Polishing apparatus and polishing method

Abstract

A polishing device is provided that prevents condensation on the inner surface of a transparent window provided on a polishing pad and can accurately measure the film thickness. The polishing device comprises a polishing pad (2) having a polishing surface (2a), a polishing head (1) for pressing a workpiece W against the polishing surface (2a), a transparent window (33) disposed within the polishing pad (2), a polishing table (3) supporting the polishing pad (2), an optical sensor head (32) disposed below the transparent window (33) for guiding light to the workpiece W through the transparent window (33) and receiving reflected light from the workpiece W through the transparent window (33), and a cooling device (63) for cooling the space (60) between the transparent window (33) and the optical sensor head (32).

Description

Technology Field

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

[0002] In the manufacturing process of semiconductor devices, various materials are repeatedly formed as films on a silicon wafer to form a stacked structure. To form this stacked structure, a technology for flattening the surface of the top layer is becoming important. Chemical mechanical polishing (CMP) is used as one means of such flattening.

[0003] Chemical mechanical polishing (CMP) is performed by a polishing device. This type of polishing device generally comprises a polishing table that supports a polishing pad, a polishing head that holds and supports a wafer having a film, and a polishing liquid supply nozzle that supplies a polishing liquid (e.g., a slurry) onto the polishing pad. The polishing device 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 by pressing the surface of the wafer against the polishing pad, while the polishing liquid is present between the wafer and 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), a polishing device generally includes an optical film thickness measuring device. This optical film thickness measuring device is configured to determine the film thickness of a wafer by guiding light emitted from a light source to the surface of a wafer from a sensor head, receiving reflected light from the wafer with a sensor head, and analyzing the spectrum of the reflected light. Based on the determined film thickness, the polishing device can terminate the polishing of the wafer or change the polishing conditions of the wafer.

[0005] During wafer polishing, polishing fluid or polishing debris is present on the polishing pad. If the polishing fluid or debris adheres to the sensor head, the intensity of light irradiated onto the wafer and the intensity of reflected light from the wafer are reduced, making it impossible to accurately measure the film thickness. Therefore, there is a technology that places a transparent window between the sensor head and the wafer. The transparent window is positioned within the polishing pad, light is irradiated onto the wafer through the window, and reflected light from the wafer passes through the window and is received by the sensor head. The transparent window provided in the polishing pad prevents the polishing fluid or polishing debris from coming into contact with the sensor head, thereby ensuring a good light path. Prior art literature

[0006] Japanese Patent Publication No. 2017-220683 The problem to be solved

[0007] When wafer polishing is completed, water is sometimes 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 on the pad, which can cause condensation to form on the inner (back) surface of the window. In particular, during wafer polishing, the polishing pad becomes high due to friction between the pad and the wafer. Furthermore, if the transparent window is suddenly cooled by water after polishing, condensation is likely to form on the inner (back) surface of the window. Condensation formed on the inner surface of the window obstructs the passage of light, thereby reducing the precision of film thickness measurement during the polishing of the next wafer.

[0008] Accordingly, the present invention provides a polishing device and a polishing method capable of accurately measuring film thickness by preventing condensation on the inner surface of a transparent window provided in a polishing pad. means of solving the problem

[0009] In one embodiment, a polishing device is provided, comprising: a polishing pad having a polishing surface; a polishing head for pressing a workpiece into contact with the polishing surface; a transparent window disposed within the polishing pad; a polishing table supporting the polishing pad; an optical sensor head disposed below the transparent window for guiding light to the workpiece through the transparent window and receiving reflected light from the workpiece through the transparent window; and a cooling device for cooling the space between the transparent window and the optical sensor head.

[0010] In one embodiment, the cooling device has a cooling surface exposed within the space.

[0011] In one embodiment, the polishing device further comprises an operation control unit that controls the cooling operation of the cooling device.

[0012] In one embodiment, the operation control unit is configured to initiate the cooling operation of the cooling device after the workpiece is polished.

[0013] In one embodiment, the operation control unit is configured to initiate the cooling operation of the cooling device during the polishing of the workpiece.

