Polishing device

Abstract

To provide a polishing device which can prevent abrasive grains of a polishing liquid and swarf of a workpiece from adhering to an optical sensor head and improve measurement accuracy of a film thickness of the workpiece.SOLUTION: A polishing device includes: a polishing table 3 supporting a polishing pad 2 provided with a through hole 4; a polishing head 1 which presses a workpiece W to the polishing pad 2; an optical film thickness measurement system 20 having an optical sensor head 25 disposed below the polishing pad 2; and a sensor head cleaning nozzle 40 which discharges a cleaning fluid to the optical sensor head 25. The sensor head cleaning nozzle 40 is disposed in the polishing table 3 and directed to the optical sensor head 25.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a technique for polishing workpieces such as wafers, wiring boards, and square substrates, and more particularly to a technique for guiding light to the workpiece through holes in a polishing pad for polishing the workpiece and measuring the film thickness of the workpiece based on the spectrum of the light reflected from the workpiece. [Background technology]

[0002] In the manufacturing process of semiconductor devices, a chemical mechanical polishing (CMP) apparatus is used to polish the surface of a workpiece such as a wafer. The CMP apparatus is equipped with a polishing table to which a polishing pad is attached, and a polishing head for pressing the workpiece against the polishing surface of the polishing pad. The CMP apparatus presses the workpiece against the polishing surface of the polishing pad with the polishing head while supplying a polishing liquid (e.g., slurry) onto the polishing pad, thereby bringing the surface of the workpiece into sliding contact with the polishing surface of the polishing pad. The surface of the workpiece is polished by the chemical action of the polishing liquid and the mechanical action of the abrasive grains contained in the polishing liquid and / or the polishing pad.

[0003] Polishing of a workpiece is terminated when the thickness of a film (such as an insulating film or a silicon layer) constituting the surface of the workpiece reaches a target film thickness. The polishing apparatus is equipped with an optical film thickness measurement system for measuring the film thickness of the workpiece. The optical film thickness measurement system is configured to irradiate light onto the workpiece using an optical sensor head arranged in the polishing table, receive reflected light from the workpiece, generate a spectrum of the reflected light from the intensity of the reflected light, and determine the film thickness of the workpiece based on the spectrum of the reflected light.

[0004] In order to stabilize film thickness measurements using an optical film thickness measurement system, it is necessary to keep the light path clean. For example, Patent Document 1 describes how the light path is filled with a transparent liquid to prevent the intrusion of polishing liquid and polishing debris. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2006-525878 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the abrasive grains contained in the polishing liquid and the polishing debris from the workpiece usually have a higher specific gravity than the transparent liquid, and the abrasive grains and the polishing debris may adhere to the optical sensor head. If the abrasive grains and the polishing debris adhere to the optical sensor head, the measured value of the intensity of the reflected light from the workpiece decreases, and the optical film thickness measurement system cannot accurately measure the film thickness.

[0007] Therefore, the present invention provides a polishing apparatus that can prevent abrasive grains in the polishing liquid and polishing debris from the workpiece from adhering to an optical sensor head, thereby improving the measurement accuracy of the film thickness of the workpiece. [Means for solving the problem]

[0008] In one aspect, a polishing apparatus is provided, comprising a polishing table supporting a polishing pad having a through hole formed therein, a polishing head pressing a workpiece against the polishing pad, an optical film thickness measurement system having an optical sensor head positioned below the polishing pad, and a sensor head cleaning nozzle that ejects a cleaning liquid toward the optical sensor head, the sensor head cleaning nozzle being positioned within the polishing table and facing the optical sensor head.

[0009] In one embodiment, the sensor head cleaning nozzle is disposed at a higher position than the optical sensor head. In one embodiment, the sensor head cleaning nozzle is inclined downward relative to the horizontal direction. In one aspect, the sensor head cleaning nozzle is disposed at the same height as the optical sensor head. In one aspect, the sensor head cleaning nozzle is oriented horizontally. In one aspect, the polishing apparatus further includes a transparent liquid inlet passage that supplies transparent liquid to the through hole, the optical sensor head is disposed within the transparent liquid inlet passage, and the sensor head cleaning nozzle is connected to the transparent liquid inlet passage. In one aspect, the sensor head cleaning nozzle is a fan-shaped nozzle configured to form a fan-shaped jet of the cleaning liquid. In one embodiment, the sensor head cleaning nozzle is a multi-nozzle having a plurality of cleaning liquid outlets arranged around the periphery of the optical sensor head.

