Grinding device and grinding method

Abstract

The present invention provides a polishing apparatus and a polishing method capable of accurately measuring a film thickness of a work used in the manufacture of a semiconductor device during polishing of the work. A processing system is configured to determine the film thickness of the work based on relative reflectance data calculated by the following calculation formula. Relative reflectance data = MD1 / [BD1 · k]. Where MD1 is first intensity measurement data representing an intensity of reflected light from the work (W) measured by a first beam splitter (27), BD1 is first reference intensity data, and k is a rate of change of second intensity measurement data relative to second reference intensity data, the second intensity measurement data representing an intensity of light of a light source measured by a second beam splitter (28) during polishing of the work (W).

Description

Technical Field

[0001] This invention relates to a grinding apparatus and grinding method for grinding workpieces used in the manufacture of semiconductor devices such as wafers, substrates, and panels, and particularly to a technique for determining the film thickness of a workpiece based on optical information contained in reflected light from the workpiece. Background Technology

[0002] In the semiconductor device manufacturing process, various materials are repeatedly formed into films on a silicon wafer to create a layered structure. To form this layered structure, techniques for planarizing the surface of the top layer become important. Chemical mechanical polishing (CMP) is used as one method of such planarization.

[0003] Chemical mechanical polishing (CMP) is performed by a polishing apparatus. Generally, such an apparatus includes: a polishing table supporting a polishing pad, a polishing head holding a wafer with a film, and a polishing slurry supply nozzle for supplying polishing slurry (e.g., a paste) to the polishing pad. The polishing apparatus supplies polishing slurry to the polishing pad from the polishing slurry supply nozzle while rotating the polishing head and polishing table separately. The polishing head polishes the film forming on the wafer surface by pressing the wafer surface against the polishing pad, with polishing slurry present between the wafer and the polishing pad.

[0004] To determine the thickness of non-metallic films such as insulating films and silicon layers (hereinafter referred to as film thickness), polishing equipment typically includes an optical film thickness measuring device. This optical film thickness measuring device is configured to guide light emitted from a light source to the surface of a wafer, and determine the film thickness of the wafer by analyzing the spectrum of the reflected light from the wafer. The polishing equipment can then terminate the wafer polishing process or change the wafer polishing conditions based on the determined film thickness.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2018-194427

[0008] The technical problem that the invention aims to solve

[0009] However, the spectrum of reflected light from the wafer fluctuates even under identical conditions (e.g., same film thickness, same measurement point). This spectral fluctuation is associated with instability in film thickness measurements, hindering accurate film thickness monitoring during wafer polishing. Stable film thickness measurements can be obtained by repeatedly measuring the film thickness at the same measurement point and calculating the average of multiple measurements using a film thickness measuring device that measures the film thickness of a stationary wafer. However, the aforementioned optical film thickness measuring device dynamically measures the film thickness while rotating the wafer, thus making such a process impossible. Summary of the Invention

[0010] Therefore, the present invention provides a grinding apparatus and grinding method that can accurately measure the film thickness of workpieces used in the manufacture of semiconductor devices such as wafers, substrates, and panels during the grinding process.

[0011] Technical means for solving technical problems

[0012] The inventors found the following two reasons for the spectral instability of the reflected light from the workpiece.

[0013] The first reason is the variation in the amount of light emitted by the light source each time it emits light. In particular, in flash light sources that emit light through discharge, the amount of light emitted each time is prone to variation due to discharge variations. Typically, during the grinding process of a workpiece, the light source flashes multiple times and illuminates multiple measurement points on the workpiece each time the grinding table rotates one revolution. The amount of light illuminating these measurement points exhibits slight fluctuations.

[0014] The second reason is the change in the optical path of the light source as it emits light each time it passes through the fiber optic cable. The light source is connected to the fiber optic cable, and the light is guided to the workpiece through the cable. When a small-diameter light source emits light, it illuminates different positions on the end face of the fiber optic cable each time. As a result, the light is guided to the workpiece through different parts of the fiber optic cable. This difference in the optical path within the fiber optic cable causes fluctuations in the spectrum of the reflected light from the workpiece.

[0015] In one embodiment, a grinding apparatus for grinding a workpiece is provided, comprising: a grinding table supporting a grinding pad; a grinding head pressing the workpiece against the grinding pad and grinding the workpiece; a light source emitting light; a projection fiber optic cable connected to the light source and guiding the light to the workpiece; a receiving fiber optic cable receiving reflected light from the workpiece; a first beam splitter connected to the receiving fiber optic cable; a second beam splitter directly connected to the light source; and a processing system having a storage program. The system includes a storage device for the program and a processing device for performing calculations according to the instructions contained in the program. The storage device internally stores first reference intensity data, second reference intensity data, and a calculation formula for calculating relative reflectance data. The first reference intensity data represents the reference intensity of light measured by the first beam splitter before grinding the workpiece. The second reference intensity data represents the reference intensity of light from the light source measured by the second beam splitter before grinding the workpiece. The processing system is configured to determine the film thickness of the workpiece based on the relative reflectance data. The calculation formula is expressed as follows:

[0016] The relative reflectance data = MD1 / [BD1·k],

[0017] Wherein, MD1 is a first intensity measurement data representing the intensity of the reflected light from the workpiece as measured by the first beam splitter, BD1 is the first reference intensity data, and k is the rate of change of the second intensity measurement data relative to the second reference intensity data, the second intensity measurement data representing the intensity of the light source as measured by the second beam splitter during the grinding process of the workpiece.

[0018] In one embodiment, the first reference intensity data, the second reference intensity data, the first intensity measurement data, and the second intensity measurement data are data representing multiple intensities of light at multiple wavelengths, and the rate of change k is a plurality of rates of change corresponding to the plurality of wavelengths.

[0019] In one embodiment, the processing system is configured to: perform interpolation on the first reference intensity data, the first intensity measurement data, the second reference intensity data, and the second intensity measurement data to make the plurality of wavelengths of the first reference intensity data and the first intensity measurement data consistent with the plurality of wavelengths of the second reference intensity data and the second intensity measurement data, and then calculate a plurality of the rates of change k.

[0020] In one embodiment, the plurality of wavelengths of the first reference intensity data, the second reference intensity data, the first intensity measurement data, and the second intensity measurement data are a plurality of wavelengths consisting of integers.

[0021] In one approach, the rate of change k is the rate of change of the representative intensity value of the second intensity measurement data relative to the representative intensity value of the second reference intensity data.

[0022] In one embodiment, the first beam splitter and the second beam splitter are configured to simultaneously measure the intensity of the reflected light from the workpiece and the intensity of the light from the light source.

[0023] In one embodiment, a direct-connect fiber optic cable is also provided, which directly connects the light source and the second beam splitter.

