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

Abstract

The present disclosure relates to a wafer film thickness measuring device, a measuring method, a wafer polishing apparatus and a polishing method. The wafer film thickness measuring device comprises a light source for providing an illumination source light beam; a light source energy adjusting module for adjusting the light intensity of the source light beam to obtain a modulated light beam with a dynamic target light intensity; a beam splitter for splitting the modulated light beam to generate a measurement light beam and a reference light beam; a flexible probe for transmitting the measurement light beam and a reflected light beam, and the flexible probe is adapted to move along the optical axis direction to keep the flexible probe in contact with the polishing pad transmission window of the wafer polishing apparatus during polishing; a light detection module for collecting the light intensity measurement value of the reference light beam and the light intensity measurement value of the reflected light beam; a processing unit for calibrating the light intensity measurement value of the reflected light beam based on the light intensity measurement value of the reference light beam to obtain the light intensity calibration value of the reflected light beam, and determining the film thickness of the wafer based on the light intensity calibration value of the reflected light beam. The present disclosure improves the film thickness measurement accuracy and prolongs the service life of the transmission window.

Description

Technical Field

[0001] This disclosure relates to the field of wafer processing, and in particular to a wafer film thickness measuring device, measuring method, wafer polishing equipment, and polishing method. Background Technology

[0002] Chemical mechanical polishing (CMP) is a crucial process step in the manufacturing of semiconductor integrated circuit chips. Furthermore, with the advancement of semiconductor technology, to achieve better and more reliable device performance, the process control of intra-wafer (WIW) and inter-wafer (WTW) film thickness variations using wafer thickness measurement devices is particularly important during CMP operations performed on wafer polishing equipment.

[0003] Related technologies primarily employ eddy current endpoint measurement, laser endpoint measurement, and white light endpoint measurement to monitor the characteristics of the film layer during CMP (Chemical Metallurgy) to appropriately control and stop the removal process. 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 mainly used for endpoint measurement of dielectric thin films. Laser technology analyzes film thickness changes by detecting the intensity of single-wavelength interference light in the dielectric film layer. However, due to the limited amount of information detected, the measurement accuracy and reliability of laser technology are relatively low, failing to meet the process requirements of advanced semiconductor nodes. White light technology uses a broadband light source and detector, increasing the measurement information and effectively improving measurement accuracy.

[0004] Specifically, regarding white light technology, during CMP (Continuous Metal Processing) using wafer polishing equipment and film thickness measurement using a wafer thickness measurement device, the transmittance of the polishing pad's transmission window gradually decreases due to polishing. This leads to a gradual decrease in the intensity of the measured beam and reflected beam after passing through the polishing pad's transmission window, thus affecting the accuracy of film thickness measurement. Furthermore, to maintain the intensity of the reflected beam, the polishing pad's transmission window needs frequent replacement, resulting in a waste of time and resources.

[0005] During the grinding process, issues such as vibration and structural precision can cause the flexible probe and the grinding pad's transmission window to lose good contact, leading to changes in the distance between the flexible probe, the grinding pad's transmission window, and the wafer, requiring frequent maintenance.

[0006] Furthermore, the light source of wafer polishing equipment is generally a pulsed light source, and the light intensity of the illumination beam provided by the light source will fluctuate to a certain extent, which will ultimately cause fluctuations in the reflected beam used to obtain the wafer film thickness.

[0007] The above issues can lead to inaccurate wafer thickness measurement, frequent maintenance requirements, and high operating costs for wafer polishing equipment. Summary of the Invention

[0008] To overcome the problems existing in related technologies, this disclosure provides a wafer film thickness measuring device, a measuring method, a wafer polishing equipment, and a polishing method.

[0009] According to a first aspect of the present disclosure, a wafer film thickness measuring device is provided for wafer polishing equipment, comprising:

[0010] A light source, used to provide a beam of light for illumination;

[0011] A light source energy adjustment module is used to regulate the light intensity of the source beam to obtain a modulated beam with dynamic target light intensity;

[0012] A beam splitter is used to split the modulated beam to generate a measurement beam and a reference beam;

[0013] A flexible probe is used to transmit the measurement beam and the reflected beam, and the flexible probe moves adaptively along the optical axis to keep the flexible probe in contact with the transmission window of the polishing pad of the wafer polishing equipment during the polishing process, wherein the measurement beam is incident on the wafer through the flexible probe to form the reflected beam;

[0014] A light detection module is used to collect the light intensity measurement value of the reference beam and the light intensity measurement value of the reflected beam;

[0015] The processing unit calibrates the light intensity measurement value of the reflected beam based on the light intensity measurement value of the reference beam to obtain the light intensity calibration value of the reflected beam, and determines the film thickness of the wafer based on the light intensity calibration value of the reflected beam.

[0016] According to a second aspect of the present disclosure, a wafer film thickness measurement method is provided, which applies the wafer film thickness measurement device involved in the first aspect or any embodiment of the first aspect. The wafer film thickness measurement method includes:

[0017] During the wafer polishing process, the light intensity of the illumination source beam provided by the light source is controlled by the light source energy adjustment module to obtain a modulated beam with dynamic target light intensity. The modulated beam is split into a measurement beam and a reference beam after passing through a beam splitter. The measurement beam is incident on the wafer through a flexible probe to form a reflected beam. The flexible probe transmits the measurement beam and the reflected beam and moves adaptively along the optical axis to keep the flexible probe in contact with the polishing pad transmission window of the wafer polishing equipment during the polishing process.

[0018] The light intensity measurement values ​​of the reflected beam and the reference beam are collected in real time by the light detection module.

[0019] The intensity measurement value of the reflected beam is calibrated based on the intensity measurement value of the reference beam to obtain the intensity calibration value of the reflected beam.

[0020] The film thickness of the wafer is determined based on the light intensity calibration value of the reflected beam.

[0021] According to a third aspect of the present disclosure, a wafer polishing apparatus is provided, including the wafer film thickness measuring device involved in the first aspect or any embodiment of the first aspect.

[0022] According to a fourth aspect of the present disclosure, a wafer polishing method is provided, the method comprising:

[0023] During the wafer polishing process using a wafer polishing equipment, the light intensity of the illumination source beam provided by the light source is controlled by the light source energy adjustment module to obtain a modulated beam with dynamic target light intensity. The modulated beam is split into a measurement beam and a reference beam after passing through a beam splitter. The measurement beam is incident on the wafer through a flexible probe to form a reflected beam. The flexible probe transmits the measurement beam and the reflected beam and moves adaptively along the optical axis to keep the flexible probe in contact with the polishing pad transmission window of the wafer polishing equipment during the polishing process.

[0024] The light intensity measurement values ​​of the reflected beam and the reference beam are collected in real time by the light detection module.

[0025] The intensity measurement value of the reflected beam is calibrated based on the intensity measurement value of the reference beam to obtain the intensity calibration value of the reflected beam.

[0026] Based on the light intensity calibration value of the reflected beam, the measured reflectance spectrum of the reflected beam is calculated;

[0027] Based on the measured reflectivity spectrum of the reflected beam, the film thickness value of the wafer is extracted in real time, and the polishing of the wafer is terminated when the film thickness value reaches the preset target value.

[0028] The technical solutions provided by the embodiments of this disclosure can include the following beneficial effects: In the embodiments of this disclosure, when the light transmittance of the polishing pad window changes with the polishing process, the light intensity of the illumination source beam provided by the light source is adjusted by timely regulating the energy adjustment module to obtain a modulated beam with a dynamic target light intensity that matches the light transmittance of the polishing pad window, so that the energy of the beam irradiating the wafer surface remains stable, thereby reducing the light intensity fluctuation of the beam reflected from the wafer surface, improving the accuracy and stability of the measurement results, that is, it can still meet the needs of wafer film thickness measurement when the light transmittance of the polishing pad transmission window changes within a large range, ensuring measurement accuracy, and allowing the polishing pad transmission window to still be used even when it is heavily worn, thereby extending the service life of the polishing pad transmission window and avoiding the economic and time costs caused by frequent replacement of the polishing pad transmission window.

[0029] Using a flexible probe that can adaptively move along the optical axis allows the probe to maintain constant contact with the polishing pad's transmission window to maintain a certain pressure even when adverse conditions such as vibration occur in the wafer polishing equipment. This results in a stable reflected beam signal, improving the measurement accuracy of the wafer film thickness and avoiding frequent maintenance caused by displacement of the flexible probe relative to the polishing pad's transmission window.

