A real-time measurement method for metal film thickness

Abstract

The present invention discloses a real-time measurement method for metal film thickness, comprising: providing a first calibration wafer to an Nth calibration wafer, wherein the surface of any nth calibration wafer has an nth metal film; obtaining a first temperature compensation calibration coefficient of the first metal film to an Nth temperature compensation calibration coefficient of the Nth metal film; fitting a film thickness prediction function; providing a wafer to be measured, wherein the surface of the wafer to be measured has the metal film to be measured; polishing the metal film to be measured to obtain a temperature change of the metal film to be measured; obtaining an initial test eddy current signal corresponding to the temperature change; obtaining an nth calibration predicted eddy current signal; obtaining a temperature compensation prediction function; obtaining a temperature compensation prediction coefficient corresponding to the initial test eddy current signal in the temperature compensation prediction function; obtaining a compensated eddy current signal; and obtaining a test thickness of the metal film to be measured corresponding to the compensated eddy current signal in the film thickness prediction function. The above-mentioned real-time measurement method for metal film thickness improves the accuracy of real-time measurement of metal film thickness.

Description

Technical Field

[0001] The invention relates to the technical field of chemical mechanical polishing, and in particular to a real-time measurement method for metal film thickness. Background Art

[0002] The online measurement process of metal films on the surface of integrated circuit wafers typically uses non-contact eddy current sensor modules integrated into process equipment. Eddy current technology for measuring metal film thickness applies a certain frequency AC voltage to the eddy current sensor coil, causing the LC circuit at the sensor end to form an oscillating loop and generate an alternating magnetic field. This alternating magnetic field creates an eddy current effect on the surface of the metal film being measured, forming a magnetic field opposite to that of the eddy current sensor coil, changing the apparent impedance of the eddy current sensor coil. By correlating the metal film thickness with related electrical parameters, metal film thickness measurement is achieved. By calibrating the metal film thickness corresponding to different eddy current sensor output signals, it is concluded that the signal value is linearly related to the metal film thickness.

[0003] This measurement method relies on the accuracy of the eddy current sensor signal. When using eddy current sensors to measure the thickness of metal films on wafer surfaces in real time, ambient temperature fluctuations can cause the sensor's output signal to vary. This feedback signal cannot reflect the actual film thickness, resulting in distorted online measurement data. During the wafer polishing process, ambient temperature fluctuations caused by factors such as friction between the polishing head and the polishing pad, as well as heat release from chemical reactions, can affect measurement accuracy.

[0004] Existing technologies improve measurement accuracy by changing the magnetic core coil and optimizing the associated parameters of the sensor, but can only achieve partial temperature compensation and cannot meet high-order process requirements. Summary of the Invention

[0005] The technical problem to be solved by the present invention is the poor accuracy of real-time testing of metal film thickness using an eddy current sensor.

[0006] The present invention provides a real-time measurement method for the thickness of a metal film, comprising: step S1: providing a first calibration wafer to an Nth calibration wafer, wherein the surface of any nth calibration wafer has an nth metal film; the thickness of the first metal film on the surface of the first calibration wafer to the Nth metal film on the surface of the Nth calibration wafer are different, where N is an integer greater than or equal to 2; step S2: obtaining a first temperature compensation calibration coefficient of the first metal film to an Nth temperature compensation calibration coefficient Ψ of the Nth metal film n ; Get any nth temperature compensation calibration coefficient Ψ n The steps include: performing an nth water polishing process on the nth calibration wafer; before the nth water polishing process, performing an nth first eddy current sensor test on the nth metal film to obtain an nth first eddy current signal S n1After the nth water-blasting treatment, the nth metal film is subjected to the nth second eddy current sensor test to obtain the nth second eddy current signal S n2 ; n is an integer greater than or equal to 1 and less than or equal to N; obtain the nth temperature change ΔT of the nth water polishing process n ; The absolute value of the difference between the nth first eddy current signal and the nth second eddy current signal and the nth temperature change ΔT n The ratio of is used as the nth temperature compensation calibration coefficient Ψ n ;Ψ n =ΔS n / ΔT n ;ΔS n =︱S n1 -S n2 ︱;ΔT n =︱T n1 -T n2 ︱; Step S3: Using the thickness of any n-th metal film and the data of the n-th first eddy current signal to fit a film thickness prediction function, the film thickness prediction function is the relationship between the test thickness and the compensated eddy current signal; Step S4: Providing a wafer to be tested, the surface of the wafer to be tested has a metal film to be tested; Step S5: Polishing the metal film to be tested, and obtaining the temperature change ΔT of the metal film to be tested during the polishing process; During the polishing process of the metal film to be tested, the eddy current sensor test of the metal film to be tested is performed in real time to obtain an initial test eddy current signal S0 corresponding to the temperature change ΔT; Step S6: Using the temperature change ΔT and any n-th temperature compensation calibration coefficient Ψ n Get the nth calibrated predicted eddy current signal I 1n ,I 1n =Ψ n *ΔT+S n1 Step S7: Using any nth temperature compensation calibration coefficient and nth calibration prediction eddy current signal I 1n Obtain a temperature compensation prediction function, which is the relationship between the temperature compensation prediction coefficient and the initial test eddy current signal; step S8: obtain the temperature compensation prediction coefficient Ψ of the metal film to be tested corresponding to the initial test eddy current signal in the temperature compensation prediction function; step S9: obtain the compensated eddy current signal S according to the temperature compensation prediction coefficient Ψ of the metal film to be tested, the temperature change ΔT, and the initial test eddy current signal S0; S=S0+ΔT*Ψ; step S10: obtain the test thickness of the metal film to be tested corresponding to the compensated eddy current signal S in the film thickness prediction function.

