CN115598934A - Photoetching model construction method, method for predicting SRAF graph exposure imaging and program product - Google Patents
Photoetching model construction method, method for predicting SRAF graph exposure imaging and program product Download PDFInfo
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- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
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Abstract
The invention relates to the technical field of computational lithography, in particular to a lithography model construction method, which comprises the following steps: acquiring an actual exposure imaging result of a part of SRAF graph on a wafer; establishing an initial photoetching model, and adding an image measuring plane and a light intensity threshold value into the initial photoetching model as variables; substituting part of SRAF graphs into the initial photoetching model for simulation, and obtaining simulation results corresponding to the part of SRAF graphs based on different image measuring planes and light intensity thresholds; comparing the simulation result with the actual exposure imaging result, and recording an image measurement plane and a light intensity threshold value corresponding to the simulation result with the highest similarity as an optimal simulation point; and calibrating the initial photoetching model according to the optimal simulation point to obtain a predicted photoetching model. The invention also provides a method and a program product for predicting the SRAF image exposure imaging, which solve the problem that the traditional OPC photoetching model can not accurately predict the SRAF exposure imaging result.
Description
[ technical field ] A method for producing a semiconductor device
The invention relates to the technical field of computational lithography, in particular to a lithography model construction method, a method for predicting S RAF pattern exposure imaging and a program product.
[ background of the invention ]
Photolithography is a key process in the manufacturing process of semiconductor devices and essentially transfers the pattern on a reticle onto a silicon wafer. In the design of the mask layout, there are usually both densely distributed patterns (such as lines with equal spacing) and sparse patterns (such as independent lines), and the photolithography process window of the sparse pattern is obviously smaller than that of the densely distributed patterns, thereby limiting the whole process window.
To solve this problem, a Sub-Resolution Assist Features (SRAF) pattern is usually added around the sparse pattern to make the sparse pattern optically look like a dense pattern, thereby improving the photolithography process window. If the SRAF pattern size is small, the improvement effect on the process window is not obvious, and if the SRAF pattern size is large, the risk of exposing and generating a pattern (sidelobe) on the wafer exists, and the sidelobe is regarded as a defect and affects the yield, so it is very important to select an appropriate SRAF.
Predicting exposure imaging of SRAF patterns on a wafer may provide an important basis for selecting a suitable SRAF.
Mainstream Optical Proximity Correction (OPC) lithography models are generally applicable to main patterns, are not applicable to SRAF patterns, and predict the results of SRAF exposure imaging are not accurate because the main patterns and the SRAF patterns have large feature size differences. Therefore, a photolithography model for predicting exposure imaging of SRAFs on a wafer with high accuracy is needed.
[ summary of the invention ]
The invention provides a lithography model construction method, a method for predicting SRAF pattern exposure imaging and a program product, aiming at solving the problem that the traditional OPC lithography model can not accurately predict SRAF exposure imaging results.
In order to solve the technical problems, the invention provides the following technical scheme: a photoetching model construction method comprises the following steps: acquiring an actual exposure imaging result of a part of SRAF graph on a wafer; establishing an initial photoetching model, and adding an image measuring plane and a light intensity threshold value into the initial photoetching model as variables; substituting the partial SRAF graph into the initial photoetching model for simulation, and obtaining a simulation result corresponding to the partial SRAF graph based on different image measuring planes and light intensity thresholds; comparing the simulation result with the actual exposure imaging result, and recording an image measurement plane and a light intensity threshold value corresponding to the simulation result with the highest similarity as an optimal simulation point; and calibrating the initial photoetching model according to the optimal simulation point to obtain a predicted photoetching model.
Preferably, obtaining the simulation results of the partial SRAF graph corresponding to different image measurement planes and light intensity thresholds comprises the following steps: constructing a two-dimensional solving space by taking the image measuring plane and the light intensity threshold value as horizontal and vertical coordinates, wherein the two-dimensional solving space comprises a plurality of process points, and each process point corresponds to one image measuring plane and the light intensity threshold value; substituting each process point and the partial SRAF graph into the initial photoetching model to carry out simulation solving to obtain the difference value between the light intensity distribution of the exposure image corresponding to the partial SRAF graph and the light intensity threshold value; and judging the printing-out probability of the current SRAF graph according to the difference value of the light intensity distribution of the exposure image and the light intensity threshold value.
