Grinding device

Abstract

To provide a polishing device that can accurately determine a frictional force generated between a wafer and a polishing pad.SOLUTION: A polishing device includes a tri-axial sensor disposed while adjacent to a head arm 20 to detect information relating to tri-axial force that acts on a polishing head 1.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This invention relates to a polishing apparatus. [Background technology]

[0002] Chemical mechanical polishing (CMP) is a well-known technique in the manufacturing process of semiconductor devices. Polishing equipment for CMP consists of a polishing table that supports a polishing pad and a polishing head that holds the wafer.

[0003] When polishing a wafer using such a polishing apparatus, the wafer is held by the polishing head and pressed against the polishing surface of the polishing pad with a predetermined pressure. At this time, the wafer slides against the polishing surface by moving the polishing table and the polishing head in relative motion, and the surface of the wafer is polished. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-091090 [Overview of the project] [Problems that the invention aims to solve]

[0005] When polishing a wafer, frictional force is generated between the wafer and the polishing pad. By monitoring this frictional force, it is possible to control the pressing force of the polishing head and determine the end point of the wafer polishing process. For example, when polishing a wafer with stacked upper and lower layers, the lower layer is exposed when the upper layer is removed by polishing. By monitoring the frictional force, the point at which the lower layer is exposed can be determined as the end point of the polishing process.

[0006] The torque current of the table motor that rotates the polishing table changes in response to the frictional force between the wafer and the polishing pad. While there are methods to determine the frictional force based on this change in torque current, such methods suffer from large errors in the current due to variations in motor design and polishing head assembly. As a result, there is a risk that the frictional force between the wafer and the polishing pad cannot be accurately determined.

[0007] Therefore, the present invention aims to provide a polishing apparatus that can accurately determine the frictional force generated between a wafer and a polishing pad. [Means for solving the problem]

[0008] In one embodiment, a polishing apparatus is provided, comprising: a polishing table supporting a polishing pad; a polishing head pressing a substrate against the polishing table; a head shaft connected to the polishing head; a head arm rotatably supporting the head shaft; and a triaxial sensor positioned adjacent to the head arm and detecting information regarding the triaxial forces acting on the polishing head.

[0009] In one embodiment, the polishing apparatus includes a control device electrically connected to the triaxial sensor, and the control device monitors the frictional force generated between the substrate and the polishing head, calculated based on the signal sent from the triaxial sensor, during the polishing of the substrate. In one embodiment, the control device measures the tilt of the substrate based on a signal sent from the three-axis sensor, and controls the posture of the polishing head based on the measured tilt of the substrate. In one embodiment, the control device compares the calculated friction force with a predetermined threshold, and determines the polishing endpoint of the substrate when the friction force reaches the threshold. In one aspect, the polishing apparatus includes a local load applying device electrically connected to the control device that applies a local load to a part of the retainer ring of the polishing head. The control device calculates the frictional force generated between the substrate and the polishing head based on the signal sent from the triaxial sensor, and controls the operation of the local load applying device based on the calculated frictional force.

[0010] In one aspect, there is provided a polishing apparatus including a polishing table that supports a polishing pad, a polishing head that presses a substrate against the polishing table, a head shaft connected to the polishing head, a head arm that rotatably supports the head shaft, first and second housing plates disposed on both sides of the head arm, a first sensor group disposed between the first housing plate and the head arm and detecting information regarding the force acting on the polishing head, and a second sensor group disposed between the second housing plate and the head arm and detecting information regarding the force acting on the polishing head.

[0011] In one aspect, each of the first sensor group and the second sensor group includes a plurality of force sensors, and the plurality of force sensors are disposed at positions where the distances from the head shaft are equal. In one aspect, the polishing apparatus includes a control device electrically connected to the first sensor group and the second sensor group. The control device monitors the frictional force generated between the substrate and the polishing head calculated based on the signals sent from the first sensor group and the second sensor group during polishing of the substrate. In one aspect, the control device measures the inclination of the substrate based on the signals sent from the first sensor group and the second sensor group, and controls the posture of the polishing head based on the measured inclination of the substrate.

