Low-Temperature Formation of High-Mobility IGZO Thin Films Transistors Fabricated with Plasma-Assisted Reactive Processes*

Low-temperature formation of In-Ga-Zn-O thin films transistor fabricated with plasma-assisted reactive processes have been demonstrated.  The plasma-assisted reactive sputtering deposition of amorphous In-Ga-Zn-O_x (a-IGZO) films for use as channel materials in TFTs has been studied, as a means of achieving low-temperature fabrication of IGZO TFTs.  This advantage of fine control of reactivity during the deposition process is of great significance for film deposition of the transparent amorphous oxide semiconductor, a-InGaZnO_x (a-IGZO), whose electrical properties are significantly sensitive to the reactivity during the film deposition.  In the formation of IGZO TFTs, it is important to control the concentration of oxygen deficiencies at post-deposition process. Therefore, low-temperature post-deposition process using plasma as alternatives to thermal annealing have been developed to improve the electrical characteristics of the TFTs.  It has been founded that the OH radical irradiation from plasma to a-IGZO thin films is more effective in improving the electrical properties of IGZO TFTs. The TFTs fabricated with IGZO thin films post-treated with plasma at a temperature as low as 300°C showed the best performance, with m values greater than 40 cm² /Vs.