Polishing apparatus and polishing method

Abstract

The present invention provides a polishing apparatus that can maintain the liquid used for measuring film thickness in a clean state and accurately measure film thickness. [Solution] The polishing apparatus comprises a polishing pad 2 having a polishing surface 2a, a polishing head 1 that presses a workpiece W against the polishing surface 2a, a polishing table 3 that supports the polishing pad 2, an optical sensor head 22 that guides light to the workpiece W through a through hole 34 formed in the polishing pad 2 and receives reflected light from the workpiece W through the through hole 34, a tank 50 that stores the liquid supplied to the through hole 34, a liquid circulation line 45 for circulating the liquid between the through hole 34 and the tank 50, and an ultraviolet irradiation head 55 that irradiates the liquid flowing through the liquid circulation line 45 with ultraviolet light to sterilize the liquid.

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 the workpiece based on optical information contained 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 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 planarization, chemical mechanical polishing (CMP) is used.

[0003] Chemical mechanical polishing (CMP) is performed by a polishing apparatus. This polishing apparatus is configured to polish the surface of the wafer by bringing the wafer into sliding contact with a polishing pad while supplying a polishing liquid to the polishing pad attached on a polishing table. The polishing of the wafer is terminated when the thickness of the film (insulating film, metal film, silicon layer, etc.) constituting its surface reaches a predetermined target value. Therefore, the film thickness is measured during the polishing of the wafer.

[0004] In order to measure the thickness of a film such as an insulating film or a silicon layer (hereinafter simply referred to as the 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 with the sensor head, and analyzing the spectrum of the reflected light.

[0005] During wafer polishing, polishing fluid and debris are present on the polishing pad. If the polishing fluid and debris adhere to the sensor head or other components, the intensity of the light irradiated onto the wafer and the intensity of the reflected light from the wafer decrease, making it impossible to accurately measure the film thickness. Therefore, there is a technique that supplies pure water from within the polishing table into through-holes to ensure a clear path for light. The through-holes are filled with pure water, and the polishing fluid and debris that enter the through-holes are discharged along with the pure water through a drain line. The flow of pure water formed in the through-holes ensures a clear path for light, enabling highly accurate film thickness measurement. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2017-220683 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, if foreign matter originating from fungi in pure water adheres to optical systems such as sensor heads, it can reduce the accuracy of film thickness measurement. Furthermore, such foreign matter can clog the pure water supply and drain lines. Additionally, if fungi adhere to the polishing pad, the device surface of the wafer may become contaminated.

[0008] Therefore, the present invention provides a polishing apparatus and polishing method that can keep the liquid used for measuring film thickness clean and measure the film thickness with high accuracy. [Means for solving the problem]

[0009] In one embodiment, a polishing apparatus is provided, comprising: a polishing pad having a polishing surface; a polishing head for pressing a workpiece against the polishing surface; a polishing table for supporting the polishing pad; an optical sensor head for guiding light to the workpiece through through holes formed in the polishing pad and receiving reflected light from the workpiece through the through holes; a tank for storing liquid supplied to the through holes; a liquid circulation line for circulating the liquid between the through holes and the tank; and an ultraviolet irradiation head for sterilizing the liquid by irradiating the liquid flowing through the liquid circulation line with ultraviolet light. In one embodiment, the polishing apparatus further comprises a light source connected to the optical sensor head and emitting light, and an optical member that reflects a portion of the light emitted from the light source, including ultraviolet light, and the ultraviolet irradiation head is connected to the optical member and configured to irradiate the liquid flowing through the liquid circulation line with the portion of the light reflected by the optical member. In one embodiment, the optical element is one of a UV-reflecting filter, a dichroic mirror, and a half-mirror. In one embodiment, the polishing apparatus further comprises a first light source connected to the optical sensor head and emitting light, and a second light source connected to the ultraviolet irradiation head and emitting light including ultraviolet light.

[0010] In one embodiment, the polishing apparatus further comprises an ozone supply device that supplies ozone to the liquid in the tank to sterilize the liquid in the tank. In one embodiment, the optical sensor head is further connected to a light source that emits light, and an ozone collection device that collects ozone generated from ultraviolet light contained in the light emitted from the light source, wherein the ozone collection device is connected to an ozone supply device and is configured to send the collected ozone to the ozone supply device. In one embodiment, the polishing apparatus further comprises a first light source connected to the optical sensor head and emitting light, a second light source connected to the ultraviolet irradiation head and emitting light including ultraviolet light, and an ozone collection device for collecting ozone generated from the ultraviolet light contained in the light emitted from the second light source, wherein the ozone collection device is connected to the ozone supply device and is configured to send the collected ozone to the ozone supply device. In one embodiment, the polishing apparatus further comprises a transparent window fitted into the through hole, and the optical sensor head is configured to guide the light to the workpiece through the through hole and the transparent window, and to receive the reflected light from the workpiece through the transparent window and the through hole.

[0011] In one embodiment, a polishing apparatus is provided, comprising: a polishing pad having a polishing surface; a polishing head for pressing a workpiece against the polishing surface; a polishing table for supporting the polishing pad; an optical sensor head for guiding light to the workpiece through through holes formed in the polishing pad and receiving reflected light from the workpiece through the through holes; a liquid supply line communicating with the through holes for supplying liquid to the through holes; a drain line communicating with the through holes for discharging the liquid from the through holes; and an ultraviolet irradiation head for sterilizing the liquid by irradiating the liquid flowing through the liquid supply line with ultraviolet light. In one embodiment, the polishing apparatus further comprises a light source connected to the optical sensor head and emitting light, and an optical member that reflects a portion of the light emitted from the light source, including ultraviolet light, and the ultraviolet irradiation head is connected to the optical member and configured to irradiate the liquid flowing through the liquid circulation line with the portion of the light reflected by the optical member. In one embodiment, the optical element is one of a UV-reflecting filter, a dichroic mirror, and a half-mirror. In one embodiment, the polishing apparatus further comprises a first light source connected to the optical sensor head and emitting light, and a second light source connected to the ultraviolet irradiation head and emitting light including ultraviolet light. In one embodiment, the polishing apparatus further comprises a transparent window fitted into the through hole, and the optical sensor head is configured to guide the light to the workpiece through the through hole and the transparent window, and to receive the reflected light from the workpiece through the transparent window and the through hole.

[0012] In one embodiment, a polishing method is provided, in which a workpiece is pressed against the polishing surface of a polishing pad to polish the workpiece, light is guided from an optical sensor head to the workpiece through through holes formed in the polishing pad during the polishing of the workpiece, reflected light from the workpiece is received by the optical sensor head through the through holes, the liquid is circulated through a liquid circulation line between the through holes and a tank that stores the liquid, and the liquid flowing through the liquid circulation line is irradiated with ultraviolet light by an ultraviolet irradiation head to sterilize the liquid. In one embodiment, light emitted from a light source is transmitted to the optical sensor head, thereby guiding the light from the optical sensor head to the workpiece. A portion of the light emitted from the light source, including ultraviolet light, is reflected by an optical element, and this portion of the light is transmitted to the ultraviolet irradiation head, thereby irradiating the liquid flowing through the liquid circulation line with ultraviolet light. In one embodiment, the optical element is one of a UV-reflecting filter, a dichroic mirror, and a half-mirror.

[0013] In one embodiment, the polishing method further includes, during idling when the workpiece is not being polished, reflecting a portion of the light emitted from the light source with the optical member and transmitting the portion of the light to the ultraviolet irradiation head, thereby irradiating the liquid flowing through the liquid circulation line with ultraviolet light. In one embodiment, light emitted from a first light source is transmitted to the optical sensor head, thereby guiding the light from the optical sensor head to the workpiece, and during the polishing of the workpiece, light including ultraviolet light emitted from a second light source is transmitted to the ultraviolet irradiation head, thereby irradiating the liquid flowing through the liquid circulation line with ultraviolet light. In one embodiment, the polishing method further includes transmitting the light emitted from the second light source to the ultraviolet irradiation head during idling when the workpiece is not being polished, thereby irradiating the liquid flowing through the liquid circulation line with ultraviolet light.

