Polishing apparatus and polishing method

Abstract

This invention provides a polishing apparatus and polishing method that monitors the distribution of liquids such as polishing fluid and chemical solutions on the polishing surface of a polishing pad, thereby enabling the polishing of wafers and other workpieces under appropriate polishing conditions. The polishing apparatus includes: a polishing table (5) supporting a polishing pad (2); a polishing head (7) pressing the workpiece (W) to be polished onto the polishing surface (2a) of the polishing pad (2); a liquid supply device (8) supplying liquid to the polishing surface (2a); a liquid monitoring device (12) acquiring optical information contained in light from multiple points on the polishing surface (2a); an optical information analysis unit (13) determining the distribution of liquid on the polishing surface (2a) based on the optical information; and an operation control unit (47) controlling the operation of the polishing apparatus.

Description

[Technical Field]

[0001] This invention relates to a grinding apparatus and grinding method for pressing a workpiece such as a wafer, substrate, or panel onto the grinding surface of a grinding pad to grind the workpiece, and more particularly to a grinding apparatus and grinding method for making the workpiece slide in contact with the grinding pad while a grinding liquid such as a slurry is present on the grinding surface of the grinding pad. [Previous Technology]

[0002] In the manufacture of semiconductor devices, various types of films are formed on wafers. In the wiring / contact formation process, after the film formation process, the wafer is polished to remove unwanted portions and surface irregularities of the film. Chemical mechanical polishing (CMP) is a representative technique for wafer polishing. CMP is performed by pressing and sliding the wafer against the polishing surface while supplying polishing slurry to the polishing surface of the polishing pad. The film formed on the wafer is polished by a combination of the chemical action based on the chemical composition of the polishing slurry supplied to the polishing surface and the mechanical action based on the abrasive particles contained in the polishing slurry and / or the polishing pad.

[0003] A polishing apparatus for performing a CMP process includes: a polishing table supporting a polishing pad and a polishing head for pressing a wafer, which is the workpiece, onto the polishing pad. The apparatus presses the wafer against the polishing surface of the polishing pad while supplying polishing fluid from a liquid supply device to the polishing surface of the polishing pad. At this time, by rotating the polishing table and the polishing head, the wafer slides into contact with the polishing surface, and the surface of the wafer is polished to a flat and mirror-like finish.

[0004] The precision requirements for each process in the manufacturing of semiconductor devices today have reached the order of several nanometers, and CMP is no exception. In addition, the high integration, miniaturization, and multilayering of semiconductor integrated circuits are accelerating. Therefore, in order to achieve these miniaturization and multilayering, in CMP, the remaining film thickness deviation after CMP must also converge to within the order of several nanometers across the entire surface of the wafer.

[0005] To reduce residual film thickness deviation, it is necessary to control various factors that affect the polishing rate, such as the surface temperature of the polishing pad, the amount of polishing slurry supplied, and the distribution of polishing slurry on the polishing pad. Furthermore, in the CMP process, after polishing, for the purpose of cleaning the wafer surface, cleaning solutions such as chemical solutions or pure water (DIW) may be supplied to the polishing pad via a liquid supply device instead of polishing slurry. The distribution of the cleaning solution supply also affects the uniformity of the cleaning performance on the wafer surface.

[0006] Furthermore, cost reduction is required for each step in the manufacturing of semiconductor devices. In the CMP process, polishing slurry is a particular target for cost reduction. Polishing slurries used in CMP are expensive, and the disposal of used slurry also incurs costs. Therefore, to reduce the operating costs of CMP equipment and the manufacturing costs of semiconductor devices, it is necessary to reduce the amount of polishing slurry used.

[0007] Liquid supply devices typically supply polishing fluid from a nozzle with a single supply port, and perform operations such as oscillating the nozzle parallel to the polishing pad according to the polishing process. Patent Document 1, however, describes a device for efficiently supplying polishing fluid to the polishing surface of a polishing pad. Patent Document 1 discloses a nozzle having multiple polishing fluid supply ports, or a nozzle with a slit-shaped supply port, which enables efficient polishing by spreading the polishing fluid on the polishing pad. Prior Art Documents Patent Documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2006-147773 Technical Problem to be Solved by the Invention

[0009] As such, the amount of polishing slurry supplied during polishing and the distribution of polishing slurry on the polishing pad have a significant impact on polishing performance (deviation of polishing rate) and polishing efficiency. Therefore, monitoring the distribution of polishing slurry on the polishing pad is necessary to maintain polishing performance and polishing efficiency.

[0010] The main reasons for changes in the distribution of polishing fluid on the polishing pad can be listed as equipment malfunction, changes in the physical properties of the polishing fluid (viscosity, etc.) due to an increase in the temperature of the polishing pad, and changes in the surface condition of the polishing pad. When equipment malfunction is the cause, abnormal polishing fluid flow is often detected by flow sensors or similar devices. For example, if the liquid supply device is a nozzle with a single supply port, a flow sensor is installed at each nozzle. Furthermore, if the liquid supply device is a nozzle with multiple supply ports, a flow sensor is installed in the main flow path connected to the nozzle.

[0011] However, in the aforementioned liquid supply device with multiple supply ports, if any one of the supply ports becomes blocked, the flow rate change is distributed according to the number of supply ports. Therefore, the flow rate change in the main flow path is relatively small. Consequently, it will not be judged as a flow abnormality, and as a result, the blockage of the supply port may not be detected. Although there are solutions to configure multiple flow sensors at multiple supply ports, the number of flow sensors needs to increase with the increase in the number of supply ports, which inevitably leads to an increase in sensor installation space and sensor cost.

[0012] Furthermore, the abrasive pad wears down due to abrasion, and the distribution of the abrasive fluid on the abrasive pad surface changes due to deviations in the amount of wear within the abrasive pad surface. For example, if the dimensions (especially the groove depth) of the grooves formed within the abrasive pad surface decrease due to wear, even if the supply flow rate of the abrasive fluid is normal, the distribution of the abrasive fluid on the abrasive pad surface will change, leading to changes and deviations in the abrasive rate distribution. Moreover, these problems also exist when the liquid supplied to the abrasive surface is a pharmaceutical solution or pure water. [Summary of the Invention]

[0013] Therefore, the object of the present invention is to provide a polishing apparatus and polishing method capable of monitoring the distribution of liquids such as polishing fluid and chemical solutions on the polishing surface of a polishing pad, and polishing wafers and other workpieces under appropriate polishing conditions based on the monitored liquid distribution. Technical means for solving the technical problem

[0014] In one embodiment, a grinding apparatus grinds a workpiece. The grinding apparatus comprises: a grinding table supporting a grinding pad; a grinding head pressing the workpiece against the grinding surface of the grinding pad; a liquid supply device supplying liquid to the grinding surface; a grinding table rotation device rotating the grinding table; a grinding head rotation device rotating the grinding head; a liquid monitoring device acquiring optical information contained in light from multiple points on the grinding surface; an optical information analysis unit determining the distribution of the amount of liquid on the grinding surface based on the optical information; and an operation control unit controlling the operation of the grinding apparatus.

[0015] In one embodiment, the motion control unit is configured to send an instruction to the liquid monitoring device before supplying the liquid, causing the liquid monitoring device to acquire first optical information of multiple points on the grinding surface; further, when supplying the liquid, the instruction is sent to the liquid monitoring device to acquire second optical information of multiple points on the grinding surface; the optical information analysis unit is configured to determine a first distribution based on the first optical information, determine a second distribution based on the second optical information, and determine the distribution of the liquid quantity by subtracting the first distribution from the second distribution. In another embodiment, the motion control unit is configured to send an instruction to the liquid monitoring device to acquire the optical information of multiple points on the grinding surface at multiple times during the grinding of the workpiece; the optical information analysis unit is configured to acquire the temporal progression of the distribution of the liquid quantity on the grinding surface based on the optical information of the multiple points on the grinding surface acquired at the multiple times.

