A method for extracting feature sizes of a lithographic structure and related apparatus
Patent Information
- Application Number
- CN202510555949.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-29
- Publication Date
- 2026-10-30
AI Technical Summary
然而，对于覆盖于金属层上的光刻结构而言，电子显微图像中光刻结构边缘位置的明暗对比度会发生偏转，导致难以准确提取光刻结构的特征尺寸
[0043]本申请实施例提供了一种光刻结构的特征尺寸提取方法，该方法中，首先，获取光刻结构的电子显微图像，以及基于光刻结构构建的仿真结构；光刻结构覆盖于金属层上方；而后，基于仿真结构以及仿真结构的预设占空比集合，通过仿真得到占空比集合中各占空比各自对应的第一类二次电子图像的第一灰度曲线和第二类二次电子图像的第二灰度曲线；第一类二次电子为由入射电子束与光刻结构表面作用激发产生的二次电子，第二类二次电子为由背散射电子的二次激发产生的二次电子；继而，基于预设比例叠加第一灰度曲线和第二灰度曲线，得到占空比集合中各占空比各自对应的仿真灰度曲线；接着，基于各个仿真灰度曲线与电子显微图像的实际灰度曲线的拟合度，确定目标占空比；最后，基于目标占空比，计算光刻结构的目标特征尺寸。
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Figure CN123015644A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of semiconductor technology, and in particular to a method and related apparatus for extracting feature dimensions of photolithographic structures. Background Technology
[0002] As semiconductor manufacturing process nodes continue to decrease, the feature size of photolithography structures becomes smaller and smaller, and the extraction of feature sizes such as the width of photoresist lines becomes increasingly difficult.
[0003] Currently, the edges of photolithographic structures are typically detected by varying the average grayscale value of electron micrographs of the structures, and then the feature dimensions of the structures are calculated based on the extracted edge information. However, for photolithographic structures superimposed on metal layers, the contrast between light and dark areas at the edges of the structures in the electron micrographs is reversed, making it difficult to accurately extract the feature dimensions of the structures.
[0004] Therefore, how to more accurately extract the feature dimensions of the photolithographic structure covering the metal layer has become a problem that needs to be solved. Summary of the Invention
[0005] To address the aforementioned issues, this application provides a method and related apparatus for extracting the feature dimensions of a photolithographic structure, which can more accurately extract the feature dimensions of the photolithographic structure covering the metal layer.
[0006] The embodiments of this application disclose the following technical solutions:
[0007] In a first aspect, embodiments of this application provide a method for extracting the feature dimensions of a photolithographic structure, the method comprising:
[0008] Obtain electron micrographs of the lithographic structure and a simulated structure based on the lithographic structure; the lithographic structure is overlaid on a metal layer.
[0009] Based on the simulation structure and the preset duty cycle set of the simulation structure, the first gray-scale curve of the first type of secondary electron image and the second gray-scale curve of the second type of secondary electron image corresponding to each duty cycle in the duty cycle set are obtained by simulation; the first type of secondary electron is a secondary electron generated by the interaction between the incident electron beam and the surface of the photolithographic structure, and the second type of secondary electron is a secondary electron generated by the secondary excitation of backscattered electrons.
[0010] Based on the preset ratio, the first grayscale curve and the second grayscale curve are superimposed to obtain the simulated grayscale curve corresponding to each duty cycle in the duty cycle set.
[0011] The target duty cycle is determined based on the fitting degree between each of the simulated grayscale curves and the actual grayscale curves of the electron micrographs.
[0012] Based on the target duty cycle, the target feature size of the lithographic structure is calculated.
[0013] Optionally, after calculating the target feature size of the photolithographic structure based on the target duty cycle, the method further includes:
[0014] Based on the scanning grayscale curve corresponding to the electron micrograph, the measurement feature dimensions of the photolithographic structure are extracted;
[0015] Based on the difference between the target feature size and the measured feature size, the deviation value corresponding to the photolithography material used in the photolithography structure is calculated;
[0016] Based on the deviation value corresponding to the photolithography material used in the photolithography structure, the target feature size of the test structure with the same photolithography material as the photolithography structure is calculated.
[0017] Optionally, extracting the measurement feature dimensions of the photolithographic structure based on the scanning grayscale curve corresponding to the electron microscope image includes:
[0018] Based on the adjacent first peak and second peak in the scanning grayscale curve corresponding to the electron micrograph, and the valley between the first peak and the second peak, the horizontal coordinates of multiple preset grayscale percentage points between the first peak and the second peak are determined.
[0019] The measurement feature size of the photolithographic structure is extracted based on the average difference of the horizontal coordinates of multiple sets of points with the same gray percentage between the first peak and the second peak.
