Atomic Layer Deposition of WO3-Doped In2O3 for Reliable and Scalable BEOL-Compatible Transistors

Chanyoung Yoo; Jonathan Hartanto; Balreen Saini; Wilman Tsai; Vivek Thampy; Somayeh Saadat Niavol; Andrew C Meng; Paul C McIntyre

doi:10.1021/acs.nanolett.4c00746

Atomic Layer Deposition of WO₃-Doped In₂O₃ for Reliable and Scalable BEOL-Compatible Transistors

Nano Lett. 2024 May 15;24(19):5737-5745. doi: 10.1021/acs.nanolett.4c00746. Epub 2024 Apr 30.

Authors

Chanyoung Yoo^{1

2

3}, Jonathan Hartanto¹, Balreen Saini¹, Wilman Tsai¹, Vivek Thampy², Somayeh Saadat Niavol⁴, Andrew C Meng⁴, Paul C McIntyre^{1

2}

Affiliations

¹ Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States.
² SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States.
³ Department of Materials Science and Engineering, Hongik University, Seoul 04066, Republic of Korea.
⁴ Department of Physics and Astronomy, University of Missouri, Columbia, Missouri 65211, United States.

PMID: 38686670
DOI: 10.1021/acs.nanolett.4c00746

Abstract

Tungsten oxide (WO₃) doped indium oxide (IWO) field-effect transistors (FET), synthesized using atomic layer deposition (ALD) for three-dimensional integration and back-end-of-line (BEOL) compatibility, are demonstrated. Low-concentration (1∼4 W atom %) WO₃-doping in In₂O₃ films is achieved by adjusting cycle ratios of the indium and tungsten precursors with the oxidant coreactant. Such doping suppresses oxygen deficiency from In₂O_2.5 to In₂O₃ stoichiometry with only 1 atom % W, allowing devices to turn off stably and enhancing threshold voltage stability. The ALD IWO FETs exhibit superior performance, including a low subthreshold slope of 67 mV/decade and negligible hysteresis. Strong tunability of the threshold voltage (V_th) is achieved through W concentration tuning, with 2 atom % IWO FETs showing an optimized V_th for enhancement-mode and a high drain current. ALD IWO FETs have remarkable stability under bias stress and nearly ideal performance extending to sub-100 nm channel lengths, making them promising candidates for high-performance monolithic 3D integrated devices.

Keywords: atomic layer deposition; field-effect transistor; indium oxide; oxide semiconductor; tungsten-doped indium oxide.