Film thickness measurement method and chemical mechanical polishing equipment

Abstract

The present invention provides a film thickness measurement method and chemical mechanical polishing equipment, wherein the method includes: obtaining the distance between a film thickness measurement device and a metal film and the material of the metal film; determining a corresponding calibration curve based on the distance and material, wherein the calibration curve is used to characterize the mapping relationship between the output signal of the film thickness measurement device and the film thickness; obtaining the output signal of the film thickness measurement device in real time; and obtaining the current film thickness of the metal film based on the calibration curve and the output signal.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical mechanical polishing, and in particular relates to a film thickness measurement method and chemical mechanical polishing equipment. Background Art

[0002] Integrated circuits are typically formed by sequentially depositing conductive, semiconducting, or insulating layers onto a silicon wafer. This results in a thin film of filler deposited on the wafer surface. During the manufacturing process, the filler layer must be continuously flattened until the patterned top surface is exposed, forming conductive paths between the raised patterns.

[0003] With the rapid development of integrated circuit manufacturing technology, the growth, characterization and non-contact precise thickness measurement of nanometer-scale metal films are extremely important. Specifically in the field of integrated circuit manufacturing, four probes are usually used to calibrate the thickness of the metal film on the wafer surface, but this method will cause the loss of the metal film on the wafer surface. Specifically in the chemical mechanical polishing process, eddy current sensors are usually used to measure the film thickness online, so as to control the process parameters of the polishing process, accurately remove the metal film on the wafer surface, and stop polishing when the specified thickness value is removed. The eddy current sensor system in the existing chemical mechanical polishing equipment mainly faces the problems of difficulty in achieving nanometer-scale thickness resolution, difficulty in achieving an edge measurement range beyond 140mm, and difficulty in measuring a variety of metal materials with the same sensor system. Summary of the Invention

[0004] In view of this, embodiments of the present invention provide a film thickness measurement method and a chemical mechanical polishing device, aiming to solve at least one of the technical problems existing in the prior art.

[0005] A first aspect of an embodiment of the present invention provides a film thickness measurement method, comprising:

[0006] Obtaining the distance between the film thickness measuring device and the metal film and the material of the metal film;

[0007] Determining a corresponding calibration curve according to the distance and material, wherein the calibration curve is used to characterize a mapping relationship between an output signal of a film thickness measuring device and the film thickness;

[0008] acquiring an output signal of the film thickness measuring device in real time;

[0009] The current film thickness of the metal film is obtained according to the calibration curve and the output signal.

[0010] A second aspect of an embodiment of the present invention provides a chemical mechanical polishing device, comprising:

[0011] a polishing plate covered with a polishing pad for polishing the wafer;

[0012] a polishing head, for holding a wafer and pressing the wafer onto the polishing pad;

[0013] a film thickness measuring device for measuring the film thickness of the wafer during polishing;

[0014] A control device is used to implement the film thickness measurement method as described above.

[0015] A third aspect of an embodiment of the present invention provides a control device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the film thickness measurement method described above when executing the computer program.

[0016] A fourth aspect of an embodiment of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the film thickness measurement method described above are implemented.

[0017] The beneficial effects of the present invention are that the film thickness of the metal film on the wafer can be accurately obtained, and the measurement linearity, precision and resolution are high. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The advantages of the present invention will become clearer and easier to understand through the detailed description made in conjunction with the following drawings, but these drawings are only exemplary and do not limit the scope of protection of the present invention, among which:

[0019] Figure 1 is a simplified schematic diagram of a chemical mechanical polishing apparatus provided by one embodiment of the present invention;

[0020] Figure 2 is a simplified schematic diagram of a chemical mechanical polishing apparatus provided by one embodiment of the present invention;

[0021] Figure 3 is a schematic diagram of a film thickness measuring device provided by one embodiment of the present invention;

[0022] Figure 4 is a three-dimensional diagram of a film thickness measuring device provided by one embodiment of the present invention;

[0023] Figure 5 is a cross-sectional view of a film thickness measuring device provided by one embodiment of the present invention;

[0024] Figure 6 This is a front view of a film thickness measuring device provided by one embodiment of the present invention;

[0025] Figure 7 is a cross-sectional view of a film thickness measuring device provided by one embodiment of the present invention;

[0026] Figure 8The equivalent circuit model is shown;