[0012] In one aspect, the control device compares the calculated frictional force with a predetermined threshold value, and determines the polishing end point of the substrate when the frictional force reaches the threshold value. In one embodiment, the polishing apparatus includes a local load application device electrically connected to the control device that applies a local load to a part of the retainer ring of the polishing head, the control device calculates the frictional force generated between the substrate and the polishing head based on signals sent from the first sensor group and the second sensor group, and controls the operation of the local load application device based on the calculated frictional force. [Effects of the Invention]

[0013] The polishing apparatus is equipped with a sensor that detects information about the force acting on the polishing head. Therefore, the polishing apparatus can accurately determine the frictional force generated between the wafer held by the polishing head and the polishing pad. [Brief explanation of the drawing]

[0014] [Figure 1] This figure shows one embodiment of a polishing device. [Figure 2] This figure shows the first sensor group and the second sensor group. [Figure 3] This figure shows an example of the components of the frictional force acting between the polishing head and the wafer. [Figure 4] This is a diagram showing the change in frictional force. [Figure 5] This figure shows an example of the components of the frictional force acting between the polishing head and the wafer. [Figure 6] This diagram shows the wafer tilted relative to the polishing pad. [Figure 7] This figure shows another embodiment of the polishing apparatus. [Modes for carrying out the invention]

[0015] Embodiments of the present invention will be described in detail below with reference to the drawings. Figure 1 shows one embodiment of a polishing apparatus. As shown in Figure 1, the polishing apparatus comprises a polishing table 3 that supports a polishing pad 2, a polishing head 1 that presses a wafer W (such as a substrate) having a film onto the polishing pad 2, a table motor 6 that rotates the polishing table 3, a polishing liquid supply nozzle 5 for supplying a polishing liquid such as slurry onto the polishing pad 2, and a control device 9 for controlling the operation of the polishing apparatus. The upper surface of the polishing pad 2 constitutes the polishing surface 2a for polishing the wafer W. The control device 9 is electrically connected to the table motor 6.

[0016] The polishing head 1 is connected to the head shaft 10, which is connected to a polishing head motor (not shown) via a connecting means such as a belt. The polishing head motor rotates the polishing head 1 together with the head shaft 10 in the direction indicated by the arrow.

[0017] The head shaft 10 is connected to a head arm 20 that rotatably supports the head shaft 10, and is configured to move up and down relative to the head arm 20 by a vertical movement mechanism (not shown). The head arm 20 is connected to an arm shaft 21 and is rotatable about the arm shaft 21. The polishing table 3 is connected to a table motor 6, and the table motor 6 is configured to rotate the polishing table 3 and the polishing pad 2 in the direction indicated by the arrow.

[0018] The wafer W is polished as follows: While the polishing table 3 and polishing head 1 are rotated in the direction indicated by the arrows in Figure 1, polishing fluid is supplied from the polishing fluid supply nozzle 5 to the polishing surface 2a of the polishing pad 2 on the polishing table 3. The wafer W is rotated by the polishing head 1 around the head shaft 10, and while the polishing fluid is present on the polishing pad 2, the wafer W is pressed against the polishing surface 2a of the polishing pad 2 by the polishing head 1. The polishing table 3 rotates around its center CP. The surface of the wafer W is polished by the chemical action of the polishing fluid and the mechanical action of the abrasive grains contained in the polishing fluid or the polishing pad 2.

[0019] The control unit 9 consists of at least one computer. The control unit 9 includes a storage device 9a in which a program is stored, and an arithmetic unit 9b that performs calculations according to the instructions contained in the program. The arithmetic unit 9b includes a CPU (Central Processing Unit) or GPU (Graphics Processing Unit), etc., that performs calculations according to the instructions contained in the program stored in the storage device 9a. The storage device 9a includes main memory (e.g., random access memory) accessible by the arithmetic unit 9b, and auxiliary storage (e.g., a hard disk drive or solid-state drive) that stores data and programs.

