POLISHING APPARATUS AND POLISHING METHOD

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority from Japanese Patent Application No. 2024-231842, filed on Dec. 27, 2024, with the Japan Patent Office, the disclosure of which is incorporated herein in its entirety by reference.

TECHNICAL FIELD

The present disclosure relates to a technique for measuring the film thickness of a workpiece used in the manufacture of semiconductor devices such as a wafer, a substrate, or a panel while polishing the workpiece, and more particularly to a technique for determining the film thickness of the workpiece based on optical information included in reflected light from the workpiece.

BACKGROUND

In the semiconductor device manufacturing process, various materials are repeatedly formed into films on a wafer to form a laminated structure. In order to form the laminated structure, a technique for planarizing the surface of the uppermost layer is important. As a method for the planarization, chemical mechanical polishing (CMP) has been used.

The chemical mechanical polishing (CMP) is performed by a polishing apparatus. The polishing apparatus is configured to polish the surface of a wafer by bringing the wafer into sliding contact with a polishing pad attached to a polishing table while supplying a polishing liquid to the polishing pad. The polishing of the wafer is terminated when the thickness of the film (such as an insulating film, a metal film, or a silicon layer) forming its surface reaches a predetermined target value. Therefore, during the polishing of the wafer, the film thickness is measured.

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 apparatus generally includes an optical film thickness measuring device. The optical film thickness measuring device is configured to guide light emitted from a light source through a sensor head to the surface of a wafer, to receive reflected light from the wafer by the sensor head, and to determine the film thickness of the wafer by analyzing the spectrum of the reflected light.

During polishing of the wafer, a polishing liquid and polishing debris may be present on the polishing pad. When the polishing liquid or polishing debris adheres to, for example, the sensor head, the intensity of light with which the wafer is irradiated and the intensity of reflected light from the wafer decrease, making it difficult to accurately measure the film thickness. Accordingly, there is a technique for supplying pure water from the inside of the polishing table through a through-hole to secure an optical path. The through-hole may be filled with pure water, and the polishing liquid and polishing debris that have entered the through-hole may be discharged together with the pure water through a drain line. The flow of pure water formed in the through-hole secures the optical path and enables highly accurate film thickness measurement. See, for example, Japanese Patent Laid-Open Publication No. 2017-220683.

SUMMARY

In an aspect, there is provided a polishing apparatus including: a polishing pad having a polishing surface; a polishing head that presses a workpiece against the polishing surface; a polishing table that supports the polishing pad; an optical sensor head that guides light to the workpiece through a through-hole formed in the polishing pad and receives reflected light from the workpiece through the through-hole; a tank that stores a liquid supplied to the through-hole; a liquid circulation line that circulates the liquid between the through-hole and the tank; and an ultraviolet irradiation head that irradiates the liquid flowing through the liquid circulation line with ultraviolet light, thereby sterilizing the liquid.

The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view illustrating an embodiment of a polishing apparatus.

FIG. 2 is a schematic view illustrating an enlarged view of the periphery of a film thickness measuring device.

FIG. 3 is a view illustrating an example of a spectrum generated by a data processor.

FIG. 4 is a schematic view illustrating an enlarged view of the periphery of a film thickness measuring device according to another embodiment of a polishing apparatus.

FIG. 5 is a schematic view illustrating an enlarged view of the periphery of a film thickness measuring device according to another embodiment of a polishing apparatus.

FIG. 6 is a schematic view illustrating still another embodiment of a polishing apparatus.

FIG. 7 is a schematic view illustrating still another embodiment of a polishing apparatus.

FIG. 8 is a schematic view illustrating still another embodiment of a polishing apparatus.

FIG. 9 is a schematic view illustrating still another embodiment of a polishing apparatus.

DETAILED DESCRIPTION

In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made without departing from the spirit or scope of the subject matter presented here.

When foreign substances derived from fungi present in pure water adhere to optical systems such as a sensor head, the accuracy of film thickness measurement may be reduced. In addition, such foreign substances may clog the pure water supply line and the drain line. Furthermore, when fungi adhere to the polishing pad, the device surface of the wafer may become contaminated.

Accordingly, the present disclosure provides a polishing apparatus and a polishing method capable of maintaining the liquid used for film thickness measurement in a clean state and accurately measuring the film thickness.

In an aspect, a polishing apparatus includes: a polishing pad having a polishing surface; a polishing head that presses a workpiece against the polishing surface; a polishing table that supports the polishing pad; an optical sensor head that guides light to the workpiece through a through-hole formed in the polishing pad and receives reflected light from the workpiece through the through-hole; a tank that stores a liquid supplied to the through-hole; a liquid circulation line that circulates the liquid between the through-hole and the tank; and an ultraviolet irradiation head that irradiates the liquid flowing through the liquid circulation line with ultraviolet light, thereby sterilizing the liquid.

In an embodiment, the polishing apparatus further includes: a light source that is connected to the optical sensor head and emits light; and an optical member that reflects a portion of the light emitted from the light source, the portion containing ultraviolet light. The ultraviolet irradiation head is connected to the optical member and is configured to irradiate the liquid flowing through the liquid circulation line with the portion of the light reflected by the optical member.

In an aspect, the optical member is one of an ultraviolet reflection filter, a dichroic mirror, or a half mirror.

In an embodiment, the polishing apparatus further includes: a first light source that is connected to the optical sensor head and emits light; and a second light source that is connected to the ultraviolet irradiation head and emits light containing ultraviolet light.

In an aspect, the polishing apparatus further includes an ozone supply device that supplies ozone to the liquid in the tank, thereby sterilizing the liquid in the tank.

In an aspect, the polishing apparatus further includes: a light source that is connected to the optical sensor head and emits light; and an ozone collecting device that collects ozone generated from ultraviolet light contained in the light emitted from the light source. The ozone collecting device is connected to the ozone supply device and is configured to transmit the collected ozone to the ozone supply device.

