Polishing method and polishing apparatus

Abstract

The present invention provides a polishing apparatus that can accurately determine the position of the measurement point for the film thickness of a workpiece. [Solution] The polishing apparatus includes a polishing head 1 that polishes a workpiece W by pressing it against a polishing pad 2 on a polishing table 3, a film thickness sensor 25 that measures the film thickness at a measurement point on the surface S1 of the workpiece W, an infrared imaging device 27 that generates a first image and a second image of a feature region 100 on the surface S1 from the back surface S2 of the workpiece W at predetermined time intervals, and a processing control unit 9 that determines the coordinates of the measurement point on the surface S1 of the workpiece W based on the first image and the second image.

Description

Technical Field

[0001] The present invention relates to a technique for polishing a workpiece such as a wafer, a substrate, or a panel while measuring the film thickness of the workpiece, and particularly to a technique for specifying a film thickness measurement point.

Background Art

[0002] In chemical mechanical polishing (CMP), while rotating a workpiece (e.g., a wafer) by a polishing head, the workpiece is pressed against a polishing pad provided on a rotating polishing table to polish the surface of the workpiece. During the polishing of the workpiece, a polishing liquid (e.g., slurry) is supplied onto the polishing pad.

[0003] In order to measure the film thickness of the workpiece, a film thickness sensor is installed inside the polishing table. The film thickness sensor measures the film thickness while crossing the workpiece during the polishing of the workpiece. Examples of the film thickness sensor include an optical sensor and an eddy current sensor. Each time the film thickness sensor crosses the workpiece, it measures the film thickness at a plurality of measurement points while moving along different paths. Therefore, the measurement points are distributed over the entire surface of the workpiece.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Variations in the film thickness of the workpiece exist not only in the radial direction of the workpiece but also in the circumferential direction of the workpiece. In order to polish the workpiece so as to reduce the variations in the film thickness existing in the circumferential direction of the workpiece, it is necessary to measure the variations in the circumferential film thickness during the polishing of the workpiece.

[0006] However, during polishing, the workpiece may not rotate in conjunction with the polishing head; instead, it may rotate relative to the polishing head within the head itself. Therefore, the rotational speed of the workpiece does not necessarily match the rotational speed of the polishing head. As a result, it was impossible to pinpoint the location of measurement points in the circumferential direction of the workpiece, leading to the problem of being unable to accurately control the circumferential film thickness of the workpiece.

[0007] Therefore, the present invention provides a polishing method and polishing apparatus that can accurately determine the position of the measurement point for the film thickness of a workpiece. [Means for solving the problem]

[0008] In one embodiment, a polishing apparatus is provided, comprising: a polishing table that supports a polishing pad; a polishing head that polishes a workpiece having a surface on which a feature region is formed by pressing the workpiece against the polishing pad on the polishing table; a polishing head motor that rotates the polishing head; a film thickness sensor fixed to the polishing table and measuring the film thickness at a measurement point on the surface of the workpiece; an infrared imaging device disposed within the polishing head and generating a first image and a second image of the feature region on the surface of the workpiece from the back surface of the workpiece at predetermined time intervals; and a processing control unit that determines the coordinates of the measurement point on the surface of the workpiece based on the first image and the second image.

[0009] In one embodiment, the processing control unit is configured to calculate the rotation angle of the workpiece per unit time based on the inclination angle of the feature region on the first image, the inclination angle of the feature region on the second image, and the predetermined time interval; calculate the time difference between the measurement time for measuring the film thickness at the measurement point and the imaging time for generating the second image; and determine the coordinates of the measurement point on the surface of the workpiece based on the relative position between the measurement point and the center point of the workpiece, the rotation angle of the workpiece per unit time, and the time difference. In one embodiment, the processing control unit determines the inclination angle of a predefined coordinate system on the surface of the workpiece based on the inclination angle of the feature region on the second image, calculates the rotation angle of the coordinate system that rotates during the time difference by multiplying the rotation angle of the workpiece per unit time by the time difference, determines the coordinate system at the measurement time by rotating the coordinate system at the imaging time around the center point of the workpiece by the calculated rotation angle, and determines the coordinate of the measurement point on the coordinate system at the measurement time from the relative position of the measurement point and the center point of the workpiece. In one embodiment, the polishing apparatus further comprises an infrared light source disposed within the polishing head, which irradiates infrared light from the back surface of the workpiece to the feature region on the surface of the workpiece, wherein the infrared light has a wavelength that penetrates the workpiece and is reflected by the feature region, and the infrared imaging device is configured to generate the first image and the second image by receiving the infrared light emitted from the infrared light source and reflected by the feature region. In one embodiment, the polishing head comprises an elastic membrane for pressing the workpiece against the polishing pad and a carrier to which the elastic membrane is fixed, the infrared imaging device and the infrared light source are fixed to the carrier, and the infrared light has wavelengths that penetrate the elastic membrane and the workpiece and reflect in the characteristic region.

[0010] In one embodiment, the polishing apparatus further comprises a half mirror disposed within the polishing head, which transmits the infrared light emitted from the infrared light source and reflects the infrared light reflected in the feature region, the half mirror being positioned diagonally on the optical path of the infrared light emitted from the infrared light source and the optical path of the infrared light reflected in the feature region, and the infrared imaging apparatus is configured to generate the first image and the second image by receiving the infrared light emitted from the infrared light source, transmitted through the half mirror, reflected in the feature region and reflected by the half mirror. In one embodiment, the polishing apparatus further comprises a half mirror disposed within the polishing head that reflects the infrared light emitted from the infrared light source and transmits the infrared light reflected in the feature region, the half mirror being positioned diagonally on the optical path of the infrared light emitted from the infrared light source and the optical path of the infrared light reflected in the feature region, and the infrared imaging apparatus is configured to generate the first image and the second image by receiving the infrared light emitted from the infrared light source, reflected by the half mirror, reflected in the feature region, and transmitted through the half mirror.

[0011] In one embodiment, the polishing apparatus further comprises a head angle detector for detecting the rotation angle of the polishing head, the infrared imaging device is fixed to the polishing head, and the processing control unit is configured to calculate the difference in the inclination angle of the feature region between the first image and the second image, calculate the relative rotation angle of the workpiece with respect to the polishing head per unit time by dividing the difference in inclination angle by the predetermined time interval, and calculate the rotation angle of the workpiece per unit time by subtracting the relative rotation angle of the workpiece with respect to the polishing head per unit time from the rotation angle of the polishing head at the predetermined time interval detected by the head angle detector. In one embodiment, the polishing apparatus further comprises a fixing member for fixing the infrared imaging device, the infrared imaging device is non-contact with the polishing head and does not rotate integrally with the polishing head, and the processing control unit is configured to calculate the difference in the inclination angle of the feature region between the first image and the second image, and to calculate the rotation angle of the workpiece per unit time by dividing the difference in inclination angle by the predetermined time interval. In one embodiment, the polishing head comprises an elastic membrane for pressing the workpiece against the polishing pad, and a carrier to which the elastic membrane is fixed, the elastic membrane having a marker for identifying the orientation of the elastic membrane in the circumferential direction, the infrared imaging device being fixed to the carrier, and the processing control unit being configured to calculate the inclination angle of the feature region on the first image based on the marker on the first image, the inclination angle of the feature region on the first image based on the marker on the second image, and the rotation angle of the workpiece per unit time based on a predetermined time interval.

[0012] In one embodiment, a polishing method is provided, in which a workpiece having a surface on which a feature region is formed is pressed against a polishing pad on a polishing table by the polishing head while rotating the polishing head, a first image and a second image of the feature region on the surface of the workpiece are generated at predetermined time intervals from the back surface of the workpiece by an infrared imaging device placed in the polishing head, a film thickness sensor fixed to the polishing table measures the film thickness at a measurement point on the surface of the workpiece, and the coordinates of the measurement point on the surface of the workpiece are determined based on the first image and the second image.

