Investigation on the Effects of Oxygen Flow Rate for the Performance of InGaSnO Thin Film Transistors

New oxide InGaSnO (IGTO) thin-film transistors (TFTs) were fabricated at room temperature using a P+Si/SiO2 substrate via radio-frequency magnetron sputtering. The effects of varying oxygen flow rates (0, 1, 3, 5 sccm) on the electrical properties and stability of the IGTO thin-film transistors were investigated. XRD characterization results confirm that IGTO films prepared under different oxygen flow rates all exhibit an amorphous structure. XPS analysis indicates that as the oxygen flow rate increases, the proportion of oxygen vacancies within the IGTO film decreased from 35.2% to 27.6%. Excessive oxygen concentration leads to an increase in acceptor defects such as adsorbed oxygen, thereby enhancing carrier scattering. Experimental results indicate that when employing an argon-oxygen ratio of Ar:O = 27:3, the device exhibits suitable electrical characteristics and stability, which are including a field-effect mobility of 19.2 cm²/V·s and a subthreshold swing of 0.5 V·dec⁻¹. This is because at an oxygen flow rate of 3 sccm, the oxygen supply during film growth is sufficient, thus effectively reducing the oxygen vacancies and defect density. Consequently, small variations in gate voltage can directly modulate the channel carrier concentration, ultimately improving and enhancing the performance of IGTO TFTs.