Bias-temperature stress on metal-oxide-semiconductor structures as compared to ionizing irradiation and tunnel injection

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Abstract
This paper presents the change of the midgap voltage ΔVMG and the surface state density Dit caused by bias temperature (BT) stress, ionizing irradiation, and tunnel injection experiments on metal-oxide-semiconductor capacitors. The irradiation tests and the tunnel injection experiments are carried out to find correlations of the degradation mechanisms among the three stress procedures. The BT stress is performed on n- and p-type samples with applied positive and negative fields (1–5 MV/cm). The stress temperatures are 100, 150, and 200 °C; the maximum aging time is 30 h. After BT stress, n- and p-type samples exhibit the same degradations of the midgap voltage VMG and of the interface state density Dit, respectively. The increase of ‖VMG‖ and Dit for negative BT stress is significantly larger than in the case of positive BT stress. An analytical expression which describes the changes of VMG and Dit for negative BT stress is developed. Drastic changes of VMG and Dit are observed after switching the stress voltage from negative values to positive ones or to ground. The ratio of (trapped hole) charges in the oxide and in the interface states is identical in all three experiments.