[0013] In one embodiment, determining the coordinates of the measurement point involves calculating the rotation angle of the workpiece per unit time based on the inclination angle of the feature region on the first image, the inclination angle of the feature region on the second image, and the predetermined time interval; calculating the time difference between the measurement time for measuring the film thickness at the measurement point and the imaging time for generating the second image; and determining the coordinates of the measurement point on the surface of the workpiece based on the relative position between the measurement point and the center point of the workpiece, the rotation angle of the workpiece per unit time, and the time difference. In one embodiment, determining the coordinates of the measurement point on the surface of the workpiece based on the relative position between the measurement point and the center point of the workpiece, the rotation angle of the workpiece per unit time, and the time difference involves determining the inclination angle of a predefined coordinate system on the surface of the workpiece based on the inclination angle of the feature region on the second image, calculating the rotation angle of the coordinate system that rotates during the time difference by multiplying the rotation angle of the workpiece per unit time by the time difference, determining the coordinate system at the measurement time by rotating the coordinate system at the imaging time around the center point of the workpiece by the calculated rotation angle, and determining the coordinates of the measurement point on the coordinate system at the measurement time from the relative position between the measurement point and the center point of the workpiece. In one embodiment, the polishing method further includes irradiating the feature region on the surface of the workpiece from the back surface of the workpiece with an infrared light source placed in the polishing head while polishing the workpiece, and generating the first and second images with the infrared imaging device, which generates the first and second images by receiving the infrared light emitted from the infrared light source and reflected from the feature region with the infrared imaging device, wherein the infrared light has a wavelength that penetrates the workpiece and is reflected from the feature region. In one embodiment, the polishing head comprises an elastic membrane for pressing the workpiece against the polishing pad and a carrier to which the elastic membrane is fixed, the infrared imaging device and the infrared light source are fixed to the carrier, and the infrared light has wavelengths that penetrate the elastic membrane and the workpiece and reflect in the characteristic region.

[0014] In one embodiment, generating the first and second images with the infrared imaging device involves generating the first and second images by receiving the infrared light emitted from the infrared light source, passing through a half-mirror placed in the polishing head, reflecting it in the feature region, and receiving the infrared light reflected by the half-mirror with the infrared imaging device, wherein the half-mirror is positioned obliquely on the optical path of the infrared light emitted from the infrared light source and the optical path of the infrared light reflected in the feature region. In one embodiment, the generation of the first and second images by the infrared imaging device is achieved by receiving the infrared light emitted from the infrared light source, reflected by a half-mirror placed in the polishing head, reflected in the feature region, and transmitted through the half-mirror, with the half-mirror being positioned obliquely on the optical path of the infrared light emitted from the infrared light source and the optical path of the infrared light reflected in the feature region.

[0015] In one embodiment, the polishing method further includes detecting the rotation angle of the polishing head, the infrared imaging device is fixed to the polishing head, and the calculation of the rotation angle of the workpiece per unit time is performed by calculating the difference in the inclination angle of the feature region between the first image and the second image, dividing the difference in inclination angle by the predetermined time interval to calculate the relative rotation angle of the workpiece with respect to the polishing head per unit time, and subtracting the relative rotation angle of the workpiece with respect to the polishing head per unit time from the rotation angle of the polishing head at the predetermined time interval detected by the head angle detector to calculate the rotation angle of the workpiece per unit time. In one aspect, the polishing head is fixed to a fixed member, is non-contact with the polishing head, does not rotate integrally with the polishing head, and calculating the rotation angle of the workpiece per unit time is to calculate the difference in the inclination angle of the feature region between the first image and the second image, and by dividing the difference in the inclination angle by the predetermined time interval, the rotation angle of the workpiece per unit time is calculated. In one aspect, the polishing head includes an elastic film for pressing the workpiece against the polishing pad and a carrier to which the elastic film is fixed. The elastic film has a mark for specifying the orientation in the circumferential direction of the elastic film. The infrared imaging device is fixed to the carrier. Calculating the rotation angle of the workpiece per unit time is to calculate the inclination angle of the feature region on the first image based on the mark on the first image, calculate the inclination angle of the feature region on the first image based on the mark on the second image, and calculate the rotation angle of the workpiece per unit time based on the predetermined time interval.

Advantages of the Invention

[0016] From the first and second images of the feature region on the surface of the workpiece, the rotation angle of the workpiece per unit time can be calculated. Based on this rotation angle per unit time, the coordinates of the measurement points of the film thickness of the workpiece can be determined.

Brief Description of the Drawings

[0017] [Figure 1] It is a schematic diagram showing an embodiment of a polishing apparatus. [Figure 2] It is a cross-sectional view showing an embodiment of a polishing head. [Figure 3] It is a schematic diagram showing a state where an infrared imaging device generates an image of a feature region formed on a workpiece. [Figure 4] It is a top view showing the positional relationship between a polishing table and a workpiece held by a polishing head. [Figure 5]It is a schematic diagram showing an example of generation of a first image and a second image by an imaging device. [Figure 6] It is a schematic diagram showing examples of a first image and a second image generated by an infrared imaging device. [Figure 7] It is a schematic diagram showing an example of a coordinate system defined on the surface of a workpiece. [Figure 8] It is a schematic diagram showing another example of a feature region. [Figure 9] It is a schematic diagram showing examples of a first image and a second image including the feature region shown in FIG. 8. [Figure 10] It is a schematic diagram showing an example of generation of an image by an imaging device and measurement of film thickness by a film thickness sensor. [Figure 11] It is a schematic diagram showing another example of generation of an image by an imaging device and measurement of film thickness by a film thickness sensor. [Figure 12] It is a top view showing another embodiment of a film thickness sensor. [Figure 13] It is a cross-sectional view of a polishing head showing another embodiment of an infrared imaging device and an infrared light source. [Figure 14] It is a top view showing the positional relationship between a polishing table according to the embodiment shown in FIG. 13 and a workpiece held by a polishing head. [Figure 15] It is a cross-sectional view of a polishing head showing still another embodiment of an infrared imaging device and an infrared light source. [Figure 16] It is a cross-sectional view of a polishing head showing still another embodiment of an infrared imaging device and an infrared light source. [Figure 17] It is a cross-sectional view of a polishing head showing still another embodiment of an infrared imaging device and an infrared light source. [Figure 18] It is a cross-sectional view of a polishing head showing still another embodiment of an infrared imaging device and an infrared light source. [Figure 19] It is a schematic diagram showing an embodiment of an elastic film having a mark. [Figure 20] It is a schematic diagram showing an example of a first image generated by an infrared imaging device disposed in a polishing head having the elastic film shown in FIG. 19. [Figure 21] This is a cross-sectional view of a polishing head showing one embodiment of an infrared imaging device that is not fixed to the polishing head. [Modes for carrying out the invention]

[0018] Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a schematic diagram showing 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 workpiece W against the polishing pad 2, a table motor 6 that rotates the polishing table 3, and a polishing liquid supply nozzle 5 for supplying polishing liquid (for example, a slurry containing abrasive particles) onto the polishing pad 2. The surface of the polishing pad 2 constitutes a polishing surface 2a for polishing the workpiece W.

[0019] Specific examples of workpiece W include wafers, wiring boards, and rectangular substrates used in the manufacture of semiconductor devices. Workpiece W has a surface on which characteristic regions are formed. Specific examples of characteristic regions include patterns such as cells that form wiring and scribe lines (dicing lines), as well as regions that are distinguished from other regions by differences in film thickness, material, etc.

[0020] The polishing table 3 is connected to a table motor 6, which is configured to rotate the polishing table 3 and the polishing pad 2 together. The polishing head 1 is fixed to the end of the polishing head shaft 11, which is rotatably supported by a head arm 15. The head arm 15 is rotatably supported by a pivot shaft 16.

[0021] The polishing head shaft 11 is connected to a polishing head vertical movement mechanism 18 located within the head arm 15. The polishing head vertical movement mechanism 18 is configured to move the polishing head shaft 11 up and down in its axial direction. The vertical movement of the polishing head shaft 11 by the polishing head vertical movement mechanism 18 allows the workpiece W held by the polishing head 1 to move closer to and further away from the polishing pad 2 on the polishing table 3. The configuration of the polishing head vertical movement mechanism 18 is not particularly limited, but in one example, the polishing head vertical movement mechanism 18 includes a servo motor, a ball screw mechanism, and the like.

[0022] The polishing head shaft 11 is connected to a polishing head motor 20 located within the head arm 15. The polishing head motor 20 is configured to rotate the polishing head shaft 11 and the polishing head 1 around their respective axes. The configuration of the polishing head motor 20 is not particularly limited, but in one example, the polishing head motor 20 includes an electric motor, a belt, pulleys, and the like.

[0023] The polishing apparatus further includes a processing control unit 9 that controls the operation of each component of the polishing apparatus. The processing control unit 9 is electrically connected to the polishing head 1, the table motor 6, the polishing liquid supply nozzle 5, the polishing head vertical movement mechanism 18, and the polishing head motor 20, and controls the operation of the polishing head 1, the table motor 6, the polishing liquid supply nozzle 5, the polishing head vertical movement mechanism 18, and the polishing head motor 20.