Preferably, the step of determining the print-out probability of the current SRAF pattern according to the difference between the light intensity distribution of the exposure image and the light intensity threshold comprises the following steps: if the difference value between the exposed light intensity and the light intensity threshold is larger than a preset tolerance interval and the light intensity is larger, judging that the printing-out probability is higher; if the difference value between the exposed light intensity and the light intensity threshold is larger than a preset tolerance interval and the light intensity threshold is larger, judging that the printing-out probability is lower; if the difference value between the exposed light intensity and the light intensity threshold is smaller than a preset tolerance interval, judging that the printing-out probability is moderate; and calculating the printing probability between 0 and 1 according to the difference value between the light intensity and the light intensity threshold value.
Preferably, acquiring the actual exposure imaging result of the partial SRAF pattern on the wafer comprises the following steps: acquiring a Scanning Electron Microscope (SEM) image of a partial SRAF pattern on a wafer; and adding a corresponding imaging state label for each SRAF figure mark according to whether the SRAF figure is generated in the SEM image after exposure and whether the generated figure is continuous.
Preferably, the SEM images include SEM images exposed under standard conditions and non-standard conditions.
Preferably, the optical information of the initial lithography model other than the image measurement plane and the light intensity threshold is consistent with the lithography model used for the actual exposure of the portion of the SRAF pattern.
Preferably, the step of acquiring the actual exposure imaging result of the partial SRAF pattern on the wafer further comprises: dividing the actual exposure imaging result of the part of the SRAF graph on the wafer into a calibration group and an inspection group; transferring the calibration set into the initial lithography model for simulating and calibrating the initial lithography model; and transmitting the inspection group into the predicted photoetching model to obtain an inspection simulation result, and comparing the inspection simulation result with the actual exposure result to inspect the reliability of the predicted photoetching model.
Preferably, if the reliability of the predicted lithography model does not meet a preset requirement, the predicted lithography model is further calibrated according to the inspection group.
In order to solve the above technical problems, the present invention provides another technical solution as follows: a method of predicting SRAF pattern exposure imaging comprising the steps of: obtaining a prediction photoetching model according to the photoetching model construction method; and predicting whether other SRAF graphs on the wafer are printed or not through the prediction photoetching model.
In order to solve the above technical problems, the present invention provides another technical solution as follows: a program product comprising computer program instructions which, when executed, implement the steps of the above-described method of lithographic model construction.
Compared with the prior art, the photoetching model construction method provided by the invention has the following beneficial effects:
1. the method for constructing the lithography model provided by the first embodiment of the invention comprises the following steps: acquiring an actual exposure imaging result of a part of SRAF graph on a wafer; establishing an initial photoetching model, and adding an image measuring plane and a light intensity threshold value into the initial photoetching model as variables; substituting part of SRAF graphs into the initial photoetching model for simulation, and obtaining simulation results corresponding to the part of SRAF graphs based on different image measuring planes and light intensity thresholds; comparing the simulation result with the actual exposure imaging result to obtain an image measurement plane and a light intensity threshold value corresponding to the simulation result with the highest similarity, and recording as an optimal simulation point; and calibrating the initial photoetching model according to the optimal simulation point to obtain a predicted photoetching model. It can be understood that, based on the exposure imaging result of the partial SRAF on the wafer, the image measurement plane and the light intensity threshold value are recalibrated, and the photoetching model suitable for the SRAF is established.
2. In the lithography model construction method provided in the first embodiment of the present invention, obtaining the simulation results of the SRAF patterns corresponding to different image measurement planes and light intensity thresholds includes the following steps: constructing a two-dimensional solving space by taking the image measuring plane and the light intensity threshold value as horizontal and vertical coordinates, wherein the two-dimensional solving space comprises a plurality of process points, and each process point corresponds to one image measuring plane and one light intensity threshold value; substituting each process point and part of the SRAF graph into the initial photoetching model to carry out simulation solving to obtain the difference value between the light intensity distribution of the exposure image corresponding to the part of the SRAF graph and the light intensity threshold value; and judging the printing-out probability of the current SRAF graph according to the difference value of the light intensity distribution of the exposure image and the light intensity threshold value. It can be understood that the simulation calculation of all the process points is more beneficial to finding out the process point which best meets the actual process from a large number of simulation results, so that the subsequent process of calibrating the model is more reliable.