[0020] Optionally, calculating the target feature size of the structure under test using the same photolithographic material as the photolithographic structure, based on the deviation value corresponding to the photolithographic material used in the photolithographic structure, includes:
[0021] Obtain electron micrographs of the structure under test that uses the same photolithography material as the photolithographic structure described above;
[0022] Based on the electron micrograph of the structure under test, the measurement feature dimensions of the structure under test are extracted;
[0023] Based on the deviation value corresponding to the photolithography material used in the photolithography structure, the measurement feature size of the structure under test is corrected to obtain the target feature size of the structure under test.
[0024] Optionally, after acquiring the electron micrograph of the photolithographic structure, the method further includes:
[0025] Calculate the actual grayscale curve of the target region in the electron micrograph; the target region includes at least one photolithographic structure period;
[0026] The simulation structure and the preset duty cycle set of the simulation structure are used to obtain, through simulation, the first grayscale curve of the first type of secondary electron image and the second grayscale curve of the second type of secondary electron image corresponding to each duty cycle in the duty cycle set, including:
[0027] Based on the simulation structure and the preset duty cycle set of the simulation structure, the first grayscale curve of the first type of secondary electronic image and the second grayscale curve of the second type of secondary electronic image corresponding to each duty cycle in the duty cycle set in the target area are obtained through simulation.
[0028] Optionally, after calculating the actual grayscale curve of the target region in the electron microscope image, the method further includes:
[0029] Interpolate the actual grayscale curve to make the number of data points in the actual grayscale curve consistent with the number of data points in the simulated grayscale curve.
[0030] Optionally, calculating the target feature size of the photolithographic structure based on the target duty cycle includes:
[0031] Based on the target duty cycle and the ideal period of the lithographic structure, the target feature size of the lithographic structure is calculated.
[0032] Secondly, embodiments of this application provide a feature size extraction device for a photolithographic structure, the device comprising: an acquisition module, a simulation module, a superposition module, a fitting module, and a first calculation module;
[0033] The acquisition module is used to acquire electron micrographs of the lithographic structure and a simulation structure constructed based on the lithographic structure; the lithographic structure covers the metal layer.
[0034] The simulation module is used to obtain, through simulation, the first grayscale curve of the first type of secondary electron image and the second grayscale curve of the second type of secondary electron image corresponding to each duty cycle in the duty cycle set, based on the simulation structure and the preset duty cycle set of the simulation structure; the first type of secondary electron is a secondary electron generated by the interaction between the incident electron beam and the surface of the photolithographic structure, and the second type of secondary electron is a secondary electron generated by the secondary excitation of backscattered electrons.
[0035] The overlay module is used to overlay the first grayscale curve and the second grayscale curve based on a preset ratio to obtain the simulated grayscale curve corresponding to each duty cycle in the duty cycle set.
[0036] The fitting module is used to determine the target duty cycle based on the fitting degree between each of the simulated grayscale curves and the actual grayscale curves of the electron microscope image.
[0037] The first calculation module is used to calculate the target feature size of the photolithographic structure based on the target duty cycle.
[0038] Thirdly, embodiments of this application provide a feature size extraction device for photolithographic structures, the device comprising: a memory and a processor;
[0039] The memory is used to store program code and transmit the program code to the processor;
[0040] The processor is configured to execute, according to the program code, the steps of the feature size extraction method for the photolithographic structure as described in any embodiment of the first aspect.
[0041] Fourthly, embodiments of this application provide a computer-readable storage medium storing a computer program. When the computer program is run on a feature size extraction device for a lithographic structure, the feature size extraction device for the lithographic structure performs the steps of the feature size extraction method for a lithographic structure as described in any embodiment of the first aspect.
[0042] Compared with the prior art, this application has the following beneficial effects:
[0043] This application provides a method for extracting the feature size of a photolithographic structure. The method involves: first, acquiring an electron micrograph of the photolithographic structure and a simulated structure constructed based on it; the photolithographic structure is overlaid on a metal layer; then, based on the simulated structure and a preset duty cycle set, obtaining, through simulation, the first grayscale curve of the first type of secondary electron image and the second grayscale curve of the second type of secondary electron image corresponding to each duty cycle in the duty cycle set; the first type of secondary electron is generated by the interaction between the incident electron beam and the surface of the photolithographic structure, and the second type of secondary electron is generated by the secondary excitation of backscattered electrons; next, by superimposing the first and second grayscale curves according to a preset ratio, obtaining the simulated grayscale curve corresponding to each duty cycle in the duty cycle set; then, determining the target duty cycle based on the fitting degree between each simulated grayscale curve and the actual grayscale curve of the electron micrograph; finally, calculating the target feature size of the photolithographic structure based on the target duty cycle.
