Wafer film thickness measuring apparatus, measuring method, wafer polishing device, and polishing method

Abstract

To provide a wafer film thickness measuring device, a measuring method, a wafer polishing device, and a polishing method.SOLUTION: A light source 11, a light source energy adjusting module 12, a beam splitter for splitting a modulated beam to generate a measuring beam and a reference beam, and a flexible probe 13 for transmitting the measuring beam and a reflected beam; A flexible probe 13 adaptively moving along an optical axis direction to maintain contact with a transmission window of a grinding pad of a wafer polishing device during a grinding process, a light detection module 15 configured to collect a light intensity measurement value of a reference beam and a light intensity measurement value of a reflected beam, and a processing unit configured to calibrate the light intensity measurement value of the reflected beam based on the light intensity measurement value of the reference beam to obtain a light intensity calibration value of the reflected beam, and determine a film thickness of a wafer based on the light intensity calibration value of the reflected beam, thereby improving film thickness measurement accuracy and prolonging a service life of the transmission window.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to the field of wafer processing, and in particular to a wafer film thickness measuring apparatus, a measuring method, and a wafer polishing device and polishing method. [Background technology]

[0002] Chemical Mechanical Polishing (CMP) is a critical process step in the manufacturing process of semiconductor integrated circuit chips. Furthermore, with the development of semiconductor technology, in order to improve device performance and reliability, when performing the CMP process using wafer polishing devices, process control of within-wafer (WIW) and between-wafer (WTW) film thickness variations using wafer film thickness measurement systems is particularly important.

[0003] Related technologies primarily use eddy current endpoint measurement, laser endpoint measurement, and white light endpoint measurement to monitor the characteristics of film layers during CMP and appropriately control and stop the removal process. Among these, eddy current technology controls the polishing endpoint by measuring the eddy current signal generated by the metal film layer on the wafer surface. Laser and white light technologies are primarily used to measure the endpoint of dielectric films. Laser technology analyzes film thickness changes by detecting the intensity of single-wavelength interference light in the dielectric film layer, but because it detects less information, laser technology has relatively low measurement accuracy and reliability and cannot meet the process requirements of advanced semiconductor nodes. White light technology uses a broadband light source and detector to increase measurement information and effectively improve measurement accuracy.

[0004] In particular, with white light technology, during the CMP process using a wafer polishing device and during the film thickness measurement process using a wafer film thickness measurement device, the transmittance of the grinding pad transmission window gradually decreases due to grinding, causing a gradual decrease in the light intensity of the measurement beam and reflected beam as they pass through the grinding pad transmission window, affecting the accuracy of film thickness measurement. Furthermore, to maintain the intensity of the reflected beam, the grinding pad transmission window must be frequently replaced, resulting in a waste of time and resources.

[0005] During the grinding process, the wafer polishing device may not be able to maintain good contact between the flexible probe and the grinding pad transmission window due to issues such as vibration and structural accuracy, which causes the distance between the flexible probe and the grinding pad transmission window and the wafer to change, requiring frequent maintenance.

[0006] In addition, the light source of the wafer polishing device is generally a pulsed light source, and the light intensity of the illumination source beam provided by the light source will fluctuate to a certain extent, which will ultimately lead to fluctuations in the reflected beam for obtaining the wafer film thickness.

[0007] The above problems cause the wafer polishing device to provide inaccurate wafer film thickness measurements, require frequent maintenance, and increase the cost of use. Summary of the Invention

[0008] To overcome the problems existing in the related art, the present invention provides a wafer film thickness measurement apparatus, a measurement method and a wafer polishing device and polishing method.

[0009] According to a first aspect of an embodiment of the present invention, there is provided a wafer film thickness measuring apparatus for use in a wafer polishing device, the wafer film thickness measuring apparatus comprising: a light source for providing an illumination source beam; a light source energy adjusting module for adjusting and controlling the light intensity of the source beam to obtain a modulated beam having a dynamic target light intensity; a beam splitter for splitting the modulated beam to produce a measurement beam and a reference beam; a flexible probe for transmitting the measurement beam and the reflected beam, the flexible probe adaptively moving along an optical axis direction so as to maintain contact with a grinding pad transmission window of a wafer polishing device during a grinding process, the measurement beam forming the reflected beam after being incident on the wafer through the flexible probe; a light detection module for collecting light intensity measurements of the reference beam and light intensity measurements of the reflected beam; and a processing unit that calibrates the light intensity measurement value of the reflected beam based on the light intensity measurement value of the reference beam to obtain a calibrated light intensity value of the reflected beam, and determines a film thickness of the wafer based on the calibrated light intensity value of the reflected beam.

[0010] According to a second aspect of the present invention, there is provided a wafer film thickness measurement method applicable to the wafer film thickness measurement apparatus according to the first aspect or any one of the first and second aspects, the wafer film thickness measurement method comprising: During a wafer grinding process, adjust and control the light intensity of an illumination source beam provided by a light source using a light source energy adjusting module to obtain a modulated beam having a dynamic target light intensity, wherein the modulated beam generates a measurement beam and a reference beam after passing through a beam splitter, and the measurement beam forms a reflected beam after being incident on a wafer through a flexible probe, and the flexible probe transmits the measurement beam and the reflected beam, and adaptively moves along an optical axis direction during the grinding process so as to maintain contact with a grinding pad transmission window of a wafer polishing device; collecting light intensity measurements of the reflected beam and a reference beam in real time using a light detection module; calibrating the measured intensity of the reflected beam based on the measured intensity of the reference beam to obtain a calibrated intensity of the reflected beam; and determining a film thickness of the wafer based on the calibrated light intensity of the reflected beam.

[0011] According to a third aspect of an embodiment of the present invention, there is provided a wafer polishing device including the wafer film thickness measurement apparatus according to the first aspect or any of the embodiments of the first aspect.

[0012] According to a fourth aspect of an embodiment of the present invention, there is provided a method of wafer polishing, the method comprising: During a process of polishing a product wafer using a wafer polishing device, adjust and control the light intensity of an illumination source beam provided by a light source using a light source energy adjusting module to obtain a modulated beam having a dynamic target light intensity, wherein the modulated beam generates a measurement beam and a reference beam after passing through a beam splitter, and the measurement beam forms a reflected beam after being incident on the wafer through a flexible probe, and the flexible probe transmits the measurement beam and the reflected beam, and adaptively moves along an optical axis direction during the polishing process so as to maintain contact with a grinding pad transmission window of the wafer polishing device; collecting light intensity measurements of the reflected beam and the reference beam in real time using a light detection module; calibrating the measured intensity of the reflected beam based on the measured intensity of the reference beam to obtain a calibrated intensity of the reflected beam; calculating an actual measured reflectance spectrum of the reflected beam based on the calibrated light intensity values ​​of the reflected beam; extracting a film thickness value of the wafer in real time based on the actual measured reflectance spectrum of the reflected beam, and terminating polishing of the wafer when the film thickness value reaches a predetermined target value.

[0013] The technical solution provided by the embodiments of the present invention may have the following beneficial effects: In the embodiments of the present invention, when the transmittance of the grinding pad window changes during the grinding process, the energy adjustment module is adjusted and controlled in a timely manner to adjust the light intensity of the illumination source beam provided by the light source to obtain a modulated beam with a dynamic target light intensity that matches the transmittance of the grinding pad window, thereby maintaining the stability of the energy of the beam irradiated on the wafer surface, reducing the variability in the light intensity of the beam reflected from the wafer surface, and improving the accuracy and stability of the measurement results; that is, even when the transmittance of the grinding pad transmission window changes over a wide range, the needs of wafer film thickness measurement can be met and measurement accuracy can be ensured. Furthermore, since the grinding pad transmission window can be used even when it is significantly worn, the service life of the grinding pad transmission window can be extended, and the economic and time costs associated with frequent replacement of the grinding pad transmission window can be avoided.

[0014] By using a flexible probe that can move adaptively along the optical axis, even when adverse conditions such as vibration occur in the wafer polishing device, the flexible probe can always be in contact with the grinding pad transmission window and maintain a constant pressure, resulting in a stable reflected beam signal, improving the measurement accuracy of the wafer film thickness, and avoiding frequent maintenance due to displacement of the flexible probe relative to the grinding pad transmission window.