3. In the method for constructing a lithography model according to the first embodiment of the present invention, determining the print-out probability of the current SRAF pattern according to the difference between the light intensity distribution of the exposure image and the light intensity threshold includes the following steps: if the difference value between the exposed light intensity and the light intensity threshold is larger than a preset tolerance interval and the light intensity is larger, judging that the printing-out probability is higher; if the difference value between the exposed light intensity and the light intensity threshold is larger than a preset tolerance interval and the light intensity threshold is larger, judging that the printing-out probability is lower; if the sum of the exposed light intensity is equal to the light intensity threshold, judging that the extraction probability is moderate; if the difference value between the exposed light intensity and the light intensity threshold is smaller than a preset tolerance interval, judging that the printing-out probability is moderate; and calculating the printing probability between 0 and 1 according to the difference value between the light intensity and the light intensity threshold value. It can be understood that the exposure imaging result of the SRAF graph at the current process point can be more accurately evaluated according to the difference between the exposed light intensity and the light intensity threshold.
4. In the method for constructing a lithography model according to the first embodiment of the present invention, obtaining an actual exposure imaging result of a partial SRAF pattern on a wafer includes the following steps: obtaining an SEM image of a partial SRAF graph on a wafer; and adding a corresponding imaging state label for each SRAF graphic mark according to whether the SRAF graphic is generated in the SEM image after exposure and whether the generated graphics are continuous. It can be understood that adding the imaging state label according to the SEM image generation graph is equivalent to classifying the actual exposure imaging result, and the classified actual exposure imaging result is more convenient to compare with the simulation result, and the optimal simulation point can be obtained only by judging whether the simulation result falls in a certain category, and without comparing one by one. Therefore, the method has the advantages of simple steps, easy realization and strong reliability.
5. In the method for constructing a lithography model according to the first embodiment of the present invention, the SEM images include SEM images exposed under standard conditions and non-standard conditions. It will be appreciated that SEM images under both conditions may provide a richer sample of the initial lithography model, improving the accuracy of the calibration model.
6. In the lithography model construction method provided by the first embodiment of the present invention, the optical information of the initial lithography model excluding the image measurement plane and the light intensity threshold is consistent with the lithography model used for actual exposure of a part of the SRAF pattern. It can be understood that the real photoetching process can be restored to the maximum extent by ensuring the consistency of other optical information, so that the simulation result is more accurate, and the obtained optimal simulation point is more practical.
7. In the method for constructing a lithography model according to the first embodiment of the present invention, after obtaining an actual exposure imaging result of a part of an SRAF pattern on a wafer, the method further includes the following steps: dividing actual exposure imaging results of a part of SRAF graphs on a wafer into a calibration group and an inspection group; transmitting the calibration group into an initial photoetching model for simulating and calibrating the initial photoetching model; and transmitting the inspection group into the predicted photoetching model to obtain an inspection simulation result, and comparing the inspection simulation result with the actual exposure result to inspect the reliability of the predicted photoetching model. It can be understood that the setting of the check group further checks the reliability degree of the prediction lithography model, and ensures the reliability in application.
8. In the lithography model construction method provided in the first embodiment of the present invention, if the reliability of the predicted lithography model does not meet the preset requirement, the predicted lithography model is further calibrated according to the verification set. It will be appreciated that the classification of the calibration and calibration groups is generally uniform, i.e., different types of SRAF patterns at different locations are uniformly grouped into two groups, and that the results of the calibration and calibration are normally substantially identical. In practical application, if the result is inconsistent, the model after calibration does not cover the type of the test set, and the reliability of the model can be ensured by calibrating the model by the test set.
9. The embodiment of the invention also provides a method for predicting the exposure imaging of the SRAF graph, which has the same beneficial effects as the method for constructing the photoetching model, and the details are not repeated herein.
10. The embodiment of the present invention further provides a program product, which has the same beneficial effects as the above-mentioned method for building a lithography model, and is not described herein again.
[ description of the drawings ]
Fig. 1 is a schematic flowchart of a lithography model building method according to a first embodiment of the present invention.
FIG. 2 is a schematic diagram of a two-dimensional solution space of a lithography model construction method according to a first embodiment of the present invention.
Fig. 3 is a diagram illustrating an example of setting criteria of label in the lithography model building method according to the first embodiment of the present invention.
FIG. 4 is a comparison graph of the label and P values of each SRAF at the optimal simulation point of the lithography model construction method according to the first embodiment of the present invention.
Fig. 5 is a diagram showing verification results of the verification group in the lithography model building method according to the first embodiment of the present invention.
Fig. 6 is a flowchart illustrating a method for predicting SRAF pattern exposure imaging according to a second embodiment of the present invention.
