Film thickness measurement method and film thickness measurement device

Abstract

The present invention provides a film thickness measurement method and a film thickness measurement device that can substantially expand the wavelength range of the spectrum of reflected light from a workpiece and measure the film thickness accurately. According to the film thickness measurement method, while rotating a polishing table (3) supporting a polishing pad (2), a workpiece (W) is pressed against the polishing pad (2) to polish the workpiece (W). During the polishing of the workpiece (W), light is guided to the workpiece (W) from a liquid-sealed sensor (25) and a transparent window sensor (31) disposed on the polishing table (3), and the reflected light from the workpiece (W) is received by the liquid-sealed sensor (25) and the transparent window sensor (31). The film thickness of the workpiece (W) is determined based on the spectrum of the reflected light from the workpiece (W).

Description

[Technical Field]

[0001] This invention relates to a technique for measuring the film thickness of a workpiece while grinding it for manufacturing semiconductor devices such as wafers, substrates, and panels, and more particularly to a technique for determining the film thickness of a workpiece based on optical information contained in reflected light from the workpiece. [Previous Technology]

[0002] In the manufacturing process of semiconductor devices, various materials are repeatedly formed into films on a silicon wafer to form a stacked structure. In order to form this stacked structure, the technique of planarizing the surface of the top layer becomes important. As one method of the above planarization, chemical mechanical polishing (CMP) is used.

[0003] Chemical mechanical polishing (CMP) is performed by a polishing apparatus. Such an apparatus generally 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., paste) to the polishing pad. The polishing apparatus rotates the polishing head and polishing table separately while supplying polishing slurry to the polishing pad from the polishing slurry supply nozzle. The polishing head presses the surface of the wafer against the polishing pad, thereby polishing the film forming on the surface of the wafer while polishing slurry is present between the wafer and the polishing pad.

[0004] To measure the thickness of films such as insulating films and silicon layers (hereinafter referred to as film thickness), polishing apparatuses generally include optical film thickness measuring devices. These optical film thickness measuring devices are configured to guide light emitted from a light source from a sensor head towards the surface of the wafer, receive the reflected light from the wafer via the sensor head, and analyze the spectrum of the reflected light to determine the film thickness of the wafer. The polishing apparatus can then terminate the wafer polishing process based on the determined film thickness or change the wafer polishing conditions.

[0005] During wafer polishing, polishing slurry and polishing debris are present on the polishing pad. When the polishing slurry and polishing debris adhere to the sensor head, the intensity of light irradiated onto the wafer and the intensity of light reflected from the wafer decrease, making it impossible to measure the accurate film thickness. Therefore, there are techniques for forming a water flow between the sensor head and the wafer, or for configuring a transparent window between the sensor head and the wafer. According to these techniques, contact between the polishing slurry and polishing debris and the sensor head is prevented, thereby ensuring a good optical path. [Prior Art Documents] [Patent Documents]

[0006] Patent Document 1: Japanese Patent Application Publication No. 2017-220683

[0007] However, there are wavelengths in water that absorb light. Furthermore, there are wavelengths in transparent windows made of resin that are difficult for light to pass through. Therefore, the wavelength range of the spectrum that generates reflected light is limited for measuring film thickness, and accurate film thickness measurement may not be possible depending on the type of film. [Summary of the Invention]

[0008] Therefore, the present invention provides a film thickness measurement method and film thickness measurement device that can substantially expand the wavelength range of the spectrum of reflected light from the workpiece and measure the film thickness accurately.

[0009] In one aspect, a film thickness measurement method is provided, wherein a workpiece is pressed against the polishing pad while the polishing table supporting the polishing pad is rotated to polish the workpiece, wherein during the polishing of the workpiece, light is guided from a liquid-sealed sensor and a transparent window sensor disposed on the polishing table to the workpiece, and the reflected light from the workpiece is received by the liquid-sealed sensor and the transparent window sensor, and the film thickness of the workpiece is determined based on the spectrum of the reflected light from the workpiece, wherein the liquid-sealed sensor has a liquid flow path for liquid flow and a first optical sensor head disposed within the liquid flow path, and the transparent window sensor has a second optical sensor head and a transparent window disposed above the second optical sensor head.

[0010] In one embodiment, the liquid-sealed sensor and the transparent window sensor are arranged on a circumference having the same center as the rotation center of the grinding table. In one embodiment, during a first grinding process, the film thickness of the workpiece is determined based on the spectrum of reflected light from the workpiece received from one of the liquid-sealed sensor and the transparent window sensor; during a second grinding process, the film thickness of the workpiece is determined based on the spectrum of reflected light from the workpiece received from the other of the liquid-sealed sensor and the transparent window sensor. In one embodiment, a composite spectrum is generated by combining the spectrum of reflected light from the workpiece received from the liquid-sealed sensor and the spectrum of reflected light from the workpiece received from the transparent window sensor, and the film thickness of the workpiece is determined based on the composite spectrum. In one embodiment, the wavelength range of the spectrum of reflected light received from the liquid-sealed sensor is different from the wavelength range of the spectrum of reflected light received from the transparent window sensor. In one embodiment, the liquid-sealed sensor and the transparent window sensor are multiple liquid-sealed sensors and multiple transparent window sensors. In another embodiment, the liquid-sealed sensor and the transparent window sensor are liquid-sealed sensors and transparent window sensors arranged on each of a plurality of concentric circles having the same center as the rotation center of the grinding table.