[0030] The measurement beam passes through the grinding pad's transmission window and enters the wafer, where it is reflected to form a reflected beam. This reflected beam then passes through the grinding pad's transmission window again and enters the flexible probe before finally reaching the photodetector module. During this process, the beam experiences significant intensity loss. By splitting the modulated beam to form a reference beam and directly incident it onto the photodetector module, the intensity loss is minimal, accurately reflecting changes in the intensity of the illumination source beam. Calibrating the intensity measurement of the reflected beam based on the intensity measurement of the reference beam effectively compensates for fluctuations in the reflected beam's intensity caused by variations in the source light intensity, thereby improving the accuracy of wafer film thickness measurement.

[0031] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0032] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0033] Figure 1 This is a schematic diagram of the structure of wafer polishing equipment involved in related technologies.

[0034] Figure 2 This is a schematic diagram of a wafer film thickness measuring device according to an exemplary embodiment.

[0035] Figure 3 This is a schematic diagram of a wafer film thickness measuring device according to an exemplary embodiment.

[0036] Figure 4 This is a schematic diagram of a light source energy regulation module structure according to an exemplary embodiment.

[0037] Figure 5 This is a schematic diagram of a light source energy regulation module structure according to an exemplary embodiment.

[0038] Figure 6 This is a schematic diagram of a light source energy regulation module structure according to an exemplary embodiment.

[0039] Figure 7 This is a schematic diagram of a wafer film thickness measuring device according to an exemplary embodiment.

[0040] Figure 8 This is a schematic diagram of a wafer film thickness measuring device according to an exemplary embodiment.

[0041] Figure 9 This is a schematic diagram illustrating the positional relationship between a flexible probe and a grinding disc according to an exemplary embodiment.

[0042] Figure 10 This is a schematic diagram of a wafer polishing apparatus according to an exemplary embodiment.

[0043] Figure 11 This is a flowchart illustrating a wafer film thickness measurement method according to an exemplary embodiment.

[0044] Figure 12 This is a flowchart illustrating a method for determining the film thickness of a wafer based on the light intensity calibration value of a reflected beam, according to an exemplary embodiment.

[0045] Figure 13A This is a flowchart illustrating real-time adjustment of light source energy in a wafer film thickness measurement method according to an exemplary embodiment.

[0046] Figure 13B This is a flowchart illustrating real-time adjustment of light source energy in a wafer film thickness measurement method according to an exemplary embodiment.

[0047] Figure 14 This is a flowchart illustrating a wafer polishing method according to an exemplary embodiment.

[0048] Figure 15 This is a flowchart illustrating a method for creating a mapping database according to an exemplary embodiment. Detailed Implementation

[0049] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0050] The wafer film thickness measurement device disclosed herein is primarily used in CMP (Chemical Metallurgy). In one example, the wafer film thickness measurement device is used in a wafer polishing equipment.

[0051] Figure 1 A schematic diagram of a wafer polishing device involved in related technologies is shown. (See also...) Figure 1As shown, a polishing pad 3A is fixed on the polishing disk 2A, and a polishing head 4A carries a wafer 5A, ensuring the wafer 5A is in close contact with the polishing pad 3A. The polishing disk 2A rotates, and the polishing head 4A rotates and reciprocates relative to the polishing disk 2A, causing friction between the wafer 5A and the polishing pad 3A, thus achieving a polishing effect. The spray arm 7A sprays polishing fluid through nozzles. The polishing fluid, after rotating on the polishing disk 2A, reaches the polishing head 4A and contacts the wafer 5A through the grooves on the polishing pad 3A, achieving a chemical polishing effect. The polishing pad dresser 6A cleans and corrects the polishing pad 3A.

[0052] The wafer film thickness measuring device is installed inside the polishing pad 2A and rotates with the polishing pad 2A. It includes a probe 13A, a cable 22A, and a control box 16A. The signal from the probe 13A is transmitted to the wafer through a transparent window on the polishing pad 3A and returns to the control box 16A from the window.

[0053] Regarding the wafer film thickness measurement device involved in related technologies, there are problems such as the inability to adjust the light source energy, poor spectral signal quality, and poor probe process adaptability when performing white light endpoint measurement technology in CMP applications.

[0054] In view of this, embodiments of the present disclosure provide a wafer film thickness measuring device.

[0055] Figure 2 This is a schematic diagram of a wafer film thickness measurement device according to an exemplary embodiment, such as... Figure 2 As shown, the wafer film thickness measurement device 1 includes a light source 11, a light source energy adjustment module 12, a beam splitter 14, a flexible probe 13, a photodetector module 15, and a processing unit.

[0056] The light source 11 provides an illumination beam. The light source energy adjustment module 12 regulates the intensity of the source beam to obtain a modulated beam with a dynamic target intensity. The beam splitter 14 splits the modulated beam to generate a measurement beam and a reference beam. The flexible probe 13 transmits the measurement beam and the reflected beam, and adaptively moves along the optical axis to maintain contact with the polishing pad transmission window of the wafer polishing equipment during the polishing process. The measurement beam is reflected after being incident on the wafer via the flexible probe 13. The photodetector module 15 acquires the intensity measurements of the reference beam and the reflected beam. The processing unit (not shown) calibrates the intensity measurement of the reflected beam based on the intensity measurement of the reference beam to obtain the calibrated intensity value of the reflected beam, and determines the wafer film thickness based on the calibrated intensity value of the reflected beam.

[0057] In the wafer film thickness measurement device provided in this embodiment, on the one hand, by adding a light source energy adjustment module 12 at the light source 11 end, the energy of the light source 11 can be adjusted in a timely manner when the transmittance of the polishing pad transmission window changes, so as to obtain a modulated beam with a dynamic target light intensity that matches the transmittance of the polishing pad window, so that the energy of the beam irradiating the wafer surface remains stable, thereby reducing the light intensity fluctuation of the beam reflected from the wafer surface and improving the accuracy and stability of the measurement results.

[0058] On the other hand, a beam splitter 14 is provided to split the modulated beam obtained by the light source energy adjustment module 12 into a measurement beam and a reference beam. The measurement beam is reflected onto the wafer by a flexible probe 13, and the reflected beam is collected by the flexible probe 13 and then incident on the photodetector module 15. The reference beam is directly incident on the photodetector module 15. Since the reference beam and the reflected beam originate from the same source beam, their intensity fluctuation trends are consistent. Therefore, the intensity measurement value of the reflected beam can be calibrated based on the intensity measurement value of the reference beam, and the optical path signal fluctuation of the measurement beam caused by the light source energy fluctuation can be corrected in real time, improving the stability of the measurement beam signal. Then, based on the intensity calibration value of the reflected beam, the film thickness of the wafer can be determined, which can improve the accuracy and stability of film thickness measurement.

[0059] On the other hand, a flexible probe 13 is configured to adaptively move along the optical axis. This flexible probe 13 allows for better contact with the polishing pad during the polishing process. Compared to non-flexible probes (probes with rigid connections) in related technologies, the flexible probe 13 automatically compensates for changes in probe position caused by the high-speed movement of the polishing pad, thereby maintaining the relative position and pressure between the probe and the polishing pad window. This ensures that the flexible probe 13 remains in contact with the polishing pad's transmission window, thus reducing the impact of movement on the measurement signal during polishing. Using a flexible probe also reduces probe maintenance frequency and avoids the challenges of restoring equipment performance caused by disassembling and reassembling the polishing pad for probe adjustments.

[0060] In this embodiment of the disclosure, the light source 11 is a white light source with a broad spectrum. Exemplarily, to increase the lifespan of the light source and reduce the exposure time of the light on the wafer, the light source 11 employs a pulsed xenon lamp to provide a pulsed illumination beam. Of course, this disclosure is not limited to this, and those skilled in the art can replace it with a laser light source or other light sources as needed.

[0061] Xenon lamp light sources have relatively poor stability, resulting in poor stability of the acquired signal from the reflected beam. In embodiments of this disclosure, at the start of grinding, the illumination source beam provided by the light source 11 can be adjusted to a modulated beam with the required initial target light intensity via the light source energy adjustment module 12. As grinding progresses, the transmittance of the grinding pad transmission window decreases. By controlling the light source energy adjustment module 12 to dynamically adjust the light intensity of the source beam to another required target light intensity in real time, the influence of the light intensity variation of the measurement beam illuminating the wafer surface on the film thickness measurement is reduced. This allows the light intensity of the reflected beam received by the photodetector module 15 to remain stable overall, improving the measurement accuracy of the film thickness.