Fig. 7 is a schematic structural diagram of a program product according to a third embodiment of the present invention.
The attached drawings indicate the following:
1. a method for constructing a lithography model; 2. predicting SRAF graph exposure imaging method; 3. a program product;
30. computer program instructions.
[ detailed description ] embodiments
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings and implementation examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to fig. 1, a first embodiment of the invention provides a method 1 for building a lithography model, including the following steps: acquiring an actual exposure imaging result of a part of SRAF graph on a wafer; establishing an initial photoetching model, and adding an image measuring plane and a light intensity threshold value into the initial photoetching model as variables; substituting part of the SRAF graphs into the initial photoetching model for simulation, and obtaining corresponding simulation results of the part of the SRAF graphs under different image measuring planes and light intensity thresholds on the basis of different image measuring planes and light intensity thresholds; comparing the simulation result with the actual exposure imaging result, and recording an image measurement plane and a light intensity threshold value corresponding to the simulation result with the highest similarity as an optimal simulation point; and calibrating the initial photoetching model according to the optimal simulation point to obtain a predicted photoetching model.
It can be understood that, based on the exposure imaging result of the partial SRAF on the wafer, the image measurement plane and the light intensity threshold value of the initial photoetching model are recalibrated, and the photoetching model suitable for the SRAF is established.
Preferably, the optical information of the initial lithography model other than the image measurement plane and the light intensity threshold is consistent with the lithography model used for the actual exposure of the portion of the SRAF pattern. It can be understood that the real photoetching process can be restored to the maximum extent by ensuring the consistency of other optical information, so that the simulation result is more accurate, and the obtained optimal simulation point is more practical. In particular, optical information that remains consistent includes.
In some embodiments, obtaining simulation results of the partial SRAF graphs corresponding to different image measurement planes and light intensity thresholds comprises the following steps: constructing a two-dimensional solving space by taking the image measuring plane and the light intensity threshold as horizontal and vertical coordinates, wherein the two-dimensional solving space comprises a plurality of process points as shown in fig. 2, and each process point corresponds to one image measuring plane and one light intensity threshold; substituting each process point and part of the SRAF graph into the initial photoetching model to carry out simulation solving to obtain the difference value between the light intensity distribution of the exposure image corresponding to the part of the SRAF graph and the light intensity threshold value; and judging the printing-out probability of the current SRAF graph according to the difference value of the light intensity distribution of the exposure image and the light intensity threshold value.
It can be understood that the simulation calculation of all the process points is more beneficial to finding out the process point which best meets the actual process from a large number of simulation results, so that the subsequent process of calibrating the model is more reliable.
Further, the step of judging the printing-out probability of the current SRAF pattern according to the difference value of the light intensity distribution of the exposure image and the light intensity threshold value comprises the following steps: if the difference value between the exposed light intensity and the light intensity threshold is larger than a preset tolerance interval and the light intensity is larger than the light intensity threshold, judging that the printing-out probability is higher; if the difference value between the exposed light intensity and the light intensity threshold is larger than a preset tolerance interval and the light intensity threshold is larger than the light intensity, judging that the printing-out probability is low; if the difference value between the exposed light intensity and the light intensity threshold is smaller than a preset tolerance interval, judging that the printing-out probability is moderate; and calculating the printing probability between 0 and 1 according to the difference value between the light intensity and the light intensity threshold value.
Specifically, the print-out probability is represented by a value P, and P represents the probability of SRAF imaging simulated by the photoetching model and is influenced by two variables, namely an image measuring plane and an intensity threshold value. When the sildelobe risk is higher, the P value is between 0.5 and 1; when the sidelibe risk comes to an end, the P value is about 0.5; when the sildelobe risk is low, the P value is between 0 and 0.5.
It can be understood that the exposure imaging result of the SRAF graph at the current process point can be more accurately evaluated according to the difference between the exposed light intensity and the light intensity threshold.
In some embodiments, obtaining actual exposure imaging results of portions of the SRAF pattern on the wafer comprises: obtaining an SEM image of a partial SRAF graph on a wafer; and adding a corresponding imaging state label (label) to each SRAF graphic mark according to whether the SRAF graphic generates a graphic in the SEM image after exposure and whether the generated graphic is continuous. It can be understood that adding the imaging state label according to the SEM image generation graph is equivalent to classifying the actual exposure imaging result, and the classified actual exposure imaging result is more convenient to compare with the simulation result, and only by judging whether the simulation result falls in a certain category, the optimal simulation point can be obtained without one-to-one comparison. Therefore, the method has the advantages of simple steps, easy realization and strong reliability.
