Polishing device and polishing method

Abstract

To provide a polishing device which can remove a polishing liquid or polishing wastes from a light passing part of a polishing pad.SOLUTION: A polishing device 1 includes: a polishing table 3 configured to support a polishing pad 2 having a light passing part 33; a polishing head 5 which presses the substrate W to a polishing surface 2a of the polishing pad 2; an optical sensor 21 which is disposed in the polishing table 3, radiates light to the substrate W through the light passing part 33, and receives reflected light from the substrate W through the light passing part 33; and a cleaning part 12 forming a cleaning space CS which covers the light passing part 33 on the light passing part 33 and configured to supply a cleaning fluid to the light passing part 33 through the cleaning space CS.SELECTED DRAWING: Figure 7

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] In the manufacturing process of semiconductor devices, a chemical mechanical polishing (CMP) apparatus is used to polish the surface of a substrate such as a wafer. The CMP apparatus is equipped with a polishing pad attached to a polishing table and a polishing head for pressing the substrate against the polishing surface of the polishing pad. The CMP apparatus presses the substrate against the polishing surface of the polishing pad with the polishing head while supplying a polishing liquid (e.g., slurry) onto the polishing pad, thereby bringing the surface of the substrate into sliding contact with the polishing surface of the polishing pad. The surface of the substrate is planarized 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 pad.

[0003] Polishing of a substrate is terminated when a film (insulating film, silicon layer, etc.) constituting the surface of the substrate is polished and its film thickness reaches a target film thickness. The polishing apparatus is equipped with an optical film thickness measuring device for measuring the film thickness of the substrate. The optical film thickness measuring device is configured to irradiate light onto the substrate by an optical sensor arranged in the polishing table, receive reflected light from the substrate, and determine the film thickness of the substrate based on the intensity of the reflected light measured by a spectroscope. The polishing pad has a through hole or a transparent window as a light passing portion for passing the light irradiated onto the substrate from the optical sensor and the reflected light from the substrate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-104191 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, as the substrate is polished, the polishing liquid or polishing debris may adhere to the light transmitting portion (through hole or transparent window) of the polishing pad, reducing the intensity of the reflected light from the substrate passing through the light transmitting portion.

[0006] Therefore, the present invention provides a polishing apparatus and a polishing method capable of removing the polishing liquid or polishing debris from the light passing portion of the polishing pad. [Means for solving the problem]

[0007] In one aspect, a polishing apparatus is provided, comprising: a polishing table that supports a polishing pad having a light passing portion; a polishing head that presses a substrate against the polishing surface of the polishing pad; an optical sensor that is disposed within the polishing table and irradiates light onto the substrate through the light passing portion and receives reflected light from the substrate through the light passing portion; and a cleaning portion that forms a cleaning space above the light passing portion to cover the light passing portion and supplies a cleaning fluid to the light passing portion through the cleaning space. In one aspect, the polishing apparatus further includes a fluid discharge line that discharges the cleaning fluid from the cleaning space and an operation control unit that controls the operation of the cleaning unit, the cleaning unit including a cleaning cover that forms the cleaning space inside, a cleaning nozzle that supplies the cleaning fluid into the cleaning space, and an actuator that moves the cleaning cover up and down, and the operation control unit is configured to give a command to the actuator to lower the cleaning cover until it contacts the polishing surface of the polishing pad, thereby surrounding the light passing portion with the cleaning cover and blocking the cleaning space.

[0008] In one embodiment, the cleaning nozzle includes at least one of a liquid nozzle that supplies a liquid as the cleaning fluid, a jet nozzle that supplies a jet of fluid as the cleaning fluid, and a chemical liquid nozzle that supplies a chemical liquid as the cleaning fluid. In one aspect, the cleaning unit includes an ultrasonic transducer that generates ultrasonic waves and is configured to propagate the ultrasonic waves through the cleaning fluid. In one aspect, the cleaning section further includes a cleaning cover that defines the cleaning space therein, and the ultrasonic transducer is disposed in the cleaning cover. In one aspect, the cleaning unit further includes a cleaning nozzle that supplies the cleaning fluid into the cleaning space, and the ultrasonic transducer is disposed in the cleaning nozzle.

[0009] In one embodiment, the light passing portion is a through hole formed in the polishing pad. In one aspect, the polishing apparatus further includes a fluid discharge line that discharges the cleaning fluid from the cleaning space, the fluid discharge line being connected to the through hole and configured to discharge the cleaning fluid from the cleaning space through the through hole. In one embodiment, the light passing portion is a transparent window made of a material that allows light to pass through. In one aspect, the polishing apparatus further includes a fluid discharge line for discharging the cleaning fluid from the cleaning space, the cleaning section includes a cleaning cover that forms the cleaning space inside, and the fluid discharge line is connected to an opening formed on the inner surface of the cleaning cover and is configured to discharge the cleaning fluid from the cleaning space through the opening.

[0010] In one aspect, the cleaning unit further includes a load measuring device that measures the load applied to the cleaning cover, and the operation control unit is configured to give a command to the actuator to lower the cleaning cover until the load measured by the load measuring device reaches a load target value. In one embodiment, the apparatus further includes a table motor for rotating the polishing table and a cleaning unit horizontal movement mechanism for moving the cleaning unit horizontally, and the operation control unit is configured to control the operation of the table motor and the cleaning unit horizontal movement mechanism, and is configured to give commands to the table motor and the cleaning unit horizontal movement mechanism to rotate the polishing table and move the cleaning unit horizontally so that the position of the light passing unit matches the position of the cleaning cover.

[0011] In one embodiment, the polishing apparatus further includes an operation control unit that controls the operation of the cleaning unit, the cleaning unit including a mirror arranged on the optical path of the light irradiated from the optical sensor through the light passing unit, the optical sensor configured to receive reflected light from the mirror through the light passing unit, and the operation control unit configured to detect the cleaning end point of the light passing unit, which is the point at which the intensity of the reflected light from the mirror exceeds a threshold value. In one aspect, the polishing apparatus further includes an operation control unit that controls the operation of the cleaning unit, the cleaning unit includes an imaging device that generates an image of the light passing portion, and the operation control unit is configured to detect the cleaning end point of the light passing portion based on the image. In one aspect, the polishing apparatus further includes an operation control unit that controls the operation of the cleaning unit, and the operation control unit is configured to determine whether or not it is time to clean the light passing unit based on the reflected light from the substrate.

[0012] In one aspect, there is provided a polishing method comprising the steps of: pressing a substrate against a polishing surface of a polishing pad supported on a polishing table to polish the substrate; and, while the substrate is being polished, an optical sensor disposed in the polishing table irradiates the substrate with light through a light transmitting portion provided in the polishing pad and receives reflected light from the substrate through the light transmitting portion; before or after the substrate is polished, a cleaning portion forms a cleaning space covering the light transmitting portion on the light transmitting portion, and the cleaning portion supplies a cleaning fluid to the light transmitting portion through the cleaning space. In one aspect, the step of forming the cleaning space covering the light transmitting portion on the light transmitting portion by the cleaning unit is a step of positioning the cleaning unit above the light passing portion and lowering a cleaning cover of the cleaning unit until it contacts the polishing surface of the polishing pad to close the cleaning space formed inside the cleaning cover and surround the light passing portion with the cleaning cover, and the step of supplying the cleaning fluid to the light passing portion through the cleaning space by the cleaning unit is a step of supplying the cleaning fluid to the light passing portion from a cleaning nozzle of the cleaning unit through the cleaning space, and the polishing method further includes discharging the cleaning fluid from the cleaning space through a fluid discharge line.

[0013] In one embodiment, the polishing method further includes generating ultrasonic waves with an ultrasonic transducer and propagating the ultrasonic waves through the cleaning fluid. In one aspect, the process of forming the cleaning space covering the light-transmitting portion on the light-transmitting portion by the cleaning unit is a process of measuring the load applied to a cleaning cover of the cleaning unit with a load measuring device, and lowering the cleaning cover until the measured load reaches a load target value, thereby forming the cleaning space covering the light-transmitting portion on the light-transmitting portion. In one embodiment, the step of positioning the cleaning unit above the light passing portion is a step of rotating the polishing table and horizontally moving the cleaning unit so that the position of the light passing portion coincides with the position of the cleaning cover, thereby positioning the cleaning unit above the light passing portion.

