On-line monitoring system for chemical mechanical polishing.

Abstract

The present invention discloses an online monitoring device for chemical mechanical polishing, which is installed within the polishing pad and can rotate with the polishing pad. The device includes a light source, an optical lens set, a reflecting unit, a detection probe, and a detector. The optical lens set receives the light beam emitted by the light source and generates a collimated beam. The reflecting unit receives the collimated beam and reflects it to form an incident light path. The detection probe is installed below the light-transmitting window of the polishing pad and includes a quartz light guide and a single-core optical fiber. The detector is connected to the single-core optical fiber and receives the output light path, obtaining corresponding spectral information and determining the endpoint of wafer polishing. The light source light path from the light source to the detection probe in the present invention uses free-space propagation, and the signal light path from the detection probe to the detector uses optical fiber propagation. The propagation modes of the two types of light beams are smoothly transitioned by the design of the detection probe, achieving high-precision detection.

Description

[Technical Field]

[0001] The present invention relates to the field of chemical mechanical polishing technology, and more particularly to an on-line monitoring device for chemical mechanical polishing. [Background technology]

[0002] Chemical mechanical polishing (CMP) is one of the key process steps in the current semiconductor integrated circuit chip manufacturing process. The CMP process uses a polishing pad and a polishing solution to polish the wafer, achieving a planar wafer surface profile through a combination of mechanical and chemical means. During the process, determining the polishing endpoint—that is, whether the desired removal amount or thickness has been achieved and the process is complete—is crucial.

[0003] In early chemical mechanical polishing processes, the process endpoint was controlled using polishing time, but this was both inaccurate and unreliable. A series of endpoint detection methods have been developed to adapt to the process. Mechanical endpoint detection primarily monitors the change in motor torque due to changes in material friction during the polishing process. However, it requires two different medium layers with significantly different friction coefficients, making it relatively limited in its scope of application. Electromagnetic endpoint detection primarily monitors eddy currents generated by the metal layer on the wafer surface and is applicable to detecting metal film thickness, but is not applicable to insulating materials. Optical endpoint detection primarily measures the intensity of light reflected from the wafer and uses a monochromatic laser to monitor changes in material reflectivity during the polishing process. This requires two different medium layers with significantly different reflectivities. For transparent medium layers, the reflected light intensity is the intensity of the interference light reflected from each medium surface. Changes in the interference light intensity can provide information about the removal volume, but not about the film thickness. Spectral endpoint detection is an advanced method from optical methods. It uses a light source such as polychromatic light, broad spectrum light, or white light to receive the spectral information reflected from the wafer, and monitors the change in film thickness based on the correspondence between the spectral information and the film thickness, and is applied to detecting the film thickness of transparent medium films. Summary of the Invention

[0004] To solve the problems of the prior art, the present invention provides an online monitoring device for chemical mechanical polishing, which combines two types of light beam propagation methods, namely, free space propagation and optical fiber propagation, to achieve high-precision detection.

[0005] The technical solutions adopted by the present invention to solve the technical problems are as follows: An online monitoring device for chemical mechanical polishing, which is installed in a polishing disc and can rotate together with the polishing disc, includes: light source. A set of optical lenses is used to receive the light beam emitted by the light source and generate a collimated beam. A reflecting unit is used to receive the collimated beam and reflect the collimated beam to form an incident optical path. The detection probe is disposed below the light-transmitting window of the polishing pad and includes at least a quartz light guide tube and a single-core optical fiber, the quartz light guide tube being used to receive an incident light path and emit the incident light path from an end of the detection probe close to the wafer, and the single-core optical fiber being used to receive the emitted light path after reflection on the wafer surface. A detector is connected to the single-core optical fiber and is used to receive the emitted light path, obtain corresponding spectral information, and determine the end point of wafer polishing.

[0006] Furthermore, the detection probe also includes a housing, wherein the quartz light guide is clad around the outer periphery of the single-core optical fiber, the housing is clad around the outer periphery of the quartz light guide, and the housing, the quartz light guide, and the single-core optical fiber are arranged concentrically. Alternatively, the quartz light guide and the single-core optical fiber may be arranged adjacent to each other, and the housing may be clad around the outer periphery of the quartz light guide and the single-core optical fiber.

