Substrate processing apparatus, polishing pad inspection apparatus, and polishing pad inspection method

Abstract

To inspect a polishing surface of an abrasive pad, which polishes a substrate, at suitable timing.SOLUTION: A substrate processing device comprises: an abrasive pad for polishing a substrate; a pod for accommodating a polishing surface of the abrasive pad that contacts the substrate; an imaging part for imaging the polishing surface of the abrasive pad via the pod; and an image processing part which processes image data captured by the imaging part, and detects deterioration of the abrasive pad.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a substrate processing apparatus, a polishing pad inspection apparatus, and a polishing pad inspection method. [Background technology]

[0002] The substrate processing apparatus described in Patent Document 1 has an inspection means for inspecting deterioration of components, which includes an imaging means for acquiring image data of the components, a color information acquisition means for acquiring color information of the components to be inspected from the image data acquired by the imaging means, and a deterioration determination means for determining the degree of deterioration of the components to be inspected based on the acquired color information.

[0003] The substrate processing apparatus described in Patent Document 2 has an inspection means for inspecting deterioration of a part coated with a first resin, and an early deterioration part coated with a second resin that deteriorates more easily than the first resin. The inspection means detects deterioration of the second resin coating to determine the degree of deterioration of the part coated with the first resin. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-29470 [Patent Document 2] Japanese Patent Application Publication No. 2019-29472 Summary of the Invention [Problem to be solved by the invention]

[0005] One aspect of the present disclosure provides a technique for inspecting the polishing surface of a polishing pad that polishes a substrate at an appropriate time, thereby improving the availability of a substrate processing apparatus. [Means for solving the problem]

[0006] A substrate processing apparatus according to one aspect of the present disclosure includes a polishing pad having a polishing surface that contacts a substrate and polishes the substrate, a bath that accommodates the polishing surface of the polishing pad, stores a cleaning liquid for cleaning the polishing surface, and has a transparent wall at its bottom that faces the polishing surface of the polishing pad, an imaging unit that images the polishing surface of the polishing pad through the transparent wall of the bath, and an image processing unit that processes image data captured by the imaging unit and detects wear of the polishing pad. The image processing unit calculates a value of the brightness with the highest probability in a probability distribution of the number of pixels measured for each brightness of the image data, and calculates a value of the brightness with the highest probability in a probability distribution of the number of pixels measured for each brightness of the image data. No. 1 Brightness exceeds Preset secondary brightness If it falls below this, wear of the abrasive surface is detected. [Effects of the Invention]

[0007] According to one aspect of the present disclosure, the polishing surface of a polishing pad that polishes a substrate can be inspected at an appropriate time, thereby improving the operating rate of a substrate processing apparatus. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view showing a state during polishing of a substrate processing apparatus according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing a state during cleaning of the substrate processing apparatus of FIG. [Figure 3] FIG. 3(A) is a perspective view showing an example of a polishing head, and FIG. 3(B) is a perspective view showing another example of a polishing head. [Figure 4] FIG. 4 is a flowchart showing a substrate processing method according to an embodiment. [Figure 5] FIG. 5 is a cross-sectional view showing a polishing pad inspection device according to one embodiment. [Figure 6] FIG. 6(A) is a cross-sectional view showing an example of the position of the illumination unit when capturing a bright-field image, and FIG. 6(B) is a cross-sectional view showing an example of the position of the illumination unit when capturing a dark-field image. [Figure 7] FIG. 7 is a cross-sectional view showing a polishing pad inspection device according to a modified example. [Figure 8] FIG. 8 is a diagram showing an example of the relationship between the number N of substrates polished with a polishing pad and the probability distribution of brightness of image data obtained by capturing an image of the polishing surface of the polishing pad. [Figure 9] Figure 9(A) is a diagram showing an example of an image of the polishing surface of a polishing pad where N is zero, Figure 9(B) is a diagram showing an example of an image obtained by binarizing Figure 9(A), Figure 9(C) is a diagram showing an example of an image of the polishing surface of a polishing pad where N is N2, and Figure 9(D) is a diagram showing an example of an image obtained by binarizing Figure 9(C). DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or corresponding components are denoted by the same reference numerals, and their description may be omitted. In this specification, the X-axis, Y-axis, and Z-axis directions are perpendicular to each other. The X-axis and Y-axis directions are horizontal directions, and the Z-axis direction is vertical.

