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

Abstract

The invention relates to a wafer film thickness measuring device, a wafer film thickness measuring method, wafer polishing equipment and a wafer polishing method. The wafer film thickness measuring device comprises a light source used for providing an illumination source light beam; the light source energy adjusting module is used for adjusting and controlling the light intensity of the source light beam to obtain a modulated light beam with dynamic target light intensity; the beam splitter is used for splitting the modulation light beam to generate a measurement light beam and a reference light beam; the flexible probe is used for transmitting a measurement light beam and a reflection light beam, and the flexible probe moves in a self-adaptive mode in the optical axis direction so that the flexible probe can make contact with a grinding pad transmission window of the wafer polishing equipment in the grinding process; the light detection module is used for collecting a light intensity measurement value of the reference light beam and a light intensity measurement value of the reflected light beam; the processing unit calibrates 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 determines the film thickness of the wafer based on the light intensity calibration value of the reflected light beam. The film thickness measuring precision is improved, and the service life of the transmission window is prolonged.

Description

TECHNICAL FIELD

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

[0002] Chemical mechanical polishing (CMP) is an important process step in the manufacturing process of semiconductor integrated circuit chips. Furthermore, with the development of semiconductor technology, in order to achieve better and more reliable device performance, it is particularly important to use a wafer film thickness measuring device to control the process of film thickness variation within a wafer (WIW) and between wafers (WTW) during the CMP process performed by a wafer polishing apparatus.

[0003] In the related art, mainly the eddy current endpoint measurement, laser endpoint measurement and white light endpoint measurement methods are used to monitor the characteristics of the film layer during the CMP process, so as to appropriately control and stop the removal process. Among them, the eddy current technology controls the polishing endpoint by measuring the eddy current signal generated by the metal film layer on the wafer surface. The laser technology and the white light technology are mainly used for the endpoint measurement of the dielectric film. The laser technology analyzes the film thickness variation by detecting the single-wavelength interference light intensity of the dielectric film layer. Since the amount of information detected is less, the measurement accuracy and reliability of the laser technology are relatively low, which cannot meet the process requirements of advanced nodes of semiconductors. The white light technology uses a wide spectrum light source and a detector to increase the measurement information and effectively improve the measurement accuracy.

[0004] Among them, for the white light technology, during the film thickness measurement process using the wafer film thickness measuring device during the CMP process performed by the wafer polishing apparatus, the light transmittance of the polishing pad transmission window will gradually decrease due to grinding, which will cause the light intensity of the measurement light beam and the reflected light beam to gradually decrease after being transmitted through the polishing pad transmission window, and then affect the accuracy of the film thickness measurement. At the same time, in order to maintain the intensity of the reflected light beam, the polishing pad transmission window needs to be frequently replaced, which causes waste of time and resources.

[0005] During the grinding process, the wafer polishing apparatus cannot maintain good contact between the flexible probe and the polishing pad transmission window due to problems such as vibration and structural precision, which will further change the distance between the flexible probe and the polishing pad transmission window and the wafer, and frequent maintenance is required.

[0006] In addition, the light source of the wafer polishing apparatus is generally a pulsed light source, and the light intensity of the illumination source light beam provided by the light source will fluctuate to some extent, which will eventually cause the reflected light beam used to obtain the wafer film thickness to fluctuate.

[0007] The above problems will cause the wafer polishing apparatus to have inaccurate wafer film thickness measurement, frequent maintenance and high use cost. SUMMARY

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

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

[0010] a light source configured to provide an illumination source light beam;

[0011] a light source energy adjustment module configured to adjust the light intensity of the source light beam to obtain a modulated light beam with a dynamic target light intensity;

[0012] a beam splitter configured to split the modulated light beam to generate a measurement light beam and a reference light beam;

[0013] a flexible probe configured to transmit 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 a polishing pad transmission window of the wafer polishing apparatus during polishing, wherein the measurement light beam forms the reflected light beam after being incident on the wafer through the flexible probe;

[0014] a light detection module configured to collect the light intensity measurement value of the reference light beam and the light intensity measurement value of the reflected light beam;

[0015] a processing unit configured to calibrate the light intensity measurement value of the reflected light beam based on the light intensity measurement value of the reference light beam to obtain a light intensity calibration value of the reflected light beam, and determine the film thickness of the wafer based on the light intensity calibration value of the reflected light beam.

[0016] According to a second aspect of the embodiments 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 one of the embodiments of the first aspect, and the wafer film thickness measurement method comprises:

[0017] During wafer polishing, the light intensity of the illumination source light beam provided by the light source is adjusted by the light source energy adjustment module to obtain a modulated light beam with a dynamic target light intensity, the modulated light beam generates a measurement light beam and a reference light beam after passing through the beam splitter, the measurement light beam forms a reflected light beam after being incident on the wafer through the flexible probe, the flexible probe transmits the measurement light beam and the 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;

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

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

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

[0021] According to a third aspect of the embodiments of the present disclosure, a wafer polishing device is provided, which comprises the wafer film thickness measuring device of the first aspect or any one of the embodiments of the first aspect.

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

[0023] In the process of polishing a product wafer using a wafer polishing device, the light intensity of the illumination source light beam provided by the light source is adjusted by the light source energy adjustment module to obtain a modulation light beam with a dynamic target light intensity, the modulation light beam generates a measurement light beam and a reference light beam after passing through a beam splitter, and the measurement light beam forms a reflected light beam after being incident on the wafer through a flexible probe; the flexible probe transmits the measurement light beam and the reflected light beam and moves adaptively along the optical axis direction to keep the flexible probe in contact with the polishing pad transmission window of the wafer polishing device during the polishing process.

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

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

[0026] The measured reflectivity spectrum of the reflected light beam is calculated based on the light intensity calibration value of the reflected light beam.