In an embodiment, the polishing apparatus further includes: a first light source that is connected to the optical sensor head and emits light; a second light source that is connected to the ultraviolet irradiation head and emits light containing ultraviolet light; and an ozone collecting device that collects ozone generated from ultraviolet light contained in the light emitted from the second light source. The ozone collecting device is connected to the ozone supply device and is configured to transmit the collected ozone to the ozone supply device.

In an aspect, the polishing apparatus further includes 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.

In an aspect, there is provided a polishing apparatus including: a polishing pad having a polishing surface; a polishing head that presses a workpiece against the polishing surface; a polishing table that supports the polishing pad; an optical sensor head that guides light to the workpiece through a through-hole formed in the polishing pad and receives reflected light from the workpiece through the through-hole; a liquid supply line that communicates with the through-hole and supplies a liquid to the through-hole; a drain line that communicates with the through-hole and discharges the liquid from the through-hole; and an ultraviolet irradiation head that irradiates the liquid flowing through the liquid supply line with ultraviolet light, thereby sterilizing the liquid.

In an embodiment, the polishing apparatus further includes: a light source that is connected to the optical sensor head and emits light; and an optical member that reflects a portion of the light emitted from the light source, the portion containing ultraviolet light. The ultraviolet irradiation head is connected to the optical member and is configured to irradiate the liquid flowing through the liquid supply line with the portion of the light reflected by the optical member.

In an aspect, the optical member is one of an ultraviolet reflection filter, a dichroic mirror, or a half mirror.

In an embodiment, the polishing apparatus further includes: a first light source that is connected to the optical sensor head and emits light; and a second light source that is connected to the ultraviolet irradiation head and emits light containing ultraviolet light.

In an aspect, the polishing apparatus further includes 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 receive the reflected light from the workpiece through the transparent window and the through-hole.

In an aspect, a polishing method includes: pressing a workpiece against a polishing surface of a polishing pad to polish the workpiece; guiding light from an optical sensor head to the workpiece through a through-hole formed in the polishing pad while polishing the workpiece; and receiving, by the optical sensor head, reflected light from the workpiece through the through-hole; circulating a liquid between the through-hole and a tank configured to store the liquid through a liquid circulation line; and irradiating the liquid flowing through the liquid circulation line with ultraviolet light by an ultraviolet irradiation head, thereby sterilizing the liquid.

In an aspect, 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 a portion of the light emitted from the light source, the portion containing ultraviolet light, is reflected by an optical member and transmitted to the ultraviolet irradiation head, such that the ultraviolet irradiation head irradiates the liquid flowing through a liquid circulation line with the ultraviolet light.

In an aspect, the optical member is one of an ultraviolet reflection filter, a dichroic mirror, or a half mirror.

In an aspect, the polishing method further includes: reflecting, during idling in which polishing of the workpiece is not performed, the portion of the light emitted from the light source by the optical member and transmitting the portion including the ultraviolet light to the ultraviolet irradiation head, thereby causing the ultraviolet irradiation head to irradiate the liquid flowing through the liquid circulation line with the ultraviolet light.

In an aspect, 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 polishing of the workpiece, light emitted from a second light source, the light containing ultraviolet light, is transmitted to the ultraviolet irradiation head, thereby causing the ultraviolet irradiation head to irradiate the liquid flowing through a liquid circulation line with the ultraviolet light.

In an aspect, the polishing method further includes transmitting the light emitted from the second light source to the ultraviolet irradiation head during idling in which polishing of the workpiece is not performed, thereby causing the ultraviolet irradiation head to irradiate the liquid flowing through the liquid circulation line with the ultraviolet light.

In an aspect, the polishing method further includes supplying ozone to the liquid in the tank, thereby sterilizing the liquid in the tank.

In an aspect, 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. The polishing method further includes collecting ozone generated from ultraviolet light contained in the light emitted from the light source, and the ozone supplied to the liquid in the tank is the collected ozone.

In an aspect, 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 light emitted from a second light source, the light containing ultraviolet light, is transmitted to the ultraviolet irradiation head, thereby causing the ultraviolet irradiation head to irradiate the liquid flowing through a 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, and the ozone supplied to the liquid in the tank is the collected ozone.

In an aspect, guiding the light from the optical sensor head to the workpiece through the through-hole and receiving the reflected light through the through-hole by the optical sensor head include 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 through the transparent window and the through-hole by the optical sensor head.

In an aspect, there is provided a polishing method including: pressing a workpiece against a polishing surface of a polishing pad to polish the workpiece; guiding light from an optical sensor head to the workpiece through a through-hole formed in the polishing pad while polishing the workpiece, and receiving reflected light from the workpiece through the through-hole by the optical sensor head; supplying a liquid to the through-hole through a liquid supply line; discharging the liquid from the through-hole through a drain line; and irradiating the liquid flowing through the liquid supply line with ultraviolet light by an ultraviolet irradiation head, thereby sterilizing the liquid.

In an aspect, 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 a portion of the light emitted from the light source, the portion containing ultraviolet light, is reflected by an optical member and transmitted to the ultraviolet irradiation head, thereby causing the ultraviolet irradiation head to irradiate the liquid flowing through the liquid supply line with the ultraviolet light.

In an aspect, the optical member is one of an ultraviolet reflection filter, a dichroic mirror, or a half mirror.

In an aspect, the polishing method further includes: reflecting, during idling in which polishing of the workpiece is not performed, the portion of the light emitted from the light source by the optical member and transmitting the portion including the ultraviolet light to the ultraviolet irradiation head, thereby causing the ultraviolet irradiation head to irradiate the liquid flowing through the liquid supply line with the ultraviolet light.

In an aspect, 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 polishing of the workpiece, light emitted from a second light source, the light containing ultraviolet light, is transmitted to the ultraviolet irradiation head, thereby causing the ultraviolet irradiation head to irradiate the liquid flowing through the liquid supply line with the ultraviolet light.

