Method and system for establishing optical critical dimension database

Abstract

This disclosure relates to a method and system for establishing an optical critical dimension database, and a method and system for measuring optical critical dimensions. The method for establishing the optical critical dimension database includes: providing a reference wafer having reference test units; obtaining the overlay accuracy of a reference target pattern in the reference test units, the reference target pattern including a wall structure and a first trench and a second trench located on both sides of the wall structure; performing optical critical dimension measurement on the reference target pattern to obtain the measurement critical dimensions of the first trench and the second trench; determining a first correlation function based on the overlay accuracy and the measurement critical dimensions, the first correlation function being used to characterize the correspondence between the overlay accuracy and the measurement critical dimensions; and determining the optical critical dimension database based on the first correlation function. This disclosure can improve the accuracy of optical critical dimension measurement and evaluation in device stacking structures.

Description

Technical Field

[0001] This disclosure relates to the field of optical measurement technology, and in particular to a method and system for establishing an optical critical size database, and a method and system for measuring optical critical sizes. Background Technology

[0002] With advancements in manufacturing processes and the shrinking of critical dimensions, monitoring the dimensions of each process layer in semiconductor integrated circuits becomes increasingly difficult, both during the R&D and mass production stages. Optical Critical Dimension (OCD), a non-destructive and non-contact measurement method, primarily utilizes the principle of light scattering to analyze the spectrum of reflected light projected onto a fixed area of ​​the wafer surface, thereby measuring the size or contour of the tested pattern structure.

[0003] Currently, for advanced semiconductor integrated circuit manufacturing processes, monitoring and evaluating the critical dimension (CD) plays a crucial role in the quality control and assurance of semiconductor integrated circuits. OCD, as a highly effective and relatively accurate measurement method, can be used in conjunction with a scanning electron microscope (CD-SEM) for feature dimension measurement to measure device CD. Here, the critical dimension refers to a feature dimension (e.g., linewidth) measured at a specific height above the substrate (e.g., within a specific layer).

[0004] However, in conventional CD measurement methods (such as CDSEM and OCD), the measurement principle based on OCD makes it difficult to qualitatively or quantitatively analyze the stacking situation between different layers in a device stack structure, which can easily affect the evaluation of OCD measurement data. Therefore, how to improve the accuracy of device CD measurement evaluation in device stack structures has become an urgent problem to be solved in related technologies. Summary of the Invention

[0005] Based on this, the present disclosure provides a method and system for establishing an optical critical size database, and a method and system for measuring optical critical sizes, which can improve the accuracy of measurement and evaluation of optical critical sizes of devices in device stacking structures.

[0006] On the one hand, some embodiments of this disclosure provide a method for establishing an optical critical size database, including the following steps.

[0007] A reference wafer is provided, wherein the reference wafer has reference test units.

[0008] The overlay accuracy of the reference target pattern in the reference test unit is obtained; the reference target pattern includes a wall structure and a first groove and a second groove located on both sides of the wall structure.

[0009] Optical critical dimension measurement is performed on the reference target pattern to obtain the measurement critical dimensions of the first groove and the second groove.

[0010] A first correlation function is determined based on the overlay accuracy and the measurement critical size. The first correlation function is used to characterize the correspondence between the overlay accuracy and the measurement critical size.

[0011] Based on the first correlation function, an optical critical size database is determined.

[0012] In some embodiments, the method for establishing the optical critical size database further includes the following steps.

[0013] The reference target pattern is sliced ​​and measured by transmission electron microscopy to obtain the reference critical dimensions of the first groove and the second groove.

[0014] A second correlation function is determined based on the measured critical dimension and the reference critical dimension. The second correlation function is used to characterize the correspondence between the measured critical dimension and the reference critical dimension corresponding to the same overlay accuracy.

[0015] The optical critical size database is determined jointly based on the first correlation function and the second correlation function.

[0016] In some embodiments, the number of benchmark testing units is multiple; wherein the overlay accuracy of the benchmark target pattern in different benchmark testing units is different.

[0017] In some embodiments, the number of the benchmark test units is an odd number greater than 1; the plurality of benchmark test units includes: a reference test unit with zero overlay accuracy, and a plurality of first series test units and a plurality of second series test units located centered on the reference test unit and respectively on the side of the reference test unit; wherein, the overlay accuracy of the plurality of first series test units increases negatively in sequence; the overlay accuracy of the plurality of second series test units increases positively in sequence.

[0018] In some embodiments, the overlay accuracy difference between adjacent first series test units is the same as the overlay accuracy difference between adjacent second series test units.

[0019] In some embodiments, the step of performing optical critical size measurement on the reference target pattern to obtain the measurement critical size of the first groove and the second groove further includes: performing optical critical size measurement on multiple different target regions of the first groove and the second groove respectively to obtain a set of measurement critical sizes consisting of multiple measurement critical sizes of the first groove and the second groove.

[0020] Accordingly, determining the first correlation function based on the overlay accuracy and the measurement critical size further includes: determining the first correlation function based on the overlay accuracy and the measurement critical size set.

[0021] In some embodiments, the method for establishing the optical critical size database further includes the following steps.

[0022] Transmission electron microscopy (TEM) measurements were performed on multiple different target regions of the first and second trenches to obtain multiple reference critical dimensions of the first and second trenches, forming a reference critical dimension set.

[0023] A second correlation function is determined based on the set of measurement critical dimensions and the set of reference critical dimensions. The second correlation function is used to characterize the correspondence between the measurement critical dimensions and the reference critical dimensions corresponding to the same overlay accuracy.

[0024] The optical critical size database is determined jointly based on the first correlation function and the second correlation function.

[0025] In some embodiments, the first correlation function includes a first linear function; the first linear function has the overlay accuracy as the independent variable and the measurement critical size as the dependent variable.

[0026] In some embodiments, the second correlation function includes a second linear function; the second linear function takes the measurement critical size corresponding to the same overlay accuracy as the independent variable and the reference critical size as the dependent variable.

[0027] On the other hand, some embodiments of this disclosure provide a system for establishing an optical critical size database, including: a reference wafer, an overlay accuracy measurement device, an optical critical size measurement device, and a processor. The reference wafer has a reference testing unit. The overlay accuracy measurement device is used to obtain the overlay accuracy of a reference target pattern in the reference testing unit; the reference target pattern includes a wall structure and a first groove and a second groove located on both sides of the wall structure. The optical critical size measurement device is used to perform optical critical size measurement on the reference target pattern to obtain the measurement critical size of the first groove and the second groove. The processor is connected to the overlay accuracy measurement device and the optical critical size measurement device, and is configured to: determine a first correlation function based on the overlay accuracy and the measurement critical size, and determine an optical critical size database based on the first correlation function; wherein, the first correlation function is used to characterize the correspondence between the overlay accuracy and the measurement critical size.

[0028] In some embodiments, the system for establishing the optical critical size database further includes a transmission electron microscope (TEM) apparatus. The TEM apparatus is used to perform TEM measurements on the reference target pattern to obtain the reference critical sizes of the first groove and the second groove. The processor is also connected to the TEM apparatus and configured to: determine a second correlation function based on the overlay accuracy, the measurement critical size, and the reference critical size; and jointly determine the optical critical size database based on the first correlation function and the second correlation function; wherein the second correlation function characterizes the correspondence between the measurement critical size and the reference critical size corresponding to the same overlay accuracy.