[0024] The processing control unit 9 comprises 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 processing control unit 9 is composed of at least one computer. The storage device 9a comprises a main memory such as random access memory (RAM) and an auxiliary storage device such as a hard disk drive (HDD) or solid-state drive (SSD). Examples of arithmetic units 9b include a CPU (central processing unit) and a GPU (graphics processing unit). However, the specific configuration of the processing control unit 9 is not limited to these examples. The processing control unit 9 may be composed of multiple computers.

[0025] The workpiece W is polished as follows: The processing control unit 9 issues commands to the table motor 6, the polishing head motor 20, and the polishing fluid supply nozzle 5 to rotate the polishing table 3 and the polishing head 1 in the direction indicated by the arrows in Figure 1, while supplying polishing fluid from the polishing fluid supply nozzle 5 to the polishing surface 2a of the polishing pad 2 on the polishing table 3. As the workpiece W is rotated by the polishing head 1, the polishing head 1 presses the workpiece W against the polishing surface 2a of the polishing pad 2 with polishing fluid present between the polishing pad 2 and the workpiece W. The surface of the workpiece W is polished by the chemical action of the polishing fluid and the mechanical action of the abrasive grains contained in the polishing fluid and / or the polishing pad 2.

[0026] The polishing apparatus further includes a film thickness sensor 25 for measuring the film thickness of a workpiece W on a polishing pad 2. The film thickness sensor 25 is fixed to the polishing table 3 and rotates integrally with the polishing table 3. The film thickness sensor 25 is configured to measure the film thickness at a measurement point on the surface of the workpiece W each time it crosses the surface of the workpiece W. Specific examples of the film thickness sensor 25 include optical film thickness sensors and eddy current film thickness sensors, but the type of film thickness sensor 25 is not particularly limited as long as it can measure the film thickness of the workpiece W. The film thickness sensor 25 is electrically connected to a processing control unit 9, and the measured film thickness is transmitted from the film thickness sensor 25 to the processing control unit 9.

[0027] The polishing apparatus further includes a head angle detector (e.g., a rotary encoder) 22 for detecting the rotation angle of the polishing head 1. The head angle detector 22 is configured to detect the rotation angle of the polishing head motor 20. The rotation angle of the polishing head motor 20 is proportional to the rotation angle of the polishing head 1. In one embodiment, the rotation angle of the polishing head motor 20 coincides with the rotation angle of the polishing head 1. Therefore, the rotation angle of the polishing head motor 20 detected by the head angle detector 22 corresponds to the rotation angle of the polishing head 1. The head angle detector 22 is electrically connected to the processing control unit 9, and the detected value of the rotation angle of the polishing head motor 20 (i.e., the detected value of the rotation angle of the polishing head 1) output from the head angle detector 22 is sent to the processing control unit 9.

[0028] Figure 2 is a cross-sectional view showing one embodiment of the polishing head 1. The polishing head 1 comprises a carrier 31 fixed to the end of the polishing head shaft 11, an elastic membrane 34 attached to the lower part of the carrier 31, and a retainer ring 32 positioned below the carrier 31. The retainer ring 32 is positioned around the elastic membrane 34. The retainer ring 32 is an annular structure that holds the workpiece W to prevent the workpiece W from flying off the polishing head 1 during polishing.

[0029] The elastic membrane 34 comprises a contact portion 35 having a contact surface 35a that can contact the upper surface of the workpiece W, and inner wall portions 36a, 36b, 36c and outer wall portion 36d connected to the contact portion 35. The contact portion 35 has substantially the same size and shape as the upper surface of the workpiece W. The inner wall portions 36a, 36b, 36c and outer wall portion 36d are endless walls arranged concentrically.

[0030] Multiple (four in this embodiment) pressure chambers 38A, 38B, 38C, and 38D are provided between the elastic membrane 34 and the carrier 31. The pressure chambers 38A, 38B, 38C, and 38D are formed by the contact portion 35, inner wall portions 36a, 36b, and 36c, and outer wall portion 36d of the elastic membrane 34. In this embodiment, the elastic membrane 34 forms four pressure chambers 38A to 38D, but in one embodiment, the elastic membrane 34 may form three pressure chambers, or five or more pressure chambers.

[0031] An annular membrane (rolling diaphragm) 40 is positioned between the carrier 31 and the retainer ring 32, and a pressure chamber 38E is formed inside this membrane 40. Gas transfer lines F1, F2, F3, F4, and F5 are connected to the pressure chambers 38A, 38B, 38C, 38D, and 38E, respectively. The gas transfer lines F1, F2, F3, F4, and F5 extend via a rotary joint 45 attached to the polishing head shaft 11.

[0032] Gas transfer lines F1, F2, F3, F4, and F5 are connected to a compressed gas supply source (not shown) which serves as a utility supply source in the factory where the polishing equipment is installed. Compressed gas, such as compressed air, is supplied to pressure chambers 38A, 38B, 38C, 38D, and 38E, respectively, through gas transfer lines F1, F2, F3, F4, and F5.

[0033] Pressure regulators Ra1, Ra2, Ra3, Ra4, and Ra5 are connected to gas transfer lines F1, F2, F3, F4, and F5, respectively. Pressure regulators Ra1 to Ra5 ​​can independently change the pressure in pressure chambers 38A to 38E. Therefore, the polishing head 1 can independently adjust the polishing pressure on four corresponding areas of the workpiece W, namely the central part, the inner middle part, the outer middle part, and the edge part, and the pressing force of the polishing pad 2 of the retainer ring 32 against the polishing surface 2a. For example, the polishing head 1 can press different areas of the surface S1 of the workpiece W against the polishing surface 2a of the polishing pad 2 with different pressing forces. Therefore, the polishing head 1 can control the film thickness profile of the workpiece W to achieve a target film thickness profile.

[0034] As shown in Figure 2, the polishing apparatus further comprises an infrared imaging device 27 that generates an image of a feature region on the surface S1 of the workpiece W, and an infrared light source 28 that emits infrared rays. The infrared imaging device 27 and the infrared light source 28 are arranged inside the polishing head 1. In this embodiment, the infrared imaging device 27 and the infrared light source 28 are fixed to the polishing head 1 and rotate integrally with the polishing head 1. In this embodiment, the infrared imaging device 27 is located in the center of the polishing head 1. The infrared imaging device 27 and the infrared light source 28 are fixed to a carrier 31 and are located above the elastic membrane 34. The carrier 31 has a recess 31a in which the light-receiving part 27a of the infrared imaging device 27 and the irradiation part 28a of the infrared light source 28 are arranged. The recess 31a opens on the lower surface of the carrier 31. In this embodiment, the recess 31a is located in the center of the polishing head 1 and communicates with the pressure chamber 38A. In one embodiment, the opening of the recess 31a may be covered with a transparent window (not shown) that transmits infrared rays.

[0035] The infrared imaging device 27 is configured to generate multiple images of feature regions on the surface S1 of the workpiece W from the back surface S2 of the workpiece W at predetermined time intervals. The infrared light source 28 is configured to irradiate the feature regions on the surface S1 of the workpiece W with infrared light from the back surface S2 of the workpiece W. The back surface S2 of the workpiece W is the surface opposite to the surface S1 on which the feature regions are formed. The infrared imaging device 27 is electrically connected to the processing control unit 9, and the images of the feature regions are transmitted from the infrared imaging device 27 to the processing control unit 9 shown in Figure 1.

[0036] Figure 3 is a schematic diagram showing how the infrared imaging device 27 generates an image of the feature region 100 of the workpiece W. The infrared light source 28 is positioned adjacent to the infrared imaging device 27. The infrared light source 28 is configured to emit infrared light having a wavelength that penetrates the elastic film 34 of the polishing head 1 and the workpiece W, and is reflected at the feature region 100 on the surface S1 of the workpiece W. Therefore, the infrared light emitted from the irradiation part 28a of the infrared light source 28 penetrates the elastic film 34, penetrates the workpiece W, and is reflected at the feature region 100 formed on the surface S1 of the workpiece W. The infrared light emitted from the infrared light source 28 is adjusted to have a wavelength that is reflected at the feature region 100, depending on the material, film thickness, etc. of the feature region 100. In one embodiment, the infrared-transmitting layer of the workpiece W is made of silicon.

