Method for measuring line width

Abstract

The present invention provides a line width measurement method. For a target graphic whose graphic contour does not match the characteristic graphic, the second measurement position is matched with the first measurement position for similarity, and for a graphic within the same matching standard range, the line width is measured using a matching second line width measurement method; for a target graphic that meets two or more matching standards at the same time, an abnormal point is generated and its position is recorded at the same time; for the abnormal point, each matching second line width measurement method is used to obtain the line width deviation in multiple different exposure units, and the second line width measurement method with the smallest sum of line width deviations is selected as the best first line width measurement method for the abnormal point. The present technology can save the tedious work of selecting different measurement methods for different graphics when establishing the measurement task in the early stage, greatly avoiding the selection error of the measurement method caused by the error in the prediction of the graphic shape; and improves the modeling efficiency to a certain extent.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and particularly to a method for measuring line width. Background Art

[0002] In the existing optical proximity correction (OPC) technology, an accurately predictive lithography model is crucial for the entire OPC correction. The prerequisite for establishing an ideal model is to collect a large amount of line width data of critical patterns that can cover the design dimensions. Therefore, the accuracy of the measurement data during the modeling process is particularly important. During a general measurement process, the measurement personnel obtain the measurement data corresponding to different patterns by setting different measurement conditions for different patterns. For example, for a designed pattern of a one-dimensional structure, the method of multi-point fitting to obtain an average value is usually used to obtain its line width size; while for a point-to-point pattern of a two-dimensional structure, due to the influence of corner rounding, the minimum value within the target range needs to be used to obtain its measurement value. The measurement data obtained by different measurement methods have different degrees of differences in their magnitudes and fluctuation ranges. Therefore, selecting a suitable measurement method targeted can, to a certain extent, ensure the accuracy of the data and the reliability of its modeling.

[0003] With the iterative update of lithography technology, especially at technology nodes below 20 nm, the exposure light source used is no longer a conventional light source shape, but a freeform illumination based on specific layout features, which makes the changes in the patterns after exposure and development more liberalized. Therefore, during the process of collecting modeling data, it is usually necessary to calibrate the measured data one by one and appropriately correct the measurement methods for the patterns after exposure and development under different pitches, in order to obtain accurate measurement data. Therefore, for a two-dimensional graphic structure with periodic changes, it is very difficult to achieve precise measurement of it using a single measurement method.

[0004] To solve the above problems, a new method for measuring line width is needed. Summary of the Invention

[0005] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a method for measuring line width, which is used to solve the problem that in the prior art, due to the liberalization of the light source shape, the differences in the changes of two-dimensional graphic structures after exposure and development are relatively large, so it is very difficult to use a single measurement method to precisely measure a graphic structure with periodic changes.

[0006] To achieve the above purpose and other related purposes, the present invention provides a method for measuring line width, including:

[0007] Step 1: Obtain a measurement scheme database, which includes feature patterns with feature pattern shapes, their corresponding line width measurement information, first measurement positions, and first line width measurement methods;

[0008] Step 2: Provide a target pattern and its second measurement position;

[0009] Step 3: Set matching criteria for the pattern with respect to the first and second measurement positions, and corresponding second line width measurement methods for the second measurement position under different matching criteria;

[0010] Step 4: Obtain the pattern profile of the target pattern after exposure and development, and then match the pattern profile with the feature pattern. For the target pattern whose pattern profile matches the feature pattern, perform line width measurement using the first line width measurement method of the feature pattern that matches it;

[0011] Step 5: For the target pattern whose pattern profile does not match the feature pattern, perform similarity matching between the second measurement position and the first measurement position. For the patterns within the same matching criteria range, perform line width measurement using the matching second line width measurement method; For the target patterns that meet two or more matching criteria simultaneously, generate abnormal points and record their positions at the same time;

[0012] Step 6: For the abnormal points, obtain the line width deviations in multiple different exposure units using each corresponding second line width measurement method, and select the second line width measurement method with the smallest sum of line width deviations as the best first line width measurement method for the abnormal points.

