Stress Power Dependent Self-Heating Degradation of Metal-Induced Laterally Crystallized n-Type Polycrystalline Silicon Thin-Film Transistors

Abstract

Self-heating degradation of n-type metal-induced laterally crystallized polycrystalline silicon thin-film transistors is systematically investigated under various stress powers. A two-stage degradation behavior with turnaround effect at the initial stage is characterized. The initial degradation stage is related to breaking of weak Si–H bonds. The floating-body effect by released hydrogen ions is responsible for the observed backshift of the transfer curve during the initial stress. On the other hand, the normal degradation stage occurs by breaking of strong Si–Si bonds and trap generation at grain boundaries (GBs) and the gate oxide/channel interface. Our model is supported by observed different activation energies related to two degradation stages and a direct observation of the continuous increase in GB trap density during the normal degradation. Furthermore, during the normal degradation stage, an anomalous continuous field-effect mobility increase along with its $V_{g}$ dependence shift is first observed. It is clarified that this behavior is not a true channel mobility increase, but a consequence of stress-related trap generation.