Breakdown-induced thermochemical reactions in $HfO2$ high-$κ$/polycrystalline silicon gate stacks

The chemistry of dielectric-breakdown-induced microstructural changes in $HfO2$ high-$κ$/polycrystalline silicon gate $nMOSFETs$ under constant voltage stress has been studied. Based on an electron energy loss spectrometry analysis, the hafnium and oxygen chemical bonding in the breakdown induced Hf-based compounds of a “ball-shaped” defect is found to be different compared to the stoichiometric $HfO2$ and $SiO2$⁠. The formation of possibly $HfSixOy$ and $HfSix$ compounds in the “ball-shaped” defect is attributed to a thermochemical reaction triggered by the gate dielectric breakdown.