Charge dissipation in e-beam lithography with Novolak-based conducting polymer films

Abstract

Charging of common resist materials during electron beam (e-beam) writing leads to deflection of the electron beam path, which can result in significant pattern displacement. Here we report a new conducting polymer to eliminate charging. A common approach is to place the conducting layer underneath the e-beam resist layer. Conductivity equal or greater than 10(-4) S cm(-1) has been reported to prevent pattern displacement. Some other properties such as a flat surface layer, chemical inertness and insolubility in both the top resist solvent and the developer are also necessary. The way to achieve all these properties consisted in synthesizing a conducting polymer inside an insulating polymer to form an interpenetrating polymer network (IPN) which could combine their properties. Novolak was used as the host polymer and terthiophene (3T) as the monomer to polymerize. Cu(ClO(4))(2) initiates simultaneously the oxidative polymerization of the 3T and its subsequent doping inside Novolak during the bake step in a one-step reaction. Solvent-resistant and homogeneous conducting films with smooth surfaces were achieved. The conductivity was of the order of 10(-2) S cm(-1). Patterning of the top resist was carried out without disturbing its lithographic performance.

Ag and Au/DNQ-novolac nanocomposites patternable by ultraviolet lithography: a fast route to plasmonic sensor microfabrication

“…We can consider that the Ag(I) reduction is approximately complete for films baked at around 210 C. At higher temperatures the LSPR intensity is slightly higher, but this is due to an increase of light absorption below 400 nm. This is attributed to the progressive crosslinking of the novolac resist induced by the bake temperature, and that it is fulfilled at 230 C, 39 and it has also been observed in DNQ-novolac samples without metallic salts. The post-bake temperature produces a notable increase of the nanoparticle mean diameter, from 6.3 AE 3.3 nm at 160 C up to 11.4 AE 4.1 nm at 240 C, as deduced from size statistics in TEM images (see histograms in Fig.…”

Plasmonic-Active Nanostructured Thin Films

“…These substrates can be easily coated with indium-tin-oxide (ITO) to make it conductive. The conductivity of the substrate is advantageous for the fabrication of PANTFs, such as during deposition by electrochemistry techniques [23] or to prevent charging during patterning on the electron beam lithography technique [24]. Although SiO 2 is an optimal substrate for transmission-based plasmonic sensing, Si wafer and mica can be used for reflection-based plasmonic sensing.…”

Organic Chemistry of Polyanilines: Tailoring Properties to Technological Applications~!2008-08-19~!2008-09-11~!2008-11-28~!

“…Holdcroft and coworkers synthesized polythiophenes bearing pendant groups which can be hydrolyzed by acids [92], making it amenable to chemically amplified lithography. Similarly, lithographic patterning of polyaniline has been achieved by changing the doping state of polyaniline (PANI) films using acid [93], or base photogenerators [94] which could alter the solubility of the polymer changing its protonation state. The polymer has to be deposited from the few solvent in which PANI is soluble, like N-methylpyrrolidone [95].…”