Dielectric breakdown and charge trapping of ultrathin ZrHfO/SiON high-k gate stacks

One- and two-step breakdown phenomena were observed on the zirconium-doped hafnium oxide (ZrHfO) high-k dielectric films with equivalent oxide thicknesses 1.8 and 2.5 nm, respectively. The difference in the breakdown sequence was attributed to the bulk high-k layer thickness and interface layer structure. The trap generation and charge trapping in the high-k stack was investigated using a new stress-relax method through analyzing the relaxation current change. The results showed that new traps were only created under the high bias condition and the density could be comparable to or even larger than that of the preexisted traps.