In some embodiments, the imaging status label setting method is as follows:
and if no image is generated after the SRAF exposure, defining the imaging state label to be 0.
If the SRAF post-exposure image is present and continuous, its imaging status flag is defined as 1.
If the image after SRAF exposure is present but not continuous, its imaging status label is defined to be 0.5. An example of the label setting criteria is shown in fig. 3.
Further, the SEM images include SEM images exposed under standard conditions and non-standard conditions. The SEM images exposed under standard conditions account for at least half of the total data set to ensure that the subject of the simulation is performing around standard conditions. It will be appreciated that SEM images under both conditions may provide a richer sample of the initial lithography model, improving the accuracy of the calibration model.
In some embodiments, the step of obtaining the actual exposure imaging result of the partial SRAF pattern on the wafer further comprises: dividing actual exposure imaging results of a part of SRAF graphs on a wafer into a calibration group and an inspection group; transferring the calibration set into an initial lithography model for simulating and calibrating the initial lithography model; and transmitting the inspection group into the predicted photoetching model to obtain an inspection simulation result, and comparing the inspection simulation result with an actual exposure result to inspect the reliability of the predicted photoetching model. It can be understood that the setting of the check group further checks the reliability degree of the prediction lithography model, and ensures the reliability in application.
Further, if the reliability of the predicted lithography model does not meet the preset requirement, the predicted lithography model is further calibrated according to the inspection group. It will be appreciated that the classification of the calibration and calibration groups is generally uniform, i.e., different types of SRAF patterns at different locations are evenly divided into two groups, and that the results of the calibration and calibration are normally substantially identical. In practical applications, if the results are inconsistent, the model after calibration does not cover the type of the test set, and the reliability of the model can be ensured by calibrating the model by the test set.
The lithography model construction method 1 according to the first embodiment of the present invention is described below with reference to specific examples:
104 pieces of data were collected for SRAF on the wafer, 84 pieces of SEM images were exposed under standard conditions and 20 pieces of SEM images were exposed under non-standard conditions. Where 27 are present and continuous on the wafer after exposure, label for these SRAFs is set to 1. There are 38 places on the wafer where there are and discontinuities after exposure, label for these SRAFs is set to 0.5. There are 39 spots on the wafer where no image is generated after exposure. The label of these SRAFs is set to 0. The data were randomly divided into two groups, 84 SRAFs for the calibration group and 20 SRAFs for the test group.
Based on the photoetching model of OPC software, the information of a light source, a photomask and photoresist is input to establish an initial photoetching model, and the thickness of the photoresist is 85nm. The exposure focus is consistent with the main pattern exposure focus and is arranged at a distance of 54nm from the top of the photoresist. The image measurement plane and the light intensity threshold are added to the model as variables.
The image measurement plane solving range is 5-85 nm from the top of the photoresist, and the step length is 5nm. The light intensity threshold solution range is 0.0966 to 0.1.046 with a step size of 0.005.
And calculating the light intensity distribution of the SRAF exposure image under the solution condition, obtaining the difference value between the peak light intensity and the light intensity threshold value, obtaining a P value through S-shaped function mapping, comparing the simulation result with the actual result, and obtaining that when the image measuring plane is 80nm and the light intensity threshold value is 0.0991, the simulation result is closest to the actual result. The label and P values of SRAFs throughout the calibration set are shown in fig. 4. The P values for 53 SRAFs with label of 0.5 and 1 were greater than 0.5. Of the 31 SRAFs with label of 0, the P value of 29 SRAFs was less than 0.5,2 and greater than 0.5. 97.6% of SRAF simulation results in the whole result are consistent with the real condition, the missing alarm phenomenon does not exist, and the false alarm phenomenon exists in 2.4% of SRAF.
The initial lithography model was calibrated with the process points whose image measurement plane was 80nm and light intensity threshold value was 0.0991 to obtain the predicted lithography model, and the test set was simulated using the predicted lithography model, with the results shown in fig. 5. The P values for 12 SRAFs with label of 0.5 and 1 were greater than 0.5. Of the 8 SRAFs with label of 0, 7 SRAFs had a P value less than 0.5,1 and greater than 0.5. And judging that the reliability of the predicted photoetching model is higher according to the verification simulation result.
