Study of high-pressure hydrogen annealing effects on InGaZnO thin-film transistors

High-pressure hydrogen annealing (HPHA) treatment is an effective hydrogen doping method to improve electrical characteristics and stability of InGaZnO (IGZO) thin film transistors (TFTs). The HPHA effects on IGZO TFTs under various pressure conditions were investigated using analytical techniques. Drive current, field effect mobility, subthreshold swing, and bias stress stability of IGZO TFTs were significantly improved as the HPHA pressure was increased up to 20 atm. To analyze the performance enhancement, secondary ion mass spectroscopy, capacitance–voltage analysis, and x-ray photoelectron spectroscopy analysis techniques were performed. As a result, it was confirmed that doped hydrogen is combined with interface trap sites and oxygen vacancy related bulk defect sites, leading to improved subthreshold swing and bias stress stability. Furthermore, bulk trap passivation also contributes to high carrier density, thereby increasing driving current and field effect mobility. With increasing HPHA pressure condition, these effects of trap passivation and increase in the carrier density are more effective due to the heavily injected hydrogen.