[0010] In one aspect, the sensor head cleaning nozzle is coupled to a cleaning liquid source, the cleaning liquid source being a pure water source or a chemical liquid source. In one aspect, the sensor head cleaning device further includes an ultrasonic vibrator that applies ultrasonic waves to the cleaning liquid supplied to the sensor head cleaning nozzle. In one aspect, the polishing apparatus further includes a flow control valve connected to the sensor head cleaning nozzle and an operation control unit that controls the operation of the flow control valve, and the operation control unit is configured to: when the workpiece is above the optical sensor head during polishing of the workpiece, command the flow control valve to release the cleaning liquid from the sensor head cleaning nozzle at a first flow rate; and when the workpiece is not above the optical sensor head during polishing of the workpiece, command the flow control valve to release the cleaning liquid from the sensor head cleaning nozzle at a second flow rate, the second flow rate being greater than the first flow rate. Effect of the Invention

[0011] The flow of cleaning liquid discharged from the sensor head cleaning nozzle toward the optical sensor head can prevent abrasive grains of the polishing liquid and polishing debris from the workpiece from adhering to the optical sensor head, and therefore the optical film thickness measurement system can accurately measure the film thickness of the workpiece based on the intensity of the reflected light from the workpiece. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram illustrating an embodiment of a polishing apparatus. [Diagram 2] FIG. 2 is a cross-sectional view showing a detailed configuration of the optical film thickness measurement system. [Diagram 3] 1 is an enlarged cross-sectional view showing an embodiment of an optical sensor head, a transparent liquid inlet channel, a transparent liquid outlet channel, and a sensor head cleaning nozzle. FIG. [Figure 4] FIG. 11 is an enlarged cross-sectional view showing another embodiment of the polishing apparatus. [Diagram 5] 5 is a top view of the sensor head cleaning nozzle and the optical sensor head of the embodiment shown in FIG. 3 or 4. FIG. [Figure 6] FIG. 13 is a top view showing another embodiment of the liquid in the sensor head cleaning nozzle. [Figure 7] FIG. 13 is a top view showing another embodiment of the liquid in the sensor head cleaning nozzle. [Figure 8] FIG. 11 is an enlarged cross-sectional view showing still another embodiment of the polishing apparatus. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a schematic diagram showing one embodiment of a polishing apparatus. As shown in Fig. 1, the polishing apparatus includes a polishing pad 2 having a through hole 4 formed therein, a polishing table 3 supporting the polishing pad 2, a polishing head 1 pressing a workpiece W against the polishing pad 2, a table motor 6 rotating the polishing table 3, a polishing liquid supply nozzle 5 for supplying a polishing liquid such as a slurry onto the polishing pad 2, and an operation control unit 9 for controlling the operation of the polishing apparatus.

[0014] The upper surface of the polishing pad 2 constitutes a polishing surface 2a for polishing a workpiece W. Through holes 4 penetrate the polishing pad 2. The workpiece W has a film that constitutes its surface. Examples of the workpiece W to be polished include wafers, wiring boards, square boards, etc. used in the manufacture of semiconductor devices.

[0015] The polishing head 1 is connected to a head shaft 10, and the head shaft 10 is connected to a polishing head rotating device 15. The polishing head rotating device 15 is configured to rotate the polishing head 1 together with the head shaft 10 in the direction indicated by the arrow. The configuration of the polishing head rotating device 15 is not particularly limited, but in one example, the polishing head rotating device 15 includes an electric motor, a belt, a pulley, and the like. The polishing table 3 is connected to a table motor 6, and the table motor 6 is configured to rotate the polishing table 3 and the polishing pad 2 in the direction indicated by the arrow. The polishing head 1, the polishing head rotating device 15, and the table motor 6 are electrically connected to an operation control unit 9.

[0016] The workpiece W is polished as follows. A polishing liquid is supplied from a polishing liquid supply nozzle 5 to the polishing surface 2a of the polishing pad 2 on the polishing table 3 while the table motor 6 and the polishing head rotating device 15 rotate the polishing table 3 and the polishing head 1 in the directions shown by the arrows in Fig. 1. While the workpiece W is rotated by the polishing head 1, the workpiece W is pressed against the polishing surface 2a of the polishing pad 2 by the polishing head 1 with the polishing liquid present on the polishing pad 2. The surface of the workpiece W is polished by the chemical action of the polishing liquid and the mechanical action of the abrasive grains contained in the polishing liquid and / or the polishing pad 2.

