Grinding device and grinding method

Abstract

The present invention provides an apparatus and a method for polishing a wafer or the like under appropriate polishing conditions by monitoring the distribution of the amount of a liquid such as a polishing liquid or a chemical liquid on the polishing surface of a polishing pad. The polishing apparatus includes a polishing table (5) that supports a polishing pad (2); a polishing head (7) that presses a wafer (W) to be polished against the polishing surface (2a) of the polishing pad (2); a liquid supply device (8) that supplies a liquid to the polishing surface (2a); a liquid monitoring device (12) that acquires optical information contained in light from a plurality of points on the polishing surface (2a); an optical information analysis section (13) that determines the distribution of the amount of the liquid on the polishing surface (2a) based on the optical information; and an operation control section (47) that controls the operation of the polishing apparatus.

Description

Technical Field

[0001] This invention relates to a polishing apparatus and method for pressing a wafer, substrate, panel, or other object to be polished onto the polishing surface of a polishing pad to polish the object. More particularly, it relates to a polishing apparatus and method for making the object to be polished slide into contact with the polishing pad while a polishing liquid such as a slurry is present on the polishing surface of the polishing pad. Background Technology

[0002] In semiconductor device manufacturing, various types of films are formed on wafers. In the wiring / contact formation process, after film deposition, the wafer is polished to remove unwanted portions and surface irregularities. 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 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] The polishing apparatus for performing the 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 nanometers, and CMP is no exception. Furthermore, the increasing integration, miniaturization, and multilayering of semiconductor integrated circuits are accelerating. Therefore, to achieve these miniaturization and multilayering, CMP requires that the remaining film thickness deviation after CMP converge to within the order of nanometers across the entire surface of the wafer.

[0005] To reduce residual film thickness deviation, it is necessary to control various factors affecting 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 process of semiconductor devices. In the CMP process, polishing slurry is a particularly significant 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 effectively supplying polishing fluid to the polishing surface of a polishing pad. Patent Document 1 discloses a nozzle with 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.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2006-147773

[0011] The technical problem that the invention aims to solve

[0012] As such, the amount of slurry supplied during grinding and the distribution of slurry on the grinding pad have a significant impact on grinding performance (deviation of grinding rate) and grinding efficiency. Therefore, monitoring the distribution of slurry on the grinding pad is necessary to maintain grinding performance and grinding efficiency.

[0013] The main reasons for changes in the distribution of polishing slurry on the polishing pad can be listed as equipment malfunction, changes in the physical properties of the polishing slurry (viscosity, etc.) due to increased polishing pad temperature, and changes in the surface condition of the polishing pad. When equipment malfunction is the cause, abnormal polishing slurry flow is often detected by flow sensors. For example, in the case where the liquid supply device is a nozzle with a single supply port, a flow sensor is installed at each nozzle. Conversely, in the case where 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.

[0014] 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 anomaly, and as a result, the blockage of the supply port may not be detected. Although there are solutions that deploy multiple flow sensors at multiple supply ports, the number of flow sensors needs to increase with the number of supply ports, which inevitably leads to an increase in sensor installation space and sensor cost.

[0015] Furthermore, the abrasive pad wears down due to abrasion, and the distribution of the abrasive slurry on the pad surface changes due to deviations in the amount of wear within the pad surface. For example, if the dimensions (especially the depth) of the grooves formed within the abrasive pad surface decrease due to wear, even if the abrasive slurry supply flow rate is normal, the distribution of the abrasive slurry on the pad surface will change, leading to variations and deviations in the abrasion 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

[0016] Therefore, the object of the present invention is to provide a grinding apparatus and grinding method that can monitor the distribution of liquids such as grinding fluid and pharmaceutical solution on the grinding surface of a grinding pad, and grind the workpiece such as a wafer according to the liquid distribution obtained by monitoring.

[0017] Technical means for solving technical problems

[0018] In one embodiment, a grinding apparatus for grinding an object comprises: a grinding table supporting a grinding pad; a grinding head pressing the object 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.

[0019] 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, and further send an instruction to the liquid monitoring device when supplying the liquid, causing 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.

[0020] In one embodiment, the motion control unit is configured to send a command to the liquid monitoring device, causing the liquid monitoring device to acquire optical information of multiple points on the grinding surface at multiple times during the grinding of the workpiece, and 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.

[0021] In one embodiment, the motion control unit is configured to send a command to the liquid monitoring device during an interval before or after grinding the workpiece, causing the liquid monitoring device to acquire the optical information.

