CN116175396B - A real-time measurement method for metal film thickness - Google Patents
A real-time measurement method for metal film thicknessInfo
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- CN116175396B CN116175396B CN202211230651.0A CN202211230651A CN116175396B CN 116175396 B CN116175396 B CN 116175396B CN 202211230651 A CN202211230651 A CN 202211230651A CN 116175396 B CN116175396 B CN 116175396B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B37/00—Lapping machines or devices; Accessories
- B24B37/005—Control means for lapping machines or devices
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B41/00—Component parts such as frames, beds, carriages, headstocks
- B24B41/007—Weight compensation; Temperature compensation; Vibration damping
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B49/00—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation
- B24B49/10—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation involving electrical means
- B24B49/105—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation involving electrical means using eddy currents
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
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- Mechanical Engineering (AREA)
- Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
- Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)
Abstract
本发明公开一种金属膜厚的实时测量方法，包括：提供第一标定晶圆至第N标定晶圆，任意第n标定晶圆的表面具有第n金属膜；获取第一金属膜的第一温度补偿标定系数至第N金属膜的第N温度补偿标定系数；拟合出膜厚预测函数；提供待测晶圆，待测晶圆的表面具有待测金属膜；对待测金属膜进行抛光处理，获取待测金属膜的温度变化量；获得对应温度变化量的初始测试涡流信号；获取第n标定预测涡流信号；获取温度补偿预测函数；获取初始测试涡流信号在温度补偿预测函数中对应的温度补偿预测系数；获取补偿涡流信号；获取补偿涡流信号在膜厚预测函数中对应的待测金属膜的测试厚度。上述金属膜厚的实时测量方法，提高了金属膜厚实时测量的准确性。
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
The invention relates to the technical field of chemical mechanical polishing, in particular to a real-time measuring method for metal film thickness.
Background
In the on-line measurement process of the metal film on the surface of the integrated circuit wafer, a non-contact eddy current sensor module integrated on process equipment is generally adopted, and the technology for measuring the metal film thickness by utilizing the eddy current is to apply alternating voltage with a certain frequency to an eddy current sensor coil, so that an LC circuit at the end of the eddy current sensor forms an oscillating loop to generate an alternating magnetic field, the alternating magnetic field forms an eddy current effect on the surface of a metal film of a measurement object, a magnetic field opposite to the eddy current sensor coil is formed, the apparent impedance of the eddy current sensor coil is changed, and the metal film thickness measurement is realized by correlating the metal film thickness with related electrical parameters. And calibrating metal film thicknesses corresponding to output signals of different eddy current sensors to obtain a linear relation between the signal values and the metal film thicknesses.
This measurement depends on the accuracy of the eddy current sensor signal. When the eddy current sensor detects the thickness of the metal film on the surface of the wafer in real time, the output signal of the eddy current sensor changes due to the change of the ambient temperature, and the feedback signal cannot reflect the actual film thickness, so that the on-line measurement data is distorted. In the polishing process of the wafer, the temperature of the environment changes due to friction between the polishing head and the polishing pad, chemical reaction heat release and other factors, so that the detection precision is affected.
In the prior art, the measurement accuracy is improved by changing the magnetic core coil, optimizing the associated parameters of the sensor and the like, but the aim of partial temperature compensation can be achieved, and the high-order process requirements cannot be met.
Disclosure of Invention
The invention aims to solve the technical problem that the accuracy of real-time testing of the metal film thickness by adopting an eddy current sensor is poor.