[0007] Optionally, the nth metal film is subjected to the nth first eddy current sensor test to obtain the nth first eddy current signal S n1The process includes: before the nth water polishing treatment, performing eddy current sensor tests on the first test point to the Qth test point of the nth metal film respectively, and obtaining the nth first eddy current first test point signal to the nth first eddy current Qth test point signal; obtaining the average value of the nth first eddy current first test point signal to the nth first eddy current Qth test point signal as the nth first eddy current signal S n1 , Q is an integer greater than or equal to 2.

[0008] Optionally, the distance from any one of the first test point to the Qth test point of the nth metal film to the center of the nth calibration wafer is 40% to 75% of the radius of the nth calibration wafer.

[0009] Optionally, the nth metal film is subjected to the nth second eddy current sensor test to obtain the nth second eddy current signal S n2 The process includes: after the nth water polishing treatment, performing eddy current sensor tests on the first test point to the Wth test point of the nth metal film respectively, and obtaining the nth second eddy current first test point signal to the nth second eddy current Wth test point signal; obtaining the average value of the nth second eddy current first test point signal to the nth second eddy current Wth test point signal as the nth second eddy current signal S n2 , W is an integer greater than or equal to 2.

[0010] Optionally, a distance from any one of the first test point to the Wth test point of the nth metal film to the center of the nth calibration wafer is 40% to 75% of the radius of the nth calibration wafer.

[0011] Optionally, any nth temperature compensation calibration coefficient and nth calibration prediction eddy current signal I 1n The step of obtaining the temperature compensation prediction function includes: obtaining any nth temperature compensation calibration coefficient and the corresponding nth calibration prediction eddy current signal I 1n The mapping function is fitted to obtain a temperature compensation prediction function.

[0012] Optionally, the method for fitting the mapping function includes a linear difference method or a least squares method.

[0013] Optionally, the process of performing eddy current sensor testing on the metal film to be tested in real time to obtain an initial test eddy current signal S0 corresponding to the temperature change ΔT includes: performing eddy current sensor testing on the first test point to the Gth test point of the metal to be tested, respectively, to obtain the first test point signal to the Gth test point signal; obtaining the average value of the first test point signal to the Gth test point signal as the initial test eddy current signal S0, where G is an integer greater than or equal to 2.

[0014] Optionally, the step of performing an eddy current sensor test on the metal film to be tested in real time to obtain an initial test eddy current signal S0 corresponding to the temperature change ΔT is as follows: in the process of polishing the metal film to be tested, performing eddy current sensor tests on the first to P-th test points of the metal film to be tested, respectively, to obtain the first to P-th initial test eddy current signals; P is an integer greater than or equal to 2; the step of obtaining the temperature compensation prediction coefficient Ψ of the metal film to be tested corresponding to the initial test eddy current signal in the temperature compensation prediction function is as follows: obtaining the first initial test eddy current signal The first temperature compensation prediction coefficient of the metal film to be measured corresponding to the temperature compensation prediction function to the Pth initial test eddy current signal in the temperature compensation prediction function corresponds to the Pth temperature compensation prediction coefficient of the metal film to be measured; the step of obtaining the compensated eddy current signal S according to the temperature compensation prediction coefficient of the metal film to be measured, the temperature change ΔT, and the initial test eddy current signal S0 includes: obtaining the first compensated eddy current signal to the Pth compensated eddy current signal; the step of obtaining any pth compensated eddy current signal is: according to the pth temperature compensation prediction coefficient Ψp, the temperature change ΔT, the pth initial test eddy current signal S 0p Get the pth compensated eddy current signal S of the metal film to be tested p , S p =S 0p +ΔT*Ψp; p is an integer greater than or equal to 1 and less than or equal to P; the step of obtaining the test thickness of the metal film to be measured corresponding to the compensated eddy current signal S in the film thickness prediction function includes: obtaining the first test thickness corresponding to the first compensated eddy current signal in the film thickness prediction function to the Pth test thickness corresponding to the Pth compensated eddy current signal in the film thickness prediction function.