[0037] During polishing of the workpiece W, polishing liquid L is present between the workpiece W and the polishing pad 2. In one embodiment, the infrared light emitted from the infrared light source 28 has a wavelength that is absorbed by the polishing liquid L present between the workpiece W and the polishing pad 2. The infrared imaging device 27 generates an image of the feature region 100 on the surface S1 of the workpiece W by receiving the infrared light reflected by the feature region 100 on the surface S1 of the workpiece W and transmitted through the elastic film 34 with the light receiving unit 27a. If the film thickness or material differs between the feature region 100 and other regions of the workpiece W, the intensity of the infrared light reflected by the feature region 100 may differ from the intensity of the infrared light reflected by other regions. This difference in the intensity of reflected infrared light appears as a difference in color (shade) in the image generated by the infrared imaging device 27. Therefore, the feature region 100 and other regions with different intensities of reflected infrared light can be distinguished by the difference in color (shade) in the image.

[0038] In this embodiment, the infrared imaging device 27 and the infrared light source 28 are arranged obliquely to the front surface S1 and back surface S2 of the workpiece W. However, the arrangement of the infrared imaging device 27 and the infrared light source 28 is not particularly limited, as long as the infrared imaging device 27 can generate an image of the feature region 100 on the front surface S1 of the workpiece W. In one embodiment, the infrared imaging device 27 and the infrared light source 28 may be arranged perpendicularly to the front surface S1 and back surface S2 of the workpiece W.

[0039] Figure 4 is a top view showing the positional relationship between the polishing table 3 and the workpiece W held by the polishing head 1. In Figure 4, the polishing pad 2 and the carrier 31 and elastic membrane 34 of the polishing head 1 are omitted from the illustration. The workpiece W is rotated by the polishing head 1, but the workpiece W may rotate relative to the polishing head 1 within the retaining ring 32. Therefore, the rotational speed of the workpiece W may not match the rotational speed of the polishing head 1. In the example shown in Figure 4, the workpiece W rotates around its center point CP within the retaining ring 32, as indicated by the arrow.

[0040] The film thickness sensor 25 moves along the path J shown in Figure 4 as the polishing table 3 rotates. In the embodiment shown in Figure 4, the radial distance of the film thickness sensor 25 from the center TP of the polishing table 3 is the same as the radial distance from the center TP of the polishing table 3 to the center of the retainer ring 32 (center of the polishing head 1). Therefore, the film thickness sensor 25 crosses the center point CP of the workpiece W each time the polishing table 3 rotates. When the film thickness sensor 25 is located below the workpiece W, the processing control unit 9 commands the film thickness sensor 25 to measure the film thickness at a predetermined measurement point on the surface S1 of the workpiece W.

[0041] The polishing apparatus is equipped with a table angle detector 50 that detects the rotation angle of the polishing table 3. In the embodiment shown in Figure 4, the table angle detector 50 has a sensor target 52 positioned adjacent to the polishing table 3 and a proximity sensor 51 fixed to the polishing table 3 that detects the sensor target 52. The sensor target 52 is fixed to a fixing member (not shown), and the position of the sensor target 52 is fixed. The proximity sensor 51 rotates integrally with the polishing table 3. Each time the polishing table 3 rotates once, the proximity sensor 51 detects the sensor target 52.

[0042] Since the sensor target 52 is stationary, the rotation angle of the polishing table 3 at the time the proximity sensor 51 detects the sensor target 52 is uniquely determined. Therefore, the table angle detector 50, which consists of the proximity sensor 51 and the sensor target 52, can detect the rotation angle of the polishing table 3. The table angle detector 50 is configured to transmit an angle detection signal to the processing control unit 9 when the proximity sensor 51 detects the sensor target 52.

[0043] The processing control unit 9 can determine other rotation angles of the polishing table 3 from the rotation speed of the polishing table 3 and from the time the proximity sensor 51 detects the sensor target 52. For example, the rotation angle of the polishing table 3 at a predetermined time after the proximity sensor 51 detects the sensor target 52 can be calculated from the rotation angle of the polishing table 3 at the time the proximity sensor 51 detects the sensor target 52, the rotation speed of the polishing table 3, and the predetermined time.

[0044] In one embodiment, the sensor target 52 is fixed to the polishing table 3, and the proximity sensor 51 may be fixed to the fixing member (not shown). In this case, the sensor target 52 rotates integrally with the polishing table 3, and the proximity sensor 51 remains stationary. In another embodiment, the table angle detector 50 that detects the rotation angle of the polishing table 3 may be a rotary encoder built into or connected to the table motor 6.

[0045] Figure 5 is a schematic diagram showing an example of the generation of the first and second images by the infrared imaging device 27. As shown in Figure 5, during polishing of the workpiece W, the infrared imaging device 27 is configured to generate a first image and a second image of the feature region 100 on the surface S1 of the workpiece W at predetermined time intervals. More specifically, during polishing of the workpiece W, the processing control unit 9 commands the infrared imaging device 27 to generate a first image of the feature region 100 on the surface S1 of the workpiece W at imaging time t1, and then generate a second image of the feature region 100 on the surface S1 of the workpiece W at imaging time t2.

[0046] Since the infrared imaging device 27 is fixed to the polishing head 1, it rotates integrally with the polishing head 1. In this embodiment, the infrared imaging device 27 is positioned in the center of the polishing head 1. Therefore, the infrared imaging device 27 generates an image of the area including the center point CP of the workpiece W. The time difference t2-t1 between the imaging time t1 for generating the first image and the imaging time t2 for generating the second image corresponds to the predetermined time interval. The first image and the second image are transmitted from the infrared imaging device 27 to the processing control unit 9.

[0047] Figure 6 is a schematic diagram showing examples of the first image PI1 and the second image PI2 generated by the infrared imaging device 27. In the example shown in Figure 6, the feature region 100 is a pattern such as a wiring pattern, cell, scribe line, or dicing line. As shown in Figure 6, the first image PI1 and the second image PI2 include the feature region 100 on the surface S1 of the workpiece W. When the workpiece W is rotating relative to the polishing head 1, the inclination angle of the feature region 100 on the first image PI1 is different from the inclination angle of the feature region 100 on the second image PI2. The processing control unit 9 calculates the inclination angle θ1 of the feature region 100 on the first image PI1 with respect to the reference line RL and the inclination angle θ2 of the feature region 100 on the second image PI2 with respect to the reference line RL. The reference line RL is not particularly limited, but for example, it is a straight line extending parallel to one side of the image captured by the infrared imaging device 27.

[0048] The processing control unit 9 is configured to calculate the rotation angle of the workpiece W per unit time based on the inclination angle θ1 of the feature region 100 on the first image PI1, the inclination angle θ2 of the feature region 100 on the second image PI2, and the predetermined time interval (t2-t1). More specifically, the processing control unit 9 calculates the difference (θ2-θ1) between the inclination angle θ1 of the feature region 100 on the first image PI1 and the inclination angle θ2 of the feature region 100 on the second image PI2, and calculates the relative rotation angle of the workpiece W with respect to the polishing head 1 per unit time by dividing the difference in inclination angles (θ2-θ1) by the time interval (t2-t1). Note that when the rotation speed of the workpiece W matches the rotation speed of the polishing head 1, the inclination angle of the feature region 100 on the first image PI1 and the inclination angle of the feature region 100 on the second image PI2 are the same. Therefore, the relative rotation angle of the workpiece W with respect to the polishing head 1 per unit time is 0.

[0049] The processing control unit 9 calculates the rotation angle of the workpiece W per unit time by subtracting the relative rotation angle of the workpiece W with respect to the polishing head 1 per unit time from the rotation angle of the polishing head 1 in the time interval (t2-t1) detected by the head angle detector 22. In this embodiment, two images PI1 and PI2 are used to calculate the rotation angle of the workpiece W per unit time, but in other embodiments, three or more images may be used to calculate the rotation angle of the workpiece W per unit time.

[0050] The film thickness sensor 25 measures the film thickness at a predetermined measurement point on the surface S1 of the workpiece W during measurement time t3, after the infrared imaging device 27 has generated the first image PI1 and the second image PI2. The imaging time t1 during which the infrared imaging device 27 generates the first image PI1, the imaging time t2 during which the infrared imaging device 27 generates the second image PI2, and the measurement time t3 during which the film thickness sensor 25 measures the film thickness at the predetermined measurement point are all included in the time it takes for the polishing table 3 to complete one rotation. That is, during the rotation of the polishing table 3, the infrared imaging device 27 generates the first and second images, and the film thickness sensor 25 measures the film thickness at the predetermined measurement point.