In an aspect, the polishing method further includes transmitting the light emitted from the second light source to the ultraviolet irradiation head during idling in which polishing of the workpiece is not performed, thereby causing the ultraviolet irradiation head to irradiate the liquid flowing through the liquid supply line with the ultraviolet light.

In an aspect, guiding the light from the optical sensor head to the workpiece through the through-hole and receiving the reflected light through the through-hole by the optical sensor head include 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 through the transparent window and the through-hole by the optical sensor head.

According to the present disclosure, the liquid used for film thickness measurement may be sterilized by irradiation with ultraviolet light to be maintained in a clean state. As a result, the film thickness of the workpiece may be measured with high accuracy.

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

FIG. 1 is a schematic view illustrating an embodiment of a polishing apparatus. As illustrated in FIG. 1, the polishing apparatus includes: a polishing table 3 that supports a polishing pad 2; a polishing head 1 that presses a workpiece W, such as a wafer, 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 that supplies a polishing liquid such as slurry onto the polishing pad 2. An upper surface of the polishing pad 2 serves as a polishing surface 2a for polishing the workpiece W.

The polishing head 1 is connected to a head shaft 15, and the head shaft 15 is connected to a polishing head motor 18 through a connecting device 17. The configuration of the connecting device 17 is not particularly limited and may include, for example, a combination of a pulley and a belt, a combination of gears, or a combination of a sprocket and a chain. The polishing head motor 18 rotates the polishing head 1 together with the head shaft 15 in a direction indicated by an arrow. The polishing table 3 is connected to the table motor 6, and the table motor 6 is configured to rotate the polishing table 3 and the polishing pad 2 in a direction indicated by an arrow.

The polishing apparatus includes an operation controller 10 configured to control the operation of the polishing apparatus. The operation controller 10 includes a storage device 10a configured to store a program and a calculation device 10b configured to perform arithmetic operations according to instructions included in the program. The operation controller 10 includes at least one computer. The storage device 10a includes a main storage such as a random-access memory (RAM), and an auxiliary storage such as a hard disk drive (HDD) or a solid-state drive (SSD). Examples of the calculation device 10b include a central processing unit (CPU) and a graphics processing unit (GPU). However, the specific configuration of the operation controller 10 is not limited to these examples.

The polishing apparatus includes a film thickness measuring device 20 configured to measure the film thickness of a workpiece W. The film thickness measuring device 20 includes: a light source 25 configured to emit light; an optical sensor head 22 configured to irradiate the workpiece W with the light from the light source 25 and to receive reflected light from the workpiece W; a spectrometer 27 configured to generate intensity measurement data of the reflected light; and a data processor 40 configured to determine the thickness of a film 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 processor 40.

The optical sensor head 22, the light source 25, and the spectrometer 27 are mounted on the polishing table 3 and rotate integrally with the polishing table 3 and the polishing pad 2. The optical sensor head 22 is disposed to face the workpiece W held by the polishing head 1. The position of the optical sensor head 22 is a position that passes across the surface of the workpiece W on the polishing pad 2 each time the polishing table 3 and the polishing pad 2 make 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 disposed above the optical sensor head 22. The transparent window 33 rotates together with the polishing table 3.

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 on 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 transmitted to the spectrometer 27. The spectrometer 27 decomposes the reflected light according to wavelength over a predetermined wavelength range and generates intensity measurement data of the reflected light by measuring the intensity of the reflected light at each wavelength. The intensity measurement data of the reflected light is transmitted from the spectrometer 27 to the data processor 40.

The data processor 40 generates a spectrum of the reflected light based on the intensity measurement data of the reflected light. This spectrum represents the relationship between the intensity and wavelength of the reflected light, and the shape of the spectrum varies according to the film thickness of the workpiece W. The data processor 40 calculates the film thickness of the workpiece W from the spectrum. The data processor 40 is electrically connected to the operation controller 10, and the calculated film thickness of the workpiece W is transmitted to the operation controller 10.

The data processor 40 includes a storage 40a configured to store a program and a calculation device 40b configured to perform arithmetic operations according to instructions included in the program. The data processor 40 includes at least one computer. The storage 40a includes a main storage such as a random-access memory (RAM) and an auxiliary storage such as a hard disk drive (HDD) or a solid-state drive (SSD). Examples of the calculation device 40b include a central processing unit (CPU) and a graphics processing unit (GPU). However, the specific configuration of the data processor 40 is not limited to these examples.

The workpiece W is polished as follows. While rotating the polishing table 3 and the polishing head 1 in the directions indicated by the arrows in FIG. 1, a polishing liquid is supplied from the polishing liquid supply nozzle 8 onto the polishing surface 2a of the polishing pad 2 on the polishing table 3. The workpiece W is rotated by the polishing head 1 and pressed against 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 by the mechanical action of the abrasive grains contained in the polishing liquid and/or the polishing pad 2.

During polishing of the workpiece W, the optical sensor head 22 irradiates a measurement point on the workpiece W with light while passing across the surface of the workpiece W on the polishing pad 2 each time the polishing table 3 makes one rotation, and receives reflected light from the workpiece W. The data processor 40 calculates the film thickness of the workpiece W based on the intensity measurement data of the reflected light. The operation controller 10 determines a polishing endpoint based on the calculated film thickness.

Hereinafter, details of the film thickness measuring device 20 will be described. FIG. 2 is a schematic enlarged view illustrating a peripheral portion of the film thickness measuring device 20. The film thickness measuring device 20 includes a projection optical fiber cable 37 configured to guide light emitted from the light source 25 to a surface of a workpiece W, and a reception optical fiber cable 38 configured to receive reflected light from the workpiece W and transmit the reflected light to the spectrometer 27. The projection optical fiber cable 37 is a light transmission unit configured to guide light emitted from the light source 25 to the surface of the workpiece W. The reception optical fiber cable 38 is a light transmission unit configured to transmit the reflected light from the workpiece W to a photodetector 28.