[0014] In one embodiment, 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 above a threshold.

[0015] In one embodiment, the polishing device further comprises a dehumidifying device that lowers the humidity within the space.

[0016] In one embodiment, a polishing method is provided, wherein a workpiece is pressed into contact with the polishing surface of a polishing pad to polish the workpiece, and during the polishing of the workpiece, light is directed 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 the space between the transparent window and the optical sensor head is cooled by a cooling device.

[0017] In one embodiment, the cooling device has a cooling surface exposed within the space.

[0018] In one embodiment, cooling of the space by the cooling device is initiated after grinding the workpiece.

[0019] In one embodiment, cooling of the space by the cooling device is initiated during the grinding of the workpiece.

[0020] In one embodiment, the temperature difference is calculated by subtracting the temperature within 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 above a threshold.

[0021] In one embodiment, the polishing method further includes lowering the humidity in the space. Effects of the invention

[0022] According to the present invention, the temperature within the space between the transparent window and the optical sensor head is cooled by a cooling device. As a result, the dew point temperature within the space is lowered, thereby preventing condensation on the inner surface of the transparent window facing the space. Brief explanation of the drawing

[0023] FIG. 1 is a schematic diagram illustrating one embodiment of a grinding device. Figure 2 is a diagram illustrating an example of a spectrum generated by a spectrum processing device. FIG. 3 is a cross-sectional view illustrating one embodiment of the arrangement of a transparent window and an optical sensor head. FIG. 4 is a cross-sectional view illustrating another embodiment of the arrangement of the transparent window and the optical sensor head. FIG. 5 is a schematic diagram illustrating one embodiment of a cooling device. FIG. 6 is a schematic diagram illustrating one embodiment of a cooling device. FIG. 7 is a cross-sectional view illustrating another embodiment of the arrangement of a transparent window and an optical sensor head. FIG. 8 is a cross-sectional view illustrating another embodiment of the arrangement of a transparent window and an optical sensor head. FIG. 9 is a schematic diagram illustrating one embodiment of a dehumidification device. Specific details for implementing the invention

[0024] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0025] FIG. 1 is a schematic diagram illustrating one embodiment of a polishing device. As shown in FIG. 1, the polishing device comprises a polishing table (3) that supports a polishing pad (2), a polishing head (1) that presses a workpiece W, such as a wafer, substrate, or panel used in the manufacture of a semiconductor device, onto the polishing pad (2), a table motor (6) that rotates the polishing table (3), a polishing liquid supply nozzle (5) for supplying a polishing liquid such as a 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) forms a polishing surface (2a) for polishing the workpiece W.

[0026] 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 configuration of the connecting device (17) is not particularly limited, but may be composed of a combination of a pulley and a belt, a combination of a gear, or a combination of a sprocket and a chain, etc. The grinding head motor (18) rotates the grinding head (1) together with the head shaft (10) in the direction indicated by the arrow. The grinding table (3) is connected to the table motor (6), and the table motor (6) is configured to rotate the grinding table (3) and the grinding pad (2) in the direction indicated by the arrow.

[0027] 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, 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). As the workpiece W is rotated by the polishing head (1), the workpiece W is pressed into contact with the polishing surface (2a) of the polishing pad (2) by the polishing head (1) while the polishing liquid is present 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 particles contained in the polishing liquid and / or the polishing pad (2).

[0028] The polishing device is equipped with a film thickness measuring device (20) for measuring the film thickness of a workpiece W. The film thickness measuring device (20) is equipped with 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 reflected light from the workpiece W, a spectrometer (40) connected to the optical sensor head (32), a spectrum processing device (45) that determines the film thickness of the workpiece W based on intensity measurement data of the reflected light from the workpiece W, and a transparent window (33) positioned above the optical sensor head (32). The transparent window (33) is positioned within the polishing pad (2), and the optical sensor head (32) is installed on the polishing table (3). The transparent window (33) and the optical sensor head (32) rotate together with the polishing table (3).

