Localized breakdown in dielectrics and macroscopic charge transport through the whole gate stack: A comparative study

Abstract

Au-Hf O2 -Si Ox -Si structures with 4 nm Hf O2 and 1.5 nm Si Ox interfacial layer (IL) have been electrically stressed by ballistic electron emission spectroscopy (BEES). The continuous BEES stressing at the same location induced gradual degradations and finally led to breakdowns in the IL. The degradation and breakdown cannot be observed using macroscopic conventional current-voltage (IV) measurements over the same area just before and after the BEES stressing process. The localized degradation and breakdown in the dielectric is masked by the macroscopic gate area. Tunneling calculations can estimate the critical area required for a macroscopic device to be able to measure such microscopic breakdown, a problem that becomes increasingly important for characterizing ultrathin gate dielectrics. © 2008 American Institute of Physics.