Tip ends of the projection optical fiber cable 37 and the reception optical fiber cable 38 are positioned inside the polishing table 3. The other end of the projection optical fiber cable 37 is connected to the light source 25, and the other end of the reception optical fiber cable 38 is connected to the spectrometer 27. More specifically, the projection optical fiber cable 37 includes a first projection optical fiber cable 37a extending from the light source 25 to a light splitter 64 described below, and a second projection optical fiber cable 37b extending from the light splitter 64 to the inside of the polishing table 3. The first projection optical fiber cable 37a is a light transmission unit configured to guide light emitted from the light source 25 to the light splitter 64, and the second projection optical fiber cable 37b is a light transmission unit configured to guide light branched from the first projection optical fiber cable 37a by the light splitter 64 to the surface of the workpiece W. The optical sensor head 22 is configured with the tip end of the projection optical fiber cable 37 (the tip end of the second projection optical fiber cable 37b) and the tip end of the reception optical fiber cable 38.

The polishing table 3 has a first hole 35A and a second hole 35B that open on the upper surface thereof. In the polishing pad 2, a through-hole 34 is formed at a position corresponding to these holes 35A and 35B, and the holes 35A and 35B communicate with the through-hole 34. A transparent window 33 is fitted into an upper portion of the through-hole 34. Accordingly, the upper portion of the through-hole 34 is closed by the transparent window 33. An outer surface of the transparent window 33 is positioned slightly lower than a polishing surface 2a of the polishing pad 2. The optical sensor head 22 is disposed in the first hole 35A and is positioned below the through-hole 34.

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 formed of a material that transmits light. The material of the transparent window 33 is not particularly limited but may be formed of, for example, a transparent resin. The transparent window 33 may prevent a polishing liquid or polishing debris from contacting the optical sensor head 22.

Although details will be described later, during polishing of the workpiece W, a liquid is supplied into the through-hole 34, and the through-hole 34 is filled with the liquid. As an example of the liquid supplied into the through-hole 34, pure water may be used. However, the liquid is not limited to this example as long as it is a light-transmissive liquid. A difference between the refractive index of the liquid and the refractive index of the transparent window 33 is smaller than a difference between the refractive index of a gas, such as air, and the refractive index of the transparent window 33. Accordingly, by filling the through-hole 34 with the liquid, refraction of light at an interface between the through-hole 34 and the transparent window 33 may be suppressed compared to a case where the through-hole 34 is filled with a gas such as air.

A pulse-type light source, such as a xenon flash lamp, is used as the light source 25. Light emitted from the light source 25 contains ultraviolet light. The light source 25 is connected to the operation controller 10, and the operation of the light source 25 is controlled by the operation controller 10. The spectrometer 27 includes a photodetector 28. In an embodiment, the photodetector 28 includes a photodiode, a CCD, a CMOS, or an 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 processor 40.

The data processor 40 is configured to generate a spectrum of reflected light from the workpiece W based on intensity measurement data of the reflected light transmitted from the spectrometer 27. The spectrum of the reflected light is represented as a line graph (e.g., a spectral waveform) indicating the relationship between wavelength and intensity of the reflected light. The intensity of the reflected light may also be expressed as a relative value such as reflectance or relative reflectance.

FIG. 3 is a view illustrating an example of a spectrum generated by the data processor 40. The spectrum is represented as a line graph (e.g., a spectral waveform) indicating the relationship between wavelength and intensity of light. In FIG. 3, the horizontal axis represents the wavelength of light reflected from the workpiece W, and the vertical axis represents relative reflectance derived from the intensity of the reflected light. The relative reflectance is an index value indicating the intensity of reflected light and is a ratio of the light intensity to a predetermined reference intensity. By dividing the light intensity (measured intensity) at each wavelength by the predetermined reference intensity, unnecessary noise such as variation in the optical system or inherent intensity fluctuation of the light source may be removed from the measured intensity.

In the example illustrated in FIG. 3, while the spectrum of the reflected light is a spectral waveform indicating the relationship between relative reflectance and wavelength of the reflected light, the spectrum of the reflected light may be a spectral waveform indicating the relationship between the intensity of the reflected light itself and the wavelength of the reflected light.

The data processor 40 receives intensity measurement data of the reflected light from the workpiece W during one rotation of the polishing table 3 and generates a spectrum of the reflected light based on the intensity measurement data. The data processor 40 is configured to determine the film thickness of the workpiece W from the spectrum of the reflected light. A known method is used to determine the film thickness of the workpiece W based on the spectrum. For example, the data processor 40 may determine, from a reference spectrum library, a reference spectrum, of which the shape most closely matches the spectrum of the reflected light, and determine the film thickness associated with the determined reference spectrum. In another example, the data processor 40 may perform Fourier transform on the spectrum of the reflected light and determine the film thickness from a frequency spectrum obtained thereby.

As illustrated in FIG. 1, the polishing apparatus further includes a tank 50 configured to store a liquid supplied to the through-hole 34, a liquid circulation line 45 configured to circulate the liquid between the through-hole 34 and the tank 50, and a pump 52 configured to circulate the liquid. The liquid circulation line 45 includes a liquid supply pipe 46 configured to supply the liquid from the tank 50 to the through-hole 34 and a liquid return pipe 47 configured to return the liquid from the through-hole 34 to the tank 50.

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.

The pump 52 is disposed in the liquid supply pipe 46. The liquid in the tank 50 is supplied to the first hole 35A and the through-hole 34 through the liquid supply pipe 46 by the pump 52, and the through-hole 34 and the first hole 35A are filled with the 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 pipe 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.

The pump 52 is connected to the operation controller 10, and the operation of the pump 52 is controlled by the operation controller 10. During the operation of the polishing apparatus, the operation controller 10 is configured to drive the pump 52 and to circulate the liquid between the through-hole 34 and the tank 50. The term “during the operation of the polishing apparatus” refers to a period in which the polishing apparatus is activated, including both during polishing of the workpiece W and during idling in which polishing of the workpiece W is not performed. In an embodiment, the operation of the pump 52 may be manually controlled.

