Three-dimensional characterization of extreme ultraviolet mask blank defects by interference contrast photoemission electron microscopy.
A photoemission electron microscope based on a new contrast mechanism "interference contrast" is applied to characterize extreme ultraviolet lithography mask blank defects. Inspection results show that positioning of interference destructive condition (node of standing wave field) on surface of multilayer in the local region of a phase defect is necessary to obtain best visibility of the defect on mask blank. A comparative experiment reveals superiority of the interference contrast photoemission electron microscope (Extreme UV illumination) over a topographic contrast one (UV illumination with Hg discharge lamp) in detecting extreme ultraviolet mask blank phase defects. A depth-resolved detection of a mask blank defect, either by measuring anti-node peak shift in the EUV-PEEM image under varying inspection wavelength condition or by counting interference fringes with a fixed illumination wavelength, is discussed.
Lin
Jingquan
J
Faculty of Physics, Ludwig Maximilians University, Munich, D 85748, Germany. Jingquan.lin@physik.uni-muenchen.de
Weber
Nils
N
Escher
Matthias
M
Maul
Jochen
J
Han
Hak-Seung
HS
Merkel
Michael
M
Wurm
Stefan
S
Schönhense
Gerd
G
Kleineberg
Ulf
U
D004867:Equipment Design; D008027:Light; D008854:Microscopy, Electron / Q000295:instrumentation* / Q000379:methods; D008857:Microscopy, Interference / Q000295:instrumentation* / Q000379:methods; D008860:Microscopy, Ultraviolet / Q000379:methods; D055095:Optics and Photonics; D014466:Ultraviolet Rays