[0010] As shown in FIGS. 1 and 2, the substrate processing apparatus 10 includes a housing 11, a cup 12, a holder 20, a rotating unit 25, a liquid supplying unit 30, a polishing head 60, a pod 70, a moving unit 80, and a control unit 90. The housing 11 defines a processing chamber therein for processing the substrate W. The cup 12 collects cleaning liquid and other liquids spun off from the substrate W. The holder 20 holds the substrate W horizontally. The rotating unit 25 rotates the holder 20, thereby rotating the substrate W together with the holder 20. The liquid supplying unit 30 supplies cleaning liquid to the substrate W. The polishing head 60 includes a polishing pad 61 (see FIG. 3) for polishing the substrate W. The pod 70 houses a polishing surface 62 of the polishing pad 61 that contacts the substrate W. The moving unit 80 presses the polishing head 60 against the substrate W and scans the polishing head 60 in the radial direction of the substrate W. The control unit 90 controls the rotation unit 25, the liquid supply unit 30, and the movement unit 80. Each component will be described below.

[0011] The holder 20 holds the substrate W horizontally. The substrate W includes a semiconductor substrate such as a silicon wafer or a compound semiconductor wafer. The substrate W may further include a dielectric film or a conductive film formed on the semiconductor substrate. The substrate W may also include a glass substrate instead of a semiconductor substrate. The holder 20 holds the substrate W horizontally. The holder 20 is, for example, a mechanical chuck that holds the outer periphery of the substrate W. However, the holder 20 may also be a vacuum chuck or an electrostatic chuck, and may hold the underside of the substrate W.

[0012] The rotating unit 25 is a rotation motor or the like, and rotates the holder 20 around a vertical rotation axis 26. The rotating unit 25 rotates the holder 20 while the holder 20 holds the substrate W. This causes the substrate W to rotate.

[0013] The liquid supply unit 30 supplies a cleaning liquid to the upper surface of the substrate W while the substrate W is held by the holder 20. For example, DIW (deionized water) is used as the cleaning liquid. Note that multiple cleaning liquids may be used, and a chemical liquid and a rinse liquid may be used in sequence as the cleaning liquid. The liquid supply unit 30 includes, for example, a first nozzle 31 and a second nozzle 41.

[0014] The first nozzle 31 supplies the cleaning liquid to the center of the upper surface of the substrate W while the substrate W is rotating. The cleaning liquid spreads over the entire upper surface of the substrate W due to centrifugal force and is then spun off at the periphery of the substrate W. The first nozzle 31 is connected to a liquid supply source 33 via a pipe 32. An on-off valve 35 and a flow rate controller 36 are provided in the pipe 32. When the on-off valve 35 opens the flow path of the pipe 32, the cleaning liquid is supplied from the liquid supply source 33 to the first nozzle 31, and the cleaning liquid is discharged from the first nozzle 31. The discharge rate is controlled by the flow rate controller 36. On the other hand, when the on-off valve 35 closes the flow path of the pipe 32, the supply of the cleaning liquid from the liquid supply source 33 to the first nozzle 31 is stopped, and the discharge of the cleaning liquid is stopped.

[0015] The second nozzle 41 moves in the radial direction of the substrate W while the substrate W is rotating, and supplies the cleaning liquid over the entire radial direction of the upper surface of the substrate W. The liquid supply unit 30 includes a moving device 51 that moves the second nozzle 41 in the radial direction of the substrate W. The second nozzle 41 is, for example, a two-fluid nozzle that crushes the cleaning liquid with a gas such as N2 gas, atomizes it, and sprays it. This can improve the cleaning power of the cleaning liquid.

[0016] Similar to the first nozzle 31, the second nozzle 41 is connected to a liquid supply source 43 via a pipe 42. An on-off valve 45 and a flow rate controller 46 are provided in the pipe 42. Furthermore, the second nozzle 41 is connected to a gas supply source 53 via a pipe 52. An on-off valve 55 and a flow rate controller 56 are provided in the pipe 52. When the on-off valve 55 opens the flow path of the pipe 52, gas is supplied from the gas supply source 53 to the second nozzle 41, and the gas is discharged from the second nozzle 41. The discharge rate is controlled by the flow rate controller 56. On the other hand, when the on-off valve 55 closes the flow path of the pipe 52, the gas supply from the gas supply source 53 to the second nozzle 41 is stopped, and the gas discharge is stopped.