[0022] In one embodiment, the motion control unit is configured to send a command 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.

[0023] In one embodiment, the motion control unit is configured to issue an instruction to the liquid supply device to supply a liquid of a different type from the polishing fluid used in the workpiece to the polishing surface of the polishing pad while the liquid monitoring device acquires the optical information.

[0024] In one embodiment, the polishing apparatus further comprises a light source that irradiates the polishing surface with light having one or more wavelengths in the range of 200 nm to 1100 nm.

[0025] In one embodiment, the liquid monitoring device has a light detection sensor that measures the amount of light having one or more wavelengths in the range of 200 nm to 1100 nm.

[0026] In one embodiment, the optical information analysis unit is configured to determine the distribution of the liquid amount on the polishing surface based on the measurement data of the light amount.

[0027] In one embodiment, the liquid monitoring device has an image sensor that generates color images.

[0028] In one embodiment, 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.

[0029] In one embodiment, the liquid monitoring device is configured to acquire optical information of the plurality of points located upstream of the grinding head within a monitoring area in the rotational direction of the grinding table.

[0030] In one embodiment, the motion control unit is configured to calculate the difference between multiple distributions of the liquid quantity 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.

[0031] In one embodiment, 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.

[0032] 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, to stop the operation of the grinding device before grinding the next workpiece.

[0033] 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, to change the pressure applied by the grinding head to the workpiece.

[0034] 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 initial distribution and the current distribution of the liquid volume on the grinding surface if the difference is greater than a threshold.

[0035] In one embodiment, the grinding apparatus is configured to, after changing the grinding conditions, recalculate 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 distribution is greater than the threshold, stop the grinding operation of the grinding apparatus before grinding the next workpiece.

[0036] In one embodiment, the motion control unit is configured to stop the grinding action 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.

[0037] In one embodiment, the motion control unit is configured to determine that an abnormality has occurred in the grinding apparatus if the distribution of the liquid amount on the grinding surface is lower than a preset threshold distribution of the liquid amount.

[0038] In one embodiment, the liquid is one of grinding fluid, pure water, pharmaceutical solution, and colored water.

[0039] In one embodiment, a grinding method involves grinding a workpiece by rotating a grinding table and a grinding head that support a grinding pad, 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.

[0040] In one approach, the distribution of the liquid volume is determined by subtracting a first distribution from a second distribution, the first distribution being determined based on first optical information of a plurality of points on the grinding surface acquired before the liquid is supplied, and the second distribution being determined based on second optical information of a plurality of points on the grinding surface acquired when the liquid is supplied.

[0041] In one approach, the step of acquiring the optical information is to acquire 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 to acquire the temporal progression of the distribution of the liquid amount on the grinding surface based on the optical information of the multiple points on the grinding surface acquired at the multiple moments.

[0042] In one approach, the process of acquiring the optical information involves acquiring the optical information while supplying liquid to the grinding surface during an interval before or after grinding the workpiece.

[0043] In one embodiment, the polishing method further includes the following steps: while supplying liquid to the polishing surface of the polishing pad in an unused state, acquiring initial optical information of multiple points on the polishing surface; while supplying liquid to the polishing surface of the polishing pad in use, acquiring current optical information of multiple points on the polishing surface; 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.

[0044] In one embodiment, 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 workpiece.

[0045] In one approach, the optical information is the amount of light from the polished surface.

[0046] In one approach, the optical information is the color distribution of the polished surface.

[0047] In one approach, the step of acquiring the optical information is to acquire optical information of the plurality of points located upstream of the grinding head in the rotation direction of the grinding table.

[0048] 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 that the difference in distributions decreases.

[0049] In one embodiment, the grinding method further includes the following steps: 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.

[0050] 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 stopping the operation of the grinding device before grinding the next workpiece if the difference in the distributions is greater than an allowable value.

[0051] 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, causing a change in the pressure applied by the grinding head to the workpiece.

[0052] 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 amount on the grinding surface is greater than a threshold, changing the grinding conditions for the workpiece in the direction that the difference in distribution decreases.

[0053] In one embodiment, the grinding method further includes the following steps: after changing the grinding conditions, recalculating the difference between the initial distribution of the liquid volume on the grinding surface and the newly determined current distribution of the liquid volume; if the difference in distribution is greater than the threshold, stopping the operation of the grinding device before grinding the next workpiece.