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

[0028] The technical solutions provided by the embodiments of the present disclosure can have the following beneficial effects: in the embodiments of the present disclosure, when the transmittance of the polishing pad window changes with the polishing process, the light intensity of the illumination source light beam provided by the light source is adjusted in time by the energy adjustment module to obtain a modulation light beam with a dynamic target light intensity that matches the transmittance of the polishing pad window, so that the energy of the light beam irradiated to the wafer surface remains stable, thereby reducing the fluctuation of the light intensity of the light beam reflected from the wafer surface, improving the accuracy and stability of the measurement result, i.e., the wafer film thickness measurement can still be met when the transmittance of the polishing pad transmission window changes in a large range, the measurement accuracy is guaranteed, and the polishing pad transmission window can still be used even in the case of large wear of the polishing pad transmission window, thereby prolonging 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] The flexible probe can be self-adaptively moved along the optical axis direction, so that the flexible probe can keep in contact with the polishing pad transmission window to maintain a certain pressure when the wafer polishing equipment is in an adverse situation such as vibration, so that a stable reflected light beam signal is obtained, the measurement accuracy of the wafer film thickness is improved, and frequent maintenance caused by displacement of the flexible probe relative to the polishing pad transmission window is avoided.

[0030] The measurement light beam passes through the polishing pad transmission window to be incident on the wafer, and is reflected by the wafer to form a reflected light beam. The reflected light beam is incident on the flexible probe again through the polishing pad transmission window, and finally reaches the light detection module. The light beam will have a large light intensity loss in the process. The reference light beam is formed by splitting the modulated light beam, and the reference light beam is directly incident on the light detection module, so that the light intensity loss is small, and the light intensity change of the illumination source light beam provided by the light source can be accurately reflected. The light intensity measurement value of the reference light beam is used to calibrate the light intensity measurement value of the reflected light beam, so that the fluctuation of the light intensity measurement value of the reflected light beam caused by the fluctuation of the light intensity of the light source is effectively compensated, and the measurement accuracy of the wafer film thickness is improved.

[0031] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0032] The accompanying drawings, which are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present disclosure and, together with the specification, serve to explain the principles of the present disclosure.

[0033] Figure 1 is a structural schematic diagram of a wafer polishing equipment related in the related art.

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

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

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

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

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

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

[0040] Figure 8 FIG. 1 is a structural schematic diagram of a wafer film thickness measurement device according to an example embodiment.

[0041] Figure 9 FIG. 2 is a schematic diagram of the positional relationship between a flexible probe and a polishing plate according to an example embodiment.

[0042] Figure 10 FIG. 3 is a structural schematic diagram of a wafer polishing device according to an example embodiment.

[0043] Figure 11 FIG. 4 is a flowchart of a wafer film thickness measurement method according to an example embodiment.

[0044] Figure 12 FIG. 5 is a flowchart of a method for determining the film thickness of a wafer based on the intensity calibration value of a reflected light beam according to an example embodiment.

[0045] Figure 13A FIG. 6 is a flowchart of a method for real-time adjustment of the light source energy in a wafer film thickness measurement method according to an example embodiment.

[0046] Figure 13B FIG. 7 is a flowchart of a method for real-time adjustment of the light source energy in a wafer film thickness measurement method according to an example embodiment.

[0047] Figure 14 FIG. 8 is a flowchart of a wafer polishing method according to an example embodiment.

[0048] Figure 15 FIG. 9 is a flowchart of a method for creating a correspondence relationship library according to an example embodiment. DETAILED DESCRIPTION

[0049] The example embodiments will be described in detail herein with reference to the attached drawings. In the following description, the same numbers refer to the same or similar elements throughout the drawings. The implementations described in the following example embodiments are not meant to represent all implementations consistent with the present disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the present disclosure as detailed in the appended claims.

[0050] The wafer film thickness measurement device provided by the present disclosure is mainly applied to CMP. In an example, the wafer film thickness measurement device is used in a wafer polishing device.

[0051] Figure 1 FIG. 1 is a structural schematic diagram of a wafer film thickness measurement device according to an example embodiment. Figure 1As shown, the polishing disc 2A is fixed with the polishing pad 3A, the polishing head 4A carries the wafer 5A to make the wafer 5A adhere to the polishing pad 3A, the polishing disc 2A rotates by itself, the polishing head 4A rotates by itself and reciprocally displaces relative to the polishing disc 2A, so that the wafer 5A and the polishing pad 3A generate friction, which plays a polishing role. The spraying arm 7A sprays the polishing liquid through the nozzle, the polishing liquid is rotated by the polishing disc 2A, reaches the polishing head 4A, and contacts the wafer 5A through the groove structure on the polishing pad 3A, which plays a chemical polishing role. The polishing pad trimmer 6A cleans and corrects the polishing pad 3A.

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

[0053] The wafer film thickness measuring device related to the related art has the problems of unadjustable light source energy, poor spectral signal quality and poor process adaptability of the probe in the process of applying the white light endpoint measurement technology in the CMP.

[0054] Therefore, the wafer film thickness measuring device is provided.

[0055] Figure 2 The wafer film thickness measuring device is provided. Figure 2 As shown, the wafer film thickness measuring device 1 includes a light source 11, a light source energy adjustment module 12, a beam splitter 14, a flexible probe 13, a light detection module 15 and a processing unit.

[0056] The light source 11 is used to provide an illumination source light beam. The light source energy adjustment module 12 is used to regulate the light intensity of the source light beam to obtain a modulated light beam with a dynamic target light intensity. The beam splitter 14 is used to split the modulated light beam to generate a measurement light beam and a reference light beam. The flexible probe 13 is used to transmit the measurement light beam and the reflected light beam, and the flexible probe 13 is adapted to move along the optical axis direction to keep contact with the polishing pad transmission window of the wafer polishing equipment during the polishing process, wherein the measurement light beam forms a reflected light beam after being incident to the wafer through the flexible probe 13. The light detection module 15 is used to collect the light intensity measurement value of the reference light beam and the light intensity measurement value of the reflected light beam. The processing unit (not shown in the figure) calibrates 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 determines the film thickness of the wafer based on the light intensity calibration value of the reflected light beam.

[0057] The wafer film thickness measuring device provided by the embodiments of the present disclosure has the following advantages. On the one hand, the light source energy adjusting module 12 is added at the end of the light source 11, so that the energy of the light source 11 can be adjusted in time in the case of the change of the light transmittance of the polishing pad transmission window, the modulated light beam with the dynamic target light intensity matched with the light transmittance of the polishing pad window is obtained, and the energy of the light beam irradiated to the wafer surface is kept stable, so as to reduce the light intensity fluctuation of the light beam reflected from the wafer surface and improve the accuracy and stability of the measurement result.