[0024] In one embodiment, a grinding apparatus for grinding a workpiece is provided, comprising: a grinding table supporting a grinding pad; a grinding head pressing the workpiece against the grinding pad and grinding the workpiece; a light source emitting light; a projection fiber optic cable connected to the light source and guiding the light to the workpiece; a receiving fiber optic cable receiving reflected light from the workpiece; a first beam splitter connected to the receiving fiber optic cable; a second beam splitter directly connected to the light source; and a processing system comprising a storage device storing a program and a processing device for performing calculations according to instructions contained in the program, the storage device internally storing multiple different first reference intensity data and multiple different second reference intensity data, the first reference intensity data representing the reference intensity of light measured by the first beam splitter before grinding the workpiece, and the second reference intensity data representing the light intensity measured by the first beam splitter before grinding the workpiece. The reference intensity of the light source measured by the second beam splitter before the workpiece is ground is given. The plurality of different first reference intensity data and the plurality of different second reference intensity data are associated in a one-to-one correspondence. The processing system is configured to: acquire first intensity measurement data, which represents the intensity of the reflected light from the workpiece measured by the first beam splitter; acquire second intensity measurement data, which represents the intensity of the light source measured by the second beam splitter during the grinding process of the workpiece; select the second reference intensity data that best matches the second intensity measurement data from the plurality of different second reference intensity data; determine the first reference intensity data associated with the selected second reference intensity data; calculate relative reflectivity data by dividing the first intensity measurement data by the determined first reference intensity data; and determine the film thickness of the workpiece based on the relative reflectivity data.

[0025] In one embodiment, the first beam splitter and the second beam splitter are configured to simultaneously measure the intensity of the reflected light from the workpiece and the intensity of the light from the light source during the grinding process of the workpiece.

[0026] In one embodiment, the polishing apparatus further comprises a direct-connection optical fiber cable that directly connects the light source and the second beam splitter. The ends of the projection optical fiber cable and the ends of the direct-connection optical fiber cable are bundled together to form a trunk optical fiber cable, which is connected to the light source.

[0027] In one embodiment, a grinding method for grinding a workpiece is provided. Before grinding the workpiece, light emitted from a light source is directed to a first beam splitter via a projection fiber optic cable and a receiving fiber optic cable. The intensity of the light is measured by the first beam splitter, thereby generating first reference intensity data representing the reference intensity of the light. Before grinding the workpiece, the intensity of the light emitted from the light source is measured by a second beam splitter, thereby generating second reference intensity data representing the reference intensity of the light. The second beam splitter is directly connected to the light source. While rotating the grinding table, the workpiece is pressed against a grinding pad on the grinding table to grind the workpiece. During the grinding process of the workpiece... First intensity measurement data is acquired, representing the intensity of reflected light from the workpiece as measured by the first beam splitter. During the grinding process of the workpiece, second intensity measurement data is acquired, representing the intensity of light from the light source as measured by the second beam splitter. The rate of change of the second intensity measurement data relative to the second reference intensity data is calculated. A corrected first reference intensity data is calculated by multiplying the first reference intensity data by the rate of change. Relative reflectance data is calculated by dividing the first intensity measurement data by the corrected first reference intensity data. The film thickness of the workpiece is determined based on the relative reflectance data.

[0028] In one embodiment, the first reference intensity data, the second reference intensity data, the first intensity measurement data, and the second intensity measurement data are data representing multiple intensities of light at multiple wavelengths, and the rate of change k is a plurality of rates of change corresponding to the plurality of wavelengths.

[0029] In one approach, the method further includes the following step: before calculating the plurality of rates of change, interpolation is performed on the first reference strength data, the first strength measurement data, the second reference strength data, and the second strength measurement data, so that the plurality of wavelengths of the first reference strength data and the first strength measurement data are consistent with the plurality of wavelengths of the second reference strength data and the second strength measurement data.

[0030] In one embodiment, the plurality of wavelengths of the first reference intensity data, the second reference intensity data, the first intensity measurement data, and the second intensity measurement data are a plurality of wavelengths consisting of integers.

[0031] In one approach, the rate of change is the rate of change of the representative intensity value of the second intensity measurement data relative to the representative intensity value of the second reference intensity data.

[0032] In one approach, during the grinding process of the workpiece, the first beam splitter and the second beam splitter simultaneously measure the intensity of the reflected light from the workpiece and the intensity of the light from the light source.

[0033] In one embodiment, a grinding method for grinding a workpiece is provided. Before grinding the workpiece, light repeatedly emitted from a light source is guided to a first beam splitter via a projection fiber optic cable and a receiving fiber optic cable. The intensity of the light is measured by the first beam splitter, thereby generating multiple different first reference intensity data representing the reference intensity of the light. The intensity of the light repeatedly emitted from the light source is measured by a second beam splitter, thereby generating multiple different second reference intensity data representing the reference intensity of the light. The second beam splitter is directly connected to the light source, and the multiple different first reference intensity data and the multiple different second reference intensity data are associated in a one-to-one correspondence. While rotating a grinding table, the workpiece is pressed onto the grinding table. The workpiece is ground using a grinding pad. During the grinding process, first intensity measurement data is acquired, representing the intensity of reflected light from the workpiece as measured by the first beam splitter. During the grinding process, second intensity measurement data is acquired, representing the intensity of light from the light source as measured by the second beam splitter. From a plurality of different second reference intensity data, a second reference intensity data that best matches the second intensity measurement data is selected. A first reference intensity data associated with the selected second reference intensity data is determined. Relative reflectance data is calculated by dividing the first intensity measurement data by the determined first reference intensity data. The film thickness of the workpiece is determined based on the relative reflectance data.

[0034] In one approach, during the grinding process of the workpiece, the first beam splitter and the second beam splitter simultaneously measure the intensity of the reflected light from the workpiece and the intensity of the light from the light source.

[0035] The effects of the invention

[0036] The second reference strength data is the original reference data, and the second strength measurement data is the reference data during grinding. According to the present invention, the first reference strength data is corrected using the rate of change of the second strength measurement data relative to the second reference strength data. Furthermore, relative reflectance data is obtained by dividing the first strength measurement data obtained during the workpiece grinding process by the corrected first reference strength data. Through this calculation, fluctuations in the amount of light from the light source are removed from the relative reflectance data. As a result, the correct film thickness can be determined based on the relative reflectance data.

[0037] Furthermore, according to the present invention, the second reference intensity data that best matches the second intensity measurement data is selected from a plurality of different second reference intensity data. The plurality of different second reference intensity data are data that differ due to the different optical paths of light traveling within the optical fiber cable. The second reference intensity data that best matches the second intensity measurement data is data that reflects such differences in optical paths. Therefore, the first reference intensity data associated with the selected second reference intensity data also reflects differences in optical paths. By dividing the first intensity measurement data by the first reference intensity data, relative reflectivity data that eliminates differences in optical paths within the optical fiber cable can be calculated. As a result, the correct film thickness can be determined based on the relative reflectivity data. Attached Figure Description

[0038] Figure 1 This is a schematic diagram illustrating one embodiment of the grinding apparatus.

[0039] Figure 2 This is a cross-sectional view showing the detailed structure of the optical film thickness measuring device.

[0040] Figure 3 This is a graph representing the spectrum generated from the first intensity measurement data.

[0041] Figure 4 This is a graph representing the spectrum generated from the corrected first reference intensity data.

[0042] Figure 5 It is a graph representing the spectrum generated from relative reflectance data.

[0043] Figure 6 This is a flowchart illustrating one embodiment of a grinding method for grinding workpieces.

