Degradation Of Metal-Induced Laterally Crystallized P-Type Polycrystalline Silicon Thin Film Transistors Under DC Bias Stress

Device degradation of solution-based metal-induced laterally crystallized (MILC) p-type polycrystalline silicon (poly-Si) thin film transistors (TFTs) is studied under dc bias stresses. While typical negative bias temperature instability (NBTI) or electron injection (EI) is observed under -V_g or -V_d only stress, respectively, no typical hot carrier (HC) degradation can be identified under high stress -V_d combined with either low or high stress -V_g. Instead, mixed NBTI and EI degradation is observed under combined low -V_g and -V_d stresses; and combined degradation of NBTI and HC occurs under high -V_d and moderate -V_g stresses. NBTI is the dominant mechanism in both cases. Grain boundary (GB) trap generation is found to correlate with the NBTI degradation with the same time exponent, suggesting the key role of GB trap generation in polycrystalline silicon TFTs'degradation.On the basis of the work in the same research group, hydrogenation effect on reliability of n-type MILC TFTs is systematically evaluated by comparing device transfer and output characteristic degradation under both HC and self-heating stresses. Under HC stress, hydrogenated device exhibits better stability in transfer characteristics, but worse stability in output characteristics. Under SH stress, hydrogenated devices are more severely degraded in both characteristics due to more channel defect creation. In addition, anomalous negative resistance effect is observed in output characteristics measured in reverse mode under HC stress, the mechanism has not been clarified yet.