[0027] Figure 9 The relationship between inductance and copper film thickness is shown;

[0028] Figure 10 The resonant tank equivalent circuit model is shown;

[0029] Figure 11 The detection principle is shown;

[0030] Figure 12 1 is a flow chart of a film thickness measurement method provided by one embodiment of the present invention;

[0031] Figure 13 A calibration curve for a tungsten film is shown;

[0032] Figure 14 The edge measurement curve of the wafer obtained by using the present application is shown. DETAILED DESCRIPTION

[0033] The technical solutions of the present invention are described in detail below in conjunction with specific embodiments and the accompanying drawings. The embodiments described herein are specific embodiments of the present invention and are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be understood as limiting the embodiments of the present invention and the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the contents disclosed in the claims of this application and its specification, including technical solutions that adopt any obvious replacements and modifications to the embodiments described herein.

[0034] In order to illustrate the technical solution of the present invention, specific embodiments are provided below.

[0035] In this application, chemical mechanical polishing (CMP) is also referred to as chemical mechanical planarization, and wafer is also referred to as chip, silicon chip, base plate or substrate, which have the same meaning and actual function.

[0036] Chemical mechanical polishing is a method for achieving global planarization in integrated circuit manufacturing. Figure 1As shown, the chemical mechanical polishing apparatus 1 includes a polishing head 10, a polishing plate 20, a liquid supply module 30, and a wafer storage module (Loadcup) 40. Before polishing begins, wafers are stored in the wafer storage module 40. After loading the wafers from the wafer storage module 40, the polishing head 10 moves radially above the polishing plate 20 to the top. During polishing, the polishing head 10 presses the wafer against the polishing pad covering the surface of the polishing plate 20. The polishing head 10 also rotates and reciprocates radially along the polishing plate 20. Simultaneously, the polishing plate 20 rotates, and the liquid supply module 30 sprays polishing liquid onto the surface of the polishing pad. Under the chemical action of the polishing liquid, the relative movement between the polishing head 10 and the polishing plate 20 causes the wafer to rub against the polishing pad, resulting in polishing.

[0037] During the polishing process, it is necessary to monitor the wafer's film thickness changes and film thickness values ​​in real time so that appropriate polishing processes can be implemented to avoid over-polishing or incomplete polishing. Eddy current testing can be used to detect film thickness. The principle of eddy current testing is that when the sensor scans the wafer, the metal film layer on the wafer surface will induce eddy currents, causing the magnetic field generated by the sensor to change. As the metal film layer is removed by polishing, the sensor measures the eddy current changes and measures the film thickness of the metal film layer.

[0038] like Figure 2 As shown, chemical mechanical polishing equipment 1 includes a polishing head 10 for holding and rotating a wafer, a polishing platen 20 covered with a polishing pad 21, a liquid supply module 30 for providing polishing liquid, a sensor 51 for online wafer film thickness measurement, and a control device. Sensor 51 is located below the surface of polishing platen 20 and rotates with it, enabling online measurement during polishing.

[0039] like Figure 3 As shown, the polishing pad 21 is provided with a frosted glass window 22 at a corresponding position above the sensor 51. The sensor 51 is mounted on the polishing pad 21 below the frosted glass window 22 through the sealing ring 61 and the slot on the polishing plate 20.

[0040] like Figure 3 As shown, a packaging shell 60 is provided on the periphery of the sensor 51, and a groove is provided near the edge of the packaging shell 60 for accommodating the sensor 51. The packaging shell 60 is made of a transparent material, such as colorless transparent organic glass.

[0041] The space on the left side of the packaging shell 60 is used to encapsulate the sensor 51, and the space on the right side can be reserved for the optical detection system, so that the laser generated from the bottom of the packaging shell 60 can pass through the transparent packaging shell 60, the frosted glass window 22 on the polishing pad 21, and finally illuminate the wafer w to be inspected, and return to the receiver of the optical detection system.

[0042] An embodiment of the present invention provides a film thickness measuring device 50 that can obtain high thickness resolution, high edge resolution, and can detect the film thickness of metal films of various materials.

[0043] The film thickness measuring device 50 includes a sensor 51, a signal generating circuit 52, and a frequency discriminator 53.

[0044] The frequency discriminator 53 can be a slope frequency discriminator.