[0015] The measurement beam must pass through the grinding pad window, strike the wafer, and then be reflected by the wafer to form a reflected beam. The reflected beam then passes through the grinding pad window, strikes the flexible probe again, and finally reaches the optical detection module. This process incurs significant optical intensity loss. Splitting the modulated beam to form a reference beam and then directly entering the optical detection module minimizes optical intensity loss and accurately reflects the intensity variations of the illumination source beam provided by the light source. Calibrating the reflected beam intensity measurement based on the reference beam intensity measurement effectively compensates for variations in the reflected beam intensity due to variations in the light source intensity, improving wafer film thickness measurement accuracy.

[0016] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. [Brief explanation of the drawings]

[0017] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments in accordance with the present invention and, together with the description, serve to explain the principles of the invention.

[0018] [Figure 1] 1 is a structural schematic diagram of a wafer polishing device according to the related art; [Figure 2] 1 is a structural schematic diagram of a wafer film thickness measuring apparatus according to an exemplary embodiment; [Figure 3] 1 is a structural schematic diagram of a wafer film thickness measuring apparatus according to an exemplary embodiment; [Figure 4] 1 is a structural schematic diagram of a light source energy adjusting module shown in an exemplary embodiment; [Figure 5] 1 is a structural schematic diagram of a light source energy adjusting module shown in an exemplary embodiment; [Figure 6] 1 is a structural schematic diagram of a light source energy adjusting module shown in an exemplary embodiment; [Figure 7] 1 is a structural schematic diagram of a wafer film thickness measuring apparatus according to an exemplary embodiment; [Figure 8] 1 is a structural schematic diagram of a wafer film thickness measuring apparatus according to an exemplary embodiment; [Figure 9] 1 is a schematic diagram of the positional relationship between a flexible probe and a grinding disk as shown in an example embodiment; [Figure 10] 1 is a structural schematic diagram of a wafer polishing device according to an exemplary embodiment; [Figure 11] 1 is a flowchart of a wafer film thickness measurement method according to an exemplary embodiment. [Figure 12]1 is a flowchart of a method for determining a film thickness of a wafer based on a calibrated light intensity value of a reflected beam, as illustrated by an example embodiment. [Figure 13A] 10 is a flowchart illustrating real-time adjustment of light source energy in a wafer film thickness measurement method as illustrated by an example embodiment. [Figure 13B] 10 is a flowchart illustrating real-time adjustment of light source energy in a wafer film thickness measurement method as illustrated by an example embodiment. [Figure 14] 1 is a flowchart of a wafer polishing method according to an example embodiment. [Figure 15] 1 is a flowchart of a method for creating a correspondence library according to an exemplary embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0019] Illustrative examples will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numerals in different accompanying drawings refer to the same or similar elements, unless otherwise specified. The embodiments described in the following illustrative examples do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present invention as detailed in the appended claims.

[0020] The wafer film thickness measuring device provided by the present invention is mainly applied to CMP. In one example, the wafer film thickness measuring device is used in a wafer polishing device.

[0021] FIG. 1 shows a schematic diagram of a wafer polishing device according to the related art. Referring to FIG. 1, a grinding pad 3A is fixed on a grinding disc 2A. A polishing head 4A carries a wafer 5A, bringing it into close contact with the grinding pad 3A. The grinding disc 2A rotates, and the polishing head 4A rotates and moves back and forth relative to the grinding disc 2A, causing the wafer 5A to rub against the grinding pad 3A, thereby performing polishing. A spray arm 7A sprays abrasive liquid from a nozzle. The polishing liquid rotates through the grinding disc 2A and reaches the polishing head 4A, where it contacts the wafer 5A through the grooves in the grinding pad 3A, performing chemical polishing. A grinding pad dresser 6A cleans and conditions the grinding pad 3A.

[0022] Among these, the wafer film thickness measuring device is installed inside the grinding disc 2A and rotates together with the grinding disc 2A. It is equipped with a probe 13A, a cable 22A, and a control box 16A. The probe 13A signal is irradiated onto the wafer through a transparent window on the grinding pad 3A and returns to the control box 16A from the window.

[0023] In the wafer film thickness measurement device according to the related art, when applying white light endpoint measurement technology to CMP, there are problems such as the inability to adjust the light source energy, poor quality of the spectral signal, and poor adaptability to probe processes.

[0024] In view of this, an embodiment of the present invention provides a wafer film thickness measurement apparatus.

[0025] FIG. 2 is a structural schematic diagram of a wafer film thickness measurement apparatus shown in an exemplary embodiment. As shown in FIG. 2, the wafer film thickness measurement apparatus 1 includes a light source 11, a light source energy adjustment module 12, a beam splitter 14, a flexible probe 13, a light detection module 15, and a processing unit.

[0026] In this system, a light source 11 is used to provide an illumination source beam. A light source energy adjustment module 12 is used to adjust and control the light intensity of the source beam to obtain a modulated beam with a dynamic target light intensity. A beam splitter 14 is used to split the modulated beam to generate a measurement beam and a reference beam. A flexible probe 13 is used to transmit the measurement beam and the reflected beam. Furthermore, the flexible probe 13 adaptively moves along the optical axis direction during the grinding process to maintain contact with the grinding pad transmission window of the wafer polishing device. The measurement beam forms a reflected beam after being incident on the wafer through the flexible probe 13. A light detection module 15 is used to collect light intensity measurements of the reference beam and the reflected beam. A processing unit (not shown) calibrates the light intensity measurements of the reflected beam based on the light intensity measurements of the reference beam to obtain a calibrated light intensity value of the reflected beam, and determines the film thickness of the wafer based on the calibrated light intensity value of the reflected beam.

[0027] In the wafer film thickness measurement device provided by the embodiment of the present invention, on the one hand, a light source energy adjustment module 12 is added to the light source 11 side, which timely adjusts and controls the energy of the light source 11 when the transmittance of the grinding pad transmission window changes, and obtains a modulated beam with a dynamic target light intensity that matches the grinding pad window transmittance, thereby maintaining the stability of the energy of the beam irradiated on the wafer surface, reducing the variability of the light intensity of the beam reflected from the wafer surface, and improving the accuracy and stability of the measurement results.

[0028] On the other hand, the beam splitter 14 splits the modulated beam adjusted and controlled by the light source energy adjustment module 12 into a measurement beam and a reference beam. The measurement beam is irradiated onto the wafer via the flexible probe 13 to form a reflected beam. The reflected beam is collected via the flexible probe 13 and then incident on the optical detection module 15, while the reference beam is directly incident on the optical detection module 15. Because the reference beam and the reflected beam originate from the same source beam, their intensity fluctuation trends are consistent. Therefore, the optical intensity measurement of the reflected beam can be calibrated based on the optical intensity measurement of the reference beam, and fluctuations in the optical path signal of the measurement beam caused by fluctuations in the light source energy can be corrected in real time, thereby improving the stability of the measurement beam signal. The film thickness of the wafer can then be determined based on the calibrated optical intensity of the reflected beam, thereby improving the accuracy and stability of film thickness measurement.

[0029] On the other hand, a flexible probe 13 is provided that can adaptively move along the optical axis direction during the grinding process. Compared to non-flexible probes (probes connected by rigid members) in the related art, the flexible probe 13 automatically compensates for changes in probe position due to high-speed movement of the grinding disk, maintaining the relative position and pressure between the probe and the grinding pad window so that the flexible probe 13 maintains contact with the grinding pad transmission window of the wafer polishing device, thereby reducing the impact of movement during the polishing process on the measurement signal. The use of a flexible probe solution also reduces the frequency of probe maintenance and avoids the problems of recovering device performance through disassembly and assembly of the grinding pad and probe debugging.

[0030] In an embodiment of the present invention, the light source 11 is a white light source having a broadband spectrum. For example, in order to extend the light source's service life and shorten the exposure time of the light on the wafer, the light source 11 employs a pulsed xenon lamp light source to provide a pulsed illumination source beam. Of course, the present invention is not limited thereto, and those skilled in the art can substitute a laser light source or other light sources as needed.

[0031] The stability of a xenon lamp light source is relatively low, and the stability of the collected signal of the reflected beam is also low. In an embodiment of the present invention, at the start of grinding, the light source energy adjustment module 12 can be used to adjust the illumination source beam provided by the light source 11 to a modulated beam with a required initial target light intensity. As grinding progresses, the transmittance of the grinding pad transmission window decreases, and the light source energy adjustment module 12 is controlled to dynamically adjust the light intensity of the source beam to a different required target light intensity in real time. This reduces the impact of changes in the light intensity of the measurement beam irradiated on the wafer surface on the film thickness measurement, and the light intensity of the reflected beam received by the light detection module 15 remains stable overall, improving the film thickness measurement accuracy.

