Improvement in reliability of amorphous indium–gallium–zinc oxide thin-film transistors with Teflon/SiO₂ bilayer passivation under gate bias stress

Abstract

The reliability of amorphous indium–gallium–zinc oxide (a-IGZO) thin-film transistors (TFTs) with Teflon/SiO2 bilayer passivation prepared under positive and negative gate bias stresses (PGBS and NGBS, respectively) was investigated. Heavier electrical degradation was observed under PGBS than under NGBS, indicating that the environmental effects under PGBS are more evident than those under NGBS. The device with bilayer passivation under PGBS shows two-step degradation. The positive threshold voltage shifts during the initial stressing period (before 500 s), owing to the charges trapped in the gate insulator or at the gate insulator/a-IGZO active layer interface. The negative threshold voltage shift accompanies the increase in subthreshold swing (SS) for the continuous stressing period (after 500 s) owing to H2O molecules from ambience diffused within the a-IGZO TFTs. It is believed that Teflon/SiO2 bilayer passivation can effectively improve the reliability of the a-IGZO TFTs without passivation even though the devices are stressed under gate bias.

Improvement of Electrical Characteristics and Stability of Amorphous Indium Gallium Zinc Oxide Thin Film Transistors Using Nitrocellulose Passivation Layer

“…The V th shifts of a-IGZO TFTs without PVLs and with NC-PVLs were −1.98 and −1.90 V, respectively. As reported in previous research, it was confirmed that the V th of a-IGZO TFTs is scarcely affected by negative bias stress because a-IGZO TFTs is n-type. Therefore, in this research, influence for negative bias voltage was negligible.…”

“…Consequently, these results show NC-PVLs have excellent barrier properties to prevent adsorption of oxygen and demonstrate an improved stability of a-IGZO TFTs. PBTS and NBTS tests at 50 °C were also conducted to verify the influence of temperature for organic PVLs and moisture in ambient air, respectively. , As shown in Figure , in the results of the PBTS test for a-IGZO TFTs without PVLs, with PMMA-PVLs, and with NC-PVLs, the values of positive V th shifts were 5.74, 4.77, and 3.88 V, respectively. In the results of the PBTS test, the stability of a-IGZO TFTs with NC-PVLs was improved up to 32 and 19% compared to PVLs ability of a-IGZO TFTs without PVLs and with PMMA-PVLs, respectively.…”

Performance Enhancement of Transparent Amorphous IGZO Thin-Film Transistor Realized by Sputtered Amorphous AlOx Passivation Layer

“…For example, for the stress duration of 5000 s, the V th of the TFT without passivation layer positively shifted by 1.02 V; in contrast, the V th of the TFT passivated by the AlO x passivation layer positively shifted by only 0.12 V. It was suggested that the adsorbed oxygen molecules could act as acceptor-ECS Journal of Solid State Science and Technology, 2021 10 045006 like states, which capture electrons leading to a positive V th shift. 39,40 As shown in Fig. 8b, the passivation can effectively prevent adsorbing O 2 molecules from the ambient, and thus the PBIS reliability is improved.…”

Correlation between passivation film density and reliability of In–Ga–Zn–O thin-film transistors

“…[8][9][10][11][12] Since a passivation layer is essential for improving the PBS reliability, many efforts have been made to understand the effects of the materials and deposition conditions of a passivation layer on the electrical properties and reliability of the IGZO TFTs. [13][14][15][16][17][18][19][20][21][22] To the best of our knowledge, there have been few research studies reported on the effect of the permeability of ambient molecules through the passivation layer on PBS reliability.…”