Amorphous NdIZO Thin Film Transistors with Contact-Resistance-Adjustable Cu S/D Electrodes

High-performance amorphous oxide semiconductor thin film transistors (AOS-TFT) with copper (Cu) electrodes are of great significance for next-generation large-size, high-refresh rate and high-resolution panel display technology. In this work, using rare earth dopant, neodymium-doped indium-zinc-oxide (NdIZO) film was optimized as the active layer of TFT with Cu source and drain (S/D) electrodes. Under the guidance of the Taguchi orthogonal design method from Minitab software, the semiconductor characteristics were evaluated by microwave photoconductivity decay (mu-PCD) measurement. The results show that moderate oxygen concentration (similar to 5%), low sputtering pressure (<= 5 mTorr) and annealing temperature (<= 300 degrees C) are conducive to reducing the shallow localized states of NdIZO film. The optimized annealing temperature of this device configuration is as low as 250 degrees C, and the contact resistance (R-C) is modulated by gate voltage (V-G) instead of a constant value when annealed at 300 degrees C. It is believed that the adjustable R-C with V-G is the key to keeping both high mobility and compensation of the threshold voltage (V-th). The optimal device performance was obtained at 250 degrees C with an I-on/I-off ratio of 2.89 x 10(7), a saturation mobility (mu(sat)) of 24.48 cm(2)/(V.s) and V-th of 2.32 V.

Automated summary

The study optimized NdIZO film as the active layer of TFT by adjusting oxygen concentration, sputtering pressure, and annealing temperature, resulting in improved semiconductor characteristics at an optimal annealing temperature of 250 degrees Celsius.