Mark W. Horn | Searcharxiv

arXiv2019

Electromagnetic modeling of near-field phase-shifting contact lithography with broadband ultraviolet illumination

Near-field phase-shifting contact lithography is modeled to characterize electromagnetic absorption in a photoresist layer with one face in contact with a quartz binary phase-shift mask. The broadband ultraviolet illumination is represented as a frequency-spectrum of normally incident plane waves. A rigorous coupled-wave analysis is carried out to determine the absorption spectrum of the photoresist layer. The specific absorption rate in the photoresist layer is calculated and examined in relation to the geometric parameters. Columnar features in the photoresist layer are of higher quality on broadband illumination in contrast to monochromatic illumination, in conformity with some recent experimental results. Feature resolution and profile are noticeably affected by the depth of the grooves in the phase-shift mask. Ideally, the feature linewidth can be less than about 100 nm for broadband illumination in the transverse-magnetic mode. These conclusions are subject to modification by the photochemistry-wavelength characteristics of the photoresist.

physics.app-ph↗

arXiv2003

Blending of nanoscale and microscale in uniform large-area sculptured thin-film architectures

The combination of large thickness ($>3$ $μ$m), large--area uniformity (75 mm diameter), high growth rate (up to 0.4 $μ$m/min) in assemblies of complex--shaped nanowires on lithographically defined patterns has been achieved for the first time. The nanoscale and the microscale have thus been blended together in sculptured thin films with transverse architectures. SiO$_x$ ($x\approx 2$) nanowires were grown by electron--beam evaporation onto silicon substrates both with and without photoresist lines (1--D arrays) and checkerboard (2--D arrays) patterns. Atomic self--shadowing due to oblique--angle deposition enables the nanowires to grow continuously, to change direction abruptly, and to maintain constant cross--sectional diameter. The selective growth of nanowire assemblies on the top surfaces of both 1--D and 2--D arrays can be understood and predicted using simple geometrical shadowing equations.

physics.optics↗