reference position and the relative angle of the polishing head based on the relationship between the reference position of the substrate in the circumferential direction and the rotational angle of the polishing head, and controls at least one of the rotational speed of the polishing head and the rotational speed of the polishing table based on the determined relative angle.

[0016] One embodiment provides a polishing method in which a substrate is pressed against the polishing surface of a polishing pad using a polishing head having a plurality of pressure chambers divided in a concentric circle. The polishing method obtains information about a specific position of the substrate on a portion of its circumference, calculates a control target film thickness value in a control target area including the specific position, and the average film thickness value of the entire substrate, and controls the pressure in the pressure chamber of the polishing head corresponding to the specific position in a manner that reduces the difference between the control target film thickness value and the average film thickness value of the entire substrate.

[0017] One approach is to specify the aforementioned specific location based on the film thickness of the aforementioned substrate measured before polishing. Another approach is to determine the maximum film thickness location and the minimum film thickness location based on the film thickness of the aforementioned substrate measured before polishing, and to determine at least one of the aforementioned maximum film thickness location and the aforementioned minimum film thickness location as the aforementioned specific location. A third approach is to determine the maximum film thickness value and the minimum film thickness value based on the film thickness of the aforementioned substrate measured before polishing, and to calculate the difference between the average film thickness value of the entire aforementioned substrate and the aforementioned maximum film thickness value, and the difference between the average film thickness value of the entire aforementioned substrate and the aforementioned minimum film thickness value, and to determine the location on the aforementioned substrate where the film thickness value with the largest difference is the aforementioned specific location.

[0018] In one embodiment, the aforementioned control object film thickness value is equivalent to at least one of the maximum and minimum film thickness values ​​determined based on the substrate film thickness measured before polishing. In another embodiment, the aforementioned control object film thickness value is the average of a plurality of film thickness values ​​in the aforementioned control object region. In yet another embodiment, the film thickness of the aforementioned control object region, including the aforementioned specific location, is measured based on the output signal of the aforementioned film thickness detector, and the pressure in the pressure chamber of the aforementioned polishing head corresponding to the aforementioned specific location is controlled based on the aforementioned measured film thickness.

[0019] One embodiment divides a plurality of pressing areas on the aforementioned substrate into specific pressing areas including the aforementioned control target area and other pressing areas excluding the aforementioned specific pressing areas, based on the aforementioned substrate film thickness, and calculates the average film thickness value in the aforementioned other pressing areas to reduce the difference between the average film thickness value of the aforementioned other pressing areas and the average film thickness value of the entire aforementioned substrate, thereby controlling the pressure in the pressure chamber corresponding to the aforementioned other pressing areas. Another embodiment obtains information about a reference position of a portion of a reference substrate different from the aforementioned substrate on the circumference. During the polishing of the aforementioned reference substrate, the aforementioned film thickness detector detects the physical quantity of the film thickness of the region on the aforementioned substrate including the aforementioned reference position, and obtains a plurality of data based on the film thickness of the aforementioned reference substrate based on a plurality of signals sent from the aforementioned film thickness detector, and correlates each of the aforementioned plurality of data with the film thickness of the aforementioned reference substrate at each of the aforementioned plurality of data acquisition. One model determines the aforementioned reference position based on the film thickness of the aforementioned reference substrate measured before polishing.

[0020] One embodiment controls at least one of the rotational speed of the polishing head and the rotational speed of the polishing table by rotating the polishing table supporting the polishing pad, such that the film thickness detector passes through the controlled object area. Another embodiment determines the reference position and the relative angle of the polishing head based on the relationship between the reference position of the substrate in the circumferential direction and the rotational angle of the polishing head, and controls at least one of the rotational speed of the polishing head and the rotational speed of the polishing table based on the determined relative angle.

[0021] One embodiment provides a polishing apparatus comprising: a polishing table supporting a polishing pad; a polishing head having a plurality of pressure chambers divided into concentric circles for pressing a substrate onto the polishing surface of the polishing pad; a plurality of pressure adjusters connected to the plurality of pressure chambers; a film thickness detector embedded in the polishing table and outputting a signal based on the film thickness of the substrate; and an operation control unit that individually controls the pressure of each of the plurality of pressure chambers via the plurality of pressure adjusters. The aforementioned motion control unit obtains specific maximum and minimum film thickness values ​​of the aforementioned substrate from the aforementioned substrate grinding using the aforementioned film thickness detector, and specifically controls at least one of the pressure chambers corresponding to the location of the aforementioned substrate before the detection of the aforementioned maximum film thickness value and the pressure chamber corresponding to the location of the aforementioned substrate before the detection of the aforementioned minimum film thickness value. When controlling the pressure of the pressure chamber related to the aforementioned maximum film thickness value, the pressure of the pressure chamber related to the aforementioned maximum film thickness value is controlled in such a way that the average film thickness value of the aforementioned substrate corresponding to the pressure chamber related to the aforementioned maximum film thickness value is lower than the average film thickness value of the entire aforementioned substrate. When controlling the pressure of the pressure chamber related to the aforementioned minimum film thickness value, the pressure of the pressure chamber related to the aforementioned minimum film thickness value is controlled in such a way that the average film thickness value of the aforementioned substrate corresponding to the pressure chamber related to the aforementioned minimum film thickness value is higher than the average film thickness value of the entire aforementioned substrate.

[0022] In one embodiment, the aforementioned motion control unit determines the aforementioned maximum film thickness value and the aforementioned minimum film thickness value based on the film thickness of the aforementioned substrate obtained at certain time intervals during the aforementioned substrate polishing. In another embodiment, the aforementioned motion control unit calculates the polishing speed during polishing from the film thickness of the aforementioned substrate obtained by the aforementioned film thickness detector, and calculates the change in the film thickness of the aforementioned substrate between the acquisition time of the film thickness of the aforementioned substrate obtained by the aforementioned film thickness detector at each measurement point of the aforementioned substrate and a reference time based on the aforementioned polishing speed. The aforementioned change is used as a correction value to correct the film thickness of the aforementioned substrate obtained during the aforementioned substrate polishing at the aforementioned time interval, and the aforementioned maximum film thickness value and the aforementioned minimum film thickness value are determined based on the corrected film thickness of the aforementioned substrate.

[0023] In one embodiment, when the pressure chamber for the maximum film thickness value and the pressure chamber for the minimum film thickness value are the same pressure chamber, the aforementioned motion control unit pre-determines, by setting a processing plan (Recipe), whether to control the pressure chamber for the maximum film thickness value in such a way that the average film thickness value of the substrate corresponding to the pressure chamber for the maximum film thickness value is lower than the average film thickness value of the entire substrate; or to control the pressure chamber for the minimum film thickness value in such a way that the average film thickness value of the substrate corresponding to the pressure chamber for the minimum film thickness value is higher than the average film thickness value of the entire substrate. In one embodiment, when the pressure chamber for the maximum film thickness and the pressure chamber for the minimum film thickness are the same pressure chamber, the aforementioned motion control unit compares a first difference between the maximum film thickness and the average film thickness of the entire substrate, and a second difference between the minimum film thickness and the average film thickness of the entire substrate. If the first difference is greater than the second difference, the pressure in the pressure chamber for the maximum film thickness is controlled such that the average film thickness of the substrate corresponding to the pressure chamber for the maximum film thickness is lower than the average film thickness of the entire substrate. If the second difference is greater than the first difference, the pressure in the pressure chamber for the minimum film thickness is controlled such that the average film thickness of the substrate corresponding to the pressure chamber for the minimum film thickness is higher than the average film thickness of the entire substrate. In one embodiment, when the pressure chamber for the maximum film thickness and the pressure chamber for the minimum film thickness are the same pressure chamber, the aforementioned motion control unit compares a first difference between the maximum film thickness and the average film thickness in the pressing area corresponding to the maximum film thickness, and a second difference between the minimum film thickness and the average film thickness in the pressing area corresponding to the minimum film thickness. If the first difference is greater than the second difference, the pressure in the pressure chamber for the maximum film thickness is controlled such that the average film thickness of the substrate corresponding to the pressure chamber for the maximum film thickness is lower than the average film thickness of the entire substrate. If the second difference is greater than the first difference, the pressure in the pressure chamber for the minimum film thickness is controlled such that the average film thickness of the substrate corresponding to the pressure chamber for the minimum film thickness is higher than the average film thickness of the entire substrate.

[0024] One embodiment provides a polishing method in which a substrate is pressed against the polishing surface of a polishing pad by a polishing head having a plurality of pressure chambers divided in a concentric circle. A specific maximum and minimum film thickness value of the substrate is obtained from the aforementioned substrate polishing process. At least one of the pressure chambers specifically corresponding to the positions of the substrate where the maximum film thickness value is detected and the pressure chambers corresponding to the positions of the substrate where the minimum film thickness value is detected is used to control the pressure of the pressure chamber corresponding to the maximum film thickness value, such that the average film thickness value of the substrate corresponding to the pressure chamber corresponding to the maximum film thickness value is lower than the average film thickness value of the entire substrate. Conversely, the pressure of the pressure chamber corresponding to the minimum film thickness value is controlled such that the average film thickness value of the substrate corresponding to the pressure chamber corresponding to the minimum film thickness value is higher than the average film thickness value of the entire substrate.

[0025] In one embodiment, during the aforementioned substrate polishing, the maximum film thickness value and the minimum film thickness value are specified based on the film thickness of the aforementioned substrate obtained at certain time intervals. In another embodiment, the polishing speed during polishing is calculated from the film thickness of the aforementioned substrate, and the change in the film thickness of the aforementioned substrate between the time of obtaining the film thickness of the aforementioned substrate at each measurement point of the aforementioned substrate and a reference time is calculated based on the aforementioned polishing speed. The change in the aforementioned change is used as a correction value to correct the film thickness of the aforementioned substrate obtained during the aforementioned substrate polishing at the aforementioned time interval, and the maximum film thickness value and the minimum film thickness value are specified based on the corrected film thickness of the aforementioned substrate.

[0026] In a configuration where the pressure chamber for the maximum film thickness value and the pressure chamber for the minimum film thickness value are the same pressure chamber, a pre-set processing scheme is used to determine whether to control the pressure chamber for the maximum film thickness value in such a way that the average film thickness value of the substrate corresponding to the pressure chamber for the maximum film thickness value is lower than the average film thickness value of the entire substrate; or to control the pressure chamber for the minimum film thickness value in such a way that the average film thickness value of the substrate corresponding to the pressure chamber for the minimum film thickness value is higher than the average film thickness value of the entire substrate. In one configuration, when the pressure chamber for the maximum film thickness and the pressure chamber for the minimum film thickness are the same pressure chamber, the pressure of the pressure chamber for the maximum film thickness is compared with a first difference between the maximum film thickness and the average film thickness of the entire substrate, and a second difference between the minimum film thickness and the average film thickness of the entire substrate. If the first difference is greater than the second difference, the pressure of the pressure chamber for the maximum film thickness is controlled such that the average film thickness of the substrate corresponding to the pressure chamber for the maximum film thickness is lower than the average film thickness of the entire substrate. If the second difference is greater than the first difference, the pressure of the pressure chamber for the minimum film thickness is controlled such that the average film thickness of the substrate corresponding to the pressure chamber for the minimum film thickness is higher than the average film thickness of the entire substrate. In one configuration, when the pressure chamber for the maximum film thickness value and the pressure chamber for the minimum film thickness value are the same pressure chamber, the pressure of the pressure chamber for the maximum film thickness value is compared with a first difference between the maximum film thickness value and the average film thickness value in the pressing area corresponding to the maximum film thickness value, and a second difference between the minimum film thickness value and the average film thickness value in the pressing area corresponding to the minimum film thickness value. If the first difference is greater than the second difference, the pressure of the pressure chamber for the maximum film thickness value is controlled such that the average film thickness value of the substrate corresponding to the pressure chamber for the maximum film thickness value is lower than the average film thickness value of the entire substrate. If the second difference is greater than the first difference, the pressure of the pressure chamber for the minimum film thickness value is controlled such that the average film thickness value of the substrate corresponding to the pressure chamber for the minimum film thickness value is higher than the average film thickness value of the entire substrate.

