Issue 41, 2023

Contact properties of a low-resistance aluminum-based electrode with metal capping layers in vertical oxide thin-film transistors

Abstract

Thin-film transistors (TFTs) with a small pitch size are necessary to realize high-resolution displays for virtual reality and augmented reality applications. Particularly, electrodes require low-resistance metals to reduce the resistance–capacitance delay caused by the increased pixel density. However, low-resistance Al can easily oxidize in bottom-contact structures of vertical TFTs owing to the oxidative deposition environment. This study quantitatively analyzed the contact properties of an Al-based metal with Mo and Ti capping layers. The Mo/Al/Mo and Ti/Al/Ti were adopted as the source/drain (S/D) electrodes, and their contact properties were compared. The top-gate bottom-contact device with Mo/Al/Mo S/D exhibited better contact properties, with a 0.02 V turn-on voltage (Von), 3.5 × 107 ON/OFF ratio, and 5.7 kΩ contact resistance (RSD). By contrast, the device with Ti/Al/Ti S/D exhibited degraded characteristics, with a −0.3 V Von, 0.9 × 107 ON/OFF ratio, and 17 kΩ RSD owing to metal oxidation. The contact properties were further examined through ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. Vertical TFTs were fabricated using Mo/Al/Mo and Ti/Al/Ti electrodes, and their electrical properties were investigated. The vertical TFT with Mo/Al/Mo electrodes exhibited reasonable performance, with a field-effect mobility of 3.3 cm2 V−1 s−1 and RSD of 15 kΩ. Conversely, the device with Ti/Al/Ti electrodes yielded degraded transfer characteristics, with a mobility of 0.05 cm2 V−1 s−1 and RSD of 984 kΩ. The analysis indicates that electrode materials significantly influence the electrical performance of vertical TFTs. Therefore, electrode materials must be carefully selected and structured to realize high-end vertical TFT arrays.

Graphical abstract: Contact properties of a low-resistance aluminum-based electrode with metal capping layers in vertical oxide thin-film transistors

  • This article is part of the themed collection: #MyFirstJMCC

Supplementary files

Article information

Article type
Paper
Submitted
12 Aug. 2023
Accepted
26 Sept. 2023
First published
27 Sept. 2023

J. Mater. Chem. C, 2023,11, 14177-14186

Contact properties of a low-resistance aluminum-based electrode with metal capping layers in vertical oxide thin-film transistors

S. Jeon, K. Lee, S. Lee, S. Cho, C. Hwang, J. B. Ko and S. K. Park, J. Mater. Chem. C, 2023, 11, 14177 DOI: 10.1039/D3TC02880A

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