[0032] In an embodiment of the present invention, after the modulated beam is split into a measurement beam and a reference beam by beam splitter 14, the reference beam is incident directly on photodetection module 15, and the measurement beam is incident on the wafer via flexible probe 13. The wafer reflects the measurement beam to form a reflected beam, which is incident on photodetection module 15 via flexible probe 13.

[0033] The reference beam is incident directly on the optical detection module 15 from the beam splitter 14, and the optical intensity of the reference beam has little loss in the corresponding transmission optical path of the reference beam, and can accurately reflect the optical intensity fluctuations of the modulated beam. Because the measurement beam and the reference beam are split from the source beam of the same light source 11 by the beam splitter 14 and have the same change trend, the optical intensity of the reflected beam received by the optical detection module 15 can be calibrated based on the change in the reference beam, preventing the optical intensity fluctuations output from the light source 11 from affecting the optical intensity of the reflected beam received by the optical detection module 15 and improving the measurement accuracy of the wafer.

[0034] In an embodiment of the present invention, a flexible probe 13 is provided that can adaptively move along the optical axis direction. This allows the flexible probe 13 to always be in contact with the grinding pad transmission window and maintain a constant pressure even when adverse conditions such as vibration occur in the wafer polishing device, thereby obtaining a stable reflected beam signal, improving the measurement accuracy of the wafer film thickness, and solving the problem of frequent maintenance caused by the flexible probe 13 being displaced relative to the grinding pad transmission window.

[0035] In an embodiment of the present invention, the light detection module 15 comprises a beam collecting element capable of detecting light intensity and is used to acquire the light intensity of the measurement beam and the reflected beam in real time.

[0036] In some embodiments, the light detection module 15 may comprise a beam collecting element, and the reference beam and the measurement beam are collected by the same beam collecting element.

[0037] In some embodiments, the light detection module 15 may include two beam collecting elements, each collecting the reference beam and the measurement beam. For example, as shown in FIG. 3 , the light detection module 15 may include a reflective beam collecting element 151 and a reference beam collecting element 152, where the measurement beam generated via the beam splitter 14 is directly incident on the reflective beam collecting element 151, and the reflected beam reflected by the wafer is incident on the reflective beam collecting element 151.

[0038] FIG. 4 is a structural schematic diagram of a light source energy adjustment module shown in an exemplary embodiment. As shown in FIG. 4, the light source energy adjustment module 12 includes a plurality of filter elements 121 with different transmittances and a rotary drive mechanism 122. The plurality of filter elements 121 are arranged around the rotation axis of the rotary drive mechanism 122. The rotary drive mechanism 122 rotates and drives the plurality of filter elements 121, thereby transmitting the source beam through a target filter element 121 among the plurality of filter elements 121, and obtaining a modulated beam with a dynamic target light intensity.

[0039] During wafer polishing, the grinding pad transmission window gradually wears and its transmittance gradually decreases. At each stage, a modulated beam with a different light intensity, i.e., a dynamic target light intensity, must be coupled to the grinding pad transmission window with a different transmittance.

[0040] In an embodiment of the present invention, multiple filter elements 121 and a rotary drive mechanism 122 are provided. The rotary drive mechanism 122 can be used to switch the positions of the multiple filter elements 121, allowing the source beam to selectively pass through different filter elements 121 and become a modulated beam with a dynamic target intensity. Depending on the selected filter element 121, the intensity of the modulated beam formed after the source beam passes through the filter element 121 also varies. By providing multiple filter elements 121, the number of transmittance levels increases, and the number of intensity levels of the modulated beam also increases. The more intensity levels of the modulated beam, the smaller the difference between different intensity levels, which can follow the continuous decrease in transmittance of the grinding pad transmission window. This reduces the impact of the decrease in transmittance of the grinding pad transmission window on the wafer film thickness measurement accuracy.

[0041] 5 is a structural schematic diagram of a light source energy adjusting module shown in an exemplary embodiment. As shown in FIG. 5, the light source energy adjusting module 12 includes a reciprocating drive mechanism 123 and a filter element 121 with gradually changing transmittance. The reciprocating drive mechanism 123 reciprocates the filter element 121 with gradually changing transmittance along the direction in which the transmittance gradually changes, so that the source beam is transmitted through the region of the filter element 121 with gradually changing transmittance, thereby obtaining a modulated beam with a dynamic target light intensity.

[0042] In an embodiment of the present invention, the filter element 121 is configured to have a gradually changing transmittance. When the reciprocating drive mechanism 123 drives the filter element 121 with gradually changing transmittance along the direction of gradually changing transmittance, the source beam passes through the filter element 121 with gradually changing transmittance at different transmittance portions, thereby forming modulated beams with different target light intensities. The modulated beams with different target light intensities are coupled with the grinding pad transmission windows, thereby improving the accuracy of wafer film thickness measurement.

[0043] In some embodiments, the graded transmittance filter element 121 is configured such that its transmittance varies from less to more from one end to the other.

[0044] In some embodiments, the filter element 121 whose transmittance gradually changes may have a transmittance that changes in steps or continuously, which can be selected by those skilled in the art as needed, and the present invention is not limited thereto.

[0045] In some embodiments, the graded transmittance filter element may be replaced with multiple filter elements 121 with different transmittances arranged in a line, as shown in FIG.

[0046] In some embodiments, the filter element 121 is a filter.

[0047] 2, in some embodiments, the light source energy adjustment module 12 can adjust the magnitude of the light intensity of the source beam provided by the light source 11. The adjustment may include decreasing the light intensity, maintaining the light intensity constant, or increasing the light intensity.

[0048] In some embodiments, for example, an auxiliary light source is provided in the light source energy adjustment module 12. By providing the auxiliary light source and the filter element 121 together, the light source energy adjustment module 12 can have the function of reducing, maintaining constant, or increasing the light intensity of the source beam provided by the light source 11.

[0049] In this embodiment of the present invention, the light source energy adjusting module 12 is used to adjust and control the illumination source beam. At the start of grinding, when the transmittance of the grinding pad window is higher, a modulated beam with a first target light intensity corresponding to the current transmittance of the grinding pad window is obtained. As grinding progresses, a modulated beam with a second target light intensity corresponding to the current transmittance of the grinding pad window is obtained. In this way, the light source energy adjusting module 12 adaptively adjusts based on changes in the transmittance of the grinding pad window, maintaining the stability of the beam energy irradiated on the wafer surface and reducing the variability in the intensity of the beam reflected from the wafer surface, thereby improving the accuracy and stability of the measurement results. The light source energy adjusting module 12 in this embodiment of the present invention can dynamically adjust the modulated beam intensity to a target light intensity according to actual needs, and has a wide adjustable range, so it can meet the needs of wafer film thickness measurement even when the transmittance of the grinding pad window changes over a wide range. Furthermore, the light source energy adjusting module 12 according to the embodiment of the present invention can be used even when the grinding pad transmission window is more worn, thereby extending the service life of the grinding pad transmission window and reducing the economic and time costs associated with frequent replacement of the grinding pad transmission window.

[0050] In some embodiments, beam splitter 14 comprises a fiber optic beam splitter that is used to split the modulated beam into a reference beam and a measurement beam, and to separate the measurement beam incident on the wafer from the reflected beam reflected from the wafer.

[0051] In some embodiments, the wafer film thickness measurement device 1 comprises an optical fiber, and the measurement beam, the reference beam, and the reflected beam are all transmitted through the optical fiber.

[0052] 7 is a schematic diagram of the structure of a wafer film thickness measurement device shown in an exemplary embodiment. As shown in FIG. 7, the optical fiber beam splitter has four port optical fibers 143 and corresponding optical fiber interfaces 144. One port optical fiber 143 connects the light source energy adjustment module 12 and one optical fiber interface 144 to carry a modulated beam, another port optical fiber 143 connects the same optical fiber interface 144 and the optical detection module 15 to carry a reference beam, another port optical fiber 143 connects the same optical fiber interface 144 and the flexible probe 13 to carry a measurement beam, and yet another port optical fiber 143 connects the flexible probe 13 and the optical detection module 15 to carry a reflected beam. The ports of the port optical fibers 143 can serve as connections.

[0053] Using optical fiber as a medium carrying beam can play the role of separating and protecting the beam, reducing the possibility that ambient light on the beam path will enter the optical fiber and affect the beam, and impurities in the air will not adversely affect the beam in the optical fiber, greatly maintaining the stability of the beam.

[0054] In some embodiments, the beam splitter 14 includes a beam splitting lens.

