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

Abstract

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 ION/IOFF 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.