[0007] Furthermore, the end face of the quartz light guide tube near the wafer and the end face of the single-core optical fiber near the wafer may be flat, and the end face of the quartz light guide tube near the wafer may be chamfered.

[0008] Furthermore, the chamfer may be a linear chamfer with an inclination angle of 0 to 45°. Alternatively, the chamfer may be a circular chamfer with a fillet curvature of 0 to 2 mm. 1 may be.

[0009] Furthermore, the single-core optical fiber may protrude from the quartz light guide at one end of the quartz light guide and the single-core optical fiber remote from the wafer.

[0010] Furthermore, the quartz light guide tube may have an outer diameter of 1 to 4 mm, and the single-core optical fiber may have an outer diameter of 0.1 to 2 mm.

[0011] Furthermore, the light source may be a broadband light source, and its wavelength may be 200 to 2000 nm. Furthermore, the diameter of the collimated beam may be 1 to 10 mm.

[0012] Furthermore, the detector may be a spectrometer, and the detector may acquire corresponding spectral information and convert it into thickness information of the medium film on the wafer surface to determine the endpoint of wafer polishing.

[0013] Furthermore, it may also include a reference light sampling unit, which is installed between the optical lens set and the detection probe and is used to monitor the light intensity of the light source.

[0014] Furthermore, the reference light sampling unit may include a first beam splitter and a second beam splitter, the collimated beam passes through the first beam splitter to form a signal light and a reference light, and the signal light may pass through the first beam splitter and enter the detection probe.

[0015] The beneficial effects of the present invention are as follows: 1) An original detection optical path system is adopted. The light source optical path from the light source to the detection probe uses free space propagation, and the signal optical path from the detection probe to the detector uses optical fiber propagation. The two types of light beam propagation methods are smoothly transitioned by the special design of the detection probe, so the entire detection optical path system combines the advantages of the two types of light beam propagation methods to achieve high-precision detection. 2) Since most of the light intensity of the light source can reach the detection probe, it is possible to overcome the relatively large coupling loss in the light beam that exists from the light source to the optical fiber. 3) Optical fiber is used in the signal optical path to collect effective signals, and the signal collection point is located sufficiently close to the wafer surface, so that stable transmission through the optical fiber allows the signal to reach the detector stably. 4) The light emitted from the end face of the quartz light guide tube can be focused, and the concentration of the detection light energy further increases the intensity of the signal light, improving detection accuracy.By reducing the detection area, the detection range of the detection probe on the wafer can be limited, allowing for more accurate positioning of the detection position. 5) The unique design of the detection optical path system and probe has the advantages of high precision, accurate positioning, low noise, etc., and can better meet current technological demands. 6) It can realize online monitoring of chemical mechanical polishing. The monitoring device is part of the chemical mechanical polishing system and relies on the polishing module of the CMP. It rotates with the polishing plate and performs detection during the polishing process to provide a reference point for when polishing should be terminated, so that polishing can be stopped immediately once the polishing endpoint is reached. 7) The overall dimensions are compact. 8) The signal control method is adopted to adjust the light source and monitor the light intensity in real time, which can ensure the stability of the measurement signal, improve the detection accuracy, and extend the service life of the light source. [Brief explanation of the drawings]

[0016] [Figure 1]1 is a structural schematic diagram of a chemical mechanical polishing system according to the present invention; [Figure 2] 1 is a plan view of a chemical mechanical polishing system according to the present invention; [Figure 3] 1 is a perspective view of a linking structure between an online monitoring device and a chemical mechanical polishing system according to a first embodiment of the present invention; [Figure 4] FIG. 1 is a structural schematic diagram of a portion where a detection probe is arranged in embodiment 1 of the present invention. [Figure 5] FIG. 2 is a transverse cross-sectional view of the detection probe according to the first embodiment of the present invention. [Figure 6] 1 is a longitudinal cross-sectional view of a detection probe according to a first embodiment of the present invention, in which the chamfer is a linear chamfer. [Figure 7] FIG. 2 is a longitudinal cross-sectional view of the detection probe according to the first embodiment of the present invention, in which the chamfer is a circular chamfer. [Figure 8] 1A and 1B are schematic diagrams illustrating light collection by a detection probe according to a first embodiment of the present invention, in which a is a detection probe having a chamfer and b is a detection probe having no chamfer. [Figure 9] 1 shows spectral reflectance curves for different film thicknesses. [Figure 10] This is a comparison of the background spectrum (dotted line) and the signal spectrum (solid line). [Figure 11] FIG. 10 is a perspective view of a linking structure between an online monitoring device and a chemical mechanical polishing system according to a second embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0017] In order to allow those skilled in the art to better understand the aspects of the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention, but it is obvious that the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without any creative work should fall within the protection scope of the present invention.

