0.6nm-EOT high-k gate stacks with HfSiOx interfacial layer grown by solid-phase reaction between HfO2 and Si substrate

We have developed a process for forming an ultra-thin HfSiOx interfacial layer (HfSiOx-IL) for high-k gate stacks. The HfSiOx-IL was grown by the solid-phase reaction between HfO2 and Si-substrate performed by repeating the sequence of ALD HfO2 deposition and RTA. The HfSiOx-IL grown by this method enables the formation of very uniform films consisting of a few mono-layers, and the dielectric constant of the HfSiOx-IL is about 7. The FUSI-NiSi/HfO2 gate stacks with HfSiOx-IL have achieved 0.6 nm EOT, a very low gate leakage currents between 1 A/cm2 and 5 × 10−2 A/cm2, an excellent subthreshold swing of 66mV/dec, and a high peak mobility of 160 cm2/Vs compared to the reference samples without HfSiOx-IL. These results indicate that the HfSiOx-IL has a good quality compared to the SiO2 interfacial layer grown by oxygen diffusion through HfO2 films.