Modeling and correcting short-range and long-range effects in E-beam lithography

1. In an electronic design automation (EDA) software tool in a computer, a method for correcting a mask layout to compensate for electron-beam (e-beam) proximity effects during e-beam lithography, the method comprising:

receiving a calibrated e-beam model which includes a long-range component which models long-range electron effects and a short-range component which models short-range electron effects;

receiving a mask layout to be corrected, wherein the mask layout is generated based on a design intent;

the EDA software tool in the computer pre-computing a first resist intensity map based on the long-range component of the calibrated e-beam model and the mask layout; and

the EDA software tool in the computer correcting a target pattern within the mask layout by, iteratively:

computing a second resist intensity map on the target pattern based on the short-range component of the calibrated e-beam model and the target pattern;

obtaining a combined resist intensity map on the target pattern by combining the first resist intensity map and the second resist intensity map; and

adjusting the target pattern based on the combined resist intensity map and the design intent.

2. The method of claim 1 , wherein pre-computing the first resist intensity map based on the long-range component of the calibrated e-beam model and the mask layout involves:

receiving a grid map for the mask layout; creating a dose distribution function over the grid map based on the mask layout; and

convolving the long-range component of the calibrated e-beam model with the dose distribution function over the grid map to obtain the first resist intensity map.

3. The method of claim 2 , wherein creating the dose distribution function involves assigning a dose value based at least on pattern size and a set of rules.

4. The method of claim 2 , wherein the method further comprises storing the first resist intensity map in a lookup table.

5. The method of claim 4 , wherein obtaining the combined resist intensity map on the target pattern involves:

retrieving, from the lookup table, one or more values of the first resist intensity map within a portion of the grid map that covers the target pattern; and

combining the one or more values of the first resist intensity map with the second resist intensity map.

6. The method of claim 1 , wherein computing the second resist intensity map based on the short-range component of the calibrated e-beam model and the target pattern involves:

creating a local dose distribution function on a local grid map associated with the target pattern; and

convolving the short-range component of the calibrated e-beam model with the local dose distribution function to obtain the second resist intensity map for the target patterns.

7. The method of claim 1 , wherein adjusting the target pattern based on the combined resist intensity map and the design intent involves:

applying a resist intensity threshold to the combined resist intensity map to obtain a simulated resist pattern edge position;

comparing the simulated resist pattern edge position with the design intent for the target pattern to determine if the simulated resist pattern edge position substantially matches the design intent; and

if not, adjusting the target pattern based on a difference between the simulated resist pattern edge position and the design intent.

8. The method of claim 7 , wherein adjusting the target pattern involves adjusting a geometric feature on the target pattern.

9. The method of claim 1 , wherein the method further comprises correcting multiple target patterns on the mask layout.

10. The method of claim 1 , wherein the method further comprises performing mask data preparation on the mask layout after the mask layout has been corrected for the e-beam proximity effects.

11. A non-transitory computer-readable storage medium storing instructions that when executed by a computer cause the computer to perform a method for correcting a mask layout to compensate for electron-beam (e-beam) proximity effects during e-beam lithography, the method comprising:

receiving a calibrated e-beam model which includes a long-range component which models long-range electron effects and a short-range component which models short-range electron effects;

receiving a mask layout to be corrected, wherein the mask layout is generated based on a design intent;

pre-computing a first resist intensity map based on the long-range component of the calibrated e-beam model and the mask layout; and

correcting a target pattern within the mask layout by, iteratively:

computing a second resist intensity map on the target pattern based on the short-range component of the calibrated e-beam model and the target pattern;

obtaining a combined resist intensity map on the target pattern by combining the first resist intensity map and the second resist intensity map; and

adjusting the target pattern based on the combined resist intensity map and the design intent.

12. The non-transitory computer-readable storage medium of claim 11 , wherein pre-computing the first resist intensity map based on the long-range component of the calibrated e-beam model and the mask layout involves:

receiving a grid map for the mask layout;

creating a dose distribution function over the grid map based on the mask layout; and

convolving the long-range component of the calibrated e-beam model with the dose distribution function over the grid map to obtain the first resist intensity map.

13. The non-transitory computer-readable storage medium of claim 12 , wherein creating the dose distribution function involves assigning a dose value based at least on pattern size and a set of rules.

