A strong analogy between the dielectric breakdown of high-K gate stacks and the progressive breakdown of ultrathin oxides

The breakdown of high-K (HK) stack gate dielectrics is shown to be analogous to the failure of ultrathin SiO2-based oxides showing progressive breakdown. The breakdown of a HK stack is shown to occur in two phases. First, one or several percolation paths are formed in the SiO 2-based interfacial layer. Then, these partial breakdowns propagate into the HK through defect generation in this layer. This propagation phase is equivalent to the progressive breakdown local degradation phenomenon. As a consequence of this analogy, the reliability assessment tools developed for ultrathin single-layer oxides can also be used without significant changes to assess the reliability of HK stacks. This analogy is so strong that the experimental distinction between HK propagation and conventional progressive breakdown appears to be rather difficult. However, the residual time distribution from first breakdown to final oxide failure is shown to be significantly different for both processes at low failure percentiles. This has allowed us to obtain experimental evidence of HK propagation (as opposed to conventional progressive breakdown effects) in relatively thick Hf-based gate stacks where the detection of first BD appears to be feasible. © 2011 American Institute of Physics.