[0029] In some embodiments, the system for establishing the optical critical size database further includes a measurement correction device. The measurement correction device is connected to the processor and is used to correct the optical critical size measurement device according to the second correlation function, so that the measured critical size corresponding to the same reference target pattern is close to the corresponding reference critical size.

[0030] In some embodiments, the number of benchmark testing units is multiple; wherein the overlay accuracy of the benchmark target pattern in different benchmark testing units is different.

[0031] In some embodiments, the number of the benchmark test units is an odd number greater than 1; the plurality of benchmark test units includes: a reference test unit with zero overlay accuracy, and a plurality of first series test units and a plurality of second series test units located centered on the reference test unit and respectively on the side of the reference test unit; wherein, the overlay accuracy of the plurality of first series test units increases negatively in sequence; the overlay accuracy of the plurality of second series test units increases positively in sequence.

[0032] In some embodiments, the overlay accuracy difference between adjacent first series test units is the same as the overlay accuracy difference between adjacent second series test units.

[0033] In another aspect, some embodiments of this disclosure provide a method for measuring optical critical dimensions, including the following steps.

[0034] A wafer to be tested is provided, wherein the wafer to be tested has test units.

[0035] Obtain the overlay accuracy of the target graphic in the test unit.

[0036] Based on the overlay accuracy of the target graphic to be tested and the optical critical size database established by the optical critical size database establishment method as described in any of the above embodiments, the critical size to be tested of the target graphic to be tested is determined.

[0037] In some embodiments, the optical critical dimension measurement method further includes the following steps.

[0038] The optical critical dimension of the target image under test is measured to obtain the measured critical dimension of the target image under test.

[0039] Determine the difference between the measured critical dimension and the critical dimension to be measured.

[0040] When the difference exceeds the target threshold, a warning message is sent or a shutdown command is triggered.

[0041] In another aspect, some embodiments of this disclosure provide an optical critical dimension measurement system, including: an overlay accuracy measuring device, a memory, and a processor. The overlay accuracy measuring device is used to acquire the overlay accuracy of a target pattern in a test cell on a wafer under test. The memory stores an optical critical dimension database established by the method for establishing an optical critical dimension database as described in any of the preceding embodiments. The processor is connected to the memory and the overlay accuracy measuring device; the processor is configured to: determine the critical dimension to be measured of the target pattern based on the overlay accuracy of the target pattern and the optical critical dimension database.

[0042] In some embodiments, the optical critical dimension measurement system further includes an optical critical dimension measuring device. The optical critical dimension measuring device is used to measure the optical critical dimension of the target graphic to obtain the measured critical dimension of the target graphic; wherein the processor is also connected to the optical critical dimension measuring device and configured to determine the difference between the measured critical dimension and the target critical dimension.

[0043] In this embodiment, a reference target pattern is formed on a reference wafer, and the reference target pattern is set as a wall structure and a first trench and a second trench located on both sides of the wall structure. A first correlation function is determined by obtaining the overlay accuracy of the reference target pattern and the measurement critical dimensions of the first and second trenches obtained after optical critical dimension measurement of the reference target pattern. This first correlation function accurately characterizes the correspondence between overlay accuracy and measurement critical dimensions. Thus, the optical critical dimension database determined by the aforementioned first correlation function can effectively reflect the influence of overlay accuracy deviation on optical critical dimension measurement, facilitating quantitative or qualitative analysis of the impact of overlay accuracy deviation on optical critical dimension measurement. This effectively leverages the role of the optical critical dimension database in optical critical dimension measurement and evaluation, enabling the measurement and evaluation of critical dimensions of semiconductor structures based on the optical critical dimension measurement database and improving the accuracy of optical critical dimension measurement and evaluation.

[0044] Furthermore, in this embodiment, by performing slice transmission electron microscopy (TEM) measurements on the reference target pattern to obtain the reference critical dimensions of the first and second trenches, a second correlation function can be determined based on the measured critical dimensions and the reference critical dimensions. This allows the second correlation function to accurately characterize the correspondence between the measured critical dimensions and the reference critical dimensions corresponding to the same overlay precision. Thus, the optical critical dimension database determined by the aforementioned first and second correlation functions can not only effectively reflect the correlation between overlay precision, measured critical dimensions, and reference critical dimensions, but also use the reference critical dimensions obtained from slice TEM measurements to assist in verifying the measured critical dimensions. This effectively improves the accuracy of the optical critical dimension database, enabling the measurement and evaluation of critical dimensions of semiconductor structures based on the optical critical dimension measurement database, and further improving the accuracy of optical critical dimension measurement and evaluation.

[0045] Furthermore, in this embodiment of the present disclosure, a measurement correction device is set in the optical critical size database establishment system. The measurement correction device can also be used to correct the optical critical size measuring device according to the aforementioned second correlation function, so as to improve the measurement accuracy of the optical critical size measuring device. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology 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.

[0047] Figure 1 This is a flowchart illustrating a method for establishing an optical critical size database in one embodiment;

[0048] Figure 2 This is a flowchart illustrating another method for establishing an optical critical size database provided in one embodiment;

[0049] Figure 3 This is a schematic diagram of the structure of a reference wafer provided in one embodiment;

[0050] Figure 4 This is a schematic diagram of the structure of another reference wafer provided in one embodiment;

[0051] Figure 5 This is a schematic cross-sectional view of a semiconductor structure provided in one embodiment with an overlay accuracy of 0 nm.

[0052] Figure 6This is a schematic cross-sectional view of a semiconductor structure provided in one embodiment with an overlay accuracy of αnm;

[0053] Figure 7 This is a schematic cross-sectional view of a semiconductor structure provided in one embodiment with an overlay accuracy of βnm;

[0054] Figure 8 This is a data regression diagram of a second correlation function provided in one embodiment;

[0055] Figure 9 This is a data regression diagram of a second correlation function provided in one embodiment;

[0056] Figure 10 This is a schematic diagram of the structure of a system for establishing an optical critical size database provided in one embodiment;

[0057] Figure 11 This is a schematic diagram of the structure of another optical critical size database establishment system provided in one embodiment;

[0058] Figure 12 This is a schematic diagram of the structure of another optical critical size database establishment system provided in one embodiment;

[0059] Figure 13 This is a flowchart illustrating an optical critical dimension measurement method provided in one embodiment;

[0060] Figure 14 This is a flowchart illustrating another optical critical dimension measurement method provided in one embodiment;

[0061] Figure 15 This is a schematic diagram of the structure of an optical critical dimension measurement system provided in one embodiment;

[0062] Figure 16 This is a schematic diagram of another optical critical dimension measurement system provided in one embodiment.