[0017] The operation control unit 9 includes a storage device 9a in which a program is stored, and a calculation device 9b that executes calculations according to instructions included in the program. The operation control unit 9 includes at least one computer. The storage device 9a includes a main storage device such as a random access memory (RAM), and an auxiliary storage device such as a hard disk drive (HDD) or a solid state drive (SSD). Examples of the calculation device 9b include a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit). However, the specific configuration of the operation control unit 9 is not limited to these examples.

[0018] The polishing apparatus is equipped with an optical film thickness measurement system 20 that measures the film thickness of the workpiece W. The optical film thickness measurement system 20 is equipped with a light source 22 that emits light, an optical sensor head 25 that irradiates the workpiece W with the light from the light source 22 and receives the light reflected from the workpiece W, a spectrometer 23 connected to the optical sensor head 25, and a spectrum processing unit 30 that determines the film thickness of the workpiece W based on the spectrum of the light reflected from the workpiece W. The optical sensor head 25 is disposed within the polishing table 3 and rotates together with the polishing table 3.

[0019] The spectrum processing unit 30 includes a storage device 30a in which a program is stored, and an arithmetic unit 30b that executes calculations according to instructions included in the program. The spectrum processing unit 30 includes at least one computer. The storage device 30a includes a main storage device such as a random access memory (RAM), and an auxiliary storage device such as a hard disk drive (HDD) or a solid state drive (SSD). Examples of the arithmetic unit 30b include a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit). However, the specific configuration of the spectrum processing unit 30 is not limited to these examples.

[0020] Each of the operation control unit 9 and the spectrum processing unit 30 may be composed of a plurality of computers. For example, each of the operation control unit 9 and the spectrum processing unit 30 may be composed of a combination of an edge server and a cloud server. In one embodiment, the operation control unit 9 and the spectrum processing unit 30 may be composed of a single computer.

[0021] 2 is a cross-sectional view showing a detailed configuration of the optical film thickness measurement system 20. The optical sensor head 25 is disposed in the polishing table 3, and the light source 22 and the spectroscope 23 are attached to the polishing table 3. The optical sensor head 25, the light source 22, and the spectroscope 23 rotate together with the polishing table 3 and the polishing pad 2. The position of the optical sensor head 25 is a position where it crosses the surface of the workpiece W on the polishing pad 2 every time the polishing table 3 and the polishing pad 2 rotate once. The optical sensor head 25 is connected to the light source 22 and the spectroscope 23, and the spectroscope 23 is connected to the spectrum processing unit 30.

[0022] The optical film thickness measuring device 20 includes a light projecting fiber optic cable 27 that guides light emitted from the light source 22 to the surface of the workpiece W, and a light receiving fiber optic cable 28 that receives the light reflected from the workpiece W and sends the reflected light to the spectroscope 23. An end of the light projecting fiber optic cable 27 and an end of the light receiving fiber optic cable 28 form an optical sensor head 25 that guides light to the surface of the workpiece W and receives the light reflected from the workpiece W. The other end of the light projecting fiber optic cable 27 is connected to the light source 22, and the other end of the light receiving fiber optic cable 28 is connected to the spectroscope 23. The spectroscope 23 is configured to resolve the light reflected from the workpiece W according to wavelength and measure the intensity of the reflected light over a predetermined wavelength range.

[0023] The optical sensor head 25, which is composed of an end of a light-projecting optical fiber cable 27 and an end of a light-receiving optical fiber cable 28, is positioned below the through-hole 4 of the polishing pad 2. Light emitted by the light source 22 passes through the light-projecting optical fiber cable 27, and is guided from the optical sensor head 25 through the through-hole 4 to the workpiece W. The reflected light from the workpiece W is received by the optical sensor head 25 through the through-hole 4 and sent to the spectrometer 23 via the light-receiving optical fiber cable 28. The spectrometer 23 breaks down the reflected light according to its wavelength 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 23 to a spectrum processing unit 30.

[0024] The spectrum processor 30 is configured to generate a spectrum of the reflected light from the workpiece W from the reflected light intensity measurement data. The spectrum of the reflected light is expressed as a line graph (i.e., a spectral waveform) showing the relationship between the wavelength and intensity of the reflected light. The intensity of the reflected light can also be expressed as a relative value such as reflectance or relative reflectance.

