Patent ID: 11927892
Assignee: ASML NETHERLANDS B.V.
Field: Optics (Instruments)
Classification: CPC G | IPC G

Claim 0:
1. A method of performing a position measurement on an alignment mark comprising at least a first periodic structure having a direction of periodicity along a first direction; the method comprising:
performing at least one alignment scan of the alignment mark in a direction other than the first direction or a second direction perpendicular to the first direction to obtain simultaneously: a first measurement signal detected in a first measurement channel and a second measurement signal detected in a second measurement channel, the first measurement signal, and the second measurement signal each relating to scattered radiation, having been scattered by the alignment mark;
processing the first measurement signal and second measurement signal, the processing comprising subtracting a first direction component of the first measurement signal from a first direction component of the second measurement signal to obtain a first processed signal, the first direction components relating to the first direction; and
determining a position of the alignment mark with respect to the first direction from the first processed signal.