Polishing apparatus and polishing method

Abstract

To provide a polishing device capable of improving measurement accuracy of a film thickness of a substrate.SOLUTION: The polishing device 1 includes a polishing table 3 having a pad support surface 3a for supporting a polishing pad 2, a polishing head 10 for pressing a substrate W against the polishing surface 2a of the polishing pad 2, an optical film-thickness measuring apparatus 30 for determining a film-thickness measurement value of the substrate W, and an operation controller 60. An optical film thickness measuring device (30) is provided with a light projecting section (32) which irradiates a substrate (W) with light, a light receiving section (33) which receives the reflected light from the substrate (W), and a first light amount sensor (41) and a second light amount sensor (42) which are arranged adjacent to the light receiving section (33) and detect the light amount of the reflected light from the substrate (W), wherein an operation control section (60) is configured so as to determine the position correction amounts of the light projecting section (32) and the light receiving section (33) corresponding to the wear amount of a polishing pad (2) on the basis of the first light amount detected by the first light amount sensor (41) and the second light amount detected by the second light amount sensor (42).SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] The manufacturing process of semiconductor devices includes a process of polishing wafers to flatten their surfaces. One known type of wafer polishing equipment is a polishing apparatus that performs chemical mechanical polishing (CMP). The polishing apparatus supplies a polishing liquid to the polishing surface of a polishing pad supported on a polishing table, presses the wafer against the polishing surface, and then moves the wafer and the polishing table relative to each other. This process polishes the wafer surface.

[0003] Generally, a polishing apparatus is equipped with a film thickness measurement device for measuring the film thickness on the surface of a wafer during polishing. The polishing apparatus stops polishing when the measured film thickness reaches a predetermined target value (in other words, the polishing endpoint). One example of a film thickness measurement device is an optical film thickness measurement device. An optical film thickness measurement device projects light from its light-emitting unit onto a measurement point on the wafer surface, and receives reflected light from the wafer surface with its light-receiving unit. The measured film thickness is determined based on this reflected light. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5167010 Summary of the Invention [Problem to be solved by the invention]

[0005] As the polishing pad is polished, it wears down and its thickness gradually decreases. The more the polishing pad thickness decreases, the closer the wafer surface pressed against the polishing pad gets to the light-emitting and light-receiving parts of the optical film thickness measurement device. If the distance between the measurement point on the wafer surface and the light-emitting and light-receiving parts changes, it affects the conditions under which the light-receiving part receives the light reflected from the wafer, which can result in a decrease in the accuracy of film thickness measurement.

[0006] Therefore, the present invention provides a polishing apparatus and a polishing method that can improve the measurement accuracy of the film thickness of a substrate. [Means for solving the problem]

[0007] In one aspect, a polishing apparatus is provided, comprising: a polishing table having a pad support surface that supports a polishing pad; a polishing head that presses a substrate against the polishing surface of the polishing pad; an optical film thickness measurement device that irradiates light onto the substrate, receives light reflected from the substrate, and determines a film thickness measurement value of the substrate based on the reflected light; and an operation control unit, wherein the optical film thickness measurement device comprises a light projecting unit that irradiates the substrate with light, a light receiving unit that receives the light reflected from the substrate, and a first light intensity sensor and a second light intensity sensor that are arranged adjacent to the light receiving unit and detect the amount of light reflected from the substrate, and the operation control unit is configured to determine a position correction amount of the light projecting unit and the light receiving unit corresponding to the amount of wear of the polishing pad based on the first light intensity detected by the first light intensity sensor and the second light intensity detected by the second light intensity sensor.

[0008] In one embodiment, the first light amount sensor and the second light amount sensor are disposed at different positions in a direction perpendicular to the pad support surface. In one embodiment, the light-emitting portion and the light-receiving portion are inclined with respect to the pad support surface. In one embodiment, the light receiving section is located between the first light amount sensor and the second light amount sensor. In one embodiment, the operation control unit is configured to determine the position correction amount based on a correlation between the difference between the first light amount and the second light amount, which has been acquired in advance, and the amount of wear on the polishing pad.

[0009] In one embodiment, the polishing apparatus further includes a sensor moving mechanism that moves the light-emitting unit and the light-receiving unit in the direction perpendicular to the pad support surface, and the operation control unit is configured to issue a command to the sensor moving mechanism to move the light-emitting unit and the light-receiving unit by the position correction amount. In one aspect, the light-emitting unit and the light-receiving unit are arranged in a hole formed inside the polishing table, and the sensor moving mechanism is configured to move the light-emitting unit and the light-receiving unit within the hole relative to the polishing table. In one embodiment, the first light amount and the second light amount are detected when the first light amount sensor and the second light amount sensor are covered by the substrate that is pressed against the polishing surface. In one embodiment, the first amount of light and the second amount of light are detected while the substrate is being polished. In one embodiment, the first light amount and the second light amount are detected during idling operation in which polishing of the substrate is not progressing and when the substrate is pressed against the polishing surface with a pressing force applied during polishing of the substrate.

[0010] In one aspect, a polishing method is provided, which includes pressing a substrate against a polishing surface of a polishing pad supported on a pad support surface of a polishing table, irradiating the substrate with light from a light-projecting unit of an optical film thickness measurement device that determines a film thickness measurement value of the substrate, receiving the light reflected from the substrate with a light-receiving unit of the optical film thickness measurement device, detecting the amount of light reflected from the substrate with a first light intensity sensor and a second light intensity sensor arranged adjacent to the light-receiving unit, and determining a position correction amount of the light-projecting unit and the light-receiving unit corresponding to the amount of wear of the polishing pad based on a first light intensity detected by the first light intensity sensor and a first light intensity detected by the second light intensity sensor.

[0011] In one embodiment, the first light amount sensor and the second light amount sensor are disposed at different positions in a direction perpendicular to the pad support surface. In one aspect, irradiating the substrate with light means irradiating the light at an angle relative to the surface of the substrate to be polished, and receiving the reflected light from the substrate means receiving the reflected light that is reflected at an angle relative to the surface of the substrate to be polished. In one embodiment, the light receiving section is located between the first light amount sensor and the second light amount sensor. In one embodiment, determining the position correction amount based on the first light amount and the second light amount means determining the position correction amount based on the correlation between the difference between the first light amount and the second light amount, which has been acquired in advance, and the amount of wear on the polishing pad.