[0015] The technical solution of the present invention has the following beneficial effects:

[0016] The metal film thickness measurement method provided by the present invention obtains the compensated eddy current signal S through the temperature compensation prediction coefficient Ψ, temperature change ΔT, and initial test eddy current signal S0 of the metal film to be measured, compensates for the drift of the eddy current signal due to temperature, and then obtains the test thickness of the metal film to be measured corresponding to the compensated eddy current signal S in the film thickness prediction function. Even if the temperature change of the test environment causes drift in the output signal of the eddy current sensor, the accurate thickness of the metal film to be measured can be obtained in real time, thereby improving the accuracy of real-time measurement of metal film thickness. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 Schematic diagram of the process of measuring the thickness of a metal film according to an embodiment of the present application;

[0019] Figure 2 A schematic diagram illustrating changes in ambient temperature during wafer water polishing according to an embodiment of the present application;

[0020] Figure 3 A schematic diagram illustrating changes in the signal output by the eddy current sensor during the wafer water polishing process according to an embodiment of the present application;

[0021] Figure 4 A linear schematic diagram of a film thickness prediction function according to an embodiment of the present application;

[0022] Figure 5 A schematic diagram of a mapping function according to an embodiment of the present application;

[0023] Figure 6 A schematic diagram of a temperature compensation prediction function obtained in one embodiment of the present application;

[0024] Figure 7 This is a schematic diagram of a temperature compensation prediction function obtained in another embodiment of the present application;

[0025] Figure 8 Schematic diagram of distribution curves of the first compensated eddy current signal to the Pth compensated eddy current signal after temperature compensation in the radial direction of the wafer to be measured according to an embodiment of the present application;

[0026] Figure 9 Schematic diagram of a distribution curve of the test thickness of the metal film to be tested corresponding to the first compensated eddy current signal to the Pth compensated eddy current signal in the film thickness prediction function in the wafer radius direction according to an embodiment of the present application;

[0027] Figure 10 A schematic diagram of the motion trajectory of the eddy current sensor according to an embodiment of the present application;

[0028] Figure 11 This is a schematic diagram comparing the initial test eddy current signal and the compensated eddy current signal before and after temperature compensation according to an embodiment of the present application. DETAILED DESCRIPTION

[0029] The technical solutions of the present invention will be described clearly and completely below. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention. In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0030] The embodiment of the present invention provides a method for measuring the thickness of a metal film. Figure 1 As shown, including:

[0031] Step S1: providing a first calibration wafer to an Nth calibration wafer, wherein the surface of any nth calibration wafer has an nth metal film; the thickness of the first metal film on the surface of the first calibration wafer to the Nth metal film on the surface of the Nth calibration wafer are different, where N is an integer greater than or equal to 2;

[0032] Step S2: Obtain the first temperature compensation calibration coefficient of the first metal film to the Nth temperature compensation calibration coefficient Ψ of the Nth metal film n ; Get any nth temperature compensation calibration coefficient Ψ n The steps include: performing an nth water polishing process on the nth calibration wafer; before the nth water polishing process, performing an nth first eddy current sensor test on the nth metal film to obtain an nth first eddy current signal S n1 After the nth water-blasting treatment, the nth metal film is subjected to the nth second eddy current sensor test to obtain the nth second eddy current signal S n2 ; n is an integer greater than or equal to 1 and less than or equal to N; obtain the nth temperature change ΔT of the nth water polishing process n ; The absolute value of the difference between the nth first eddy current signal and the nth second eddy current signal and the nth temperature change ΔT n The ratio of is used as the nth temperature compensation calibration coefficient Ψ n ;Ψ n =ΔS n / ΔT n ;ΔS n =︱S n1 -S n2 ︱;ΔT n =︱T n1 -T n2 ︱;

[0033] Step S3: fitting a film thickness prediction function using the thickness of any n-th metal film and the data of the n-th first eddy current signal, wherein the film thickness prediction function is the relationship between the test thickness and the compensated eddy current signal;

[0034] Step S4: providing a wafer to be tested, wherein the surface of the wafer to be tested has a metal film to be tested;

[0035] Step S5: polishing the metal film to be tested, and obtaining a temperature change ΔT of the metal film to be tested during the polishing process; performing an eddy current sensor test on the metal film to be tested in real time during the polishing process to obtain an initial test eddy current signal S0 corresponding to the temperature change ΔT;

[0036] Step S6: Using the temperature change ΔT and any nth temperature compensation calibration coefficient Ψ n Get the nth calibrated predicted eddy current signal I 1n ,I 1n =Ψ n *ΔT+S n1 ;

[0037] Step S7: Using any nth temperature compensation calibration coefficient and nth calibration prediction eddy current signal I 1n Obtaining a temperature compensation prediction function, where the temperature compensation prediction function is a relationship between a temperature compensation prediction coefficient and an initial test eddy current signal;

[0038] Step S8: obtaining the temperature compensation prediction coefficient Ψ of the metal film to be tested corresponding to the initial test eddy current signal in the temperature compensation prediction function;

[0039] Step S9: obtaining a compensated eddy current signal S according to the temperature compensation prediction coefficient Ψ, the temperature change ΔT, and the initial test eddy current signal S0 of the metal film to be tested; S=S0+ΔT*Ψ;

[0040] Step S10: obtaining the test thickness of the metal film to be measured corresponding to the compensated eddy current signal S in the film thickness prediction function.

