Extreme-ultraviolet lensless Fourier-transform holography.
We demonstrate 100-nm-resolution holographic aerial image monitoring based on lensless Fourier-transform holography at extreme-UV (EUV) wavelengths, using synchrotron-based illumination. This method can be used to monitor the coherent imaging performance of EUV lithographic optical systems. The system has been implemented in the EUV phase-shifting point-diffraction interferometer recently developed at Lawrence Berkeley National Laboratory. Here we introduce the idea of the holographic aerial image-recording technique and present imaging performance characterization results for a 10x Schwarzschild objective, a prototype EUV lithographic optic. The results are compared with simulations, and good agreement is obtained. Various object patterns, including phase-shift-enhanced patterns, have been studied. Finally, the application of the holographic aerial image-recording technique to EUV multilayer mask-blank defect characterization is discussed.
Lee
S H
SH
Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, California 94720, USA. shlee@lbl.gov
Naulleau
P
P
Goldberg
K A
KA
Cho
C H
CH
Jeong
S
S
Bokor
J
J