[0012] In one embodiment, the polishing method further includes moving the light projecting unit and the light receiving unit by the position correction amount along the direction perpendicular to the pad support surface. In one embodiment, the light projecting unit and the light receiving unit are moved relative to the polishing table within a hole formed inside the polishing table. In one embodiment, the first light amount and the second light amount are detected when the first light amount sensor and the second light amount sensor are covered by the substrate that is pressed against the polishing surface. In one embodiment, pressing the substrate against the polishing surface comprises rotating the polishing table and pressing the substrate against the polishing surface with the polishing head to polish the substrate, and detecting the first light amount and the second light amount while the substrate is being polished. In one embodiment, pressing the substrate against the polishing surface means pressing the substrate against the polishing surface with a pressing force applied during polishing of the substrate while the polishing table is stopped during idling operation in which polishing of the substrate is not progressing, and the detection of the first light amount and the second light amount is performed during the idling operation. [Effects of the Invention]

[0013] The operation control unit is configured to determine the position correction amount of the light-emitting unit and the light-receiving unit corresponding to the amount of wear of the polishing pad based on the first light amount detected by the first light amount sensor and the second light amount detected by the second light amount sensor. As a result, the polishing apparatus can improve the measurement accuracy of the film thickness of the substrate. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram illustrating an embodiment of a polishing apparatus. [Figure 2] FIG. 2 is a top view showing the positional relationship between the wafer and the polishing table during polishing. [Figure 3] FIG. 2 is an enlarged view of the optical film thickness measurement device shown in FIG. [Figure 4] FIG. 4 is an enlarged perspective view of the light-receiving sensor head shown in FIG. 3. [Figure 5] 10A and 10B are diagrams illustrating the change in the reflected light from the substrate W received by the light-receiving sensor head due to wear of the polishing pad. [Figure 6] Figure 6(a) is a diagram explaining the amount of reflected light detected by the light receiving sensor head before the polishing pad shown in Figure 5 is worn out, and Figure 6(b) is a diagram explaining the amount of reflected light detected by the light receiving sensor head after the polishing pad shown in Figure 5 is worn out. [Figure 7] 2 is a flowchart showing an example of a polishing method using the polishing apparatus shown in FIG. [Figure 8] 10 is a flowchart showing another example of a polishing method using the polishing apparatus shown in FIG. [Figure 9] FIG. 10 is a schematic diagram showing an optical film thickness measurement device according to another embodiment of the polishing apparatus. [Figure 10] FIG. 10 is a schematic view showing still another embodiment of the polishing apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing one embodiment of a polishing apparatus. The polishing apparatus 1 shown in FIG. 1 is an apparatus for chemically and mechanically polishing a substrate such as a wafer. The polishing apparatus 1 includes a polishing pad 2, a polishing table 3 that supports the polishing pad 2, a polishing head 10 that holds a substrate W and presses it against the polishing pad 2, a polishing liquid supply nozzle 20 that supplies a polishing liquid (e.g., a slurry containing abrasive grains) onto the polishing pad 2, an optical film thickness measurement device 30 that measures the film thickness on the surface of the substrate W, and an operation control unit 60 that controls the operation of these components.

[0016] The polishing pad 2 is supported on a pad support surface 3a of the polishing table 3. In this embodiment, the pad support surface 3a is formed from the flat upper surface of the polishing table 3. The upper surface of the polishing pad 2 forms a polishing surface 2a for polishing the substrate W. The polishing pad 2 has a thickness. Hereinafter, the distance from the upper surface (polishing surface 2a) of the polishing pad 2 to the lower surface (contact surface with the pad support surface 3a of the polishing table 3) is referred to as the thickness of the polishing pad 2. A through hole 2b is formed in the polishing pad 2. A hole 3b is formed in the upper surface of the polishing table 3. The through hole 2b and the hole 3b are connected. As will be described later, the through hole 2b allows light to pass through for film thickness measurement.

[0017] The polishing table 3 is connected to a table motor 6 via a table shaft 5. The table motor 6 is configured to rotate the polishing table 3. The polishing table 3 is rotated around its axis by the table motor 6. The polishing pad 2 rotates integrally with the polishing table 3. For example, the polishing table 3 is rotated in the direction indicated by the arrow in FIG. 1.

[0018] The polishing head 10 is connected to a polishing head motor (not shown) via a polishing head shaft 12. The polishing head motor is configured to rotate the polishing head 10. The polishing head 10 is rotated about its axis by the polishing head motor. The polishing head 10 rotates integrally with the polishing head shaft 12. For example, the polishing head 10 is rotated in the direction indicated by the arrow in FIG. 1.

[0019] The lower surface of the polishing head 10 is configured to hold the substrate W. A vacuum source (not shown) that vacuum-sucks the substrate W is connected to the lower surface of the polishing head 10. The substrate W is held by suction on the lower surface of the polishing head 10 by the vacuum source. In other words, the lower surface of the polishing head 10 forms a wafer holding surface that holds the substrate W.

[0020] Furthermore, an air bag (not shown) is provided on the underside of the polishing head 10 to press the substrate W against the polishing surface 2a of the polishing pad 2. The air bag generates pressure to press the held substrate W. A gas supply line (not shown) is connected to the air bag, and the pressure is adjusted by the amount of gas supplied. The air bag presses the substrate W from its rear side. The polishing head 10 presses the substrate W against the polishing surface 2a of the polishing pad 2 by using the air bag.

[0021] The polishing head 10 is connected to a polishing head lifting mechanism (not shown) via a polishing head shaft 12. The polishing head lifting mechanism is configured to lift and lower (move up and down) the polishing head 10. The polishing head 10 is moved up and down relative to the polishing pad 2 by the polishing head lifting mechanism. The polishing head 10 moves up and down integrally with the polishing head shaft 12. The polishing head lifting mechanism lowers the polishing head 10 holding the substrate W toward the polishing pad 2, thereby bringing the surface of the substrate W (in other words, the surface to be polished) into contact with the polishing surface 2a of the polishing pad 2. The polishing head lifting mechanism may further lower the polishing head 10 to press the surface of the substrate W against the polishing surface 2a of the polishing pad 2.

[0022] The operation control unit 60 is composed of at least one computer. The operation control unit 60 includes a storage device 60a in which a program is stored, and an arithmetic unit 60b that executes calculations according to instructions included in the program. The storage device 60a includes a main storage device such as RAM, and an auxiliary storage device such as a hard disk drive (HDD) or a solid-state drive (SSD). Examples of the arithmetic unit 60b include a CPU (central processing unit) and a GPU (graphics processing unit). However, the specific configuration of the operation control unit 60 is not limited to these examples.

[0023] The polishing of the substrate W is performed as follows. The polishing head 10 holds the substrate W with its surface (surface to be polished) facing the polishing pad 2. While the polishing table 3 is rotated by the table motor 6, a polishing liquid is supplied from the polishing liquid supply nozzle 20 onto the polishing surface 2a of the polishing pad 2. In this state, the polishing head 10 is rotated by the polishing head motor and lowered by the polishing head lifting mechanism. As a result, the surface of the substrate W comes into contact with the polishing surface 2a of the polishing pad 2. Furthermore, the polishing head 10 presses the substrate W against the polishing pad 2. The surface of the substrate W is polished by the chemical action of the polishing liquid and the mechanical action of the abrasive grains contained in the polishing liquid and / or the polishing surface 2a.