[0051] The position of a predetermined measurement point on the surface S1 of the workpiece W is determined by coordinates in the coordinate system shown in Figure 7. Figure 7 is a schematic diagram showing an example of a coordinate system defined on the surface S1 of the workpiece W. The workpiece W has a notch 60 at its edge. In this example, the Y-axis of the coordinate system passes through the notch 60 and the center point CP of the workpiece W, and the X-axis passes through the center point CP of the workpiece W and is perpendicular to the Y-axis. This coordinate system is a Cartesian coordinate system. In the following description, the coordinate system defined on the surface S1 of the workpiece W may be referred to as the XY coordinate system.

[0052] As shown in Figure 7, multiple feature regions 100 form a pattern on the surface S1 of the workpiece W. These patterns are arranged along the Y and X axes of the XY coordinate system. That is, the arrangement direction of the multiple patterns is parallel to the Y and X axes of the XY coordinate system.

[0053] Figure 8 is a schematic diagram showing another example of the feature region 100. In the example shown in Figure 8, the workpiece W is a blanket wafer having a film, and the feature region 100 is a region that is distinguished from other regions by differences in film thickness. In one example, the feature region 100 is a region with a larger film thickness than other regions of the workpiece W. In another example, the feature region 100 may be a region with a smaller film thickness than other regions of the workpiece W. In this embodiment, the feature region 100 is located near the center of the workpiece W and below the infrared imaging device 27 and the infrared light source 28.

[0054] Figure 9 is a schematic diagram showing an example of a first image PI1 and a second image PI2 that include the feature region 100 shown in Figure 8. As shown in Figure 9, the first image PI1 and the second image PI2 include the feature region 100 on the surface S1 of the workpiece W. In other words, the feature region 100 is located within the imaging area of ​​the infrared imaging device 27 at least during imaging times t1 and t2.

[0055] In the example shown in Figure 9, as in the example described with reference to Figure 6, the processing control unit 9 calculates the inclination angle θ1 of the feature region 100 on the first image PI1 with respect to the reference line RL and the inclination angle θ2 of the feature region 100 on the second image PI2 with respect to the reference line RL. The reference line RL is not particularly limited, but is, for example, a straight line extending parallel to one side of the image captured by the infrared imaging device 27. Based on the inclination angle θ1 of the feature region 100 on the first image PI1, the inclination angle θ2 of the feature region 100 on the second image PI2, and the predetermined time interval (t2-t1), the processing control unit 9 calculates the rotation angle of the workpiece W per unit time.

[0056] As long as the processing control unit 9 can calculate the inclination angle θ1 of the feature region 100 on the first image PI1 and the inclination angle θ2 of the feature region 100 on the second image PI2, the shape of the feature region 100 may change as the workpiece W is polished.

[0057] Figure 10 is a schematic diagram showing an example of image generation by the infrared imaging device 27 and measurement of film thickness by the film thickness sensor 25. As described above, at imaging time t2, the processing control unit 9 gives a command to the infrared imaging device 27 to generate a second image PI2 of the feature region 100 on the surface S1 of the workpiece W (imaging time t2). Based on the tilt angle of the feature region 100 on the second image PI2 (for example, angle θ2 in Figure 6 or Figure 9), the processing control unit 9 determines the tilt angle of the XY coordinate system defined on the surface S1 of the workpiece W. The tilt angle of the XY coordinate system at imaging time t2 matches the tilt angle of the feature region 100 on the second image PI2.

[0058] During polishing of the workpiece W, the processing control unit 9 issues a command to the film thickness sensor 25 when it is located below the workpiece W, causing it to measure the film thickness at a predetermined measurement point MP on the surface S1 of the workpiece W (measurement time t3). The measurement time t3, during which the film thickness sensor 25 measures the film thickness at the measurement point MP on the surface S1 of the workpiece W, is after the imaging time t2, during which the infrared imaging device 27 generates the second image PI2. The coordinates of the measurement point MP in the coordinate system described with reference to Figure 7 are unknown at this point, but the relative position of the measurement point MP with respect to the center point CP of the workpiece W can be determined from the radial distance between the film thickness sensor 25 and the center TP of the polishing table 3 and the rotation angle of the polishing table 3 at measurement time t3. During polishing of the workpiece W, the position of the center point CP of the workpiece W relative to the polishing table 3 is fixed. On the other hand, the film thickness sensor 25 moves relative to the center point CP of the workpiece W. The path J that the film thickness sensor 25 takes across the surface S1 of the workpiece W is determined by the radial distance between the film thickness sensor 25 and the center TP of the polishing table 3. The processing control unit 9 can uniquely determine the relative position of the film thickness sensor 25 with respect to the center point CP of the workpiece W based on the radial distance between the film thickness sensor 25 and the center TP of the polishing table 3 and the rotation angle of the polishing table 3.

[0059] In one example, the processing control unit 9 calculates a measurement time t3, which is the time after a predetermined delay has elapsed from the moment it receives an angle detection signal from the table angle detector 50, consisting of a proximity sensor 51 and a sensor target 52. At measurement time t3, it commands the film thickness sensor 25 to measure the film thickness at the measurement point MP on the surface S1 of the workpiece W. The predetermined delay time is determined from the difference between the position of the film thickness sensor 25 and the position of the measurement point MP on the workpiece W at the time the processing control unit 9 receives the angle detection signal, and the rotation speed of the polishing table 3.

[0060] In another example, the processing control unit 9 receives the rotation angle of the polishing table 3 from the table angle detector 50, which consists of a rotary encoder, and commands the film thickness sensor 25 at measurement time t3, when the rotation angle of the polishing table 3 reaches a predetermined measurement angle, to measure the film thickness at measurement point MP on the surface S1 of the workpiece W. In this way, the relative position of measurement point MP with respect to the center point CP of the workpiece W can be determined from the radial distance between the film thickness sensor 25 and the center TP of the polishing table 3 and the rotation angle of the polishing table 3 at measurement time t3.

[0061] As shown in Figure 10, the position of the film thickness sensor 25 at imaging time t2 is away from the measurement point MP on the surface S1 of the workpiece W in the circumferential direction of the polishing table 3. Therefore, there is a time difference t3-t2 between the measurement time t3 when the film thickness sensor 25 measures the film thickness at the measurement point MP, and the imaging time t2 when the imaging device 24 generates the second image PI2 of the workpiece W (see Figures 6 and 9). During this time difference t3-t2, the workpiece W rotates around its center point CP. The rotation speed of the workpiece W at this time is expressed as the rotation angle of the workpiece W per unit time as described above.

[0062] The processing control unit 9 determines the coordinates of the measurement point MP on the surface S1 of the workpiece W as follows: The processing control unit 9 calculates the time difference t3-t2 between the measurement time t3 when the film thickness at the measurement point MP is measured and the imaging time t2 when the second image PI2 is generated, and determines the coordinates of the measurement point MP on the surface S1 of the workpiece W based on the relative position between the measurement point MP and the center point CP of the workpiece W, the rotation angle of the workpiece W per unit time, and the time difference t3-t2.

[0063] During the time difference t3-t2, the workpiece W rotates around its center point CP. Therefore, the XY coordinate system defined on the surface S1 of the workpiece W also rotates around the center point CP of the workpiece W during the time difference t3-t2. The processing control unit 9 calculates the rotation angle of the XY coordinate system that rotates during the time difference t3-t2 by multiplying the rotation angle of the workpiece W per unit time by the time difference t3-t2. Furthermore, as shown in Figure 10, the processing control unit 9 determines the XY coordinate system at measurement time t3 by rotating the XY coordinate system at imaging time t2 around the center point CP of the workpiece W by the calculated rotation angle. The actual position of the measurement point MP on the surface S1 of the workpiece W is determined by the coordinates of the measurement point MP on the XY coordinate system at measurement time t3.

[0064] In this way, the processing control unit 9 can determine the coordinates of the measurement point MP (i.e., the actual position of the measurement point MP) that reflect the free rotation of the workpiece W within the retainer ring 32. These coordinates of the measurement point MP specify not only the radial position of the workpiece W but also its circumferential position. Therefore, it is possible to obtain not only the radial film thickness profile of the workpiece W but also the circumferential film thickness profile of the workpiece W.

