Ultra-thin atomic-layer-deposited InGaZnO thin film transistors with Back-End-of-Line Compatibility

In this work, we report on ultra-thin InGaZnO (IGZO) thin film transistors (TFTs) with a channel thickness (Tch) ranging from 0.7 nm to 4.3 nm and a channel length (Lch) below 100 nm. These IGZO channels were derived by atomic-layer-deposition, with a high In atomic ratio of 92%. It is found that Tch has a significant effect on the electron transport in the IGZO channel. Well behaved performance can be achieved for TFTs with Tch between 1.5 nm and 3.5 nm. Gate bias stress stability test were also systematically studied on these IGZO TFTs under various gate biases. It is believed that the generation of donor-like traps possibly originating from ionized oxygen vacancy, in addition to electron (de)trapping could be the underlying mechanism. This study shows that IGZO TFTs could be highly promising for back-end-of-line (BEOL) applications.