[0024] The optical film thickness measurement device 30 includes a light source 31, a light-projecting unit 32, a light-receiving unit 33, a spectrometer 37, and a spectral processing unit 39. The light-receiving unit 33 is provided in a light-receiving sensor head 35 (described later). The light-projecting unit 32 and the light-receiving unit 33 are disposed inside the polishing table 3. The light source 31, the light-projecting unit 32, the light-receiving unit 33, and the spectrometer 37 are attached to the polishing table 3 and rotate integrally with the polishing table 3 and the polishing pad 2. The light-projecting unit 32 is optically connected to the light source 31. The light-receiving unit 33 is optically connected to the spectrometer 37. The light source 31 is connected to an operation control unit 60. The spectrometer 37 is connected to the spectral processing unit 39, which is connected to the operation control unit 60. The spectral processing unit 39, like the operation control unit 60, is composed of at least one computer including a storage device storing a program and an arithmetic unit that executes calculations according to instructions included in the program.

[0025] As an example, the light-projecting unit 32 and the light-receiving unit 33 are each formed of an optical fiber cable. One end (tip) of the light-projecting unit 32 and one end (tip) of the light-receiving unit 33 are directed upward and face the substrate W held by the polishing head 10. One end of the light-projecting unit 32 and one end of the light-receiving unit 33 are inclined in directions approaching each other. The other end of the light-projecting unit 32 is optically connected to the light source 31, and the other end of the light-receiving unit 33 is optically connected to the spectroscope 37.

[0026] A light emitting diode (LED), a halogen lamp, a xenon lamp, or the like can be used as the light source 31. The light projecting unit 32 guides the light from the light source 31 and irradiates it onto the surface of the substrate W, and the light receiving unit 33 receives the light reflected from the surface of the substrate W. The spectroscope 37 is configured to resolve the reflected light received by the light receiving unit 33 according to wavelength and measure the intensity of the reflected light over a predetermined wavelength range.

[0027] The spectral processing unit 39 generates a reflected light spectrum representing the intensity of reflected light for each wavelength from the light intensity data obtained by the spectrometer 37, and determines the film thickness of the substrate W based on the reflected light spectrum. A known technique is used to determine the film thickness of the substrate W based on the spectrum. For example, the spectral processing unit 39 selects a reference spectrum from a reference spectrum library whose shape is closest to the spectrum of the reflected light, and determines the film thickness associated with this selected reference spectrum. In another example, the spectral processing unit 39 performs a Fourier transform on the spectrum of the reflected light and determines the film thickness from the resulting frequency spectrum. The measured film thickness value obtained by the spectral processing unit 39 is sent to the operation control unit 60. The operation control unit 60 determines that the polishing endpoint has been reached when the measured film thickness value reaches a predetermined target value.

[0028] The light-projecting unit 32 and the light-receiving unit 33 are disposed inside the hole 3b of the polishing table 3. The light-projecting unit 32 and the light-receiving unit 33 may be disposed below the polishing surface 2a of the polishing pad 2. In other words, one end of the light-projecting unit 32 and one end of the light-receiving unit 33 may be disposed below the polishing surface 2a of the polishing pad 2. As shown in FIG. 1 , one end of the light-projecting unit 32 and one end of the light-receiving unit 33 are disposed below the pad support surface 3a of the polishing table 3. In one embodiment, one end of the light-projecting unit 32 and one end of the light-receiving unit 33 may be disposed inside the through-hole 2b as long as they are below the polishing surface 2a of the polishing pad 2.

[0029] Through-hole 2b and hole 3b are filled with a liquid (e.g., pure water) as a medium that transmits light. In other words, the space between the surface of substrate W to be polished and the tips of light-projecting unit 32 and light-receiving unit 33 is filled with liquid. Therefore, light incident on the surface of substrate W from light-projecting unit 32 and light reflected from the surface of substrate W to light-receiving unit 33 pass through the liquid. This liquid is supplied by a liquid supply line (not shown) connected to hole 3b and discharged by a liquid discharge line (not shown) connected to hole 3b.

[0030] The light-transmitting medium may be air instead of a liquid. A transparent window (not shown) may be provided instead of a light-transmitting liquid. The window may be provided inside the through-hole 2b or the hole 3b, as long as it is located below the polishing surface 2a of the polishing pad 2 and above the tips of the light-emitting unit 32 and the light-receiving unit 33. In this case, the window is provided so as to close at least one of the through-hole 2b and the hole 3b.

[0031] FIG. 2 is a top view showing the positional relationship between the substrate W and the polishing table 3 during polishing. The light-projecting unit 32 and the light-receiving sensor head 35, including the light-receiving unit 33, cross (i.e., pass through) the substrate W along the trajectory shown by the dashed line in FIG. 2 each time the polishing table 3 rotates. The light-projecting unit 32 and the light-receiving sensor head 35 are disposed at a predetermined distance from the center O of the polishing table 3 in the radial direction of the polishing table 3. The center of the substrate W is disposed at a predetermined distance from the center O of the polishing table 3 in the radial direction of the polishing table 3. In FIG. 2, the distance from the center O of the polishing table 3 to the light-projecting unit 32 and the light-receiving sensor head 35 is equal to the distance from the center O of the polishing table 3 to the center of the substrate W. Therefore, in FIG. 2, the light-projecting unit 32 and the light-receiving sensor head 35 cross the center of the substrate W as the polishing table 3 rotates.

[0032] 2 shows an example in which the light projecting unit 32 and the light receiving sensor head 35 are arranged to cross the center of the substrate W, but the arrangement of the light projecting unit 32 and the light receiving sensor head 35 is not limited to this. The light projecting unit 32 and the light receiving sensor head 35 only need to cross the surface of the substrate W. The operation control unit 60 is electrically connected to the table motor 6 (see FIG. 1). The operation control unit 60 receives information regarding the rotation of the polishing table 3 from the table motor 6. The operation control unit 60 determines that the light projecting unit 32 and the light receiving sensor head 35 are moving below the substrate W when the polishing table 3 is within a predetermined rotation angle range.

[0033] The light projecting unit 32 intermittently projects light onto the surface of the substrate W at predetermined time intervals while moving below the substrate W. Specifically, the operation control unit 60 controls the light source 31 to cause the light source 31 to emit light intermittently at predetermined time intervals. The light from the light source 31 is projected onto the surface of the substrate W intermittently at predetermined time intervals via the light projecting unit 32. As a result, the light is projected onto a plurality of measurement points on the surface of the substrate W, and the film thickness at each measurement point is measured.

[0034] The light-projecting unit 32 and the light-receiving unit 33 of the light-receiving sensor head 35 may measure the film thickness by continuing to irradiate the surface of the substrate W with light while moving below the substrate W. In other words, the light-projecting unit 32 may continuously irradiate the surface of the substrate W with light. In this case, the operation control unit 60 controls the light source 31 to maintain emission of light while the light-projecting unit 32 moves below the substrate W. Light from the light source 31 continues to be irradiated onto the surface of the substrate W via the light-projecting unit 32. The spectrometer 37 measures the intensity of the reflected light at predetermined time intervals. As a result, the spectral processing unit 39 generates a spectrum of the reflected light representing the intensity of the reflected light for each wavelength from the light intensity data obtained by the spectrometer 37 at predetermined time intervals, and determines the film thickness at each measurement point on the substrate W based on the spectrum of the reflected light.