[0027] One embodiment provides a polishing method in which a substrate is pressed against the polishing surface of a polishing pad by a polishing head having a plurality of pressure chambers including specific pressure chambers. The polishing method includes: a first polishing step in which the substrate is polished under first polishing conditions; and a second polishing step in which the substrate is polished under second polishing conditions determined in advance by polishing a substrate different from the substrate under the first polishing conditions based on a first polishing morphology along the radial direction of a specific area of ​​the substrate corresponding to the specific pressure chamber; the second polishing conditions include polishing conditions predetermined in order to form a second polishing morphology having a distribution opposite to that of the first polishing morphology, and the second polishing step is performed after the first polishing step.

[0028] In one embodiment, the aforementioned specific pressure chamber includes an edge pressure chamber that presses the outermost periphery of the aforementioned substrate. In another embodiment, the aforementioned second polishing condition includes polishing conditions determined by adjusting the pressure of pressure chambers other than the aforementioned specific pressure chamber. In yet another embodiment, the aforementioned second polishing condition includes polishing conditions determined by adjusting the pressure of adjacent pressure chambers adjacent to the edge pressure chamber that presses the outermost periphery of the aforementioned substrate.

[0029] In one embodiment, the aforementioned second polishing condition includes polishing conditions determined by the pressure applied to the polishing surface by adjusting the retaining ring configured to surround the outermost periphery of the aforementioned substrate. In another embodiment, the aforementioned first polishing condition includes polishing conditions in which the pressure of each of the aforementioned plurality of pressure chambers is controlled by feedback based on the film thickness of the aforementioned substrate corresponding to each of the aforementioned plurality of pressure chambers as measured using a film thickness detector during polishing, and the aforementioned substrate is polished. In yet another embodiment, the aforementioned substrate is polished under the aforementioned first polishing condition, and after a specified switching condition is met, the aforementioned substrate is polished under the aforementioned second polishing condition.

[0030] In one embodiment, the switching condition is that when the difference between the maximum and minimum film thicknesses of the aforementioned specific region significantly exceeds a specified threshold, the process switches from the first polishing condition to the second polishing condition. In another embodiment, the switching condition is based on the time required to eliminate the difference between the maximum and minimum film thicknesses of the aforementioned specific region by polishing under the second polishing condition, and the remaining polishing time before reaching the final target film thickness. In yet another embodiment, the specific pressure chamber includes an edge pressure chamber that presses against the outermost periphery of the aforementioned substrate, and the pressure of the edge pressure chamber is controlled according to the second polishing condition, while the pressure of the other pressure chambers, excluding the edge pressure chamber, is controlled according to the first polishing condition. (Effects of the Invention)

[0031] By controlling the pressure in the pressure chamber of the grinding head, since it corresponds to a control target area containing a specific location for planarizing the film thickness of the wafer, the uniformity of the wafer film thickness can be improved.

[0032] The polishing method includes a second polishing step of polishing the substrate under second polishing conditions. By polishing the substrate in the second polishing step, the uniformity of film thickness in a specific area of ​​the wafer can be improved.

Implementation Method

[0034] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG1 is a schematic diagram showing one embodiment of the polishing apparatus. As shown in FIG1, the polishing apparatus includes: a polishing table 3 supporting a polishing pad 2; a polishing head 1 for pressing a wafer W (substrate, etc.) having a film onto the polishing pad 2; a table motor 6 for rotating the polishing table 3; a polishing slurry supply nozzle 5 for supplying polishing slurry, such as slurry, onto the polishing pad 2; a film thickness detector 40 (in this embodiment, an optical film thickness detector 40) for measuring the film thickness of the wafer W; and an operation control unit 9 for controlling the operation of the polishing apparatus. The polishing surface 2a of the wafer W is formed on the surface of the polishing pad 2.

[0035] The grinding head 1 is connected to the head shaft 10, which is connected to a grinding head motor (not shown) via a belt or other connecting mechanism. The grinding head motor causes the grinding head 1 and the head shaft 10 to rotate together in the direction indicated by the arrow. The grinding table 3 is connected to the table motor 6, which is configured to rotate the grinding table 3 and the grinding pad 2 in the direction indicated by the arrow.

[0036] The wafer W is polished as follows. The polishing table 3 and polishing head 1 are rotated in the direction indicated by the arrow in Figure 1, and polishing slurry is supplied from the polishing slurry supply nozzle 5 to the polishing surface 2a of the polishing pad 2 on the polishing table 3. The wafer W is pressed against the polishing surface 2a of the polishing pad 2 by the polishing head 1 rotating around the head shaft 10, with polishing slurry present on the polishing pad 2. The polishing table 3 rotates with its center CP as the center. The surface of the wafer W is polished by the chemical action of the polishing slurry, the abrasive particles contained in the polishing slurry, or the mechanical action of the polishing pad 2.

[0037] The motion control unit 9 comprises at least one computer. The motion control unit 9 includes: a memory device 9a storing a program; and a computing device 9b that performs calculations according to commands contained in the program. The computing device 9b includes a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit) that performs calculations according to commands contained in the program stored in the memory device 9a. The memory device 9a includes: a main memory device (e.g., random access memory) accessible by the computing device 9b; and an auxiliary memory device (e.g., a hard disk drive or solid-state drive) for storing data and programs.

[0038] The motion control unit 9 is electrically connected to the film thickness detector 40. In this embodiment, the film thickness detector 40 guides light to the surface of the wafer W, detects the reflected light from the wafer W, and outputs a signal based on the film thickness of the wafer W to the motion control unit 9. The motion control unit 9 measures the film thickness of the wafer W based on the signal sent from the film thickness detector 40 (more specifically, the intensity measurement data of the reflected light from the wafer W).

[0039] The film thickness detector 40 in this embodiment is an optical film thickness detector. However, it can also be any other film thickness detector as long as the film thickness of the wafer W can be measured by the motion control unit 9. In other words, the film thickness detector 40 is a detector that detects a physical quantity related to the film thickness of the wafer W. One example of the film thickness detector 40 can be an eddy current detector. An eddy current detector generates eddy currents by passing magnetic flux through the conductive film of the wafer W using its detector coil, detects the eddy currents according to the film thickness of the wafer W, and outputs an eddy current signal. The motion control unit 9 measures the film thickness of the wafer W based on the eddy current signal.

[0040] The film thickness detector 40 of this embodiment includes: a light source 44 emitting light; a beam splitter 47; and an optical detector head 7 connected to the light source 44 and the beam splitter 47. The optical detector head 7, the light source 44, and the beam splitter 47 are mounted on the polishing table 3 and rotate integrally with the polishing table 3 and the polishing pad 2. The position of the optical detector head 7 is the position through which the polishing table 3 and the polishing pad 2 pass on the surface of the wafer W on the polishing pad 2 each time the polishing table 3 and the polishing pad 2 rotate once.

[0041] The memory device 9a stores within it a program for generating the spectrum described later and detecting the film thickness of the wafer W. Light emitted from the light source 44 is transmitted to the optical detector head 7 and guided from the optical detector head 7 to the surface of the wafer W. The light is reflected on the surface of the wafer W, and the reflected light from the surface of the wafer W is received by the optical detector head 7 and sent to the beam splitter 47. The beam splitter 47 decomposes the reflected light according to wavelength. In this way, the film thickness detector 40 detects the intensity of the reflected light at each wavelength and sends the intensity measurement data of the reflected light to the motion control unit 9.

[0042] Figure 2 is a cross-sectional view of the grinding head. As shown in Figure 2, the grinding head 1 includes: an elastic film 65 for pressing the grinding surface 2a of the grinding pad 2 onto the wafer W; a head body 21 for holding the elastic film 65; an annular drive ring 62 disposed below the head body 21; and an annular retaining ring 60 fixed below the drive ring 62.

[0043] An elastic membrane 65 is installed on the lower part of the head body 21. The head body 21 is fixed to the end of the head shaft 10. The head body 21, elastic membrane 65, drive ring 62, and retaining ring 60 are configured to rotate as a whole by rotating the head shaft 10. The retaining ring 60 and drive ring 62 are configured to move up and down relative to the head body 21. The head body 21 is formed of resin such as engineering plastic (e.g., PEEK).

[0044] The substrate pressing surface 65a is formed below the elastic film 65, which presses the polishing surface 2a of the polishing pad 2 against the wafer W. The retaining ring 60 is arranged to surround the substrate pressing surface 65a, and the wafer W is surrounded by the retaining ring 60. Four pressure chambers 70, 71, 72, and 73 are provided between the elastic film 65 and the head body 21.

[0045] Pressure chamber 70 is a central pressure chamber in the shape of a circle located in the center, pressure chamber 73 is an outermost annular edge pressure chamber located in the outermost circle, and pressure chambers 71 and 72 are intermediate pressure chambers located between pressure chamber 70 and pressure chamber 73, respectively.

[0046] Pressure chambers 70, 71, 72, and 73 are formed by the elastic membrane 65 and the head body 21. The central pressure chamber 70 is circular, while the other pressure chambers 71, 72, and 73 are annular. These pressure chambers 70, 71, 72, and 73 are arranged (divided) in concentric circles. In this embodiment, the elastic membrane 65 forms four pressure chambers 70 to 73; however, the number of pressure chambers described above is merely an example and can be appropriately changed.

[0047] Gas delivery lines F1, F2, F3, and F4 are respectively connected to pressure chambers 70, 71, 72, and 73. One end of each gas delivery line F1, F2, F3, and F4 is connected to a compressed gas supply source (not shown) located in a factory equipped with a polishing device, which serves as a utility facility. Compressed gas, such as compressed air, can be supplied to pressure chambers 70, 71, 72, and 73 through gas delivery lines F1, F2, F3, and F4, respectively. By supplying compressed gas to pressure chambers 70-73, the elastic membrane 65 expands, and the compressed gas in pressure chambers 70-73 presses the wafer W onto the polishing surface 2a of the polishing pad 2 via the elastic membrane 65. Pressure chambers 70-73 function as actuators for pressing the wafer W onto the polishing surface 2a of the polishing pad 2.

[0048] The retaining ring 60 is disposed around the elastic film 65 and is an annular member that contacts the polishing surface 2a of the polishing pad 2. The retaining ring 60 is disposed in such a way that it surrounds the outermost periphery (peripheral part) of the wafer W to prevent the wafer from being ejected from the polishing head 1 during the polishing of the wafer W, and the elastic movement (rebound) of the polishing pad 2 can be adjusted to adjust the film thickness distribution of the outermost periphery of the wafer W.

[0049] The upper part of the drive ring 62 is connected to the annular buckle pressing device 80. The buckle pressing device 80 applies a downward load to the entire upper surface 60b of the buckle 60 via the drive ring 62, thereby pressing the lower surface 60a of the buckle 60 against the grinding surface 2a of the grinding pad 2.

[0050] The retaining ring pressing device 80 includes: an annular piston 81 fixed to the upper part of the drive ring 62; and an annular rolling diaphragm 82 connected to the upper part of the piston 81. A retaining ring pressure chamber 83 is formed inside the rolling diaphragm 82. The retaining ring pressure chamber 83 is connected to the compressed gas supply source via a gas delivery line F5. Compressed gas is supplied to the retaining ring pressure chamber 83 through the gas delivery line F5.

[0051] When compressed gas is supplied from the aforementioned compressed gas supply source to the retaining ring pressure chamber 83, the rolling diaphragm 82 presses the piston 81 downwards, the piston 81 presses into the drive ring 62, and the drive ring 62 further presses the entire retaining ring 60 downwards. Thus, the retaining ring pressing device 80 presses the lower surface 60a of the retaining ring 60 against the grinding surface 2a of the grinding pad 2. The drive ring 62 is detachably connected to the retaining ring pressing device 80. In one embodiment, the retaining ring pressing device 80 may also have a structure in which the lower surface 60a of the retaining ring 60 is pressed against the grinding surface 2a of the grinding pad 2 by the downward force of the grinding head 1 acting on the retaining ring 60.

[0052] Gas delivery lines F1, F2, F3, F4, and F5 extend via a rotary joint 25 mounted on the head shaft 10. The grinding apparatus further includes pressure regulators R1, R2, R3, R4, and R5, which are respectively installed on the gas delivery lines F1, F2, F3, F4, and F5. Compressed gas from the compressed gas supply source is independently supplied to pressure chambers 70-73 and the retaining ring pressure chamber 83 via pressure regulators R1 to R5. Pressure regulators R1 to R5 are configured to adjust the pressure of the compressed gas in pressure chambers 70-73 and the retaining ring pressure chamber 83. Pressure regulators R1 to R5 are connected to the operation control unit 9.

