Polishing apparatus and polishing method

Abstract

To provide a polishing device which can prevent dew condensation on an inner surface of a transparent window provided in an abrasive pad, and can correctly measure a film thickness.SOLUTION: A polishing device comprises: an abrasive pad 2 having a polishing surface 2a; a polishing pad 1 for pressing a work-piece W against the polishing surface 2a; a transparent window 33 located in the abrasive pad 2; a polishing table 3 which supports the abrasive pad 2; an optical sensor head 32 which is located below the transparent window 33, guides light to the work-piece W through the transparent window 33, and receives reflected light from the work-piece W through the transparent window 33; and a cooler 63 for cooling a space 60 between the transparent window 33 and the optical sensor head 32.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a technique for measuring the film thickness of a workpiece used in the manufacture of semiconductor devices such as wafers, substrates, and panels while polishing the workpiece, and particularly relates to a technique for determining the film thickness of a workpiece based on optical information included in the reflected light from the workpiece.

Background Art

[0002] In the manufacturing process of semiconductor devices, various materials are repeatedly formed in a film shape on a silicon wafer to form a laminated structure. In order to form such a laminated structure, a technique for flattening the surface of the uppermost layer is important. As one means of such flattening, chemical mechanical polishing (CMP) is used.

[0003] Chemical mechanical polishing (CMP) is performed by a polishing apparatus. This type of polishing apparatus generally includes a polishing table that supports a polishing pad, a polishing head that holds a wafer having a film, and a polishing liquid supply nozzle that supplies a polishing liquid (for example, slurry) onto the polishing pad. The polishing apparatus supplies the polishing liquid from the polishing liquid supply nozzle onto the polishing pad while rotating the polishing head and the polishing table respectively. The polishing head polishes the film forming the surface of the wafer in a state where the polishing liquid exists between the wafer and the polishing pad by pressing the surface of the wafer against the polishing pad.

[0004] In order to measure the thickness of a film such as an insulating film or a silicon layer (hereinafter simply referred to as film thickness), the polishing apparatus generally includes an optical film thickness measuring apparatus. This optical film thickness measuring apparatus is configured to determine the film thickness of the wafer by guiding the light emitted from a light source to the surface of the wafer from a sensor head, receiving the reflected light from the wafer by the sensor head, and analyzing the spectrum of the reflected light. The polishing apparatus can terminate the polishing of the wafer or change the polishing conditions of the wafer based on the determined film thickness.

[0005] During wafer polishing, polishing liquid and polishing debris exist on the polishing pad. When the polishing liquid and polishing debris adhere to the sensor head, the intensity of the light irradiated on the wafer and the intensity of the reflected light from the wafer decrease, and an accurate film thickness cannot be measured. Therefore, there is a technique of arranging a transparent window between the sensor head and the wafer. The transparent window is arranged inside the polishing pad. Light is irradiated on the wafer through the transparent window, and the reflected light from the wafer passes through the transparent window and is received by the sensor head. The transparent window provided in the polishing pad can prevent the polishing liquid and polishing debris from contacting the sensor head and ensure a good optical path.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] When wafer polishing is completed, water may be supplied onto the polishing pad to clean the polished surface of the wafer or the polishing pad. However, the water supplied onto the polishing pad cools the transparent window provided in the polishing pad, and dew condensation may occur on the inner surface (back surface) of the transparent window. In particular, during wafer polishing, the polishing pad becomes hot due to the friction between the polishing pad and the wafer. Then, when the transparent window is suddenly cooled by water after wafer polishing, dew condensation is likely to occur on the inner surface (back surface) of the transparent window. The dew condensation generated on the inner surface of the transparent window hinders the passage of light and reduces the film thickness measurement accuracy during the polishing of the next wafer.

[0008] Therefore, the present invention provides a polishing apparatus and a polishing method that can prevent dew condensation on the inner surface of the transparent window provided in the polishing pad and can measure an accurate film thickness.

