A lithography overlay error compensation method, device, system, and medium

Abstract

The application provides a photolithography overlay error compensation method, device, system and medium. According to different stress compensation overlay error distribution, different coefficients of high-order polynomial corresponding to different stress compensation overlay error distribution are obtained by using least square method. The overlay error sensitivity of different coefficients is sorted, and the overlay error sensitivity is accumulated one by one according to the order from large to small. When the obtained cumulative value is greater than or equal to a preset threshold, the remaining different coefficients are excluded to select the main coefficients from the different coefficients. The product of the preset analytic coefficient and the main coefficient is used as the final compensation stress, and the final compensation stress is applied to the photolithography mask to compensate the initial overlay error. By screening the overlay error sensitivity of different coefficients, the coefficients with low sensitivity are excluded, and the coefficients with high sensitivity are collected and analyzed to obtain the final compensation stress applied to the photolithography mask, so that the effective compensation of the photolithography overlay error can be realized, and the overlay error is reduced.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and in particular to a method, apparatus, system and medium for compensating for overlay errors in a lithography machine. Background Technology

[0002] In the integrated circuit manufacturing process, the process involves repeatedly building up a silicon wafer layer by layer according to a pre-designed circuit mask. The misalignment between layers is called overlay error. Overlay error can quantitatively describe the deviation of the current pattern relative to the reference pattern along the X and Y directions, as well as the distribution of this deviation on the wafer surface.

[0003] According to the requirements of the International Technology Roadmap for Semiconductors (ITRS) for each technology node, the overlay error requirement (|mean|+3σ) for the critical layer in the 28nm node is 9nm, and the overlay error for the critical layer in the 14nm node is required to be controlled within 6.4nm. For lithography equipment, overlay error compensation functionality is essential. With the implementation of various full functions, the required overlay error per unit becomes increasingly fine, only about 1 / 2 to 1 / 3 of the aforementioned values.

[0004] As manufacturing technology nodes continue to advance, chip integration is becoming increasingly sophisticated, and the requirements for critical dimensions and overlay errors are becoming more stringent. In traditional projection lithography systems, optical lenses are often used to compensate for and correct overlay errors.

[0005] Today, near-field lithography technology has also seen rapid development, such as nanoimprint lithography. As projection lithography systems continue to shrink in technology nodes, the precision requirements for overlay error correction are becoming increasingly stringent; however, the correctable effect is approaching its limit. The development of near-field lithography technology has also provided new ideas for the future advancement of integrated circuits, and methods for compensating for overlay errors are a key process in large-scale integrated circuit manufacturing.

[0006] In the integrated circuit manufacturing process, multiple photolithography steps are required. Photolithography quality is a key factor affecting the performance, yield, and reliability of integrated circuits; and overlay error is a critical factor affecting photolithography quality. Overlay error is one of the main causes of short circuits and open circuits in devices. Without compensation measures, it is difficult to ensure accurate connections between different parts of the device. However, because the controllable parts of lithography machines such as nanoimprint lithography and near-field lithography differ from those of deep ultraviolet lithography machines, their overlay error compensation methods differ significantly from traditional lithography. In particular, these devices lack lens systems, making high-precision control of the mask essential.

[0007] Therefore, how to effectively compensate for the overlay error of the lithography machine and reduce the overlay error is a technical problem that needs to be solved in this field. Summary of the Invention

[0008] In view of this, a summary section is provided to briefly introduce the concepts, which will be described in detail in the detailed description section below. This summary section is not intended to identify key or essential features of the claimed technical solution, nor is it intended to limit the scope of the claimed technical solution.

[0009] The purpose of this application is to provide a method, apparatus, system and medium for compensating overlay errors in a lithography machine, which can effectively compensate for overlay errors in the lithography machine and reduce overlay errors.

[0010] To achieve the above objectives, this application provides the following technical solution:

[0011] In a first aspect, embodiments of this application provide a method for compensating for overlay errors in a lithography machine, including:

[0012] Obtain the initial overlay error;

[0013] The initial overlay error and different stress compensation conditions are input into a pre-established overlay error distribution model to obtain the overlay error distribution after different stress compensations.

[0014] Based on the overlay error distribution after different stress compensations, the coefficients of the higher-order polynomials corresponding to the overlay error distributions after different stress compensations are obtained by using the least squares method.

[0015] The quotient of the overprinting error corresponding to different positions for different coefficients, divided by the total overprinting error after different stress compensation, is taken as the overprinting error sensitivity for the different coefficients.

[0016] The overlay error sensitivity of the different coefficients is sorted, and the overlay error sensitivity is accumulated one by one in descending order. When the accumulated value is greater than or equal to a preset threshold, the remaining different coefficients are excluded in order to select the main coefficients from the different coefficients.

[0017] The product of the preset analytical coefficient and the main coefficient is used as the final compensation stress, which is then applied to the photomask to compensate for the initial overlay error.

