Claims
- 1. A method comprising:
receiving an indication of an edge fragment in a photolithographic design, said edge fragment having a tag classification defining a contrast of the edge fragment; and applying a resolution enhancement to the edge fragment based on the tag classification to introduce an additional feature in the photolithographic design, said additional feature to change the contrast of the edge fragment.
- 2. The method of claim 1 wherein the edge fragment comprises one of a plurality of edge fragments comprising the photolithographic design and wherein the tag classification comprises one of a plurality of tag classifications, each of said plurality of tag classifications defining a particular contrast, and each of the plurality of edge fragments belonging to one of the plurality of tag classifications.
- 3. The method of claim 2 wherein applying the resolution enhancement comprises:
generating an original contrast signature for the plurality of edge fragments prior to modifying any of the plurality of edge fragments with the resolution enhancement; selecting one of the plurality of tag classifications as a selected tag classification; modifying each edge fragment among the plurality of edge fragments having the selected tag classification with the resolution enhancement; generating a current contrast signature for the plurality of edge fragments after applying the resolution enhancement; and determining a signature change between the original contrast signature and the current contrast signature.
- 4. The method of claim 3 wherein the resolution enhancement comprises one of a plurality of resolution enhancements, and wherein applying the resolution enhancement further comprises:
selecting each of the plurality of resolution enhancements one at a time as a selected resolution enhancement; and for each of the selected resolution enhancements, repeating the modifying, generating a current contrast signature, and determining a signature change.
- 5. The method of claim 3 wherein applying the resolution enhancement further comprises:
selecting each of the plurality of tag classifications one at a time as a selected tag classification; and for each of the selected tag classifications, repeating the modifying, generating a current contrast signature, and determining a signature change.
- 6. The method of claim 3 wherein the signature change comprises one of a plurality of signature changes, each of the plurality of signature changes corresponding to a particular resolution enhancement applied to edge fragments of a particular tag classification, and wherein applying the resolution enhancement further comprises:
for each tag classification, identifying a best signature change, each best signature change corresponding to a best resolution enhancement applied to edge fragments of a best tag classification; prioritizing the best signature changes into a priority order from most contrast improvement to least contrast improvement; and modifying edge fragments corresponding to particular best tag classifications with respective best resolution enhancements in the priority order.
- 7. The method of claim 6 further comprising:
comparing an enhanced contrast to an original contrast for each of the plurality of edge fragments; and removing resolution enhancements from edge fragments for which the enhanced contrast is worse than the original contrast.
- 8. The method of claim 6 further comprising:
comparing an enhanced contrast to an original contrast for each of the plurality of edge fragments; forming a subset of the plurality of edge fragments comprising edge fragments for which the enhanced contrast is worse than the original contrast; generating a new original contrast signature for the subset of edge fragments; and repeating the modifying, generating a current contrast signature, and determining a signature change for each of a new plurality of resolution enhancements and each of the plurality of tag classifications.
- 9. The method of claim 6 wherein a best signature change comprises a largest increase of edge fragments having a contrast over a target contrast and with a smallest resolution enhancement.
- 10. The method of claim 2 wherein receiving an indication of an edge fragment comprises:
fragmenting the photolithographic design into the plurality of edge fragments; identifying a simulation site in each of the plurality of edge fragments; calculating an intensity profile along a perpendicular cut line at each simulation site; determining a maximum slope of the intensity profile, said maximum slope comprising an image log scale (ILS) for a respective edge fragment, and said ILS corresponding to a contrast of the respective edge fragment; tagging each of the plurality of edge fragments with one of the plurality of tag classifications corresponding to a respective ILS; and selecting the edge fragment from among the plurality of edge fragments.
- 11. The method of claim 1 wherein applying the resolution enhancement to the edge fragment comprises:
inserting one or more sub-resolution assist features (SRAFs) in the photolithographic design for the edge fragment.
- 12. The method of claim 4 wherein the plurality of resolution enhancements comprise at least one of a distance for a sub-resolution assist feature (SRAF), a number of SRAFs, and a width of an SRAF.
- 13. The method of claim 1 wherein applying the resolution enhancement to the edge fragment comprises:
assigning the edge fragment to a phase shift mask; and creating a shield for the edge fragment in a trim mask.
- 14. The method of claim 4 wherein the plurality of resolution enhancements comprise at least one extension size for a shield in a trim mask.