[0044] Figure 7 It is a graph showing the intensity and wavelength of light measured by the first and second beam splitters.

[0045] Figure 8 It is a graph that shows the state in which the wavelength of the light intensity measured by the first spectrometer and the wavelength of the light intensity measured by the second spectrometer are consistent through interpolation.

[0046] Figure 9 It is a schematic diagram showing the location of the light incident point at the end face of the trunk optical fiber cable and the optical path of the light in the projection optical fiber cable and the direct connection optical fiber cable.

[0047] Figure 10 This is a flowchart illustrating one embodiment of a grinding method for grinding workpieces.

[0048] Figure 11 This is a schematic diagram illustrating other embodiments of the grinding apparatus.

[0049] Symbol Explanation

[0050] 1 Grinding head

[0051] 2. Grinding pad

[0052] 2a Grinding surface

[0053] 3 Grinding table

[0054] 5 Grinding fluid supply nozzle

[0055] 6 Grinding table motor

[0056] 9. Motion Control Department

[0057] 10-head shaft

[0058] 20 Optical film thickness measuring device

[0059] 22 Light Sources

[0060] 25 Optical sensor head

[0061] 27 First beam splitter

[0062] 28 Second beam splitter

[0063] 30 Processing System

[0064] 31. Fiber optic cable

[0065] 32 Optical fiber receiving cable

[0066] 33 Direct-connect fiber optic cables

[0067] 35. Main fiber optic cable

[0068] 40 Optical path switching device

[0069] W workpiece Detailed Implementation

[0070] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0071] Figure 1 This is a schematic diagram illustrating one embodiment of the grinding apparatus. (As shown) Figure 1 As shown, the polishing apparatus includes a polishing table 3 supporting a polishing pad 2, a polishing head 1 pressing a workpiece W with a film onto the polishing pad 2, a polishing table motor 6 rotating the polishing table 3, a polishing fluid supply nozzle 5 for supplying polishing fluid such as slurry to the polishing pad 2, and an operation control unit 9 for controlling the operation of the polishing apparatus. The upper surface of the polishing pad 2 forms a polishing surface 2a for polishing the workpiece W. Examples of workpiece W include wafers, substrates, and panels used in the manufacture of semiconductor devices.

[0072] The grinding head 1 is connected to the head shaft 10, which in turn is connected to a grinding head motor (not shown). The grinding head motor rotates the grinding head 1 and the head shaft 10 together in the direction indicated by the arrow. The grinding table 3 is connected to a grinding table motor 6, which is configured to rotate the grinding table 3 and the grinding pad 2 in the direction indicated by the arrow. The grinding head 1, the grinding head motor, and the grinding table motor 6 are connected to the motion control unit 9.

[0073] The workpiece W is ground as follows. While the grinding table 3 and the grinding head 1 are moving towards... Figure 1 The grinding head rotates in the direction indicated by the arrow, while supplying grinding fluid from the grinding fluid supply nozzle 5 to the grinding surface 2a of the grinding pad 2 on the grinding table 3. As the workpiece W rotates through the grinding head 1, and with the grinding fluid present on the grinding pad 2, the workpiece W is pressed against the grinding surface 2a of the grinding pad 2 by the grinding head 1. The surface of the workpiece W is ground by the chemical action of the grinding fluid, the abrasive particles contained in the grinding fluid, and the mechanical action of the grinding pad 2.

[0074] The motion control unit 9 includes: a storage device 9a storing a program; and a processing device 9b executing operations according to the instructions contained in the program. The motion control unit 9 is composed of at least one computer. The storage device 9a includes a main storage device such as RAM and an auxiliary storage device such as a hard disk drive (HDD) or a solid-state drive (SSD). Examples of the processing device 9b include a CPU (central processing unit) and a GPU (graphics processing unit). However, the specific structure of the motion control unit 9 is not limited to these examples.

[0075] The grinding apparatus includes an optical film thickness measuring device 20 for measuring the film thickness of a workpiece W. The optical film thickness measuring device 20 includes: a light source 22 that emits light; an optical sensor head 25 that illuminates the workpiece W with light from the light source 22 and receives reflected light from the workpiece W; a first beam splitter 27 connected to the optical sensor head 25; a second beam splitter 28 directly connected to the light source 22; and a processing system 30 that determines the film thickness of the workpiece W based on the relative reflectivity data of the reflected light from the workpiece W. The optical sensor head 25 is disposed within the grinding table 3 and rotates together with the grinding table 3. Multiple optical sensor heads 25 connected to the first beam splitter 27 and the light source 22 may also be provided.

[0076] The processing system 30 includes: a storage device 30a storing a program; and a processing device 30b performing operations according to the instructions contained in the program. The processing system 30 comprises at least one computer. The storage device 30a includes a main storage device such as RAM and an auxiliary storage device such as a hard disk drive (HDD) or a solid-state drive (SSD). Examples of the processing device 30b include a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit). However, the specific structure of the processing system 30 is not limited to these examples.

[0077] The motion control unit 9 and the processing system 30 may each be composed of multiple computers. For example, the motion control unit 9 and the processing system 30 may each be composed of a combination of an edge server and a cloud server. In one embodiment, the motion control unit 9 and the processing system 30 may also be composed of a single computer.

[0078] Figure 2 This is a cross-sectional view showing the detailed structure of the optical film thickness measuring device 20. The optical film thickness measuring device 20 includes: a light-emitting fiber optic cable 31 connected to a light source 22; a light-receiving fiber optic cable 32 connected to a first beam splitter 27; and a direct-connection fiber optic cable 33 directly connecting the light source 22 and the second beam splitter 28. The tip 31a of the light-emitting fiber optic cable 31 and the tip 32a of the light-receiving fiber optic cable 32 constitute an optical sensor head 25. That is, the light-emitting fiber optic cable 31 guides the light from the light source 22 to the workpiece W on the polishing pad 2, and the light-receiving fiber optic cable 32 receives the reflected light from the workpiece W and transmits it to the first beam splitter 27. One end of the direct-connection fiber optic cable 33 is connected to the light source 22, and the other end is connected to the second beam splitter 28.

[0079] The first beam splitter 27 and the second beam splitter 28 are connected to the processing system 30. The projection fiber optic cable 31, the receiving fiber optic cable 32, the direct-connect fiber optic cable 33, the light source 22, the first beam splitter 27, and the second beam splitter 28 are mounted on the polishing table 3 and rotate integrally with the polishing table 3 and the polishing pad 2. An optical sensor head 25, formed by the top end 31a of the projection fiber optic cable 31 and the top end 32a of the receiving fiber optic cable 32, is positioned opposite the surface of the workpiece W on the polishing pad 2. The position of the optical sensor head 25 is such that it traverses the surface of the workpiece W on the polishing pad 2 with each rotation of the polishing table 3 and the polishing pad 2. The polishing pad 2 has a through-hole 2b located above the optical sensor head 25. Each time the polishing table 3 rotates once, the optical sensor head 25 illuminates the workpiece W through the through-hole 2b and receives reflected light from the workpiece W through the through-hole 2b.