[0018] In one possible implementation, the overlay error distribution after different stress compensations includes overlay error distributions in different directions after different stress compensations.

[0019] In one possible implementation, the different coefficients are calculated using the following formula:

[0020] Overlay x =k1+k3·ix+k5·iy+k7·ix 2 +k9·ixy+k 11 ·iy 2 +k 13 ·ix 3 +k 15 ·ix 2 y+k 17 ·ixy 2 +k 19 ·iy 3 ;

[0021] Overlay y =k2+k4·iy+k6·ix+k8·iy 2 +k 10 ·iyx+k 12 ·ix 2 +k 14 ·iy 3 +k 16 ·iy 2 x+k 18 ·iyx 2 +k 20 ·ix 3 ;

[0022] Among them, Overlay x and Overlay y The overlay error distributions in different directions after different stress compensations are k1-k, respectively. 20 Let be the different coefficients, i be a positive integer, and x and y be the coordinates of different positions corresponding to the overlay error distribution in different directions after different stress compensation.

[0023] In one possible implementation, the product of the preset analytical coefficients and the main coefficients is used as the final compensation stress, specifically calculated using the following formula:

[0024]

[0025] Among them, F j For the final compensation stress, Z j Let k be the preset analytical coefficient. j These are the main coefficients.

[0026] Secondly, embodiments of this application provide a lithography machine overlay error compensation device, comprising:

[0027] The acquisition unit is used to acquire the initial overlay error;

[0028] The input unit is used to input the initial overlay error and different stress compensation conditions into a pre-established overlay error distribution model to obtain the overlay error distribution after different stress compensations;

[0029] The solving unit is used to solve for the different coefficients of the higher-order polynomials corresponding to the different stress-compensated overlay error distributions using the least squares method based on the different stress-compensated overlay error distributions.

[0030] The sensitivity unit is used to divide the overlay error corresponding to different positions of the different coefficients by the total overlay error after different stress compensation, and use the quotient as the overlay error sensitivity of the different coefficients.

[0031] The filtering unit is used to sort the overlay error sensitivity of the different coefficients, and to accumulate the overlay error sensitivity one by one in descending order. When the accumulated value is greater than or equal to a preset threshold, the remaining different coefficients are excluded, so as to filter out the main coefficients from the different coefficients.

[0032] The compensation unit is used to apply the final compensation stress to the photomask as the product of the preset resolution coefficient and the main coefficient, so as to compensate for the initial overlay error.

[0033] In one possible implementation, the overlay error distribution after different stress compensations includes overlay error distributions in different directions after different stress compensations.

[0034] In one possible implementation, the solving unit is specifically used to calculate the different coefficients using the following formula:

[0035] Overlay x =k1+k3·ix+k5·iy+k7·ix 2 +k9·ixy+k 11 ·iy 2 +k 13 ·ix 3 +k 15 ·ix 2 y+k 17 ·ixy 2 +k 19 ·iy 3 ;

[0036] Overlay y =k2+k4·iy+k6·ix+k8·iy 2 +k 10 ·iyx+k 12 ·ix 2 +k 14 ·iy 3+k 16 ·iy 2 x+k 18 ·iyx 2 +k 20 ·ix 3 ;

[0037] Among them, Overlay x and Overlay y The overlay error distributions in different directions after different stress compensations are k1-k, respectively. 20 Let be the different coefficients, i be a positive integer, and x and y be the coordinates of different positions corresponding to the overlay error distribution in different directions after different stress compensation.

[0038] In one possible implementation, the compensation unit is specifically used to calculate the final compensation stress using the following formula:

[0039]

[0040] Among them, F j For the final compensation stress, Z j Let k be the preset analytical coefficient. j These are the main coefficients.

[0041] Thirdly, embodiments of this application provide a lithography machine overlay error compensation system, including:

[0042] Memory, used to store computer programs;

[0043] A processor is used to execute the computer program to implement the steps of the lithography machine overlay error compensation method as described above.

[0044] Fourthly, embodiments of this application provide a computer-readable medium storing a computer program, which, when processed and executed, implements the steps of the lithography machine overlay error compensation method described above.

[0045] Compared with the prior art, the embodiments of this application have the following beneficial effects:

[0046] This application provides a method, apparatus, system, and medium for compensating overlay errors in a lithography machine. The method includes: acquiring an initial overlay error; inputting the initial overlay error and different stress compensation conditions into a pre-established overlay error distribution model to obtain overlay error distributions after different stress compensations; using the least squares method to solve for the different coefficients of the higher-order polynomials corresponding to the overlay error distributions after different stress compensations based on the overlay error distributions after different stress compensations; dividing the overlay error at different positions corresponding to different coefficients by the quotient of the total overlay error after different stress compensations, and using this quotient as the overlay error sensitivity of different coefficients; sorting the overlay error sensitivity of different coefficients, and accumulating the overlay error sensitivity one by one in descending order, and when the accumulated value is greater than or equal to a preset threshold, excluding the remaining different coefficients to select the main coefficients from the different coefficients; and applying the final compensation stress to the lithography mask as the product of the preset analytical coefficients and the main coefficients to compensate for the initial overlay error. This application filters overlay error sensitivity coefficients of different values, eliminates coefficients with low sensitivity, and focuses on summarizing and analyzing the coefficients with high sensitivity to obtain the final compensation stress applied to the photomask. This can effectively compensate for overlay error in the photolithography machine and reduce overlay error. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] The above and other features, advantages, and aspects of the embodiments of this disclosure will become more apparent from the accompanying drawings and the following detailed description. Throughout the drawings, the same or similar reference numerals denote the same or similar elements. It should be understood that the drawings are schematic, and the originals and elements are not necessarily drawn to scale.

