High performance solution-deposited bilayer channel indium-zinc-oxide thin film transistors by low-temperature microwave annealing

We report the high-performance solution-deposited indium-zinc-oxide (IZO) TFTs with a bilayer channel structure fabricated at low temperature using a microwave irradiation (MWI) post-deposition annealing (PDA) process. Although, the MWI process temperature (89 °C) was much lower than the baking temperature (180 °C) of solution precursors, the microwave irradiated film has comparable chemical binding states to the thermal annealed film at 600 °C. For the enhancement of channel performance, channel engineering was applied by exploiting bilayer channel with different composition-ratios of In and Zn (In:Zn = 3:1, 2:1, 1:1, 1:2 and 1:3). Bilayer channel IZO TFTs consist of electron transfer channel layer and capping layer. The electrical characteristics for various combinations of bilayer channel were investigated. As a result, the transfer channel layer of In:Zn = 1:1 and the capping layer of In:Zn = 3:1 turned out to be effective for improving the mobility, subthreshold swing and hysteresis of IZO TFTs. We found that the electrical characteristics of solution-deposited IZO TFTs can be greatly improved by using bilayer channel structure and low temperature MWI-PDA process.