[0062] In the embodiments of this disclosure, the modulated beam is split into a measurement beam and a reference beam by the beam splitter 14. The reference beam is directly incident on the photodetector module 15, and the measurement beam is incident on the wafer via the flexible probe 13. The wafer reflects the measurement beam to form a reflected beam, which is then incident on the photodetector module 15 via the flexible probe 13.

[0063] The reference beam is directly incident on the photodetector module 15 from the beam splitter 14. The intensity loss of the reference beam is small in the corresponding transmission optical path, which can accurately reflect the intensity fluctuation of the modulated beam. The measurement beam and the reference beam are split from the same source beam of the light source 11 in the beam splitter 14, and their change trends are the same. Therefore, the intensity of the reflected beam received by the photodetector module 15 can be calibrated by the change of the reference beam, avoiding the influence of the intensity fluctuation of the light source 11 on the intensity of the reflected beam received by the photodetector module 15, thereby improving the measurement accuracy of the wafer.

[0064] In this embodiment, a flexible probe 13 capable of adaptively moving along the optical axis is provided. In the event of adverse conditions such as vibration in the wafer polishing equipment, the flexible probe 13 can always maintain contact with the transmission window of the polishing pad to maintain a certain pressure, 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 displacement of the flexible probe 13 relative to the transmission window of the polishing pad.

[0065] In this embodiment of the disclosure, the light detection module 15 includes a beam acquisition element capable of detecting light intensity, used to acquire the light intensity of the measurement beam and the reflected beam in real time.

[0066] In some embodiments, the light detection module 15 may include a beam acquisition element, and the reference beam and the measurement beam are acquired by the same beam acquisition element.

[0067] In some embodiments, the light detection module 15 may include two beam acquisition elements, which respectively acquire a reference beam and a measurement beam. For example, Figure 3As shown, the optical detection module 15 may include a reflected beam acquisition element 151 and a reference beam acquisition element 152. The measurement beam generated by the beam splitter 14 is directly incident on the reflected beam acquisition element 151, and the reflected beam reflected by the wafer is incident on the reflected beam acquisition element 151.

[0068] Figure 4 This is a schematic diagram of a light source energy regulation module structure according to an exemplary embodiment, such as... Figure 4 As shown, the light source energy adjustment module 12 includes several filter elements 121 with different transmittance and a rotation drive mechanism 122. The filter elements 121 are arranged around the rotation axis of the rotation drive mechanism 122. The rotation drive mechanism 122 drives the filter elements 121 to rotate so that the source light beam is transmitted through the target filter element 121 among the filter elements 121 to obtain a modulated light beam with dynamic target light intensity.

[0069] When polishing a wafer, the wear of the polishing pad transmission window is a gradual process, and the decrease in its transmittance is also a gradual process. At different stages, modulated beams with different light intensities, i.e., dynamic target light intensities, are needed to match the polishing pad transmission windows with different transmittances.

[0070] In the embodiments of this disclosure, by setting a plurality of filter elements 121 and a rotation drive mechanism 122, the positions of the plurality of filter elements 121 can be switched by the rotation drive mechanism 122, thereby selectively transmitting the source beam through different filter elements 121 as a modulated beam with a dynamic target light intensity. Different selected filter elements 121 result in different light intensities of the modulated beam formed after the source beam passes through the filter elements 121. By setting a plurality of filter elements 121, the number of transmittance levels is increased, thereby increasing the number of intensity levels of the modulated beam. The more intensity levels of the modulated beam, the smaller the difference between the different intensity levels, which better matches the continuously decreasing transmittance of the grinding pad transmission window, thereby reducing the impact of the decrease in transmittance of the grinding pad transmission window on the accuracy of wafer film thickness measurement.

[0071] Figure 5 This is a schematic diagram illustrating the structure of a light source energy regulation module according to an exemplary embodiment. For example... Figure 5 As shown, the light source energy adjustment module 12 includes a reciprocating drive mechanism 123 and a filter element 121 with a gradient transmittance. The reciprocating drive mechanism 123 drives the filter element 121 with a gradient transmittance to reciprocate along the transmittance gradient direction so that the source beam is transmitted through the region with the target transmittance in the filter element 121 with a gradient transmittance to obtain a modulated beam with a dynamic target light intensity.

[0072] In the embodiments of this disclosure, the filter element 121 is configured to have a gradient transmittance. When the reciprocating drive mechanism 123 drives the filter element 121 with a gradient transmittance along the transmittance gradient direction, the source beam will be transmitted through the portion of the filter element 121 with a gradient transmittance that has different transmittance, thereby forming a modulated beam with different target light intensity. The modulated beam with different target light intensity cooperates with the transmission window of the polishing pad to improve the accuracy of wafer film thickness measurement.

[0073] In some embodiments, the filter element 121 with gradient transmittance is configured such that the transmittance gradually increases from one end to the other.

[0074] In some embodiments, the light filter element 121 with gradient transmittance may have a transmittance that varies in a stepwise manner or continuously. Those skilled in the art can choose according to their needs, and this disclosure does not limit this.

[0075] In some embodiments, such as Figure 6 As shown, the filter element with gradient transmittance can also be replaced by several linearly arranged filter elements 121 with different transmittances.

[0076] In some embodiments, the filter element 121 is a filter sheet.

[0077] like Figure 2 As shown, in some embodiments, the light source energy adjustment module 12 can adjust the light intensity of the source beam provided by the light source 11. This adjustment may include reducing the light intensity, keeping the light intensity constant, or increasing the light intensity.

[0078] In some embodiments, an auxiliary light source is provided in the light source energy adjustment module 12. The auxiliary light source and the filter element 121 are provided simultaneously, so that the light source energy adjustment module 12 can have the function of reducing, maintaining, or increasing the light intensity of the source beam provided by the light source 11.

[0079] In the embodiments of this disclosure, the illumination source beam is controlled by the light source energy adjustment module 12. At the beginning of grinding, the transmittance of the grinding pad transmission window is high, and a modulated beam with a first target light intensity matching the transmittance of the grinding pad window at this time is obtained. As grinding progresses, a modulated beam with a second target light intensity matching the transmittance of the grinding pad window at this time is obtained. Thus, the light source energy adjustment module 12 adapts to the changes in the transmittance of the grinding pad window to keep the energy of the beam illuminating the wafer surface stable, thereby reducing the intensity fluctuation of the beam reflected from the wafer surface and improving the accuracy and stability of the measurement results. The light source energy adjustment module 12 in the embodiments of this disclosure can obtain the modulated beam intensity with a dynamic target light intensity according to actual needs, and has a wide adjustable range. Therefore, it can still meet the needs of wafer film thickness measurement when the transmittance of the grinding pad transmission window varies within a large range. Furthermore, through the light source energy adjustment module 12 involved in the embodiments of this disclosure, the grinding pad transmission window can still be used even under significant wear, extending the service life of the grinding pad transmission window and reducing the economic and time costs caused by frequent replacement of the grinding pad transmission window.

[0080] In some embodiments, the beam splitter 14 includes an optical fiber beam splitter. The optical fiber beam splitter splits the modulated beam into a reference beam and a measurement beam, and separates the measurement beam incident on the wafer from the reflected beam reflected from the wafer.

[0081] In some embodiments, the wafer film thickness measuring device 1 includes an optical fiber, through which the measuring beam, the reference beam, and the reflected beam are all transmitted.

[0082] Figure 7 This is a schematic diagram of a wafer film thickness measurement device according to an exemplary embodiment, such as... Figure 7 As shown, the fiber optic beam splitter includes four port fibers 143 and corresponding fiber optic interfaces 144. One port fiber 143 connects to the light source energy adjustment module 12 and one fiber optic interface 144 to carry the modulated beam; another port fiber 143 connects to the same fiber optic interface 144 and the photodetector module 15 to carry the reference beam; yet another port fiber 143 connects to the same fiber optic interface 144 and the flexible probe 13 to carry the measurement beam; and a third port fiber 143 connects to the flexible probe 13 and the photodetector module 15 to carry the reflected beam. The ports of the port fibers 143 can serve as connectors.

[0083] Using optical fiber as a medium to carry the light beam can isolate and protect the beam. Ambient light in the beam path is difficult to enter the optical fiber and affect the beam, and impurities in the air cannot have a negative effect on the beam in the optical fiber, thus greatly maintaining the stability of the beam.

