Reliability of Multiple Oxides Integrated with thin HfSiOₓ gate Dielectric on Thick SiO₂ Layers

Reliability and performance in metal gate/high-k device with multiple gate dielectrics were investigated. MOSFETs with a thin HfSiOₓ layer on a thermal Si02 dielectric as gate dielectrics exhibit excellent mobility and low interface trap density. However, the distribution of threshold voltages of HfSiOₓ/SiO₂ stack devices were wider than those of SiO₂ and HfSiOₓ single layer devices due to the penetration of Hf and/or intermixing of HfSiOₓ with underlying SiO₂. The results of TZDB and SILC characteristics suggested that a certain portion of HfSiOₓ layer reacted with the underlying thick SiO₂ layer, which in turn affected the reliability characteristics.