[0055] A beam splitting lens is a device that can transmit a part of a beam irradiated onto the beam splitting lens and reflect a part of the beam. There are various implementation methods and specific structures, and the present invention is not limited thereto.

[0056] In the embodiment of the present invention, a beam splitting lens is adopted as the beam splitter, and the task of generating the modulated beam, measurement beam and reference beam is completed using the beam splitting lens, and the generation of the corresponding beams can be realized by setting the angle and position of the beam splitting lens, which has a simple structure.

[0057] 8 is a structural schematic diagram of a wafer film thickness measurement apparatus according to an exemplary embodiment. As shown in FIG. 8, the beam splitting lens includes a first beam splitting lens 141 and a second beam splitting lens 142. The modulated beam emitted from the light source energy adjusting module 12 is irradiated onto the first beam splitting lens 141. A portion of the modulated beam passes through the first beam splitting lens 141 to form a reference beam. The reference beam is directly incident on the light detection module 15. A portion of the modulated beam is reflected by the first beam splitting lens 141 to form a measurement beam. The measurement beam is irradiated onto the wafer and reflected by the wafer to form a reflection beam. The reflection beam is incident on the light detection module 15.

[0058] In some embodiments, the beam splitting lens includes a first beam splitting lens 141 and a second beam splitting lens 142, the modulated beam emitted from the light source energy adjusting module 12 is irradiated onto the first beam splitting lens 141, a portion of the modulated beam is reflected through the first beam splitting lens 141 to form a reference beam, the reference beam is directly incident on the light detection module 15, and a portion of the modulated beam passes through the first beam splitting lens 141 to form a measurement beam, the measurement beam is irradiated towards the wafer and forms a reflected beam after being reflected through the wafer, and the reflected beam light is incident on the detection module 15.

[0059] In some embodiments, the measurement beam emitted from the first beam splitting lens 141 passes through the second beam splitting lens 142, is irradiated towards the wafer after passing through the second beam splitting lens 142, is reflected through the wafer to form a reflected beam, and the reflected beam is reflected by the second beam splitting lens 142 and is irradiated towards the light detection module 15.

[0060] In some embodiments, the measurement beam emitted from the first beam splitting lens 141 is reflected through the second beam splitting lens 142 before being irradiated towards the wafer, and after being reflected through the wafer forms a reflected beam, which passes through the second beam splitting lens 142 before being irradiated towards the light detection module 15.

[0061] In the embodiment of the present invention, a beam splitting lens is used as a beam splitter, and the beam is directly irradiated onto the beam splitting lens to produce the splitting effect, eliminating the need for a medium in the beam. The distances between the light source energy adjustment module, the beam splitting lens, the light detection module, and the flexible probe can be flexibly adjusted without considering the volume of the beam medium, thereby improving the flexibility of the setup of the entire device.

[0062] In the following, in the embodiment of the present invention, the implementation process of calibrating the light intensity measurement value of the reflected beam based on the light intensity measurement value of the reference beam of the processing unit to obtain the light intensity calibration value of the reflected beam will be described.

[0063] In an embodiment of the present invention, the optical detection module is used to collect multiple measurements of the optical intensity of the reference beam and calculate the average value to obtain the calibrated optical intensity value of the reference beam.

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[0064] In an embodiment of the present invention, a light detection module is used to collect real-time light intensity measurements of the reference beam and real-time light intensity measurements of the reflected beam during the grinding process.

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[0065] The measured light intensity of the reflected beam is calibrated by the following equation (1) to obtain the calibrated light intensity value of the reflected beam.

[0066]

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[0067] The source beam provided by the light source is not actually stable, and there is a certain degree of fluctuation in the light intensity of the source beam. Because wafer film thickness measurement is analyzed and calculated based on the light intensity of the reflected beam received by the optical detection module, fluctuations in the light intensity of the source beam provided by the light source directly affect the accuracy of wafer film thickness measurement.

[0068] In an embodiment of the present invention, a reference beam having the same light source as the measurement beam is set, and the fluctuation synchronization between the reference beam and the measurement beam is utilized to calibrate the light intensity measurement value of the reflected beam measured by the light detection module based on the fluctuation of the reference beam, and the calibrated light intensity value of the calibrated reflected beam is used to obtain the wafer film thickness, thereby preventing the light intensity fluctuation of the source beam from adversely affecting the accuracy of the measured wafer film thickness.

[0069] In an embodiment of the present invention, the light intensity calibration value of the reference beam can be determined in advance using a standard sample (also called a standard wafer). For example, before grinding a wafer, the energy adjustment module 12 adjusts and controls the source beam of the light source so that the reflective beam collecting element 151 and the reference beam collecting element 152 are in a high-performance state, i.e., meet the requirements of the corresponding target light intensity. The reflective beam collecting element 151 and the reference beam collecting element 152 each collect the light intensity of the standard sample n times consecutively, and calculate the average value of the light intensity of the standard sample collected n times consecutively by the reference beam collecting element 152.

number

[0070] In this regard, in the embodiment of the present invention, in order to improve the accuracy of the light intensity calibration value of the reference beam, the light intensity calibration value of the reference beam needs to be periodically updated. For example, in one example, the embodiment of the present invention can preset the transmittance of the grinding pad transmission window, which is the reference transmittance of the grinding pad transmission window. When the real-time transmittance of the grinding pad transmission window falls below the predetermined transmittance, the grinding pad transmission window is significantly worn, and the current modulated beam can no longer effectively pass through the grinding pad transmission window. The light intensity of the reflected beam received by the optical detection module is already too small, which means that the requirement for accurately measuring the wafer film thickness cannot be met. At this time, the light source energy adjustment module is controlled to increase the light intensity of the modulated beam and re-determine the light intensity calibration value of the reference beam.

[0071] In some embodiments, the processing unit may determine the film thickness of the wafer based on the calibrated light intensity values ​​of the reflected beam by adopting the following method: obtain theoretical reflectance spectra of the wafer corresponding to different film thickness values; calculate actual measured reflectance spectra of the reflected beam based on the calibrated light intensity values ​​of the reflected beam; obtain a target theoretical reflectance spectrum that matches the actual measured reflectance spectrum from the theoretical reflectance spectra of the wafer corresponding to different film thickness values; and determine the film thickness value corresponding to the target theoretical reflectance spectrum as the film thickness of the wafer.

[0072] In an embodiment of the present invention, theoretical reflectance spectra of a wafer corresponding to different film thickness values ​​can be determined using a modeling algorithm.

[0073] In determining the wafer film thickness, the embodiment of the present invention uses the reflected beam collecting element 151 to collect and measure the light intensity measurement value of the reflected beam in real time, and uses the reference beam collecting element 152 to collect and measure the light intensity measurement value of the reference beam in real time. The light intensity measurement value of the reflected beam is calibrated according to Equation (1) to obtain the calibrated light intensity value of the reflected beam. The actual measured reflectance spectrum of the reflected beam is calculated based on the calibrated light intensity value of the reflected beam.

[0074] In an embodiment of the present invention, the calibrated light intensity value of the calibrated reflected beam is used to calculate the actual measured reflectance spectrum of the reflected beam, which can eliminate the adverse effects of light intensity fluctuations of the source beam, thereby improving the measurement accuracy of the wafer film thickness.

[0075] The present invention also relates to the positional relationship between a flexible probe and a grinding disk in a wafer film thickness measurement device. During the wafer polishing process, the wafer film thickness measurement device must rotate along with the grinding disk. As the grinding disk and wafer film thickness measurement device rotate, factors such as vibration and assembly inaccuracy can cause the probe, which is in contact with the grinding pad transmission window, to shift, affecting the wafer film thickness measurement accuracy. To maintain wafer film thickness measurement accuracy, the probe must be frequently reset, increasing maintenance costs. To solve this problem, the present invention provides a flexible probe that satisfies the positional relationship between the flexible probe and the grinding pad transmission window, ensuring that the flexible probe is always in contact with the grinding pad transmission window. Figure 9 shows a schematic diagram of the positional relationship between a flexible probe and a grinding disk in an exemplary embodiment of the present invention. As shown in Figure 9, the flexible probe 13 includes a probe optical fiber 131, a connector 132, an elastic member 133, and a position control member 134.

[0076] The probe optical fiber 131 has a first port 1311 for transmitting a measurement beam and a reflected beam, the measurement beam is incident on the wafer 5 through the first port 1311, and the reflected beam is received by the first port 1311 and then transmitted to the photodetection module 15.