[0054] In one embodiment, the grinding method further includes the step of stopping the 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.

[0055] In one embodiment, the grinding method further includes the step of determining that an abnormality has occurred in the grinding apparatus when the distribution of the liquid volume is lower than a preset threshold distribution of the liquid volume.

[0056] In one embodiment, the liquid is one of grinding fluid, pure water, pharmaceutical solution, and colored water.

[0057] The effects of the invention

[0058] According to the present invention, the distribution of liquids such as polishing slurry and pharmaceutical solution on the polishing pad can be monitored. Furthermore, by feeding back this monitoring result to the operation of the polishing apparatus, the workpiece, such as a wafer, can be polished under appropriate polishing conditions. Attached Figure Description

[0059] Figure 1 This is a perspective view schematically illustrating one embodiment of the grinding apparatus.

[0060] Figure 2 yes Figure 1 The image shows a cross-sectional view of the grinding head.

[0061] Figure 3 It is a top view of the grinding pad, liquid supply device, and grinding head.

[0062] Figure 4 This is an example of a graph showing the distribution of grinding fluid volume.

[0063] Figure 5 This is an example of a graph showing the distribution of grinding fluid volume.

[0064] Figure 6 (a) and Figure 6 (b) is a graph showing the distribution of polishing slurry volume as it changes during the polishing of a wafer.

[0065] Figure 7 It is a graph showing how the overall distribution of grinding fluid decreases due to an abnormality in the grinding device.

[0066] Figure 8 It is a graph illustrating the change in the distribution of liquid volume when one of the multiple supply ports is blocked.

[0067] Figure 9 It is a graph representing the initial distribution and current distribution of liquid volume.

[0068] Figure 10 It is a graph illustrating an implementation method for determining whether the difference between the distributions of liquid quantities is within a specified range.

[0069] Figure 11 It is a graph illustrating the change in the distribution of liquid volume when one of the multiple supply ports is blocked.

[0070] Figure 12 (a) is a graph representing the first distribution obtained based on the first optical information acquired before the liquid is supplied. Figure 12 (b) is a graph representing the second distribution obtained based on the second optical information acquired during the supply of the liquid. Figure 12 (c) is a graph representing the distribution of liquid volume obtained by subtracting the first distribution from the second distribution.

[0071] Symbol Explanation

[0072] 2 Grinding pad

[0073] 2a Grinding surface

[0074] 5 Grinding table

[0075] 5a Axle

[0076] 7 Grinding head

[0077] 8. Liquid supply device

[0078] 9. Liquid Nozzle

[0079] 9a Supply Port

[0080] 10. Nozzle oscillation mechanism

[0081] 12 Liquid monitoring devices

[0082] 13 Optical Information Analysis Department

[0083] 14 support shafts

[0084] 16 Grinding head swing arm

[0085] 18 Grinding head shaft

[0086] 20 Grinding head rotation device

[0087] 21 Grinding table rotation device

[0088] 25 First Liquid Supply Line

[0089] 27 Second Liquid Supply Line

[0090] 31 First flow control valve

[0091] 32 Second Flow Control Valve

[0092] 40 Light Source

[0093] 47 Motion Control Department

[0094] 71 Carrier

[0095] 72 retaining rings

[0096] 74. Membrane (elastic membrane)

[0097] 76 Rolling diaphragm

[0098] W wafer (the material being ground)

[0099] M monitoring area

[0100] F1, F2, F3, F4, F5 fluid paths

[0101] Pressure chambers G1, G2, G3, G4, and G5

[0102] R1, R2, R3, R4, R5 pressure regulators Detailed Implementation

[0103] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0104] Figure 1 This is a perspective view schematically illustrating one embodiment of the grinding apparatus. (As shown) Figure 1 As shown, 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.

[0105] The polishing head 7 is configured to hold the wafer W on its lower surface by means of vacuum adsorption or the like. In this embodiment, the wafer W is circular. The object being polished can be any workpiece used in the manufacture of semiconductor devices, and is not limited to wafers. Other examples of objects being polished include angular wafers, substrates, panels, etc.

[0106] The grinding apparatus also includes: a support shaft 14; a grinding head swing arm 16 connected to the upper end of the support shaft 14 and used to swing 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. 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. An electric motor can be cited as a specific example of the grinding head rotating device 20.

[0107] 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.

