Role of MoTi diffusion barrier in amorphous indium-gallium-zinc-oxide thin-film transistors with a copper source/drain electrode

Abstract This paper reports why the Cu/MoTi/In-Ga-Zn-O(IGZO) contact schematic exhibited acceptable electrical properties and stability in an IGZO transistor that is used in a state-of-the-art active-matrix organic-light-emitting-diodes television as the switcher and driver. For a comparative study, different Cu/diffusion barrier(DB)/IGZO contact schemes (DB = Mo, Ti, and MoTi) were applied in IGZO transistors to evaluate the suitability of different diffusion barriers. The IGZO transistor with the Cu/(Mo, Ti)/IGZO contact exhibited improved carrier mobility and a lower gate swing compared to those of the control device with direct Cu/IGZO contact. The role of the Mo DB was to effectively prevent in-diffusion of Cu atoms during thermal annealing, which is responsible for its superior performance. In contrast, the Ti DB was found to be suitable for low-ohmic contact due to its higher oxidation power, leading to enhanced transport properties. a-IGZO thin-film transistors with the Cu/MoTi/IGZO stack showed the best transport properties in terms of the mobility, gate swing, and contact resistance. Our findings are discussed on the basis of the synergic effect of the MoTi alloy system based on various structural and chemical analyses.