[0017] The various fluids discharged from the liquid supply unit 30 are collected in the cup 12. The cup 12 accommodates the holder 20 and the substrate W held by the holder 20 therein, and collects droplets that are shaken off from the substrate W. A drain pipe and an exhaust pipe (not shown) are provided on the bottom wall of the cup 12. The drain pipe discharges the cleaning liquid, and the exhaust pipe discharges gas.

[0018] 1, the polishing head 60 contacts the upper surface of the substrate W while the substrate W is held by the holder 20, and polishes the upper surface of the substrate W. In this embodiment, the polishing head 60 polishes the upper surface of the substrate W, but it may also polish the lower surface of the substrate W. When the polishing head 60 polishes the lower surface of the substrate W, the liquid supply unit 30 may supply a cleaning liquid to the lower surface of the substrate W.

[0019] The polishing head 60 is connected to a rotary motor 69 via a vertical rotary shaft 68. The rotary motor 69 rotates the polishing head 60 around the rotary shaft 68. A transmission member that transmits the rotational force (torque) of the rotary motor 69 to the rotary shaft 68 may be disposed between the rotary motor 69 and the rotary shaft 68. The transmission member includes, for example, a belt and a pulley.

[0020] 3, the polishing head 60 includes a polishing pad 61 that polishes the substrate W. The polishing pad 61 has a polishing surface 62 that contacts the substrate W. The polishing pad 61 includes, for example, a sheet 63 that forms the polishing surface 62 and a substrate 64 to which the sheet 63 is attached.

[0021] The base material 64 is made of, for example, resin. The material of the base material 64 is hard resin, for example, PVC (polyvinyl chloride). The base material 64 is, for example, cylindrical.

[0022] On the other hand, the sheet 63 may be circular as shown in Fig. 3(A) or arc-shaped as shown in Fig. 3(B). A plurality of arc-shaped sheets 63 may be provided at intervals along the outer periphery of the substrate 64, and a groove may be formed between adjacent sheets 63. The number of sheets 63 is not limited to two, and may be one, or three or more. The sheet 63 contains abrasive particles. The abrasive particles are, for example, diamond particles or silicon carbide particles.

[0023] The sheet 63 includes, for example, an abrasive layer made of abrasive particles solidified with resin, and a resin film supporting the abrasive layer. The abrasive layer may have an uneven pattern on the abrasive surface 62 to prevent clogging, and may have, for example, stripe-shaped grooves on the abrasive surface 62.

[0024] The structure of the polishing pad 61 is not limited to the structure shown in Fig. 3. For example, the polishing head 60 may not include the sheet 63, and may include only a cylindrical body made of hard resin. The material of the cylindrical body may be, for example, PEEK (polyether ether ketone). The polishing surface 62 of the cylindrical body may not have an uneven pattern, and may be a flat surface.

[0025] 1 and 2, the pod 70 is provided outside the cup 12. As shown in FIG. 5, the pod 70 accommodates the polishing surface 62 of the polishing pad 61. The pod 70 is, for example, a bath that stores a cleaning liquid. The cleaning liquid can clean the polishing surface 62, thereby removing dirt from the polishing surface 62.

[0026] The bath may be provided with a supply pipe 77 for supplying the cleaning liquid and a discharge pipe 78 for discharging the cleaning liquid. The supply pipe 77 and the discharge pipe 78 allow a flow of cleaning liquid to be formed inside the bath, and the flow of cleaning liquid can efficiently remove dirt from the polishing surface 62. The cleaning liquid discharged from the discharge pipe 78 may be passed through a filter and then returned to the supply pipe 77. In other words, the cleaning liquid may be circulated.

[0027] 1 and 2, the moving unit 80 moves the polishing head 60 between the pod 70 and the substrate W held by the holder 20. The moving unit 80 includes, for example, a first moving unit 81 and a second moving unit 82. The first moving unit 81 moves the polishing head 60 in the Z-axis direction and presses it against the substrate W. The second moving unit 82 moves the polishing head 60 in the X-axis direction and scans the substrate W in the radial direction.

