Microwave Annealing as a Low Thermal Budget Technique for ZnO Thin-Film Transistors Fabricated Using Atomic Layer Deposition

Microwave annealing (MWA) and furnace annealing are compared for their low thermal budget capability to improve the characteristics of ZnO-based thin-film transistors (TFTs). Both the ZnO channel and the Al
₂
O
₃
gate dielectric are fabricated using atomic layer deposition. Using Si-wafer-susceptor assisted MWA with a substantial reduction of both annealing temperature and duration, significant improvements of the characteristics of the ZnO TFTs can be attained. A multi-step MWA process is found to further improve the characteristics of the TFTs. For the same microwave power and total duration, the field-effect mobility of the multi-step MWA TFT is 42% greater than that of the one-step MWA TFT with a similar sub-threshold swing. The multi-step MWA process can serve the purpose at temperatures as low as 220 °C.