The invention provides a real-time measurement method of metal film thickness, which comprises the steps of S1, providing a first calibration wafer to an N calibration wafer, wherein the surface of any N calibration wafer is provided with an N-th metal film, the thicknesses of the first metal film to the N metal film on the surface of the first calibration wafer are different, N is an integer greater than or equal to 2, S2, obtaining a first temperature compensation calibration coefficient of the first metal film to an N temperature compensation calibration coefficient psi n of the N metal film, obtaining any N temperature compensation calibration coefficient psi n, performing N-th water polishing treatment on the N calibration wafer, performing N-th first electric vortex sensor test on the N-th metal film before the N-th water polishing treatment to obtain an N-th first vortex signal S n1, performing N-th second electric vortex sensor test on the N-th metal film after the N-th water polishing treatment, obtaining an N-th second vortex signal S n2, wherein N is greater than or equal to 1 and less than or equal to the integer, obtaining a value of the N-th temperature compensation coefficient of the N-th metal film, performing a step of which is equal to or equal to the N-th temperature compensation signal to the N-th vortex signal, and the absolute value of the N-th water polishing signal is measured, and the step of which is equal to the N-th water polishing signal has a value of the N-th vortex value of the first vortex signal to be measured, and is measured, and the absolute value of the N-th water vortex signal is measured, and the step is measured, and the absolute value is equal to the N-th signal is measured, and is 4, and the step is 4, and is a step is a value, and is obtained, and is a value, the method comprises the steps of obtaining a temperature change delta T in the polishing process of a metal film to be tested, testing an eddy current sensor of the metal film to be tested in real time in the polishing process of the metal film to be tested to obtain an initial test eddy current signal S 0 corresponding to the temperature change delta T, obtaining an nth calibration predicted eddy current signal I 1n,I1n＝Ψn*ΔT+Sn1 by adopting the temperature change delta T and an nth temperature compensation calibration coefficient psi n, obtaining a temperature compensation prediction function by adopting the nth temperature compensation calibration coefficient and the nth calibration predicted eddy current signal I 1n, obtaining the temperature compensation prediction function, wherein the temperature compensation prediction function is the change relation of the temperature compensation prediction coefficient along with the initial test eddy current signal, obtaining the temperature compensation prediction coefficient psi of the metal film to be tested corresponding to the initial test eddy current signal in the temperature compensation prediction function, and obtaining the temperature compensation prediction coefficient psi of the metal film to be tested according to the temperature compensation prediction coefficient psi of the metal film to be tested, and obtaining the temperature compensation prediction coefficient psi of the metal film to be tested, The method comprises the steps of obtaining a temperature change delta T and an initial test eddy current signal S 0 to obtain a compensation eddy current signal S, wherein S=S 0 +delta T is psi, and step S10 is to obtain the test thickness of the metal film to be tested corresponding to the compensation eddy current signal S in the film thickness prediction function.
Optionally, the process of performing the first eddy current sensor test on the nth metal film to obtain the first eddy current signal S n1 includes performing the eddy current sensor test on the first test point to the Q test point of the nth metal film respectively before the nth water polishing treatment, correspondingly obtaining the first eddy current first test point signal to the first eddy current Q test point signal of the nth time, and obtaining the average value of the first eddy current first test point signal to the first eddy current Q test point signal of the nth time as the first eddy current signal S n1 of the nth time, wherein Q is an integer greater than or equal to 2.
Optionally, the distance from any one of the first test point to the Q test point of the nth metal film to the center of the circle of the nth calibration wafer is 40% -75% of the radius of the nth calibration wafer.
Optionally, the process of carrying out the second eddy current sensor test on the nth metal film to obtain the second eddy current signal S n2 comprises respectively carrying out the eddy current sensor test on the first test point to the W test point of the nth metal film after the nth water polishing treatment to correspondingly obtain the first test point signal of the second eddy current to the W test point signal of the second eddy current, and obtaining the average value of the first test point signal of the second eddy current to the W test point signal of the second eddy current of the nth as the second eddy current signal S n2 of the nth, wherein W is an integer greater than or equal to 2.
Optionally, the distance from any one of the first test point to the W test point of the nth metal film to the center of the nth calibration wafer is 40% -75% of the radius of the nth calibration wafer.
Optionally, the step of obtaining the temperature compensation prediction function by adopting any nth temperature compensation calibration coefficient and the nth calibration predicted vortex signal I 1n comprises obtaining a mapping function of any nth temperature compensation calibration coefficient and the corresponding nth calibration predicted vortex signal I 1n, and fitting the mapping function to obtain the temperature compensation prediction function.
Optionally, the method for fitting the mapping function includes a linear difference method or a least square method.
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 S 0 corresponding to the temperature variation DeltaT comprises performing eddy current sensor testing on a first to a G to-be-tested point of the metal to be tested respectively to obtain a first to a G to-be-tested point signal correspondingly, and obtaining an average value of the first to the G to-be-tested point signals as the initial test eddy current signal S 0, wherein G is an integer greater than or equal to 2.
Optionally, the step of performing eddy current sensor testing on the metal film to be tested in real time to obtain an initial test eddy current signal S 0 corresponding to the temperature variation DeltaT comprises the steps of performing eddy current sensor testing on a first to-be-tested point to a P-th to-be-tested point of the metal film to be tested respectively in the polishing process of the metal film to be tested, correspondingly obtaining first to P-th initial test eddy current signals, wherein P is an integer greater than or equal to 2, obtaining a temperature compensation prediction coefficient psi of the metal film corresponding to the initial test eddy current signals in the temperature compensation prediction function, obtaining a first temperature compensation prediction coefficient of the metal film to be tested corresponding to the first initial test eddy current signals in the temperature compensation prediction function, obtaining a compensating eddy current signal S according to the temperature compensation prediction coefficient of the metal film to be tested, the temperature variation DeltaT, and the initial test eddy current signal S 0 comprises the steps of obtaining first to P-th eddy current signals, and obtaining any P-th eddy current signals according to the temperature compensation prediction coefficient of the temperature compensation eddy current signals in the temperature compensation prediction coefficient of the temperature compensation prediction function, the method comprises the steps of obtaining a P-th initial test eddy current signal S 0p to obtain a P-th compensation eddy current signal S p,Sp＝S0p +DeltaT psip of a metal film to be tested, wherein P is an integer which is more than or equal to 1 and less than or equal to P, and obtaining the test thickness of the metal film to be tested corresponding to the compensation eddy current signal S in the film thickness prediction function, wherein the step of obtaining the first test thickness of the first compensation eddy current signal corresponding to the film thickness prediction function to the P-th test thickness of the P-th compensation eddy current signal corresponding to the film thickness prediction function.