Referring to fig. 6, a second embodiment of the present invention provides a method 2 for predicting SRAF pattern exposure imaging, comprising the following steps: obtaining a predictive lithography model according to a lithography model construction method 1 as provided in the first embodiment of the present invention; and predicting whether other SRAF graphs on the wafer are printed or not through the prediction photoetching model. It should be understood that other SRAF patterns refer to SRAF patterns that were not obtained from a wafer when the predictive lithography model was built.
Referring to fig. 7, a program product 3 according to a third embodiment of the present invention includes computer program instructions 30, and the computer program instructions 3, when executed, implement the steps of the above-mentioned lithography model building method 1.
In the embodiments provided herein, it should be understood that "B corresponding to a" means that B is associated with a from which B can be determined. It should also be understood, however, that determining B from a does not mean determining B from a alone, but may also be determined from a and/or other information.
It should be appreciated that reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Those skilled in the art should also appreciate that the embodiments described in this specification are exemplary and alternative embodiments, and that the acts and modules illustrated are not required in order to practice the invention.
In various embodiments of the present invention, it should be understood that the sequence numbers of the above-mentioned processes do not imply an inevitable order of execution, and the execution order of the processes should be determined by their functions and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.
The flowchart and block diagrams in the figures of the present application illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present application. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It should be particularly noted that each block in the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems for performing the specified functions or operations, or by a lithography model building method provided by the present invention, which has the following advantages compared with the prior art:
1. the method for constructing the lithography model provided by the first embodiment of the invention comprises the following steps: acquiring an actual exposure imaging result of a part of SRAF graph on a wafer; establishing an initial photoetching model, and adding an image measuring plane and a light intensity threshold value into the initial photoetching model as variables; substituting part of SRAF graphs into the initial photoetching model for simulation, and obtaining simulation results corresponding to the part of SRAF graphs based on different image measuring planes and light intensity thresholds; comparing the simulation result with the actual exposure imaging result to obtain an image measurement plane and a light intensity threshold value corresponding to the simulation result with the highest similarity, and recording as an optimal simulation point; and calibrating the initial photoetching model according to the optimal simulation point to obtain a predicted photoetching model. Understandably, based on the exposure imaging result of partial SRAF on the wafer, the image measuring plane and the light intensity threshold value are recalibrated, and the photoetching model suitable for SRAF is established.
2. In the lithography model construction method provided in the first embodiment of the present invention, obtaining the simulation results of the SRAF patterns corresponding to different image measurement planes and light intensity thresholds includes the following steps: constructing a two-dimensional solving space by taking the image measuring plane and the light intensity threshold value as horizontal and vertical coordinates, wherein the two-dimensional solving space comprises a plurality of process points, and each process point corresponds to one image measuring plane and one light intensity threshold value; substituting each process point and part of the SRAF graph into the initial photoetching model to carry out simulation solving to obtain the difference value between the light intensity distribution of the exposure image corresponding to the part of the SRAF graph and the light intensity threshold value; and judging the printing-out probability of the current SRAF graph according to the difference value of the light intensity distribution of the exposure image and the light intensity threshold value. It can be understood that the simulation calculation of all the process points is more beneficial to finding out the process point which best meets the actual process from a large number of simulation results, so that the subsequent process of calibrating the model is more reliable.
3. In the method for constructing a lithography model according to the first embodiment of the present invention, determining the print-out probability of the current SRAF pattern according to the difference between the light intensity distribution of the exposure image and the light intensity threshold includes the following steps: if the difference value between the exposed light intensity and the light intensity threshold is larger than a preset tolerance interval and the light intensity is larger, judging that the printing-out probability is higher; if the difference value between the exposed light intensity and the light intensity threshold is larger than a preset tolerance interval and the light intensity threshold is larger, judging that the printing-out probability is lower; if the exposed light intensity is equal to the light intensity threshold, judging that the extraction probability is moderate; if the difference value between the exposed light intensity and the light intensity threshold is smaller than a preset tolerance interval, judging that the printing-out probability is moderate; and calculating the printing probability between 0 and 1 according to the difference value between the light intensity and the light intensity threshold value. It can be understood that the exposure imaging result of the SRAF graph at the current process point can be more accurately evaluated according to the difference between the exposed light intensity and the light intensity threshold.