[0029] Whenever the polishing table (3) rotates once, 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 spectrometer (40). The spectrometer (40) separates the reflected light according to wavelength over a predetermined wavelength range and generates reflected light intensity measurement data by measuring the intensity of the reflected light at each wavelength. The reflected light intensity measurement data is sent from the spectrometer (40) to the spectrum processing device (45).

[0030] The spectrum processing device (45) is configured to generate a spectrum of reflected light of workpiece W from the intensity measurement data of the reflected light. The spectrum of the reflected light is displayed 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 may also be displayed as a relative value, such as reflectance or relative reflectance.

[0031] The spectrum processing unit (45) is equipped with a memory unit (45a) in which a program is stored and an arithmetic unit (45b) that executes operations according to instructions included in the program. The spectrum processing unit (45) is composed of at least one computer. The memory unit (45a) is equipped with a main memory such as random access memory (RAM) and an auxiliary memory such as a hard disk drive (HDD) or a solid-state drive (SSD). Examples of the arithmetic unit (45b) include a CPU (central processing unit) and a GPU (graphics processing unit). However, the specific configuration of the spectrum processing unit (45) is not limited to these examples.

[0032] FIG. 2 is a diagram illustrating an example of a spectrum generated by a spectrum processing device (45). The spectrum is displayed as a line graph (i.e., a spectral waveform) representing the relationship between the wavelength and intensity of light. In FIG. 2, the horizontal axis represents the wavelength of light reflected from the workpiece W, and the vertical axis represents the relative reflectance derived from the intensity of the reflected light. Relative reflectance is an indicator value representing the intensity of reflected light, and is the ratio of the light intensity to a predetermined reference intensity. By dividing the light intensity (measured intensity) at each wavelength by a predetermined reference intensity, unnecessary noise, such as fluctuations in the intensity of the device's optical system or the light source itself, can be removed from the measured intensity.

[0033] In the example illustrated in FIG. 2, the spectrum of the reflected light is a spectral waveform representing the relationship between the relative reflectance and the wavelength of the reflected light, but the spectrum of the reflected light may also be a spectral waveform representing the relationship between the intensity of the reflected light itself and the wavelength of the reflected light.

[0034] The spectrum processing device (45) receives intensity measurement data of reflected light from workpiece W while the polishing table (3) rotates once, and generates a spectrum of reflected light from this intensity measurement data. The spectrum processing device (45) is configured to determine the film thickness of workpiece W from the spectrum of reflected light. Known techniques are used for the method of determining the film thickness of workpiece W based on the spectrum. For example, the spectrum processing device (45) determines a reference spectrum that is closest in shape to the spectrum of reflected light from a reference spectrum library and determines the film thickness associated with the determined reference spectrum. In another example, the spectrum processing device (45) performs a Fourier transform on the spectrum of reflected light and determines the film thickness from the obtained frequency spectrum.

[0035] With reference to FIG. 1, details of the film thickness measuring device (20) will be described. The spectrometer (40) is equipped with a photodetector (41). In one embodiment, the photodetector (41) is composed of a photodiode, CCD, CMOS, or InGaAs (indium gallium arsenide) sensor, etc. An optical sensor head (32) is optically connected to a light source (22) and a photodetector (41). The photodetector (41) is electrically connected to a spectrum processing device (45).

[0036] The film thickness measuring device (20) is equipped with a light-transmitting optical fiber cable (51) that guides light emitted from a light source (22) to the surface of a workpiece W, and a light-receiving optical fiber cable (56) that receives reflected light from the workpiece W and sends the reflected light to a spectrometer (40). The tip of the light-transmitting optical fiber cable (51) and the tip of the light-receiving optical fiber cable (56) are located within a polishing table (3). The optical sensor head (32) is composed of the tip of the light-transmitting optical fiber cable (51) and the tip of the light-receiving optical fiber cable (56).

