Methods and patterning devices for measuring phase aberration

摘要

A method of measuring a phase difference between two regions in an aberration function: Reference structures are produced on a substrate using illumination that minimizes effects of phase aberration. A grating is produced on the substrate using a phase-shift grating reticle to produce, in the exit pupil, a pair of diffracted non-zero orders, while forbidding other diffracted orders and produces interference fringes formed by interference between the pair. The interference contributes to a first grating on the substrate. Overlay error is measured between the grating and the reference structure using diffraction-based or image-based overlay measurements. A phase aberration function for the exit pupil of the lithographic apparatus can then be determined from the measured overlay errors.

主权项

1. A method comprising:
producing, using a lithographic apparatus, a first reference structure on a substrate; producing, using the lithographic apparatus, a first grating on the substrate by illuminating a reticle with radiation, the reticle comprising an area with a phase-shift grating periodic in first and second directions and configured to produce:
in an exit pupil of the lithographic apparatus, a pair of diffracted orders of the radiation other than the zeroth order, while forbidding other diffracted orders of the radiation in the exit pupil; andinterference fringes formed by interference between the pair of diffracted orders of the radiation, the interference fringes contributing to the definition of the first grating on the substrate; and measuring overlay error between the first grating and the first reference structure.