[0065] Figure 11 is a schematic diagram showing another example of image generation by the infrared imaging device 27 and measurement of film thickness by the film thickness sensor 25. In this embodiment, the position of the film thickness sensor 25 at imaging time t2 coincides with the measurement point MP on the surface S1 of the workpiece W. In other words, the infrared imaging device 27 generates the second image PI2 at the same time that the film thickness sensor 25 measures the film thickness at the measurement point MP. Therefore, the time difference t3-t2 is 0. In this example, the workpiece W does not rotate relative to the polishing head 1 between imaging time t2 and measurement time t3. Therefore, the inclination angle of the XY coordinate system at measurement time t3 is the same as the inclination angle of the XY coordinate system at imaging time t2. The coordinates of the measurement point MP are the coordinates on the XY coordinate system at imaging time t2 (measurement time t3).

[0066] Although the rotational speed of the workpiece W, which rotates freely within the retainer ring 32, is substantially constant, it may fluctuate slightly. Therefore, it is desirable that the time difference t3-t2 between the measurement time t3, when the film thickness at the measurement point MP is measured, and the imaging time t2, when the second image PI2 is generated, be as short as possible. According to the embodiment shown in Figure 11, since the time difference t3-t2 is 0, the coordinates of the measurement point MP can be determined with high accuracy.

[0067] Figure 12 is a top view showing another embodiment of the film thickness sensor 25. In this embodiment, the film thickness sensor 25 is positioned to pass through the edge of the workpiece W. That is, the radial distance of the film thickness sensor 25 from the center TP of the polishing table 3 is shorter than the distance from the center TP of the polishing table 3 to the infrared imaging device 27 and the center point TP of the workpiece W. The film thickness sensor 25 moves along the path K shown in Figure 12, crossing the edge of the workpiece W, and measures the film thickness at the measurement point on the edge. In this embodiment as well, similar to the embodiments described with reference to Figures 1 to 11, the processing control unit 9 can determine the coordinates of the measurement point on the edge of the workpiece W.

[0068] In the embodiments shown in Figures 1 to 12, the infrared imaging device 27 is located in the center of the polishing head 1, but the position of the infrared imaging device 27 within the polishing head 1 is not particularly limited. Figure 13 is a cross-sectional view of the polishing head 1 showing another embodiment of the infrared imaging device 27 and the infrared light source 28. As shown in Figure 13, the infrared imaging device 27 may be located on the outer periphery of the polishing head 1. The infrared light source 28 is located adjacent to the infrared imaging device 27. The recess 31a in which the light-receiving portion 27a of the infrared imaging device 27 and the irradiation portion 28a of the infrared light source 28 are located is on the outer periphery of the polishing head 1 and opens at the bottom of the carrier 31.

[0069] Figure 14 is a top view showing the positional relationship between the polishing table 3 and the workpiece W held by the polishing head 1 according to the embodiment shown in Figure 13. Since the infrared imaging device 27 is fixed to the polishing head 1, it moves along the path N shown in Figure 14 as the polishing head 1 rotates. Therefore, the infrared imaging device 27 generates an image of the edge portion of the workpiece W. In this embodiment as well, similar to the embodiment described with reference to Figures 1 to 11, the processing control unit 9 calculates the rotation angle of the workpiece W per unit time based on the inclination angle θ1 of the feature region 100 on the first image PI1, the inclination angle θ2 of the feature region 100 on the second image PI2, and the predetermined time interval (t2-t1), and can determine the coordinates of the measurement points on the surface S1 of the workpiece W based on the calculated rotation angle of the workpiece W per unit time.

[0070] Figure 15 is a cross-sectional view of the polishing head 1 showing yet another embodiment of the infrared imaging device 27 and infrared light sources 28. As shown in Figure 15, the polishing device may include a plurality of (two in this embodiment) infrared light sources 28. In this embodiment, the infrared imaging device 27 is positioned perpendicular to the front surface S1 and back surface S2 of the workpiece W, and the plurality of infrared light sources 28 are positioned adjacent to both sides of the infrared imaging device 27. The plurality of infrared light sources 28 can irradiate the feature region 100 on the surface S1 of the workpiece W with infrared light at a high intensity. Therefore, the intensity of infrared light reflected by the feature region 100 on the surface S1 of the workpiece W is also high, so that the infrared imaging device 27 can generate a clear image of the feature region 100 on the surface S1 of the workpiece W.

[0071] Figure 16 is a cross-sectional view of the polishing head 1 showing yet another embodiment of the infrared imaging device 27 and the infrared light source 28. As shown in Figure 16, the polishing device may further include a half mirror 70 disposed within the polishing head 1. The half mirror 70 is configured to transmit infrared light emitted from the infrared light source 28 and reflect infrared light reflected from a feature region 100 on the surface S1 of the workpiece W. The half mirror 70 is located in a recess 31a and is fixed to the carrier 31 of the polishing head 1. In this embodiment, the infrared imaging device 27 is positioned to the side of the half mirror 70, parallel to the surface S1 and back surface S2 of the workpiece W, and the infrared light source 28 is positioned above the half mirror 70, perpendicular to the surface S1 and back surface S2 of the workpiece W.

[0072] The half mirror 70 is positioned diagonally on the optical path of infrared light emitted from the infrared light source 28 and the optical path of infrared light reflected from the feature region 100. The infrared imaging device 27 generates an image of the feature region 100 on the surface S1 of the workpiece W by receiving infrared light emitted from the infrared light source 28, transmitted through the half mirror 70, reflected from the feature region 100 on the surface S1 of the workpiece W, and reflected by the half mirror 70.

[0073] Figure 17 is a cross-sectional view of the polishing head 1 showing yet another embodiment of the infrared imaging device 27 and the infrared light source 28. In this embodiment, the half mirror 70 is configured to reflect infrared light emitted from the infrared light source 28 and to transmit infrared light reflected from the feature region 100 on the surface S1 of the workpiece W. In this embodiment, the infrared imaging device 27 is positioned above the half mirror 70, perpendicular to the surface S1 and back surface S2 of the workpiece W, and the infrared light source 28 is positioned to the side of the half mirror 70, parallel to the surface S1 and back surface S2 of the workpiece W.

[0074] The half mirror 70 is positioned diagonally on the optical path of infrared light emitted from the infrared light source 28 and the optical path of infrared light reflected from the feature region 100. The infrared imaging device 27 receives infrared light emitted from the infrared light source 28, reflected by the half mirror 70, reflected by the feature region 100 on the surface S1 of the workpiece W, and transmitted through the half mirror 70, thereby generating an image of the feature region 100 on the surface S1 of the workpiece W.

[0075] Figure 18 is a cross-sectional view of the polishing head 1 showing yet another embodiment of the infrared imaging device 27 and the infrared light source 28. As shown in Figure 18, the polishing device may comprise a plurality of (two in this embodiment) infrared imaging devices 27, a plurality of (two in this embodiment) infrared light sources 28, and a plurality of (two in this embodiment) half mirrors 70. In this embodiment, the polishing device comprises two sets of configurations consisting of the combination of infrared imaging devices 27, infrared light sources 28, and half mirrors 70 described with reference to Figure 17.

[0076] The configuration, consisting of two sets of infrared imaging devices 27, infrared light sources 28, and half mirrors 70, is positioned on the outer periphery of the polishing head 1. The carrier 31 has two recesses 31a located on the outer periphery of the polishing head 1, and the infrared imaging devices 27, infrared light sources 28, and half mirrors 70 are arranged in each recess 31a. By using multiple infrared imaging devices 27 in this way, the number of images generated during one rotation of the polishing table 3 can be increased.

[0077] When measuring the film thickness at multiple measurement points on the surface S1 of the workpiece W using the film thickness sensor 25 while the polishing table 3 rotates once, it is necessary to generate multiple first and second images corresponding to multiple measurement points in order to calculate the rotation angle of the workpiece W per unit time used to determine the coordinates of each measurement point. Therefore, according to the embodiment shown in Figure 18, even when there are many measurement points, many images can be generated while the polishing table 3 rotates once, and the rotation angle of the workpiece W per unit time used to determine the coordinates of each measurement point can be calculated.

[0078] In one embodiment, the elastic film 34 of the polishing head 1 may have a mark to identify the orientation of the elastic film 34 in the circumferential direction. Figure 19 is a schematic diagram showing one embodiment of the elastic film 34 having a mark 80. The mark 80 is printed in ink on the contact surface 35a of the elastic film 34. As shown in Figure 19, the mark 80 in this embodiment is a figure consisting of a cross and an arrow. The mark 80 is located below the recess 31a of the carrier 31 and is on the optical path of infrared light emitted from the infrared light source 28. The ink used for the mark 80 is made of a material that reflects infrared light emitted from the infrared light source 28. Therefore, the infrared imaging device 27 is configured to generate an image of the mark 80 by receiving the infrared light reflected by the mark 80.