The technical scheme of the invention has the following beneficial effects:
According to the method for measuring the metal film thickness, provided by the invention, the compensation vortex signal S is obtained through the temperature compensation prediction coefficient psi, the temperature variation delta T and the initial test vortex signal S 0 of the metal film to be measured, so that the drift of the temperature to the vortex signal is compensated, and then the test thickness of the metal film to be measured corresponding to the compensation vortex signal S in the film thickness prediction function is obtained, so that the accurate thickness of the metal film to be measured can be obtained in real time even if the drift is caused to the output signal of the eddy current sensor by the temperature variation of the test environment, and the accuracy of real-time measurement of the metal film thickness is improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a method for measuring a metal film thickness according to an embodiment of the application;
FIG. 2 is a schematic diagram showing the change of the ambient temperature during wafer polishing calibration according to an embodiment of the present application;
FIG. 3 is a schematic diagram showing the variation of signals output by the eddy current sensor in the wafer water polishing process according to the embodiment of the application;
FIG. 4 is a linear schematic of a film thickness prediction function according to an embodiment of the present application;
FIG. 5 is a schematic diagram of a mapping function according to an embodiment of the present application;
FIG. 6 is a schematic diagram of a temperature compensated prediction function according to an embodiment of the present application;
FIG. 7 is a schematic diagram of a temperature compensated prediction function obtained according to another embodiment of the present application;
FIG. 8 is a schematic diagram of a distribution curve of temperature compensated first to P-th compensation eddy signals in a radial direction of a wafer to be measured according to an embodiment of the present application;
FIG. 9 is a schematic diagram of a distribution curve of a test thickness of a metal film to be tested corresponding to a first to a P-th compensation eddy current signals in the film thickness prediction function in a radial direction of a wafer according to an embodiment of the present application;
FIG. 10 is a schematic diagram of a motion profile of an eddy current sensor according to an embodiment of the application;
FIG. 11 is a schematic diagram showing comparison of initial test eddy current signals and compensated eddy current signals before and after temperature compensation according to an embodiment of the application.
Detailed Description
The following description of the present invention will be made clearly and fully, and it is apparent that the embodiments described are some, but not all, of the embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention. In addition, the technical features of the different embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
The embodiment of the invention provides a method for measuring the thickness of a metal film, which is shown in figure 1 and comprises the following steps:
step S1, providing a first calibration wafer to an Nth calibration wafer, wherein the surface of any nth calibration wafer is provided with an nth metal film, the thicknesses 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, and N is an integer greater than or equal to 2;
Step S2, obtaining a first temperature compensation calibration coefficient of a first metal film to an nth temperature compensation calibration coefficient ψ n of an nth metal film, obtaining an optional nth temperature compensation calibration coefficient ψ n, comprising the steps of performing an nth water polishing treatment on an nth calibration wafer, performing an nth first eddy current sensor test on the nth metal film before the nth water polishing treatment to obtain an nth first eddy current signal S n1, performing an nth second eddy current sensor test on the nth metal film after the nth water polishing treatment to obtain an nth second eddy current signal S n2, wherein N is an integer which is greater than or equal to 1 and less than or equal to N, obtaining an nth temperature variation delta T n in the nth water polishing treatment process, taking the ratio of the absolute value of the difference value of the nth first eddy current signal and the nth second eddy current signal to the nth temperature variation delta T n as the nth temperature compensation calibration coefficient Ψn;Ψn＝ΔSn/ΔTn;ΔSn＝︱Sn1-Sn2︱;ΔTn＝︱Tn1-Tn2︱;
Step S3, fitting a film thickness prediction function by adopting the thickness of any nth metal film and the data of the nth first eddy current signal, wherein the film thickness prediction function is the relation between the test thickness and the compensation eddy current signal;
Step S4, providing a wafer to be tested, wherein the surface of the wafer to be tested is provided with a metal film to be tested;
Step S5, polishing the metal film to be tested to obtain the temperature change delta T in the process of polishing the metal film to be tested, and testing the eddy current sensor of the metal film to be tested in real time in the process of polishing the metal film to be tested to obtain an initial test eddy current signal S 0 corresponding to the temperature change delta T;
step S6, acquiring an nth calibration predicted vortex signal I 1n,I1n＝Ψn*ΔT+Sn1 by adopting a temperature variation delta T and an optional nth temperature compensation calibration coefficient psi n;
s7, acquiring a temperature compensation prediction function by adopting any nth temperature compensation calibration coefficient and an nth calibration prediction eddy current signal I 1n, wherein the temperature compensation prediction function is the change relation of the temperature compensation prediction coefficient along with an initial test eddy current signal;
step S8, obtaining a temperature compensation prediction coefficient psi of the metal film to be detected corresponding to the initial test eddy current signal in the temperature compensation prediction function;
Step S9, obtaining a compensating vortex signal S according to a temperature compensating prediction coefficient psi, a temperature variation delta T and an initial testing vortex signal S 0 of the metal film to be tested;
And S10, obtaining the test thickness of the metal film to be tested corresponding to the compensation vortex signal S in the film thickness prediction function.