[0044] Therefore, a multi-duty-cycle image library was constructed through simulation, fusing signals of type I secondary electrons reflecting surface morphology and signals of type II secondary electrons related to the material, to obtain simulated grayscale curves. The target duty cycle was determined by fitting the simulated grayscale curves to the actual grayscale curves, and then the feature dimensions of the lithographic structure were calculated. This feature dimension extraction method eliminates the need for direct measurement of the feature dimensions of the lithographic structure based on electron microscopy images, effectively overcoming high backscattering interference from the metal layer and more accurately extracting the feature dimensions of the lithographic structure covering the metal layer. Attached Figure Description
[0045] 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 only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0046] Figure 1 A flowchart illustrating a method for extracting feature dimensions of a photolithographic structure, as provided in an embodiment of this application;
[0047] Figure 2 This is a schematic diagram of the structure of a sample to be tested provided in an embodiment of this application;
[0048] Figure 3 This application provides a schematic diagram of simulated first-type secondary electron images corresponding to different duty cycles in an embodiment of the present application.
[0049] Figure 4 This application provides a schematic diagram of simulated second-type secondary electron images corresponding to different duty cycles in an embodiment of the present application.
[0050] Figure 5 A schematic diagram of a first grayscale curve and a second grayscale curve provided for embodiments of this application;
[0051] Figure 6 A schematic diagram of an electron micrograph of a target region provided in an embodiment of this application;
[0052] Figure 7 This application provides a schematic diagram of the actual grayscale curve corresponding to a target area.
[0053] Figure 8 This is a schematic diagram of a grayscale curve fitting effect provided in an embodiment of this application;
[0054] Figure 9 A flowchart illustrating a method for extracting feature dimensions of a structure under test based on deviation value calibration, provided in this application embodiment;
[0055] Figure 10 A schematic diagram of the position of a preset grayscale percentage point provided in an embodiment of this application;
[0056] Figure 11 A schematic diagram of a feature size extraction device for a photolithographic structure provided in an embodiment of this application;
[0057] Figure 12 This is a structural diagram of a feature size extraction device for a photolithographic structure provided in an embodiment of this application. Detailed Implementation
[0058] The feature size extraction method and related apparatus for photolithographic structures provided in this application can be used in the semiconductor field. The above is only an example and does not limit the application field of the feature size extraction method and related apparatus for photolithographic structures provided in this application.
[0059] The terms "first," "second," "third," and "fourth," etc., used in this application specification, claims, and drawings are used to distinguish different objects, not to limit a specific order.
[0060] In the embodiments of this application, the terms "as an example" or "for example" are used to indicate that they are examples, illustrations, or explanations. Any embodiment or design that is described as "as an example" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design options. Specifically, the use of terms such as "as an example" or "for example" is intended to present the relevant concepts in a specific manner.
[0061] The terminology used in the implementation section of this application is for the purpose of explaining specific embodiments of this application only, and is not intended to limit this application.
[0062] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.
[0063] See Figure 1 The figure is a flowchart of a method for extracting the feature size of a photolithographic structure according to an embodiment of this application. The method includes:
[0064] S101: Obtain electron micrographs of the lithographic structure and the simulated structure based on the lithographic structure.
[0065] In this embodiment, the photolithographic structure covers the metal layer. For example... Figure 2 As shown in the figure, this figure is a schematic diagram of a sample structure to be tested provided in an embodiment of this application. In this figure, a substrate 01, a metal layer 02 and a photolithography structure 03 are stacked in sequence. The metal layer may include, but is not limited to, films such as gold, silver and titanium layers, as well as films such as tantalum nitride (TaN) absorption layer, ruthenium (Ru) capping layer or molybdenum / silicon (Mo / Si) multilayer reflective film in extreme ultraviolet lithography technology.
[0066] For example, based on structural parameters such as the lithographic structure period and duty cycle in the lithographic structure, and structural parameters such as the material and thickness of each layer in the sample under test, a simulated structure of the sample under test can be constructed. Electron microscopy images can be electron beam images or scanning electron microscope images, which can reflect morphological features such as the contour of the lithographic structure of the sample under test through grayscale changes. In the embodiments of this application, scanning electron microscope images, commonly used in the field of lithography, are used as examples of electron microscopy images for description.
[0067] S102: Based on the simulation structure and the preset duty cycle set of the simulation structure, the first gray-scale curve of the first type of secondary electronic image and the second gray-scale curve of the second type of secondary electronic image corresponding to each duty cycle in the duty cycle set are obtained through simulation.
[0068] In this embodiment, the first type of secondary electron is a secondary electron generated by the interaction between the incident electron beam and the surface of the photolithographic structure, and the second type of secondary electron is a secondary electron generated by the secondary excitation of backscattered electrons.