[0016] In one embodiment, the motion control unit is configured to send an instruction to the liquid monitoring device during an interval before or after grinding the workpiece, causing the liquid monitoring device to acquire the optical information. In one embodiment, the motion control unit is configured to send an instruction to the liquid monitoring device, causing the liquid monitoring device to acquire initial optical information from multiple points on the grinding surface of the grinding pad in an unused state and current optical information from multiple points on the grinding surface of the grinding pad in use. The optical information analysis unit determines the initial distribution of the liquid volume based on the initial optical information and determines the current distribution of the liquid volume on the grinding surface based on the current optical information. The motion control unit is configured to calculate the difference between the initial distribution and the current distribution. In one embodiment, the motion control unit is configured to send an instruction to the liquid supply device, during the period when the liquid monitoring device acquires the optical information, causing the liquid supply device to supply a liquid of a different type than the grinding fluid used in the grinding of the workpiece to the grinding surface of the grinding pad.

[0017] In one embodiment, the polishing apparatus further includes a light source that illuminates the polishing surface with light having one or more wavelengths in the range of 200 nm to 1100 nm. In one embodiment, the liquid monitoring device includes a light detection sensor that measures the amount of light having one or more wavelengths in the range of 200 nm to 1100 nm. In one embodiment, the optical information analysis unit is configured to determine the distribution of the amount of liquid on the polishing surface based on the measured light amount data. In one embodiment, the liquid monitoring device includes an image sensor that generates a color image. In one embodiment, the optical information analysis unit is configured to determine the distribution of the amount of liquid on the polishing surface by analyzing the color distribution, which is optical information, appearing on the color image. In one embodiment, the liquid monitoring device is configured to acquire optical information of the plurality of points located upstream of the polishing head in the rotation direction of the polishing table.

[0018] In one embodiment, the motion control unit is configured to calculate the difference between multiple distributions of the liquid volume on the grinding surface determined at multiple moments during the grinding of the workpiece, and if the difference in distribution is greater than an allowable value, change the grinding conditions for the workpiece in the direction that the difference in distribution decreases. In one embodiment, the motion control unit is configured to, after changing the grinding conditions, recalculate the difference between the multiple distributions of the liquid volume determined during the grinding of the workpiece, and if the difference in distribution is greater than an allowable value, stop the operation of the grinding device before grinding the next workpiece. In one embodiment, the motion control unit is configured to calculate the difference between multiple distributions of the liquid volume determined at multiple moments during the grinding of the workpiece, and if the difference in distribution is greater than an allowable value, stop the operation of the grinding device before grinding the next workpiece. In one embodiment, the motion control unit is configured to calculate the difference between multiple distributions of the liquid volume determined at multiple moments during the grinding of the workpiece, and if the difference in distribution is greater than an allowable value, change the pressure of the grinding head on the workpiece.

[0019] In one embodiment, the motion control unit is configured to change the grinding conditions for the workpiece to decrease in the direction of decreasing the difference in the distribution when the difference between the initial distribution and the current distribution of the liquid volume on the grinding surface is greater than a threshold. In one embodiment, the grinding apparatus is configured to, after changing the grinding conditions, recalculate the difference between the initial distribution and the newly determined current distribution of the liquid volume, and stop the grinding operation of the grinding apparatus before grinding the next workpiece when the difference in the distribution is greater than the threshold. In one embodiment, the motion control unit is configured to stop the grinding operation of the grinding apparatus before grinding the next workpiece when the difference between the initial distribution and the current distribution of the liquid volume on the grinding surface is greater than a threshold. In one embodiment, the motion control unit is configured to determine that an abnormality has occurred in the grinding apparatus when the distribution of the liquid volume on the grinding surface is lower than a preset threshold distribution of the liquid volume. In one embodiment, the liquid is one of grinding fluid, pure water, medicinal solution, and colored water.

[0020] In one embodiment, a grinding method is used to grind a workpiece. The grinding method involves rotating a grinding table and a grinding head that support a grinding pad, and pressing the workpiece against the grinding surface of the grinding pad with the grinding head to grind the workpiece. Before, during, or after grinding the workpiece, liquid is supplied to the grinding surface while acquiring optical information contained in light from multiple points on the grinding surface, and the distribution of the amount of liquid on the grinding surface is determined based on the optical information.

[0021] In one embodiment, the distribution of the liquid amount is determined by subtracting a first distribution from a second distribution. The first distribution is determined based on first optical information of multiple points on the grinding surface acquired before the liquid is supplied, and the second distribution is determined based on second optical information of multiple points on the grinding surface acquired during the supply of the liquid. In one embodiment, the step of acquiring the optical information is a step of acquiring the optical information of multiple points on the grinding surface at multiple moments during the grinding of the workpiece while supplying liquid to the grinding surface, and the step of determining the distribution of the liquid amount is a step of obtaining the temporal progression of the distribution of the liquid amount on the grinding surface based on the optical information of multiple points on the grinding surface acquired at the multiple moments.

[0022] In one embodiment, the step of acquiring the optical information is a step of acquiring the optical information while supplying liquid to the polishing surface during an interval before or after polishing the workpiece. In one embodiment, the polishing method further includes the following steps: acquiring initial optical information of multiple points on the polishing surface while supplying liquid to the polishing surface of the polishing pad in an unused state, acquiring current optical information of multiple points on the polishing surface while supplying liquid to the polishing surface of the polishing pad in use, determining an initial distribution of the amount of liquid on the polishing surface based on the initial optical information, determining a current distribution of the amount of liquid on the polishing surface based on the current optical information, and calculating the difference between the initial distribution and the current distribution.

[0023] In one embodiment, the liquid supplied to the polishing surface of the polishing pad during the acquisition of the optical information is a different type of liquid from the polishing slurry used in the workpiece being polished. In one embodiment, the optical information is the amount of light from the polishing surface. In one embodiment, the optical information is the color distribution of the polishing surface. In one embodiment, the step of acquiring the optical information is the step of acquiring optical information of the plurality of points located upstream of the polishing head in the rotation direction of the polishing table.

[0024] In one embodiment, the grinding method further includes the steps of: calculating the difference between multiple distributions of the liquid volume determined at multiple moments during the grinding of the workpiece, and, if the difference in distributions is greater than an allowable value, changing the grinding conditions for the workpiece in the direction where the difference in distributions decreases. In one embodiment, the grinding method further includes the steps of: after changing the grinding conditions, recalculating the difference between multiple distributions of the liquid volume determined at multiple moments during the grinding of the workpiece, and, if the difference in distributions is greater than an allowable value, stopping the operation of the grinding device before grinding the next workpiece. In one embodiment, the grinding method further includes the steps of: calculating the difference between multiple distributions of the liquid volume determined at multiple moments during the grinding of the workpiece, and, if the difference in distributions is greater than an allowable value, stopping the operation of the grinding device before grinding the next workpiece. In one embodiment, the grinding method further includes the steps of: calculating the difference between multiple distributions of the liquid volume determined at multiple moments during the grinding of the workpiece, and, if the difference in distributions is greater than an allowable value, changing the pressure applied by the grinding head to the workpiece.

[0025] In one embodiment, the grinding method further includes the step of: if the difference between the initial distribution and the current distribution of the liquid volume on the grinding surface is greater than a threshold, changing the grinding conditions for the workpiece to decrease in the direction of the difference in distribution. In one embodiment, the grinding method further includes the step of: after changing the grinding conditions, recalculating the difference between the initial distribution and the newly determined current distribution of the liquid volume on the grinding surface, and if the difference in distribution is greater than the threshold, stopping the operation of the grinding device before grinding the next workpiece. In one embodiment, the grinding method further includes the step of: if the difference between the initial distribution and the current distribution of the liquid volume on the grinding surface is greater than a threshold, stopping the operation of the grinding device before grinding the next workpiece. In one embodiment, the grinding method further includes the step of: if the distribution of the liquid volume is lower than a preset threshold distribution of the liquid volume, determining that an abnormality has occurred in the grinding device. In one embodiment, the liquid is one of grinding fluid, pure water, pharmaceutical solution, and colored water. Effects of the Invention

[0026] According to the present invention, the distribution of liquids such as polishing slurry and chemical solution on the polishing pad can be monitored. In addition, by feeding back the monitoring result to the operation of the polishing apparatus, the workpiece such as a wafer can be polished under appropriate polishing conditions.

