Metrology system and method for determining a characteristic of one or more structures on a substrate
Described is a metrology system for determining a characteristic of interest relating to at least one structure on a substrate, and associated method. The metrology system comprises a processor being configured to computationally determine phase and amplitude information from a detected characteristic of scattered radiation having been reflected or scattered by the at least one structure as a result of illumination of said at least one structure with illumination radiation in a measurement acquisition, and use the determined phase and amplitude to determine the characteristic of interest.
1. An apparatus for determining a characteristic of interest relating to at least one structure on a substrate, the apparatus comprising:
an illumination branch comprising a radiation source and configured to direct illumination radiation at the substrate;
a detection branch comprising a detector and configured to detect scattered radiation from the at least one structure on the substrate; and
a processor configured to:
computationally determine phase and amplitude information from an electric field of the scattered radiation in a measurement acquisition, and
computationally re-image the measurement acquisition of the at least one structure to obtain at least one computationally re-imaged image,
wherein computationally re-imaging the measurement acquisition comprises digitally altering an apodization of the measurement acquisition, and
wherein the digitally altering the apodization is based on a characteristic corresponding to the at least one structure.
2. The apparatus of claim 1 , wherein the digitally altering the apodization comprises digitally altering an apodization in the detection branch.
3. The apparatus of claim 2 , wherein the computationally re-imaging the measurement acquisition comprises digitally altering an apodization of the scattered radiation for the measurement acquisition.
4. The apparatus of claim 2 , wherein the digitally altering the apodization comprises applying a non-physical apodizer, wherein the non-physical apodizer is digitally modeled in or near a pupil plane of the detection branch.
5. The apparatus of claim 1 , wherein the digitally altering the apodization comprises digitally altering an apodization in the illumination branch.
6. The apparatus of claim 5 , wherein the computationally re-imaging the measurement acquisition comprises digitally altering an apodization of the illumination radiation for the measurement acquisition.
7. The apparatus of claim 5 , wherein the digitally altering the apodization comprises applying a non-physical apodizer, wherein the non-physical apodizer is digitally modeled in or near a pupil plane of the illumination branch.
8. The apparatus of claim 1 , wherein the digitally altering the apodization comprises dynamically tuning the apodization.
9. The apparatus of claim 8 , wherein the dynamically tuning the apodization is based on the characteristic of interest.
10. The apparatus of claim 8 , wherein the dynamically tuning the apodization is based on a point spread function of the apparatus.
11. A method of determining a characteristic of interest relating to at least one structure on a substrate, the method comprising:
computationally determining phase and amplitude information from an electric field of scattered radiation in a measurement acquisition; and
computationally re-imaging the measurement acquisition of the at least one structure to obtain at least one computationally re-imaged image,
wherein the computationally re-imaging the measurement acquisition comprises digitally altering an apodization of the measurement acquisition, and
wherein the digitally altering the apodization is based on a characteristic corresponding to the at least one structure.
12. The method of claim 11 , wherein the digitally altering the apodization comprises digitally altering an apodization in a detection branch configured to detect the scattered radiation.
13. The method of claim 12 , wherein the computationally re-imaging the measurement acquisition comprises digitally altering an apodization of the scattered radiation for the measurement acquisition.
14. The method of claim 12 , wherein the digitally altering the apodization comprises applying a non-physical apodizer, wherein the non-physical apodizer is digitally modeled in or near a pupil plane of the detection branch.
15. The method of claim 11 , wherein the digitally altering the apodization comprises digitally altering an apodization in an illumination branch configured to direct illumination radiation at the substrate.
16. The method of claim 15 , wherein the computationally re-imaging the measurement acquisition comprises digitally altering an apodization of the illumination radiation for the measurement acquisition.
17. The method of claim 15 , wherein the digitally altering the apodization comprises applying a non-physical apodizer, wherein the non-physical apodizer is digitally modeled in or near a pupil plane of the illumination branch.
18. The method of claim 11 , wherein the digitally altering the apodization comprises dynamically tuning the apodization.
19. The method of claim 18 , wherein the dynamically tuning the apodization is based on the characteristic of interest.
20. A non-transitory computer program product comprising machine-readable instructions for causing a processor to cause performance of the method of claim 11 .