[0028] The control unit 90 is, for example, a computer, and includes a CPU (Central Processing Unit) 91 and a storage medium 92 such as a memory. The storage medium 92 stores programs that control various processes executed in the substrate processing apparatus 10. The control unit 90 controls the operation of the substrate processing apparatus 10 by causing the CPU 91 to execute the programs stored in the storage medium 92.

[0029] Next, the operation of the substrate processing apparatus 10, that is, the substrate processing method, will be described with reference to Fig. 4 etc. As shown in Fig. 4, the substrate processing method includes steps S1 to S5. Steps S1 to S5 are performed under the control of a control unit 90.

[0030] In step S1, a transport device (not shown) carries the substrate W into the housing 11 and hands it over to the holder 20. The holder 20 holds the substrate W horizontally. After handing over the substrate W to the holder 20, the transport device exits the housing 11. After step S1, the moving unit 80 removes the polishing head 60 from the pod 70 and moves it toward the substrate W held by the holder 20.

[0031] In step S2, the substrate W is polished by the polishing head 60 while being held by the holder 20. For example, the moving unit 80 presses the polishing head 60 against the substrate W and scans it in the radial direction of the substrate W. The polishing head 60 may scan once or multiple times. The rotating unit 25 rotates the holder 20, and rotates the substrate W together with the holder 20. The rotation motor 69 rotates the polishing head 60. The liquid supply unit 30 also supplies a cleaning liquid to the upper surface of the substrate W, forming a liquid film of the cleaning liquid between the polishing head 60 and the substrate W.

[0032] The control unit 90 controls the moving unit 80 to control the polishing pressure of the polishing head 60 and the scan speed of the polishing head 60. The control unit 90 also controls the rotating unit 25 to control the rotation speed of the substrate W. The control unit 90 also controls the rotation motor 69 to control the rotation speed of the polishing head 60. The control unit 90 also controls the liquid supply unit 30 to control the thickness of the liquid film formed between the polishing head 60 and the substrate W. After step S2, the moving unit 80 moves the polishing head 60 away from the substrate W held by the holder 20 and toward the pod 70.

[0033] In step S3, the liquid supply unit 30 supplies a cleaning liquid to the substrate W to wash away contaminants such as polishing debris. For example, first, the first nozzle 31 supplies the cleaning liquid to the center of the upper surface of the substrate W. The cleaning liquid spreads over the entire upper surface by centrifugal force, and washes away contaminants that have separated from the substrate W radially outward from the substrate W. As the cleaning liquid, for example, a rinse liquid such as DIW is used. Note that a chemical liquid and a rinse liquid may be used in sequence as the cleaning liquid.

[0034] Next, the second nozzle 41 gradually moves from a position directly above the center of the substrate W to a position directly above the periphery of the substrate W while discharging the cleaning liquid toward the upper surface of the substrate W, and stops at the position directly above the periphery of the substrate W for a set time. This is because dirt is likely to adhere to the periphery of the substrate W. Note that the movement direction of the second nozzle 41 is outward in the radial direction of the substrate W in this embodiment, but it may also be inward in the radial direction of the substrate W. Furthermore, the number of scans by the second nozzle 41 is one in this embodiment, but it may be multiple times.

[0035] In step S4, the substrate W is dried. For example, the rotation unit 25 rotates the holder 20 at high speed to shake off the cleaning liquid remaining on the substrate W. At the end of step S3, the liquid film of the rinsing liquid may be replaced with a liquid film of a drying liquid having a lower surface tension than the rinsing liquid. In that case, in step S4, the drying liquid is shaken off. For example, IPA (isopropyl alcohol) or the like is used as the drying liquid.

[0036] In step S5, a transport device (not shown) enters the interior of the housing 11, receives the substrate W from the holder 20, and transports the substrate W to the exterior of the housing 11. After that, the current process ends.

[0037] Next, a polishing pad inspection device provided in the substrate processing apparatus 10 according to this embodiment will be described with reference to Fig. 5 and other figures. The polishing pad inspection device 100 includes an imaging unit 110 that captures an image of the polishing surface 62 of the polishing pad 61 via the pod 70, and an image processing unit 120 that processes image data captured by the imaging unit 110 and detects deterioration of the polishing pad 61. Deterioration of the polishing pad 61 includes, for example, wear of the polishing pad 61 and peeling of the sheet 63 and the substrate 64.

