Improving the Electrical Properties of Zinc-Tin Oxide Thin-Film Transistors by Additive using Electrohydrodynamic Jet Technology

Oxide thin-film transistors (TFTs) are important semiconductor materials for display backplanes. To fabricate flexible displays, not only display modes but also TFTs are important. Flexible TFTs are especially needed for flexible displays, and related processes need to be developed. Printing is a good choice for the new fabrication of oxide TFTs. Electrohydrodynamic (EHD) jet printing is an excellent alternative for making flexible TFTs. To improve the electrical properties of oxide TFTs using EHD jet printing, propylene monomethyl ether acetate (PGMEA) was added to a zinc-tin oxide (ZTO) formulation. EHD jet printing was performed by Taylor cone jet mode with parameters of 2.4 kV and 0.064 & mu;L/s to obtain uniform thin films at a substrate temperature of 50oC. Much improved TFT properties were obtained, including a mobility of 7.11 cm2/V s, on-to-off current ratio of 2.8 x 106 and subthreshold slope of 1.44 V/dec for ZTO TFT with 5 wt% of PGMEA, and a mobility of 1.43 cm2/V s, on-to-off current ratio of 2.7 x 105 and subthreshold slope of 1.32 V/dec for the ZTO TFT. Almost no hysteresis behavior was observed in the oxide TFTs with added PGMEA. We report a new way to improve the electrical properties of oxide TFTs, by the simple addition of PGMEA.