The polishing apparatus further includes a liquid replacement line 81 connected to the tank 50, a supply line 82 connected to the liquid replacement line 81, and a discharge line 83 connected to the liquid replacement line 81. The supply line 82 and the discharge line 83A are respectively provided with first opening/closing valve 85 and a second opening/closing valve 86. During the operation of the polishing apparatus, the first opening/closing valve 85 and the second opening/closing valve 86 are closed.

The liquid replacement 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 illustrated). When the second opening/closing valve 86 is closed and the first opening/closing valve 85 is opened, the liquid is supplied from the liquid supply source to the tank 50 through the supply line 82 and the liquid replacement line 81. When the first opening/closing valve 85 is closed and the second opening/closing valve 86 is opened, the liquid in the tank 50 is discharged through the liquid replacement line 81 and the discharge line 83.

According to such a configuration, by returning the liquid supplied to the through-hole 34 to the tank 50 and circulating the liquid, the amount of liquid used may be reduced, and as a result, costs may be reduced. However, when the liquid is circulated for a long period of time, fungi (e.g., bacteria or mold) in the liquid may propagate, and foreign substances originating from the fungi may be generated. Such foreign substances may adhere to an optical system, such as the optical sensor head 22 or the transparent window 33, and may reduce the accuracy of film thickness measurement or clog a pipe of the liquid circulation line 45. Furthermore, when fungi adhere to the polishing pad 2, a device surface of a workpiece W may become contaminated. Accordingly, the polishing apparatus of this embodiment is configured to sterilize the liquid.

The polishing apparatus further includes an ultraviolet irradiation head 55 configured to irradiate the liquid flowing through the liquid circulation line 45 to sterilize the liquid with ultraviolet light. In this embodiment, the ultraviolet irradiation head 55 is mounted on the liquid supply pipe 46 of the liquid circulation line 45 and is configured to irradiate the liquid flowing through the liquid supply pipe 46 with ultraviolet light so as to sterilize the liquid.

The polishing apparatus includes an optical fiber cable 65 branched and extending from the projection optical fiber cable 37, and a light splitter 64 configured to branch the optical fiber cable 65 from the projection optical fiber cable 37. More specifically, the light splitter 64 is configured to branch the first projection optical fiber cable 37a of the projection optical fiber cable 37 into the second projection optical fiber cable 37b and the optical fiber cable 65. Examples of the light splitter 64 include, for example, an optical coupler and an optical splitter. However, the method of branching the optical fiber cable 65 from the projection optical fiber cable 37 is not limited to these embodiments using the light splitter 64. For example, the first projection optical fiber cable 37a may include a bundle of multiple optical fiber cables, and the optical fiber cable 65 may include at least one optical fiber cable extracted from the bundle of multiple optical fiber cables. The second projection optical fiber cable 37b may include the remaining optical fiber cables. In this case, the optical fiber cable 65 may be branched from the projection optical fiber cable 37 without providing the light splitter 64.

The optical fiber cable 65 is a light transmission unit configured to guide light emitted from the light source 25 and branched from the projection optical fiber cable 37 to the liquid flowing through the liquid supply pipe 46. The ultraviolet irradiation head 55 includes the tip end of the optical fiber cable 65 and a head case 67 surrounding a portion of the liquid supply pipe 46. The head case 67 is configured to support the tip end of the optical fiber cable 65. As illustrated in FIG. 2, the liquid supply pipe 46 includes an irradiation window 70 formed of a material that transmits ultraviolet light. The tip end of the optical fiber cable 65 is positioned to face the irradiation window 70. The head case 67 is arranged to surround the irradiation window 70.

In this embodiment, light emitted from the light source 25 contains ultraviolet light. Accordingly, the light transmitted to the ultraviolet irradiation head 55 through the optical fiber cable 65 contains 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 may be maintained in a clean state. In an embodiment, the ultraviolet irradiation head 55 may be mounted on the liquid return pipe 47 of the liquid circulation line 45 and may be configured to irradiate the liquid flowing through the liquid return pipe 47 with ultraviolet light so as to sterilize the liquid.

As illustrated in FIG. 1, the polishing apparatus further includes: an ozone supply device 60 configured to sterilize the liquid in the tank 50 by supplying ozone into the liquid in the tank 50; and an ozone collecting device 62 configured to collect ozone generated from ultraviolet light contained in light emitted from the light source 25. In this embodiment, the ozone supply device 60 is an aeration device disposed in the tank 50 and generates ozone water by supplying ozone gas into the liquid in the tank 50. Thus, the liquid in the tank 50 is sterilized by ozone. As a result, the liquid used for measuring the film thickness of the workpiece W may be maintained in a clean state.

The configuration of the ozone supply device 60 is not limited to this embodiment as long as ozone can be supplied into the liquid in the tank 50. In an embodiment, the ozone supply device 60 may be an ozone gas supply device configured to create an ozone atmosphere inside the tank 50. By forming an ozone atmosphere inside the tank 50, ozone gas is dissolved into the liquid in the tank 50, thereby generating ozone water.

The ozone supply device 60 is connected to an ozone gas supply line 73 extending from the ozone collecting device 62. Ozone gas is transmitted from the ozone collecting device 62 to the ozone supply device 60 through the ozone gas supply line 73. The ozone collecting device 62 is disposed to surround the light source 25. As described above, the light source 25 emits light containing ultraviolet light. The ozone collecting device 62 is configured to collect ozone generated when an oxygen-containing gas (e.g., air) is irradiated with ultraviolet light emitted from the light source 25.

The ozone collecting device 62 is connected to a purge gas supply line 76 extending from a purge gas supply source (not illustrated). By supplying purge gas to the ozone collecting device 62 through the purge gas supply line 76, the collected ozone is transmitted as ozone gas to the ozone supply device 60. In an embodiment, instead of the ozone collecting 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.

