US 12,244,926 B2
Overlay measurement device and method for controlling focus movement and program storage medium therefor
Seong-Yun Choi, Hwaseong-si (KR); and Hyo-Sik Ham, Hwaseong-si (KR)
Assigned to AUROS TECHNOLOGY, INC., Hwaseong-Si (KR)
Filed by AUROS TECHNOLOGY, INC., Hwaseong-si (KR)
Filed on Apr. 5, 2024, as Appl. No. 18/627,900.
Application 18/627,900 is a continuation of application No. 18/205,254, filed on Jun. 2, 2023, granted, now 12,010,425.
Claims priority of application No. 10-2022-0148326 (KR), filed on Nov. 9, 2022.
Prior Publication US 2024/0259682 A1, Aug. 1, 2024
Int. Cl. H04N 23/67 (2023.01); G02B 7/105 (2021.01)
CPC H04N 23/676 (2023.01) [G02B 7/105 (2013.01)] 22 Claims
OG exemplary drawing
 
1. An overlay measurement device controlling a focus movement, comprising:
a lighting part being configured to orient lighting toward an overlay measurement target;
a collection part comprising an objective lens and a detector for obtaining one or more of images of each focus in the overlay measurement target;
a lens focus actuator moving the objective lens to adjust a distance between the objective lens and a wafer; and
a processor controlling an operation of the lens focus actuator,
wherein the processor is configured to:
obtain focus graphs of each of two layer from one or more of the images of each focus,
identify a reference focus in relation to the obtained focus graphs,
identify two third contrast indexes of the obtained measurement image,
identify two fourth contrast indexes of the obtained measurement image,
identify whether a third contrast index and a fourth contrast index having the shortest focus distance are the same, and
move the objective lens according to a corresponding contrast index.