Impact of Annealing on Contact Formation and Stability of IGZO TFTs
In this work, bottom-gate top-contact TFTs are fabricated using sputtered IGZO. Molybdenum and aluminum were investigated as contact metals which defined the working source/drain electrodes. Annealing processes applied either before or after metal deposition were investigated. Annealing was done at 400 °C in various gas ambients including air, oxygen, nitrogen, forming gas (5% H2 in N2) and vacuum. Channel passivation materials including SiO2 and Al2O3 were also investigated. The annealing ambient and arrangement of process steps were found to have a significant influence on the contact behavior and the uniformity and stability of electrical characteristics. These details have a significant impact on circuit operation, which will be discussed along with results of test circuits including inverters and ring oscillators.