Method for determining an imaging quality of an optical system when illuminated by illumination light within a pupil to be measured

US12372431B2 · kind B2 · utility

Assignee

• Carl Zeiss SMT GmbH · DE

Inventors

• Markus Koch · Neu-Ulm, DE
• Renzo Capelli · Heidenheim, DE
• Klaus Gwosch · Oettingen, DE
• Dmitry Simakov · Jena, DE

Key dates

• Filing date: May 23, 2022
• Grant date: Jul 29, 2025
• Expiry date: Apr 11, 2043

Classification

• Technology area (CPC G): Physics
• CPC primary: G03F1/84
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

To determine an imaging quality of an optical system when illuminated by illumination light within a pupil to be measured of the optical system and/or to qualify the phase effect of a test structure, a test structure that is periodic in at least one dimension is initially arranged in an object plane of the optical system. An initial illumination angle distribution for illuminating the test structure with an initial pupil region, whose area is less than 10% of a total pupil area, is specified and the test structure is illuminated thereby in different distance positions relative to the object plane. In this way, an initial measured aerial image of the test structure is determined. Specifying the illumination distribution, illuminating and determining the aerial image are then repeated for a further illumination angle distribution and an imaging contribution of the optical system is determined from a comparison of the measured aerial images, the imaging quality parameter to be determined and/or a complex-valued diffraction spectrum of the test structure being determined from said imaging contribution. A metrology system for carrying out the method comprises a holder for the test struc…