SiO2 dielectric breakdown mechanism studied by the post-breakdownresistance statistics

Abstract

The dielectric breakdown mechanism of ultra-thin SiO2 is discussedon the basis of the experimental results of the post-breakdown resistance(Rbd) distribution. We have noticed that the Rbd of SiO2 in MOSdevices is strongly related to the SiO2 breakdown characteristics such as thepolarity dependence, the oxide field dependence or the oxidation processdependence of Qbd. In this paper, we discuss the dielectric breakdownmechanism of SiO2 from the viewpoint of the statistical correlation betweenthe Rbd distribution, the Qbd distribution and the discharging energyat the SiO2 breakdown, by changing the stress polarity, the stress field, theoxide thickness and the oxidation process. In the case of hard breakdown, it hasbeen clarified that the Rbd distribution for substrate electron injectionis clearly different from that for gate electron injection. We have also foundthat, irrespective of the stress current density, the gate oxide thickness, thestressing polarity and the oxidation process, Rbd can be uniquelycorrelated to the discharging energy at dielectric breakdown, in the case ofhard breakdown. Furthermore, it has been clarified that the Rbd does notdepend on the energy dissipation at soft breakdown.