[0014] In one aspect, the polishing method further includes using the optical sensor to irradiate light through the light passing portion onto a mirror, receive reflected light from the mirror, and detect a cleaning endpoint of the light passing portion, which is the point at which the intensity of the reflected light exceeds a threshold value. In one embodiment, the polishing method further includes generating an image of the light emitting / receiving surface by an imaging device, and detecting a cleaning end point of the light passing portion based on the image. In one embodiment, the polishing method further includes determining, based on the light reflected from the substrate, whether or not it is time to clean the light passing portion. Effect of the Invention

[0015] According to the present invention, the cleaning section can supply cleaning fluid to the light transmitting section through the closed cleaning space facing the light transmitting section of the polishing pad, thereby removing the polishing liquid or polishing debris from the light transmitting section. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a perspective view showing an embodiment of a polishing apparatus. [Diagram 2] 2 is a cross-sectional view of the polishing apparatus shown in FIG. [Diagram 3] FIG. 4 is a diagram showing an example of a spectrum generated by a data processing unit. [Figure 4] 2 is a plan view showing an example of the positional relationship between a substrate and a polishing table; FIG. [Diagram 5] FIG. 2 is a schematic diagram showing an embodiment of a cleaning unit. [Figure 6] 6(a) and 6(b) are plan views showing an example of the positional relationship between the cleaning unit and the polishing table. [Figure 7] 13 is a schematic diagram showing a state in which the actuator has lowered the cleaning cover. FIG. [Figure 8] 10 is a schematic diagram showing how a liquid nozzle supplies liquid into a cleaning space. FIG. [Figure 9] 1 is a schematic diagram showing how a jet nozzle supplies a jet of fluid into a cleaning space. FIG. [Figure 10] 10 is a schematic diagram showing a state in which a chemical nozzle supplies a chemical solution into a cleaning space. FIG. [Figure 11] 1 is a schematic diagram illustrating an embodiment in which an ultrasonic transducer propagates ultrasonic waves through a cleaning fluid to a light passing portion. FIG. [Figure 12] FIG. 13 is a schematic diagram showing another embodiment of the cleaning unit. [Figure 13] 13 is a schematic diagram showing an embodiment in which a mirror in the cleaning section is used to detect the cleaning end point of the light passing section; FIG. [Figure 14] FIG. 13 is a schematic diagram showing still another embodiment of the cleaning unit. [Figure 15] 1 is a flow chart illustrating an embodiment of a method for polishing a substrate. [Figure 16] 1 is a flow chart illustrating an embodiment of a method for polishing a substrate. [Figure 17] FIG. 11 is a cross-sectional view showing another embodiment of the polishing apparatus. [Figure 18] 18 is a schematic diagram showing one embodiment of a cleaning unit of the polishing apparatus shown in FIG. 17. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing one embodiment of a polishing apparatus 1, and FIG. 2 is a cross-sectional view showing the embodiment of the polishing apparatus 1 shown in FIG. 1. The polishing apparatus 1 is an apparatus for chemically and mechanically polishing a substrate W such as a wafer or a panel. As shown in FIG. 1, the polishing apparatus 1 includes a polishing table 3 for supporting a polishing pad 2, a polishing head 5 for pressing the substrate W against a polishing surface 2a of the polishing pad 2, a table motor 6 for rotating the polishing table 3, and a polishing liquid supply nozzle 8 for supplying a polishing liquid (e.g., a slurry) to the polishing pad 2. The polishing pad 2 is attached to the upper surface of the polishing table 3. The exposed surface of the polishing pad 2 constitutes the polishing surface 2a for polishing the substrate W.

[0018] The table motor 6 is disposed below the polishing table 3, and the polishing table 3 is connected to the table motor 6 via a table shaft 3a. The table motor 6 is configured to rotate the polishing table 3 and the polishing pad 2 around the table shaft 3a in the direction indicated by the arrow in FIG. 2. An example of the table motor 6 is a servo motor. The table motor 6 is equipped with an angle detector 7 that detects the rotation angle of the polishing table 3. An example of the angle detector 7 is a rotary encoder.

[0019] The polishing head 5 is connected to a polishing head shaft 10, which is connected to a polishing head rotating mechanism (not shown). The polishing head rotating mechanism is composed of, for example, a combination of a motor, a timing pulley, and a belt. The polishing head rotating mechanism rotates the polishing head 5 together with the polishing head shaft 10 in the direction shown by the arrow in FIG. 2. The polishing head 5 is configured so that the substrate W can be held on its underside by vacuum suction. The substrate W is held by the polishing head 5 so that the surface to be polished faces downward.

[0020] The polishing apparatus 1 further includes an operation control unit 40. The polishing head 5, the table motor 6, the angle detector 7, the polishing liquid supply nozzle 8, and the polishing head rotation mechanism are electrically connected to the operation control unit 40, and the operations of the polishing head 5, the table motor 6, the polishing liquid supply nozzle 8, and the polishing head rotation mechanism are controlled by the operation control unit 40. The angle detector 7 detects the rotation angle of the polishing table 3, and outputs a signal indicating the detected rotation angle. The signal output from the angle detector 7 is sent to the operation control unit 40.

[0021] The operation control unit 40 includes a storage device 40a in which a program is stored, and a calculation device 40b that executes calculations according to instructions included in the program. The operation control unit 40 is composed of at least one computer. The storage device 40a includes a main storage device such as a random access memory (RAM), and an auxiliary storage device such as a hard disk drive (HDD) or a solid state drive (SSD). Examples of the calculation device 40b include a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit). However, the specific configuration of the operation control unit 40 is not limited to these examples.

[0022] The substrate W is polished as follows. The polishing head 5 and the polishing table 3 are rotated in the directions shown by the arrows in Fig. 2, and a polishing liquid is supplied from the polishing liquid supply nozzle 8 onto the polishing surface 2a of the polishing pad 2. In this state, the polishing head 5 presses the substrate W against the polishing surface 2a of the polishing pad 2.

[0023] More specifically, the operation control unit 40 issues commands to the polishing head 5, the table motor 6, the polishing liquid supply nozzle 8, and the polishing head rotating mechanism to rotate the polishing head 5 and the polishing table 3 while supplying a polishing liquid (slurry) from the polishing liquid supply nozzle 8 onto the polishing pad 2. In this state, the polishing head 5 presses the substrate W against the polishing surface 2a of the polishing pad 2 to polish the substrate W. The surface of the substrate W is polished by a combination of the chemical action of the polishing liquid and the mechanical action of the abrasive grains contained in the polishing liquid and / or the polishing pad 2.

[0024] The polishing apparatus 1 includes an optical film thickness measuring device 20 that measures the film thickness of the substrate W. The optical film thickness measuring device 20 includes an optical sensor 21, a light source 22, a spectroscope 23, and a data processing unit 25. The optical sensor 21 is disposed in the polishing table 3, and the light source 22 and the spectroscope 23 are attached to the polishing table 3. The optical sensor 21, the light source 22, and the spectroscope 23 rotate together with the polishing table 3 and the polishing pad 2. The position of the optical sensor 21 is a position where it crosses the surface of the substrate W on the polishing pad 2 every time the polishing table 3 and the polishing pad 2 rotate once. The optical sensor 21 is connected to the light source 22 and the spectroscope 23, and the spectroscope 23 is connected to the data processing unit 25.

[0025] The optical film thickness measuring device 20 includes a light projecting optical fiber cable 27 that guides light emitted from the light source 22 to the surface of the substrate W, and a light receiving optical fiber cable 28 that receives the reflected light from the substrate W and sends the reflected light to the spectroscope 23. The tip of the light projecting optical fiber cable 27 and the tip of the light receiving optical fiber cable 28 are located inside the polishing table 3. The tip of the light projecting optical fiber cable 27 and the tip of the light receiving optical fiber cable 28 constitute an optical sensor 21 that guides light to the surface of the substrate W and receives the reflected light from the substrate W. The other end of the light projecting optical fiber cable 27 is connected to the light source 22, and the other end of the light receiving optical fiber cable 28 is connected to the spectroscope 23. The spectroscope 23 is configured to resolve the reflected light from the substrate W according to wavelength and measure the intensity of the reflected light over a predetermined wavelength range.

[0026] As shown in FIG. 2, the polishing table 3 has a first hole 30 and a second hole 31 opening on its upper surface. The polishing pad 2 has a light passing portion at a position corresponding to the first hole 30 and the second hole 31. In this embodiment, the light passing portion is a through hole 33 formed in the polishing pad 2. The first hole 30 and the second hole 31 communicate with the through hole 33, and the through hole 33 opens on the polishing surface 2a. The optical sensor 21, which is composed of the tip of the light-projecting optical fiber cable 27 and the tip of the light-receiving optical fiber cable 28, is disposed in the first hole 30 and is located below the through hole 33.

[0027] Light emitted by the light source 22 is guided from the light projecting optical fiber cable 27 to the optical sensor 21 through the through hole 33 and to the substrate W. The reflected light from the substrate W is received by the optical sensor 21 through the through hole 33 and sent to the spectrometer 23 through the light receiving optical fiber cable 28. The spectrometer 23 resolves the reflected light according to its wavelength and generates reflected light intensity measurement data by measuring the intensity of the reflected light at each wavelength. The reflected light intensity measurement data is sent from the spectrometer 23 to the data processing unit 25.

[0028] The data processing unit 25 is configured to generate a spectrum of the reflected light from the substrate W from the reflected light intensity measurement data. The spectrum of the reflected light is expressed as a line graph (i.e., a spectral waveform) showing the relationship between the wavelength and intensity of the reflected light. The intensity of the reflected light can also be expressed as a relative value such as reflectance or relative reflectance.

[0029] The data processing unit 25 is configured to determine the film thickness of the substrate W from the spectrum of the reflected light. A known method is used to determine the film thickness of the substrate W based on the spectrum. For example, the data processing unit 25 determines a reference spectrum having a shape closest to the spectrum of the reflected light from a reference spectrum library, and determines the film thickness associated with the determined reference spectrum. In another example, the data processing unit 25 performs a Fourier transform on the spectrum of the reflected light, and determines the film thickness from the obtained frequency spectrum.