Means for Solving the Problems

[0009] In one aspect, a polishing apparatus is provided that includes a polishing pad having a polishing surface, a polishing head for pressing the workpiece against the polishing surface, a transparent window disposed within the polishing pad, a polishing table for supporting the polishing pad, an optical sensor head disposed below the transparent window for guiding light through the transparent window to the workpiece and receiving reflected light from the workpiece through the transparent window, and a cooling device for cooling a space between the transparent window and the optical sensor head.

[0010] In one aspect, the cooling device has a cooling surface exposed within the space. In one aspect, the polishing apparatus further includes an operation control unit for controlling a cooling operation of the cooling device. In one aspect, the operation control unit is configured to start the cooling operation of the cooling device after polishing of the workpiece. In one aspect, the operation control unit is configured to start the cooling operation of the cooling device during polishing of the workpiece. In one aspect, the operation control unit is configured to calculate a temperature difference by subtracting a temperature within the space from a temperature of the polishing surface, and control the cooling operation of the cooling device so that the temperature difference is maintained at a threshold value or more. In one aspect, the polishing apparatus further includes a dehumidifying device for reducing humidity within the space.

[0011] In one aspect, a polishing method is provided in which a workpiece is pressed against a polishing surface of a polishing pad to polish the workpiece, during polishing of the workpiece, light is guided from an optical sensor head to the workpiece through a transparent window disposed within the polishing pad, reflected light from the workpiece is received by the optical sensor head through the transparent window, and a space between the transparent window and the optical sensor head is cooled by a cooling device.

[0012] In one aspect, the cooling device has a cooling surface exposed within the space. In one aspect, the cooling of the space by the cooling device starts after the polishing of the workpiece. In one aspect, the cooling of the space by the cooling device starts during the polishing of the workpiece. In one aspect, a temperature difference is calculated by subtracting the temperature in the space from the temperature of the polished surface, and the space is cooled by the cooling device so that the temperature difference is maintained at a threshold value or more. In one aspect, the polishing method further includes reducing the humidity in the space.

Advantages of the Invention

[0013] According to the present invention, the temperature in the space between the transparent window and the optical sensor head is cooled by the cooling device. As a result, the dew point temperature in the space decreases, and condensation on the inner surface of the transparent window facing the space is prevented.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

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Figure 8

Figure 9

Modes for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing an embodiment of a polishing apparatus. As shown in FIG. 1, the polishing apparatus includes a polishing table 3 that supports a polishing pad 2, a polishing head 1 that presses a workpiece W such as a wafer, a substrate, or a panel used in the manufacture of semiconductor devices against the polishing pad 2, a table motor 6 that rotates the polishing table 3, a polishing liquid supply nozzle 5 for supplying a polishing liquid such as slurry onto the polishing pad 2, and a pure water supply nozzle 8 for supplying pure water onto the polishing pad 2 after polishing the workpiece W. The upper surface of the polishing pad 2 constitutes a polishing surface 2a for polishing the workpiece W.

[0016] The polishing head 1 is connected to a head shaft 10, and the head shaft 10 is connected to a polishing head motor 18 via a connecting device 17. The configuration of the connecting device 17 is not particularly limited, and it is composed of a combination of a pulley and a belt, or a combination of gears, or a combination of a sprocket and a chain. The polishing head motor 18 rotates the polishing head 1 together with the head shaft 10 in the direction indicated by the arrow. The polishing table 3 is connected to a table motor 6, and the table motor 6 is configured to rotate the polishing table 3 and the polishing pad 2 in the direction indicated by the arrow.

[0017] The workpiece W is polished as follows. While rotating the polishing table 3 and the polishing head 1 in the direction indicated by the arrow in FIG. 1, the polishing liquid is supplied from the polishing liquid supply nozzle 5 to the polishing surface 2a of the polishing pad 2 on the polishing table 3. While the workpiece W is rotated by the polishing head 1, the workpiece W is pressed against the polishing surface 2a of the polishing pad 2 by the polishing head 1 in a state where the polishing liquid exists on the polishing pad 2. The surface of the workpiece W is polished by the chemical action of the polishing liquid and the mechanical action of the abrasive grains contained in the polishing liquid and / or the polishing pad 2.

