The influence on electrical characteristics of amorphous indium tungsten oxide thin film transistors with multi-stacked active layer structure

In order to effectively enhance the carrier mobility and device stability, simultaneously, a multi-stacked active layer of thin film transistor with a novel type of channel material, amorphous indium-tungsten-oxide, is proposed in this work. Atop-cappingoxygen-rich indium-tungsten-zinc-oxide thin film is used for suppressing the influence of the molecular adsorption or desorption from the ambient at the back channel in the gate bias stress test. In addition, a bottom-bufferingoxygen-rich indium-tungsten-zinc-oxide thin film is deposited to avoid the oxygen vacancy generation during the following thermal process. On the other hand, a 1-nm thick WO₃ film is inserted between the high-k gate insulator and active layer, which play important roles as interfacial layer for improving the interface quality and keeping the stability of front channel film. Besides, an HfO₂ dielectric film is chosen as gate insulator for realizing the low-voltage operation. As a result, the novel tungsten doped channel material with both-sideoxygen-rich active layer exhibits a high I_ON/I_OFF current ratio of ~6 × 10⁷ for low gate leakage current, attributing to the top-cappingoxygen-rich thin film. Then, a high field-effect mobility of ~27.9 cm²/V.s and a low sub-threshold swing of 0.079 V/decade are achieved by the good interface quality. This structure with both-sideoxygen-rich active layer exhibits its potential application for the future high-resolution and large-size display manufacture.