[0030] Fig. 3 is a diagram showing an example of a spectrum generated by the data processing unit 25. The spectrum is expressed as a line graph (i.e., a spectral waveform) showing the relationship between the wavelength and intensity of light. In Fig. 3, the horizontal axis represents the wavelength of light reflected from the substrate W, and the vertical axis represents the relative reflectance derived from the intensity of the reflected light. The relative reflectance is an index value indicating the intensity of reflected light, and is the ratio of the light intensity to a predetermined reference intensity. By dividing the light intensity (actual intensity) at each wavelength by the predetermined reference intensity, it is possible to remove unnecessary noise, such as variations in intensity inherent to the optical system of the apparatus or the light source, from the actual intensity.

[0031] In the example shown in FIG. 3, the spectrum of the reflected light is a spectral waveform that indicates the relationship between the relative reflectance and the wavelength of the reflected light, but the spectrum of the reflected light may also be a spectral waveform that indicates the relationship between the intensity of the reflected light itself and the wavelength of the reflected light.

[0032] FIG. 4 is a plan view showing an example of the positional relationship between the substrate W and the polishing table 3. The optical sensor 21 is disposed facing the substrate W held by the polishing head 5. As shown in FIG. 4, during polishing of the substrate W, the optical sensor 21 moves across the substrate W by the rotation of the polishing table 3. Every time the polishing table 3 rotates, light is irradiated from the optical sensor 21 to a measurement point on the substrate W. In this embodiment, the optical film thickness measuring device 20 includes one optical sensor 21, but in one embodiment, the optical film thickness measuring device 20 may include a plurality of optical sensors 21. For example, the optical film thickness measuring device 20 may include two optical sensors 21 at positions with different distances from the center of the polishing table 3, and the two optical sensors 21 may irradiate light to different regions of the substrate W, and the film thicknesses of the different regions of the substrate W may be measured by the two optical sensors 21.

[0033] 2, the polishing apparatus 1 includes a fluid supply line 35 that supplies fluid to the through hole 33 through the first hole 30, a fluid discharge line 36 that discharges the fluid from the through hole 33 through the second hole 31, a supply pump 37 connected to the fluid supply line 35, and a discharge pump 38 connected to the fluid discharge line 36. The fluid supply line 35 is connected to the first hole 30 and communicates with the through hole 33. The fluid discharge line 36 is connected to the second hole 31 and communicates with the through hole 33.

[0034] A fluid (e.g., pure water) sent from a fluid supply source (not shown) flows through the fluid supply line 35. The supply pump 37 is configured to pressurize the fluid flowing through the fluid supply line 35. The fluid pressurized by the supply pump 37 is supplied from the fluid supply line 35 to the through hole 33 through the first hole 30. The discharge pump 38 is configured to suck the fluid flowing through the fluid discharge line 36. The fluid supplied to the through hole 33 flows into the second hole 31 and is discharged from the fluid discharge line 36. The supply pump 37 and the discharge pump 38 are electrically connected to the operation control unit 40, and the operations of the supply pump 37 and the discharge pump 38 are controlled by the operation control unit 40.

[0035] During polishing of the substrate W, the operation control unit 40 issues a command to the supply pump 37 to supply the fluid to the first hole 30 and the through hole 33 through the fluid supply line 35. As a result, the fluid fills the first hole 30 and the through hole 33, and flows from the through hole 33 into the second hole 31. The operation control unit 40 issues a command to the discharge pump 38 to discharge the fluid through the fluid discharge line 36. The polishing liquid used in polishing the substrate W is discharged together with the fluid, thereby ensuring an optical path for measuring the film thickness of the substrate W.

[0036] The data processing unit 25 of the optical film thickness measuring device 20 is electrically connected to the operation control unit 40. The operation control unit 40 controls the polishing operation of the substrate W based on the film thickness of the substrate W determined by the data processing unit 25. For example, the operation control unit 40 is configured to detect the polishing end point of the substrate W, which is the time when the film thickness of the substrate W reaches a target film thickness, and to end the polishing of the substrate W based on the detected polishing end point. In this case, the operation control unit 40 issues a command to the table motor 6 and the polishing head rotating mechanism based on the polishing end point of the substrate W to stop the rotation of the polishing table 3 and the polishing head 5, and to end the polishing of the substrate W.

[0037] In one embodiment, the operation control unit 40 is configured to detect a change in the polishing conditions of the substrate W, which is the point at which the thickness of the substrate W reaches a predetermined value, and to change the polishing conditions of the substrate W based on the detected change in the polishing conditions.

[0038] The data processing unit 25 includes a storage device 25a in which a program is stored, and an arithmetic unit 25b that executes calculations according to instructions included in the program. The data processing unit 25 is composed of at least one computer. The storage device 25a includes a main storage device such as a random access memory (RAM), and an auxiliary storage device such as a hard disk drive (HDD) and a solid state drive (SSD). Examples of the arithmetic unit 25b include a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit). However, the specific configuration of the data processing unit 25 is not limited to these examples. In one embodiment, the data processing unit 25 and the operation control unit 40 may be integrally configured from at least one computer.

[0039] 1, the polishing apparatus 1 further includes a cleaning unit 12 that supplies a cleaning fluid to a through hole (light passing portion) 33 of the polishing pad 2, a cleaning arm 16 connected to the cleaning unit 12, a spindle 15 connected to the cleaning arm 16, and a cleaning unit horizontal movement mechanism 18 that moves the cleaning unit 12 horizontally. The cleaning unit horizontal movement mechanism 18 is disposed within the cleaning arm 16 and connected to the spindle 15. The cleaning unit horizontal movement mechanism 18 is configured to swing (i.e., move horizontally) the cleaning arm 16 and the cleaning unit 12 about the axis of the spindle 15.

[0040] When the cleaning arm 16 is moved horizontally by the cleaning unit horizontal movement mechanism 18, the cleaning unit 12 moves between a position above the polishing table 3 and a position radially outward of the polishing table 3. The cleaning unit horizontal movement mechanism 18 is, for example, a combination of a servo motor, a timing pulley, and a belt. The cleaning unit horizontal movement mechanism 18 includes an angle detector 19 that detects the rotation angle of the cleaning unit 12 around the support shaft 15. An example of the angle detector 19 is a rotary encoder. The cleaning unit horizontal movement mechanism 18 is electrically connected to the operation control unit 40, and the operation of the cleaning unit horizontal movement mechanism 18 is controlled by the operation control unit 40. The angle detector 19 detects the rotation angle of the cleaning unit 12 around the support shaft 15, and outputs a signal indicating the detected rotation angle. The signal output from the angle detector 19 is sent to the operation control unit 40.

[0041] FIG. 5 is a schematic diagram showing one embodiment of the cleaning unit 12. The cleaning unit 12 is configured to form a cleaning space CS covering the through hole (light passing portion) 33 on the through hole (light passing portion) 33, and to supply a cleaning fluid to the through hole (light passing portion) 33 through the cleaning space CS. The cleaning unit 12 includes a housing 51 connected to the cleaning arm 16, a cleaning cover 52 forming the cleaning space CS, a cleaning nozzle 54 supplying the cleaning fluid into the cleaning space CS, an actuator 56 moving the cleaning cover 52 up and down, and a load measuring device 58 measuring the load applied to the cleaning cover 52. A part of the cleaning cover 52, the actuator 56, and the load measuring device 58 are accommodated in the housing 51. The housing 51 and the cleaning cover 52 have a cylindrical shape with a closed top, and the inner diameter of the housing 51 is larger than the outer diameter of the cleaning cover 52. A cleaning space CS is formed inside the cleaning cover 52. The cleaning cover 52 and the cleaning space CS are open downward. The shapes of the housing 51 and the cleaning cover 52 are not limited to those in this embodiment. For example, the housing 51 and the cleaning cover 52 may have a horizontal cross-sectional shape that is elliptical or polygonal, such as a square.

[0042] When cleaning the through hole (light passing portion) 33, the cleaning unit 12 and the through hole (light passing portion) 33 are aligned, and the cleaning unit 12 is disposed above (directly above) the through hole (light passing portion) 33 of the polishing pad 2. The inner diameter D1 of the cleaning cover 52 is the same as or larger than the inner diameter D2 of the through hole (light passing portion) 33. In other words, the horizontal cross section of the cleaning space CS is the same as or larger than the horizontal cross section of the through hole (light passing portion) 33.

[0043] 6(a) and 6(b) are plan views showing an example of the positional relationship between the cleaning unit 12 and the polishing table 3. Fig. 6(a) shows a state in which the cleaning unit 12 and the through-hole (light passing unit) 33 are not aligned, and Fig. 6(b) shows a state in which the cleaning unit 12 and the through-hole (light passing unit) 33 are aligned.

[0044] The operation control unit 40 is configured to rotate the polishing table 3 and horizontally move the cleaning unit 12 so that the position of the through hole (light passing portion) 33 coincides with the position of the cleaning cover 52 of the cleaning unit 12 when viewed from above the polishing table 3. More specifically, the operation control unit 40 rotates the polishing table 3 and horizontally moves the cleaning unit 12 so that the position of the through hole (light passing portion) 33 coincides with the position of the cleaning cover 52 of the cleaning unit 12, based on a signal indicating the rotation angle of the polishing table 3 output from the angle detector 7 (see FIG. 1) and a signal indicating the rotation angle of the cleaning unit 12 output from the angle detector 19 (see FIG. 1). In this way, as shown in the example of FIG. 6(b), the operation control unit 40 positions the cleaning unit 12 above (directly above) the through hole (light passing portion) 33 of the polishing pad 2.

