| 摘要 |
An alignment measurement arrangement includes a source, an optical system and a detector. The source generates a radiation beam with a plurality of wavelength ranges. The optical system receives the radiation beam, produces an alignment beam, directs the alignment beam to a mark located on an object, receives alignment radiation back from the mark, and transmits the received radiation. The detector receives the alignment radiation and detects an image of the alignment mark and outputs a plurality of alignment signals, r, each associated with one of the wavelength ranges. A processor, in communication with the detector, receives the alignment signals, determines signal qualities of the alignment signals; determines aligned positions of the alignment signals, and calculates a position of the alignment mark based on the signal qualities, aligned positions, and a model relating the aligned position to the range of wavelengths and mark characteristics, including mark depth and mark asymmetry. |
