Oxygen partial pressure and annealing temperature influence on the performance of back-channel-etch zinc tin oxide thin film transistors

Zinc tin oxide (ZTO) thin film transistors (TFTs) with back-channel-etch (BCE) structure are demonstrated. The influence of oxygen partial pressure during ZTO layer sputtering is discussed and an optimal O₂/Ar ratio of 1% is achieved. The effect of annealing temperature is studied and the device annealed at 300°C performs well. The wet etching of Mo source/drain electrodes is carried out in Mo etchant which shows little damage to ZTO layer. The BCE ZTO TFT exhibits a field effect mobility of 1.88 cm²V^-1s^-1, a subthreshold slope of 0.37V/decade, and an on-off current ratio larger than 10⁷. The comparable performances between BCE ZTO TFT and lift-off ZTO TFT indicate back-channel-etch ZTO TFT is a feasible technique and suitable for mass production.