Reflective optical imaging system with balanced distortion

US5973826A · kind A · utility

Assignee

• The Regents of the University of California · US

Inventors

• Henry N. Chapman · Hamburg, DE
• Russell Hudyma · San Ramon, US
• David Shafer · Fairfield, US
• Donald W. Sweeney · San Ramon, US

Key dates

• Filing date: Feb 20, 1998
• Grant date: Oct 26, 1999
• Expiry date: Feb 20, 2018

Classification

• Technology area (CPC G): Physics
• CPC primary: G02B13/22
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

An optical system compatible with short wavelength (extreme ultraviolet) An optical system compatible with short wavelength (extreme ultraviolet) radiation comprising four reflective elements for projecting a mask image onto a substrate. The four optical elements comprise, in order from object to image, convex, concave, convex and concave mirrors. The optical system is particularly suited for step and scan lithography methods. The invention enables the use of larger slit dimensions associated with ring field scanning optics, improves wafer throughput and allows higher semiconductor device density. The inventive optical system is characterized by reduced dynamic distortion because the static distortion is balanced across the slit width.