[0025] The spectrum processor 30 is configured to determine the film thickness of the workpiece W based on 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 spectrum processor 30 determines a reference spectrum from a reference spectrum library that has a shape closest to the spectrum of the reflected light, and determines the film thickness associated with the determined reference spectrum. In another example, the spectrum processor 30 performs a Fourier transform on the spectrum of the reflected light, and determines the film thickness from the obtained frequency spectrum.

[0026] The polishing apparatus includes a sensor head cleaning nozzle 40 that ejects a cleaning liquid toward the optical sensor head 25 and cleans the optical sensor head 25 with the cleaning liquid. The sensor head cleaning nozzle 40 is disposed in the polishing table 3 and rotates integrally with the polishing table 3. The sensor head cleaning nozzle 40 is connected to a cleaning liquid supply line 52 that extends through the polishing table 3, and the cleaning liquid supply line 52 is connected to a cleaning liquid supply source 54. The sensor head cleaning nozzle 40 is connected to the cleaning liquid supply source 54 via the cleaning liquid supply line 52. In one embodiment, the sensor head cleaning nozzle 40 and the cleaning liquid supply line 52 may be integrally configured.

[0027] Examples of the cleaning liquid supply source 54 include a pure water supply source that supplies pure water as the cleaning liquid, and a chemical liquid supply source that supplies a chemical liquid as the cleaning liquid. An example of the chemical liquid is a potassium hydroxide (KOH) solution that has an etching effect. In this embodiment, the cleaning liquid supply source 54 is a pure water supply source, and pure water is used as the cleaning liquid. However, the type of the cleaning liquid is not particularly limited as long as it can clean the optical sensor head 25.

[0028] The polishing apparatus further includes a flow rate control valve 56 attached to the cleaning liquid supply line 52. The flow rate control valve 56 is electrically connected to the operation control unit 9, and the operation of the flow rate control valve 56 is controlled by the operation control unit 9. The flow rate control valve 56 is connected to the sensor head cleaning nozzle 40 via the cleaning liquid supply line 52. The flow rate control valve 56 is configured to adjust the flow rate of the cleaning liquid flowing through the cleaning liquid supply line 52. Therefore, the flow rate of the cleaning liquid discharged from the sensor head cleaning nozzle 40 toward the optical sensor head 25 is adjusted by the flow rate control valve 56.

[0029] The flow rate control valve 56 is an actuator-driven type such as an electric valve, a solenoid valve, or an air-operated valve. The operation control unit 9 can give a command to the flow rate control valve 56 to control the flow rate of the cleaning liquid discharged from the sensor head cleaning nozzle 40 toward the optical sensor head 25.

[0030] The polishing table 3 has a transparent liquid inlet channel 50 and a transparent liquid outlet channel 51 which communicate with the through hole 4. The transparent liquid inlet channel 50 and the transparent liquid outlet channel 51 are provided in the polishing table 3 and rotate integrally with the polishing table 3. The polishing apparatus 1 includes a transparent liquid supply line 35 connected to the transparent liquid inlet channel 50, a transparent liquid discharge line 36 connected to the transparent liquid outlet channel 51, and a flow rate control valve 41 connected to the transparent liquid supply line 35. The flow rate control valve 41 is configured to control the flow rate of the transparent liquid flowing through the transparent liquid supply line 35. Therefore, the flow rate of the transparent liquid supplied to the transparent liquid inlet channel 50 and the through hole 4 is controlled by the flow rate control valve 41.

[0031] One end of the transparent liquid supply line 35 is connected to the transparent liquid inlet path 50, and the other end is connected to a transparent liquid supply source 55. The transparent liquid inlet path 50 may be configured integrally with the transparent liquid supply line 35. An example of the transparent liquid supply source 55 is a pure water supply source that supplies pure water as the transparent liquid. The transparent liquid (e.g., pure water) is supplied into the through hole 4 of the polishing pad 2 through the transparent liquid supply line 35 and the transparent liquid inlet path 50. The transparent liquid supplied into the through hole 4 of the polishing pad 2 is discharged from the through hole 4 through the transparent liquid outlet path 51, and further discharged through the transparent liquid discharge line 36. The transparent liquid outlet path 51 may be configured integrally with the transparent liquid discharge line 36.

