	US 12,019,377 B2
	Target for measuring a parameter of a lithographic process
Maurits Van Der Schaar, Eindhoven (NL); Olger Victor Zwier, Eindhoven (NL); and Patrick Warnaar, Tilburg (NL)
Assigned to ASML Netherlands B.V., Veldhoven (NL)
Appl. No. 17/299,531
Filed by ASML Netherlands B.V., Veldhoven (NL)
PCT Filed Dec. 4, 2019, PCT No. PCT/EP2019/083666 § 371(c)(1), (2) Date Jun. 3, 2021, PCT Pub. No. WO2020/115125, PCT Pub. Date Jun. 11, 2020.
Claims priority of provisional application 62/775,295, filed on Dec. 4, 2018.
Prior Publication US 2022/0035255 A1, Feb. 3, 2022
Int. Cl. G03F 7/00 (2006.01); G01N 21/47 (2006.01)

CPC G03F 7/70633 (2013.01) [G01N 21/4788 (2013.01); G03F 7/70683 (2013.01)]

16 Claims

1. A target for determining a performance parameter of a lithographic process, the target comprising:

a first sub-target formed by at least two overlapping gratings, wherein an underlying grating of the first sub-target has a first pitch P_b1and a top lying grating of the first sub-target has a second pitch P_t1,

wherein a predetermined wavelength generates n scattered orders for the underlying grating of the first sub-target and m scattered orders for the top lying grating of the first sub-target such that the n scattered orders and the m scattered orders generate a Moire pitch according to

and

at least a second sub-target formed by at least two overlapping gratings, wherein an underlying grating of the second sub-target has a third pitch P_b2and a top lying grating of the second sub-target has a fourth pitch P_t2,

wherein a predetermined wavelength generates n scattered orders for the underlying grating of the second sub-target and m scattered orders for the top lying grating of the second sub-target such that the n scattered orders and the m scattered orders generate a Moire pitch according to

and

wherein the first pitch P_b1and the third pitch P_b2comprise a same bottom pitch P₀, which produces an overlay proportionality between a phase and an overlay that is linearly dependent on the bottom pitch P₀according to