[0108] The grinding apparatus also includes a grinding table rotation device 21, which rotates the grinding pad 2 and the grinding table 5 about their respective 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 grinding wafer W. As a specific example of the grinding table rotation device 21, an electric motor can be cited.

[0109] The liquid supply device 8 includes: a liquid nozzle 9 having a supply port 9a at its top; a nozzle oscillation mechanism 10 that oscillates 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 liquid nozzle 9 with a grinding fluid (typically a slurry) as the first liquid, 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).

[0110] 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.

[0111] 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.

[0112] The optical information analysis unit 13 includes a storage device 13a storing a program and a processing unit 13b executing calculations according to the commands contained in the program. The storage device 13a includes a main storage device such as random access memory (RAM), 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.

[0113] The motion control unit 47 includes a storage device 47a storing a program and a processing unit 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 processing units 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.

[0114] 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 a single computer. The optical information analysis unit 13 and the motion control unit 47 can be physically not independent and can be hypothetically constructed using at least one computer.

[0115] 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 radially along the polishing pad 2. In one embodiment, multiple monitoring areas may be provided. These monitoring areas extend radially along the polishing pad 2 and are arranged circumferentially along the polishing pad 2. One of the multiple monitoring areas is as follows: Figure 1 As indicated by the mark M, it is located upstream of the grinding head 7.

[0116] The polishing apparatus also includes a light source 40 that illuminates the polishing surface 2a of the polishing pad 2 with light having one or more wavelengths in the range of 200 nm to 1100 nm. The light source 40 is configured to emit at least visible light, for example, and includes a light-emitting diode (LED). 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 LEDs, or it may have a light-dispersing plate. The light source 40 is configured to illuminate the monitoring area M uniformly.

[0117] Figure 2 yes Figure 1 The image shows a cross-sectional view of the grinding head 7. The grinding head 7 includes a carrier 71 fixed to the grinding head shaft 18 and a retaining ring 72 disposed below the carrier 71. A flexible diaphragm (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 diaphragm 74 and the carrier 71. The pressure chambers G1, G2, G3, and G4 are formed by the diaphragm 74 and the carrier 71. The central pressure chamber G1 is circular, while 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 fewer than three pressure chambers may be provided.

[0118] Compressed gases, such as compressed air, are supplied from the gas supply source 77 to pressure chambers G1, G2, G3, and G4 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 areas of the wafer W: the central portion, the inner middle portion, the outer middle portion, and the periphery.

[0119] 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.

[0120] 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.

[0121] 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 installed in fluid paths F1, F2, F3, F4, and F5, respectively. 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.

[0122] 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.

[0123] Figure 3 This is a top view of the grinding pad 2, the liquid supply device 8, and the grinding head 7. Figure 3As shown, 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 radially outward due to centrifugal force and comes into contact with the wafer W held in the polishing head 7. Initially, the polishing slurry has not yet fully expanded on the polishing surface 2a. Therefore, typically, after a preset time elapses from the start of the polishing slurry supply, the polishing head 7 presses the wafer W against the polishing surface 2a.

[0124] 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.

[0125] Typically, the polishing slurry and 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, which represents the concentration of the polishing slurry color within the monitoring area M, and creates a polishing slurry volume distribution curve representing the amount of polishing slurry expressed by the liquid color index value at each location within the monitoring area M.

[0126] Figure 4 This is an example of a graph showing the distribution of grinding slurry volume. In Figure 4 In the diagram, the vertical axis represents the amount of liquid corresponding to the liquid color index value, and the horizontal axis represents the location within the monitoring area M. Figure 4 In the example shown, the position represented by the horizontal axis is the position of the abrasive pad 2 in the radial direction. The liquid color index value varies depending on the amount of abrasive present on the abrasive surface 2a, therefore the liquid color index value is equivalent to the amount of abrasive. Figure 4 The vertical axis represents the amount of grinding fluid expressed using liquid color index values.

[0127] The color index value of a liquid varies according to the color model (or color space) that defines the colors within a color image. Examples of color models used to quantitatively represent colors include RGB, CMY, CMYK, HSL, and HSV.

[0128] The liquid color index value can be a single value from multiple components that define various color models. 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 R (red), G (green), and B (blue) components is represented by a value ranging from 0 to 255. By applying only one component, the polishing fluid on the polishing surface 2a can be detected with high accuracy.