In an embodiment, the liquid supply source connected to the supply line 82 may be an ozone water supply source, and ozone water may be supplied to the tank 50 through the supply line 82 and the liquid replacement line 81. In this case, the polishing apparatus may not include the ozone supply device 60 and the ozone collecting device 62.

The ozone supply device 60 is connected to the operation controller 10, and the operation of the ozone supply device 60 is controlled by the operation controller 10. During the operation of the polishing apparatus, the operation controller 10 is configured to drive the ozone supply device 60 to supply ozone into the liquid in the tank 50 so as to sterilize the liquid in the tank 50. In an embodiment, the operation of the ozone supply device 60 may be manually controlled.

As described above, during polishing of the workpiece W, the film thickness measuring device 20 measures the film thickness of the workpiece W. Specifically, during polishing of the workpiece W, the operation controller 10 gives a command to the light source 25 to emit light from the light source 25 and to cause 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 the liquid flowing through the liquid supply pipe 46 is irradiated with ultraviolet light. Accordingly, while the film thickness measuring device 20 is measuring the film thickness of the workpiece W, the ultraviolet irradiation head 55 irradiates the liquid flowing through the liquid supply pipe 46 with ultraviolet light. Thus, during polishing of the workpiece W, the liquid flowing through the liquid supply pipe 46 is sterilized by the ultraviolet light.

In this embodiment, the operation controller 10 is configured to give a command to the light source 25 to emit light from the light source 25 during idling in which polishing of the workpiece W is not performed and to cause the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply pipe 46 with ultraviolet light. The term “idling” refers to a period during which the operation of the polishing apparatus continues, for example, after a polished workpiece is unloaded from the polishing apparatus and before the next workpiece to be polished is loaded into the polishing apparatus and polishing is started. Thus, not only during polishing of the workpiece W but also during idling, the liquid flowing through the liquid supply pipe 46 is sterilized by ultraviolet light. 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.

In an embodiment, the operation controller 10 may be configured to give a command to the light source 25 to emit light from the light source 25 at predetermined time intervals during idling in which polishing of the workpiece W is not performed and to cause the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply pipe 46 with ultraviolet light at predetermined time intervals.

FIG. 4 is a schematic enlarged view illustrating a peripheral portion of the film thickness measuring device 20 according to another embodiment of the polishing apparatus. Since the configuration and operation of this embodiment not specifically described are the same as those of the embodiment described with reference to FIGS. 1 to 3, redundant descriptions will be omitted. In the embodiment illustrated in FIG. 4, the polishing apparatus further includes an optical member 58 configured to reflect a portion, containing ultraviolet light, of light emitted from the light source 25.

In this embodiment, the optical fiber cable 65 includes a first optical fiber cable 65a branched and extending from the projection optical fiber cable 37, and a second optical fiber cable 65b extending from the optical member 58. The first optical fiber cable 65a is a light transmission unit configured to guide light emitted from the light source 25 and branched from the projection optical fiber cable 37 to the optical member 58, and the second optical fiber cable 65b is a light transmission unit configured to guide reflected light from the optical member 58 to the liquid flowing through the liquid supply pipe 46. The ultraviolet irradiation head 55 includes a tip end of the second optical fiber cable 65b of the optical fiber cable 65 and a head case 67 surrounding a portion of the liquid supply pipe 46.

The optical member 58 is disposed obliquely with respect to an optical path of light emitted from the light source 25 and guided by the first optical fiber cable 65a. The optical member 58 is optically connected to the ultraviolet irradiation head 55. In this embodiment, light emitted from the light source 25 contains ultraviolet light. The optical member 58 is configured to reflect a portion, containing ultraviolet light, of the light emitted from the light source 25 and to transmit the remaining light. Light reflected by the optical member 58 is transmitted to the ultraviolet irradiation head 55. That is, the light reflected by the optical member 58 is guided to the liquid flowing through the liquid supply pipe 46 through the second optical fiber cable 65b of the optical fiber cable 65.

The optical member 58 is one of an ultraviolet reflection filter, a dichroic mirror, and a half mirror. The ultraviolet reflection filter (e.g., a non-absorptive ultraviolet cut filter) is configured to reflect ultraviolet light and transmit other light. When the optical member 58 is an ultraviolet reflection filter, the optical member 58 reflects ultraviolet light contained in the light emitted from the light source 25. The ultraviolet light reflected by the optical member 58 is transmitted to the ultraviolet irradiation head 55. The optical member 58 transmits light other than the ultraviolet light in the light emitted from the light source 25.

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

The half mirror is configured to reflect light at a predetermined reflectance and to transmit other light. When the optical member 58 is a half mirror, the optical member 58 reflects light emitted from the light source 25 at a predetermined reflectance (e.g., 50%). Light reflected by the optical member 58 is transmitted to the ultraviolet irradiation head 55. This reflected light is composed of substantially the same components as the light emitted from the light source 25. Accordingly, the light reflected by the optical member 58 contains ultraviolet light. The optical member 58 transmits light other than the reflected light (e.g., the remaining 50% of the light) in the light emitted from the light source 25.

The light reflected by the optical member 58 contains 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 may be maintained in a clean state.

FIG. 5 is a schematic enlarged view illustrating a periphery of the film thickness measuring device 20 according to another embodiment of the polishing apparatus. Since the configuration and operation of this embodiment not specifically described are the same as those of the embodiment described with reference to FIG. 4, redundant descriptions will be omitted. In the embodiment illustrated in FIG. 5, the arrangement of the optical member 58 differs from that of the embodiment illustrated in FIG. 4, and the light splitter 64 is not provided.

In this embodiment, the first projection optical fiber cable 37a extends to the optical member 58, and the second projection optical fiber cable 37b extends from the optical member 58 to the inside of the polishing table 3. The first projection optical fiber cable 37a is a light transmission unit configured to guide light emitted from the light source 25 to the optical member 58, and the second projection optical fiber cable 37b is a light transmission unit configured to guide light transmitted through the optical member 58 to the surface of the workpiece W.