[0080] Light source 22 is a flash light source that emits light repeatedly within short time intervals. An example of light source 22 is a xenon flash lamp. Light source 22 is electrically connected to the motion control unit 9 and emits light upon receiving trigger signals from the motion control unit 9. More specifically, light source 22 receives multiple trigger signals and emits light multiple times while the optical sensor head 25 traverses the surface of the workpiece W on the polishing pad 2. Therefore, light is irradiated onto multiple measurement points on the workpiece W each time the polishing table 3 rotates once.

[0081] The second beam splitter 28 is directly connected to the light source 22 via a direct-connect fiber optic cable 33. The direct-connect fiber optic cable 33 extends from the light source 22 to the second beam splitter 28. The second beam splitter 28 is not connected to the optical sensor head 25 and only receives light from the light source 22. The ends of the projection fiber optic cable 31 and the direct-connect fiber optic cable 33 are bundled together to form a trunk fiber optic cable 35. The trunk fiber optic cable 35 is connected to the light source 22. That is, the trunk fiber optic cable 35 branches into the projection fiber optic cable 31 and the direct-connect fiber optic cable 33. Therefore, the light emitted from the light source 22 branches into two beams, which are then transmitted to the optical sensor head 25 and the second beam splitter 28 respectively via the projection fiber optic cable 31 and the direct-connect fiber optic cable 33.

[0082] In addition, the optical fiber cable 31 and the direct-connect optical fiber cable 33 can also be structures in which multiple thinner optical fibers (bare optical fibers) are bundled together.

[0083] The light emitted by the light source 22 is simultaneously transmitted to the optical sensor head 25 and the second beam splitter 28. That is, the light is transmitted to the optical sensor head 25 through the projection fiber optic cable 31 and emitted from the optical sensor head 25. The light passes through the through hole 2b of the polishing pad 2 and is incident on the workpiece W on the polishing pad 2. The light reflected from the workpiece W passes through the through hole 2b of the polishing pad 2 again and is received by the optical sensor head 25. The reflected light from the workpiece W is transmitted to the first beam splitter 27 through the light receiving fiber optic cable 32. At the same time, the light from the light source 22 is not sent to the optical sensor head 25, but is transmitted to the second beam splitter 28 through the direct connection fiber optic cable 33.

[0084] The first beam splitter 27 and the second beam splitter 28 are configured to decompose light according to wavelength and measure the intensity of reflected light at each wavelength across a predetermined wavelength range. Specifically, the first beam splitter 27 decomposes the reflected light from the workpiece W according to wavelength and measures the intensity of reflected light at each wavelength across a predetermined wavelength range, thereby generating first intensity measurement data. Simultaneously, the second beam splitter 28 decomposes the light from the light source 22 according to wavelength and measures the intensity of light at each wavelength across the aforementioned wavelength range, thereby generating second intensity measurement data. The intensity of the light emitted by the light source 22 is simultaneously measured by the first beam splitter 27 and the second beam splitter 28. The first intensity measurement data and the second intensity measurement data are sent to the processing system 30.

[0085] The storage device 30a of the processing system 30 internally stores first reference intensity data and second reference intensity data. The first reference intensity data represents the reference intensity of light measured in advance by the first beam splitter 27 before the workpiece W is ground, and the second reference intensity data represents the reference intensity of light from the light source 22 measured in advance by the second beam splitter 28 before the workpiece W is ground. The first reference intensity data and the second reference intensity data are data acquired in advance before the workpiece W is ground. On the other hand, the aforementioned first intensity measurement data and second intensity measurement data are data acquired during the grinding process of the workpiece W.

[0086] The first reference intensity data, the second reference intensity data, the first intensity measurement data, and the second intensity measurement data each represent multiple intensities of light at multiple wavelengths within the aforementioned specified wavelength range. For example, the first intensity measurement data represents multiple intensities of light at multiple wavelengths reflected from workpiece W. The multiple intensities of light represented by the above data can also be relative intensities to a black level (background intensity obtained under shading conditions) that serves as a reference for light intensity. Specifically, the light intensity included in each data can also be the value obtained by subtracting the black level from the measured value of the light intensity at each wavelength. For example, when the measured value of the light intensity at wavelength λ is set as M(λ), the light intensity E(λ) at wavelength λ included in each data can also be obtained using the following formula.

[0087] E(λ)=M(λ)-D(λ) (1)

[0088] Here, λ represents the wavelength, and D(λ) represents the black level at wavelength λ.

[0089] The light intensity represented by each data is not limited to this example; for example, it can also be the measured value of the light intensity obtained by the first beam splitter 27 and the second beam splitter 28.

[0090] The first intensity measurement data, representing the intensity of reflected light from workpiece W, includes information about the film thickness of workpiece W. In other words, the first intensity measurement data varies depending on the film thickness of workpiece W. Therefore, as described below, the processing system 30 can determine the film thickness of workpiece W by processing the first intensity measurement data.

[0091] In contrast, the first reference intensity data represents the reference intensity of light pre-measured for each wavelength. The first reference intensity data is obtained, for example, by illuminating light from the optical sensor head 25 onto the mirror and measuring the intensity of the reflected light from the mirror by the first beam splitter 27. Alternatively, the first reference intensity data may also be the intensity of the reflected light from the silicon wafer measured by the first beam splitter 27 when the uncoated silicon wafer (bare wafer) is wet-polished or slurry-polished on the polishing pad 2, or when the silicon wafer (bare wafer) is placed on the polishing pad 2.

[0092] In this embodiment, the relative reflectance data is determined by dividing the first intensity measurement data by the first reference intensity data. The relative reflectance data is an indicator representing the intensity of reflected light at each wavelength. By dividing the first intensity measurement data by the first reference intensity data, unwanted noise such as fluctuations in the optical system of the device and the inherent intensity of the light source 22 can be removed from the measured intensity.

[0093] The second reference intensity data and the second intensity measurement data are both measurement data of the light intensity of the light source 22, and are independent of the reflected light from the workpiece W. The second reference intensity data represents the reference intensity of the light from the light source 22, and the second intensity measurement data represents the intensity of the light from the light source 22 during the grinding process of the workpiece W. In this embodiment, the second reference intensity data and the second intensity measurement data are used as correction coefficients to eliminate fluctuations in the relative reflectivity data caused by changes in the amount of light at each measurement point of the light source 22.

[0094] The second reference intensity data is acquired at the same time point as the first reference intensity data before the workpiece W is ground. That is, the first beam splitter 27 measures the intensity of the light transmitted from the optical sensor head 25 within a specified wavelength range, while the second beam splitter 28 measures the intensity of the light from the light source 22 within the same wavelength range.

[0095] The second intensity measurement data is acquired at the same time point as the first intensity measurement data before the workpiece W is ground. That is, the first beam splitter 27 measures the intensity of the reflected light from the workpiece W transmitted from the optical sensor head 25 within a specified wavelength range, while the second beam splitter 28 measures the intensity of the light from the light source 22 within the same wavelength range.

[0096] The storage device 30a of the processing system 30 stores calculation formulas for calculating relative reflectivity data. The processing system 30 is configured to determine the film thickness of the workpiece W based on the relative reflectivity data. The calculation formulas are shown below.