4. In the method for constructing a lithography model according to the first embodiment of the present invention, obtaining an actual exposure imaging result of a partial SRAF pattern on a wafer includes the following steps: obtaining an SEM image of a partial SRAF graph on a wafer; and adding a corresponding imaging state label for each SRAF graphic mark according to whether the SRAF graphic is generated in the SEM image after exposure and whether the generated graphics are continuous. It can be understood that adding the imaging state label according to the SEM image generation graph is equivalent to classifying the actual exposure imaging result, and the classified actual exposure imaging result is more convenient to compare with the simulation result, and only by judging whether the simulation result falls in a certain category, the optimal simulation point can be obtained without one-to-one comparison. Therefore, the method has the advantages of simple steps, easy realization and strong reliability.
5. In the method for constructing a lithography model according to the first embodiment of the present invention, the SEM images include SEM images exposed under standard conditions and non-standard conditions. It will be appreciated that SEM images under both conditions may provide a richer sample of the initial lithography model, improving the accuracy of the calibration model.
6. In the lithography model construction method provided by the first embodiment of the present invention, the optical information of the initial lithography model excluding the image measurement plane and the light intensity threshold is consistent with the lithography model used for the actual exposure of the partial SRAF pattern. It can be understood that the real photoetching process can be restored to the maximum extent by ensuring the consistency of other optical information, so that the simulation result is more accurate, and the obtained optimal simulation point is more practical.
7. In the method for constructing a lithography model according to the first embodiment of the present invention, after obtaining an actual exposure imaging result of a part of an SRAF pattern on a wafer, the method further includes the following steps: dividing actual exposure imaging results of a part of SRAF graphs on a wafer into a calibration group and an inspection group; transferring the calibration set into an initial lithography model for simulating and calibrating the initial lithography model; and transmitting the inspection group into the predicted photoetching model to obtain an inspection simulation result, and comparing the inspection simulation result with an actual exposure result to inspect the reliability of the predicted photoetching model. It can be understood that the setting of the check group further checks the reliability degree of the prediction lithography model, and ensures the reliability in application.
8. In the lithography model construction method provided in the first embodiment of the present invention, if the reliability of the predicted lithography model does not meet the preset requirement, the predicted lithography model is further calibrated according to the verification set. It will be appreciated that the classification of the calibration and calibration groups is generally uniform, i.e., different types of SRAF patterns at different locations are uniformly grouped into two groups, and that the results of the calibration and calibration are normally substantially identical. In practical applications, if the results are inconsistent, the model after calibration does not cover the type of the test set, and the reliability of the model can be ensured by calibrating the model by the test set.
9. The embodiment of the invention also provides a method for predicting the exposure imaging of the SRAF graph, which has the same beneficial effects as the method for constructing the photoetching model, and the details are not repeated herein.
10. The embodiment of the present invention further provides a program product, which has the same beneficial effects as the above method for constructing a lithography model, and details are not described herein.
The lithography model construction method, the method for predicting SRAF pattern exposure imaging and the program product disclosed in the embodiments of the present invention are described in detail above, and the specific embodiments are applied herein to explain the principle and the implementation of the present invention, and the description of the embodiments above is only used to help understanding the method and the core idea of the present invention; meanwhile, for the persons skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present description should not be construed as a limitation to the present invention, and any modification, equivalent replacement, and improvement made within the principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A method for constructing a lithography model is characterized in that: the method comprises the following steps:
acquiring an actual exposure imaging result of a part of SRAF graph on a wafer;
establishing an initial photoetching model, and adding an image measuring plane and a light intensity threshold value into the initial photoetching model as variables;
substituting the partial SRAF graphs into the initial photoetching model for simulation, and obtaining simulation results corresponding to the partial SRAF graphs on the basis of different image measuring planes and light intensity thresholds;
comparing the simulation result with the actual exposure imaging result, and marking an image measurement plane and a light intensity threshold value corresponding to the simulation result with the highest similarity as an optimal simulation point;
and calibrating the initial photoetching model according to the optimal simulation point to obtain a predicted photoetching model.
2. A lithographic model building method according to claim 1, wherein: the method for obtaining the corresponding simulation results of the partial SRAF graphs under different image measurement planes and light intensity thresholds comprises the following steps:
constructing a two-dimensional solving space by taking the image measuring plane and the light intensity threshold value as horizontal and vertical coordinates, wherein the two-dimensional solving space comprises a plurality of process points, and each process point corresponds to one image measuring plane and the light intensity threshold value;
substituting each process point and the partial SRAF graph into the initial photoetching model to carry out simulation solving to obtain the difference value between the light intensity distribution of the exposure image corresponding to the partial SRAF graph and the light intensity threshold value;
and judging the printing-out probability of the current SRAF graph according to the difference value of the light intensity distribution of the exposure image and the light intensity threshold value.