[0077] The connector 132 is provided on the circumferential side surface of the probe optical fiber 131, and has a first connection portion 1321 and a second connection portion 1322, and the first connection portion 1321 is connected to the circumferential side surface of the probe optical fiber 131.

[0078] One end of the elastic member 133 is connected to the second connecting portion 1322, and the other end is connected to the wafer polishing device body.

[0079] The position control member 134 is threadedly connected to the wafer polishing device body, and adjusts and controls the compression state of the elastic member 133, thereby causing the elastic member 133 to move the probe optical fiber 131 along the optical axis direction, ensuring that the first port 1311 maintains contact with the grinding pad transmission window 31 during the grinding process.

[0080] In an embodiment of the present invention, a connector 132 and an elastic member 133 are used to connect the probe optical fiber 131 to the wafer polishing device body, and a position control member is used to adjust and control the compression state of the elastic member 133. The elastic force of the elastic member 133 is used to adaptively move the probe optical fiber 131 along the optical axis direction during the grinding process, ensuring that the first port 1311 and the grinding pad transmission window 31 maintain contact. This prevents the first port 1311 from being displaced relative to the grinding pad transmission window 31 during use, which could affect the measurement accuracy of the film thickness of the wafer 5, and avoids the adverse impact on maintenance work caused by frequent adjustment of the first port 1311 of the probe optical fiber 131.

[0081] In some embodiments, as shown in FIG. 9, the position control member 134 contacts the elastic member 133 and applies pressure to the elastic member 133 based on the adjustment of the amount of screwing and the amount of turning, thereby adjusting and controlling the compression state of the elastic member 133.

[0082] In an embodiment of the present invention, by adjusting the screwing amount and unscrewing amount of the position control member 134, the compression state of the elastic member 133 can be adjusted and the displacement amount of the probe optical fiber 131 along the optical axis direction can be changed, so that it can be adapted to different wafer polishing devices and can prevent the probe optical fiber 131 from coming off the grinding pad transmission window 31 or the probe optical fiber 131 from contacting the grinding pad transmission window 31 excessively and damaging it.

[0083] In some embodiments, the resilient member 133 is sleeved onto the circumferential side of the probe optical fiber 131 .

[0084] The elastic member 133 is sleeved on the circumferential side of the probe optical fiber 131 and exerts a balanced elastic force on the probe optical fiber 131 .

[0085] In some embodiments, the resilient member 133 is a spring that is sleeved onto the circumferential side of the probe optical fiber 131 .

[0086] 9, the elastic member 133 includes multiple springs, which are distributed around the circumferential side of the probe optical fiber 131. In this way, it is possible to prevent a single spring from failing due to aging or damage, causing the probe optical fiber 131 to lose its elastic connection, and to keep the elastic forces of the probe optical fiber 131 as balanced as possible in all directions.

[0087] In some embodiments, the wafer polishing device is provided with a receiving chamber 21 and the flexible probe 13 is provided within the receiving chamber 21 .

[0088] By providing the flexible probe 13 inside the accommodation chamber 21, it is possible to avoid a decrease in the reliability of the structure of the flexible probe 13 due to the entire structure of the flexible probe 13 being exposed to the outside.

[0089] Based on the wafer film thickness measuring apparatus 1 provided by the above embodiment of the present invention, the present invention further proposes a wafer film thickness measuring method, which is applied to the wafer film thickness measuring apparatus 1 of the present invention.

[0090] 11 is a flowchart of a wafer film thickness measurement method according to an exemplary embodiment. As shown in FIG. 11, the wafer film thickness measurement method includes the following steps:

[0091] In S101, during the wafer grinding process, the light intensity of the illumination source beam provided by the light source is adjusted and controlled using the light source energy adjusting module to obtain a modulated beam with a dynamic target light intensity, the modulated beam generates a measurement beam and a reference beam after passing through a beam splitter, the measurement beam forms a reflected beam after being incident on the wafer through a flexible probe, and the flexible probe transmits the measurement beam and the reflected beam and adaptively moves along the optical axis direction during the grinding process so as to maintain contact with the grinding pad transmission window of the wafer polishing device.

[0092] At S102, a light detection module is used to collect light intensity measurements of the reflected beam and the reference beam in real time.

[0093] In S103, the measured light intensity of the reflected beam is calibrated based on the measured light intensity of the reference beam to obtain a calibrated light intensity value of the reflected beam.

[0094] In S104, the film thickness of the wafer is determined based on the calibrated light intensity value of the reflected beam.

[0095] The light intensity of the light source fluctuates to a certain extent, causing the reflected beam to fluctuate. However, factors that affect the reflected beam intensity include not only light source fluctuations, but also changes in the transmittance of the grinding pad transmission window and changes in wafer film thickness. Therefore, the fluctuations in the reflected beam intensity measurements measured by the optical detection module do not fully represent the fluctuations in the light source. Because the reference beam and measurement beam (reflected beam) share the same light source, the fluctuations of the reference beam and measurement beam are synchronized. Calibrating the reflected beam intensity measurements based on the reference beam intensity measurement eliminates the impact of light source fluctuations on the reflected beam intensity. This allows the calibrated reflected beam intensity value to more accurately reflect the wafer film thickness, resulting in more accurate wafer film thickness measurements.

[0096] In step S103, calibrating the light intensity measurement value of the reflected beam based on the light intensity measurement value of the reference beam to obtain a light intensity calibration value of the reflected beam includes obtaining the light intensity calibration value of the reflected beam according to equation (1) based on the light intensity measurement value of the reference beam, the light intensity measurement value of the reflected beam, and the light intensity calibration value of the reference beam.

[0097] Among these, the optical detection module is used to collect the light intensity measurement value of the reference beam multiple times, and the average value of the collected light intensity measurement value of the reference beam is calculated to obtain the light intensity calibration value of the reference beam.

[0098] 12 is a flowchart of a method for determining a film thickness of a wafer based on a calibrated light intensity value of a reflected beam according to an exemplary embodiment. As shown in FIG. 12, the method for determining a film thickness of a wafer based on a calibrated light intensity value of a reflected beam includes the following steps:

[0099] In S201, theoretical reflectance spectra corresponding to different film thickness values ​​are obtained.

[0100] In S202, the actual measured reflectance spectrum of the reflected beam is calculated based on the calibrated light intensity values ​​of the reflected beam.

[0101] In S203, a target theoretical reflectance spectrum that matches the actually measured reflectance spectrum is obtained from the theoretical reflectance spectra corresponding to different film thickness values, and the film thickness value corresponding to the target theoretical reflectance spectrum is determined as the film thickness of the wafer.

[0102] In an embodiment of the present invention, the measurement accuracy can be improved by obtaining different film thickness values ​​and theoretical reflectance spectra of the wafer corresponding to the film thickness values, and then obtaining the film thickness of the wafer based on the actual measured reflectance spectrum obtained from the light intensity calibration value of the reflected beam using a mapping method.

[0103] 13A is a flowchart illustrating the real-time adjustment of light source energy in the wafer film thickness measurement method according to an exemplary embodiment. The wafer film thickness measurement method in this embodiment further includes the following steps:

[0104] In S301, the real-time transmittance of the grinding pad transmission window is monitored.

[0105] In S302, if the real-time transmittance is less than or equal to the predetermined transmittance, the light source energy adjusting module is used to adjust and control the light intensity of the illumination source beam provided by the light source to improve the light intensity measurements of the reference beam and the reflected beam collected by the light detection module.

[0106] In an embodiment of the present invention, when the real-time transmittance of the grinding pad transmission window falls below a predetermined transmittance, it means that the grinding pad transmission window has been significantly worn, and the current modulated beam can no longer effectively pass through the grinding pad transmission window. The light intensity of the reflected beam received by the optical detection module is already too small to meet the requirement of accurately measuring the wafer film thickness. At this time, the light source energy adjusting module can be controlled to increase the light intensity of the modulated beam, and the energy of the measurement beam and the reflected beam after passing through the grinding pad transmission window can be increased respectively, so that the optical detection module can be basically stabilized within a certain range and the accuracy of film thickness detection can be improved.

[0107] In some embodiments, as shown in FIG. 13B, real-time adjustment of the light source energy can also be performed in the following manner.

[0108] In S401, the transmittance of the grinding pad transmission window is preset.

[0109] In S402, the real-time transmittance of the grinding pad transmission window is measured.

[0110] In S403, the measured real-time transmittance is compared with the magnitude of a predetermined transmittance, and if the measured real-time transmittance is equal to or less than the predetermined transmittance, S404 is executed, otherwise S402 is executed.

