ZnO Thin-Film Transistor Grown by rf Sputtering Using Carbon Dioxide and Substrate Bias Modulation

Abstract EN

ZnO thin-film transistor (TFT) grown by rf magnetron sputtering in Ar/O2 atmosphere shows inferior turn-off characteristics compared to ZnO TFT grown by other methods.

We thought that reactions between Zn and O2 might produce defects responsible for the poor turn-off behavior.

In order to solve this problem, we studied sputtering growth in Ar/CO2 atmosphere at 450°C.

During sputtering growth, we modulated substrate dc bias to control ion supply to the substrate.

After growth ZnO was annealed in CO2 and O2 gas.

With these methods, our bottom-gate ZnO thin-film transistor showed 4.7 cm2/Vsec mobility, 4 × 10 6 on/off ratio, and –2 V threshold voltage.