Thin film transistors (TFTs) using In-Ga-Zn Oxide (IGZO) as active layer and the gate insulator was treated with NH3 plasma and N2O plasma, respectively, which is fabricated on flexible PI substrate in this work. The performance of IGZO TFTs with different plasma species and treatment time are investigated and compared. The experiment results show that the plasma species and treatment time play an important role in the threshold voltage, field-effect mobility, Ion/Ioff ratio, sub-threshold swing (SS) and bias stress stability of the devices. The TFT with a 10 seconds NH3 plasma treatment shows the best performance; specifically, threshold voltage of 0.34 V, field-effect mobility of 15.97 cm2/Vs, Ion/Ioff ratio of 6.33×107, and sub-threshold swing of 0.36 V/dec. The proposed flexible IGZO-TFTs in this paper can be used as driving devices in the next-generation flexible displays.

An ultraviolet (UV) nanosecond pulsed laser with a wavelength of 355 nm was applied to anneal amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFT) at various laser beam powers ranging from 0 to 280 mW. Laser irradiation was selectively carried out on the a-IGZO channel area using the beam scanning method after the a-IGZO TFT was formed through indium-tin oxide (ITO) electrode patterning and a subsequent lift-off process. After laser annealing, negative shifts in the threshold voltages and enhanced on-currents were observed at laser-beam powers ranging from 54 to 120 mW. No meaningful parameters were investigated for laser beams higher than 200 mW. By extracting the energy band gap and work function of a-IGZO from the transmittance and ultraviolet photoelectron spectroscopy (UPS) results, the ITO electrode/a-IGZO channel energy band structures were established under different laser annealing conditions, and the electron injection mechanism from the ITO to the a-IGZO channel was analyzed and optimized at a laser beam power of 120 mW. The results show that the electrical characteristics of the a-IGZO TFTs can be improved without any heat damage to the substrate because of the selective annealing process.

The electrical performance of the back-channel etched Indium–Gallium–Zinc–Oxide (IGZO) thin-film transistors (TFTs) with copper (Cu) source and drain (S/D) which are patterned by a selective etchant was investigated. The Cu S/D were fabricated on molybdenum (Mo) layer to prevent the Cu diffusion to the active layer (IGZO). We deposited the Cu layer using thermal evaporation and performed the selective wet etching of Cu using non-acidic special etchant without damaging the IGZO active layer. We fabricated the IGZO TFTs and compare the performance in terms of linear and saturation region mobility, threshold voltage and ON current (ION). The IGZO TFTs with Mo/Cu S/D exhibits good electrical properties as the linear region mobility is 12.3 cm2/V-s, saturation region mobility is 11 cm2/V-s, threshold voltage is 1.2 V and ION is 3.16 x 10-6 A. We patterned all the layers by photolithography process. Finally, we introduced SiO2-ESL layer to protect the device from the external influence. The results show that the prevention of Cu and introduced ESL layer enhances the electrical properties of IGZO TFTs.