Effects of Stacked Mo–Ti/Cu Source and Drain Electrodes on the Performance of Amorphous In–Ga–Zn-O Thin-Film Transistors

In this letter, the performance of amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs) is investigated using the stacked Mo-Ti/Cu source (S) and drain (D) electrodes. The test samples A and B of the a-IGZO TFT have interlayers with Mo/Ti ratios of 2.29 and 1.15, respectively, for the SD electrodes, and each has a core layer of Cu stacked on the top of the interlayers. They were fabricated and measured to compare their performance in terms of the transfer characteristic and mobility. The measurement results showed that the sample B with a lower Mo/Ti ratio exhibited better performance than the sample A: higher field-effect mobility by 4.4 cm
²
/V-s, higher saturation mobility by 3.2 cm
²
/V-s, smaller sub-threshold slope by 0.91 V/decade, and lower threshold voltage by 1.4 V. In addition, the material properties of samples A and B were obtained using the line scan of the energy dispersive spectroscopy and analyzed with technology computer-aided design simulation. As a result, the performance of a-IGZO TFTs can be optimized by tuning the Mo/Ti ratios of the interlayer in the stacked SD electrodes.