[0045] As Figures 4 to 7 shown, the sensor 51 includes a pot-shaped magnetic core 54 and a coil 55. The pot-shaped magnetic core 54 includes a bottom surface, an inner cylinder provided at the center of the bottom surface, and a peripheral wall provided at the periphery of the bottom surface. A coaxial through hole is provided at the center of the inner cylinder, and gaps are provided at symmetric positions on the peripheral wall. A multi-turn coil 55 is closely wound around the inner cylinder of the pot-shaped magnetic core 54.

[0046] The coil 55 is wound with enameled wire. The diameter of the enameled wire is generally selected from 0.05 mm to 0.15 mm, preferably 0.1 mm. The number of turns of the coil 55 can be 50 - 200 turns. The axis of the coil 55 needs to coincide with the axis of the pot-shaped magnetic core 54. It can be wound in a multi-layer close-wound manner. As Figure 5 shown, first wind X turns from the first layer, then wind the second layer, and wind up to the Y layer in sequence. During the winding process, on the premise of ensuring that the coil 55 is not damaged, by increasing the winding tension, the air gap between the coils 55 is minimized as much as possible, which can effectively reduce the parasitic capacitance of the coil 55 itself and ensure the consistency of different production batches. <000,0126>

[0047] The material of the pot-shaped magnetic core 54 is nickel-zinc ferrite or manganese-zinc ferrite. Preferably, nickel-zinc ferrite with a magnetic permeability of 1000 or manganese-zinc ferrite with a magnetic permeability of 2000 is selected, and the performance such as the temperature drift characteristic of the selected ferrite should be stable.

[0048] The size and shape of the pot-shaped magnetic core 54 are as Figure 6 and Figure 7 shown, where the diameter D of the coaxial through hole satisfies 0 < D < 1.2 mm, the outer diameter C of the inner cylinder satisfies 2 mm < C < 3 mm, the inner diameter B of the peripheral wall satisfies 7 mm < B < 10 mm, the outer diameter A of the peripheral wall satisfies 10 mm < A < 13 mm, the overall height E of the pot-shaped magnetic core 54 satisfies 4 mm < E < 5.5 mm, and the height F of the peripheral wall satisfies 2.5 mm < F < 4 mm.

[0049] The pot-shaped magnetic core 54 can not only well concentrate the magnetic field, making the magnetic field excited by the coil 55 more concentrated, and the region of the metal film perpendicular to the axial space range that can be detected is within the positive projection range of the outer diameter of the coil 55. Moreover, the structure of the pot-shaped magnetic core 54 has a magnetic shielding function by itself, which can well weaken the influence of the external electromagnetic field environment on the sensor 51. In addition, its structure is also convenient for winding and has a relatively large winding area.

[0050] Coil 55, as the core part of sensor 51, is mainly used to generate eddy currents in the metal film being measured, and convert the detected thickness signal into the impedance signal of the coil through the magnetic field energy coupling of the mutual inductance effect. The impedance signal contains resistance components and inductance components, and its variation is mainly related to the distance x between sensor 51 and the metal film being measured, the film thickness t of the metal film being measured, the resistivity σ and the frequency of the AC excitation. When other conditions remain unchanged, the thickness of the metal film can be inferred from the collected electrical signal. Compared with air core coils, coils with magnetic cores can make the magnetic field intensity excited by the sensor stronger and the spatial distribution of the magnetic field more concentrated below the sensor, thereby obtaining a greater inductance change sensitivity for thickness detection and enhancing the resolution in the thickness direction and lateral space.

[0051] The interaction between the coil 55 and the metal film to be measured is usually explained using a transformer equivalent model, and its equivalent circuit is as follows: Figure 8 As shown. The primary coil of the transformer can be equivalent to coil 55, in which the equivalent inductor L1 and the resistor R1 are connected in series. The secondary coil can be equivalent to the metal film to be measured, in which the equivalent inductor L2 and the resistor R2 are connected in series. Among them, the primary current is i1 and the secondary current is i2. According to Kirchhoff's voltage law:

[0052]

[0053] Where M is the mutual inductance, ω is the angular frequency, ω = 2πf.

[0054] From formula (1), the equivalent impedance Z of coil 55 can be obtained as:

[0055]

[0056] From this, the equivalent inductance L and equivalent resistance R of the coil 55 can be obtained as follows:

[0057]

[0058] When the metal film thickness changes while other conditions remain unchanged, the equivalent inductance L will also change.