[0111] In S404, the light source energy adjusting module is used to adjust and control the light intensity of the illumination source beam provided by the light source to improve the light intensity measurements of the reference beam and the reflected beam collected by the light detection module.

[0112] In an embodiment of the present invention, the transmittance of the grinding pad transmission window is preset, and then the real-time transmittance of the grinding pad transmission window is measured, so that the change in the transmittance of the grinding pad transmission window can be accurately controlled, and further, the light source energy adjusting device can be accurately controlled, so as to achieve higher film thickness measurement accuracy.

[0113] In some embodiments, the real-time transmittance of the grinding pad transmission window can be obtained in various ways, such as by setting a 1:1 split ratio between the reference beam and the measurement beam and collecting light intensity measurements of the reflected beam in real time during the grinding process.

number

number

[0114]

number

[0115] Setting the reference beam to measurement beam split ratio to 1:1 is not unique, and other ratios are possible as long as they are converted and substituted in the calculations.

[0116] In some embodiments, whether the light source energy adjusting module needs to be controlled and adjusted to change the light intensity of the modulated beam can also be determined directly by the measured light intensity value of the reflected beam. For example, if the measured light intensity value of the reflected beam is smaller than a predetermined value, it can be considered that the transmittance of the grinding pad transmission window has decreased, and the light source energy adjusting module needs to be controlled to increase the light intensity of the modulated beam.

[0117] In some embodiments, whether the light source energy adjusting module needs to be controlled and adjusted to change the light intensity of the modulated beam can be determined by directly measuring the wear level of the grinding pad transmission window. If the wear level is greater than a predetermined value, it can be considered that the transmittance of the grinding pad transmission window has decreased, and the light source energy adjusting module needs to be controlled to increase the light intensity of the modulated beam. The wear level of the grinding pad transmission window can be measured in various ways, and the present invention is not limited thereto.

[0118] It is noted that the wafer film thickness measurement method provided by the above embodiment of the present invention is similar to the wafer film thickness measurement implementation process of the wafer film thickness measurement apparatus 1 provided by the above embodiment, and for details that are not fully explained in the wafer film thickness measurement method, reference can be made to the relevant description of the above wafer film thickness measurement apparatus 1, and they will not be repeated here.

[0119] Based on a similar idea, the present invention further proposes a wafer polishing device, which includes the wafer film thickness measuring apparatus 1 of the present invention.

[0120] A wafer polishing device is an apparatus for removing excess material from a wafer surface or thinning the film thickness to a predetermined thickness. The wafer polishing device of the present invention may refer to a CMP apparatus or other wafer polishing devices.

[0121] 10 is a structural schematic diagram of a wafer polishing device according to an exemplary embodiment. As shown in FIGS. 9 and 10, the wafer polishing device includes a rotatable grinding disc 2 and a grinding pad 3 placed on the grinding disc 2. Other structures may be provided between the grinding pad 3 and the grinding disc 2 as needed; the present invention is not limited thereto. An optically transparent grinding pad transmission window 31 is provided on the grinding pad 3. The wafer polishing device includes an opening in the storage chamber 21, at least a portion of which is located within the grinding disc 2. The storage chamber 21 has an opening facing the grinding pad transmission window 31.

[0122] The wafer polishing device further includes a polishing head 4 disposed above the grinding pad 3, the polishing head 4 being positioned to avoid the center of rotation of the grinding pad 3, and the wafer 5 being disposed between the polishing head 4 and the grinding pad 3, and being rotated around the axis of the polishing head 4 by driving the polishing head 4. When polishing the wafer 5, the grinding disk 2 and the polishing head 4 rotate separately to grind the wafer 5. When the grinding disk 2 rotates, the wafer 5 comes into contact with the grinding pad transmission window 31 for at least a portion of the time.

[0123] The wafer film thickness measuring device 1 is provided in the accommodation chamber 21, and includes a flexible probe 13, which includes a probe optical fiber 131, a connector 132, a position control member 134, and an elastic member 133. Of these, a first port 1311 of the probe optical fiber 131 faces the grinding pad transmission window 31 and contacts the grinding pad transmission window 31.

[0124] As shown in FIG. 9 , a connector 132 is arranged on the circumferential side of the probe optical fiber 131, a first connection portion 1321 of the connector 132 is sleeved onto the circumferential side of the probe optical fiber 131 and fixedly connected to the circumferential side of the probe optical fiber 131, and a second connection portion 1322 of the connector 132 extends outward from the circumferential edge of the first connection portion 1321 to form a ring-shaped second connection portion 1322.

[0125] An abutment portion 211 is provided on the inner wall of the accommodation chamber 21, and the elastic member 133 is provided between the second connection portion 1322 and the abutment portion 211 and is in a compressed state. The elastic member 133 applies an elastic thrust to the second connection portion 1322 toward the grinding pad transmission window 31, and the elastic thrust is transmitted to the probe optical fiber 131 via the second connection portion 1322 and the first connection portion 1321, thereby maintaining the probe optical fiber 131 in contact with the grinding pad transmission window 31. This prevents the probe optical fiber 131 from coming out of the observation window of the grinding pad 3 due to factors such as vibration, which could reduce the measurement accuracy of the film thickness of the wafer 5, and also avoids frequent maintenance due to the probe optical fiber 131 coming out of the observation window of the grinding pad 3.

[0126] The position control member 134 is threadedly connected to the inner wall of the accommodating chamber 21 and is provided on the second connecting portion 1322. During the placement process, the flexible probe 13 is passed upward along the accommodating chamber 21 from below the grinding disk 2, and the elastic member 133, connector 132, and position control member 134 are provided in this order from the upper opening of the accommodating chamber 21. The position control member 134 is screwed into the accommodating chamber 21 and contacts the second connecting portion 1322, and the elastic member 133 is subsequently screwed and compressed. With at least a portion of the probe optical fiber 131 protruding from the opening of the accommodating chamber 21, a grinding pad 3 having a grinding pad transmission window 31 is placed on the grinding disk 2, and the first port 1311 of the probe optical fiber 131 contacts the grinding pad transmission window 31. The first port 1311 of the probe optical fiber 131 moves inside the accommodating chamber 21 under the pressure of the grinding pad transmission window 31, the elastic member 133 is further compressed, and the position control member 134 is separated from the second connection portion 1322 of the connector 132.

[0127] In an embodiment of the present invention, a position control member 134 connected to the inner peripheral side wall of the accommodating chamber 21 is provided to limit the position of the probe optical fiber 131, thereby preventing the probe optical fiber 131 from being pushed out and damaged by the excessive elastic force of the elastic member 133.

[0128] The wafer polishing device further includes a spray arm 7 and a grinding pad dresser 6 disposed above the grinding pad 3. The spray arm 7 is used to spray a polishing liquid onto the grinding pad 3 to promote polishing. The grinding pad dresser 6 is used to contact the grinding pad 3 and clean and dress the surface of the grinding pad 3.

[0129] The present invention further proposes a method for polishing a wafer using the wafer polishing device of the present invention. As shown in Figure 14, the wafer polishing method includes the following steps:

[0130] In S501, during the process of polishing a product wafer using a wafer polishing device, the light source energy adjusting module is used to adjust and control the light intensity of the illumination source beam provided by the light source to obtain a modulated beam having a dynamic target light intensity, the modulated beam generates a measurement beam and a reference beam after passing through a beam splitter, the measurement beam forms a reflected beam after incident on the wafer through a flexible probe, and the flexible probe transmits the measurement beam and the reflected beam and adaptively moves along the optical axis direction during the polishing process so as to maintain contact with the grinding pad transmission window of the wafer polishing device.

[0131] In S502, a light detection module is used to collect light intensity measurements of the reflected beam and the reference beam in real time.

[0132] In S503, the light intensity measurement value of the reflected beam is calibrated based on the light intensity measurement value of the reference beam to obtain a light intensity calibration value of the reflected beam.

[0133] In S504, the actual measured reflectance spectrum of the reflected beam is calculated based on the calibrated light intensity values ​​of the reflected beam.

[0134] In S505, the film thickness value of the wafer is extracted in real time based on the actually measured reflectance spectrum of the reflected beam, and the wafer polishing is terminated when the film thickness value reaches a predetermined target value.

[0135] In an embodiment of the present invention, the reference beam has the same light source as the measurement beam, and fluctuations in the reference beam can reflect fluctuations in the measurement beam. By calibrating the light intensity measurement of the reflected beam based on the light intensity measurement of the reference beam, the influence of light source fluctuations on the reflected beam can be eliminated, thereby improving the accuracy of the actually measured reflectance spectrum obtained by the calibrated light intensity value of the reflected beam. Furthermore, the accuracy of determining film thickness based on the actually measured reflectance spectrum and determining the end of polishing of product wafers can also be improved.