[0020] In order to accurately control the pressing force of the polishing head 1 and accurately determine the polishing endpoint of the wafer W, it is important to accurately determine the frictional force generated between the wafer W and the polishing pad 2. Therefore, in this embodiment, the polishing apparatus is equipped with a first sensor group 30 and a second sensor group 31 arranged adjacent to the head arm 20 in order to accurately determine the frictional force. The configuration of these sensor groups 30 and 31 will be described below with reference to the drawings.

[0021] Figure 2 shows the first sensor group and the second sensor group. As shown in Figure 2, the first sensor group 30 and the second sensor group 31 are each located on the tip side of the head arm 20 (i.e., the connecting side of the head shaft 10).

[0022] The polishing device includes a first housing plate 25A and a second housing plate 25B positioned on both sides of the head arm 20 (above and below the head arm 20 in the embodiment shown in Figure 2). In Figure 1, these housing plates 25A and 25B are omitted for clarity, but even in the embodiment shown in Figure 1, the polishing device includes housing plates 25A and 25B.

[0023] Housing plates 25A and 25B have the same structure. Each of the housing plates 25A and 25B has a flat plate shape that extends parallel to the head arm 20. The first housing plate 25A is positioned below the head arm 20, and the second housing plate 25B is positioned above the head arm 20.

[0024] As shown in Figure 2, the first sensor group 30 is positioned between the first housing plate 25A and the head arm 20 and is configured to detect information regarding the force acting on the polishing head 1. More specifically, the first sensor group 30 comprises a plurality of force sensors 30A, 30B, and 30C. These force sensors 30A, 30B, and 30C are positioned around the head shaft 10 at equal distances from the head shaft 10 (see Figures 1 and 2). The force sensors 30A, 30B, and 30C are positioned above the first housing plate 25A and within the same plane.

[0025] The second sensor group 31 has the same configuration as the first sensor group 30. The second sensor group 31 is positioned between the second housing plate 25B and the head arm 20 and is configured to detect information regarding the force acting on the polishing head 1. More specifically, the second sensor group 31 comprises a plurality of force sensors 31A, 31B, and 31C. These force sensors 31A, 31B, and 31C are positioned around the head shaft 10 at equal distances from the head shaft 10 (see Figures 1 and 2). The force sensors 31A, 31B, and 31C are positioned below the second housing plate 25B and within the same plane.

[0026] In the embodiments shown in Figures 1 and 2, each of the first sensor group 30 and the second sensor group 31 is equipped with three force sensors, but the number of force sensors is not limited to this embodiment. The number of force sensors may be determined according to the size of the polishing head 1 and the pressing force of the polishing head 1. In one embodiment, each of the first sensor group 30 and the second sensor group 31 may be equipped with at least one force sensor.

[0027] In the embodiments shown in Figures 1 and 2, each of the force sensors 30A, 30B, 30C (and force sensors 31A, 31B, 31C) is a triaxial sensor that detects information regarding the force acting on the polishing head 1 in three axial directions (i.e., the x-axis, y-axis, and z-axis). An example of a triaxial sensor is a quartz piezoelectric element. Here, the x-axis and y-axis directions are directions that extend perpendicular to the head shaft 10 (i.e., directions that extend parallel to the polishing pad 2), and in this embodiment, they are horizontal directions. The z-axis direction is a direction that extends parallel to the head shaft 10 (i.e., directions that extend perpendicular to the polishing pad 2), and in this embodiment, they are vertical directions.

[0028] In one embodiment, each of the force sensors 30A, 30B, 30C (and force sensors 31A, 31B, 31C) may be a biaxial sensor that detects force information in two axes (i.e., the x-axis and y-axis), or a uniaxial sensor that detects force information in one axis (i.e., the z-axis). In another embodiment, each of the force sensors 30A, 30B, 30C (and force sensors 31A, 31B, 31C) may be a combination of a biaxial sensor and a uniaxial sensor. Even with such a configuration, the polishing device can accurately determine the friction force.

