Method for position determination, method for overlay optimization, and lithographic projection apparatus

摘要

A method for optimizing an alignment condition of a lithographic projection apparatus. This method comprises projecting a beam of radiation on a target portion of a substrate and measuring a plurality of diffracted signals emitted by the target portion. This method further comprises calculating a variance for each of the plurality of diffracted signals, such that a plurality of variances of the diffracted signals is determined, and adjusting the alignment condition of the lithographic projection apparatus based on analysis of the plurality of variances.