Grinding device

Abstract

The present invention provides a polishing apparatus capable of preventing abrasive grains of a polishing liquid and abrasive scraps of a workpiece from adhering to an optical sensor head and improving measurement accuracy of a film thickness of the workpiece. A polishing device is provided with: a polishing table (3) that supports a polishing pad (2) in which a through-hole (4) is formed; an optical film thickness measurement system (20) having an optical sensor head (25) attached to the polishing table (3); a transparent liquid inflow path (50) for supplying a transparent liquid to the through hole (4); and a light-projecting-side transparent liquid outflow path (51) and a light-receiving-side transparent liquid outflow path (52) that communicate with the through-hole (4). The optical sensor head (25) has a light-projecting surface (71) that emits light obliquely upward and a light-receiving surface (72) that receives reflected light from the workpiece (W), the light-projecting surface (71) facing the light-projecting-side transparent liquid outflow path (51), and the light-receiving surface (72) facing the light-receiving-side transparent liquid outflow path (52).

Description

Technical Field

[0001] The present invention relates to a technique for grinding workpieces such as wafers, wiring substrates, and square substrates, and more particularly to a technique for guiding light to the workpiece through a through hole 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 has a polishing table with a polishing pad attached thereto and a polishing head for pressing the workpiece against the polishing surface of the polishing pad. The CMP device supplies a polishing liquid (e.g., slurry) to the polishing pad while pressing the workpiece against the polishing surface of the polishing pad using 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 thickness of the film (insulating film, silicon layer, etc.) constituting the surface of the workpiece reaches the target film thickness. The grinding device is equipped with an optical film thickness measurement system to measure the film thickness of the workpiece. The optical film thickness measurement system is configured to irradiate light to the workpiece using 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] In order to stabilize the film thickness measurement by the optical film thickness measurement system, it is necessary to keep the light path clean. For example, Patent Document 1 describes that the entry of polishing liquid and polishing debris is restricted by filling the light path with a transparent liquid.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2003-197587

[0008] Technical problem to be solved by the invention

[0009] However, the abrasive particles contained in the polishing liquid and the grinding debris of the workpiece usually have a larger specific gravity than the transparent liquid, and the abrasive particles and grinding debris sometimes adhere to the optical sensor head. When the abrasive particles and grinding 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. Summary of the invention

[0010] Therefore, the present invention provides a polishing device that can prevent abrasive particles of a polishing liquid and polishing debris of a workpiece from adhering to an optical sensor head, thereby improving the measurement accuracy of a film thickness of the workpiece.

[0011] Technical solutions for solving technical problems

[0012] In one embodiment, a grinding device is provided, comprising: a grinding table, which supports a grinding pad formed with a through hole; a grinding head, which presses a workpiece against the grinding pad; an optical film thickness measuring system, which has an optical sensor head mounted on the grinding table; a transparent liquid inlet path, which supplies transparent liquid to the through hole; and a light-projecting side transparent liquid outflow path and a light-receiving side transparent liquid outflow path, which are connected to the through hole, the optical sensor head having a light-projecting surface that emits light obliquely upward and a light-receiving surface that receives reflected light from the workpiece, the light-projecting surface facing the light-projecting side transparent liquid outflow path, and the light-receiving surface facing the light-receiving side transparent liquid outflow path.

[0013] In one embodiment, the light-projecting surface and the light-receiving surface face obliquely upward.

[0014] In one embodiment, the light-projecting surface is located in the light-projecting-side transparent liquid outflow path, and the light-receiving surface is located in the light-receiving-side transparent liquid outflow path.

[0015] In one embodiment, the transparent liquid inflow path is located between the light-projecting-side transparent liquid outflow path and the light-receiving-side transparent liquid outflow path.

[0016] In one embodiment, the light-projecting-side transparent liquid outflow path and the light-receiving-side transparent liquid outflow path are arranged symmetrically with respect to the transparent liquid inflow path.

[0017] In one embodiment, the transparent liquid inflow path is connected to a transparent liquid supply source, and the transparent liquid supply source is a pure water supply source or a chemical solution supply source.

[0018] In one embodiment, an ultrasonic vibrator for applying ultrasonic waves to the transparent liquid flowing in the transparent liquid inflow path is further provided.