[0129] In one embodiment, the optical information analysis unit 13 can use composite values ​​such as lightness and brightness, in addition to the components of the aforementioned color model (or color space), 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. Thus, by analyzing a color image reflecting the density of the polishing slurry on the polishing pad 2, the optical information analysis unit 13 can determine the relative distribution of the polishing slurry on the polishing pad 2. Alternatively, the optical information analysis unit 13 can be configured to pre-acquire data 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.

[0130] 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 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.

[0131] A 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 an 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 measured light amount data. In areas where polishing slurry is present on the polishing surface 2a of the polishing pad 2, light is easily reflected by the polishing slurry, resulting in a greater amount of light. Therefore, the optical information analysis unit 13 can determine the distribution of polishing slurry on the polishing surface 2a based on the measured light amount data obtained by the liquid monitoring device 12.

[0132] Figure 5 This is an example of a graph showing the distribution of grinding slurry volume. In Figure 5 In the diagram, 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 location within the monitoring area M. Figure 5 In the example shown, the position represented by the horizontal axis is the position of the polishing pad 2 in the radial direction. The amount of light reflected from the polishing slurry varies depending on the presence or absence of polishing slurry on the polishing surface 2a; therefore, the amount of light is equivalent to the amount of polishing slurry present on the polishing surface 2a. Figure 5 The vertical axis represents the amount of polishing fluid used in light intensity measurement.

[0133] 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 radiation that depends 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, a temperature difference exists between the polishing surface 2a and the polishing slurry. The intensity of the infrared radiation 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 infrared radiation 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 measured data of the infrared radiation intensity. The intensity of the infrared radiation is equivalent to the amount of polishing slurry present on the polishing surface 2a. When using an infrared sensor, this parameter can be omitted. Figure 1 The light source shown is 40.

[0134] When the polishing slurry is close to the color of polishing pad 2, or when the polishing slurry is transparent, colored water can be used and the distribution of colored water on polishing surface 2a can be analyzed during the interval before or after polishing of wafer W, such as when the polishing apparatus is idling. More specifically, during the interval before or after polishing of wafer W, the motion control unit 47 is turned off. Figure 1The first flow control valve 31 is opened and the second flow control valve 32 is opened, thereby supplying colored water as a second liquid from the liquid supply device 8 to the grinding surface 2a of the grinding 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, causing the liquid monitoring device 12 to acquire optical information contained in the light from the grinding surface 2a and the colored water. More specifically, the liquid monitoring device 12 generates a color image of the colored water on the grinding surface 2a and sends this color image to the optical information analysis unit 13. By analyzing the color image, the optical information analysis unit 13 can determine the distribution of the amount of colored water on the grinding surface 2a. Furthermore, the distribution of the obtained optical information (e.g., brightness value) based on the color of the colored water and the grinding surface 2a of the grinding 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.

[0135] As the liquid supplied during the interval, pure water can also be used instead of colored water. The motion control unit 47 shuts off the operation during the interval before or after the wafer W is polished. Figure 1 The first flow control valve 31 is opened and the second flow control valve 32 is opened, thereby supplying pure water as a second liquid from the liquid supply device 8 to the grinding surface 2a of the grinding 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 in the monitoring area M and sends the measurement data to the optical information analysis unit 13, which determines the distribution of pure water on the grinding surface 2a based on the light measurement data.

[0136] Furthermore, the liquid supplied during the interval can be a medicinal solution instead of colored water. In this case, the distribution of the medicinal solution on the grinding surface 2a is determined in the same manner as in the embodiment described above.

[0137] Polishing slurries used in wafer polishing are generally expensive. According to the above-described embodiment, which uses colored water, pure water, or a chemical solution instead of polishing slurry, the cost required to determine the distribution of liquid volume on the polishing surface 2a can be reduced.

[0138] 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 slurry, and this color may contrast with the liquid such as the grinding slurry 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, thereby also being able to use this color distribution as the distribution of the amount of liquid on the grinding pad 2.

[0139] 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 motion 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 temporal progression of the polishing slurry distribution by analyzing the optical information acquired at the aforementioned multiple moments.

[0140] 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.

[0141] Figure 6 (a) and Figure 6 (b) is a graph showing the distribution of varying polishing slurry volume during the polishing of a wafer W. For example... Figure 6 As shown in (a), during the polishing of wafer W, the current distribution of polishing slurry volume may decrease based on the initial distribution of polishing slurry volume at the start of polishing. The motion control unit 47 calculates the difference in these distributions of the polishing slurry, and if the distribution difference exceeds an allowable value, the motion control unit 47... Figure 6 As shown in (b), the polishing conditions for the wafer W are changed in the direction of decreasing difference. For example, the motion control unit 47 increases the opening of the first flow control valve 31, thereby increasing the flow rate of polishing slurry supplied to the polishing surface 2a. When the distribution of polishing slurry 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.

