Method of measuring a structure, inspection apparatus, lithographic system and device manufacturing method

• Main Authors: Bozkurt, Murat, Van Der Schaar, Maurits, Den Boef, Arie Jeffrey, Sanguinetti, Gonzalo Roberto
• Format: Patent
• Language: English
• Published: 08.12.2020
• Subjects: ACCESSORIES THEREFOR; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USINGWAVES OTHER THAN OPTICAL WAVES; APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FORPROJECTING OR VIEWING THEM; APPARATUS SPECIALLY ADAPTED THEREFOR; CINEMATOGRAPHY; ELECTROGRAPHY; HOLOGRAPHY; MATERIALS THEREFOR; MEASURING; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS; MEASURING LENGTH, THICKNESS OR SIMILAR LINEARDIMENSIONS; ORIGINALS THEREFOR; PHOTOGRAPHY; PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES,e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTORDEVICES; PHYSICS; TESTING

Overlay error of a lithographic process is measured using a plurality of target structures, each target structure having a known overlay bias. A detection system captures a plurality of images (740) representing selected portions of radiation diffracted by the target structures under a plurality of different capture conditions (λ1, λ2). Pixel values of the captured images are combined (748) to obtain one or more synthesized images (750). A plurality of synthesized diffraction signals are extracted (744) from the synthesized image or images, and used to calculate a measurement of overlay. The computational burden is reduced compared with extracting diffraction signals from the captured images individually. The captured images may be dark-field images or pupil images, obtained using a scatterometer.