Impact of NH₃ plasma treatment for solution-processed indium oxide thin-film transistors with low thermal budget

The challenges associated with low-temperature solution-processed metal oxide thin-film transistors (TFTs) have hindered the realization of flexible oxide electronics at temperatures lower than 200 °C. NH₃ plasma treatment is embarked upon as a route to effectively transform the chemical precursors to semiconducting metal oxides with high electrical quality. NH₃ plasma-activated indium oxide (InO_x) TFTs with saturated mobility 2.48 cm²V⁻¹s⁻¹ have been obtained at temperature as low as 150 °C. The low-temperature activation mechanism of NH₃ plasma treatment for InO_x films and the role of post-annealing in the fabrication process of InO_x TFTs have been explored. Research shows that NH₃ plasma treatment activates InO_x films based on plasma bombardment, radicals doping and radical reactions; then, unreacted radicals and interstitial radicals were effectively removed by extra thermal energy from post-annealing. In comparison to thermal annealing, NH₃ plasma treatment with moderate post-annealing is capable of achieving high degrees of condensation and densification reactions for InO_x film and modulating the carrier concentration in a manner suitable for high-performance semiconducting behavior with low thermal budget. However, The InO_x film after NH₃ plasma treatment exhibited a non-uniform geometry due to the effect of plasma-induced damage in the local regions of InO_x film, which restricts its commercial application. Some strategies were reported to eliminate the effect of plasma-induced damage by changing plasma conditions or pre-annealing temperature. The results demonstrated that changing plasma conditions by decreasing the plasma chamber temperature or the plasma power can eliminate plasma-induced damage, but attenuate the electrical performance of InO_x TFT; nevertheless, changing pre-annealing temperature to 30 °C not only effectively eliminate plasma-induced damage, but also further improve the electrical performances of InO_x TFT. These results provide a way for fabricating low-temperature oxide circuitry and supply an effective idea for avoiding plasma-induced damage.