[0053] Pressure regulators R1 to R5 allow the internal pressures of pressure chambers 70 to 73 and the retaining ring pressure chamber 83 to change independently. This allows for independent adjustment of the pressing pressure of the wafer W on the polishing surface 2a in four corresponding areas of the wafer W: the central portion, the inner middle portion, the outer middle portion, and the edge portion, as well as the pressing pressure of the retaining ring 60 on the polishing pad 2. Gas delivery lines F1, F2, F3, F4, and F5 are also connected to atmospheric opening valves (not shown), allowing pressure chambers 70 to 73 and the retaining ring pressure chamber 83 to be opened to the atmosphere. In this embodiment, the elastic membrane 65 forms four pressure chambers 70 to 73; however, in another embodiment, the elastic membrane 65 may form fewer or more pressure chambers than four.

[0054] Figure 3 is an example diagram showing the spectrum generated by the motion control unit. In Figure 3, the horizontal axis represents the wavelength of light reflected from the wafer, and the vertical axis represents the relative reflectivity derived from the intensity of the reflected light. The relative reflectivity is an index value representing the intensity of the reflected light, and is the ratio of the light intensity to a specified reference intensity. At each wavelength, by dividing the light intensity (measured intensity) by the specified reference intensity, unwanted noise such as the intensity variation inherent in the optical system of the device and the light source can be removed from the measured intensity.

[0055] The reference intensity is the light intensity measured in advance for each wavelength, and the relative reflectance is calculated for each wavelength. Specifically, the relative reflectance is obtained by dividing the light intensity (measured intensity) of each wavelength by the corresponding reference intensity.

[0056] The motion control unit 9 is configured to generate the spectrum of reflected light from the intensity measurement data of the reflected light. The spectrum of the reflected light is represented as a curve (i.e., a spectroscopic waveform) showing the relationship between the wavelength and intensity of the reflected light. The intensity of the reflected light can also be represented as a relative value such as reflectivity or relative reflectivity.

[0057] In actual polishing, the corrected measured intensity is obtained by subtracting the black level (background intensity obtained under light-shielding conditions) from the measured intensity. The corrected reference intensity is then obtained by subtracting the aforementioned black level from the reference intensity. Finally, the relative reflectivity is obtained by dividing the corrected measured intensity by the corrected reference intensity. Specifically, the relative reflectivity R(λ) can be obtained using the following formula (1). [Mathematical Formula 1] (1) Wherein, λ is the wavelength of light reflected from the substrate, E(λ) is the intensity of wavelength λ, B(λ) is the reference intensity of wavelength λ, and D(λ) is the background intensity (black level) of wavelength λ measured under light-shielding conditions.

[0058] The motion control unit 9 generates the spectrum shown in FIG3 from the intensity measurement data of the reflected light. Furthermore, the motion control unit 9 determines the film thickness of the wafer W from the spectrum of the reflected light. The spectrum of the reflected light varies with the film thickness of the wafer W. Therefore, the motion control unit 9 can determine the film thickness of the wafer W from the spectrum of the reflected light. Hereinafter, in this specification, the spectrum generated from the reflected light from the polished wafer W will be referred to as the measurement spectrum.

[0059] The motion control unit 9 is configured to determine the film thickness by comparing a measured spectrum (i.e., measurement data) with a plurality of reference spectra (i.e., reference data). The motion control unit 9 determines the reference spectrum whose shape is closest to the measured spectrum by comparing the measured spectrum generated during grinding with the plurality of reference spectra, and obtains the film thickness associated with the determined reference spectrum. The reference spectrum whose shape is closest to the measured spectrum is the spectrum with the smallest difference in relative reflectance between the reference spectrum and the measured spectrum.

[0060] The plurality of reference spectra are obtained in advance by grinding a reference wafer that is the same as the wafer to be ground (hereinafter, in this specification, wafer W is equivalent to the wafer to be ground), or has the same initial film thickness. The wafer to be ground is a different wafer from the reference wafer, and is a wafer for which a film thickness planarization process is performed. The reference wafer is a wafer for which a process of correlating the reference spectra with the corresponding film thickness is performed.

[0061] Each reference spectrum can be correlated with the film thickness at which its reference spectrum was obtained. That is, each reference spectrum is obtained at different film thicknesses, and multiple reference spectra correspond to multiple different film thicknesses. Therefore, the current film thickness can be estimated by determining the reference spectrum whose shape is closest to the measured spectrum.

[0062] Figure 4 is an example diagram showing the process of obtaining a plurality of reference spectra. First, a reference wafer with the same or the same film thickness as the wafer W is prepared. The reference wafer is transported to the film thickness measuring device 170 (refer to Figure 1), and the initial film thickness of the reference wafer is measured by the film thickness measuring device 170 (refer to step S101). The film thickness measuring device 170 is electrically connected to the motion control unit 9.

[0063] Next, a slurry is supplied to the polishing head 1 as a polishing fluid, and a reference wafer is polished (see step S102). During the polishing of the reference wafer, light is irradiated on the surface of the reference wafer to obtain the spectrum of the reflected light from the reference wafer (i.e., the reference spectrum) (see step S103).

[0064] The reference spectrum is obtained every time the polishing table 3 rotates once. Therefore, multiple reference spectra are obtained during the polishing of the reference wafer. After the polishing of the reference wafer is completed, the reference wafer is transported again to the film thickness measuring device 170 to measure the film thickness of the polished reference wafer (i.e., the final film thickness) (refer to step S104).

[0065] When the polishing rate of the reference wafer is constant, the film thickness decreases linearly along with the polishing time. The polishing rate can be calculated by dividing the difference between the initial film thickness and the final film thickness by the polishing time required to reach the final film thickness. As mentioned above, the reference spectrum is obtained periodically every revolution of the polishing table 3. Therefore, the polishing time for obtaining each reference spectrum can be calculated from the rotation speed of the polishing table 3. Thus, the motion control unit 9 determines the film thickness corresponding to each reference spectrum (refer to step S105).

[0066] Each reference spectrum can be correlated with the corresponding film thickness (can be combined). Therefore, by determining the reference spectrum whose shape is closest to the measured spectrum during wafer W grinding, the motion control unit 9 can determine the current film thickness of wafer W from the film thickness correlated with its reference spectrum.

[0067] The following describes the process of grinding the wafer W to be ground. First, it is necessary to determine the first grinding conditions (in other words, the final target film thickness flatness conditions) to keep the film thickness uniformity of the wafer W to be ground within a specified allowable range.

[0068] The first polishing condition may also be a polishing condition predetermined in order to achieve a flat final target film thickness (controlling the pressure of each of the plurality of pressure chambers 70, 71, 72, 73, 83). The motion control unit 9 is configured to polish the wafer W by controlling the pressure of each of the plurality of pressure chambers 70, 71, 72, 73, 83 according to the first polishing condition.

[0069] Figure 5 is a diagram showing a plurality of pressing regions on a wafer divided by a plurality of pressure chambers. As shown in Figure 5, the motion control unit 9 divides the wafer W into a plurality of pressing regions A1 to A4 by a plurality of pressure chambers 70, 71, 72, and 73. These pressing regions A1 to A4 are arranged concentrically with the center CPW of the wafer W. A groove Nt is formed on the outer edge of the wafer W.

[0070] In one embodiment, the first polishing condition may also be a polishing condition (CLC: closed-loop control) that controls the pressure of each pressure chamber 70-73 in real time by using the average film thickness (measured by the film thickness detector 40 during wafer W polishing) to make the film thickness of each region A1-A4 of wafer W the average film thickness of the entire wafer W. More specifically, the motion control unit 9 calculates the average film thickness value in each pressing region A1-A4 based on the film thickness of wafer W measured by the signal output from the film thickness detector 40. Then, the motion control unit 9 controls the pressure in the pressure chambers 70-73 corresponding to the pressing regions A1-A4 by controlling each pressure regulator R1-R4 in a way that reduces the difference between the average film thickness value of each pressing region A1-A4 and the average film thickness value of the entire wafer W.

[0071] The motion control unit 9 can also control the pressure in the buckle pressure chamber 83 by controlling the pressure regulator R5 in the same way as the above method.

[0072] Figure 6 shows the grinding morphology of the wafer when it is ground under the first grinding conditions. In Figure 6, the horizontal axis represents the distance in the radial direction of the wafer W, and the vertical axis represents the film thickness distribution of the wafer W. The thick line in Figure 6 represents the boundary line between the pressing area A4 corresponding to the pressure chamber 73 located at the outermost periphery of the wafer W and the pressing area inside the pressing area A4. The embodiment shown in Figure 6 illustrates the film thickness distribution in the radial direction of the wafer W after grinding when the wafer W is ground for a specified time. However, the grinding morphology of the wafer W may also include the grinding rate distribution in the radial direction of the wafer W.

[0073] When polishing wafer W under the first polishing conditions, the uniformity of the film thickness of wafer W is maintained within a specified allowable range in other regions including the central part of wafer W (i.e., except for the outermost peripheral region). However, the residual film (film thickness after polishing) of wafer W in a specific region including the outermost peripheral region of wafer W exhibits a large degree of variation in the radial direction. That is, in the specific region including the outermost peripheral region of wafer W, the difference in film thickness between the thicker and thinner portions increases. Due to the influence of the springback of polishing pad 2, the polishing morphology of the outermost peripheral region of wafer W is prone to abruptly becoming asymmetrical. It is not easy to obtain a flat film thickness distribution by simply adjusting the pressure of the pressure chamber in the specific region including the outermost peripheral region of wafer W. The degree of variation in the film thickness after polishing in the specific region including the outermost peripheral region of wafer W (i.e., the so-called residual film range) tends to increase with the longer the polishing time under the first polishing conditions.

[0074] Therefore, in this embodiment, the motion control unit 9 is configured to grind the wafer W according to a second grinding condition that reduces the degree of variation in film thickness in the radial direction of the outermost periphery of the wafer W. The embodiment shown below, as an example of a specific region of the wafer W, illustrates an embodiment that reduces the degree of variation in film thickness of the wafer W at the outermost periphery of the wafer W. However, the specific region of the wafer W is not limited to the outermost periphery of the wafer W. Variations in film thickness of the wafer W can still occur even in regions other than the outermost periphery of the wafer W.

[0075] Figure 7 is a diagram showing the second polishing conditions. In Figure 7, the horizontal axis represents the distance in the radial direction of wafer W, and the vertical axis represents the film thickness distribution of wafer W. The polishing morphology of wafer W shown in Figure 7 illustrates the film thickness distribution in the radial direction of wafer W after polishing when wafer W is polished at a specified time. However, the polishing morphology of wafer W may also include the polishing rate distribution in the radial direction of wafer W.

[0076] The motion control unit 9 grinds a wafer W that is the same as the wafer W to be ground, or has the same initial film thickness, according to the first grinding conditions. Then, the motion control unit 9 determines the second grinding conditions based on the first grinding morphology (film thickness distribution or grinding rate distribution of the wafer W after grinding) obtained by grinding under the first grinding conditions. The second grinding conditions are grinding conditions that are predetermined (adjusted) in a way that forms a second grinding morphology with a distribution opposite to that of the first grinding morphology (more specifically, the distribution of pressing areas on the wafer W corresponding to a specific pressure chamber).

[0077] In other words, the second polishing condition is a polishing condition that more aggressively polishes the portion of the outermost periphery of the wafer W after polishing under the first polishing condition where the film thickness is thick, while suppressing polishing of the portion of the outermost periphery of the wafer W after polishing where the film thickness is thin. The distribution of the second polishing morphology relative to the first polishing morphology has a distribution in which the positive and negative signs of the values ​​representing the film thickness or polishing rate of the wafer W are reversed. Ideally, the curve showing the distribution of the second polishing morphology and the curve showing the distribution of the first polishing morphology are linearly symmetrical to each other.

[0078] The embodiment shown in Figure 7 is a curve showing the film thickness distribution of the outermost periphery of wafer W (showing the distribution of the second polishing morphology) in a specific coordinate system, with the baseline as the center, and symmetrical to the curve showing the film thickness distribution of the outermost periphery of wafer W polished under the first polishing conditions (refer to the one-point chain line in Figure 7). Furthermore, the embodiment shown in Figure 7 depicts the distribution of the second polishing morphology as an ideal curve.