3. A lithographic model building method according to claim 2, wherein: the step of judging the printing probability of the current SRAF graph according to the difference value of the light intensity distribution of the exposure image and the light intensity threshold value comprises the following steps:
if the difference value between the exposed light intensity and the light intensity threshold is larger than a preset tolerance interval and the light intensity is larger, judging that the printing-out probability is higher;
if the difference value between the exposed light intensity and the light intensity threshold is larger than a preset tolerance interval and the light intensity threshold is larger, judging that the printing-out probability is lower;
if the difference value between the exposed light intensity and the light intensity threshold is smaller than a preset tolerance interval, judging that the printing-out probability is moderate;
and calculating the printing probability between 0 and 1 according to the difference value between the light intensity and the light intensity threshold value.
4. A lithographic model building method according to claim 1, wherein: the method for acquiring the actual exposure imaging result of the partial SRAF graph on the wafer comprises the following steps:
obtaining an SEM image of a partial SRAF graph on a wafer;
and adding a corresponding imaging state label for each SRAF figure mark according to whether the SRAF figure is generated in the SEM image after exposure and whether the generated figure is continuous or not, and comparing the imaging state label with the simulation result.
5. The lithography model building method of claim 4, wherein:
the SEM images include SEM images exposed under standard conditions and non-standard conditions.
6. A lithographic model building method according to claim 1, wherein: the optical information of the initial lithography model, except for the image measurement plane and the light intensity threshold, is consistent with the lithography model used for the actual exposure of the partial SRAF pattern.
7. A lithographic model building method according to claim 1, wherein: the method also comprises the following steps after the actual exposure imaging result of the partial SRAF graph on the wafer is obtained:
dividing the actual exposure imaging result of the part of the SRAF graph on the wafer into a calibration group and an inspection group;
transferring the calibration set into the initial lithography model for simulating and calibrating the initial lithography model;
and transmitting the inspection group into the predicted photoetching model to obtain an inspection simulation result, and comparing the inspection simulation result with the actual exposure result to inspect the reliability of the predicted photoetching model.
8. The lithography model building method of claim 7, wherein: and if the reliability of the predicted photoetching model does not meet the preset requirement, further calibrating the predicted photoetching model according to the inspection group.
9. A method of predicting SRAF pattern exposure imaging, comprising: the method comprises the following steps:
obtaining a predictive lithography model in accordance with a lithography model construction method according to any one of claims 1 to 8;
and predicting whether other SRAF graphs on the wafer are printed or not through the prediction photoetching model.
10. A program product comprising computer program instructions characterized in that: the computer program instructions when executed perform the steps of the method of lithography model construction according to any one of claims 1 to 8.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116579907A (en) * | 2023-07-06 | 2023-08-11 | 武汉中导光电设备有限公司 | Wafer image acquisition method, device, equipment and readable storage medium |
| CN117008428A (en) * | 2023-09-26 | 2023-11-07 | 全芯智造技术有限公司 | Lithographic simulation method, apparatus and medium |
| CN117148689A (en) * | 2023-11-01 | 2023-12-01 | 合肥晶合集成电路股份有限公司 | Simulation processing method, device, equipment and medium for photoetching process |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116579907A (en) * | 2023-07-06 | 2023-08-11 | 武汉中导光电设备有限公司 | Wafer image acquisition method, device, equipment and readable storage medium |
| CN116579907B (en) * | 2023-07-06 | 2023-09-22 | 武汉中导光电设备有限公司 | Wafer image acquisition method, device, equipment and readable storage medium |
| CN117008428A (en) * | 2023-09-26 | 2023-11-07 | 全芯智造技术有限公司 | Lithographic simulation method, apparatus and medium |
| CN117008428B (en) * | 2023-09-26 | 2024-01-26 | 全芯智造技术有限公司 | Lithographic simulation method, apparatus and medium |
| CN117148689A (en) * | 2023-11-01 | 2023-12-01 | 合肥晶合集成电路股份有限公司 | Simulation processing method, device, equipment and medium for photoetching process |
| CN117148689B (en) * | 2023-11-01 | 2024-03-01 | 合肥晶合集成电路股份有限公司 | Simulation processing method, device, equipment and medium for photoetching process |
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