[0136] Among these, the light intensity calibration value of the reflected beam is obtained by equation (1) based on the light intensity measurement value of the reference beam, the light intensity measurement value of the reflected beam, and the light intensity calibration value of the reference beam.

[0137] Among these, the optical detection module is used to collect the light intensity measurement value of the reference beam multiple times, and the average value of the collected light intensity measurement value of the reference beam is calculated as the light intensity calibration value of the reference beam.

[0138] The target film thickness in step S505 refers to the film thickness corresponding to the product wafer sample at the end of polishing.

[0139] The real-time film thickness value of the product wafer can be obtained by the following method: different theoretical reflectance spectra and wafer film thickness values ​​corresponding to the different theoretical reflectance spectra are stored in advance to build a correspondence library, and based on the actually measured reflectance spectrum of the reflected beam, the corresponding theoretical reflectance spectrum is searched for in the correspondence library, and the wafer film thickness value corresponding to the theoretical reflectance spectrum is extracted as the real-time film thickness value of the product wafer.

[0140] By constructing a correspondence library, the mapping method can directly map the corresponding wafer film thickness based on the actual measured reflectance spectrum, which does not require additional calculations, reduces the burden on the hardware, and has a faster response speed.

[0141] In some embodiments, the correspondence library further includes the grinding time and grinding disk rotation speed from the start to the end of grinding of the product wafer sample. When determining whether to terminate polishing of the wafer in step S506, the grinding time and grinding disk rotation speed can be used as judgment indicators. Polishing of the product wafer can be terminated only when the grinding time and grinding disk rotation speed are simultaneously satisfied and the actually measured reflectance spectrum matches the target theoretical reflectance spectrum of the corresponding target film thickness in the correspondence relationship library.

[0142] In the embodiment of the present invention, the grinding time and the grinding disk rotation speed are used as redundant judgment indexes to avoid judgment errors due to accidental errors in the reflectance spectrum and improve the accuracy of grinding end point judgment.

[0143] In some embodiments, the present invention provides a method for creating a correspondence library. As shown in Figure 15, the correspondence library is created in advance by the following method.

[0144] In S601, a standard light intensity is collected during a polishing process of a standard wafer sample by a wafer polishing device, and a reflectance spectrum of the standard wafer sample is determined based on the standard light intensity.

[0145] Among these, the standard wafer sample may be bare silicon or a wafer with a specific film thickness.

[0146] In S602, a calibration value of the light intensity of a reflected beam from the product wafer sample is collected while the product wafer sample is being polished by the wafer polishing device.

[0147] It should be understood that in an embodiment of the present invention, the light intensities collected in S601 and S602 above can be light intensities calibrated by the method of calibrating a reflected beam based on a reference beam according to the above embodiment of the present invention.

[0148] In S603, the theoretical reflectance spectrum of the product wafer is calculated using equation (3).

[0149]

number

[0150] I stray is the light intensity measurement external to the product wafer sample and is obtained by the following method:

[0151] The wafer is replaced with a black sample that does not reflect the beam, and the light intensity of the reflected beam is measured using the light detection module, i.e., I stray and I stray is also called the stray light intensity.

[0152] Of course, there are other ways to stray However, the present invention is not limited thereto.

[0153] In S604, the wafer film thickness corresponding to the theoretical reflectance spectrum is obtained.

[0154] In the embodiments of the present invention, there are various methods for obtaining the wafer film thickness, such as a method of measuring using a special device, a method of calculating based on a reflectance spectrum, or other methods. Those skilled in the art can obtain the wafer film thickness by various methods, and the present invention is not limited thereto.

[0155] In S605, it is determined whether polishing has been completed to the target film thickness, and if so, S606 is executed, and if not, S602 is executed.

[0156] In S606, the polishing time and the number of polishing disc revolutions are recorded.

[0157] In S607, different wafer film thicknesses and corresponding theoretical reflectance spectra are stored, and polishing times and polishing disk rotation speeds are stored to establish a correspondence library.

[0158] In an embodiment of the present invention, an actual measured reflectance spectrum is obtained in a relatively simple manner, and the stray light intensity I stray The influence of the above factors is eliminated, and the obtained actual measured reflectance spectrum is relatively accurate, which helps to improve the control accuracy of the polishing focus.

[0159] In some embodiments, after polishing a plurality of wafers, the transmittance of the grinding pad window is significantly reduced. To improve the accuracy of measuring the film thickness at the end of wafer polishing, the wafer polishing method further includes measuring the real-time transmittance of the grinding pad transmission window. If the real-time transmittance is lower than a predetermined transmittance, the light source energy adjusting module adjusts and controls the light intensity of the illumination source beam provided by the light source to improve the light intensity measurements of the reference beam and the reflected beam collected by the light detection module.

[0160] When the light source energy adjusting module is used to adjust and control the light intensity of the illumination source beam provided by the light source, a standard wafer sample is placed on the polishing head 4 and the light source energy adjusting module 12 is readjusted, so that the sample measurement light intensity and reference light intensity received by the reflective beam collecting element 151 and the reference beam collecting element 152 are increased, allowing the reflective beam collecting element 151 and the reference beam collecting element 152 to enter a high-performance state (high signal-to-noise ratio). Without the light source energy adjusting module 12, the detected light intensity of the reflective beam collecting element 151 and the reference beam collecting element 152 would be weak, significantly reducing the signal-to-noise ratio of the collected signals and directly affecting the stability of the film thickness measurement results.

[0161] In an embodiment of the present invention, when the real-time transmittance of the grinding pad transmission window falls below a predetermined transmittance, it means that the grinding pad transmission window has worn out significantly, and the current modulated beam can no longer effectively transmit through the grinding pad transmission window. The light intensity of the reflected beam received by the optical detection module is already too small to meet the requirement of accurately measuring the wafer film thickness. At this time, the light source energy adjusting module can be controlled to increase the light intensity of the modulated beam, improving the transmittance of the measurement beam and the reflected beam through the grinding pad transmission window, and basically stabilizing the optical detection module within a certain range. This not only eliminates the impact of changes in the transmittance of the grinding pad transmission window on wafer film thickness measurement, but also allows the usage requirements to be met even when the transmittance of the grinding pad transmission window changes significantly. This eliminates the need to frequently replace the grinding pad transmission window and reduces usage costs.

[0162] In an embodiment of the present invention, a film thickness measurement device for CMP is provided with a light source energy adjusting module, a flexible probe, and a reference optical path (reference beam). In addition, in the calibration and measurement method, a reference beam is introduced to correct the reflected beam of the measurement beam, and energy adjustment is performed in real time after the transmittance of the grinding pad transmission window decreases, thereby not only improving the film thickness measurement accuracy and stability, but also extending the life of consumables, reducing maintenance frequency, and reducing equipment operating costs.

[0163] It should be understood that "plurality" in the present invention means two or more, and similarly applies to other quantifiers. "And / or" indicates a relation between related objects, and indicates that three types of relation may exist, for example, A and / or B can represent A occurring alone, A and B occurring simultaneously, and B occurring alone. The character " / " generally indicates that the related objects before and after are in an "or" relation. The singular forms "a," "said," and "the" are intended to include the plural unless the context clearly indicates otherwise.

[0164] Furthermore, while terms such as "first" and "second" are used to describe various pieces of information, it should be understood that such information should not be limited to these terms. These terms are used only to distinguish between pieces of information of the same type and do not indicate a particular order or importance. In fact, terms such as "first" and "second" can be used completely interchangeably. For example, first information can also be referred to as second information, and similarly, second information can also be referred to as first information, without departing from the scope of the present invention.

[0165] Furthermore, it should be understood that the orientations or positional relationships indicated by terms such as "center," "longitudinal," "lateral," "front," "rear," "upper," "lower," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" are based on those shown in the accompanying drawings, are intended only to facilitate and simplify the description of the present embodiments, and are not intended to indicate or imply that the referred-to devices or elements must have a particular orientation, be configured, or operate in a particular orientation.

[0166] Furthermore, unless otherwise specified, "connection" should be understood to include not only a direct connection between two elements without other elements involved, but also an indirect connection between two elements involving other elements.

[0167] Additionally, although embodiments of the present invention describe operations in a particular order in the accompanying figures, it should be understood that this should not be construed as requiring the operations to be performed in the particular order or serial order shown, or to perform all of the operations shown, to achieve desirable results. Multitasking or parallel processing may be advantageous in certain environments.

