System and method for suppression of tool induced shift in scanning overlay metrology

1 . An overlay metrology system comprising:

a controller comprising one or more processors configured to execute program instructions causing the one or more processors to execute a metrology recipe by:

receiving first detection signals from one or more detectors from a first cell of two or more cells of an overlay target;

receiving second detection signals from the one or more detectors from a second cell of the two or more cells;

generating an overlay measurement of the first cell based on the first detection signals;

generating an overlay measurement of the second cell based on the second detection signals;

generating an overlay measurement associated with the overlay target based on a value indicative of an average of the overlay measurement of the first cell and the overlay measurement of the second cell,

wherein the first cell is defined as a first cell type characterized by an order of structures in layers, the order characterized by pitches of the structures in the layers, wherein the second cell is defined as a second cell type characterized by a second order of second structures in the layers, the second order characterized by second pitches of the second structures in the layers,

wherein the first cell includes a first layer of structures having a first pitch and a second layer having a second pitch, wherein the second cell includes a first layer of structures having the second pitch and a second layer having the first pitch such that the pitches of structures within layers of the second cell are reversed relative to the first cell, wherein the order of structures in layers of the first cell type and second cell type are configured to suppress tool induced shift (TIS) error by averaging overlay measurements of cells with reversed pitch orders,

wherein the receiving the first detection signals and the receiving the second detection signals comprises receiving time-varying interference signals as the overlay target is scanned while the overlay target is in motion;

extracting at least one of intensity or phase information associated with the received time-varying interference signals using a phase locking technique; and

determining an overlay error between the first and second layers of the overlay target based on at least one of intensity or phase information.

2 . The overlay metrology system of claim 1 , wherein the controller is configured to execute the program instructions causing the one or more processors to execute the metrology recipe by: determining a tool induced shift (TIS) error of the overlay target based on a difference between the overlay measurement of the first cell and the overlay measurement of the second cell.

3 . The overlay metrology system of claim 1 , wherein the one or more detectors comprise at least one detector located in a pupil plane.

4 . The overlay metrology system of claim 1 , wherein the one or more detectors comprise at least one detector located in a field plane.

5 . The overlay metrology system of claim 1 , wherein the one or more detectors comprise at least one diode array sensor.

6 . The overlay metrology system of claim 1 , wherein the one or more detectors comprise at least one charge-coupled device (CCD) sensor.

7 . The overlay metrology system of claim 1 , wherein an illumination pupil plane distribution of an illumination beam is circular.

8 . The overlay metrology system of claim 1 , wherein an illumination pupil plane distribution of an illumination beam is annular.

9 . The overlay metrology system of claim 1 , wherein the structures of the two or more cells of the overlay target are at 45 degree angles relative to a scan direction.

10 . The overlay metrology system of claim 9 , wherein the two or more cells of the overlay target comprise waffle cells with periodic structures in a same layer at plus 45 degrees and minus 45 degrees from the scan direction such that a waffle pattern is formed.

11 . The overlay metrology system of claim 9 , wherein the two or more cells comprise four cells in a row, wherein the four cells in the row comprise two first cell types adjacent to each other with the structures at a positive diagonal angle relative to the scan direction and two second cell types adjacent to each other with the structures at a negative diagonal angle relative to the scan direction.

12 . The overlay metrology system of claim 9 , wherein the two or more cells comprise at least three cells in a row and a fourth cell adjacent to a third cell of the at least three cells, wherein a first and second cell of the at least three cells are configured to be used with the scan direction, while the fourth cell and the third cell are configured to be used with a different scan direction orthogonal to the scan direction.

13 . The overlay metrology system of claim 1 , wherein the two or more cells comprise three or more layers of varying pitches.

14 . The overlay metrology system of claim 1 , wherein a first location comprising a first detector comprises a location of +1 Moiré order diffraction, wherein a second location comprising a second detector comprises a location of −1 Moiré order diffraction.

15 . An overlay metrology system comprising:

an illumination sub-system comprising:

an illumination source configured to generate an illumination beam;

a collection sub-system comprising:

one or more detectors; and

an objective lens configured to collect measurement light emanating from a sample in response to the illumination beam as the sample is scanned along a scan direction, wherein the sample comprises an overlay target according to a metrology recipe, wherein the overlay target comprises two or more cells comprising structures with periodicity along the scan direction; and

a controller communicatively coupled to the collection sub-system, the controller comprising one or more processors configured to execute program instructions causing the one or more processors to execute the metrology recipe by:

receiving first detection signals from the one or more detectors from a first cell of the two or more cells;

receiving second detection signals from the one or more detectors from a second cell of the two or more cells;

generating an overlay measurement of the first cell based on the first detection signals;

generating an overlay measurement of the second cell based on the second detection signals;

generating an overlay measurement associated with the overlay target based on a value indicative of an average of the overlay measurement of the first cell and the overlay measurement of the second cell,

wherein the first cell is defined as a first cell type characterized by an order of the structures in layers, the order characterized by pitches of the structures in the layers, wherein the second cell is defined as a second cell type characterized by a second order of second structures in the layers, the second order characterized by second pitches of the second structures in the layers,

wherein the first cell includes a first layer of structures having a first pitch and a second layer having a second pitch, wherein the second cell includes a first layer of structures having the second pitch and a second layer having the first pitch such that the pitches of structures within layers of the second cell are reversed relative to the first cell, wherein the order of structures in layers of the first cell type and second cell type are configured to suppress tool induced shift (TIS) error by averaging overlay measurements of cells with reversed pitch orders,

wherein the receiving the first detection signals and the receiving the second detection signals comprises receiving time-varying interference signals as the overlay target is scanned while the overlay target is in motion;

extracting at least one of intensity or phase information associated with the received time-varying interference signals using a phase locking technique; and

determining an overlay error between the first and second layers of the overlay target based on at least one of intensity or phase information.

