US 12,253,805 B2
Scatterometry overlay metrology with orthogonal fine-pitch segmentation
Vladimir Levinski, Nazareth Ilit (IL); Daria Negri, Nesher (IL); and Amnon Manassen, Haifa (IL)
Assigned to KLA Corporation, Milpitas, CA (US)
Filed by KLA Corporation, Milpitas, CA (US)
Filed on Aug. 11, 2022, as Appl. No. 17/885,909.
Prior Publication US 2024/0053687 A1, Feb. 15, 2024
Int. Cl. G03F 7/00 (2006.01); G01N 21/95 (2006.01)
CPC G03F 7/70633 (2013.01) [G01N 21/9501 (2013.01); G03F 7/70683 (2013.01)] 45 Claims
OG exemplary drawing
 
1. An overlay metrology system comprising:
an illumination source configured to generate an illumination beam;
one or more illumination optics to direct the illumination beam to a sample with a field of view including one or more overlay targets when implementing a metrology recipe, wherein a particular one of the one or more overlay targets in accordance with the metrology recipe comprises:
one or more grating-over-grating structures formed from a lower grating structure with a first coarse pitch and an upper grating structure with a second coarse pitch, wherein the upper grating structure and the lower grating structure overlap on the sample, wherein at least one of the upper grating structure or the lower grating structure further includes features with a fine pitch smaller than a wavelength of the illumination beam and arranged to rotate first-order diffraction of the illumination beam with respect to at least one of specular reflection from a top surface of the sample or zero-order diffraction from the one or more grating-over-grating structures, wherein the first-order diffraction corresponds to +1 diffraction from one of the upper grating structure or the lower grating structure and −1 diffraction from the other of the upper grating structure or the lower grating structure;
an objective lens to collect light from the sample within the field of view when implementing the metrology recipe;
a polarizer arranged to pass portions of the light from the sample associated with the first-order diffraction;
one or more detectors to generate one or more images of the sample including the one or more overlay targets; and
a controller communicatively coupled to the one or more detectors, the controller including one or more processors configured to execute program instructions causing the one or more processors to determine overlay measurements of the sample based on the one or more images of the one or more overlay targets.