Teflon/SiO₂ Bilayer Passivation for Improving the Electrical Reliability of Oxide TFTs Fabricated Using a New Two-Photomask Self-Alignment Process

• Published in: Materials Vol. 8; no. 4; pp. 1704 - 1713
• Main Authors: Fan, Ching-Lin, Shang, Ming-Chi, Li, Bo-Jyun, Lin, Yu-Zuo, Wang, Shea-Jue, Lee, Win-Der, Hung, Bohr-Ran
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 13.04.2015; MDPI
• Subjects: Channels; Deposition; Electrodes; Engineering; Evaporation; Glass substrates; indium gallium zinc oxide (IGZO); Oxides; Passivation; passivation layer; Plasma etching; Polytetrafluoroethylenes; Semiconductor devices; Semiconductors; Silicon dioxide; SiO2; Teflon; Thin film transistors; thin film transistors (TFTs); Transistors; Zinc oxides; Taiwan; Teflon; indium gallium zinc oxide (IGZO); passivation layer; thin film transistors (TFTs); SiO2
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma8041704

This study proposes a two-photomask process for fabricating amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs) that exhibit a self-aligned structure. The fabricated TFTs, which lack etching-stop (ES) layers, have undamaged a-IGZO active layers that facilitate superior performance. In addition, we demonstrate a bilayer passivation method that uses a polytetrafluoroethylene (Teflon) and SiO₂ combination layer for improving the electrical reliability of the fabricated TFTs. Teflon was deposited as a buffer layer through thermal evaporation. The Teflon layer exhibited favorable compatibility with the underlying IGZO channel layer and effectively protected the a-IGZO TFTs from plasma damage during SiO₂ deposition, resulting in a negligible initial performance drop in the a-IGZO TFTs. Compared with passivation-free a-IGZO TFTs, passivated TFTs exhibited superior stability even after 168 h of aging under ambient air at 95% relative humidity.