[0084] In some embodiments, beam splitter 14 includes a beam splitter mirror.

[0085] A beam splitter is a device that allows part of a light beam incident on it to be transmitted and part to be reflected. There are various ways to implement it and its specific structure, which are not limited in this disclosure.

[0086] In this embodiment, the beam splitter uses a beam splitter to generate a measurement beam and a reference beam by modulating the beam. The generation of the corresponding beam can be achieved by setting the angle and position of the beam splitter, which is simple in structure.

[0087] Figure 8 This is a schematic diagram illustrating the structure of a wafer film thickness measurement device according to an exemplary embodiment. Figure 8 As shown, the beam splitter includes a first beam splitter 141 and a second beam splitter 142. The modulated beam emitted from the light source energy adjustment module 12 illuminates the first beam splitter 141. Part of the modulated beam is transmitted through the first beam splitter 141 to form a reference beam, which is directly incident on the photodetector module 15. Part of the modulated beam is reflected by the first beam splitter 141 to form a measurement beam, which illuminates the wafer. After being reflected by the wafer, it forms a reflected beam, which is incident on the photodetector module 15.

[0088] In some embodiments, the beam splitter includes a first beam splitter 141 and a second beam splitter 142. The modulated beam emitted from the light source energy adjustment module 12 illuminates the first beam splitter 141. Part of the modulated beam is reflected by the first beam splitter 141 to form a reference beam, which is directly incident on the photodetector module 15. Part of the modulated beam is transmitted through the first beam splitter 141 to form a measurement beam. The measurement beam illuminates the wafer and is reflected by the wafer to form a reflected beam, which is incident on the photodetector module 15.

[0089] In some embodiments, the measurement beam emitted from the first beam splitter 141 is transmitted through the second beam splitter 142, and then illuminates the wafer after passing through the second beam splitter 142. After being reflected by the wafer, a reflected beam is formed, and the reflected beam is reflected by the second beam splitter 142 and then illuminates the photodetector module 15.

[0090] In some embodiments, the measurement beam emitted from the first beam splitter 141 is reflected by the second beam splitter 142 and then directed toward the wafer. After being reflected by the wafer, a reflected beam is formed. The reflected beam is transmitted through the second beam splitter 142 and then illuminates the photodetector module 15.

[0091] This embodiment uses a beam splitter as a beam splitter. The beam can be split by directly illuminating the beam splitter. There is no need to set a medium for the beam. The distance between the light source energy adjustment module and the beam splitter, the light detection module and the flexible probe can be flexibly adjusted without considering the volume of the beam medium, making the entire device more flexible in its setup.

[0092] The following embodiments of this disclosure will describe the process by which the processing unit calibrates the light intensity measurement value of the reflected beam based on the light intensity measurement value of the reference beam to obtain the light intensity calibration value of the reflected beam.

[0093] In this embodiment of the disclosure, the light intensity measurement value of the reference beam is obtained by repeatedly acquiring the light intensity measurement value of the reference beam through the light detection module and calculating the average value. The following uses... This represents the light intensity calibration value of the reference beam obtained by averaging the light intensity measurements of the reference beam from n acquisitions. Here, n is a positive integer.

[0094] In this embodiment of the disclosure, the light intensity measurement value of the reference beam and the light intensity measurement value of the reflected beam are acquired in real time during the grinding process by a photodetector module. (Hereinafter referred to as I) mea This indicates the real-time acquisition of the light intensity measurement value of the reflected beam. (Used as I) ref This represents the measured light intensity of the reference beam acquired in real time during the grinding process.

[0095] The intensity measurement value of the reflected beam is calibrated using the following formula (1) to obtain the intensity calibration value of the reflected beam:

[0096]

[0097] in, I is the intensity calibration value for the reference beam. ref I represents the light intensity measurement of the reference beam acquired in real time during the grinding process. mea I represents the light intensity measurement value of the reflected beam acquired in real time during the grinding process, and I represents the light intensity calibration value of the reflected beam.

[0098] The source beam provided by the light source is actually not stable, and its intensity fluctuates. The wafer film thickness measurement is based on the intensity of the reflected beam received by the photodetector module, so the intensity fluctuation of the source beam directly affects the accuracy of the wafer film thickness measurement.

[0099] In the embodiments of this disclosure, by setting a reference beam that is from the same source as the measurement beam, and utilizing the synchronicity of the fluctuations between the reference beam and the measurement beam, the light intensity measurement value of the reflected beam measured by the photodetector module is calibrated according to the fluctuations of the reference beam. The wafer film thickness is obtained by using the calibrated light intensity calibration value of the reflected beam. This avoids the negative impact of the light intensity fluctuations of the source beam on the accuracy of the measured wafer film thickness.

[0100] In this embodiment, the intensity calibration value of the reference beam can be determined in advance using a standard sample (also known as a standard wafer). For example, before grinding the wafer, the energy adjustment module 12 regulates the source beam of the light source so that the reflected beam acquisition element 151 and the reference beam acquisition element 152 are in a high-performance state, i.e., meeting the requirements of the corresponding target intensity. The reflected beam acquisition element 151 and the reference beam acquisition element 152 acquire the intensity of the standard sample n times consecutively, and the average value of the intensity of the standard sample acquired by the reference beam acquisition element 152 n times consecutively is calculated to obtain...

[0101] In this embodiment of the disclosure, to improve the accuracy of the reference beam's intensity calibration value, it is necessary to periodically update the reference beam's intensity calibration value. For example, in one example, this embodiment of the disclosure can preset the transmittance of the grinding pad's transmission window, which is the reference transmittance of the grinding pad's transmission window. When the real-time transmittance of the grinding pad's transmission window drops below the preset transmittance, it indicates that the grinding pad's transmission window is severely worn, and the current modulated beam can no longer effectively penetrate the grinding pad's transmission window. The intensity of the reflected beam received by the photodetector module is already very low, which cannot meet the requirements for accurately measuring the wafer film thickness. At this time, the light source energy adjustment module is controlled to increase the intensity of the modulated beam, and the intensity calibration value of the reference beam is re-determined.

[0102] In some embodiments, the processing unit determines the wafer film thickness based on the light intensity calibration value of the reflected beam in the following manner: The theoretical reflectance spectrum of the wafer corresponding to different film thickness values ​​is obtained. The measured reflectance spectrum of the reflected beam is calculated based on the light intensity calibration value of the reflected beam. From the theoretical reflectance spectra of the wafers corresponding to different film thickness values, a target theoretical reflectance spectrum matching the measured reflectance spectrum is obtained, and the film thickness value corresponding to the target theoretical reflectance spectrum is taken as the film thickness of the wafer.

[0103] In this embodiment of the disclosure, the theoretical reflectance spectrum of the wafer corresponding to different film thickness values ​​can be determined using a modeling algorithm.

[0104] In this embodiment of the present disclosure, when determining the wafer film thickness, the light intensity measurement value of the reflected beam is acquired and measured in real time through the reflected beam acquisition element 151, and the light intensity measurement value of the reference beam is acquired and measured in real time through the reference beam acquisition element 152. The light intensity measurement value of the reflected beam is calibrated using formula (1) to obtain the light intensity calibration value of the reflected beam. The measured reflectivity spectrum of the reflected beam is calculated based on the light intensity calibration value of the reflected beam.

[0105] In the embodiments of this disclosure, the measured reflectivity spectrum of the reflected beam is calculated by using the calibrated light intensity value of the reflected beam, which can eliminate the adverse effects of light intensity fluctuations in the source beam and thus improve the measurement accuracy of wafer film thickness.

[0106] This disclosure also relates to the positional relationship between the flexible probe and the polishing pad in a wafer thickness measurement device. During wafer polishing, the wafer thickness measurement device needs to rotate with the polishing pad. During this rotation, factors such as vibration and assembly precision may cause displacement of the probe in contact with the polishing pad's transmission window, affecting the measurement accuracy of the wafer thickness. Maintaining measurement accuracy requires frequent probe resetting, increasing maintenance costs. To solve this problem, this disclosure provides a flexible probe, and the positional relationship between the flexible probe and the polishing pad's transmission window ensures that the flexible probe is always in contact with the polishing pad's transmission window. Figure 9 A schematic diagram illustrating the positional relationship between a flexible probe and a grinding disc in an exemplary embodiment of this disclosure is shown. Figure 9 As shown, the flexible probe 13 includes a probe fiber 131, a connector 132, an elastic element 133, and a positioning element 134.

