CAFM based spectroscopy of stress-induced defects in HfO2 with experimental evidence of the clustering model and metastable vacancy defect state

In this study, we perform random telegraph noise (RTN) spectroscopy on ultra-thin HfÜ2 dielectric films using a conductive atomic force microscope (CAFM), enabling accurate assessment of single or cluster defect kinetics in very small area regions with an ultra-sharp tip having radius of 15±5 nm. Our characterization results show that bias-dependent RTN trends can be clearly detected at high spatial resolution using CAFM technique. Experimental evidence of the metastable nature of oxygen vacancy defects is presented and the nanoscale breakdown results provide further support to the time-dependent defect clustering model that is recently proposed for oxide breakdown [1,2]. Statistical plots of the CAFM breakdown voltage show a trimodal distribution that corresponds to evolution of percolation cores at the grain (G), grain boundary/triple point (GB/TP) sites and G-GB interface regions.