[0018] The grinding device is equipped with a film thickness measuring device 20 for measuring the film thickness of the workpiece W. The film thickness measuring device 20 includes a light source 22 that emits light, an optical sensor head 32 that irradiates the light from the light source 22 onto the workpiece W and receives the reflected light from the workpiece W, a spectroscope 40 connected to the optical sensor head 32, a spectrum processing device 45 that determines the thickness of the film of the workpiece W based on the intensity measurement data of the reflected light from the workpiece W, and a transparent window 33 disposed above the optical sensor head 32. The transparent window 33 is disposed within the polishing pad 2, and the optical sensor head 32 is attached to the polishing table 3. The transparent window 33 and the optical sensor head 32 rotate together with the polishing table 3.

[0019] Each time the polishing table 3 makes one rotation, the light emitted from the light source 22 is transmitted to the optical sensor head 32 and guided from the optical sensor head 32 to the surface of the workpiece W. The light is reflected from the surface of the workpiece W, and the reflected light from the surface of the workpiece W is received by the optical sensor head 32 and sent to the spectroscope 40. The spectroscope 40 decomposes the reflected light according to the wavelength over a predetermined wavelength range and generates intensity measurement data of the reflected light by measuring the intensity of the reflected light at each wavelength. The intensity measurement data of the reflected light is sent from the spectroscope 40 to the spectrum processing device 45.

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

[0021] The spectrum processing device 45 includes a storage device 45a in which a program is stored, and an arithmetic device 45b that executes operations according to instructions included in the program. The spectrum processing device 45 is composed of at least one computer. The storage device 45a includes a main storage device such as a random access memory (RAM), and auxiliary storage devices such as a hard disk drive (HDD) and a solid state drive (SSD). Examples of the arithmetic device 45b include a CPU (central processing unit) and a GPU (graphics processing unit). However, the specific configuration of the spectrum processing device 45 is not limited to these examples.

[0022] FIG. 2 is a diagram showing an example of a spectrum generated by the spectrum processing device 45. The spectrum is represented as a line graph (i.e., a spectral waveform) showing the relationship between the wavelength and intensity of light. In FIG. 2, the horizontal axis represents the wavelength of the light reflected from the workpiece W, and the vertical axis represents the relative reflectance derived from the intensity of the reflected light. The relative reflectance is an index value indicating the intensity of the reflected light, and is the ratio of the intensity of the light to a predetermined reference intensity. By dividing the intensity of the light (measured intensity) at each wavelength by the predetermined reference intensity, unnecessary noise such as variations in the intensity inherent in the optical system and light source of the device can be removed from the measured intensity.

[0023] In the example shown in FIG. 2, the spectrum of the reflected light is a spectral waveform showing the relationship between the relative reflectance and the wavelength of the reflected light. However, the spectrum of the reflected light may be a spectral waveform showing the relationship between the intensity itself of the reflected light and the wavelength of the reflected light.

[0024] The spectrum processing device 45 receives intensity measurement data of the reflected light from the workpiece W while the polishing table 3 makes one rotation, and generates a spectrum of the reflected light from this intensity measurement data. The spectrum processing device 45 is configured to determine the film thickness of the workpiece W from the spectrum of the reflected light. Known techniques are used for the method of determining the film thickness of the workpiece W based on the spectrum. For example, the spectrum processing device 45 determines a reference spectrum having the closest shape to the spectrum of the reflected light from a reference spectrum library, and determines the film thickness associated with this determined reference spectrum. In another example, the spectrum processing device 45 performs a Fourier transform on the spectrum of the reflected light, and determines the film thickness from the obtained frequency spectrum.