[0142] In one embodiment, after a predetermined time has elapsed since the motion control unit 47 changed the polishing conditions of the polishing apparatus, the optical information analysis unit 13 determines the current distribution of polishing slurry volume again during the polishing of the wafer W. The motion control unit 47 calculates the difference between the distribution of polishing slurry volume at the start of polishing the wafer W and the current distribution of polishing slurry 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.

[0143] Furthermore, in one embodiment, the motion control unit 47 may calculate the difference between multiple distributions of polishing fluid volume determined at multiple moments 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 apparatus before polishing the next wafer.

[0144] 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 the wafer W, and if the distribution difference exceeds an allowable value, change the pressing pressure of the polishing head 7 on the wafer W. Figure 6 As shown in (a), when the amount of polishing slurry decreases during the polishing of wafer W, it is anticipated that the polishing rate of wafer W will decrease due to the reduced amount of polishing slurry. Therefore, the motion control unit 47 increases the pressing pressure of the polishing head 7 on wafer W to compensate for the decreased polishing rate. Specifically, the motion control unit 47... Figure 2 At least one of the pressure regulators R1 to R4 shown issues a command to increase 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 force, thus maintaining the desired polishing rate.

[0145] 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 equipment malfunction, temperature rise of the grinding pad 2 causing changes in the physical properties (viscosity, etc.) of the grinding fluid, and changes in the surface state of the grinding pad 2. In the case of equipment malfunction, monitoring the distribution of the grinding fluid on the grinding pad 2 can detect the equipment malfunction.

[0146] In one embodiment, the motion control unit 47 may be configured such that if the distribution of the liquid (e.g., polishing slurry, pure water, pharmaceutical solution, or colored water) is below a preset threshold distribution, the motion control unit 47 determines that an abnormality has occurred in the polishing device. For example, as Figure 7 As shown, when the overall distribution of liquid volume is lower than a preset threshold distribution (or reference distribution), it can be considered that the liquid nozzle 9 or the first liquid supply line 25 (refer to...) is below the threshold distribution (or reference distribution). Figure 1The cause is blockage, etc. When the liquid volume distribution is lower than the preset threshold distribution, the action control unit 47 can also generate an alarm signal.

[0147] Figure 1 The liquid nozzle 9 shown 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 easily forms 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 locally decreases. On the other hand, the overall liquid flow rate caused by the blockage of such a single supply port hardly changes. Therefore, it is difficult to detect the blockage of a single supply port based on changes in flow rate. According to the above-described embodiment for monitoring the distribution of liquid volume, as Figure 8 As shown, when the liquid volume distribution is lower than the threshold distribution, the motion control unit 47 determines that an abnormality has occurred, and thus can detect partial blockage of the liquid nozzle 9.

[0148] 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 remains unchanged, the distribution of the amount of polishing slurry on the polishing surface 2a may change.

[0149] 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 the initial optical information of the polishing surface 2a of the polishing pad 2 in the unused state and the 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.

[0150] The liquid used can be any of a polishing slurry, pure water, a medicinal solution, or colored water. However, polishing slurries are generally expensive, so the liquid used is preferably any of pure water, a medicinal solution, or colored water. Specific examples of optical information about 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 when it is not in use, and generates a recent color image of the liquid on the polishing surface 2a of the polishing pad 2 when it is 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 when it is not in use, and measures the recent amount of light from the liquid on the polishing surface 2a of the polishing pad 2 when it is in use.

[0151] The optical information analysis unit 13 determines the initial distribution of liquid volume on the grinding surface 2a based on initial optical information (e.g., initial color image or measurement data of initial light intensity), and determines the current distribution of liquid volume on the grinding surface 2a based on current optical information (e.g., recent color image or measurement data of recent light intensity). Figure 9 This is a graph showing the initial distribution and the current distribution of liquid volume on grinding surface 2a. (Example) Figure 9 As shown, the distribution of liquid on the grinding surface 2a changes over time due to the wear of the grinding pad 2.

[0152] 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 if this difference exceeds a threshold, generate an alarm signal notifying the polishing pad 2 of wear.

