All solution-processed amorphous oxide thin-film transistors using UV/O₃ treatment

Abstract

In the fabrication of amorphous oxide thin-film transistors (TFTs) by all-solution process, an ultraviolet–ozone (UV/O3) treatment and solution materials were adopted. By applying the UV/O3 treatment for solution-processed In2− x Ga x ZnO4 channel layers, enhancement of TFT characteristics was achieved. In particular, the most appropriate metal composition for the In2− x Ga x ZnO4 system with UV/O3 treatment was found to be x = 1.0. In addition to the channel layers, solution-processed LaNiO3, Bi–Nb–O/La–Ta–O stacked layer, and ITO films were formed as the gate electrode, gate insulator, and source and drain electrodes, respectively, for TFT fabrication. Using UV/O3 treatment and solution materials, all-solution-processed amorphous oxide TFTs were successfully fabricated, and superior TFT properties, including an on–off current ratio of 107, a threshold voltage of 1.6 V, a subthreshold swing of 200 mV/decade, and a field-effect mobility of 0.49 cm2 V−1 s−1, were achieved.

Recent Progress in Photonic Processing of Metal‐Oxide Transistors

“…Low‐pressure mercury lamps feature strong and clearly defined emission peaks at 253.7 nm (90% of emission power) and 184.9 nm (10%). The energies at these wavelengths (472 and 647 kJ mol −1 ) are adequate to break the bonds of common chemical groups such CO, CC and CH which are found in many soluble metal‐oxide precursors . Additionally, the shorter wavelength photons promote the formation of ozone (O 3 ) when the DUV treatment is carried out in an air environment, which results in further chemical reactions …”

“…However, choosing air as the process atmosphere for a DUV treatment can have beneficial effect as well. Umeda et al studied the effect of DUV irradiation alone without ozone (N 2 environment), ozone without DUV (using a separate ozonizer) and the combination of both (DUV in ambient air) before thermal annealing (TA) . They concluded that high energy photons are responsible for the decomposition of relevant organic ligands (e.g., CO and CH bonds) but that the presence of O 3 is critical in removing the decomposed elements.…”

“…Overall, for the fabrication of metal‐oxide electronic devices such as thin‐film transistors, there is a wide range of precursors to choose from. The most common choices include metal compounds based on nitrates, acetylacetonates, alkoxides, or acetates and to a lesser extent chlorides, acrylates, and hydroxides . The kinds of materials that were successfully processed with the help of DUV irradiation include all those that are required to form metal‐oxide TFTs, i.e., semiconductors, dielectrics, and conductors.…”

“…The kinds of materials that were successfully processed with the help of DUV irradiation include all those that are required to form metal‐oxide TFTs, i.e., semiconductors, dielectrics, and conductors. Among them, the most commonly employed n‐type semiconductors are IGZO, IZO, zinc tin oxide (ZTO), as well as the binary compounds ZnO, In 2 O 3 , and GaO x . For p‐type oxides, there are far fewer studies available, with Cu 2 O being one of the exceptions …”

47-3:Invited Paper: Various Low-Temperature Activation Methods for IGZO TFTs in Flexible Displays

“…SUT method could activate IGZO TFTs at lower temperatures due to the formation of oxygen radicals by UV irradiation. UV irradiation at wavelengths of 185 and 254 nm generates reactive oxygen radicals in air as shown below [7] O2 + hv (185 nm…”