[0097] Relative reflectance data = MD1 / [BD1·k] (2)

[0098] Here, MD1 represents the first intensity measurement data, which is measured by the first beam splitter 27 during the grinding process of workpiece W. BD1 represents the aforementioned first reference intensity data, which is measured by the first beam splitter 27 before the grinding of workpiece W. k is the rate of change of the second intensity measurement data relative to the second reference intensity data, which represents the intensity of the light source 22 measured by the second beam splitter 28 during the grinding process of workpiece W.

[0099] The change in the second intensity measurement data relative to the second reference intensity data does not depend on the film thickness change of the workpiece W, but only on the change in the light intensity of the light source 22. Therefore, by multiplying the rate of change k by the first reference intensity data, the first reference intensity data is corrected (i.e., the change in the light intensity of the light source 22 is reflected in the first reference intensity data). Since the first intensity measurement data MD1 reflects the change in the light intensity of the light source 22 in the same way as the second intensity measurement data, the change in the light intensity of the light source 22 is removed (cancelled) by dividing the first intensity measurement data MD1 by the corrected first reference intensity data. As a result, the processing system 30 is able to determine the correct film thickness based on the relative reflectivity data.

[0100] Figure 3 This represents the spectrum generated from the first intensity measurement data. Figure 4 This represents the spectrum generated from the corrected first reference intensity data. Figure 5 This represents the spectrum generated from the relative reflectance data obtained by dividing the first intensity measurement data by the corrected first reference intensity data. The shape of the spectrum generated from the relative reflectance data varies depending on the film thickness of the workpiece W. The processing system 30 generates the spectrum from the relative reflectance data obtained by the above calculation formula. Figure 5 The spectrum is shown, and the film thickness of workpiece W is determined based on this spectrum.

[0101] The method for determining the film thickness of workpiece W based on spectrum uses known techniques. For example, processing system 30 determines a reference spectrum from a reference spectrum library that most closely matches the spectral shape, and determines the film thickness associated with that determined reference spectrum. In another example, processing system 30 performs a Fourier transform on the spectrum and determines the film thickness based on the resulting frequency spectrum.

[0102] Figure 6 This is a flowchart illustrating one embodiment of a grinding method for grinding workpiece W.

[0103] In step 101, before grinding the workpiece W, light emitted from the light source 22 is guided to the first beam splitter 27 through the projection fiber optic cable 31 and the receiving fiber optic cable 32, and the intensity of the light is measured by the first beam splitter 27, thereby generating first reference intensity data representing the reference intensity of the light. The processing system 30 obtains the first reference intensity data from the first beam splitter 27 and stores the first reference intensity data in the storage device 30a.

[0104] In step 102, before grinding the workpiece W, light emitted from the light source 22 is guided to the second beam splitter 28 through the direct-connection optical fiber cable 33, and the intensity of the light is measured by the second beam splitter 28, thereby generating second reference intensity data representing the reference intensity of the light from the light source 22. The processing system 30 acquires the second reference intensity data from the second beam splitter 28 and stores the second reference intensity data in the storage device 30a. The light intensity measurement performed by the first beam splitter 27 in step 101 and the light intensity measurement performed by the second beam splitter 28 in step 102 are performed simultaneously.

[0105] In step 103, while the grinding table 3 is rotated, the workpiece W is pressed onto the grinding pad 2 through the grinding head 1 and the grinding of the workpiece W begins.

[0106] In step 104, during the grinding process of workpiece W, the processing system 30 acquires first intensity measurement data, which represents the intensity of reflected light from workpiece W as measured by the first spectrometer 27.

[0107] In step 105, during the grinding process of workpiece W, the processing system 30 acquires second intensity measurement data, which represents the intensity of light from light source 22 as measured by the second beam splitter 28. The intensity measurement of reflected light performed by the first beam splitter 27 in step 104 and the intensity measurement of light from light source 22 performed by the second beam splitter 28 in step 105 are performed simultaneously.

[0108] In step 106, the processing system 30 calculates the rate of change of the second strength measurement data relative to the second reference strength data.

[0109] In step 107, the processing system 30 calculates the corrected first reference strength data by multiplying the first reference strength data by the rate of change.

[0110] In step 108, the processing system 30 calculates the relative reflectance data by dividing the first intensity measurement data by the corrected first reference intensity data.

[0111] In step 109, the processing system 30 determines the film thickness of the workpiece W based on the relative reflectivity data.

[0112] The rate of change k used in the above calculation formula can be multiple rates of change corresponding to multiple wavelengths, or it can be a single rate of change defined for multiple wavelengths. Multiple rates of change k(λ) corresponding to multiple wavelengths can also be obtained using the following formula.

[0113] k(λ)=MV2(λ) / BV2(λ), λ=λLL~λHL (3)

[0114] Here, λ represents the wavelength of light, k(λ) represents the rate of change at wavelength λ, MV2(λ) represents the intensity of light at wavelength λ included in the second intensity measurement data, BV2(λ) represents the intensity of light at wavelength λ included in the second reference intensity data, λLL represents the lower limit of the wavelength range of light intensity measured by the first beam splitter 27 and the second beam splitter 28, and λHL represents the upper limit of the aforementioned wavelength range. Wavelength λ is any wavelength from the lower limit λLL to the upper limit λHL.

[0115] According to this embodiment, since the rate of change is calculated according to each wavelength, the first reference intensity data can be further corrected accurately.

[0116] The above calculation formula (2) can be expressed using formula (3) as follows.

[0117] R(λ)=MV1(λ) / [BV1(λ)·k(λ)], λ=λLL~λHL (4)

[0118] Here, R(λ) represents the relative reflectivity at wavelength λ, MV1(λ) represents the intensity of reflected light at wavelength λ contained in the first intensity measurement data MD1, and BV1(λ) represents the reference intensity of light at wavelength λ contained in the first reference intensity data BD1.

[0119] In formulas (3) and (4) above, MV1(λ), ​​BV1(λ), ​​MV2(λ), and BV2(λ) represent the light intensity at wavelength λ measured by the first beam splitter 27 and the second beam splitter 28. The first beam splitter 27 and the second beam splitter 28 are respectively configured to decompose light according to wavelength and measure the intensity of light at each wavelength. However, due to mechanical differences between the first beam splitter 27 and the second beam splitter 28, there may be a difference between the wavelength of the intensity measured by the first beam splitter 27 and the wavelength of the intensity measured by the second beam splitter 28. For this, refer to... Figure 7 Please provide an explanation.

[0120] Figure 7 This is a graph showing the intensity and wavelength of light measured by the first beam splitter 27 and the second beam splitter 28. The first beam splitter 27 measures the intensity MV1(λ1), MV1(λ2), MV1(λ3) of light with wavelengths λ1, λ2, and λ3, and the second beam splitter 28 similarly measures the intensity MV2(λ1), MV2(λ2), MV2(λ3) of light with wavelengths λ1, λ2, and λ3. However, as... Figure 7As shown, due to the mechanical differences between the first beam splitter 27 and the second beam splitter 28, there are slight differences between the wavelengths λ1, λ2, λ3 of the light intensity measured by the first beam splitter 27 and the wavelengths λ1, λ2, λ3 of the light intensity measured by the second beam splitter 28. Such wavelength differences can adversely affect the accuracy of the relative reflectance data.