[0063] Explanation of reference numerals in the attached figures:

[0064] 1-Reference wafer, 2-Overlay accuracy measurement device, 3-Optical critical dimension measurement device, 4-Transmission electron microscope device, 5-Measurement calibration device; PU-Processor, M-Memory;

[0065] 10 - First test group, 20 - Second test group, 30 - Third test group;

[0066] 101 - First test unit, 102 - Second test unit, 103 - Third test unit, 104 - Fourth test unit, 105 - Fifth test unit;

[0067] 11-Substrate, 12-Shallow trench isolation structure, 13-Wall structure, G1-First trench, G2-Second trench. Detailed Implementation

[0068] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0069] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0070] It should be understood that when a component or layer is referred to as being "on," "adjacent to," "connected to," or "coupled to" other components or layers, it may be directly on, adjacent to, connected to, or coupled to other components or layers, or there may be intervening components or layers. Conversely, when a component is referred to as being "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other components or layers, there are no intervening components or layers.

[0071] It should be understood that although the terms first, second, etc., may be used to describe various elements, components, regions, layers, doping types, and / or portions, these elements, components, regions, layers, doping types, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, doping type, or portion from another element, component, region, layer, doping type, or portion. Therefore, without departing from the teachings of this invention, the first element, component, region, layer, doping type, or portion discussed below may be referred to as the second element, component, region, layer, or portion.

[0072] Spatial relation terms such as “below,” “under,” “below,” “under,” “above,” “above,” etc., are used herein to describe the relationship between one element or feature shown in the figure and other elements or features. It should be understood that, in addition to the orientation shown in the figure, spatial relation terms also include different orientations of the device in use and operation. For example, if the device in the figure is flipped, the element or feature described as “below,” “under,” or “below” will be oriented “above” the other element or feature. Therefore, the exemplary terms “below” and “under” can include both above and below orientations. Furthermore, the device may also include other orientations (e.g., rotated 90 degrees or other orientations), and the spatial descriptive terms used herein will be interpreted accordingly.

[0073] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, in this specification, the term “and / or” includes any and all combinations of the associated listed items.

[0074] Embodiments of the invention are described herein with reference to cross-sectional views that serve as schematic diagrams of ideal embodiments (and intermediate structures), thus allowing for the anticipation of variations in the illustrated shapes due to, for example, manufacturing techniques and / or tolerances. Therefore, embodiments of the invention should not be limited to the specific shapes of the regions shown herein, but rather include shape deviations due to, for example, manufacturing techniques. Consequently, the regions shown in the figures are substantially schematic, and their shapes do not represent the actual shapes of regions of the device, nor do they limit the scope of the invention.

[0075] In conventional CD measurement methods (such as CDSEM and OCD), the measurement principle based on OCD makes it difficult to qualitatively or quantitatively analyze the stacking situation between different layers in a device stack structure, which can easily affect the evaluation of OCD measurement data. Therefore, how to improve the accuracy of device CD measurement evaluation in device stack structures has become an urgent problem to be solved in related technologies.

[0076] Based on this, please refer to Figure 1 This disclosure provides a critical dimension measurement and evaluation method in some embodiments, including the following steps.

[0077] The S100 provides a reference wafer with reference test cells.

[0078] S200, obtain the overlay accuracy of the reference target pattern in the reference test unit; the reference target pattern includes the wall structure and the first and second grooves located on both sides of the wall structure.

[0079] S300 performs optical critical dimension measurement on the reference target pattern to obtain the measurement critical dimensions of the first and second grooves.

[0080] S400, determine the first correlation function based on the overlay accuracy and the critical measurement dimension. The first correlation function is used to characterize the correspondence between the overlay accuracy and the critical measurement dimension.

[0081] S500 determines the optical critical size database based on the first correlation function.

[0082] In this embodiment, a reference target pattern is formed on a reference wafer, and the reference target pattern is set as a wall structure and a first trench and a second trench located on both sides of the wall structure. A first correlation function is determined by obtaining the overlay accuracy of the reference target pattern and the measurement critical dimensions of the first and second trenches obtained after optical critical dimension measurement of the reference target pattern. This first correlation function accurately characterizes the correspondence between overlay accuracy and measurement critical dimensions. Thus, the optical critical dimension database determined by the aforementioned first correlation function can effectively reflect the influence of overlay accuracy deviation on optical critical dimension measurement, facilitating quantitative or qualitative analysis of the impact of overlay accuracy deviation on optical critical dimension measurement. This effectively leverages the role of the optical critical dimension database in optical critical dimension measurement and evaluation, enabling the measurement and evaluation of critical dimensions of semiconductor structures based on the optical critical dimension measurement database and improving the accuracy of optical critical dimension measurement and evaluation.

[0083] In other embodiments, please refer to Figure 2 The present disclosure provides a method for establishing an optical critical size database in some embodiments, including steps S100 to S700'. Among them, steps S100 to S400 are the same as in the previous embodiments, and will not be described in detail here.

[0084] S500' performs slice transmission electron microscopy measurements on the reference target pattern to obtain the reference critical dimensions of the first and second grooves.

[0085] S600', a second correlation function is determined based on the measurement critical dimension and the reference critical dimension. The second correlation function is used to characterize the correspondence between the measurement critical dimension and the reference critical dimension corresponding to the same set of engraving accuracy.

[0086] S700', together with the first correlation function and the second correlation function, determines the optical critical size database.

[0087] In this embodiment, based on the foregoing embodiments, the reference critical dimensions of the first and second trenches are obtained by performing cross-sectional transmission electron microscopy (TEM) measurements on the reference target pattern. Furthermore, a second correlation function is determined based on the measured critical dimensions and the reference critical dimensions. This second correlation function accurately characterizes the correspondence between the measured critical dimensions and the reference critical dimensions for the same overlay precision. Thus, the optical critical dimension database determined by the aforementioned first and second correlation functions not only effectively reflects the correlation between overlay precision, measured critical dimensions, and reference critical dimensions, but also allows for auxiliary verification of the measured critical dimensions using the reference critical dimensions obtained from cross-sectional TEM measurements. This effectively improves the accuracy of the optical critical dimension database, enabling the measurement and evaluation of critical dimensions in semiconductor structures based on the optical critical dimension measurement database, and further enhancing the accuracy of optical critical dimension measurement and evaluation.

[0088] It is understood that the overlay accuracy (OVL) mentioned above refers to the alignment accuracy of the current thin film pattern relative to the previous thin film pattern between two consecutive photolithography processes. For device stacking structures, the overlay accuracy can be determined by detecting the offset between corresponding overlay marks of adjacent thin films, for example, through optical inspection.

[0089] Optical Critical Dimension (OCD), as an optical measurement method, can measure critical dimensions such as the thickness of single or multiple thin films, groove depth, and even angles in semiconductor structures. Measuring the critical dimensions of a semiconductor structure using OCD involves collecting the reflectance spectral characteristics of the target semiconductor structure and comparing these characteristics with those in an optical critical dimension measurement database to obtain the data with the highest spectral fit, which is then used as the measurement data for the target. Therefore, the accuracy of OCD measurement and evaluation of the critical dimensions of semiconductor structures depends on the accuracy of the established optical critical dimension database.

[0090] In addition, the target pattern that can be measured by optical critical dimension measurement (OCD) can be an array of lines or grooves.