[0045] 5, the cleaning nozzle 54 is fixed to the cleaning cover 52, and at least an end of the cleaning nozzle 54 is located inside the cleaning cover 52. In the present embodiment, the cleaning nozzle 54 includes a liquid nozzle 54A that supplies a liquid as the cleaning fluid, a jet nozzle 54B that supplies a jet of fluid as the cleaning fluid, and a chemical liquid nozzle 54C that supplies a chemical liquid as the cleaning fluid.

[0046] The liquid nozzle 54A, the jet nozzle 54B, and the chemical nozzle 54C are connected to the fluid valves 55A, 55B, and 55C, respectively. The liquid, the fluid for forming the jet, and the chemical are supplied to the liquid nozzle 54A, the jet nozzle 54B, and the chemical nozzle 54C, respectively, through the fluid valves 55A, 55B, and 55C. The fluid valves 55A, 55B, and 55C are actuator-driven open / close valves such as motorized valves, solenoid valves, or air-operated valves. The fluid valves 55A, 55B, and 55C are electrically connected to the operation control unit 40, and the operations of the fluid valves 55A, 55B, and 55C are controlled by the operation control unit 40.

[0047] The configuration of the cleaning nozzle 54 is not limited to this embodiment, and may include at least one of the liquid nozzle 54A, the jet nozzle 54B, and the chemical nozzle 54C. For example, the cleaning nozzle 54 may include only the jet nozzle 54B, or may include only the liquid nozzle 54A and the jet nozzle 54B.

[0048] The actuator 56 is fixed to the housing 51 by a support member (not shown). The actuator 56 is connected to the cleaning cover 52 by a connecting member 57, and is configured to move the cleaning cover 52 up and down. More specifically, the actuator 56 is configured to move the cleaning cover 52 and the cleaning nozzle 54 (liquid nozzle 54A, jet nozzle 54B, and chemical liquid nozzle 54C) together up and down relative to the housing 51. The actuator 56 may be a combination of a ball screw and a servo motor. In one embodiment, the cleaning nozzle 54 is not fixed to the cleaning cover 52 but is fixed to a stationary member (not shown), and the actuator 56 may be configured to move only the cleaning cover 52 up and down.

[0049] 7 is a schematic diagram showing a state in which the actuator 56 has lowered the cleaning cover 52. The actuator 56 is electrically connected to the operation control unit 40, and the operation of the actuator 56 is controlled by the operation control unit 40. As described above, after the cleaning unit 12 and the through hole (light passing unit) 33 of the polishing pad 2 are aligned, the operation control unit 40 issues a command to the actuator 56 while keeping the polishing table 3 stationary, to lower the cleaning cover 52 until it comes into contact with the polishing pad 2. More specifically, the operation control unit 40 issues a command to the actuator 56 to lower the cleaning cover 52 until the lower surface 52a of the cleaning cover 52 comes into contact with the polishing surface 2a of the polishing pad 2.

[0050] The load measuring device 58 is attached to the upper part of the cleaning cover 52 and is configured to measure the load applied to the cleaning cover 52. The load measuring device 58 is connected to the actuator 56 via a connecting member 57 and is located between the actuator 56 and the cleaning cover 52. When the lower surface 52a of the cleaning cover 52 comes into contact with the polishing surface 2a of the polishing pad 2, a reaction force is applied from the polishing surface 2a to the cleaning cover 52. This reaction force is measured by the load measuring device 58 as the load applied to the cleaning cover 52. A load cell can be used as the load measuring device 58.

[0051] The load measuring device 58 is electrically connected to the operation control device 40, and the load applied to the cleaning cover 52 measured by the load measuring device 58 is sent to the operation control device 40. The operation control device 40 lowers the cleaning cover 52 by the actuator 56 until the load measured by the load measuring device 58 reaches a load target value. Thereafter, the operation control device 40 controls the operation of the actuator 56 so that the load measured by the load measuring device 58 is maintained at the load target value. The load target value is a predetermined load such that the polishing surface 2a of the polishing pad 2 and the lower surface 52a of the cleaning cover 52 come into close contact with each other and the cleaning space CS is closed by the polishing pad 2.

[0052] The cleaning unit 12 forms a cleaning space CS covering the through hole (light passing portion) 33 on the through hole (light passing portion) 33. When the cleaning cover 52 having the cleaning space CS therein that opens downward comes into contact with the polishing surface 2a of the polishing pad 2, the cleaning space CS is blocked by the polishing pad 2. The cleaning cover 52 is disposed so as to surround the through hole (light passing portion) 33 of the polishing pad 2. The blocked cleaning space CS faces the through hole (light passing portion) 33 of the polishing pad 2, the first hole 30 (including the optical sensor 21) of the polishing table 3, and the second hole 31. The cleaning nozzle 54 is configured to supply a cleaning fluid into the cleaning space CS. More specifically, the cleaning nozzle 54 supplies the cleaning fluid to the through hole (light passing portion) 33 through the cleaning space CS. In this embodiment, the liquid nozzle 54A supplies liquid into the cleaning space CS, the jet nozzle 54B supplies a jet of fluid into the cleaning space CS, and the chemical nozzle 54C supplies chemical liquid into the cleaning space CS. The specific configuration of the cleaning nozzle 54 is not limited to this embodiment as long as it can supply the cleaning fluid into the cleaning space CS.

[0053] The distance L from the tip of the cleaning nozzle 54 to the lower surface 52a of the cleaning cover 52 is determined based on the type of nozzle and the state of the deposit on the through hole (light passing portion) 33. In one embodiment, the cleaning unit 12 further includes a nozzle position adjustment mechanism (not shown) connected to the cleaning nozzle 54, and the nozzle position adjustment mechanism may be configured to adjust the distance L from the tip of the cleaning nozzle 54 to the lower surface 52a of the cleaning cover 52. In one embodiment, the distance L from the cleaning nozzle 54 to the lower surface 52a of the cleaning cover 52 is 2 to 5 mm. In one embodiment, the distances from the tips of the liquid nozzle 54A, the jet nozzle 54B, and the chemical liquid nozzle 54C to the lower surface 52a of the cleaning cover 52 may be different. For example, the distance from the tip of the jet nozzle 54B to the lower surface 52a of the cleaning cover 52 and the distance from the tip of the chemical liquid nozzle 54C to the lower surface 52a of the cleaning cover 52 may be smaller than the distance from the tip of the liquid nozzle 54A to the lower surface 52a of the cleaning cover 52.

[0054] In one embodiment, the cleaning unit 12 further includes a nozzle angle adjustment mechanism (not shown) connected to the cleaning nozzle 54, and the nozzle angle adjustment mechanism may be configured to adjust the angle θ of the cleaning nozzle 54 with respect to the horizontal plane. In one embodiment, the angles of the liquid nozzle 54A, the jet nozzle 54B, and the chemical liquid nozzle 54C with respect to the horizontal plane may be different. For example, the angles of the liquid nozzle 54A, the jet nozzle 54B, and the chemical liquid nozzle 54C with respect to the horizontal plane may be adjusted so that the tips of the liquid nozzle 54A, the jet nozzle 54B, and the chemical liquid nozzle 54C are each directed toward the optical sensor 21.

[0055] The above-mentioned fluid discharge line 36 communicates with the cleaning space CS through the second hole 31 and the through hole (light passing portion) 33, and is configured to discharge the cleaning fluid from the cleaning space CS and the through hole (light passing portion) 33 through the second hole 31. The cleaning fluid is supplied from the cleaning nozzles 54 (liquid nozzle 54A, jet nozzle 54B, and chemical liquid nozzle 54C) to the through hole (light passing portion) 33 through the cleaning space CS, and removes the polishing liquid or polishing debris adhering to the through hole (light passing portion) 33. The cleaning fluid is discharged from the cleaning space CS and the through hole (light passing portion) 33 through the fluid discharge line 36 together with the polishing liquid or polishing debris.

[0056] In this way, the cleaning unit 12 can supply the cleaning fluid to the through hole (light passing portion) 33 through the closed cleaning space CS, and remove the polishing liquid or polishing debris from the through hole (light passing portion) 33. Therefore, it is possible to prevent a decrease in the intensity of the reflected light from the substrate W passing through the light passing portion 33. As a result, the data processing unit 25 can accurately determine the film thickness of the substrate W. In this embodiment, the cleaning unit 12 can also supply the cleaning fluid to the optical sensor 21 located in the first hole 30, and remove the polishing liquid or polishing debris from the optical sensor 21.

[0057] During cleaning of the through holes (light passing portions) 33, the cleaning fluid is supplied into the closed cleaning space CS and discharged from the cleaning space CS through the fluid discharge line 36, so that the cleaning fluid does not flow out of the cleaning space CS, i.e., outside the cleaning cover 52. This makes it possible to prevent contamination of the polishing surface 2a and changes in the properties of the polishing surface 2a due to the cleaning fluid adhering to the outside of the through holes (light passing portions) 33 of the polishing pad 2. In addition, since the cleaning fluid is selectively supplied to the through holes (light passing portions) 33 to be cleaned, the through holes (light passing portions) 33 can be efficiently cleaned and the amount of cleaning fluid used can be reduced.