[0069] During scanning using a scanning electron microscope, the incident electron beam directly interacts with the atoms of the lithographic structure through inelastic scattering, transferring energy to valence electrons or weakly bound electrons, causing them to detach from the sample surface. This generates type I secondary electrons with energies below 50 eV. Due to their shallow escape depth, type I secondary electron images can clearly reflect the morphological details such as the edge contours and roughness of the lithographic structure lines.
[0070] After an incident electron beam undergoes elastic or inelastic collisions with atoms in a photolithographic structure, some electrons bounce off the surface at angles greater than 90°, and are called backscattered electrons. Backscattered electrons retain high energy and penetrate to a greater depth. During their escape from the sample, they undergo inelastic collisions with atoms along their path, exciting the underlying material of the photolithographic structure and transferring energy to bound electrons in the sample. This excites secondary electrons of the second kind with energies below 50 eV, resulting in contrast reversal or blurred edges in the final electron micrograph. The image of secondary electrons of the second kind is related to factors such as the atomic number and surface morphology of the material.
[0071] Duty cycle is the ratio of line width to period in a periodic structure, and it can be used to infer the feature size of a lithographic structure.
[0072] In photolithography, due to the influence of processes such as exposure and development, as well as the properties of the photoresist itself, the feature size of the developed photolithographic structure usually deviates from the ideal size designed.
[0073] Therefore, based on the ideal duty cycle, a duty cycle range and step size can be pre-defined to obtain a duty cycle set. Then, programs can be created to construct the simulated structure at different duty cycles, facilitating the extraction of the feature dimensions of the lithographic structure by fitting the simulated structure and the lithographic structure. For example, if the ideal duty cycle is 0.5, a duty cycle range of 0.35–0.6 and a step size of 0.01 can be set based on this, resulting in a duty cycle set such as [0.35, 0.36, 0.37, …, 0.59, 0.60].
[0074] Monte Carlo simulation can accurately simulate the secondary electron generation process in scanning electron microscopy imaging, and can distinguish between type I and type II secondary electrons, generating two independent simulation images. It can also construct a high-precision, multi-parameter simulation image library that includes both type I and type II secondary electron images, in order to extract key dimensions with higher accuracy.
[0075] After creating programs to construct the simulated structure at different duty cycles, first-type and second-type secondary electron images corresponding to different duty cycles can be obtained using methods such as Monte Carlo simulation. The grayscale curves of each image are then calculated to obtain the first grayscale curve of the first-type secondary electron image and the second grayscale curve of the second-type secondary electron image. The grayscale curves represent the average grayscale value along the horizontal direction of the image. Changes in grayscale values provide edge information of the lithographic structure, which can then be used to extract the feature dimensions of the lithographic structure.
[0076] For example, see Figure 3 This figure is a schematic diagram of simulated first-type secondary electron images corresponding to different duty cycles provided in an embodiment of this application. Figure 3 The duty cycle corresponding to (a) is 0.4. Figure 3 In (b), the duty cycle is 0.5. Figure 3 The duty cycle corresponding to (c) is 0.6.
[0077] For example, see Figure 4 This figure is a schematic diagram of simulated second-type secondary electron images corresponding to different duty cycles provided in an embodiment of this application. Figure 4 The duty cycle corresponding to (a) is 0.4. Figure 4 In (b), the duty cycle is 0.5. Figure 4 The duty cycle corresponding to (c) is 0.6.
[0078] For example, see Figure 5 This figure is a schematic diagram of a first grayscale curve and a second grayscale curve provided in an embodiment of this application. The horizontal axis represents the horizontal position of the feature point when measured along the grayscale curve, and the vertical axis represents the grayscale value of the feature point on the grayscale curve. The first grayscale curve (SE1 image) is a solid line, corresponding to... Figure 3 (b) is the first type of secondary electron image with a duty cycle of 0.5; the second grayscale curve (SE2 image) is a dashed line, corresponding to... Figure 4 (b) is a second type of secondary electron image with a duty cycle of 0.5.
[0079] As an example, the actual grayscale curve of the target region in the electron microscope image can be calculated at any time after acquiring the electron microscope image of the photolithographic structure and before performing step S104. The electron microscope image of the target region is as follows: Figure 6 As shown, the actual grayscale curve corresponding to the target area is as follows: Figure 7 As shown, where, Figure 7 The vertical axis represents the normalized grey level of the actual grey curve.
[0080] Since actual photolithographic structures may have defects in some areas, and the quality of electron micrographs is affected by many factors, regions with better image quality can be pre-selected as target regions in the electron micrograph. The target region includes at least one photolithographic structure cycle; there can be one or multiple target regions. This application embodiment describes an example with only one target region. In the case of multiple target regions, steps S102 to S105 of this application embodiment can be performed separately for each target region to obtain multiple feature sizes at different locations of the photolithographic structure.