[0025] Referring to FIG. 1, the details of the film thickness measuring device 20 will be described. The spectroscope 40 includes a photodetector 41. In one embodiment, the photodetector 41 is composed of a photodiode, a CCD, a CMOS, or an InGaAs (indium gallium arsenide) sensor, etc. The optical sensor head 32 is optically connected to the light source 22 and the photodetector 41. The photodetector 41 is electrically connected to the spectrum processing device 45.

[0026] The film thickness measuring device 20 includes a light projecting optical fiber cable 51 that guides the light emitted from the light source 22 to the surface of the workpiece W, and a light receiving optical fiber cable 56 that receives the reflected light from the workpiece W and sends the reflected light to the spectroscope 40. The tip of the light projecting optical fiber cable 51 and the tip of the light receiving optical fiber cable 56 are located inside the polishing table 3. The optical sensor head 32 is composed of the tip of the light projecting optical fiber cable 51 and the tip of the light receiving optical fiber cable 56.

[0027] The light source 22 sends light to the optical sensor head 32 through the light-projecting optical fiber cable 51, and the optical sensor head 32 emits the light toward the workpiece W through the transparent window 33. The reflected light from the workpiece W passes through the transparent window 33 and is received by the optical sensor head 32. Further, the reflected light from the workpiece W is sent to the spectroscope 40 through the light-receiving optical fiber cable 56. The spectroscope 40 decomposes the reflected light according to its wavelength and measures the intensity of the reflected light at each wavelength over a predetermined wavelength range. The spectroscope 40 sends the intensity measurement data of the reflected light to the spectrum processing device 45. The spectrum processing device 45 generates a spectrum of the reflected light from 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.

[0028] FIG. 3 is a cross-sectional view showing an embodiment of the arrangement of the transparent window 33 and the optical sensor head 32. As shown in FIG. 3, the optical sensor head 32 is installed in the polishing table 3, and the transparent window 33 is disposed in the through hole 34 formed in the polishing pad 2. The transparent window 33 completely closes the through hole 34 of the polishing pad 2, thereby preventing the polishing liquid and polishing debris from contacting the optical sensor head 32.

[0029] A space 60 is formed in the polishing pad 2. The space 60 is formed by the inner surface (rear surface) 33a of the transparent window 33, the through hole 34 of the polishing pad 2, and the polishing table 3. This space 60 is a closed space. The space 60 is located between the transparent window 33 and the optical sensor head 32. The inner surface 33a of the transparent window 33 and the optical sensor head 32 face the space 60. The outer surface of the transparent window 33 is at a position slightly lower than the polishing surface 2a of the polishing pad 2.

[0030] The optical sensor head 32 composed of the tip of the light-projecting optical fiber cable 51 and the tip of the light-receiving optical fiber cable 56 emits light toward the workpiece W through the space 60 and the transparent window 33, and the reflected light from the workpiece W is received by the optical sensor head 32 after passing through the transparent window 33 and the space 60. The transparent window 33 is a window made of a material that transmits light. The material of the transparent window 33 is not particularly limited, but for example, it is made of a transparent resin.

[0031] The polishing apparatus includes a cooling device 63 for cooling the space 60. The cooling surface 63a of the cooling device 63 is exposed to the space 60. Examples of the cooling device 63 include a cooling element, a combination of a cooling element and a heat-conductive material, and a water-cooling device. An example of the cooling element is a Peltier element. Examples of the heat-conductive material include metals such as copper, aluminum, and stainless steel.

[0032] In the embodiment shown in FIG. 3, a Peltier element is used as the cooling device 63. A part of the Peltier element constituting the cooling device 63 is located in the space 60, and the other part is located on the polishing table 3. More specifically, the cooling surface 63a of the Peltier element is exposed in the space 60, and the heat-radiating surface 63b of the Peltier element is disposed in the polishing table 3.

