SYSTEMS AND METHODS FOR MEASURING INTENSITY IN A LITHOGRAPHIC ALIGNMENT APPARATUS

摘要

A metrology system includes a radiation source, an adjustable diffractive element, an optical system, an optical element, and a processor. The radiation source generate-, radiation. The adjustable diffractive element diffracts (he radiation to generate first and second beams of radiation. The first and second beams have first and second different non-zero diffraction orders, respectively. The optical system directs the first and second beams toward a target structure such that first and second scattered beams of radiation are generated based on the first and second beams, respectively. The metrology system adjusts a phase difference of the first and second scattered beams. The optical element interferes the first and second scattered beams at an imaging detector that generates a detection signal. The processor receives and analyzes the detection signal to determine a property of the target structure based on the adjusted phase difference.