Advanced Cu Interconnection via Electroless-Plated Ni Interlayer on the Gate of Oxide Thin-Film Transistors

Abstract

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 SiO 2 , 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 /SiO 2 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.Until recently, amorphous (a)-Si based thin-film transistor (TFT) has led the liquid crystal display (LCD) industry due to its superior uniformity at large scale. However, the more developed display industry is now demanding higher performance and resolution than available in general a-Si TFTs. High-performance TFT-LCD and active matrix organic light-emitting diodes (AMOLEDs) are now being fabricated with low-temperature poly-Si (LTPS) TFT technology, which has limitations in large-scale displays in addition to process complexity and cost. As an alternative to such Si-based TFTs, amorphous oxide semiconductor TFTs have recently attracted much attention due to their mobility, operational stability, and simple fabrication process.