[0058] In this specification, the cleaning space CS being closed is not limited to the cleaning space CS being completely closed (sealed), and as long as the above-mentioned effect can be obtained, there may be a slight gap between the cleaning cover 52 and the polishing pad 2. In other words, in this specification, the cleaning space CS being closed also includes a state in which there is a slight gap between the cleaning cover 52 and the polishing pad 2 to an extent that the through hole (light passing portion) 33 can be efficiently cleaned without affecting contamination of the polishing surface 2a or change in the properties of the polishing surface 2a, and the cleaning cover 52 is not in complete contact (adherence) with the polishing surface 2a of the polishing pad 2.

[0059] The liquid nozzle 54A, jet nozzle 54B, and chemical nozzle 54C to be used are appropriately selected depending on the condition and type of the polishing liquid or polishing debris adhering to the through hole (light passing portion) 33, or a combination of these nozzles 54A, 54B, and 54C is used.

[0060] 8 is a schematic diagram showing how the liquid nozzle 54A supplies liquid into the cleaning space CS. In this embodiment, the liquid nozzle 54A supplies liquid (e.g., pure water) as a cleaning fluid to the cleaning space CS, the through hole (light passing portion) 33, and the first hole 30 (including the optical sensor 21). While the liquid nozzle 54A supplies liquid into the cleaning space CS and the through hole (light passing portion) 33, the discharge pump 38 discharges the liquid from the cleaning space CS and the through hole (light passing portion) 33 through the fluid discharge line 36. In one embodiment, the discharge pump 38 may discharge the liquid from the cleaning space CS and the through hole (light passing portion) 33 through the fluid discharge line 36 when a predetermined time has elapsed since the liquid nozzle 54A supplied the liquid into the cleaning space CS and the through hole (light passing portion) 33.

[0061] 9 is a schematic diagram showing how the jet nozzle 54B supplies a jet of fluid into the cleaning space CS. In this embodiment, the jet nozzle 54B supplies a jet of fluid as a cleaning fluid to the cleaning space CS, the through hole (light passing portion) 33, and the first hole 30 (including the optical sensor 21). The jet of fluid supplied from the jet nozzle 54B may be any of a jet of liquid (e.g., pure water), a jet of gas (e.g., an inert gas such as nitrogen), and a jet of a mixed fluid of liquid and gas.

[0062] While the jet nozzle 54B supplies a jet of fluid into the cleaning space CS and the through hole (light passing portion) 33, the discharge pump 38 discharges the fluid from the cleaning space CS and the through hole (light passing portion) 33 through the fluid discharge line 36. In one embodiment, the discharge pump 38 may discharge the fluid from the cleaning space CS and the through hole (light passing portion) 33 through the fluid discharge line 36 when a predetermined time has elapsed since the jet nozzle 54B supplied a jet of fluid into the cleaning space CS and the through hole (light passing portion) 33. In one embodiment, after the jet of fluid is supplied by the jet nozzle 54B, the liquid nozzle 54A may supply a liquid (e.g., pure water) into the cleaning space CS and the through hole (light passing portion) 33 to rinse and clean the cleaning space CS and the through hole (light passing portion) 33.

[0063] FIG. 10 is a schematic diagram showing a state in which the chemical nozzle 54C supplies the chemical into the cleaning space CS. In this embodiment, the chemical nozzle 54C supplies the chemical as a cleaning fluid to the cleaning space CS, the through hole (light passing portion) 33, and the first hole 30 (including the optical sensor 21). The type of chemical is a chemical suitable for the type of polishing liquid or polishing debris adhering to the through hole (light passing portion) 33. For example, the acidic chemical may be a solution of hydrofluoric acid, oxalic acid, citric acid, hydrochloric acid, or sulfuric acid, or a combination of these. The alkaline chemical may be a solution of ammonia or TMAH (tetramethylammonium hydroxide), or a combination of these. Furthermore, a surfactant solution may be used as the chemical.

[0064] While the chemical liquid nozzle 54C supplies the chemical liquid into the cleaning space CS and the through hole (light passing portion) 33, the discharge pump 38 discharges the chemical liquid from the cleaning space CS and the through hole (light passing portion) 33 through the fluid discharge line 36. In one embodiment, the discharge pump 38 may discharge the chemical liquid from the cleaning space CS and the through hole (light passing portion) 33 through the fluid discharge line 36 when a predetermined time has elapsed since the chemical liquid nozzle 54C supplied the chemical liquid into the cleaning space CS and the through hole (light passing portion) 33. In one embodiment, after the chemical liquid is supplied by the chemical liquid nozzle 54C, the liquid nozzle 54A may supply a liquid (e.g., pure water) to the cleaning space CS and the through hole (light passing portion) 33 to rinse and clean the cleaning space CS and the through hole (light passing portion) 33.

[0065] As shown in FIG. 11, the cleaning unit 12 further includes an ultrasonic transducer 60 that generates ultrasonic waves. In this embodiment, the cleaning unit 12 includes two ultrasonic transducers 60, which are disposed in the cleaning cover 52. More specifically, the ultrasonic transducer 60 is disposed inside the cleaning cover 52. The number of ultrasonic transducers 60 is not limited to this embodiment, and the cleaning unit 12 may include one or three or more ultrasonic transducers 60. The ultrasonic transducer 60 is configured to generate ultrasonic waves. When the cleaning fluid is supplied from the cleaning nozzle 54 into the cleaning space CS and the cleaning fluid is present in the cleaning space CS, the ultrasonic transducer 60 propagates ultrasonic waves through the cleaning fluid. In this embodiment, the ultrasonic waves generated by the ultrasonic transducer 60 are propagated to the through hole (light passing portion) 33 using the liquid supplied into the cleaning space CS by the liquid nozzle 54A as a medium. In one embodiment, ultrasonic waves generated by the ultrasonic transducer 60 may be propagated to the through hole (light passing portion) 33 through the cleaning cover 52 and the polishing pad 2 in a state where no cleaning fluid is present in the cleaning space CS.

[0066] The ultrasonic transducer 60 is electrically connected to the operation control unit 40, and the operation of the ultrasonic transducer 60 is controlled by the operation control unit 40. With the discharge pump 38 stopped, the operation control unit 40 issues a command to the fluid valve 55A to supply liquid from the liquid nozzle 54A into the cleaning space CS. In one embodiment, the operation control unit 40 issues a command to the fluid valve 55A to supply liquid from the liquid nozzle 54A into the cleaning space CS until the liquid level reaches a level higher than the position of the ultrasonic transducer 60. Thereafter, the operation control unit 40 issues a command to the ultrasonic transducer 60 to cause the ultrasonic transducer 60 to generate ultrasonic waves. After operating the ultrasonic transducer 60 until a predetermined cleaning time has elapsed, the operation control unit 40 issues a command to the discharge pump 38 to discharge the liquid from the cleaning space CS and the through hole (light passing portion) 33 through the fluid discharge line 36. In one embodiment, while supplying liquid from the liquid nozzle 54A into the cleaning space CS and the through hole (light passing portion) 33, and while discharging the liquid from the cleaning space CS and the through hole (light passing portion) 33 through the fluid discharge line 36, the operation control unit 40 may give a command to the ultrasonic transducer 60 to cause the ultrasonic transducer 60 to generate ultrasonic waves.

[0067] The ultrasonic waves propagated to the through hole (light passing portion) 33 can remove the polishing liquid or polishing debris from the through hole (light passing portion) 33. In this embodiment, the ultrasonic transducer 60 also propagates the ultrasonic waves to the optical sensor 21 located inside the first hole 30, and can remove the polishing liquid or polishing debris from the optical sensor 21.

[0068] FIG. 12 is a schematic diagram showing another embodiment of the cleaning unit 12. The ultrasonic transducer 60 of this embodiment is disposed in the cleaning nozzle 54. The ultrasonic transducer 60 is configured to propagate ultrasonic waves through the cleaning fluid supplied from the cleaning nozzle 54 into the cleaning space CS. In this embodiment, the ultrasonic transducer 60 is disposed in the liquid nozzle 54A. The ultrasonic waves generated by the ultrasonic transducer 60 are propagated to the through hole (light passing portion) 33 using the liquid flowing out from the liquid nozzle 54A as a medium while the liquid is being supplied from the liquid nozzle 54A into the cleaning space CS. In one embodiment, the ultrasonic transducer 60 may be disposed in the jet nozzle 54B or the chemical liquid nozzle 54C.

[0069] The operation control unit 40 issues a command to the fluid valve 55A to supply liquid from the liquid nozzle 54A, while issuing a command to the ultrasonic transducer 60 to cause the ultrasonic transducer 60 to generate ultrasonic waves. With the discharge pump 38 stopped, the operation control unit 40 issues a command to the ultrasonic transducer 60 to propagate ultrasonic waves to the through hole (light passing portion) 33 through the liquid flowing out of the liquid nozzle 54A. The operation control unit 40 operates the ultrasonic transducer 60 until a predetermined cleaning time has elapsed, and then issues a command to the discharge pump 38 to discharge the liquid from the cleaning space CS and the through hole (light passing portion) 33 through the pure water discharge line 36. In one embodiment, while supplying liquid from the liquid nozzle 54A into the cleaning space CS and the through hole (light passing portion) 33 and discharging the liquid from the cleaning space CS and the through hole (light passing portion) 33 through the fluid discharge line 36, the operation control unit 40 may issue a command to the ultrasonic transducer 60 to cause the ultrasonic transducer 60 to generate ultrasonic waves.

