Patterning of poly(3-alkylthiophene) thin films by direct-write ultraviolet laser lithography

Thin films of poly(3-methylthiophene) (P3MT), poly(3-butylthiophene) (P3BT) and poly(3-hexylthiophene) (P3HT) have been patterned into microstructures using the 325 nm radiation from a helium-cadmium laser. At sufficiently high energy fluences, spontaneous mass removal occurred in all three polymers to give groove structures about 3 μm wide. At lower incident fluences, both P3BT and P3HT underwent crosslinking as a result of the irradiation. Using chloroform as a developer, 1–6 μm wide line structures were obtained on glass substrates. For the lowest fluences, the P3BT linewidths after development were narrower than the nominal beam diameter. The present results are potentially useful to the fabrication of polymer electronic devices and microlithography.