[0018] Embodiment 1 As shown in Figure 1, in the chemical mechanical polishing (CMP) process, a polishing pad 2 is fixed to a polishing platen 1, a polishing head 5 carries a wafer 8, and the wafer 8 is pressed against the polishing pad 2. The polishing platen 1 rotates, and the polishing head 5 rotates and moves back and forth relative to the polishing platen 1, generating friction between the wafer 8 and the polishing pad 2 and achieving mechanical polishing. A polishing liquid spray arm 3 sprays a polishing liquid through a nozzle, and the polishing liquid reaches the polishing head 5 via the rotation of the polishing platen 1 and contacts the wafer 8 through the grooves on the polishing pad 2, achieving chemical polishing. A trimmer 6 conditions the polishing pad 2 to maintain its flatness and roughness.

[0019] As shown in Figures 2 to 5, the online monitoring device for chemical mechanical polishing is installed in the internal space of the polishing disc 1 and can rotate together with the polishing disc 1, and includes a light source 9, an optical lens set 10, a reflecting unit 12, a detection probe 13 and a detector 11.

[0020] The light source 9 is a broad spectrum white light source, and its wavelength is 200 to 2000 nm. The light beam emitted by the light source 9 enters the optical lens set 10.

[0021] The optical lens set 10 receives the light beam emitted by the light source 9 and generates a collimated beam with a diameter of 1 to 10 mm. Specifically, the optical lens set 10 is composed of a series of ray lenses, which collect the light beam, reduce the light beam diameter, and collimate the light beam. The light beam entering the optical lens set 10 forms a collimated small-spot parallel light output through the optical lens set 10 and reaches the reflecting unit 12 in the form of spatial light. The optical lens set 10 realizes coupling of the light emitted by the light source 9 in a beam converging and collimating manner, which solves the problem of low light intensity utilization rate of the light source in conventional optical fiber coupling, allowing a larger proportion of the light energy to be involved in detection, improving measurement accuracy, and reducing the power required by the light source 9.

[0022] The reflecting unit 12 receives the collimated light beam and reflects it to form an incident light path. The reflecting unit 12 is a reflecting mirror in this embodiment.

[0023] The detection probe 13 is disposed below the light-transmitting window 4 of the polishing pad 2, and includes a quartz light guide tube 131, a single-core optical fiber 132, and a housing 133. The quartz light guide tube 131 is provided to receive an incident light path and emit the incident light path from a proximal end 134 of the detection probe 13 (the end of the detection probe 13 on the wafer 8 side is defined as the proximal end), and the single-core optical fiber 132 is provided to receive an emitted light path reflected from the surface of the wafer 8.

[0024] 5, the quartz light guide tube 131 covers the outer periphery of the single-core optical fiber 132, the housing 133 covers the outer periphery of the quartz light guide tube 131, and the housing 133, quartz light guide tube 131, and single-core optical fiber 132 are arranged concentrically. The outer diameter of the quartz light guide tube 131 is 1 to 4 mm, i.e., D1 = 1 to 4 mm in the figure. The outer diameter of the single-core optical fiber 132 is 0.1 to 2 mm, i.e., D2 = 0.1 to 2 mm in the figure. The inner diameter of the quartz light guide tube 131 matches the outer diameter of the single-core optical fiber 132, and the single-core optical fiber 132 is located in the central bore of the quartz light guide tube 131, and the two are arranged concentrically. The inner diameter of the housing 133 matches the outer diameter of the quartz light guide tube 131.

[0025] Of course, in other embodiments, the quartz light guide tube 131 and the single-core optical fiber 132 are arranged adjacent to each other, and the housing 133 covers the outer periphery of the quartz light guide tube 131 and the single-core optical fiber 132, i.e., the three do not have to be arranged concentrically.

