Fabrication of top-contact pentacene-based organic thin-film transistors with short channels using two-step SU8/poly(vinyl alcohol) lift-off photolithography process

We propose a two-step SU8/poly(vinyl alcohol) (PVA) lift-off photolithography scheme for fabricating top-contact pentacene-based organic thin-film transistors (OTFTs) with small channels. The bilayer of PVA and SU8 will not damage the pentacene channel layer in the lift-off photolithography process used in forming the patterned pentacene channel layer and source/drain metal electrodes. We demonstrate a device that not only obtains a 5 µm short channel length for source/drain metal-electrode patterning but also avoids fringe current resulting from pentacene channel layer patterning. The field-effect mobility and threshold voltage of the pentacene-based OTFTs were changed from 0.29 to 0.12 cm2 V−1 s−1 and from −5.74 to −3.19 V by varying the channel length from 50 to 5 µm, respectively. The proposed scheme is a good candidate for use in the design and fabrication of high-performance short-channel organic electronics.