Detection aided two-stage phase unwrapping on pattern wafer geometry measurement
Systems and methods for unwrapping a phase map are disclosed. Such systems and methods may include receiving a wrapped phase map associated with an interferometric measurement of a sample including patterned features; removing a tilt from the wrapped phase map; generating a background; detecting features in the wrapped phase, the features in the wrapped phase map corresponding to least some of the patterned features of the sample; replacing phases of the features with the background at corresponding locations in the wrapped phase map; unwrapping the modified wrapped phase map using a global phase-unwrapping; applying local phase-unwrapping to restore the phases of the features; and reapplying the tilt to generate an output unwrapped phase map.
1. A metrology system comprising:
a controller communicatively coupled to an interferometry tool, the controller including one or more processors configured to execute program instructions causing the one or more processors to:
receive a wrapped phase map associated with an interferometric measurement of a sample including patterned features;
remove a tilt from the wrapped phase map;
generate a background;
detect features in the wrapped phase map, wherein the features in the wrapped phase map correspond to at least some of the patterned features of the sample;
replace phases of the features with the background at corresponding locations in the wrapped phase map to generate a modified wrapped phase map;
unwrap the modified wrapped phase map using a global phase-unwrapping to generate a temporary unwrapped phase map;
apply local phase-unwrapping to restore the phases of the features of the temporary unwrapped phase map at the corresponding locations; and
reapply the tilt to the temporary unwrapped phase map to generate an output unwrapped phase map.
2. The metrology system of claim 1 , wherein the remove the tilt from the wrapped phase map comprises:
extracting a surface profile measurement from the wrapped phase map; and removing a linear signal from the surface profile measurement.
3. The metrology system of claim 1 , wherein the remove the tilt from the wrapped phase map comprises:
extracting a thickness measurement from the wrapped phase map; and
removing a linear signal from the thickness measurement.
4. The metrology system of claim 1 , wherein the background is limited to spatial frequencies below a selected threshold, wherein the selected threshold is selected to exclude the features.
5. The metrology system of claim 1 , wherein the background is based on prior knowledge of the sample.
6. The metrology system of claim 1 , wherein the detect the features in the wrapped phase map comprises:
detecting step-wise phase changes in the wrapped phase map greater than a selected threshold.
7. The metrology system of claim 1 , wherein the apply the local phase-unwrapping to restore the phases of the features comprises replacing the background at the corresponding locations with the features and unwrapping the features.
8. A metrology system comprising:
an interferometry tool; and
a controller communicatively coupled with the interferometry tool, the controller including one or more processors configured to execute program instructions causing the one or more processors to:
receive a wrapped phase map from the interferometry tool, wherein the wrapped phase map corresponds to an interferometric measurement of a sample including patterned features;
remove a tilt from the wrapped phase map;
generate a background;
detect features in the wrapped phase map;
replace phases of the features with the background at corresponding locations in the wrapped phase map to generate a modified wrapped phase map;
unwrap the modified wrapped phase map using a global phase-unwrapping to generate a temporary unwrapped phase map;
apply local phase-unwrapping to restore the phases of the features of the temporary unwrapped phase map at the corresponding locations; and
reapply the tilt to the temporary unwrapped phase map to generate an output unwrapped phase map.
9. The metrology system of claim 8 , wherein the interferometry tool generates the wrapped phase map based on interference of a reference beam with light reflected from a surface of the sample.
10. The metrology system of claim 8 , wherein the remove the tilt from the wrapped phase map comprises:
extracting a surface profile measurement from the wrapped phase map; and
removing a linear signal from the surface profile measurement.
11. The metrology system of claim 8 , wherein the remove the tilt from the wrapped phase map comprises:
extracting a surface slope measurement from the wrapped phase map; and
removing a linear signal from the surface slope measurement.
12. The metrology system of claim 8 , wherein the remove the tilt from the wrapped phase map comprises:
extracting a thickness measurement from the wrapped phase map; and
removing a linear signal from the thickness measurement.
13. The metrology system of claim 8 , wherein the background is limited to spatial frequencies below a selected threshold, wherein the selected threshold is selected to exclude the features.
14. The metrology system of claim 8 , wherein the background is based on prior knowledge of the sample.
15. The metrology system of claim 8 , wherein the detect the features in the wrapped phase map comprises:
detecting step-wise phase changes in the wrapped phase map greater than a selected threshold.
16. The metrology system of claim 8 , wherein the apply the local phase-unwrapping to restore the phases of the features comprises replacing the background at the corresponding locations with the features and unwrapping the features.
17. A metrology method comprising:
receiving a wrapped phase map associated with an interferometric measurement of a sample including patterned features;
removing a tilt from the wrapped phase map;
generating a background;
detecting features in the wrapped phase, wherein the features in the wrapped phase map correspond to at least some of the patterned features of the sample;
replacing phases of the features with the background at corresponding locations in the wrapped phase map to generate a modified wrapped phase map;
unwrapping the modified wrapped phase map using a global phase-unwrapping to generate a temporary unwrapped phase map;
applying local phase-unwrapping to restore the phases of the features of the temporary unwrapped phase map at the corresponding locations; and
reapplying the tilt to the temporary unwrapped phase map to generate an output unwrapped phase map.
18. The metrology method of claim 17 , wherein the removing the tilt from the wrapped phase map comprises:
extracting a surface profile measurement from the wrapped phase map; and
removing a linear signal from the surface profile measurement.
19. The metrology method of claim 17 , wherein the removing the tilt from the wrapped phase map comprises:
extracting a surface slope measurement from the wrapped phase map; and
removing a linear signal from the surface slope measurement.
20. The metrology method of claim 17 , wherein the removing the tilt from the wrapped phase map comprises:
extracting a thickness measurement from the wrapped phase map; and
removing a linear signal from the thickness measurement.
21. The metrology method of claim 17 , wherein the background is limited to spatial frequencies below a selected threshold, wherein the selected threshold is selected to exclude the features.
22. The metrology method of claim 17 , wherein the background is based on prior knowledge of the sample.
23. The metrology method of claim 17 , wherein the detecting the features in the wrapped phase map comprises:
detecting step-wise phase changes in the wrapped phase map greater than a selected threshold.
24. The metrology method of claim 17 , wherein the applying the local phase-unwrapping to restore the phases of the features comprises replacing the background at the corresponding locations with the features and unwrapping the features.