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

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 80 MeV Ni ions to study ion induced inter-diffusion of Hf and Si across HfO₂/Si interface as a function of ion fluence