[0013] Preferably, the measurement scheme database described in Step 1 includes a default measurement pattern database and a feature measurement pattern database.

[0014] Preferably, the feature measurement pattern database described in Step 4 is used to match the pattern profile of the target pattern that meets the feature pattern match with the feature pattern.

[0015] Preferably, the default measurement pattern database described in Step 5 is used to provide similarity matching of measurement positions for the target pattern that does not match the feature pattern.

[0016] Preferably, the first line width measurement methods for the first measurement positions described in Step 1 do not repeat each other.

[0017] Preferably, the second line width measurement methods for the second measurement positions described in Step 3 can be repeated.

[0018] Preferably, in step three, the matching standard is that the contour line similarity at the first and second measurement positions reaches a set standard value.

[0019] Preferably, the matching criteria in step three include a graphic shape matching criterion and a measurement position matching criterion.

[0020] Preferably, in step 4, a grayscale recognition method is used to extract the contour of the target graphic to determine the matching ratio between its shape and the characteristic graphic in the measurement solution database.

[0021] Preferably, in step five, a curvature fitting method is used to perform similarity matching between the second measured position and the first measured position.

[0022] As described above, the line width measurement method of the present invention has the following beneficial effects:

[0023] The present invention inputs a characteristic exposure and development pattern and assigns a corresponding first line width measurement method, thereby establishing a deep learning database for the measuring machine, so that the measuring machine can automatically match the corresponding line width measurement method according to the shape of the pattern after exposure and development through the database in the later measurement process, thereby realizing accurate line width measurement of different patterns in different environments. The present technology can save the tedious work of selecting different measurement methods for different patterns when establishing measurement tasks in the early stage, greatly avoiding the selection errors of measurement methods caused by errors in pattern shape prediction; it can effectively reduce the staff's later measurement data calibration work, liberate a certain amount of labor, and provide data support for OPC modeling in terms of data collection time and data accuracy, thereby improving modeling efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of a measuring method according to a first embodiment of the present invention;

[0025] Figure 2 It is a schematic diagram of a measuring method according to a second embodiment of the present invention;

[0026] Figure 3 It is a schematic diagram of a measuring method according to a third embodiment of the present invention;

[0027] Figure 4 It is a schematic diagram of a measuring method according to a fourth embodiment of the present invention;

[0028] Figure 5 It is a schematic diagram showing measurement data of the target measurement pattern of the present invention obtained in different exposure units under different measurement modes;

[0029] Figure 6 Shown is a schematic diagram of the method of the present invention. DETAILED DESCRIPTION

[0030] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand the other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0031] Please refer to Figure 6 , the present invention provides a method for measuring line width, including:

[0032] Step 1: Obtain a measurement scheme database, which includes characteristic patterns with characteristic pattern shapes and their corresponding line width measurement information, the first measurement position and the first line width measurement method, the exposed and developed image of the characteristic pattern, and the measurement method depends on the line width accuracy covered by the target measurement pattern and the lithography technology node it is in; its characteristic pattern can be, for example, Figures 1 to 4 rectangles, circles, and ellipses in

[0033] In an alternative embodiment, the measurement scheme database in Step 1 includes a default measurement pattern database and a characteristic measurement pattern database.

[0034] In an alternative embodiment, the first line width measurement methods at the first measurement positions in Step 1 do not repeat each other.

[0035] Step 2: Provide a target pattern and its second measurement position. Since the exposed and developed patterns of the target pattern with the same line width are different under different repetition cycle (Pitch) conditions, it is difficult to set a suitable measurement method for this pattern before measurement, and thus it is difficult to obtain accurate measurement data.

[0036] Step 3: Set the matching criteria for the pattern with respect to the first and second measurement positions, and the corresponding second line width measurement methods for different matching criteria at the second measurement position.