[0035] 3 is an enlarged view of the optical film thickness measuring device 30 shown in FIG. 1. As shown in FIG. 3, the light-projecting unit 32 and the light-receiving unit 33 of the light-receiving sensor head 35 are inclined with respect to the pad support surface 3a of the polishing table 3. That is, the tip of the light-projecting unit 32, which is made up of a light-projecting optical fiber, and the tip of the light-receiving unit 33, which is made up of a light-receiving optical fiber, are inclined at a predetermined angle with respect to the surface of the substrate W. The tip of the light-receiving unit 33, which is made up of a light-receiving optical fiber, is inclined at an angle that allows it to receive reflected light. The light-projecting unit 32 is configured to irradiate light obliquely onto the surface of the substrate W (the surface to be polished), and the light-receiving unit 33 is configured to receive light reflected obliquely from the surface of the substrate W.

[0036] It is preferable that the light receiving unit 33 receives light at an angle substantially equal to the angle of reflection of the light on the surface of the substrate W. In other words, it is preferable that the tip of the light receiving unit 33 made of a light-receiving optical fiber is inclined so that the reflected light enters substantially perpendicularly to the tip of the light receiving unit 33. In this case, as shown in Fig. 3, the tip of the light projecting unit 32 made of a light-projecting optical fiber and the tip of the light receiving unit made of a light-receiving optical fiber 33 are inclined at the same angle in directions approaching each other.

[0037] As shown in FIG. 3, the light-receiving sensor head 35 has a first light intensity sensor 41 and a second light intensity sensor 42 arranged adjacent to the light-receiving unit 33. The first light intensity sensor 41 and the second light intensity sensor 42 are configured to detect the intensity of light reflected from the substrate W. One end (tip) of the first light intensity sensor 41 and one end (tip) of the second light intensity sensor 42 are directed obliquely upward and face the substrate W held by the polishing head 10. The first light intensity sensor 41 and the second light intensity sensor 42 are inclined with respect to the pad support surface 3a of the polishing table 3. The first light intensity sensor 41 and the second light intensity sensor 42 are arranged at different positions in a direction perpendicular to the pad support surface 3a of the polishing table 3. The tip of the first light intensity sensor 41 and the tip of the second light intensity sensor 42 are inclined at a predetermined angle with respect to the surface of the substrate W. The tip of the first light intensity sensor 41 and the tip of the second light intensity sensor 42 are arranged at an angle that allows them to receive reflected light.

[0038] In this embodiment, the first light intensity sensor 41, the second light intensity sensor 42, and the light receiving unit 33 have the same inclination angle with respect to the surface of the substrate W (and the pad support surface 3a). The tip of the first light intensity sensor 41, the tip of the second light intensity sensor 42, and the tip of the light-receiving optical fiber 33 are located in a plane perpendicular to the path of the reflected light from the substrate W. As an example, the tips of the first light intensity sensor 41 and the second light intensity sensor 42 are made up of optical fiber cables. As another example, the first light intensity sensor 41 and the second light intensity sensor 42 may be made up of a light-receiving element arranged at the tip of the light-receiving sensor head 35.

[0039] In this embodiment, the tip of the light-projecting unit 32 has a light-projecting surface large enough to enable the light-receiving unit 33, the first light intensity sensor 41, and the second light intensity sensor 42 to receive light reflected from the substrate W. For example, as shown in FIG. 3, the light-projecting surface of the light-projecting unit 32, which is made up of a light-projecting optical fiber, is larger than the light-receiving surface of the light-receiving unit 33, which is made up of a light-receiving optical fiber.

[0040] Fig. 4 is an enlarged perspective view of the light-receiving sensor head 35 shown in Fig. 3. As shown in Fig. 4, the light-receiving sensor head 35 has a head housing 45 at its end, and the end of the light-receiving unit 33, the end of the first light amount sensor 41, and the end of the second light amount sensor 42 are supported by the head housing 45. The relative positional relationship between the light-receiving unit 33, the first light amount sensor 41, and the second light amount sensor 42 is fixed by the head housing 45. In this embodiment, the light-receiving unit 33 is located between the first light amount sensor 41 and the second light amount sensor 42.

[0041] In this specification, the amount of light reflected from the substrate W detected by the first light amount sensor 41 is referred to as the "first light amount," and the amount of light reflected from the substrate W detected by the second light amount sensor 42 is referred to as the "second light amount." The first light amount sensor 41 and the second light amount sensor 42 are connected to the operation control unit 60. The first light amount detected by the first light amount sensor 41 and the second light amount detected by the second light amount sensor 42 are sent to the operation control unit 60.

[0042] FIG. 5 is a diagram illustrating how the reflected light from the substrate W received by the light-receiving sensor head 35 changes as the polishing pad 2 wears down. The thickness of the polishing pad 2 gradually becomes thinner as the substrate W is polished. In other words, the thickness of the polishing pad 2 gradually decreases. As shown in FIG. 5, as the thickness of the polishing pad 2 decreases, the position of the surface of the substrate W pressed against the polishing pad 2 changes in a direction closer to the light-projecting unit 32 and the light-receiving sensor head 35. In other words, the distance from the surface of the substrate W to the tip of the light-projecting optical fiber 32 and the tip of the light-receiving sensor head 35 decreases as the polishing pad 2 wears down.

[0043] As described above, the light projecting optical fiber 32 projects light obliquely onto the surface of the substrate W. Therefore, when the distance from the surface of the substrate W to the tip of the light projecting optical fiber 32 and the tip of the light receiving sensor head 35 becomes short, the position of the light reflected from the substrate W shifts relative to the light receiving sensor head 35. This prevents the light receiving unit 33 from properly receiving the light reflected from the substrate W, and as a result, there is a risk that the film thickness of the substrate W cannot be measured accurately.

[0044] Therefore, in this embodiment, position correction amounts for the light-projecting unit 32 and the light-receiving sensor head 35 are determined according to the amount of wear of the polishing pad 2. Fig. 6(a) is a diagram illustrating the amount of reflected light detected by the light-receiving sensor head 35 before the polishing pad 2 shown in Fig. 5 is worn, and Fig. 6(b) is a diagram illustrating the amount of reflected light detected by the light-receiving sensor head 35 after the polishing pad 2 shown in Fig. 5 is worn. As shown in Figs. 6(a) and 6(b), the amount of reflected light from the substrate W is greatest at the center in a plane perpendicular to the path of the reflected light and decreases with increasing distance from the center.

[0045] 6(a) and 6(b), light-receiving position R1 represents the range in which the light-receiving unit 33 receives reflected light from the substrate W, light-receiving position R2 represents the range in which the first light intensity sensor 41 receives reflected light from the substrate W, and light-receiving position R3 represents the range in which the second light intensity sensor 42 receives reflected light from the substrate W. As shown in FIG. 6(a), before the polishing pad 2 is worn out, the light-receiving unit 33 receives the central portion of the reflected light from the substrate W. At such light-receiving position R1, the light-receiving unit 33 can receive a sufficient amount of reflected light to accurately measure the film thickness of the substrate W. Before the polishing pad 2 is worn out, the first light intensity detected by the first light intensity sensor 41 and the second light intensity detected by the second light intensity sensor 42 are equal.