14. The non-transitory computer-readable storage medium of claim 12 , wherein the method further comprises storing the first resist intensity map in a lookup table.

15. The non-transitory computer-readable storage medium of claim 14 , wherein obtaining the combined resist intensity map on the target pattern involves:

retrieving, from the lookup table, one or more values of the first resist intensity map within a portion of the grid map that covers the target pattern; and

combining the one or more values of the first resist intensity map with the second resist intensity map.

16. The non-transitory computer-readable storage medium of claim 11 , wherein computing the second resist intensity map based on the short-range component of the calibrated e-beam model and the target pattern involves:

creating a local dose distribution function on a local grid map associated with the target pattern; and

convolving the short-range component of the calibrated e-beam model with the local dose distribution function to obtain the second resist intensity map for the target patterns.

17. The non-transitory computer-readable storage medium of claim 11 , wherein adjusting the target pattern based on the combined resist intensity map and the design intent involves:

applying a resist intensity threshold to the combined resist intensity map to obtain a simulated resist pattern edge position;

comparing the simulated resist pattern edge position with the design intent for the target pattern to determine if the simulated resist pattern edge position substantially matches the design intent; and

if not, adjusting the target pattern based on a difference between the simulated resist pattern edge position and the design intent.

18. The non-transitory computer-readable storage medium of claim 17 , wherein adjusting the target pattern involves adjusting a geometric feature on the target pattern.

19. The non-transitory computer-readable storage medium of claim 11 , wherein the method further comprises correcting multiple target patterns on the mask layout.

20. The non-transitory computer-readable storage medium of claim 11 , wherein the method further comprises performing mask data preparation on the mask layout after the mask layout has been corrected for the e-beam proximity effects.

21. In an electronic design automation (EDA) software tool in a computer, a method for modeling electron-beam (e-beam) proximity effects using an e-beam lithography model, the method comprising:

receiving an uncalibrated e-beam model which includes a long-range component which models long-range electron effects and a short-range component which models short-range electron effects, and a set of model parameters to be calibrated;

receiving a test pattern for calibrating the uncalibrated e-beam model;

the EDA software tool in the computer pre-computing a first intensity map based on the long-range component of the uncalibrated e-beam model and the test layout; and

the EDA software tool in the computer iteratively calibrating the uncalibrated e-beam model by:

computing a second intensity map based on the short-range component of the uncalibrated e-beam model and the test pattern;

obtaining a combined resist intensity map on the target pattern by combining the first resist intensity map and the second resist intensity map; and

adjusting the set of model parameters associated with the uncalibrated e-beam model based on the combined intensity map and the test pattern.

22. The method of claim 21 , wherein adjusting the set of model parameters associated with the uncalibrated e-beam model based on the combined intensity map and the test pattern involves:

applying a resist intensity threshold on the combined resist intensity map to obtain one or more simulated critical dimensions (CDs); and

optimizing the set of model parameters to minimize the differences between the simulated CDs and corresponding measured CDs obtained from the fabricated test pattern on a wafer.

23. A non-transitory computer-readable storage medium storing instructions that when executed by a computer cause the computer to perform a method for modeling electron-beam (e-beam) proximity effects using an e-beam lithography model, the method comprising:

receiving an uncalibrated e-beam model which includes a long-range component which models long-range electron effects and a short-range component which models short-range electron effects, and a set of model parameters to be calibrated;

receiving a test pattern for calibrating the uncalibrated e-beam model;

pre-computing a first intensity map based on the long-range component of the uncalibrated e-beam model and the test layout; and

iteratively calibrating the uncalibrated e-beam model by:

computing a second intensity map based on the short-range component of the uncalibrated e-beam model and the test pattern;

obtaining a combined resist intensity map on the target pattern by combining the first resist intensity map and the second resist intensity map; and

adjusting the set of model parameters associated with the uncalibrated e-beam model based on the combined intensity map and the test pattern.

24. The non-transitory computer-readable storage medium of claim 23 , wherein adjusting the set of model parameters associated with the uncalibrated e-beam model based on the combined intensity map and the test pattern involves:

applying a resist intensity threshold on the combined resist intensity map to obtain one or more simulated critical dimensions (CDs); and

optimizing the set of model parameters to minimize the differences between the simulated CDs and corresponding measured CDs obtained from the fabricated test pattern on a wafer.