[0107] The probe 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 transmitted to the photodetector module 15.

[0108] The connector 132 is disposed on the periphery of the probe optical fiber 131. The connector 132 has a first connecting part 1321 and a second connecting part 1322, wherein the first connecting part 1321 is connected to the periphery of the probe optical fiber 131.

[0109] One end of the elastic element 133 is connected to the second connecting part 1322, and the other end is connected to the main body of the wafer polishing equipment.

[0110] The positioning component 134 is threadedly connected to the main body of the wafer polishing equipment and is used to adjust the compression state of the elastic component 133 so that the elastic component 133 drives the probe fiber 131 to move along the optical axis, ensuring that the first port 1311 and the polishing pad transmission window 31 remain in contact during the polishing process.

[0111] In this embodiment, the probe fiber 131 is connected to the main body of the wafer polishing equipment using a connector 132 and an elastic element 133. The compression state of the elastic element 133 is adjusted by a control element, thereby utilizing the elastic force of the elastic element 133 to ensure that the probe fiber 131 moves adaptively along the optical axis during the polishing process so that the first port 1311 remains in contact with the polishing pad transmission window 31. This avoids the position of the first port 1311 relative to the polishing pad transmission window 31 changing during use, which would affect the measurement accuracy of the wafer 5 film thickness. It also avoids the negative impact of frequent adjustments to the first port 1311 of the probe fiber 131 on maintenance work.

[0112] In some embodiments, such as Figure 9As shown, the control element 134 adjusts the amount of thread screwing in and out to contact the elastic element 133 and apply pressure to the elastic element 133, thereby regulating the compression state of the elastic element 133.

[0113] In this embodiment of the present disclosure, the compression state of the elastic element 133 can be adjusted by adjusting the amount of screwing in and out of the control element 134, which can change the displacement of the probe fiber 131 along the optical axis direction, so as to adapt to different wafer polishing equipment and avoid the probe fiber 131 deviating from the polishing pad transmission window 31 or the probe fiber 131 excessively contacting and damaging the polishing pad transmission window 31.

[0114] In some embodiments, the elastic element 133 is sleeved around the periphery of the probe optical fiber 131.

[0115] By fitting the elastic element 133 around the periphery of the probe fiber 131, a relatively balanced elastic force can be applied to the probe fiber 131.

[0116] In some embodiments, the elastic element 133 is a spring, which is sleeved around the periphery of the probe optical fiber 131.

[0117] In some embodiments, such as Figure 9 As shown, the elastic element 133 includes several springs distributed around the periphery of the probe fiber 131. This not only prevents the probe fiber 131 from losing its elastic connection due to the failure of a single spring caused by aging or damage, but also maintains the elastic force of the probe fiber 131 in all directions as much as possible.

[0118] In some embodiments, the wafer polishing apparatus has a receiving cavity 21, and the flexible probe 13 is disposed in the receiving cavity 21.

[0119] By placing the flexible probe 13 inside the receiving cavity 21, the overall structure of the flexible probe 13 can be avoided from being exposed to the outside, thus reducing the reliability of the flexible probe 13 structure.

[0120] Based on the wafer film thickness measuring device 1 provided in the above embodiments of this disclosure, this disclosure also proposes a wafer film thickness measuring method. The wafer film thickness measuring method provided in this disclosure is applied to the wafer film thickness measuring device 1 of this disclosure.

[0121] Figure 11 This is a flowchart illustrating a wafer film thickness measurement method according to an exemplary embodiment. Figure 11 As shown, the wafer film thickness measurement methods include:

[0122] S101: During the wafer polishing process, the light intensity of the illumination source beam provided by the light source is controlled by the light source energy adjustment module to obtain a modulated beam with dynamic target light intensity. The modulated beam is split into a measurement beam and a reference beam after passing through a beam splitter. The measurement beam is incident on the wafer through a flexible probe to form a reflected beam. The flexible probe transmits the measurement beam and the reflected beam and moves adaptively along the optical axis to keep the flexible probe in contact with the polishing pad transmission window of the wafer polishing equipment during the polishing process.

[0123] S102: The light intensity measurement values ​​of the reflected beam and the reference beam are collected in real time through the light detection module.

[0124] S103: Based on the light intensity measurement value of the reference beam, calibrate the light intensity measurement value of the reflected beam to obtain the light intensity calibration value of the reflected beam.

[0125] S104: Determine the film thickness of the wafer based on the light intensity calibration value of the reflected beam.

[0126] The light intensity of a light source fluctuates, causing fluctuations in the reflected beam as well. However, factors affecting the intensity of the reflected beam include not only light source fluctuations but also changes in the transmittance of the grinding pad's transmission window and the wafer film thickness. Therefore, the fluctuations in the intensity measurements of the reflected beam acquired by the photodetector module do not fully represent the light source fluctuations. Since the reference beam and the measurement beam (reflected beam) originate from the same source, their fluctuations are synchronized. Calibrating the intensity measurement of the reflected beam based on the fluctuations in the reference beam's intensity eliminates the influence of light source fluctuations on the reflected beam's intensity. This allows the calibrated intensity value of the reflected beam to more accurately reflect the wafer film thickness, resulting in more accurate wafer film thickness measurements.

[0127] In step S103, the light intensity measurement value of the reflected beam is calibrated based on the light intensity measurement value of the reference beam to obtain the light intensity calibration value of the reflected beam. This includes obtaining the light intensity calibration value of the reflected beam 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 using formula (1).

[0128] Specifically, the light intensity measurement value of the reference beam is collected multiple times by the light detection module, and the average value of the light intensity measurement value of the reference beam collected multiple times is calculated as the light intensity calibration value of the reference beam.

[0129] Figure 12 This is a flowchart illustrating a method for determining the film thickness of a wafer based on the light intensity calibration value of a reflected beam, according to an exemplary embodiment. Figure 12 As shown, the method for determining the wafer film thickness based on the light intensity calibration value of the reflected beam includes:

[0130] S201: Obtain the theoretical reflectance spectrum corresponding to different film thickness values.

[0131] S202: Calculate the measured reflectivity spectrum of the reflected beam based on the light intensity calibration value of the reflected beam.

[0132] S203: Obtain the target theoretical reflectance spectrum that matches the measured reflectance spectrum from the theoretical reflectance spectra corresponding to different film thickness values, and take the film thickness value corresponding to the target theoretical reflectance spectrum as the film thickness of the wafer.

[0133] In the embodiments of this disclosure, the film thickness of the wafer can be obtained by acquiring different film thickness values ​​and the theoretical reflectivity spectra of the wafer corresponding to the film thickness values, and then obtaining the measured reflectivity spectra of the reflected beam from the light intensity calibration value based on the mapping method, which can improve the measurement accuracy.

[0134] Figure 13A This is a flowchart illustrating real-time adjustment of light source energy in a wafer film thickness measurement method according to an exemplary embodiment. The wafer film thickness measurement method in this embodiment further includes:

[0135] S301: Monitor the real-time transmittance of the transmission window of the abrasive pad.

[0136] S302: If the real-time transmittance is less than or equal to the preset transmittance, the light intensity of the illumination source beam provided by the light source is adjusted by the light source energy adjustment module to improve the light intensity measurement values ​​of the reference beam and the reflected beam collected by the light detection module.

[0137] In the embodiments of this disclosure, when the real-time transmittance of the polishing pad transmission window drops below the preset transmittance, it indicates that the polishing pad transmission window is severely worn. The current modulated beam can no longer effectively penetrate the polishing pad transmission window, and the light intensity of the reflected beam received by the photodetector module is very small, which cannot meet the requirements for accurate measurement of wafer film thickness. At this time, controlling the light source energy adjustment module to increase the light intensity of the modulated beam can enhance the energy of the measurement beam and the reflected beam after passing through the polishing pad transmission window, thereby enabling the photodetector module to be basically stable within a certain range and improving the accuracy of film thickness detection.

[0138] In some embodiments, such as Figure 13B As shown, the energy of the light source can also be adjusted in real time using the following methods:

[0139] S401: Preset transmittance of the abrasive pad transmission window.

[0140] S402: Measure the real-time transmittance of the transmission window of the abrasive pad.

[0141] S403: Compare the measured real-time transmittance with the preset transmittance. If the measured real-time transmittance is less than or equal to the preset transmittance, execute S404; otherwise, execute S402.

