US 11,947,185 B2
Autofocusing method for an imaging device
Dirk Seidel, Jena-Leutra (DE)
Assigned to Carl Zeiss SMT GmbH, Oberkochen (DE)
Filed by Carl Zeiss SMT GmbH, Oberkochen (DE)
Filed on Nov. 8, 2021, as Appl. No. 17/521,230.
Application 17/521,230 is a continuation of application No. PCT/EP2020/025213, filed on May 8, 2020.
Claims priority of application No. 102019112156.6 (DE), filed on May 9, 2019.
Prior Publication US 2022/0057598 A1, Feb. 24, 2022
Int. Cl. G03F 7/20 (2006.01); G02B 7/28 (2021.01); G02B 21/24 (2006.01); G03F 1/70 (2012.01); G03F 9/00 (2006.01); H04N 23/67 (2023.01)
CPC G02B 7/28 (2013.01) [G02B 21/244 (2013.01); G03F 1/70 (2013.01); G03F 9/7026 (2013.01); H04N 23/671 (2023.01)] 20 Claims
OG exemplary drawing
 
1. An autofocusing method for an imaging device (for semiconductor lithography) comprising an imaging optical unit, an object to be measured and an autofocusing device having a reflective illumination, comprising the following method steps:
a) defining at least three basis measurement points M(xj, yj) on a surface of the object,
b) determining a deviation Az(M)j of a nominal position of the surface of the object from a focal plane of the autofocusing device at each of the defined basis measurement points M(xj, yj),
c) storing the deviations Az(M)j from the defined basis measurement points M(xj, yj),
d) using the stored deviation Az(M)j for determining a deviation Az(P)k at an arbitrary point P(xk, yk) of the surface different from the defined basis measurement points, and
e) using the deviation Az(P)k for focusing onto the point P(xk, yk).