[0033] Although not shown, in one embodiment, the heat-radiating surface 63b of the cooling element (Peltier element in this embodiment) constituting the cooling device 63 shown in FIG. 3 may be brought into contact with the cooling surface of at least one cooling element (for example, a Peltier element) to constitute a cooling device 63 including a plurality of stacked cooling elements. The plurality of stacked cooling elements can sequentially transfer the heat in the space 60. In other embodiments, a water-cooling device may be brought into contact with the heat-radiating surface 63b of the cooling element constituting the cooling device 63 shown in FIG. 3.

[0034] The cooling device 63 is connected to the operation control unit 65, and the cooling operation of the cooling device 63 is controlled by the operation control unit 65. The operation control unit 65 includes a storage device 65a in which a program is stored, and an arithmetic device 65b that executes arithmetic operations according to instructions included in the program. The operation control unit 65 is composed of at least one computer. The storage device 65a includes a main storage device such as a random access memory (RAM), and auxiliary storage devices such as a hard disk drive (HDD) and a solid state drive (SSD). Examples of the arithmetic device 65b include a CPU (central processing unit) and a GPU (graphics processing unit). However, the specific configuration of the operation control unit 65 is not limited to these examples.

[0035] During the polishing of the workpiece W, the polishing pad 2 becomes hot due to the friction between the polishing pad 2 and the workpiece W. After the polishing of the workpiece W, for the purposes of cleaning the polished surface of the workpiece W, or cleaning the polishing pad 2, or dressing the polishing pad 2, etc., pure water is supplied from the pure water supply nozzle 8 to the polishing surface 2a of the polishing pad 2. Along with the supply of pure water, the temperature of the transparent window 33 decreases. As a result, condensation may occur on the inner surface (back surface) 33a of the transparent window 33. The condensation generated on the inner surface 33a of the transparent window 33 hinders the passage of light and reduces the film thickness measurement accuracy during the polishing of the next workpiece.

[0036] Therefore, in order to prevent condensation on the inner surface 33a of the transparent window 33, the operation control unit 65 drives the cooling device 63 to cool the space 60. By cooling the space 60 by the cooling device 63, the dew point temperature in the space 60 decreases, and as a result, condensation on the inner surface 33a of the transparent window 33 facing the space 60 is prevented.

[0037] The operation control unit 65 is configured to start the cooling operation of the cooling device 63 after the polishing of the workpiece W. For example, after the polishing of the workpiece W and before or simultaneously with the supply of pure water to the polishing pad 2, the operation control unit 65 starts the cooling operation of the cooling device 63.

[0038] In one embodiment, the operation control unit 65 may be configured to start the cooling operation of the cooling device 63 during the polishing of the workpiece W. During the polishing of the workpiece W, the temperature in the space 60 rises due to the frictional heat between the polishing pad 2 and the workpiece W. When the temperature in the space 60 rises, condensation is likely to occur on the inner surface 33a of the transparent window 33 when the transparent window 33 is cooled by pure water after the polishing of the workpiece W. Therefore, the operation control unit 65 cools the space 60 by the cooling device 63 during the polishing of the workpiece W, thereby reducing the temperature (i.e., the dew point temperature) in the space 60. By such an operation, when the transparent window 33 is cooled by pure water after the polishing of the workpiece W, condensation on the inner surface 33a of the transparent window 33 facing the space 60 can be prevented.

[0039] FIG. 4 is a cross-sectional view showing another embodiment of the arrangement of the transparent window 33 and the optical sensor head 32. The configuration and operation of this embodiment not specifically described are the same as those of the embodiment described with reference to FIG. 3, and thus the overlapping description thereof is omitted. In the embodiment shown in FIG. 4, the polishing apparatus includes a pad surface temperature measuring device 67 that measures the temperature of the polishing surface 2a (and the transparent window 33) of the polishing pad 2, and an internal temperature measuring device 68 that measures the temperature in the space 60.