[0029] As shown in Figure 2, the head shaft 10 passes through through holes formed in the central portions of the housing plates 25A and 25B. The polishing device includes a first bearing 26A positioned between the head shaft 10 and the first housing plate 25A, and a second bearing 26B positioned between the head shaft 10 and the second housing plate 25B.

[0030] Each of the bearings 26A and 26B is configured to receive the load of the polishing head 1 (more specifically, radial load and axial load (i.e., thrust load)) through the head shaft 10. When the polishing head 1 presses the wafer W against the polishing pad 2, the load of the polishing head 1 acts on each of the force sensors 30A, 30B, 30C, 31A, 31B, and 31C.

[0031] In this embodiment, the polishing device has a structure that supports the head shaft 10 by housing plates 25A and 25B (and bearings 26A and 26B), and has a structure that sandwiches sensor groups 30 and 31 between the housing plates 25A and 25B and the head arm 20. With this structure, the polishing device can uniformly transmit the load acting on the polishing head 1 to each of the sensor groups 30 and 31 via the head shaft 10.

[0032] By arranging multiple force sensors in the spaces formed above and below the head arm 20, compact force sensors can be used, resulting in space savings for the polishing apparatus. Furthermore, this configuration allows for the use of multiple compact, high-resolution force sensors, enabling more accurate detection of information regarding the force acting on the polishing head 1.

[0033] The control device 9 is electrically connected to each of the force sensors 30A, 30B, 30C, 31A, 31B, and 31C. Based on the signals detected by each of the force sensors 30A, 30B, 30C, 31A, 31B, and 31C, the control device 9 calculates the load on the polishing head 1 and calculates the frictional force F acting on the wafer W from the calculated load on the polishing head 1. As shown in Figure 2, the frictional force F is the sum of the absolute value of the force component FL acting on force sensors 30A, 30B, and 30C and the absolute value of the force component FU acting on force sensors 31A, 31B, and 31C (F = |FL| + |FU|).

[0034] FIG. 3 is a diagram showing an example of the components of the frictional force acting between the polishing head and the wafer. As shown in FIG. 3, when the polishing head 1 is viewed from above, the x-axis components of the forces acting on the force sensors 30A, 30B, 30C, 31A, 31B, 31C are f x1 , f x2 , f x3 , f x4 , f x5 , f x6 are defined, and the y-axis components are f y1 , f y2 , f y3 , f y4 , f y5 , f y6 are defined.

[0035] The x-axis component FxL of the force acting on the force sensors 30A, 30B, 30C is f x1 + f x2 + f x3 and is expressed as, and the y-axis component FyL is f y1 + f y2 + f y3 and is expressed as. The x-axis component FxU of the force acting on the force sensors 31A, 31B, 31C is f x4 + f x5 + f x6 and is expressed as, and the y-axis component FyU is f y4 + f y5 + f y6 and is expressed as.

[0036] The combined components of the forces acting on the force sensors 30A, 30B, 30C and the force sensors 31A, 31B, 31C in the x-axis direction and the y-axis direction perpendicular to each other (i.e., the frictional force generated between the polishing pad 2 and the wafer W) F is expressed by the following Equation 1.

Equation

[0037] The control device 9 stores the data related to the above equation 1 in the storage device 9a. Therefore, the control device 9 calculates the friction force F based on the signals sent from each force sensor belonging to the sensor groups 30 and 31 and the above equation 1. The control device 9 may continuously monitor the calculated friction force F during the polishing of the wafer W. By monitoring the friction force F, the control device 9 can accurately determine the polishing endpoint of the wafer W in response to changes in the friction force F.