[0049] Figure 1 A flowchart of a lithography machine overlay error compensation method provided in an embodiment of this application is shown;

[0050] Figure 2 This paper illustrates a vector field diagram of the overlay error distribution in an exposure area according to an embodiment of this application.

[0051] Figure 3 This diagram illustrates the overlay error distribution in the X direction without stress compensation, as provided in an embodiment of this application.

[0052] Figure 4This diagram illustrates the overlay error distribution in the Y direction without stress compensation, as provided in an embodiment of this application.

[0053] Figure 5 This illustration shows the overlay error distribution in the X direction after applying four sets of 20N forces to the four hinges provided in this application embodiment.

[0054] Figure 6 This illustration shows the overlay error distribution in the Y direction after applying four sets of 20N forces to the four hinges provided in this application embodiment.

[0055] Figure 7 This illustration shows a schematic diagram of the overlay error distribution in the X direction after stress compensation based on the feedback k parameter, according to an embodiment of this application.

[0056] Figure 8 This illustration shows a schematic diagram of the overlay error distribution in the Y direction after stress compensation based on the feedback k parameter, according to an embodiment of this application.

[0057] Figure 9 This paper illustrates a vector field diagram of the original overlay error distribution provided in an embodiment of this application.

[0058] Figure 10 This paper shows the overlay error distribution vector field diagram after the overlay error compensation method for lithography provided in the embodiments of this application;

[0059] Figure 11 This paper presents a trend diagram of overlay error compensation under stress compensation conditions according to an embodiment of this application.

[0060] Figure 12 A schematic diagram of a lithography machine overlay error compensation device provided in an embodiment of this application is shown. Detailed Implementation

[0061] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0062] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0063] As described in the background section, the applicant's research has revealed that in the integrated circuit manufacturing process, the process involves repeatedly building up layers from a single silicon wafer according to a pre-designed circuit mask. The misalignment between layers is called overlay error. Overlay error can quantitatively describe the deviation of the current pattern relative to a reference pattern along the X and Y directions, as well as the distribution of this deviation on the wafer surface.

[0064] According to the requirements of the International Technology Roadmap for Semiconductors (ITRS) for each technology node, the overlay error requirement for critical layers in the 28nm node is 9nm, and for the 14nm node, the overlay error is controlled to 6.4nm. For lithography equipment, overlay error compensation functionality is essential. With the implementation of various full functions, the required overlay error per unit becomes increasingly fine, only about 1 / 2 to 1 / 3 of the aforementioned values.

[0065] As manufacturing technology nodes continue to advance, chip integration is becoming increasingly sophisticated, and the requirements for critical dimensions and overlay errors are becoming more stringent. In traditional projection lithography systems, optical lenses are often used to compensate for and correct overlay errors.

[0066] Today, near-field lithography technology has also seen rapid development, such as nanoimprint lithography. As projection lithography systems continue to shrink in technology nodes, the precision requirements for overlay error correction are becoming increasingly stringent; however, the correctable effect is approaching its limit. The development of near-field lithography technology has also provided new ideas for the future advancement of integrated circuits, and methods for compensating for overlay errors are a key process in large-scale integrated circuit manufacturing.

[0067] In the integrated circuit manufacturing process, multiple photolithography steps are required. Photolithography quality is a key factor affecting the performance, yield, and reliability of integrated circuits; and overlay error is a critical factor affecting photolithography quality. Overlay error is one of the main causes of short circuits and open circuits in devices. Without compensation measures, it is difficult to ensure accurate connections between different parts of the device. However, because the controllable parts of lithography machines such as nanoimprint lithography and near-field lithography differ from those of deep ultraviolet lithography machines, their overlay error compensation methods differ significantly from traditional lithography. In particular, these devices lack lens systems, making high-precision control of the mask essential.

[0068] Therefore, how to effectively compensate for the overlay error of the lithography machine and reduce the overlay error is a technical problem that needs to be solved in this field.

