Metrology method and associated computer product
Disclosed is a method comprising measuring radiation reflected from a metrology target and decomposing the measured radiation in components, for example Fourier components or spatial components. Further, there is disclosed a recipe selection method which provides an algorithm to select a parameter of the metrology apparatus based on re-calculated dependencies of 5 the measured radiation based on single components.
1. A method for determining overlay at plural heights of a non-flat, buried metrology target having another metrology target disposed thereon, the method comprising:
measuring radiation reflected by metrology targets;
inferring data of a parameter of the buried metrology target from the measurement as a function of the parameter verses wavelength, which yields a periodical variation of the parameter; and
decomposing the periodical variation of the parameter to isolate the plural heights of the buried metrology target as a function of amplitude verses wavelength.
2. The method of claim 1 , wherein the decomposing comprises performing a Fourier transform, a wavelet transform, or a Laplace transform.
3. The method of claim 1 , wherein the decomposing to isolate the plural heights of the buried metrology target comprises determining a top and a bottom of the buried metrology target.
4. The method of claim 1 , wherein the decomposing to isolate the plural heights of the buried metrology target comprises determining a tilt of the buried metrology target.
5. The method of claim 1 , wherein the decomposing to isolate the plural heights of the buried metrology target comprises determining an overlay between the metrology targets.
6. The method of claim 1 , wherein the decomposing to isolate the plural heights of the buried metrology target comprises determining an intermediate height of the buried metrology target.
7. The method of claim 1 , wherein the decomposing comprises filtering.
8. The method of claim 7 , wherein the filtering comprises using an upper and a lower value that defines an individual component.
9. The method of claim 7 , wherein the filtering comprises using an upper and a lower value that defines plural components.
10. The method of claim 7 , further comprising varying the filtering.
11. A metrology system for determining overlay at plural heights of a non-flat, buried metrology target having another metrology target disposed thereon, the metrology system comprising:
an illumination source configured to direct a beam of radiation at a metrology target;
a detector configured to detect scattered radiation from the target; and
a controller configured to:
measure the detected radiation;
infer data of a parameter of the buried metrology target from the measurement as a function of the parameter verses wavelength, which yields a periodical variation of the parameter; and
decompose the periodical variation of the parameter to isolate the plural heights of the buried metrology target as a function of amplitude verses wavelength.
12. The metrology system of claim 11 , wherein the decomposing comprises performing a Fourier transform, a wavelet transform, or a Laplace transform.
13. The metrology system of claim 11 , wherein the decomposing to isolate the plural heights of the buried metrology target comprises determining a top and a bottom of the buried metrology target.
14. The metrology system of claim 11 , wherein the decomposing to isolate the plural heights of the buried metrology target comprises determining a tilt of the buried metrology target.
15. The metrology system of claim 11 , wherein the decomposing to isolate the plural heights of the buried metrology target comprises determining an overlay between the metrology targets.
16. The metrology system of claim 11 , wherein the decomposing to isolate the plural heights of the buried metrology target comprises determining an intermediate height of the buried metrology target.
17. The metrology system of claim 11 , wherein the decomposing comprises filtering.
18. The metrology system of claim 17 , wherein the filtering comprises using an upper and a lower value that defines an individual component.
19. The metrology system of claim 17 , wherein the filtering comprises using an upper and a lower value that defines plural components.
20. A lithography system comprising the metrology system of claim 11 .