[0037] The light source (22) sends light to the optical sensor head (32) through the light-transmitting optical fiber cable (51), and the optical sensor head (32) emits 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). Additionally, the reflected light from the workpiece W is sent to the spectrometer (40) through the light-receiving optical fiber cable (56). The spectrometer (40) separates the reflected light along its wavelength and measures the intensity of the reflected light at each wavelength over a predetermined wavelength range. The spectrometer (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.

[0038] FIG. 3 is a cross-sectional view illustrating an embodiment of the arrangement of a transparent window (33) and an optical sensor head (32). As shown in FIG. 3, the optical sensor head (32) is installed within a polishing table (3), and the transparent window (33) is placed within a through hole (34) formed in a polishing pad (2). The transparent window (33) completely closes the through hole (34) of the polishing pad (2), thereby preventing polishing liquid or polishing debris from coming into contact with the optical sensor head (32).

[0039] A space (60) is formed within the polishing pad (2). The space (60) is formed by the inner surface (back side) (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 located slightly lower than the polishing surface (2a) of the polishing pad (2).

[0040] An optical sensor head (32), comprising the tip of a light-transmitting optical fiber cable (51) and the tip of a light-receiving optical fiber cable (56), emits light toward a workpiece W through a space (60) and a transparent window (33), and 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 is, for example, made of a transparent resin.

[0041] The polishing device is equipped with 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-conducting material, and a water cooling device. Examples of the cooling element include a Peltier element. Examples of the heat-conducting material include metals such as copper, aluminum, and stainless steel.

[0042] In the embodiment illustrated in FIG. 3, a Peltier element is used in a cooling device (63). A part of the Peltier element constituting the cooling device (63) is located within the space (60), and another part is located on a polishing table (3). More specifically, the cooling surface (63a) of the Peltier element is exposed within the space (60), and the heat dissipation surface (63b) of the Peltier element is placed within the polishing table (3).

[0043] Although not illustrated, in one embodiment, a cooling device (63) may be configured by contacting the cooling surface (63b) of at least one cooling element (e.g., a Peltier element) to the heat dissipation surface (63b) of a cooling element (in this embodiment, a Peltier element) constituting the cooling device (63) illustrated in FIG. 3, thereby having a plurality of stacked cooling elements. The plurality of stacked cooling elements can sequentially transfer heat within the space (60). In another embodiment, a water cooling device may be contacted to the heat dissipation surface (63b) of a cooling element constituting the cooling device (63) illustrated in FIG. 3.

[0044] A cooling device (63) is connected to an 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) is equipped with a memory device (65a) in which a program is stored, and an arithmetic unit (65b) that executes operations according to instructions included in the program. The operation control unit (65) is composed of at least one computer. The memory device (65a) is equipped with 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 drive (SSD). Examples of the arithmetic unit (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.

[0045] During the polishing of workpiece W, the polishing pad (2) becomes hot due to friction between the polishing pad (2) and the workpiece W. After polishing the workpiece W, pure water is supplied from the pure water supply nozzle (8) to the polished surface (2a) of the polishing pad (2) for purposes such as cleaning the polished surface of the workpiece W, cleaning the polishing pad (2), or dressing 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 that occurs on the inner surface (33a) of the transparent window (33) obstructs the passage of light, thereby reducing the precision of the film thickness measurement during the polishing of the next workpiece.

[0046] Accordingly, 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 within the space (60) is lowered, and as a result, condensation is prevented on the inner surface (33a) of the transparent window (33) facing the space (60).

[0047] The operation control unit (65) is configured to initiate the cooling operation of the cooling device (63) after polishing the workpiece W. For example, after polishing the workpiece W, and before or simultaneously with the supply of pure water to the polishing pad (2), the operation control unit (65) initiates the cooling operation of the cooling device (63).

[0048] In one embodiment, the operation control unit (65) may be configured to initiate the cooling operation of the cooling device (63) during the polishing of the workpiece W. During the polishing of the workpiece W, the temperature inside the space (60) rises due to the frictional heat between the polishing pad (2) and the workpiece W. When the temperature inside 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 polishing 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 lowering the temperature inside the space (60) (i.e., the dew point temperature). By such operation, condensation on the inner surface (33a) of the transparent window (33) facing the space (60) can be prevented when the transparent window (33) is cooled by pure water after polishing the workpiece W.

