Optimized characterization method, device and system for overlay error of photoetching process

Abstract

The invention relates to the technical field of integrated circuit photoetching process overlay measurement, and discloses a photoetching process overlay error optimization characterization method, device and system, and the method comprises the steps: obtaining a DBO sample, calculating various indexes of electromagnetic field simulation minimization characterization quantity to optimize the performance of measurement configuration, and determining an optimal measurement configuration set; performing Mueller matrix measurement under the optimal measurement configuration set, and matching the Mueller matrix with a Mueller matrix obtained by simulation; performing polar decomposition on a Mueller matrix obtained by actual measurement of each wavelength point in the optimal measurement configuration set; calculating the intrinsic polarization state of each wavelength point in the optimal measurement configuration set; and after average weighting is carried out on the characterization quantity of the intrinsic polarization state obtained by each wavelength point in the optimal measurement configuration set, OVL solution is carried out, and an overlay error is obtained. Compared with the traditional method, the method has the advantages that the accuracy is greatly improved on the characterization of the overlay error of the photoetching process, and the robustness is better.

Description

Technical Field

[0001] The present application relates to the technical field of overlay measurement of integrated circuit lithography processes, and in particular to an optimized characterization method, device and system for overlay error of lithography processes. Background Art

[0002] Photolithography is one of the most complex and critical process steps in integrated circuit manufacturing, and overlay error is one of the important indicators to measure the quality of photolithography process. Overlay error refers to the alignment error between the current layer (the pattern retained on the photoresist after exposure and development) and the reference layer (the existing pattern on the wafer) during exposure, that is, the relative offset from the designed position of the current layer. Generally speaking, the overlay error should usually be less than about 20%-30% of the critical dimension (CD). If the overlay error is large, it will lead to poor device yield. Therefore, in semiconductor manufacturing, accurate measurement of critical dimensions is particularly critical, among which accurate measurement of overlay error is particularly important.

[0003] Diffraction-based overlay error measurement (DBO), also known as scattering-based overlay error measurement (SCOL), is one of the main technical routes for measuring overlay error. The DBO method is mainly divided into mDBO and eDBO. As pointed out in the technical solution of patent publication number CN103472004A, the mDBO method requires real-time solution of complex partial differential equations to construct an overlay mark optical model, so it is difficult to meet the time requirements for in-situ measurement of overlay error.

[0004] The traditional eDBO method mainly relies on the local linear relationship between the proposed light intensity characterization and the overlay error to measure the overlay error. Compared with the traditional light intensity information, the Mueller matrix can obtain a 4×4 order zero-order diffraction Mueller matrix under each measurement configuration, which contains richer optical information. The measurement of the overlay error δ can be converted into the Mueller matrix measurement corresponding to the zero-order diffraction light, from which the characterization is found, and the overlay error is solved by using the linear relationship between the characterization and the overlay error δ. For example, a linear empirical extraction method based on the non-diagonal elements of the Mueller matrix for measuring the overlay error of a three-dimensional complex overlay structure has been proposed in the art (YNKim et al., Opt. Express, Vol. 17 (23), pp. 21336-21343, 2009), and an empirical extraction method based on the non-diagonal elements of the Mueller matrix for measuring the overlay error of a one-dimensional overlay structure has been proposed in the art (J. Li et al., Proc. SPIE, Vol. 7638, pp. 78382C1-78382C10). At the same time, the eDBO method using the Mueller matrix is ​​mentioned in the disclosed technical solutions such as patent numbers CN202310116536.9, CN202110470725.7, CN202011056590.1, and CN201210544767.1. However, the existing methods have limitations in some aspects, such as small linear range, low sensitivity, poor robustness, and unusable at an azimuth angle of 90°.

[0005] Therefore, it is urgent to construct an overlay characterization scheme with good linearity, sensitivity and robustness. Summary of the invention

[0006] In order to solve the above problems, the present application provides a method, device and system for optimizing characterization of overlay error in a lithography process, so as to construct a method for characterizing a quantity with good linearity, sensitivity and robustness.