[0059] Here, the normalized inductance value L′ is used for characterization, and the calculation formula is:

[0060]

[0061] Wherein, L0 is the reference inductance measured when the metal film thickness is 0.

[0062] If the normalized inductance value L' is known, the thickness t of the metal film to be measured can be calculated. Taking the copper metal film as an example, the relationship curve between the two is as follows: Figure 9 As shown. Figure 9 As can be seen from the figure, the normalized inductance value L' gradually decreases as the metal film thickness increases, and the rate of decrease increases initially and then decreases. This indicates that the smaller the thickness range of the measured metal film, the better the overall measurement linearity. Furthermore, within the sensor's measurement range, the smaller the thickness of the measured metal, the higher the inductance sensitivity.

[0063] In addition, due to the skin effect, the eddy current intensity in the conductor decreases exponentially as the depth of the conductor increases. For non-magnetic materials, the calculation formula for the skin depth is: Where f is the operating frequency, μ0 is the relative magnetic permeability of the conductor, and σ is the electrical conductivity of the conductor.

[0064] In order to accurately measure the thickness of the metal film, the skin depth at the selected operating frequency f must be greater than the maximum thickness of the metal film, that is, the electromagnetic field can completely penetrate the metal film to be measured.

[0065] During the measurement, the coil 55 is placed as follows Figure 10 In the equivalent circuit shown, L is the equivalent inductance, R is the equivalent resistance, and C is the capacitance of the sensor 51, which is composed of the parasitic capacitance of the coil 55 and the parallel capacitance. The resonant frequency of the circuit is f re It can be expressed as:

[0066]

[0067] According to the above formula, the equivalent inductance L and resonant frequency f can be derived re The relationship between:

[0068]

[0069] Since the coil 55 has a certain parasitic capacitance, the coil 55 has a self-resonant frequency f se The selection of the parallel resonant capacitor value must not only consider the skin depth, so that the excitation electromagnetic field at the resonant frequency can penetrate the metal film, but also generally make the resonant frequency f re Less than 0.7 times the self-resonant frequency f se , which can improve the stability of the film thickness measuring device 50.

[0070] In order to obtain the change of the loop resonant frequency of the film thickness measuring device 50 when the metal film thickness changes, and then calculate the equivalent inductance, the design is as follows: Figure 11 The detection system shown.

[0071] The signal generating circuit 52 provides a constant amplitude frequency modulated current signal within a certain frequency range to the coil 55. When the frequency of the constant amplitude frequency modulated current signal is Figure 10When the resonant frequency of the equivalent circuit shown is reached, the impedance value of the equivalent circuit will reach its maximum, and the output voltage signal at both ends will also be the maximum. Therefore, the slope frequency discriminator is used to perform frequency-amplitude conversion on the constant-amplitude frequency modulated current signal and the output voltage amplitude signal at both ends of the equivalent circuit to obtain the frequency corresponding to the maximum voltage amplitude, which is the resonant frequency f re . Set the resonant frequency f re The data is transmitted to the MCU and the equivalent inductance L is calculated according to formula (6).

[0072] The calibration curve to be used is determined according to the type of metal film material and the distance between the film thickness measuring device and the metal film. The resonant frequency f is converted to re The data is converted into the film thickness of the metal film and transmitted to the host computer to achieve the measurement of the metal film thickness.

[0073] Based on the above, another embodiment of the present invention provides a film thickness measurement method for chemical mechanical polishing. This method is suitable for measuring the film thickness of a wafer using an eddy current film thickness sensor, and the film layer on the surface of the wafer is a metal material, such as copper, aluminum, tungsten, cobalt, tantalum, titanium, etc.

[0074] like Figure 12 As shown, the film thickness measurement method provided by the embodiment of the present invention includes:

[0075] Step S1, obtaining the distance between the film thickness measuring device 50 and the metal film and the material of the metal film;

[0076] Step S2, determining a corresponding calibration curve according to the distance and material, wherein the calibration curve is used to represent a mapping relationship between an output signal of the film thickness measuring device 50 and the film thickness;

[0077] Step S3, obtaining the output signal of the film thickness measuring device 50 in real time;

[0078] Step S4: obtaining the current film thickness of the metal film according to the calibration curve and the output signal.