[0069] To address the aforementioned technical problems, embodiments of this application provide a method, apparatus, system, and medium for compensating overlay errors in a lithography machine. The method includes: acquiring an initial overlay error; inputting the initial overlay error and different stress compensation conditions into a pre-established overlay error distribution model to obtain overlay error distributions after different stress compensations; using the least squares method to solve for the different coefficients of the higher-order polynomials corresponding to the overlay error distributions after different stress compensations based on the overlay error distributions after different stress compensations; dividing the overlay error at different positions corresponding to different coefficients by the quotient of the total overlay error after different stress compensations, using this quotient as the overlay error sensitivity of different coefficients; sorting the overlay error sensitivity of different coefficients, accumulating them one by one in descending order, and when the accumulated value is greater than or equal to a preset threshold, excluding the remaining different coefficients to select the main coefficients from the different coefficients; and applying the final compensation stress to the lithography mask as the final compensation stress to compensate for the initial overlay error. This application filters overlay error sensitivity coefficients of different values, eliminates coefficients with low sensitivity, and focuses on summarizing and analyzing the coefficients with high sensitivity to obtain the final compensation stress applied to the photomask. This can effectively compensate for overlay error in the photolithography machine and reduce overlay error.

[0070] Exemplary methods

[0071] See Figure 1 The diagram shown is a flowchart of a lithography machine overlay error compensation method provided in an embodiment of this application, including:

[0072] S101: Obtain the initial overlay error.

[0073] In this embodiment of the application, in order to perform lithography machine overlay error compensation, it is first necessary to obtain the initial overlay error so that targeted lithography machine overlay error compensation can be performed subsequently.

[0074] Specifically, embodiments of this application can acquire a lithography machine and a lithography mask, and perform lithography operations using a wafer. The lithography machines provided in embodiments of this application include nanoimprint lithography machines, super diffraction lithography machines, proximity lithography machines, contact lithography machines, deep ultraviolet lithography machines, or extreme ultraviolet lithography machines, etc., which use masks as image transmission devices.

[0075] A photolithography mask includes the mask clamping method, the mask material and its optical and mechanical properties, the mask pattern density and transmittance, and the mask thermal effect parameters. These parameters are used to construct a rigorous feedback model.

[0076] Wafers include materials such as silicon wafers, germanium wafers, quartz glass substrates, and III-V group material substrates, which are substrate materials that can be used for photolithography. The wafer contains photoresist and related transition layer materials, allowing mask patterns to be transferred to the wafer surface during the operation of the aforementioned photolithography machine.

[0077] Then, photolithography is performed to obtain the overlay error distribution within the exposed area of ​​the wafer, which is used as the initial overlay error. The initial overlay error refers to the difference in precise positioning marks between the overlay markers of the current layer and the overlay markers of the target layer on the wafer.

[0078] S102: Input the initial overlay error and different stress compensation conditions into the pre-established overlay error distribution model to obtain the overlay error distribution after different stress compensation.

[0079] In the embodiments of this application, an overlay error distribution model can be established in advance to analyze the overlay error distribution after different stress compensations.

[0080] Specifically, the pre-established overlay error distribution model is a rigorous simulation model built based on the actual conditions of near-field lithography masks. The model should conform to actual working conditions and reflect the process requirements of advanced nodes. Since the input of exposure heat is ultimately considered, the actual distribution of the mask pattern should be appropriately taken into account.

[0081] Specifically, in order to improve the analytical accuracy of the overlay error distribution model, the overlay error distribution model can be trained to obtain a pre-established overlay error distribution model.

[0082] First, a training set for the overlay error distribution model can be obtained. The training set includes: known overlay errors and known stress compensation conditions, as well as the known overlay error distribution after stress compensation.

[0083] By using the training set to learn the mapping relationship between known overlay errors and known stress compensation conditions and the overlay error distribution after known stress compensation, the model parameters of the function model are determined based on the mapping relationship, thereby obtaining the trained overlay error distribution model, which can be used as a pre-established overlay error distribution model.

[0084] Then, in this embodiment of the application, the initial overlay error and different stress compensation conditions can be input into a pre-established overlay error distribution model to obtain the overlay error distribution after different stress compensations.

[0085] For example, in this embodiment of the application, the deformation distribution of the mask under stress compensation conditions is simulated using finite element method to obtain the overlay error distribution after different stress compensations.

[0086] Optionally, considering symmetry and actual mechanical application, the overlay error distribution after different stress compensations in this embodiment includes overlay error distributions in different directions after different stress compensations. The forces are divided into: F1 (outer force in the X direction), F2 (inner force in the X direction), F3 (inner force in the X direction), and F4 (outer force in the X direction). Seventeen different types of mechanical compensation distribution forms of experimental groups were designed, with each experimental group containing several sub-items.

[0087] Simulation experiments were conducted using the above experimental scheme, and the X and Y directions of the mask deformation results were collected. Furthermore, the overlay error distribution vector field diagram, i.e., the overlay error distribution after different stress compensations, can be obtained, such as... Figure 2 As shown.

[0088] S103: Based on the overlay error distribution after different stress compensations, the coefficients of the higher-order polynomials corresponding to the overlay error distributions after different stress compensations are obtained by using the least squares method.