In this embodiment, the temperature compensation prediction coefficient ψ, the temperature variation Δt and the initial test eddy current signal S 0 of the metal film to be tested are used to obtain the compensation eddy current signal S, so as to compensate the drift of the eddy current signal due to temperature, and then obtain the test thickness of the metal film to be tested corresponding to the compensation eddy current signal S in the film thickness prediction function, so that even if the drift of the output signal of the eddy current sensor is caused by the temperature variation of the test environment, the accurate thickness of the metal film to be tested can be obtained in real time, and the accuracy of real-time measurement of the metal film thickness is improved.
In this embodiment, the diameters of the first calibration wafer to the nth calibration wafer are not limited, and the diameters may be 50mm, 75mm, 100mm, 125mm, 150mm, 200mm or 300mm, as long as the diameters of the first calibration wafer to the nth calibration wafer are the same. The specific thickness of the first metal film on the first calibration wafer surface to the nth metal film on the nth calibration wafer surface is not limited as long as the film thickness of the first metal film on the first calibration wafer surface to the nth metal film on the nth calibration wafer surface is uniform. The value of N is an integer greater than or equal to 2, and the larger the value of N is, the more accurate the fitted temperature compensation prediction function and film thickness prediction function are, and the more accurate the thickness of the obtained metal film to be measured is.
In this embodiment, the nth calibration wafer is subjected to the nth water polishing treatment, the nth water polishing treatment does not use a corrosive polishing solution, and water is used as a medium in the polishing process of the nth calibration wafer. The thickness of the nth metal film does not change during the nth water polishing process.
During the water polishing process, the environmental temperature of the water polishing process, for example, the temperature of the polishing pad, is increased, as shown in fig. 2, the abscissa of fig. 2 indicates the number of tests, and the ordinate of fig. 2 indicates the environmental temperature. As shown in fig. 3, during the water polishing process, the output vortex signal of the eddy current sensor will be reduced due to the increase of the environmental temperature of the water polishing process, the abscissa of fig. 3 is the number of tests, and the ordinate of fig. 3 is the output vortex signal of the eddy current sensor.
In the embodiment, the process of performing the nth first eddy current sensor test on the nth metal film to obtain the nth first eddy current signal S n1 includes performing the eddy current sensor test on the first test point to the Q test point of the nth metal film respectively before the nth water polishing treatment to correspondingly obtain the nth first eddy current first test point signal to the nth first eddy current Q test point signal, and obtaining the average value of the nth first eddy current first test point signal to the nth first eddy current Q test point signal as the nth first eddy current signal S n1, wherein Q is an integer greater than or equal to 2. The average value of the first test point signal from the first eddy current at the nth time to the first eddy current at the nth time and the first eddy current at the Q test point signal at the nth time is used as the first eddy current signal S n1 at the nth time, so that the measurement error can be reduced.
And (3) performing eddy current sensor testing on the Q test point of the n-th metal film to obtain the Q test point signal of the n-th first eddy current, wherein Q is an integer greater than or equal to 1 and less than or equal to Q.
When the eddy current sensor is respectively tested on the first test point to the Q test point of the nth metal film, the adopted test instrument is an eddy current metal film thickness detector, the eddy current metal film thickness detector is internally provided with an eddy current sensor, and the eddy current sensor is positioned below the polishing table and can rotate along with the polishing table and sweep the surface of the nth metal film during rotation. The distances from each of the first test point to the Q test point of the nth metal film to the eddy current metal film thickness detector are consistent. The distances from each of the first test point to the Q test point of the nth metal film to the eddy current metal film thickness detector may also be inconsistent. The method only needs to ensure that any q test point of the nth metal film to the eddy current metal film thickness detector is within the metal film thickness test range.
In this embodiment, the distance between any one of the first test point to the Q test point of the nth metal film and the center of the nth calibration wafer is 40% -75%, for example 40%, 45%, 50%, 55%, 60%, 65%, 70% or 75% of the radius of the nth calibration wafer. In general, the thickness of the metal film is uniform within the range of 40% -75% of the radius of the calibration wafer, and the eddy current signal obtained by any one test point within the range is uniform and accurate, so that the measurement accuracy can be improved.
