Suppress Dynamic Hot-Carrier Induced Degradation in Polycrystalline Si Thin-Film Transistors by Using a Substrate Terminal

Dynamic hot-carrier induced degradation is a major reliability issue for polycrystalline Si thin-film transistors (TFTs) under various pulsed voltage operations. To suppress the degradation, four-terminal TFT with an additional substrate terminal connected to the floating channel is proposed. The role of the substrate terminal is to supply majority carriers during the fast voltage transition and eliminate the nonequilibrium state associated with the channel/source and channel/drain junctions. It is demonstrated that device lifetime can be extended by more than one order of magnitude using the proposed structure. It can be more effective for forward biased substrate terminal and for narrow width TFTs, providing a feasible solution to enhance the TFT reliability.