[0014] In one embodiment, the polishing method further includes supplying ozone to the liquid in the tank to sterilize the liquid in the tank. In one embodiment, light emitted from a light source is transmitted to the optical sensor head, thereby guiding the light from the optical sensor head to the workpiece, and the polishing method further includes collecting ozone generated from ultraviolet light contained in the light emitted from the light source, wherein the ozone supplied to the liquid in the tank is the collected ozone. In one embodiment, light emitted from a first light source is transmitted to the optical sensor head, thereby guiding the light from the optical sensor head to the workpiece; light containing ultraviolet light emitted from a second light source is transmitted to the ultraviolet irradiation head, thereby irradiating the liquid flowing through the liquid circulation line with the ultraviolet light; the polishing method further includes collecting ozone generated from the ultraviolet light contained in the light emitted from the second light source, and the ozone supplied to the liquid in the tank is the collected ozone. In one embodiment, guiding the light from the optical sensor head to the workpiece through the through-hole and receiving the reflected light at the optical sensor head through the through-hole is equivalent to guiding the light from the optical sensor head to the workpiece through the through-hole and a transparent window fitted into the through-hole, and receiving the reflected light at the optical sensor head through the transparent window and the through-hole.

[0015] In one embodiment, a polishing method is provided, which involves pressing a workpiece against the polishing surface of a polishing pad to polish the workpiece, guiding light from an optical sensor head to the workpiece through through holes formed in the polishing pad during polishing, receiving reflected light from the workpiece through the through holes with the optical sensor head, supplying liquid to the through holes through a liquid supply line, discharging the liquid from the through holes through a drain line, and sterilizing the liquid by irradiating the liquid flowing through the liquid supply line with ultraviolet light using an ultraviolet irradiation head. In one embodiment, light emitted from a light source is transmitted to the optical sensor head, thereby guiding the light from the optical sensor head to the workpiece. A portion of the light emitted from the light source, including ultraviolet light, is reflected by an optical element, and this portion of the light is transmitted to the ultraviolet irradiation head, thereby irradiating the liquid flowing through the liquid circulation line with ultraviolet light. In one embodiment, the optical element is one of a UV-reflecting filter, a dichroic mirror, and a half-mirror. In one embodiment, the polishing method further includes, during idling when the workpiece is not being polished, reflecting a portion of the light emitted from the light source with the optical member and transmitting the portion of the light to the ultraviolet irradiation head, thereby irradiating the liquid flowing through the liquid circulation line with ultraviolet light.

[0016] In one aspect, the light emitted from the first light source is transmitted to the optical sensor head, so that the light is guided from the optical sensor head to the workpiece. During the polishing of the workpiece, the light including ultraviolet light emitted from the second light source is transmitted to the ultraviolet irradiation head, so that the ultraviolet irradiation head irradiates the liquid flowing through the liquid circulation line with the ultraviolet light. In one aspect, the polishing method further includes transmitting the light emitted from the second light source to the ultraviolet irradiation head during idling when the workpiece is not being polished, so that the ultraviolet irradiation head irradiates the liquid flowing through the liquid circulation line with the ultraviolet light. In one aspect, guiding the light from the optical sensor head to the workpiece through the through hole and receiving the reflected light by the optical sensor head through the through hole means guiding the light from the optical sensor head to the workpiece through the through hole and a transparent window fitted in the through hole, and receiving the reflected light by the optical sensor head through the transparent window and the through hole.

Advantages of the Invention

[0017] According to the present invention, the liquid used for film thickness measurement can be sterilized by irradiation with ultraviolet light and kept in a clean state. As a result, the film thickness of the workpiece can be measured with high accuracy.

Brief Description of the Drawings

[0018] [Figure 1] It is a schematic diagram showing an embodiment of a polishing apparatus. [Figure 2] It is a schematic diagram showing an enlarged view of the periphery of a film thickness measurement apparatus. [Figure 3] It is a diagram showing an example of a spectrum generated by a data processing unit. [Figure 4] It is a schematic diagram showing an enlarged view of the periphery of a film thickness measurement apparatus according to another embodiment of a polishing apparatus. [Figure 5] It is a schematic diagram showing an enlarged view of the periphery of a film thickness measurement apparatus according to still another embodiment of a polishing apparatus. [Figure 6] This is a schematic diagram showing yet another embodiment of the polishing apparatus. [Figure 7] This is a schematic diagram showing yet another embodiment of the polishing apparatus. [Figure 8] This is a schematic diagram showing yet another embodiment of the polishing apparatus. [Figure 9] This is a schematic diagram showing yet another embodiment of the polishing apparatus. [Modes for carrying out the invention]

[0019] Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a schematic diagram showing one embodiment of a polishing apparatus. As shown in Figure 1, the polishing apparatus includes 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 semiconductor devices against the polishing pad 2, a table motor 6 that rotates the polishing table 3, and a polishing liquid supply nozzle 8 for supplying a polishing liquid such as slurry onto the polishing pad 2. The upper surface of the polishing pad 2 constitutes a polishing surface 2a for polishing the workpiece W.

[0020] The polishing head 1 is connected to the head shaft 15, which is connected to the polishing head motor 18 via a coupling device 17. The configuration of the coupling device 17 is not particularly limited, but it can consist of a combination of pulleys and belts, a combination of gears, or a combination of sprockets and chains. The polishing head motor 18 rotates the polishing head 1 together with the head shaft 15 in the direction indicated by the arrow. The polishing table 3 is connected to the table motor 6, which is configured to rotate the polishing table 3 and the polishing pad 2 in the direction indicated by the arrow.

[0021] The polishing apparatus includes an operation control unit 10 that controls the operation of the polishing apparatus. The operation control unit 10 includes a storage device 10a in which a program is stored, and an arithmetic unit 10b that performs calculations according to the instructions contained in the program. The operation control unit 10 is composed of at least one computer. The storage device 10a includes a main memory such as random access memory (RAM) and an auxiliary storage device such as a hard disk drive (HDD) or solid state drive (SSD). Examples of arithmetic units 10b include a CPU (central processing unit) and a GPU (graphics processing unit). However, the specific configuration of the operation control unit 10 is not limited to these examples.

[0022] The polishing 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 25 that emits light, an optical sensor head 22 that irradiates the workpiece W with light from the light source 25 and receives reflected light from the workpiece W, a spectrometer 27 that generates intensity measurement data of the reflected light, and a data processing unit 40 that determines the film thickness of the workpiece W based on the intensity measurement data of the reflected light from the workpiece W. The optical sensor head 22 is connected to the light source 25 and the spectrometer 27. The spectrometer 27 is connected to the data processing unit 40.

[0023] The optical sensor head 22, light source 25, and spectrometer 27 are mounted on the polishing table 3 and rotate together with the polishing table 3 and polishing pad 2. The optical sensor head 22 is positioned facing the workpiece W held by the polishing head 1. The position of the optical sensor head 22 is such that it crosses the surface of the workpiece W on the polishing pad 2 each time the polishing table 3 and polishing pad 2 complete one rotation. The polishing apparatus includes a transparent window 33 fitted into a through hole 34 formed in the polishing pad 2. The transparent window 33 is positioned above the optical sensor head 22. The transparent window 33 rotates together with the polishing table 3.

