Method and apparatus for performing model-based layout conversion for use with dipole illumination
A method of generating complementary masks for use in a multiple-exposure lithographic imaging process. The method includes the steps of: identifying a target pattern having a plurality of features comprising horizontal and vertical edges; generating a horizontal mask based on the target pattern; generating a vertical mask based on the target pattern; performing a shielding step in which at least one of the vertical edges of the plurality of features in the target pattern is replaced by a shield in the horizontal mask, and in which at least one of the horizontal edges of the plurality of features in the target pattern is replaced by a shield in the vertical mask, where the shields have a width which is greater that the width of the corresponding feature in the target pattern; performing an assist feature placement step in which sub-resolution assist features are disposed parallel to at least one of the horizontal edges of the plurality of features in the horizontal mask, and are disposed parallel to at least one of the vertical edges of the plurality of features in the vertical mask, and performing a feature biasing step in which at least one of the horizontal edges of the plurality of features in the horizontal mask are adjusted such that the resulting feature accurately reproduces the target pattern, and at least one of the vertical edges of the plurality of features in the vertical mask are adjusted such that the resulting feature accurately reproduces the target pattern.
1. A method for preparing masks for printing a pattern on a substrate utilizing multiple exposure lithography imaging comprising dipole illumination, the dipole illumination comprising first and second different poles, the pattern being intended to be an accurate reproduction of a design comprising a target pattern having a plurality of features, the method comprising:
decomposing input design data into first and second masks for use with the first and second poles of the dipole illumination, respectively, with the plurality of features; and
applying shielding to the first and second masks, including:
identifying at least a first one of the plurality of features in the target pattern for treatment with a first shield in the first mask, the first feature having an edge which extends in a direction in the mask that is substantially parallel to the first pole, and
using an OPC model to determine dimensions of the first shield.
2. The method of claim 1 , wherein both of the initialized first and second masks comprise substantially all of the plurality of features.
3. The method of claim 1 , further comprising:
determining one or more sub-resolution assist features to be disposed parallel to an edge of at least a second one of the plurality of features in the first mask.
4. The method of claim 3 , wherein the sub-resolution assist feature determination is performed prior to the step of determining the shielding.
5. The method of claim 1 , further comprising:
determining biasing to be made to an edge of at least a second one of the plurality of features in the first mask such that the resulting feature accurately reproduces the target pattern.
6. The method of claim 1 , comprising the steps of:
prior to using the OPC model, defining a system pseudo-intensity function, said system pseudo-intensity function approximating the imaging performance of said dipole illumination process, and
including the defined system pseudo-intensity function in the OPC model.
7. The method of claim 6 , wherein the system pseudo-intensity function is determined utilizing one of a calibrated model of the dipole illumination process and a theoretical model of the dipole illumination process.
8. The method of claim 1 , further comprising:
generating the OPC model in accordance with the imaging performance of said dipole illumination process; and
generating a simulated image utilizing the OPC model and the target pattern in the shielding determination step.
9. The method of claim 1 , wherein the shielding determination step further includes:
segmenting the first one of the features into a plurality of first segments; and
determining the dimensions of the corresponding first shield in the first mask for each respective first segment.
10. The method of claim 1 , wherein the shielding determination step further includes:
determining not to apply a shield to at least a first different one of the plurality of features in the target pattern in the first mask, the determination being made using the OPC model.
11. A method for preparing masks for printing a pattern on a substrate utilizing multiple exposure lithography imaging comprising dipole illumination, the dipole illumination comprising horizontal and vertical poles, the pattern being intended to be an accurate reproduction of a design comprising a target pattern having a plurality of features, the method comprising:
decomposing input design data into horizontal and vertical masks for use with the vertical and horizontal poles of the dipole illumination, respectively, with the plurality of features; and
applying shielding to the horizontal and vertical masks, including:
identifying at least a first one of the plurality of features in the target pattern for treatment with a first shield in the horizontal mask, the first feature having an edge which extends in a substantially vertical direction in the mask, and
using an OPC model to determine dimensions of the first shield.
12. The method of claim 11 , wherein both of the horizontal and vertical masks comprise substantially all of the plurality of features.
13. The method of claim 11 , further comprising:
determining one or more sub-resolution assist features to be disposed parallel to an edge of at least a second one of the plurality of features in the horizontal mask.
14. The method of claim 13 , wherein the sub-resolution assist feature determination is performed prior to the step of determining the shielding.
15. The method of claim 11 , further comprising:
determining biasing to be made to an edge of at least a second one of the plurality of features in the horizontal mask such that the resulting feature accurately reproduces the target pattern.
16. The method of claim 11 , comprising the steps of:
prior to using the OPC model, defining a system pseudo-intensity function, said system pseudo-intensity function approximating the imaging performance of said dipole illumination process, and
including the defined system pseudo-intensity function in the OPC model.
17. The method of claim 16 , wherein the system pseudo-intensity function is determined utilizing one of a calibrated model of the dipole illumination process and a theoretical model of the dipole illumination process.
18. The method of claim 11 , further comprising:
generating the OPC model in accordance with the imaging performance of said dipole illumination process; and
generating a simulated image utilizing the OPC model and the target pattern in the shielding determination step.
19. The method of claim 11 , wherein the shielding determination step further includes:
segmenting the first one of the features into a plurality of first segments; and
determining the dimensions of the corresponding first shield in the horizontal mask for each respective first segment.
20. The method of claim 11 , wherein the shielding determination step further includes:
determining not to apply a shield to at least a first different one of the plurality of features in the target pattern in the horizontal mask, the determination being made using the OPC model.