Electrical and chemical properties of the HfO_2/SiO_2/Si stack: impact of HfO_2 thickness and thermal budget

摘要

In this paper, we investigate the impact of thermal budget and HfO_2 thickness on the chemical and electronic properties of the HfO_2/SiO_2/Si stack. In the first part, we have seen that high temperature anneal at 750℃ induces both the regrowth and the reoxidation of the SiO_2 interfacial layer. A bias drop of 1.1 eV is observed along the whole stack via the Cls core level shift and is ascribed both to the interfacial dipole and to fixed charges in the dielectric. Electrical measurements suggest dipole strength of 0.2 eV. In the second part, ellipsometry and ultraviolet photoelectron spectroscopy are combined to deduce the HfO_2 electron affinity (1.8+0.2 eV). This value does not change with increasing thermal budget or dielectric thickness. HfO_2/Si barrier height of 2.1+0.2 eV is henceforward deduced, in agreement with previous IPE results.