[0024] Light emitted from the light source 25 is transmitted to the optical sensor head 22, and guided from the optical sensor head 22 to the surface of the workpiece W through the through-hole 34 and the transparent window 33. The light is reflected from the surface of the workpiece W, and the reflected light from the workpiece W is received by the optical sensor head 22 through the transparent window 33 and the through-hole 34 and sent to the spectrometer 27. The spectrometer 27 decomposes the reflected light according to its 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 27 to the data processing unit 40.

[0025] The data processing unit 40 generates a reflected light spectrum from the measurement data of the reflected light intensity. This spectrum shows the relationship between the reflected light intensity and wavelength, and the shape of the spectrum changes according to the film thickness of the workpiece W. The data processing unit 40 calculates the film thickness of the workpiece W from the spectrum. The data processing unit 40 is electrically connected to the operation control unit 10, and the calculated film thickness of the workpiece W is sent to the operation control unit 10.

[0026] The data processing unit 40 comprises a storage device 40a in which a program is stored, and an arithmetic unit 40b that performs calculations according to the instructions contained in the program. The data processing unit 40 is composed of at least one computer. The storage device 40a comprises a main memory such as random access memory (RAM) and an auxiliary storage device such as a hard disk drive (HDD) or solid state drive (SSD). Examples of arithmetic units 40b include a CPU (central processing unit) and a GPU (graphics processing unit). However, the specific configuration of the data processing unit 40 is not limited to these examples.

[0027] The workpiece W is polished as follows: While the polishing table 3 and polishing head 1 are rotated in the direction indicated by the arrows in Figure 1, polishing fluid is supplied from the polishing fluid supply nozzle 8 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 against the polishing surface 2a of the polishing pad 2 by the polishing head 1 while the polishing fluid is present on the polishing pad 2. The surface of the workpiece W is polished by the chemical action of the polishing fluid and the mechanical action of the abrasive grains contained in the polishing fluid and / or the polishing pad 2.

[0028] During polishing of the workpiece W, the optical sensor head 22 traverses the surface of the workpiece W on the polishing pad 2 each time the polishing table 3 rotates, irradiating light onto measurement points on the workpiece W and receiving reflected light from the workpiece W. The data processing unit 40 calculates the film thickness of the workpiece W from the measured data of the intensity of the reflected light. The operation control unit 10 determines the polishing endpoint based on the calculated film thickness.

[0029] The details of the film thickness measuring device 20 are described below. Figure 2 is a schematic diagram showing an enlarged view of the area around the film thickness measuring device 20. The film thickness measuring device 20 includes a light-emitting optical fiber cable 37 that guides light emitted from the light source 25 to the surface of the workpiece W, and a light-receiving optical fiber cable 38 that receives reflected light from the workpiece W and sends the reflected light to the spectrometer 27. The light-emitting optical fiber cable 37 is an optical transmission unit that guides light emitted from the light source 25 to the surface of the workpiece W. The light-receiving optical fiber cable 38 is an optical transmission unit that sends reflected light from the workpiece W to the photodetector 28.

[0030] The ends of the light-emitting optical fiber cable 37 and the light-receiving optical fiber cable 38 are located inside the polishing table 3. The other end of the light-emitting optical fiber cable 37 is connected to the light source 25, and the other end of the light-receiving optical fiber cable 38 is connected to the spectrometer 27. More specifically, the light-emitting optical fiber cable 37 has a first light-emitting optical fiber cable 37a that extends from the light source 25 to the optical splitter 64 (described later), and a second light-emitting optical fiber cable 37b that extends from the optical splitter 64 to inside the polishing table 3. The first light-emitting optical fiber cable 37a is an optical transmission section that guides the light emitted by the light source 25 to the optical splitter 64, and the second light-emitting optical fiber cable 37b is an optical transmission section that guides the light branched from the first light-emitting optical fiber cable 37a by the optical splitter 64 to the surface of the workpiece W. The optical sensor head 22 consists of the tip of the light-emitting optical fiber cable 37 (the tip of the second light-emitting optical fiber cable 37b) and the tip of the light-receiving optical fiber cable 38.

[0031] The polishing table 3 has a first hole 35A and a second hole 35B that open on its upper surface. The polishing pad 2 also has through holes 34 formed at positions corresponding to these holes 35A and 35B, and the holes 35A and 35B communicate with the through holes 34. The transparent window 33 is fitted over the through holes 34. Therefore, the top of the through holes 34 is closed by the transparent window 33. The outer surface of the transparent window 33 is slightly lower than the polishing surface 2a of the polishing pad 2. The optical sensor head 22 is positioned in the first hole 35A and below the through holes 34.

[0032] The optical sensor head 22 is configured to guide light emitted from the light source 25 to the workpiece W through the through-hole 34 and the transparent window 33, and to receive reflected light from the workpiece W through the transparent window 33 and the through-hole 34. The transparent window 33 is made of a light-transmitting material. The material of the transparent window 33 is not particularly limited, but for example, it is made of a transparent resin. The transparent window 33 can prevent polishing liquid and polishing debris from coming into contact with the optical sensor head 22.

[0033] As will be explained in detail later, during the polishing of the workpiece W, liquid is supplied to the through-hole 34, and the through-hole 34 is filled with liquid. An example of the liquid supplied to the through-hole 34 is pure water. However, the liquid is not particularly limited to this example, as long as it is a light-transmitting liquid. The difference between the refractive index of the liquid and the refractive index of the transparent window 33 is smaller than the difference between the refractive index of a gas such as air and the refractive index of the transparent window 33. Therefore, by filling the through-hole 34 with liquid, the refraction of light at the interface between the through-hole 34 and the transparent window 33 can be suppressed compared to the case where the through-hole 34 is filled with a gas such as air.

[0034] A pulsed-on light source such as a xenon flash lamp is used as the light source 25. The light emitted from the light source 25 includes ultraviolet light. The light source 25 is connected to the operation control unit 10, and the operation of the light source 25 is controlled by the operation control unit 10. The spectrometer 27 is equipped with a photodetector 28. In one embodiment, the photodetector 28 is composed of a photodiode, CCD, CMOS, or InGaAs (indium gallium arsenide) sensor. The optical sensor head 22 is optically connected to the light source 25 and the photodetector 28. The photodetector 28 is electrically connected to the data processing unit 40.

[0035] The data processing unit 40 is configured to generate a spectrum of reflected light from the workpiece W using intensity measurement data of the reflected light sent from the spectrometer 27. The spectrum of reflected light is represented as a line graph (i.e., spectral 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 reflectance or relative reflectance.

[0036] Figure 3 shows an example of a spectrum generated by the data processing unit 40. The spectrum is represented as a line graph (i.e., spectral waveform) showing the relationship between the wavelength and intensity of light. In Figure 3, 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 index value indicating 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, unwanted noise such as variations in intensity inherent to the optical system or light source of the device can be removed from the measured intensity.

[0037] In the example shown in Figure 3, the spectrum of the reflected light is a spectral waveform that shows the relationship between the relative reflectance and the wavelength of the reflected light. However, the spectrum of the reflected light may also be a spectral waveform that shows the relationship between the intensity of the reflected light itself and the wavelength of the reflected light.

[0038] The data processing unit 40 receives intensity measurement data of reflected light from the workpiece W while the polishing table 3 rotates once, and generates a reflected light spectrum from this intensity measurement data. The data processing unit 40 is configured to determine the film thickness of the workpiece W from the reflected light spectrum. Known techniques are used to determine the film thickness of the workpiece W based on the spectrum. For example, the data processing unit 40 determines a reference spectrum from a reference spectrum library that has the shape closest to the reflected light spectrum, and determines the film thickness associated with this determined reference spectrum. In another example, the data processing unit 40 performs a Fourier transform on the reflected light spectrum and determines the film thickness from the resulting frequency spectrum.