Implementation Method

[0028] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG1 is a perspective view schematically showing one embodiment of the polishing apparatus. As shown in FIG1, the polishing apparatus includes: a polishing table 5 supporting a polishing pad 2 having a polishing surface 2a; a polishing head 7 pressing a wafer, which is the workpiece to be polished, against the polishing surface 2a; a liquid supply device 8 supplying a liquid such as polishing slurry to the polishing surface 2a; a liquid monitoring device 12 acquiring optical information contained in the light from the polishing surface 2a; an optical information analysis unit 13 determining the distribution of the amount of liquid on the polishing surface 2a based on the optical information acquired by the liquid monitoring device 12; and an operation control unit 47 controlling the operation of the polishing apparatus.

[0029] The grinding head 7 is configured to hold the wafer W on its lower surface by vacuum adsorption or the like. In this embodiment, the wafer W is circular. The object being ground can be any workpiece used in the manufacture of semiconductor devices, and is not limited to a wafer. Other examples of objects being ground include square wafers, substrates, panels, etc.

[0030] The grinding apparatus further includes: a support shaft 14; a grinding head swing arm 16 connected to the upper end of the support shaft 14 and swinging the grinding head 7; a grinding head shaft 18 rotatably supported on the free end of the grinding head swing arm 16; and a grinding head rotating device 20 for rotating the grinding head 7 around its axis. The grinding head rotating device 20 is fixed to the grinding head swing arm 16 and connected to the grinding head shaft 18 via a torque transmission mechanism (not shown) consisting of a belt and pulleys, etc. The grinding head 7 is connected to the lower end of the grinding head shaft 18. The grinding head rotating device 20 rotates the grinding head shaft 18 via the aforementioned torque transmission mechanism, and the grinding head 7 and the grinding head shaft 18 rotate together. Thus, the grinding head 7 rotates in the direction indicated by the arrow around its axis via the grinding head rotating device 20. As a specific example of the grinding head rotating device 20, an electric motor can be cited.

[0031] The grinding head shaft 18 can move up and down relative to the grinding head swing arm 16 via a lifting mechanism (not shown). Through the up and down movement of the grinding head shaft 18, the grinding head 7 can move up and down relative to the grinding head swing arm 16.

[0032] The grinding apparatus also includes a grinding table rotation device 21, which rotates the grinding pad 2 and the grinding table 5 about their axes. The grinding table 5 is connected to the grinding table rotation device 21 via a table shaft 5a. The grinding table 5 and the grinding pad 2 rotate about the table shaft 5a in the direction indicated by the arrow via the grinding table rotation device 21. The grinding pad 2 is attached to the upper surface of the grinding table 5. The upper surface of the grinding pad 2 forms the grinding surface 2a of the wafer W. As a specific example of the grinding table rotation device 21, an electric motor can be cited.

[0033] The liquid supply device 8 includes: a liquid nozzle 9 having a supply port 9a at its top; a nozzle swinging mechanism 10 for swinging the supply port 9a of the liquid nozzle 9 in the radial direction of the grinding pad 2; a first liquid supply line 25 and a second liquid supply line 27 connected to the liquid nozzle 9; and a first flow control valve 31 and a second flow control valve 32 respectively installed on the first liquid supply line 25 and the second liquid supply line 27. The first liquid supply line 25 is a line for supplying the grinding fluid (typically a slurry) as the first liquid to the liquid nozzle 9, and the second liquid supply line 27 is a line for supplying the liquid nozzle 9 with a liquid of a different type than the first liquid (e.g., pure water, pharmaceutical solution, or colored water).

[0034] The first flow control valve 31 and the second flow control valve 32 are connected to the action control unit 47, and the operation of the first flow control valve 31 and the second flow control valve 32 is controlled by the action control unit 47. When the second flow control valve 32 is closed, and the action control unit 47 opens the first flow control valve 31, a first liquid (grinding slurry) is supplied to the grinding surface 2a of the grinding pad 2. When the first flow control valve 31 is closed, and the action control unit 47 opens the second flow control valve 32, a second liquid (different from the grinding slurry) is supplied to the grinding surface 2a of the grinding pad 2.

[0035] The polishing of wafer W is performed as follows. Polishing fluid is supplied to the polishing surface 2a of polishing pad 2 from the liquid nozzle 9 of liquid supply device 8 while the polishing head 7 and polishing table 5 are rotated. An example of polishing fluid supplied to polishing pad 2 is a slurry containing abrasive grains. Polishing pad 2 rotates integrally with polishing table 5 around its axis. Polishing head 7 is lowered to a predetermined polishing position via a lifting mechanism (not shown). Then, at the polishing position, polishing head 7 presses wafer W against the polishing surface 2a of polishing pad 2 with a predetermined pressure. With polishing fluid present on the polishing surface 2a of polishing pad 2, wafer W is brought into sliding contact with the polishing surface 2a of polishing pad 2. The surface of wafer W is polished by a combination of the chemical action of the polishing fluid supplied to polishing surface 2a and the mechanical action of the abrasive grains contained in the polishing fluid and / or polishing pad 2.

[0036] The optical information analysis unit 13 includes a storage device 13a storing a program and a processing unit 13b executing operations according to the commands contained in the program. The storage device 13a includes a main storage device such as 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 processing unit 13b include a CPU (central processing unit) and a GPU (graphics processing unit). However, the specific structure of the optical information analysis unit 13 is not limited to this embodiment.

[0037] The motion control unit 47 includes a storage device 47a storing a program and a computing device 47b executing operations according to the commands contained in the program. The storage device 47a includes a main storage device such as random access memory (RAM) and an auxiliary storage device such as a hard disk drive (HDD) or a solid-state drive (SSD). Examples of computing devices 47b include a CPU (central processing unit) and a GPU (graphics processing unit). However, the specific structure of the motion control unit 47 is not limited to this embodiment.

[0038] The optical information analysis unit 13 and the motion control unit 47 can each be composed of one computer or multiple computers. Alternatively, the optical information analysis unit 13 and the motion control unit 47 can also be composed of one computer. The optical information analysis unit 13 and the motion control unit 47 may not be physically independent and can be virtually constructed using at least one computer.

[0039] A liquid monitoring device 12 is disposed above the polishing pad 2, facing the polishing surface 2a. More specifically, the liquid monitoring device 12 is configured to acquire optical information contained in the light from the monitoring area M, which is at least upstream of the polishing head 7 in the rotational direction of the polishing table 5 and the polishing pad 2. The monitoring area M extends along the radial direction of the polishing pad 2. In one embodiment, multiple monitoring areas may be provided. These monitoring areas extend along the radial direction of the polishing pad 2 and are arranged circumferentially along the polishing pad 2. One of the multiple monitoring areas, as indicated by the label M in FIG1, is located upstream of the polishing head 7.

[0040] The polishing apparatus also includes a light source 40, which illuminates the polishing surface 2a of the polishing pad 2 with light having one or more wavelengths in the range of 200nm to 1100nm. The light source 40 is configured to emit at least visible light, for example, and includes a light-emitting diode. The light source 40 preferably illuminates the polishing surface 2a of the polishing pad 2 uniformly. For example, the light source 40 may have multiple light-emitting diodes, or it may have a light-dispersing plate. The light source 40 is configured to illuminate light uniformly at least toward the monitoring area M.

[0041] Figure 2 is a cross-sectional view of the grinding head 7 shown in Figure 1. The grinding head 7 includes a carrier 71 fixed to the grinding head shaft 18 and a retainer ring 72 disposed below the carrier 71. A flexible membrane (elastic membrane) 74, which abuts against the wafer W, is held at the lower part of the carrier 71. Four pressure chambers G1, G2, G3, and G4 are formed between the membrane 74 and the carrier 71. The pressure chambers G1, G2, G3, and G4 are formed by the membrane 74 and the carrier 71. The central pressure chamber G1 is circular, and the other pressure chambers G2, G3, and G4 are annular. These pressure chambers G1, G2, G3, and G4 are arranged concentrically. In one embodiment, more than five pressure chambers may be provided, or less than three pressure chambers may be provided.

