Axicon produces a deep focused Bessel beam whose transverse focal spot is smaller than the size of an airy disk
produced by conventional lens with the same numerical aperture. Rieko Arimoto et al. applied axicon to a beamscanning
system and established the beam-scanning imaging system which is free from need of precise positioning.
Meanwhile, the allowed amount of rotation is severely restricted due to the unwanted tilt in the focused ring. We analyze
the tilt in the focused ring quantitatively and suggest an appropriate method of designing the aberration corrected lens.
An exemplary lens design for 1° tilt in the scanning mirror is presented and it is shown that the amount of degradation is
clearly suppressed in the optimized system.
Patterning of contact hole is always the most difficult process among many types of pattern formations. Specially
for the Extreme Ultra-Violet Lithography (EUVL), it will be even more difficult to make perfectly circled contact hole
due to the shadow effect. The shape of contact hole will be elliptical because the vertical axis opening is different from
the horizontal axis opening. We studied this behavior for 22 nm node contact hole patterns. We varied the pitch of the
regular contact hole array. The dependency of the position and density is studied for the random array. In addition to that
the thickness of the absorber and the reflectivity of the multilayer are varied to see non-circular contact hole. In order to
make desired circular contact hole with uniform width, direction dependent mask bias is applied in addition to the
normal optical proximity correction.