[0079] The second polishing condition is determined by polishing the same wafer W as the object of polishing, or a wafer with the same initial film thickness. First, the wafer W is polished under the first polishing condition, and the first polishing morphology is confirmed. Then, another wafer is further polished, and the second polishing condition is experimentally determined so that the polishing morphology after polishing has a distribution opposite to that of the first polishing morphology. Alternatively, in one embodiment, the wafer W is first polished under the first polishing condition, and then the polishing condition is switched from the first polishing condition to polish the wafer W. The second polishing condition from the switching condition of the first polishing condition is experimentally determined so that the polishing morphology after polishing has a flat distribution. In another embodiment, the second polishing condition can also be selected from a database consisting of polishing conditions and polishing morphologies pre-stored in the memory device 9a, and / or determined by polishing simulation.

[0080] The motion control unit 9 is configured to store second polishing conditions in its memory device 9a and to polish the wafer W according to the second polishing conditions. More specifically, the motion control unit 9 controls the polishing of the wafer W by pre-determining a fixed value of the pressure in a specific pressure chamber in a plurality of pressure chambers 70, 71, 72, 73, and 83 according to the second polishing conditions. The second polishing conditions include polishing conditions for polishing the wafer W by pre-determining a fixed value of the pressure in a specific pressure chamber according to a second polishing morphology.

[0081] The specific pressure chamber of this embodiment includes: an edge pressure chamber 73 pressing the outermost periphery of the wafer W; and an adjacent pressure chamber adjacent to the edge pressure chamber 73. The adjacent pressure chamber includes at least one pressure chamber, namely an intermediate pressure chamber 72 and a retaining ring pressure chamber 83. In this embodiment, the adjacent pressure chamber is both the intermediate pressure chamber 72 and the retaining ring pressure chamber 83. In one embodiment, the specific pressure chamber may also be only the edge pressure chamber 73.

[0082] The second grinding conditions include grinding conditions determined by adjusting the pressure of a specific pressure chamber. In one embodiment, the second grinding conditions may also include grinding conditions determined by adjusting the pressure of a pressure chamber other than the specific pressure chamber. For example, when the specific pressure chamber is the edge pressure chamber 73, the second grinding conditions include grinding conditions determined by adjusting the pressure of the adjacent pressure chamber adjacent to the edge pressure chamber 73.

[0083] In one embodiment, the second polishing condition may also include polishing conditions determined by adjusting the pressing pressure of the retaining ring 60, which is configured to surround the outermost periphery of the wafer W, on the polishing surface 2a. In this case, the motion control unit 9 controls the retaining ring pressing device 80 to apply the downward force of the polishing head 1 to the retaining ring 60 according to the second polishing condition.

[0084] In this embodiment, the motion control unit 9 controls the pressure of each edge pressure chamber 73 and adjacent pressure chambers 72 and 83 according to the second grinding conditions, and at the same time controls the pressure of each other pressure chamber 70 and 71 of the edge pressure chamber 73 and adjacent pressure chambers 72 and 83 according to the feedback of the first grinding conditions.

[0085] The first polishing condition is that, during polishing, the polishing conditions of each pressure in the pressure chambers 70 and 71 are controlled by feedback based on the signal output from the film thickness detector 40 in order to reduce the difference between the average film thickness value of the region corresponding to each other pressure chamber 70 and 71 and the average film thickness value of the entire wafer W.

[0086] Figure 8 is a graph showing the polishing rate of a wafer polished under the first polishing condition and the second polishing condition. In Figure 8, the horizontal axis represents the radial distance of the wafer W, and the vertical axis represents the polishing rate of the wafer W. Figure 8 shows an enlarged view of the polishing rate of the outer portion of the wafer W. As shown in Figure 8, the polishing rate of the pressing area A4 on the wafer W under the first polishing condition is reversed with that under the second polishing condition. Therefore, by combining the first polishing condition and the second polishing condition to polish the wafer W, the motion control unit 9 can improve the uniformity of the film thickness on the outermost periphery of the wafer W.

[0087] Figure 9 is an example diagram showing a process of grinding a wafer to be ground. As shown in step S201 of Figure 9, the motion control unit 9 grinds the wafer W under the first grinding conditions (first grinding process). Then, the motion control unit 9 determines whether the specified switching conditions are met (refer to step S202). If the switching conditions are not met (refer to "No" in step S202), step S201 continues. If the switching conditions are met (refer to "Yes" in step S202), the motion control unit 9 switches the grinding conditions from the first grinding conditions to the second grinding conditions (refer to step S203), and grinds the wafer W under the second grinding conditions (second grinding process).

[0088] When the degree of variation in the residual film thickness at the outermost periphery (i.e., a specific region) of wafer W is quite large (more specifically, the difference between the maximum and minimum film thickness values), even if the polishing conditions are switched from the first polishing condition to the second polishing condition, the variation in the film thickness at the outermost periphery of wafer W may still not be eliminated. Therefore, regarding the aforementioned switching conditions, the operation control unit 9 may also switch the polishing conditions from the first polishing condition to the second polishing condition (first switching condition) when, during the polishing of wafer W, the difference between the maximum and minimum film thickness values ​​at the outermost periphery of wafer W (i.e., the so-called residual film range) significantly exceeds a specified threshold value under the first polishing condition.

[0089] When the film thickness variation of the wafer W corresponding to a specific pressure chamber is large in a specific area, even if the pressure of the specific pressure chamber is adjusted, the film thickness variation may still not be eliminated. Therefore, in the above embodiment, when the residual film range of the wafer W under the first polishing condition significantly exceeds the specified threshold value, the motion control unit 9 switches the polishing condition from the first polishing condition to the second polishing condition.

[0090] When the remaining grinding time is quite short, even if the grinding conditions are switched from the first grinding condition to the second grinding condition, it may still be impossible to eliminate the film thickness variation in a specific area of ​​the wafer W. Therefore, the motion control unit 9 may also switch the grinding conditions from the first grinding condition to the second grinding condition (second switching condition) based on the time required to eliminate the difference between the maximum and minimum film thickness of the outermost periphery of the wafer W by grinding under the second grinding condition and the remaining grinding time to reach the final target film thickness.

[0091] The grinding rate when grinding wafer W under the second grinding condition is known in advance through the process of determining the second grinding condition. Therefore, when grinding wafer W under the second grinding condition, the motion control unit 9 can calculate the time required to reduce (eliminate) the residual film area of ​​wafer W during grinding under the first grinding condition. Therefore, in one embodiment, the motion control unit 9 can also switch the grinding condition from the first grinding condition to the second grinding condition when the grinding time required under the second grinding condition reaches or approaches a specified remaining time. The specified remaining time is, for example, the same as the time required for the film thickness of wafer W to reach the final target film thickness when grinding wafer W under the second grinding condition after the switching time.

[0092] More specifically, the motion control unit 9 calculates the time required to reduce the residual film area of ​​wafer W under the second polishing condition in the first polishing condition (i.e., the required polishing time) and the remaining polishing time (i.e., the remaining time). The remaining polishing time is calculated according to the following formula: Remaining polishing time = (Current film thickness of wafer W - Target film thickness of wafer W) / Assumed polishing rate of the second polishing condition

[0093] When the required grinding time is less than the remaining time (required grinding time << remaining time), the grinding time under the second grinding condition becomes longer, leading to a deterioration in the residual film morphology of wafer W. When the required grinding time is the same as the remaining time (required grinding time = remaining time), the residual film area on wafer W is eliminated, and the film thickness on wafer W reaches the target film thickness (ideal state). When the required grinding time is greater than the remaining time (required grinding time > remaining time), the film thickness on wafer W becomes the target film thickness before the residual film area is eliminated, and the residual film area cannot be eliminated. Continuing to grind under such circumstances leads to over-grinding. Therefore, when the required grinding time is the same as the remaining time, the motion control unit 9 should switch the grinding condition from the first grinding condition to the second grinding condition.

[0094] If the second switching condition is used and the total grinding amount is different, since the range of residual film that can be ground under the first grinding condition can be changed, for example, when the initial film thickness of wafer W is different, it can be optimized accordingly. In addition, the so-called "time required to reach the final target film thickness" refers to the time required to remove the film on wafer W when the final target film thickness is zero, that is, the time required to remove the excess film.

[0095] In one embodiment, the motion control unit 9 can also switch the polishing conditions from the first polishing condition to the second polishing condition based on the first switching condition and the second switching condition. In another embodiment, the motion control unit 9 can also switch the polishing conditions from the first polishing condition to the second polishing condition when the average film thickness of the entire wafer W becomes a specified film thickness. In yet another embodiment, the motion control unit 9 can also switch the polishing conditions from the first polishing condition to the second polishing condition when the polishing time of the wafer W reaches a specified polishing time.

[0096] After executing step S203 of FIG. 9, the motion control unit 9 ends the grinding of the wafer W by receiving an endpoint detection signal from the film thickness detector 40 indicating that the average film thickness of the entire wafer W has reached the target film thickness, or that the material formed on the wafer W has reached the interface with different materials (refer to "Yes" in step S204) (refer to step S205). If no endpoint detection signal is received (refer to "No" in step S204), the motion control unit 9 continues to grind the wafer W under the second grinding conditions. The motion control unit 9 may also continue to grind the wafer W under the second grinding conditions if the residual film range in a specific area is not below the specified value when the endpoint detection signal is received. In addition, the motion control unit 9 may also issue an alarm if the residual film range in a specific area is not below the specified value when the endpoint detection signal is received.

[0097] In the above embodiment, the grinding head 1 has a plurality of pressure chambers (air bladders); however, the pressing element for pressing the wafer W is not limited to this. The technical concept of the present invention can be applied when a plurality of pressing elements that apply the same pressure to the wafer W are arranged in the radial direction of the wafer W. The pressing element may be, for example, a piezoelectric element.

[0098] Figure 10 is an example diagram showing a process of correlating a reference spectrum with a corresponding film thickness. First, a reference wafer identical to or having the same film thickness as wafer W is prepared. The reference wafer is transported to a film thickness measuring device 170 (refer to Figure 1), where the initial film thickness of the reference wafer is measured (refer to step S301). The film thickness measuring device 170 is electrically connected to the motion control unit 9. The motion control unit 9 determines the reference position for obtaining a reference spectrum over a wide range of film thicknesses based on the film thickness (distribution) of the reference wafer measured by the film thickness measuring device 170 (refer to step S302).

[0099] Thus, the motion control unit 9 obtains information from the film thickness gauge 170 regarding a specific position on a portion of the circumference of the reference wafer. The film thickness gauge 170 may also be disposed inside the polishing apparatus. In this case, the film thickness gauge 170 constitutes part of the constituent elements of the polishing apparatus. In one embodiment, the film thickness gauge 170 may also be disposed outside the polishing apparatus.

[0100] The reference wafer is polished to obtain reference spectra corresponding to various film thicknesses. The motion control unit 9 determines, based on the measured film thickness of the reference wafer, the maximum film thickness position (i.e., the thickest part of the reference wafer) and the minimum film thickness position (i.e., the thinnest part of the reference wafer), and designates one of these positions as the reference position. In one embodiment, the motion control unit 9 may also designate both the maximum and minimum film thickness positions as the reference position.

[0101] In one embodiment, the motion control unit 9 can also determine the maximum film thickness value and the minimum film thickness value based on the film thickness of the measured reference wafer, and calculate the difference between the average film thickness value of the entire reference wafer and the maximum film thickness value, and the difference between the average film thickness value of the entire reference wafer and the minimum film thickness value, and determine the position on the reference wafer with the film thickness value with the largest difference as the reference position.

[0102] Next, the slurry used as polishing fluid is supplied to the polishing head 1 and the reference wafer is polished (see step S303). During the polishing of the reference wafer, light is irradiated on the surface of the reference wafer to obtain the spectrum of reflected light from the reference wafer (i.e., the reference spectrum) (see step S304).