[0046] As shown in FIG. 6(b), after the polishing pad 2 is worn, the light receiving unit 33 receives a portion of the reflected light from the substrate W that is shifted from the center. At this light receiving position R1, the light receiving unit 33 cannot receive a sufficient amount of reflected light to accurately measure the film thickness of the substrate W. After the polishing pad 2 is worn, the first light amount detected by the first light amount sensor 41 and the second light amount detected by the second light amount sensor are different. As described above, the first light amount sensor 41 and the second light amount sensor 42 are disposed at different positions in the direction perpendicular to the pad support surface 3a of the polishing table 3 (i.e., the thickness direction of the polishing pad 2). Therefore, as the polishing pad 2 is worn, the amount of reflected light received by the first light amount sensor 41 and the second light amount sensor 42 changes. In the example of FIG. 6(b), the first light amount detected at the light receiving position R2 is greater than the second light amount detected at the light receiving position R3. In this way, the relationship between the first light amount and the second light amount changes with wear of the polishing pad 2. However, the arrangement of the first light amount sensor 41 and the second light amount sensor 42 is not particularly limited to this embodiment as long as the positional relationship causes a change in the detected light amount with wear of the polishing pad 2.

[0047] The operation control unit 60 is configured to determine position correction amounts for the light-projecting unit 32 and the light-receiving sensor head 35 (including the light-receiving unit 33, the first light intensity sensor 41, and the second light intensity sensor 42) corresponding to the amount of wear of the polishing pad 2, based on the first light intensity detected by the first light intensity sensor 41 and the second light intensity detected by the second light intensity sensor 42. A correlation between the difference between the first light intensity and the second light intensity, which has been acquired in advance, and the amount of wear of the polishing pad 2 is stored in the storage device 60a of the operation control unit 60. The operation control unit 60 calculates the difference between the first light intensity detected by the first light intensity sensor 41 and the second light intensity detected by the second light intensity sensor 42. The operation control unit 60 determines position correction amounts for the light-projecting unit 32 and the light-receiving sensor head 35 based on the calculated difference between the first light intensity and the second light intensity, and the correlation between the difference between the first light intensity and the second light intensity and the amount of wear of the polishing pad 2.

[0048] The first light amount and the second light amount are detected when the first light amount sensor 41 and the second light amount sensor 42 are covered by the substrate W pressed against the polishing surface 2a of the polishing pad 2. The operation control unit 60 determines that the first light amount sensor 41 and the second light amount sensor 42 are covered by the substrate W on the polishing pad 2 based on the rotation angle of the polishing table 3 and the relative position between the polishing table 3 and the polishing head 10.

[0049] In one embodiment, the first light amount and the second light amount are detected during polishing of the substrate W. The operation control unit 60 determines the position correction amounts of the light projecting unit 32 and the light receiving sensor head 35 based on the first light amount and the second light amount detected during polishing of the substrate W. The determination of the position correction amounts of the light projecting unit 32 and the light receiving sensor head 35 may be performed every time a substrate W is polished, or may be performed every time a predetermined number of substrates W are polished.

[0050] In another embodiment, the first light intensity and the second light intensity are detected during idling operation in which polishing of the substrate W is not progressing, and when the substrate W is pressed against the polishing surface 2a of the polishing pad 2 with a pressing force applied during polishing of the substrate W. During idling operation of the substrate W, the supply of polishing liquid to the polishing surface 2a and the rotation of the polishing table 3 are stopped, and polishing of the substrate W does not progress. The pressing force applied during polishing of the substrate W is determined in advance based on, for example, a polishing recipe for polishing the substrate W held by the polishing head 10.

[0051] The operation control unit 60 determines the position correction amounts of the light projecting unit 32 and the light receiving sensor head 35 based on the first light amount and the second light amount detected during idling operation. The determination of the position correction amounts of the light projecting unit 32 and the light receiving sensor head 35 may be performed every time a substrate W is polished during idling operation, or may be performed during idling operation after a predetermined number of substrates W have been polished.

[0052] As shown in FIG. 3, the polishing apparatus 1 further includes a sensor moving mechanism 50 that moves a light-receiving sensor head 35, including a light-projecting unit 32 and a light-receiving unit 33, in a direction perpendicular to the pad support surface 3a of the polishing table 3 (i.e., in the thickness direction of the polishing pad 2). The sensor moving mechanism 50 includes a sensor support member 51 that supports the light-projecting unit 32 and the light-receiving sensor head 35, a first gear 53 connected to the sensor support member 51, a second gear 56 that meshes with the first gear 53, and a motor 58 connected to the second gear 56. Examples of the motor 58 include a servo motor and a stepping motor. The sensor support member 51 is disposed inside the hole 3b in the polishing table 3.

[0053] At least a portion of the light-projecting unit 32 and the light-receiving sensor head 35 is supported by a sensor support member 51. The relative positions of the light-projecting unit 32 and the light-receiving sensor head 35 are fixed by the sensor support member 51. In this embodiment, the sensor support member 51 is attached to the inner surface of the polishing table 3, which defines the hole 3b, via a sealing member (not shown) so as to be movable relative to the polishing table 3. This prevents liquid filling the hole 3b from leaking between the sensor support member 51 and the inner surface of the polishing table 3 and adhering to the first gear 53, the second gear 56, the motor 58, and the like. In one embodiment, instead of the sealing member, a cover may be provided to prevent liquid from adhering to the first gear 53, the second gear 56, the motor 58, and the like.

[0054] The first gear 53 is connected to a screw 54. The screw 54 is threaded into a threaded hole 51a provided in the sensor support member 51. The second gear 56 is connected to a rotation shaft 58a of a motor 58. When the motor 58 is driven, the second gear 56 rotates via the rotation shaft 58a. When the second gear 56 rotates, the first gear 53 rotates in conjunction with the second gear 56. The rotation of the second gear 53 rotates the screw 54, and the sensor support member 51, and the light-projecting unit 32 and the light-receiving sensor head 35 (including the light-receiving unit 33, the first light intensity sensor 41, and the second light intensity sensor 42) supported by the sensor support member 51 are moved together in a direction perpendicular to the pad support surface 3a. In this way, the sensor moving mechanism 50 moves the light-projecting unit 32 and the light-receiving sensor head 35 within the hole 3b relative to the polishing table 3.

[0055] The specific configuration of the sensor moving mechanism 50 is not particularly limited to this embodiment, as long as it can move the light projecting unit 32 and the light receiving sensor head 35 in a direction perpendicular to the pad support surface 3a. For example, the screw 54 may be directly connected to the rotation shaft 58a of the motor 58. The sensor moving mechanism 50 is connected to an operation control unit 60, and the operation of the sensor moving mechanism 50 is controlled by the operation control unit 60.

