Ion beam studies of Hafnium based alternate high-k dielectric films deposited on silicon

Abstract

Hafnium based high dielectric constant materials are critical for the state-of-the-art integrated circuit technology. As the size of the transistor decreases, the thickness of the gate dielectric (SiO2) should be reduced to maintain device capacitance at a desired level. This thickness reduction results in high OFF-state leakage current due to quantum tunneling. Recently alternate high-k materials, like HfO2, have been introduced as gate dielectrics. However deposition of these high-k materials on Si wafers results in high concentration of interface defects due to their thermodynamic instability on Si. Introduction of thin inter layer of Silicon oxide/nitrides between Si and HfO2 is expected to improve interface quality. Hence it is important to study the composition, thickness and intermixing effects to optimize the fabrication of Hafnium based Metal-Oxide-Semiconductor (MOS) devices. Here, we have performed High Resolution Rutherford Backscattering Spectrometry (HRBS) and X-ray Reflectivity (XRR) measurements to characterize HfO2/SiO2/Si samples. These samples were further irradiated by 80MeV Ni ions to study ion induced inter-diffusion of Hf and Si across HfO2/Si interface as a function of ion fluence.