[0011] In one embodiment, a film thickness measuring device is provided, comprising: a liquid-sealed sensor and a transparent window sensor, the liquid-sealed sensor and the transparent window sensor being disposed on a grinding table, the grinding table being for supporting a grinding pad for grinding a workpiece and being rotatable; and a spectral processing device, the spectral processing device determining the film thickness of the workpiece based on the spectrum of reflected light from the workpiece received from the liquid-sealed sensor and the transparent window sensor, the liquid-sealed sensor having a liquid flow path for supplying liquid flow and a first optical sensor head disposed within the liquid flow path, the transparent window sensor having a second optical sensor head and a transparent window disposed above the second optical sensor head.

[0012] In one embodiment, the liquid-sealed sensor and the transparent window sensor are arranged on a circumference having the same center as the rotation center of the grinding table. In one embodiment, the spectral processing apparatus is configured to determine the film thickness of the workpiece during a first grinding process based on the spectrum of reflected light from the workpiece received from one of the liquid-sealed sensor and the transparent window sensor, and to determine the film thickness of the workpiece during a second grinding process based on the spectrum of reflected light from the workpiece received from the other of the liquid-sealed sensor and the transparent window sensor. In one embodiment, the spectral processing apparatus is configured to combine the spectrum of reflected light from the workpiece received from the liquid-sealed sensor and the spectrum of reflected light from the workpiece received from the transparent window sensor to generate a composite spectrum, and to determine the film thickness of the workpiece based on the composite spectrum. In one embodiment, the film thickness measuring device further comprises: a first spectrometer connected to the liquid-sealed sensor; and a second spectrometer connected to the transparent window sensor. The first spectrometer is configured to measure the intensity of reflected light from the workpiece in a first wavelength range and generate first intensity measurement data. The second spectrometer is configured to measure the intensity of reflected light from the workpiece in a second wavelength range and generate second intensity measurement data. The first wavelength range is different from the second wavelength range. In one embodiment, the liquid-sealed sensor and the transparent window sensor are a plurality of liquid-sealed sensors and a plurality of transparent window sensors. In one embodiment, the liquid-sealed sensor and the transparent window sensor are arranged on each of a plurality of concentric circles having the same center as the rotation center of the grinding table. [Effects of the Invention]

[0013] Liquid-sealed sensors and transparent window sensors transmit and receive light through different media, namely pure water and a transparent window. The spectra of reflected light obtained through the aforementioned different types of sensors represent the good intensity of reflected light in different wavelength ranges. According to the present invention, during the grinding of the workpiece, since the spectra of reflected light obtained through both liquid-sealed sensors and transparent window sensors are used, the wavelength range of reflected light used for film thickness measurement is substantially expanded. As a result, the thickness of various types of films can be accurately measured.

Implementation Method

[0015] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG1 is a schematic diagram showing one embodiment of the polishing apparatus. As shown in FIG1, the polishing apparatus includes: a polishing table 3 supporting a polishing pad 2; a polishing head 1 pressing a workpiece W such as a wafer, substrate, or panel used in the manufacture of semiconductor devices onto the polishing pad 2; a stage motor 6 rotating the polishing table 3; and a polishing slurry supply nozzle 5 for supplying polishing slurry such as a slurry to the polishing pad 2. The upper surface of the polishing pad 2 forms the polishing surface 2a of the workpiece W.

[0016] The grinding head 1 is connected to the head shaft 10, and the head shaft 10 is connected to the grinding head motor 18 via a connecting device 17. The structure of the connecting device 17 is not particularly limited, and may include a combination of pulleys and belts, a combination of gears, or a combination of sprockets and chains, etc. The grinding head motor 18 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 the worktable motor 6, and the worktable motor 6 is configured to rotate the grinding table 3 and the grinding pad 2 in the direction indicated by the arrow.

[0017] The workpiece W is ground as described below. While rotating the grinding table 3 and the grinding head 1 in the direction indicated by the arrow in Figure 1, grinding fluid is supplied from the grinding fluid supply nozzle 5 to the grinding surface 2a of the grinding pad 2 on the grinding table 3. While rotating the workpiece W by the grinding head 1, the workpiece W is pressed against the grinding surface 2a of the grinding pad 2 by the grinding head 1 while the grinding fluid is present on the grinding pad 2. The surface of the workpiece W is ground by the chemical action of the grinding fluid and the abrasive particles contained in the grinding fluid and / or the mechanical action of the grinding pad 2.

[0018] The grinding apparatus includes a film thickness measuring device 20 for measuring the film thickness of a workpiece W. The film thickness measuring device 20 includes: a light source 22 that emits light; a liquid-sealed sensor 25 and a transparent window sensor 31 that illuminate the workpiece W with light from the light source 22 and receive reflected light from the workpiece W; a spectrometer 40 connected to the liquid-sealed sensor 25 and the transparent window sensor 31; and a spectral processing device 45 that determines the film thickness of the workpiece W based on intensity measurement data of reflected light from the workpiece W. The liquid-sealed sensor 25 and the transparent window sensor 31 are mounted on the grinding table 3 and rotate together with the grinding table 3.

[0019] Each time the grinding table 3 rotates once, light emitted from the light source 22 is alternately transmitted to the liquid-sealed sensor 25 and the transparent window sensor 31, and alternately guided from the liquid-sealed sensor 25 and the transparent window sensor 31 to the surface of the workpiece W. The light is reflected on the surface of the workpiece W, and the reflected light from the surface of the workpiece W is alternately received by the liquid-sealed sensor 25 and the transparent window sensor 31, and transmitted to the beam splitter 40. The beam splitter 40 decomposes the reflected light according to the wavelength within a specified wavelength range, measures the intensity of the reflected light at each wavelength, and thus generates intensity measurement data of the reflected light. The intensity measurement data of the reflected light is transmitted from the beam splitter 40 to the spectral processing device 45.