[0039] As shown in Figure 1, the polishing apparatus further includes a tank 50 for storing the liquid supplied to the through hole 34, a liquid circulation line 45 for circulating the liquid between the through hole 34 and the tank 50, and a pump 52 for circulating the liquid. The liquid circulation line 45 includes a liquid supply pipe 46 for supplying liquid from the tank 50 to the through hole 34 and a liquid return pipe 47 for returning the liquid from the through hole 34 to the tank 50.

[0040] The liquid circulation line 45 is connected to the first hole 35A and the second hole 35B. More specifically, one end of the liquid supply pipe 46 of the liquid circulation line 45 is connected to the first hole 35A, and the other end of the liquid supply pipe 46 is connected to the tank 50. One end of the liquid return pipe 47 is connected to the second hole 35B, and the other end of the liquid return pipe 47 is connected to the tank 50. The liquid supply pipe 46 and the liquid return pipe 47 of the liquid circulation line 45 are in communication with the through hole 34.

[0041] Pump 52 is located in the liquid supply piping 46. Liquid in the tank 50 is supplied by pump 52 through the liquid supply piping 46 to the first hole 35A and the through hole 34, filling the through hole 34 and the first hole 35A with liquid. The liquid in the through hole 34 flows into the second hole 35B and is returned to the tank 50 through the liquid return piping 47. In this embodiment, since the through hole 34 is closed by the transparent window 33, the liquid circulates between the through hole 34 and the tank 50 through the liquid circulation line 45.

[0042] The pump 52 is connected to the operation control unit 10, and the operation of the pump 52 is controlled by the operation control unit 10. During operation of the polishing apparatus, the operation control unit 10 is configured to drive the pump 52 to circulate the liquid between the through hole 34 and the tank 50. Operation of the polishing apparatus refers to the period during which the polishing apparatus is running, including during polishing of the workpiece W and during idling when the workpiece W is not being polished. In one embodiment, the operation of the pump 52 may be controlled manually.

[0043] The polishing apparatus further includes a liquid exchange line 81 connected to the tank 50, a supply line 82 connected to the liquid exchange line 81, and a discharge line 83 connected to the liquid exchange line 81. A first on-off valve 85 and a second on-off valve 86 are installed on the supply line 82 and the discharge line 83, respectively. During operation of the polishing apparatus, the first on-off valve 85 and the second on-off valve 86 are closed.

[0044] The liquid exchange line 81 is used when replacing or replenishing the liquid in the tank 50. The supply line 82 is connected to a liquid supply source (not shown). When the first on-off valve 85 is opened with the second on-off valve 86 closed, liquid is supplied from the liquid supply source to the tank 50 through the supply line 82 and the liquid exchange line 81. When the second on-off valve 86 is opened with the first on-off valve 85 closed, the liquid in the tank 50 is discharged through the liquid exchange line 81 and the discharge line 83.

[0045] With this configuration, the amount of liquid used can be reduced by returning the liquid supplied to the through-hole 34 to the tank 50 and circulating the liquid, resulting in cost savings. However, if the liquid is circulated for a long time, fungi (e.g., bacteria and mold) in the liquid may proliferate, generating foreign matter derived from the fungi. Such foreign matter may adhere to optical systems such as the optical sensor head 22 and the transparent window 33, reducing the accuracy of film thickness measurement or clogging the piping of the liquid circulation line 45. Furthermore, if fungi adhere to the polishing pad 2, the device surface of the workpiece W may become contaminated. Therefore, the polishing apparatus of this embodiment is configured to sterilize the liquid.

[0046] The polishing apparatus further includes an ultraviolet irradiation head 55 that irradiates the liquid flowing through the liquid circulation line 45 with ultraviolet light to sterilize the liquid flowing through the liquid circulation line 45. In this embodiment, the ultraviolet irradiation head 55 is attached to the liquid supply pipe 46 of the liquid circulation line 45 and is configured to sterilize the liquid flowing through the liquid supply pipe 46 by irradiating it with ultraviolet light.

[0047] The polishing apparatus includes an optical fiber cable 65 that branches off from the light-emitting optical fiber cable 37, and an optical splitter 64 that branches the optical fiber cable 65 from the light-emitting optical fiber cable 37. More specifically, the optical splitter 64 is configured to branch the first light-emitting optical fiber cable 37a of the light-emitting optical fiber cable 37 into a second light-emitting optical fiber cable 37b and an optical fiber cable 65. Examples of optical splitters 64 include optical couplers and optical splitters. However, the method of branching the optical fiber cable 65 from the light-emitting optical fiber cable 37 is not limited to these embodiments using an optical splitter 64. For example, the first light-emitting optical fiber cable 37a may consist of a bundle of multiple optical fiber cables, and the optical fiber cable 65 may consist of at least one optical fiber cable taken from this bundle of multiple optical fiber cables. The second light-emitting optical fiber cable 37b consists of the remaining optical fiber cables. In this case, the optical fiber cable 65 can be branched from the light-emitting optical fiber cable 37 without the need for an optical fiber splitter 64.

[0048] The optical fiber cable 65 is an optical transmission unit that transmits light emitted by the light source 25 and branched from the light-emitting optical fiber cable 37 to the liquid flowing through the liquid supply pipe 46. The ultraviolet irradiation head 55 includes the tip of the optical fiber cable 65 and a head case 67 that surrounds a portion of the liquid supply pipe 46. The head case 67 is configured to support the tip of the optical fiber cable 65. As shown in Figure 2, the liquid supply pipe 46 has an irradiation window 70 made of a material that transmits ultraviolet light. The tip of the optical fiber cable 65 is positioned facing the irradiation window 70. The head case 67 is positioned to surround the irradiation window 70.

[0049] In this embodiment, the light emitted from the light source 25 includes ultraviolet light. Therefore, the light transmitted to the ultraviolet irradiation head 55 through the optical fiber cable 65 includes ultraviolet light. The ultraviolet irradiation head 55 is configured to irradiate the liquid flowing through the liquid supply pipe 46 with ultraviolet light through the irradiation window 70. The liquid flowing through the liquid supply pipe 46 is sterilized by the ultraviolet light. As a result, the liquid used for measuring the film thickness of the workpiece W can be kept clean. In one embodiment, the ultraviolet irradiation head 55 may be attached to the liquid return pipe 47 of the liquid circulation line 45 and configured to sterilize the liquid flowing through the liquid return pipe 47 by irradiating it with ultraviolet light.

[0050] As shown in Figure 1, the polishing apparatus further includes an ozone supply device 60 that supplies ozone to the liquid in the tank 50 to sterilize the liquid in the tank 50, and an ozone collection device 62 that collects ozone generated from ultraviolet light contained in the light emitted from the light source 25. In this embodiment, the ozone supply device 60 is an aeration device placed inside the tank 50, and generates ozonated water by supplying ozone gas to the liquid in the tank 50. As a result, the liquid in the tank 50 is sterilized by ozone. Consequently, the liquid used for measuring the film thickness of the workpiece W can be kept clean.

[0051] The configuration of the ozone supply device 60 is not limited to this embodiment, as long as it can supply ozone to the liquid in the tank 50. In one embodiment, the ozone supply device 60 may be an ozone gas supply device for creating an ozone atmosphere inside the tank 50. By creating an ozone atmosphere inside the tank 50, ozone gas dissolves into the liquid in the tank 59, and ozonated water is produced.

[0052] The ozone supply device 60 is connected to an ozone gas supply line 73 extending from the ozone collection device 62. Ozone gas is supplied from the ozone collection device 62 to the ozone supply device 60 through the ozone gas supply line 73. The ozone collection device 62 is positioned to surround the light source 25. The light source 25 emits light including ultraviolet light, as described above. The ozone collection device 62 is configured to collect ozone generated when ultraviolet light emitted from the light source 25 irradiates an oxygen-containing gas (e.g., air).