[0121] Therefore, in one embodiment, the processing system 30 is configured to perform interpolation on the first reference intensity data, the first intensity measurement data, the second reference intensity data, and the second intensity measurement data, thereby aligning multiple wavelengths of the first reference intensity data and the first intensity measurement data with multiple wavelengths of the second reference intensity data and the second intensity measurement data. After performing the interpolation, the processing system 30 calculates multiple rates of change k and further calculates relative reflectance data.

[0122] Figure 8 This is a graph showing the state where the wavelengths λ1, λ2, λ3 of the light intensity measured by the first beam splitter 27 and the wavelengths λ1, λ2, λ3 of the light intensity measured by the second beam splitter 28 are consistent through interpolation. In this example, the wavelengths λ1, λ2, λ3 of the first intensity measurement data after interpolation and the wavelengths λ1, λ2, λ3 of the second intensity measurement data after interpolation are multiple wavelengths consisting of integers. That is, the processing system 30 performs interpolation on the first intensity measurement data to calculate the light intensities MV1(λ1), MV1(λ2), MV1(λ3) of the multiple wavelengths λ1, λ2, λ3 consisting of integers, and further performs interpolation on the second intensity measurement data to calculate the light intensities MV2(λ1), MV2(λ2), MV2(λ3) of the multiple wavelengths λ1, λ2, λ3 consisting of integers. As a result, the wavelengths are consistent between the first intensity measurement data and the second intensity measurement data.

[0123] Similarly, the wavelengths λ1, λ2, λ3 of the interpolated first reference intensity data and the wavelengths λ1, λ2, λ3 of the interpolated second reference intensity data are multiple wavelengths consisting of integers. That is, the processing system 30 performs interpolation on the first reference intensity data to calculate the light intensities BV1(λ1), BV1(λ2), BV1(λ3) of the multiple wavelengths λ1, λ2, λ3 consisting of integers, and further performs interpolation on the second intensity measurement data to calculate the light intensities BV2(λ1), BV2(λ2), BV2(λ3) of the multiple wavelengths λ1, λ2, λ3 consisting of integers. As a result, the wavelengths are consistent between the first reference intensity data and the second reference intensity data.

[0124] Therefore, the wavelengths within the wavelength range of the light intensity measured by the first beam splitter 27 and the second beam splitter 28 are all the same.

[0125] In one embodiment, the rate of change k can also be a rate of change set for multiple wavelengths. In this case, the interpolation described above is not required. The processing system 30 determines the representative intensity value of the second reference intensity data and the representative intensity value of the second intensity measurement data, and calculates the rate of change k of the representative intensity value of the second intensity measurement data relative to the representative intensity value of the second reference intensity data. Examples of representative intensity values ​​include the average value, maximum value, and maximum value of multiple intensities corresponding to multiple wavelengths.

[0126] According to the embodiments described above, the processing system 30 can remove fluctuations in the emission of the light source 22, and also remove changes in the amount of light emitted by the light source 22 over time. That is, both fluctuations in the emission of the light source 22 and changes in the amount of light emitted by the light source 22 over time can be expressed as changes in the second intensity measurement data relative to the second reference intensity data. Therefore, by performing data processing using the aforementioned calculation formula, the processing system 30 can not only eliminate fluctuations in the emission of the light source 22, but also eliminate changes in the amount of light emitted by the light source 22 over time.

[0127] Next, other embodiments of the grinding apparatus will be described. Since the structure and operation of this embodiment, unless otherwise specifically described, are similar to those described in the reference illustrative section... Figure 1 and Figure 2 The implementation methods described are the same, so repeated descriptions are omitted.

[0128] like Figure 2 As shown, the light source 22 is connected to the trunk optical fiber cable 35. The light emitted by the light source 22 first enters the end face of the trunk optical fiber cable 35, and then is distributed to the projection optical fiber cable 31 and the direct connection optical fiber cable 33. Figure 9 This is a schematic diagram showing the location of the light incident point at the end face 35a of the trunk optical fiber cable 35 and the optical path of the light within the projection optical fiber cable 31 and the direct connection optical fiber cable 33. For example... Figure 9 As shown, the incident point S of the light emitted by the light source 22 is smaller than the end face 35a of the trunk optical fiber cable 35, and the incident point S is located within the end face 35a of the trunk optical fiber cable 35.

[0129] During the grinding process of workpiece W, light source 22 emits light repeatedly within short time intervals. The position of the incident point S of the light within the end face 35a of the trunk optical fiber 35 is not constant, but changes with each emission of light from light source 22. The optical path P1 of the light traveling within the projection optical fiber 31 (i.e., the point position of the light within the projection optical fiber 31) and the optical path P2 of the light traveling within the direct connection optical fiber 33 change with the position of the incident point S of the light within the end face 35a of the trunk optical fiber 35. Figure 9The circle shown by the dashed line represents the change in the position of the light incident point S and the corresponding changes in the optical paths P1 and P2. Such changes in the optical paths P1 and P2 within the projection fiber optic cable 31 and the direct connection fiber optic cable 33 cause changes in the spectrum of the reflected light from the workpiece W.

[0130] Although the optical path P1 within the projection fiber optic cable 31 and the optical path P2 within the direct-connect fiber optic cable 33 change, there is a one-to-one relationship between the positions of the optical paths P1 and P2 within these fiber optic cables 31 and 33. In other words, the position of the optical path P1 of the light traveling within the projection fiber optic cable 31 uniquely corresponds to the position of the optical path P2 of the light traveling within the direct-connect fiber optic cable 33. The second intensity measurement data, representing the intensity of the light from the light source 22 measured by the second beam splitter 28 during the grinding process of the workpiece W, changes with the optical path P2 of the light traveling within the direct-connect fiber optic cable 33, that is, with the position of the incident point S of the light within the end face 35a of the trunk fiber optic cable 35. Therefore, the first intensity measurement data, representing the intensity of the reflected light from the workpiece W measured by the first beam splitter 27 during the grinding process of the workpiece W, also changes in a one-to-one relationship with the second intensity measurement data.

[0131] In this embodiment, before the workpiece W is ground, the light source 2 is repeatedly emitted while the light intensity is measured by the first beam splitter 27 and the second beam splitter 28, generating multiple first reference intensity data and multiple second reference intensity data. The second reference intensity data are acquired at the same time point as the first reference intensity data before the workpiece W is ground. That is, the first beam splitter 27 measures the intensity of the light transmitted from the optical sensor head 25 across a predetermined wavelength range, while the second beam splitter 28 measures the intensity of the light from the light source 22 across the same wavelength range.

[0132] Whenever the light source 22 emits light, the position of the incident point S of the light within the end face 35a of the trunk optical fiber 35 changes, thus generating multiple different first reference intensity data and multiple different second reference intensity data. A reference library containing multiple different first reference intensity data and multiple different second reference intensity data is stored in the storage device 30a of the processing system 30. The multiple different first reference intensity data and multiple different second reference intensity data are associated with a one-to-one correspondence.