[0026] The detector 11 is a spectrometer that receives the above-mentioned output light path, i.e., receives the signal light reflected by the wafer 8, thereby obtaining corresponding spectral information, which is used to determine the polishing endpoint of the wafer 8. The detector 11 is connected to a single-core optical fiber 132. Specifically, as shown in FIG. 10, the difference between the signal spectrum and the background spectrum represents spectral information including the film thickness.

[0027] As shown in Figures 6 and 7, the quartz light guide tube 131 and the single-core optical fiber 132 have flattened end faces at one end close to the wafer 8, i.e., the end face of the proximal end 134 of the detector 11 is also flat. The end face of the quartz light guide tube 131 close to the wafer 8 has a chamfer 136. This chamfer may be a straight chamfer with an inclination angle of 0 to 45°, i.e., the α angle in Figure 6 is 0 to 45°. This chamfer may have a fillet curvature of 0 to 2 mm, as shown in Figure 7. 1 At one end of the quartz light guide tube 131 and the single-core optical fiber 132 away from the wafer 8, i.e., at a distal end 135 of the detector 11, the single-core optical fiber 132 protrudes from the quartz light guide tube 131.

[0028] The quartz light guide 131 itself acts as a transition medium between free-space propagation and medium propagation, propagating the light beam and ensuring the sealing and stability of the entire detection system. While the proximal end 134 of the detector 11 in Figure 8b has a flat structure, as shown in Figure 8a, the proximal end 134 of the detector 11 has a chamfer 136. This focuses the light emitted from the end face of the quartz light guide 131. The angle and curvature of the end face of the quartz light guide are designed according to the thickness of the light-transmitting window, focusing the light spot on the detection surface of the wafer 8. The concentration of the detection light energy further increases the signal light intensity and improves detection accuracy. The reduced detection area limits the detection range of the detection probe 13 on the wafer 8, more precisely positions the detection position, avoids signal blockage caused by various patterns and microdevices on the wafer 8, and increases the effective detection point. Compared to conventional multi-core optical fiber probes, the divergence angle is typically 20 to 30 degrees. Adding to the diameter of the optical fiber itself, the detection area often reaches several millimeters. The present invention limits the size of the detection light spot to the order of tens to hundreds of micrometers, and does not require adding structures such as focusing mirrors in front of the detection probe, thereby avoiding increased structural complexity and surface reflection noise caused by lenses.With the further development of current wafer processes, the complexity of patterns on wafers continues to increase and the dimensions of elements continue to decrease, making the detection accuracy of traditional large light spots no longer able to meet process demands.The detection system proposed by the present invention has the advantages of high precision, accurate positioning, low noise, etc., thanks to the unique design of the detection light path system and probe, and further meets current process demands.

[0029] The detector 11 obtains the corresponding spectral information, converts it into thickness information of the medium film on the surface of the wafer 8, and determines the polishing endpoint of the wafer 8. In other embodiments, the determination may be based on whether a signal such as a characteristic spectral line or characteristic point reaches a target value, which depends on the endpoint detection algorithm used and is not limited to film thickness information. As shown in Figure 9, the spectral reflectance curve varies depending on the film thickness, and the polishing endpoint can be determined based on this.

[0030] The operation process of the present invention is as follows: a light beam emitted from a light source 9 is collected and collimated by an optical lens set 10, reflected by a reflecting unit 12 to a detection probe 13, and emitted from a proximal end 134 of the detection probe 13 via a quartz light guide tube 131. The light passes through a light-transmitting window 4 on the polishing pad 2 and is irradiated onto the surface of a wafer 8 pressed onto the polishing pad 2. The light reflected from the surface of the wafer 8 passes through the light-transmitting window 4, is received by a single-core optical fiber 17 on the detection probe 16, and then reaches a detector 11. The detector 11 is a spectrometer that receives the signal light reflected by the wafer 8 and obtains the corresponding spectral information.

