Examination of degradation mechanism due to negative bias temperature stress from a perspective of hole energy for accurate lifetime prediction

An evaluation method using the modified hole injection method is proposed to evaluate Negative Bias Temperature Instability (NBTI) in this paper. The physical backgrounds of the evaluation method are strictly discussed. The proposed method accelerates the degradation such as the threshold voltage (Vth) shift by the amount of the hole injection without the high gate voltage stress. Our experimental and theoretical frameworks clarify that two degradation mechanisms, one follows the reaction–diffusion (R–D) model and another follows the hole trap/de-trap (HTD) model, coexist in NBTI. In the inversion layer, holes distributed in the quantized upper energy levels especially induce the degradation that follows the R–D model, and holes distributed in the ground energy level induce the degradation that follows the HTD model. Finally, the accurate NBTI lifetime prediction is demonstrated using the proposed acceleration method.