The EUV phase-shifting point diffraction interferometer

Abstract

The extreme ultraviolet (EUV) phase-shifting point diffraction interferometer (PS/PDI) was developed and implemented at Lawrence Berkeley National Laboratory to meet the significant measurement challenge of characterizing EUV projection lithography optics. The PS/PDI has been in continuous use and under ongoing development since 1996. Here we describe recent improvements made to the interferometer, and we summarize metrology results from state-of-the-art 10×-reduction EUV projection optics.