[0038] Conventionally, the replacement timing of the polishing pad 61 has been controlled based on the number of substrates W polished with the polishing pad 61. However, the wear rate of the polishing pad 61 varies depending on the material of the substrate surface and polishing conditions such as the polishing pressure. In addition, abnormalities such as peeling of the sheet 63 and the substrate 64 can occur suddenly. For this reason, the replacement timing of the polishing pad 61 has conventionally been set earlier to allow for a safety margin.

[0039] According to this embodiment, the polishing surface 62 of the polishing pad 61 is imaged, the image data is processed, and deterioration of the polishing pad 61 is detected. Therefore, the polishing pad 61 can be used to the end of its lifespan, and the polishing pad 61 can be effectively utilized. Furthermore, the replacement time of the polishing pad 61 can be delayed, and the frequency of replacement of the polishing pad 61 can be reduced, thereby improving the operating rate of the substrate processing apparatus 10. When the image processing unit 120 detects deterioration of the polishing pad 61, the image processing unit 120 may notify the user of the substrate processing apparatus 10 of the deterioration of the polishing pad 61 using an image, sound, or the like.

[0040] Furthermore, according to this embodiment, the polishing surface 62 of the polishing pad 61 is imaged via the pod 70. Since the polishing surface 62 of the polishing pad 61 is imaged while it is housed in the pod 70, the polishing pad 61 can be inspected when it is not in use. For example, the polishing pad 61 can be inspected while the substrate processing apparatus 10 is idling. If the polishing pad 61 has deteriorated, it can be replaced while the substrate processing apparatus 10 is idling, thereby improving the operating rate of the substrate processing apparatus 10.

[0041] The pod 70 has, for example, a transparent wall 71 facing the polishing surface 62 of the polishing pad 61. The transparent wall 71 transmits, for example, visible light. The visible light transmittance of the transparent wall 71 is, for example, 90% or more and 100% or less. The transparent wall 71 is made of, for example, a resin such as an acrylic resin, or glass.

[0042] The imaging unit 110 is, for example, a CCD camera or a CMOS camera. The frame rate, gain, etc. of the camera are set appropriately. The imaging unit 110 captures an image of the polishing surface 62 of the polishing pad 61 through the transparent wall 71 of the pod 70. A clear image of the polishing surface 62 can be obtained, and deterioration of the polishing pad 61 can be detected with high accuracy.

[0043] When the pod 70 is a bath that stores a cleaning liquid, the bottom wall of the bath is a transparent wall 71. The cleaning liquid stored in the bath can remove dirt from the polishing surface 62 of the polishing pad 61. Therefore, the polishing surface 62 can be imaged after the dirt on the polishing surface 62 has been removed. Therefore, a clear image of the polishing surface 62 can be obtained, and deterioration of the polishing pad 61 can be detected with high accuracy.

[0044] The imaging unit 110 may capture an image of the polishing surface 62 of the polishing pad 61 while the cleaning liquid remains in the bath. This eliminates the need to empty the bath and refill it with cleaning liquid. While capturing an image of the polishing surface 62, the control unit 90 may stop the supply of cleaning liquid through the supply pipe 77 and the discharge of cleaning liquid through the discharge pipe 78, thereby stopping the flow of cleaning liquid inside the bath. This can prevent image distortion caused by the flow of cleaning liquid.

[0045] The substrate processing apparatus 10 may include a nozzle 79 that supplies gas into the inside of the pod 70. The nozzle 79 can blow off cleaning liquid adhering to the polishing surface 62 of the polishing pad 61, thereby drying the polishing surface 62. After droplets on the polishing surface 62 have been removed, the polishing surface 62 can be imaged. This allows a clear image of the polishing surface 62 to be acquired, and deterioration of the polishing pad 61 to be detected with high accuracy. In this case, the control unit 90 may stop the supply of cleaning liquid through the supply pipe 77 and discharge the cleaning liquid through the discharge pipe 78 to empty the inside of the bath before imaging the polishing surface 62.

[0046] When the polishing head 60 polishes the lower surface of the substrate W, the upper surface of the polishing pad 61 is the polishing surface 62. In this case, the transparent wall 71 of the pod 70 is provided above the polishing pad 61, and the imaging unit 110 is provided above the transparent wall 71 of the pod 70.