[0020] The spectral processing device 45 is configured to generate the spectrum of the reflected light from the workpiece W based on the intensity measurement data of the reflected light. The spectrum of the reflected light is represented as a graph (i.e., a spectroscopic waveform) showing the relationship between the wavelength and intensity of the reflected light. The intensity of the reflected light can also be expressed as a relative value such as reflectivity or relative reflectivity.

[0021] The spectrum processing apparatus 45 includes: a memory device 45a storing a program; and a processing device 45b performing calculations according to the instructions included in the program. The spectrum processing apparatus 45 is composed of at least one computer. The memory device 45a includes a main memory device such as random access memory (RAM) and an auxiliary memory device such as a hard disk drive (HDD) or a solid state disk (SSD). Examples of processing devices 45b include a CPU (central processing unit) and a GPU (graphics processing unit). However, the specific structure of the spectrum processing apparatus 45 is not limited to the above examples.

[0022] Figure 2 is a diagram showing an example of a spectrum generated by the spectral processing device 45. The spectrum is represented as a graph (i.e., a spectroscopic waveform) showing the relationship between the wavelength and intensity of light. In Figure 2, the horizontal axis represents the wavelength of light reflected from the workpiece W, and the vertical axis represents the relative reflectivity derived from the intensity of the reflected light. The relative reflectivity is an index value representing the intensity of the reflected light, which is the ratio of the light intensity to a specified reference intensity. Unwanted noise such as the inherent intensity deviation of the optical system of the device and the light source can be removed from the measured intensity by dividing the light intensity (measured intensity) at each wavelength by the specified reference intensity.

[0023] According to the example shown in Figure 2, the spectrum of the reflected light is a spectroscopic waveform that represents the relationship between the relative reflectivity and the wavelength of the reflected light. However, the spectrum of the reflected light can also be a spectroscopic waveform that represents the relationship between the intensity of the reflected light itself and the wavelength of the reflected light.

[0024] The spectral processing apparatus 45 receives intensity measurement data of reflected light from the workpiece W during one revolution of the grinding table 3, and generates a spectrum of the reflected light based on the intensity measurement data. The spectral processing apparatus 45 is configured to determine the film thickness of the workpiece W based on the spectrum of the reflected light. Well-known techniques are used for methods of determining the film thickness of the workpiece W based on the spectrum. For example, the spectral processing apparatus 45 determines a reference spectrum from a reference spectral library that has a shape closest to the spectrum of the reflected light, and determines the film thickness associated with the aforementioned determined reference spectrum. In other examples, the spectral processing apparatus 45 performs a Fourier transform on the spectrum of the reflected light and determines the film thickness based on the resulting spectrum.

[0025] Details of the film thickness measurement device 20 will be described with reference to FIG1. ​​The spectrometer 40 includes a photodetector 41. In one embodiment, the photodetector 41 is composed of a photodiode, CCD, or CMOS, etc. The liquid-sealed sensor 25 and the transparent window sensor 31 are optically connected to the light source 22 and the photodetector 41. The photodetector 41 is electrically connected to the spectral processing device 45.

[0026] The film thickness measuring device 20 includes: a first light-emitting optical cable 51 and a second light-emitting optical cable 52 that guide light emitted from the light source 22 to the surface of the workpiece W; and a first light-receiving optical cable 56 and a second light-receiving optical cable 57 that receive reflected light from the workpiece W and transmit the reflected light to the beam splitter 40. The tips of the first light-emitting optical cable 51 and the first light-receiving optical cable 56 are located within the grinding table 3. Similarly, the tips of the second light-emitting optical cable 52 and the second light-receiving optical cable 57 are located within the grinding table 3.

[0027] The liquid-sealed sensor 25 includes a liquid flow path 26 for pure water, which is used as a rinsing fluid, to flow through, and a first optical sensor head 27 disposed within the liquid flow path 26. The first optical sensor head 27 is composed of the tip of a first light-emitting optical cable 51 and the tip of a first light-receiving optical cable 56. The first optical sensor head 27 emits light to the workpiece W through the pure water flowing within the liquid flow path 26, and receives reflected light from the workpiece W that passes through the pure water flowing within the liquid flow path 26.

[0028] A liquid flow path 26 is formed on the grinding table 3 and opens on the upper surface of the grinding table 3. The grinding table 3 has a drain hole 60 opening on the aforementioned upper surface. The drain hole 60 is adjacent to the liquid flow path 26. The grinding pad 2 has a first through hole 61 formed at a position corresponding to the liquid flow path 26 and the drain hole 60. The liquid flow path 26 and the drain hole 60 communicate with the first through hole 61, which opens on the grinding surface 2a. The liquid flow path 26 is connected to a liquid supply line 63, and the drain hole 60 is connected to a drain line 64. A liquid-sealed sensor 25 is located below the first through hole 61.

[0029] During the grinding of workpiece W, pure water, as a transparent rinsing fluid, is supplied to the liquid flow path 26 via the liquid supply line 63, and further supplied to the first through hole 61 via the liquid flow path 26. The flow of pure water is formed between the surface of workpiece W (the surface being ground) and the first optical sensor head 27. Pure water flows into the drain hole 60 and is discharged through the drain line 64. The pure water flowing in the liquid flow path 26 and the first through hole 61 prevents the grinding fluid and grinding debris from contacting the first optical sensor head 27, thereby ensuring the optical path.

