Advanced Cu interconnection via electroless-plated Ni interlayer on the gate of oxide thin-film transistors

We demonstrate Cu interconnection/electrode formation in bottom gate InGaZnO (IGZO) thin-film transistors (TFTs), so that conductivity may be enhanced and a more advanced display panel may replace conventional Al and Mo. To date, the development of a Cu interconnection/electrode has been hampered by the poor adhesion between Cu and SiO₂, the main gate insulator (GI) for IGZO TFTs. However, our research shows that an electro-less selective plating of Na-free Ni on pre-patterned Cu electrodes can make this goal obtainable. According to the bias- and photo-stability measurements, our IGZO TFT with Na-free Ni-plated Cu electrodes are much more stable than IGZO TFTs prepared with conventional methods such as NaOH-induced Ni plating on Cu and H-containing SiN_x/SiO₂ double layer GI on Cu. Moreover, the conventionally-prepared devices were also photo-sensitive due to the Na or H ions diffused into the GI/channel interface area. We conclude that electro-less plating of Na-free Ni on Cu is a promising approach for advanced future display panel by oxide TFTs.