[0038] Figure 4 shows the change in frictional force. In the embodiment shown in Figure 4, the wafer W has a stacked upper layer and a lower layer. Since the upper layer is made of a softer material than the lower layer, the frictional force generated between the upper layer and the polishing pad 2 is smaller than the frictional force generated between the lower layer and the polishing pad 2. As the wafer W is polished, the upper layer is eventually removed and the lower layer is exposed. As shown in the graph in Figure 4, when the lower layer is exposed, the frictional force F changes. Note that the graph in Figure 4 shows the change in frictional force F over time.

[0039] The control device 9 can determine the polishing endpoint (i.e., the point at which the underlying film is exposed) by monitoring the friction force F during the polishing of the wafer W. More specifically, the control device 9 stores a threshold value in the storage device 9a that corresponds to the type of film on the wafer W being polished. This threshold value corresponds to the friction force at the polishing endpoint. The control device 9 compares the calculated friction force F with the predetermined threshold value and determines the polishing endpoint of the wafer W when the current friction force F reaches the threshold value.

[0040] In the embodiment shown in Figure 4, the upper layer is made of a softer material than the lower layer, so the frictional force F increases as the wafer W is polished. However, depending on the type of wafer W, the upper layer may be made of a harder material than the lower layer. In this case, the frictional force F decreases as the wafer W is polished. Even in this case, the control device 9 compares the calculated frictional force F with a predetermined threshold and determines the end point of wafer W polishing when the current frictional force F reaches the predetermined threshold.

[0041] The control device 9 may determine the friction force based on the change in the torque current of the table motor 6, but due to variations in the motor and variations in the assembly of the polishing head 1, it may not be possible to determine the friction force accurately. According to this embodiment, the control device 9 determines the friction force F based on a force sensor that detects information about the force acting on the polishing head 1. Therefore, the control device 9 can accurately determine the friction force F generated between the wafer W held by the polishing head 1 and the polishing pad 2.

[0042] Figure 5 shows an example of the components of the frictional force acting between the polishing head and the wafer. As shown in Figure 5, the z-axis component of the force acting on force sensors 30A, 30B, 30C, 31A, 31B, and 31C is f z1 ,f z2 ,f z3 ,f z4 ,f z5 ,f z6 This is defined as follows: The z-axis component (i.e., the normal force) N of the force acting on force sensors 30A, 30B, 30C, 31A, 31B, and 31C is f z1 +f z2 +f z3 +f z4 +f z5 +f z6 Expressed as (N=f z1 +f z2 +f z3 +f z4 +f z5 +f z6 ).

[0043] The frictional force F generated between the polishing pad 2 and the wafer W is expressed by the following equation 2. Formula 2: F=μ×N

[0044] Here, μ represents the coefficient of friction. The coefficient of friction μ varies depending on the type of wafer W, and furthermore, it changes during the polishing of the wafer W. Therefore, the control device 9 may determine (estimate) the coefficient of friction μ to an arbitrary value, and then determine the frictional force F based on the determined coefficient of friction μ and the normal force N. Even by this method, the control device 9 can accurately determine the frictional force F.

[0045] In this embodiment, each of the force sensors 30A, 30B, 30C, 31A, 31B, and 31C is a triaxial sensor. Therefore, the control device 9 can derive the friction force F from equation 1 and calculate the normal force N, thereby deriving the friction coefficient μ from equation 2. The control device 9 can then determine the friction force F more accurately from the friction coefficient μ and the normal force N.

[0046] Since equation 2 above includes the coefficient of friction μ, a proportional relationship exists between equation 1 and equation 2 depending on the coefficient of friction μ. Therefore, the control device 9 can determine an abnormality in the force sensor (and / or an assembly abnormality in the polishing head 1) by comparing the friction force F derived from equation 1 with the friction force F derived from equation 2. More specifically, during the polishing of the wafer W, the control device 9 may compare the two friction forces F derived from equations 1 and 2, and if a proportional relationship does not exist between these two friction forces F, it may determine that an abnormality has occurred in at least one of the force sensors 30A, 30B, 30C, 31A, 31B, or 31C.