[0081] After obtaining the actual grayscale curve, interpolation can be performed on the actual grayscale curve to make the number of data points in the actual grayscale curve consistent with the number of data points in the simulated grayscale curve.
[0082] Here, data points refer to the sequence of pixel grayscale values along the scan line direction, such as perpendicular to the photoresist line direction. Physically, they represent the intensity of the secondary electron signal at each location when the electron beam scans the sample surface. Interpolation processing can align the number of data points on the actual grayscale curve, the first grayscale curve, and the second grayscale curve, thus facilitating the calculation of the goodness of fit.
[0083] After obtaining the first type of secondary electron image and the second type of secondary electron image through simulation, the same position as the target area can be selected in the first type of secondary electron image to calculate the first grayscale curve; the same position as the target area can be selected in the second type of secondary electron image to calculate the second grayscale curve.
[0084] S103: Based on the preset ratio, the first grayscale curve and the second grayscale curve are superimposed to obtain the simulation grayscale curve corresponding to each duty cycle in the duty cycle set.
[0085] The actual acquired electron microscopy image is a superposition of the first and second type secondary electron images, with some noise information considered in the superposition. The intensity of the first and second type secondary electron images is related to the incident electron beam energy, as well as factors such as the atomic number and surface morphology of the sample material. This intensity can be obtained by fitting the superposition ratio of the first and second grayscale curves within the range allowed by intrinsic laws. This allows for fitting the superimposed simulated grayscale curve with the actual grayscale curve of the electron microscopy image to determine the target duty cycle.
[0086] Specifically, the normalized gray values of the first gray-scale curve SE1 and the second gray-scale curve SE2 can be superimposed according to a predetermined ratio. For example, the normalized gray values of the first gray-scale curve and the second gray-scale curve can be superimposed at a ratio of 1:1.5 (k=1.50) to obtain a simulated gray-scale curve. Figure 8 The solid line shown.
[0087] S104: Determine the target duty cycle based on the fitting degree between each simulated grayscale curve and the actual grayscale curve of the electron microscope image.
[0088] For example, see Figure 8 This figure illustrates a grayscale curve fitting effect provided in an embodiment of this application. The solid line represents the simulated grayscale curve obtained by superimposing the first grayscale curve SE1 and the second grayscale curve SE2, while the dashed line represents the actual grayscale curve of the electron microscope image. Fitting the actual grayscale curve and the simulated grayscale curve (Fit Curve) results in a higher degree of fit between the two curves, indicating a greater overlap between the simulated and actual grayscale curves. For example, Figure 8 The simulated grayscale curve shown has a duty cycle of 0.43, and the fitting degree between the simulated grayscale curve and the actual grayscale curve is 0.97619.
[0089] For each simulated grayscale curve with a different duty cycle, the fitting degree between the simulated grayscale curve and the actual grayscale curve is calculated. This allows us to find the target simulated grayscale curve with the highest fitting degree and determine the duty cycle corresponding to the target simulated grayscale curve as the target duty cycle.
[0090] Optionally, in some embodiments, the first type of secondary electron image and the second type of secondary electron image can be superimposed to obtain the simulation image corresponding to each duty cycle in the duty cycle set; then, the target duty cycle is determined based on the fitting degree between each simulation image and the electron micrograph.
[0091] S105: Calculate the target feature size of the photolithographic structure based on the target duty cycle.
[0092] In some embodiments, the target feature size of the lithographic structure can be obtained by multiplying the target duty cycle by the ideal period of the lithographic structure. For example, if the target duty cycle is 0.43 and the ideal period of the lithographic structure is 100 nm, then the feature size of the lithographic result is 43 nm.
[0093] Different lithographic structures often have different ideal periods. The feature size of the lithographic structure is obtained by calculating the product of the target duty cycle and the ideal period of the lithographic structure. When dealing with lithographic structures with different periods, it is necessary to repeat steps S101 to S104 to perform simulations to obtain a new target duty cycle in order to calculate the feature size of the lithographic structure with different periods.
[0094] Therefore, in this embodiment, a multi-duty-cycle image library is constructed through simulation, fusing signals of type I secondary electrons reflecting surface morphology and signals of type II secondary electrons related to the material to obtain a simulated grayscale curve. The target duty cycle is determined by fitting the simulated grayscale curve to the actual grayscale curve, and then the feature size of the lithographic structure is calculated. This feature size extraction method does not require direct measurement of the feature size of the lithographic structure based on electron microscopy images, effectively overcoming high backscattering interference from the metal layer and more accurately extracting the feature size of the lithographic structure covering the metal layer.
[0095] For photolithographic structures formed with the same photolithographic material, the deviation between the measured feature size extracted from the scanning grayscale curve corresponding to the scanning electron microscope image and the target feature size calculated through steps S101 to S105 is usually fixed.
