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Title: Reflective optical imaging systems with balanced distortion

Patent ·
OSTI ID:873706

Optical systems compatible with extreme ultraviolet radiation comprising four reflective elements for projecting a mask image onto a substrate are described. The four optical elements comprise, in order from object to image, convex, concave, convex and concave mirrors. The optical systems are 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 systems are characterized by reduced dynamic distortion because the static distortion is balanced across the slit width.

Research Organization:
Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
DOE Contract Number:
W-7405-ENG-48
Assignee:
Regents of University of California (Oakland, CA)
Patent Number(s):
US 6226346
OSTI ID:
873706
Country of Publication:
United States
Language:
English

References (4)

Reflective optical designs for soft x-ray projection lithography conference December 1991
Design of reflective relay for soft x-ray lithography conference January 1991
Reflective systems design study for soft x-ray projection lithography journal November 1990
Optical system design issues in development of projection camera for EUV lithography conference May 1995