[0089] In the embodiments of this application, the experimental scheme and results of the deterministic screening experiment design can be used to fit the model using the least squares method to obtain the coefficient estimates of each factor.

[0090] In other words, the embodiments of this application can use the least squares method to solve for the different coefficients of the higher-order polynomials corresponding to different overlay error distributions after different stress compensations.

[0091] Specifically, the different coefficients can be calculated using the following formula:

[0092] Overlay x =k1+k3·ix+k5·iy+k7·ix 2 +k9·ixy+k 11 ·iy 2 +k 13 ·ix 3 +k 15 ·ix 2 y+k 17 ·ixy 2 +k 19 ·iy 3 ;

[0093] Overlay y =k2+k4·iy+k6·ix+k8·iy 2 +k 10 ·iyx+k 12 ·ix 2 +k 14 ·iy 3 +k 16 ·iy2 x+k 18 ·iyx 2 +k 20 ·ix 3 ;

[0094] Among them, Overlay x and Overlay y The overlay error distributions in different directions after different stress compensations are shown, k1-k 20 For different coefficients, i is a positive integer, and x and y are the coordinates of different positions corresponding to the overlay error distribution in different directions after different stress compensation.

[0095] Furthermore, the higher-order polynomials in the embodiments of this application can also be even higher-order polynomials, i.e., with more coefficients, to provide better fitting results. The embodiments of this application are not specifically limited herein, and can be set by those skilled in the art according to actual circumstances.

[0096] S104: The quotient of the overprinting error corresponding to different positions for different coefficients divided by the total overprinting error after different stress compensation is used as the overprinting error sensitivity of the different coefficients.

[0097] S105: Sort the overlay error sensitivity of the different coefficients, and accumulate the overlay error sensitivity one by one in descending order. When the accumulated value is greater than or equal to a preset threshold, exclude the remaining different coefficients to select the main coefficients from the different coefficients.

[0098] In the embodiments of this application, the overlay error corresponding to different positions for different coefficients may be affected by stress changes to varying degrees. Therefore, it is necessary to screen out the coefficients that are more affected so as to carry out targeted overlay error compensation in the future.

[0099] Specifically, in the embodiments of this application, the quotient of the overprinting error corresponding to different positions with different coefficients divided by the total overprinting error after different stress compensations can be used as the overprinting error sensitivity of different coefficients.

[0100] For example, for the coefficient k3, k3x divided by Overlay x The quotient of k3 can be used as the overlay error sensitivity of the coefficient k3.

[0101] In this embodiment, the overlay error sensitivity of different coefficients can be sorted and accumulated one by one in descending order. When the accumulated value is greater than or equal to a preset threshold, the remaining different coefficients are excluded so as to select the main coefficients from the different coefficients.

[0102] Specifically, in this application embodiment, the sensitivity of the polynomial's k-parameters to overlay error results in different directions can be sorted, and the key overlay error identification threshold can be determined according to actual needs, and the main k-parameter terms can be selected.

[0103] For example, the sensitivity of overprinting error to different coefficients actually represents the proportion of overprinting error at different positions corresponding to different coefficients to the total overprinting error. For example, a preset threshold of 95% can be set. When the overprinting error sensitivity is accumulated one by one in descending order, if it is found to exceed 95%, the remaining different coefficients can be excluded in order to select the main coefficients from the different coefficients.

[0104] The total sensitivity of overlay error is the sum of single-item sensitivity, second-order effect sensitivity, and higher-order sensitivity. Therefore, this invention sorts the sensitivity and selects the key overlay error identification preset threshold according to the actual near-field lithography requirements. Based on the preset threshold, the most important k-parameter items are selected, and some uncompensable k-parameters are excluded to simplify subsequent analysis and software calculation time.

[0105] For example, see Figure 3 The diagram shown illustrates the overlay error distribution in the X direction without stress compensation, according to an embodiment of this application. See also... Figure 4 The diagram shown illustrates the overlay error distribution in the Y direction without stress compensation, according to an embodiment of this application. (See also...) Figure 5 The diagram shown illustrates the overlay error distribution in the X direction after applying four sets of 20N forces (each force is 20N) to the four hinges according to an embodiment of this application. See also... Figure 6 The diagram shown is a schematic diagram of the overlay error distribution in the Y direction after applying four sets of 20N forces to the four hinges according to an embodiment of this application.

[0106] S106: The product of the preset resolution coefficient and the main coefficient is used as the final compensation stress, and the final compensation stress is applied to the photomask to compensate for the initial overlay error.

[0107] In this embodiment of the application, after the main coefficients with high sensitivity are selected, the most important k parameters and the four sets of stress compensation can be summarized and optimized into an analytical formula.

[0108] Specifically, in this embodiment, based on the stress characteristics and the k-parameter, the effect of the corresponding overlay error can be known. Through continuous attempts and optimizations, an analytical formula is found to characterize the relationship between the main coefficients and the final compensation stress, and the coefficients of the analytical formula are determined, namely the preset analytical coefficients.