[0040] The pad surface temperature measuring device 67 is a non-contact type temperature sensor disposed above the polishing pad 2. For example, an infrared temperature sensor can be used as the pad surface temperature measuring device 67. The internal temperature measuring device 68 is disposed in the space 60. The arrangement and configuration of the internal temperature measuring device 68 are not particularly limited as long as the internal temperature measuring device 68 can measure the temperature in the space 60.

[0041] The pad surface temperature measuring device 67 and the internal temperature measuring device 68 are connected to the operation control unit 65, and the measured values of the temperature of the polishing surface 2a and the temperature in the space 60 are transmitted to the operation control unit 65. The operation control unit 65 is configured to control the cooling operation of the cooling device 63 based on the measured value of the temperature of the polishing surface 2a and the measured value of the temperature of the space 60. More specifically, the operation control unit 65 subtracts the measured value of the temperature in the space 60 from the measured value of the temperature of the polishing surface 2a to calculate a temperature difference, and controls the cooling operation of the cooling device 63 so that the temperature difference is maintained at a threshold value or more.

[0042] By such a cooling operation, the temperature in the space 60 is always maintained lower than the temperature of the polishing surface 2a, and dew condensation on the inner surface 33a of the transparent window 33 facing the space 60 can be prevented. Since the above-mentioned threshold value for preventing dew condensation is likely to depend on the environment in which the polishing apparatus is placed, the threshold value may be determined from dew condensation observation data obtained during past polishing.

[0043] FIG. 5 is a schematic diagram showing another embodiment of the cooling device 63. The configuration and operation of this embodiment not particularly described are the same as those of the embodiment described with reference to FIG. 3, and thus the overlapping description thereof is omitted. In this embodiment, as the cooling device 63, a combination of a cooling element 73 and a heat conduction material 75 is used. More specifically, the entire cooling element 73 is disposed below the space 60 and outside the space 60. The heat conduction material 75 is in contact with the cooling surface 73a of the cooling element 73. A part of the heat conduction material 75 is located in the space 60, and the other part is located in the polishing table 3. More specifically, a part of the heat conduction material 75 is exposed in the space 60, and the cooling surface 63a of the cooling device 63 is composed of the exposed surface of the heat conduction material 75. Examples of the cooling element 73 include a Peltier element, and examples of the heat conduction material 75 include metals such as copper, aluminum, and stainless steel.

[0044] According to the embodiment shown in FIG. 5, the heat conductive material 75 is cooled by the cooling element 73, and the space 60 is cooled by the heat conductive material 75. Since the entire cooling element 73 such as a Peltier element is embedded in the polishing table 3, there is an advantage that the heat radiated from the cooling element 73 is difficult to be transmitted to the space 60.

[0045] Although not shown, in one embodiment, a cooling device 63 including a plurality of stacked cooling elements may be configured by bringing the cooling surface of at least one cooling element into contact with the heat radiating surface 73b of the cooling element 73. The plurality of stacked cooling elements can sequentially transfer the heat in the space 60. In another embodiment, a water cooling device may be brought into contact with the heat radiating surface 73b of the cooling element 73.

[0046] FIG. 6 is a schematic diagram showing still another embodiment of the cooling device 63. Since the configuration and operation of this embodiment not particularly described are the same as those of the embodiment described with reference to FIG. 3, the overlapping description thereof is omitted. In this embodiment, a water cooling device is used as the cooling device 63. More specifically, the cooling device 63 includes a coolant flow path 77 through which a coolant such as water flows, and a heat conductive material 78 at least a part of which is exposed in the space 60. The coolant flow path 77 is located directly below the space 60 and extends in the heat conductive material 78.

[0047] In this embodiment, a part of the heat conductive material 78 is located in the space 60, and the other part is located in the polishing table 3. In one embodiment, the entire heat conductive material 78 may be located in the space 60. The cooling surface 63a of the cooling device 63 is composed of the exposed surface of the heat conductive material 78. The coolant flowing through the coolant flow path 77 cools the heat conductive material 78, and the heat conductive material 78 can cool the inside of the space 60.