[0096] In view of this, in some embodiments, after the target feature size of the photolithographic structure is calculated through steps S101 to S105, the deviation value bias between the measured feature size corresponding to the photolithographic material used in the photolithographic structure and the target feature size can be calibrated based on the target feature size. When extracting the feature size of other test structures with the same photolithographic material in the future, the measured feature size of the test structure directly extracted from the scanning grayscale curve can be corrected with the deviation value bias, so as to obtain the feature size of the test structure with high precision.
[0097] Specifically, see Figure 9 The figure is a flowchart of a method for extracting the feature dimensions of a structure under test based on deviation value calibration according to an embodiment of this application. The method can specifically be as follows:
[0098] S901: Extract the measurement feature dimensions of the photolithographic structure based on the scanning grayscale curve corresponding to the scanning electron microscope image.
[0099] For example, such as Figure 10 As shown, the abscissas of multiple preset grayscale percentage points between the first peak max1 and the second peak max2 can be determined based on the adjacent first peak max1 and second peak max2 in the scanning grayscale curve (actual grayscale curve) corresponding to the scanning electron microscope image, as well as the valley value min located between the first peak max1 and the second peak max2. For example, the preset grayscale percentage points can be... Figure 10 The points shown are at 60%, 50%, or 40%; then the difference in the abscissa of the same grayscale percentage points between the first peak max1 and the second peak max2 is calculated to extract the measured feature size d of the photolithographic structure. As an example, by conducting numerous experiments, the grayscale percentage with the abscissa difference between two points that is closest to the target feature size can be selected from multiple grayscale percentages as the preset grayscale percentage point.
[0100] Among them, the grayscale percentage points can be selected from the areas with large grayscale value changes in the scanned grayscale curve, so as to obtain more accurate measurement feature dimensions.
[0101] S902: Calculate the deviation value corresponding to the photolithography material used in the photolithography structure based on the difference between the target feature size and the measured feature size.
[0102] The target feature size d of the photolithographic structure with high precision can be calculated through steps S101 to S105. real Calculate the target feature size d real The difference between the measured feature size d and the value of d is based on equation d. real-d = 2bias, which gives the bias value corresponding to the photolithographic material used in the photolithographic structure.
[0103] S903: Based on the deviation value corresponding to the photolithography material used in the photolithography structure, calculate the target feature size of the structure under test that uses the same photolithography material as the photolithography structure.
[0104] Specifically, a scanning electron microscope (SEM) image of the structure under test (SUT) using the same photolithography material as the photolithography structure can be obtained first. Then, based on the scanning grayscale curve of the SEM image of the SUT, the measurement feature dimensions of the SUT are extracted using the method described in step S901. Finally, the measurement feature dimensions of the SUT are corrected based on the deviation value corresponding to the photolithography material used in the photolithography structure, thereby obtaining the target feature dimensions of the SUT with higher accuracy.
[0105] Therefore, the deviation between the measured feature size and the target feature size calculated through steps S101 to S105 of the photolithographic structure formed using the same photolithographic material is usually fixed. By correcting the measured feature size of the structure under test using the pre-calibrated deviation value, the high-precision target feature size of the structure under test can be derived in reverse. This not only ensures the accuracy of the feature size extraction result, but also simplifies the feature size extraction process and improves the efficiency of feature size extraction.
[0106] See Figure 11 The figure is a schematic diagram of a feature size extraction device for a photolithographic structure provided in an embodiment of this application. The device includes: an acquisition module 1101, a simulation module 1102, a superposition module 1103, a fitting module 1104, and a first calculation module 1105.
[0107] The acquisition module 1101 is used to acquire electron micrographs of the photolithographic structure and a simulation structure constructed based on the photolithographic structure; the photolithographic structure covers the metal layer.
[0108] The simulation module 1102 is used to obtain the first grayscale curve of the first type of secondary electron image and the second grayscale curve of the second type of secondary electron image corresponding to each duty cycle in the set of the simulation structure and the preset duty cycle of the simulation structure through simulation. The first type of secondary electron is a secondary electron generated by the interaction between the incident electron beam and the surface of the photolithographic structure, and the second type of secondary electron is a secondary electron generated by the secondary excitation of backscattered electrons.
[0109] The overlay module 1103 is used to overlay the first grayscale curve and the second grayscale curve based on a preset ratio to obtain the simulation grayscale curve corresponding to each duty cycle in the duty cycle set.
[0110] The fitting module 1104 is used to determine the target duty cycle based on the fitting degree between each simulated grayscale curve and the actual grayscale curve of the electron microscope image.
[0111] The first calculation module 1105 is used to calculate the target feature size of the photolithographic structure based on the target duty cycle.