[0042] Compressed gases, such as compressed air, are supplied to pressure chambers G1, G2, G3, and G4 from the gas supply source 77 via fluid paths F1, F2, F3, and F4, respectively. The wafer W is pressed against the polishing surface 2a of the polishing pad 2 by a diaphragm 74. More specifically, the pressure of the compressed gases in pressure chambers G1, G2, G3, and G4 acts on the wafer W via the diaphragm 74, pressing the wafer W against the polishing surface 2a. The internal pressures of pressure chambers G1, G2, G3, and G4 can be independently varied, thereby allowing independent adjustment of the polishing pressure on four corresponding regions of the wafer W: the central portion, the inner middle portion, the outer middle portion, and the periphery.

[0043] An annular rolling diaphragm 76 is disposed between the carrier 71 and the retaining ring 72, and a pressure chamber G5 is formed inside the rolling diaphragm 76. The pressure chamber G5 is connected to the gas supply source 77 via a fluid passage F5. The gas supply source 77 supplies compressed gas into the pressure chamber G5, and the compressed gas in the pressure chamber G5 presses the retaining ring 72 against the grinding surface 2a of the grinding pad 2 via the rolling diaphragm 76.

[0044] The peripheral end of the wafer W and the lower surface of the diaphragm 74 (i.e., the wafer pressing surface) are surrounded by a retaining ring 72. During the polishing of the wafer W, the retaining ring 72 presses the polishing surface 2a of the polishing pad 2 on the outside of the wafer W, thereby preventing the wafer W from flying out of the polishing head 7 during polishing.

[0045] Fluid paths F1, F2, F3, F4, and F5 extend from pressure chambers G1, G2, G3, G4, and G5 to gas supply source 77. Pressure regulators R1, R2, R3, R4, and R5 are respectively installed in fluid paths F1, F2, F3, F4, and F5. Compressed gas is supplied from gas supply source 77 to pressure chambers G1 to G5 through pressure regulators R1 to R5 and fluid paths F1 to F5.

[0046] Pressure regulators R1, R2, R3, R4, and R5 are configured to control the pressure within pressure chambers G1, G2, G3, G4, and G5. Pressure regulators R1, R2, R3, R4, and R5 are connected to an action control unit 47. The action control unit 47 is configured to generate target pressure values ​​for each pressure chamber G1 to G5. The action control unit 47 sends the target pressure values ​​to the pressure regulators R1 to R5, thereby causing the pressure regulators R1 to R5 to operate in a manner where the pressure within pressure chambers G1 to G5 matches the corresponding target pressure value.

[0047] Figure 3 is a top view of the polishing pad 2, the liquid supply device 8, and the polishing head 7. As shown in Figure 3, the polishing slurry is supplied from the liquid nozzle 9 of the liquid supply device 8 to the area near the center of the polishing surface 2a of the polishing pad 2. The polishing slurry on the rotating polishing pad 2 expands outward in the radial direction due to centrifugal force and comes into contact with the wafer W held in the polishing head 7. After the polishing slurry is initially supplied, it has not yet fully expanded on the polishing surface 2a. Therefore, typically, after a preset time has elapsed since the start of the polishing slurry supply, the polishing head 7 presses the wafer W against the polishing surface 2a.

[0048] The liquid monitoring device 12 is configured to acquire optical information contained in the light from the polishing surface 2a of the polishing pad 2 and the light from the liquid (e.g., polishing slurry) present on the polishing surface 2a. Specific examples of the optical information include the color of the polishing surface 2a and the liquid (i.e., the color distribution on the polishing surface 2a), the amount of light from the polishing surface 2a and the liquid, etc. In this embodiment, the liquid monitoring device 12 includes an image sensor that generates a color image. Examples of image sensors include CCD sensors, CMOS sensors, etc. The liquid monitoring device 12 is configured to generate a color image of the monitoring area M within the polishing surface 2a and acquire the color distribution as optical information appearing on the color image.

[0049] Typically, the polishing slurry and the polishing pad 2 have different colors. Therefore, the polishing slurry present on the polishing surface 2a of the polishing pad 2 can be visually identified from the polishing surface 2a. The optical information analysis unit 13 is connected to the liquid monitoring device 12 and acquires a color image from the liquid monitoring device 12. Furthermore, the optical information analysis unit 13 performs image processing on the color image to determine the distribution of the amount of polishing slurry present on the polishing surface 2a. More specifically, the optical information analysis unit 13 determines the color image based on the liquid color index value representing the concentration of the polishing slurry color within the monitoring area M, and creates a polishing slurry amount distribution curve representing the amount of polishing slurry expressed by the liquid color index value at each location within the monitoring area M.

[0050] Figure 4 is an example of a polishing slurry volume distribution curve. In Figure 4, the vertical axis represents the amount of slurry corresponding to the liquid color index value, and the horizontal axis represents the position within the monitoring area M. In the example shown in Figure 4, the position represented by the horizontal axis is the position in the radial direction of the polishing pad 2. The liquid color index value varies depending on the amount of polishing slurry present on the polishing surface 2a, therefore the liquid color index value is equivalent to the amount of polishing slurry. The vertical axis of Figure 4 represents the amount of polishing slurry expressed using the liquid color index value.

[0051] The liquid color index value varies according to the color model (or color space) that defines the color within the color image. Examples of color models used to quantitatively represent color include RGB, CMY, CMYK, HSL, HSV, etc.

[0052] The liquid color index value can be a single value from among the multiple components that define each color model. For example, the RGB color model uses R (red), G (green), and B (blue) as primary colors, but the liquid color index value can also be represented by the value of any one of these three components. In one example, each of the components R (red), G (green), and B (blue) is represented by a value in the range of 0 to 255. By applying only one component, the polishing fluid on the polishing surface 2a can be detected with good accuracy.

[0053] In one embodiment, the optical information analysis unit 13 may use composite values ​​such as lightness and brightness, in addition to the components of the color model (or color space) described above, to determine the liquid color index value. Lightness is the average of the maximum and minimum values ​​of each component of RGB, and brightness is the brightness perceived by the human eye, calculated as red component (R) × 0.21 + green component (G) × 0.72 + blue component (B) × 0.07. In this way, the optical information analysis unit 13 can determine the relative distribution of the polishing slurry on the polishing pad 2 by analyzing a color image reflecting the density of the polishing slurry on the polishing pad 2. Alternatively, the optical information analysis unit 13 may be configured to acquire data in advance representing the relationship between the thickness and color of the polishing slurry film, and determine the film thickness distribution of the polishing slurry present on the polishing surface 2a based on the color image.

[0054] When the color of the polishing slurry is similar to the color of the polishing pad 2, or when the polishing slurry is transparent, it is difficult to determine the distribution of the amount of polishing slurry on the polishing pad 2 by processing a color image. Therefore, in one embodiment, the liquid monitoring device 12 replaces the image sensor that generates the color image with a light detection sensor that measures the amount of light, which is another example of optical information. In one example, the light detection sensor is configured to measure the amount of light with a wavelength in the range of 200 nm to 1100 nm. As an example of a light detection sensor, a photodiode can be cited.

[0055] The liquid monitoring device 12, equipped with a light detection sensor, measures the amount of light reflected from the polishing slurry within the monitoring area M and sends this measurement data to the optical information analysis unit 13. The optical information analysis unit 13 is configured to determine the distribution of polishing slurry on the polishing surface 2a based on the light amount measurement data. In areas where polishing slurry exists on the polishing surface 2a of the polishing pad 2, light is easily reflected by the polishing slurry, resulting in an increased light amount. Therefore, the optical information analysis unit 13 can determine the distribution of polishing slurry on the polishing surface 2a based on the light amount measurement data obtained by the liquid monitoring device 12.

[0056] Figure 5 is an example of a graph showing the distribution curve of the polishing slurry. In Figure 5, the vertical axis represents the amount of liquid equivalent to the amount of light reflected from the polishing slurry, and the horizontal axis represents the position within the monitoring area M. In the example shown in Figure 5, the position represented by the horizontal axis is the position in the radial direction of the polishing pad 2. The amount of light reflected from the polishing slurry varies depending on the presence or absence of polishing slurry on the polishing surface 2a, and therefore the amount of light is equivalent to the amount of polishing slurry present on the polishing surface 2a. The vertical axis of Figure 5 represents the amount of polishing slurry represented by the amount of light.

