Effects of channel thickness on oxide thin film transistor with double-stacked channel layer

Abstract

To improve the field effect mobility and control the threshold voltage (V _th ) of oxide thin film transistors (TFTs), we fabricated the oxide TFTs with double-stacked channel layers which consist of thick Zn-Sn-O (ZTO) and very thin In-Zn-O (IZO) layers. We investigated the effects of the thickness of thin conductive layer and the conductivity of thick layer on oxide TFTs with doublestacked channel layer. When we changed the thickness of thin conductive IZO channel layer, the resistivity values were changed. This resistivity of thin channel layer affected on the saturation field effect mobility and the off current of TFTs. In case of the thick ZTO channel layer which was deposited by sputtering in Ar: O₂ = 10: 1, the device showed better performances than that which was deposited in Ar: O₂ = 1: 1. Our TFTs showed high mobility (μ _FE ) of ~ 40.7 cm²/Vs and V _th of ~ 4.3 V. We assumed that high mobility and the controlled V _th were caused by thin conductive IZO layer and thick stable ZTO layer. Therefore, this double-stacked channel structure can be very promising way to improve the electrical characteristics of various oxide thin film transistors.