Patent ID: 11947185
Assignee: CARL ZEISS SMT GMBH
Field: Audio-visual technology (Electrical engineering)
Classification: CPC G  H | IPC G  H

Claim 0:
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).