[0056] The operation control unit 60 is configured to issue a command to the sensor moving mechanism 50 to move the light projecting unit 32 and the light receiving sensor head 35 by the position correction amount determined as described above. The operation control unit 60 of this embodiment has the function of a motor driver that controls the rotation amount of the motor 58 of the sensor moving mechanism 50. A storage device 60a of the operation control unit 60 stores a correlation between the movement amount of the light projecting unit 32 and the light receiving sensor head 35 and the rotation amount of the motor 58, which has been acquired in advance. Based on the correlation between the movement amount of the light projecting unit 32 and the light receiving sensor head 35 and the rotation amount of the motor 58, the operation control unit 60 controls the rotation amount of the motor 58 so as to move the light projecting unit 32 and the light receiving sensor head 35 by the determined position correction amount.

[0057] In one embodiment, the operation control unit 60 may be configured to issue a command to the sensor moving mechanism 50 to move the light projecting unit 32 and the light receiving sensor head 35 by the determined position correction amount when the determined position correction amount exceeds a predetermined threshold. The predetermined threshold is a value corresponding to the amount of wear of the polishing pad 2 that exceeds the range in which the light receiving unit 33 can properly receive reflected light from the substrate W, and is determined in advance by experiment or the like.

[0058] In one embodiment, the operation control unit 60 may directly control the amount of rotation of the motor 58 for correcting the positions of the light projecting unit 32 and the light receiving sensor head 35, based on the first light amount detected by the first light amount sensor 41 and the second light amount detected by the second light amount sensor 42. In this case, the storage device 60a of the operation control unit 60 may store a correlation between the difference between the first light amount and the second light amount, which has been acquired in advance, and the amount of rotation of the motor 58 for correcting the positions of the light projecting unit 32 and the light receiving sensor head 35. In this case, the operation control unit 60 still indirectly determines the amount of position correction of the light projecting unit 32 and the light receiving sensor head 35.

[0059] FIG. 7 is a flowchart showing an example of a polishing method using the polishing apparatus 1 shown in FIG. In step S101, the polishing apparatus 1 starts polishing the substrate W. Specifically, the operation control unit 60 issues commands to the table motor 6, the polishing head motor, and the polishing liquid supply nozzle 20 to rotate the polishing table 3 and the polishing head 10 while supplying the polishing liquid onto the polishing surface 2a of the polishing pad 2. Furthermore, the operation control unit 60 issues a command to the polishing head lifting mechanism to lower the polishing head 10, and issues a command to the polishing head 10 to press the substrate W against the polishing pad 2. As a result, the surface of the substrate W is polished by the chemical action of the polishing liquid and the mechanical action of the abrasive grains contained in the polishing liquid and / or the polishing surface 2a.

[0060] In step S102, the optical film thickness measuring device 30 measures the film thickness on the surface of the substrate W while the substrate W is being polished. In step S103, the first light intensity sensor 41 and the second light intensity sensor 42 detect the first and second light intensities of the reflected light from the substrate W when light is irradiated onto the substrate W from the light projecting unit 32 during film thickness measurement. In step S104, the operation control section 60 determines the amount of position correction for the light receiving sensor head 35 including the light projecting section 32 and the light receiving section 33 based on the first light amount and the second light amount. In step S105, the operation control unit 60 issues a command to the sensor moving mechanism 50 to move the light projecting unit 32 and the light receiving sensor head 35 by the position correction amount.

[0061] In step S106, the optical film thickness measurement device 30 measures the film thickness on the surface of the substrate W. In step S107, the operation control unit 60 determines the polishing endpoint based on the measured film thickness of the substrate W. In step S108, the polishing apparatus 1 finishes polishing the substrate W. Specifically, the operation control unit 60 issues a command to the polishing head 10 to stop pressing the substrate W against the polishing pad 2, and issues a command to the polishing head lifting mechanism to lift the polishing head 10. Furthermore, the operation control unit 60 issues commands to the table motor 6, the polishing head motor, and the polishing liquid supply nozzle 20 to stop the rotation of the polishing table 3 and the polishing head, and to stop the supply of the polishing liquid onto the polishing surface 2a.

[0062] The timing for performing step S103 is not particularly limited as long as the first light intensity sensor 41 and the second light intensity sensor 42 are covered by the substrate W pressed against the polishing surface 2a of the polishing pad 2 during polishing of the substrate W. Furthermore, step S105 may be performed after polishing of the substrate W.

[0063] FIG. 8 is a flowchart showing another example of a polishing method using the polishing apparatus 1 shown in FIG. In step S201, while the substrate W is idling, the operation control unit 60 issues a command to the polishing head 10 to press the substrate W against the polishing surface 2a of the polishing pad 2 with the pressing force applied during polishing of the substrate W. While the substrate W is idling, the supply of polishing liquid to the polishing surface 2a and the rotation of the polishing table 3 are stopped, and polishing of the substrate W does not proceed.

[0064] In step S202, the light projecting unit 32 of the optical film thickness measuring device 30 irradiates light onto the surface of the substrate W, and the first light intensity sensor 41 and the second light intensity sensor 42 detect the first and second light intensities of the light reflected from the substrate W. In step S203, the operation control unit 60 determines the amount of position correction for the light receiving sensor head 35 including the light projecting unit 32 and the light receiving unit 33 based on the first light amount and the second light amount. In step S204, the operation control unit 60 issues a command to the sensor moving mechanism 50 to move the light projecting unit 32 and the light receiving sensor head 35 by the position correction amount.

[0065] Steps S205 to S208 are the same operations as steps S101 and S106 to S108 shown in FIG. 7, and therefore redundant explanations will be omitted.

[0066] 1 to 8, the position correction amounts of the light-projecting unit 32 and the light-receiving sensor head 35 corresponding to the amount of wear of the polishing pad 2 are determined based on the first light amount and the second light amount. By moving the light-projecting unit 32 and the light-receiving sensor head 35 by the position correction amounts, the light reflected from the substrate W can be properly received by the light-receiving unit 33 even if the polishing pad 2 is worn.

[0067] 9 is a schematic diagram showing an optical film thickness measurement device 30 according to another embodiment of the polishing apparatus 1. The configuration and operation of this embodiment, which will not be specifically described, are the same as those of the above-described embodiment, and therefore, redundant description thereof will be omitted. In this embodiment, the polishing apparatus 1 is provided with a distance measurement device 70 that measures the distance to the substrate W, instead of the first light intensity sensor 41 and the second light intensity sensor 42 of the optical film thickness measurement device 30. The polishing apparatus 1 of this embodiment differs from the above-described embodiment in that the amount of position correction is determined based on the distance to the substrate W measured by the distance measurement device 70.

[0068] In this embodiment, the light-receiving unit 33 of the optical film thickness measurement device 30 is not provided in the light-receiving sensor head 35. The distance measurement device 70 is disposed inside the polishing table 3. The distance measurement device 70 is disposed between the light-projecting unit 32 and the light-receiving unit 33 of the optical film thickness measurement device 30, and is supported by the sensor support member 51 of the sensor moving mechanism 50. Specifically, the distance measurement device 70 is disposed inside the hole 3b of the polishing table 3, and is disposed below the pad support surface 3a of the polishing table 3. The distance measurement device 70 is configured to measure the distance between the distance measurement device 70 and the surface of the substrate W.

