Polishing apparatus and transparent liquid filling method

Abstract

The invention provides a polishing device and a transparent liquid filling method, which can stabilize an optical path in a space between a transparent window of a polishing pad and an optical sensor head and can accurately measure the film thickness of a workpiece. A polishing device is provided with: a polishing pad (2) having a transparent window (4) that allows light to pass therethrough; a polishing table (3) that supports the polishing pad (2); a polishing head (1) that presses the workpiece (W) against the polishing pad (2); and an optical film thickness measurement system (20) having an optical sensor head (25) disposed below the transparent window (4). A space (32) formed between the transparent window (4) and the optical sensor head (25) is filled with a transparent liquid.

Description

Technical Field

[0001] The present invention relates to a technology for grinding workpieces such as wafers, wiring substrates, corner substrates, and more particularly to a technology for directing light to the workpiece through a transparent window of a grinding pad used for grinding the workpiece and measuring the film thickness of the workpiece based on the spectrum of reflected light from the workpiece. Background Art

[0002] In the manufacturing process of semiconductor devices, a chemical mechanical polishing (CMP) device is used to polish the surface of a workpiece such as a wafer. The CMP device includes a polishing pad attached to a polishing table and a polishing head for pressing the workpiece against the polishing surface of the polishing pad. The CMP device supplies a polishing liquid (such as slurry) to the polishing pad while pressing the workpiece against the polishing surface of the polishing pad through the polishing head, so that the surface of the workpiece and the polishing surface of the polishing pad are in sliding contact. The surface of the workpiece is polished by the chemical action of the polishing liquid and the mechanical action of the abrasive particles contained in the polishing liquid and / or the polishing pad.

[0003] The grinding of the workpiece is terminated when the film thickness of the film (insulating film, silicon layer, etc.) constituting the surface thereof reaches the target film thickness. In order to measure the film thickness of the workpiece, the grinding device is equipped with an optical film thickness measurement system. The optical film thickness measurement system is configured to irradiate light to the workpiece through an optical sensor head arranged in the grinding table, receive reflected light from the workpiece, generate a spectrum of reflected light according to the intensity of the reflected light, and determine the film thickness of the workpiece based on the spectrum of the reflected light.

[0004] The polishing pad on the polishing table has a transparent window constituting a part thereof. The transparent window can prevent the polishing liquid and polishing debris on the polishing pad from contacting the optical sensor head. There is a space between the optical sensor head and the transparent window. The light emitted from the optical sensor head is guided to the workpiece through the space and the transparent window, and the reflected light from the workpiece reaches the optical sensor head through the transparent window and the space.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2019-24036

[0008] Technical problem to be solved by the invention

[0009] In addition to the polishing liquid, pure water for dressing and cleaning the polishing pad is also supplied to the polishing pad. The polishing liquid or pure water or other liquids are immersed in the polishing pad made of the foaming material, and sometimes in the above-mentioned space between the optical sensor head and the transparent window. The liquid in the space sometimes changes the direction of light travel or scatters the light. In particular, when there are bubbles in the liquid in the space, the liquid changes the intensity of the reflected light from the workpiece, hindering the correct film thickness measurement. Summary of the invention

[0010] Therefore, the present invention provides a polishing device and a transparent liquid filling method that stabilize the optical path in the space between the transparent window of the polishing pad and the optical sensor head, thereby enabling accurate film thickness measurement of the workpiece.

[0011] Technical means for solving technical problems

[0012] In one embodiment, a polishing device is provided, comprising: a polishing pad having a transparent window that allows light to pass through; a polishing table that supports the polishing pad; a polishing head that presses a workpiece against the polishing pad; and an optical film thickness measuring system, the optical film thickness measuring system having an optical sensor head arranged below the transparent window, and a space formed between the transparent window and the optical sensor head is filled with a transparent liquid.

[0013] In one embodiment, the lower surface of the transparent window includes a light receiving surface that receives light from the optical sensor head and a receding surface located higher than the light receiving surface.

[0014] In one embodiment, the receding surface surrounds the light receiving surface.

[0015] In one embodiment, the polishing device further includes a transparent liquid supply conduit communicating with the space, and the transparent window includes a transparent liquid discharge port communicating with the space.

[0016] In one embodiment, the polishing device further includes a transparent liquid supply conduit and a transparent liquid discharge conduit communicating with the space, and the transparent liquid discharge conduit extends inside the polishing table.

[0017] In one embodiment, the grinding device further comprises: a flow measuring device, which is arranged in at least one of the transparent liquid supply pipeline and the transparent liquid discharge pipeline; and an action control unit, which is electrically connected to the flow measuring device, the flow measuring device is configured to measure the flow rate of the transparent liquid flowing in the transparent liquid supply pipeline, and the action control unit is configured to generate an alarm signal when the measured value of the flow rate of the transparent liquid exceeds a preset flow rate range.

[0018] In one embodiment, the grinding device further comprises: a pressure measuring device, which is arranged in at least one of the transparent liquid supply pipeline and the transparent liquid discharge pipeline; and an action control unit, which is electrically connected to the pressure measuring device, the pressure measuring device is configured to measure the pressure of the transparent liquid flowing in the transparent liquid supply pipeline, and the action control unit is configured to generate an alarm signal when the measured value of the pressure of the transparent liquid exceeds a preset pressure range.