[0047] The polishing pad inspection device 100 includes an illumination unit 130 that irradiates light onto the polishing surface 62 of the polishing pad 61. The illumination unit 130 includes a light source such as an LED. By irradiating the polishing surface 62 with light, the imaging unit 110 can receive reflected light that is specularly reflected by the polishing surface 62 or scattered light that is scattered by the polishing surface 62. The light that the illumination unit 130 irradiates onto the polishing surface 62 is, for example, visible light. The intensity of the light that the illumination unit 130 irradiates onto the polishing surface 62 is set appropriately.

[0048] The polishing pad inspection device 100 includes an illumination moving unit 140 that moves the illumination unit 130 along the optical axis A (see FIG. 6) of the imaging unit 110. By moving the illumination unit 130, the angle of incidence of light on the polishing surface 62 of the polishing pad 61 can be changed, and an image suitable for inspection can be acquired. For example, a bright-field image and a dark-field image can be acquired.

[0049] 6(A), the bright-field image is an image acquired by irradiating the polished surface 62 with light from the illumination unit 130 and receiving the light specularly reflected by the polished surface 62 with the imaging unit 110. The bright-field image can brighten the entire field of view and is suitable for acquiring brightness and color information.

[0050] 6(B), the dark-field image is an image obtained by receiving, by the imaging unit 110, the scattered light scattered by the polished surface 62, without receiving, by the imaging unit 110, the light that is irradiated onto the polished surface 62 from the illumination unit 130 and that is specularly reflected by the polished surface 62. The dark-field image is likely to have high contrast, and is suitable for observing fine uneven patterns.

[0051] The illumination unit 130 is formed, for example, in an annular shape so as to surround the optical axis A of the imaging unit 110. The optical axis A of the imaging unit 110 and the rotation center line of the polishing head 60 are arranged, for example, on the same straight line. By forming the illumination unit 130 in an annular shape, light can be evenly irradiated all around the polishing surface 62 in the circumferential direction. The illumination unit 130 is formed in a circular annular shape, but may also be formed in an angular annular shape by combining multiple rod-shaped light sources.

[0052] The inner diameter of the illumination unit 130 may be larger than the outer diameter of at least a portion of the imaging unit 110. This can increase the movable range of the illumination unit 130. The inner diameter of the illumination unit 130 may be larger than the outer diameter of the entire imaging unit 110, and the illumination unit 130 may be disposed below the imaging unit 110.

[0053] 7, multiple illumination units 130 may be provided at intervals along the optical axis A of the imaging unit 110. In this case, the polishing pad inspection device 100 includes an illumination control unit 150 that individually operates the multiple illumination units 130. By switching the illumination unit 130 used during imaging, the angle of incidence of light on the polishing surface 62 of the polishing pad 61 can be changed, and an image suitable for inspection can be acquired. For example, a bright-field image and a dark-field image can be acquired.

[0054] The image processing unit 120 is, for example, a computer. The image processing unit 120 may be common to a plurality of substrate processing apparatuses 10, and may process image data captured by a plurality of imaging units 110. This allows the number of image processing units 120 to be reduced. Note that an imaging unit 110 is provided for each substrate processing apparatus 10.

[0055] Figure 8 shows an example of the relationship between the number N of substrates W polished with the polishing pad 61 and the probability distribution of brightness of image data obtained by capturing an image of the polishing surface 62 of the polishing pad 61. In Figure 8, the horizontal axis represents pixel brightness, and the vertical axis represents the number of pixels, i.e., probability. The larger the number N of substrates W polished with the polishing pad 61, the more advanced the wear and the greater the degree of wear.

[0056] 8, the larger N becomes, that is, the more wear progresses, the more the brightness with the highest probability shifts to a higher brightness. This is because, as the polishing pad 61 becomes more worn, the more abrasive particles fall off or the uneven pattern wears away, the surface roughness of the polishing surface 62 decreases, and light is more easily reflected by the polishing surface 62.

[0057] Therefore, the image processing unit 120 may detect wear on the polishing surface 62 from, for example, a probability distribution of brightness of the image data. A bright-field image is suitable for examining the probability distribution of brightness. The relationship between the probability distribution of brightness of the image data and the degree of wear on the polishing surface 62 is examined in advance by an experiment or the like, and is then read out and used from a storage medium such as a memory.