[0133] During the grinding process of workpiece W, processing system 30 acquires first intensity measurement data representing the intensity of reflected light from workpiece W as measured by first beam splitter 27, and acquires second intensity measurement data representing the intensity of light from light source 22 as measured by second beam splitter 28. The second intensity measurement data is acquired at the same time point as the first intensity measurement data during the grinding process of workpiece W. That is, first beam splitter 27 measures the intensity of reflected light from workpiece W across a predetermined wavelength range, while second beam splitter 28 measures the intensity of light from light source 22 across the same wavelength range.

[0134] The processing system 30 selects the second reference strength data that best matches the second strength measurement data from multiple different second reference strength data contained in the reference library, and determines the first reference strength data associated with the selected second reference strength data. "Best match" includes not only the most similar but also complete similarity. As a method for selecting the second reference strength data that best matches the second strength measurement data (i.e., a method for determining the similarity of the strength data), curve fitting and regeneration discrimination methods can be used.

[0135] The spectrum of reflected light from workpiece W is affected by the optical path within the optical fiber cable 31. Therefore, when calculating the relative reflectance from the first intensity measurement data and the first reference intensity data, if intensity data of light passing through different optical paths are used, the film thickness cannot be accurately measured due to the influence of the optical path. On the other hand, since the first reference intensity data and the second reference intensity data, as well as the first intensity measurement data and the second intensity measurement data, are intensity data of light passing through the same optical path, they have corresponding relationships. Therefore, from multiple second reference intensity data, the following second reference intensity data is selected: this second reference intensity data is considered to have passed through the same optical path within the direct-connection optical fiber cable 33 and has spectral similarity with the second intensity measurement data. The first reference intensity data (measured simultaneously) corresponding to the selected second reference intensity data is then obtained. Thus, by calculating the relative reflectance between the first intensity measurement data and the obtained first reference intensity data, the influence of the optical path can be eliminated, improving the accuracy of film thickness measurement.

[0136] The processing system 30 calculates relative reflectance data by dividing the first intensity measurement data by the determined first reference intensity data, and determines the film thickness of the workpiece W based on the relative reflectance data. This division removes the positional variation of the light incident point S within the end face 35a of the trunk optical fiber 35 from the relative reflectance data. As a result, the processing system 30 is able to determine the correct film thickness based on the relative reflectance data.

[0137] Figure 10 This is a flowchart illustrating one embodiment of a grinding method for grinding workpiece W.

[0138] In step 201, before grinding the workpiece W, light repeatedly emitted from the light source 22 is guided to the first beam splitter 27 through the projection fiber optic cable 31 and the receiving fiber optic cable 32, and the intensity of the light is measured by the first beam splitter 27, thereby generating multiple different first reference intensity data representing the reference intensity of the light. The processing system 30 acquires the multiple different first reference intensity data from the first beam splitter 27 and stores the multiple different first reference intensity data in the storage device 30a.

[0139] In step 202, before grinding the workpiece W, light repeatedly emitted from the light source 22 is guided to the second beam splitter 28 via a direct-connect fiber optic cable 33, and the intensity of the light is measured by the second beam splitter 28, thereby generating multiple different second reference intensity data representing the reference intensity of the light from the light source 22. The processing system 30 acquires the multiple different second reference intensity data from the second beam splitter 28 and stores the multiple different second reference intensity data in the storage device 30a. The light intensity measurement performed by the first beam splitter 27 in step 201 and the light intensity measurement performed by the second beam splitter 28 in step 202 are performed simultaneously.

[0140] In step 203, while the grinding table 3 is rotated, the workpiece W is pressed onto the grinding pad 2 through the grinding head 1 and the grinding of the workpiece W begins.

[0141] In step 204, during the grinding process of workpiece W, the processing system 30 acquires first intensity measurement data, which represents the intensity of reflected light from workpiece W as measured by the first spectrometer 27.

[0142] In step 205, during the grinding process of workpiece W, the processing system 30 acquires second intensity measurement data, which represents the intensity of light from light source 22 as measured by the second beam splitter 28. The intensity measurement of reflected light performed by the first beam splitter 27 in step 204 and the intensity measurement of light from light source 22 performed by the second beam splitter 28 in step 205 are performed simultaneously.

[0143] In step 206, the processing system 30 selects the second reference strength data that is most consistent with the second strength measurement data from the above multiple different second reference strength data.

[0144] In step 207, the processing system 30 determines the first reference strength data associated with the selected second reference strength data.

[0145] In step 208, the processing system 30 calculates the relative reflectance data by dividing the first intensity measurement data by the determined first reference intensity data.

[0146] In step 209, the processing system 30 determines the film thickness of the workpiece W based on the relative reflectivity data.

[0147] In the embodiments described above, although only one optical sensor head 25 is provided, the present invention is not limited to the above embodiments, and multiple optical sensor heads 25 may also be provided in the grinding table 3. For example, as Figure 11 As shown, the light-receiving optical fiber cable 32 constituting multiple optical sensor heads 25 can also be connected to the first beam splitter 27 via an optical path switching device 40 such as an optical switch or shutter. The positions of the multiple optical sensor heads 25 are not particularly limited; for example, multiple optical sensor heads 25 can be arranged at positions passing through the center and edge of the workpiece W. Figure 11 In the embodiment shown, although two optical sensor heads 25 are provided, three or more optical sensor heads 25 can also be provided.

[0148] The above embodiments are described with the aim of enabling those skilled in the art to carry out the present invention. Various modifications of the above embodiments can obviously be implemented by those skilled in the art, and the technical concept of the present invention can also be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, and the technical concept defined according to the scope of the claims is interpreted as the broadest scope.

Claims

1. A grinding apparatus for grinding a workpiece, characterized in that it comprises: Grinding table, which supports the grinding pad; A grinding head that presses the workpiece onto the grinding pad and grinds the workpiece; A light source that emits light; A fiber optic cable for transmitting light, which is connected to the light source and directs the light to the workpiece; A light-receiving optical fiber cable that receives reflected light from the workpiece; A first optical splitter, which is connected to the optical fiber receiving cable; A second beam splitter, which is directly connected to the light source; as well as The processing system includes a storage device for storing a program and an arithmetic device for performing operations according to the instructions contained in the program. The storage device internally stores first reference intensity data, second reference intensity data, and a calculation formula for calculating relative reflectance data. The first reference intensity data represents the reference intensity of light measured by the first beam splitter before the workpiece is ground, and the second reference intensity data represents the reference intensity of light from the light source measured by the second beam splitter before the workpiece is ground. The processing system is configured to determine the film thickness of the workpiece based on the relative reflectivity data. The calculation formula is expressed as follows: The relative reflectance data = MD1 / [BD1·k], Wherein, MD1 is a first intensity measurement data representing the intensity of the reflected light from the workpiece as measured by the first beam splitter, BD1 is the first reference intensity data, and k is the rate of change of the second intensity measurement data relative to the second reference intensity data, the second intensity measurement data representing the intensity of the light source as measured by the second beam splitter during the grinding process of the workpiece.

2. The grinding apparatus according to claim 1, characterized in that, The first reference intensity data, the second reference intensity data, the first intensity measurement data, and the second intensity measurement data are data representing multiple intensities of light at multiple wavelengths. The rate of change k is a plurality of rates of change corresponding to the plurality of wavelengths.