[0019] In one embodiment, a transparent liquid filling method is provided, wherein a space formed between a transparent window and an optical sensor head of an optical film thickness measuring system is evacuated to form a negative pressure in the space, the transparent window constituting a part of a polishing pad for polishing a workpiece, the optical film thickness measuring system being used to measure the film thickness of the workpiece, and the transparent liquid is supplied into the space through a transparent liquid supply pipeline in a state where a negative pressure is formed in the space.

[0020] In one embodiment, the transparent liquid is supplied into the space through the transparent liquid supply line while the space is being evacuated.

[0021] In one embodiment, after the vacuum exhaust of the space is stopped and a negative pressure is formed in the space, the transparent liquid is supplied into the space through the transparent liquid supply line.

[0022] In one embodiment, after the entire space is filled with the transparent liquid, supply of the transparent liquid into the space is stopped.

[0023] Effects of the Invention

[0024] The transparent liquid filling the space between the transparent window of the polishing pad and the optical sensor head forms a stable optical path in the space. Therefore, the optical film thickness measurement system can measure the accurate film thickness of the workpiece.

[0025] By vacuuming the space between the transparent window of the polishing pad and the optical sensor head, moisture and garbage in the space can be removed. After the vacuum exhaust of the space, transparent liquid is supplied to the space, so that the space is filled with transparent liquid. The transparent liquid filling the space forms a stable optical path in the space. Therefore, the optical film thickness measurement system can measure the correct film thickness of the workpiece. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram showing one embodiment of the polishing device.

[0027] Figure 2 It is a cross-sectional view showing the detailed structure of the optical film thickness measurement system.

[0028] Figure 3 It is an enlarged cross-sectional view showing one embodiment of a transparent window and an optical sensor head.

[0029] Figure 4 is an enlarged cross-sectional view showing another embodiment of the transparent window and the optical sensor head.

[0030] Figure 5 This is a diagram showing an embodiment in which the space between the transparent window and the optical sensor head is filled with pure water.

[0031] Figure 6 This is a diagram showing an embodiment of forming a flow of pure water in the space between the transparent window and the optical sensor head.

[0032] Figure 7 This is a diagram showing one embodiment of a transparent liquid filling method for filling pure water into the space between the transparent window and the optical sensor head.

[0033] Figure 8 1 is a flow chart illustrating one embodiment of a transparent liquid filling method.

[0034] Fig. 9 is a flow chart illustrating another embodiment of the transparent liquid filling method.

[0035] Fig.10 It is an enlarged cross-sectional view showing another embodiment of the polishing device.

[0036] Fig.11 This is an enlarged cross-sectional view showing still another embodiment of the polishing device.

[0037] Fig.12 This is an enlarged cross-sectional view showing still another embodiment of the polishing device.

[0038] Fig.13 This is an enlarged cross-sectional view showing still another embodiment of the polishing device.

[0039] Fig.14 This is an enlarged cross-sectional view showing still another embodiment of the polishing device.

[0040] Fig.15 It is a cross-sectional view showing another embodiment of the transparent window.

[0041] Fig.16 It is a cross-sectional view showing still another embodiment of the transparent window.

[0042] Fig.17 This is an enlarged cross-sectional view showing still another embodiment of the polishing device.

[0043] Fig.18 This is an enlarged cross-sectional view showing still another embodiment of the polishing device.

[0044] Explanation of symbols

[0045] W workpiece

[0046] 1 grinding head

[0047] 2 polishing pad

[0048] 2a Grinding surface

[0049] 3 grinding tables

[0050] 4 Transparent windows

[0051] 5. Grinding liquid supply nozzle

[0052] 6 Grinding table motor

[0053] 9Motion Control Unit

[0054] 10-head shaft

[0055] 15 Grinding head rotating device

[0056] 20Optical film thickness measurement system

[0057] 22 Light Source

[0058] 23. Beam splitter

[0059] 25 optical sensor heads

[0060] 27 Optical fiber cable for light projection

[0061] 28 Optical fiber cable for light reception

[0062] 30 Spectrum Processing Unit

[0063] 32 Space

[0064] 35 Transparent liquid supply pipeline

[0065] 36 Transparent liquid discharge pipeline

[0066] 37 Supply Pump

[0067] 39 Pressure Regulator

[0068] 41 Transparent liquid supply valve

[0069] 42 Transparent liquid discharge valve

[0070] 45 through holes

[0071] 46 Depression

[0072] 50 discharge pump

[0073] 52 Inflow side measuring device

[0074] 53 Outflow side measurement device

[0075] 61 light receiving surface

[0076] 62 Back side

[0077] 70 transparent liquid outlet

[0078] 80 check valve. DETAILED DESCRIPTION

[0079] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Figure 1 Schematic diagram showing one embodiment of a grinding device. Figure 1 As shown, the grinding device comprises: a grinding pad 2 with a transparent window 4; a grinding table 3 supporting the grinding pad 2; a grinding head 1 pressing the workpiece W against the grinding pad 2; a grinding table motor 6 for rotating the grinding table 3; a grinding liquid supply nozzle 5 for supplying a grinding liquid such as slurry to the grinding pad 2; and an action control unit 9 for controlling the action of the grinding device.