[0032] During polishing of the workpiece W, the through holes 4 of the polishing pad 2 are filled with transparent liquid. The flow of transparent liquid in the through holes 4 can restrict the intrusion of the polishing liquid and polishing debris of the workpiece W into the transparent liquid inlet path 50.

[0033] The flow rate control valve 41 is an actuator-driven type such as an electric valve, a solenoid valve, or an air-operated valve. The operation control unit 9 can give a command to the flow rate control valve 41 to control the flow rate of the transparent liquid supplied to the transparent liquid inflow channel 50.

[0034] During polishing of the workpiece W, the polishing pad 2 rotates together with the polishing table 3, whereas the workpiece W held by the polishing head 1 does not rotate together with the polishing table 3. Therefore, there are times when the workpiece W is above the optical sensor head 25 and times when the workpiece W is not above the optical sensor head 25.

[0035] In one embodiment, when the workpiece W is above the optical sensor head 25, the operation control unit 9 issues a command to the flow rate adjustment valve 41 to supply transparent liquid to the transparent liquid inlet channel 50 at a preset measurement flow rate, and when the workpiece W is not above the optical sensor head 25, issues a command to the flow rate adjustment valve 41 to supply transparent liquid to the transparent liquid inlet channel 50 at a flow rate lower than the measurement flow rate, or stops the supply of transparent liquid to the transparent liquid inlet channel 50. By such an operation, it is possible to prevent the polishing liquid on the polishing pad 2 from being diluted with the transparent liquid (e.g., pure water) when the workpiece W is not above the optical sensor head 25.

[0036] Fig. 3 is an enlarged cross-sectional view showing one embodiment of the optical sensor head 25, the transparent liquid inflow path 50, the transparent liquid outflow path 51, and the sensor head cleaning nozzle 40. As shown in Fig. 3, the optical sensor head 25, which is composed of the end 27a of the light-projecting fiber optic cable 27 and the end 28a of the light-receiving fiber optic cable 28, is located below the through-hole 4 of the polishing pad 2. The optical sensor head 25 faces the through-hole 4.

[0037] The optical sensor head 25 has a light projecting surface 71 that emits light and a light receiving surface 72 that receives reflected light from the workpiece W. In this embodiment, the light projecting surface 71 is formed from the tip surface of the light projecting fiber optic cable 27, and the light receiving surface 72 is formed from the tip surface of the light receiving fiber optic cable 28. In one embodiment, the light projecting surface 71 and the light receiving surface 72 may be formed from optical elements such as lenses or glass attached to the ends 27a, 28a of the light projecting fiber optic cable 27 and the light receiving fiber optic cable 28.

[0038] The upper ends of the transparent liquid inlet path 50 and the transparent liquid outlet path 51 open at the upper surface of the polishing table 3 and communicate with the through hole 4. The transparent liquid outlet path 51 is adjacent to the transparent liquid inlet path 50. The optical sensor head 25 is disposed within the transparent liquid inlet path 50. The light-projecting surface 71 of the optical sensor head 25 emits light toward the surface of the workpiece W and guides the light to the surface of the workpiece W. The reflected light from the workpiece W travels toward the light-receiving surface 72 of the optical sensor head 25 and is incident on the light-receiving surface 72.

[0039] During polishing of the workpiece W, the through hole 4 is filled with a transparent liquid (e.g., pure water). Light emitted from an optical sensor head 25 consisting of an end 27a of a light-projecting optical fiber cable 27 and an end 28a of a light-receiving optical fiber cable 28 passes through the pure water filling the through hole 4 and is irradiated onto the workpiece W on the polishing pad 2. The reflected light from the workpiece W passes through the pure water filling the through hole 4 and is received by the optical sensor head 25.

[0040] The sensor head cleaning nozzle 40 is disposed in the polishing table 3 and is adjacent to the optical sensor head 25. The sensor head cleaning nozzle 40 communicates with the transparent liquid inflow path 50. As shown in FIG. 3, the tip of the sensor head cleaning nozzle 40 may protrude into the transparent liquid inflow path 50. The relative positions of the sensor head cleaning nozzle 40 and the optical sensor head 25 are fixed, and the sensor head cleaning nozzle 40 and the optical sensor head 25 rotate together with the polishing table 3 and the polishing pad 2.