[0037] In an alternative embodiment, the second line width measurement methods at the second measurement positions in Step 3 can be repeated.

[0038] In an alternative embodiment, the matching criteria in Step 3 is that the contour line similarity at the first and second measurement positions reaches a set standard value, and the size of the matching ratio is set depending on the coverage range of the characteristic pattern input in Step 1 (such as pattern type, aspect ratio of rectangular patterns, etc.).

[0039] In an alternative embodiment, the matching criteria in Step 3 include a pattern shape matching criterion and a measurement position matching criterion.

[0040] Step 4: Obtain the graphic contour after the target graphic is exposed and developed, and then match the graphic contour with the characteristic graphic. For the target graphic whose graphic contour matches the characteristic graphic, the first line width measurement method of the characteristic graphic it matches is used;

[0041] Specifically, before measuring the line width, first extract the graphic contour of the target graphic after exposure and development, and then match it with the shape of the characteristic graphic in the database to determine the selection range of the measurement mode. For example, the target measurement graphic shown in the appendix Figure 3 matches the elliptical shape shown in the appendix Figure 3 . Then, use the measurement database shown in the appendix Figure 3 graphic, so as to narrow down the matching scheme of the measurement library. For the target graphic that does not match the characteristic graphic in the database, directly enter the default graphic database for similarity matching of the line width measurement position;

[0042] In an alternative embodiment, in Step 4, the characteristic measurement graphic database is used to match the graphic contour of the target graphic that meets the characteristic graphic match with the characteristic graphic.

[0043] In an alternative embodiment, in Step 4, the gray scale recognition method is adopted. By extracting the contour of the target graphic, it is used to judge the matching ratio of its shape with the characteristic graphic in the measurement scheme database.

[0044] Step 5: For the target graphic whose graphic contour does not match the characteristic graphic, perform similarity matching between the second measurement position and the first measurement position. For the graphics within the same matching standard range, use the matching second line width measurement method to measure the line width; for the target graphics that meet two or more matching standards at the same time, generate abnormal points and record their positions at the same time;

[0045] Specifically, perform similarity matching between the measurement position of the target graphic and the measurement position of the graphic in the locked database above. For the graphics within the matching standard range, assign the corresponding line width measurement method to measure the line width. For example, if the similarity between the contour lines of the measurement positions reaches the set standard value, use the measurement method set in the appendix Figure 3 . For the contour of the measurement position in the appendix Figure 3 simultaneously meets the measurement methods shown in the appendix Figure 3 and the appendix Figure 3 and the appendix Figure 4 shown, then mark the measurement position of the elliptical target graphic as an abnormal point, record its position information, and enter the abnormal handling scheme, that is, proceed to the next step.

[0046] In an alternative embodiment, in Step 5, the default measurement graphic database is used to provide similarity matching of the measurement position for the target graphic that does not meet the characteristic graphic match.

[0047] In an alternative embodiment, in step five, the similarity matching between the second measurement position and the first measurement position is performed by using the curvature fitting method, but it is not limited to the curvature fitting method.

[0048] Step six: For the abnormal points, use each corresponding second line width measurement method to obtain the line width deviation in multiple different exposure units, and select the second line width measurement method with the smallest sum of line width deviations as the best first line width measurement method for the abnormal points.

[0049] Specifically, for the above abnormal points (attached Figure 3 ), different measurement modes that meet the matching criteria (the measurement methods mode1 and 2 shown in attached Figure 3 and attached Figure 4 ) are adopted to collect the line width measurement data respectively. By measuring the line width data of this position in 5 different exposure units, calculate the cost function under different measurement modes. The specific data results are shown in attached Figure 5 . By selecting the measurement mode (mode1) with the smallest cost function value as the best measurement mode for this abnormal point, that is, adopt the measurement method shown in attached Figure 3 as the best measurement method for this abnormal point;

[0050] After that, the above measurement points and their measurement results can be sorted out, a measurement report can be generated, and the abnormal measurement points can be recorded.