[0053] The ozone collection device 62 is connected to a purge gas supply line 76 extending from a purge gas supply source (not shown). Purge gas is supplied to the ozone collection device 62 through the purge gas supply line 76, and the collected ozone is sent to the ozone supply device 60 as ozone gas. In one embodiment, instead of the ozone collection device 62, an ozone gas supply source may be provided, and ozone gas may be supplied from the ozone gas supply source to the ozone supply device 60.

[0054] In one embodiment, the liquid supply source connected to the supply line 82 is an ozonated water supply source, and ozonated water may be supplied to the tank 50 through the supply line 82 and the liquid exchange line 81. In this case, the polishing apparatus does not need to be equipped with an ozone supply device 60 and an ozone collection device 62.

[0055] The ozone supply device 60 is connected to the operation control unit 10, and the operation of the ozone supply device 60 is controlled by the operation control unit 10. During operation of the polishing machine, the operation control unit 10 is configured to drive the ozone supply device 60 to supply ozone to the liquid in the tank 50 to sterilize the liquid in the tank 50. In one embodiment, the operation of the ozone supply device 60 may be controlled manually.

[0056] As described above, while the workpiece W is being polished, the film thickness measuring device 20 measures the film thickness of the workpiece W. Specifically, while the workpiece W is being polished, the operation control unit 10 commands the light source 25 to emit light, causing the film thickness measuring device 20 to measure the film thickness of the workpiece W. When light is emitted from the light source 25, the light from the light source 25 is transmitted to the ultraviolet irradiation head 55 through the optical fiber cable 65, and ultraviolet light is irradiated onto the liquid flowing through the liquid supply pipe 46. Therefore, while the film thickness measuring device 20 is measuring the film thickness of the workpiece W, the ultraviolet irradiation head 55 irradiates ultraviolet light onto the liquid flowing through the liquid supply pipe 46. As a result, while the workpiece W is being polished, the liquid flowing through the liquid supply pipe 46 is sterilized by ultraviolet light.

[0057] In this embodiment, the operation control unit 10 is configured to issue a command to the light source 25 during idling, when the workpiece W is not being polished, to emit light from the light source 25 and cause the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply pipe 46 with ultraviolet light. Idling refers to the period, for example, from when the polished workpiece is removed from the polishing device until the next workpiece to be polished is brought into the polishing device and polishing begins, during which the operation of the polishing device continues. As a result, the liquid flowing through the liquid supply pipe 46 is sterilized by ultraviolet light not only during the polishing of the workpiece W but also during idling. The light emitted from the light source 25 during idling is also transmitted to the optical sensor head 22, but film thickness measurement is not performed.

[0058] In one embodiment, the operation control unit 10 may be configured to, during idling when the workpiece W is not being polished, issue a command to the light source 25 at predetermined time intervals to emit light from the light source 25, causing the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply pipe 46 with ultraviolet light at predetermined time intervals.

[0059] Figure 4 is a schematic diagram showing an enlarged view of the area surrounding the film thickness measuring device 20 according to another embodiment of the polishing apparatus. The configuration and operation of this embodiment, which are not specifically described, are the same as those of the embodiments described with reference to Figures 1 to 3, so redundant descriptions are omitted. In the embodiment shown in Figure 4, the polishing apparatus further includes an optical member 58 that reflects some of the light emitted from the light source 25, including ultraviolet light.

[0060] In this embodiment, the optical fiber cable 65 has a first optical fiber cable 65a that branches off from the light-emitting optical fiber cable 37 and a second optical fiber cable 65b that extends from the optical member 58. The first optical fiber cable 65a is an optical transmission section that guides the light emitted by the light source 25 and branched off from the light-emitting optical fiber cable 37 to the optical member 58, and the second optical fiber cable 65b is an optical transmission section that guides the reflected light from the optical member 58 to the liquid flowing through the liquid supply pipe 46. The ultraviolet irradiation head 55 includes the tip of the second optical fiber cable 65b of the optical fiber cable 65 and a head case 67 that surrounds a part of the liquid supply pipe 46.

[0061] The optical element 58 is positioned obliquely to the optical path of light emitted from the light source 25 and guided by the first optical fiber cable 65a. The optical element 58 is optically connected to the ultraviolet irradiation head 55. In this embodiment, the light emitted from the light source 25 includes ultraviolet light. The optical element 58 is configured to reflect some of the light emitted from the light source 25, including ultraviolet light, and transmit the remaining light. The light reflected by the optical element 58 is transmitted to the ultraviolet irradiation head 55. That is, the light reflected by the optical element 58 is guided to the liquid flowing through the liquid supply pipe 46 via the second optical fiber cable 65b of the optical fiber cable 65.

[0062] The optical element 58 is one of a UV-reflecting filter, a dichroic mirror, or a half-mirror. A UV-reflecting filter (for example, a non-absorbent UV-cut filter) is configured to reflect ultraviolet light and transmit other light. If the optical element 58 is a UV-reflecting filter, it reflects the ultraviolet light contained in the light emitted from the light source 25. The ultraviolet light reflected by the optical element 58 is transmitted to the UV irradiation head 55. The optical element 58 transmits light other than ultraviolet light from the light source 25.

[0063] A dichroic mirror is configured to reflect only light in a specific wavelength range and transmit light in other wavelength ranges. When the optical element 58 is a dichroic mirror, the optical element 58 reflects ultraviolet light as light in a specific wavelength range from the light source 25. The ultraviolet light reflected by the optical element 58 is transmitted to the ultraviolet irradiation head 55. The optical element 58 transmits light other than ultraviolet light from the light source 25.

[0064] A half-mirror is configured to reflect light with a predetermined reflectivity and transmit other light. When the optical element 58 is a half-mirror, the optical element 58 reflects the light emitted from the light source 25 with a predetermined reflectivity (e.g., 50%). The light reflected by the optical element 58 is transmitted to the ultraviolet irradiation head 55. This reflected light consists of basically the same components as the light emitted from the light source 25. Therefore, the light reflected by the optical element 58 includes ultraviolet light. The optical element 58 transmits the light emitted from the light source 25 other than the reflected light (e.g., the remaining 50% of the light).

[0065] The light reflected by the optical element 58 includes ultraviolet light. The ultraviolet irradiation head 55 is configured to irradiate the liquid flowing through the liquid supply pipe 46 with ultraviolet light through the irradiation window 70. The liquid flowing through the liquid supply pipe 46 is sterilized by the ultraviolet light. As a result, the liquid used for measuring the film thickness of the workpiece W can be kept clean.

[0066] Figure 5 is a schematic diagram showing an enlarged view of the area surrounding a film thickness measuring device 20 according to yet another embodiment of the polishing apparatus. The configuration and operation of this embodiment, which are not specifically described, are the same as those of the embodiment described with reference to Figure 4, so redundant explanations are omitted. In the embodiment shown in Figure 5, the arrangement of the optical members 58 is different from the embodiment shown in Figure 4, and the optical splitter 64 is not provided.

[0067] In this embodiment, the first light-emitting optical fiber cable 37a extends to the optical member 58, and the second light-emitting optical fiber cable 37b extends from the optical member 58 into the polishing table 3. The first light-emitting optical fiber cable 37a is an optical transmission section that guides the light emitted by the light source 25 to the optical member 58, and the second light-emitting optical fiber cable 37b is an optical transmission section that guides the light that has passed through the optical member 58 to the surface of the workpiece W.