[0041] The sensor head cleaning nozzle 40 faces the optical sensor head 25 and is configured to discharge a cleaning liquid onto the optical sensor head 25. More specifically, the sensor head cleaning nozzle 40 faces the light projection surface 71 and the light receiving surface 72 of the optical sensor head 25 and cleans the light projection surface 71 and the light receiving surface 72 of the optical sensor head 25 with the cleaning liquid. In this embodiment, the sensor head cleaning nozzle 40 is disposed at a position higher than the light projection surface 71 and the light receiving surface 72 of the optical sensor head 25. The sensor head cleaning nozzle 40 is inclined downward with respect to the horizontal direction. Therefore, the sensor head cleaning nozzle 40 discharges the cleaning liquid obliquely downward toward the light projection surface 71 and the light receiving surface 72 of the optical sensor head 25.

[0042] The flow of the cleaning liquid discharged from the sensor head cleaning nozzle 40 comes into contact with the light projection surface 71 and the light receiving surface 72 of the optical sensor head 25, and can prevent the abrasive grains contained in the polishing liquid and the polishing debris of the workpiece W from adhering to the light projection surface 71 and the light receiving surface 72. Therefore, the light projection surface 71 and the light receiving surface 72 of the optical sensor head 25 can be kept clean.

[0043] The light receiving surface 72 of the optical sensor head 25 receives the light reflected from the workpiece W. The optical film thickness measurement system 20 can accurately measure the film thickness of the workpiece W based on the intensity of the light reflected from the workpiece W.

[0044] During polishing of the workpiece W, the flow control valve 56 is opened and the cleaning liquid is supplied to the sensor head cleaning nozzle 40 through the cleaning liquid supply line 52 .

[0045] The flow rate control valve 56 is connected to the sensor head cleaning nozzle 40 via the cleaning liquid supply line 52. This flow rate control valve 56 can adjust the flow rate of the cleaning liquid discharged from the sensor head cleaning nozzle 40 toward the optical sensor head 25. The operation of the flow rate control valve 56 is controlled by the operation control unit 9. In one embodiment, the flow rate of the cleaning liquid discharged from the sensor head cleaning nozzle 40 is maintained constant by the flow rate control valve 56 while the workpiece W is being polished.

[0046] In one embodiment, when the workpiece W is above the optical sensor head 25 during polishing of the workpiece W, the operation control unit 9 is configured to give a command to the flow rate control valve 41 to supply transparent liquid to the transparent liquid inlet channel 50 at a preset measurement flow rate, and on the other hand, give a command to the flow rate control valve 56 to discharge the cleaning liquid from the sensor head cleaning nozzle 40 at a first flow rate. When the workpiece W is not above the optical sensor head 25 during polishing of the workpiece W, the operation control unit 9 is configured to give a command to the flow rate control valve 41 to supply transparent liquid to the transparent liquid inlet channel 50 at a flow rate lower than the measurement flow rate, and on the other hand, give a command to the flow rate control valve 56 to discharge the cleaning liquid from the sensor head cleaning nozzle 40 at a second flow rate higher than the first flow rate. By such an operation, when the workpiece W is not above the optical sensor head 25, a strong flow of the cleaning liquid is formed in the transparent liquid inlet channel 50, and the cleaning liquid reaches the optical sensor head 25 without being hindered by the flow of the transparent liquid. Therefore, the cleaning effect of the cleaning liquid on the optical sensor head 25 can be improved.

[0047] In one embodiment, the transparent liquid supply line 35 and transparent liquid supply source 55 may be omitted if the flow rate of the cleaning liquid is high enough to prevent the polishing liquid and polishing debris of the workpiece W from entering the transparent liquid inlet passage 50.

[0048] In one embodiment, cleaning of the optical sensor head 25 with the cleaning liquid may be performed before or after polishing of the workpiece W. In this case, the supply of the transparent liquid to the transparent liquid inlet path 50 and the through hole 4 is stopped during cleaning of the optical sensor head 25. When a chemical liquid supply source is used as the cleaning liquid supply source 54 (see FIG. 2), that is, when a chemical liquid is used as the cleaning liquid, cleaning of the optical sensor head 25 may be performed during polishing of the workpiece W under conditions in which it is acceptable for the chemical liquid to flow onto the polishing pad 2. Under conditions in which it is undesirable for the chemical liquid to flow onto the polishing pad 2, cleaning of the optical sensor head 25 with the chemical liquid may be performed before or after polishing of the workpiece W.

[0049] 4 is an enlarged cross-sectional view showing 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 FIGS. 1 to 3, and therefore the duplicated description will be omitted.