[0041] In this embodiment, the compensated eddy current signal S is obtained by using the temperature compensation prediction coefficient Ψ, the temperature change ΔT, and the initial test eddy current signal S0 of the metal film to be tested, and the drift of the eddy current signal due to temperature is compensated. Then, the test thickness of the metal film to be tested corresponding to the compensated eddy current signal S in the film thickness prediction function is obtained. This ensures that even if the temperature change of the test environment causes drift in the output signal of the eddy current sensor, the accurate thickness of the metal film to be tested can be obtained in real time, thereby improving the accuracy of real-time measurement of the metal film thickness.

[0042] In this embodiment, there is no restriction on the diameters of the first calibration wafer to the Nth calibration wafer, and the diameters can be 50 mm, 75 mm, 100 mm, 125 mm, 150 mm, 200 mm, or 300 mm, as long as the diameters of the first calibration wafer to the Nth calibration wafer are the same. There is no restriction on the specific thickness of the first metal film on the surface of the first calibration wafer to the Nth metal film on the surface of the Nth calibration wafer, as long as the thickness of the first metal film on the surface of the first calibration wafer to the Nth metal film on the surface of the Nth calibration wafer is uniform. The value of N is an integer greater than or equal to 2. The larger the value of N, the more accurate the fitted temperature compensation prediction function and film thickness prediction function, and the more accurate the thickness of the metal film to be measured.

[0043] In this embodiment, the nth calibration wafer is subjected to an nth water polishing process. The nth water polishing process does not use a corrosive polishing liquid. Instead, water is used as a polishing medium. The thickness of the nth metal film does not change during the nth water polishing process.

[0044] During the water polishing process, the ambient temperature of the water polishing process will increase, for example, the temperature of the polishing pad will increase. Figure 2 As shown, Figure 2 The horizontal axis is the number of tests. Figure 2 The vertical axis is the ambient temperature. Figure 3 As shown in the figure, during the water blasting process, the ambient temperature of the water blasting process will increase, which will cause the output eddy current signal of the eddy current sensor to decrease. Figure 3 The horizontal axis is the number of tests. Figure 3 The vertical axis is the output eddy current signal of the eddy current sensor.

[0045] In this embodiment, the nth metal film is subjected to the nth first eddy current sensor test to obtain the nth first eddy current signal S n1 The process includes: before the nth water polishing treatment, performing eddy current sensor tests on the first test point to the Qth test point of the nth metal film respectively, and obtaining the nth first eddy current first test point signal to the nth first eddy current Qth test point signal; obtaining the average value of the nth first eddy current first test point signal to the nth first eddy current Qth test point signal as the nth first eddy current signal S n1 , Q is an integer greater than or equal to 2. The average value of the first test point signal of the nth first eddy current to the Qth test point signal of the nth first eddy current is taken as the nth first eddy current signal S n1 , which can reduce measurement errors.

[0046] An eddy current sensor test is performed on the qth test point of the nth metal film to obtain the nth first eddy current qth test point signal, where q is an integer greater than or equal to 1 and less than or equal to Q.

[0047] When the eddy current sensor test is performed on the first test point to the Qth test point of the nth metal film, the test instrument used is an eddy current metal film thickness detector. The eddy current metal film thickness detector has an eddy current sensor. The eddy current sensor is located below the polishing table and can rotate with the polishing table, sweeping the surface of the nth metal film during rotation. The distance from each test point from the first test point to the Qth test point of the nth metal film to the eddy current metal film thickness detector is consistent. The distance from each test point from the first test point to the Qth test point of the nth metal film to the eddy current metal film thickness detector can also be inconsistent. It is only necessary to ensure that the distance from any qth test point of the nth metal film to the eddy current metal film thickness detector is within the metal film thickness test range.

[0048] In this embodiment, the distance between any one of the first and Q test points of the nth metal film and the center of the nth calibration wafer is 40% to 75% of the radius of the nth calibration wafer, for example, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or 75%. Typically, the metal film thickness within the range of 40% to 75% of the radius of the calibration wafer is uniform, and the eddy current signal obtained at any test point within this range is uniform and accurate, thereby improving measurement accuracy.

[0049] In this embodiment, the nth metal film is subjected to the nth second eddy current sensor test to obtain the nth second eddy current signal S n2 The process includes: after the nth water polishing treatment, performing eddy current sensor tests on the first test point to the Wth test point of the nth metal film respectively, and obtaining the nth second eddy current first test point signal to the nth second eddy current Wth test point signal; obtaining the average value of the nth second eddy current first test point signal to the nth second eddy current Wth test point signal as the nth second eddy current signal S n2 , W is an integer greater than or equal to 2. The average value of the signal from the first test point of the nth second eddy current to the Wth test point of the nth second eddy current is taken as the nth second eddy current signal S n2 , which can reduce measurement errors.