[0057] In one embodiment, the light detection sensor of the liquid monitoring device 12 can be an infrared sensor. The polishing surface 2a and the polishing slurry emit infrared rays that depend on these temperatures. During the polishing of the wafer W, the temperature of the polishing surface 2a of the polishing pad 2 rises through sliding contact with the wafer W. In contrast, the temperature of the polishing slurry is approximately room temperature. Therefore, there is a temperature difference between the polishing surface 2a and the polishing slurry. The intensity of the infrared rays emitted from the polishing surface 2a and the polishing slurry varies depending on these temperatures. The liquid monitoring device 12, equipped with an infrared sensor, measures the intensity of the infrared rays within the monitoring area M and sends this measurement data to the optical information analysis unit 13. The optical information analysis unit 13 determines the distribution of the amount of polishing slurry on the polishing surface 2a based on the measurement data of the intensity of the infrared rays. The intensity of the infrared rays is equivalent to the amount of polishing slurry present on the polishing surface 2a. When using an infrared sensor, the light source 40 shown in FIG1 can also be omitted.

[0058] When the color of the polishing slurry is close to the color of the polishing pad 2, or when the polishing slurry is transparent, colored water can be used and the distribution of colored water on the polishing surface 2a can be analyzed during the interval before or after polishing of the wafer W, such as when the polishing apparatus is idling. More specifically, during the interval before or after polishing of the wafer W, the operation control unit 47 closes the first flow control valve 31 shown in FIG. 1 and opens the second flow control valve 32, thereby supplying colored water as a second liquid from the liquid supply device 8 to the polishing surface 2a of the polishing pad 2. Examples of colored water include black water containing carbon, etc. The operation control unit 47 issues a command to the liquid monitoring device 12 to acquire optical information contained in the light from the polishing surface 2a and the colored water. More specifically, the liquid monitoring device 12 generates a color image of the colored water on the polishing surface 2a and sends the color image to the optical information analysis unit 13. The optical information analysis unit 13 can determine the distribution of colored water on the polishing surface 2a by analyzing the color image. Furthermore, the distribution of optical information (e.g., brightness values) obtained based on the color of the colored water and the polishing surface 2a of the polishing pad 2 may be inversely related to the actual liquid volume distribution. In this case, the liquid volume distribution can be determined using data that has undergone data processing such as inverted brightness values.

[0059] As the liquid supplied during the interval, pure water can also be used instead of colored water. During the interval before or after polishing the wafer W, the operation control unit 47 closes the first flow control valve 31 shown in FIG. 1 and opens the second flow control valve 32, thereby supplying pure water as a second liquid from the liquid supply device 8 to the polishing surface 2a of the polishing pad 2. In this case, according to a different embodiment than described above, the liquid monitoring device 12 measures the amount of light reflected from the pure water within the monitoring area M and sends this measurement data to the optical information analysis unit 13, which determines the distribution of pure water on the polishing surface 2a based on the light measurement data.

[0060] Furthermore, the liquid supplied during the interval can be a medicinal solution instead of colored water. In this case, the distribution of the amount of medicinal solution on the grinding surface 2a is determined in the same manner as in the embodiment described above.

[0061] Polishing slurries used in wafer polishing are generally expensive. According to the above embodiment, which uses colored water, pure water, or chemical solution instead of polishing slurry, the cost required to determine the distribution of liquid amount on the polishing surface 2a can be reduced.

[0062] Depending on the grinding process, the grinding products may color the grinding surface 2a of the grinding pad 2. For example, in copper grinding, the grinding surface 2a of the grinding pad 2 is colored because copper ions in the grinding products mix with the grinding liquid, and may form a color contrast with the liquid such as the grinding liquid supplied by the liquid supply device 8. The liquid monitoring device 12 generates a color image of the colored grinding surface 2a, and the optical information analysis unit 13 determines the color distribution of the grinding surface 2a based on the color image, so that the color distribution can also be used as the distribution of the amount of liquid on the grinding pad 2.

[0063] In the polishing of wafer W, it is preferable that the polishing slurry is uniformly distributed on the polishing surface 2a. This is because the polishing rate of the film on wafer W varies depending on the amount of polishing slurry present on the polishing surface 2a. Therefore, the operation control unit 47 is configured to issue a command to the liquid monitoring device 12, causing the liquid monitoring device 12 to acquire optical information (e.g., generate multiple color images) of the polishing surface 2a at multiple moments during the polishing of wafer W. The optical information analysis unit 13 is configured to obtain the time progression of the polishing slurry amount distribution by analyzing the optical information acquired at the aforementioned multiple moments.

[0064] If the distribution of polishing slurry on polishing surface 2a changes during the polishing of wafer W, the motion control unit 47 can also change the polishing conditions for wafer W to restore the distribution of polishing slurry. More specifically, the motion control unit 47 calculates the differences between multiple distributions of polishing slurry determined at multiple moments during the polishing of wafer W. If the distribution difference is greater than an allowable value, it determines that the distribution of polishing slurry is abnormal and changes the polishing conditions in the direction of reducing the distribution difference. For example, the motion control unit 47 reduces the above-mentioned distribution difference by changing at least one of the rotational speed of polishing head 7, the rotational speed of polishing table 5, the flow rate of polishing slurry supplied from liquid supply device 8, and the oscillation of liquid nozzle 9. Through such operation, unexpected changes in the polishing rate and polishing rate distribution of wafer W can be prevented.

[0065] Figures 6(a) and 6(b) are graphs showing the distribution of polishing slurry volume during the polishing of a wafer W. As shown in Figure 6(a), during the polishing of wafer W, the current distribution of polishing slurry volume may decrease depending on the initial distribution of polishing slurry volume at the start of polishing. The motion control unit 47 calculates the difference between these distributions of polishing slurry. If the difference exceeds an allowable value, the motion control unit 47 changes the polishing conditions for wafer W in the direction of decreasing difference, as shown in Figure 6(b). For example, the motion control unit 47 increases the opening of the first flow control valve 31 to increase the flow rate of polishing slurry supplied to the polishing surface 2a. If the distribution of polishing slurry volume is biased towards the inner or outer periphery of the polishing pad 2, the motion control unit 47 may also issue a command to the polishing table rotation device 21 to increase or decrease the rotation speed of the polishing table 5.

[0066] In one embodiment, after a predetermined time has elapsed since the polishing conditions of the polishing apparatus were changed by the motion control unit 47, the optical information analysis unit 13 determines the current distribution of polishing fluid volume again during the polishing of the wafer W. The motion control unit 47 calculates the difference between the distribution of polishing fluid volume at the start of polishing of the wafer W and the distribution of the current polishing fluid volume determined again. If the distribution difference is greater than the above-mentioned allowable value, the operation of the polishing apparatus can be stopped before polishing the next wafer.

[0067] Moreover, in one embodiment, the motion control unit 47 may calculate the difference between multiple distributions of the amount of polishing fluid determined at multiple times during the polishing of wafer W, and if the distribution difference is greater than the allowable value, without changing the polishing conditions of wafer W, stop the operation of the polishing device before polishing the next wafer.

[0068] Furthermore, in one embodiment, the motion control unit 47 may calculate the differences in the distribution of polishing slurry volume determined at multiple moments during the polishing of wafer W, and if the distribution difference exceeds an allowable value, change the pressing pressure of the polishing head 7 on wafer W. As shown in FIG6(a), if the distribution of polishing slurry volume decreases during the polishing of wafer W, it is anticipated that the polishing rate of wafer W will decrease due to the decrease in polishing slurry volume. Therefore, the motion control unit 47 increases the pressing pressure of the polishing head 7 on wafer W to compensate for the decrease in polishing rate. Specifically, the motion control unit 47 issues a command to at least one of the pressure regulators R1 to R4 shown in FIG2, thereby increasing the pressure in at least one of the pressure chambers G1 to G4 of the polishing head 7. As a result, the polishing head 7 can press the wafer W against the polishing pad 2 with a higher pressing pressure, and can maintain the desired polishing rate.