[0007] In order to achieve the above purpose, the technical solution adopted in this application is as follows:

[0008] In a first aspect, the present application provides a method for optimizing characterization of overlay error in a lithography process, the method comprising:

[0009] Obtain DBO samples, calculate various indicators of electromagnetic field simulation minimization to optimize the performance of the measurement configuration, and determine the best measurement configuration set;

[0010] Performing Mueller matrix measurement under the optimal measurement configuration set, and selecting the measured Mueller matrix to match the Mueller matrix obtained by simulation;

[0011] Polar decomposition is performed on the Mueller matrix actually measured at each wavelength point in the optimal measurement configuration set;

[0012] Calculate the intrinsic polarization state of each wavelength point in the optimal measurement configuration set;

[0013] After averaging and weighting the characteristic quantities of the intrinsic polarization state obtained at each wavelength point in the optimal measurement configuration set, the OVL solution is performed to obtain the overlay error.

[0014] Furthermore, DBO samples are obtained, and various indicators of the electromagnetic field simulation minimization characterization quantity are calculated to optimize the performance of the measurement configuration, and the best measurement configuration set is determined, including:

[0015] The various indicators of the characterization quantity are expressed as {L, -S, Ro}, and the measurement configuration is optimized by minimizing {L, -S, Ro} to obtain the Pareto optimal solution as the best measurement configuration set; where L is the linearity, L = || f OVL±d -k(OVL±d)||, f is the real indication curve, k is the slope, OVL is the overlay error, d is the artificially introduced bias; S is the sensitivity, Ro is robustness, σ is the standard deviation of a set of data, and μ is the mean of the means of a set of data.

[0016] Furthermore, a wide spectrum ellipsometer is used to perform Mueller matrix measurement under the optimal measurement configuration set.

[0017] Furthermore, the calculation process of polar decomposition of the Mueller matrix actually measured at each wavelength point in the optimal measurement configuration set is expressed as:

[0018] M=M Δ M R M D

[0019] Where M is the measured Mueller matrix, M D is the amplitude bidirectional attenuation matrix of the sample for the incident light, which is used to represent the differential loss between orthogonal polarization eigenstates; M R is the phase delay matrix of the sample to the incident light, which is used to represent the differential phase delay between the two eigenstates; M Δ is the depolarization matrix of the sample for the incident light; D represents the bidirectional attenuation vector, P Δ represents the polarization vector, T represents the matrix transpose, m D By deleting M D The first row and first column of M are obtained D A 3x3 submatrix ofR By deleting M R The first row and first column of M are obtained R A 3x3 submatrix of Δ By deleting M Δ The first row and first column of M are obtained Δ A 3x3 submatrix of .

[0020] Further, M is calculated by the following formula D and M R :

[0021]

[0022] Where D = (M 12 ,M 13 ,M 14 ) T , M 12 ,M 13 ,M 14 Respectively represent the second, third, and fourth elements of the first row of the Mueller matrix, M D is the double decay vector of M, D′ is the unit vector along D, and I is the 3×3 identity matrix.

[0023] Furthermore, the eigenpolarization state of each wavelength point in the calculated optimal measurement configuration set is expressed as:

[0024]

[0025] Where α = (1, a1, a2, a3) is the intrinsic polarization state, M R is the differential delay matrix of the sample for the incident light, a1, a2, a3 represent the second, third, and fourth elements in the normalized intrinsic polarization state, respectively, and a2 in the intrinsic polarization state is used as the characterization quantity.

[0026] The calculation expressions of each element of the intrinsic polarization state are as follows:

[0027]

[0028] In the formula, represents the phase delay function, δ ij is the Kronecker function, ∈ ijk is the Levi–Civita permutation symbol, (m R ) ij is m R The element in the i-th row and j-th column of i is the i+1 element in the intrinsic polarization state, a j is the j+1 element in the intrinsic polarization state, ak is the k+1 element in the intrinsic polarization state, i is (m R ) ij Elements in m R The corresponding row number in , j is (m R ) ij Elements in m R The corresponding column number in , k is the indicator variable.

[0029] Furthermore, the characteristic quantities of the intrinsic polarization state obtained at each wavelength point in the optimal measurement configuration set are averaged and weighted, and then the OVL solution is performed to obtain the calculation formula of the overlay error:

[0030]

[0031] Where OVL is the measured overlay error, d is the artificially introduced bias, It is the characteristic quantity measured under the corresponding mark of d+OVL.