[0058] On the other hand, the beam splitter 14 is arranged to split the modulated light beam obtained by the light source energy adjusting module 12 to generate a measurement light beam and a reference light beam. The measurement light beam irradiates to the wafer through the flexible probe 13 to form a reflected light beam, and the reflected light beam is collected by the flexible probe 13 and then enters the light detection module 15. The reference light beam directly enters the light detection module 15. The reference light beam and the reflected light beam are derived from the same source light beam, so the intensity fluctuation trend is consistent, and the light intensity measurement value of the reference light beam can be used to calibrate the light intensity measurement value of the reflected light beam, so as to correct the light path signal fluctuation of the measurement light beam caused by the light source energy fluctuation in real time and improve the stability of the measurement light beam signal. Then, the light intensity calibration value of the reflected light beam is used to determine the film thickness of the wafer, so as to improve the accuracy and stability of the film thickness measurement.

[0059] In addition, the flexible probe 13 can be automatically moved along the optical axis direction. The flexible probe 13 is arranged to be in contact with the polishing pad transmission window during the polishing process. Compared with the non-flexible probe (a probe connected by a rigid member) in the related art, the flexible probe 13 can automatically compensate the position change of the probe caused by the high-speed movement of the polishing disc, so as to keep the relative position and pressure of the probe and the polishing pad window, keep the flexible probe 13 in contact with the polishing pad transmission window of the wafer polishing equipment, and further reduce the influence of the movement on the measurement signal during the polishing process. The use of the flexible probe scheme can also reduce the maintenance frequency of the probe and avoid the difficulty in restoring the performance of the equipment caused by the disassembly of the polishing pad for debugging the probe.

[0060] In the embodiments of the present disclosure, the light source 11 is a white light source with a wide spectrum. For example, in order to increase the service life of the light source and reduce the exposure time of the light on the wafer, the light source 11 is a pulsed xenon lamp light source to provide a pulsed illumination source light beam. Of course, the present disclosure is not limited to this, and those skilled in the art can also replace it with a laser light source or other light source according to the needs.

[0061] The stability of the xenon lamp light source is relatively poor, resulting in poor stability of the collected signal of the reflected light beam. In the embodiments of the present disclosure, the light source 11 can be adjusted by the light source energy adjustment module 12 to provide a light source light beam with a required initial target light intensity at the beginning of polishing. As the polishing proceeds, the light transmittance of the polishing pad transmission window decreases, and the light intensity of the source light beam is dynamically adjusted in real time by controlling the light source energy adjustment module 12 to be another target light intensity required, so as to reduce the influence of the change of the light intensity of the measurement light beam irradiating the wafer surface on the film thickness measurement, so that the light intensity of the reflected light beam received by the light detection module 15 can be kept stable as a whole, and the measurement accuracy of the film thickness is improved.

[0062] In the embodiments of the present disclosure, after the modulated light beam is split into the measurement light beam and the reference light beam by the beam splitter 14, the reference light beam is directly incident on the light detection module 15, and the measurement light beam is incident on the wafer through the flexible probe 13. The wafer reflects the measurement light beam to form a reflected light beam, and the reflected light beam is incident on the light detection module 15 through the flexible probe 13.

[0063] The reference light beam is directly incident on the light detection module 15 from the beam splitter 14, and the light intensity of the reference light beam has less loss on the corresponding transmission light path of the reference light beam, and can accurately reflect the light intensity fluctuation of the modulated light beam. The measurement light beam and the reference light beam are split from the source light beam of the same light source 11 in the beam splitter 14, and the change trends of the two are the same, so the light intensity of the reflected light beam received by the light detection module 15 can be calibrated by the change of the reference light beam, the influence of the light intensity fluctuation of the light source 11 on the light intensity of the reflected light beam received by the light detection module 15 is avoided, and the measurement accuracy of the wafer is improved.

[0064] In the embodiments of the present disclosure, the flexible probe 13 capable of moving along the optical axis direction is arranged to maintain contact with the polishing pad transmission window to maintain a certain pressure when the wafer polishing equipment is in an adverse situation such as vibration, so that a stable reflected light beam signal is obtained, the measurement accuracy of the wafer film thickness is improved, and the problem of frequent maintenance caused by the displacement of the flexible probe 13 relative to the polishing pad transmission window is solved.

[0065] In the embodiments of the present disclosure, the light detection module 15 includes a light beam collection element capable of detecting light intensity, which is used to acquire the light intensity of the measurement light beam and the reflected light beam in real time.

[0066] In some embodiments, the light detection module 15 can include one light beam collection element, and the reference light beam and the measurement light beam are collected by the same light beam collection element.

[0067] In some embodiments, the light detection module 15 can include two light beam collection elements, and the two light beam collection elements collect the reference light beam and the measurement light beam respectively. For example, as shown in FIG. 2, the light detection module 15 includes two light beam collection elements 151 and 152, and the reference light beam and the measurement light beam are collected by the two light beam collection elements respectively. Figure 3As shown, the light detection module 15 can include a reflected light beam collection element 151 and a reference light beam collection element 152. The measurement light beam generated by the beam splitter 14 is directly incident on the reflected light beam collection element 151, and the reflected light beam reflected by the wafer is incident on the reflected light beam collection element 151.

[0068] Figure 4 is a schematic diagram of a light source energy adjustment module structure according to an example embodiment. As shown, Figure 4 As shown, the light source energy adjustment module 12 includes a plurality of light filtering elements 121 having different light transmittances and a rotary driving mechanism 122. The plurality of light filtering elements 121 are arranged around the rotation axis of the rotary driving mechanism 122, and the rotary driving mechanism 122 drives the plurality of light filtering elements 121 to rotate, so that the source light beam is transmitted from a target light filtering element 121 among the plurality of light filtering elements 121 to obtain a modulated light beam having a dynamic target light intensity.

[0069] When polishing the wafer, the wear of the polishing pad transmission window is a gradual process, and the decrease of the light transmittance is also a gradual process. At different stages, a modulated light beam having a different light intensity, i.e., a dynamic target light intensity, is needed to cooperate with the polishing pad transmission window having a different light transmittance.