[0049] FIG. 4 is a cross-sectional view illustrating another embodiment of the arrangement of the transparent window (33) and the optical sensor head (32). The configuration and operation of the present embodiment, which are not specifically described, are identical to the embodiment described with reference to FIG. 3, so the redundant description is omitted. In the embodiment shown in FIG. 4, the polishing device is equipped with a pad surface temperature measuring device (67) for measuring the temperature of the polishing surface (2a) (and the transparent window (33)) of the polishing pad (2), and an internal temperature measuring device (68) for measuring the temperature within the space (60).

[0050] The pad surface temperature measuring device (67) is a non-contact temperature sensor positioned above the polishing pad (2). For example, an infrared temperature sensor may be used as the pad surface temperature measuring device (67). The internal temperature measuring device (68) is positioned within the space (60). As long as the internal temperature measuring device (68) can measure the temperature within the space (60), the positioning and configuration of the internal temperature measuring device (68) are not particularly limited.

[0051] 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 within 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 values ​​of the temperature of the polishing surface (2a) and the temperature within the space (60). More specifically, the operation control unit (65) calculates the temperature difference by subtracting the measured value of the temperature within the space (60) from the measured value of the temperature of the polishing surface (2a), and controls the cooling operation of the cooling device (63) so that the temperature difference is maintained above a threshold.

[0052] Through such cooling operation, the temperature within the space (60) is always maintained lower than the temperature of the polishing surface (2a), thereby preventing condensation on the inner surface (33a) of the transparent window (33) facing the space (60). Since the threshold for preventing condensation is likely to depend on the environment in which the polishing device is placed, the threshold may be determined from condensation observation data obtained during past polishing.

[0053] FIG. 5 is a schematic diagram illustrating another embodiment of the cooling device (63). The configuration and operation of this embodiment, which are not specifically described, are identical to the embodiment described with reference to FIG. 3, so the redundant description is omitted. In this embodiment, a combination of a cooling element (73) and a heat-conducting material (75) is used as the cooling device (63). More specifically, the entire cooling element (73) is positioned below the space (60) and is outside the space (60). The heat-conducting material (75) is in contact with the cooling surface (73a) of the cooling element (73). A part of the heat-conducting material (75) is located within the space (60), and another part is located within the grinding table (3). More specifically, a part of the heat-conducting material (75) is exposed within the space (60), and the cooling surface (63a) of the cooling device (63) is composed of the exposed surface of the heat-conducting material (75). Examples of cooling elements (73) include Peltier elements, and examples of heat-conducting materials (75) include metals such as copper, aluminum, and stainless steel.

[0054] According to the embodiment illustrated in FIG. 5, the heat-conducting material (75) is cooled by the cooling element (73), and the space (60) is cooled by the heat-conducting material (75). Since the entire cooling element (73), such as a Peltier element, is embedded within the polishing table (3), there is an advantage that heat dissipated from the cooling element (73) is difficult to transfer to the space (60).

[0055] Although not illustrated, in one embodiment, a cooling device (63) may be configured having a plurality of stacked cooling elements by contacting the cooling surface of at least one cooling element to the heat dissipation surface (73b) of a cooling element (73). The stacked plurality of cooling elements can sequentially transfer heat within the space (60). In another embodiment, a water cooling device may be contacted to the heat dissipation surface (73b) of a cooling element (73).

[0056] FIG. 6 is a schematic diagram illustrating another embodiment of a cooling device (63). Since the configuration and operation of this embodiment, which is not specifically described, are identical to the embodiment described with reference to FIG. 3, the redundant description thereof is omitted. In this embodiment, a water cooling device is used as the cooling device (63). More specifically, the cooling device (63) is provided with a cooling liquid channel (77) through which a cooling liquid, such as water, flows, and a heat-conducting material (78) in which at least a portion is exposed within the space (60). The cooling liquid channel (77) is located directly below the space (60) and extends within the heat-conducting material (78).