[0103] The motion control unit 9 acquires reference spectra at various measurement points on the reference wafer for each revolution of the polishing table 3. During polishing, the motion control unit 9 controls at least one of the rotation speed of the polishing head 1 and the rotation speed of the polishing table 3, such that the film thickness detector 40 passes through the reference position on the reference wafer. By controlling in this way, the film thickness detector 40 detects the reflected light at the reference position, and the motion control unit 9 acquires a reference spectrum including the reference position.

[0104] By acquiring a reference spectrum that includes a reference position, the motion control unit 9 can obtain a reference spectrum in a wide range of film thickness values. Therefore, the motion control unit 9 can more accurately determine the reference spectrum whose shape is closest to the measurement spectrum generated during grinding, and as a result, the film thickness of the wafer W with all film thicknesses can be measured (obtained).

[0105] A reference spectrum is obtained for each rotation of the grinding table 3. Therefore, multiple reference spectra are obtained during the grinding of the reference wafer. After the grinding of the reference wafer is completed, the reference wafer is transferred to the film thickness measuring device 170 again to measure the film thickness of the reference wafer after grinding (i.e., the final film thickness) (refer to step S305).

[0106] When the polishing rate of the reference wafer is constant, the film thickness decreases linearly along with the polishing time. The polishing rate can be calculated by dividing the difference between the initial film thickness and the final film thickness by the polishing time required to reach the final film thickness. As mentioned above, the reference spectrum is obtained periodically every revolution of the polishing table 3. Therefore, the polishing time for obtaining each reference spectrum can be calculated from the rotation speed of the polishing table 3. Thus, the motion control unit 9 determines the film thickness corresponding to each reference spectrum (refer to step S306).

[0107] Each reference spectrum can be correlated with the corresponding film thickness (can be combined). Therefore, by determining the reference spectrum whose shape is closest to the measured spectrum during wafer W grinding, the motion control unit 9 can determine the current film thickness of wafer W from the film thickness correlated with its reference spectrum.

[0108] Figure 11 is an example diagram showing a process of grinding a wafer to be ground. In order to improve the film thickness uniformity of the wafer W to be ground, it is necessary to determine a specific position on a portion of the circumference of the wafer W. Therefore, as shown in step S401 of Figure 11, the wafer W is transported to the film thickness measuring device 170, and the initial film thickness of the wafer W is measured by the film thickness measuring device 170.

[0109] Then, similar to step S302 in FIG10, the motion control unit 9 determines the specific position of the wafer W based on the film thickness of the wafer W measured by the film thickness measuring device 170 (refer to step S402).

[0110] The method for determining the specific position is the same as the method for determining the reference position. The motion control unit 9 determines the maximum film thickness position (i.e., the part of the wafer W with a thick film thickness) and the minimum film thickness position (i.e., the part of the wafer W with a thin film thickness) based on the film thickness of the wafer W measured before grinding, and determines at least one of the maximum film thickness position and the minimum film thickness position as the specific position.

[0111] In one embodiment, the motion control unit 9 can also determine the maximum film thickness value and the minimum film thickness value based on the film thickness of the wafer W measured before grinding, and calculate the difference between the average film thickness value of the entire wafer W and the maximum film thickness value, and the difference between the average film thickness value of the entire wafer W and the minimum film thickness value, and determine the position on the wafer W with the film thickness value with the largest difference as a specific position.

[0112] The motion control unit 9 obtains the film thickness distribution information of the wafer W measured by the film thickness measuring instrument 170, and determines a specific position of the wafer W. In one embodiment, when the film thickness measuring instrument 170 is disposed outside the polishing apparatus, the motion control unit 9 can also obtain position information of only the specified specific position from the film thickness distribution of the wafer W.

[0113] After determining a specific position of wafer W, the motion control unit 9 begins grinding wafer W (refer to step S403). During this grinding, light is irradiated onto the surface of wafer W, and the motion control unit 9 acquires the spectrum of the reflected light from wafer W (i.e., the measurement spectrum). The motion control unit 9 determines a reference spectrum whose shape is closest to the acquired measurement spectrum, and obtains a film thickness related to the determined reference spectrum (refer to step S404).

[0114] The motion control unit 9 adjusts the pressing pressure of the wafer W on the polishing surface 2a according to the film thickness of the wafer W by controlling the pressure adjusters R1, R2, R3, and R4. In this embodiment, the motion control unit 9 divides the area on the wafer W into a plurality of pressing areas A1, A2, A3, and A4 according to a plurality of pressure chambers 70, 71, 72, and 73 (refer to Figure 12).

[0115] Figure 12 shows a diagram of the wafer being divided into a plurality of pressing areas. Figure 12 divides the area on the wafer W into pressing area A1 corresponding to pressure chamber 70; pressing area A2 corresponding to pressure chamber 71; pressing area A3 corresponding to pressure chamber 72; and pressing area A4 corresponding to pressure chamber 73. Pressing area A1 has a circular shape, and pressing areas A2 to A4 each have an annular shape. These pressing areas A1 to A4 are arranged concentrically with the center CPW of the wafer W. The motion control unit 9 is configured to independently adjust the pressing pressure of the wafer W by means of the plurality of pressing areas.

[0116] As shown in FIG12, a specific position IP exists in the pressing area A4 of the wafer W. In the embodiment shown in FIG12, the specific position IP is a point on the wafer W. However, when multiple points exist in a narrow area on the wafer W, the specific position IP can also be multiple points existing in a wide area on the wafer W. Therefore, the motion control unit 9 determines the control target area CA that includes the specific position IP. Furthermore, when an area of ​​a certain size including the specific position IP is used as the control target area, the film thickness uniformity adjustment described below can be stably performed. In this embodiment, the control target area CA is determined within a circumferential range (that is, within one of the regions A1 to A4). In one embodiment, when the specific position IP is a point on the wafer W, the control target area CA can also be a point on the wafer W.

[0117] The motion control unit 9 determines the control object film thickness value in the control object region CA, and calculates the average film thickness value of the entire wafer W based on the film thickness of the wafer W measured by the film thickness detector 40. The control object film thickness value may also be equivalent to the maximum film thickness value or the minimum film thickness value determined based on the film thickness of the wafer W measured by the film thickness detector 40, or it may be both the maximum film thickness value and the minimum film thickness value. In one embodiment, the control object film thickness value may also be the average of a plurality of film thickness values ​​in the control object region CA.

[0118] The motion control unit 9 controls at least one of the rotational speed of the polishing head 1 and the rotational speed of the polishing table 3 by passing the film thickness detector 40 through the control target area CA on the wafer W. In order to perform this control, the motion control unit 9 needs to determine the position of the control target area CA during the polishing of the wafer W.

[0119] One example of a method for determining the position of the control target area CA is that the motion control unit 9 determines the position of the control target area CA as the wafer angle by taking the reference position (e.g., the groove position Nt in FIG12) of the angle (i.e., the wafer angle) of a specific wafer W circumferential direction during wafer W grinding.

[0120] Assuming that the wafer W has no deviation from the polishing head 1 in the circumferential direction, the installation angle of the wafer W relative to the polishing head 1 remains constant at the start of polishing. By controlling the rotation angle of the polishing head 1 via the rotary encoder 152 (see Figure 13), the motion control unit 9 specifies the groove position Nt and determines the position of the controlled area CA. Even if the position of the groove position Nt is not specified, since the positional relationship between the groove position Nt and the controlled area CA is predetermined, the position of the controlled area CA can still be determined from the rotation angle of the polishing head 1.

[0121] In addition, the wafer W may deviate from the polishing head 1 in the circumferential direction due to the frictional force acting between the wafer W and the polishing head 1. At this time, since the relative angle between the groove position Nt and the polishing head 1 also deviates, the motion control unit 9 specifies the groove position Nt of the wafer W in real time during the polishing of the wafer W, and determines the position of the control target area CA based on the groove position Nt.

[0122] Figure 13 shows a groove detection device. As shown in Figure 13, the polishing apparatus may also include a groove detection device 151 for detecting the groove position Nt of the wafer W. The groove detection device 151 may also be composed of a detector such as an eddy current detector, an optical detector, or an image detector. The embodiment shown in Figure 13 has the groove detection device 151 arranged on the side of the polishing table 3. The polishing head 1 is moved to a position where the periphery of the wafer W held on the polishing head 1 (more specifically, the groove position Nt) is extruded from the polishing pad 2, and the wafer W is rotated.

[0123] The groove detection device 151 detects the groove position Nt of the wafer W rotating in the extrusion state from the polishing pad 2 and outputs the detection signal to the motion control unit 9. The rotary encoder 152 detects the signal based on the rotation angle of the polishing head 1 and outputs the detection signal to the motion control unit 9. In this way, the motion control unit 9 obtains the relationship between the groove position Nt and the rotation angle of the polishing head 1, and can determine the relative angle between the groove position Nt and the polishing head 1 in real time. In one embodiment, the motion control unit 9 can also specify the groove position Nt based on the signal output from the film thickness detector 40. In this case, the film thickness detector 40 is equivalent to the groove detection device.

[0124] Figures 14A and 14B show the movement path of the film thickness detector 40 across the wafer surface. Figures 14A and 14B show the movement path of the film thickness detector 40 with five dashed lines. The embodiment shown in Figures 14A and 14B shows the film thickness detector 40 passing through a specific position IP when the polishing table 3 rotates for the first time.

[0125] As shown in Figures 14A and 14B, the motion control unit 9 controls the movement path of the film thickness detector 40 by controlling at least one of the rotational speed of the polishing head 1 and the rotational speed of the polishing table 3. Therefore, the motion control unit 9 controls at least one of the rotational speed of the polishing head 1 and the rotational speed of the polishing table 3 according to the determined relative angle, so that the film thickness detector 40 passes through a specific position IP on the surface of the wafer W.

[0126] For example, the motion control unit 9 determines the movement path of the film thickness detector 40 by determining the rotational speed ratio between the rotational speed of the polishing head 1 and the rotational speed of the polishing table 3. The rotational speed ratio in the embodiment shown in FIG14A is different from that in the embodiment shown in FIG14B. Therefore, when the relative angle between the groove position Nt and the polishing head 1 is changed, the motion control unit 9 determines the rotational speed ratio between the rotational speed of the polishing head 1 and the rotational speed of the polishing table 3 in such a way that the film thickness detector 40 passes through a specific position IP on the surface of the wafer W.

[0127] Thus, the motion control unit 9 measures the film thickness of the control target area CA containing a specific position IP in the grinding process based on the signal output from the film thickness detector 40, and controls the pressure in the pressure chambers 70 to 73 of the grinding head 1 corresponding to the control target area CA by controlling the pressure adjusters R1 to R4 based on the measured film thickness.

[0128] More specifically, as shown in step S405 of FIG11, the motion control unit 9 controls the pressure in the pressure chambers 70-73 of the polishing head 1 corresponding to a specific position IP (or the control target area CA) by reducing the difference between the control target film thickness value and the average film thickness value of the entire wafer W. In the embodiment shown in FIG12, the control target area CA is located at the position corresponding to the pressing area A4 on the wafer W, and area A4 corresponds to the pressure chamber 73. Therefore, the motion control unit 9 controls the pressure adjuster R4 to control the pressure in the pressure chamber 73.

[0129] The motion control unit 9 divides the plurality of pressing areas A1 to A4 on the wafer W, which are divided by the plurality of pressure chambers 70 to 73, into a specific pressing area containing a specific position IP, and other pressing areas other than the specific pressing area. In this embodiment, the specific pressing area corresponds to pressing area A4, and the other pressing areas correspond to pressing areas A1 to A3.

[0130] The motion control unit 9 calculates the average film thickness value in each of the other pressing areas A1 to A3 based on the film thickness of the wafer W measured by the film thickness detector 40. Then, the motion control unit 9 controls the pressure in the pressure chambers 70 to 72 corresponding to the other pressing areas A1 to A3 by controlling each pressure regulator R1 to R3 in a way that reduces the difference between the average film thickness value of each of the other pressing areas A1 to A3 and the average film thickness value of the entire wafer W.

[0131] Figures 15A and 15B are diagrams illustrating the effect of the polishing process of this embodiment. Figure 15A shows the morphology of the average film thickness of wafer W before and after polishing using a polishing process as a comparative example, and Figure 15B shows the morphology of the average film thickness of wafer W before and after polishing using the polishing process of this embodiment. In Figures 15A and 15B, each horizontal axis represents the distance from the center CPW of wafer W, and the vertical axis represents the film thickness of wafer W. In Figures 15A and 15B, the film thickness of wafer W is represented by a box plot as the film thickness of each measurement point in the pressing areas A1 to A4.

