Influence of the SiO_2 layer thickness on the degradation of HfO_2/SiO_2 stacks subjected to static and dynamic stress conditions

摘要

The substitution of the SiO_2 gate oxide in MOS devices by a material with a high-κ dielectric constant is being deeply studied nowadays to solve the problem of the leakage currents that appear with the progressive scaling of SiO_2 thickness. To improve the quality of the high-κ/Si interface a very thin SiO_2 film is grown between both materials. In this work, HfO_2/SiO_2 stacks with different SiO_2 thickness were subjected to different types of stress (static and dynamic) to analyze the effect of this interfacial layer of SiO_2 in the degradation of the stack. The results show that the dielectric degradation depends on the stress applied and that the thickness of the SiO_2 interfacial layer influences the advanced stages of the stack degradation.