[0031] The present invention employs a unique detection optical path system. The light source optical path from the light source 9 to the detection probe 16 uses free-space propagation, while the signal optical path from the detection probe 16 to the detector 11 uses fiber propagation. The special design of the detection probe 16 ensures a smooth transition between the two light beam propagation modes. The entire detection optical path system combines the advantages of the two beam propagation modes, enabling high-precision detection. Compared with the traditional technical solution of using Y-shaped fiber optics, the present invention employs free-space propagation for the light source optical path and utilizes a lens set to collect and collimate the beam. The reflecting unit 12 adjusts the beam direction, ensuring that most of the light intensity from the light source 9 reaches the detection probe 13, solving the problem of relatively large coupling loss from the light beam from the light source 9 to the fiber. By fully utilizing the power of the xenon lamp light source, a lower-power light source can be used to meet detection needs, or a higher-intensity light can be used for detection in the detection probe 13. The present invention uses optical fiber in the signal optical path to collect the effective signal, and the signal collection point and the detection target, i.e., the wafer surface, are sufficiently close, and the signal reaches the detector stably due to the stable transmission of the optical fiber. The present invention combines the advantages of both free space and optical fiber transmission, improving the detection accuracy of the entire system.

[0032] Embodiment 2 As shown in FIG. 11, based on embodiment 1, this embodiment further includes a reference light sampling unit 14, which is disposed between the optical lens set 10 and the detection probe 13, is used to monitor the light intensity of the light source 9, and includes a light intensity detector.

[0033] The reference light sampling unit 14 includes a beam splitter 141. The light beam emitted from the light source 9 is collimated by the optical lens set 10, and the collimated beam reaches the reference light sampling unit 14 and is split into two beams by the beam splitter 141, that is, a signal beam and a reference beam are formed after passing through the beam splitter 141. The transmitted beam is the signal beam, and the signal beam passes through the beam splitter 141 and enters the reflecting unit 12. The reflected beam is the reference beam, which reaches the light intensity detector to obtain the light intensity value of the reference beam.

[0034] This embodiment also includes a controller for controlling the on / off and light intensity of the light source 9 and for calculating the polishing endpoint of the wafer 8 based on the spectral information acquired by the detector 11. The controller is connected to the light source 9, the detector 11, and the light intensity detector. The controller may be located inside the polishing table 1, or may be connected to the light source 9, the detector 11, and the light intensity detector outside the polishing table 1 by a method such as a conductive slip ring.

[0035] The controller directly sends a control signal to the light source 9, or indirectly, the controller sends a control signal to the detector 11, and the detector 11 sends a control signal to the light source 9, the control signal including a first control signal and a second control signal.

[0036] The first control signal is a pulse voltage signal, the pulse width of which is generally 10-100 us, and the pulse frequency of which is 100-1000 Hz, and is used to control the turning on and off of the light source 9. The light source 9 receives the pulse signal, turns on after a certain delay, and turns off after a certain period of time, and the light source 9 turns on and off according to the frequency of the pulse signal, and the detector 11 also performs sampling detection according to the frequency of the pulse signal, so that the light source 9 and the detector 11 are synchronized.

[0037] The second control signal is a level signal, which is a variable voltage signal, typically 0-5V, used to control the light intensity of the light source 9. The light source 9 receives the level signal and amplifies the voltage according to a certain ratio to make the light source 9 brighter; the higher the voltage, the greater the light intensity of the light source 9. Therefore, the magnitude of the level signal is directly correlated with the brightness of the light source 9.

[0038] Taking film thickness monitoring as an example, during the polishing process, the polishing table 1 and the polishing pad 2 fixed thereon rotate at a set speed, and the light-transmitting window 4 on the polishing pad 2 also rotates accordingly, forming a light-transmitting window path 7. As the light-transmitting window 4 passes under the wafer 8 held on the polishing head 5, the spectral information reflected by the wafer 8 is acquired by the detector 11 via the reflecting unit 12 and the detection probe 13. By comparing the spectral information with the film thickness on the surface of the wafer 8, online measurement of the film thickness on the surface of the wafer 8 is possible. The time it takes for the light-transmitting window 4 to pass under the wafer 8 held on the polishing head 5 varies depending on the rotation speed of the polishing table 1. The signal sampling frequency can be adjusted by the first control signal to ensure sufficient sampling points and sufficient signal data. As the polishing process progresses, the degree of wear on the light-transmitting window 4 gradually changes, and the signal intensity varies due to the different concentration components of different process polishing solutions and the different signal optical path conditions. By controlling the magnitude of the voltage value of the second control signal, the light intensity of the signal light can be kept within the appropriate range of the detector 11, thereby improving the accuracy and precision of film thickness measurement.