[0050] An eddy current sensor test is performed on the wth test point of the nth metal film to obtain an nth second eddy current wth test point signal, where w is an integer greater than or equal to 1 and less than or equal to W.

[0051] When the eddy current sensor test is performed on the first test point to the W test point of the n-th metal film, the test instrument used is an eddy current metal film thickness detector, which has an eddy current sensor. The eddy current sensor is located below the polishing table and can rotate with the polishing table to sweep the surface of the n-th metal film during rotation. The distances from each test point to the eddy current metal film thickness detector from the first test point to the W test point of the n-th metal film are consistent. The distances from each test point to the eddy current metal film thickness detector from the first test point to the W test point of the n-th metal film can also be inconsistent. It is only necessary to ensure that the distance from any w-th test point of the n-th metal film to the eddy current metal film thickness detector is within the film thickness test range.

[0052] In this embodiment, the distance between any test point between the first test point and the Wth test point of the nth metal film and the center of the nth calibration wafer is 40% to 75% of the radius of the nth calibration wafer, for example, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or 75%. Typically, the metal film thickness within the range of 40% to 75% of the radius of the calibration wafer is uniform, and the eddy current signal obtained at any test point within this range is uniform and accurate, thereby improving measurement accuracy.

[0053] In this embodiment, an arbitrary nth temperature compensation calibration coefficient and an nth calibration prediction eddy current signal I are used. 1n The step of obtaining the temperature compensation prediction function includes: obtaining any nth temperature compensation calibration coefficient and the corresponding nth calibration prediction eddy current signal I 1n The mapping function, such as Figure 5 The schematic diagram of the mapping function is shown in Figure 5 The horizontal axis is the calibrated predicted eddy current signal, Figure 5 The vertical axis represents the temperature compensation calibration coefficient. The mapping function is fitted to obtain a temperature compensation prediction function. This temperature compensation prediction function allows for quick and convenient determination of the temperature compensation prediction coefficient of the metal film to be measured, corresponding to the initial test eddy current signal, thereby obtaining a more accurate thickness of the metal film to be measured.

[0054] In this embodiment, the method for fitting the mapping function includes a linear difference method or a least squares method. By fitting the mapping function to obtain a temperature compensation prediction function, the temperature compensation prediction coefficient of the metal film to be tested on any wafer to be tested can be obtained from the temperature compensation prediction function.

[0055] In one embodiment, the method for fitting the mapping function is a linear interpolation method, such as Figure 6 The schematic diagram of the temperature compensation prediction function obtained by fitting the mapping function using the linear interpolation method is shown in FIG. Figure 6The horizontal axis is the initial test eddy current signal, and the vertical axis is the temperature compensation prediction coefficient. Using the linear difference method to fit the temperature compensation prediction function, the temperature compensation prediction coefficient of the metal film of any wafer under test can be easily and quickly obtained.

[0056] In another embodiment, the method for fitting the mapping function is the least squares method. The least squares method is used to fit the mapping function to obtain the temperature compensation prediction function. Since a cubic fitting is used, the relationship between the measured eddy current signal and the temperature compensation prediction coefficient can be more accurately expressed, such as Figure 7 The schematic diagram of the temperature compensation prediction function obtained by fitting the mapping function using the least squares method is shown in FIG. Figure 7 The horizontal axis is the initial test eddy current signal, and the vertical axis is the temperature compensation prediction coefficient. Figure 7 Medium R 2 represents the goodness of fit, R 2 The closer the value is to 1, the better the fit.

[0057] In step 3, the corresponding relationship between the thickness of any n-th metal film and the data of the n-th first eddy current signal is not affected by the ambient temperature. The film thickness prediction function is fitted with the data of the n-th metal film thickness and the n-th first eddy current signal, as shown in FIG. Figure 4 The film thickness prediction function shown is Figure 4 The horizontal axis is the compensated eddy current signal, Figure 4 The vertical axis is the test thickness, and the film thickness prediction function is the relationship between the test thickness and the compensated eddy current signal. Figure 4 Medium R 2 represents the goodness of fit, R 2 The closer the value is to 1, the better the fit.

[0058] In one embodiment, a process of performing eddy current sensor testing on a metal film to be tested in real time to obtain an initial test eddy current signal S0 corresponding to a temperature change ΔT includes: performing eddy current sensor testing on a first to a Gth test point of the metal film to be tested, respectively, to obtain signals from the first to the Gth test point; and obtaining an average value of the signals from the first to the Gth test point as the initial test eddy current signal S0, where G is an integer greater than or equal to 2. Using the average value of the signals from the first to the Gth test point as the initial test eddy current signal S0 can reduce measurement errors.