[0132] As shown in Figure 15A, in the film thickness of the wafer W before polishing, the minimum film thickness value of the pressing area A3 is particularly small (or thinner) than the film thickness of the other pressing areas A1, A2, and A4. Furthermore, the maximum film thickness value of the pressing area A4 is particularly large (or thicker) than the film thickness of the other pressing areas A1, A2, and A3. In the polishing process as a comparative example, the motion control unit 9 calculates the average film thickness value of each pressing area A1 to A4 and the average film thickness value of the entire wafer W based on the signal detected by the film thickness detector 40. Therefore, because the motion control unit 9 calculates the average film thickness values ​​of each pressing area A3 and A4, sometimes the difference between the average film thickness values ​​of each pressing area A1 and A2 and the average film thickness values ​​of each pressing area A3 and A4 is small.

[0133] Even in this case, the motion control unit 9 still controls the pressure of each pressure chamber 70 to 73 to grind the wafer W by reducing the difference between the average film thickness values ​​of each pressing area A1 to A4 and the average film thickness value of the entire wafer W. Therefore, the thickness of the film in the entire wafer W after grinding is sometimes not kept within the specified (desired) allowable range.

[0134] In this embodiment, the motion control unit 9 individually controls the pressure of a specific pressing area with a pressure different from that of other pressing areas. More specifically, the motion control unit 9 controls the pressure in pressure chambers 72 and 73 by reducing the difference between the film thickness value of the controlled object in each pressing area A3 and A4 and the average film thickness value of the entire wafer W, and controls the pressure in each pressure chamber 70 and 71 by reducing the difference between the average film thickness values ​​of other pressing areas A1 and A2 and the average film thickness value of the entire wafer W. As shown in FIG15B, the motion control unit 9 can also determine a plurality of specific pressing areas and individually control the pressure of the determined plurality of specific pressing areas.

[0135] In the embodiment shown in FIG15B, because the thickness of the controlled object film in pressing region A3 is smaller than the average film thickness, the pressure in pressure chamber 72 is reduced compared to the pressure in the comparative example. As a result, the grinding amount in pressing region A3 is generally smaller compared to the grinding amount in the comparative example. Because the thickness of the controlled object film in pressing region A4 is larger than the average film thickness, the pressure in pressure chamber 73 is increased compared to the pressure in the comparative example. As a result, the grinding amount in pressing region A4 is generally larger compared to the grinding amount in the comparative example. With this configuration, the grinding head 1 can maintain the thickness of the thickest and thinnest parts of the film in the entire wafer W within the desired allowable range (see FIG15B). As a result, the uniformity of the film thickness of the entire wafer W can be improved.

[0136] In the above embodiment, the grinding head has a plurality of pressure chambers (air bladders), but the technical concept of the present invention can be applied to any grinding head having concentrically arranged pressing elements. The pressing force applied to the substrate by the concentrically arranged pressing elements is controlled based on the thickness value of the control object film in the control object region containing a specific location. The pressing element may be, for example, a piezoelectric element.

[0137] In the above embodiment, the method of estimating the film thickness is adopted by determining the reference spectrum that is closest to the measured spectrum. However, other algorithms may also be used to estimate the film thickness.

[0138] In the above embodiment, the motion control unit 9 is configured to determine a specific position of the wafer W based on the film thickness of the wafer W measured by the film thickness measuring instrument 170, and then control the pressure in the pressure chamber of the polishing head 1 corresponding to that specific position. In another embodiment, the motion control unit 9 can also control the pressure in the pressure chamber of the polishing head 1 without prior measurement of the film thickness of the wafer W. The configuration of this type of motion control unit 9 will be described below with reference to the accompanying drawings.

[0139] Figure 16 is a flowchart showing the pressure control in the pressure chamber implemented by the motion control unit. As shown in step S501 of Figure 16, the motion control unit 9 determines the maximum and minimum film thickness values ​​from the film thickness of the entire wafer W obtained by the film thickness detector 40 during grinding. More specifically, the motion control unit 9 determines the maximum and minimum film thickness values ​​of the entire wafer W from the signal output by the film thickness detector 40.

[0140] The motion control unit 9 divides the area on the wafer W into a plurality of pressing areas A1, A2, A3, and A4 according to a plurality of pressure chambers 70, 71, 72, and 73. In other words, the motion control unit 9 distinguishes the measurement data obtained by the film thickness detector 40 in each pressing area A1, A2, A3, and A4 according to the trajectory of the film thickness detector 40 as it passes through the surface of the wafer W. In addition to the maximum and minimum film thickness values, the motion control unit 9 also specifies the average film thickness values ​​of each of the plurality of pressing areas A1, A2, A3, and A4. Furthermore, the motion control unit 9 also specifies the average film thickness value of the entire wafer W.

[0141] As shown in step S502 of Figure 16, the motion control unit 9 determines whether the difference between the maximum and minimum film thickness values ​​(i.e., the film thickness range) in the entire wafer W is within the desired (specified) allowable range. When the film thickness range is within the allowable range (refer to "Yes" in step S502), the motion control unit 9 controls the pressure in each pressure chamber by controlling each pressure regulator in a way that reduces the difference between the average film thickness value of each pressing area and the average film thickness value of the entire wafer W (refer to step S503).

[0142] When the film thickness range exceeds the allowable range (refer to "No" in step S502), the motion control unit 9 specifies at least one of the pressure chambers corresponding to the wafer W position where the maximum film thickness value is detected and the pressure chambers corresponding to the wafer W position where the minimum film thickness value is detected (refer to step S504).

[0143] When controlling the pressure of the pressure chamber related to the maximum film thickness value, the motion control unit 9 controls the pressure of the pressure chamber in such a way that the average film thickness value of the wafer W corresponding to the pressure chamber being targeted is lower than the average film thickness value of the entire wafer W (refer to step S505A). When controlling the pressure of the pressure chamber related to the minimum film thickness value, the motion control unit 9 controls the pressure of the pressure chamber in such a way that the average film thickness value of the wafer W corresponding to the pressure chamber being targeted is higher than the average film thickness value of the entire wafer W (refer to step S505B).

[0144] Specifically, when controlling the pressure of the pressure chamber related to the maximum film thickness value, the motion control unit 9 calculates a target film thickness value that is reduced by a specified amount or a specified ratio to the average film thickness value of the entire wafer W, and adjusts the pressure of the target pressure chamber in such a way that the average film thickness value of the pressing area to which the measurement point of the maximum film thickness value belongs is close to the target film thickness value. More specifically, when the average film thickness value of the pressing area to which the measurement point of the maximum film thickness value belongs exceeds the target film thickness value, the motion control unit 9 increases the pressure of the pressure chamber related to the pressing area to which the measurement point of the maximum film thickness value belongs.

[0145] In order to narrow the film thickness range, the motion control unit 9 may, as described above, control only the pressure of the pressure chamber related to the maximum film thickness value, or, as described above, control only the pressure of the pressure chamber related to the minimum film thickness value, or, as described above, control both the pressure of the pressure chamber related to the maximum film thickness value and the pressure of the pressure chamber related to the minimum film thickness value. Furthermore, regarding other pressure chambers, the motion control unit 9 controls the other pressure chambers by reducing the difference between the average film thickness value of the corresponding pressing area and the average film thickness value of the entire wafer W.

[0146] By this configuration, when the film thickness range exceeds the allowable range, the grinding amount or grinding speed within a certain period corresponding to the pressing area with the maximum film thickness value is greater than when the present invention is not applied, and the grinding amount or grinding speed within a certain period corresponding to the pressing area with the minimum film thickness value is smaller than when the present invention is not applied. As a result, the grinding head 1 can keep the difference between the thickness of the thickest part and the thinnest part of the film in the entire wafer W within a desired allowable range.

[0147] Figure 17 is a diagram illustrating the effect of the grinding process in other embodiments. In the embodiment shown in Figure 17, the maximum and minimum film thickness values ​​in the pressing areas A1 and A2 are within the allowable range during wafer W grinding. Therefore, the motion control unit 9 controls the pressure of each pressure chamber 70 and 71 corresponding to each pressing area A1 and A2 by reducing the difference between the average film thickness values ​​of each pressing area A1 and A2 and the average film thickness value of the entire wafer W.

[0148] Because the minimum film thickness value in the pressing area A3 exceeds the allowable range, the motion control unit 9 controls the pressure of the pressure chamber 72 in such a way that the average film thickness value of the pressing area A3 is higher than the average film thickness value of the entire wafer W. As a result, the grinding amount of the pressing area A3 becomes smaller, and the grinding head 1 can keep the film thickness of the pressing area A3 within the allowable range.

[0149] Because the maximum film thickness in the pressing area A4 exceeds the allowable range, the motion control unit 9 controls the pressure of the pressure chamber 73 in such a way that the average film thickness of the pressing area A4 is lower than the average film thickness of the entire wafer W. As a result, the grinding amount of the pressing area A4 increases, and the grinding head 1 can keep the film thickness of the pressing area A4 within the allowable range.

[0150] When this embodiment is adopted, the motion control unit 9 does not measure the film thickness of the wafer W in advance, but can keep the difference in film thickness within the wafer W surface within an acceptable range based on the film thickness of the wafer W measured by the film thickness detector 40 during wafer W grinding.

[0151] In addition, even if the film thickness range exceeds the allowable range in the pressing area on the wafer W other than the pressing area on the wafer W corresponding to the maximum film thickness value and the pressing area on the wafer W corresponding to the minimum film thickness value, the motion control unit 9 can also perform pressure control of the pressing area in the same way as described above.

[0152] In one embodiment, the motion control unit 9 can also determine the maximum and minimum film thickness values ​​in the wafer W based on the film thickness of the wafer W obtained at a certain time interval during wafer W polishing. For example, when the rotational speed ratio between the polishing table 3 and the polishing head 1 (rotational speed of polishing table 3 / rotational speed of polishing head 1) is 100 / 90 min⁻¹, the polishing table 3 rotates the polishing head 1 10 more times in 60 seconds.

[0153] When the above rotational speed ratio is used, since the polishing table 3 rotates 10 times in 6 seconds and the polishing head 1 rotates 9 times in 6 seconds, the relative positions of the polishing table 3 and the polishing head 1 return to their original positions once every 6 seconds. Because the film thickness detector 40 is embedded in the polishing table 3, the number of times the film thickness detector 40 passes through the surface of the wafer W depends on the rotation of the polishing table 3. Therefore, the movement path of the film thickness detector 40 returns to its original position at a frequency of once every 6 seconds. In this way, the motion control unit 9 can also specify the maximum and minimum film thickness values ​​based on the film thickness of the wafer W obtained from the time interval of the movement path of the film thickness detector 40 returning to its original position.

[0154] In one embodiment, the motion control unit 9 can also control the pressure of each pressure chamber 70, 71, 72, 73 by the maximum and minimum film thickness values ​​of each of the specific plurality of pressing areas A1, A2, A3, A4, for each rotation of the grinding table 3 (that is, each time the film thickness detector 40 passes through one moving path).

[0155] Each time the film thickness detector 40 passes through a movement path, that is, when controlling the pressure of each of the pressure chambers 70, 71, 72, and 73, it performs grinding by controlling (adjusting) the pressure. Before the change in film thickness of the wafer W is reflected, the motion control unit 9 may start the next pressure adjustment.

[0156] Furthermore, when the difference between the maximum and minimum film thickness values ​​is calculated based on the film thickness measurements taken over a certain period, and the pressure of the pressure chamber is adjusted quite frequently, the pressure responsiveness of the elastic membrane may become uncontrollable. Therefore, the motion control unit 9 should allow a period during which the pressure adjustment effect of the pressure chamber occurs, and check the next film thickness range at certain intervals. In addition, even after pressure adjustment, the motion control unit 9 can measure the film thickness again at the same measurement point to confirm the effect of the pressure adjustment.