In the embodiment, the process of carrying out the second eddy current sensor test on the nth metal film to obtain the second eddy current signal S n2 comprises the steps of respectively carrying out the eddy current sensor test on the first test point to the W test point of the nth metal film after the nth water polishing treatment to correspondingly obtain the second eddy current first test point signal to the second eddy current W test point signal, and obtaining the average value of the second eddy current first test point signal to the second eddy current W test point signal as the second eddy current signal S n2, wherein W is an integer greater than or equal to 2. The average value of the nth second eddy current first test point signal to the nth second eddy current W test point signal is used as the nth second eddy current signal S n2, so that measurement errors can be reduced.
And (3) performing eddy current sensor testing on the W test point of the n metal film to obtain a W test point signal of the n second eddy current, wherein W is an integer greater than or equal to 1 and less than or equal to W.
When the eddy current sensor is respectively tested on the first test point to the W test point of the nth metal film, the adopted test instrument is an eddy current metal film thickness detector, the eddy current metal film thickness detector is internally provided with an eddy current sensor, and the eddy current sensor is positioned below the polishing table and can rotate along with the polishing table and sweep the surface of the nth metal film during rotation. The distances from each of the first test point to the W test point of the nth metal film to the eddy current metal film thickness detector are consistent. The distances from each of the first test point to the W test point of the nth metal film to the eddy current metal film thickness detector may also be inconsistent. The distance from any w test point of the nth metal film to the eddy current metal film thickness detector is only required to be ensured to be within the film thickness test range.
In this embodiment, the distance between any one of the first test point to the W test point of the nth metal film and the center of the nth calibration wafer is 40% -75%, for example 40%, 45%, 50%, 55%, 60%, 65%, 70% or 75% of the radius of the nth calibration wafer. In general, the thickness of the metal film is uniform within the range of 40% -75% of the radius of the calibration wafer, and the eddy current signal obtained by any one test point within the range is uniform and accurate, so that the measurement accuracy can be improved.
In this embodiment, the step of obtaining the temperature compensation prediction function by using the optional nth temperature compensation calibration coefficient and the nth calibration predicted vortex signal I 1n includes obtaining a mapping function of the optional nth temperature compensation calibration coefficient and the corresponding nth calibration predicted vortex signal I 1n, as shown in a schematic diagram of the mapping function in fig. 5, wherein the abscissa of fig. 5 is the calibration predicted vortex signal, and the ordinate of fig. 5 is the temperature compensation calibration coefficient, and fitting the mapping function to obtain the temperature compensation prediction function. The temperature compensation prediction function can be used for rapidly and conveniently obtaining the temperature compensation prediction coefficient of the metal film to be detected corresponding to the initial test eddy current signal, so that the thickness of the metal film to be detected is more accurate.
In this embodiment, the method for fitting the mapping function includes a linear difference method or a least square method. And fitting the mapping function to obtain a temperature compensation prediction function, so that the temperature compensation prediction coefficient of the metal film to be measured of any wafer to be measured can be obtained from the temperature compensation prediction function.
In an embodiment, the method for fitting the mapping function is a linear difference method, as shown in fig. 6, which is a schematic diagram of a temperature compensation prediction function obtained by fitting the mapping function by using the linear difference method, and the abscissa of fig. 6 is an initial test eddy current signal and the ordinate is a temperature compensation prediction coefficient. The temperature compensation prediction function is fitted by adopting a linear difference method, so that the temperature compensation prediction coefficient of the metal film of any wafer to be detected can be simply and rapidly obtained.
In another embodiment, the method of fitting the mapping function is a least squares method. The mapping function is fitted by adopting a least square method to obtain a temperature compensation prediction function, and the relation between the actually measured eddy current signal and the temperature compensation prediction coefficient can be expressed more conveniently by adopting tertiary fitting, as shown in a schematic diagram of the temperature compensation prediction function obtained by fitting the mapping function by adopting the least square method in fig. 7, the abscissa of fig. 7 is an initial test eddy current signal, the ordinate is the temperature compensation prediction coefficient, and in fig. 7, R 2 represents the fitting degree, and the closer the value of R 2 is to 1, the better the fitting degree is.
In step 3, the corresponding relation between the thickness of any nth metal film and the data of the nth first eddy current signal is not affected by the ambient temperature, and a film thickness prediction function is fitted by using the thickness of any nth metal film and the data of the nth first eddy current signal, as shown in fig. 4, wherein the abscissa of fig. 4 is the compensated eddy current signal, the ordinate of fig. 4 is the test thickness, and the film thickness prediction function is the relation between the test thickness and the compensated eddy current signal. In fig. 4, R 2 represents the fitness, and a closer value of R 2 to 1 indicates a better fitness.
