Change of electrical properties of a-IGZO TFT depending on processing parameters

Abstract

Recently, colossal researches are conducted about a-IGZO as an alternative of a-Si. We studied on the electrical property changes of a- IGZO TFT depending on the process parameters. We used p+ Si substrate as a gate electrode and thermal SiO2 as a gate insulator. An a-IGZO active layer was fabricated using rf-magnetron sputtering on the thermal SiO2 with various power and O2 ratio. We varied rf-power, O2 ratio from 1.5 W/cm2 to 5 W/cm2 and from 1.2 to 1.8, respectively, and we investigated the relation between rf-power, O2 ratio and TFT characteristic such as Vth, on current, S.S, hysteresis changes. We found out that there were remarkable changes in the TFT characteristics with varying power and O2 ratio. As increasing power, S.S was deteriorated and on current was decreased while hysteresis was increased, and as increasing O2 ratio, Vth shifted positive while on current decreased. In order to demonstrate the mechanism of the property change, we investigated the interface between channel layer and gate insulator layer, and also analyzed the density of states(DOS) of the channel layer.