Corrosion Behavior and Metallization of Cu-Based Electrodes Using MoNi Alloy and Multilayer Structure for Back-Channel-Etched Oxide Thin-Film Transistor Circuit Integration

Abstract

Mo/Cu bilayer is the most conventional metal electrode with an excellent electrical conductivity and high environmental resistance for large-area back-channel-etch amorphous oxide thin-film transistors (TFTs) circuit integration. However, the Mo/Cu bilayer is metallized with a poor etch profile in conventional weak acidic H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -based etchant solution. This is attributed to the formation of Mo-related oxide residue and a high etch rate ratio between Mo and Cu, which results in short circuit and electrical degradation in the following microscale metallization and induces electrical instability on oxide TFT. We have replaced Mo with a MoNi (Mo:Ni = 1:3) alloy that has a larger galvanic potential difference in Cu-Ni (E° <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Cu-Ni</sub> : 0.597 V > E° <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Cu-Mo</sub> : 0.492 V) and seldom induces metal oxide residues in conventional etchants. In addition, an alternative three-electrode structure (MoNi/Cu/MoNi) was proposed to suppress Cu ionization by offering sufficient galvanic current from top and bottom MoNi layers. As a result, this MoNi/Cu/MoNi exhibits a wet-etched morphology with a rectangular profile, optimal taper angle, and less CD loss, which allows the formation of microscale metal linewidth. Furthermore, the application of MoNi/Cu/MoNi three-layer electrode in TFTs leads to more reliable electrical performance and good uniformity.