Ultrathin In2O3 Thin-Film Transistors Deposited from Trimethylindium and Ozone.

Indium oxide (In2O3) is a promising channel material for thin-film transistors (TFTs). In this work, we develop an atomic layer deposition (ALD) process of using trimethylindium (TMIn) and ozone (O3) to deposit In2O3 films and fabricate ultrathin In2O3 TFTs. The In2O3 TFTs with 4 nm channel thickness show generally good switching characteristics with a high Ion/Ioff of 108, a high mobility (μFE) of 16.2 cm^2 V^(-1) s^(-1) and a positive threshold voltage (Vth) of 0.48 V. Although the 4 nm In2O3 TFTs also exhibit short channel effect, it can be improved by adding an ALD Ga2O3 capping layer to afford the bilayer In2O3/Ga2O3 channel structure. The afforded In2O3/Ga2O3 TFTs exhibit improved immunity to the short channel effect, with good TFT characteristics of Ion/Ioff of 107, μFE of 9.3 cm^2 V^(-1) s^(-1), and positive Vth of 2.23 V. Overall, the thermal budget of the entire process is only 400 °C, which is suitable for the display and CMOS back-end-of-line (BEOL)-compatible applications.