The optical member 58 is disposed obliquely with respect to an optical path of light emitted from the light source 25. The optical member 58 is optically connected to the ultraviolet irradiation head 55. In this embodiment, light emitted from the light source 25 contains ultraviolet light. The optical member 58 is configured to reflect a portion, containing ultraviolet light, of the light emitted from the light source 25 and to transmit the remaining light. Light reflected by the optical member 58 is transmitted to the ultraviolet irradiation head 55, and light transmitted through the optical member 58 is transmitted to the optical sensor head 22. More specifically, the light emitted from the light source 25 is guided to the optical member 58 through the first projection optical fiber cable 37a of the projection optical fiber cable 37. Light reflected by the optical member 58 is guided to the liquid flowing through the liquid supply pipe 46 through the optical fiber cable 65. Light transmitted through the optical member 58 is guided to the workpiece W through the second projection optical fiber cable 37b of the projection optical fiber cable 37. That is, the light transmitted through the optical member 58 is transmitted to the optical sensor head 22.

A material such as a transparent resin that forms the transparent window 33 may deteriorate due to ultraviolet light. Light transmitted through the optical member 58 and transmitted to the optical sensor head 22 includes no ultraviolet light or includes less ultraviolet light than the ultraviolet light contained in the light emitted from the light source 25. Specifically, when the optical member 58 is an ultraviolet reflection filter or a dichroic mirror, the light transmitted through the optical member 58 and transmitted to the optical sensor head 22 includes no ultraviolet light. When the optical member 58 is a half mirror, the ultraviolet light contained in the light transmitted through the optical member 58 and transmitted to the optical sensor head 22 is ultraviolet light obtained by removing the ultraviolet light reflected by the optical member 58 from the ultraviolet light contained in the light emitted from the light source 25. According to this embodiment, deterioration of the transparent window 33 caused by ultraviolet light may be prevented.

FIG. 6 is a schematic view illustrating still another embodiment of the polishing apparatus. Since the configuration and operation of this embodiment not specifically described are the same as those of the embodiment described with reference to FIGS. 1 to 3, redundant descriptions will be omitted. In the embodiment illustrated in FIG. 6, the polishing apparatus further includes a second light source 90 connected to the 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 a first light source 25. The polishing apparatus of this embodiment does not include the light splitter 64, and light emitted from the first light source 25 is used only for measuring the film thickness of the workpiece W. In an embodiment, the light emitted from the first light source 25 may not contain ultraviolet light.

The second light source 90 is configured to emit light containing ultraviolet light. Examples of the second light source 90 include a xenon lamp and an ultraviolet lamp. The second light source 90 is connected to the operation controller 10, and operation of the second light source 90 is controlled by the operation controller 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 a light transmission unit that guides light from the second light source 90 to the liquid flowing through the liquid supply pipe 46. Light, containing ultraviolet light, emitted from the second light source 90 is transmitted to the ultraviolet irradiation head 55.

In this embodiment, the ozone collecting device 62 is disposed to surround the second light source 90. The ozone collecting device 62 is configured to collect ozone generated when an oxygen-containing gas (e.g., air) is irradiated with ultraviolet light emitted from the second light source 90. In an embodiment, the ozone collecting device 62 may be disposed on the first light source 25 or on both the first light source 25 and the second light source 90.

During polishing of the workpiece W, the operation controller 10 gives a command to the first light source 25 to emit light from the first light source 25 and to cause the film thickness measuring device 20 to measure the film thickness of the workpiece W. Furthermore, the operation controller 10 is configured to give a command to the second light source 90 to emit light from the second light source 90 and to cause the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply pipe 46 with ultraviolet light. Thus, during polishing of the workpiece W, the liquid flowing through the liquid supply pipe 46 is sterilized by the ultraviolet light. In an embodiment, the operation controller 10 may be configured to give a command to the second light source 90 to emit light from the second light source 90 at predetermined time intervals during polishing of the workpiece W and to cause the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply pipe 46 with ultraviolet light at predetermined time intervals.

During idling in which polishing of the workpiece W is not performed, emission of light from the first light source 25 is stopped because measurement of the film thickness by the film thickness measuring device 20 is not performed. The operation controller 10 is configured to give a command to the second light source 90 to emit light from the second light source 90 during idling and to cause the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply pipe 46 with ultraviolet light. Accordingly, even during idling, the liquid flowing through the liquid supply pipe 46 is sterilized by ultraviolet light. In an embodiment, the operation controller 10 may be configured to give a command to the second light source 90 to emit light from the second light source 90 at predetermined time intervals during idling and to cause the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply pipe 46 with ultraviolet light at predetermined time intervals.

FIG. 7 is a schematic view illustrating still another embodiment of the polishing apparatus. Since the configuration and operation of this embodiment that are not specifically described are the same as those of the embodiments described with reference to FIGS. 1 to 3, redundant descriptions will be omitted. In the embodiment illustrated in FIG. 7, the polishing apparatus includes, instead of the liquid circulation line 45 and the tank 50, a liquid supply line 92 configured to supply liquid to the through-hole 34 and a drain line 93 configured to discharge liquid from the through-hole 34.

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 a 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. The liquid supply line 92 and the drain line 93 are respectively provided with a liquid supply valve 95 and a drain valve 96. During the operation of the polishing apparatus, the liquid supply valve 95 and the drain valve 96 are opened, 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 operation of the polishing apparatus is stopped, the liquid supply valve 95 is closed to stop the supply of liquid from the liquid supply source 98.

In this embodiment, the ultraviolet irradiation head 55 is mounted on the liquid supply line 92 and is configured to irradiate the liquid flowing through the liquid supply line 92 with ultraviolet light to sterilize the liquid. The configuration of the ultraviolet irradiation head 55 is the same as that of the embodiment described with reference to FIG. 2.

