US 12,422,363 B2
Scanning scatterometry overlay metrology
Amnon Manassen, Haifa (IL); Andrew V. Hill, Berkeley, CA (US); Yuri Paskover, Milpitas, CA (US); Itay Gdor, Tel-Aviv (IL); Yonatan Vaknin, Yoqneam Llit (IL); and Yuval Lubashevsky, Haifa (IL)
Assigned to KLA Corporation, Milpitas, CA (US)
Filed by KLA Corporation, Milpitas, CA (US)
Filed on Mar. 30, 2022, as Appl. No. 17/708,958.
Prior Publication US 2023/0314319 A1, Oct. 5, 2023
Int. Cl. G01N 21/47 (2006.01); G01B 11/27 (2006.01); G01N 21/956 (2006.01)
CPC G01N 21/4788 (2013.01) [G01B 11/272 (2013.01); G01N 21/956 (2013.01); G01B 2210/56 (2013.01)] 51 Claims
OG exemplary drawing
 
1. An overlay metrology system comprising:
an illumination sub-system configured to implement a metrology recipe, the illumination sub-system comprising:
an illumination source configured to generate an illumination beam; and
one or more illumination optics configured to direct the illumination beam to an overlay target on a sample as the sample is scanned relative to the illumination beam along a scan direction when implementing the metrology recipe, wherein the overlay target in accordance with the metrology recipe includes one or more cells having Moiré structures formed as overlapping grating structures with different pitches on a first layer and a second layer of the sample, wherein the overlapping grating structures are periodic along at least one of the scan direction or a direction orthogonal to the scan direction;
a collection sub-system configured to implement the metrology recipe, the collection sub-system comprising:
a first photodetector located in a pupil plane at a first location to capture at least one of Moiré diffraction orders or overlapping diffraction orders from the Moiré structures in the one or more cells when implementing the metrology recipe; and
a second photodetector located in the pupil plane at a second location to capture at least one of Moiré diffraction orders or overlapping diffraction orders from the Moiré structures in the one or more cells when implementing the metrology recipe; and
a controller communicatively coupled to the first photodetector and the second photodetector, the controller including one or more processors configured to execute program instructions causing the one or more processors to:
receive time-varying interference signals from the first photodetector and the second photodetector associated with the Moiré structures in the one or more cells as the overlay target is scanned in accordance with the metrology recipe; and
determine an overlay error between the first layer and the second layer of the sample based on the time-varying interference signals.