[0030] The light source 22 transmits light to the liquid-sealed sensor 25 through the first light-emitting optical cable 51. The liquid-sealed sensor 25 emits light towards the workpiece W through the pure water in the liquid flow path 26 and the first through hole 61. The reflected light from the workpiece W is received by the liquid-sealed sensor 25 through the pure water and transmitted to the beam splitter 40 through the first light-receiving optical cable 56. The beam splitter 40 decomposes the reflected light according to its wavelength and measures the intensity of the reflected light at each wavelength within a specified wavelength range. The beam splitter 40 sends the intensity measurement data of the reflected light to the spectral processing device 45. The spectral processing device 45 generates the spectrum of the reflected light based on the intensity measurement data of the reflected light and determines the film thickness of the workpiece W based on the spectrum of the reflected light.

[0031] The transparent window sensor 31 includes a second optical sensor head 32 and a transparent window 33 disposed above the second optical sensor head 32. The second optical sensor head 32 is composed of the top end of the second light-emitting optical cable 52 and the top end of the second light-receiving optical cable 57. The second optical sensor head 32 is disposed within the polishing table 3, and the transparent window 33 is disposed within the second through hole 34 formed in the polishing pad 2. The transparent window 33 completely closes the second through hole 34 of the polishing pad 2, thereby preventing polishing fluid and polishing debris from contacting the second optical sensor head 32.

[0032] The second optical sensor head 32 emits light through the transparent window 33 toward the workpiece W and receives reflected light from the workpiece W that passes through the transparent window 33. The transparent window 33 is a window made of a material that allows light to pass through. The material of the transparent window 33 is not particularly limited, for example, it is made of transparent resin.

[0033] The light source 22 transmits light to the transparent window sensor 31 through the second light-emitting optical cable 52. The transparent window sensor 31 emits light towards the workpiece W through the transparent window 33. The reflected light from the workpiece W is received by the transparent window sensor 31 and transmitted to the beam splitter 40 through the second light-receiving optical cable 57. The beam splitter 40 decomposes the reflected light according to its wavelength and measures the intensity of the reflected light at each wavelength within a specified wavelength range. The beam splitter 40 transmits the intensity measurement data of the reflected light to the spectral processing device 45. The spectral processing device 45 generates the spectrum of the reflected light based on the intensity measurement data of the reflected light and determines the film thickness of the workpiece W based on the spectrum of the reflected light.

[0034] The first optical fiber for projection 51 and the second optical fiber for projection 52 are connected to the first optical path switching device 71, and are connected to the light source 22 via the first optical path switching device 71. The first optical path switching device 71 has an optical switch or shutter, etc., and is configured to optically connect the light source 22 to either the first optical fiber for projection 51 or the second optical fiber for projection 52. Therefore, the light emitted from the light source 22 is transmitted to either the liquid-sealed sensor 25 or the transparent window sensor 31 through the first optical path switching device 71.

[0035] The first light-receiving optical cable 56 and the second light-receiving optical cable 57 are connected to the second optical path switching device 72, and are connected to the beam splitter 40 via the second optical path switching device 72. The second optical path switching device 72 has an optical switch or shutter, etc., and is configured to optically connect the beam splitter 40 to either the first light-receiving optical cable 56 or the second light-receiving optical cable 57. Therefore, the beam splitter 40 is optically connected to either the liquid-sealed sensor 25 or the transparent window sensor 31 via the second optical path switching device 72.

[0036] Each time the grinding table 3 rotates one revolution, the first optical path switching device 71 and the second optical path switching device 72 are activated, optically connecting the light source 22 and the beam splitter 40 to either the liquid-sealed sensor 25 or the transparent window sensor 31. More specifically, when the liquid-sealed sensor 25 is located below the workpiece W held by the grinding head 1, the first optical path switching device 71 and the second optical path switching device 72 connect the light source 22 and the beam splitter 40 to the liquid-sealed sensor 25; when the transparent window sensor 31 is located below the workpiece W held by the grinding head 1, the first optical path switching device 71 and the second optical path switching device 72 connect the light source 22 and the beam splitter 40 to the transparent window sensor 31. In this way, the shared light source 22 can alternately transmit light to the liquid-sealed sensor 25 and the transparent window sensor 31, and the shared beam splitter 40 can alternately receive reflected light from the workpiece W through the liquid-sealed sensor 25 and the transparent window sensor 31.

[0037] FIG3 is a top view showing the configuration of the liquid-sealed sensor 25 and the transparent window sensor 31. As shown in FIG3, the liquid-sealed sensor 25 and the transparent window sensor 31 are arranged on a circumference CE having the same center as the rotation center CP of the grinding table 3. The liquid-sealed sensor 25 and the transparent window sensor 31 are arranged at equal intervals around the rotation center CP of the grinding table 3. The liquid-sealed sensor 25 and the transparent window sensor 31 trace the same trajectory and rotate integrally with the grinding table 3. In the example shown in FIG3, the liquid-sealed sensor 25 and the transparent window sensor 31 are arranged to alternately pass through the center of the workpiece W each time the grinding table 3 rotates once. The circumference CE is an imaginary circle representing the movement trajectory of the liquid-sealed sensor 25 and the transparent window sensor 31. In one embodiment, the liquid-sealed sensor 25 and the transparent window sensor 31 may also be arranged on different circumferences having the same center as the rotation center CP of the grinding table 3.