[0019] In one embodiment, the grinding device further comprises: a flow regulating valve connected to the transparent liquid inflow path; and an action control unit, which controls the action of the flow regulating valve, and the action control unit is configured to issue a command to the flow regulating valve to supply the transparent liquid to the through hole at a first flow rate when the workpiece is on the through hole during grinding of the workpiece, and to issue a command to the flow regulating valve to supply the transparent liquid to the through hole at a second flow rate when the workpiece is not on the through hole during grinding of the workpiece, and the second flow rate is smaller than the first flow rate.

[0020] Effects of the Invention

[0021] The transparent liquid supplied from the transparent liquid supply path to the through hole of the polishing pad forms a flow toward the transparent liquid outflow path on the light-emitting side and the transparent liquid outflow path on the light-receiving side. The light-emitting surface and the light-receiving surface of the optical sensor head face the transparent liquid outflow path on the light-emitting side and the transparent liquid outflow path on the light-receiving side, respectively, so the flow of the transparent liquid in the transparent liquid outflow path on the light-emitting side and the transparent liquid outflow path on the light-receiving side contacts the light-emitting surface and the light-receiving surface of the optical sensor head, and can clean the light-emitting surface and the light-receiving surface. The optical sensor head guides light to the workpiece and receives reflected light from the workpiece. 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

[0022] Figure 1 It is a schematic diagram showing one embodiment of a polishing device.

[0023] Figure 2 It is a cross-sectional view showing the detailed structure of the optical film thickness measurement system.

[0024] Figure 3 This is an enlarged cross-sectional view showing one embodiment of the optical sensor head, the transparent liquid inflow path, the light-projecting-side transparent liquid outflow path, and the light-receiving-side transparent liquid outflow path.

[0025] Figure 4 It is an enlarged cross-sectional view showing another embodiment of the polishing device.

[0026] Figure 5 This is an enlarged cross-sectional view showing still another embodiment of the polishing device.

[0027] Description of Reference Numerals

[0028] W Workpiece

[0029] 1 Grinding head

[0030] 2 Abrasive pad

[0031] 2a Grinding surface

[0032] 3 Grinding table

[0033] 4 Through holes

[0034] 5 Grinding fluid supply nozzle

[0035] 6. Workbench motor

[0036] 9 Motion Control Unit

[0037] 10 Head axis

[0038] 15 Grinding head rotating device

[0039] 20 Optical film thickness measurement system

[0040] 22 Light Source

[0041] 23. Beam splitter

[0042] 25 Optical sensor head

[0043] 27 Optical fiber cable for light projection

[0044] 28 Optical fiber cable for light reception

[0045] 30 Spectrum Processing Unit

[0046] 35 Transparent liquid supply line

[0047] 36 Transparent liquid discharge line

[0048] 37 Supply Pump

[0049] 41 Flow Control Valve

[0050] 50 Transparent liquid inflow path

[0051] 51 Transparent liquid outflow path on the light-emitting side

[0052] 52 Transparent liquid outflow path on the light receiving side

[0053] 71 light projection surface

[0054] 72 light receiving surface

[0055] 80 Ultrasonic vibrator. DETAILED DESCRIPTION

[0056] 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 1As shown, the grinding device includes: a grinding pad 2 formed with a through hole 4, a grinding table 3 supporting the grinding pad 2, a grinding head 1 pressing the workpiece W against the grinding pad 2, a worktable 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.

[0057] The upper surface of the polishing pad 2 constitutes a polishing surface 2a for polishing the workpiece W. The through hole 4 penetrates the polishing pad 2. The workpiece W has a film constituting the surface of the workpiece W. Examples of the workpiece W to be polished include wafers, wiring substrates, and square substrates used in the manufacture of semiconductor devices.

[0058] 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. 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 workbench motor 6, and the workbench 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 workbench motor 6 are electrically connected to the action control unit 9.

[0059] The workpiece W is ground as follows. The 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. The workpiece W is rotated by the polishing head 1, and the polishing head 1 presses the workpiece W against the polishing surface 2a of the polishing pad 2 in the state where the polishing liquid exists 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.

[0060] The motion control unit 9 includes a storage device 9a for storing programs and a computing device 9b for performing operations according to the commands included in the programs. 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.

[0061] 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 that emits light, an optical sensor head 25 that irradiates the light of the light source 22 to the workpiece W and receives reflected light from the workpiece W, the optical sensor head 23 connected to the optical sensor head 25, a spectrometer 23, and a spectrum processing unit 30 that determines 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 mounted on the polishing table 3 and rotates together with the polishing table 3.

[0062] 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.

[0063] The motion control unit 9 and the spectrum processing unit 30 may also be composed of multiple computers. For example, the motion control unit 9 and the spectrum processing unit 30 may also be composed of a combination of an edge server and a cloud server. In one embodiment, the motion control unit 9 and the spectrum processing unit 30 may also be composed of one computer.