[0168] Other embodiments of the present invention will be readily apparent to those skilled in the art from a consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present invention in accordance with the general principles of the present invention, including means common knowledge or customary in the art that are not invented by the present invention. The specification and examples are considered exemplary only, with the true scope and spirit of the invention being indicated by the following claims.

[0169] It should be understood that the present invention is not limited to the exact construction described above and illustrated in the accompanying drawings, but that various modifications and changes are possible without departing from the scope of the present invention, which is limited only by the appended claims.

Claims

1. A wafer film thickness measuring device, The wafer film thickness measuring device is used in a wafer polishing device, The wafer film thickness measuring device includes: a light source for providing an illumination source beam; a light source energy adjusting module for adjusting and controlling the light intensity of the source beam to obtain a modulated beam having a dynamic target light intensity; a beam splitter for splitting the modulated beam to produce a measurement beam and a reference beam; a flexible probe for transmitting the measurement beam and the reflected beam, the flexible probe adaptively moving along an optical axis direction so as to maintain contact with a grinding pad transmission window of a wafer polishing device during a grinding process, the measurement beam forming the reflected beam after being incident on the wafer through the flexible probe; a light detection module for collecting light intensity measurements of the reference beam and light intensity measurements of the reflected beam; a processing unit that calibrates the light intensity measurement value of the reflected beam based on the light intensity measurement value of the reference beam to obtain a calibrated light intensity value of the reflected beam, and determines a film thickness of the wafer based on the calibrated light intensity value of the reflected beam. A wafer film thickness measuring device characterized by:

2. the light source energy adjustment module includes a plurality of filter elements having different transmittances and a rotary drive mechanism, the plurality of filter elements are arranged around a rotation axis of the rotary drive mechanism, and the rotary drive mechanism rotates the plurality of filter elements to transmit the source beam through a target filter element among the plurality of filter elements, thereby obtaining a modulated beam having the dynamic target light intensity; or the light source energy adjusting module includes a reciprocating drive mechanism and a filter element with gradually varying transmittance, the reciprocating drive mechanism reciprocating along a direction in which the transmittance of the gradually varying transmittance filter element gradually varies, so as to transmit the source beam through an area of ​​the gradually varying transmittance filter element having a target transmittance, and obtain a modulated beam with the dynamic target light intensity; 2. The wafer film thickness measuring device according to claim 1.

3. the beam splitter comprises a fiber optic beam splitter or a beam splitting lens; 3. The wafer film thickness measuring device according to claim 1 or 2.

4. The flexible probe is a probe optical fiber having a first port for transmitting the measurement beam and the reflected beam, wherein the measurement beam is incident on the wafer through the first port, and the reflected beam is received by the first port and then transmitted to the light detection module; a connector disposed on a circumferential side surface of the probe optical fiber, the connector having a first connection portion and a second connection portion, the first connection portion being connected to the circumferential side surface of the probe optical fiber; an elastic member having one end connected to the second connection portion and the other end connected to the wafer polishing device body; a position control member that is threadably connected to the wafer polishing device body and that adjusts and controls the compression state of the elastic member to move the probe optical fiber along the optical axis direction of the elastic member and ensure that the first port maintains contact with the grinding pad transmission window during polishing and grinding.

2. The wafer film thickness measuring device according to claim 1.

5. the position control member contacts the elastic member and applies pressure to the elastic member based on adjustment of the screwing amount and the screw rotation amount, thereby adjusting and controlling the compression state of the elastic member.

5. The wafer film thickness measuring device according to claim 4.

6. the resilient member is sleeved onto a circumferential side of the probe optical fiber; or the elastic member includes a plurality of springs, the plurality of springs being distributed on a circumferential side surface of the probe optical fiber; 5. The wafer film thickness measuring device according to claim 4.

7. The wafer polishing device is provided with a receiving chamber, and the flexible probe is disposed in the receiving chamber.

5. The wafer film thickness measuring device according to claim 4.

8. The processing unit calibrating the light intensity measurement value of the reflected beam based on the light intensity measurement value of the reference beam to obtain a calibrated light intensity value of the reflected beam includes: collecting and averaging multiple light intensity measurements of the reference beam using the light detection module to obtain a calibrated light intensity value for the reference beam; calibrating the measured light intensity of the reflected beam by the following equation to obtain a calibrated light intensity value of the reflected beam: [Equation 1] [Equation 2] is the calibration value of the reference beam's light intensity, [Equation 3] is the optical intensity measurement of the reference beam collected in real time during the grinding process; [Equation 4] is the light intensity measurement of the reflected beam collected in real time during the grinding process; [Equation 5] is the calibrated light intensity value of the reflected beam, 2. The wafer film thickness measuring device according to claim 1.

9. The processing unit determines a film thickness of the wafer based on a calibrated light intensity value of the reflected beam, obtaining theoretical reflectance spectra corresponding to different film thickness values; calculating an actual measured reflectance spectrum of the reflected beam based on the calibrated light intensity values ​​of the reflected beam; obtaining a target theoretical reflectance spectrum that matches the actually measured reflectance spectrum from theoretical reflectance spectra corresponding to different film thickness values, and determining the film thickness value corresponding to the target theoretical reflectance spectrum as the film thickness of the wafer.

2. The wafer film thickness measuring device according to claim 1.

10. A wafer film thickness measurement method, comprising: The wafer film thickness measuring method is applied to the wafer film thickness measuring apparatus according to any one of claims 1 to 9, The wafer film thickness measuring method includes: During a wafer grinding process, adjust and control the light intensity of an illumination source beam provided by a light source using a light source energy adjusting module to obtain a modulated beam having a dynamic target light intensity, wherein the modulated beam generates a measurement beam and a reference beam after passing through a beam splitter, and the measurement beam forms a reflected beam after being incident on a wafer through a flexible probe, and the flexible probe transmits the measurement beam and the reflected beam, and adaptively moves along an optical axis direction during the grinding process so as to maintain contact with a grinding pad transmission window of a wafer polishing device; collecting light intensity measurements of the reflected beam and a reference beam in real time using a light detection module; calibrating the measured intensity of the reflected beam based on the measured intensity of the reference beam to obtain a calibrated intensity of the reflected beam; and determining a film thickness of the wafer based on the calibrated light intensity value of the reflected beam. A wafer film thickness measuring method comprising:

11. determining a film thickness of the wafer based on the calibrated light intensity value of the reflected beam, obtaining theoretical reflectance spectra corresponding to different film thickness values; calculating an actual measured reflectance spectrum of the reflected beam based on the calibrated light intensity values ​​of the reflected beam; obtaining a target theoretical reflectance spectrum that matches the actually measured reflectance spectrum from theoretical reflectance spectra corresponding to different film thickness values, and determining the film thickness value corresponding to the target theoretical reflectance spectrum as the film thickness of the wafer.

11. The wafer film thickness measuring method according to claim 10.

12. monitoring real-time transmittance of the grinding pad transmission window; If the real-time transmittance is equal to or less than a predetermined transmittance, adjusting and controlling the light intensity of the illumination source beam provided by the light source using a light source energy adjusting module to improve the light intensity measurements of the reference beam and the reflected beam collected by the light detection module.

11. The wafer film thickness measuring method according to claim 10.

13. A wafer film thickness measuring device according to any one of claims 1 to 9, A wafer polishing device comprising:

14. During a process of polishing a product wafer using a wafer polishing device, adjust and control the light intensity of an illumination source beam provided by a light source using a light source energy adjusting module to obtain a modulated beam having a dynamic target light intensity, wherein the modulated beam generates a measurement beam and a reference beam after passing through a beam splitter, and the measurement beam forms a reflected beam after being incident on the wafer through a flexible probe, and the flexible probe transmits the measurement beam and the reflected beam, and adaptively moves along an optical axis direction during the polishing process so as to maintain contact with a grinding pad transmission window of the wafer polishing device; collecting light intensity measurements of the reflected beam and the reference beam in real time using a light detection module; calibrating the measured intensity of the reflected beam based on the measured intensity of the reference beam to obtain a calibrated intensity of the reflected beam; calculating an actual measured reflectance spectrum of the reflected beam based on the calibrated light intensity values ​​of the reflected beam; extracting a film thickness value of the wafer in real time based on the actual measured reflectance spectrum of the reflected beam, and terminating polishing of the wafer when the film thickness value reaches a predetermined target value. A wafer polishing method comprising:

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