[0068] The optical element 58 is positioned obliquely to the optical path of the light emitted from the light source 25. The optical element 58 is optically connected to the ultraviolet irradiation head 55. In this embodiment, the light emitted from the light source 25 includes ultraviolet light. The optical element 58 is configured to reflect some of the light emitted from the light source 25, including ultraviolet light, and transmit the remaining light. The light reflected by the optical element 58 is transmitted to the ultraviolet irradiation head 55, and the light transmitted through the optical element 58 is transmitted to the optical sensor head 22. More specifically, the light emitted from the light source 25 is guided to the optical element 58 through the first light-emitting optical fiber cable 37a of the light-emitting optical fiber cable 37. The light reflected by the optical element 58 is guided to the liquid flowing through the liquid supply pipe 46 through the optical fiber cable 65. The light transmitted through the optical element 58 is guided to the workpiece W through the second light-emitting optical fiber cable 37b of the light-emitting optical fiber cable 37. In other words, the light that passes through the optical element 58 is transmitted to the optical sensor head 22.

[0069] The transparent resin and other materials that make up the transparent window 33 may deteriorate due to ultraviolet light. The light transmitted to the optical sensor head 22 through the optical element 58 does not contain ultraviolet light, or contains less ultraviolet light than the ultraviolet light contained in the light from the light source 25. Specifically, if the optical element 58 is an ultraviolet reflection filter or a dichroic mirror, the light transmitted to the optical sensor head 22 through the optical element 58 does not contain ultraviolet light. Also, if the optical element 58 is a half mirror, the ultraviolet light contained in the light transmitted to the optical sensor head 22 through the optical element 58 is the ultraviolet light contained in the light from the light source 25 with the ultraviolet light reflected by the optical element 58 removed. According to this embodiment, deterioration of the transparent window 33 due to ultraviolet light can be prevented.

[0070] Figure 6 is a schematic diagram showing yet another embodiment of the polishing apparatus. The configuration and operation of this embodiment, which are not specifically described, are the same as those of the embodiments described with reference to Figures 1 to 3, so redundant descriptions are omitted. In the embodiment shown in Figure 6, the polishing apparatus further includes a second light source 90 connected to an ultraviolet irradiation head 55, in addition to the light source 25 connected to the optical sensor head 22. In this embodiment, the light source 25 connected to the optical sensor head 22 is referred to as the first light source 25. The polishing apparatus of this embodiment does not include an optical splitter 64, and the light emitted from the first light source 25 is used only for measuring the film thickness of the workpiece W. In one embodiment, the light emitted from the first light source 25 does not have to include ultraviolet light.

[0071] The second light source 90 is configured to emit light including ultraviolet light. Examples of the second light source 90 include xenon lamps and ultraviolet lamps. The second light source 90 is connected to the operation control unit 10, and the operation of the second light source 90 is controlled by the operation control unit 10. The second light source 90 is connected to the ultraviolet irradiation head 55. In this embodiment, the optical fiber cable 65 extends from the second light source 90 and functions as an optical transmission unit that guides the light from the second light source 90 to the liquid flowing through the liquid supply pipe 46. The light including ultraviolet light emitted from the second light source 90 is transmitted to the ultraviolet irradiation head 55.

[0072] In this embodiment, the ozone collection device 62 is arranged to surround the second light source 90. The ozone collection device 62 is configured to collect ozone generated when ultraviolet light emitted from the second light source 90 irradiates an oxygen-containing gas (for example, air). In one embodiment, the ozone collection device 62 may be placed on the first light source 25, or it may be placed on both the first light source 25 and the second light source 90.

[0073] During the polishing of the workpiece W, the operation control unit 10 commands the first light source 25 to emit light from the first light source 25, causing the film thickness measuring device 20 to measure the film thickness of the workpiece W. Furthermore, the operation control unit 10 is configured to command the second light source 90 to emit light from the second light source 90, causing the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply pipe 46 with ultraviolet light. As a result, during the polishing of the workpiece W, the liquid flowing through the liquid supply pipe 46 is sterilized by ultraviolet light. In one embodiment, the operation control unit 10 may be configured to command the second light source 90 at predetermined time intervals during the polishing of the workpiece W, causing the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply pipe 46 with ultraviolet light at predetermined time intervals.

[0074] During idling, when the workpiece W is not being polished, the film thickness is not measured by the film thickness measuring device 20, and therefore the emission of light from the first light source 25 is stopped. The operation control unit 10 is configured to, during idling, issue a command to the second light source 90 to emit light from the second light source 90, causing the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply pipe 46 with ultraviolet light. As a result, even during idling, the liquid flowing through the liquid supply pipe 46 is sterilized by ultraviolet light. In one embodiment, the operation control unit 10 may, during idling, issue a command to the second light source 90 at predetermined time intervals to emit light from the second light source 90, causing the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply pipe 46 with ultraviolet light at predetermined time intervals.

[0075] Figure 7 is a schematic diagram showing yet another embodiment of the polishing apparatus. The configuration and operation of this embodiment, which are not specifically described, are the same as those of the embodiments described with reference to Figures 1 to 3, so redundant descriptions are omitted. In the embodiment shown in Figure 7, the polishing apparatus includes a liquid supply line 92 for supplying liquid to the through hole 34 and a drain line 93 for discharging liquid from the through hole 34, instead of the liquid circulation line 45 and the tank 50.

[0076] One end of the liquid supply line 92 is connected to the first hole 35A, and the other end of the liquid supply line 92 is connected to the liquid supply source 98. The drain line 93 is connected to the second hole 35B. The liquid supply line 92 and the drain line 93 are in communication with the through hole 34. A liquid supply valve 95 and a drain valve 96 are attached to the liquid supply line 92 and the drain line 93, respectively. When the polishing machine is in operation, the liquid supply valve 95 and the drain valve 96 are open, and liquid is supplied from the liquid supply source 98 to the through hole 34 through the liquid supply line 92 and discharged from the through hole 34 through the drain line 93. When the polishing machine is stopped, the liquid supply valve 95 is closed to stop the supply of liquid from the liquid supply source 98.

[0077] In this embodiment, the ultraviolet irradiation head 55 is attached to the liquid supply line 92 and is configured to sterilize the liquid flowing through the liquid supply line 92 by irradiating it with ultraviolet light. The configuration of the ultraviolet irradiation head 55 is the same as in the embodiment described with reference to Figure 2.

[0078] In this embodiment, the polishing apparatus does not include an ozone supply device 60 and an ozone collection device 62. In one embodiment, the liquid supplied from the liquid supply source 98 may be ozonated water.

[0079] Similar to the embodiments described with reference to Figures 1 to 3, during the polishing of the workpiece W, the operation control unit 10 commands the light source 25 to emit light, causing the film thickness measuring device 20 to measure the film thickness of the workpiece W, and also causes the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply line 92 with ultraviolet light. As a result, during the polishing of the workpiece W, the liquid flowing through the liquid supply line 92 is sterilized by ultraviolet light.

[0080] The operation control unit 10 may, during idling when the workpiece W is not being polished, issue a command to the light source 25 to emit light from the light source 25, causing the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply line 92 with ultraviolet light. This ensures that the liquid flowing through the liquid supply line 92 is sterilized by ultraviolet light even during idling. In one embodiment, the operation control unit 10 may, during idling, issue a command to the light source 25 at predetermined time intervals to emit light from the light source 25, causing the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply line 92 with ultraviolet light at predetermined time intervals.