[0069] Examples of the distance measurement device 70 include an optical distance measurement device, a radio distance measurement device, an ultrasonic distance measurement device, and a camera equipped with an image sensor (e.g., a stereo camera). The distance measurement device 70 measures the distance between the distance measurement device 70 and the surface of the substrate W when the distance measurement device 70 is covered by the substrate W pressed against the polishing surface 2a of the polishing pad 2. The operation control unit 60 determines that the distance measurement device 70 is covered by the substrate W on the polishing surface 2a based on the rotation angle of the polishing table 3 and the relative position between the polishing table 3 and the polishing head 10.

[0070] The distance measurement device 70 is connected to the operation control unit 60, and the distance measured by the distance measurement device 70 between the distance measurement device 70 and the surface of the substrate W is sent to the operation control unit 60. The operation control unit 60 determines the position correction amounts of the light projector 32 and the light receiver 33 corresponding to the amount of wear of the polishing pad 2 based on the distance between the distance measurement device 70 and the substrate W measured by the distance measurement device 70. Specifically, the storage device 60a of the operation control unit 60 stores the distance between the distance measurement device 70 and the surface of the substrate measured in advance by the distance measurement device 70 before the wear of the polishing pad 2 (hereinafter referred to as the "initial distance"). The operation control unit 60 determines the position correction amounts of the light projector 32 and the light receiver 33 corresponding to the amount of wear of the polishing pad 2 from the difference between the measured value of the distance between the distance measurement device 70 and the surface of the substrate W and the initial distance.

[0071] The operation control unit 60 is configured to issue a command to the sensor moving mechanism 50 to move the light-projecting unit 32 and the light-receiving unit 33 by the determined position correction amount. The sensor support member 51, and the light-projecting unit 32, the light-receiving unit 33, and the distance measuring device 70 supported by the sensor support member 51 are moved together in a direction perpendicular to the pad support surface 3 a.

[0072] In the polishing apparatus 1 of Figure 9, steps S103 and S104 described with reference to Figure 7 and steps S202 and S203 described with reference to Figure 8 can be replaced with a step of measuring the distance between the distance measurement device 70 and the surface of the substrate W using the distance measurement device 70, and a step of determining a position correction amount based on the distance between the distance measurement device 70 and the surface of the substrate W.

[0073] FIG. 10 is a schematic diagram showing yet another embodiment of the polishing apparatus 1. The configuration and operation of this embodiment, which are not specifically described, are the same as those of the embodiment described with reference to FIG. 9, and therefore, redundant description will be omitted. In this embodiment, the polishing apparatus 1 includes, instead of the distance measurement device 70, a capacitance measurement device 80 that measures the capacitance between a capacitance sensor 82 disposed in the thickness direction of the polishing pad 2 and a conductive target 83. The polishing apparatus 1 of this embodiment differs from the embodiment described with reference to FIG. 9 in that the amount of position correction is determined based on the capacitance between the capacitance sensor 82 and the conductive target 83 measured by the capacitance measurement device 80.

[0074] The capacitance measuring device 80 includes a capacitance sensor 82 disposed within the polishing table 3, a conductive target 83 disposed within a retainer ring 75 of the polishing head 10, a conductor 85 electrically connecting the capacitance sensor 82 and the conductive plate 83, and rotary connectors 88 and 87 attached to the conductor 85. The retainer ring 75 is an annular structure disposed along the outer periphery at the bottom of the polishing head 10. The retainer ring 75 has the function of holding the substrate W to prevent it from flying out of the polishing head 10 during polishing. The retainer ring 75 is made of an insulating material such as ceramic.

[0075] In this embodiment, the capacitance sensor 82 is disposed at the same height as the pad support surface 3a of the polishing table 3. The capacitance sensor 82 is configured to detect the capacitance ε between itself and the electrically connected conductive target 83. The capacitance sensor 82 is connected to the operation control unit 60, and the measured value of the capacitance ε between the capacitance sensor 82 and the conductive target 83 is sent to the operation control unit 60.

[0076] When measuring the capacitance, the capacitance sensor 82 and the conductive target 83 are positioned opposite each other with the polishing pad 2 in between. The capacitance sensor 82 measures the capacitance ε between itself and the conductive target 83 when the conductive target 83 is located below the capacitance sensor 82. The operation control unit 60 determines that the conductive target 83 is located below the capacitance sensor 82 based on the rotation angle of the polishing table 3 and the relative position of the polishing table 3 and the polishing head 10.

[0077] The capacitance sensor 82 and the conductive target 83 are electrically connected by a conductor 85 via a rotary connector 87 on the capacitance sensor 82 side and a rotary connector 88 on the conductive target 83 side. Examples of the rotary connectors 87, 88 include slip rings. The capacitance measuring device 80 is configured to measure the capacitance ε between the capacitance sensor 82 and the conductive target 83 by passing a current through the capacitance sensor 82 and the conductive target 83 from a power source (not shown) through the conductor 85.

[0078] The operation control unit 60 is configured to determine a distance d1 between the pad support surface 3a of the polishing table 3 and the retaining ring 75 based on the capacitance ε between the capacitance sensor 82 and the conductive target 83 measured by the capacitance measurement device 80. The storage device 60a of the operation control unit 60 stores a correlation between the capacitance ε between the capacitance sensor 82 and the conductive target 83, which has been acquired in advance, and the distance d1 between the pad support surface 3a of the polishing table 3 and the retaining ring 75. The operation control unit 60 determines the distance d1 between the pad support surface 3a and the retaining ring 75 based on the capacitance ε between the capacitance sensor 82 and the conductive target 83 measured by the capacitance sensor 82, and the correlation between the capacitance ε and the distance d1.

[0079] To prevent the substrate W from flying off the polishing head 10 during polishing, the pressing force of the polishing pad 10 against the polishing pad 2 is adjusted so that it is greater in the area where the retaining ring 75 is located than in the area where the substrate W is located. The polishing pad 2, which is made of an elastic material, changes in thickness depending on the pressing force. Therefore, the distance d1 between the pad support surface 3a and the retaining ring 75 is smaller than the distance d2 between the pad support surface 3a and the substrate W. The correlation between the distance d1 and the distance d2 can be calculated from the elastic modulus of the polishing pad 2, the area of ​​the lower surface of the retaining ring 75, the area of ​​the substrate W, the amount of gas supplied to the airbag of the polishing head 10, and other factors. The correlation between the distance d1 and the distance d2 is stored in the memory device 60a of the operation control unit 60. The operation control unit 60 determines the distance d2 between the pad support surface 3a and the substrate W from the determined distance d1 based on the correlation between the distance d1 and the distance d2.

[0080] Based on the determined distance d2, the operation control unit 60 determines the position correction amounts of the light projecting unit 32 and the light receiving unit 33 corresponding to the amount of wear of the polishing pad 2. Specifically, the storage device 60a of the operation control unit 60 stores a distance d2 (hereinafter referred to as the "initial distance") determined in advance using a similar method before the wear of the polishing pad 2. The operation control unit 60 determines the position correction amounts of the light projecting unit 32 and the light receiving unit 33 corresponding to the amount of wear of the polishing pad 2 from the difference between the determined distance d2 and the initial distance.