[0157] When the motion control unit 9 specifies the maximum and minimum film thickness values, the polishing table 3 and polishing head 1 continue to rotate and polish the wafer W as usual. Therefore, for example, if the time interval is set to 6 seconds, in the relationship between the film thickness of the wafer W obtained in the 1st second and the film thickness of the wafer W obtained in the 5th second, the motion control unit 9 will calculate that the film thickness obtained in the 5th second is thinner than the film thickness obtained in the 1st second, and will not be able to accurately assess the uniformity of the actual film thickness. Therefore, the motion control unit 9 is configured to correct the film thickness value of the wafer W at each acquisition time based on the polishing speed of the wafer W.

[0158] Figure 18 is a diagram showing the process of correcting the film thickness value by the motion control unit. As shown in step S601 of Figure 18, the motion control unit 9 calculates the grinding speed of the wafer W during grinding from the film thickness of the wafer W obtained by the film thickness detector 40. Then, the motion control unit 9 calculates the change in film thickness of the wafer W between the time when the film thickness detector 40 obtains the film thickness of the wafer W at each measurement point of the wafer W and a specified reference time, based on the grinding speed of the wafer W (refer to step S602).

[0159] The motion control unit 9 uses the change in film thickness as a correction value to correct the film thickness of wafer W obtained during the grinding process at certain time intervals (refer to step S603). For example, if the specified reference time is the start time of the above time interval, that is, when it is 0 seconds, since the film thickness of wafer W will gradually decrease from the reference time, the motion control unit 9 adds the decrease in film thickness as a correction value to the film thickness of wafer W obtained during the grinding process to correct the film thickness of wafer W.

[0160] Conversely, if the specified reference time is used as the end time of the aforementioned time interval (6 seconds in the above embodiment), since the film thickness of wafer W is measured to be thicker than the film thickness at the reference time, the motion control unit 9 subtracts the film thickness change as a correction value from the film thickness of wafer W obtained during grinding to correct the film thickness of wafer W. The reference time can be arbitrarily determined as the start time or the middle time of the aforementioned time interval.

[0161] After step S603, the motion control unit 9 determines the maximum and minimum film thickness values ​​based on the corrected film thickness of the wafer W (refer to step S604). After step S604, the motion control unit 9 controls the pressure of pressure chambers 70, 71, 72, and 73 in the same way as the pressure control process shown in FIG16.

[0162] The above embodiment describes the case where the pressure chamber for the maximum film thickness value and the pressure chamber for the minimum film thickness value are different (or different) pressure chambers. However, sometimes the pressure chamber for the maximum film thickness value and the pressure chamber for the minimum film thickness value are the same pressure chamber. In this case, the motion control unit 9 can also pre-determine, by setting the polishing scheme, whether to control the pressure of the target pressure chamber in a manner where the average film thickness value of the wafer W corresponding to the pressure chamber is lower than the average film thickness value of the entire wafer W, or to control the pressure of the target pressure chamber in a manner where the average film thickness value of the wafer W corresponding to the pressure chamber is higher than the average film thickness value of the entire wafer W.

[0163] In one embodiment, when the pressure chamber for the maximum film thickness value and the pressure chamber for the minimum film thickness value are the same pressure chamber, the motion control unit 9 can also calculate the first difference between the maximum film thickness value and the average film thickness value of the entire wafer W, and the second difference between the minimum film thickness value and the average film thickness value of the entire wafer W.

[0164] The motion control unit 9 compares the first difference and the second difference. If the first difference is larger than the second difference, the pressure of the target pressure chamber can be controlled in a manner corresponding to the average film thickness of the wafer W of the pressure chamber with the maximum film thickness being lower than the average film thickness of the entire wafer W. If the second difference is larger than the first difference, the motion control unit 9 can also control the pressure of the target pressure chamber in a manner corresponding to the average film thickness of the wafer W of the pressure chamber with the minimum film thickness being higher than the average film thickness of the entire wafer W.

[0165] In the above embodiment, the difference between the maximum film thickness value and the average film thickness value of the entire wafer W is set as the first difference, and the difference between the minimum film thickness value and the average film thickness value of the entire wafer W is set as the second difference. However, the difference between the maximum film thickness value and the average film thickness in the pressing area corresponding to the maximum film thickness value can also be set as the first difference, and the difference between the minimum film thickness value and the average film thickness in the pressing area corresponding to the minimum film thickness value can be set as the second difference.

[0166] In the above embodiment, the motion control unit 9 determines whether the difference (film thickness range) between the maximum and minimum film thickness values ​​is within a desired (specified) allowable range. If it exceeds the allowable range, the pressure of the pressure chamber related to the maximum film thickness value and / or the pressure chamber related to the minimum film thickness value is adjusted. In another embodiment, the motion control unit 9 may adjust the pressure of the pressure chamber related to the maximum film thickness value and / or the pressure chamber related to the minimum film thickness value without comparing the difference between the maximum and minimum film thickness values ​​with the allowable range. In this way, since the pressure of the pressure chamber is controlled either in a manner where the average film thickness value of the pressing area related to the maximum film thickness value is lower than the average film thickness value of the entire wafer W, or in a manner where the average film thickness value of the pressing area related to the minimum film thickness value is higher than the average film thickness value of the entire wafer W, the difference between the maximum and minimum film thickness values ​​can be reduced, thereby improving the uniformity of the film thickness of the wafer W.

[0167] The above embodiments are described with the aim of enabling those skilled in the art to implement the present invention. Those skilled in the art can naturally create various modifications to the above embodiments, and the technical concept of the present invention can be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is interpreted in the broadest sense of the technical concept defined by the claims. [Industrial Applicability]

[0168] This invention can be applied to grinding devices and grinding methods. [Simplified Explanation of the Diagram]

[0033] Figure 1 is a schematic diagram showing one embodiment of the polishing apparatus. Figure 2 is a cross-sectional view of the polishing head. Figure 3 is an example diagram showing a spectrum generated by the motion control unit. Figure 4 is an example diagram showing a process of obtaining a plurality of reference spectra. Figure 5 is a diagram showing a plurality of pressing regions of a wafer divided by a plurality of pressure chambers. Figure 6 is a diagram showing the polishing morphology of a wafer when polishing it under the first polishing condition. Figure 7 is a diagram showing the second polishing condition. Figure 8 is a diagram showing the polishing rate of a wafer polished under the first polishing condition and the second polishing condition. Figure 9 is an example diagram showing a process of polishing a wafer to be polished. Figure 10 is an example diagram showing a process of correlating a reference spectrum with a corresponding film thickness. Figure 11 is an example diagram showing a process of polishing a wafer to be polished. Figure 12 is a diagram showing a wafer divided into a plurality of pressing regions. Figure 13 is a diagram showing a groove detection device. Figure 14A is a diagram showing the movement path of a film thickness detector passing through the surface of the wafer. Figure 14B shows the movement path of the film thickness detector passing through the wafer surface. Figure 15A is a diagram illustrating the effect of the polishing process in this embodiment. Figure 15B is a diagram illustrating the effect of the polishing process in this embodiment. Figure 16 is a flowchart showing the pressure control in the pressure chamber implemented by the motion control unit. Figure 17 is a diagram illustrating the effect of the polishing process in other embodiments. Figure 18 is a flowchart showing the process of correcting the film thickness value by the motion control unit.

Claims

1. A polishing apparatus comprising: a polishing table supporting a polishing pad; a polishing head having a plurality of pressure chambers divided into concentric circles for pressing a substrate against the polishing surface of the polishing pad; a plurality of pressure adjusters connected to the plurality of pressure chambers; a film thickness detector embedded in the polishing table and outputting a signal based on the film thickness of the substrate; and an operation control unit that individually controls the pressure of each of the plurality of pressure chambers via the plurality of pressure adjusters; wherein the operation control unit acquires information about a specific position on a portion of the circumference determined by film thickness distribution information of the entire substrate, determines the pressure chamber of the polishing head corresponding to the specific position, calculates a control target film thickness value in a control target area including the specific position and an average film thickness value of the entire substrate, and controls the pressure in the pressure chamber of the polishing head corresponding to the specific position by reducing the difference between the control target film thickness value and the average film thickness value of the entire substrate.

2. The polishing apparatus of claim 1, wherein the aforementioned motion control unit determines the aforementioned specific position based on the film thickness of the aforementioned substrate measured before polishing.

3. The polishing apparatus of claim 1 or 2, wherein the aforementioned motion control unit determines the maximum film thickness position for obtaining the maximum film thickness value and the minimum film thickness position for obtaining the minimum film thickness value based on the film thickness of the aforementioned substrate measured before polishing, and determines at least one of the aforementioned maximum film thickness position and the aforementioned minimum film thickness position as the aforementioned specific position.

4. The polishing apparatus of claim 1 or 2, wherein the aforementioned motion control unit determines the maximum film thickness value and the minimum film thickness value based on the film thickness of the aforementioned substrate measured before polishing, and calculates the difference between the average film thickness value of the entire aforementioned substrate and the aforementioned maximum film thickness value, and the difference between the average film thickness value of the entire aforementioned substrate and the aforementioned minimum film thickness value, and determines the position on the aforementioned substrate where the film thickness value with the largest difference is obtained as the aforementioned specific position.

5. The polishing apparatus of claim 1 or 2, wherein the aforementioned controlled object film thickness value is equivalent to at least one of the maximum film thickness value and the minimum film thickness value determined based on the aforementioned substrate film thickness measured before polishing.

6. The grinding apparatus of claim 1 or 2, wherein the aforementioned controlled object film thickness value is the average of a plurality of film thickness values ​​in the aforementioned controlled object region.

7. The grinding apparatus of claim 1 or 2, wherein the aforementioned motion control unit measures the film thickness in the aforementioned controlled object region including the aforementioned specific position during grinding based on the signal output from the aforementioned film thickness detector, and controls the pressure in the pressure chamber of the aforementioned grinding head corresponding to the aforementioned specific position based on the aforementioned measured film thickness.

8. The polishing apparatus of claim 1 or 2, wherein the aforementioned motion control unit divides the plurality of pressing areas on the aforementioned substrate into a specific pressing area including the aforementioned control target area and other pressing areas excluding the aforementioned specific pressing area according to the aforementioned plurality of pressure chambers, and calculates the average film thickness value in the aforementioned other pressing areas based on the film thickness of the aforementioned substrate, thereby reducing the difference between the average film thickness value of the aforementioned other pressing areas and the average film thickness value of the entire aforementioned substrate, and controls the pressure in the pressure chamber corresponding to the aforementioned other pressing areas.

9. The polishing apparatus of claim 1 or 2, wherein the aforementioned motion control unit obtains information about a reference position of a portion of a reference substrate different from the aforementioned substrate on the circumference, and during the polishing of the aforementioned reference substrate, the aforementioned film thickness detector detects a physical quantity of film thickness in a region on the aforementioned substrate including the aforementioned reference position, and obtains a plurality of data on the film thickness of the aforementioned reference substrate based on a plurality of signals sent from the aforementioned film thickness detector, and correlates each of the aforementioned plurality of data with the film thickness of the aforementioned reference substrate at the time when each of the aforementioned plurality of data is obtained.

10. The polishing apparatus of claim 9, wherein the aforementioned motion control unit determines the aforementioned reference position based on the film thickness of the aforementioned reference substrate measured before polishing.

11. The grinding apparatus of claim 1 or 2, wherein the aforementioned motion control unit controls at least one of the rotational speed of the aforementioned grinding head and the rotational speed of the aforementioned grinding table in such a way that the aforementioned film thickness detector passes through the aforementioned controlled object area.

12. The polishing apparatus of claim 11, wherein the aforementioned motion control unit determines the aforementioned reference position and the relative angle of the aforementioned polishing head based on the relationship between the reference position of the aforementioned substrate in the circumferential direction and the rotation angle of the aforementioned polishing head, and controls at least one of the rotation speed of the aforementioned polishing head and the rotation speed of the aforementioned polishing table based on the aforementioned determined relative angle.

13. A polishing method comprising pressing a substrate against the polishing surface of a polishing pad using a polishing head having a plurality of pressure chambers divided in a concentric circle, and obtaining information about a specific position on a portion of the circumference determined by film thickness distribution information of the entire substrate, determining the pressure chamber of the polishing head corresponding to the specific position, calculating the control target film thickness value in the control target area including the specific position and the average film thickness value of the entire substrate, and controlling the pressure in the pressure chamber of the polishing head corresponding to the specific position by reducing the difference between the control target film thickness value and the average film thickness value of the entire substrate.

