Effects of TiOx Interlayer on Performance of Dual-Gate InGaZnO Thin-Film Transistor

InGaZnO is sensitive to the air moisture, which leads to the formation of metal-hydroxyl defects at the back channel and thus causes TFT stability issues. In this work, dual-gate TFT with an unisolated top gate directly contacting with IGZO is used to suppress the above stability issues because of its simple fabrication processes. On one hand, increasing the top gate region (or passivation region) is effective to block the moisture absorption; on the other hand, the post-deposition annealing facilitates the formation of an interfacial layer TiOx at the unisolated gate/IGZO back interface. It is found that this TiOx acts as acceptor-like deep-level traps and the TiOx region increases with increasing the top gate region, which is detrimental to the TFT performance and especially the sub-threshold swing and off-current.