Bias Stability of Zinc-Tin-Oxide Thin Film Transistors with Al2O3 Gate Dielectrics

TitleBias Stability of Zinc-Tin-Oxide Thin Film Transistors with Al2O3 Gate Dielectrics
Publication TypeConference Paper
Year of Publication2009
AuthorsTriska, J., J. F. Conley, R. Presley, and J. F. Wager
Conference NameIEEE International Integrated Reliability Workshop (IRW)
Pagination86 - 89
Date Published10/2009
PublisherIEEE
Conference LocationSouth Lake Tahoe, CA
ISBN Number978-1-4244-3921-8
Abstract

Zinc-tin-oxide (ZTO) thin film transistors (TFTs) with atomic layer deposition (ALD) Al₂O₃ gate dielectrics were fabricated and compared to devices with PECVD SiO₂ gate dielectrics. The Al₂O₃ devices showed acceptable mobility (~14 cm2/V·s), subthreshold slope (~0.4 V/dec), and ION/IOFF (~107). However, a pronounced positive VT shift was observed during initial gate voltage sweeps, consistent with electron trapping. In an effort to stabilize operation, devices were made with varying Al₂O₃ deposition temperature, O₂ plasma exposure, and a plasma-enhanced chemical vapor deposited (PECVD) SiO₂ capping layer. It was found that capping of the Al₂O₃ with a thin (2-3 nm) layer of PECVD SiO₂ altered the trapping behavior and reduced the bias instability significantly, suggesting that the Al₂O₃/ZTO interface is the source of the trapping.

DOI10.1109/IRWS.2009.5383025