[0080] The upper surface of the polishing pad 2 constitutes a polishing surface 2a for polishing the workpiece W. The transparent window 4 constitutes a part of the polishing pad 2 and is made of a transparent material (e.g., a transparent resin) that allows light to pass through. The workpiece W has a film constituting its surface. Examples of the workpiece W to be polished include wafers, wiring substrates, and corner substrates used in the manufacture of semiconductor devices.

[0081] The grinding head 1 is connected to the head shaft 10, and the head shaft 10 is connected to the grinding head rotating device 15. The grinding head rotating device 15 is configured to rotate the grinding head 1 together with the head shaft 10 in the direction indicated by the arrow. The structure of the grinding head rotating device 15 is not particularly limited, but in one example, the grinding head rotating device 15 includes a motor, a belt, a pulley, etc. The grinding table 3 is connected to the grinding table motor 6, and the grinding table motor 6 is configured to rotate the grinding table 3 and the grinding pad 2 in the direction indicated by the arrow. The grinding head 1, the grinding head rotating device 15 and the grinding table motor 6 are connected to the action control unit 9.

[0082] The workpiece W is ground as follows. The grinding table motor 6 and the grinding head rotating device 15 rotate the grinding table 3 and the grinding head 1. Figure 1 The polishing head 1 rotates in the direction indicated by the arrow while supplying the polishing liquid from the polishing liquid supply nozzle 5 to the polishing surface 2a of the polishing pad 2 on the polishing table 3. While the workpiece W is rotated by the polishing head 1, the workpiece W is pressed against the polishing surface 2a of the polishing pad 2 by the polishing head 1 in a state where the polishing liquid is present on the polishing pad 2. The surface of the workpiece W is polished by the chemical action of the polishing liquid and the mechanical action of the abrasive grains contained in the polishing liquid and / or the polishing pad 2.

[0083] The motion control unit 9 includes: a storage device 9a storing a program; and a computing device 9b performing a calculation according to the command included in the program. The motion control unit 9 is composed of 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) and a solid state drive (SSD). Examples of the computing device 9b include a CPU (central processing unit) and a GPU (graphics processing unit). However, the specific structure of the motion control unit 9 is not limited to these examples.

[0084] The polishing device includes an optical film thickness measuring system 20 for measuring the film thickness of the workpiece W. The optical film thickness measuring system 20 includes a light source 22 for emitting light, an optical sensor head 25 for irradiating the workpiece W with the light of the light source 22 and receiving the reflected light from the workpiece W, a spectrometer 23 connected to the optical sensor head 25, and a spectrum processing unit 30 for determining the film thickness of the workpiece W based on the spectrum of the reflected light from the workpiece W. The optical sensor head 25 is arranged in the polishing table 3 and rotates together with the polishing table 3.

[0085] The spectrum processing unit 30 includes: a storage device 30a storing a program; and a computing device 30b executing a calculation according to the command included in the program. The spectrum processing unit 30 is composed of 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) and a solid state drive (SSD). Examples of the computing device 30b include a CPU (central processing unit) and a GPU (graphics processing unit). However, the specific structure of the spectrum processing unit 30 is not limited to these examples.

[0086] The action control unit 9 and the spectrum processing unit 30 may also be composed of multiple computers respectively. For example, the action control unit 9 and the spectrum processing unit 30 may also be composed of a combination of an edge server and a cloud server respectively. In one embodiment, the action control unit 9 and the spectrum processing unit 30 may also be composed of one computer.

[0087] Figure 2 2 is a cross-sectional view showing the detailed structure of the optical film thickness measuring system 20. The optical sensor head 25 is arranged in the polishing table 3, and the light source 22 and the spectrometer 23 are installed on the polishing table 3. The optical sensor head 25, the light source 22 and the spectrometer 23 rotate integrally with the polishing table 3 and the polishing pad 2. The position of the optical sensor head 25 is a position where the surface of the workpiece W on the polishing pad 2 is crossed every time the polishing table 3 and the polishing pad 2 rotate one circle. The optical sensor head 25 is connected to the light source 22 and the spectrometer 23, and the spectrometer 23 is connected to the spectrum processing unit 30.

[0088] The optical film thickness measuring system 20 includes an optical fiber cable 27 for projecting light, which guides light emitted from a light source 22 to the surface of a workpiece W, and an optical fiber cable 28 for receiving light, which receives reflected light from the workpiece W and sends the reflected light to a spectrometer 23. The top end of the optical fiber cable 27 for projecting light and the top end of the optical fiber cable 28 for receiving light are exposed on the polishing table 3. The top end of the optical fiber cable 27 for projecting light and the top end of the optical fiber cable 28 for receiving light constitute an optical sensor head 25 that guides light to the surface of the workpiece W and receives reflected light from the workpiece W. The other end of the optical fiber cable 27 for projecting light is connected to the light source 22, and the other end of the optical fiber cable 28 for receiving light is connected to the spectrometer 23. The spectrometer 23 is configured to decompose the reflected light from the workpiece W according to the wavelength and measure the intensity of the reflected light over a predetermined wavelength range.

[0089] The optical sensor head 25 composed of the distal ends of the optical fiber cable 27 for projecting light and the optical fiber cable 28 for receiving light is located below the transparent window 4 of the polishing pad 2 .