[0142] S404: The light intensity of the illumination source beam provided by the light source is adjusted by the light source energy adjustment module to improve the light intensity measurement values ​​of the reference beam and reflected beam collected by the light detection module.

[0143] In the embodiments of this disclosure, after setting the transmittance of the grinding pad transmission window, the real-time transmittance of the grinding pad transmission window is measured. This allows for accurate control of the transmittance changes of the grinding pad transmission window, thereby accurately controlling the light source energy adjustment device to obtain higher film thickness measurement accuracy.

[0144] In some embodiments, there are various methods for obtaining the real-time transmittance of the transmission window of the polishing pad. For example, the splitting ratio of the reference beam and the measurement beam is set to 1:1, and the light intensity measurement value I of the reflected beam is collected in real time during the polishing process. ref The light intensity measurement value I of the reference beam acquired in real time during the grinding process. mea The transmittance K is calculated using formula (2):

[0145]

[0146] Of course, the transmittance K at this point is not the exact transmittance of the polishing pad's transmission window, as factors such as the wafer's own reflectivity must be considered. However, this transmittance K can be used as the real-time transmittance of the polishing pad's transmission window. When setting the transmittance, factors such as the wafer's own reflectivity should be considered accordingly, and a reasonable preset transmittance value should be set. Thus, the light source energy adjustment module can be adjusted by measuring and controlling the transmittance of the polishing pad's transmission window.

[0147] Setting the splitting ratio of the reference beam and the measurement beam to 1:1 is not the only option; other ratios can also be used, as long as they are converted and substituted during the calculation.

[0148] In some embodiments, determining whether it is necessary to control and adjust the light source energy adjustment module to change the light intensity of the modulated beam can also be done directly by measuring the light intensity value of the reflected beam. For example, when the measured light intensity value of the reflected beam is lower than a preset value, it can be considered that the light transmittance of the grinding pad transmission window has decreased, and it is necessary to control the light source energy adjustment module to increase the light intensity of the modulated beam.

[0149] In some embodiments, determining whether it is necessary to control and adjust the light source energy adjustment module to change the light intensity of the modulated beam can also be done directly by measuring the wear degree of the grinding pad's transmission window. When the wear degree is greater than a preset value, it can be considered that the light transmittance of the grinding pad's transmission window has decreased, and it is necessary to control the light source energy adjustment module to increase the light intensity of the modulated beam. The wear degree of the grinding pad's transmission window can be measured by various methods, and this disclosure does not limit this method.

[0150] It should be noted that the wafer film thickness measurement method provided in the above embodiments of this disclosure is similar to the wafer film thickness measurement device 1 provided in the above embodiments in terms of the implementation process of wafer film thickness measurement. For any parts of the wafer film thickness measurement method that are not described in detail, please refer to the relevant description of the wafer film thickness measurement device 1 above, which will not be repeated here.

[0151] Based on the same concept, this disclosure also proposes a wafer polishing apparatus, including the wafer film thickness measuring device 1 of this disclosure.

[0152] Wafer polishing equipment is a device used to remove excess material from the surface of a wafer or to reduce the film thickness to a specified thickness. The wafer polishing equipment disclosed herein may refer to a CMP device or other wafer polishing equipment.

[0153] Figure 10 This is a schematic diagram illustrating the structure of a wafer polishing apparatus according to an exemplary embodiment. Figure 9 , Figure 10 As shown, the wafer polishing equipment includes a rotatable polishing disk 2 and a polishing pad 3 laid on the polishing disk 2. Other structures can be provided between the polishing pad 3 and the polishing disk 2 as needed, and this disclosure does not limit this. The polishing pad 3 is provided with a light-transmitting window 31. The wafer polishing equipment has a receiving cavity 21, which is at least partially disposed within the polishing disk 2. The receiving cavity 21 has an opening opposite to the polishing pad window 31.

[0154] The wafer polishing equipment also includes a polishing head 4 disposed above the polishing pad 3. The polishing head 4 is positioned to avoid the rotation center of the polishing pad 3. The wafer 5 is disposed between the polishing head 4 and the polishing pad 3 and rotates around the axis of the polishing head 4 under the drive of the polishing head 4. During the polishing of the wafer 5, the polishing disk 2 and the polishing head 4 rotate independently, thus polishing the wafer 5. When the polishing disk 2 rotates, the wafer 5 is in contact with the polishing pad's transmission window 31 for at least a portion of the time.

[0155] The wafer film thickness measuring device 1 is disposed in the receiving cavity 21. The wafer film thickness measuring device 1 includes a flexible probe 13, which includes a probe optical fiber 131, a connector 132, a positioning element 134, and an elastic element 133. The first port 1311 of the probe optical fiber 131 faces the polishing pad transmission window 31 and is in contact with the polishing pad transmission window 31.

[0156] like Figure 9 As shown, a connector 132 is provided around the probe fiber 131. The first connecting part 1321 of the connector 132 is sleeved on the periphery of the probe fiber 131 and fixedly connected to the periphery of the probe fiber 131. The second connecting part 1322 of the connector 132 extends outward from the circumferential edge of the first connecting part 1321 to form an annular second connecting part 1322.

[0157] An abutment portion 211 is provided on the inner wall of the receiving cavity 21. An elastic element 133 is disposed between the second connecting portion 1322 and the abutment portion 211 and is in a compressed state. The elastic element 133 applies an elastic thrust to the second connecting portion 1322 in the direction of the polishing pad transmission window 31. The elastic thrust is transmitted to the probe fiber 131 through the second connecting portion 1322 and the first connecting portion 1321, so that the probe fiber 131 keeps in contact with the polishing pad transmission window 31. This avoids the probe fiber 131 from detaching from the polishing pad 3 observation window due to vibration or other factors, thus reducing the measurement accuracy of the wafer 5 film thickness. It also avoids frequent maintenance due to the probe fiber 131 detaching from the polishing pad 3 observation window.

[0158] The positioning element 134 is threaded to the inner wall of the receiving cavity 21 and is positioned on the second connecting part 1322. During installation, the flexible probe 13 is inserted upwards from below the polishing disc 2 along the receiving cavity 21. The elastic element 133, the connecting part 132, and the positioning element 134 are sequentially inserted from the upper opening of the receiving cavity 21. The positioning element 134 is screwed into the receiving cavity 21, contacting the second connecting part 1322, and then screwed in, compressing the elastic element 133. The probe fiber 131 is kept at least partially protruding from the opening of the receiving cavity 21. A polishing pad 3 with a polishing pad transmission window 31 is laid on the polishing disc 2. The first port 1311 of the probe fiber 131 contacts the polishing pad transmission window 31. The first port 1311 of the probe fiber 131 moves into the receiving cavity 21 under the pressure of the polishing pad transmission window 31, further compressing the elastic element 133. The positioning element 134 disengages from the second connecting part 1322 of the connecting part 132.

[0159] In the embodiments of this disclosure, the probe fiber 131 is limited by the positioning element 134 connected to the inner peripheral sidewall of the receiving cavity 21, so as to avoid the probe fiber 131 being damaged by the excessive elastic force of the elastic element 133 pushing out the polishing pad transmission window 31.

[0160] The wafer polishing equipment also includes a spray arm 7 and a polishing pad dresser 6 positioned above the polishing pad 3. The spray arm 7 is used to spray polishing fluid onto the polishing pad 3 to promote polishing. The polishing pad dresser 6 contacts the polishing pad 3 to clean and dress its surface.

[0161] This disclosure also proposes a method for wafer polishing using the wafer polishing equipment disclosed herein. For example... Figure 14 As shown, the wafer polishing method includes:

[0162] S501: During the wafer polishing process using a wafer polishing equipment, the light intensity of the illumination source beam provided by the light source is adjusted by the light source energy adjustment module to obtain a modulated beam with dynamic target light intensity. The modulated beam is split into a measurement beam and a reference beam after passing through a beam splitter. The measurement beam is incident on the wafer through a flexible probe to form a reflected beam. The flexible probe transmits the measurement beam and the reflected beam and moves adaptively along the optical axis to keep the flexible probe in contact with the polishing pad transmission window of the wafer polishing equipment during the polishing process.

[0163] S502: Real-time acquisition of light intensity measurements of the reflected beam and the reference beam via the light detection module.

[0164] S503: Based on the light intensity measurement value of the reference beam, calibrate the light intensity measurement value of the reflected beam to obtain the light intensity calibration value of the reflected beam.