[0070] In the embodiments of the present disclosure, by arranging the plurality of light filtering elements 121 and the rotary driving mechanism 122, the position of the plurality of light filtering elements 121 can be switched by the rotary driving mechanism 122, so that the source light beam is selectively transmitted from different light filtering elements 121 to form a modulated light beam having a dynamic target light intensity. The selected light filtering element 121 is different, and the light intensity of the modulated light beam formed after the source light beam is transmitted through the light filtering element 121 is also different. By arranging the plurality of light filtering elements 121, the number of light transmittance levels is increased, and the number of light intensity levels of the modulated light beam is also increased. The more the light intensity levels of the modulated light beam, the smaller the difference between different light intensity levels, and the more the modulated light beam can cooperate with the continuously decreasing light transmittance of the polishing pad transmission window, thereby reducing the influence of the decrease of the light transmittance of the polishing pad transmission window on the wafer film thickness measurement accuracy.

[0071] Figure 5 is a schematic diagram of a light source energy adjustment module structure according to an example embodiment. As shown, Figure 5 As shown, the light source energy adjustment module 12 includes a reciprocating driving mechanism 123 and a light filtering element 121 having a gradually changing light transmittance. The reciprocating driving mechanism 123 drives the light filtering element 121 having the gradually changing light transmittance to reciprocate along the light transmittance changing direction, so that the source light beam is transmitted from a region having a target light transmittance in the light filtering element 121 having the gradually changing light transmittance to obtain a modulated light beam having a dynamic target light intensity.

[0072] In the embodiments of the present disclosure, the light filtering element 121 is arranged to have a gradual change in transmittance. When the reciprocating driving mechanism 123 drives the light filtering element 121 having a gradual change in transmittance in the direction of the gradual change in transmittance, the source light beam is transmitted from the portions of the light filtering element 121 having different transmittance, thereby forming a modulated light beam having different target light intensities. The modulated light beam having different target light intensities is combined with the polishing pad transmission window, thereby improving the accuracy of wafer film thickness measurement.

[0073] In some embodiments, the light filtering element 121 having a gradual change in transmittance is arranged to have a gradual change in transmittance from one end to the other end.

[0074] In some embodiments, the light filtering element 121 having a gradual change in transmittance can have a step change in transmittance or a continuous change in transmittance. Those skilled in the art can choose as needed, and the present disclosure does not limit this.

[0075] In some embodiments, as shown in Figure 6 the light filtering element having a gradual change in transmittance can be replaced by a plurality of linearly arranged light filtering elements 121 having different transmittance.

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

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

[0078] In some embodiments, an auxiliary light source is arranged in the light source energy adjustment module 12. The auxiliary light source and the light filtering element 121 are arranged at the same time, so that the light source energy adjustment module 12 can have the functions of reducing, keeping unchanged, or increasing the light intensity of the source light beam provided by the light source 11.

[0079] In the embodiment of the present disclosure, the light source energy adjustment module 12 regulates the light beam of the illumination source. At the beginning of the grinding, the transmittance of the grinding pad transmission window is high, and a modulated light beam with a first target light intensity matching the transmittance of the grinding pad window at this time is obtained. As the grinding proceeds, a modulated light beam with a second target light intensity matching the transmittance of the grinding pad window at this time is obtained. In this way, the light source energy adjustment module 12 adjusts adaptively based on the change of the transmittance of the grinding pad window, so that the energy of the light beam irradiating the wafer surface remains stable, thereby reducing the light intensity fluctuation of the light beam reflected from the wafer surface and improving the accuracy and stability of the measurement result. The light source energy adjustment module 12 in the embodiment of the present disclosure can obtain a modulated light beam with a dynamic target light intensity according to actual needs, has a wide adjustable range, and thus can still meet the needs of wafer film thickness measurement when the transmittance of the grinding pad transmission window changes in a large range. Further, the light source energy adjustment module 12 related by the embodiment of the present disclosure enables the grinding pad transmission window to be used even in the case of heavy wear, prolonging 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 comprises a fiber-optic beam splitter. The modulated light beam is split into the reference light beam and the measurement light beam by the fiber-optic beam splitter, and the measurement light beam incident on the wafer and the reflected light beam reflected from the wafer are separated by the fiber-optic beam splitter.

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

[0082] Figure 7 is a structure diagram of a wafer film thickness measurement device according to an exemplary embodiment. As shown in Figure 7 The fiber-optic beam splitter comprises four port optical fibers 143 and corresponding fiber-optic interfaces 144. One port optical fiber 143 is connected to the light source energy adjustment module 12 and one fiber-optic interface 144, and is used to carry the modulated light beam. Another port optical fiber 143 is connected to the same fiber-optic interface 144 and the light detection module 15, and is used to carry the reference light beam. Still another port optical fiber 143 is connected to the same fiber-optic interface 144 and the flexible probe 13, and is used to carry the measurement light beam. The remaining port optical fiber 143 is connected to the flexible probe 13 and the light detection module 15, and is used to carry the reflected light beam. The ports of the port optical fibers 143 can play a connecting role.

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

[0084] In some embodiments, the beam splitter 14 comprises a beamsplitter.

[0085] The beamsplitter is a device that can allow part of the light beam irradiated onto the beamsplitter to be transmitted and part of the light beam to be reflected. There are various implementations and specific structures, which are not limited in the present disclosure.

[0086] In the embodiments of the present disclosure, the beamsplitter uses a beamsplitter to complete the work of generating the measurement light beam and the reference light beam from the modulated light beam. The corresponding light beam can be generated by setting the angle and position of the beamsplitter, and the structure is simple.

[0087] Figure 8 is a structural schematic diagram of a wafer film thickness measurement device according to an exemplary embodiment. As shown in Figure 8 The beamsplitter comprises a first beamsplitter 141 and a second beamsplitter 142. The modulated light beam emitted from the light source energy adjustment module 12 is irradiated onto the first beamsplitter 141. Part of the modulated light beam is transmitted through the first beamsplitter 141 to form a reference light beam, which is directly incident on the light detection module 15. Part of the modulated light beam is reflected by the first beamsplitter 141 to form a measurement light beam, which is irradiated towards the wafer. After being reflected by the wafer, a reflected light beam is formed, which is incident on the light detection module 15.

[0088] In some embodiments, the beamsplitter comprises a first beamsplitter 141 and a second beamsplitter 142. The modulated light beam emitted from the light source energy adjustment module 12 is irradiated onto the first beamsplitter 141. Part of the modulated light beam is reflected by the first beamsplitter 141 to form a reference light beam, which is directly incident on the light detection module 15. Part of the modulated light beam is transmitted through the first beamsplitter 141 to form a measurement light beam, which is irradiated towards the wafer. After being reflected by the wafer, a reflected light beam is formed, which is incident on the light detection module 15.