[0051] It should be noted that the diagrams provided in this embodiment only illustrate the basic concept of the present invention in a schematic manner. Therefore, only the components related to the present invention are shown in the diagrams, rather than being drawn according to the number, shape, and size of the components in actual implementation. The types, quantities, and proportions of the components in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0052] In summary, the present invention inputs the exposure and development patterns with characteristics and assigns the corresponding first line width measurement methods, thereby establishing a deep learning database for the measurement machine. So that the measurement machine can automatically match the corresponding line width measurement methods according to the shape of the pattern after exposure and development through this database during the later measurement process, thereby realizing the accurate line width measurement of different patterns in different environments. The technology of the present invention can save the cumbersome work of selecting different measurement methods for different patterns when establishing measurement tasks in the early stage, and greatly avoid the selection errors of measurement methods caused by incorrect prediction of the pattern shape; it can effectively reduce the later measurement data calibration work of the staff, liberate a certain amount of labor, and provide data support for OPC modeling in terms of both data collection time and data accuracy, improving the modeling efficiency. Therefore, the present invention effectively overcomes various disadvantages in the prior art and has high industrial utilization value.

[0053] The above embodiments are only illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A method for measuring line width, characterized in that, At least including: Step 1: Obtain a measurement plan database, which includes characteristic patterns with characteristic pattern shapes, their corresponding line width measurement information, first measurement positions, and first line width measurement methods at the first measurement positions, where the first line width measurement methods at the first measurement positions do not repeat each other; Step 2: Provide a target pattern and its second measurement position; Step 3: Set matching criteria for the pattern with respect to the first and second measurement positions, and corresponding second line width measurement methods for different matching criteria at the second measurement position, where the second line width measurement methods can be repeated; Step 4: Obtain the pattern profile after the target pattern is exposed and developed, and then match the pattern profile with the characteristic pattern. For the target pattern whose pattern profile matches the characteristic pattern, perform line width measurement using the first line width measurement method of the characteristic pattern that matches it; Step 5: For the target pattern whose pattern profile does not match the characteristic pattern, perform similarity matching between the second measurement position and the first measurement position. For patterns within the same matching criterion range, perform line width measurement using the matching second line width measurement method; for target patterns that satisfy two or more matching criteria simultaneously, generate abnormal points and record their positions at the same time; Step 6: For the abnormal points, obtain the line width deviations in multiple different exposure units using each corresponding second line width measurement method, and select the second line width measurement method with the smallest sum of line width deviations as the best first line width measurement method for the abnormal points.

2. The method for measuring line width according to claim 1, characterized in that: The measurement plan database described in Step 1 includes a default measurement pattern database and a characteristic measurement pattern database.

3. The method for measuring line width according to claim 2, characterized in that: The characteristic measurement pattern database described in Step 4 is used to match the pattern profile of the target pattern that conforms to the characteristic pattern match with the characteristic pattern.

4. The method for measuring line width according to claim 2, wherein: The default measurement pattern database described in Step 5 is used to provide similarity matching of measurement positions for the target pattern that does not match the characteristic pattern.

5. The method for measuring line width according to claim 1, wherein: The matching criterion in Step 3 is that the contour line similarity at the first and second measurement positions reaches a set standard value.

6. The method for measuring the line width according to claim 1, wherein: The matching criteria in Step 3 include a pattern shape matching criterion and a measurement position matching criterion.

7. The method for measuring the line width according to claim 1, characterized in that: In Step 4, the gray scale recognition method is adopted to extract the contour of the target pattern for judging the matching ratio of its shape with the characteristic pattern in the measurement plan database.

8. The method for measuring line width according to claim 7, wherein: In Step 5, the curvature fitting method is used to perform similarity matching between the second measurement position and the first measurement position.

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