[0059] In another embodiment, the step of performing an eddy current sensor test on the metal film to be tested in real time to obtain an initial test eddy current signal S0 corresponding to the temperature change ΔT is as follows: in the process of polishing the metal film to be tested, the eddy current sensor test is performed on the first to the P-th test point of the metal film to be tested, respectively, to obtain the first initial test eddy current signal to the P-th initial test eddy current signal; P is an integer greater than or equal to 2; the step of obtaining the temperature compensation prediction coefficient Ψ of the metal film to be tested corresponding to the initial test eddy current signal in the temperature compensation prediction function is as follows: obtaining the first initial test eddy current signal The first temperature compensation prediction coefficient of the metal film to be tested corresponding to the signal in the temperature compensation prediction function to the Pth initial test eddy current signal in the temperature compensation prediction function corresponds to the Pth temperature compensation prediction coefficient of the metal film to be tested; the step of obtaining the compensated eddy current signal S according to the temperature compensation prediction coefficient of the metal film to be tested, the temperature change ΔT, and the initial test eddy current signal S0 includes: obtaining the first compensated eddy current signal to the Pth compensated eddy current signal; the step of obtaining any pth compensated eddy current signal is: according to the pth temperature compensation prediction coefficient Ψp, the temperature change ΔT, the pth initial test eddy current signal S 0p Get the pth compensated eddy current signal S of the metal film to be tested p , S p =S 0p +ΔT*Ψp; p is an integer greater than or equal to 1 and less than or equal to P; the step of obtaining the test thickness of the metal film to be measured corresponding to the compensated eddy current signal S in the film thickness prediction function includes: obtaining the first test thickness corresponding to the first compensated eddy current signal in the film thickness prediction function to the Pth test thickness corresponding to the Pth compensated eddy current signal in the film thickness prediction function.

[0060] like Figure 8 As shown, Figure 8 The horizontal axis is the diameter of the wafer to be measured, and the vertical axis is the first compensation eddy current signal to the Pth compensation eddy current signal after temperature compensation, from Figure 8 It can be seen intuitively that the first compensated eddy current signal to the Pth compensated eddy current signal after temperature compensation is evenly distributed in the radial direction of the wafer to be measured; the thickness of the metal film to be measured corresponding to the first compensated eddy current signal to the Pth compensated eddy current signal after temperature compensation in the film thickness prediction function is obtained; and a distribution curve of the test thickness of the metal film to be measured corresponding to the first compensated eddy current signal to the Pth compensated eddy current signal after temperature compensation in the film thickness prediction function is generated, as shown Figure 9 As shown, Figure 9 The horizontal axis is the diameter of the wafer to be measured. Figure 9 The vertical axis is the test thickness, from Figure 9It can be seen intuitively that the test thickness of the metal film to be measured corresponding to the first compensation eddy current signal to the Pth compensation eddy current signal in the film thickness prediction function is evenly distributed in the radial direction of the wafer to be measured.

[0061] In this embodiment, when the first initial test eddy current signal to the Pth initial test eddy current signal are obtained, the distance from the first test point to any one of the Pth test points of the metal film to the center of the wafer to be tested is calculated, and a distribution curve of the first test point signal to the Pth test point signal in the radial direction of the wafer to be tested is generated; the following relationship is satisfied:

[0062]

[0063] Wherein, T1 is the moment when the eddy current sensor scans to the first fixed point A, T2 is the moment when the eddy current sensor scans to the test point B, α is ∠AO1C, n is the rotation speed of the polishing table (in revolutions / s), R1 is the radius of the eddy current sensor track, R2 is the distance between O1 and O2, and R is the distance between the test points B and O2; Figure 10 As shown in the figure, 1 is the polishing table, 2 is the wafer to be tested, and 3 is the motion trajectory of the eddy current sensor, which can scan the wafer to be tested. O1 is the center of the polishing table, O2 is the center of the wafer to be tested, and D is the second fixed point. When the eddy current sensor is used to test the metal film to be tested, the eddy current sensor can be scanned from point A to point B and then to point D, or it can be scanned from point D to point B and then to point A, without affecting the final test results. The output signal of the eddy current sensor includes an eddy current signal and a mark position. When the eddy current sensor scans from test point B to the first fixed point A, the mark position of the eddy current sensor output signal will change; alternatively, when the eddy current sensor scans from the second fixed point D to test point B, the mark position of the eddy current sensor output signal will change.