[0089] In some embodiments, the measurement light beam emitted from the first beamsplitter 141 is transmitted through the second beamsplitter 142, irradiated towards the wafer after passing through the second beamsplitter 142, and forms a reflected light beam after being reflected by the wafer. The reflected light beam is reflected by the second beamsplitter 142 and irradiated onto the light detection module 15.

[0090] In some embodiments, the measurement light beam emitted from the first beamsplitter 141 is reflected by the second beamsplitter 142 after passing through the second beamsplitter 142, irradiated towards the wafer, and forms a reflected light beam after being reflected by the wafer. The reflected light beam is transmitted through the second beamsplitter 142 and irradiated onto the light detection module 15.

[0091] In the embodiments of the present disclosure, the beamsplitter uses a beamsplitter as the beam splitter. The beamsplitting effect can be achieved by directly irradiating the light beam on the beamsplitter, without the need to set a medium for the light beam. The distance between the light source energy adjustment module and the beamsplitter, the light detection module, and the flexible probe can be flexibly adjusted without considering the volume of the light beam medium, making the entire device more flexible to set.

[0092] The following describes an implementation process of calibrating the light intensity measurement value of the reflected light beam based on the light intensity measurement value of the reference light beam by the processing unit to obtain the light intensity calibration value of the reflected light beam.

[0093] In the embodiments of the present disclosure, the light intensity calibration value of the reference light beam is obtained by the light detection module collecting the light intensity measurement value of the reference light beam multiple times and averaging the values. represents the light intensity calibration value of the reference light beam obtained by averaging the light intensity measurement values of the reference light beam collected n times. n is a positive integer.

[0094] In the embodiments of the present disclosure, the light intensity calibration value of the reference light beam is obtained by the light detection module collecting the light intensity measurement value of the reference light beam in real time during the grinding process, and collecting the light intensity measurement value of the reflected light beam in real time. mea represents the light intensity measurement value of the reflected light beam collected in real time. represents the light intensity calibration value of the reflected light beam. ref represents the light intensity measurement value of the reference light beam collected in real time during the grinding process.

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

[0096]

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

[0098] The source light beam provided by the light source is actually not stable, and the light intensity of the source light beam fluctuates to a certain extent. The film thickness measurement of the wafer is based on the light intensity of the reflected light beam received by the light detection module for analysis and calculation, so the fluctuation of the light intensity of the source light beam provided by the light source will directly affect the film thickness measurement accuracy of the wafer.

[0099] In the embodiments of the present disclosure, by setting the reference light beam which is homologous to the measurement light beam, using the fluctuation synchronization between the reference light beam and the measurement light beam, and calibrating the light intensity measurement value of the reflected light beam measured by the light detection module according to the fluctuation of the reference light beam, the film thickness of the wafer is obtained by using the light intensity calibration value of the reflected light beam after calibration, which can avoid the negative impact of the fluctuation of the light intensity of the source light beam on the measured film thickness accuracy of the wafer.

[0100] In the embodiments of the present disclosure, the light intensity calibration value of the reference light beam can be determined in advance using a standard sample (also referred to as a standard wafer). For example, before the wafer is polished, the energy adjustment module 12 adjusts the source light beam of the light source so that the reflected light beam collection element 151 and the reference light beam collection element 152 are in a high performance state, i.e., meet the requirements of the corresponding target light intensity. The reflected light beam collection element 151 and the reference light beam collection element 152 continuously collect the light intensity of the standard sample n times, respectively, and the average value of the light intensity of the standard sample collected by the reference light beam collection element 152 n times is obtained as follows.

[0101] In the embodiments of the present disclosure, in order to improve the accuracy of the light intensity calibration value of the reference light beam, the light intensity calibration value of the reference light beam needs to be updated regularly. For example, in an example, the present disclosure can preset the light transmittance of the polishing pad transmission window, which is the reference light transmittance of the polishing pad transmission window. When the real-time light transmittance of the polishing pad transmission window decreases below the preset light transmittance, it indicates that the polishing pad transmission window is severely worn, and the current modulated light beam cannot effectively transmit the polishing pad transmission window. The light intensity of the reflected light beam received by the light detection module is already very small and cannot meet the requirement of accurate measurement of the film thickness of the wafer. At this time, the control light source energy adjustment module increases the light intensity of the modulated light beam, and the determination of the light intensity calibration value of the reference light beam is re-performed.

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

[0103] In the embodiments of the present disclosure, the theoretical reflectivity spectrum of the wafer corresponding to different film thickness values can be determined by a modeling algorithm.

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

[0105] In the embodiments of the present disclosure, the measured reflectivity spectrum of the reflected light beam is calculated based on the calibrated light intensity calibration value of the reflected light beam, which can exclude the adverse effects of the light intensity fluctuation of the source light beam, thereby improving the measurement accuracy of the film thickness of the wafer.

[0106] The present disclosure also relates to the position relationship between the flexible probe of the wafer film thickness measuring device and the polishing plate. During the polishing process of the wafer, the wafer film thickness measuring device needs to rotate with the polishing plate. The probe in contact with the polishing pad transmission window may be displaced due to vibration, assembly accuracy and other factors when the polishing plate and the wafer film thickness measuring device rotate, which affects the measurement accuracy of the wafer film thickness. If the measurement accuracy of the wafer film thickness is to be maintained, the probe needs to be frequently reset, which increases the maintenance cost. To solve this problem, the present disclosure provides a flexible probe, and the position relationship between the flexible probe and the polishing pad transmission window satisfies that the flexible probe is always in contact with the polishing pad transmission window. Figure 9 A schematic diagram of the position relationship between the flexible probe and the polishing plate in an exemplary embodiment of the present disclosure is shown. As shown in Figure 9 The flexible probe 13 includes a probe optical fiber 131, a connecting piece 132, an elastic piece 133 and a position control piece 134.

[0107] The probe optical fiber 131 has a first port 1311 for transmitting a measurement light beam and a reflected light beam. The measurement light beam is incident on the wafer 5 through the first port 1311, and the reflected light beam is transmitted to the light detection module 15 after being received by the first port 1311.

[0108] The connecting piece 132 is arranged on the circumferential side of the probe optical fiber 131. The connecting piece 132 has a first connecting part 1321 and a second connecting part 1322. The first connecting part 1321 is connected to the circumferential side of the probe optical fiber 131.