[0153] The motion control unit 47 can also be configured to change the polishing conditions for the wafer 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 exceeds 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 polishing rate and polishing rate distribution of the wafer can be prevented.

[0154] 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 again determines the current distribution of liquid volume on the polishing surface 2a. 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.

[0155] Furthermore, in one embodiment, if the difference between the initial distribution and the current distribution of liquid volume on the polishing surface 2a is greater than a threshold, the motion control unit 47 may not change the polishing conditions of the wafer, but may stop the operation of the polishing apparatus before polishing the next wafer.

[0156] Furthermore, in one embodiment, the motion control unit 47 may change the pressing pressure of the polishing head 7 on the wafer if the difference between the initial distribution and the current distribution of liquid on the polishing surface 2a is greater than a threshold. For example... Figure 9 As shown, when the wear of the polishing pad 2 progresses, it is anticipated that the amount of polishing slurry on the polishing surface 2a of the polishing pad 2 will decrease, thereby leading to 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 polishing rate. Specifically, the motion control unit 47 increases the pressing pressure of the polishing head 7 on the wafer. Figure 2 At least one of the pressure regulators R1 to R4 shown issues a command to increase 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 force, thus maintaining the desired polishing rate.

[0157] The allowable value and the threshold value, which are compared with the difference between the liquid volume distribution on the polishing surface 2a, can also be determined based on the difference between the normal liquid volume distribution and the distribution that has changed by a predetermined proportion, such as 10%, from the normal liquid volume distribution. The normal liquid volume distribution can be set, for example, the polishing rate profile of the wafer as the normal liquid volume distribution.

[0158] Sometimes, due to manufacturing deviations in the abrasive pad 2, the distribution of liquid volume may also be inaccurate even under normal conditions. In such cases, data on multiple liquid volume distributions from past normal conditions can be accumulated in the storage device 47a of the motion control unit 47, and then... Figure 10 As shown, the motion control unit 47 determines whether the aforementioned difference exists within the range determined based on the data.

[0159] The aforementioned allowable value and threshold, which are compared with the difference in liquid distribution on the grinding surface 2a, can also be automatically determined based on artificial intelligence (AI). For example, the liquid distribution data can be combined with information on consumable materials such as the grinding pad and liquid, as well as information on the occurrence of grinding abnormalities, and stored in the storage device 47a of the motion control unit 47. Furthermore, through machine learning such as artificial intelligence (AI) that shifts the liquid distribution of each combination of the grinding pad and liquid, if consumable material information is input into the motion control unit 47, the aforementioned allowable value and threshold can be automatically set.

[0160] In addition, such as Figure 11 As shown, in cases where the anomaly in the liquid volume distribution is localized and small, it may sometimes be impossible to detect such anomalies correctly. In such cases, the normal / abnormal status 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 treated as anomaly data and processed by machine learning to be recognized by the motion control unit 47, thereby determining an anomaly when a similar liquid volume distribution is detected.

[0161] 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, the amount of light reflected from the liquid on the abrasive pad 2 may deviate depending on the position of the light source 40. 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.

[0162] Therefore, in the embodiment described below, the motion control unit 47 is configured to issue a command to the liquid monitoring device 12 before liquid is supplied, 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 liquid is supplied, 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 volume by subtracting the first distribution from the second distribution.

[0163] Figure 12(a) is a graph representing the first distribution obtained based on the first optical information of the polished surface 2a acquired by the liquid monitoring device 12 before the liquid is supplied. 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 representing the distribution of liquid quantity obtained by subtracting the first distribution from the second distribution. For example... Figure 12 (a) and Figure 12 As shown in (b), noise caused by light-blocking objects such as trimmers appeared in both the first and second distributions. Therefore, as Figure 12 As shown in (c), by subtracting the first distribution from the second distribution, the distribution of liquid volume with noise removed can be obtained.

[0164] The above-described embodiments are intended to enable those skilled in the art to carry out the invention. Various modifications of the above-described embodiments can obviously be implemented by those skilled in the art, and the technical concept of the invention can also be applied to other embodiments. Therefore, the 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 scope of the patent claims.

Claims

1. A grinding apparatus for grinding a workpiece, characterized in that, have: A grinding table that supports 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; A grinding head rotating device that rotates the grinding head; A liquid monitoring device that acquires optical information contained in light from multiple points on the polishing surface; An optical information analysis unit determines the distribution of liquid volume on the polishing surface based on the optical information; and The motion control unit controls the operation of the grinding device. The motion 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 of 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 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.