In one embodiment, 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 S 0 corresponding to a temperature variation delta T comprises the steps of performing eddy current sensor testing on a first to a G to-be-tested point of the metal to be tested respectively to obtain a first to a G to-be-tested point signal correspondingly, and obtaining an average value of the first to the G to-be-tested point signals as an initial test eddy current signal S 0, wherein G is an integer greater than or equal to 2. The average value of the first to the G-th to-be-measured point signals is used as the initial test eddy current signal S 0, so that the measurement error can be reduced.
In another embodiment, the step of performing the eddy current sensor test on the metal film to be tested in real time to obtain the initial test eddy current signal S 0 corresponding to the temperature variation DeltaT comprises the steps of performing the eddy current sensor test on the first to P-th points to be tested of the metal film to be tested respectively in the polishing process of the metal film to be tested to obtain the first to P-th initial test eddy current signals correspondingly, wherein P is an integer greater than or equal to 2, the step of obtaining the temperature compensation prediction coefficient psi of the metal film corresponding to the initial test eddy current signals in the temperature compensation prediction function comprises the steps of obtaining the first to P-th eddy current signals correspondingly from the first to P-th temperature compensation prediction coefficients of the metal film to be tested in the temperature compensation prediction function, and the step of obtaining the compensation eddy current signals S according to the temperature compensation prediction coefficients of the metal film to be tested, the temperature variation DeltaT and the initial test eddy current signals S 0 comprises the steps of obtaining the first to P-th eddy current signals, obtaining the arbitrary P-th eddy current signals according to the temperature compensation prediction coefficients of the temperature compensation DeltaT and the P-th eddy current signals corresponding to the temperature compensation test eddy current signals, the method comprises the steps of obtaining a P-th initial test eddy current signal S 0p to obtain a P-th compensation eddy current signal S p,Sp＝S0p +DeltaT psip of a metal film to be tested, wherein P is an integer which is more than or equal to 1 and less than or equal to P, and obtaining the test thickness of the metal film to be tested corresponding to the compensation eddy current signal S in the film thickness prediction function, wherein the step of obtaining the first test thickness of the first compensation eddy current signal corresponding to the film thickness prediction function to the P-th test thickness of the P-th compensation eddy current signal corresponding to the film thickness prediction function.
As shown in FIG. 8, the abscissa in FIG. 8 is the diameter of the wafer to be measured, the ordinate is the first to the P-th compensating eddy current signals after temperature compensation, the distribution of the first to the P-th compensating eddy current signals after temperature compensation in the radial direction of the wafer to be measured can be intuitively seen from FIG. 8, the thickness of the metal film to be measured corresponding to the first to the P-th compensating eddy current signals after temperature compensation in the film thickness prediction function is obtained, the distribution curve of the test thickness of the metal film to be measured corresponding to the first to the P-th compensating eddy current signals after temperature compensation in the film thickness prediction function in the radial direction of the wafer to be measured is generated, as shown in FIG. 9, the abscissa in FIG. 9 is the diameter of the wafer to be measured, and the ordinate in FIG. 9 is the test thickness, the distribution of the first to the P-th compensating eddy current signals in the radial direction of the wafer to be measured corresponding to the test thickness of the metal film in the film thickness prediction function can be intuitively seen from FIG. 9.
In the embodiment, when the first to the P-th initial test eddy current signals are obtained, the distance between any one of the first to the P-th test points of the metal film to be tested and the center of the wafer to be tested is calculated, the distribution curve of the first to the P-th test point signals in the radial direction of the wafer to be tested is generated, the following relation is satisfied,
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, alpha is AO1C, n is the rotating speed (unit is rotation/s) of the polishing table, R 1 is the track radius of the eddy current sensor, R 2 is the distance between O1 and O2, R is the distance between the test point B and O2, in the figure, 1 is the polishing table, 2 is the wafer to be tested, 3 is the motion track of the eddy current sensor, the wafer to be tested can be scanned, 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 for testing the metal film to be tested, the eddy current sensor can sweep from the point A, pass through the point B and then reach the point D, and also can sweep from the point D, pass through the point B and then reach the point A, so that the final test result is not influenced. The output signal of the eddy current sensor comprises an eddy current signal and a mark bit, the eddy current sensor sweeps the test point B to the first fixed point A, the mark bit of the output signal of the eddy current sensor changes, or the eddy current sensor sweeps the second fixed point D to the test point B, and the mark bit of the output signal of the eddy current sensor changes.