[0032] In a second aspect, the present application provides a device for optimizing and characterizing overlay error in a lithography process, the device comprising:

[0033] The best configuration determination module is configured to obtain DBO samples, calculate various indicators of the electromagnetic field simulation minimization characterization quantity to optimize the performance of the measurement configuration, and determine the best measurement configuration set;

[0034] A matrix matching module is configured to perform Mueller matrix measurement under the optimal measurement configuration set, and select the measured Mueller matrix to match the Mueller matrix obtained by simulation;

[0035] A matrix polar decomposition module is configured to perform polar decomposition on the Mueller matrix actually measured at each wavelength point in the optimal measurement configuration set;

[0036] A polarization state calculation module is configured to calculate the intrinsic polarization state of each wavelength point in the optimal measurement configuration set;

[0037] The overlay error solving module is configured to perform an OVL solution after averaging and weighting the characteristic quantities of the intrinsic polarization state obtained at each wavelength point in the optimal measurement configuration set to obtain the overlay error.

[0038] In a third aspect, the present application provides a system for optimizing characterization of overlay errors in a lithography process, the system comprising: a memory for storing a computer program; and a processor for executing the computer program to implement the method as described above.

[0039] This application has at least the following beneficial effects:

[0040] The measurement of the characterization quantity α2 calculated in the present application is not restricted by the azimuth angle, and can achieve full-angle measurement under non-zero azimuth angles. In addition, in the characterization of the overlay error of the lithography process, compared with traditional methods, it greatly improves the accuracy and has better robustness. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The present invention is a flowchart of a method for optimizing the characterization of overlay error in a photolithography process according to an embodiment of the present application.

[0042] Figure 2 Schematic diagram of the measurement sample marking structure according to an embodiment of the present application; wherein (a) is a cross-sectional view of the overlay mark; and (b) is a three-dimensional view of the overlay mark.

[0043] Figure 3 These are performance diagrams at different wavelengths according to an embodiment of the present application, wherein: (a) 200 nm wavelength; (b) 400 nm wavelength; (c) 600 nm wavelength; (d) 800 nm wavelength; and (e) 1000 nm wavelength.

[0044] Figure 4 It is a comparison diagram of measurement errors under ideal measurement conditions according to an embodiment of the present application.

[0045] Figure 5 These are the SEM images of real samples according to the embodiments of the present application and the actual size images marked in the FIB images, wherein: (a) is the SEM image of the real sample; (b) is the actual size image marked in the FIB image.

[0046] Figure 6 It is a structural diagram of an optimization characterization device for overlay error of a photolithography process according to an embodiment of the present application. DETAILED DESCRIPTION

[0047] The following describes the embodiments of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. The present application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0048] The specific implementation of the present application is further described in detail below in conjunction with the drawings and examples.

[0049] Embodiment 1:

[0050] See also Figure 1, is a flow chart of an optimization characterization method for overlay error of a lithography process. The optimization characterization method for overlay error of a lithography process includes steps S1 to S5, which are described in detail as follows.

[0051] S1, obtain DBO samples, calculate the various indicators of electromagnetic field simulation minimization characterization quantity to optimize the performance of the measurement configuration, and determine the best measurement configuration set.

[0052] In this embodiment, for a given DBO sample, under known prior distribution information, a computational electromagnetic field simulation is performed to evaluate the performance of the characterization quantity index α2, and the performance of each index can be evaluated for a series of sampling points within a given OVL variation range. L is the linearity, L = || f OVL±d -k(OVL±d)||, the linear error is defined as the distance between the true indication curve f and the approximate linear function with a slope of k, OVL is the overlay error, and d is the artificially introduced bias. S is the sensitivity, The sensitivity index is used to indicate the ability of the characterization index to evaluate small overlay errors. Ro is the robustness, Where σ is the standard deviation of a set of data, and μ is the mean of the average values ​​of a set of data. This indicator is designed to minimize the impact of any disturbance (for example, a small change in the measurement wavelength λ or azimuth). The measurement configuration is optimized by minimizing the three indicator performances {L, -S, Ro} to obtain the Pareto optimal solution and determine the Pareto optimal measurement configuration set.