16 . The overlay metrology system of claim 15 , wherein the controller is configured to execute the program instructions causing the one or more processors to execute the metrology recipe by: determining a tool induced shift (TIS) error of the overlay target based on a difference between the overlay measurement of the first cell and the overlay measurement of the second cell.

17 . The overlay metrology system of claim 15 , wherein the one or more detectors comprise at least one detector located in a pupil plane.

18 . The overlay metrology system of claim 15 , wherein the one or more detectors comprise at least one detector located in a field plane.

19 . The overlay metrology system of claim 15 , wherein the one or more detectors comprise at least one diode array sensor.

20 . The overlay metrology system of claim 15 , wherein the one or more detectors comprise at least one charge-coupled device (CCD) sensor.

21 . The overlay metrology system of claim 15 , wherein an illumination pupil plane distribution of the illumination beam is circular.

22 . The overlay metrology system of claim 15 , wherein an illumination pupil plane distribution of the illumination beam is annular.

23 . The overlay metrology system of claim 15 , wherein the structures of the two or more cells of the overlay target are at 45 degree angles relative to the scan direction.

24 . The overlay metrology system of claim 23 , wherein the two or more cells of the overlay target comprise waffle cells with periodic structures in a same layer at plus 45 degrees and minus 45 degrees from the scan direction such that a waffle pattern is formed.

25 . The overlay metrology system of claim 23 , wherein the two or more cells comprise at least four cells in a row, wherein the at least four cells in the row comprise at least two first cell types adjacent to each other with the structures at a positive diagonal angle relative to the scan direction and at least two second cell types adjacent to each other with the structures at a negative diagonal angle relative to the scan direction.

26 . The overlay metrology system of claim 23 , wherein the two or more cells comprise at least three cells in a row and a fourth cell adjacent to a third cell of the at least three cells, wherein the first cell and the second cell of the at least three cells are configured to be used with the scan direction, while the fourth cell and the third cell are configured to be used with a different scan direction orthogonal to the scan direction.

27 . The overlay metrology system of claim 15 , wherein the two or more cells comprise three or more layers of varying pitches.

28 . The overlay metrology system of claim 15 , wherein a first location comprising a first detector comprises a location of +1 Moiré order diffraction, wherein a second location comprising a second detector comprises a location of −1 Moiré order diffraction.

29 . An overlay target comprising:

four cells aligned in a row comprising:

a first cell and a third cell comprising periodic structures at plus 45 degrees from a scan direction; and

a second cell and a fourth cell comprising periodic structures at minus 45 degrees from the scan direction,

wherein the first cell and the second cell are of a first cell type, and the third cell and the fourth cell are of a second cell type,

wherein the first cell type is characterized by an order of structures in layers, the order characterized by pitches of the structures in the layers, wherein the second cell type is characterized by a second order of second structures, the second order characterized by second pitches of the second structures in the layers,

wherein the first cell includes a first layer of structures having a first pitch and a second layer having a second pitch, wherein the second cell includes a first layer of structures having the second pitch and a second layer having the first pitch such that the pitches of structures within layers of the second cell are reversed relative to the first cell, wherein the first cell type and second cell type are configured to suppress tool induced shift (TIS) error by averaging overlay measurements of cells with reversed pitch orders,

wherein time-varying interference signals of the overlay target are obtained when the overlay target is in motion;

wherein at least one of intensity or phase information associated with the received time-varying interference signals is extracted from the overlay target using a phase locking technique; and

wherein overlay error between layers of the overlay target is determined based on at least one of intensity or phase information.

30 . A method comprising:

receiving first detection signals from one or more detectors from a first cell of two or more cells of an overlay target of a sample comprising structures with periodicity along a scan direction;

receiving second detection signals from the one or more detectors from a second cell of the two or more cells;

generating an overlay measurement of the first cell based on the first detection signals;

generating an overlay measurement of the second cell based on the second detection signals;

generating an overlay measurement associated with the overlay target based on a value indicative of an average of the overlay measurement of the first cell and the overlay measurement of the second cell,

wherein the first cell is defined as a first cell type characterized by an order of the structures in layers, the order characterized by pitches of the structures in the layers, wherein the second cell is defined as a second cell type characterized by a second order of second structures in the layers, the second order characterized by second pitches of the second structures in the layers,

wherein the first cell includes a first layer of structures having a first pitch and a second layer having a second pitch, wherein the second cell includes a first layer of structures having the second pitch and a second layer having the first pitch such that the pitches of structures within layers of the second cell are reversed relative to the first cell, wherein the order of structures in layers of the first cell type and second cell type are configured to suppress tool induced shift (TIS) error by averaging overlay measurements of cells with reversed pitch orders,

wherein the receiving the first detection signals and the receiving the second detection signals comprises receiving time-varying interference signals as the overlay target is scanned while the overlay target is in motion;

extracting at least one of intensity or phase information associated with the received time-varying interference signals using a phase locking technique; and

determining an overlay error between the first and second layers of the overlay target based on at least one of intensity or phase information.

31 . The method of claim 30 further comprising:

determining a tool induced shift (TIS) error of the overlay target based on a difference between the overlay measurement of the first cell and the overlay measurement of the second cell.