| 摘要 |
An overlay error between two successive layers produced by a lithographic process on a substrate is determined by using the lithographic process to form at least one periodic structure of a same pitch on each of the layers. One or more overlaid pairs of the periodic structures are formed in parallel, but offset relative to each other. A spectrum, produced by directing a beam of radiation onto the one or more pairs of periodic structures is measured. One or more portions of the spectrum are determined in which the relationship between the offset between the one or more pairs of periodic structures and the resultant variation in measured intensity of the spectrum at the one or more portions is more linear than the relationship outside the one or more portions. The offset between the one or more pairs of periodic structures on the basis of intensity measurements of the spectrum in the one or more portions of the spectrum is determined and used to determine the overlay error.
|