[0057] In this embodiment, a portion of the heat-conducting material (78) is located within the space (60), and another portion is located within the grinding table (3). In one embodiment, the entire heat-conducting material (78) may be located within the space (60). The cooling surface (63a) of the cooling device (63) is composed of the exposed surface of the heat-conducting material (78). The cooling liquid flowing through the cooling liquid channel (77) cools the heat-conducting material (78), and the heat-conducting material (78) can cool the space (60).

[0058] A flow control valve (79) is provided in the coolant passage (77), and the flow rate of the coolant flowing through the coolant passage (77) is controlled by the flow control valve (79). The flow control valve (79) is electrically connected to an operation control unit (65), and the operation of the flow control valve (79) is controlled by the operation control unit (65).

[0059] The embodiment described with reference to FIG. 4 is applicable to the embodiment described with reference to FIG. 5 and FIG. 6.

[0060] FIG. 7 is a cross-sectional view illustrating another embodiment of the arrangement of the transparent window (33) and the optical sensor head (32). Since the configuration and operation of the present embodiment, which are not specifically described, are identical to the embodiment described with reference to FIG. 4, the redundant description thereof is omitted. In the embodiment shown in FIG. 7, the polishing device is equipped with a dehumidifying device (85) that lowers the humidity in the space (60). The dehumidifying device (85) is positioned within the space (60). Specific examples of the dehumidifying device (85) include a dehumidifying element equipped with a solid polymer electrolyte membrane, a dry gas dehumidifying device that supplies dry gas into the space (60), a dehumidifying agent such as silica gel, or a combination thereof.

[0061] In this embodiment, the dehumidification device (85) is composed of a dehumidification element having a solid polymer electrolyte membrane. The dehumidification device (85) is connected to an operation control unit (65), and the dehumidification operation of the dehumidification device (85) is controlled by the operation control unit (65). Since the dehumidification device (85) can remove moisture within the space (60), it can prevent condensation on the inner surface (33a) of the transparent window (33) facing the space (60).

[0062] In one embodiment, as illustrated in FIG. 8, the polishing device may further be equipped with a humidity measuring device (86) for measuring humidity within a space (60). The humidity measuring device (86) is positioned within the space (60). The humidity measuring device (86) is connected to an operation control unit (65), and the measured value of humidity within the space (60) is transmitted to the operation control unit (65). The operation control unit (65) is configured to control the dehumidification operation of the dehumidification device (85) based on the measured value of humidity within the space (60).

[0063] FIG. 9 is a schematic diagram illustrating another embodiment of a dehumidification device (85). In this embodiment, the dehumidification device (85) is equipped with a combination of a dry gas dehumidification device and a dehumidifying agent. More specifically, the dehumidification device (85) has a dry gas circulation line (90) through which dry gas, such as air, flows, a dehumidifying agent (92) provided within the dry gas circulation line (90), and a fan (95) that transports the dry gas within the dry gas circulation line (90). An example of the dehumidifying agent (92) is silica gel.

[0064] The dry gas circulation line (90) is open in the space (60) and is connected to the space (60). When the fan (95) is driven, dry gas such as air flows into the space (60) from the dry gas circulation line (90), fills the space (60), and flows into the dry gas circulation line (90) from the space (60). The dry gas flowing through the space (60) comes into contact with the dehumidifier (92) and is dehumidified. The dehumidified dry gas flows back into the space (60) from the dry gas circulation line (90). In this way, the dry gas circulates between the space (60) and the dehumidifier (92). In one embodiment, a dehumidification element equipped with a solid polymer electrolyte membrane may be provided instead of the dehumidifier (92).

[0065] The embodiment described with reference to FIG. 8 can be applied to the embodiment described with reference to FIG. 9. The embodiment described with reference to FIG. 7 to 9 may be combined with any of the embodiments described with reference to FIG. 3 to 6.

[0066] In the embodiment described so far, the polishing device is equipped with one set of transparent windows (33) and an optical sensor head (32), but the polishing device may be equipped with multiple sets of transparent windows (33) and optical sensor heads (32).