[0038] The liquid-sealed sensor 25 and the transparent window sensor 31 transmit and receive light through different media, namely pure water and the transparent window 33. The spectra of the reflected light obtained by the above-mentioned different types of sensors 25 and 31 represent good intensity of reflected light in different wavelength ranges. According to this embodiment, during the grinding of the workpiece W, since the spectra of the reflected light obtained by both the liquid-sealed sensor 25 and the transparent window sensor 31 are used, the wavelength range of the reflected light used for film thickness measurement is substantially expanded. As a result, the thickness of various types of films can be accurately measured.

[0039] The spectral processing apparatus 45 determines the film thickness of the workpiece W based on the spectrum of reflected light alternately received from the liquid-sealed sensor 25 and the transparent window sensor 31. In the embodiment shown in FIG3, during one revolution of the grinding table 3, the spectral processing apparatus 45 determines the film thickness of the workpiece W based on the spectrum of reflected light received from the liquid-sealed sensor 25 and the spectrum of reflected light received from the transparent window sensor 31.

[0040] Depending on the type of film on the workpiece W and / or the surface structure of the workpiece W, in the initial stage of grinding the workpiece W, the shape of the spectrum in the shorter wavelength range does not change significantly, while the shape of the spectrum in the longer wavelength range changes significantly. Conversely, in the latter half of grinding the workpiece W, the shape of the spectrum in the longer wavelength range does not change significantly, while the shape of the spectrum in the shorter wavelength range changes significantly. Since the film thickness of the workpiece W decreases with grinding time, the spectrum that does not undergo shape change cannot accurately reflect the change in film thickness. Pure water has the property of allowing shorter wavelength light to pass through but absorbing longer wavelength light. On the other hand, the transparent window 33 made of resin has the property of allowing longer wavelength light to pass through but making it difficult for shorter wavelength light to pass through.

[0041] Therefore, in one embodiment, the spectral processing apparatus 45 is configured to determine the film thickness of the workpiece W based on the spectrum of reflected light from the workpiece W received from the transparent window sensor 31 during a first grinding period, and to determine the film thickness of the workpiece W based on the spectrum of reflected light from the workpiece W received from the liquid-sealed sensor 25 during a second grinding period. The first grinding period and the second grinding period are different pre-set grinding periods. For example, the first grinding period is the grinding period from the initial grinding point to a predetermined grinding midpoint, and the second grinding period is the grinding period from the predetermined grinding midpoint to the grinding end point, but is not limited thereto. According to the operation described above, the spectral processing apparatus 45 can determine the film thickness of the workpiece W based on the spectrum that accurately reflects the change in the film thickness of the workpiece W throughout the entire grinding period.

[0042] Depending on the type of film on the workpiece W and / or the surface structure of the workpiece W, during the initial grinding of the workpiece W, there may be cases where the shape of the spectrum over a longer wavelength range does not change significantly, while the shape of the spectrum over a shorter wavelength range changes significantly. Therefore, in one embodiment, the spectral processing apparatus 45 may also be configured to determine the film thickness of the workpiece W based on the spectrum of reflected light from the workpiece W received from the liquid-sealed sensor 25 during the first grinding period of grinding the workpiece W, and to determine the film thickness of the workpiece W based on the spectrum of reflected light from the workpiece W received from the transparent window sensor 31 during the second grinding period of grinding the workpiece W.

[0043] In one embodiment, in addition to the first grinding period and the second grinding period, a plurality of grinding periods, including at least one grinding period, may be provided. Alternatively, during the grinding period of the workpiece W, the spectral processing device 45 alternately switches the liquid-sealed sensor 25 and the transparent window sensor 31, and simultaneously, during each grinding period, the spectral processing device 45 determines the film thickness of the workpiece W based on the spectrum of the reflected light from the workpiece W received from the liquid-sealed sensor 25 or the transparent window sensor 31.

[0044] In one embodiment, the spectral processing apparatus 45 may also be configured to combine the spectrum of reflected light from the workpiece W received from the liquid-sealed sensor 25 and the spectrum of reflected light from the workpiece W received from the transparent window sensor 31 to generate a composite spectrum, and determine the film thickness of the workpiece W based on the composite spectrum. Hereinafter, this embodiment will be described with reference to FIGS. 4 and 5.

[0045] Figure 4 is a graph showing the spectrum SP1 of the reflected light from the workpiece W received from the liquid-sealed sensor 25 and the spectrum SP2 of the reflected light from the workpiece W received from the transparent window sensor 31. Since the spectrum SP1 and spectrum SP2 are generated based on intensity measurement data generated from the same spectrometer 40, they have the same wavelength range but different amplitudes.

[0046] Figure 5 illustrates the generation of a composite spectrum by combining the spectrum SP1 of the reflected light from the workpiece W received from the liquid-sealed sensor 25 and the spectrum SP2 of the reflected light from the workpiece W received from the transparent window sensor 31. The spectral processing device 45 generates a composite spectrum by combining a portion PN1 from the first wavelength (e.g., the lower limit wavelength) LL of spectrum SP1 to a predetermined intermediate wavelength MP with a portion PN2 from the aforementioned predetermined intermediate wavelength MP of spectrum SP2 to the second wavelength (e.g., the upper limit wavelength) UL. In order to smoothly combine spectra SP1 and spectrum SP2, the spectral processing device 45 may also magnify or reduce or shift either or both of spectra SP1 and spectrum SP2 along the light intensity (along the relative reflectivity).

