Influences of Oxygen Plasma Posttreatment on Electrical Characteristics of Amorphous Indium–Gallium–Zinc–Oxide Thin-Film Transistors

摘要

A thin-film transistor (TFT) using amorphous indium–gallium–zinc oxide (a-IGZO) as an active layer is annealed at 300 °C after deposition and then treatedwith oxygen plasma. To analyze the effect of radio frequency (RF) power of theplasma generator on the a-IGZO TFT, as-deposited and plasma-treated devicesusing RF power levels of 60, 120, and 180W are fabricated and characterized. It isdemonstrated that the RF power setting of the plasma generator influences thethreshold voltage (Vth), electron mobility, on/off current ratio and subthresholdswing of the devices alongside the transmittance and absorption coefficient of thea-IGZO layer. The a-IGZO TFT with oxygen plasma treatment at 60W shows thebest performance with a V_th of 0.4 V, electron mobility of 14.8 cm~2 V~(-1) s~(-1), an on/off current ratio of 4.8 ×10~8, and a subthreshold swing of 0.6 V dec~(-1). Inaddition, compared to the as-deposited device, the bandgap widens from 3.65 to3.72 eV, and the absorption coefficient of the 2.0–3.7 eV energy range decreases,which is due to the decreased density of tail states, and that improves electronmobility. When the RF power applied in the oxygen plasma treatment is increasedto 120 and 180 W, the optical, electrical, and surface characteristics deteriorate.