Electrical performance of a-Si:H and poly-Si TFTs with heating stress

The amorphous channel (a-Si:H) TFT-LCD technology dominates the large-area flat panel display (FPD) market, but a-Si:H TFTs propose some adverse characteristics, especially in mobility. Therefore, developing poly-Si TFTs to promote mobility and implement the chip-on-glass (CoG) dream is indeed necessary. Using a green continuous-wave laser on amorphous silicon channel formed as poly-crystallization is a possible way in increasing the mobility value up to 450 cm²/V·sec. However, the electrical characteristics for them face the identical trend with temperature heating is degraded. However, the degradation of a-Si:H TFT is worse than that of poly-Si TFT when the device temperature is raised. In this study, the a-Si:H TFTs and poly-Si TFTs with furnace and green laser anneal were chosen. Comparing the transfer characteristics, subthreshold swing (S.S.), threshold voltage (V_th), ON/OFF ratio, field effect mobility (μ_FE), interface state density (N_it) with temperature effect, some trends are very interesting. The bulk traps were recovered by pseudo-crystallization with increasing temperature, and the transfer characteristics become better than the initial.