[0070] The ultrasonic waves propagated to the through hole (light passing portion) 33 can remove the polishing liquid or polishing debris from the through hole (light passing portion) 33. In this embodiment, the ultrasonic transducer 60 also propagates the ultrasonic waves to the optical sensor 21 located inside the first hole 30, and can remove the polishing liquid or polishing debris from the optical sensor 21.

[0071] In one embodiment, the cleaning section 12 may not include the ultrasonic transducer 60 described with reference to FIGS.

[0072] 13, in one embodiment, the cleaning unit 12 includes a mirror 62 for detecting the cleaning end point of the through hole (light passing portion) 33. The mirror 62 is disposed inside the cleaning cover 52. In other words, the mirror 62 is disposed in the cleaning space CS. The mirror 62 is disposed on the optical path of the light irradiated from the optical sensor 21 through the through hole (light passing portion) 33, and the optical sensor 21 is configured to receive the reflected light from the mirror 62 through the through hole (light passing portion) 33.

[0073] During cleaning of the through hole (light passing portion) 33, the light emitted by the light source 22 passes through the light projecting optical fiber cable 27, and is guided from the optical sensor 21 through the through hole (light passing portion) 33 to the mirror 62. The reflected light from the mirror 62 passes through the through hole (light passing portion) 33 and is received by the optical sensor 21, and is sent to the spectrometer 23 through the light receiving optical fiber cable 28. The spectrometer 23 breaks down the reflected light according to its wavelength, and generates reflected light intensity measurement data by measuring the intensity of the reflected light at each wavelength. The reflected light intensity measurement data is sent from the spectrometer 23 to the operation control unit 40 through the data processing unit 25. In one embodiment, the operation control unit 40 may be directly connected to the spectrometer 23, and the reflected light intensity measurement data may be sent directly from the spectrometer 23 to the operation control unit 40.

[0074] The optical sensor 21 may irradiate the mirror 62 with light when cleaning fluid is present in the cleaning space CS, or when the cleaning fluid has been discharged from the cleaning space CS and no cleaning fluid is present.

[0075] The operation control unit 40 is configured to detect the cleaning end point of the through hole (light passing portion) 33, which is the time point when the intensity of the reflected light exceeds a threshold value, based on the intensity measurement data of the reflected light from the mirror 62. For example, the operation control unit 40 may detect the cleaning end point of the through hole (light passing portion) 33, which is the time point when the intensity of the reflected light at a predetermined wavelength exceeds a threshold value, or may detect the cleaning end point of the through hole (light passing portion) 33, which is the time point when the average intensity of the reflected light, which is the average of the intensities of the reflected light at each wavelength, exceeds a threshold value.

[0076] FIG. 14 is a schematic diagram showing yet another embodiment of the cleaning unit 12. The cleaning unit 12 of this embodiment includes an imaging device 64 that generates an image of the through hole (light passing portion) 33, and an illuminator 65 for illuminating the through hole (light passing portion) 33, instead of the mirror 62. The imaging device 64 and the illuminator 65 are disposed inside the cleaning cover 64. In other words, the imaging device 64 and the illuminator 65 are disposed in the cleaning space CS. As the imaging device 64, a camera equipped with an image sensor such as a CCD sensor or a CMOS sensor, or a fiberscope can be used. In one embodiment, the imaging device 64 has an illumination function for illuminating the through hole (light passing portion) 33, and the cleaning unit 12 does not need to include the illuminator 65.

[0077] The imaging device 64 is disposed above the through hole (light passing section) 33 in the closed cleaning space CS, and is configured to generate an image of the through hole (light passing section) 33. The imaging device 64 is electrically connected to the operation control section 40. The image of the through hole (light passing section) 33 generated by the imaging device 64 is sent to the operation control section 40. The operation control section 40 is configured to detect the cleaning end point of the through hole (light passing section) 33 based on the image sent from the imaging device 64. For example, the operation control section 40 detects the cleaning end point of the through hole (light passing section) 33 based on a comparison between a reference image, which is an image of the through hole (light passing section) 33 in a state where cleaning has been completed, and the acquired image.

[0078] The detection of the cleaning end point of the through hole (light passing portion) 33 described with reference to Figures 13 and 14 may be performed at a predetermined time interval while the cleaning unit 12 is supplying cleaning fluid to the through hole (light passing portion) 33, or may be performed after the cleaning unit 12 has finished supplying cleaning fluid to the through hole (light passing portion) 33 based on a predetermined cleaning recipe.

[0079] As described with reference to FIG. 13 and FIG. 14, the operation control unit 40 issues a command to the fluid valves 55A, 55B, and 55C based on the detected cleaning end point to stop the supply of the cleaning fluid from the cleaning nozzle 54. In one embodiment, the operation control unit 40 may issue a command to the fluid valves 55A, 55B, and 55C to stop the supply of the cleaning fluid from the cleaning nozzle 54 when a predetermined transition time has elapsed from the cleaning end point of the through hole (light passing portion) 33. As described with reference to FIG. 11 and FIG. 12, when ultrasonic waves are generated by the ultrasonic vibrator 60, the operation control unit 40 issues a command to the ultrasonic vibrator 60 to stop the generation of ultrasonic waves by the ultrasonic vibrator 60. The operation control unit 40 issues a command to the discharge pump 38 to discharge the cleaning fluid from the cleaning space CS through the fluid discharge line. After the cleaning fluid is discharged from the cleaning space CS, the operation control unit 40 issues a command to the actuator 56 to raise the cleaning cover 52 and move the cleaning cover 52 away from the polishing pad 2. Furthermore, the operation control unit 40 issues a command to the cleaning unit horizontal movement mechanism 18 to horizontally move the cleaning arm 16 and move the cleaning unit 12 away from the polishing pad 2 .

[0080] In one embodiment, the operation control unit 40 is configured to determine whether or not it is time to clean the through hole (light passing portion) 33 based on the reflected light from the substrate W when measuring the film thickness of the substrate W during polishing of the substrate W. If the polishing liquid or polishing debris adheres to the through hole (light passing portion) 33, the intensity of the reflected light from the substrate W received by the optical sensor 21 decreases. Therefore, the operation control unit 40 can determine whether or not it is time to clean the through hole (light passing portion) 33 based on the intensity of the reflected light from the substrate W received by the optical sensor 21. More specifically, the operation control unit 40 is configured to determine whether or not it is time to clean the through hole (light passing portion) 33 based on the intensity measurement data of the reflected light from the substrate W generated by the spectroscope 23. For example, the operation control unit 40 may determine that it is time to clean the through hole (light passing portion) 33 when the intensity of the reflected light at a predetermined wavelength falls below a reference value. Alternatively, the operation control unit 40 may determine that it is time to clean the through hole (light passing portion) 33 when the average intensity of the reflected light, which is the average of the intensities of the reflected light within a predetermined wavelength range, falls below a reference value.

[0081] In one embodiment, the operation control unit 40 may determine whether it is time to clean the through hole (light passing portion) 33 based on the spectrum of reflected light from the substrate W generated by the data processing unit 25. For example, the operation control unit 40 determines whether it is time to clean the through hole (light passing portion) 33 based on a comparison between a reference spectrum, which is the spectrum of reflected light when the through hole (light passing portion) 33 is to be cleaned, and the spectrum of reflected light generated by the data processing unit 25.

[0082] The operation control unit 40 may be configured to clean the through hole (light passing portion) 33 after polishing the substrate W when it is determined that it is time to clean the through hole (light passing portion) 33 during polishing of the substrate W. In one embodiment, the operation control unit 40 may be configured to clean the through hole (light passing portion) 33 after polishing a predetermined number of substrates after determining that it is time to clean the through hole (light passing portion) 33. According to this embodiment, cleaning of the through hole (light passing portion) 33 can be automatically performed at an appropriate timing, so that the efficiency of the cleaning operation of the through hole (light passing portion) 33 can be improved.

[0083] The spectrum of the reflected light from the substrate W generated by the data processing unit 25 may change depending on the type of polishing liquid or polishing debris adhering to the through hole (light passing portion) 33. In one embodiment, the operation control unit 40 is configured to determine the type of attachment based on the spectrum of the reflected light from the substrate W generated by the data processing unit 25. The operation control unit 40 may be configured to select the cleaning nozzle 54 (liquid nozzle 54A, jet nozzle 54B, and chemical liquid nozzle 54C) to be used when supplying the cleaning fluid to the through hole (light passing portion) 33 based on the determined type of attachment.

[0084] 15 and 16 are flow charts illustrating an embodiment of a method for polishing a substrate W. In FIG. In step S101, the operation control unit 40 issues commands to the polishing head 5, the table motor 6, the polishing liquid supply nozzle 8, and the polishing head rotating mechanism to rotate the polishing head 5 and the polishing table 3 while supplying a polishing liquid (slurry) from the polishing liquid supply nozzle 8 onto the polishing pad 2. In this state, the polishing head 5 presses the substrate W against the polishing surface 2a of the polishing pad 2, and polishing of the substrate W begins.