[0048] A flow rate control valve 79 is provided in the coolant flow path 77, and the flow rate of the coolant flowing through the coolant flow path 77 is adjusted by the flow rate control valve 79. The flow rate control valve 79 is electrically connected to the operation control unit 65, and the operation of the flow rate control valve 79 is controlled by the operation control unit 65.

[0049] The embodiment described with reference to FIG. 4 is also applicable to the embodiments described with reference to FIGS. 5 and 6.

[0050] FIG. 7 is a cross-sectional view showing still another embodiment of the arrangement of the transparent window 33 and the optical sensor head 32. The configuration and operation of this embodiment which are not particularly described are the same as those of the embodiment described with reference to FIG. 4, and thus the overlapping description thereof is omitted. In the embodiment shown in FIG. 7, the polishing apparatus includes a dehumidifying device 85 for reducing the humidity in the space 60. The dehumidifying device 85 is disposed in the space 60. Specific examples of the dehumidifying device 85 include a dehumidifying element having a solid polymer electrolyte membrane, a dry gas dehumidifying device for supplying dry gas into the space 60, a dehumidifying agent such as silica gel, or a combination thereof.

[0051] In this embodiment, the dehumidifying device 85 is composed of a dehumidifying element having a solid polymer electrolyte membrane. The dehumidifying device 85 is connected to the operation control unit 65, and the dehumidifying operation of the dehumidifying device 85 is controlled by the operation control unit 65. Since the dehumidifying device 85 can remove moisture in the space 60, condensation on the inner surface 33a of the transparent window 33 facing the space 60 can be prevented.

[0052] In one embodiment, as shown in FIG. 8, the polishing apparatus may further include a humidity measuring device 86 for measuring the humidity in the space 60. The humidity measuring device 86 is disposed in the space 60. The humidity measuring device 86 is connected to the operation control unit 65, and the measured value of the humidity in the space 60 is transmitted to the operation control unit 65. The operation control unit 65 is configured to control the dehumidifying operation of the dehumidifying device 85 based on the measured value of the humidity in the space 60.

[0053] FIG. 9 is a schematic diagram showing another embodiment of the dehumidifying device 85. In this embodiment, the dehumidifying device 85 includes a combination of a dry gas dehumidifying device and a dehumidifying agent. More specifically, the dehumidifying device 85 has a dry gas circulation line 90 through which a dry gas such as air flows, a dehumidifying agent 92 provided in the dry gas circulation line 90, and a fan 95 for transferring the dry gas in the dry gas circulation line 90. An example of the dehumidifying agent 92 is silica gel.

[0054] The dry gas circulation line 90 opens in the space 60 and communicates with the space 60. When the fan 95 is driven, a dry gas such as air flows from the dry gas circulation line 90 into the space 60, fills the space 60, and further flows from the space 60 into the dry gas circulation line 90. The dry gas flowing through the space 60 contacts the dehumidifying agent 92 and is dehumidified. The dehumidified dry gas flows again from the dry gas circulation line 90 into the space 60. In this way, the dry gas circulates between the space 60 and the dehumidifying agent 92. In one embodiment, instead of the dehumidifying agent 92, a dehumidifying element provided with a solid polymer electrolyte membrane may be provided.

[0055] The embodiment described with reference to FIG. 8 can be applied to the embodiment described with reference to FIG. 9. The embodiments described with reference to FIGS. 7 to 9 may be combined with any of the embodiments described with reference to FIGS. 3 to 6.

[0056] In the embodiments described so far, the polishing device includes a set of transparent windows 33 and an optical sensor head 32, but the polishing device may include a plurality of sets of transparent windows 33 and optical sensor heads 32.

[0057] The above-described embodiments are described for the purpose of enabling a person having ordinary skill in the technical field to which the present invention pertains to practice the present invention. Various modifications of the above embodiments can be naturally made by those skilled in the art, and the technical idea of the present invention can be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is construed in the broadest scope in accordance with the technical idea defined by the claims.