[0079] Specifically, step S1 includes: installing a film thickness measuring device 50 on the chemical mechanical polishing equipment 1 , and measuring the distance between the film thickness measuring device 50 and the metal film.

[0080] In the present application, a calibration curve is obtained in advance during the calibration process, and then the obtained calibration curve is used to perform data conversion during the measurement process to obtain the current film thickness of the metal film. The process is simple and the result is accurate.

[0081] In one embodiment, a calibration process is performed using a wafer sample with a known film thickness, that is, the calibration curve acquisition step includes:

[0082] Step a1: Obtain the installation distance between the sensor 51 and the metal film.

[0083] Before calibration, the sensor 51 is placed parallel to the wafer sample, and the sensor 51 is separated from the metal film on the wafer sample by a certain distance, which can be represented by x. Generally, the installation distance x is set to be less than 4 mm, preferably 3.5 mm.

[0084] Step a2: inputting a constant-amplitude frequency-modulated current signal within a certain frequency range into the sensor 51 through the signal generating circuit 52 .

[0085] The frequency range of the constant amplitude frequency modulated current signal is between 100kHz and 5MHz.

[0086] In step a3, the frequency discriminator 53 performs frequency-amplitude conversion on the constant-amplitude frequency modulated current signal and the voltage amplitude outputted at both ends of the sensor equivalent circuit to obtain the frequency corresponding to the maximum voltage amplitude, which is the resonant frequency.

[0087] In step a4, a film thickness measuring device 50 is used to detect metal films of different film thicknesses to obtain resonance frequencies corresponding to different film thicknesses, wherein the film thickness and material of the metal film are known.

[0088] The thickness of the metal film ranges from 10nm to 2.5um. Multiple sets of different film thicknesses and corresponding resonant frequencies (t0, f0), (t1, f1) ... (tn, fn) are obtained.

[0089] In step a5, the equivalent inductance is calculated based on the resonant frequency, and the inductance-film thickness calibration curve corresponding to the known film thickness is fitted. The inductance-film thickness calibration curve is the calibration curve of the metal film of this material at the lift-off height of the installation distance.

[0090] Specifically, according to formula (6), substitute the resonant frequency f re , calculate the equivalent inductance L; according to formula (4), substitute the equivalent inductance L to calculate the normalized inductance value L'; one-to-one correspondence between the normalized inductance value L' and the film thickness t, we get Figure 13 The inductance-film thickness calibration curve shown can be referred to as the L′-t curve.

[0091] In one embodiment, the measurement process includes:

[0092] Step b1, inputting a constant amplitude frequency modulated current signal within a certain frequency range to the sensor 51 through the signal generating circuit 52;

[0093] Step b2: performing frequency-amplitude conversion on the constant-amplitude frequency modulated current signal and the voltage amplitude outputted from both ends of the sensor equivalent circuit by the frequency discriminator 53 to obtain the frequency corresponding to the maximum voltage amplitude;

[0094] Step b3, calculating the corresponding equivalent inductance according to the frequency corresponding to the maximum voltage amplitude;

[0095] Step b4: Calculate the current film thickness of the metal film based on the equivalent inductance and the inductance-film thickness calibration curve.

[0096] Specifically, using Figure 13 The inductance-film thickness calibration curve shown, namely the L′-t curve, is used to obtain the film thickness.

[0097] like Figure 13 As shown, the present application has good linearity and accuracy in measuring tungsten films in the range of 0-500nm at a distance of 3.5mm, with a correlation coefficient of 0.9969, which can achieve nanometer-level thickness resolution.

[0098] like Figure 14 As shown, the present application performs polishing tests on standard copper sheets of 100nm, 200nm, 400nm, 600nm, 800nm ​​and 1000nm with deionized water at a distance of 3.5mm. The polishing measurement time is relatively short, and it can be assumed that the metal film thickness on the wafer surface does not change. The edge range of the metal film thickness distribution on the surface of a 300mm diameter wafer that can be measured by the film thickness measuring device 50 under different copper film thicknesses is measured. It can be seen that the present application can achieve accurate measurement of the metal film thickness within the radial coordinate position of ±145mm of a 300mm diameter wafer, that is, it achieves accurate measurement of the wafer edge.

