Method and apparatus to determine a patterning process parameter

1. A metrology target comprising:

a first structure arranged to be created by a first patterning process; and

a second structure arranged to be created by a second patterning process, wherein the first structure and/or second structure is not used to create a functional aspect of a device pattern,

wherein the first and second structures together form one or more instances of a unit cell, the unit cell having geometric symmetry at a nominal physical configuration and wherein the unit cell has a feature that causes, at a different physical configuration than the nominal physical configuration due to a relative shift in pattern placement in the first patterning process, the second patterning process and/or another patterning process, an asymmetry in the unit cell, and

wherein the first structure is arranged to have a removed portion caused by the second patterning process or the other patterning process and/or the second structure is arranged to have a removed portion caused by the other patterning process.

2. The target of claim 1 , wherein the first structure comprises a structure of a first dimension and/or material and the second structure comprises a structure of a second dimension, or material, wherein the feature comprises the first dimension and/or material being different than the second dimension and/or material.

3. The target of claim 1 , wherein the first structure comprises closed curve structures and the second structure comprises closed curve structures.

4. The target of claim 1 , wherein the structures are arranged in a first array in a direction substantially perpendicular to a direction in which the structures are arranged in a second array or in which the structures are arranged in a third array of structures.

5. A computer program product comprising a computer non-transitory readable medium having a computer-readable data structure therein, the data structure having information for manufacturing the metrology target of claim 1 .

6. One or more reticles comprising one or more patterns configured to produce the structures of the metrology target of claim 1 .

7. The target of claim 1 , wherein the first structure comprises structures arranged in an array in a first direction and at least one such structure comprises a plurality of sub-structures separated by voids arranged along a second direction substantially perpendicular to the first direction and/or the second structure comprises structures arranged in an array in the first direction and at least one such structure comprises a plurality of sub-structures separated by voids arranged along the second direction substantially perpendicular to the first direction, wherein the feature comprises the voids of the first structure and/or the second structure.

8. The target of claim 7 , wherein the voids of the first structure and/or the second structure are produced using a different patterning process than the first and second patterning processes.

9. The target of claim 7 , wherein e first structure comprises the voids and the second structure comprises the voids.

10. The target of claim 9 , wherein the voids of the first structure have a different pitch than the voids of the second structure.

11. The target of claim 9 , wherein at least one void of the first structure lines up with at least one void of the second structure at the nominal physical configuration.

12. A method comprising:

measuring radiation redirected by the metrology target of claim 1 transferred to a substrate using a patterning process; and

determining a value of a parameter of the patterning process based on the measured radiation.

13. The method of claim 12 , wherein the parameter comprises overlay and/or edge placement error.

14. A computer program product comprising a computer non transitory readable medium having instructions therein, the instructions when executed by a computer implementing the method of claim 12 .

15. A metrology apparatus for measuring an object of a patterning process, the metrology apparatus comprising an optical system configured to supply radiation and comprising the computer program product of claim 14 .

16. A method comprising:

creating a first structure for a metrology target, the first structure to be created by a first patterning process that creates a corresponding device feature of a device;

creating a second structure for the metrology target, the second structure to be created by a second patterning process that creates a further corresponding device feature of device, wherein the first and second structures together form one or more instances of a unit cell, the unit cell having geometric symmetry at a nominal physical configuration; and

introducing a feature in the metrology target that causes, at a different physical configuration than the nominal physical configuration due to a relative shift in location of device features in the device from an expected location of the device features in the device, an asymmetry in the unit cell,

wherein the first structure has a removed portion caused by the second patterning process or by another patterning process and/or the second structure has a removed portion caused by the other patterning process.

17. The method of claim 16 , wherein a feature of the first structure has a substantially same dimension and/or pitch as the corresponding feature of the device and/or a feature of the second structure has a substantially same dimension and/or pitch as the corresponding feature of the device.

18. The method of claim 16 , wherein the feature in the metrology target causes a first type of asymmetry in the unit cell for a relative shift in a first direction and causes a second different type of asymmetry in the unit cell for a relative shift in a second different direction.

19. The method of claim 16 , further comprising evaluating one or more selected from: printability of the metrology target, detectability of the metrology target, robustness of the metrology target to process variations, and/or matching of the metrology target to a device pattern.

20. The method of claim 19 , comprising iteratively evaluating matching of the metrology target to a device pattern and detectability of the metrology target.

21. A computer program product comprising a computer non-transitory readable medium having instructions therein, the instructions when executed by a computer configured to cause the computer to at least cause:

creation of a first structure for a metrology target, the first structure to be created by a first patterning process that creates a corresponding device feature of a device;

creation of a second structure for the metrology target, the second structure to be created by a second patterning process that creates a further corresponding device feature of device, wherein the first and second structures together form one or more instances of a unit cell, the unit cell having geometric symmetry at a nominal physical configuration; and

introduction of a feature in the metrology target that causes, at a different physical configuration than the nominal physical configuration due to a relative shift in location of device features in the device from an expected location of the device features in the device, an asymmetry in the unit cell,

wherein the first structure is arranged to have a removed portion caused by the second patterning process or by another patterning process and/or the second structure is arranged to have a removed portion caused by the other patterning process.