Electron-beam image reconstruction

1. A computer-implemented method for calculating an image, the method comprising:

receiving a first electron-beam (EB) image of a pattern, wherein the first EB image is associated with an EB system;

generating a multi-valued representation of the first EB image; and

calculating, using the computer, a second EB image based on the multi-valued representation of the first EB image and a model of an electro-optical transfer function associated with the EB system, wherein the second EB image is calculated using an inverse calculation in which the multi-valued representation of the first EB image is at an image plane in the model of the electro-optical transfer function and the second EB image is at an object plane in the model of the electro-optical transfer function; and

wherein the inverse calculation restores edges in the first EB image.

2. The method of claim 1 , wherein the multi-valued representation of the first EB image includes a level-set function.

3. The method of claim 1 , wherein the inverse calculation deconvolves the electro-optical transfer function from the multi-valued representation of the first EB image, thereby filtering noise.

4. The method of claim 1 , wherein the model of the electro-optical transfer function has an analytical derivative.

5. The method of claim 4 , wherein the analytical derivative is represented by a closed-form expression.

6. The method of claim 1 , wherein the model of the electro-optical transfer function corresponds to an EB-size distribution, a secondary-electron bulk-generation distribution, a distribution associated with shadowing effects in the pattern, a background EB intensity and a foreground EB intensity.

7. The method of claim 6 , wherein the model of the electro-optical transfer function further corresponds to an overshoot amplitude and an undershoot amplitude.

8. The method of claim 1 , wherein the pattern includes one of: a photo-mask and a wafer pattern.

9. The method of claim 1 , wherein the method further comprises rendering a third EB image based on the second EB image.

10. The method of claim 1 , wherein the pattern corresponds to a target pattern; and

wherein the second EB image is further based on the target pattern.

11. The method of claim 1 , wherein the method further comprises identifying a feature in the second EB image.

12. The method of claim 11 , wherein the feature includes a critical dimension in the pattern.

13. The method of claim 12 , wherein the pattern corresponds to a target pattern; and

wherein the feature corresponds to a difference between the pattern and the target pattern.

14. The method of claim 11 , wherein the method further comprises determining an acceptance condition of the pattern in accordance with the feature.

15. A computer-program product for use in conjunction with a computer system, the computer-program product comprising a computer-readable storage medium and a computer-program mechanism embedded therein to calculate an image, the computer-program mechanism including:

instructions for receiving a first EB image of a pattern, wherein the first EB image is associated with an EB system;

instructions for generating a multi-valued representation of the first EB image; and

instructions for calculating a second EB image based on the multi-valued representation of the first EB image and a model of an electro-optical transfer function associated with the EB system, wherein the second EB image is calculated using an inverse calculation in which the multi-valued representation of the first EB image is at an image plane in the model of the electro-optical transfer function and the second EB image is at an object plane in the model of the electro-optical transfer function; and

wherein the inverse calculation restores edges in the first EB image.

16. The computer-program product of claim 15 , wherein the inverse calculation deconvolves the electro-optical transfer function from the multi-valued representation of the first EB image, thereby filtering noise.

17. The computer-program product of claim 15 , wherein the model of the electro-optical transfer function has an analytical derivative.

18. The computer-program product of claim 15 , wherein the pattern corresponds to a target pattern; and

wherein the second EB image is further based on the target pattern.

19. The computer-program product of claim 15 , wherein the computer-program mechanism includes instructions for identifying a feature in the second EB image.

20. A computer system, comprising:

at least one processor;

at least one memory; and

at least one program module, the program module stored in the memory and configured to be executed by the processor to calculate an image, the program module including:

instructions for receiving a first EB image of a pattern, wherein the first EB image is associated with an EB system;

instructions for generating a multi-valued representation of the first EB image; and

instructions for calculating a second EB image based on the multi-valued representation of the first EB image and a model of an electro-optical transfer function associated with the EB system, wherein the second EB image is calculated using an inverse calculation in which the multi-valued representation of the first EB image is at an image plane in the model of the electro-optical transfer function and the second EB image is at an object plane in the model of the electro-optical transfer function; and

wherein the inverse calculation restores edges in the first EB image.