[0067] The above-described embodiments are described for the purpose of enabling a person skilled in the art to practice the present invention. Various modifications of the above embodiments are naturally achievable by those skilled in the art, and the technical concept of the present invention may be applied to other embodiments. Accordingly, the present invention is not limited to the described embodiments but is interpreted within the broadest scope according to the technical concept defined by the claims. Explanation of the symbols

[0068] W: Workpiece 1: Grinding head 2: Polishing pad 2a: Polished surface 3: Grinding table 5: Polishing fluid supply nozzle 6: Table motor 8: Pure water supply nozzle 10: Head shaft 17: Connection device 18: Grinding head motor 20: Film thickness measuring device 22: Light source 32: Optical sensor head 33: Transparent window 34: Passage hole 40: Spectrometer 41: Photodetector 45: Spectrum processing unit 45a: Memory device 45b: Arithmetic Unit 51: Light-transmitting optical fiber cable 56: Optical fiber cable for light reception 60: Space 63: Cooling device 65: Operation control unit 65a: Memory device 65b: Arithmetic Unit 67: Pad surface temperature measuring device 68: Internal temperature measuring device 73: Cooling element 75: Thermal conductive materials 77: Coolant flow path 78: Thermal Conductive Materials 79: Flow control valve 85: Dehumidification device 86: Humidity measuring device 90: Dry gas circulation line 92: Dehumidifier 95: Fan

Claims

Claim 1 A polishing device comprising: a polishing pad having a polishing surface; a polishing head for pressing a workpiece into contact with the polishing surface; a transparent window disposed within the polishing pad; a polishing table supporting the polishing pad; an optical sensor head disposed below the transparent window for guiding light to the workpiece through the transparent window and receiving reflected light from the workpiece through the transparent window; a cooling device for cooling the 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; and an operation control unit for controlling the cooling operation of the cooling device, wherein the operation control unit calculates a temperature difference by subtracting the temperature within the space from the temperature of the polishing surface, and controls the cooling operation of the cooling device so that the temperature difference is maintained above a threshold. Claim 2 A polishing device 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. Claim 3 A polishing device comprising: 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 onto the polishing surface; a transparent window disposed within the polishing pad; a polishing table supporting the polishing pad; an optical sensor head disposed below the transparent window for guiding light to the workpiece through the transparent window and receiving reflected light from the workpiece through the transparent window; a cooling device for cooling the space between the transparent window and the optical sensor head; and an operation control unit for controlling the cooling operation of the cooling device, wherein the operation control unit is configured to initiate 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 polishing surface. Claim 4 A polishing method comprising: polishing a workpiece by pressing it against the polishing surface of a polishing pad; guiding light from an optical sensor head to the workpiece through a transparent window disposed within the polishing pad during the polishing of the workpiece; receiving reflected light from the workpiece through the transparent window to the optical sensor head; measuring the temperature in the space between the transparent window and the optical sensor head and the temperature of the polishing surface; calculating a temperature difference by subtracting the temperature in the space from the temperature of the polishing surface; and cooling the space by a cooling device so that the temperature difference is maintained above a threshold. Claim 5 In paragraph 4, the above cooling device cools the space so that the temperature within the space is maintained lower than the temperature of the polishing surface, in a polishing method. Claim 6 A polishing method comprising: polishing a workpiece by pressing it against the polishing surface of a polishing pad; guiding light from an optical sensor head to the workpiece through a transparent window disposed within the polishing pad during the polishing of the workpiece; receiving reflected light from the workpiece through the transparent window to the optical sensor head; supplying pure water to the polishing surface from a pure water supply nozzle after polishing the workpiece; and cooling the space between the transparent window and the optical sensor head by a cooling device after polishing the workpiece and before or simultaneously with the supply of pure water to the polishing surface from the pure water supply nozzle. Claim 7 delete Claim 8 delete Claim 9 delete Claim 10 delete Claim 11 delete Claim 12 delete Claim 13 delete

Images