SiO_2 dielectric breakdown mechanism studied by the post-breakdown resistance statistics

摘要

The dielectric breakdown mechanism of ultra--thin SiO_2 is discussed on the basis of the experimental results of the post--breakdown resistance (R_bd ) distribution. We have noticed that the R_bd of SiO_2 in MOS devices is strongly related to the SiO_2 breakdown characteristics such as the polarity dependence, the oxide field dependence or the oxidation process dependence of Q_bd. In this paper, we discuss the dielectric breakdown mechanism of SiO_2 from the viewpoint of the statistical correlation between the R_bd distribution, the Q_bd distribution and the discharging energy at the SiO_2 breakdown, by changing the stress polarity, the stress fie]d, the oxide thickness and the oxidation process. In the case of hard breakdown, it has been clarified that the R_bd distribution for substrate electron injection is clearly different from that for gate electron injection. We have also found that, irrespective of the stress current density, the gate oxide thickness, the stressing polarity and the oxidation process, R_bd can be uniquely correlated to the discharging energy at dielectric breakdown, in the case of hard breakdown. Furthermore, it has been clarified that the R_bd does not depend on the energy dissipation at soft breakdown.