[0053] S2, perform Mueller matrix measurement under the best measurement configuration set, and select the measured Mueller matrix to match the Mueller matrix obtained by simulation.

[0054] In this embodiment, a wide spectrum ellipsometer is used to perform Mueller matrix measurement under the optimal measurement configuration set, and then the measured Mueller matrix is ​​selected to match the Mueller matrix obtained by simulation.

[0055] S3, performing polar decomposition on the Mueller matrix actually measured at each wavelength point in the optimal measurement configuration set.

[0056] In this embodiment, the Mueller matrix actually measured at each wavelength point in the Pareto front solution is subjected to polar decomposition, and the specific process of polar decomposition is as follows:

[0057] M=M Δ M R M D

[0058] in M Dis the amplitude bidirectional attenuation matrix of the sample for the incident light, which is used to represent the differential loss between orthogonal polarization eigenstates; M R is the phase delay matrix of the sample to the incident light, which is used to represent the differential phase delay between the two eigenstates; M Δ is the depolarization matrix of the sample for the incident light; D represents the bidirectional attenuation vector, P Δ represents the polarization vector. In the experiment, the depolarization matrix M Δ can be extracted from the measured Mueller matrix separately and for M D No effect. Therefore, with no depolarization matrix M Δ The Mueller matrix M′ of the bidirectional attenuation matrix M D , and the phase delay matrix M R . It can be obtained by the following formula:

[0059]

[0060] Where D=(M 12 ,M 13 ,M 14 ) T , M 12 ,M 13 ,M 14 Respectively represent the second, third, and fourth elements of the first row of the Mueller matrix, M D is the double decay vector of M, D′ is the unit vector along D, and I is the 3×3 identity matrix.

[0061] S4, calculating the intrinsic polarization state of each wavelength point in the optimal measurement configuration set.

[0062] In this embodiment, the eigenpolarization state of each wavelength point in the Pareto front solution is calculated, and the expression is as follows:

[0063]

[0064] Where α = (1, a1, a2, a3) is the intrinsic polarization state, a1, a2, a3 represent the second, third, and fourth elements of the normalized intrinsic polarization state, respectively, M R is the differential delay matrix of the sample for the incident light. The calculation expressions of each element of the intrinsic polarization state are as follows:

[0065]

[0066] In the formula, represents the phase delay function, δ ij is the Kronecker function, ∈ ijkis the Levi–Civita permutation symbol, (m R ) ij is m R The element in the i-th row and j-th column of i is the i+1 element in the intrinsic polarization state, a j is the j+1 element in the intrinsic polarization state, a k is the k+1 element in the intrinsic polarization state, i is (m R ) ij Elements in m R The corresponding row number in , j is (m R ) ij Elements in m R The corresponding column number in , k is the indicator variable.

[0067] S5, after averaging and weighting the characteristic quantities of the intrinsic polarization state obtained at each wavelength point in the optimal measurement configuration set, perform OVL solution to obtain the overlay error.

[0068] In this embodiment, the overlay error measurement can be obtained by measuring several DBO samples with opposite artificially introduced biases d and -d, and the calculation formula is:

[0069]

[0070] Where OVL is the measured overlay error, d is the artificially introduced bias, It is the characteristic quantity measured under the corresponding mark of d+OVL.

[0071] Embodiment 2:

[0072] The present application embodiment provides a specific embodiment of the method for optimizing the characterization of the overlay error of the photolithography process described in Example 1. The parameters of the samples selected in this embodiment are described as follows:

[0073] The structural design and material settings refer to existing studies, such as Figure 2 As shown. More detailed parameter values ​​are shown in Table 1. Here, the total offset δ includes the preset offset (d) and the overlay error (ε) generated during the manufacturing process. The former is fixed, while the latter varies according to the simulation requirements. Two opposite preset offsets are considered in the simulation. The line width or critical dimension (CD) of the two layers of gratings is the same. The optical constants of Si and SiO2 are taken from. The Tauc-Lorentz model is used to represent the dielectric constant of the photoresist (PR), where A, Eg, E0, C and ε-∞. are set to 21.1496eV, 3.4597eV, 9.9492eV, 0.9877eV and 1.4268.