[0064] In one embodiment, the metal film thickness is provided as follows: and The wafers are several calibration wafers, and the metal film thickness is The wafer with a thickness of The first eddy current sensor test is performed on the metal film with a thickness of The metal film is subjected to a second eddy current sensor test to obtain a second eddy current signal; the temperature change ΔT during the water polishing process is obtained; the ratio of the absolute value of the difference between the first eddy current signal and the second eddy current signal to the temperature change ΔT is used as the film thickness. Repeat the above steps to obtain the temperature compensation calibration coefficient of the metal film with a film thickness of and Temperature compensation calibration coefficient of the metal film; using and The film thickness is fitted with the data of the corresponding first eddy current signal to obtain a film thickness prediction function, which is the relationship between the test thickness and the compensated eddy current signal; The metal film with a thickness of The temperature change during the polishing process of the metal film with a thickness of During the polishing process of the metal film with a thickness of The eddy current sensor test is carried out on the metal film to obtain the initial test eddy current signal corresponding to the temperature change; the temperature change and film thickness are used as the The metal film temperature compensation calibration coefficient is used to obtain the film thickness: The metal film calibration predicts the eddy current signal; the film thickness is The metal film temperature compensation calibration coefficient and film thickness are The metal film calibration prediction eddy current signal is used to obtain the temperature compensation prediction function. The temperature compensation prediction function is the relationship between the temperature compensation prediction coefficient and the initial test eddy current signal. The eddy current sensor test is performed on the first test point to the P-th test point of the metal film, and the first initial test eddy current signal to the P-th initial test eddy current signal are obtained correspondingly; P is an integer greater than or equal to 2; the first temperature compensation prediction coefficient corresponding to the first initial test eddy current signal in the temperature compensation prediction function to the P-th temperature compensation prediction coefficient corresponding to the P-th initial test eddy current signal in the temperature compensation prediction function are obtained; according to the first temperature compensation prediction coefficient to the P-th temperature compensation prediction coefficient, the temperature change, the first initial test eddy current signal to the P-th initial test eddy current signal, the film thickness is obtained. The first compensation eddy current signal to the Pth compensation eddy current signal of the metal film, such as Figure 11 As shown, Figure 11 The horizontal axis is the number of tests, and the vertical axis is the eddy current signal. In the figure, RawData represents the initial test eddy current signal, and NewData represents the compensated eddy current signal. The first test thickness corresponding to the first compensated eddy current signal in the film thickness prediction function to the Pth test thickness corresponding to the Pth compensated eddy current signal in the film thickness prediction function are obtained. The obtained first test thickness to the Pth test thickness and the film thickness are The actual thickness error of the metal film during the polishing process is very small.

[0065] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A real-time measurement method for metal film thickness, characterized in that: include: Step S1: providing a first calibration wafer to an Nth calibration wafer, wherein the surface of any nth calibration wafer has an nth metal film; the thickness of the first metal film on the surface of the first calibration wafer to the Nth metal film on the surface of the Nth calibration wafer are different, where N is an integer greater than or equal to 2; Step S2: Obtain the first temperature compensation calibration coefficient of the first metal film to the Nth temperature compensation calibration coefficient Ψ of the Nth metal film n ; Get any nth temperature compensation calibration coefficient Ψ n The steps include: performing an nth water polishing process on the nth calibration wafer; before the nth water polishing process, performing an nth first eddy current sensor test on the nth metal film to obtain an nth first eddy current signal S n1 After the nth water-blasting treatment, the nth metal film is subjected to the nth second eddy current sensor test to obtain the nth second eddy current signal S n2 ; n is an integer greater than or equal to 1 and less than or equal to N; obtain the nth temperature change ΔT of the nth water polishing process n ; The absolute value of the difference between the nth first eddy current signal and the nth second eddy current signal and the nth temperature change ΔT n The ratio of is used as the nth temperature compensation calibration coefficient Ψ n ;Ψ n =ΔS n / ΔT n ;ΔS n =︱S n1 -S n2 ︱;ΔT n =︱T n1 -T n2 ︱; Step S3: fitting a film thickness prediction function using the thickness of any n-th metal film and the data of the n-th first eddy current signal, wherein the film thickness prediction function is the relationship between the test thickness and the compensated eddy current signal; Step S4: providing a wafer to be tested, wherein the surface of the wafer to be tested has a metal film to be tested; Step S5: polishing the metal film to be tested, and obtaining a temperature change ΔT of the metal film to be tested during the polishing process; performing an eddy current sensor test on the metal film to be tested in real time during the polishing process to obtain an initial test eddy current signal S0 corresponding to the temperature change ΔT; Step S6: Using the temperature change ΔT and any nth temperature compensation calibration coefficient Ψ n Get the nth calibrated predicted eddy current signal I 1n ,I 1n =Ψ n *ΔT+S n1 ; Step S7: Using any nth temperature compensation calibration coefficient and nth calibration prediction eddy current signal I 1n Obtaining a temperature compensation prediction function, where the temperature compensation prediction function is a relationship between a temperature compensation prediction coefficient and an initial test eddy current signal; Step S8: obtaining the temperature compensation prediction coefficient Ψ of the metal film to be tested corresponding to the initial test eddy current signal in the temperature compensation prediction function; Step S9: obtaining a compensated eddy current signal S according to the temperature compensation prediction coefficient Ψ, the temperature change ΔT, and the initial test eddy current signal S0 of the metal film to be tested; S=S0+ΔT*Ψ; Step S10: obtaining the test thickness of the metal film to be measured corresponding to the compensated eddy current signal S in the film thickness prediction function.