[0039] During the polishing process, the light intensity detector can continuously monitor and measure the reference light beam to obtain the light intensity of the reference light. The reference light reflects the state of the light source 9, and the reference light spectrum information and light intensity value can be used to correct fluctuations in the light intensity of the light source 9 caused by factors such as deterioration of the light source 9 and voltage instability. By controlling the magnitude of the voltage value of the second control signal, the light intensity of the light source 9 can be kept stable, improving the accuracy and precision of film thickness measurement.

[0040] The above specific embodiments are intended to illustrate the present invention, but are not intended to limit the present invention. Any modifications and changes made to the present invention within the spirit of the present invention and the scope of protection of the claims are also included in the scope of protection of the present invention. [Explanation of symbols]

[0041] 1 Polishing machine 2 polishing pads 3 Abrasive spray arms 4 Light passing window 5 Polishing Heads 6. Trimmer 7. Light passing window path 8 wafers 9 light source 10 Optical Lens Set 11 Detector 12 Reflection Unit 13 Detection probe 131 Quartz light guide tube 132 Single-core optical fiber 133 Housing 134 Proximal end of detection probe 135 Distal end of detection probe 136 Chamfering of quartz light guide tube 14 Reference light sampling unit 141 Beam Splitter

Claims

1. an on-line monitoring device for chemical mechanical polishing, the device being mounted within the polishing table and capable of rotating with the polishing table; A light source and an optical lens set used to receive the light beam emitted by the light source and generate a collimated beam; a reflecting unit used to receive the collimated beam and reflect the collimated beam to form an incident optical path; a detection probe disposed below the light-transmitting window of the polishing pad, the detection probe including at least a quartz light guide tube and a single-core optical fiber, the quartz light guide tube being used to receive an incident light path and emit the incident light path from one end of the detection probe close to the wafer, and the single-core optical fiber being used to receive an emitted light path reflected by the wafer surface; and a detector connected to the single-core optical fiber for receiving the output light path, for obtaining corresponding spectral information and determining the end point of wafer polishing.

2. the sensing probe further comprises a housing; the quartz light guide tube is coated on the outer periphery of the single-core optical fiber, the housing is coated on the outer periphery of the quartz light guide tube, and the housing, the quartz light guide tube and the single-core optical fiber are concentrically arranged; Alternatively, the quartz light guide tube and the single-core optical fiber are installed adjacent to each other, and the housing is coated on the outer circumference of the quartz light guide tube and the single-core optical fiber.

3. 3. The online monitoring device for chemical mechanical polishing according to claim 1, wherein an end face of the quartz light guide tube near the wafer and an end face of the single-core optical fiber near the wafer are flat, and the end face of the quartz light guide tube near the wafer is chamfered.

4. The chamfer is a straight chamfer, and the inclination angle is 0 to 45°; Alternatively, the chamfer is a circular chamfer, and the fillet curvature is 0 to 2 mm. １ 4. The apparatus for monitoring chemical mechanical polishing online according to claim 3, wherein:

5. 2. The apparatus for monitoring chemical mechanical polishing online according to claim 1, wherein the single-core optical fiber protrudes from the quartz light guide at one end of the quartz light guide and the single-core optical fiber remote from the wafer.

6. 2. The chemical mechanical polishing online monitoring device according to claim 1, wherein the outer diameter of the quartz light guide tube is 1 to 4 mm, and the outer diameter of the single-core optical fiber is 0.1 to 2 mm.

7. 2. The chemical mechanical polishing online monitoring apparatus of claim 1, wherein the light source is a broadband light source, the wavelength of which is 200-2000 nm, and the diameter of the collimated beam is 1-10 mm.

8. 2. The chemical mechanical polishing online monitoring device of claim 1, wherein the detector is a spectrometer, and the detector acquires corresponding spectral information and converts it into thickness information of the medium film on the wafer surface to determine the end point of wafer polishing.

9. 2. The chemical mechanical polishing online monitoring device of claim 1, further comprising a reference light sampling unit, which is installed between the optical lens set and the detection probe and is used to monitor the light intensity of the light source.

10. 10. The chemical mechanical polishing online monitoring device of claim 9, wherein the reference light sampling unit includes a first beam splitter and a second beam splitter, the collimated beam passes through the first beam splitter to form a signal light and a reference light, and the signal light passes through the first beam splitter to enter the detection probe.

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