[0091] In some embodiments, the first correlation function determined based on the overlay accuracy and the measurement critical size includes a first linear function; the first linear function has the overlay accuracy as the independent variable and the measurement critical size as the dependent variable. However, it is not limited to this; any other function that can be used to characterize the correspondence between the overlay accuracy and the measurement critical size can also be used as the first correlation function.

[0092] In some embodiments, the second correlation function determined based on the measured critical size and the reference critical size includes a second linear function; the second linear function uses the measured critical size corresponding to the same set of calibration precision as the independent variable and the reference critical size as the dependent variable. However, it is not limited to this; any other function that can be used to characterize the correspondence between the measured critical size and the reference critical size corresponding to the same set of calibration precision can also be used as the second correlation function.

[0093] In some embodiments, please combine Figure 3 and Figure 4 It is understood that multiple reference test cells are required to determine the optical critical size database. Furthermore, multiple reference test cells can be fabricated on the same reference wafer to facilitate measurement.

[0094] For example, one or more sets of benchmark test units can be set on the same reference wafer; wherein, the reference target patterns of each benchmark test unit in any set of benchmark test units are the same, and the overlay accuracy of the reference target patterns of different benchmark test units in any set of benchmark test units is different.

[0095] For example, the number of benchmark test units in a set of benchmark test units is an odd number greater than 1, and the multiple benchmark test units include: a reference test unit with zero overlay accuracy, and multiple first series test units and multiple second series test units located on the side of the reference test unit with the reference test unit as the center; wherein, the overlay accuracy of the multiple first series test units increases negatively in sequence; and the overlay accuracy of the multiple second series test units increases positively in sequence.

[0096] Furthermore, optionally, the overlay accuracy difference between adjacent first-series test units is the same as the overlay accuracy difference between adjacent second-series test units. That is, the overlay accuracy of multiple first-series test units increases negatively at equal intervals; the overlay accuracy of multiple second-series test units increases positively at equal intervals.

[0097] Furthermore, optionally, the plurality of first series test units and the plurality of second series test units may be located on both sides of the reference test unit, and the overlay accuracy of the plurality of first series test units increases negatively in the direction away from the reference test unit; the overlay accuracy of the plurality of second series test units increases positively in the direction away from the reference test unit.

[0098] In one possible implementation, such as Figure 3As shown, taking a reference wafer 1 as an example, a set of reference test units is provided, and the set of reference test units includes 5 test units (but is not limited to this). The set of reference test units includes: a first test unit 101, a second test unit 102, a third test unit 103, a fourth test unit 104, and a fifth test unit 105; wherein, the first test unit 101 is the aforementioned reference test unit, and the overlay accuracy OVL of the first test unit 101 can be, for example, 0 nm; the second test unit 102 and the fourth test unit 104 are the aforementioned first series of test units, and the overlay accuracy OVL of the second test unit 102 can be, for example, -2 nm, and the overlay accuracy OVL of the fourth test unit 104 can be, for example, -4 nm; the third test unit 103 and the fifth test unit 105 are the aforementioned second series of test units, and the overlay accuracy OVL of the third test unit 103 can be, for example, 2 nm, and the overlay accuracy OVL of the fifth test unit 105 can be, for example, 4 nm.

[0099] In another possible implementation, such as Figure 4 As shown, the reference wafer 1 may be provided with multiple sets of reference test units, such as a first test group 10, a second test group 20, and a third test group 30; wherein, different test groups can be used to measure different reference target patterns. In this embodiment, only the structure and arrangement of each reference test unit in the first test group 10 are illustrated. The structure and arrangement of the reference test units in the second test group 20, the third test group 30, or more test groups can be selected and set according to actual needs.

[0100] exist Figure 4In the first test group 10 shown, the first test unit 101 is the aforementioned reference test unit, and the overlay accuracy (OVL) of the first test unit 101 can be, for example, 0 nm. The second test unit 102 and the fourth test unit 104 are the aforementioned first series of test units, and the third test unit 103 and the fifth test unit 105 are the aforementioned second series of test units. Multiple first series test units and multiple second series test units are located on both sides of the first test unit 101. For example, the second test unit 102 and the fourth test unit 104 are arranged sequentially on the left side of the first test unit 101 in a direction away from the reference test unit (i.e., the first test unit 101), and the third test unit 103 and the fifth test unit 105 are arranged sequentially on the right side of the first test unit 101 in a direction away from the reference test unit (i.e., the first test unit 101). The overlay accuracy (OVL) of the second test unit 102 can be, for example, -2 nm; the overlay accuracy (OVL) of the fourth test unit 104 can be, for example, -4 nm; the overlay accuracy (OVL) of the third test unit 103 can be, for example, 2 nm; and the overlay accuracy (OVL) of the fifth test unit 105 can be, for example, 4 nm. This facilitates the measurement and evaluation of the overlay accuracy, measurement critical size, and regularity of the reference critical size of each reference test unit.

[0101] It is understood that an array of wall structures and / or trenches can be set up in any benchmark testing unit as a benchmark target pattern. Thus, when performing optical critical dimension measurement on the benchmark target pattern, any single wall structure and / or trench can be measured, or multiple wall structures and / or multiple trenches can be measured. The benchmark target pattern in this embodiment can be selected and determined according to measurement requirements.

[0102] For example, please refer to Figures 5-7 The reference target pattern includes a wall structure 13 and a first groove G1 and a second groove G2 located on both sides of the wall structure 13. Furthermore, in a reference test unit with an overlay accuracy OVL of 0 nm, the first groove G1 and the second groove G2 are arranged in parallel and spaced apart, and the first groove G1 and the second groove G2 are symmetrical about the geometric center of the interval between them (or the wall structure 13) as the center of symmetry.

[0103] Accordingly, in some embodiments, step S300, which involves performing optical critical size measurement on the reference target pattern to obtain the measurement critical sizes of the first groove and the second groove, further includes: performing optical critical size measurement on multiple different target regions of the first groove GA and the second groove G2 respectively, to obtain a set of measurement critical sizes for the first groove G1 and the second groove G2. Correspondingly, step S400, which involves determining the first correlation function based on the overlay accuracy and the measurement critical sizes, further includes: determining the first correlation function based on the overlay accuracy and the set of measurement critical sizes.

[0104] Here, the multiple different target regions of the first trench G1 can be, for example, the geometric center region, the middle region, and the edge region of the first trench G1. Similarly, the multiple different target regions of the second trench G2 can be, for example, the geometric center region, the middle region, and the edge region of the second trench G2. In this way, it is beneficial to increase the number of data samples corresponding to the first correlation function, thereby improving the accuracy of the first correlation function.

[0105] Based on this, in some possible implementations, step S500' involves performing slice transmission electron microscopy (TEM) measurements on the reference target pattern to obtain the reference critical dimensions of the first and second trenches. This includes performing TEM measurements on multiple different target regions of the first and second trenches to obtain a set of reference critical dimensions for the first and second trenches. Correspondingly, step S600', which determines the second correlation function based on the measured critical dimensions and the reference critical dimensions, further includes determining the second correlation function based on the set of measured critical dimensions and the set of reference critical dimensions.