[0099] The embodiment of the present invention further provides a control device, which includes: a processor, a memory, and a computer program stored in the memory and capable of running on the processor. When the processor executes the computer program, the following is achieved: Figure 12 The method steps shown. The control device refers to a terminal with data processing capabilities, including but not limited to computers, workstations, servers, and even some high-performance smart phones, PDAs, tablet computers, personal digital assistants (PDAs), smart TVs, etc. The control device is generally installed with an operating system, including but not limited to: Windows operating system, LINUX operating system, Android operating system, Symbian operating system, Windows mobile operating system, and iOS operating system, etc. The above lists specific examples of the control device in detail. Those skilled in the art will appreciate that the control device is not limited to the above-listed examples.

[0100] The embodiment of the present invention further provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the computer program is executed as follows: Figure 12The method steps shown. The computer program may be stored in a computer-readable storage medium, and when the computer program is executed by a processor, the steps of each of the above-mentioned method embodiments may be implemented. The computer program includes computer program code, and the computer program code may be in source code form, object code form, executable file or some intermediate form, etc. The computer-readable medium may include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a mobile hard disk, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunications signal, and a software distribution medium, etc.

[0101] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present invention.

[0102] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included in the scope of protection of the present invention.

Claims

1. A film thickness measurement method, characterized in that: include: Obtaining the distance between the film thickness measuring device and the metal film and the material of the metal film; Determining a corresponding calibration curve according to the distance and material, wherein the calibration curve is used to characterize a mapping relationship between an output signal of a film thickness measuring device and the film thickness; acquiring an output signal of the film thickness measuring device in real time; Obtaining the current film thickness of the metal film according to the calibration curve and the output signal; The film thickness measuring device includes a sensor, a signal generating circuit and a frequency discriminator; The film thickness measurement method further includes the following calibration curve acquisition steps: Obtaining the installation distance between the sensor and the metal film; Inputting a constant amplitude frequency modulated current signal within a certain frequency range into the sensor through the signal generating circuit; The frequency discriminator performs frequency-amplitude conversion on the constant-amplitude frequency modulated current signal and the voltage amplitude output at both ends of the sensor equivalent circuit to obtain the frequency corresponding to the maximum voltage amplitude, which is the resonant frequency; Using a film thickness measuring device to detect metal films of different film thicknesses to obtain the corresponding resonant frequencies of the different film thicknesses, wherein the film thickness and material of the metal film are known; The equivalent inductance is calculated based on the resonant frequency, and an inductance-film thickness calibration curve is obtained by fitting. The inductance-film thickness calibration curve is the calibration curve of the metal film of the material at the lift-off height of the installation distance; Obtaining the current film thickness of the metal film according to the calibration curve and the output signal includes: Input a constant-amplitude frequency-modulated current signal within a certain frequency range to the sensor through a signal generating circuit; The frequency-amplitude conversion is performed on the constant-amplitude frequency modulated current signal and the voltage amplitude output at both ends of the sensor equivalent circuit through the frequency discriminator to obtain the frequency corresponding to the maximum voltage amplitude; Calculating the corresponding equivalent inductance according to the frequency corresponding to the maximum voltage amplitude; The current film thickness of the metal film is calculated based on the equivalent inductance and the inductance-film thickness calibration curve.

2. The film thickness measurement method according to claim 1, wherein: The sensor comprises a pot-shaped magnetic core and a coil. The pot-shaped magnetic core comprises a bottom surface, an inner cylinder arranged at the center of the bottom surface and a peripheral wall arranged around the bottom surface. Multiple turns of the coil are wound around the inner cylinder of the pot-shaped magnetic core.

3. The film thickness measurement method according to claim 1, wherein: The frequency discriminator is a slope frequency discriminator.

4. The film thickness measurement method according to claim 1, wherein: The obtaining of the distance between the film thickness measuring device and the metal film comprises: A film thickness measuring device is installed on the chemical mechanical polishing equipment to measure the distance between the film thickness measuring device and the metal film.

5. A chemical mechanical polishing device, characterized in that: include: a polishing plate covered with a polishing pad for polishing the wafer; a polishing head, for holding a wafer and pressing the wafer onto the polishing pad; a film thickness measuring device for measuring the film thickness of the wafer during polishing; A control device for implementing the film thickness measurement method according to any one of claims 1 to 4.

6. A control device, characterized in that: The method comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the film thickness measurement method according to any one of claims 1 to 4 when executing the computer program.

7. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the film thickness measurement method according to any one of claims 1 to 4 are implemented.

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