[0090] The light emitted by the light source 22 is guided to the workpiece W from the optical sensor head 25 through the transparent window 4 via the optical fiber cable 27 for projecting light. The reflected light from the workpiece W is received by the optical sensor head 25 through the transparent window 4, and is sent to the spectrometer 23 via the optical fiber cable 28 for receiving light. The spectrometer 23 decomposes the reflected light according to its wavelength, and generates the intensity measurement data of the reflected light by measuring the intensity of the reflected light at each wavelength. The intensity measurement data of the reflected light is sent from the spectrometer 23 to the spectrum processing unit 30.

[0091] The spectrum processing unit 30 is configured to generate a spectrum of the reflected light from the workpiece W based on the intensity measurement data of the reflected light. The spectrum of the reflected light is represented as a graph showing the relationship between the wavelength and intensity of the reflected light (i.e., a spectral waveform). The intensity of the reflected light can also be represented as a relative value such as reflectivity or relative reflectivity.

[0092] The spectrum processing unit 30 is configured to determine the film thickness of the workpiece W based on the spectrum of the reflected light. In the method of determining the film thickness of the workpiece W based on the spectrum, a well-known method is used. For example, the spectrum processing unit 30 determines a reference spectrum whose shape is closest to the spectrum of the reflected light from a reference spectrum library, and determines the film thickness associated with the determined reference spectrum. In another example, the spectrum processing unit 30 performs Fourier transform on the spectrum of the reflected light, and determines the film thickness based on the obtained frequency spectrum.

[0093] The polishing device includes: a transparent liquid supply line 35 for supplying pure water as a transparent liquid to a space 32 formed between the transparent window 4 and the optical sensor head 25; a transparent liquid discharge line 36 for discharging pure water from the space 32; a supply pump 37 and a transparent liquid supply valve 41 connected to the transparent liquid supply line 35; and a transparent liquid discharge valve 42 connected to the transparent liquid discharge line 36. The transparent liquid supply line 35 and the transparent liquid discharge line 36 are in communication with the space 32. The transparent liquid supply line 35 and the transparent liquid discharge line 36 extend in the polishing table 3. In one embodiment, a plurality of transparent liquid discharge lines 36 may be provided.

[0094] Pure water as a transparent liquid delivered from a transparent liquid supply source (not shown) flows in the transparent liquid supply line 35. In one embodiment, the transparent liquid may be a liquid other than pure water as long as it does not hinder the transmission of light. The supply pump 37 is configured to pressurize the pure water flowing in the transparent liquid supply line 35. The pure water pressurized by the supply pump 37 is supplied to the space 32 through the transparent liquid supply line 35. The pure water supplied to the space 32 is discharged from the space 32 through the transparent liquid discharge line 36.

[0095] In one embodiment, the polishing device includes a pressure regulator 39 connected to the transparent liquid supply line 35. The pressure regulator 39 is configured to adjust the pressure of pure water as the transparent liquid supplied to the space 32 through the transparent liquid supply line 35. The pressure of the transparent liquid supplied to the space 32 can also be adjusted by the supply pump 37. When a public facility of a factory in which the polishing device is installed is used as the transparent liquid supply source, the supply pump 37 may not be provided.

[0096] The transparent liquid supply valve 41 and the transparent liquid discharge valve 42 are actuator-driven valves such as electric valves, solenoid valves or pneumatic valves. The transparent liquid supply valve 41 and the transparent liquid discharge valve 42 are electrically connected to the action control unit 9, and the actions of the transparent liquid supply valve 41 and the transparent liquid discharge valve 42 are controlled by the action control unit 9. In one embodiment, the transparent liquid supply valve 41 and the transparent liquid discharge valve 42 can also be manual valves.

[0097] Figure 3 FIG. 2 is an enlarged cross-sectional view showing an embodiment of the transparent window 4 and the optical sensor head 25. Figure 3 As shown, the transparent window 4 is arranged in the through hole 45 formed in the polishing pad 2 and closes the through hole 45. The thickness of the transparent window 4 is smaller than the thickness of the polishing pad 2, and the lower surface of the transparent window 4 is located at a position higher than the lower surface of the polishing pad 2. The optical sensor head 25 composed of the top end of the optical fiber cable 27 for projecting light and the top end of the optical fiber cable 28 for receiving light is located below the transparent window 4 of the polishing pad 2 and faces the space 32.

[0098] exist Figure 3In the embodiment shown, the space 32 between the transparent window 4 and the optical sensor head 25 is formed in the polishing pad 2. That is, the space 32 is formed by the lower surface of the transparent window 4, the through hole 45 of the polishing pad 2, and the upper surface of the polishing table 3. Figure 4 As shown in FIG. 1 , a space 32 between the transparent window 4 and the optical sensor head 25 is formed in the polishing table 3. That is, the space 32 is formed by the lower surface of the transparent window 4 and the recess 46 formed on the upper surface of the polishing table 3. Figure 4 In the embodiment shown, the thickness of the transparent window 4 can also be the same as the thickness of the polishing pad 2. In one embodiment, it is also possible to combine Figure 3 The embodiments shown and Figure 4 The embodiment shown.