[0106] It should be added that, during the slicing transmission electron microscopy (TEM) measurement process, the target areas for slicing in the first and second trenches correspond to the same target areas for measuring optical critical dimensions. Thus, the critical dimensions of the same target area can be accurately and effectively verified based on the reference critical dimensions measured by TEM. Furthermore, in this embodiment, the second correlation function determined based on the aforementioned reference critical dimensions can also effectively assess the inconsistencies in the corresponding critical dimensions of the first and second trenches caused by overlay accuracy, thereby further improving the accuracy of critical dimension measurement and evaluation in device stacking structures.

[0107] To more clearly illustrate the method for establishing the optical critical size database in some of the above embodiments, the following embodiments exemplarily provide a reference wafer on which a semiconductor structure is formed as a reference test unit, and the optical critical size database is established based on the reference target pattern in the reference test unit.

[0108] In some embodiments, please refer to Figures 5-7The semiconductor structure includes a substrate 11, a trench isolation structure 12, and a wall structure 13. The trench isolation structure 12 is formed within the substrate 11, dividing the substrate 11 into multiple active regions. Multiple wall structures 13 are arranged in parallel and spaced apart. The wall structures 13 are, for example, bit line structures, and can contact and connect with the active regions of the substrate 11. When forming the multiple wall structures 13, the fabrication of the trench isolation structure 12 (i.e., the active regions) is the preceding layer structure, and the formation of the wall structures 13 is affected by the overlay accuracy. Accordingly, the spacing between adjacent wall structures 13 is directly related to the formation of the wall structures 13. Furthermore, when forming the spacing between adjacent wall structures 13, the back etching of the substrate 11 and the trench isolation structure 12 can simultaneously form a first trench G1 and a second trench G2 on both sides of the wall structure 13, so that the first trench G1 and the second trench G2 serve as contact trenches for fabricating the contact structure. Thus, the optical critical dimensions of the first groove G1 and the second groove G2 are easily affected by the overlay accuracy of the wall structure 13. For example, the overlay accuracy of the wall structure 13 may cause unequal depths of the first groove G1 and the second groove G2 located on both sides of it.

[0109] For example, such as Figure 5 As shown, the overlay accuracy OVL of the wall structure 13 is 0 nm; that is, the formation of the wall structure 13 has no offset relative to the baseline. Thus, when the overlay accuracy OVL of the wall structure 13 is 0 nm, the depths of the first groove G1 and the second groove G2 formed on the left and right sides of the wall structure 13 are theoretically the same, i.e., X1 = X2 = X0, where X1 is the depth of the first groove G1, X2 is the depth of the second groove G2, and X0 is the average of X1 and X2. Furthermore, by performing OCD measurements on the first groove G1 and the second groove G2, the critical measurement dimensions X of the depths of the first groove G1 and the second groove G2 can be obtained respectively. 1a and X 2b And X 1a and X 2b They are equal or approximately equal. Then, by performing transmission electron microscopy measurements on sections of the first groove G1 and the second groove G2, the reference critical dimensions X of the depths of the first groove G1 and the second groove G2 can be obtained, respectively. 1A and X 2B And X 1A and X 2B Equal or approximately equal.

[0110] For example, such as Figure 6As shown, the overlay accuracy OVL of the wall structure 13 is αnm; that is, the formation of the wall structure 13 is offset by αnm relative to the baseline, for example, offset to the right by αnm. Thus, when the overlay accuracy OVL of the wall structure 13 is αnm, the depths of the first groove G1 and the second groove G2 formed on the left and right sides of the wall structure 13 are unequal. For example, the depth X3 of the first groove G1 is greater than the depth X1 it should form when the overlay accuracy OVL = 0nm, and the depth X4 of the second groove G2 is less than the depth X2 it should form when the overlay accuracy OVL = 0nm, and (X3 + X4) / 2 = X0. Furthermore, by performing OCD measurements on the first groove G1 and the second groove G2, the critical measurement dimensions X of the depths of the first groove G1 and the second groove G2 can be obtained respectively. 3a and X 4b For example, X 3a >X 1a X 4b <X 2b By performing transmission electron microscopy measurements on sections of the first trench G1 and the second trench G2, the reference critical dimension X of the depth of the first trench G1 and the second trench G2 can be obtained, respectively. 3A and X 3B For example, X 3A >X 1A X 4B <X 2B .

[0111] For example, such as Figure 7 As shown, the overlay accuracy OVL of the wall structure 13 is βnm, where β > α; that is, the formation of the wall structure 13 has an offset of βnm relative to the baseline, for example, an offset of βnm to the right. Thus, when the overlay accuracy OVL of the wall structure 13 is βnm, the depths of the first groove G1 and the second groove G2 formed on the left and right sides of the wall structure 13 are unequal. For example, the depth X5 of the first groove G1 is greater than the depth X3 it should form when the overlay accuracy OVL = αnm, and the depth X6 of the second groove G2 is less than the depth X4 it should form when the overlay accuracy OVL = αnm, and (X5 + X6) / 2 = X0. Furthermore, by performing OCD measurements on the first groove G1 and the second groove G2, the critical measurement dimensions X of the depths of the first groove G1 and the second groove G2 can be obtained respectively. 5a and X 6b For example, X 5a >X 3a X 6b <X 4b By performing transmission electron microscopy measurements on sections of the first trench G1 and the second trench G2, the reference critical dimension X of the depth of the first trench G1 and the second trench G2 can be obtained, respectively. 5A and X6B For example, X 5A >X 3A X 6B <X 4B .

[0112] Based on the above, according to the critical measurement dimensions and reference critical dimensions of the depths of the first groove G1 and the second groove G2 under different overlay accuracies, the correspondence between overlay accuracy and the critical measurement dimensions (i.e., the first correlation function) and the correspondence between the critical measurement dimensions and the reference critical dimensions under the same overlay accuracy (i.e., the second correlation function) can be accurately determined. Furthermore, in this embodiment, by combining the aforementioned critical measurement dimensions and reference critical dimensions, it is also possible to effectively evaluate whether the depths of the first groove G1 and the second groove G2 are equal. For example, when the depths of the first groove G1 and the second groove G2 are not equal, the correspondence between the difference between them and the overlay accuracy OVL can be clarified.

[0113] Here, when the overlay accuracy β is greater than the overlay accuracy α, the difference between the depth X5 of the first trench G1 and the depth X6 of the second trench G2 when the overlay accuracy OVL = β nm is greater than the difference between the depth X3 of the first trench G1 and the depth X4 of the second trench G2 when the overlay accuracy OVL = α nm.

[0114] In step S100, considering the dimensional variations of the first trench G1 and the second trench G2 in the aforementioned semiconductor structure under different overlay dimensional accuracy (OVL), a reference test unit can be formed on the reference wafer 1, such as... Figure 3 or Figure 4 As shown in the figure. That is, multiple benchmark test units are set as a group of benchmark test units based on the same benchmark target pattern, for example, five or more benchmark test units are set as a group of benchmark test units; wherein, the overlay accuracy of the benchmark target pattern of different benchmark test units in any group of benchmark test units is different.