[0047] The synthesized spectrum includes the intensity of reflected light reflecting the film thickness of the workpiece W over a wide wavelength range from a first wavelength (e.g., lower limit wavelength) LL to a second wavelength (e.g., upper limit wavelength) UL. Therefore, the spectral processing device 45 is able to accurately determine the film thickness of the workpiece W based on the synthesized spectrum. In particular, the spectral processing device 45 is able to accurately determine the thickness of various types of films.

[0048] FIG6 is a schematic diagram showing another embodiment of the film thickness measuring device 20. Unless otherwise specified, the structure and operation of this embodiment are the same as those described with reference to FIGS. 1 to 5, and therefore repeated descriptions are omitted. In the embodiment shown in FIG6, the film thickness measuring device 20 includes a first beam splitter 40A and a second beam splitter 40B connected to the liquid-sealed sensor 25 and the transparent window sensor 31, respectively. A second optical path switching device 72 is not provided. The first beam splitter 40A is connected to the liquid-sealed sensor 25 via a first light-receiving optical cable 56, and the second beam splitter 40B is connected to the transparent window sensor 31 via a second light-receiving optical cable 57.

[0049] The first beam splitter 40A and the second beam splitter 40B are configured to measure the intensity of reflected light from the workpiece W in different wavelength ranges. More specifically, the first beam splitter 40A is configured to measure the intensity of the reflected light in a first wavelength range and generate first intensity measurement data, and the second beam splitter 40B is configured to measure the intensity of the reflected light in a second wavelength range and generate second intensity measurement data. The first wavelength range is different from the second wavelength range.

[0050] Figure 7 is a diagram showing spectrum SP3 generated based on first intensity measurement data generated by first spectrometer 40A and spectrum SP4 generated based on second intensity measurement data generated by second spectrometer 40B. The spectral processing device 45 generates spectrum SP3 based on the first intensity measurement data and determines the film thickness of workpiece W based on spectrum SP3. Similarly, the spectral processing device 45 generates spectrum SP4 based on the second intensity measurement data and determines the film thickness of workpiece W based on spectrum SP4.

[0051] As shown in Figure 7, the first wavelength range R1 of spectrum SP3 is different from the second wavelength range R2 of spectrum SP4, but the first wavelength range R1 and the second wavelength range R2 partially overlap. In one example, the first wavelength range R1 is 200nm to 1100nm, and the second wavelength range R2 is 900nm to 1700nm.

[0052] The spectrum SP3, which has a first wavelength range R1 with a short wavelength side, is the spectrum of reflected light received from the liquid-sealed sensor 25. The wavelength range of light absorbed by water is not included in the first wavelength range R1 of the spectrum SP3. Therefore, the spectrum processing device 45 can accurately determine the film thickness of the workpiece W based on the spectrum SP3.

[0053] The spectrum SP4, which has a second wavelength range R2 on the long wavelength side, is the spectrum of reflected light received from the transparent window sensor 31. The wavelength range of light that is difficult to pass through the transparent window 33 is not included in the second wavelength range R2 of the spectrum SP4. Therefore, the spectrum processing device 45 can accurately determine the film thickness of the workpiece W based on the spectrum SP4.

[0054] In one embodiment, as described with reference to FIG5, the spectral processing apparatus 45 may also be configured to combine the spectrum SP3 of the reflected light from the workpiece W received from the liquid-sealed sensor 25 and the spectrum SP4 of the reflected light from the workpiece W received from the transparent window sensor 31 to generate a composite spectrum, and determine the film thickness of the workpiece W based on the composite spectrum.

[0055] In one embodiment, as shown in FIG8, the film thickness measuring device 20 may include a first light source 22A and a second light source 22B connected to the liquid-sealed sensor 25 and the transparent window sensor 31, respectively. The first optical path switching device 71 is not provided. The first light source 22A is connected to the liquid-sealed sensor 25 via a first projection optical cable 51, and the second light source 22B is connected to the transparent window sensor 31 via a second projection optical cable 52. Other structures and operations of this embodiment, unless otherwise specified, are the same as those described with reference to FIG6, and therefore repeated descriptions are omitted.

[0056] The number and configuration of the liquid-sealed sensor 25 and the transparent window sensor 31 are not limited to the embodiments described above. In one embodiment, as shown in Figures 9 and 10, the film thickness measuring device 20 may include one liquid-sealed sensor 25 and two transparent window sensors 31. In the embodiments shown in Figures 9 and 10, the liquid-sealed sensor 25 is connected to a common light source 22 via a first light-emitting optical cable 51 through a first optical path switching device 71, and further connected to a common beam splitter 40 via a first light-receiving optical cable 56 through a second optical path switching device 72. The two transparent window sensors 31 are connected to the common light source 22 via a second light-emitting optical cable 52 and a third light-emitting optical cable 53 through a first optical path switching device 71, and further connected to the common beam splitter 40 via a second light-receiving optical cable 57 and a third light-receiving optical cable 58 through a second optical path switching device 72.

[0057] Each time the grinding table 3 rotates one revolution, the first optical path switching device 71 and the second optical path switching device 72 activate, optically connecting the light source 22 and the beam splitter 40 to either the liquid-sealed sensor 25 or the two transparent window sensors 31. More specifically, when the liquid-sealed sensor 25 is located below the workpiece W held by the grinding head 1, the first optical path switching device 71 and the second optical path switching device 72 connect the light source 22 and the beam splitter 40 to the liquid-sealed sensor 25. When one of the two transparent window sensors 31 is located below the workpiece W held by the grinding head 1, the first optical path switching device 71 and the second optical path switching device 72 connect the light source 22 and the beam splitter 40 to the aforementioned transparent window sensor 31. When the other transparent window sensor 31 is located below the workpiece W held by the grinding head 1, the first optical path switching device 71 and the second optical path switching device 72 connect the light source 22 and the beam splitter 40 to that transparent window sensor 31.