[0058] The image processing unit 120 detects wear on the polishing surface 62 by, for example, detecting the luminance with the highest probability. As the polishing pad 61 becomes more worn, the luminance with the highest probability shifts to a higher luminance. When the luminance with the highest probability exceeds a preset luminance, the image processing unit 120 determines that the degree of wear on the polishing surface 62 has exceeded its usage limit. The image processing unit 120 may detect the degree of wear on the polishing surface 62 in stages, and may change the content of the notification to the user in stages.

[0059] Note that, although the polishing surface 62 of this embodiment includes abrasive grains and also includes an uneven pattern, the technology of the present disclosure is not limited thereto. As described above, the polishing surface 62 may be flat when unused. In this case, as the polishing surface 62 wears, the surface roughness of the polishing surface 62 increases, and light is more likely to be scattered by the polishing surface 62. Therefore, the image processing unit 120 may determine that the degree of wear of the polishing surface 62 has exceeded its usable limit when the brightness with the highest probability falls below a preset brightness.

[0060] Fig. 9(A) is a diagram showing an example of an image captured of polishing surface 62 of polishing pad 61 where N is zero, and Fig. 9(B) is a diagram showing an example of an image obtained by binarizing Fig. 9(A). Fig. 9(C) is a diagram showing an example of an image captured of polishing surface 62 of polishing pad 61 where N is N2 (N2>0), and Fig. 9(D) is a diagram showing an example of an image obtained by binarizing Fig. 9(C).

[0061] 9, when the polishing surface 62 of the polishing pad 61 includes linear grooves 65 in an unused state, the larger N becomes, that is, the more wear there is, the less clear the grooves 65 extracted from the image data become, and the less distinct the grooves 65 become. This is because the more wear there is in the polishing pad 61, the more wear there is in the grooves 65.

[0062] Therefore, when the polishing surface 62 of the polishing pad 61 includes linear grooves 65 in an unused state, the image processing unit 120 may detect wear on the polishing surface 62 from the clarity of the grooves 65 extracted from the image data. Dark-field images are suitable for examining the clarity of the grooves 65. The relationship between the clarity of the grooves 65 and the degree of wear on the polishing surface 62 is examined in advance by experiments or the like, and the result is read out and used from a storage medium such as a memory.

[0063] The image processing unit 120 extracts the grooves 65 from the image data by, for example, binarization processing, pattern recognition, or template matching, and calculates the clarity of the grooves 65. The clarity of the grooves 65 is represented by the size of the grooves 65, for example, the length, width, or area (product of length and width) of the grooves 65. The smaller the size of the grooves 65, the lower the clarity of the grooves 65 and the greater the degree of wear.

[0064] The image processing unit 120 determines that the degree of wear of the polishing surface 62 has exceeded its usage limit when the clarity of the grooves 65, i.e., the size of the grooves 65, falls below a preset value. The image processing unit 120 may detect the degree of wear of the polishing surface 62 in stages, and may change the content of the notification to the user in stages.

[0065] Although the polishing surface 62 of this embodiment includes linear grooves 65 in an unused state, the technology of the present disclosure is not limited to this. As described above, the polishing surface 62 may be flat in an unused state. In this case, as the polishing surface 62 wears, it becomes more susceptible to scratches. Therefore, the image processing unit 120 may extract scratches from the image data and detect wear on the polishing surface 62 from the size or number of scratches.

[0066] Incidentally, the sheet 63 may peel off from the base material 64. Furthermore, the colors contained in the image data may change before and after the peeling. This is because when the sheet 63 and the base material 64 peel off, the adhesive bonding the sheet 63 and the base material 64 together or the base material 64 itself becomes exposed. The surface of the base material 64 may be color-coded to separate the area where the sheet 63 is attached from the surrounding area.

[0067] Therefore, when the polishing pad 61 includes the sheet 63 and the substrate 64, the image processing unit 120 may detect the separation of the sheet 63 and the substrate 64 from the color data included in the image data.

