Back-channel etched in-ga-zn-o thin-film transistor utilizing selective wet-etching of copper source and drain

The electrical performance of the back-channel etched Indium–Gallium–Zinc–Oxide (IGZO) thin-film transistors (TFTs) with copper (Cu) source and drain (S/D) which are patterned by a selective etchant was investigated. The Cu S/D were fabricated on a molybdenum (Mo) layer to prevent the Cu diffusion to the active layer (IGZO). We deposited the Cu layer using thermal evaporation and performed the selective wet etching of Cu using a non-acidic special etchant without damaging the IGZO active layer. We fabricated the IGZO TFTs and compared the performance in terms of linear and saturation region mobility, threshold voltage and ON current (I_ON ). The IGZO TFTs with Mo/Cu S/D exhibit good electrical properties, as the linear region mobility is 12.3 cm² /V-s, saturation region mobility is 11 cm² /V-s, threshold voltage is 1.2 V and I_ON is 3.16 × 10⁻⁶ A. We patterned all the layers by a photolithography process. Finally, we introduced a SiO₂-ESL layer to protect the device from external influence. The results show that the prevention of Cu and the introduced ESL layer enhances the electrical properties of IGZO TFTs.