[0079] In other embodiments, the marker 80 may be formed by embossing on the contact surface 35a of the elastic film 34. Since the thickness of the elastic film 34 in the area where the embossed marker 80 is located is greater than the thickness of other areas, some of the infrared light emitted from the infrared light source 28 is reflected without being completely transmitted. The infrared imaging device 27 generates an image of the marker 80 by receiving some of the infrared light reflected by the marker 80. The shape of the marker 80 is not particularly limited to this embodiment and may be circular, rectangular, grid-like, or a string of characters.

[0080] Figure 20 is a schematic diagram showing an example of a first image PI1 generated by an infrared imaging device 27 placed inside a polishing head 1 having an elastic film 34 as shown in Figure 19. As shown in Figure 20, the first image PI1 includes a feature region 100 on the surface S1 of the workpiece W and a marker 80 on the elastic film 34. In Figure 20, the feature region 100 is described as an example of a pattern formed on the surface S1 of the workpiece W, but the feature region 100 may be a region that is distinguished from other regions by differences in film thickness, material, etc., as described with reference to Figures 8 and 9.

[0081] In this embodiment, the processing control unit 9 uses the marker 80 on the first image PI1 as the reference line RL described above. That is, the processing control unit 9 calculates the inclination angle θ1 of the feature region 100 on the first image PI1 based on the marker 80 on the first image PI1. In this embodiment, the processing control unit 9 uses the arrow constituting the marker 80 as the reference line RL to calculate the inclination angle θ1 of the feature region 100 on the first image PI1.

[0082] Since the infrared imaging device 27 is fixed to the polishing head 1, the position of the marker 80 on the image remains fixed even when the polishing head 1 rotates. Similarly, for the second image PI2, the processing control unit 9 calculates the inclination angle θ2 of the feature region 100 on the second image PI2 based on the marker 80 on the second image PI2. In this embodiment as well, similar to the embodiment described above, the processing control unit 9 calculates the rotation angle of the workpiece W per unit time and determines the coordinates of the measurement point MP on the surface S1 of the workpiece W.

[0083] In the embodiments described with reference to Figures 1 to 20, the infrared imaging device 27 is fixed to the polishing head 1 and rotates integrally with the polishing head 1. In one embodiment, the infrared imaging device 27 may not be fixed to the polishing head 1 and may be configured not to rotate integrally with the polishing head 1. Figure 21 is a cross-sectional view of the polishing head 1 showing one embodiment of the infrared imaging device 27 not fixed to the polishing head 1. In this embodiment, the infrared imaging device 27 is fixed to a head arm 15 as a fixing member. More specifically, the power transmission unit 27b of the infrared imaging device 27 is fixed to the head arm 15. However, the fixing member is not particularly limited to the head arm 15, as long as it is a member that does not rotate integrally with the polishing head 1.

[0084] In this embodiment, the polishing head shaft 11 has a hollow structure and has a passage 11a that penetrates axially. The power supply unit 27b of the infrared imaging device 27 extends from the head arm 15 through the passage 11a of the polishing head shaft 11 to a recess 31a in the polishing head 1. In this embodiment, the recess 31a communicates with the passage 11a of the polishing head shaft 11, and the infrared imaging device 27 is positioned inside the polishing head 1 without contact with the polishing head 1. In one embodiment, as shown in Figure 21, the polishing device includes a slip ring 75 that rotatably supports the polishing head shaft 11, and the power supply unit 27b of the infrared imaging device 27 may be supported by the slip ring 75 inside the polishing head shaft 11. The slip ring 75 is positioned inside the passage 11a of the polishing head shaft 11 and is configured to rotatably support the polishing head shaft 11 with its outer surface. With this configuration, the infrared imaging device 27 does not rotate integrally with the polishing head 1 while the polishing head 1 and polishing head shaft 11 are rotating.

[0085] In this embodiment, the rotation angle of the workpiece W per unit time is calculated as follows. The processing control unit 9 gives a command to the infrared imaging device 27 to generate a first image PI1 of the feature region on the surface S1 of the workpiece W at imaging time t1, and then generate a second image PI2 of the feature region on the surface S1 of the workpiece W at imaging time t2. The processing control unit 9 calculates the rotation angle of the workpiece W per unit time based on the inclination angle θ1 of the feature region on the first image PI1, the inclination angle θ2 of the feature region on the second image PI2, and the predetermined time interval (t2-t1). More specifically, the processing control unit 9 calculates the difference (θ2-θ1) between the inclination angle θ1 of the feature region on the first image PI1 and the inclination angle θ2 of the feature region on the second image PI2, and calculates the rotation angle of the workpiece W per unit time by dividing the difference in inclination angles (θ2-θ1) by the time interval (t2-t1). In this embodiment, since the infrared imaging device 27 does not rotate integrally with the polishing head 1, the rotation angle of the workpiece W per unit time can be directly calculated without calculating the relative rotation angle of the workpiece W with respect to the polishing head 1 per unit time.

[0086] The film thickness sensor 25 measures the film thickness at a predetermined measurement point MP on the surface S1 of the workpiece W during measurement time t3, after the infrared imaging device 27 has generated the first image PI1 and the second image PI2. The determination of the coordinates of the measurement point MP on the surface S1 of the workpiece W by the processing control unit 9 is the same as in the embodiment described above, so a redundant explanation is omitted.

[0087] 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]

[0088] 1 Polishing head 2 polishing pads 2a Polished surface 3 Polishing Table 5. Polishing fluid supply nozzle 6 Table motors 9 Processing Control Unit 9a Storage device 9b Arithmetic unit 11 Polished Head Shaft 15 Head Arm 16 Spindle 18. Polishing head vertical movement mechanism 20 Polishing head motor 22 Head Angle Detector 25 Film Thickness Sensor 27 Infrared imaging device 27a Light receiving part 28 Infrared light source 28a Irradiation section 31 Careers 31a Recess 32 Retainer Rings 34 Elastic membrane 35 Contact area 35a Contact surface 36a,36b,36c Inner wall 36d Exterior wall 38A, 38B, 38C, 38D, 38E Pressure Chambers 40 membranes F1, F2, F3, F4, F5 Gas Transfer Line 45 Rotary Joint Ra1, Ra2, Ra3, Ra4, Ra5 pressure regulator 50 Table Angle Detector 51 Proximity Sensor 52 Sensor Targets 60 Notches 70 Half Mirror 75 Slip Rings 80 Landmarks 100 Feature Regions PI1 First Image PI2 Image 2

Claims

1. A polishing table that supports the polishing pad, A polishing head that polishes a workpiece having a surface in which a characteristic region is formed by pressing the workpiece against a polishing pad on the polishing table, A polishing head motor that rotates the polishing head, A film thickness sensor fixed to the polishing table measures the film thickness at a measurement point on the surface of the workpiece, An infrared imaging device is disposed within the polishing head and generates a first image and a second image of the feature region on the surface of the workpiece from the back surface of the workpiece at predetermined time intervals. A polishing apparatus comprising a processing control unit that determines the coordinates of the measurement points on the surface of the workpiece based on the first image and the second image.

2. The processing control unit, Based on the inclination angle of the feature region in the first image, the inclination angle of the feature region in the second image, and the predetermined time interval, the rotation angle of the workpiece per unit time is calculated. The time difference between the measurement time for measuring the film thickness at the aforementioned measurement point and the imaging time for generating the second image is calculated. The polishing apparatus according to claim 1, configured to determine the coordinates of the measurement point on the surface of the workpiece based on the relative position between the measurement point and the center point of the workpiece, the rotation angle of the workpiece per unit time, and the time difference.

3. The processing control unit, Based on the inclination angle of the feature region on the second image, the inclination angle of a predefined coordinate system on the surface of the workpiece is determined. By multiplying the rotation angle of the workpiece per unit time by the time difference, the rotation angle of the coordinate system that rotates during the time difference is calculated. The coordinate system at the time of imaging is rotated around the center point of the workpiece by the calculated rotation angle to determine the coordinate system at the time of measurement. The polishing apparatus according to claim 2, configured to determine the coordinates of the measurement point on the coordinate system at the measurement time from the relative position of the measurement point and the center point of the workpiece.