[0074] Table 1: Parameter settings of the DBO overlay mark sample corresponding to the simulation

[0075]

[0076] Experimental configuration:

[0077] In this embodiment, the incident broad spectrum Mueller matrix ellipsometer is simulated by the rigorous coupled wavelength analysis (RCWA) method, with the incident angle fixed at 65°, the simulation wavelength range being [200 nm, 800 nm], the step size being 10 nm, and the azimuth angle being fixed at 10°.

[0078] Experimental band selection:

[0079] The simulation is used to evaluate the performance of the characterization index α2 and optimize the target {L, -S, Ro}, where L is the linearity and L = || f OVL±d -k(OVL±d)||, the linear error is defined as the distance between the true indication curve f and the approximate linear function with a slope of k. S is the sensitivity, The sensitivity index is used to indicate the ability of the characterization index to evaluate small overlay errors. Ro is the robustness, Where σ is the standard deviation of a set of data, and μ is the mean of the average values ​​of a set of data. This indicator is to minimize the impact of any disturbance (for example, a small change in the measurement wavelength λ or azimuth angle). The waveband suitable for measurement is selected for subsequent measurement.

[0080] Spectral matching: Perform Mueller matrix measurement under the best measurement configuration set, and then select the measured Mueller matrix to match the simulated Mueller matrix;

[0081] Polar decomposition processing: The Mueller matrix actually measured at each wavelength point in the Pareto frontier solution is polar decomposed, and the expression is as follows:

[0082] M=M Δ M R M D

[0083] in M D is the amplitude bidirectional attenuation matrix of the sample for the incident light, which is used to represent the differential loss between orthogonal polarization eigenstates; M R is the phase delay matrix of the sample to the incident light, which is used to represent the differential phase delay between the two eigenstates; M Δ is the depolarization matrix of the sample for the incident light; D represents the bidirectional attenuation vector, P Δrepresents the polarization vector.

[0084] Solution of eigenpolarization state: Extract the differential delay matrix from the polar decomposition result and solve its eigenpolarization state. The expression is as follows:

[0085]

[0086] α=(a1,a2,a3) is the intrinsic polarization state, M R is the differential delay matrix of the sample for the incident light. In the experiment, the depolarization matrix M Δ can be extracted from the measured Mueller matrix alone and has no effect on MD. Δ The Mueller matrix M′ of the bidirectional attenuation matrix M D. , and the phase delay matrix M R . It can be obtained by the following formula:

[0087]

[0088] Where D=(M 12 ,M 13 ,M 14 ) T is the double decay vector of M, D′ is the unit vector along D, and I is the 3×3 identity matrix.

[0089] Eigenpolarization state solution:

[0090] Calculate the eigenpolarization state of each wavelength point in the Pareto front solution, the expression is as follows:

[0091]

[0092] α=(1,a1,a2,a3) is the intrinsic polarization state, M R is the differential delay matrix of the sample for the incident light. The calculation expressions of each element of the intrinsic polarization state are as follows:

[0093]

[0094] in represents the phase delay function, δ ij is the Kronecker delta, ∈ ijk It is the Levi–Civita permutation symbol.

[0095] Overlay Error Extraction:

[0096] The a2 obtained at each wavelength point in the Pareto frontier solution is averaged and weighted, and then the OVL solution is performed.

[0097]

[0098] Simulation verification:

[0099] 1) Linearity verification: In order to quickly verify the effectiveness of this method, this implementation simulates and verifies the above samples. Figure 3 The relationship between the characterization quantity and the total offset δ at the wavelengths of 200nm, 400nm, 600nm, 800nm ​​and 1000nm, corresponding to the azimuth angles of 30°, 60° and 90°, and the specific corresponding linearity values ​​are shown in Table 2.

[0100] Table 2: Linearity R at different wavelengths and azimuth angles 2

[0101]

[0102] 2) Accuracy verification:

[0103] In order to quickly verify the accuracy of this method, ε is fixed to 10m, d is changed from 5nm to 50nm, and compared with other methods, the measurement error is as follows Figure 4 Here, the a2 characterization proposed in this implementation is called PE-OI after average weighting. Other methods call the differential Mueller matrix LB' characterization LD'-OI (linear dichroism along ±45° axes, LD'-OI), and the non-diagonal elements of the Mueller matrix will be called MMD-OI, where M 13 +M 31 For example.