[0112] Therefore, in this embodiment, a multi-duty-cycle image library is constructed through simulation, fusing signals of type I secondary electrons reflecting surface morphology and signals of type II secondary electrons related to the material to obtain a simulated grayscale curve. The target duty cycle is determined by fitting the simulated grayscale curve to the actual grayscale curve, and then the feature size of the lithographic structure is calculated. This feature size extraction method does not require direct measurement of the feature size of the lithographic structure based on electron microscopy images, effectively overcoming high backscattering interference from the metal layer and more accurately extracting the feature size of the lithographic structure covering the metal layer.
[0113] Optionally, in some embodiments, the feature size extraction device for the photolithographic structure further includes: a second calculation module; the second calculation module includes a size extraction unit, a deviation calculation unit, and a size calculation unit; wherein, the size extraction unit is used to extract the measurement feature size of the photolithographic structure based on the scanning grayscale curve corresponding to the electron micrograph; the deviation calculation unit is used to calculate the deviation value corresponding to the photolithographic material used in the photolithographic structure based on the difference between the target feature size and the measurement feature size; the size calculation unit is used to calculate the target feature size of the structure under test that uses the same photolithographic material as the photolithographic structure based on the deviation value corresponding to the photolithographic material used in the photolithographic structure.
[0114] Optionally, in some embodiments, the size extraction unit is specifically used to: determine the abscissa of multiple preset grayscale percentage points between the first peak and the second peak based on the adjacent first peak and second peak in the scanning grayscale curve corresponding to the electron micrograph, and the valley value located between the first peak and the second peak; and extract the measurement feature size of the photolithographic structure based on the average difference of the abscissas of multiple sets of the same grayscale percentage points between the first peak and the second peak.
[0115] Optionally, in some embodiments, the size calculation unit is specifically used for: acquiring an electron micrograph of the structure under test that uses the same photolithography material as the photolithography structure; extracting the measurement feature size of the structure under test based on the electron micrograph of the structure under test; correcting the measurement feature size of the structure under test based on the deviation value corresponding to the photolithography material used in the photolithography structure, and obtaining the target feature size of the structure under test.
[0116] Optionally, in some embodiments, the feature size extraction device for the photolithographic structure further includes: a curve calculation module for calculating the actual grayscale curve of the target region in the electron micrograph; the target region includes at least one photolithographic structure period; and a simulation module 1102 specifically used for: based on the simulation structure and a preset duty cycle set of the simulation structure, obtaining, through simulation, the first grayscale curve of the first type of secondary electron image and the second grayscale curve of the second type of secondary electron image corresponding to each duty cycle in the duty cycle set in the target region.
[0117] Optionally, in some embodiments, the feature size extraction device for the photolithographic structure further includes an interpolation module for interpolating the actual grayscale curve so that the number of data points in the actual grayscale curve is consistent with the number of data points in the simulated grayscale curve.
[0118] Optionally, in some embodiments, the first calculation module 1105 is specifically used to: calculate the target feature size of the lithographic structure based on the target duty cycle and the ideal period of the lithographic structure.
[0119] See Figure 12 The figure is a structural diagram of a feature size extraction device for a photolithographic structure provided in an embodiment of this application. The device includes a memory 1201 and a processor 1202.
[0120] Memory 1201: Used to store program code and transfer program code to the processor.
[0121] Processor 1202: Used to execute the steps of the above-described method for extracting the feature size of the lithographic structure according to the instructions in the program code.
[0122] In addition, this application also provides a computer-readable storage medium storing computer instructions, which, when executed on a feature size extraction device for a photolithographic structure, perform the steps of the aforementioned feature size extraction method for the photolithographic structure.
[0123] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for the device and storage medium embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts can be referred to the description of the method embodiments. The device and storage medium embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components indicated as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment solution according to actual needs. Those skilled in the art can understand and implement this without creative effort.
[0124] The above description is merely one specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
Claims
1. A method for extracting feature dimensions of a photolithographic structure, characterized in that, The method includes: Obtain electron micrographs of the lithographic structure and a simulated structure based on the lithographic structure; the lithographic structure is overlaid on a metal layer. Based on the simulation structure and the preset duty cycle set of the simulation structure, the first gray-scale curve of the first type of secondary electron image and the second gray-scale curve of the second type of secondary electron image corresponding to each duty cycle in the duty cycle set are obtained by simulation; the first type of secondary electron is a secondary electron generated by the interaction between the incident electron beam and the surface of the photolithographic structure, and the second type of secondary electron is a secondary electron generated by the secondary excitation of backscattered electrons. Based on the preset ratio, the first grayscale curve and the second grayscale curve are superimposed to obtain the simulated grayscale curve corresponding to each duty cycle in the duty cycle set. The target duty cycle is determined based on the fitting degree between each of the simulated grayscale curves and the actual grayscale curves of the electron micrographs. Based on the target duty cycle, the target feature size of the lithographic structure is calculated.
