Lithographic applications of conducting polymers

Abstract

Electrically conducting polyaniline is found to be suitable for several lithographic applications. Because the polyaniline is not significantly soluble in the conducting state, the material has generally been processed by first applying the soluble, nonconducting version of the material, and in a second step externally doping the polymer film with aqueous acids. We have eliminated the need for this type of external doping by developing methods of inducing the doping in a dry fashion in situ in the polymer. This-is accomplished by incorporating onium salts or amine triflate salts in the polyaniline which decompose upon radiation or thermal treatment, respectively, to generate the active dopant species, i.e., protonic acids. The use of these in situ dopants simplifies the processing of the conducting polyaniline and makes the material more convenient for lithographic applications. With the use of onium salts, the polyaniline is made into a high resolution negative conducting resist. 0.25 f-Lm conducting lines have been patterned with e-beam radiation. Polyaniline is found· to be an effective discharge layer for e-beam lithography and a removable discharge layer for the high resolution inspection and dimensional measurements of xray and optical masks by scanning electron microscopy (SEM). In addition, the poly aniline can be used for both electrolytic and electro less-type metallization processes.

Photolithographically-Patterned Electroactive Films and Electrochemically Modulated Diffraction Gratings

“…Conjugated Polymers. Because of the significant potential for the use of conjugated (semi)conducting polymers such as polyaniline, polypyrrole, polythiophene, and polyphenylene vinylene (PPV) in electronic and photonic devices, there has been a surge of interest in the development of lithographic methods that can be utilized to fabricate arbitrary micron-scale patterns of these materials on a variety of substrates. − ,,,− ,,,− , Due to the widespread interest in this field, in the following paragraphs we only review work that is directly relevant to our own research on lithographic patterning of conjugated polymers.…”

“…Most work in the area of modified electrodes has focused on approaches to producing films that are spatially homogeneous in the plane defined by the electrode surface. − However, within the past decade a number of groups have devised methods for modifying electrodes with electroactive films that are microscopically patterned within the plane defined by a surface. ,− These methods include laser writing, − ,, e-beam writing, , photolithography, ,− ,− ,, microcontact printing, ink-jet printing, , and holography . Although these efforts have been motivated primarily by interest in basic science, it is possible to envision a number of technologically important uses for surfaces that are modified with microscopically patterned redox- or electronically-conducting polymer films such as fabrication of microelectronic or -photonic devices 31,41 or microsensor arrays …”

Thermally Activated in Situ Doping Enables Solid-State Processing of Conducting Polymers

“…Heat has been used as a stimulus to immobilize thin-film structures of conjugated polymers by thermal cleavage of solubilizing side chains or thermally activated cross-linking. − Using heat to trigger a doping event post-processing would eliminate thickness-dependent diffusion and activation limitations. Fortunately, some acid precursors can also be activated via heatcommonly referred to as thermal acid generators (TAGs)which are primarily used as curing agents for coatings. , In 1991, Angelopoulos et al considered in situ doping of thin spin-coated polyaniline films with diethylammonium triflate salt through thermal activation and then went on to use these latent dopants for lithography through activation via e-beam irradiation . We argue that the use of TAGs as dopant precursors is an intriguing route for coprocessing of conjugated polymers and dopants, which would considerably simplify manufacturing of thick conducting polymer structures.…”

“…48,49 In 1991, Angelopoulos et al considered in situ doping of thin spin-coated polyaniline films with diethylammonium triflate salt through thermal activation and then went on to use these latent dopants for lithography through activation via e-beam irradiation. 50 We argue that the use of TAGs as dopant precursors is an intriguing route for coprocessing of conjugated polymers and dopants, which would considerably simplify manufacturing of thick conducting polymer structures.…”

Approaching Rapid, High‐Resolution, Large‐Area Patterning of Semiconducting Polymers Using Projection Photothermal Lithography

“…Typically, specific chemical functionalization is required to selectively render areas of the film insoluble, either by polymerizing under exposure to UV light, or controlling film solubility with molecular dopants. [13][14][15][16][17] Due to the excellent solution processability of SPs, the majority of patterning techniques focus on printing technologies. Several printing methods, including inkjet printing and stamp/liftoff techniques have been developed for SPs.…”