[0115] In step S200, the overlay accuracy of the reference target pattern in the reference test unit is obtained. For example, the first test unit 101 is a reference test unit, and the overlay accuracy (OVL) of the first test unit 101 is 0 nm. The second test unit 102 and the fourth test unit 104 are a first series of test units, with the overlay accuracy (OVL) of the second test unit 102 being -2 nm and the overlay accuracy (OVL) of the fourth test unit 104 being -4 nm. The third test unit 103 and the fifth test unit 105 are a second series of test units, with the overlay accuracy (OVL) of the third test unit 103 being 2 nm and the overlay accuracy (OVL) of the fifth test unit 105 being 4 nm.

[0116] In step S300, OCD measurements are performed on the reference target patterns in the reference test unit one by one to obtain the measurement critical dimensions of the first trench G1 and the second trench G2 respectively. Taking the measurement critical dimensions of the first trench G1 and the second trench G2 as the measurement critical dimensions of their depths as an example, OCD measurements are performed on multiple different target regions of the first trench G1 and the second trench G2 in the same reference target pattern to obtain multiple measurement critical dimensions of the depths of the first trench G1 and the second trench G2, forming a set of measurement critical dimensions.

[0117] Here, the first trench G1 and the second trench G2 can have multiple different target regions, such as their geometric center region, middle region and edge region.

[0118] In step S500', slice transmission electron microscopy (TEM) measurements are performed on the reference target patterns in the reference test unit one by one to obtain the reference critical dimensions of the first trench G1 and the second trench G2 respectively. Taking the reference critical dimensions of the first trench G1 and the second trench G2 as the reference critical dimensions of their depths as an example, slice TEM measurements are performed on multiple different target regions of the first trench G1 and the second trench G2 in the same reference target pattern to obtain multiple reference critical dimensions of the depths of the first trench G1 and the second trench G2, forming a set of reference critical dimensions.

[0119] Here, during the slice TEM measurement process, the first groove G1 and the second groove G2 are used for the target area of ​​the slice, which corresponds to the same target area used for optical critical size measurement.

[0120] by Figure 4 Taking the first test group 10 in the reference wafer as an example, Table 1 shows multiple sets of measurement data after performing corresponding measurements on each reference test unit in steps S200, S300, and S500'. Wherein, OVL is the overlay accuracy of the corresponding reference test unit, A(TEM) is the reference critical dimension of the depth of the first trench G1 measured by TEM, B(TEM) is the reference critical dimension of the depth of the second trench G2 measured by TEM, a(OCD) is the measurement critical dimension of the depth of the first trench G1 measured by OCD, and b(OCD) is the measurement critical dimension of the depth of the second trench G2 measured by OCD.

[0121] Table 1

[0122]

[0123]

[0124] In step S400, a first correlation function is determined based on the overlay accuracy and the critical measurement dimension. The first correlation function is used to characterize the correspondence between the overlay accuracy and the critical measurement dimension.

[0125] Optionally, the first correlation function includes a first linear function; the first linear function takes the overlay accuracy as the independent variable and the measurement critical dimension as the dependent variable.

[0126] Here, based on the data shown in Table 1, we can determine a = f1(OVL) and b = f2(OVL) as the first linear function through data regression.

[0127] In step S600', a second correlation function is determined based on the measurement critical size and the reference critical size. The second correlation function is used to characterize the correspondence between the measurement critical size and the reference critical size corresponding to the same set of engraving accuracy.

[0128] Optionally, the second correlation function includes a second linear function; the second linear function takes the measurement critical size corresponding to the same set of engraving accuracy as the independent variable and the reference critical size as the dependent variable.

[0129] Please refer to Table 1 for more information. Figure 8 and Figure 9 Taking A(TEM) and B(TEM) as the reference critical dimensions for TEM measurement as an example, we can determine A = k1a + c1 and B = k2b + c2 as the second linear function through data regression, where c1 and c2 are constants.

[0130] Therefore, in step S700, an optical critical size measurement database can be established based on the first correlation function and the second correlation function.

[0131] It is understood that, in the embodiments of this disclosure, unless explicitly stated herein, the execution order of the steps in the method is not strictly limited. These steps may not necessarily be executed in the described order, but may be executed in other ways. Moreover, at least a portion of any step may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but may be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but may be executed alternately or in turn with other steps or at least a portion of the sub-steps or stages of other steps.

[0132] Please see Figure 10This disclosure also provides a system for establishing an optical critical dimension database, used to establish the optical critical dimension database described in the above embodiments. The system includes: a reference wafer 1, an overlay accuracy measurement device 2, an optical critical dimension measurement device 3, and a processor PU. The reference wafer 1 has a reference testing unit. The overlay accuracy measurement device 2 is used to obtain the overlay accuracy of a reference target pattern in the reference testing unit; the reference target pattern includes a wall structure and a first groove and a second groove located on both sides of the wall structure. The optical critical dimension measurement device 3 is used to perform optical critical dimension measurement on the reference target pattern to obtain the measurement critical dimensions of the first groove and the second groove. The processor PU is connected to the overlay accuracy measurement device 2 and the optical critical dimension measurement device 3, and is configured to: determine a first correlation function based on the overlay accuracy and the measurement critical dimension, and determine the optical critical dimension database based on the first correlation function; wherein, the first correlation function is used to characterize the correspondence between the overlay accuracy and the measurement critical dimension.

[0133] The technical advantages of the aforementioned method for establishing the optical critical size database in this embodiment are also present in this system, and will not be elaborated here.

[0134] Furthermore, the structure of the aforementioned reference wafer 1 can be found in the relevant description in the foregoing embodiments.

[0135] For example, the number of reference test cells on reference wafer 1 is multiple; among them, the overlay accuracy of the reference target pattern in different reference test cells is different.

[0136] For example, one or more sets of reference test units can be set on the same reference wafer 1; wherein, the reference target patterns of each reference test unit in any set of reference test units are the same, and the overlay accuracy of the reference target patterns of different reference test units in any set of reference test units is different.

[0137] For example, the number of reference test cells on reference wafer 1 is an odd number greater than 1; the multiple reference test cells include: a reference test cell with zero overlay accuracy, and multiple first series test cells and multiple second series test cells located on the side of the reference test cell; wherein, the overlay accuracy of the multiple first series test cells increases negatively in sequence; and the overlay accuracy of the multiple second series test cells increases positively in sequence.

[0138] Furthermore, optionally, the overlay accuracy difference between adjacent first-series test units is the same as the overlay accuracy difference between adjacent second-series test units. That is, the overlay accuracy of multiple first-series test units increases negatively at equal intervals; the overlay accuracy of multiple second-series test units increases positively at equal intervals.

[0139] Furthermore, optionally, the plurality of first series test units and the plurality of second series test units may be located on both sides of the reference test unit, and the overlay accuracy of the plurality of first series test units increases negatively in the direction away from the reference test unit; the overlay accuracy of the plurality of second series test units increases positively in the direction away from the reference test unit.