[0047] Figure 6 shows a wafer tilted relative to the polishing pad. As shown in Figure 6, during the polishing of wafer W, the wafer W may tilt relative to the polishing pad 2. If the wafer W is continued to be polished in this state, not only will the uniformity of the film thickness of the wafer W decrease, but it may also become impossible to accurately determine the polishing endpoint of the wafer W. More specifically, if the wafer W is tilted, the upper layer may not be polished uniformly, and a portion of the lower layer may be exposed while the upper layer remains partially intact. In this case, since the wafer W is polished with a mixture of parts of the upper and lower layers, the frictional force F changes gradually over time, and even when the frictional force F reaches a threshold, the polishing endpoint of the wafer W may not have been reached.

[0048] Therefore, the control device 9 may calculate the normal force N acting on each force sensor based on the signals sent from the force sensors 30A, 30B, 30C, 31A, 31B, and 31C, and measure the tilt of the wafer W from these normal forces N. By arranging multiple force sensors belonging to sensor groups 30 and 31 around the head shaft 10, the control device 9 can accurately measure the tilt of the wafer W.

[0049] The control device 9 may control the orientation of the polishing head 1 based on the measured inclination of the wafer W. The polishing head 1 is equipped with an elastic membrane (not shown) for pressing the wafer W against the polishing surface 2a of the polishing pad 2. Therefore, the control device 9 may supply compressed gas to the elastic membrane to control the orientation of the polishing head 1 so that it is parallel to the polishing pad 2.

[0050] Furthermore, according to this embodiment, the control device 9 can determine whether the pressing force of the polishing head 1 acting on the entire wafer W is uniform or not based on the signals sent from each of the multiple force sensors. If the signals sent from each force sensor are different, the control device 9 can determine that the pressing force of the polishing head 1 is not uniform. In this case, the control device 9 may supply compressed gas to the elastic membrane and control the pressing force of the polishing head 1 so that the pressing force of the polishing head 1 becomes uniform.

[0051] Figure 7 shows another embodiment of the polishing apparatus. In the embodiment shown in Figure 7, the polishing head 1 includes a retainer ring 40 surrounding the wafer W. As shown in Figure 7, the polishing apparatus includes a first local load application device 50A that applies a local load to a part of the retainer ring 40, and a second local load application device 50B that applies a local load to a part of the retainer ring 40.

[0052] The localized load application devices 50A and 50B are positioned above the retainer ring 40 and are fixed to the head arm 20. Therefore, while the retainer ring 40 rotates around its axis during polishing, the localized load application devices 50A and 50B remain stationary and do not rotate together with the retainer ring 40.

[0053] The first local load application device 50A is positioned upstream of the retainer ring 40 (on one side of the retainer ring 40 into which polishing fluid flows onto the polishing surface 2a) in the direction of travel of the polishing surface 2a of the polishing pad 2, and the second local load application device 50B is positioned downstream of the retainer ring 40 (on the opposite side of the retainer ring 40 into which polishing fluid flows onto the polishing surface 2a) in the direction of travel of the polishing surface 2a of the polishing pad 2. The control device 9 is electrically connected to each of the local load application devices 50A and 50B, and each of the local load application devices 50A and 50B applies a downward local load to a part of the retainer ring 40.

[0054] When polishing fluid flows between the wafer W and the polishing pad 2, the frictional force between the wafer W and the polishing pad 2 may differ between the upstream and downstream sides of the retainer ring 40. It is desirable that the frictional force acting on the wafer W be uniform throughout the wafer W. Therefore, the control device 9 may calculate the frictional force F acting on the entire wafer W based on the signals sent from each of the multiple force sensors, and if the frictional force F differs between the upstream and downstream sides of the retainer ring 40, it may control the operation of the local load application devices 50A and 50B. With this configuration, the control device 9 can make the frictional force acting on the entire wafer W uniform and maintain the frictional force constant.

