Reusable silicon shadow mask with sub-5 μm gap for low cost patterning

For electrical characterization of bio-molecules and to make metallic contacts with the sensing element e.g. nano-wires, carbon nanotubes (CNTs), Graphene etc, the stability and minimization of contact resistance are always desirable, which is really challenging and needs development of simple and low-cost technology. This paper reports reusable silicon shadow mask, fabricated using conventional photolithography process has minimum gap size of 1 μm to 5 μm to make stable metallic contacts to the objects of few microns size. The fabricated shadow masks not only provide low cost patterning but also essential, when chemical free lithography is required to make contacts with bio-molecules, CNTs, graphene etc. E-beam metal deposition was carried out using fabricated shadow mask, feature sizes of shadow and the transferred pattern confirms the perfect use of mask. The metallic contacts on the dispersed single walled carbon nanotubes (SWNTs) were also made using this mask, followed by electrical characterization of the SWNTs chemiresistors.