2. The grinding apparatus according to claim 1, characterized in that, The motion control unit is configured to send instructions to the liquid monitoring device, causing the liquid monitoring device to acquire optical information of multiple points on the grinding surface at multiple moments during the grinding of the workpiece. The optical information analysis unit is configured to obtain the temporal shift of the distribution of the liquid quantity on the grinding surface based on the optical information of multiple points on the grinding surface acquired at the multiple times.

3. The grinding apparatus according to claim 1, characterized in that, 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. The grinding apparatus according to claim 3, characterized in that, 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 is acquiring the optical information.

5. The grinding apparatus according to any one of claims 1-4, characterized in that, 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.

6. The grinding apparatus according to any one of claims 1-4, characterized in that, 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.

7. The grinding apparatus according to claim 6, characterized in that, The optical information analysis unit is configured to determine the distribution of the liquid amount on the grinding surface based on the light quantity measurement data.

8. The grinding apparatus according to any one of claims 1-4, characterized in that, The liquid monitoring device has an image sensor that generates color images.

9. The grinding apparatus according to claim 8, characterized in that, 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.

10. The grinding apparatus according to any one of claims 1-4, characterized in that, 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.

11. The grinding apparatus according to claim 2, characterized in that, 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.

12. The grinding apparatus according to claim 11, characterized in that, 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.

13. The grinding apparatus according to claim 2, characterized in that, 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.

14. The grinding apparatus according to claim 2, characterized in that, 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.

15. A grinding method for grinding a workpiece, characterized in that, While rotating the grinding table and grinding head that support the grinding pad, the grinding head presses the workpiece against the grinding surface of the grinding pad to grind the workpiece. Before, during, or after grinding the workpiece, while supplying liquid to the grinding surface, optical information contained in light from multiple points on the grinding surface is acquired. The distribution of liquid on the grinding surface is determined based on the optical information. The distribution of the liquid volume is determined by subtracting a first distribution from a second distribution, the first distribution being determined based on first optical information of a plurality of points on the grinding surface obtained before the liquid is supplied, and the second distribution being determined based on second optical information of a plurality of points on the grinding surface obtained when the liquid is supplied.

16. The grinding method according to claim 15, characterized in that, The process of acquiring the optical information involves supplying liquid to the grinding surface while acquiring optical information at multiple points on the grinding surface at multiple moments during the grinding of the workpiece. The process of determining the distribution of the liquid volume is a process of obtaining the temporal shift of the distribution of the liquid volume on the grinding surface based on the optical information of multiple points on the grinding surface obtained at the multiple times.

17. The grinding method according to claim 15, characterized in that, 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.

18. The grinding method according to claim 17, characterized in that, 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.

19. The grinding method according to any one of claims 15-18, characterized in that, The optical information refers to the amount of light from the polished surface.

20. The grinding method according to any one of claims 15-18, characterized in that, The optical information is the color distribution of the polished surface.

21. The grinding method according to any one of claims 15-18, characterized in that, The process of acquiring the optical information is a process of acquiring the optical information of the plurality of points located upstream of the grinding head in the rotation direction of the grinding table.

22. The grinding method according to claim 16, characterized in that, It also includes the following processes: The differences between multiple distributions of the liquid volume determined at multiple moments during the grinding of the workpiece are calculated. If the difference in the distribution is greater than the allowable value, the grinding conditions for the workpiece are changed in the direction that the difference in the distribution decreases.

23. The grinding method according to claim 22, characterized in that, It also includes the following processes: After changing the grinding conditions, the differences between multiple distributions of the liquid volume determined at multiple moments during the grinding of the workpiece were calculated again. If the difference in the distribution is greater than the allowable value, the operation of the grinding device shall be stopped before grinding the next workpiece.

24. The grinding method according to claim 16, characterized in that, It also includes the following processes: The differences between multiple distributions of the liquid volume determined at multiple moments during the grinding of the workpiece are calculated. If the difference in the distribution is greater than the allowable value, the operation of the grinding device shall be stopped before grinding the next workpiece.

25. The grinding method according to claim 16, characterized in that, It also includes the following processes: The differences between multiple distributions of the liquid volume determined at multiple moments during the grinding of the workpiece are calculated. When the difference in the distribution is greater than the allowable value, the pressure applied by the grinding head to the workpiece is changed.

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