[0109] In this embodiment, the product of the preset analytical coefficients and the main coefficients is used as the final compensation stress, which can be calculated using the following formula:

[0110]

[0111] Among them, F j To ultimately compensate for the stress, Z j k is the preset analytical coefficient. j Z is the principal coefficient. Specifically, Z... j Represented in matrix form; F j The final compensation stress is represented by different forces of varying magnitudes and locations.

[0112] Finally, embodiments of this application can apply a final compensation stress to the photolithography mask to compensate for initial overlay errors. Specifically, embodiments of this application can calculate the compensation stress that the photolithography machine can perform, apply stress to the mask, and then perform photolithography.

[0113] Specifically, in this embodiment, the k-parameter fed back from the lithography machine can be input into the analytical formula, and the calculation result can be input into the actuator to operate the actuator to complete stress compensation.

[0114] For example, see Tables 1 and 2. In this embodiment, F can be obtained by substituting the feedback result of a certain photolithography machine operation into the analytical formula. j To obtain F by selecting several k values ​​through the fitting formula and solving the problem. j The situation. F j The input is fed into a piezoelectric actuator, enabling it to perform the near-field lithography stress compensation method obtained in this invention.

[0115]

[0116] Table 1. Results of stress compensation schemes based on k-parameter feedback in the X direction.

[0117]

[0118]

[0119] Table 2 Results of stress compensation schemes based on k-parameter feedback in the Y direction

[0120] Then, stress can be applied to the mask and photolithography can be performed according to the data in Tables 1 and 2 above.

[0121] Specifically, in this embodiment, a stress compensation data table can be input into the lithography machine. Based on the input results, the lithography machine's stress compensation mechanism manipulates the actuators to apply corresponding stress compensation and perform lithography. For example... Figure 7-8The figures show the distribution of overlay errors in the X and Y directions after compensation.

[0122] Furthermore, in this embodiment, the wafer overlay error deformation after compensation can be photolithographically etched and measured, and the distribution of overlay error over time can be statistically analyzed. If the overlay error exceeds the overlay error threshold, the above-described overlay error compensation method can continue. If the overlay error exceeds the threshold after three cycles, the cycle is terminated, and the overlay error compensation ends.

[0123] Finally, the overprinting error distribution maps of the exposure areas before and after compensation can be compared, such as... Figure 9-10 As shown, Figure 9 This is the vector field diagram of the original overlay error distribution. Figure 10 This is a vector field diagram of the overlay error distribution after using the overlay error compensation method for lithography machines provided in the embodiments of this application.

[0124] By comparison Figure 9 and Figure 10 It is evident that the overlay error is significantly improved after adopting this method, and the larger overlay errors are distributed at the edges of the exposure area, having a relatively limited impact on the final circuit performance. According to the feedback k parameter, the overlay error in the X direction is better, with |mean|+3σ being 3.0960nm. Compared to the overlay error in the X direction of 22.49nm under stress-compensated conditions, the overlay error in the X direction has become nearly 1 / 8 of the original.

[0125] This invention innovatively proposes a method for correcting the mask during the photolithography process, which can effectively reduce overlay errors and achieve overlay error compensation, thus achieving high-precision quantitative compensation for overlay errors. In actual operation, compensation with the same stress magnitude on all four sides is used, such as... Figure 11 The result shows that the overlay error |mean|+3σ is reduced to about 1.5nm, which meets the requirements for overlay error in advanced nodes.

[0126] This invention applies numerical theories such as data analysis, sensitivity analysis, and finite element method to obtain the F required for the k parameter feedback from the lithography machine. j The present invention provides an analytical formula for the distribution of [missing information]. This method can be used to compensate for overlay errors in nanoimprint lithography, super-diffraction lithography, and near-field lithography. It can also be used to analyze the sources and distribution characteristics of overlay errors under mask stress in extreme ultraviolet (EUV) and deep ultraviolet (DUV) lithography. The reliability of the method is verified through finite element simulation, avoiding the increased costs caused by destructive experiments. Furthermore, the coefficients of different terms in the analytical formula are continuously corrected, making the R-squared of the final analytical formula close to 1.

[0127] This application provides a method for compensating overlay errors in a lithography machine. The method includes: obtaining an initial overlay error; inputting the initial overlay error and different stress compensation conditions into a pre-established overlay error distribution model to obtain overlay error distributions after different stress compensations; using the least squares method to solve for the different coefficients of the higher-order polynomials corresponding to the overlay error distributions after different stress compensations; dividing the overlay error at different positions corresponding to different coefficients by the quotient of the total overlay error after different stress compensations, and using this quotient as the overlay error sensitivity of different coefficients; sorting the overlay error sensitivity of different coefficients, and accumulating the overlay error sensitivity one by one in descending order, and when the accumulated value is greater than or equal to a preset threshold, excluding the remaining different coefficients to select the main coefficients from the different coefficients; and applying the final compensation stress to the lithography mask as the product of the preset analytical coefficients and the main coefficients to compensate for the initial overlay error. This application filters overlay error sensitivity coefficients of different values, eliminates coefficients with low sensitivity, and focuses on summarizing and analyzing the coefficients with high sensitivity to obtain the final compensation stress applied to the photomask. This can effectively compensate for overlay error in the photolithography machine and reduce overlay error.