[0165] S504: Calculate the measured reflectance spectrum of the reflected beam based on the light intensity calibration value of the reflected beam.

[0166] S505: Based on the measured reflectivity spectrum of the reflected beam, the wafer thickness value is extracted in real time, and the wafer polishing is terminated when the film thickness value reaches the preset target value.

[0167] In the embodiments of this disclosure, the reference beam and the measurement beam originate from the same source. Fluctuations in the reference beam can represent fluctuations in the measurement beam. Calibrating the intensity measurement of the reflected beam based on the intensity measurement of the reference beam eliminates the influence of light source fluctuations on the reflected beam, making the measured reflectivity spectrum obtained from the calibrated intensity value of the reflected beam more accurate. Furthermore, determining the film thickness and the termination of wafer polishing based on the measured reflectivity spectrum becomes more precise.

[0168] The intensity calibration value of the reflected beam can be obtained by formula (1) based on the intensity measurement value of the reference beam, the intensity measurement value of the reflected beam, and the intensity calibration value of the reference beam.

[0169] Specifically, the light intensity measurement value of the reference beam is collected multiple times by the light detection module, and the average value of the light intensity measurement value of the reference beam collected multiple times is calculated as the light intensity calibration value of the reference beam.

[0170] The target value for film thickness in step S505 refers to the film thickness of the product wafer sample at the time of termination of polishing.

[0171] The real-time film thickness value of the product wafer can be obtained by the following method: pre-store different theoretical reflectivity spectra and the corresponding wafer film thickness values ​​to establish a corresponding relationship library; based on the measured reflectivity spectrum of the reflected beam, find the corresponding theoretical reflectivity spectrum in the corresponding relationship library; and extract the wafer film thickness value corresponding to the theoretical reflectivity spectrum as the real-time film thickness value of the product wafer.

[0172] By establishing a correspondence library, the corresponding wafer film thickness can be directly mapped from the measured reflectance spectrum using a mapping method, eliminating the need for further calculations, reducing the burden on the hardware, and allowing for faster response times.

[0173] In some embodiments, the correspondence database may further include the grinding time and the number of grinding disk rotations from the start to the end of grinding of the product wafer sample. When determining whether to terminate wafer polishing in step S506, the grinding time and the number of grinding disk rotations can be used together as the judgment criteria. The product wafer polishing can only be terminated when the grinding time and the number of grinding disk rotations are satisfied simultaneously, and the measured reflectance spectrum matches the target theoretical reflectance spectrum of the corresponding target film thickness in the correspondence database.

[0174] In the embodiments of this disclosure, grinding time and the number of rotations of the grinding disc are used as redundant judgment indicators, which can avoid judgment errors caused by random errors in the reflectance spectrum and improve the accuracy of grinding endpoint judgment.

[0175] In some embodiments, this disclosure provides a method for creating a correspondence database. For example... Figure 15 As shown, the corresponding relational database is pre-created in the following manner:

[0176] S601: Collect the standard light intensity during the polishing process of the wafer polishing equipment on the standard wafer sample, and determine the reflectance spectrum of the standard wafer sample based on the standard light intensity.

[0177] The standard wafer sample can be bare silicon or a wafer with a specific film thickness.

[0178] S602: Collect the light intensity calibration value of the reflected beam of the product wafer sample when the wafer polishing equipment polishes the product wafer sample.

[0179] It is understood that the light intensity collected in S601 and S602 of the embodiments of this disclosure can be the light intensity after calibration using the method of calibrating the reflected beam based on the reference beam involved in the embodiments of this disclosure.

[0180] S603: Calculate the theoretical reflectance spectrum of the product wafer using formula (3).

[0181]

[0182] Among them, R product This is the theoretical reflectance spectrum of the product wafer sample, and I is the calibrated value of the reflected beam intensity. stray It is the light intensity measurement value outside the product wafer sample, I stdndard R is the standard light intensity obtained during the polishing process of a standard wafer sample. standard It is the reflectance spectrum of a standard wafer sample.

[0183] I stray This is the measured light intensity outside the product wafer sample, which can be obtained through the following methods:

[0184] Replace the wafer with a black sample that does not reflect light beams, and use a photodetector module to obtain the light intensity measurement value of the reflected light beam at this time, which is I. stray Also known as stray light intensity.

[0185] Of course, I can also be obtained through other methods. stray This disclosure does not impose any limitations on this matter.

[0186] S604: Obtain the wafer film thickness corresponding to the theoretical reflectance spectrum.

[0187] In this disclosure, there are various methods for obtaining wafer film thickness, such as measurement using specialized equipment, calculation via reflectance spectroscopy, or other methods. Those skilled in the art can employ various methods to obtain wafer film thickness, and this disclosure does not limit such methods.

[0188] S605: Determine if the target film thickness has been achieved. If so, execute S606; otherwise, execute S602.

[0189] S606: Records polishing time and the number of rotations of the polishing disc.

[0190] S607: Store the film thickness of different wafers and the corresponding theoretical reflectivity spectra, store the polishing time and the number of rotations of the polishing disk, and establish a corresponding relational library.

[0191] In the embodiments of this disclosure, the measured reflectance spectrum was obtained using a relatively simple method, and stray light intensity I was excluded. stray Due to the influence of the measured reflectance spectrum, the obtained actual reflectance spectrum is more accurate, which is beneficial to improving the control accuracy of the polishing focus.

[0192] In some embodiments, after polishing multiple wafers, the transmittance of the polishing pad window decreases significantly. To improve the accuracy of the wafer polishing termination film thickness measurement, the wafer polishing method further includes measuring the real-time transmittance of the polishing pad's transmission window. If the real-time transmittance is less than or equal to a preset transmittance, the light intensity of the illumination source beam provided by the light source is adjusted by the light source energy adjustment module to improve the light intensity measurement values ​​of the reference beam and reflected beam collected by the light detection module.

[0193] In this process, when adjusting the light intensity of the illumination beam provided by the light source through the light source energy adjustment module, a standard wafer sample can be placed at the polishing head 4. The light source energy adjustment module 12 is then readjusted to ensure that the sample measurement light intensity and reference light intensity received by the reflected beam acquisition element 151 and the reference beam acquisition element 152 are high, and that the reflected beam acquisition element 151 and the reference beam acquisition element 152 are in a high-performance state (high signal-to-noise ratio). Without the light source energy adjustment module 12, the detected light intensity of the reflected beam acquisition element 151 and the reference beam acquisition element 152 would be weak, and the signal-to-noise ratio of the acquired signal would be significantly reduced, directly affecting the stability of the film thickness measurement results.

[0194] In the embodiments of this disclosure, when the real-time transmittance of the polishing pad transmission window drops below the preset transmittance, it indicates that the polishing pad transmission window is severely worn. The current modulated beam can no longer effectively penetrate the polishing pad transmission window, and the light intensity of the reflected beam received by the photodetector module is very small, which cannot meet the requirements for accurate measurement of wafer film thickness. At this time, controlling the light source energy adjustment module to increase the light intensity of the modulated beam can enhance the transmission capability of the measurement beam and the reflected beam through the polishing pad transmission window, so that the photodetector module can be basically stabilized within a certain range. This not only eliminates the influence of the transmittance change of the polishing pad transmission window on the wafer film thickness measurement, but also ensures that the transmittance of the polishing pad transmission window can still meet the usage requirements when it undergoes a large range of changes, eliminating the need for frequent replacement of the polishing pad transmission window and reducing usage costs.

[0195] In this embodiment of the disclosure, the CMP film thickness measurement device includes a light source energy adjustment module, a flexible probe, and a reference optical path (reference beam). Furthermore, in the calibration and measurement methods, the reference beam is introduced to correct the reflected beam of the measurement beam, and real-time energy adjustment is performed after the transmittance of the polishing pad's transmission window decreases. This not only improves the accuracy and stability of film thickness measurement but also extends the lifespan of consumables, reduces maintenance frequency, and lowers equipment operating costs.

[0196] It is understood that in this disclosure, "multiple" refers to two or more, and other quantifiers are similar. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, and B alone. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. The singular forms "a," "the," and "the" are also intended to include the plural forms unless the context clearly indicates otherwise.

[0197] It is further understood that the terms "first," "second," etc., are used to describe various types of information, but this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another, and do not indicate a specific order or degree of importance. In fact, the expressions "first," "second," etc., are completely interchangeable. For example, without departing from the scope of this disclosure, first information can also be referred to as second information, and similarly, second information can also be referred to as first information.