[0140] Furthermore, optionally, the orthographic projection area of ​​the benchmark testing unit on the reference wafer 1 is larger than the spot area of ​​the optical critical size measurement device 3. For example, the orthographic projection area of ​​the benchmark testing unit on the reference wafer 1 can be 50um × 60um.

[0141] In some embodiments, please refer to Figure 11 The system for establishing the optical critical size database also includes a transmission electron microscope (TEM) device 4. The TEM device 4 is used to perform TEM measurements on a reference target pattern to obtain the reference critical sizes of the first and second grooves. The processor PU is also connected to the TEM device 4 and is configured to: determine a second correlation function based on the overlay accuracy, the measured critical size, and the reference critical size; and jointly determine the optical critical size database based on the first and second correlation functions; wherein the second correlation function characterizes the correspondence between the measured critical size and the reference critical size corresponding to the same overlay accuracy.

[0142] The present invention does not limit the structure of the overlay accuracy measuring device 2, the optical critical size measuring device 3, and the transmission electron microscope device 4, but only to the extent that they can achieve the corresponding measurement functions and have better measurement results.

[0143] In some embodiments, please refer to Figure 12 The system for establishing the optical critical size database also includes a measurement correction device 5. The measurement correction device 5 is connected to the processor PU and is used to correct the optical critical size measuring device 3 according to a second correlation function, so that the measured critical size corresponding to the same reference target pattern is close to the corresponding reference critical size. Thus, the measurement correction device 5 can also be used to correct the optical critical size measuring device 3 according to the aforementioned second correlation function to improve the measurement accuracy of the optical critical size measuring device 3.

[0144] Here, the structure of the measurement correction device 5 can be matched with the optical critical size measurement device 3. After obtaining the second correlation function, the optical critical size measurement device 3 can be corrected according to the correspondence between the measurement critical size and the reference critical size corresponding to the same reference target pattern, such as the difference between the two, to ensure that the measurement critical size is as close as possible to the reference critical size, thereby ensuring that the optical critical size measurement device 3 used for subsequent optical critical size measurement has higher measurement accuracy.

[0145] Based on the above embodiments, please refer to Figure 13 This disclosure provides a method for measuring optical critical dimensions, comprising the following steps, through some embodiments.

[0146] S10 provides a wafer to be tested, which has test units on it.

[0147] S20, obtain the overlay accuracy of the target graphic in the test unit.

[0148] S30. Based on the overlay accuracy of the target graphic and the optical critical size database, determine the critical size of the target graphic to be measured.

[0149] Here, the optical critical size database is obtained using the methods described in some of the above embodiments, which can achieve high accuracy. After knowing the overlay accuracy of the target pattern in the test unit, the critical size of the target pattern can be predetermined based on the optical critical size database.

[0150] For example, the optical critical size database is determined based on a first correlation function. Correspondingly, the critical size to be measured of the target image is determined based on the first correlation function in the optical critical size database.

[0151] For example, the optical critical size database is determined jointly by a first correlation function and a second correlation function. Correspondingly, the critical size to be measured of the target image is determined jointly by the first correlation function and the second correlation function in the optical critical size database.

[0152] Please see Figure 14 In some embodiments, the optical critical dimension measurement method further includes the following steps.

[0153] S40, perform optical critical dimension measurement on the target image to obtain the measured critical dimension of the target image.

[0154] S50, determine the difference between the measured critical dimension and the critical dimension to be measured.

[0155] S60, when the difference is greater than the target threshold, send a warning message or trigger a shutdown command.

[0156] Here, the target threshold can be set to match the product manufacturing process on the wafer under test.

[0157] Optionally, warning messages can be sent to engineers and relevant personnel so that they can analyze the cause of the difference between the measured critical dimension and the critical dimension to be measured in a timely manner, and adjust the corresponding product's process accordingly to improve production yield and efficiency. Alternatively, a stop command can be directly triggered to stop subsequent products from undergoing processes related to forming that dimensional morphology, thereby reducing unnecessary production losses.

[0158] In this embodiment of the disclosure, the role of the optical critical size database in optical critical size measurement and evaluation can be effectively utilized. The critical size measurement and evaluation of semiconductor structures can be performed based on the optical critical size measurement database, and the accuracy of optical critical size measurement and evaluation can be effectively improved. This is beneficial to improving product production yield and production efficiency, as well as avoiding unnecessary production losses.

[0159] Please see Figure 15 This disclosure also provides an optical critical dimension measurement system in some embodiments, including: an overlay accuracy measurement device 2, a memory M, and a processor PU. The overlay accuracy measurement device 2 is used to acquire the overlay accuracy of the target pattern in the test cell on the wafer under test. The memory M stores an optical critical dimension database established as described in any of the preceding embodiments. The processor PU is connected to the memory M and the overlay accuracy measurement device 2; the processor PU is configured to determine the critical dimension of the target pattern under test based on the overlay accuracy of the target pattern and the optical critical dimension database.

[0160] It is understood that the overlay accuracy measuring device 2 in the optical critical dimension measurement system and the overlay accuracy measuring device 2 in the aforementioned optical critical dimension database establishment system can be the same overlay accuracy measuring device. Furthermore, the processor PU in the optical critical dimension measurement system and the processor PU in the aforementioned optical critical dimension database establishment system can also be the same processor PU. However, this is not limited to this; for example, the processor PU in the optical critical dimension measurement system and the processor PU in the aforementioned optical critical dimension database establishment system can also be different processors.

[0161] Optionally, the memory M includes at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), flash memory, optical memory, magnetic random access memory (MRAM), or ferroelectric random access memory (FRAM), etc. Volatile memory may include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc.

[0162] Optionally, the processor PU may include, but is not limited to, a general-purpose processor, a central processing unit, a digital signal processor, a programmable logic device, or a data processing logic device.

[0163] Please see Figure 16 In some embodiments, the optical critical dimension measurement system further includes an optical critical dimension measuring device 3. The optical critical dimension measuring device 3 is used to measure the optical critical dimension of the target graphic to obtain the measured critical dimension of the target graphic; wherein, the processor PU is also connected to the optical critical dimension measuring device 3 and is configured to determine the difference between the measured critical dimension and the critical dimension to be measured.

[0164] It can be understood that the optical critical dimension measuring device 3 in the optical critical dimension measurement system and the optical critical dimension measuring device 3 in the aforementioned optical critical dimension database establishment system can be the same precision measuring device.

[0165] Optionally, the optical critical size measuring device 3 can be the optical critical size measuring device 3 calibrated by the measurement calibration device 5 in the aforementioned optical critical size database establishment system.

[0166] Optionally, in conjunction with the aforementioned optical critical dimension measurement method, the processor (PU) can also send a warning message or a shutdown command when the difference between the measured critical dimension and the critical dimension to be measured exceeds a target threshold. For example, the warning message can be sent to engineers and relevant personnel so they can analyze the cause of the difference and adjust the corresponding product's manufacturing process accordingly, thereby improving production yield and efficiency. Alternatively, the shutdown command can be sent to the production equipment to directly stop subsequent products from undergoing processes related to forming that dimensional morphology, reducing unnecessary production losses.