[0085] In step S102, the optical sensor head 21 irradiates the substrate W with light through the through hole (light passing portion) 33 of the polishing pad 2, and receives reflected light from the substrate W through the through hole (light passing portion) 33. In step S103, the data processing unit 25 generates a spectrum of the reflected light from the substrate W from the intensity measurement data of the reflected light, and determines the film thickness of the substrate W from the spectrum of the reflected light. In step S104, the operation control unit 40 detects the polishing end point of the substrate W based on the film thickness of the substrate W. For example, the operation control unit 40 is configured to detect the polishing end point of the substrate W, which is the time when the film thickness of the substrate W reaches a target film thickness. When the operation control unit 40 does not detect the polishing end point of the substrate W ("NO" in step S104), it continues polishing the substrate W and repeats steps S102 to S104. When the operation control unit 40 detects the polishing end point of the substrate W ("YES" in step S104), it ends the polishing of the substrate W (step S105). Specifically, the operation control unit 40 issues a command to the table motor 6 and the polishing head rotating mechanism based on the polishing end point of the substrate W to stop the rotation of the polishing table 3 and the polishing head 5, and ends the polishing of the substrate W.

[0086] Steps S106 to S113 described below are one embodiment of a method for cleaning the through-hole (light passing portion) 33. In step S106, the operation control unit 40 judges whether or not it is time to clean the through hole (light passing portion) 33 based on the reflected light from the substrate W received by the optical sensor 21 in step S102. In one embodiment, step S106 is performed in parallel with steps S102 to S104. When step S102 is repeated, step S106 is also repeated. When it is determined that it is time to clean the through hole (light passing portion) 33 ("YES" in step S106), the operation control unit 40 disposes the cleaning unit 12 above the through hole (light passing portion) 33 after polishing of the substrate W is completed (step S107). Specifically, the operation control unit 40 issues a command to the table motor 6 and the cleaning unit horizontal movement mechanism 18 to rotate the polishing table 3 and horizontally move the cleaning unit 12 so that the position of the through hole (light passing portion) 33 coincides with the position of the cleaning cover 52 of the cleaning unit 12. If it is determined that it is not time to clean the through-hole (light passing portion) 33 ("NO" in step S106), the operation control portion 40 starts polishing the next substrate after polishing of the substrate W is completed (step S114).

[0087] In step S108, the operation control unit 40 issues a command to the actuator 56 while keeping the polishing table 3 stationary to lower the cleaning cover 52 until it comes into contact with the polishing pad 2. This causes the cleaning space CS formed within the cleaning cover 52 to be closed. In step S109, the operation control unit 40 issues a command to at least one of the fluid valves 55A, 55B, and 55C to supply cleaning fluid from the cleaning nozzle 54 into the cleaning space CS. The cleaning fluid supplied into the cleaning space CS can remove the polishing liquid and polishing debris from the through hole (light passing portion) 33. In one embodiment, as described with reference to FIGS. 11 and 12, the operation control unit 40 may generate ultrasonic waves using the ultrasonic vibrator 60 and propagate the ultrasonic waves through the cleaning fluid to remove the polishing liquid and polishing debris from the through hole (light passing portion) 33. In step S110, while supplying cleaning fluid from the cleaning nozzle 54 into the cleaning space CS, or after supplying cleaning fluid from the cleaning nozzle 54 into the cleaning space CS, the operation control unit 40 gives a command to the discharge pump 38 to discharge the cleaning fluid from the cleaning space CS through the fluid discharge line 36.

[0088] In step S111, the operation control unit 40 detects the cleaning end point of the through hole (light passing portion) 33. As described with reference to Fig. 13, the operation control unit 40 may detect the cleaning end point of the through hole (light passing portion) 33, which is the time point at which the intensity of the reflected light exceeds a threshold value, based on the intensity measurement data of the reflected light from the mirror 62. Alternatively, as described with reference to Fig. 14, the operation control unit 40 may detect the cleaning end point of the through hole (light passing portion) 33 based on an image generated by the imaging device 64.

[0089] When the operation control unit 40 does not detect the end point of cleaning of the through hole (light passing portion) 33 ("NO" in step S111), it continues supplying the cleaning fluid to the through hole (light passing portion) 33 and repeats steps S109 to S111. When the operation control unit 40 detects the end point of cleaning of the through hole (light passing portion) 33 ("YES" in step S111), the operation control unit 40 issues a command to at least one of the fluid valves 55A, 55B, and 55C based on the end point of cleaning of the through hole (light passing portion) 33 to stop the supply of the cleaning fluid from the cleaning nozzle 54 (step S112). In one embodiment, the operation control unit 40 may issue a command to at least one of the fluid valves 55A, 55B, and 55C to stop the supply of the cleaning fluid from the cleaning nozzle 54 when a predetermined transition time has elapsed from the end point of cleaning of the through hole (light passing portion) 33. 11 and 12, when ultrasonic waves are being generated by the ultrasonic transducer 60, the operation control unit 40 issues a command to the ultrasonic transducer 60 to stop the generation of ultrasonic waves by the ultrasonic transducer 60. The operation control unit 40 issues a command to the discharge pump 38 to discharge the cleaning fluid from the cleaning space CS through the fluid discharge line.

[0090] In step S113, after the cleaning fluid is discharged from the cleaning space CS, the operation control unit 40 issues a command to the actuator 56 to raise the cleaning cover 52 and move the cleaning cover 52 away from the polishing pad 2. Furthermore, the operation control unit 40 issues a command to the cleaning unit horizontal movement mechanism 18 to horizontally move the cleaning arm 16 and retract the cleaning unit 12 to the outside of the polishing pad 2.

[0091] In step S114, the operation control unit 40 starts polishing the next substrate. In this manner, the cleaning unit 12 can remove the polishing liquid or polishing debris from the through hole (light passing portion) 33 by supplying the cleaning fluid to the through hole (light passing portion) 33 through the closed cleaning space CS after or before polishing the substrate.

[0092] FIG. 17 is a cross-sectional view showing another embodiment of the polishing apparatus 1. The configuration and operation of this embodiment that are not particularly described are the same as those of the embodiment described with reference to FIG. 1 and FIG. 2, and therefore the duplicated description will be omitted. In this embodiment, the light passing portion is a transparent window 70 made of a material that allows light to pass through. That is, the polishing pad 2 has the transparent window 70 as the light passing portion. The polishing apparatus 1 of this embodiment does not include the above-mentioned fluid supply line 35 and fluid discharge line 36, and the polishing table 3 does not have the above-mentioned second hole 31.

[0093] The transparent window 70 is fitted into a through hole 33 formed in the polishing pad 2. The transparent window 70 is located directly above the first hole 30 and the optical sensor 21. Therefore, the optical sensor 21 irradiates light onto the substrate W through the transparent window 70 and receives reflected light from the substrate W through the transparent window 70. The material of the transparent window 70 is not particularly limited, but it is made of, for example, a transparent resin.

[0094] FIG. 18 is a schematic diagram showing an embodiment of the cleaning unit 12 of the polishing apparatus 1 shown in FIG. 17. The configuration and operation of this embodiment not specifically described are the same as those of the embodiment described with reference to FIGS. 5 to 10 and 12, and therefore the overlapping description will be omitted. In this embodiment, the polishing apparatus 1 includes a fluid discharge line 72 communicating with an opening 52b formed on the inner surface of the cleaning cover 52, and a discharge pump 73 connected to the fluid discharge line 72. The cleaning cover 52 has two openings 52b formed on its inner surface and two flow paths 52c extending upward from the two openings 52b. The fluid discharge line 72 is connected to the flow path 52c and communicates with the cleaning space CS through the flow path 52c and the opening 52b.

[0095] In this embodiment, the opening 52b is located in a plane parallel to the lower surface 52a of the cleaning cover 52. The position of the opening 52b is not limited to this embodiment, and may be located, for example, in a side surface of the cleaning cover 52. In this embodiment, the cleaning cover 52 has two openings 52b and flow paths 52c, but the number of openings 52b and flow paths 52c is not limited to this embodiment. In one embodiment, the cleaning cover 52 may have one opening 52b and flow path 52c, or three or more openings 52b and flow paths 52c.

[0096] The fluid discharge line 72 is configured to discharge the cleaning fluid from the cleaning space CS. The discharge pump 73 is configured to suck the cleaning fluid in the cleaning space CS through the fluid discharge line 72. The discharge pump 73 is electrically connected to the operation control unit 40, and the operation of the discharge pump 73 is controlled by the operation control unit 40.

[0097] In this embodiment, the cleaning cover 52 is disposed so as to surround the transparent window (light transmitting portion) 70 of the polishing pad 2. The cleaning space CS closed by the polishing pad 2 faces the transparent window (light transmitting portion) 70 of the polishing pad 2. In this embodiment, the cleaning nozzle 54 supplies a cleaning fluid to the upper surface of the transparent window (light transmitting portion) 70 through the cleaning space CS. The cleaning fluid supplied from the cleaning nozzles 54 (liquid nozzle 54A, jet nozzle 54B, and chemical liquid nozzle 54C) into the cleaning space CS removes the polishing liquid or polishing debris adhering to the transparent window (light transmitting portion) 70, and is discharged from the cleaning space CS through the fluid discharge line 72.

