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, u sing synchrotron-based illumination. This method can be used to monitor the coherent imaging performance of EW lithographic optical systems. The syste m has been implemented in the EUV phase-shifting point-diffraction interfer ometer 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 10 x Schwarzsch ild objective, a prototype EW 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 ap plication of the holographic aerial image-recording technique to EUV multil ayer mask-blank defect characterization is discussed. (C) 2001 Optical Soci ety of America.