[0099] exist Figure 5 In one embodiment shown, the space 32 is filled with pure water as a transparent liquid. Both the transparent liquid supply valve 41 and the transparent liquid discharge valve 42 are closed. Therefore, the pure water is confined in the space 32, and during the polishing process of the workpiece W, no pure water flows in the space 32. The light emitted from the optical sensor head 25 composed of the top of the optical fiber cable 27 for projecting light and the top of the optical fiber cable 28 for receiving light passes through the pure water filling the space 32 and the transparent window 4, and is irradiated to the workpiece W on the polishing pad 2. The reflected light from the workpiece W passes through the transparent window 4 and the pure water filling the space 32 and is received by the optical sensor head 25.

[0100] according to Figure 5 In the illustrated embodiment, the space 32 is filled with pure water during the grinding process of the workpiece W. Therefore, a stable optical path for measuring the film thickness of the workpiece W is ensured in the space 32. As a result, the optical film thickness measurement system 20 can accurately measure the film thickness of the workpiece W.

[0101] exist Figure 6 In one embodiment shown, the space 32 is filled with pure water as a transparent liquid, and both the transparent liquid supply valve 41 and the transparent liquid discharge valve 42 are opened. During the grinding process of the workpiece W, a flow of pure water is formed in the space 32. That is, the pure water flows into the space 32 through the transparent liquid supply pipe 35, flows in the space 32, and then flows out through the transparent liquid discharge pipe 36. During the grinding process of the workpiece W, since the space 32 is filled with pure water, the optical path for measuring the film thickness of the workpiece W is ensured. As a result, the optical film thickness measurement system 20 can accurately measure the film thickness of the workpiece W.

[0102] exist Figures 3 to 6In the illustrated embodiment, the transparent window 4 has a flat lower surface. The lower surface of the transparent window 4 is perpendicular to the direction of the optical sensor head 25. More specifically, it is perpendicular to the top of the optical fiber cable 27 for projection and the top of the optical fiber cable 28 for receiving light that constitute the optical sensor head 25. Since the lower surface of the transparent window 4 is perpendicular to the optical path of the light generated from the optical sensor head 25, the light from the optical sensor head 25 is incident perpendicularly to the lower surface of the transparent window 4. In one embodiment, the optical sensor head 25 may be arranged obliquely with respect to the lower surface of the transparent window 4, and the light from the optical sensor head 25 may be incident obliquely with respect to the lower surface of the transparent window 4.

[0103] Next, refer to Figure 7 An embodiment of a method for filling a transparent liquid with pure water as an example of a transparent liquid in the space 32 between the transparent window 4 and the optical sensor head 25 before grinding the workpiece W is described. First, the transparent liquid discharge pipe 36 is connected to the discharge pump 50. The discharge pump 50 is configured to be able to transfer liquid and gas. As an example of the discharge pump 50, a piezoelectric pump having a piezoelectric vibrator can be cited.

[0104] The transparent liquid supply valve 41 is closed, and the transparent liquid discharge valve 42 is opened. When the discharge pump 50 is operated, a negative pressure is formed in the space 32. By vacuum exhausting the space 32 by the discharge pump 50, moisture and dirt existing in the space 32 can be removed. In particular, the operation of the discharge pump 50 can remove the liquid containing bubbles existing in the space 32.

[0105] When the transparent liquid supply valve 41 is opened in a state where negative pressure is formed in the space 32, pure water as the transparent liquid is supplied into the space 32 through the transparent liquid supply pipe 35. After the entire space 32 is filled with pure water, the transparent liquid supply valve 41 is closed to stop the supply of pure water into the space 32. The pure water filling the space 32 forms a stable optical path in the space 32. Therefore, the optical film thickness measurement system 20 can measure the accurate film thickness of the workpiece W.

[0106] The operation of the transparent liquid supply valve 41 and the transparent liquid discharge valve 42 is performed by the motion control unit 9. In one embodiment, the transparent liquid supply valve 41 and the transparent liquid discharge valve 42 may be manual valves, and the operation of the transparent liquid supply valve 41 and the transparent liquid discharge valve 42 may be performed manually.

[0107] Figure 8 1 is a flow chart for explaining one embodiment of a method for filling a transparent liquid. In this embodiment, pure water as a transparent liquid is supplied into the space 32 through the transparent liquid supply line 35 while the space 32 is evacuated. The details are as follows.

[0108] In step 101 , the discharge pump 50 is operated with the transparent liquid supply valve 41 closed and the transparent liquid discharge valve 42 open, thereby generating a negative pressure in the space 32 .

[0109] In step 102 , the transparent liquid supply valve 41 is opened while the transparent liquid discharge valve 42 is opened and the discharge pump 50 is operated. Pure water as the transparent liquid is supplied into the space 32 through the transparent liquid supply line 35 .

[0110] In step 103, after the entire space 32 is filled with pure water, the transparent liquid supply valve 41 and the transparent liquid discharge valve 42 are closed, and the operation of the discharge pump 50 is stopped. Thus, the supply of pure water into the space 32 is stopped.

[0111] In one embodiment, instead of the operation in step 103, after the entire space 32 is filled with pure water, the transparent liquid supply valve 41 and the transparent liquid discharge valve 42 are maintained in an open state, and the discharge pump 50 is continued to operate. In this embodiment, even after the entire space 32 is filled with pure water, the supply and discharge of pure water to the space 32 are continued. Therefore, in a state where the entire space 32 is filled with pure water, a flow of pure water is formed in the space 32.

