| 摘要 |
Aberrations in a lithographic apparatus are detected by printing a test pattern having at least one degree of symmetry and that is sensitive to a particular aberration in the apparatus and using a scatterometer to derive information concerning the aberration. The test structure may comprise a two- bar grating (20), in which case the inner and outer duty ratios (Pi,PO) can be reconstructed to derive information indicative of comatic aberration. Alternatively, a hexagonal array of dots can be used, in which case the scatterometry data can be used to reconstruct the dot diameters which are indicative of 3-wave aberration.
|