[0055] The embodiments described above are intended to enable persons with ordinary skill in the art to implement the present invention. Various modifications of the above embodiments can be made naturally by those skilled in the art, and the technical idea of ​​the present invention can be applied to other embodiments as well. Therefore, the present invention is not limited to the embodiments described, but is to be interpreted in the broadest sense according to the technical idea defined by the claims. [Explanation of symbols]

[0056] 1 Polishing head 2 polishing pads 2a Polished surface 3 Polishing Table 5. Polishing fluid supply nozzle 6 Table motors 9 Control device 9a Storage device 9b Arithmetic unit 10 Head Shaft 20 Head Arm 25A First Housing Plate 25B Second Housing Plate 30 First Sensor Group 30A, 30B, 30C Force Sensor 31. Second Sensor Group 31A, 31B, 31C Force Sensors 40 Retainer Rings 50A First local load application device 50B Second Local Loading Device

Claims

1. A polishing apparatus, A polishing table that supports the polishing pad, A polishing head that presses the substrate against the polishing table, A head shaft connected to the polishing head, A head arm that rotatably supports the head shaft, The system includes a triaxial sensor positioned adjacent to the head arm and for detecting information regarding the three-axis forces acting on the polishing head, The polishing apparatus includes a control device electrically connected to the three-axis sensor, The control device monitors the frictional force generated between the substrate and the polishing head, calculated based on the signal sent from the three-axis sensor, during the polishing of the substrate. The polishing apparatus includes a local load application device electrically connected to the control device, which applies a local load to a part of the retainer ring of the polishing head. The control device is Based on the signal sent from the three-axis sensor, the frictional force generated between the substrate and the polishing head is calculated. A polishing device that controls the operation of the local load application device based on the calculated friction force.

2. The control device is Based on the signal sent from the three-axis sensor, the tilt of the substrate is measured. The polishing apparatus according to claim 1, wherein the posture of the polishing head is controlled based on the measured inclination of the substrate.

3. The control device is The calculated friction force is compared with a predetermined threshold, The polishing apparatus according to claim 1 or claim 2, wherein the polishing endpoint of the substrate is determined when the frictional force reaches the threshold.

4. A polishing table that supports the polishing pad, A polishing head that presses the substrate against the polishing table, A head shaft connected to the polishing head, A head arm that rotatably supports the head shaft, A first housing plate and a second housing plate are arranged on both sides of the head arm, A group of first sensors is positioned between the first housing plate and the head arm and detects information regarding the force acting on the polishing head. A polishing apparatus comprising: a second group of sensors disposed between the second housing plate and the head arm, which detects information relating to the force acting on the polishing head.

5. Each of the first sensor group and the second sensor group is equipped with multiple force sensors, The polishing apparatus according to claim 4, wherein the plurality of force sensors are arranged at positions equal in distance from the head shaft.

6. The polishing apparatus includes a control device electrically connected to the first sensor group and the second sensor group, The polishing apparatus according to claim 4 or 5, wherein the control device monitors the frictional force generated between the substrate and the polishing head, calculated based on signals sent from the first sensor group and the second sensor group, during the polishing of the substrate.

7. The control device is Based on the signals sent from the first sensor group and the second sensor group, the tilt of the substrate is measured. The polishing apparatus according to claim 6, wherein the posture of the polishing head is controlled based on the measured inclination of the substrate.

8. The control device is The calculated friction force is compared with a predetermined threshold, The polishing apparatus according to claim 6, wherein the polishing endpoint of the substrate is determined when the frictional force reaches the threshold.

9. The polishing apparatus includes a local load application device electrically connected to the control device, which applies a local load to a part of the retainer ring of the polishing head. The control device is Based on the signals sent from the first sensor group and the second sensor group, the frictional force generated between the substrate and the polishing head is calculated. The polishing apparatus according to claim 6, wherein the operation of the local load application device is controlled based on the calculated friction force.

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