[0104] 3) Robustness verification:

[0105] In order to ensure that this implementation still has good results under wavelength / azimuth oscillation, the change in robustness of the characterization quantity when there is a ±1° disturbance in the wavelength / azimuth is explored. The degree of robustness is represented by the above-mentioned robustness index. The final results are shown in Table 3.

[0106] Table 3: Robustness of different characterization quantities in simulation

[0107]

[0108] Experimental verification:

[0109] In order to verify the effectiveness of this method, similar samples were prepared in this implementation. The specific dimensions are shown in Figure 5FIB image. At the same time, the above steps are followed to measure and compare with the measurement results of the other two characterization quantities. After PC weighting, LD'-OI obtains OVL = -15.3nm, and MME-OI obtains OVL = -9.7nm after PC weighting. The true value corresponding to FIB is -17nm. The corresponding robustness and its various index parameters are shown in Table 4.

[0110] Table 4: Robustness of different representations in the experiment

[0111]

[0112] In summary, all the above experimental results demonstrate the effectiveness of the nanostructure overlay error extraction method based on the Mueller matrix proposed in the present invention.

[0113] Those skilled in the art will readily understand that the above-mentioned ellipsometric measurement is based on the results with x and y as orthogonal directions, which is only a preferred embodiment of the present invention, and other orthogonal directions (left circle, right circle, etc.) are not used to limit the present invention.

[0114] Embodiment 3:

[0115] The present application also provides a device for optimizing the characterization of overlay error in a photolithography process. Figure 6 As shown, the device comprises:

[0116] The optimal configuration determination module 601 is configured to obtain DBO samples, calculate various indicators of the electromagnetic field simulation minimization characterization quantity to optimize the performance of the measurement configuration, and determine the optimal measurement configuration set;

[0117] A matrix matching module 602 is configured to perform Mueller matrix measurement under the optimal measurement configuration set, and select the measured Mueller matrix to match the Mueller matrix obtained by simulation;

[0118] The matrix polar decomposition module 603 is configured to perform polar decomposition on the Mueller matrix actually measured at each wavelength point in the optimal measurement configuration set;

[0119] The polarization state calculation module 604 is configured to calculate the intrinsic polarization state of each wavelength point in the optimal measurement configuration set;

[0120] The overlay error solving module 605 is configured to perform an OVL solution on the average weighted representation of the intrinsic polarization state obtained at each wavelength point in the optimal measurement configuration set to obtain the overlay error.

[0121] In some embodiments, the optimal configuration determination module is further configured to:

[0122] The various indicators of the characterization quantity are expressed as {L, -S, Ro}, and the measurement configuration is optimized by minimizing {L, -S, Ro} to obtain the Pareto optimal solution as the best measurement configuration set; where L is the linearity, L = || f OVL±d -k(OVL±d)||, f is the real indication curve, k is the slope, OVL is the overlay error, d is the artificially introduced bias; S is the sensitivity, Ro is robustness, σ is the standard deviation of a set of data, and μ is the mean of the means of a set of data.

[0123] In some embodiments, the matrix matching module is further configured to perform Mueller matrix measurement under the optimal measurement configuration set using a wide spectrum ellipsometer.

[0124] In some embodiments, the matrix polar decomposition module is further configured to express the calculation process of polar decomposition of the Mueller matrix actually measured at each wavelength point in the optimal measurement configuration set as follows:

[0125] M=M Δ M R M D

[0126] Where M is the measured Mueller matrix, M D is the amplitude bidirectional attenuation matrix of the sample for the incident light, which is used to represent the differential loss between orthogonal polarization eigenstates; M R is the phase delay matrix of the sample to the incident light, which is used to represent the differential phase delay between the two eigenstates; M Δ is the depolarization matrix of the sample for the incident light; D represents the bidirectional attenuation vector, P Δ represents the polarization vector, T represents the matrix transpose, m D By deleting M D The first row and first column of M are obtained D A 3x3 submatrix of R By deleting M R The first row and first column of M are obtained R A 3x3 submatrix of Δ By deleting M Δ The first row and first column of M are obtained Δ A 3x3 submatrix of .