[0069] During grinding, the main reasons for changes in the distribution of the grinding fluid on the grinding surface 2a of the grinding pad 2 can be listed as changes in the physical properties (viscosity, etc.) of the grinding fluid caused by equipment failure, temperature rise of the grinding pad 2, and surface condition of the grinding pad 2. In the case of equipment failure, the equipment failure can be detected by monitoring the distribution of the grinding fluid on the grinding pad 2.

[0070] In one embodiment, the motion control unit 47 may be configured to determine that an abnormality has occurred in the grinding apparatus when the distribution of liquid (e.g., grinding slurry, pure water, pharmaceutical solution, or colored water) is lower than a preset threshold distribution. For example, as shown in FIG7, when the overall distribution of liquid volume is lower than a preset threshold distribution (or reference distribution), it may be considered that the cause is blockage of the liquid nozzle 9 or the first liquid supply line 25 (see FIG1). The motion control unit 47 may also generate an alarm signal when the liquid volume distribution is lower than the preset threshold distribution.

[0071] The liquid nozzle 9 shown in FIG1 has a supply port 9a at its tip, but in another embodiment, the liquid nozzle 9 may also have multiple supply ports arranged along the radial direction of the abrasive pad 2. In this case, the liquid nozzle 9 can easily form a uniform film of liquid on the abrasive surface 2a of the abrasive pad 2. However, when any one of the multiple supply ports is blocked, the distribution of liquid volume is locally reduced. On the other hand, the overall flow rate of the liquid caused by the blockage of such a supply port hardly changes. Therefore, it is difficult to detect the blockage of a supply port based on the change in flow rate. According to the above embodiment of monitoring the distribution of liquid volume, as shown in FIG8, when the distribution of liquid volume is lower than the threshold distribution, the action control unit 47 determines that an abnormality has occurred, and thus it is possible to detect partial blockage of the liquid nozzle 9.

[0072] Typically, multiple grooves for controlling the flow of polishing slurry are formed on the polishing surface 2a of the polishing pad 2. As the polishing pad 2 polishes a large number of wafers, the depth of the grooves on the polishing surface 2a gradually becomes shallower. As a result, even if the flow rate of polishing slurry supplied from the liquid supply device 8 does not change, the distribution of the amount of polishing slurry on the polishing surface 2a may change.

[0073] Therefore, in order to investigate the temporal variation of the polishing slurry volume distribution, in the embodiments described below, the slurry volume distribution when the polishing pad 2 is unused is compared with the slurry volume distribution when the polishing pad 2 is in use. More specifically, the motion control unit 47 is configured to issue a command to the slurry monitoring device 12, causing the slurry monitoring device 12 to acquire initial optical information of the polishing surface 2a of the polishing pad 2 in the unused state and current optical information of the polishing surface 2a of the polishing pad 2 after polishing. The polishing pad 2 in the unused state is a brand new polishing pad that has not been used for polishing wafers.

[0074] The liquid used can be any one of polishing slurry, pure water, medicinal solution, or colored water. However, polishing slurry is generally expensive, so the liquid used is preferably any one of pure water, medicinal solution, or colored water. Specific examples of optical information of the polishing surface 2a include the color distribution on the polishing surface 2a, the amount of light from the polishing surface 2a and the liquid, etc. As described above, the liquid monitoring device 12 includes an image sensor, a light detection sensor, an infrared sensor, etc. For example, the liquid monitoring device 12 generates an initial color image of the liquid on the polishing surface 2a of the polishing pad 2 in an unused state, and generates a recent color image of the liquid on the polishing surface 2a of the polishing pad 2 in use. Alternatively, the liquid monitoring device 12 measures the initial amount of light from the liquid on the polishing surface 2a of the polishing pad 2 in an unused state, and measures the recent amount of light from the liquid on the polishing surface 2a of the polishing pad 2 in use.

[0075] The optical information analysis unit 13 determines the initial distribution of liquid volume on the polishing surface 2a based on initial optical information (e.g., initial color image or initial light intensity measurement data), and determines the current distribution of liquid volume on the polishing surface 2a based on current optical information (e.g., most recent color image or most recent light intensity measurement data). Figure 9 is a graph showing the initial distribution of liquid volume on the polishing surface 2a and the current distribution of liquid volume on the polishing surface 2a. As shown in Figure 9, the distribution of liquid volume on the polishing surface 2a changes over time due to the wear of the polishing pad 2.

[0076] The motion control unit 47 receives data on the initial and current distribution of liquid volume on the polishing surface 2a from the optical information analysis unit 13 and stores it in the storage device 47a. The motion control unit 47 is configured to determine the state of the polishing pad 2 based on the difference between the initial and current distribution of liquid volume on the polishing surface 2a. More specifically, the motion control unit 47 is configured to calculate the difference between the initial and current distribution of liquid volume on the polishing surface 2a, and generate an alarm signal notifying the polishing pad 2 of wear if the difference exceeds a threshold.

[0077] The motion control unit 47 may also be configured to change the wafer polishing conditions in a direction that reduces the distribution difference when the difference between the initial distribution and the current distribution of liquid on the polishing surface 2a is greater than a threshold. More specifically, the motion control unit 47 reduces the aforementioned distribution difference by changing at least one of the rotational speed of the polishing head 7, the rotational speed of the polishing table 5, the flow rate of liquid supplied from the liquid supply device 8, and the oscillation of the liquid nozzle 9. Through such an operation, unexpected changes in the wafer polishing rate and polishing rate distribution can be prevented.

[0078] In one embodiment, after a predetermined time has elapsed since the motion control unit 47 changed the polishing conditions, the optical information analysis unit 13 determines the current distribution of liquid volume on the polishing surface 2a again. The motion control unit 47 calculates the difference between the initial distribution of liquid volume and the current distribution of liquid volume determined again. If the difference is greater than the threshold value mentioned above, the operation of the polishing apparatus is stopped before polishing the next wafer.

[0079] Furthermore, in one embodiment, if the difference between the initial distribution and the current distribution of liquid volume on the grinding surface 2a is greater than a threshold, the action control unit 47 may not change the grinding conditions of the wafer, but may stop the operation of the grinding device before grinding the next wafer.

[0080] Furthermore, in one embodiment, the motion control unit 47 may change the pressing pressure of the polishing head 7 on the wafer when the difference between the initial distribution and the current distribution of the liquid amount on the polishing surface 2a is greater than a threshold. As shown in FIG9, when the wear of the polishing pad 2 progresses, it is anticipated that the amount of polishing fluid on the polishing surface 2a of the polishing pad 2 will decrease, thereby causing a decrease in the polishing rate of the wafer. Therefore, the motion control unit 47 increases the pressing pressure of the polishing head 7 on the wafer to compensate for the decrease in the polishing rate. Specifically, the motion control unit 47 issues a command to at least one of the pressure regulators R1 to R4 shown in FIG2, thereby increasing the pressure in at least one of the pressure chambers G1 to G4 of the polishing head 7. As a result, the polishing head 7 can press the wafer against the polishing pad 2 with a higher pressing pressure, thus maintaining the desired polishing rate.

[0081] The allowable value and the threshold value for comparing the difference between the liquid quantity distribution on the polishing surface 2a and the distribution under normal conditions can also be determined based on the difference between the liquid quantity distribution under normal conditions and the distribution under normal conditions that has changed by a predetermined proportion, such as 10%. The liquid quantity distribution under normal conditions can be set, for example, the polishing rate profile of the wafer as the liquid quantity distribution under normal conditions.

[0082] Sometimes, due to manufacturing deviations in the abrasive pad 2, the distribution of liquid volume during normal operation may also be deviated. In this case, data on multiple liquid volume distributions during past normal operation can be stored in the storage device 47a of the motion control unit 47, and as shown in FIG10, the motion control unit 47 determines whether the aforementioned deviation exists within the range determined based on the data.