[0128] Exemplary device

[0129] See Figure 12 The diagram shown is a schematic of a lithography machine overlay error compensation device provided in an embodiment of this application, comprising:

[0130] Acquisition unit 201 is used to acquire the initial overlay error;

[0131] Input unit 202 is used to input the initial overlay error and different stress compensation conditions into a pre-established overlay error distribution model to obtain the overlay error distribution after different stress compensation.

[0132] Solver 203 is used to solve for the different coefficients of the higher-order polynomials corresponding to the different stress-compensated overlay error distributions using the least squares method based on the different stress-compensated overlay error distributions.

[0133] Sensitivity unit 204 is used to divide the overprinting error corresponding to different positions of the different coefficients by the quotient of the total overprinting error after different stress compensation, and use it as the overprinting error sensitivity of the different coefficients.

[0134] The filtering unit 205 is used to sort the overlay error sensitivity of the different coefficients, and accumulate the overlay error sensitivity one by one in descending order. When the accumulated value is greater than or equal to a preset threshold, the remaining different coefficients are excluded so as to filter out the main coefficients from the different coefficients.

[0135] The compensation unit 206 is used to apply the final compensation stress to the photomask as the product of the preset resolution coefficient and the main coefficient, so as to compensate for the initial overlay error.

[0136] In one possible implementation, the overlay error distribution after different stress compensations includes overlay error distributions in different directions after different stress compensations.

[0137] In one possible implementation, the solving unit is specifically used to calculate the different coefficients using the following formula:

[0138] Overlay x =k1+k3·ix+k5·iy+k7·ix 2 +k9·ixy+k 11 ·iy 2 +k 13 ·ix 3 +k 15 ·ix 2 y+k 17 ·ixy 2 +k 19 ·iy 3 ;

[0139] Overlay y =k2+k4·iy+k6·ix+k8·iy 2 +k 10 ·iyx+k 12 ·ix 2 +k 14 ·iy 3 +k 16 ·iy 2 x+k 18 ·iyx 2 +k 20 ·ix 3 ;

[0140] Among them, Overlay x and Overlay y The overlay error distributions in different directions after different stress compensations are k1-k, respectively. 20 Let be the different coefficients, i be a positive integer, and x and y be the coordinates of different positions corresponding to the overlay error distribution in different directions after different stress compensation.

[0141] In one possible implementation, the compensation unit is specifically used to calculate the final compensation stress using the following formula:

[0142]

[0143] Among them, F j For the final compensation stress, Z j Let k be the preset analytical coefficient. j These are the main coefficients.

[0144] This application provides a lithography machine overlay error compensation device. The method applied to this device includes: acquiring an initial overlay error; inputting the initial overlay error and different stress compensation conditions into a pre-established overlay error distribution model to obtain overlay error distributions after different stress compensations; using the least squares method to solve for the different coefficients of the higher-order polynomials corresponding to the overlay error distributions after different stress compensations based on the overlay error distributions after different stress compensations; dividing the overlay error at different positions corresponding to different coefficients by the quotient of the total overlay error after different stress compensations, using this quotient as the overlay error sensitivity of different coefficients; sorting the overlay error sensitivity of different coefficients, accumulating them one by one in descending order, and when the accumulated value is greater than or equal to a preset threshold, excluding the remaining different coefficients to select the main coefficients from the different coefficients; and applying the product of the preset analytical coefficients and the main coefficients as the final compensation stress to the lithography mask to compensate for the initial overlay error. This application filters overlay error sensitivity coefficients of different values, eliminates coefficients with low sensitivity, and focuses on summarizing and analyzing the coefficients with high sensitivity to obtain the final compensation stress applied to the photomask. This can effectively compensate for overlay error in the photolithography machine and reduce overlay error.

[0145] Based on the above embodiments, this application provides a lithography machine overlay error compensation system, including:

[0146] Memory, used to store computer programs;

[0147] A processor is used to execute the computer program to implement the steps of the lithography machine overlay error compensation method described above.

[0148] Based on the above embodiments, this application also provides a computer-readable medium storing a computer program, which, when processed and executed, implements the steps of the above-described lithography machine overlay error compensation method.

[0149] It should be noted that the computer-readable medium described in this disclosure can be a computer-readable signal medium or a computer-readable storage medium, or any combination thereof. A computer-readable storage medium can be, for example,—but not limited to—an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of a computer-readable storage medium may include, but are not limited to: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In this disclosure, a computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in connection with an instruction execution system, apparatus, or device. In this disclosure, a computer-readable signal medium can include a data signal propagated in baseband or as part of a carrier wave, carrying computer-readable program code. Such propagated data signals can take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A computer-readable signal medium can be any computer-readable medium other than a computer-readable storage medium, which can send, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device. The program code contained on the computer-readable medium can be transmitted using any suitable medium, including but not limited to: wires, optical fibers, RF (radio frequency), etc., or any suitable combination thereof.

