Stress polarity dependence of degradation and breakdown of SiO/sub 2//high-k stacks

In this paper, we summarize our findings on two material systems: SiO/sub 2//Al/sub 2/O/sub 3/ and SiO/sub 2//ZrO/sub 2/. Relatively thick high-k layers are used to avoid defect related problems and to assess the bulk properties of the layers. We show Time-Dependent Dielectric Breakdown data for both polarities and at various stress conditions. We explain how the properties of the time-to-breakdown distribution provide valuable information that can help identify the physical degradation mechanism. We demonstrate that the degradation in double layers strongly depends on the injection polarity and this can only be explained consistently if the conduction mechanism through both constitutive layers and the energy of the injected carriers are taken into account. Furthermore, we hint at how the process impact on the reliability can be observed and evaluated.