[0081] The operation control unit 60 is configured to issue a command to the sensor moving mechanism 50 to move the light-projecting unit 32 and the light-receiving unit 33 by the determined position correction amount. The sensor support member 51, and the light-projecting unit 32, the light-receiving unit 33, and the distance measuring device 70 supported by the sensor support member 51 are moved together in a direction perpendicular to the pad support surface 3 a.

[0082] In the polishing apparatus 1 of Figure 10, steps S103 and S104 described with reference to Figure 7 and steps S202 and S203 described with reference to Figure 8 can be replaced with a step of measuring the capacitance between the capacitance sensor 82 and the conductive target 83 using the capacitance measuring device 80, and a step of determining the amount of position correction based on the capacitance between the capacitance sensor 82 and the conductive target 83.

[0083] The above-described embodiments have been described for the purpose of enabling a person of ordinary skill in the art to practice the present invention. Various modifications of the above-described embodiments would naturally be possible for a person skilled in the art, and the technical concept of the present invention may also be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be interpreted in the broadest scope in accordance with the technical concept defined by the claims. [Explanation of symbols]

[0084] 1 Polishing equipment 2 polishing pads 2a Polished surface 2b through hole 3 Polishing table 3a Pad support surface 3b hole 5 Table shaft 6 Table Motor 10 Polishing Head 12 Grinding head shaft 20 Polishing liquid supply nozzle 30 Optical film thickness measuring device 31 Light source 32 Light projection unit (light projection optical fiber) 33 Light receiving unit (light receiving optical fiber) 35 Light receiving sensor head 37 Spectrometer 39 Spectral Processing Section 41 First light sensor 42 Second light sensor 45 Head housing 50 Sensor movement mechanism 51 Sensor support member 51a screw hole 53 1st Gear 54 Screw 56 2nd gear 58 Motor 58a Rotation axis 60 Motion control section 60a Storage device 60b Arithmetic unit 70 Distance measuring device 75 Retainer ring 80 Capacitance measuring device 82 Capacitive Sensor 83 Conductor Target 85 Conductor 87,88 Rotary Connector

Claims

1. a polishing table having a pad support surface for supporting a polishing pad; a polishing head that presses the substrate against the polishing surface of the polishing pad; an optical film thickness measurement device that irradiates the substrate with light, receives reflected light from the substrate, and determines a film thickness measurement value for the substrate based on the reflected light; An operation control unit is provided, The optical film thickness measuring device is a light projecting unit that projects the light onto the substrate; a light receiving unit that receives the reflected light from the substrate; a first light amount sensor and a second light amount sensor disposed adjacent to the light receiving unit and configured to detect the amount of light reflected from the substrate; The operation control unit is configured to determine a position correction amount of the light-emitting unit and the light-receiving unit corresponding to the amount of wear of the polishing pad based on a first light amount detected by the first light amount sensor and a second light amount detected by the second light amount sensor.

2. 2. The polishing apparatus according to claim 1, wherein the first light amount sensor and the second light amount sensor are disposed at different positions in a direction perpendicular to the pad support surface.

3. 2. The polishing apparatus according to claim 1, wherein the light-emitting portion and the light-receiving portion are inclined with respect to the pad support surface.

4. 2. The polishing apparatus according to claim 1, wherein the light receiving portion is located between the first light quantity sensor and the second light quantity sensor.

5. 2. The polishing apparatus according to claim 1, wherein the operation control unit is configured to determine the position correction amount based on a correlation between a difference between the first light amount and the second light amount, which is acquired in advance, and an amount of wear of the polishing pad.

6. a sensor moving mechanism that moves the light projecting unit and the light receiving unit in the direction perpendicular to the pad support surface, 2. The polishing apparatus according to claim 1, wherein said operation control section is configured to issue a command to said sensor moving mechanism to move said light projecting section and said light receiving section by said position correction amount.

7. the light-emitting unit and the light-receiving unit are disposed in a hole formed inside the polishing table, 7. The polishing apparatus according to claim 6, wherein said sensor moving mechanism is configured to move said light projecting unit and said light receiving unit within said hole relative to said polishing table.

8. 2. The polishing apparatus according to claim 1, wherein the first light amount and the second light amount are detected when the first light amount sensor and the second light amount sensor are covered by the substrate pressed against the polishing surface.

9. 9. The polishing apparatus according to claim 8, wherein the first amount of light and the second amount of light are detected while the substrate is being polished.

10. 9. The polishing apparatus according to claim 8, wherein the first light amount and the second light amount are detected during idling operation in which polishing of the substrate is not progressing and when the substrate is pressed against the polishing surface with a pressing force applied during polishing of the substrate.

11. pressing the substrate against a polishing surface of a polishing pad supported on a pad support surface of a polishing table; irradiating the substrate with light from a light projecting unit of an optical film thickness measuring device that determines a film thickness measurement value of the substrate, and receiving reflected light from the substrate with a light receiving unit of the optical film thickness measuring device; detecting the amount of the reflected light from the substrate using a first light amount sensor and a second light amount sensor disposed adjacent to the light receiving unit; a polishing method for determining a position correction amount of the light-emitting unit and the light-receiving unit corresponding to an amount of wear of the polishing pad based on a first light amount detected by the first light amount sensor and a first light amount detected by the second light amount sensor.

12. 12. The polishing method according to claim 11, wherein the first light amount sensor and the second light amount sensor are arranged at different positions in a direction perpendicular to the pad support surface.

13. irradiating the substrate with the light means irradiating the substrate with the light obliquely with respect to the surface to be polished, 12. The polishing method according to claim 11, wherein receiving the reflected light from the substrate comprises receiving the reflected light that is obliquely reflected by the surface of the substrate to be polished.

14. 12. The polishing method according to claim 11, wherein the light receiving portion is located between the first light quantity sensor and the second light quantity sensor.

15. The polishing method according to claim 11, wherein determining the position correction amount based on the first light amount and the second light amount is determining the position correction amount based on a correlation between a difference between the first light amount and the second light amount, which has been acquired in advance, and an amount of wear of the polishing pad.

16. 12. The polishing method according to claim 11, further comprising moving the light projecting unit and the light receiving unit by the position correction amount along the direction perpendicular to the pad support surface.

17. 17. The polishing method according to claim 16, wherein the light projecting unit and the light receiving unit are moved relative to the polishing table within a hole formed inside the polishing table.

18. 12. The polishing method according to claim 11, wherein the detection of the first light amount and the second light amount is performed when the first light amount sensor and the second light amount sensor are covered by the substrate pressed against the polishing surface.

19. pressing the substrate against the polishing surface comprises rotating the polishing table and pressing the substrate against the polishing surface with the polishing head to polish the substrate; 20. The polishing method according to claim 18, wherein the first amount of light and the second amount of light are detected while the substrate is being polished.

20. pressing the substrate against the polishing surface means pressing the substrate against the polishing surface with a pressing force applied during polishing of the substrate, while the polishing table is stopped from rotating during idling operation in which polishing of the substrate does not progress, 19. The polishing method according to claim 18, wherein the first light amount and the second light amount are detected during the idling operation.

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