[0064] 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 that crosses the surface of the workpiece W on the polishing pad 2 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.

[0065] The optical film thickness measuring device 20 includes a light-emitting optical fiber cable 27 for guiding light emitted from a light source 22 to the surface of a workpiece W, and a light-receiving optical fiber cable 28 for receiving light that receives reflected light from the workpiece W and transmits the reflected light to a spectrometer 23. The end 27a of the light-emitting optical fiber cable 27 and the end 28a of the light-receiving optical fiber cable 28 constitute an optical sensor head 25 for guiding light to the surface of the workpiece W and receiving reflected light from the workpiece W. The other end of the light-emitting optical fiber cable 27 is connected to the light source 22, and the other end of the light-receiving optical fiber cable 28 is connected to the spectrometer 23. The spectrometer 23 is configured to decompose the reflected light from the workpiece W according to wavelength and measure the intensity of the reflected light within a predetermined wavelength range.

[0066] The optical sensor head 25, which is composed of the end 27a of the optical fiber cable 27 for projecting light and the end 28a of the optical fiber cable 28 for receiving light, is located below the through hole 4 of the polishing pad 2 and faces the through hole 4. The light emitted by the light source 22 is guided from the optical sensor head 25 to the workpiece W through the through hole 4 through 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 through hole 4 and is transmitted to the spectrometer 23 through the optical fiber cable 28 for receiving light. The spectrometer 23 generates the intensity measurement data of the reflected light by decomposing the reflected light according to the wavelength of the reflected light and 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.

[0067] The spectrum processing unit 30 is configured to generate a spectrum of the reflected light from the workpiece W based on the reflected light intensity measurement data. The spectrum of the reflected light is represented 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 represented as a relative value such as reflectivity or relative reflectivity.

[0068] The spectrum processing unit 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 as a method for determining the film thickness of the workpiece W based on the spectrum. 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 other examples, 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.

[0069] The polishing table 3 has a transparent liquid inflow path 50, a light-projecting side transparent liquid outflow path 51, and a light-receiving side transparent liquid outflow path 52, which are connected to the through hole 4. The transparent liquid inflow path 50, the light-projecting side transparent liquid outflow path 51, and the light-receiving side transparent liquid outflow path 52 are provided in the polishing table 3, and rotate integrally with the polishing table 3. The polishing device includes a transparent liquid supply line 35 connected to the transparent liquid inflow path 50, a transparent liquid discharge line 36 connected to the light-projecting side transparent liquid outflow path 51 and the light-receiving side transparent liquid outflow path 52, a supply pump 37 connected to the transparent liquid supply line 35, and a flow rate regulating valve 41.

[0070] One end of the transparent liquid supply line 35 is connected to the transparent liquid inflow path 50, and the other end is connected to the transparent liquid supply source 55. The transparent liquid inflow path 50 may be formed integrally with the transparent liquid supply line 35. As an example of the transparent liquid supply source 55, a pure water supply source that supplies pure water as the transparent liquid can be cited. Pure water as the transparent liquid is supplied into the through hole 4 of the polishing pad 2 through the transparent liquid supply line 35 and the transparent liquid inflow path 50.

[0071] The pure water supplied to the through hole 4 of the polishing pad 2 is discharged from the through hole 4 through the light-emitting side transparent liquid outflow path 51 and the light-receiving side transparent liquid outflow path 52, and further discharged through the transparent liquid outflow path 36. The light-emitting side transparent liquid outflow path 51 and the light-receiving side transparent liquid outflow path 52 may be formed integrally with the transparent liquid outflow path 36.

[0072] 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 through hole 4 through the transparent liquid supply line 35 and the transparent liquid inflow path 50.

[0073] The flow control valve 41 is an actuator-driven valve such as an electric valve, a solenoid valve, or a pneumatic valve, and is electrically connected to the motion control unit 9 , and the motion of the flow control valve 41 is controlled by the motion control unit 9 .

[0074] Figure 3 FIG. 2 is an enlarged cross-sectional view showing an embodiment of the optical sensor head 25, the transparent liquid inflow path 50, the light-projecting side transparent liquid outflow path 51, and the light-receiving side transparent liquid outflow path 52. Figure 3 As shown, the optical sensor head 25 composed of the end 27a of the optical fiber cable 27 for projecting light and the end 28a of the optical fiber cable 28 for receiving light is located below the through hole 4 of the polishing pad 2. The end 27a of the optical fiber cable 27 for projecting light is inclined upward, and the end 28a of the optical fiber cable 28 for receiving light is also inclined upward at the same angle.