2. The real-time measurement method of metal film thickness according to claim 1, characterized in that: Perform the nth first eddy current sensor test on the nth metal film to obtain the nth first eddy current signal S n1 The process includes: before the nth water polishing treatment, performing eddy current sensor tests on the first test point to the Qth test point of the nth metal film respectively, and obtaining the nth first eddy current first test point signal to the nth first eddy current Qth test point signal; obtaining the average value of the nth first eddy current first test point signal to the nth first eddy current Qth test point signal as the nth first eddy current signal S n1 , Q is an integer greater than or equal to 2.

3. The real-time measurement method of metal film thickness according to claim 2, characterized in that: The distance from any one of the first test point to the Qth test point of the nth metal film to the center of the nth calibration wafer is 40% to 75% of the radius of the nth calibration wafer.

4. The real-time measurement method of metal film thickness according to claim 1, characterized in that: Perform the nth second eddy current sensor test on the nth metal film to obtain the nth second eddy current signal S n2 The process includes: after the nth water polishing treatment, performing eddy current sensor tests on the first test point to the Wth test point of the nth metal film respectively, and obtaining the nth second eddy current first test point signal to the nth second eddy current Wth test point signal; obtaining the average value of the nth second eddy current first test point signal to the nth second eddy current Wth test point signal as the nth second eddy current signal S n2 , W is an integer greater than or equal to 2.

5. The real-time measurement method of metal film thickness according to claim 4, characterized in that: The distance from any one of the first test point to the Wth test point of the nth metal film to the center of the nth calibration wafer is 40% to 75% of the radius of the nth calibration wafer.

6. The real-time measurement method of metal film thickness according to claim 1, characterized in that: Using any nth temperature compensation calibration coefficient and nth calibration prediction eddy current signal I 1n The step of obtaining the temperature compensation prediction function includes: obtaining any nth temperature compensation calibration coefficient and the corresponding nth calibration prediction eddy current signal I 1n The mapping function is fitted to obtain a temperature compensation prediction function.

7. The real-time measurement method of metal film thickness according to claim 6, characterized in that: Methods for fitting the mapping function include linear difference method or least square method.

8. The real-time measurement method of metal film thickness according to claim 1, characterized in that: The process of performing eddy current sensor testing on a metal film to be tested in real time to obtain an initial test eddy current signal S0 corresponding to a temperature change ΔT includes: performing eddy current sensor testing on a first test point to a Gth test point of the metal to be tested, respectively, to obtain signals from the first test point to the Gth test point; and obtaining an average value of the signals from the first test point to the Gth test point as the initial test eddy current signal S0, where G is an integer greater than or equal to 2.

9. The real-time measurement method of metal film thickness according to claim 1, characterized in that: The steps of performing an eddy current sensor test on the metal film to be tested in real time to obtain an initial test eddy current signal S0 corresponding to the temperature change ΔT are as follows: during the polishing process of the metal film to be tested, performing eddy current sensor tests on the first to Pth test points of the metal film to be tested, respectively, to obtain the first to Pth initial test eddy current signals; P is an integer greater than or equal to 2; The step of obtaining the temperature compensation prediction coefficient Ψ of the metal film to be measured corresponding to the initial test eddy current signal in the temperature compensation prediction function is as follows: obtaining a first temperature compensation prediction coefficient of the metal film to be measured corresponding to the first initial test eddy current signal in the temperature compensation prediction function to a Pth temperature compensation prediction coefficient of the metal film to be measured corresponding to the Pth initial test eddy current signal in the temperature compensation prediction function; The steps of obtaining the compensated eddy current signal S according to the temperature compensation prediction coefficient, temperature variation ΔT and initial test eddy current signal S0 of the metal film to be tested include: obtaining the first compensated eddy current signal to the Pth compensated eddy current signal; the steps of obtaining any pth compensated eddy current signal are: obtaining the pth compensated eddy current signal according to the pth temperature compensation prediction coefficient Ψp, temperature variation ΔT and the pth initial test eddy current signal S0; and obtaining any pth compensated eddy current signal according to the pth temperature compensation prediction coefficient Ψp, temperature variation ΔT and the pth initial test eddy current signal S0. 0p Get the pth compensated eddy current signal S of the metal film to be tested p , S p =S 0p +ΔT*Ψp; p is an integer greater than or equal to 1 and less than or equal to P; The step of obtaining the test thickness of the metal film to be measured corresponding to the compensated eddy current signal S in the film thickness prediction function includes: obtaining the first test thickness corresponding to the first compensated eddy current signal in the film thickness prediction function to the Pth test thickness corresponding to the Pth compensated eddy current signal in the film thickness prediction function.

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