3. The grinding apparatus according to claim 2, characterized in that, The processing system is configured to: perform interpolation on the first reference strength data, the first strength measurement data, the second reference strength data, and the second strength measurement data to make the plurality of wavelengths of the first reference strength data and the first strength measurement data consistent with the plurality of wavelengths of the second reference strength data and the second strength measurement data, and then calculate a plurality of the change rates k.

4. The grinding apparatus according to claim 3, characterized in that, The plurality of wavelengths in the first reference strength data, the second reference strength data, the first strength measurement data, and the second strength measurement data are all integer wavelengths.

5. The grinding apparatus according to claim 1, characterized in that, The rate of change k is the rate of change of the representative strength value of the second strength measurement data relative to the representative strength value of the second reference strength data.

6. The grinding apparatus according to any one of claims 1 to 5, characterized in that, The first beam splitter and the second beam splitter are configured to simultaneously measure the intensity of the reflected light from the workpiece and the intensity of the light from the light source.

7. The grinding apparatus according to any one of claims 1 to 5, characterized in that, It also has a direct-connect fiber optic cable that directly connects the light source and the second beam splitter.

8. A grinding apparatus for grinding a workpiece, characterized in that it comprises: Grinding table, which supports the grinding pad; A grinding head that presses the workpiece onto the grinding pad and grinds the workpiece; A light source that emits light; A fiber optic cable for transmitting light, which is connected to the light source and directs the light to the workpiece; A light-receiving optical fiber cable that receives reflected light from the workpiece; A first optical splitter, which is connected to the optical fiber receiving cable; A second beam splitter, which is directly connected to the light source; as well as The processing system includes a storage device for storing a program and an arithmetic device for performing operations according to the instructions contained in the program. The storage device internally stores multiple different first reference intensity data and multiple different second reference intensity data. The first reference intensity data represents the reference intensity of light measured by the first beam splitter before the workpiece is ground, and the second reference intensity data represents the reference intensity of light from the light source measured by the second beam splitter before the workpiece is ground. The multiple different first reference strength data and the multiple different second reference strength data are associated in a one-to-one correspondence. The processing system is configured as follows: Acquire first intensity measurement data, which represents the intensity of the reflected light from the workpiece as measured by the first beam splitter. Acquire second intensity measurement data, which represents the intensity of the light source measured by the second spectrometer during the grinding process of the workpiece. Select the second reference strength data that best matches the second strength measurement data from the plurality of different second reference strength data. Determine the first reference strength data associated with the selected second reference strength data. The relative reflectance data is calculated by dividing the first intensity measurement data by the determined first reference intensity data. The film thickness of the workpiece is determined based on the relative reflectivity data.

9. The grinding apparatus according to claim 8, characterized in that, The first beam splitter and the second beam splitter are configured to simultaneously measure the intensity of the reflected light from the workpiece and the intensity of the light from the light source during the grinding process of the workpiece.

10. The grinding apparatus according to claim 8 or 9, characterized in that, The grinding device also includes a direct-connection optical fiber cable that directly connects the light source and the second beam splitter. The ends of the optical fiber cable and the ends of the direct-connect optical fiber cable are bundled together to form the backbone optical fiber cable. The backbone optical fiber cable is connected to the light source.

11. A grinding method for grinding a workpiece, characterized in that, Before the workpiece is ground, light emitted from a light source is directed to a first beam splitter via a projection fiber optic cable and a receiving fiber optic cable. The intensity of the light is measured by the first beam splitter, thereby generating first reference intensity data representing the reference intensity of the light. Before the workpiece is ground, the intensity of the light emitted from the light source is measured by a second beam splitter, thereby generating second reference intensity data representing the reference intensity of the light. The second beam splitter is directly connected to the light source. While the grinding table is rotating, the workpiece is pressed against the grinding pad on the grinding table to grind the workpiece. During the grinding process of the workpiece, first intensity measurement data is acquired, which represents the intensity of reflected light from the workpiece as measured by the first spectrometer. During the grinding process of the workpiece, second intensity measurement data is acquired, which represents the intensity of the light from the light source as measured by the second spectrometer. Calculate the rate of change of the second strength measurement data relative to the second reference strength data. The corrected first reference strength data is calculated by multiplying the first reference strength data by the rate of change. The relative reflectance data is calculated by dividing the first intensity measurement data by the corrected first reference intensity data. The film thickness of the workpiece is determined based on the relative reflectivity data.

12. The grinding method according to claim 11, characterized in that, The first reference intensity data, the second reference intensity data, the first intensity measurement data, and the second intensity measurement data are data representing multiple intensities of light at multiple wavelengths. The rate of change is a plurality of rates of change corresponding to the plurality of wavelengths respectively.

13. The grinding method according to claim 12, characterized in that, It also includes the following steps: before calculating the plurality of rates of change, interpolation is performed on the first reference strength data, the first strength measurement data, the second reference strength data, and the second strength measurement data, so that the plurality of wavelengths of the first reference strength data and the first strength measurement data are consistent with the plurality of wavelengths of the second reference strength data and the second strength measurement data.

14. The grinding method according to claim 13, characterized in that, The plurality of wavelengths in the first reference strength data, the second reference strength data, the first strength measurement data, and the second strength measurement data are all integer wavelengths.

15. The grinding method according to claim 11, characterized in that, The rate of change is the rate of change of the representative strength value of the second strength measurement data relative to the representative strength value of the second reference strength data.

16. The grinding method according to any one of claims 11 to 15, characterized in that, During the grinding process of the workpiece, the first beam splitter and the second beam splitter simultaneously measure the intensity of the reflected light from the workpiece and the intensity of the light from the light source.

17. A grinding method for grinding a workpiece, characterized in that, Before the workpiece is ground, light repeatedly emitted from a light source is directed to a first beam splitter through a projection fiber optic cable and a receiving fiber optic cable. The intensity of the light is measured by the first beam splitter, thereby generating multiple different first reference intensity data representing the reference intensity of the light. The intensity of the light repeatedly emitted from the light source is measured by a second beam splitter, thereby generating multiple different second reference intensity data representing the reference intensity of the light, and the second beam splitter is directly connected to the light source. The multiple different first reference strength data and the multiple different second reference strength data are associated in a one-to-one correspondence. While the grinding table is rotating, the workpiece is pressed against the grinding pad on the grinding table to grind the workpiece. During the grinding process of the workpiece, first intensity measurement data is acquired, which represents the intensity of reflected light from the workpiece as measured by the first spectrometer. During the grinding process of the workpiece, second intensity measurement data is acquired, which represents the intensity of the light from the light source as measured by the second spectrometer. Select the second reference strength data that best matches the second strength measurement data from the plurality of different second reference strength data. Determine the first reference strength data associated with the selected second reference strength data. The relative reflectance data is calculated by dividing the first intensity measurement data by the determined first reference intensity data. The film thickness of the workpiece is determined based on the relative reflectivity data.

18. The grinding method according to claim 17, characterized in that, During the grinding process of the workpiece, the first beam splitter and the second beam splitter simultaneously measure the intensity of the reflected light from the workpiece and the intensity of the light from the light source.

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