[0068] Although the embodiments of the substrate processing apparatus, polishing pad inspection apparatus, and polishing pad inspection method according to the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments. Various changes, modifications, substitutions, additions, deletions, and combinations are possible within the scope of the claims. These naturally fall within the technical scope of the present disclosure. [Explanation of symbols]

[0069] 10. Substrate processing equipment 61 Polishing Pad 62 Polished surface 70 pods 100 Polishing pad inspection device 110 Imaging unit 120 Image processing unit

Claims

1. a polishing pad having a polishing surface that contacts the substrate and polishes the substrate; a bath that accommodates the polishing surface of the polishing pad, stores a cleaning liquid for cleaning the polishing surface, and has a transparent bottom wall that faces the polishing surface of the polishing pad; an imaging unit that images the polishing surface of the polishing pad through the transparent wall of the bath; an image processing unit that processes image data captured by the imaging unit and detects wear on the polishing pad; Equipped with The image processing unit detects wear on the polishing surface when the brightness with the highest probability in the probability distribution of the number of pixels measured for each brightness of the image data exceeds a predetermined first brightness or falls below a predetermined second brightness.

2. the polishing surface of the polishing pad includes linear grooves for preventing clogging; The substrate processing apparatus according to claim 1 , wherein the image processing unit detects wear on the polishing surface when a size of the groove extracted from the image data is smaller than a preset value.

3. an illumination unit that irradiates the polishing surface of the polishing pad with light; an illumination moving unit that moves the illumination unit along an optical axis of the imaging unit between a position where the image data for examining the probability distribution is acquired and a position where the image data for examining the size of the groove is acquired; The substrate processing apparatus of claim 2 , comprising:

4. a plurality of illumination units that irradiate the polishing surface of the polishing pad with light, the illumination units being spaced apart along the optical axis of the imaging unit; The substrate processing apparatus according to claim 2 , further comprising an illumination control unit that switches the illumination unit to be activated when acquiring the image data for examining the probability distribution and when acquiring the image data for examining the size of the groove.

5. The substrate processing apparatus according to claim 3 , wherein the illumination unit is formed in a ring shape so as to surround an optical axis of the imaging unit.

6. a polishing pad having a polishing surface that contacts the substrate and polishes the substrate; a bath that accommodates the polishing surface of the polishing pad, stores a cleaning liquid for cleaning the polishing surface, and has a transparent bottom wall that faces the polishing surface of the polishing pad; an imaging unit that images the polishing surface of the polishing pad through the transparent wall of the bath; an image processing unit that processes image data captured by the imaging unit and detects wear on the polishing pad; Equipped with the polishing surface of the polishing pad includes linear grooves for preventing clogging; The image processing unit detects wear on the polishing surface when the size of the groove extracted from the image data is smaller than a preset value.

7. 7. The substrate processing apparatus according to claim 1, wherein the imaging unit images the polishing surface of the polishing pad while the cleaning liquid remains in the bath.

8. a nozzle for supplying a gas into the bath to blow off the cleaning liquid attached to the polishing surface of the polishing pad; 7. The substrate processing apparatus according to claim 1, wherein the imaging unit images the polishing surface of the polishing pad in a dry state.

9. 9. The substrate processing apparatus according to claim 1, further comprising: a supply pipe for supplying the cleaning liquid into the inside of the bath; and a discharge pipe for discharging the cleaning liquid from the inside of the bath.

10. an imaging unit that accommodates a polishing surface of a polishing pad that contacts a substrate and polishes the substrate, stores a cleaning liquid for cleaning the polishing surface, and has a transparent wall at its bottom that faces the polishing surface of the polishing pad, and images the polishing surface of the polishing pad through the transparent wall; an image processing unit that processes image data captured by the imaging unit and detects wear on the polishing pad; Equipped with The image processing unit detects wear on the polishing surface when the brightness with the highest probability in the probability distribution of the number of pixels measured for each brightness of the image data exceeds a predetermined first brightness or falls below a predetermined second brightness.

11. an imaging unit that accommodates a polishing surface of a polishing pad that contacts a substrate and polishes the substrate, stores a cleaning liquid for cleaning the polishing surface, and has a transparent wall at its bottom that faces the polishing surface of the polishing pad, and images the polishing surface of the polishing pad through the transparent wall; an image processing unit that processes image data captured by the imaging unit and detects wear on the polishing pad; Equipped with the polishing surface of the polishing pad includes linear grooves for preventing clogging; The image processing unit detects wear on the polishing surface when the size of the groove extracted from the image data is below a preset value.

12. A polishing pad inspection method, comprising inspecting the polishing pad using the polishing pad inspection apparatus according to claim 10 or 11.

Images