14. The polishing method of claim 13, wherein the aforementioned specific location is specified based on the film thickness of the aforementioned substrate measured before polishing.

15. The polishing method of claim 13 or 14, wherein, based on the film thickness of the aforementioned substrate measured before polishing, the maximum film thickness position for obtaining the maximum film thickness value and the minimum film thickness position for obtaining the minimum film thickness value are determined, and at least one of the aforementioned maximum film thickness position and the aforementioned minimum film thickness position is determined as the aforementioned specific position.

16. The polishing method of claim 13 or 14, wherein a maximum film thickness value and a minimum film thickness value are determined based on the film thickness of the aforementioned substrate measured before polishing, and the difference between the average film thickness value of the entire aforementioned substrate and the aforementioned maximum film thickness value, and the difference between the average film thickness value of the entire aforementioned substrate and the aforementioned minimum film thickness value are calculated, and the position on the aforementioned substrate where the film thickness value with the largest difference is obtained is determined as the aforementioned specific position.

17. The polishing method of claim 13 or 14, wherein the aforementioned controlled object film thickness value is equivalent to at least one of the maximum film thickness value and the minimum film thickness value determined based on the substrate film thickness measured before polishing.

18. The grinding method of claim 13 or 14, wherein the aforementioned control object film thickness value is the average of a plurality of film thickness values ​​in the aforementioned control object region.

19. The grinding method of claim 13 or 14, wherein the film thickness in the aforementioned controlled object region including the aforementioned specific location is measured based on the output signal of a film thickness detector, and the pressure in the pressure chamber of the aforementioned grinding head corresponding to the aforementioned specific location is controlled based on the aforementioned measured film thickness.

20. The polishing method of claim 13 or 14, wherein the plurality of pressing areas on the aforementioned substrate are divided into a specific pressing area including the aforementioned controlled object area and other pressing areas other than the aforementioned specific pressing area according to the aforementioned plurality of pressure chambers, and the average film thickness value in the aforementioned other pressing areas is calculated based on the film thickness of the aforementioned substrate, so as to reduce the difference between the average film thickness value of the aforementioned other pressing areas and the average film thickness value of the entire aforementioned substrate, and the pressure in the pressure chamber corresponding to the aforementioned other pressing areas is controlled.

21. The polishing method of claim 13 or 14, wherein information about a reference position of a portion of a reference substrate different from the aforementioned substrate on the circumference is obtained, and in the polishing of the aforementioned reference substrate, a physical quantity of film thickness of a region on the aforementioned substrate including the aforementioned reference position is detected by a film thickness detector, and a plurality of data on the film thickness of the aforementioned reference substrate are obtained based on a plurality of signals sent from the aforementioned film thickness detector, and each of the aforementioned plurality of data is correlated with the film thickness of the aforementioned reference substrate at each of the aforementioned plurality of data.

22. The polishing method of claim 21, wherein the aforementioned reference position is determined based on the film thickness of the aforementioned reference substrate measured before polishing.

23. The polishing method of claim 13 or 14, wherein at least one of the rotational speed of the polishing head and the rotational speed of the polishing table is controlled by rotating the polishing table supporting the polishing pad, such that a film thickness detector passes through the controlled object area.

24. The polishing method of claim 23, wherein the reference position and the relative angle of the polishing head are determined based on the relationship between the reference position of the substrate in the circumferential direction and the rotation angle of the polishing head, and at least one of the rotation speed of the polishing head and the rotation speed of the polishing table is controlled based on the determined relative angle.

25. A polishing apparatus comprising: a polishing table supporting a polishing pad; a polishing head having a plurality of pressure chambers divided into concentric circles for pressing a substrate against the polishing surface of the polishing pad; a plurality of pressure adjusters connected to the plurality of pressure chambers; a film thickness detector embedded in the polishing table and outputting a signal based on the film thickness of the substrate; and an operation control unit that individually controls the pressure of each of the plurality of pressure chambers via the plurality of pressure adjusters; wherein the operation control unit obtains a specific maximum film thickness value and a specific minimum film thickness value of the substrate from the substrate polishing process using the film thickness detector, and specifically assigns at least one pressure chamber corresponding to the position of the substrate where the maximum film thickness value is detected, and at least one pressure chamber corresponding to the position of the substrate where the minimum film thickness value is detected. When controlling the pressure of the pressure chamber with the maximum film thickness value, the pressure of the pressure chamber with the maximum film thickness value is controlled in such a way that the average film thickness value of the substrate corresponding to the pressure chamber with the maximum film thickness value is lower than the average film thickness value of the entire substrate. When controlling the pressure of the pressure chamber with the minimum film thickness value, the pressure of the pressure chamber with the minimum film thickness value is controlled in such a way that the average film thickness value of the substrate corresponding to the pressure chamber with the minimum film thickness value is higher than the average film thickness value of the entire substrate.

26. The polishing apparatus of claim 25, wherein the aforementioned motion control unit, during the aforementioned substrate polishing, specifies the aforementioned maximum film thickness value and the aforementioned minimum film thickness value based on the film thickness of the aforementioned substrate obtained at a certain time interval.

27. The polishing apparatus of claim 26, wherein the aforementioned motion control unit calculates the polishing speed during polishing from the film thickness of the aforementioned substrate obtained by the aforementioned film thickness detector, and calculates the change in the film thickness of the aforementioned substrate between the acquisition time of the film thickness of the aforementioned substrate obtained by the aforementioned film thickness detector at each measurement point of the aforementioned substrate and a reference time based on the aforementioned polishing speed, uses the aforementioned change as a correction value, corrects the film thickness of the aforementioned substrate obtained during the polishing of the aforementioned substrate at the aforementioned time interval, and specifies the aforementioned maximum film thickness value and the aforementioned minimum film thickness value based on the corrected film thickness of the aforementioned substrate.

28. The polishing apparatus of any one of claims 25 to 27, wherein when the pressure chamber for the maximum film thickness value and the pressure chamber for the minimum film thickness value are the same pressure chamber, the aforementioned motion control unit pre-determines, by setting a processing scheme, whether to control the pressure chamber for the maximum film thickness value in such a way that the average film thickness value of the substrate corresponding to the pressure chamber for the maximum film thickness value is lower than the average film thickness value of the entire substrate; or to control the pressure chamber for the minimum film thickness value in such a way that the average film thickness value of the substrate corresponding to the pressure chamber for the minimum film thickness value is higher than the average film thickness value of the entire substrate.

29. The polishing apparatus according to any one of claims 25 to 27, wherein when the pressure chamber for the maximum film thickness value and the pressure chamber for the minimum film thickness value are the same pressure chamber, the aforementioned operation control unit compares a first difference between the maximum film thickness value and the average film thickness value of the entire substrate, and a second difference between the minimum film thickness value and the average film thickness value of the entire substrate. If the first difference is greater than the second difference, the pressure of the pressure chamber for the maximum film thickness value is controlled such that the average film thickness value of the substrate corresponding to the pressure chamber for the maximum film thickness value is lower than the average film thickness value of the entire substrate. If the second difference is greater than the first difference, the pressure of the pressure chamber for the minimum film thickness value is controlled such that the average film thickness value of the substrate corresponding to the pressure chamber for the minimum film thickness value is higher than the average film thickness value of the entire substrate.

30. The polishing apparatus according to any one of claims 25 to 27, wherein when the pressure chamber for the maximum film thickness value and the pressure chamber for the minimum film thickness value are the same pressure chamber, the aforementioned action control unit compares a first difference between the maximum film thickness value and the average film thickness value in the pressing area corresponding to the maximum film thickness value, and a second difference between the minimum film thickness value and the average film thickness value in the pressing area corresponding to the minimum film thickness value; when the first difference is greater than the second difference, the pressure of the pressure chamber for the maximum film thickness value is controlled such that the average film thickness value of the substrate corresponding to the pressure chamber for the maximum film thickness value is lower than the average film thickness value of the entire substrate; when the second difference is greater than the first difference, the pressure of the pressure chamber for the minimum film thickness value is controlled such that the average film thickness value of the substrate corresponding to the pressure chamber for the minimum film thickness value is higher than the average film thickness value of the entire substrate.

31. A polishing method comprising pressing a substrate against the polishing surface of a polishing pad using a polishing head having a plurality of pressure chambers divided in a concentric circle, obtaining a specific maximum and minimum film thickness value of the substrate during the polishing process, and specifying at least one of the pressure chambers corresponding to the position of the substrate where the maximum film thickness value is detected and the pressure chamber corresponding to the position of the substrate where the minimum film thickness value is detected. When controlling the pressure of the pressure chamber for the maximum film thickness value, the pressure is controlled such that the average film thickness value of the substrate corresponding to the pressure chamber for the maximum film thickness value is lower than the average film thickness value of the entire substrate. When controlling the pressure of the pressure chamber for the minimum film thickness value, the pressure is controlled such that the average film thickness value of the substrate corresponding to the pressure chamber for the minimum film thickness value is higher than the average film thickness value of the entire substrate.

32. The polishing method of claim 31, wherein in the aforementioned substrate polishing, the aforementioned maximum film thickness value and the aforementioned minimum film thickness value are specified based on the film thickness of the aforementioned substrate obtained at a certain time interval.

33. The polishing method of claim 32, wherein the polishing speed during polishing is calculated from the film thickness of the aforementioned substrate, and the change in the film thickness of the aforementioned substrate between the time of obtaining the film thickness of the aforementioned substrate at each measurement point on the aforementioned substrate and a reference time is calculated based on the aforementioned polishing speed, the aforementioned change is used as a correction value, the film thickness of the aforementioned substrate obtained during the polishing of the aforementioned substrate is corrected at the aforementioned time interval, and the aforementioned maximum film thickness value and the aforementioned minimum film thickness value are specified based on the corrected film thickness of the aforementioned substrate.

34. The polishing method according to any one of claims 31 to 33, wherein when the pressure chamber for the aforementioned maximum film thickness value and the pressure chamber for the aforementioned minimum film thickness value are the same pressure chamber, the pressure of the pressure chamber for the aforementioned maximum film thickness value is controlled in advance by setting a processing scheme in such a way that the average film thickness value of the aforementioned substrate corresponding to the pressure chamber for the aforementioned maximum film thickness value is lower than the average film thickness value of the entire aforementioned substrate; or the pressure of the pressure chamber for the aforementioned minimum film thickness value is controlled in such a way that the average film thickness value of the aforementioned substrate corresponding to the pressure chamber for the aforementioned minimum film thickness value is higher than the average film thickness value of the entire aforementioned substrate.

35. The polishing method according to any one of claims 31 to 33, wherein when the pressure chamber for the maximum film thickness value and the pressure chamber for the minimum film thickness value are the same pressure chamber, the pressure of the pressure chamber for the maximum film thickness value is compared with a first difference between the maximum film thickness value and the average film thickness value of the entire substrate, and a second difference between the minimum film thickness value and the average film thickness value of the entire substrate. If the first difference is greater than the second difference, the pressure of the pressure chamber for the maximum film thickness value is controlled such that the average film thickness value of the substrate corresponding to the pressure chamber for the maximum film thickness value is lower than the average film thickness value of the entire substrate. If the second difference is greater than the first difference, the pressure of the pressure chamber for the minimum film thickness value is controlled such that the average film thickness value of the substrate corresponding to the pressure chamber for the minimum film thickness value is higher than the average film thickness value of the entire substrate.

36. The polishing method according to any one of claims 31 to 33, wherein when the pressure chamber for the maximum film thickness value and the pressure chamber for the minimum film thickness value are the same pressure chamber, the pressure of the pressure chamber for the maximum film thickness value is compared with a first difference between the maximum film thickness value and the average film thickness value in the pressing area corresponding to the maximum film thickness value, and with a second difference between the minimum film thickness value and the average film thickness value in the pressing area corresponding to the minimum film thickness value. If the first difference is greater than the second difference, the pressure of the pressure chamber for the maximum film thickness value is controlled such that the average film thickness value of the substrate corresponding to the pressure chamber for the maximum film thickness value is lower than the average film thickness value of the entire substrate. If the second difference is greater than the first difference, the pressure of the pressure chamber for the minimum film thickness value is controlled such that the average film thickness value of the substrate corresponding to the pressure chamber for the minimum film thickness value is higher than the average film thickness value of the entire substrate.

Images