Device for automatically determining the deviation between the structures of a pattern and those of an object compared therewith

US4796999A · kind A · utility

Assignee

• Ernst Leitz Wetzlar, GmbH · DE

Inventors

• Erich Schuster · Gammertingen, DE
• Manfred Kartzow · Wetzlar, DE

Key dates

• Filing date: Jan 16, 1987
• Grant date: Jan 10, 1989
• Expiry date: Jan 16, 2007

Classification

• Technology area (CPC G): Physics
• CPC primary: G03F9/7023
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

In a device for automatically determining the deviation between the structures of a pattern and those of a reference object, the structures to be compared are imaged, in a superposed condition, on a measurement gap, a polarization characteristic being imparted to the individual image channels. By relative movement between the superposed object image and the measurement gap and the subsequent separation of the image channels in dependence upon their polarization characteristic, photometric signal curves are obtained, from which errors in the superposition of the structures are quantitatively determined. A measurement in two coordinate directions is possible by insertion of an image-rotating prism. In an observation beam path which is branched off, the polarization characteristic is converted into a color characteristic, so that an additional double-image presentation of the structure superposition is produced. The photometric scanning range can be made visible by back-illumination of the measurement gap and reflection into the observation beam path.