Optimizing an optical parametric model for structural analysis using optical critical dimension (OCD) metrology

1. A method of optimizing optical parametric models for structural analysis using optical critical dimension (OCD) metrology with an optical metrology system, the optical metrology system including a processor coupled with a memory and an optical metrology tool, the method performed by the optical metrology system comprising:

measuring values of far field diffraction signals for a structure, the measurement being performed by the optical metrology tool of the optical metrology system;

determining a first optical model fit for a parameter of the structure, the first optical model fit based on a domain of quantities for a first model of the structure;

determining a first near optical field response for a first quantity of the domain of quantities and a second near optical field response for a second, different quantity of the domain of quantities, wherein the domain of quantities is a domain of wavelengths, the first quantity being a first wavelength and the second quantity being a second wavelength, and wherein determining the first and second near optical field responses comprises:

identifying a region of low correlation of the first optical model fit with measured values for the structure, and

selecting the first and second wavelengths from the region of low correlation of the first optical model fit;

comparing the first and second near optical field responses to locate a common region of high near optical field intensity for the parameter of the structure;

modifying the first model of the structure based at least in part on the common region of high near optical field intensity to provide a second, different model of the structure; and determining a second, different optical model fit for the parameter of the structure based on the second model of the structure.

2. The method of claim 1 , wherein determining the first optical model fit for the parameter of the structure comprises determining the first optical model fit for a shape of the structure or for a film thickness within the structure.

3. The method of claim 1 , wherein selecting the first and second wavelengths from the region of low correlation of the first optical model fit comprises selecting an angle of incidence for the first wavelength and using the angle of incidence for the second wavelength.

4. The method of claim 1 , wherein determining the first and second near optical field responses comprises generating a pair of contour plots, and wherein comparing the first and second near optical field responses comprises comparing the pair of contour plots.

5. The method of claim 1 , further comprising: determining a third, different optical model fit for the parameter of the structure based on a third model of the structure.

6. The method of claim 1 , further comprising:

computing a near optical field for the structure.

7. A method of optimizing optical parametric models for three-dimensional structural analysis using optical critical dimension (OCD) metrology with an optical metrology system, the optical metrology system including a processor coupled with a memory and an optical metrology tool, the method performed by the optical metrology system comprising:

measuring values of far field diffraction signals for a three-dimensional structure, the measurement being performed by the optical metrology tool of the optical metrology system;

determining a first optical model fit for a parameter of the three-dimensional structure, the first optical model fit based on a domain of wavelengths for a first model of the three-dimensional structure;

determining a first near optical field response for a first wavelength of the domain of wavelengths at a plurality of azimuth angles;

determining a second near optical field response for a second, different wavelength of the domain of wavelengths at one of the plurality of azimuth angles,

wherein determining the first and second near optical field responses comprises:

identifying a region of low correlation of the first optical model fit with measured values for the structure, and

selecting the first and second wavelengths from the region of low correlation of the first optical model fit;

comparing the first and second near optical field responses to locate a common region of high near optical field intensity for the parameter of the three-dimensional structure;

modifying the first model of the three-dimensional structure based at least in part on the common region of high near optical field intensity to provide a second, different model of the three-dimensional structure; and determining a second, different optical model fit for the parameter of the three-dimensional structure based on the second model of the three-dimensional structure.

8. The method of claim 7 , wherein determining the first optical model fit for the parameter of the three-dimensional structure comprises determining the first optical model fit for a shape of the three-dimensional structure or for a film thickness within the three-dimensional structure.

9. The method of claim 7 , wherein selecting the first and second wavelengths from the region of low correlation of the first optical model fit comprises selecting an angle of incidence for the first wavelength and using the angle of incidence for the second wavelength.

10. The method of claim 7 , wherein determining the first and second near optical field responses comprises generating a pair of contour plots, and wherein comparing the first and second near optical field responses comprises comparing the pair of contour plots.

11. The method of claim 7 , further comprising: determining a third, different optical model fit for the parameter of the three-dimensional structure based on a third model of the three-dimensional structure.

12. The method of claim 7 , further comprising:

computing a near optical field for the three-dimensional structure.