[0075] The optical sensor head 25 has a light-emitting surface 71 for emitting light and a light-receiving surface 72 for receiving reflected light from the workpiece W. In the present embodiment, the light-emitting surface 71 is formed by the front end surface of the light-emitting optical fiber cable 27, and the light-receiving surface 72 is formed by the front end surface of the light-receiving optical fiber cable 28. In one embodiment, the light-emitting surface 71 and the light-receiving surface 72 may be formed by optical elements such as lenses, glass, or mirrors arranged opposite to the front end surfaces of the light-emitting optical fiber cable 27 and the light-receiving optical fiber cable 28.

[0076] The light-projecting surface 71 and the light-receiving surface 72 face obliquely upward at the same angle. More specifically, the light-projecting surface 71 and the light-receiving surface 72 face the same measuring point MP on the surface of the workpiece W on the polishing pad 2. Therefore, the light-projecting surface 71 of the optical sensor head 25 emits light obliquely upward and guides the light toward the measuring point MP on the surface of the workpiece W. The reflected light from the measuring point MP travels obliquely downward toward the light-receiving surface 72 of the optical sensor head 25 and is incident on the light-receiving surface 72.

[0077] The upper ends of the transparent liquid inflow path 50, the light-projecting side transparent liquid outflow path 51, and the light-receiving side transparent liquid outflow path 52 are opened on the upper surface of the polishing table 3 and communicated with the through hole 4. The transparent liquid inflow path 50, the light-projecting side transparent liquid outflow path 51, and the light-receiving side transparent liquid outflow path 52 extend downward from the upper surface of the polishing table 3. The transparent liquid inflow path 50 is connected to the transparent liquid supply line 35, and the light-projecting side transparent liquid outflow path 51 and the light-receiving side transparent liquid outflow path 52 are connected to the transparent liquid discharge line 36.

[0078] During the polishing of the workpiece W, the through hole 4 is filled with pure water as a transparent liquid. Light emitted from the optical sensor head 25 composed of the end 27a of the light-emitting optical fiber cable 27 and the end 28a of the light-receiving optical fiber cable 28 passes through the pure water filling the through hole 4 and is irradiated toward 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.

[0079] The end 27a of the optical fiber cable 27 for light projection constituting the optical sensor head 25 is connected to the light projection side transparent liquid outflow path 51, and the light projection surface 71 of the optical sensor head 25 faces the light projection side transparent liquid outflow path 51. The end 28a of the optical fiber cable 28 for light reception constituting the optical sensor head 25 is connected to the light reception side transparent liquid outflow path 52, and the light reception surface 72 of the optical sensor head 25 faces the light reception side transparent liquid outflow path 52.

[0080] The transparent liquid inflow path 50 is located directly below the measurement point MP (i.e., the irradiation point of light from the optical sensor head 25) of the workpiece W. The transparent liquid inflow path 50 is located between the light-projecting side transparent liquid outflow path 51 and the light-receiving side transparent liquid outflow path 52, and pure water as the transparent liquid flows upward from the transparent liquid inflow path 50. The light-projecting side transparent liquid outflow path 51 and the light-receiving side transparent liquid outflow path 52 are arranged symmetrically with respect to the transparent liquid inflow path 50.

[0081] Pure water as a transparent liquid flows from the transparent liquid inflow path 50 into the through hole 4, and flows toward the measuring point MP on the surface of the workpiece W on the polishing pad 2. The pure water changes direction in the through hole 4 and flows into the light-projecting side transparent liquid outflow path 51 and the light-receiving side transparent liquid outflow path 52. The pure water flowing in the light-projecting side transparent liquid outflow path 51 and the light-receiving side transparent liquid outflow path 52 contacts the light-projecting surface 71 and the light-receiving surface 72 of the optical sensor head 25, and can prevent the abrasive particles contained in the polishing liquid and the polishing debris of the workpiece W from adhering to the light-projecting surface 71 and the light-receiving surface 72. Therefore, the light-projecting surface 71 and the light-receiving surface 72 of the optical sensor head 25 can be kept clean.

[0082] The light receiving surface 72 of the optical sensor head 25 receives the reflected light from the measurement point MP of the workpiece W. The optical film thickness measurement system 20 can accurately measure the film thickness at the measurement point MP of the workpiece W based on the intensity of the reflected light from the workpiece W.