Explanation of Signs

[0058] W Workpiece 1 Polishing head 2 Polishing pad 2a Polishing surface 3 Polishing table 5 Polishing liquid supply nozzle 6 Table motor 8 Pure water supply nozzle 10 Head shaft 17 Connecting device 18 Polishing head motor 20 Film thickness measuring device 22 Light source 32 Optical sensor head 33 Transparent window 34 Through hole 40 Spectrometer 41 Photodetector 45 Spectrum processing device 45a Storage device 45b Arithmetic unit 51 Light projection optical fiber cable 56 Light reception optical fiber cable 60 Space 63 Cooling device 65 Operation control unit 65a Storage device 65b Arithmetic unit 67 Pad surface temperature measuring device 68 Internal temperature measuring device 73 Cooling element 75 Heat conductive material 77 Cooling liquid flow path 78 Heat conductive material 79 Flow control valve 85 Dehumidifying device 86 Humidity measuring device 90 Dry gas circulation line 92 Desiccant 95 Fan

Claims

1. A polishing pad having a polishing surface; A polishing head for pressing a workpiece against the polishing surface; A transparent window disposed within the polishing pad; A polishing table for supporting the polishing pad; An optical sensor head disposed below the transparent window for guiding light through the transparent window to the workpiece and receiving reflected light from the workpiece through the transparent window; A cooling device for cooling a space between the transparent window and the optical sensor head; A pad surface temperature measuring device for measuring the temperature of the polishing surface; An internal temperature measuring device for measuring the temperature within the space; Comprising an operation control unit for controlling a cooling operation of the cooling device; The operation control unit is configured to calculate a temperature difference by subtracting the temperature within the space from the temperature of the polishing surface, and to control the cooling operation of the cooling device so that the temperature difference is maintained at a threshold value or more. A polishing apparatus.

2. The polishing apparatus according to claim 1, wherein the operation control unit operates to maintain the temperature within the space lower than the temperature of the polishing surface.

3. A polishing pad having a polishing surface; A pure water supply nozzle for supplying pure water onto the polishing pad; A polishing head for pressing a workpiece against the polishing surface; A transparent window disposed within the polishing pad; A polishing table for supporting the polishing pad; An optical sensor head disposed below the transparent window for guiding light through the transparent window to the workpiece and receiving reflected light from the workpiece through the transparent window; A cooling device for cooling a space between the transparent window and the optical sensor head; Comprising an operation control unit for controlling a cooling operation of the cooling device; The operation control unit is configured to start the cooling operation of the cooling device after polishing the workpiece and before or simultaneously with the supply of pure water from the pure water supply nozzle to the polished surface. Polishing apparatus.

4. Press the workpiece against the polishing surface of the polishing pad to polish the workpiece, During the polishing of the workpiece, light is guided from the optical sensor head to the workpiece through a transparent window disposed in the polishing pad, and the reflected light from the workpiece is received by the optical sensor head through the transparent window. Measure the temperature in the space between the transparent window and the optical sensor head and the temperature of the polishing surface, Calculate the temperature difference by subtracting the temperature in the space from the temperature of the polishing surface, A polishing method for cooling the space with a cooling device so that the temperature difference is maintained at or above a threshold value.

5. The cooling device cools the space so that the temperature in the space is maintained lower than the temperature of the polishing surface. The polishing method according to claim 4.

6. Press the workpiece against the polishing surface of the polishing pad to polish the workpiece, During the polishing of the workpiece, light is guided from the optical sensor head to the workpiece through a transparent window disposed in the polishing pad, and the reflected light from the workpiece is received by the optical sensor head through the transparent window. After polishing the workpiece, supply pure water from the pure water supply nozzle to the polishing surface, After polishing the workpiece and before or simultaneously with the supply of pure water from the pure water supply nozzle to the polishing surface, cool the space between the transparent window and the optical sensor head with a cooling device. Polishing method.

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