The use of high density plasma system to improve the etch properties of the zinc tin oxide thin film for transparent thin film transistors active layers

In this work, the etching characteristics of the zinc tin oxide (ZTO) thin films were investigated as a function of the BCl3/Ar gas mixture ratio in the inductively coupled plasma system. As the BCl3 content in Ar plasma increased, the etch rate of ZTO and indium tin oxide (ITO) thin films, and the selectivity of ITO over ZTO increased reaching the maximum of 54.2 nm/min, 126.2 nm/min, and 2.33 in the BCl3/Ar (6:14 sccm) gas mixing ratio, respectively. The chemical mechanism and byproduct of the etching process were determined by XPS analysis. It was confirmed that the etching process affects the surface of the active layers. Clearly, the damage caused by the etching process can affect the surface roughness of the active layers.