[0058] In the above embodiment, as described with reference to FIG5, the spectral processing apparatus 45 may also be configured to combine the spectrum of reflected light from the workpiece W received from the liquid-sealed sensor 25 and the spectrum of reflected light from the workpiece W received from the two transparent window sensors 31 to generate a composite spectrum, and determine the film thickness of the workpiece W based on the composite spectrum. More specifically, the spectral processing apparatus 45 generates an average spectrum of the spectra of reflected light received from the two transparent window sensors 31, combines the spectrum of reflected light received from the liquid-sealed sensor 25 and the average spectrum to generate a composite spectrum, and determines the film thickness of the workpiece W based on the composite spectrum.

[0059] In one embodiment, as shown in FIG11, the film thickness measuring device 20 may include: a first beam splitter 40A, which is connected to a liquid-sealed sensor 25 via a first light-receiving optical cable 56; and a second beam splitter 40B, which is connected to two transparent window sensors 31 via a second light-receiving optical cable 57 and a third light-receiving optical cable 58. The two transparent window sensors 31 are connected to the second beam splitter 40B via a second optical path switching device 72, while the liquid-sealed sensor 25 is connected to the first beam splitter 40A without via the second optical path switching device 72. The structure and operation of the first beam splitter 40A and the second beam splitter 40B are the same as those in the embodiments shown with reference to FIGS. 6 and 7, therefore, repeated descriptions are omitted.

[0060] As shown in Figures 12 to 15, the film thickness measuring device 20 may also include multiple liquid-sealed sensors 25 and multiple transparent window sensors 31. In the embodiments shown in Figures 12 and 13, the multiple liquid-sealed sensors 25 and the multiple transparent window sensors 31 are arranged on the same circumference CE.

[0061] In the embodiment shown in FIG. 14, a liquid-sealed sensor 25 and a transparent window sensor 31 are arranged on each of a plurality of concentric circles CF having the same center as the rotation center CP of the grinding table 3. The plurality of concentric circles CF represent the movement trajectories of the liquid-sealed sensor 25 and the transparent window sensor 31. One of the plurality of concentric circles CF passes through the center of the workpiece W held by the grinding head 1, and another of the plurality of concentric circles CF passes through the edge of the workpiece W held by the grinding head 1. Alternatively, as shown in FIG. 15, a plurality of liquid-sealed sensors 25 and a plurality of transparent window sensors 31 may be arranged on each of the plurality of concentric circles CF. In the embodiment shown in FIG. 14, although two concentric circles CF are provided, three or more concentric circles may also be provided.

[0062] The number and configuration of the liquid-sealed sensor 25 and the transparent window sensor 31 are not limited to the illustrated embodiment, and various numbers and configurations can be applied.

[0063] The above embodiments are described with the aim of enabling those skilled in the art to implement the present invention. Various modifications of the above embodiments can of course be made by those skilled in the art, and the technical concept of the present invention is also applicable to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be interpreted as encompassing the largest scope of the technical concept defined according to the scope of the claims. [Simplified Explanation of the Diagram]

[0014] Figure 1 is a schematic diagram showing one embodiment of the grinding apparatus. Figure 2 is a diagram showing an example of a spectrum generated by the spectral processing apparatus. Figure 3 is a top view showing the configuration of a liquid-sealed sensor and a transparent window sensor. Figure 4 is a diagram showing the spectrum of reflected light from the workpiece received from the liquid-sealed sensor and the spectrum of reflected light from the workpiece received from the transparent window sensor. Figure 5 is a diagram illustrating the generation of a composite spectrum. Figure 6 is a schematic diagram showing another embodiment of the film thickness measuring apparatus. Figure 7 is a diagram showing a spectrum generated based on first intensity measurement data generated by a first spectrometer and a spectrum generated based on second intensity measurement data generated by a second spectrometer. Figure 8 is a schematic diagram showing another embodiment of the film thickness measuring apparatus. Figure 9 is a top view showing one embodiment of a film thickness measuring apparatus having one liquid-sealed sensor and two transparent window sensors. Figure 10 is a schematic diagram showing one embodiment of a film thickness measuring apparatus having one liquid-sealed sensor and two transparent window sensors. Figure 11 is a schematic diagram illustrating another embodiment of the film thickness measurement device. Figure 12 is a schematic diagram illustrating one embodiment of the film thickness measurement device having multiple liquid-sealed sensors and multiple transparent window sensors arranged on the same circumference. Figure 13 is a schematic diagram illustrating one embodiment of the film thickness measurement device having multiple liquid-sealed sensors and multiple transparent window sensors arranged on the same circumference. Figure 14 is a schematic diagram illustrating one embodiment of the film thickness measurement device having multiple liquid-sealed sensors and multiple transparent window sensors arranged on the same circle. Figure 15 is a schematic diagram illustrating one embodiment of the film thickness measurement device having multiple liquid-sealed sensors and multiple transparent window sensors arranged on the same circle.