[0050] The embodiment shown in Figure 4 is the same as the embodiment described with reference to Figures 1 to 3 in that the sensor head cleaning nozzle 40 faces the light projection surface 71 and the light receiving surface 72 of the optical sensor head 25, but differs in that the sensor head cleaning nozzle 40 is positioned at the same height as the light projection surface 71 and the light receiving surface 72 of the optical sensor head 25, and the sensor head cleaning nozzle 40 faces horizontally.

[0051] The flow of the cleaning liquid discharged from the sensor head cleaning nozzle 40 comes into contact with the light projection surface 71 and the light receiving surface 72 of the optical sensor head 25, and can prevent the abrasive grains contained in the polishing liquid and the polishing debris of the workpiece W from adhering to the light projection surface 71 and the light receiving surface 72. Therefore, the light projection surface 71 and the light receiving surface 72 of the optical sensor head 25 can be kept clean.

[0052] Figure 5 is a top view of the sensor head cleaning nozzle 40 and the optical sensor head 25 of the embodiment shown in Figure 3 or Figure 4. As shown in Figure 5, the sensor head cleaning nozzle 40 faces the light projection surface 71 and the light receiving surface 72 of the optical sensor head 25. In one embodiment, as shown in Figure 6, the sensor head cleaning nozzle 40 may be a fan-shaped nozzle configured to form a fan-shaped jet of cleaning liquid. A fan-shaped nozzle can direct the cleaning liquid over a wide area.

[0053] In the embodiment shown in Figures 5 and 6, the sensor head cleaning nozzle 40 is positioned closer to the light projection surface 71 than the light receiving surface 72 of the optical sensor head 25, but the relative position of the sensor head cleaning nozzle 40 with respect to the optical sensor head 25 is not particularly limited, as long as the cleaning liquid released from the sensor head cleaning nozzle 40 can contact both the light projection surface 71 and the light receiving surface 72.

[0054] In one embodiment, as shown in Fig. 7, the sensor head cleaning nozzle 40 may be a multi-nozzle having a plurality of cleaning liquid outlets 81 arranged around the optical sensor head 25. The sensor head cleaning nozzle 40 of the embodiment shown in Fig. 7 includes a flow path structure 85 having a plurality of cleaning liquid outlets 81 and a cleaning liquid flow path 83. The flow path structure 85 extends around the optical sensor head 25. The cleaning liquid flow path 83 extends around the optical sensor head 25 and communicates with the plurality of cleaning liquid outlets 81.

[0055] The flow path structure 85 has a cleaning liquid inlet 87 communicating with the cleaning liquid flow path 83, and this cleaning liquid inlet 87 is connected to the cleaning liquid supply line 52. The cleaning liquid is supplied from the cleaning liquid supply line 52 through the cleaning liquid inlet 87 to the cleaning liquid flow path 83, and is discharged from the multiple cleaning liquid discharge ports 81 towards the optical sensor head 25. The multiple cleaning liquid discharge ports 81 face inward in the radial direction of the transparent liquid inflow path 50 when viewed from above.

[0056] The flow of the cleaning liquid discharged from the multiple cleaning liquid discharge ports 81 comes into contact with the light projection surface 71 and the light receiving surface 72 of the optical sensor head 25, and can prevent the abrasive grains contained in the polishing liquid and the polishing debris of the workpiece W from adhering to the light projection surface 71 and the light receiving surface 72. Therefore, the light projection surface 71 and the light receiving surface 72 of the optical sensor head 25 can be kept clean.

[0057] Although not shown, another embodiment of the multi-nozzle having multiple cleaning liquid outlets 81 may be a multi-nozzle equipped with multiple nozzles having multiple cleaning liquid outlets 81 arranged around the optical sensor head 25.

[0058] The embodiments described with reference to FIGS. 6 and 7 are also applicable to the embodiments described below.

[0059] 8 is an enlarged cross-sectional view showing another embodiment of the polishing apparatus. The configuration and operation of this embodiment that are not particularly described are the same as those of the embodiment described with reference to FIGS. 1 to 3, so that the overlapping description will be omitted. In this embodiment, the polishing apparatus includes an ultrasonic transducer 90 that applies ultrasonic waves to the cleaning liquid supplied to the sensor head cleaning nozzle 40. The ultrasonic transducer 90 is installed in the polishing table 3 and is adjacent to the sensor head cleaning nozzle 40. The ultrasonic transducer 90 may be attached to the sensor head cleaning nozzle 40. In one embodiment, the ultrasonic transducer 90 may be attached to the cleaning liquid supply line 52 connected to the sensor head cleaning nozzle 40.