[0112] Fig. 9 1 is a flow chart for explaining another embodiment of the transparent liquid filling method. In this embodiment, after the vacuum exhaust of the space 32 is stopped and a negative pressure is formed in the space 32, pure water as the transparent liquid is supplied into the space 32 through the transparent liquid supply pipe 35. The details are as follows.

[0113] In step 201 , the discharge pump 50 is operated with the transparent liquid supply valve 41 closed and the transparent liquid discharge valve 42 open, thereby generating a negative pressure in the space 32 .

[0114] In step 202 , the transparent liquid discharge valve 42 is closed to stop the operation of the discharge pump 50 .

[0115] In step 203, the transparent liquid supply valve 41 is opened in a state where negative pressure is formed in the space 32. Pure water as the transparent liquid is supplied into the space 32 through the transparent liquid supply line 35.

[0116] In step 204, after the entire space 32 is filled with pure water, the transparent liquid supply valve 41 is closed. Thus, the supply of pure water into the space 32 is stopped.

[0117] Reference Figures 7 to 9 The transparent liquid filling method described is performed before grinding the workpiece W. In one example, referring to Figures 7 to 9The transparent liquid filling method described is performed after a new polishing pad 2 that has not been used for polishing a workpiece is placed on the polishing table 3 and before the workpiece is polished with the new polishing pad 2 .

[0118] Fig.10 2 is an enlarged cross-sectional view showing another embodiment of a polishing device including a transparent window 4 and an optical sensor head 25. The structure and operation of this embodiment not specifically described are the same as those of the above-mentioned embodiment, so their repeated description is omitted. The polishing device of this embodiment includes an inflow side measuring device 52 provided in the transparent liquid supply pipeline 35. The inflow side measuring device 52 is arranged downstream of the transparent liquid supply valve 41.

[0119] The inflow-side measuring device 52 is configured to measure the physical quantity (flow rate or pressure) of the transparent liquid flowing in the transparent liquid supply pipe 35. The inflow-side measuring device 52 is electrically connected to the operation control unit 9, and the measured value of the physical quantity (flow rate or pressure) of the transparent liquid obtained by the inflow-side measuring device 52 is sent to the operation control unit 9.

[0120] In one embodiment, the inflow side measuring device 52 is a flow measuring device for measuring the flow rate of the transparent liquid. The action control unit 9 is configured to generate an alarm signal when the measured value of the flow rate of the transparent liquid exceeds a preset flow rate range. When a malfunction occurs in the transparent liquid supply system, the flow rate of the transparent liquid is expected to increase or decrease significantly. For example, when the transparent liquid supply pipeline 35 is blocked or the supply pump 37 fails, the flow rate of the transparent liquid is expected to decrease. On the other hand, when the pressure regulator 39 fails or the transparent liquid leaks through the gap around the transparent window 4, the flow rate of the transparent liquid is expected to increase. When the flow rate of the transparent liquid changes significantly, there is a concern that bubbles enter the transparent liquid and reduce the quality of the intensity measurement data of the reflected light used in the film thickness measurement. The change in the flow rate of the transparent liquid sometimes also changes the pressure of the transparent liquid. When the pressure of the transparent liquid in the space 32 rises, there is a concern that the transparent window 4 is deformed.

[0121] In one embodiment, the inflow-side measuring device 52 is a pressure measuring device for measuring the pressure of the transparent liquid. The operation control unit 9 is configured to generate an alarm signal when the measured value of the pressure of the transparent liquid exceeds a preset pressure range.

[0122] The action control unit 9 generates an alarm signal when the measured value of the flow rate of the transparent liquid exceeds the preset flow rate range, or when the measured value of the pressure of the transparent liquid exceeds the preset pressure range. In one embodiment, the action control unit 9 provides an instruction to the optical film thickness measurement system 20 to stop the film thickness measurement operation of the workpiece W when the measured value of the flow rate of the transparent liquid exceeds the preset flow rate range, or when the measured value of the pressure of the transparent liquid exceeds the preset pressure range.

[0123] Fig.11 2 is an enlarged cross-sectional view showing another embodiment of a polishing device including a transparent window 4 and an optical sensor head 25. The structure and operation of this embodiment not specifically described are the same as those of the above-mentioned embodiment, so their repeated description is omitted. The polishing device of this embodiment includes an outflow side measuring device 53 provided in the transparent liquid discharge pipeline 36. The outflow side measuring device 53 is arranged upstream of the transparent liquid discharge valve 42.

[0124] The outflow-side measuring device 53 is configured to measure the physical quantity (flow rate or pressure) of the transparent liquid flowing in the transparent liquid discharge pipe 36. The outflow-side measuring device 53 is electrically connected to the operation control unit 9, and the measured value of the physical quantity (flow rate or pressure) of the transparent liquid obtained by the outflow-side measuring device 53 is sent to the operation control unit 9.

[0125] In one embodiment, the outflow-side measuring device 53 is a flow rate measuring device that measures the flow rate of the transparent liquid. The operation control unit 9 is configured to generate an alarm signal when the measured value of the flow rate of the transparent liquid exceeds a preset flow rate range.