In one embodiment, the metal film thicknesses are provided as followsAndIs a plurality of calibration wafers, and the thickness of the metal film isThe wafer is subjected to water polishing treatment, and the film thickness is set to beIs subjected to a first eddy current sensor test to obtain a first eddy current signal, and after water polishing treatment, the film thickness is set to beThe metal film of the water polishing process is tested by a second eddy current sensor to obtain a second eddy current signal, the temperature change delta T of the water polishing process is obtained, and the ratio of the absolute value of the difference value of the first eddy current signal and the second eddy current signal to the temperature change delta T is taken as the film thicknessThe temperature compensation calibration coefficient of the metal film is repeated to obtain the film thickness of the metal film AndTemperature compensation calibration coefficient of metal film of (C) by AndFitting a film thickness prediction function to the corresponding data of the first eddy current signal, wherein the film thickness prediction function is the relation between the test thickness and the compensation eddy current signal, and the film thickness is as followsPolishing the metal film to obtain a film having a specific thicknessTemperature variation in polishing process of metal film, film thickness of the metal film is as followsIn the polishing process of the metal film, the film thickness is real-timeThe metal film of the film is tested by an eddy current sensor to obtain an initial test eddy current signal corresponding to the temperature variation, and the temperature variation and the film thickness are adoptedThe film thickness obtained by the metal film temperature compensation calibration coefficient isThe eddy current signal is predicted by metal film calibration, and the film thickness is adopted asThe metal film temperature compensation calibration coefficient and the film thickness are as followsThe metal film calibration prediction eddy current signal obtains a temperature compensation prediction function, wherein the temperature compensation prediction function is the change relation of a temperature compensation prediction coefficient along with an initial test eddy current signal, and the film thickness is real-timeRespectively performing eddy current sensor test on the first to-be-measured point to the P to-be-measured point of the metal film to correspondingly obtain first to P initial test eddy current signals, wherein P is an integer greater than or equal to 2, obtaining the corresponding P temperature compensation prediction coefficient of the first to P initial test eddy current signals in the temperature compensation prediction function, and obtaining the film thickness of the film according to the first to P temperature compensation prediction coefficient, the temperature variation and the first to P initial test eddy current signalsAs shown in FIG. 11, the abscissa of FIG. 11 is the number of tests, the ordinate is the eddy current signal, rawData is the initial test eddy current signal, newData is the compensated eddy current signal, and the corresponding first test thickness of the first compensated eddy current signal in the film thickness prediction function to the corresponding P test thickness of the P compensated eddy current signal in the film thickness prediction function are obtained. The first test thickness to the P test thickness and the film thickness areThe actual thickness error of the metal film during the polishing process is small.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. While still being apparent from variations or modifications that may be made by those skilled in the art are within the scope of the invention.
Claims (9)
1. A real-time measuring method of metal film thickness is characterized by comprising the following steps:
step S1, providing a first calibration wafer to an Nth calibration wafer, wherein the surface of any nth calibration wafer is provided with an nth metal film, the thicknesses 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, and N is an integer greater than or equal to 2;
Step S2, obtaining a first temperature compensation calibration coefficient of a first metal film to an nth temperature compensation calibration coefficient ψ n of an nth metal film, obtaining an optional nth temperature compensation calibration coefficient ψ n, comprising the steps of performing an nth water polishing treatment on an nth calibration wafer, performing an nth first eddy current sensor test on the nth metal film before the nth water polishing treatment to obtain an nth first eddy current signal S n1, performing an nth second eddy current sensor test on the nth metal film after the nth water polishing treatment to obtain an nth second eddy current signal S n2, wherein N is an integer which is greater than or equal to 1 and less than or equal to N, obtaining an nth temperature variation delta T n in the nth water polishing treatment process, taking the ratio of the absolute value of the difference value of the nth first eddy current signal and the nth second eddy current signal to the nth temperature variation delta T n as the nth temperature compensation calibration coefficient Ψn;Ψn＝ΔSn/ΔTn;ΔSn＝︱Sn1-Sn2︱;ΔTn＝︱Tn1-Tn2︱;
Step S3, fitting a film thickness prediction function by adopting the thickness of any nth metal film and the data of the nth first eddy current signal, wherein the film thickness prediction function is the relation between the test thickness and the compensation eddy current signal;
Step S4, providing a wafer to be tested, wherein the surface of the wafer to be tested is provided with a metal film to be tested;
Step S5, polishing the metal film to be tested to obtain the temperature change delta T in the process of polishing the metal film to be tested, and testing the eddy current sensor of the metal film to be tested in real time in the process of polishing the metal film to be tested to obtain an initial test eddy current signal S 0 corresponding to the temperature change delta T;
step S6, acquiring an nth calibration predicted vortex signal I 1n,I1n＝Ψn*ΔT+Sn1 by adopting a temperature variation delta T and an optional nth temperature compensation calibration coefficient psi n;
s7, acquiring a temperature compensation prediction function by adopting any nth temperature compensation calibration coefficient and an nth calibration prediction eddy current signal I 1n, wherein the temperature compensation prediction function is the change relation of the temperature compensation prediction coefficient along with an initial test eddy current signal;
step S8, obtaining a temperature compensation prediction coefficient psi of the metal film to be detected corresponding to the initial test eddy current signal in the temperature compensation prediction function;
Step S9, obtaining a compensating vortex signal S according to a temperature compensating prediction coefficient psi, a temperature variation delta T and an initial testing vortex signal S 0 of the metal film to be tested;
And S10, obtaining the test thickness of the metal film to be tested corresponding to the compensation vortex signal S in the film thickness prediction function.
