Improved performance of the amorphous indium-gallium-zinc oxide thin film transistor with Cu-Mo source/drain electrode

Copper is an alternative material for aluminum electrode to meet the stringent requirement for high mobility and low resistance-capacitance (RC) delay of amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistor (TFT) for next generation of display technology due to its intrinsic high conductivity. However, low bonding strength between copper layer and insulator/glass and easy diffusion into active layer restrict its application in the field of TFT. In this work, a 30 nm thin film of molybdenum is introduced into copper electrode to form a copper-molybdenum source/drain electrode of a-IGZO TFT, which not only inhibits the diffusion of copper, but also enhances the interfacial adhesion between electrode and substrate. The obtained Cu-Mo TFT possesses a high mobility of 9.26 cm2·V-1·s-1 and a low subthreshold swing of 0.11 V/Decade. Moreover, it has shorter current transfer length(0.2 μm), lower contact resistance (1072 Ω), and effective contact resistance (1×10-4Ω·cm2) than the pure copper electrode. Cu-Mo electrode with low contact resistance and high adhesion to substrates paves the way to the application of copper in high conductivity interconnection of a-IGZO TFT.