[0126] In one embodiment, the outflow-side measuring device 53 is a pressure measuring device for measuring the pressure of the transparent liquid. The operation control unit 9 is configured to generate an alarm signal when the measured value of the pressure of the transparent liquid exceeds a preset pressure range.

[0127] The action control unit 9 generates an alarm signal when the measured value of the flow rate of the transparent liquid exceeds the preset flow rate range, or when the measured value of the pressure of the transparent liquid exceeds the preset pressure range. In one embodiment, the action control unit 9 provides an instruction to the optical film thickness measurement system 20 to stop the film thickness measurement operation of the workpiece W when the measured value of the flow rate of the transparent liquid exceeds the preset flow rate range, or when the measured value of the pressure of the transparent liquid exceeds the preset pressure range.

[0128] In one embodiment, if Fig.12 As shown, the outflow side measuring device 53 may also be arranged downstream of the transparent liquid discharge valve 42 and the discharge pump 50. In one embodiment, as Fig.13 As shown, it is also possible to combine Fig.10 The inflow side measuring device 52 and Fig.11 The outflow side measuring device 53 shown, or Fig.14 As shown, it is also possible to combine Fig.10 The inflow side measuring device 52 and Fig.12 The outflow side measuring device 53 is shown.

[0129] Fig.15 4 is a cross-sectional view showing another embodiment of the transparent window 4. The structure of this embodiment not particularly described and the reference Figure 3 or Figure 4 The embodiments described are the same, so the repeated description is omitted. Fig.15 As shown in FIG. 1 , the lower surface of the transparent window 4 includes a light receiving surface 61 for receiving light from the optical sensor head 25 and a receding surface 62 located at a position higher than the light receiving surface 61. The receding surface 62 is adjacent to the light receiving surface 61. Fig.15 In the illustrated embodiment, the receding surface 62 is connected to the light receiving surface 61 and is inclined upward toward the outside.

[0130] The light receiving surface 61 is located at the center of the lower surface of the transparent window 4, and the receding surface 62 surrounds the light receiving surface 61. In one embodiment, the receding surface 62 has an inverted frustum shape. The light receiving surface 61 is a flat surface and is perpendicular to the direction of the optical sensor head 25. The light receiving surface 61 is perpendicular to the optical path of the light generated from the optical sensor head 25, and the light from the optical sensor head 25 is perpendicular to the light receiving surface 61. In one embodiment, the portion of the transparent window 4 constituting the receding surface 62 may also be composed of a material different from the transparent material constituting the light receiving surface 61.

[0131] When bubbles exist on the light receiving surface 61, the bubbles move from the light receiving surface 61 to the receding surface 62, and then move outward along the inclined receding surface 62, and gather on the outer area of ​​the receding surface 62. Therefore, the bubbles are removed from the light receiving surface 61, and a stable optical path can be maintained. As a result, the optical film thickness measurement system 20 can accurately measure the film thickness of the workpiece W.

[0132] Fig.16 4 is a cross-sectional view showing another embodiment of the transparent window 4. The structure of this embodiment not particularly described and the reference Fig.15 The embodiments described are the same, so repeated descriptions are omitted. Fig.16 In the embodiment shown in FIG. 1 , there is a step between the light receiving surface 61 and the receding surface 62. The receding surface 62 is a flat surface located at a higher position than the light receiving surface 61. In one embodiment, the receding surface 62 may also be Fig.15 As in the illustrated embodiment, it may be inclined upward toward the outside or may be curved.

[0133] When bubbles exist on the light receiving surface 61, the bubbles move from the light receiving surface 61 to the receding surface 62 and gather on the receding surface 62. Therefore, the bubbles are removed from the light receiving surface 61, and a stable optical path can be maintained. As a result, the optical film thickness measurement system 20 can accurately measure the film thickness of the workpiece W.

[0134] Reference Fig.15 and Fig.16 The described embodiments can be applied to Figures 4 to 9 Description of the embodiment.

[0135] Fig.172 is a cross-sectional view showing another embodiment of the grinding device. Figures 1 to 6 The embodiments described are the same, so repeated descriptions are omitted. Fig.17 In the illustrated embodiment, the transparent window 4 has a transparent liquid discharge port 70 that communicates with the space 32. The transparent liquid discharge port 70 is a through hole that penetrates the transparent window 4 and extends from the lower surface to the upper surface of the transparent window 4. The transparent liquid discharge port 70 is located outside the light receiving surface 61 that receives light from the optical sensor head 25 and is away from the light path. In this embodiment, the transparent liquid discharge pipeline 36 and the transparent liquid discharge valve 42 are not provided.

[0136] During the grinding process of the workpiece W, the transparent liquid supply valve 41 is opened, and pure water as the transparent liquid is supplied to the space 32 through the transparent liquid supply pipeline 35. The space 32 is filled with pure water, and the pure water flows out from the space 32 through the transparent liquid discharge port 70. During the grinding process of the workpiece W, the transparent window 4 and the space 32 rotate together with the grinding table 3, so there are times when the workpiece W is on the transparent window 4 and times when the workpiece W is not on the transparent window 4. When the workpiece W is not on the transparent window 4, the pure water in the space 32 flows out to the grinding pad 2 through the transparent liquid discharge port 70. Therefore, a flow of pure water is formed in the space 32. The flow rate of the pure water (transparent liquid) supplied to the space 32 through the transparent liquid supply pipeline 35 is a flow rate that does not reduce the grinding rate of the workpiece W due to the dilution of the grinding liquid supplied to the grinding pad 2 by the pure water.