13. A non-transitory machine-accessible storage medium having instructions stored thereon which cause a data processing system to perform a method of optimizing optical parametric models for structural analysis using optical critical dimension (OCD) metrology with an optical metrology system, the optical metrology system including a processor coupled with a memory and an optical metrology tool, the method comprising:

measuring values of far field diffraction signals for a structure with the optical metrology tool of the optical metrology system;

determining a first optical model fit for a parameter of the structure, the first optical model fit based on a domain of quantities for a first model of the structure;

determining a first near optical field response for a first quantity of the domain of quantities and a second near optical field response for a second, different quantity of the domain of quantities, wherein the domain of quantities is the first quantity being a first wavelength and the second quantity being a second wavelength, and wherein determining the first and second near optical field responses comprises:

identifying a region of low correlation of the first optical model fit with measured values for the structure, and

selecting the first and second wavelengths from the region of low correlation of the first optical model fit; comparing the first and second near optical field responses to locate a common region of high near optical field intensity for the parameter of the structure;

modifying the first model of the structure based at least in part on the common region of high near optical field intensity to provide a second, different model of the structure; and determining a second, different optical model fit for the parameter of the structure based on the second model of the structure.

14. The storage medium as in claim 13 , wherein determining the first optical model fit for the parameter of the structure comprises determining the first optical model fit for a shape of the structure or for a film thickness within the structure.

15. The storage medium as in claim 13 , wherein selecting the first and second wavelengths from the region of low correlation of the first optical model fit comprises selecting an angle of incidence for the first wavelength and using the angle of incidence for the second wavelength.

16. The storage medium as in claim 13 , wherein determining the first and second near optical field responses comprises generating a pair of contour plots, and wherein comparing the first and second near optical field responses comprises comparing the pair of contour plots.

17. The storage medium as in claim 13 , the method further comprising: determining a third, different optical model fit for the parameter of the structure based on a third model of the structure.

18. The storage medium as in claim 13 , wherein the method further comprises: computing a near optical field for the structure.

19. A non-transitory machine-accessible storage medium having instructions stored thereon which cause a data processing system to perform a method of optimizing optical parametric models for three-dimensional structural analysis using optical critical dimension (OCD) metrology with an optical metrology system, the method comprising:

measuring values of far field diffraction signals for a three-dimensional structure with an optical metrology tool of the optical metrology system;

determining a first optical model fit for a parameter of the three-dimensional structure, the first optical model fit based on a domain of wavelengths for a first model of the three-dimensional structure;

determining a first near optical field response for a first wavelength of the domain of wavelengths at a plurality of azimuth angles;

determining a second near optical field response for a second, different wavelength of the domain of wavelengths at one of the plurality of azimuth angles,

wherein determining the first and second near optical field responses comprises:

identifying a region of low correlation of the first optical model fit with measured values for the three-dimensional structure, and

selecting the first and second wavelengths from the region of low correlation of the first optical model fit;

comparing the first and second near optical field responses to locate a common region of high near optical field intensity for the parameter of the three-dimensional structure;

modifying the first model of the three-dimensional structure based at least in part on the common region of high near optical field intensity to provide a second, different model of the three-dimensional structure; and determining a second, different optical model fit for the parameter of the three-dimensional structure based on the second model of the three-dimensional structure.

20. The storage medium as in claim 17 , wherein determining the first optical model fit for the parameter of the three-dimensional structure comprises determining the first optical model fit for a shape of the three-dimensional structure or for a film thickness within the three-dimensional structure.

21. The storage medium as in claim 19 , wherein selecting the first and second wavelengths from the region of low correlation of the first optical model fit comprises selecting an angle of incidence for the first wavelength and using the angle of incidence for the second wavelength.

22. The storage medium as in claim 19 , wherein determining the first and second near optical field responses comprises generating a pair of contour plots, and wherein comparing the first and second near optical field responses comprises comparing the pair of contour plots.

23. The storage medium as in claim 19 , the method further comprising: determining a third, different optical model fit for the parameter of the three-dimensional structure based on a third model of the three-dimensional structure.

24. The storage medium as in claim 19 , wherein the method further comprises: computing a near optical field for the three-dimensional structure.