A new breakdown failure mechanism in HfO/sub 2/ gate dielectric

The breakdown failure mechanism in HfO/sub 2/ high-k gate dielectrics under constant voltage stress in inversion and accumulation mode is physically analyzed with the aid of high resolution transmission electron microscopy. The results show that the breakdown phenomenon in HfO/sub 2/ gate dielectrics is different from that of ultrathin SiO/sub x/N/sub y/ and Si/sub 3/N/sub 4/ gate dielectrics. Dielectric-breakdown-induced epitaxy, which is the failure defect responsible for breakdown in SiO/sub x/N/sub y/ and Si/sub 3/N/sub 4/, has also been observed in HfO/sub 2/ but in a slightly different morphology. The microstructural damages observed in the breakdown of HfO/sub 2/ gate dielectrics are probably related to HfSi/sub x/ and HfSiO/sub x/ formation during BD event.