2. The method according to claim 1, wherein the step of performing the first eddy current sensor test on the nth metal film to obtain the first eddy current signal S n1 includes performing the first eddy current sensor test on the first test point to the Q test point of the nth metal film, respectively, before the nth water polishing process, to obtain the first eddy current first test point signal to the first eddy current Q test point signal, respectively, and obtaining an average value of the first eddy current first test point signal to the first eddy current Q test point signal as the first eddy current signal S n1, wherein Q is an integer of 2 or more.
3. The method for measuring the thickness of a metal film in real time according to claim 2, wherein the distance from any one of the first test point to the Q test point of the nth metal film to the center of the circle of the nth calibration wafer is 40% -75% of the radius of the nth calibration wafer.
4. The method for measuring the thickness of a metal film in real time according to claim 1, wherein the process of performing the second eddy current sensor test on the nth metal film to obtain the second eddy current signal S n2 includes performing the eddy current sensor test on the first test point to the W test point of the nth metal film after the nth water polishing process, respectively, correspondingly obtaining the second eddy current first test point signal to the second eddy current W test point signal, and obtaining the average value of the second eddy current first test point signal to the second eddy current W test point signal as the second eddy current signal S n2, wherein W is an integer greater than or equal to 2.
5. The method for measuring the thickness of a metal film in real time according to claim 4, wherein the distance from any one of the first test point to the W test point of the n-th metal film to the center of the n-th calibration wafer is 40% -75% of the radius of the n-th calibration wafer.
6. The method for measuring the thickness of a metal film in real time according to claim 1, wherein the step of obtaining the temperature compensation prediction function by using any nth temperature compensation calibration coefficient and an nth calibration prediction eddy current signal I 1n comprises obtaining a mapping function of any nth temperature compensation calibration coefficient and a corresponding nth calibration prediction eddy current signal I 1n, and fitting the mapping function to obtain the temperature compensation prediction function.
7. The method according to claim 6, wherein the method of fitting the mapping function comprises a linear difference method or a least square method.
8. The method for measuring the thickness of a metal film in real time according to claim 1, wherein the step of performing an eddy current sensor test on the metal film to be measured in real time to obtain an initial test eddy current signal S 0 corresponding to the temperature change amount Deltat comprises the steps of performing the eddy current sensor test on a first to a G-th points to be measured of the metal to be measured respectively to obtain first to the G-th signals to be measured correspondingly, and obtaining an average value of the first to the G-th signals to be measured as the initial test eddy current signal S 0, wherein G is an integer greater than or equal to 2.
9. The method for measuring the thickness of a metal film in real time according to claim 1, wherein the step of performing an eddy current sensor test on the metal film to be measured in real time to obtain an initial test eddy current signal S 0 corresponding to the temperature variation Deltat comprises the steps of performing the eddy current sensor test on a first to P-th to-be-measured point of the metal film to be measured respectively in the polishing process of the metal film to be measured to correspondingly obtain a first to P-th initial test eddy current signal;
the step of obtaining the temperature compensation prediction coefficient psi of the metal film to be detected corresponding to the initial test eddy current signal in the temperature compensation prediction function comprises the steps of obtaining a first temperature compensation prediction coefficient of the metal film to be detected corresponding to a first initial test eddy current signal in the temperature compensation prediction function to a P temperature compensation prediction coefficient of the metal film to be detected corresponding to a P initial test eddy current signal in the temperature compensation prediction function;
The step of obtaining the compensating vortex signal S according to the temperature compensating prediction coefficient, the temperature variation delta T and the initial testing vortex signal S 0 of the metal film to be detected comprises the steps of obtaining a first compensating vortex signal to a P compensating vortex signal, wherein the step of obtaining any P compensating vortex signal comprises the steps of obtaining the P compensating vortex signal S p,Sp＝S0p +delta T of the metal film to be detected according to the P temperature compensating prediction coefficient psip, the temperature variation delta T and the P initial testing vortex signal S 0p of the metal film to be detected, wherein P is an integer which is more 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 tested corresponding to the compensation vortex signal S in the film thickness prediction function comprises the steps of obtaining a first test thickness corresponding to a first compensation vortex signal in the film thickness prediction function to a P test thickness corresponding to a P compensation vortex signal in the film thickness prediction function.
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