Method of determining focus corrections, lithographic processing cell and device manufacturing method

摘要

A method of, and associated apparatus for, determining focus corrections for a lithographic projection apparatus. The method comprises exposing a plurality of global correction fields on a test substrate, each comprising a plurality of global correction marks, and each being exposed with a tilted focus offset across it; measuring a focus dependent characteristic for each of the plurality of global correction marks to determine interfield focus variation information; and calculating interfield focus corrections from the interfield focus variation information.

主权项

1. A method of determining focus corrections for a lithographic projection apparatus, the method comprising:
measuring a focus dependent characteristic for each of a plurality of intrafield correction marks on a test substrate, wherein the intrafield correction marks are arranged in a plurality of intrafield correction fields, the intrafield correction marks having been exposed using varying focus; determining intrafield focus variation information for each intrafield correction mark location from the measured focus dependent characteristic; calculating the intrafield focus corrections from the intrafield focus variation information while taking into account scan-up-scan-down effects and grid plate focus errors induced as a result of a grid plate forming part of the lithographic apparatus, wherein the calculating intrafield focus corrections comprises modeling the different intrafield focus variation information using a filter to filter out a particular region of the test substrate.