[0083] The allowable value and the threshold value, which are compared with the difference between the distribution of liquid volume on the grinding surface 2a, can also be automatically determined based on artificial intelligence (AI). For example, the liquid volume distribution data can be combined with information on consumable materials such as the grinding pad and liquid, and information on the occurrence of grinding abnormalities, and stored in the storage device 47a of the motion control unit 47. Furthermore, by using machine learning such as artificial intelligence (AI) to shift the liquid volume distribution of each combination of the grinding pad and liquid, if consumable material information is input into the motion control unit 47, the allowable value and the threshold value can be automatically set.

[0084] Furthermore, as shown in FIG11, in cases where the anomaly in the liquid volume distribution is localized and small, such anomalies may sometimes be difficult to detect correctly. In such cases, the normal / abnormal condition is determined based on the shape of the liquid volume distribution, rather than on tolerance values ​​or thresholds, thereby enabling accurate determination. Specifically, the liquid volume distribution at the time of the anomaly is recognized as anomaly data through machine learning by the motion control unit 47, thereby determining an anomaly when a similar liquid volume distribution is detected.

[0085] In the embodiments described so far, the optical information analysis unit 13 determines the distribution of liquid on the abrasive surface 2a of the abrasive pad 2 based on optical information (e.g., color in a color image, light intensity measurement data, etc.) acquired from the liquid monitoring device 12. However, although not shown, there are light-shielding objects above the abrasive pad 2, such as a trimmer for trimming (regenerating) the abrasive surface 2a of the abrasive pad 2 and a sprayer for cleaning the abrasive surface 2a. Furthermore, depending on the position of the light source 40, the amount of light reflected by the liquid on the abrasive pad 2 may also deviate. In addition, there is the color of the abrasive pad 2 itself and its deviation. The presence of such light-shielding objects, the influence of the light source 40, and the color and deviation of the abrasive pad 2 can hinder the optical information analysis unit 13 from determining the correct distribution of liquid on the abrasive surface 2a.

[0086] Therefore, in the embodiment described below, the motion control unit 47 is configured to issue a command to the liquid monitoring device 12 before supplying liquid, causing the liquid monitoring device 12 to acquire first optical information contained in the light from the polishing surface 2a of the polishing pad 2, and then issue a command to the liquid monitoring device 12 when supplying liquid, causing the liquid monitoring device 12 to acquire second optical information contained in the light from the polishing surface 2a. Furthermore, the optical information analysis unit 13 is configured to determine a first distribution based on the first optical information, and a second distribution based on the second optical information, and determine the distribution of the liquid quantity by subtracting the first distribution from the second distribution.

[0087] Figure 12(a) is a graph showing the first distribution obtained based on the first optical information of the grinding surface 2a acquired by the liquid monitoring device 12 before liquid supply. Figure 12(b) is a graph showing the second distribution obtained based on the second optical information of the grinding surface 2a acquired by the liquid monitoring device 12 during liquid supply. Figure 12(c) is a graph showing the distribution of liquid volume obtained by subtracting the first distribution from the second distribution. As shown in Figures 12(a) and 12(b), noise caused by light-blocking objects such as trimmers appears in both the first and second distributions. Therefore, as shown in Figure 12(c), by subtracting the first distribution from the second distribution, a liquid volume distribution with noise removed can be obtained.

[0088] The above-described embodiments are intended to enable those skilled in the art to implement the present invention. Various modifications of the above-described embodiments can naturally be implemented by those skilled in the art, and the technical concept of the present invention can also be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but should be interpreted as conforming to the maximum scope of the technical concept defined by the claims. [Simplified Explanation of the Diagram]

[0027] Figure 1 is a perspective view schematically showing one embodiment of the polishing apparatus. Figure 2 is a cross-sectional view of the polishing head shown in Figure 1. Figure 3 is a top view of the polishing pad, the liquid supply device, and the polishing head. Figure 4 is a diagram showing an example of a polishing slurry volume distribution curve. Figure 5 is a diagram showing an example of a polishing slurry volume distribution curve. Figures 6(a) and 6(b) are curves showing the distribution of polishing slurry volume as it changes during the polishing of a wafer. Figure 7 is a curve showing how an abnormality in the polishing apparatus leads to an overall decrease in the distribution of polishing slurry volume. Figure 8 is a curve illustrating the change in the distribution of liquid volume when one of the multiple supply ports is blocked. Figure 9 is a curve showing the initial distribution and the current distribution of liquid volume. Figure 10 is a curve illustrating an embodiment for determining whether the difference between the distributions of liquid volume is within a specified range. Figure 11 is a curve illustrating the change in the distribution of liquid volume when one of the multiple supply ports is blocked. Figure 12(a) is a graph showing the first distribution obtained based on the first optical information obtained before the liquid is supplied, Figure 12(b) is a graph showing the second distribution obtained based on the second optical information obtained during the liquid supply, and Figure 12(c) is a graph showing the distribution of liquid quantity obtained by subtracting the first distribution from the second distribution.

Claims

1. A grinding apparatus for grinding a workpiece, the grinding apparatus comprising: a grinding table supporting a grinding pad; A grinding head that presses the workpiece against the grinding surface of a grinding pad; A liquid supply device that supplies liquid to the grinding surface; A grinding table rotation device that rotates the grinding table; The device comprises: a grinding head rotation mechanism for rotating the grinding head; a liquid monitoring device for acquiring optical information contained in light from multiple points on the grinding surface; an optical information analysis unit for determining the distribution of the amount of liquid (hereinafter referred to as "the amount of liquid") on the grinding surface based on the optical information; and an operation control unit for controlling the operation of the grinding device. The operation control unit is configured to send a command to the liquid monitoring device before supplying the liquid, causing the liquid monitoring device to acquire first optical information from multiple points on the grinding surface, and further send a command to the liquid monitoring device when supplying the liquid, causing the liquid monitoring device to acquire second optical information from multiple points on the grinding surface. The optical information analysis unit is configured to determine a first distribution based on the first optical information, determine a second distribution based on the second optical information, and determine the distribution of the amount of liquid by subtracting the first distribution from the second distribution.

2. The grinding apparatus according to claim 1, wherein, The motion control unit is configured to send instructions to the liquid monitoring device to enable the liquid monitoring device to acquire optical information of multiple points on the grinding surface at multiple times during the grinding of the workpiece. The optical information analysis unit is configured to acquire the temporal shift of the distribution of the amount of liquid on the grinding surface based on the optical information of the multiple points on the grinding surface acquired at the multiple times.

3. The grinding apparatus according to claim 1, wherein, The motion control unit is configured to send a command to the liquid monitoring device during the interval before or after grinding the workpiece, so that the liquid monitoring device acquires the optical information.

4. A grinding apparatus for grinding a workpiece, the grinding apparatus comprising: a grinding table supporting a grinding pad; A grinding head that presses the workpiece against the grinding surface of a grinding pad; A liquid supply device that supplies liquid to the grinding surface; A grinding table rotation device that rotates the grinding table; The device comprises: a grinding head rotation device for rotating the grinding head; a liquid monitoring device for acquiring optical information contained in light from multiple points on the grinding surface; an optical information analysis unit for determining the distribution of the amount of liquid (hereinafter referred to as "the amount of liquid") on the grinding surface based on the optical information; and an action control unit for controlling the operation of the grinding device. The action control unit is configured to send a command to the liquid monitoring device to acquire initial optical information from multiple points on the grinding surface of the grinding pad when it is not in use and current optical information from multiple points on the grinding surface of the grinding pad when it is in use. The optical information analysis unit determines an initial distribution of the amount of liquid based on the initial optical information and determines a current distribution of the amount of liquid on the grinding surface based on the current optical information. The action control unit is configured to calculate the difference between the initial distribution and the current distribution.

5. The grinding apparatus according to claim 3, wherein, The motion control unit is configured to issue a command to the liquid supply device to supply a liquid of a different type than the polishing fluid used in polishing the workpiece to the polishing surface of the polishing pad while the liquid monitoring device acquires the optical information.

6. The grinding apparatus according to claim 1 or 2, wherein, It also has a light source that irradiates the polished surface with light having one or more wavelengths in the range of 200nm to 1100nm.