[0060] According to this embodiment, the cleaning liquid to which ultrasonic waves have been applied by the ultrasonic vibrator 90 is discharged from the sensor head cleaning nozzle 40, and the light projection surface 71 and the light receiving surface 72 of the optical sensor head 25 can be effectively cleaned.

[0061] The embodiment described with reference to FIG. 8 is also applicable to the embodiments described with reference to FIGS.

[0062] The above-described embodiments have been described for the purpose of enabling a person having ordinary skill in the art to practice the present invention. Various modifications of the above-described embodiments are naturally possible for a person skilled in the art, and the technical idea of ​​the present invention can be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be interpreted in the broadest scope according to the technical idea defined by the claims. [Explanation of symbols]

[0063] W Workpiece 1 Polishing head 2 Polishing Pads 2a Polished surface 3 Polishing table 4 through hole 5 Polishing fluid supply nozzle 6 Table Motor 9. Operation control section 10 Head shaft 15 Polishing head rotation device 20 Optical Film Thickness Measurement System 22 Light source 23 Spectrometer 25 Optical sensor head 27 Optical fiber cable for floodlight 28 Receiving optical fiber cable 30 Spectral Processing Section 35 Transparent liquid supply line 36 Transparent liquid discharge line 41 Flow control valve 50 Clear liquid inlet channel 51 Clear liquid outflow path 71 Light-projecting surface 72 Photosensitive surface 81 Cleaning liquid outlet 83 Cleaning fluid flow path 85 Flow path structure 87 Cleaning fluid inlet 90 Ultrasonic transducer

Claims

1. a polishing table supporting a polishing pad having a through hole; a polishing head for pressing a workpiece against the polishing pad; an optical film thickness measurement system having an optical sensor head disposed below the polishing pad; a sensor head cleaning nozzle that ejects a cleaning liquid toward the optical sensor head; The polishing apparatus, wherein the sensor head cleaning nozzle is disposed within the polishing table and faces the optical sensor head.

2. 2. The polishing apparatus according to claim 1, wherein the sensor head cleaning nozzle is disposed at a higher position than the optical sensor head.

3. 3. The polishing apparatus according to claim 2, wherein the sensor head cleaning nozzle is inclined downward with respect to the horizontal direction.

4. 2. The polishing apparatus according to claim 1, wherein the sensor head cleaning nozzle is disposed at the same height as the optical sensor head.

5. 5. The polishing apparatus according to claim 4, wherein the sensor head cleaning nozzle is oriented horizontally.

6. the polishing apparatus further includes a transparent liquid inlet passage for supplying a transparent liquid to the through hole, the optical sensor head is disposed within the transparent liquid inlet channel; 2. The polishing apparatus according to claim 1, wherein the sensor head cleaning nozzle communicates with the transparent liquid inflow path.

7. 2. The polishing apparatus according to claim 1, wherein the sensor head cleaning nozzle is a fan-shaped nozzle configured to form a fan-shaped jet of the cleaning liquid.

8. 2. The polishing apparatus according to claim 1, wherein the sensor head cleaning nozzle is a multi-nozzle having a plurality of cleaning liquid outlets arranged around the periphery of the optical sensor head.

9. 2. The polishing apparatus according to claim 1, wherein the sensor head cleaning nozzle is connected to a cleaning liquid supply source, the cleaning liquid supply source being a pure water supply source or a chemical liquid supply source.

10. 2. The polishing apparatus according to claim 1, further comprising an ultrasonic vibrator that applies ultrasonic waves to the cleaning liquid supplied to the sensor head cleaning nozzle.

11. a flow rate control valve connected to the sensor head cleaning nozzle; An operation control unit that controls the operation of the flow rate control valve is further provided.

2. The polishing apparatus of claim 1, wherein the operation control unit is configured to: when the workpiece is above the optical sensor head during polishing of the workpiece, command the flow control valve to release the cleaning liquid from the sensor head cleaning nozzle at a first flow rate; and when the workpiece is not above the optical sensor head during polishing of the workpiece, command the flow control valve to release the cleaning liquid from the sensor head cleaning nozzle at a second flow rate, the second flow rate being greater than the first flow rate.

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