[0081] In this embodiment, while the polishing device is in operation, new liquid is supplied from the liquid supply line 92 and the liquid is discharged through the drain line 93, thus keeping the liquid clean. However, if the polishing device is stopped for a long period of time for maintenance or other reasons, fungi contained in the liquid in the liquid supply source 98 and the liquid supply line 92 are more likely to proliferate. Therefore, in one embodiment, the operation control unit 10 may, after the polishing device has been stopped for a specified time or longer, issue a command to the light source 25 to emit light, causing the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply line 92 with ultraviolet light. However, the timing of the ultraviolet irradiation head 55 irradiating the liquid flowing through the liquid supply line 92 with ultraviolet light is not particularly limited.

[0082] Figure 8 is a schematic diagram showing yet another embodiment of the polishing apparatus. The configuration and operation of this embodiment, which are not specifically described, are the same as those of the embodiment described with reference to Figure 7, so a redundant explanation is omitted. As shown in Figure 8, the polishing apparatus of this embodiment does not have a transparent window 33, and the through hole 34 opens at the polishing surface 2a of the polishing pad 2. Light emitted from the light source 25 is transmitted to the optical sensor head 22 and guided from the optical sensor head 22 through the through hole 34 to the surface of the workpiece W. The light is reflected from the surface of the workpiece W, and the reflected light from the workpiece W is received by the optical sensor head 22 through the through hole 34.

[0083] In this embodiment, the through-hole 34 is filled with liquid, and the polishing liquid and polishing debris on the polishing pad 2 are discharged together with the liquid from the drain line 93, thereby ensuring an optical path for measuring film thickness.

[0084] Each embodiment equipped with the optical element 58 described with reference to Figures 4 and 5 can also be applied to each embodiment described with reference to Figures 7 and 8.

[0085] Figure 9 is a schematic diagram showing yet another embodiment of the polishing apparatus. The configuration and operation of this embodiment, which are not specifically described, are the same as those of the embodiment described with reference to Figure 7, so redundant descriptions are omitted. The embodiment shown in Figure 9 is obtained by applying the first light source 25 and the second light source 90 shown in Figure 6 to the embodiment described with reference to Figure 7. The configuration and operation of the first light source 25 and the second light source 90 in the embodiment shown in Figure 9 are basically the same as those of the first light source 25 and the second light source 90 shown in Figure 6.

[0086] The second light source 90 is configured to emit light including ultraviolet light. The second light source 90 is connected to an ultraviolet irradiation head 55. In this embodiment, the optical fiber cable 65 extends from the second light source 90 and functions as an optical transmission unit that guides the light from the second light source 90 to the liquid flowing through the liquid supply line 92. The light including ultraviolet light emitted from the second light source 90 is transmitted to the ultraviolet irradiation head 55 and irradiated onto the liquid flowing through the liquid supply line 92. As a result, the liquid flowing through the liquid supply line 92 is sterilized by ultraviolet light.

[0087] Similar to the embodiment described with reference to Figure 6, during polishing of the workpiece W, the operation control unit 10 commands the first light source 25 to emit light from the first light source 25, causing the film thickness measuring device 20 to measure the film thickness of the workpiece W. Furthermore, the operation control unit 10 is configured to command the second light source 90 to emit light from the second light source 90, causing the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply line 92 with ultraviolet light. As a result, during polishing of the workpiece W, the liquid flowing through the liquid supply line 92 is sterilized by ultraviolet light. In one embodiment, the operation control unit 10 may be configured to command the second light source 90 at predetermined time intervals during polishing of the workpiece W, to emit light from the second light source 90, causing the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply line 92 with ultraviolet light at predetermined time intervals.

[0088] The operation control unit 10 may, during idling when the workpiece W is not being polished, issue a command to the second light source 90 to emit light from the second light source 90, causing the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply line 92 with ultraviolet light. This ensures that the liquid flowing through the liquid supply line 92 is sterilized by ultraviolet light even during idling. In one embodiment, the operation control unit 10 may, during idling, issue a command to the second light source 90 at predetermined time intervals to emit light from the second light source 90, causing the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply line 92 with ultraviolet light at predetermined time intervals.

[0089] In one embodiment, the operation control unit 10 may, after the polishing device has been stopped for a specified time or longer, issue a command to the second light source 90 to emit light from the second light source 90, causing the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply line 92 with ultraviolet light. However, the timing of the ultraviolet irradiation head 55 irradiating the liquid flowing through the liquid supply line 92 with ultraviolet light is not particularly limited.

[0090] The polishing pad 2 without the transparent window 33, as described with reference to Figure 8, can also be applied to the embodiment described with reference to Figure 9.

[0091] In the embodiments described so far, the polishing apparatus is equipped with one set of transparent windows 33 and an optical sensor head 22, but the polishing apparatus may be equipped with multiple sets of transparent windows 33 and optical sensor heads 22.

[0092] The embodiments described above are intended to enable persons with ordinary skill in the art to implement the present invention. Various modifications of the above embodiments can be made naturally by those skilled in the art, and the technical idea of ​​the present invention can be applied to other embodiments as well. Therefore, the present invention is not limited to the embodiments described, but is to be interpreted in the broadest sense according to the technical idea defined by the claims. [Explanation of symbols]

[0093] 1 Polishing head 2 polishing pads 2a Polished surface 3 Polishing Table 6 Table motors 8. Polishing fluid supply nozzle 10 Operation Control Unit 10a storage device 10b Arithmetic unit 15 Head Shaft 17 Coupling device 18 Polishing head motor 20 Film Thickness Measuring Device 22 Optical sensor heads 25 Light source (1st light source) 27 Spectrometer 28 Photodetector 33 Transparent window 34 Through hole 35A First hole 35B Second hole 37. Optical fiber cable for floodlighting 38 Optical fiber cable for receiving light 40 Data Processing Unit 40a storage device 40b Arithmetic unit 45 Liquid circulation line 46 Liquid supply piping 47 Liquid return piping 50 tanks 52 pumps 55 UV irradiation head 58 Optical components 60 Ozone supply devices 62 Ozone collection devices 64 Optical Splitter 65 Fiber optic cables 67 Head Case 70 Irradiation window 73 Ozone gas supply lines 76 Purge gas supply line 81. Fluid exchange line 82 supply lines 83 Discharge Line 85. First shut-off valve 86 Second shut-off valve 90 Second light source 92 Liquid supply line 93 Drain line 95 Liquid supply valve 96 Drain valve 98 Liquid Source W Workpiece

Claims

1. A polishing pad having a polishing surface, A polishing head that presses the workpiece against the polishing surface, A polishing table that supports the polishing pad, An optical sensor head that guides light to the workpiece through through holes formed in the polishing pad and receives reflected light from the workpiece through the through holes, A tank for storing the liquid supplied to the through hole, A liquid circulation line for circulating the liquid between the through hole and the tank, A polishing apparatus equipped with an ultraviolet irradiation head that irradiates ultraviolet light onto the liquid flowing through the aforementioned liquid circulation line to sterilize the liquid.

2. A light source that emits light is connected to the aforementioned optical sensor head, The optical member further comprises an optical member that reflects a portion of the light emitted from the light source, including ultraviolet light. The polishing apparatus according to claim 1, wherein the ultraviolet irradiation head is connected to the optical member and configured to irradiate the liquid flowing through the liquid circulation line with a portion of the light reflected by the optical member.

3. The polishing apparatus according to claim 2, wherein the optical element is one of an ultraviolet reflective filter, a dichroic mirror, and a half mirror.

4. A first light source that emits light is connected to the optical sensor head, The polishing apparatus according to claim 1, further comprising a second light source connected to the ultraviolet irradiation head and emitting light including ultraviolet light.

5. The polishing apparatus according to claim 1, further comprising an ozone supply device for supplying ozone to the liquid in the tank to sterilize the liquid in the tank.

