Method for ascertaining distortion properties of an optical system in a measurement system for microlithography

US9785058B2 · kind B2 · utility

Assignee

• Carl Zeiss SMT GmbH · DE

Inventors

• Dirk Seidel · Jena, DE
• Susanne Toepfer · Etzleben, DE
• Michael Himmelhaus · Karlsruhe, DE

Key dates

• Filing date: Aug 13, 2015
• Grant date: Oct 10, 2017
• Expiry date: Dec 20, 2035

Classification

• Technology area (CPC G): Physics
• CPC primary: G01N2021/95676
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A method for ascertaining distortion properties of an optical system in a measurement system for microlithography is provided, wherein the optical system images at least one structure to be measured into a measurement image. In accordance with one aspect, a method according to the invention comprises the following steps: measuring the field-dependent image aberrations of the optical system; determining a first distortion pattern present in the first image field generated by the optical system during measurement of at least one predefined structure; carrying out an optical forward simulation for the predefined structure taking account of the field-dependent image aberrations measured previously, with a second image field being generated; determining a second distortion pattern for the second image field generated previously; and ascertaining the structure-independent distortion properties of the optical system by calculating a third distortion pattern as the difference between the first distortion pattern and the second distortion pattern.