Scatterometry overlay metrology targets and methods
Scatterometry overlay (SCOL) targets as well as design, production and measurement methods thereof are provided. The SCOL targets have several periodic structures at different measurement directions which share some of their structural target elements or parts thereof. An array of common elements may have symmetry directions which are parallel to the measurement directions and thus enable compacting the targets or alternatively increasing the area use efficiency of the targets. Various configurations enable high flexibility in arranging the number of layers in the target and measurement directions, and carrying out respective overlay measurements among the layers.
1. A scatterometry overlay (SCOL) target comprising:
a periodic structure including a plurality of target elements configured for measurements in a first measurement direction; and
a plurality of pivoting elements disposed between the plurality of target elements,
wherein:
the SCOL target is embodied in a first layer; and
the plurality of pivoting elements are configured to align with a plurality of pivoting elements in a second SCOL target embodied in a second layer when the SCOL target and the second SCOL target are angularly offset relative to each other.
2. The SCOL target of claim 1 , wherein the target elements are segmented.
3. The SCOL target of claim 1 , wherein the pivoting elements have symmetry which correspond to the measurement direction.
4. The SCOL target of claim 1 , wherein the pivoting elements are circular.
5. The SCOL target of claim 1 , wherein the SCOL target and the second SCOL target are angularly offset relative to each other by one of: 30°, 45°, 60°, and 90°.
6. The SCOL target of claim 1 , wherein the plurality of pivoting elements are further configured to align with a plurality of pivoting elements in a third SCOL target when the SCOL target, the second SCOL target, and the third SCOL target are angularly offset relative to each other.
7. The SCOL target of claim 1 , wherein at least some of the target elements are segmented.
8. The SCOL target of claim 1 , wherein the periodic structure and plurality of pivoting elements are configured to generate distinct first order diffraction patterns at a pupil plane of a specified measurement tool.
9. A scatterometry overlay (SCOL) target comprising:
a first periodic structure including a plurality of target elements configured for measurements in a first measurement direction;
a second periodic structure including a plurality of target elements configured for measurement in a second direction; and
a plurality of pivoting elements disposed between the plurality of target elements,
wherein:
the SCOL target is embodied in a first layer; and
the plurality of pivoting elements are configured to align with a plurality of pivoting elements in a second SCOL target embodied in a second layer when the SCOL target and the second SCOL target are angularly offset relative to each other.
10. The SCOL target of claim 9 , wherein the first measurement direction and second measurement direction are respectively at any of: 30°, 45°, 60°, and 90°.
11. The SCOL target of claim 9 , further comprising a third periodic structure including a plurality of target elements configured for measurement in a third direction.
12. The SCOL target of claim 9 , wherein the pivoting elements have symmetry directions which correspond to the measurement directions.
13. The SCOL target of claim 9 , wherein the pivoting elements are circular.
14. The SCOL target of claim 9 , wherein at least one of the target elements are segmented.
15. The SCOL target of claim 9 , wherein the first periodic structure, second periodic structure, and plurality pivoting elements are configured to generate distinct first order diffraction patterns at a pupil plane of a specified measurement tool.
16. A method for aligning two or more periodic structures in at least one scatterometry overlay (SCOL) target comprising aligning a first plurality of pivoting elements disposed between target elements in a first periodic structure having a first measurement direction with a second plurality of pivoting elements disposed between target elements in a second periodic structure having a second measurement direction,
wherein:
the first plurality of pivoting elements and second plurality of pivoting elements are configured to align when the first periodic structure and second periodic structure are angularly offset.
17. The method of claim 16 , wherein the first plurality of pivoting elements and first plurality of pivoting elements have symmetry directions which are parallel to the measurement directions.
18. The method of claim 16 , wherein the pivoting elements are segmented periodic structures.
19. The method of claim 16 , wherein the first periodic structure and second periodic structure are disposed in separate target layers.
20. The method of claim 16 , further comprising generating distinct first order diffraction patterns at a pupil plane of a specified measurement tool.
21. The method of claim 16 , further comprising generating a target design file of the SCOL target.
22. The method of claim 16 , further comprising producing the SCOL target.
23. A SCOL target produced according to the method of claim 22 .
24. The method of claim 16 , further comprising producing the pivoting elements by multiple exposures.
25. The method of claim 16 , further comprising measuring one or more diffraction patterns of the SCOL target.
26. A computer program product comprising a computer readable storage medium having a computer readable program embodied therewith, the computer readable program configured to carry out the method of claim 16 .