[0098] In this way, the cleaning unit 12 supplies the cleaning fluid to the transparent window (light passing portion) 70 through the closed cleaning space CS. The cleaning fluid supplied into the cleaning space CS can remove the polishing liquid or polishing debris from the transparent window (light passing portion) 70. This can prevent a decrease in the intensity of the reflected light from the substrate W passing through the transparent window (light passing portion) 70. As a result, the data processing unit 25 can accurately determine the film thickness of the substrate W.

[0099] The embodiment of the transparent window (light passing portion) 70 shown in Fig. 18 can be similarly applied to the embodiment of detecting the cleaning end point of the through hole (light passing portion) 33 described with reference to Fig. 13 and Fig. 14 and the embodiment of determining the cleaning time of the through hole (light passing portion) 33. In addition, the embodiment of the transparent window (light passing portion) 70 shown in Fig. 18 can also be applied to the embodiment of the ultrasonic transducer 60 arranged in the cleaning cover 52 as described with reference to Fig. 11.

[0100] The above-described embodiments have been described for the purpose of enabling a person having ordinary skill in the art to practice the present invention. Various modifications of the above-described embodiments are naturally possible for a person skilled in the art, and the technical idea of ​​the present invention can 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 according to the technical idea defined by the claims. [Explanation of symbols]

[0101] 1 Polishing equipment 2 Polishing Pads 2a Polished surface 3 Polishing table 3a Table axis 5 Polishing Head 6 Table Motor 7 Angle detector 8 Polishing fluid supply nozzle 10 Grinding head shaft 12 Cleaning section 15 Spindle 16 Washing Arm 18 Cleaning section horizontal movement mechanism 19 Angle detector 20 Optical film thickness measuring device 21 Optical Sensor 22 Light source 23 Spectrometer 25 Data Processing Section 27 Optical fiber cable for floodlight 28 Receiving optical fiber cable 30 First Hole 31 Second Hole 33 Through hole (light passage part) 35 Fluid Supply Line 36 Fluid discharge line 37 Supply Pump 38 Discharge Pump 40 Motion control section 40a storage device 40b Arithmetic unit 51 Housing 52 Cleaning cover 52a Bottom side 52b opening 52c Flow path 54 Cleaning nozzle 54A Liquid Nozzle 54B Jet Nozzle 54C Chemical Nozzle 55A, 55B, 55C Fluid valves 56 Actuator 57 Connecting members 58 Load measuring device 60 Ultrasonic transducer 62 Mirror 64 Imaging Device 65 Illumination Equipment 70 Transparent window (light passing part) 72 Fluid discharge line 73 Discharge Pump W substrate

Claims

1. a polishing table supporting a polishing pad having a light transmitting portion; a polishing head for pressing a substrate against a polishing surface of the polishing pad; an optical sensor disposed within the polishing table, irradiating light onto the substrate through the light passing portion and receiving reflected light from the substrate through the light passing portion; The polishing apparatus includes a cleaning section that forms a cleaning space covering the light passing section above the light passing section and supplies a cleaning fluid to the light passing section through the cleaning space.

2. a fluid discharge line for discharging the cleaning fluid from the cleaning space; An operation control unit that controls the operation of the cleaning unit is further provided. The cleaning unit includes: A cleaning cover that defines the cleaning space therein; a cleaning nozzle that supplies the cleaning fluid into the cleaning space; An actuator for moving the cleaning cover up and down is provided, 2. The polishing apparatus according to claim 1, wherein the operation control unit is configured to give a command to the actuator to lower the cleaning cover until it contacts the polishing surface of the polishing pad, thereby surrounding the light passing portion with the cleaning cover and closing the cleaning space.

3. 3. The polishing apparatus according to claim 2, wherein the cleaning nozzle includes at least one of a liquid nozzle that supplies a liquid as the cleaning fluid, a jet nozzle that supplies a jet of fluid as the cleaning fluid, and a chemical nozzle that supplies a chemical liquid as the cleaning fluid.

4. 2. The polishing apparatus according to claim 1, wherein the cleaning section includes an ultrasonic transducer that generates ultrasonic waves and is configured to propagate the ultrasonic waves through the cleaning fluid.

5. The cleaning unit further includes a cleaning cover that defines the cleaning space therein, The polishing apparatus according to claim 4 , wherein the ultrasonic vibrator is disposed in the cleaning cover.

6. The cleaning unit further includes a cleaning nozzle that supplies the cleaning fluid into the cleaning space, The polishing apparatus according to claim 4 , wherein the ultrasonic vibrator is disposed in the cleaning nozzle.

7. 2. The polishing apparatus according to claim 1, wherein the light passing portion is a through hole formed in the polishing pad.

8. a fluid discharge line for discharging the cleaning fluid from the cleaning space; 8. The polishing apparatus according to claim 7, wherein the fluid discharge line is in communication with the through hole and is configured to discharge the cleaning fluid from the cleaning space through the through hole.

9. 2. The polishing apparatus according to claim 1, wherein the light passing portion is a transparent window made of a material that allows light to pass therethrough.

10. a fluid discharge line for discharging the cleaning fluid from the cleaning space; The cleaning unit includes a cleaning cover that defines the cleaning space therein, 10. The polishing apparatus according to claim 9, wherein the fluid discharge line is configured to communicate with an opening formed in an inner surface of the cleaning cover and to discharge the cleaning fluid from the cleaning space through the opening.

11. The cleaning unit further includes a load measuring device that measures a load applied to the cleaning cover, 3. The polishing apparatus according to claim 2, wherein the operation control unit is configured to give a command to the actuator to lower the cleaning cover until the load measured by the load measuring device reaches a load target value.

12. a table motor for rotating the polishing table; A cleaning unit horizontal movement mechanism for horizontally moving the cleaning unit is further provided, The operation control unit is configured to control the operation of the table motor and the cleaning unit horizontal movement mechanism; 3. The polishing apparatus according to claim 2, configured to give commands to the table motor and the cleaning unit horizontal movement mechanism to rotate the polishing table and horizontally move the cleaning unit so that the position of the light passing unit coincides with the position of the cleaning cover.

13. An operation control unit that controls the operation of the cleaning unit is further provided. the cleaning unit includes a mirror disposed on an optical path of the light irradiated from the optical sensor through the light passing unit; the optical sensor is configured to receive reflected light from the mirror through the light passing portion, 2. The polishing apparatus according to claim 1, wherein the operation control section is configured to detect an end point of cleaning of the light passing section, which is a time point when the intensity of the light reflected from the mirror exceeds a threshold value.

14. An operation control unit that controls the operation of the cleaning unit is further provided. the cleaning unit includes an imaging device that generates an image of the light passing portion; The polishing apparatus according to claim 1 , wherein the operation control unit is configured to detect an end point of cleaning of the light passing portion based on the image.

15. An operation control unit that controls the operation of the cleaning unit is further provided.

2. The polishing apparatus according to claim 1, wherein the operation control section is configured to determine whether or not it is time to clean the light passing section based on the reflected light from the substrate.

16. a polishing pad supported on a polishing table to polish the substrate; During polishing of the substrate, an optical sensor disposed in the polishing table irradiates the substrate with light through a light passing portion provided in the polishing pad and receives reflected light from the substrate through the light passing portion; before or after polishing the substrate, a cleaning space is formed on the light transmitting portion so as to cover the light transmitting portion by a cleaning portion; The polishing method further comprises: supplying a cleaning fluid to the light passing portion through the cleaning space by the cleaning portion.

17. the step of forming the cleaning space covering the light transmitting portion on the light transmitting portion by the cleaning unit includes a step of disposing the cleaning unit above the light passing portion, lowering a cleaning cover of the cleaning unit until it contacts the polishing surface of the polishing pad, closing the cleaning space formed inside the cleaning cover, and surrounding the light passing portion with the cleaning cover; the step of supplying the cleaning fluid to the light passing part through the cleaning space by the cleaning part is a step of supplying the cleaning fluid to the light passing part from a cleaning nozzle of the cleaning part through the cleaning space, The polishing method according to claim 16, further comprising discharging the cleaning fluid from the cleaning space through a fluid discharge line.

18. The polishing method according to claim 16, further comprising generating ultrasonic waves with an ultrasonic transducer and propagating the ultrasonic waves through the cleaning fluid.

19. 17. The polishing method according to claim 16, wherein the step of forming the cleaning space covering the light transmitting portion on the light transmitting portion by the cleaning portion is a step of measuring a load applied to a cleaning cover of the cleaning portion by a load measuring device, and lowering the cleaning cover until the measured load reaches a load target value, thereby forming the cleaning space covering the light transmitting portion on the light transmitting portion.

20. 18. The polishing method according to claim 17, wherein the step of positioning the cleaning unit above the light passing unit is a step of rotating the polishing table and horizontally moving the cleaning unit so that the position of the light passing unit coincides with the position of the cleaning cover, thereby positioning the cleaning unit above the light passing unit.

21. The optical sensor irradiates light onto a mirror through the light passing portion and receives reflected light from the mirror; 17. The polishing method according to claim 16, further comprising detecting a cleaning endpoint of the light passing portion, which is a point in time when the intensity of the reflected light exceeds a threshold value.

22. generating an image of the light emitting and receiving surface with an imaging device; The polishing method according to claim 16 , further comprising detecting a cleaning end point of the light passing portion based on the image.

23. 17. The polishing method according to claim 16, further comprising determining whether or not it is time to clean the light passing portion based on the reflected light from the substrate.

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