[0198] It is further understood that the terms “center,” “longitudinal,” “lateral,” “front,” “rear,” “up,” “down,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” and “outer,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this embodiment and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation.

[0199] It can be further understood that, unless otherwise specified, "connection" includes both direct connections where no other components exist between the two parties and indirect connections where other components exist between them.

[0200] It is further understood that although operations are described in a specific order in the accompanying drawings in the embodiments of this disclosure, this should not be construed as requiring these operations to be performed in the specific order or serial order shown, or requiring all of the shown operations to be performed to obtain the desired result. In certain environments, multitasking and parallel processing may be advantageous.

[0201] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the following claims.

[0202] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

Claims

1. A wafer film thickness measuring device, characterized in that, Used in wafer polishing equipment, including: A light source, used to provide a beam of light for illumination; A light source energy adjustment module is used to regulate the light intensity of the source beam to obtain a modulated beam with dynamic target light intensity; A beam splitter is used to split the modulated beam to generate a measurement beam and a reference beam; A flexible probe is used to transmit the measurement beam and the reflected beam, and the flexible probe moves adaptively along the optical axis to keep the flexible probe in contact with the transmission window of the polishing pad of the wafer polishing equipment during the polishing process, wherein the measurement beam is incident on the wafer through the flexible probe to form the reflected beam; A light detection module is used to collect the light intensity measurement value of the reference beam and the light intensity measurement value of the reflected beam; The processing unit calibrates the light intensity measurement value of the reflected beam based on the light intensity measurement value of the reference beam to obtain the light intensity calibration value of the reflected beam, and determines the film thickness of the wafer based on the light intensity calibration value of the reflected beam.

2. The wafer film thickness measuring device according to claim 1, characterized in that, The light source energy adjustment module includes several filter elements with different transmittance and a rotation drive mechanism. The filter elements are arranged around the rotation axis of the rotation drive mechanism. The rotation drive mechanism drives the filter elements to rotate so that the source light beam is transmitted through the target filter element among the filter elements to obtain the modulated light beam with dynamic target light intensity. or The light source energy adjustment module includes a reciprocating drive mechanism and a filter element with a gradient transmittance. The reciprocating drive mechanism drives the filter element with a gradient transmittance to reciprocate along the transmittance gradient direction so that the source beam is transmitted through the region with the target transmittance in the filter element with a gradient transmittance to obtain the modulated beam with the dynamic target light intensity.

3. The wafer film thickness measuring device according to claim 1 or 2, characterized in that, The beam splitter includes an optical fiber beam splitter or a beam splitter mirror.

4. The wafer film thickness measuring device according to claim 1, characterized in that, The flexible probe includes: The probe fiber has a first port for transmitting the measurement beam and the reflected beam. The measurement beam is incident on the wafer through the first port, and the reflected beam is received by the first port and transmitted to the optical detection module. A connector is disposed on the periphery of the probe optical fiber and has a first connecting part and a second connecting part, wherein the first connecting part is connected to the periphery of the probe optical fiber. The elastic element has one end connected to the second connecting part and the other end connected to the main body of the wafer polishing equipment; The positioning component is threadedly connected to the main body of the wafer polishing equipment and is used to adjust the compression state of the elastic component so that the elastic component drives the probe fiber to move along the optical axis, ensuring that the first port remains in contact with the transmission window of the polishing pad during the polishing process.

5. The wafer film thickness measuring device according to claim 4, characterized in that, The positioning element adjusts the amount of thread insertion and withdrawal to contact the elastic element and apply pressure to it, thereby regulating the compression state of the elastic element.

6. The wafer film thickness measuring device according to claim 4, characterized in that, The elastic element is sleeved around the periphery of the probe optical fiber; or The elastic element includes a plurality of springs distributed around the periphery of the probe optical fiber.

7. The wafer film thickness measuring device according to claim 4, characterized in that, The wafer polishing equipment is provided with a receiving cavity, and the flexible probe is disposed in the receiving cavity.

8. The wafer film thickness measuring device according to claim 1, characterized in that, The processing unit calibrates the intensity measurement value of the reflected beam based on the intensity measurement value of the reference beam to obtain the intensity calibration value of the reflected beam, including: The light intensity measurement value of the reference beam is obtained by repeatedly collecting the light intensity measurement value of the reference beam by the light detection module and calculating the average value. The intensity measurement value of the reflected beam is calibrated using the following formula to obtain the calibrated intensity value of the reflected beam: in, I is the intensity calibration value of the reference beam. ref I represents the light intensity measurement value of the reference beam acquired in real time during the grinding process. mea I represents the light intensity measurement value of the reflected beam acquired in real time during the grinding process, and I represents the light intensity calibration value of the reflected beam.

9. The wafer film thickness measuring device according to claim 1, characterized in that, The processing unit determines the film thickness of the wafer based on the light intensity calibration value of the reflected beam, including: Obtain the theoretical reflectance spectra corresponding to different film thicknesses; The measured reflectance spectrum of the reflected beam is calculated based on the light intensity calibration value of the reflected beam; In the theoretical reflectance spectra corresponding to different film thickness values, a target theoretical reflectance spectrum that matches the measured reflectance spectrum is obtained, and the film thickness value corresponding to the target theoretical reflectance spectrum is taken as the film thickness of the wafer.

10. A method for measuring wafer film thickness, characterized in that, The wafer film thickness measuring apparatus used in any one of claims 1-9, the wafer film thickness measuring method includes: During the wafer polishing process, the light intensity of the illumination source beam provided by the light source is controlled by the light source energy adjustment module to obtain a modulated beam with dynamic target light intensity. The modulated beam is split into a measurement beam and a reference beam after passing through a beam splitter. The measurement beam is incident on the wafer through a flexible probe to form a reflected beam. The flexible probe transmits the measurement beam and the reflected beam and moves adaptively along the optical axis to keep the flexible probe in contact with the polishing pad transmission window of the wafer polishing equipment during the polishing process. The light intensity measurement values ​​of the reflected beam and the reference beam are collected in real time by the light detection module. The intensity measurement value of the reflected beam is calibrated based on the intensity measurement value of the reference beam to obtain the intensity calibration value of the reflected beam. The film thickness of the wafer is determined based on the light intensity calibration value of the reflected beam.

11. The wafer film thickness measurement method according to claim 10, characterized in that, Determining the film thickness of the wafer based on the light intensity calibration value of the reflected beam includes: Obtain the theoretical reflectance spectra corresponding to different film thicknesses; The measured reflectance spectrum of the reflected beam is calculated based on the light intensity calibration value of the reflected beam; In the theoretical reflectance spectra corresponding to different film thickness values, a target theoretical reflectance spectrum that matches the measured reflectance spectrum is obtained, and the film thickness value corresponding to the target theoretical reflectance spectrum is taken as the film thickness of the wafer.

12. The wafer film thickness measurement method according to claim 10, characterized in that, The method further includes: Monitor the real-time light transmittance of the transmission window of the grinding pad; If the real-time transmittance is less than or equal to the preset transmittance, the light intensity of the illumination source beam provided by the light source is adjusted by the light source energy adjustment module to improve the light intensity measurement values ​​of the reference beam and the reflected beam collected by the light detection module.

13. A wafer polishing device, characterized in that, The wafer film thickness measuring device includes any one of claims 1-9.

14. A wafer polishing method, characterized in that, The method includes: During the wafer polishing process using wafer polishing equipment, the light intensity of the illumination source beam provided by the light source is controlled by the light source energy adjustment module to obtain a modulated beam with dynamic target light intensity. The modulated beam is split into a measurement beam and a reference beam after passing through a beam splitter. The measurement beam is incident on the wafer through a flexible probe to form a reflected beam. The flexible probe transmits the measurement beam and the reflected beam and moves adaptively along the optical axis to keep the flexible probe in contact with the polishing pad transmission window of the wafer polishing equipment during the polishing process. The light intensity measurement values ​​of the reflected beam and the reference beam are collected in real time by the light detection module. The intensity measurement value of the reflected beam is calibrated based on the intensity measurement value of the reference beam to obtain the intensity calibration value of the reflected beam. Based on the light intensity calibration value of the reflected beam, the measured reflectance spectrum of the reflected beam is calculated; Based on the measured reflectivity spectrum of the reflected beam, the film thickness value of the wafer is extracted in real time, and the polishing of the wafer is terminated when the film thickness value reaches the preset target value.

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