4. The polishing head further comprises an infrared light source that is positioned within the polishing head and irradiates infrared light from the back surface of the workpiece to the characteristic region on the surface of the workpiece, The infrared light has a wavelength that penetrates the workpiece and is reflected in the characteristic region. The polishing apparatus according to claim 1, wherein the infrared imaging device is configured to generate the first image and the second image by receiving the infrared light emitted from the infrared light source and reflected in the feature region.

5. The polishing head is An elastic membrane for pressing the workpiece against the polishing pad, The carrier to which the elastic membrane is fixed is provided, The infrared imaging device and the infrared light source are fixed to the carrier. The polishing apparatus according to claim 4, wherein the infrared radiation has a wavelength that penetrates the elastic film and the workpiece and reflects in the characteristic region.

6. The polishing head further comprises a half-mirror that is disposed within the polishing head and transmits the infrared light emitted from the infrared light source and reflects the infrared light reflected in the characteristic region, The half-mirror is positioned obliquely on the optical path of the infrared light emitted from the infrared light source and the optical path of the infrared light reflected in the characteristic region. The polishing apparatus according to claim 4, wherein the infrared imaging device is configured to generate the first image and the second image by receiving the infrared light emitted from the infrared light source, transmitted through the half mirror, reflected in the feature region, and reflected by the half mirror.

7. The polishing head further comprises a half-mirror that is disposed within the polishing head and reflects the infrared light emitted from the infrared light source and transmits the infrared light reflected in the characteristic region, The half-mirror is positioned obliquely on the optical path of the infrared light emitted from the infrared light source and the optical path of the infrared light reflected in the characteristic region. The polishing apparatus according to claim 4, wherein the infrared imaging device is configured to generate the first image and the second image by receiving the infrared light emitted from the infrared light source, reflected by the half mirror, reflected in the feature region, and transmitted through the half mirror.

8. The system further includes a head angle detector for detecting the rotation angle of the polishing head, The infrared imaging device is fixed to the polishing head, The processing control unit, The difference in the inclination angle of the feature region between the first image and the second image is calculated, and the relative rotation angle of the workpiece with respect to the polishing head per unit time is calculated by dividing the difference in inclination angle by the predetermined time interval. The polishing apparatus according to claim 1, configured to calculate the rotation angle of the workpiece per unit time by subtracting the relative rotation angle of the workpiece with respect to the polishing head per unit time from the rotation angle of the polishing head at a predetermined time interval detected by the head angle detector.

9. The infrared imaging device is further provided with a fixing member for fixing the device. The infrared imaging device is non-contact with the polishing head and does not rotate integrally with the polishing head. The polishing apparatus according to claim 1, wherein the processing control unit is configured to calculate the difference in the inclination angle of the feature region between the first image and the second image, and to calculate the rotation angle of the workpiece per unit time by dividing the difference in inclination angle by the predetermined time interval.

10. The polishing head is An elastic membrane for pressing the workpiece against the polishing pad, The carrier to which the elastic membrane is fixed is provided, The elastic membrane has a mark for identifying the orientation in the circumferential direction of the elastic membrane, The infrared imaging device is fixed to the carrier, The processing control unit, Based on the markers on the first image, the inclination angle of the feature region on the first image is calculated. Based on the markers on the second image, the inclination angle of the feature region on the first image is calculated. The polishing apparatus according to claim 1, configured to calculate the rotation angle of the workpiece per unit time based on the predetermined time interval.

11. While rotating the polishing head, the polishing head presses the workpiece having a surface on which a characteristic region has been formed against the polishing pad on the polishing table to polish the workpiece. During the polishing of the workpiece, an infrared imaging device positioned within the polishing head generates first and second images of the feature region on the surface of the workpiece from the back surface of the workpiece at predetermined time intervals. During the polishing of the workpiece, the film thickness at a measurement point on the surface of the workpiece is measured by a film thickness sensor fixed to the polishing table. A polishing method for determining the coordinates of the measurement points on the surface of the workpiece based on the first and second images.

12. Determining the coordinates of the measurement point is: Based on the inclination angle of the feature region in the first image, the inclination angle of the feature region in the second image, and the predetermined time interval, the rotation angle of the workpiece per unit time is calculated. The time difference between the measurement time for measuring the film thickness at the aforementioned measurement point and the imaging time for generating the second image is calculated. The polishing method according to claim 11, wherein the coordinates of the measurement point on the surface of the workpiece are determined based on the relative position between the measurement point and the center point of the workpiece, the rotation angle of the workpiece per unit time, and the time difference.

13. Determining the coordinates of the measurement point on the surface of the workpiece based on the relative position between the measurement point and the center point of the workpiece, the rotation angle of the workpiece per unit time, and the time difference, Based on the inclination angle of the feature region on the second image, the inclination angle of a predefined coordinate system on the surface of the workpiece is determined. By multiplying the rotation angle of the workpiece per unit time by the time difference, the rotation angle of the coordinate system that rotates during the time difference is calculated. The coordinate system at the time of imaging is rotated around the center point of the workpiece by the calculated rotation angle to determine the coordinate system at the time of measurement. The polishing method according to claim 12, wherein the coordinates of the measurement point on the coordinate system at the measurement time are determined from the relative position of the measurement point and the center point of the workpiece.

14. The process further includes, during the polishing of the workpiece, irradiating the feature region on the surface of the workpiece from the back surface of the workpiece with infrared light from an infrared light source positioned within the polishing head, The generation of the first and second images by the infrared imaging device is achieved by receiving the infrared light emitted from the infrared light source and reflected in the characteristic region with the infrared imaging device, The polishing method according to claim 11, wherein the infrared light has a wavelength that penetrates the workpiece and is reflected in the characteristic region.

15. The polishing head is An elastic membrane for pressing the workpiece against the polishing pad, The carrier to which the elastic membrane is fixed is provided, The infrared imaging device and the infrared light source are fixed to the carrier. The polishing method according to claim 14, wherein the infrared radiation has a wavelength that penetrates the elastic film and the workpiece and reflects in the characteristic region.

16. The generation of the first and second images by the infrared imaging device is achieved by receiving the infrared light emitted from the infrared light source, transmitted through a half-mirror placed in the polishing head, reflected in the feature region, and then received by the infrared imaging device. The polishing method according to claim 14, wherein the half-mirror is positioned obliquely on the optical path of the infrared light emitted from the infrared light source and the optical path of the infrared light reflected in the characteristic region.

17. The generation of the first and second images by the infrared imaging device is achieved by receiving the infrared light emitted from the infrared light source, reflected by the half-mirror placed in the polishing head, reflected in the feature region, and transmitted through the half-mirror, with the infrared imaging device, thereby generating the first and second images. The polishing method according to claim 14, wherein the half-mirror is positioned obliquely on the optical path of the infrared light emitted from the infrared light source and the optical path of the infrared light reflected in the characteristic region.

18. The method further includes detecting the rotation angle of the polishing head, The infrared imaging device is fixed to the polishing head, Calculating the rotation angle of the workpiece per unit time is: The difference in the inclination angle of the feature region between the first image and the second image is calculated, and the relative rotation angle of the workpiece with respect to the polishing head per unit time is calculated by dividing the difference in inclination angle by the predetermined time interval. The polishing method according to claim 11, wherein the rotation angle of the workpiece per unit time is calculated by subtracting the relative rotation angle of the workpiece with respect to the polishing head per unit time from the rotation angle of the polishing head at a predetermined time interval detected by a head angle detector.

19. The polishing head is fixed to a fixing member, is non-contact with the polishing head, and does not rotate integrally with the polishing head. The polishing method according to claim 11, wherein the rotation angle of the workpiece per unit time is calculated by calculating the difference in the inclination angle of the feature region between the first image and the second image, and dividing the difference in inclination angle by the predetermined time interval to calculate the rotation angle of the workpiece per unit time.

20. The polishing head is An elastic membrane for pressing the workpiece against the polishing pad, The carrier to which the elastic membrane is fixed is provided, The elastic membrane has a mark for identifying the orientation in the circumferential direction of the elastic membrane, The infrared imaging device is fixed to the carrier, Calculating the rotation angle of the workpiece per unit time is: Based on the markers on the first image, the inclination angle of the feature region on the first image is calculated. Based on the markers on the second image, the inclination angle of the feature region on the first image is calculated. The polishing method according to claim 11, wherein the rotation angle of the workpiece per unit time is calculated based on the predetermined time interval.

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