[0109] One end of the elastic piece 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 position control piece 134 is threadedly connected to the main body of the wafer polishing equipment, and is used to regulate the compression state of the elastic piece 133 to make the elastic piece 133 drive the probe optical fiber 131 to move along the optical axis direction, so as to ensure that the first port 1311 maintains contact with the polishing pad transmission window 31 during the polishing process.

[0111] In the embodiment of the present disclosure, the probe optical fiber 131 is connected to the main body of the wafer polishing equipment by using the connecting piece 132 and the elastic piece 133, and the compression state of the elastic piece 133 is regulated by the position control piece, so as to utilize the elastic force of the elastic piece 133 to ensure that the probe optical fiber 131 moves adaptively along the optical axis direction to maintain the contact between the first port 1311 and the polishing pad transmission window 31 during the polishing process. This avoids the change of the position of the first port 1311 relative to the polishing pad transmission window 31 during the use, which affects the measurement accuracy of the wafer film thickness, and also avoids the negative impact of frequent adjustment of the first port 1311 of the probe optical fiber 131 on the maintenance work.

[0112] In some embodiments, 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 equipment 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: In the wafer grinding process, the light intensity of the illumination source light beam provided by the light source is adjusted by the light source energy adjustment module to obtain a modulated light beam with a dynamic target light intensity. The modulated light beam generates a measurement light beam and a reference light beam after passing through the beam splitter. The measurement light beam forms a reflected light beam after being incident on the wafer through the flexible probe. The flexible probe transmits the measurement light beam and the reflected light beam and moves adaptively along the optical axis direction to maintain contact between the flexible probe and the transmission window of the polishing pad of the wafer polishing equipment during the grinding process.

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

[0124] S103: The light intensity measurement value of the reflected light beam is calibrated based on the light intensity measurement value of the reference light beam to obtain a light intensity calibration value of the reflected light beam.

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

[0126] The light intensity of the light source will have certain fluctuations, which will cause the reflected light beam to also fluctuate. However, the factors affecting the light intensity of the reflected light beam are not only the fluctuations of the light source, but also the changes in the light transmission rate of the polishing pad transmission window and the film thickness of the wafer. Therefore, the fluctuations of the light intensity measurement value of the reflected light beam collected by the light detection module cannot completely represent the fluctuations of the light source. The reference light beam and the measurement light beam (reflected light beam) are homologous, so the fluctuations of the reference light beam and the measurement light beam are synchronized. The light intensity measurement value of the reflected light beam is calibrated based on the fluctuations of the light intensity measurement value of the reference light beam, which can eliminate the influence of the fluctuations of the light source on the light intensity of the reflected light beam, so that the obtained light intensity calibration value of the reflected light beam can more accurately reflect the film thickness of the wafer, and the measurement of the film thickness of the wafer is more accurate.

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

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

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

[0130] S201: Obtain a theoretical reflectivity 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: Regulate the light intensity of the illumination source light beam provided by the light source through the light source energy adjustment module, so as to improve the light intensity measurement values of the reference light beam and the reflected light beam collected by the light detection module.

[0143] In the embodiments of the present disclosure, after the light transmittance of the preset polishing pad transmission window is measured, the real-time light transmittance of the polishing pad transmission window is measured, so that the change of the light transmittance of the polishing pad transmission window can be accurately controlled, and the light source energy adjustment device can be accurately controlled, so as to obtain higher film thickness measurement accuracy.

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

[0145]

[0146] Of course, the light transmittance K at this time is not the accurate light transmittance of the polishing pad transmission window, because the wafer reflectivity and other factors also need to be considered. However, this light transmittance K can be used as the real-time light transmittance of the polishing pad transmission window, and the wafer reflectivity and other factors should be considered when the preset light transmittance is set, and a reasonable preset light transmittance value is set. Thus, the light source energy adjustment module is controlled and adjusted through the measurement of the light transmittance of the polishing pad transmission window.

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

[0148] In some embodiments, whether the light source energy adjustment module needs to be controlled and adjusted to change the light intensity of the modulation light beam can also be directly judged by the measured light intensity value of the reflected light beam. For example, when the measured light intensity value of the reflected light beam is lower than a preset value, it can be considered that the light transmittance of the polishing pad transmission window is reduced, and the light source energy adjustment module needs to be controlled to increase the light intensity of the modulation light beam.

[0149] In some embodiments, whether the light source energy adjustment module needs to be controlled and adjusted to change the light intensity of the modulation light beam can also be directly judged by measuring the wear degree of the polishing pad transmission window. When the wear degree is greater than a preset value, it can be considered that the light transmittance of the polishing pad transmission window is reduced, and the light source energy adjustment module needs to be controlled to increase the light intensity of the modulation light beam. The wear degree of the polishing pad transmission window can be measured by various methods, which are not limited in the present disclosure.

[0150] It should be noted that the wafer film thickness measurement method provided by the above embodiments of the present disclosure is similar to the wafer film thickness measurement implementation process of the wafer film thickness measurement device 1 provided by the above embodiments. For the wafer film thickness measurement method description is not detailed enough, can refer to the related description of the wafer film thickness measurement device 1, hereinafter will not be repeated.

[0151] Based on the same concept, the present disclosure also provides a wafer polishing device comprising the wafer film thickness measurement device 1 of the present disclosure.

[0152] The wafer polishing device is a device for removing excess material on the surface of the wafer or reducing the film thickness to a specified thickness. The wafer polishing device of the present disclosure can refer to a CMP device, or other wafer polishing devices.

[0153] Figure 10 is a schematic diagram of a wafer polishing device structure according to an exemplary embodiment. As shown in Figure 9 、 Figure 10 , the wafer polishing device comprises a rotatable polishing disc 2 and a polishing pad 3 laid on the polishing disc 2. Other structures can be provided between the polishing pad 3 and the polishing disc 2 as needed, which are not limited by the present disclosure. The polishing pad 3 is provided with a polishing pad transmission window 31 having light transmission capability. The wafer polishing device is provided with a receiving cavity 21, which is at least partially arranged in the polishing disc 2. And the receiving cavity 21 has an opening opposite to the polishing pad transmission window 31.