[0167] In this embodiment of the disclosure, the optical critical dimension measurement system can effectively leverage the role of the optical critical dimension database in optical critical dimension measurement and evaluation. It can perform critical dimension measurement and evaluation of semiconductor structures based on the optical critical dimension measurement database, and effectively improve the accuracy of optical critical dimension measurement and evaluation. This is beneficial to improving product production yield and efficiency, as well as avoiding unnecessary production losses.

[0168] In the description of this specification, references to terms such as "some embodiments," "other embodiments," and "ideal embodiments" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0169] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features of the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0170] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for establishing an optical critical size database, characterized in that, include: A reference wafer is provided, the reference wafer having reference test units, the number of reference test units being an odd number greater than 1; The plurality of reference test units include: a reference test unit with zero overlay accuracy, and a plurality of first series test units and a plurality of second series test units located centered on the reference test unit and respectively on the sides of the reference test unit; wherein, the overlay accuracy of the plurality of first series test units increases negatively in sequence; and the overlay accuracy of the plurality of second series test units increases positively in sequence. The overlay accuracy of the reference target pattern in the reference test unit is obtained; the reference target pattern includes a wall structure and a first groove and a second groove located on both sides of the wall structure; Optical critical dimension measurement is performed on the reference target pattern to obtain the measurement critical dimensions of the first groove and the second groove; A first correlation function is determined based on the overlay accuracy and the measurement critical size, and the first correlation function is used to characterize the correspondence between the overlay accuracy and the measurement critical size; The reference target pattern is sliced ​​and measured by transmission electron microscopy to obtain the reference critical dimensions of the first groove and the second groove; A second correlation function is determined based on the measured critical dimension and the reference critical dimension. The second correlation function is used to characterize the correspondence between the measured critical dimension and the reference critical dimension corresponding to the same overlay accuracy. The optical critical size database is determined jointly based on the first correlation function and the second correlation function.

2. The method for establishing an optical critical size database according to claim 1, characterized in that, The overlay accuracy difference between adjacent first series test units is the same as the overlay accuracy difference between adjacent second series test units.

3. The method for establishing an optical critical size database according to claim 1, characterized in that, The step of performing optical critical size measurement on the reference target pattern to obtain the measurement critical size of the first groove and the second groove further includes: performing optical critical size measurement on multiple different target regions of the first groove and the second groove respectively to obtain a set of measurement critical sizes consisting of multiple measurement critical sizes of the first groove and the second groove; The step of determining the first correlation function based on the overlay accuracy and the measurement critical size further includes: determining the first correlation function based on the overlay accuracy and the measurement critical size set.

4. The method for establishing an optical critical size database according to claim 3, characterized in that, Also includes: Transmission electron microscopy (TEM) measurements were performed on multiple different target regions of the first trench and the second trench to obtain multiple reference critical dimensions of the first trench and the second trench, forming a reference critical dimension set. A second correlation function is determined based on the set of measurement critical dimensions and the set of reference critical dimensions. The second correlation function is used to characterize the correspondence between the measurement critical dimensions and the reference critical dimensions corresponding to the same overlay accuracy. The optical critical size database is determined jointly based on the first correlation function and the second correlation function.

5. The method for establishing an optical critical size database according to claim 4, characterized in that, The first correlation function includes a first linear function; the first linear function takes the overlay accuracy as the independent variable and the measurement critical size as the dependent variable.

6. The method for establishing an optical critical size database according to claim 4, characterized in that, The second correlation function includes a second linear function; the second linear function takes the measurement critical size corresponding to the same overlay accuracy as the independent variable, and the reference critical size as the dependent variable.

7. A system for establishing an optical critical size database, characterized in that, include: A reference wafer having reference test units, wherein the number of reference test units is an odd number greater than 1; The plurality of reference test units include: a reference test unit with zero overlay accuracy, and a plurality of first series test units and a plurality of second series test units located centered on the reference test unit and respectively on the sides of the reference test unit; wherein, the overlay accuracy of the plurality of first series test units increases negatively in sequence; and the overlay accuracy of the plurality of second series test units increases positively in sequence. An overlay accuracy measuring device is used to obtain the overlay accuracy of a reference target pattern in the reference test unit; the reference target pattern includes a wall structure and a first groove and a second groove located on both sides of the wall structure; An optical critical size measuring device is used to measure the optical critical size of the reference target pattern and obtain the measurement critical size of the first groove and the second groove; A transmission electron microscope (TEM) apparatus is used to perform cross-sectional TEM measurements on the reference target pattern to obtain the reference critical dimensions of the first groove and the second groove. The processor, connected to the overlay accuracy measuring device, the optical critical size measuring device, and the transmission electron microscope device, is configured to: determine a first correlation function based on the overlay accuracy and the measurement critical size; determine a second correlation function based on the overlay accuracy, the measurement critical size, and the reference critical size; and jointly determine an optical critical size database based on the first correlation function and the second correlation function. Wherein, the first correlation function is used to characterize the correspondence between the overlay accuracy and the measurement critical size, and the second correlation function is used to characterize the correspondence between the measurement critical size and the reference critical size corresponding to the same overlay accuracy.

8. The system for establishing an optical critical size database according to claim 7, characterized in that, Also includes: A measurement correction device, connected to the processor, is used to correct the optical critical size measurement device according to the second correlation function, so that the measurement critical size corresponding to the same reference target pattern is close to the corresponding reference critical size.

9. The system for establishing an optical critical size database according to claim 7, characterized in that, The overlay accuracy difference between adjacent first series test units is the same as the overlay accuracy difference between adjacent second series test units.

10. A method for measuring optical critical dimensions, characterized in that, include: A wafer to be tested is provided, wherein the wafer to be tested has test units; Obtain the overlay accuracy of the target graphic in the test unit under test; Based on the overlay accuracy of the target graphic to be tested and the optical critical dimension database established by the method for establishing the optical critical dimension database as described in any one of claims 1 to 6, the critical dimension to be tested of the target graphic to be tested is determined.

11. The optical critical dimension measurement method according to claim 10, characterized in that, Also includes: The optical critical size of the target image under test is measured to obtain the measured critical size of the target image under test; Determine the difference between the measured critical dimension and the critical dimension to be measured; When the difference exceeds the target threshold, a warning message is sent or a shutdown command is triggered.

12. An optical critical dimension measurement system, characterized in that, include: An overlay accuracy measuring device is used to obtain the overlay accuracy of the target pattern in the test unit on the wafer under test; The memory stores an optical critical size database established by the method for establishing an optical critical size database as described in any one of claims 1 to 6; A processor is connected to the memory and the overlay accuracy measuring device; the processor is configured to determine the critical dimension of the target graphic to be measured based on the overlay accuracy of the target graphic to be measured and the optical critical dimension database.

13. The optical critical dimension measurement system according to claim 12, characterized in that, Also includes: An optical critical size measuring device is used to measure the optical critical size of the target image under test and obtain the measured critical size of the target image under test. The processor is also connected to the optical critical size measuring device and is configured to determine the difference between the measured critical size and the critical size to be measured.

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