[0127] In some embodiments, the matrix decomposition module is further configured to calculate M by the following formula: D and M R :

[0128]

[0129] In the formula, D=(M 12 ,M 13 ,M 14 ) T , M 12 ,M 13 ,M 14 They represent the second, third, and fourth elements of the first row of the Mueller matrix, respectively. D′ is the unit vector along D, and I is the 3×3 identity matrix.

[0130] In some embodiments, the eigenpolarization state of each wavelength point in the calculated optimal measurement configuration set is expressed as:

[0131]

[0132] Where α = (1, a1, a2, a3) is the intrinsic polarization state, M R is the differential delay matrix of the sample for the incident light, a1, a2, a3 represent the second, third, and fourth elements in the normalized intrinsic polarization state, respectively, and a2 in the intrinsic polarization state is used as the characterization quantity.

[0133] The calculation expressions of each element of the intrinsic polarization state are as follows:

[0134]

[0135] In the formula, represents the phase delay function, δ ij is the Kronecker function, ∈ ijk is the Levi–Civita permutation symbol, (m R ) ij is m R The element in the i-th row and j-th column of i is the i+1 element in the intrinsic polarization state, a j is the j+1 element in the intrinsic polarization state, a k is the k+1 element in the intrinsic polarization state, i is (m R ) ij Elements in m R The corresponding row number in , j is (m R ) ij Elements in m R The corresponding column number in , k is the indicator variable.

[0136] In some embodiments, the characteristic quantities of the intrinsic polarization state obtained at each wavelength point in the optimal measurement configuration set are averaged and weighted, and then an OVL solution is performed to obtain a calculation formula for the overlay error, which is expressed as:

[0137]

[0138] Where OVL is the measured overlay error, d is the artificially introduced bias, It is the characteristic quantity measured under the corresponding mark of d+OVL.

[0139] It should be noted that the device described in this embodiment and the method described previously belong to the same technical concept, have the same technical principles, and can achieve the same beneficial effects, so they will not be repeated here.

[0140] An embodiment of the present application further provides a system for optimizing characterization of overlay error in a photolithography process, the system comprising: a memory for storing a computer program; and a processor for executing the computer program to implement the method described in any of the above embodiments.

[0141] An embodiment of the present application further provides a non-temporary computer-readable storage medium storing instructions, and when the instructions are executed by a processor, the method described in any of the above embodiments is executed.

[0142] The above implementation modes are only used to illustrate the present application, and are not intended to limit the present application. Ordinary technicians in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present application. Therefore, all equivalent technical solutions also belong to the scope of the present application, and the scope of patent protection of the present application shall be limited by the claims.

Claims

1. A method for optimizing the characterization of overlay error in a photolithography process, characterized in that: The method comprises: Obtain DBO samples, calculate various indicators of electromagnetic field simulation minimization to optimize the performance of the measurement configuration, and determine the best measurement configuration set; Performing Mueller matrix measurement under the optimal measurement configuration set, and selecting the measured Mueller matrix to match the Mueller matrix obtained by simulation; Polar decomposition is performed on the Mueller matrix actually measured at each wavelength point in the optimal measurement configuration set; Calculate the intrinsic polarization state of each wavelength point in the optimal measurement configuration set; After averaging and weighting the characteristic quantities of the intrinsic polarization state obtained at each wavelength point in the optimal measurement configuration set, the OVL solution is performed to obtain the overlay error.

2. The method for optimizing the characterization of overlay error in a photolithography process according to claim 1, characterized in that: Obtain DBO samples, calculate various indicators of electromagnetic field simulation minimization to optimize the performance of the measurement configuration, and determine the best measurement configuration set, including: The various indicators of the characterization quantity are expressed as {L, -S, Ro}, and the measurement configuration is optimized by minimizing {L, -S, Ro} to obtain the Pareto optimal solution as the best measurement configuration set; where L is the linearity, L = || f OVL±d -k(OVL±d)||, f is the real indication curve, k is the slope, OVL is the overlay error, d is the artificially introduced bias; S is the sensitivity, Ro is robustness, σ is the standard deviation of a set of data, and μ is the mean of the means of a set of data.

