Submicron-channel-length organic thin-film transistors on flexible substrates

Abstract

A process for the fabrication of organic thin-film transistors (TFTs) with channel lengths as short as 0.5 μm on flexible plastic substrates has been developed. The TFTs are fabricated in the bottom-gate, top-contact (inverted staggered) architecture and employ vacuum-deposited small-molecule organic semiconductors and a low-temperature-processed gate dielectric that is sufficiently thin to allow the TFTs to operate with voltages of about 2 to 3 V. For a channel length of 0.5 μm, the TFTs have effective field-effect mobilities of 0.08 cm2/Vs (p-channel TFTs) and 0.03 cm2/Vs (n-channel TFTs), on/off current ratios of at least 106, and subthreshold swings of about 140 mV/decade. For 11-stage complementary and unipolar ring oscillators based on TFTs with a channel length of 1 μm, signal propagation delays per stage as short as 6.6 μs and 420 ns have been measured at a supply voltage of 3 V.