- 15. The method of claim 1 wherein applying the resolution enhancement to the edge fragment comprises:
assigning the edge fragment to either a horizontal dipole mask or a vertical dipole mask; and creating a shield for the edge fragment in an opposite mask to which the edge fragment is assigned.
- 16. The method of claim 15 wherein assigning the edge fragment comprises:
determining a first contrast for the edge fragment using a horizontal dipole illumination; determining a second contrast for the edge fragment using a vertical dipole illumination; assigning the edge fragment to the vertical dipole mask if the first contrast is larger; and assigning the edge fragment to the horizontal dipole mask if the second contrast is larger.
- 17. The method of claim 3 wherein the original contrast signature corresponds to a first dipole illumination orientation, and the method further comprises:
repeating the method for a second dipole illumination orientation.
- 18. The method of claim 4 wherein the plurality of resolution enhancements comprise at least one extension size for a shield.
- 19. The method of claim 1 further comprising:
applying model-based optical proximity correction (OPC) to the edge fragment following application of the resolution enhancement.
- 20. The method of claim 3 wherein
generating the original contrast signature comprises:
counting a first set of numbers of edge fragments in each of the plurality of tag classifications prior to modifying any of the plurality of edge fragments; and forming a first histogram of edge fragments versus contrast based on the first set of numbers; and generating the current contrast signature comprises:
determining a new contrast for each of the plurality of edge fragments; retagging each of the plurality of edge fragments to one of the plurality of tag classifications base on respect new contrasts; counting a second set of numbers of edge fragments in each of the plurality of tag classifications after retagging; and forming a second histogram of edge fragments versus contrast based on the second set of numbers.
- 21. The method of claim 3 wherein determining the signature change comprises:
determining a target contrast for the photolithographic design; calculating a first number of edge fragments in the original contrast signature that meet or exceed the target contrast; calculating a second number of edge fragments in the current contrast signature that meet or exceed the target contrast; and calculating the signature change as a difference in the first number and the second number.
- 22. The method of claim 21 wherein the second number is weighted by a weight function to emphasize at least one of large contrast increases and large contrast decreases.
- 23. A method for correcting an integrated device layout, comprising:
reading at least a portion of the layout, said layout portion containing at least one edge fragment; using a simulator to predict a property associated with said edge fragment; storing the predicted property as a tag associated with the edge fragment; and applying a rule for modifying the layout, with the parameters for the application of the rule determined from the values of the tag associated with the edge fragment.
- 24. A method for correcting an integrated circuit layout, comprising:
reading at least a portion of the layout, said layout portion containing at least one edge fragment; using a simulator to predict a contrast of the image that will be formed when the layout is patterned on a photomask and that patterned mask is used in a photolithography exposure system; storing the simulated contrast value as a tag associated with the edge fragment; creating a sub-resolution assist feature (SRAF) in the layout, with the width of the SRAF and its distance from the tagged edge fragment determined based on the contrast value.
- 25. A method for correcting an integrated circuit layout, comprising:
reading at least a portion of the layout, said layout portion containing at least one edge fragment; using a simulator to predict the contrast of the image that will be formed when the layout is patterned on a photomask and that patterned mask is used in a photolithography exposure system; storing the simulated contrast value as a tag associated with the edge fragment; and moving the edge fragment within the layout, with the magnitude and direction of the motion of the edge fragment determined based on the contrast value.
- 26. A machine readable medium having stored thereon machine executable instructions that when executed implement a method comprising:
reading at least a portion of the layout, said layout portion containing at least one edge fragment; using a simulator to predict a property associated with said edge fragment; storing the predicted property as a tag associated with the edge fragment; and applying a rule for modifying the layout, with the parameters for the application of the rule determined from the values of the tag associated with the edge fragment.
- 27. An apparatus comprising:
means for reading at least a portion of the layout, said layout portion containing at least one edge fragment; means for using a simulator to predict a property associated with said edge fragment; means for storing the predicted property as a tag associated with the edge fragment; and means for applying a rule for modifying the layout, with the parameters for the application of the rule determined from the values of the tag associated with the edge fragment.
RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Application No. 60/354,042, entitled “Contrast-Based Assist Feature Optimization,” filed on Jan. 31, 2002, which is hereby fully incorporated by reference, and to U.S. Provisional Application No. 60/360,692, entitled “Contrast-Based RET,” filed on Feb. 28, 2002, which is hereby fully incorporated by reference.
Provisional Applications (2)
|
Number |
Date |
Country |
|
60354042 |
Jan 2002 |
US |
|
60360692 |
Feb 2002 |
US |