Claims

1. A film thickness measurement method for grinding a workpiece by pressing it against a grinding pad while rotating a grinding table supporting a grinding pad, wherein during the grinding of the workpiece, light is guided from a liquid-sealed sensor and a transparent window sensor disposed on the grinding table to the workpiece, and reflected light from the workpiece is received by the liquid-sealed sensor and the transparent window sensor, and the film thickness of the workpiece is determined based on the spectrum of the reflected light from the workpiece, wherein the liquid-sealed sensor has a liquid flow path for liquid flow and a first optical sensor head disposed within the liquid flow path, the transparent window sensor has a second optical sensor head and a transparent window disposed above the second optical sensor head, and a composite spectrum is generated by combining the spectrum of the reflected light from the workpiece received from the liquid-sealed sensor and the spectrum of the reflected light from the workpiece received from the transparent window sensor, and the film thickness of the workpiece is determined based on the composite spectrum.

2. A film thickness measurement method for grinding a workpiece by pressing it against a grinding pad while rotating a grinding table supporting a grinding pad, wherein during the grinding of the workpiece, light is guided from a liquid-sealed sensor and a transparent window sensor disposed on the grinding table to the workpiece, and reflected light from the workpiece is received by the liquid-sealed sensor and the transparent window sensor, and the film thickness of the workpiece is determined based on the spectrum of the reflected light from the workpiece, wherein the liquid-sealed sensor has a liquid flow path for liquid flow and a first optical sensor head disposed within the liquid flow path, the transparent window sensor has a second optical sensor head and a transparent window disposed above the second optical sensor head, and the wavelength range of the spectrum of the reflected light from the liquid-sealed sensor is different from the wavelength range of the spectrum of the reflected light from the transparent window sensor.

3. The film thickness measurement method as described in claim 1 or 2, wherein, The liquid-sealed sensor and the transparent window sensor are arranged on a circumference having the same center as the rotation center of the grinding table.

4. The film thickness measurement method as described in claim 2, wherein, During the first grinding process, the film thickness of the workpiece is determined based on the spectrum of reflected light from the workpiece received from one of the liquid-sealed sensor and the transparent window sensor. During the second grinding process, the film thickness of the workpiece is determined based on the spectrum of reflected light from the workpiece received from the other of the liquid-sealed sensor and the transparent window sensor.

5. The film thickness measurement method as described in claim 1 or 2, wherein, The liquid-sealed sensor and the transparent window sensor are multiple liquid-sealed sensors and multiple transparent window sensors.

6. The film thickness measurement method as described in claim 1 or 2, wherein, The liquid-sealed sensor and the transparent window sensor are arranged on each of a plurality of concentric circles having the same center as the rotation center of the grinding table.

7. A film thickness measuring device comprising: a liquid-sealed sensor and a transparent window sensor, the liquid-sealed sensor and the transparent window sensor being disposed on a grinding table, the grinding table being for supporting a grinding pad for grinding a workpiece and being rotatable; and a spectral processing device, the spectral processing device determining the film thickness of the workpiece based on the spectrum of reflected light from the workpiece received from the liquid-sealed sensor and the transparent window sensor, the liquid-sealed sensor having a liquid flow path for supplying liquid flow and a first optical sensor head disposed within the liquid flow path, the transparent window sensor having a second optical sensor head and a transparent window disposed above the second optical sensor head, the spectral processing device being configured to combine the spectrum of reflected light from the workpiece received from the liquid-sealed sensor and the spectrum of reflected light from the workpiece received from the transparent window sensor to generate a composite spectrum, and determining the film thickness of the workpiece based on the composite spectrum.

8. A film thickness measuring device comprising: a liquid-sealed sensor and a transparent window sensor, the liquid-sealed sensor and the transparent window sensor being disposed on a grinding table, the grinding table being used to support a grinding pad for grinding a workpiece and being rotatable; A spectral processing device that determines the film thickness of the workpiece based on the spectrum of reflected light from the workpiece received from the liquid-sealed sensor and the transparent window sensor. A first beam splitter, which is connected to the liquid-sealed sensor; The system includes a second beam splitter connected to the transparent window sensor. The liquid-sealed sensor has a liquid flow path for supplying liquid flow and a first optical sensor head disposed within the liquid flow path. The transparent window sensor has a second optical sensor head and a transparent window disposed above the second optical sensor head. The first beam splitter is configured to measure the intensity of reflected light from the workpiece in a first wavelength range and generate first intensity measurement data. The second beam splitter is configured to measure the intensity of reflected light from the workpiece in a second wavelength range and generate second intensity measurement data. The first wavelength range is different from the second wavelength range.

9. The film thickness measuring device as described in claim 7 or 8, wherein, The liquid-sealed sensor and the transparent window sensor are arranged on a circumference having the same center as the rotation center of the grinding table.

10. The film thickness measuring device as described in claim 8, wherein, The spectral processing apparatus is configured to determine the film thickness of the workpiece during a first grinding process based on the spectrum of reflected light from the workpiece received from one of the liquid-sealed sensor and the transparent window sensor, and to determine the film thickness of the workpiece during a second grinding process based on the spectrum of reflected light from the workpiece received from the other of the liquid-sealed sensor and the transparent window sensor.

11. The film thickness measuring device as described in claim 7 or 8, wherein, The liquid-sealed sensor and the transparent window sensor are multiple liquid-sealed sensors and multiple transparent window sensors.

12. The film thickness measuring device as described in claim 7 or 8, wherein, The liquid-sealed sensor and the transparent window sensor are arranged on each of a plurality of concentric circles having the same center as the rotation center of the grinding table.

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