[0137] According to the present embodiment, when bubbles exist in the space 32, the bubbles are discharged from the space 32 together with the pure water through the transparent liquid discharge port 70. Therefore, a stable optical path for measuring the film thickness of the workpiece W is ensured in the space 32. As a result, the optical film thickness measurement system 20 can accurately measure the film thickness of the workpiece W. In one embodiment, the transparent window 4 may also have a plurality of transparent liquid discharge ports 70 communicating with the space 32.

[0138] like Fig.18 As shown, in one embodiment, a check valve 80 connected to the transparent liquid discharge port 70 may also be provided. The check valve 80 is disposed in the polishing pad. Fig.18 In the illustrated embodiment, a check valve 80 is disposed in the space 32. The check valve 80 is configured to allow the transparent liquid in the space 32 to flow out through the transparent liquid discharge port 70, but not to allow the transparent liquid to flow into the space 32 through the transparent liquid discharge port 70. For example, the check valve 80 is configured by a sheet-shaped valve. The check valve 80 can prevent the polishing liquid on the polishing surface 2a of the polishing pad 2 and the pure water used for dressing the polishing pad 2 from flowing into the space 32.

[0139] Reference Fig.17 and Fig.18 The described embodiments can also be applied to Fig.15 and Fig.16 Specifically, the transparent liquid outlet 70 can also be Fig.15 and Fig.16 The setback surface 62 is shown as being open therein.

[0140] The above-mentioned embodiments are recorded for the purpose of enabling a person with common knowledge in the technical field to which the present invention belongs to implement the present invention. Various modifications of the above-mentioned embodiments can be accomplished by those skilled in the art as a matter of course, and the technical idea of ​​the present invention can also be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but should comply with the widest scope of the technical idea defined according to the scope to be protected by the invention.

Claims

1. A grinding device, characterized in that: have: an abrasive pad having a transparent window that allows light to pass through; a grinding table supporting the grinding pad; a grinding head, the grinding head pressing the workpiece against the grinding pad; as well as An optical film thickness measuring system, the optical film thickness measuring system comprising an optical sensor head arranged below the transparent window, The space formed between the transparent window and the optical sensor head is filled with a transparent liquid.

2. The grinding device according to claim 1, characterized in that: The lower surface of the transparent window includes a light receiving surface that receives light from the optical sensor head and a receding surface located at a higher position than the light receiving surface.

3. The grinding device according to claim 2, characterized in that: The receding surface surrounds the light receiving surface.

4. The grinding device according to claim 1, characterized in that: The grinding device also includes a transparent liquid supply pipeline communicating with the space. The transparent window has a transparent liquid discharge port communicating with the space.

5. The grinding device according to claim 1, characterized in that: The grinding device further comprises a transparent liquid supply pipeline and a transparent liquid discharge pipeline communicated with the space. The transparent liquid discharge pipeline extends inside the grinding table.

6. The grinding device according to claim 5, characterized in that: The grinding device also has: a flow rate measuring device provided in at least one of the transparent liquid supply pipeline and the transparent liquid discharge pipeline; and an action control unit, the action control unit being electrically connected to the flow measurement device, The flow rate measuring device is configured to measure the flow rate of the transparent liquid flowing in the transparent liquid supply pipeline. The operation control unit is configured to generate an alarm signal when a measured value of the flow rate of the transparent liquid exceeds a preset flow rate range.

7. The grinding device according to claim 5, characterized in that: The grinding device also has: a pressure measuring device provided in at least one of the transparent liquid supply pipeline and the transparent liquid discharge pipeline; and an action control unit, the action control unit being electrically connected to the pressure measuring device, The pressure measuring device is configured to measure the pressure of the transparent liquid flowing in the transparent liquid supply pipeline. The operation control unit is configured to generate an alarm signal when a measured value of the pressure of the transparent liquid exceeds a preset pressure range.

8. A transparent liquid filling method, characterized in that: A negative pressure is formed in the space by vacuum exhausting a space formed between a transparent window constituting a part of a polishing pad for polishing a workpiece and an optical sensor head of an optical film thickness measuring system for measuring the film thickness of the workpiece, wherein the transparent window constitutes a part of a polishing pad for polishing a workpiece, and the optical film thickness measuring system is used to measure the film thickness of the workpiece, In a state where negative pressure is formed in the space, the transparent liquid is supplied into the space through the transparent liquid supply pipe.

9. The transparent liquid filling method according to claim 8, characterized in that: The transparent liquid is supplied into the space through the transparent liquid supply line while the space is being evacuated.

10. The transparent liquid filling method according to claim 8, characterized in that: After the vacuum exhaust of the space is stopped and a negative pressure is formed in the space, the transparent liquid is supplied into the space through the transparent liquid supply pipe.

11. The transparent liquid filling method according to claim 8, characterized in that: After the entire space is filled with the transparent liquid, supply of the transparent liquid into the space is stopped.

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