3. The method for optimizing the characterization of overlay error in a photolithography process according to claim 1, wherein: Mueller matrix measurements were performed using a broad spectrum ellipsometer under the optimal measurement configuration set.

4. The method for optimizing the characterization of overlay error in a photolithography process according to claim 1, wherein: The calculation process of polar decomposition of the Mueller matrix actually measured at each wavelength point in the optimal measurement configuration set is expressed as: M=M Δ M R M D Where M is the measured Mueller matrix, M D is the amplitude bidirectional attenuation matrix of the sample for the incident light, which is used to represent the differential loss between orthogonal polarization eigenstates; M R is the phase delay matrix of the sample to the incident light, which is used to represent the differential phase delay between the two eigenstates; M Δ is the depolarization matrix of the sample for the incident light; D represents the bidirectional attenuation vector, P Δ represents the polarization vector, T represents the matrix transpose, m D By deleting M D The first row and first column of M are obtained D A 3x3 submatrix of R By deleting M R The first row and first column of M are obtained R A 3x3 submatrix of Δ By deleting M Δ The first row and first column of M are obtained Δ A 3x3 submatrix of .

5. The method for optimizing the characterization of overlay error in a photolithography process according to claim 4, characterized in that: M is calculated by the following formula D and M R : In the formula, D=(M 12 ,M 13 , M 14 ) T , M 12 ,M 13 , M 14 They represent the second, third, and fourth elements of the first row of the Mueller matrix, respectively. D′ is the unit vector along D, and I is the 3×3 identity matrix.

6. The method for optimizing the characterization of overlay error in a photolithography process according to claim 1, wherein: The eigenpolarization state of each wavelength point in the calculated optimal measurement configuration set is expressed as: Where α = (1, a1, a2, a3) is the intrinsic polarization state, M R is the differential delay matrix of the sample for the incident light, a1, a2, a3 represent the second, third, and fourth elements in the normalized eigenpolarization state, respectively, and a2 in the eigenpolarization state is used as the characterization quantity. The calculation expressions of each element of the intrinsic polarization state are as follows: In the formula, represents the phase delay function, δ ij is the Kronecker function, ∈ ijk is the substitution symbol, (m R ) ij is m R The element corresponding to the i-th row and j-th column of a i is the i+1 element in the intrinsic polarization state, a j is the j+1 element in the intrinsic polarization state, a k is the k+1 element in the intrinsic polarization state, i is (m R ) ij Elements in m R The corresponding row number in , j is (m R ) ij Elements in m R The corresponding column number in , k is the indicator variable.

7. The method for optimizing the characterization of overlay error in a photolithography process according to claim 1, wherein: After averaging and weighting the characteristic quantities of the intrinsic polarization state obtained at each wavelength point in the optimal measurement configuration set, the OVL solution is performed, and the calculation formula for the overlay error is obtained as follows: Where OVL is the measured overlay error, d is the artificially introduced bias, It is the characteristic quantity measured under the corresponding mark of d+OVL.

8. An optimization characterization device for overlay error in a photolithography process, characterized in that: The device comprises: The best configuration determination module is configured to obtain DBO samples, calculate various indicators of the electromagnetic field simulation minimization characterization quantity to optimize the performance of the measurement configuration, and determine the best measurement configuration set; A matrix matching module is configured to perform Mueller matrix measurement under the optimal measurement configuration set, and select the measured Mueller matrix to match the Mueller matrix obtained by simulation; A matrix polar decomposition module is configured to perform polar decomposition on the Mueller matrix actually measured at each wavelength point in the optimal measurement configuration set; A polarization state calculation module is configured to calculate the intrinsic polarization state of each wavelength point in the optimal measurement configuration set; The overlay error solving module is configured to perform an OVL solution after averaging and weighting the characteristic quantities of the intrinsic polarization state obtained at each wavelength point in the optimal measurement configuration set to obtain the overlay error.

9. An optimization characterization system for overlay error in a photolithography process, characterized in that: The system comprises: Memory for storing computer programs; A processor, configured to execute the computer program to implement the method according to any one of claims 1 to 7.

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