公开(公告)号：US10571812B2

公开(公告)日：2020-02-25

申请号：US16045979

申请日：2018-07-26

申请人： ASML Netherlands B.V.

发明人： Fahong Li ,  Miguel Garcia Granda ,  Carlo Cornelis Maria Luijten ,  Bart Peter Bert Segers ,  Cornelis Andreas Franciscus Johannes Van Der Poel ,  Frank Staals ,  Anton Bernhard Van Oosten ,  Mohamed Ridane

IPC分类号： G03F7/20 ,  G01M11/02

摘要： Focus performance of a lithographic apparatus is measured using pairs of targets that have been exposed (1110) with an aberration setting (e.g. astigmatism) that induces a relative best focus offset between them. A calibration curve (904) is obtained in advance by exposing similar targets on FEM wafers (1174, 1172). In a set-up phase, calibration curves are obtained using multiple aberration settings, and an anchor point (910) is recorded, where all the calibration curves intersect. When a new calibration curve is measured (1192), the anchor point is used to produce an adjusted updated calibration curve (1004′) to cancel focus drift and optionally to measure drift of astigmatism. Another aspect of the disclosure (FIGS. 13-15) uses two aberration settings (+AST, −AST) in each measurement, reducing sensitivity to astigmatism drift. Another aspect (FIGS. 16-17) uses pairs of targets printed with relative focus offsets, by double exposure in one resist layer.