4.3: Invited Paper: High Mobility Oxide TFT for Large Area High Resolution AMOLED

Abstract

The adoption of bi‐layered etch stop layer (BiESL) for oxide thin film transistor with high carrier mobility was proposed for the application to the large area high resolution AMOLED. A novel bi‐layered etch stop structure composed of Al2O3/SiO2, in which thin and dense Al2O3 film prepared by atomic layer deposition was deposited on the PECVD SiO2 layer. High mobility of In‐Ga‐Zn‐O TFT with the proposed BiESL showed no significant change in turn‐on voltage, even without passivation film. The field‐effect saturation mobility and sub‐threshold swing were measured as 29 cm2/V.s and 0.21 V/dec, respectively. Hydrogen doping during the PECVD SiNx passivation process can be effectively prevented by the introduction of Al2O3. Furthermore organic planarization film can be coated directly on top of the TFT array without causing any significant degradation of TFT performance.

Beneficial effect of hydrogen in aluminum oxide deposited through the atomic layer deposition method on the electrical properties of an indium–gallium–zinc oxide thin-film transistor

“…In oxide TFTs, active layers with a higher carrier concentration are preferred because the mobility is proportional to the carrier concentration [1], but V th control difficulty simultaneously occurs [2]. The oxygen vacancy and hydrogen in oxide semiconductors are mainly regarded as sources of charge carrier.…”

“…The source of hydrogen in the active layer can be any of the following: (1) ambient atmosphere; (2) incorporation during the deposition of an active layer, such as the gate insulator or passivation layer; and (3) diffusion from the adjacent layers with an active layer during post-annealing. The first can be negligible when a passivation layer is adopted, but the other sources occur very often during the fabrication of oxide TFTs.…”

Combination of Gate-Stack Process and Cationic Composition Control for Boosting the Performance of Thin-Film Transistors Using In–Ga–Zn–O Active Channels Prepared by Atomic Layer Deposition

“…However, the maximum value of carrier mobility was obtained to be no more than 15 cm 2 /V s, which was regarded as too a low value to meet severe mobility specifications for highly functional applications such as super Hi-vision 25 and glass-free 3D TV. 26 In these next-generation FPD applications, the carrier mobility should be improved to be higher than 25 cm 2 /V s for securing sufficient current drivability. 27,28 Thus, it is an urgent issue to enhance the carrier mobility of the TFTs exploiting the ALD-IGZO channel layers, and two technical approaches can be implemented.…”

AlO sputtered self‐aligned source/drain formation technology for highly reliable oxide thin film transistor backplane

“…Depending on the target application, for example, OLED displays, high barrier performance may be required during the TFT backplane fabrication process. Some researchers have reported that AlO layers formed by atomic layer deposition (ALD) offer excellent barrier performances . However, the ALD method provides limited productivity and limited substrate size scalability because of difficulty in performing deposition over large substrate areas within a suitably productive deposition time.…”