[0154] The wafer polishing device further comprises a polishing head 4 arranged above the polishing pad 3, the polishing head 4 is arranged away from the rotation center of the polishing pad 3, and the wafer 5 is arranged between the polishing head 4 and the polishing pad 3 and rotates under the drive of the polishing head 4 with the axis of the polishing head 4 as the rotation center. When polishing the wafer 5, the polishing disc 2 and the polishing head 4 rotate respectively to form grinding on the wafer 5. When the polishing disc 2 rotates, the wafer 5 is in contact with the polishing pad transmission window 31 at least part of the time.

[0155] The wafer film thickness measurement device 1 is arranged in the receiving cavity 21, and the wafer film thickness measurement device 1 comprises a flexible probe 13, the flexible probe 13 comprises a probe optical fiber 131, a connecting piece 132, a position control piece 134 and an elastic piece 133. Among them, the first port 1311 of the probe optical fiber 131 is directed to the polishing pad transmission window 31 and in contact with the polishing pad transmission window 31.

[0156] As shown in Figure 9 , the connecting piece 132 is arranged on the periphery of the probe optical fiber 131, the first connecting part 1321 of the connecting piece 132 is sleeved on the periphery of the probe optical fiber 131 and is fixedly connected with the periphery of the probe optical fiber 131, and the second connecting part 1322 of the connecting piece 132 extends outward from the circumferential edge of the first connecting part 1321, forming a ring-shaped second connecting part 1322.

[0157] An abutting portion 211 is arranged on the inner wall of the accommodating cavity 21, and the elastic member 133 is arranged between the second connecting portion 1322 and the abutting portion 211 and is in a compressed state. The elastic member 133 applies an elastic pushing force to the second connecting portion 1322 in the direction of the polishing pad transmission window 31. The elastic pushing force is transmitted to the probe optical fiber 131 through the first connecting portion 1321 via the second connecting portion 1322, so that the probe optical fiber 131 is kept in contact with the polishing pad transmission window 31, thereby avoiding the probe optical fiber 131 from being separated from the polishing pad 3 observation window due to vibration and other factors, reducing the measurement accuracy of the film thickness of the wafer 5, and avoiding frequent maintenance due to the separation of the probe optical fiber 131 from the polishing pad 3 observation window.

[0158] The position control member 134 is threadedly connected with the inner wall of the accommodating cavity 21 and is arranged above the second connecting portion 1322. During installation, the flexible probe 13 is arranged upward along the accommodating cavity 21 from below the polishing disc 2, and the elastic member 133, the connecting member 132, and the position control member 134 are sequentially arranged into the upper opening of the accommodating cavity 21. The position control member 134 is screwed into the accommodating cavity 21 and comes into contact with the second connecting portion 1322, and is further screwed in and compresses the elastic member 133. At least part of the probe optical fiber 131 protrudes out of the opening of the accommodating cavity 21. The polishing pad 3 with the polishing pad transmission window 31 is arranged on the polishing disc 2. The first port 1311 of the probe optical fiber 131 is in contact with the polishing pad transmission window 31. The first port 1311 of the probe optical fiber 131 is moved toward the inside of the accommodating cavity 21 under the pressure of the polishing pad transmission window 31. The elastic member 133 is further compressed, and the position control member 134 is separated from the second connecting portion 1322 of the connecting member 132.

[0159] In the embodiment of the present disclosure, the position control member 134 connected with the inner circumferential wall of the accommodating cavity 21 is arranged to limit the probe optical fiber 131, so as to avoid the probe optical fiber 131 from being damaged due to the excessive elastic force of the elastic member 133 pushing the polishing pad transmission window 31 out.

[0160] The wafer polishing device further comprises a spraying arm 7 arranged above the polishing pad 3 and a polishing pad trimmer 6. The spraying arm 7 is used to spray polishing liquid to the polishing pad 3 to promote polishing. The polishing pad trimmer 6 is in contact with the polishing pad 3 and is used to clean and trim the surface of the polishing pad 3.

[0161] The present disclosure further provides a wafer polishing method using the wafer polishing device of the present disclosure. As shown in FIG. 8, the wafer polishing method comprises the following steps. Figure 14

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

[0163] S502: The light intensity measurement value of the reflected light beam and the light intensity measurement value of the reference light beam are collected in real time by the light detection module.

[0164] S503: The light intensity measurement value of the reflected light beam is calibrated based on the light intensity measurement value of the reference light beam to obtain a light intensity calibration value of the reflected light beam.

[0165] S504: The measured reflectivity spectrum of the reflected light beam is calculated based on the light intensity calibration value of the reflected light beam.

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

[0167] In the embodiments of the present disclosure, the reference light beam is homologous to the measurement light beam, and the fluctuation of the reference light beam can represent the fluctuation of the measurement light beam. The light intensity measurement value of the reflected light beam is calibrated based on the light intensity measurement value of the reference light beam, which can eliminate the influence of light source fluctuation on the reflected light beam, so that the measured reflectivity spectrum obtained by the light intensity calibration value of the reflected light beam is more accurate. Furthermore, the determination of the film thickness based on the measured reflectivity spectrum and the determination of the termination of the polishing of the product wafer can be more accurate.

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

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

[0170] The target value of the film thickness in step S505 refers to the film thickness corresponding to the product wafer sample when the polishing is terminated.

[0171] The real-time film thickness value of the product wafer can be obtained by the following method: pre-storing different theoretical reflectivity spectra and wafer film thickness values corresponding to the different theoretical reflectivity spectra to establish a corresponding relationship library, finding a corresponding theoretical reflectivity spectrum in the corresponding relationship library based on the measured reflectivity spectrum of the reflected light beam, and extracting 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 the corresponding relationship library, the corresponding wafer film thickness can be directly mapped from the measured reflectivity spectrum in a mapping manner, without the need for further calculation, thereby reducing the burden on the hardware and enabling faster reaction speed.

[0173] In some embodiments, the corresponding relationship library can further include the polishing time and the number of polishing disc rotations of the product wafer sample from the start of self-polishing to the end of polishing. When it is determined whether to terminate polishing of the wafer in step S506, the polishing time and the number of polishing disc rotations can be used as a judgment index together. When the polishing time, the number of polishing disc rotations, and the measured reflectivity spectrum match the target theoretical reflectivity spectrum corresponding to the target film thickness in the corresponding relationship library are satisfied at the same time, polishing of the product wafer can be terminated.

