Analysis of the blurring in stencil lithography

Abstract

A quantitative analysis of blurring and its dependence on the stencil-substrate gap and the deposition parameters in stencil lithography, a high resolution shadow mask technique, is presented. The blurring is manifested in two ways: first, the structure directly deposited on the substrate is larger than the stencil aperture due to geometrical factors, and second, a halo of material is formed surrounding the deposited structure, presumably due to surface diffusion. The blurring is studied as a function of the gap using dedicated stencils that allow a controlled variation of the gap. Our results show a linear relationship between the gap and the blurring of the directly deposited structure. In our configuration, with a material source of ∼5 mm and a source-substrate distance of 1 m, we find that a gap size of ∼10 μm enlarges the directly deposited structures by ∼50 nm. The measured halo varies from 0.2 to 3 μm in width depending on the gap, the stencil aperture size and other deposition parameters. We also show that the blurring can be reduced by decreasing the nominal deposition thickness, the deposition rate and the substrate temperature.

Room temperature dry processing of patterned CVD graphene devices

“…Stencil lithography is therefore an attractive method of choice, usually used for metal evaporation through micro-or nanostructures [27] for the purpose of electrical interconnects. Previous studies were mostly aimed at optimizing the morphology of deposited metal structures by controlling the clogging of apertures and deformation in stencil membranes [28,29]. A few attempts of graphene device interconnects involving metal electrodes evaporation through stencil lithography have been reported on pre-patterned exfoliated graphene strips [30] or flakes of suitable size and shape [31].…”

High resolution fabrication of nanostructures using controlled proximity nanostencil lithography

“…Owing to the direct transfer of the stencil, the thickness of the spin-coated PMMA spacer allows for precise control of the gap between the stencil and the substrate. The gap size has been reported to have a significant impact on the achievable resolution with nanostencil lithography, which is traditionally limited by geometric blurring (blurring from non-normal angle of incidence of material evaporated through the stencil), halo blurring (blurring from surface diffusion of deposited material), and stencil clogging (reduction in stencil aperture size due to deposition of material onto the stencil) 28,29 . For example, feature sizes of ~ 100 nm, and feature resolution down to 25 nm, were reported when the stencil is contacted directly with a flexible substrate, indicative primarily of the potential benefits of reductions in the gap between stencil and substrate 30 .…”

Stenciled conducting bismuth nanowires

“…When the ratio of substrate-stencil gap G to aperture width A becomes larger than the ratio of source-stencil distance D to source size S, G / A Ͼ D / S, the effective source size as seen from the substrate through the aperture shrinks and the material flux decreases. 16 In our case D = 50 cm and S = 0.3 cm. For a local gap G =20 m, the source size is effectively shrinking starting with an aperture width A = 120 nm.…”