In this embodiment, the polishing apparatus does not include the ozone supply device 60 or the ozone collecting device 62. In an embodiment, the liquid supplied from the liquid supply source 98 may be ozone water.

Similarly to the embodiment described with reference to FIGS. 1 to 3, during polishing of the workpiece W, the operation controller 10 gives a command to the light source 25 to emit light from the light source 25, to cause the film thickness measuring device 20 to measure the film thickness of the workpiece W, and to cause the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply line 92 with ultraviolet light. Thus, during polishing of the workpiece W, the liquid flowing through the liquid supply line 92 is sterilized by ultraviolet light.

The operation controller 10 may give a command to the light source 25 to emit light from the light source 25 during idling in which polishing of the workpiece W is not performed and to cause the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply line 92 with ultraviolet light. Accordingly, even during idling, the liquid flowing through the liquid supply line 92 is sterilized by ultraviolet light. In an embodiment, the operation controller 10 may be configured to give a command to the light source 25 to emit light from the light source 25 at predetermined time intervals during idling and to cause the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply line 92 with ultraviolet light at predetermined time intervals.

In this embodiment, during the operation of the polishing apparatus, because new liquid is supplied from the liquid supply line 92 and discharged through the drain line 93, the liquid may be maintained in a clean state. However, when the operation of the polishing apparatus is stopped for a long period of time for, for example, maintenance, fungi included in the liquid in the liquid supply source 98 and the liquid supply line 92 may easily propagate. Accordingly, in an embodiment, after the operation of the polishing apparatus has been stopped for a predetermined period or longer, the operation controller 10 may be configured to give a command to the light source 25 to emit light from the light source 25 and to cause the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply line 92 with ultraviolet light. However, the timing at which the ultraviolet irradiation head 55 irradiates the liquid flowing through the liquid supply line 92 with ultraviolet light is not particularly limited.

FIG. 8 is a schematic view illustrating still another embodiment of the polishing apparatus. Since the configuration and operation of this embodiment not specifically described are the same as those of the embodiment described with reference to FIG. 7, redundant descriptions will be omitted. As illustrated in FIG. 8, the polishing apparatus of this embodiment does not include a transparent window 33, and the through-hole 34 is open 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 to the surface of the workpiece W through the through-hole 34. The light is reflected on 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.

In this embodiment, since the through-hole 34 is filled with a liquid and the polishing liquid and polishing debris on the polishing pad 2 are discharged together with the liquid through a drain line 93, an optical path for film thickness measurement is secured.

Each embodiment including the optical member 58 described with reference to FIGS. 4 and 5 may also be applied to each embodiment described with reference to FIGS. 7 and 8.

FIG. 9 is a schematic view illustrating still another embodiment of the polishing apparatus. Since the configuration and operation of this embodiment not particularly described are the same as those of the embodiment described with reference to FIG. 7, redundant descriptions are omitted. The embodiment illustrated in FIG. 9 applies the first light source 25 and the second light source 90 illustrated in FIG. 6 to the embodiment described with reference to FIG. 7. The configurations and operations of the first light source 25 and the second light source 90 in the embodiment illustrated in FIG. 9 are basically the same as those of the first light source 25 and the second light source 90 illustrated in FIG. 6.

The second light source 90 is configured to emit light containing ultraviolet light. 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 a light transmission storage that guides light from the second light source 90 to the liquid flowing through the liquid supply line 92. Light, containing ultraviolet light, emitted from the second light source 90 is transmitted to the ultraviolet irradiation head 55, and the liquid flowing through the liquid supply line 92 is irradiated with the ultraviolet light. Accordingly, the liquid flowing through the liquid supply line 92 is sterilized by the ultraviolet light.

Similarly to the embodiment described with reference to FIG. 6, during polishing of the workpiece W, the operation controller 10 gives a command to the first light source 25 to emit light from the first light source 25 and to cause the film thickness measuring device 20 to measure the film thickness of the workpiece W. Further, the operation controller 10 is configured to give a command to the second light source 90 to emit light from the second light source 90 and to cause the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply line 92 with ultraviolet light. Thus, during polishing of the workpiece W, the liquid flowing through the liquid supply line 92 is sterilized by ultraviolet light. In an embodiment, the operation controller 10 may be configured to give a command to the second light source 90 to emit light from the second light source 90 at predetermined time intervals during polishing of the workpiece W and to cause the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply line 92 with ultraviolet light at the predetermined time intervals.

The operation controller 10 may give a command to the second light source 90 to emit light from the second light source 90 during idling in which polishing of the workpiece W is not performed and to cause the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply line 92 with ultraviolet light. Accordingly, even during idling, the liquid flowing through the liquid supply line 92 is sterilized by ultraviolet light. In an embodiment, the operation controller 10 may be configured to give a command to the second light source 90 to emit light from the second light source 90 at predetermined time intervals during idling and to cause the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply line 92 with ultraviolet light at the predetermined time intervals.

In an embodiment, after the operation of the polishing apparatus has been stopped for a predetermined period or longer, the operation controller 10 may be configured to give a command to the second light source 90 to emit light from the second light source 90 and to cause the ultraviolet irradiation head 55 to irradiate the liquid flowing through the liquid supply line 92 with ultraviolet light. However, the timing at which the ultraviolet irradiation head 55 irradiates the liquid flowing through the liquid supply line 92 with ultraviolet light is not particularly limited.

The polishing pad 2 that does not include the transparent window 33 described with reference to FIG. 8 may also be applied to the embodiment described with reference to FIG. 9.

In the embodiments described above, a polishing apparatus includes one set of a transparent window 33 and an optical sensor head 22, but a polishing apparatus may include a plurality of sets of transparent windows 33 and optical sensor heads 22.

From the foregoing, it will be appreciated that various embodiments of the present disclosure have been described herein for purposes of illustration, and that various modifications may be made without departing from the scope and spirit of the present disclosure. Accordingly, the various embodiments disclosed herein are not intended to be limiting, with the true scope and spirit being indicated by the following claims.