Phase contrast X-ray microscopy at 4 keV photon energy with 60 nm resolution

Abstract

X-ray microscopy in the multi-keV photon energy range offers unique possibilities to study relatively thick samples with high spatial resolution. When employing a high N.A. condenser zone plate for sample illumination in combination with a high resolution micro zone plate objective lens, a spatial resolution of currently 60 nm is achieved. We report here on phase contrast X-ray microscopy at 4 keV photon energy on copper interconnect structures, buried in silicon dioxide. While the amplitude contrast in these samples is only 7 %, negative as well as positive phase contrast were demonstrated using 2.2 pm and 0.7 pm high Nickel phase rings with a contrast of 30 % and 39 %, respectively.