Effect of Source/Drain Electrode Materials on the Electrical Performance and Stability of Amorphous Indium-Tin-Zinc-Oxide FETs

• Published in: IEEE transactions on electron devices Vol. 71; no. 9; pp. 5437 - 5442
• Main Authors: An, Seong Ui, Ahn, Dae-Hwan, Ju, Gijun, Chen, Simin, Seop Ji, Yo, Han, Jae-Hoon, Kim, Jaekyun, Kim, Younghyun
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.09.2024; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Amorphous indium-tin-zinc-oxide (a-ITZO); Amorphous materials; Bias; bias stability; electrical performance; Electrode materials; Electrodes; Field effect transistors; field-effect transistors (FETs); Indium; Iron; Logic gates; Molybdenum; Nickel; Oxygen; oxygen diffusion; Photoelectrons; Semiconductor devices; Sputtering; Stability; Stability criteria; X ray photoelectron spectroscopy; Zinc
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2024.3433831

The gate-bias stability of amorphous indium-tin-zinc-oxide (a-ITZO) field-effect transistors (FETs) is critical for their display and emerging memory applications. However, a-ITZO FETs suffer from insufficient gate-bias stability induced by oxygen vacancies in the channel layer. To address this issue, we examined the impact of source/drain (S/D) electrode materials (W, Mo, and Ni) on the oxygen vacancy formation and electrical characteristics in the a-ITZO FETs. Through X-ray photoelectron spectroscopy (XPS) analysis, we found that the Ni S/D electrode is effective in forming fewer oxygen vacancies in the a-ITZO channel, whereas W and Mo induce many oxygen vacancies. Our proposed model suggests that the Ni electrode absorbing less oxygen from the a-ITZO films compared to other electrodes leads to fewer oxygen vacancies in the a-ITZO channel. Notably, the a-ITZO FETs incorporating Ni S/D electrodes exhibit not only excellent electrical performance, including a high field-effect mobility of 27.6 cm2/Vs, a steep subthreshold swing (SS) of 71.8 mV/decade, and high on/off ratio of <inline-formula> <tex-math notation="LaTeX">\sim 10^{{7}} </tex-math></inline-formula>, but also an outstanding gate-bias stability (<inline-formula> <tex-math notation="LaTeX">\Delta V_{\text {th}} = -0.04 </tex-math></inline-formula> V) under negative bias stress (NBS) testing. These findings underscore the potential of Ni S/D electrodes in advancing the development of high-performance, stable a-ITZO FETs for the next-generation semiconductor devices.