Effects of O₂ plasma treatment on low temperature solution-processed zinc tin oxide thin film transistors

The electrical characteristics such as threshold voltage, saturation mobility, and electrical reliability of low temperature (350 °C) solution-processed zinc tin oxide (ZTO) thin film transistors (TFTs) were improved considerably by employing O₂ plasma treatment. O₂ plasma treatment was performed by plasma asher and causes preferential dissociation of weak halide-related bonding such as Cl bonding by ion bombardment. After O₂ plasma treatment, the threshold voltage decreased from 25.0 to 10.7 V because of an increase in electron concentration due to the reduction of Cl bonding and simultaneous composition of O-related bonding. The saturation mobility was increased from 0.09 to 0.58 cm² V^-1 s^-1 because of the increase in electron concentration and reduction of the halide residues such as Cl atoms acting as trap states by employing O₂ plasma treatment. Moreover, the electrical reliability such as threshold voltage shift was improved from 5.34 to 3.23 V for positive gate bias-stress because O₂ plasma reduced the halide residues such as Cl atoms acting as trap states.