[0174] In the embodiments of the present disclosure, the polishing time and the number of polishing disc rotations are used as redundant judgment indexes, which can avoid judgment errors caused by accidental errors of the reflectivity spectrum and improve the accuracy of the polishing endpoint judgment.

[0175] In some embodiments, the embodiments of the present disclosure provide a method for creating a corresponding relationship library. As shown in Figure 15 The corresponding relationship library is pre-created in the following manner:

[0176] S601: Collecting the standard light intensity during polishing of the standard wafer sample by the wafer polishing device, and determining the reflectivity spectrum of the standard wafer sample based on the standard light intensity.

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

[0178] S602: Collecting the light intensity calibration value of the reflected light beam of the product wafer sample during polishing of the product wafer sample by the wafer polishing device.

[0179] It can be understood that the light intensity collected in S601 and S602 of the embodiments of the present disclosure can be the light intensity after calibration in the manner of calibrating the reflected light beam based on the reference light beam according to the above embodiments of the present disclosure.

[0180] S603: Calculating the theoretical reflectivity spectrum of the product wafer by formula (3).

[0181]

[0182] wherein R product is the theoretical reflectance spectrum of the product wafer sample, I is the light intensity calibration value of the reflected light beam, I stray is the light intensity measurement value outside the product wafer sample, I stdndard is the standard light intensity obtained during the polishing process of the standard wafer sample, R standard is the reflectance spectrum of the standard wafer sample.

[0183] I stray is the light intensity measurement value outside the product wafer sample, which can be obtained in the following manner:

[0184] the wafer is replaced with a black sample that does not reflect the light beam, and the light intensity measurement value of the reflected light beam at this time is obtained by the light detection module, that is, I stray , which is also called stray light intensity.

[0185] Of course, I stray may also be obtained by other methods, which are not limited in the present disclosure.

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

[0187] In the embodiments of the present disclosure, there are various methods for obtaining the wafer film thickness, such as measuring by using a special device, or calculating by using the reflectance spectrum, or other methods. Those skilled in the art can obtain the wafer film thickness in various ways, which are not limited in the present disclosure.

[0188] S605: Determine whether the polishing is to the target film thickness, if yes, execute S606, otherwise execute S602.

[0189] S606: Record the polishing time and the polishing disc rotation number.

[0190] S607: Store the different wafer film thicknesses and the corresponding theoretical reflectance spectra, store the polishing time and the polishing disc rotation number, and establish a corresponding relationship library.

[0191] In the embodiments of the present disclosure, the measured reflectance spectrum is obtained in a relatively simple manner, and the influence of the stray light intensity I stray is excluded, so that the measured reflectance spectrum obtained is relatively accurate, which is conducive to improving the control accuracy of the polishing focus.

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

[0193] In the process of adjusting the light intensity of the illumination source light beam provided by the light source by the light source energy adjustment module, the standard wafer sample can be placed at the polishing head 4, and the light source energy adjustment module 12 is readjusted so that the sample measurement light intensity and the reference light intensity received by the reflected light beam collection element 151 and the reference light beam collection element 152 are higher, and the reflected light beam collection element 151 and the reference light beam collection element 152 are in a high-performance state (high signal-to-noise ratio). If there is no light source energy adjustment module 12, the detection light intensity of the reflected light beam collection element 151 and the reference light beam collection element 152 is weak at this time, and the signal-to-noise ratio of the collected signal is significantly reduced, which will directly affect the stability of the film thickness measurement result.

[0194] In the embodiments of the present disclosure, when the real-time transmittance of the polishing pad transmission window decreases below the preset transmittance, it indicates that the polishing pad transmission window is severely worn, and the current modulated light beam cannot effectively transmit the polishing pad transmission window. The light intensity of the reflected light beam received by the light detection module is already very small, which cannot meet the demand of accurate measurement of wafer film thickness. At this time, the light source energy adjustment module is controlled to increase the light intensity of the modulated light beam, which can enhance the transmission capability of the measurement light beam and the reflected light beam to the polishing pad transmission window, so that the light detection 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 enables the transmittance of the polishing pad transmission window to still meet the use requirements when it changes in a large range, without the need to frequently replace the polishing pad transmission window, thereby reducing the use cost.

[0195] In the embodiments of the present disclosure, when applied to the CMP film thickness measurement device, the light source energy adjustment module, the flexible probe, and the reference light path (reference light beam) are provided. In the calibration and measurement method, the reflected light beam of the measurement light beam is corrected by the reference light beam, and the real-time energy adjustment is performed after the transmittance of the polishing pad transmission window is reduced. Therefore, not only the film thickness measurement accuracy and stability are improved, but also the service life of consumables is prolonged, the maintenance frequency is reduced, and the equipment use cost is reduced.

[0196] It can be understood that, in the present disclosure, "multiple" refers to two or more, and other quantifiers are similar. The association relationship of "and / or" describing the associated objects means that there can be three relationships, for example, A and / or B can represent the three cases of A existing alone, A and B existing together, and B existing alone. The character " / " generally represents that the associated objects before and after it are in an "or" relationship. The singular forms "a", "said" and "the" are also intended to include the plural forms, unless the context clearly indicates otherwise.

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

[0198] It can be further understood that the terms "center", "longitudinal", "transverse", "front", "back", "up", "down", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the embodiments and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation.

[0199] It can be further understood that, unless otherwise specified, "connection" includes direct connection between the two without other components, and also includes indirect connection between the two with other elements.

[0200] It can be further understood that, although the operations are described in a specific order in the embodiments of the present disclosure in the drawings, it should not be understood as requiring the operations to be performed in the specific order shown or in a serial order, or requiring all the operations to be performed to obtain the desired results. In a particular environment, multi-tasking and parallel processing can be advantageous.

[0201] Other embodiments of the present disclosure will be apparent to those skilled in the art with the consideration of the specification and practice of the invention disclosed herein. The present application is intended to cover any variations, uses, or adaptive changes of the present disclosure that follow the general principles of the present disclosure and include common knowledge or conventional techniques in the art that are not disclosed by the present disclosure. The specification and examples are only considered as exemplary, and the true scope and spirit of the present disclosure are indicated by the following claims.

[0202] It should be understood that the present disclosure is not limited to the precise construction that has been described above and shown in the accompanying drawings, and that various modifications and changes can be made by those skilled in the art without departing from the scope of the present disclosure. The scope of the present 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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