The half-tone phase shift mask (PSM) has been suggested for better imaging performances like image contrast,
NILS and H-V bias compared to the binary mask (BIM) in EUV lithography. In this paper, we measured
imaging performance of a fabricated half-tone attenuated PSM with Coherent Scattering Microscopy (CSM) and
the results were compared with simulation data obtained by EM-suite tool. We prepared a half-tone attenuated
PSM which has 12.7% reflectivity and 180° phase shift with absorber stack of 16.5mn-thick TaN absorber and
24nm-thick Mo phase shifter. With CSM, an actinic inspection tool, we measured the imaging properties of
PSM. The diffraction efficiencies of BIM were measured as 31%, 36%, and 44% for 88 nm, 100 nm, and 128
nm mask CD, respectively, while those of PSM were measured as 45%, 62%, and 81%. Also the aerial image at
wafer level obtained by CSM with high volume manufacturing tool’s (HVM) illumination condition (NA=0.33,
σ=0.9) showed higher image contrast and NILS with phase shift effect. And the measured data were consistent
with the simulation data.
In EUV Lithography, mask shadowing effect and photon shot noise effect are the main sources of patterning limit,
critical dimension (CD) non-uniformity and low imaging properties. In this paper, the patterning performance of a 6%
attenuated phase shift mask (PSM) is valuated, and the results show that this can be used for half-pitch (hp) down to 14 nm with 0.33NA due to the improved stochastic patterning properties. The proposed PSM consists of 26.5 nm of TaN as an absorber layer and 14 nm of Mo as a phase shifter on 2.5 nm thick Ru capped Mo/Si multilayers. This structure has ~6% reflectivity at the absorber stack and 180° phase shift. The improved stochastic resist patterning properties of PSM were compared with those of conventional binary intensity mask (BIM) with a 70 nm-thick TaN absorber for the 14 ~ 22 nm line and space (L/S) 1:1 dense pattern with 0.33NA off-axis illumination conditions with a EUV generic resist model.