6. A light source that emits light is connected to the aforementioned optical sensor head, The device further comprises an ozone collection device for collecting ozone generated from ultraviolet light contained in the light emitted from the aforementioned light source, The polishing apparatus according to claim 5, wherein the ozone collection device is connected to the ozone supply device and configured to supply the collected ozone to the ozone supply device.

7. A first light source that emits light is connected to the optical sensor head, A second light source connected to the aforementioned ultraviolet irradiation head, which emits light including ultraviolet light, The system further includes an ozone collection device that collects ozone generated from ultraviolet light contained in the light emitted from the second light source, The polishing apparatus according to claim 5, wherein the ozone collection device is connected to the ozone supply device and configured to supply the collected ozone to the ozone supply device.

8. The transparent window is further fitted into the aforementioned through hole, The polishing apparatus according to claim 1, wherein the optical sensor head is configured to guide the light to the workpiece through the through-hole and the transparent window, and to receive the reflected light from the workpiece through the transparent window and the through-hole.

9. A polishing pad having a polishing surface, A polishing head that presses the workpiece against the polishing surface, A polishing table that supports the polishing pad, An optical sensor head that guides light to the workpiece through through holes formed in the polishing pad and receives reflected light from the workpiece through the through holes, A liquid supply line that communicates with the aforementioned through hole and supplies liquid to the aforementioned through hole, A drain line that communicates with the through hole and discharges the liquid from the through hole, A polishing apparatus comprising an ultraviolet irradiation head for sterilizing the liquid flowing through the liquid supply line by irradiating the liquid with ultraviolet light.

10. A light source that emits light is connected to the aforementioned optical sensor head, The optical member further comprises an optical member that reflects a portion of the light emitted from the light source, including ultraviolet light. The polishing apparatus according to claim 9, wherein the ultraviolet irradiation head is connected to the optical member and configured to irradiate the liquid flowing through the liquid circulation line with a portion of the light reflected by the optical member.

11. The polishing apparatus according to claim 10, wherein the optical element is one of an ultraviolet reflective filter, a dichroic mirror, and a half mirror.

12. A first light source that emits light is connected to the optical sensor head, The polishing apparatus according to claim 9, further comprising a second light source connected to the ultraviolet irradiation head and emitting light including ultraviolet light.

13. The transparent window is further fitted into the aforementioned through hole, The polishing apparatus according to claim 9, wherein the optical sensor head is configured to guide the light to the workpiece through the through-hole and the transparent window, and to receive the reflected light from the workpiece through the transparent window and the through-hole.

14. The workpiece is pressed 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 through-hole formed in the polishing pad, and the reflected light from the workpiece is received by the optical sensor head through the through-hole. The liquid is circulated between the through-hole and the tank that stores the liquid through a liquid circulation line. A polishing method comprising irradiating the liquid flowing through the liquid circulation line with ultraviolet light using an ultraviolet irradiation head to sterilize the liquid.

15. By transmitting light emitted from the light source to the optical sensor head, the light is guided from the optical sensor head to the workpiece. The polishing method according to claim 14, wherein a portion of the light emitted from the light source, including ultraviolet light, is reflected by an optical member, and the portion of the light is transmitted to the ultraviolet irradiation head, thereby irradiating the liquid flowing through the liquid circulation line with ultraviolet light by the ultraviolet irradiation head.

16. The polishing method according to claim 15, wherein the optical element is one of an ultraviolet reflective filter, a dichroic mirror, and a half mirror.

17. The polishing method according to claim 15, further comprising, during idling when the workpiece is not being polished, reflecting a portion of the light emitted from the light source with the optical member and transmitting the portion of the light to the ultraviolet irradiation head, thereby irradiating the liquid flowing through the liquid circulation line with ultraviolet light by the ultraviolet irradiation head.

18. By transmitting light emitted from the first light source to the optical sensor head, the light is guided from the optical sensor head to the workpiece. The polishing method according to claim 14, wherein, during the polishing of the workpiece, light including ultraviolet light emitted from a second light source is transmitted to the ultraviolet irradiation head, so that the ultraviolet irradiation head irradiates the liquid flowing through the liquid circulation line with the ultraviolet light.

19. The polishing method according to claim 18, further comprising transmitting the light emitted from the second light source to the ultraviolet irradiation head during idling when the workpiece is not being polished, thereby irradiating the liquid flowing through the liquid circulation line with ultraviolet light by the ultraviolet irradiation head.

20. The polishing method according to claim 14, further comprising supplying ozone to the liquid in the tank to sterilize the liquid in the tank.

21. By transmitting light emitted from the light source to the optical sensor head, the light is guided from the optical sensor head to the workpiece. The polishing method further includes collecting ozone generated from ultraviolet light contained in the light emitted from the light source, The polishing method according to claim 20, wherein the ozone supplied to the liquid in the tank is the collected ozone.

22. By transmitting light emitted from the first light source to the optical sensor head, the light is guided from the optical sensor head to the workpiece. By transmitting light containing ultraviolet light emitted from the second light source to the ultraviolet irradiation head, the ultraviolet irradiation head irradiates the liquid flowing through the liquid circulation line with the ultraviolet light. The polishing method further includes collecting ozone generated from ultraviolet light contained in the light emitted from the second light source, The polishing method according to claim 20, wherein the ozone supplied to the liquid in the tank is the collected ozone.

23. The polishing method according to claim 14, wherein guiding the light from the optical sensor head to the workpiece through the through hole and receiving the reflected light with the optical sensor head through the through hole means guiding the light from the optical sensor head to the workpiece through the through hole and a transparent window fitted into the through hole, and receiving the reflected light with the optical sensor head through the transparent window and the through hole.

24. The workpiece is pressed 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 through-hole formed in the polishing pad, and the reflected light from the workpiece is received by the optical sensor head through the through-hole. A liquid is supplied to the through hole through the liquid supply line. The liquid is discharged from the through-hole through the drain line. A polishing method comprising irradiating the liquid flowing through the liquid supply line with ultraviolet light using an ultraviolet irradiation head to sterilize the liquid.

25. By transmitting light emitted from the light source to the optical sensor head, the light is guided from the optical sensor head to the workpiece. The polishing method according to claim 24, wherein a portion of the light emitted from the light source, including ultraviolet light, is reflected by an optical element and transmitted to the ultraviolet irradiation head, thereby irradiating the liquid flowing through the liquid circulation line with ultraviolet light by the ultraviolet irradiation head.

26. The polishing method according to claim 25, wherein the optical member is one of an ultraviolet reflective filter, a dichroic mirror, and a half mirror.

27. The polishing method according to claim 25, further comprising, during idling when the workpiece is not being polished, reflecting a portion of the light emitted from the light source with the optical member and transmitting the portion of the light to the ultraviolet irradiation head, thereby irradiating the liquid flowing through the liquid circulation line with ultraviolet light by the ultraviolet irradiation head.

28. By transmitting light emitted from the first light source to the optical sensor head, the light is guided from the optical sensor head to the workpiece. The polishing method according to claim 24, wherein, during the polishing of the workpiece, light including ultraviolet light emitted from a second light source is transmitted to the ultraviolet irradiation head, so that the ultraviolet irradiation head irradiates the liquid flowing through the liquid circulation line with the ultraviolet light.

29. The polishing method according to claim 28, further comprising transmitting the light emitted from the second light source to the ultraviolet irradiation head during idling when the workpiece is not being polished, thereby irradiating the liquid flowing through the liquid circulation line with ultraviolet light by the ultraviolet irradiation head.

30. The polishing method according to claim 24, wherein guiding the light from the optical sensor head to the workpiece through the through hole and receiving the reflected light with the optical sensor head through the through hole means guiding the light from the optical sensor head to the workpiece through the through hole and a transparent window fitted into the through hole, and receiving the reflected light with the optical sensor head through the transparent window and the through hole.

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