2. The method according to claim 1, characterized in that, After calculating the target feature size of the photolithographic structure based on the target duty cycle, the method further includes: Based on the scanning grayscale curve corresponding to the electron micrograph, the measurement feature dimensions of the photolithographic structure are extracted; Based on the difference between the target feature size and the measured feature size, the deviation value corresponding to the photolithography material used in the photolithography structure is calculated; Based on the deviation value corresponding to the photolithography material used in the photolithography structure, the target feature size of the test structure with the same photolithography material as the photolithography structure is calculated.
3. The method according to claim 2, characterized in that, The step of extracting the measurement feature dimensions of the photolithographic structure based on the scanning grayscale curve corresponding to the electron micrograph includes: Based on the adjacent first peak and second peak in the scanning grayscale curve corresponding to the electron micrograph, and the valley between the first peak and the second peak, the horizontal coordinates of multiple preset grayscale percentage points between the first peak and the second peak are determined. The measurement feature size of the photolithographic structure is extracted based on the average difference of the horizontal coordinates of multiple sets of points with the same gray percentage between the first peak and the second peak.
4. The method according to claim 2, characterized in that, The step of calculating the target feature size of the structure under test, which uses the same photolithographic material as the photolithographic structure, based on the deviation value corresponding to the photolithographic material used in the photolithographic structure, includes: Obtain electron micrographs of the structure under test that uses the same photolithography material as the photolithographic structure described above; Based on the electron micrograph of the structure under test, the measurement feature dimensions of the structure under test are extracted; Based on the deviation value corresponding to the photolithography material used in the photolithography structure, the measurement feature size of the structure under test is corrected to obtain the target feature size of the structure under test.
5. The method according to claim 1, characterized in that, After acquiring the electron micrograph of the photolithographic structure, the method further includes: Calculate the actual grayscale curve of the target region in the electron micrograph; the target region includes at least one photolithographic structure period; The simulation structure and the preset duty cycle set of the simulation structure are used to obtain, through simulation, the first grayscale curve of the first type of secondary electron image and the second grayscale curve of the second type of secondary electron image corresponding to each duty cycle in the duty cycle set, including: Based on the simulation structure and the preset duty cycle set of the simulation structure, the first grayscale curve of the first type of secondary electronic image and the second grayscale curve of the second type of secondary electronic image corresponding to each duty cycle in the duty cycle set in the target area are obtained through simulation.
6. The method according to claim 5, characterized in that, After calculating the actual grayscale curve of the target region in the electron microscope image, the method further includes: Interpolate the actual grayscale curve to make the number of data points in the actual grayscale curve consistent with the number of data points in the simulated grayscale curve.
7. The method according to claim 1, characterized in that, The step of calculating the target feature size of the photolithographic structure based on the target duty cycle includes: Based on the target duty cycle and the ideal period of the lithographic structure, the target feature size of the lithographic structure is calculated.
8. A feature dimension extraction device for a photolithographic structure, characterized in that, The device includes: an acquisition module, a simulation module, a superposition module, a fitting module, and a first calculation module; The acquisition module is used to acquire electron micrographs of the lithographic structure and a simulation structure constructed based on the lithographic structure; the lithographic structure covers the metal layer. The simulation module is used to obtain, through simulation, the first grayscale curve of the first type of secondary electron image and the second grayscale curve of the second type of secondary electron image corresponding to each duty cycle in the duty cycle set, based on the simulation structure and the preset duty cycle set of the simulation structure; the first type of secondary electron is a secondary electron generated by the interaction between the incident electron beam and the surface of the photolithographic structure, and the second type of secondary electron is a secondary electron generated by the secondary excitation of backscattered electrons. The overlay module is used to overlay the first grayscale curve and the second grayscale curve based on a preset ratio to obtain the simulated grayscale curve corresponding to each duty cycle in the duty cycle set. The fitting module is used to determine the target duty cycle based on the fitting degree between each of the simulated grayscale curves and the actual grayscale curves of the electron micrograph. The first calculation module is used to calculate the target feature size of the photolithographic structure based on the target duty cycle.
9. A feature dimension extraction device for a photolithographic structure, characterized in that, The device includes: a memory and a processor; The memory is used to store program code and transmit the program code to the processor; The processor is configured to execute the steps of the feature size extraction method for the photolithographic structure according to any one of claims 1-7, based on the program code.
10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, which, when run on a feature size extraction device for a lithographic structure, performs the steps of the feature size extraction method for a lithographic structure as described in any one of claims 1-7.