[0150] The aforementioned computer-readable medium may be included in the aforementioned system, or it may exist independently and not assembled into the system.

[0151] In particular, according to embodiments of this disclosure, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, embodiments of this disclosure include a computer program product comprising a computer program carried on a non-transitory computer-readable medium, the computer program containing program code for performing the methods shown in the flowcharts.

[0152] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on its differences from other embodiments. In particular, the apparatus embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0153] The above description is merely a preferred embodiment of this application. Although this application has disclosed preferred embodiments above, it is not intended to limit this application. Any person skilled in the art can make many possible variations and modifications to the technical solutions of this application using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the scope of the technical solutions of this application. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this application without departing from the content of the technical solutions of this application shall still fall within the protection scope of the technical solutions of this application.

Claims

1. A method for compensating overlay errors in a photolithography machine, characterized in that, include: Obtain the initial overlay error; The initial overlay error and different stress compensation conditions are input into a pre-established overlay error distribution model to obtain the overlay error distribution after different stress compensations. Based on the overlay error distribution after different stress compensations, the coefficients of the higher-order polynomials corresponding to the overlay error distributions after different stress compensations are obtained by using the least squares method. The quotient of the overprinting error corresponding to different positions for different coefficients, divided by the total overprinting error after different stress compensation, is taken as the overprinting error sensitivity for the different coefficients. The overlay error sensitivity of the different coefficients is sorted, and the overlay error sensitivity is accumulated one by one in descending order. When the accumulated value is greater than or equal to a preset threshold, the remaining different coefficients are excluded in order to select the main coefficients from the different coefficients. The product of the preset resolution coefficient and the main coefficient is used as the final compensation stress, which is then applied to the photomask to compensate for the initial overlay error.

2. The method according to claim 1, characterized in that, The overlay error distribution after different stress compensations includes the overlay error distribution in different directions after different stress compensations.

3. The method according to claim 2, characterized in that, The different coefficients are calculated using the following formula: ； ； in, and These represent the overlay error distributions in different directions after different stress compensations. - Let be the different coefficients, i be a positive integer, and x and y be the coordinates of different positions corresponding to the overlay error distribution in different directions after different stress compensation.

4. The method according to claim 3, characterized in that, The product of the preset analytical coefficients and the main coefficients is taken as the final compensation stress, which is specifically calculated using the following formula: ； in, For the final compensation stress, The preset analytical coefficients, These are the main coefficients.

5. A photolithography machine overlay error compensation device, characterized in that, include: The acquisition unit is used to acquire the initial overlay error; The input unit is used to input the initial overlay error and different stress compensation conditions into a pre-established overlay error distribution model to obtain the overlay error distribution after different stress compensations; The solving unit is used to solve for the different coefficients of the higher-order polynomials corresponding to the different stress-compensated overlay error distributions using the least squares method based on the different stress-compensated overlay error distributions. The sensitivity unit is used to divide the overlay error corresponding to different positions of the different coefficients by the total overlay error after different stress compensation, and use the quotient as the overlay error sensitivity of the different coefficients. The filtering unit is used to sort the overlay error sensitivity of the different coefficients, and to accumulate the overlay error sensitivity one by one in descending order. When the accumulated value is greater than or equal to a preset threshold, the remaining different coefficients are excluded, so as to filter out the main coefficients from the different coefficients. The compensation unit is used to apply the final compensation stress to the photomask as the product of the preset resolution coefficient and the main coefficient, so as to compensate for the initial overlay error.

6. The apparatus according to claim 5, characterized in that, The overlay error distribution after different stress compensations includes the overlay error distribution in different directions after different stress compensations.

7. The apparatus according to claim 6, characterized in that, The solving unit is specifically used to calculate the different coefficients using the following formula: ； ； in, and These represent the overlay error distributions in different directions after different stress compensations. - Let be the different coefficients, i be a positive integer, and x and y be the coordinates of different positions corresponding to the overlay error distribution in different directions after different stress compensation.

8. The apparatus according to claim 7, characterized in that, The compensation unit is specifically used to calculate the final compensation stress using the following formula: ； in, For the final compensation stress, The preset analytical coefficients, These are the main coefficients.

9. A lithography machine overlay error compensation system, characterized in that, include: Memory, used to store computer programs; A processor, configured to execute the computer program to implement the steps of the lithography machine overlay error compensation method as described in any one of claims 1-4.

10. A computer-readable medium, characterized in that, The computer-readable medium stores a computer program that, when processed and executed, implements the steps of the lithography machine overlay error compensation method as described in any one of claims 1-4.

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