7. The grinding apparatus according to claim 1 or 2, wherein, The liquid monitoring device has a light detection sensor that measures the amount of light with one or more wavelengths in the range of 200 nm to 1100 nm.

8. The grinding apparatus according to claim 7, wherein, The optical information analysis unit is configured to determine the distribution of the liquid amount on the polishing surface based on the light quantity measurement data.

9. The grinding apparatus according to claim 1 or 2, wherein, The liquid monitoring device has an image sensor that generates color images.

10. The grinding apparatus according to claim 9, wherein, The optical information analysis unit is configured to determine the distribution of the liquid amount on the grinding surface by analyzing the color distribution, which is optical information, appearing on the color image.

11. The grinding apparatus according to claim 1 or 2, wherein, The liquid monitoring device is configured to acquire optical information of the plurality of points located upstream of the grinding head in the rotation direction of the grinding table.

12. The grinding apparatus according to claim 2, wherein, The motion control unit is configured to calculate the differences between multiple distributions of the liquid volume on the grinding surface determined at multiple moments during the grinding of the workpiece, and if the difference in distribution is greater than an allowable value, change the grinding conditions for the workpiece in the direction that the difference in distribution decreases.

13. The grinding apparatus according to claim 12, wherein, The motion control unit is configured to, after changing the grinding conditions, recalculate the difference between multiple distributions of the liquid volume determined during the grinding of the workpiece, and if the difference in distributions is greater than an allowable value, stop the operation of the grinding device before grinding the next workpiece.

14. The grinding apparatus according to claim 2, wherein, The motion control unit is configured to calculate the difference between multiple distributions of the liquid volume determined at multiple moments during the grinding of the workpiece, and if the difference in distribution is greater than an allowable value, to stop the operation of the grinding device before grinding the next workpiece.

15. The grinding apparatus according to claim 2, wherein, The motion control unit is configured to calculate the difference between multiple distributions of the liquid volume determined at multiple moments during the grinding of the workpiece, and if the difference in distribution is greater than an allowable value, to change the pressure of the grinding head on the workpiece.

16. The grinding apparatus according to claim 4, wherein, The motion control unit is configured to change the grinding conditions for the workpiece to decrease in the direction of decreasing the difference between the initial distribution and the current distribution of the liquid volume on the grinding surface when the difference is greater than a threshold.

17. The grinding apparatus according to claim 16, wherein, The grinding device is configured such that, after changing the grinding conditions, it recalculates the difference between the initial distribution of the liquid volume and the newly determined current distribution of the liquid volume, and if the difference in the distribution is greater than the threshold, it stops the grinding operation of the grinding device before grinding the next object to be ground.

18. The grinding apparatus according to claim 4, wherein, The motion control unit is configured to stop the grinding operation of the grinding device before grinding the next workpiece if the difference between the initial distribution and the current distribution of the liquid volume on the grinding surface is greater than a threshold.

19. The grinding apparatus according to claim 1 or 2, wherein, The motion control unit is configured to determine that an abnormality has occurred in the grinding device when the distribution of the liquid amount on the grinding surface is lower than a preset threshold distribution of the liquid amount.

20. The grinding apparatus according to claim 1, wherein, The liquid is one of the following: grinding fluid, pure water, medicinal solution, and colored water.

21. A grinding method for grinding a workpiece, wherein the grinding method involves rotating a grinding table and a grinding head supporting a grinding pad, and pressing the workpiece against the grinding surface of the grinding pad using the grinding head to grind the workpiece, wherein before, during, or after grinding the workpiece, liquid is supplied to the grinding surface while acquiring optical information contained in light from multiple points on the grinding surface, and the distribution of the amount of liquid (hereinafter referred to as "the amount of liquid") on the grinding surface is determined based on the optical information, wherein... The distribution of the liquid volume is determined by subtracting a first distribution from a second distribution. The first distribution is determined based on first optical information of multiple points on the grinding surface obtained before the liquid is supplied, and the second distribution is determined based on second optical information of multiple points on the grinding surface obtained when the liquid is supplied.

22. The grinding method according to claim 21, wherein, The process of acquiring the optical information is a process of acquiring the optical information of multiple points on the grinding surface at multiple moments during the grinding of the workpiece while supplying liquid to the grinding surface. The process of determining the distribution of the liquid amount is a process of acquiring the temporal progression of the distribution of the liquid amount on the grinding surface based on the optical information of multiple points on the grinding surface acquired at the multiple moments.

23. The grinding method according to claim 21, wherein, The process of acquiring the optical information is a process of acquiring the optical information while supplying liquid to the grinding surface during the interval before or after grinding the workpiece.

24. A grinding method for grinding a workpiece, wherein the method comprises: supplying liquid to the grinding surface of a grinding pad in an unused state while acquiring initial optical information of multiple points on the grinding surface; determining an initial distribution of the amount of liquid (hereinafter referred to as "the amount of liquid") on the grinding surface based on the initial optical information; rotating a grinding table and a grinding head supporting the grinding pad while pressing the workpiece to be ground against the grinding surface of the grinding pad by the grinding head to grind the workpiece; supplying liquid to the grinding surface of a grinding pad in use while acquiring current optical information of multiple points on the grinding surface; determining a current distribution of the amount of liquid on the grinding surface based on the current optical information; and calculating the difference between the initial distribution and the current distribution.

25. The grinding method according to claim 23, wherein, The liquid supplied to the abrasive surface of the abrasive pad during the acquisition of the optical information is a different type of liquid from the abrasive fluid used in the abrasive grinding of the workpiece.

26. The grinding method according to claim 21, wherein, The optical information refers to the amount of light from the polished surface.

27. The grinding method according to claim 21, wherein, The optical information refers to the color distribution of the polished surface.

28. The grinding method according to claim 21, wherein, The process of acquiring the optical information is a process of acquiring optical information of the plurality of points located upstream of the grinding head in the rotation direction of the grinding table.

29. The grinding method according to claim 22, wherein, It also includes the following steps: calculating the difference between multiple distributions of the liquid volume determined at multiple moments during the grinding of the workpiece, and if the difference in the distributions is greater than an allowable value, changing the grinding conditions for the workpiece in the direction that the difference in the distributions decreases.

30. The grinding method according to claim 29, wherein, It also includes the following steps: After changing the grinding conditions, the difference between multiple distributions of the liquid volume determined at multiple moments during the grinding of the workpiece is calculated again; if the difference in the distribution is greater than an allowable value, the operation of the grinding device is stopped before grinding the next workpiece.

31. The grinding method according to claim 22, wherein, It also includes the following steps: calculating the difference between multiple distributions of the liquid volume determined at multiple moments during the grinding of the workpiece, and stopping the operation of the grinding device before grinding the next workpiece if the difference in the distributions is greater than an allowable value.

32. The grinding method according to claim 22, wherein, It also includes the following steps: calculating the difference between multiple distributions of the liquid volume determined at multiple moments during the grinding of the workpiece, and, if the difference in distribution is greater than an allowable value, changing the pressure of the grinding head on the workpiece.

33. The grinding method according to claim 24, wherein, It also includes the following steps: if the difference between the initial distribution and the current distribution of the liquid amount on the grinding surface is greater than a threshold, the grinding conditions for the workpiece are changed in the direction that the difference in distribution decreases.

34. The grinding method according to claim 33, wherein, It also includes the following steps: After changing the grinding conditions, the difference between the initial distribution of the liquid volume on the grinding surface and the current distribution of the newly determined liquid volume is calculated again. If the difference in the distribution is greater than the threshold, the operation of the grinding device is stopped before grinding the next workpiece.

35. The grinding method according to claim 24, wherein, It also includes the following steps: if the difference between the initial distribution and the current distribution of the liquid volume on the grinding surface is greater than a threshold, the operation of the grinding device is stopped before grinding the next workpiece.

36. The grinding method according to claim 21, wherein, It also includes the following steps: if the distribution of the liquid volume is lower than a preset threshold distribution of the liquid volume, it is determined that an abnormality has occurred in the grinding device.

37. The grinding method according to claim 21, wherein, The liquid is one of the following: grinding fluid, pure water, medicinal solution, and colored water.

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