[0083] exist Figure 3 In the illustrated embodiment, in order to improve the cleaning effect of the light-projecting surface 71 and the light-receiving surface 72 of the optical sensor head 25 by the flow of pure water, the end 27a of the light-projecting optical fiber cable 27 protrudes into the light-projecting side transparent liquid outflow path 51, and the light-projecting surface 71 of the optical sensor head 25 is located in the light-projecting side transparent liquid outflow path 51. Similarly, the end 28a of the light-receiving optical fiber cable 28 protrudes into the light-receiving side transparent liquid outflow path 52, and the light-receiving surface 72 of the optical sensor head 25 is located in the light-receiving side transparent liquid outflow path 52. Pure water forms a rapid flow in the light-projecting side transparent liquid outflow path 51 and the light-receiving side transparent liquid outflow path 52, and the cleanliness of the light-projecting surface 71 and the light-receiving surface 72 of the optical sensor head 25 can be maintained by the flow of pure water.

[0084] During the grinding of the workpiece W, the flow regulating valve 41 is opened, and pure water as the transparent liquid is supplied into the through hole 4 through the transparent liquid supply line 35 and the transparent liquid inflow path 50. During the grinding of the workpiece W, the grinding pad 2 rotates together with the grinding table 3, while the workpiece W held by the grinding head 1 does not rotate together with the grinding table 3, so there are times when the workpiece W is on the through hole 4 and times when the workpiece W is not on the through hole 4. That is, while the grinding pad 2 and the grinding table 3 rotate, the workpiece W periodically covers the through hole 4.

[0085] The flow regulating valve 41 is connected to the transparent liquid inlet path 50 via the transparent liquid supply line 35. The flow regulating valve 41 can regulate the flow rate of pure water supplied to the through hole 4. The operation of the flow regulating valve 41 is controlled by the action control unit 9. In one embodiment, during the grinding of the workpiece W, the flow rate of pure water supplied to the through hole 4 is maintained constant by the flow regulating valve 41. In other embodiments, the action control unit 9 is configured to issue a command to the flow regulating valve 41 to supply pure water to the through hole 4 at a first flow rate when the workpiece W is on the through hole 4 during the grinding of the workpiece W, and to issue a command to the flow regulating valve 41 to supply pure water to the through hole 4 at a second flow rate smaller than the first flow rate when the workpiece W is not on the through hole 4 during the grinding of the workpiece W.

[0086] When the workpiece W is on the through hole 4, the through hole 4 is closed by the workpiece W. Therefore, by supplying pure water to the through hole 4 at a first flow rate greater than the second flow rate, a rapid flow of pure water can be formed in the light-projecting side transparent liquid outflow path 51 and the light-receiving side transparent liquid outflow path 52. The rapid flow of pure water can improve the cleaning effect of the light-projecting surface 71 and the light-receiving surface 72 of the optical sensor head 25.

[0087] exist Figure 3 In the embodiment shown, the light-projecting surface 71 and the light-receiving surface 72 of the optical sensor head 25 are located below the polishing pad 2. Figure 4 As shown, the polishing table 3 may also have a protrusion 3a located in the through hole 4 of the polishing pad 2, and the light-projecting surface 71 and the light-receiving surface 72 of the optical sensor head 25, the upper end of the transparent liquid inflow path 50, and the upper ends of the light-projecting side transparent liquid outflow path 51 and the light-receiving side transparent liquid outflow path 52 are located in the protrusion 3a. The protrusion 3a protrudes upward and fits into the lower part of the through hole 4. The transparent liquid inflow path 50, the light-projecting side transparent liquid outflow path 51 and the light-receiving side transparent liquid outflow path 52 are open on the upper surface of the protrusion 3a.

[0088] Figure 4 The embodiment shown in the figure is different from the embodiment shown in that the light-projecting surface 71 and the light-receiving surface 72 of the optical sensor head 25 are located in the light-projecting side transparent liquid outflow path 51 and the light-receiving side transparent liquid outflow path 52. Figure 3 The illustrated embodiments are the same, but differ in that the light projecting surface 71 and the light receiving surface 72 of the optical sensor head 25 are located inside the polishing pad 2 .

[0089] exist Figure 4 In the illustrated embodiment, the pure water flowing in the light-projecting side transparent liquid outflow path 51 and the light-receiving side transparent liquid outflow path 52 also contacts the light-projecting surface 71 and the light-receiving surface 72 of the optical sensor head 25, and can prevent the abrasive particles contained in the polishing liquid and the polishing debris of the workpiece W from adhering to the light-projecting surface 71 and the light-receiving surface 72. Therefore, the light-projecting surface 71 and the light-receiving surface 72 of the optical sensor head 25 can be kept clean.

