Static and Dynamic Water Motion-Induced Instability in Oxide Thin-Film Transistors and Its Suppression by Using Low‑k Fluoropolymer Passivation

• Published in: ACS applied materials & interfaces Vol. 9; no. 31; pp. 26161 - 26168
• Main Authors: Choi, Seungbeom, Jo, Jeong-Wan, Kim, Jaeyoung, Song, Seungho, Kim, Jaekyun, Park, Sung Kyu, Kim, Yong-Hoon
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 09.08.2017
• Subjects: liquid-contact-electrification; water stability; solution process; thin-film transistors; fluoropolymer passivation; indium−gallium−zinc oxide
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.7b05948

Here, we report static and dynamic water motion-induced instability in indium–gallium–zinc-oxide (IGZO) thin-film transistors (TFTs) and its effective suppression with the use of a simple, solution-processed low-k (ε ∼ 1.9) fluoroplastic resin (FPR) passivation layer. The liquid-contact electrification effect, in which an undesirable drain current modulation is induced by a dynamic motion of a charged liquid such as water, can cause a significant instability in IGZO TFTs. It was found that by adopting a thin (∼44 nm) FPR passivation layer for IGZO TFTs, the current modulation induced by the water-contact electrification was greatly reduced in both off- and on-states of the device. In addition, the FPR-passivated IGZO TFTs exhibited an excellent stability to static water exposure (a threshold voltage shift of +0.8 V upon 3600 s of water soaking), which is attributed to the hydrophobicity of the FPR passivation layer. Here, we discuss the origin of the current instability caused by the liquid-contact electrification as well as various static and dynamic stability tests for IGZO TFTs. On the basis of our findings, we believe that the use of a thin, solution-processed FPR passivation layer is effective in suppressing the static and dynamic water motion-induced instabilities, which may enable the realization of high-performance and environment-stable oxide TFTs for emerging wearable and skin-like electronics.