EUV lithography has the ability to support 22 nm logic manufacturing and beyond. Similar to the DUV lithographic
systems, partial coherence on EUV lithographic systems can have a big impact on process latitude for critical layers.
Thus, it is important to understand the effect of partial coherence on EUV imaging systems. In this paper, process
windows with various illumination settings are investigated. The experiments are conducted using the MET station at
the Advance Light Source (ALS). In addition to the annular and dipole illuminations which reported in our last
paper1, C-quad and Quad illuminations are used to explore the impact of the partial coherence on the process window.
Even though the MET system has resolutions below 30nm dense lines, the exposures are targeted for 60nm, 50nm, and
45nm dense features due to the resist limitation. The experimental results are compared with simulation results using
Intel's lithography modeling tool, I-Photo. Resist and aerial image threshold models are used for the comparison
study. The experimental results correlate well with the resist based simulation results, but some discrepancies are
observed for the aerial image threshold cases. We believe the discrepancies are due to the resist limitations. We found
that the dipole shows the largest Depth of Focus for dense lines and spaces.