[0090] Figure 5 FIG. 1 is an enlarged cross-sectional view showing another embodiment of the grinding device. The structure and operation of this embodiment not specifically described are similar to those of the reference Figures 1 to 3 The described implementation modes are the same, so repeated descriptions thereof are omitted.

[0091] exist Figure 5 In the illustrated embodiment, the polishing device includes an ultrasonic vibrator 80 for applying ultrasonic waves to pure water as a transparent liquid flowing in the transparent liquid inflow path 50. The ultrasonic vibrator 80 is provided in the polishing table 3 and adjacent to the transparent liquid inflow path 50.

[0092] According to this embodiment, pure water to which ultrasonic waves are applied by the ultrasonic vibrator 80 fills the through hole 4, and then flows through the light-emitting side transparent liquid outflow path 51 and the light-receiving side transparent liquid outflow path 52, thereby effectively cleaning the light-emitting surface 71 and the light-receiving surface 72 of the optical sensor head 25. The ultrasonic vibrator 80 can also be applied to the reference Figure 4 Description of the embodiment.

[0093] In one embodiment, the transparent liquid supply source 55 (see Figure 2 ) can also be a liquid supply source instead of a pure water supply source. A transparent liquid is used instead of pure water. As an example of a liquid, a potassium hydroxide (KOH) solution having an etching effect can be cited.

[0094] When the chemical liquid is used as a transparent liquid, in order to prevent the chemical liquid from flowing on the polishing pad 2 during polishing of the workpiece W, the light projection surface 71 and the light receiving surface 72 of the optical sensor head 25 can also be cleaned before or after polishing the workpiece W.

[0095] 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 certainly be thought of by those skilled in the art, 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 be interpreted as the widest scope of the technical idea defined by the scope of protection claimed by the present invention.

Claims

1. A grinding device, characterized in that: have: a grinding table supporting a grinding pad having a through hole formed therein; a grinding head, the grinding head pressing the workpiece against the grinding pad; an optical film thickness measuring system having an optical sensor head mounted on the polishing table; a transparent liquid inflow path, the transparent liquid inflow path supplying the transparent liquid to the through hole; as well as a light-projecting side transparent liquid outflow path and a light-receiving side transparent liquid outflow path, wherein the light-projecting side transparent liquid outflow path and the light-receiving side transparent liquid outflow path are connected to the through hole, The optical sensor head has a light-projecting surface for emitting light obliquely upward and a light-receiving surface for receiving reflected light from the workpiece. The light-projecting surface faces the light-projecting-side transparent liquid outflow path, and the light-receiving surface faces the light-receiving-side transparent liquid outflow path.

2. The grinding device according to claim 1, characterized in that: The light-projecting surface and the light-receiving surface face obliquely upward.

3. The grinding device according to claim 1, characterized in that: The light-projecting surface is located in the transparent liquid outflow path on the light-projecting side, and the light-receiving surface is located in the transparent liquid outflow path on the light-receiving side.

4. The grinding device according to claim 1, characterized in that: The transparent liquid inflow path is located between the light-projecting-side transparent liquid outflow path and the light-receiving-side transparent liquid outflow path.

5. The grinding device according to claim 4, characterized in that: The light-projecting-side transparent liquid outflow path and the light-receiving-side transparent liquid outflow path are arranged symmetrically with respect to the transparent liquid inflow path.

6. The grinding device according to claim 1, characterized in that: The transparent liquid inflow path is connected to a transparent liquid supply source, and the transparent liquid supply source is a pure water supply source or a chemical liquid supply source.

7. The grinding device according to claim 1, characterized in that: The invention further includes an ultrasonic vibrator for applying ultrasonic waves to the transparent liquid flowing in the transparent liquid inflow path.

8. The grinding device according to claim 1, characterized in that: Also available: a flow regulating valve connected to the transparent liquid inflow path; and an action control unit, the action control unit controls the action of the flow control valve, The action control unit is configured to issue a command to the flow regulating valve to supply the transparent liquid to the through hole at a first flow rate when the workpiece is on the through hole during grinding of the workpiece, and to issue a command to the flow regulating valve to supply the transparent liquid to the through hole at a second flow rate when the workpiece is not on the through hole during grinding of the workpiece, wherein the second flow rate is smaller than the first flow rate.

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