Optical spectroscopic study of the SiN/HfO2 interfacial formation during rf sputtering of HfO2

High-k stacks formed by chemical-vapor-deposited SiN and high-pressure sputtered HfO2 in either O2 or Ar atmosphere have been studied. The introduction of a SiN layer is proposed to prevent the uncontrollable SiO2 growth while sputtering. The formation of Si-O bonds after the sputtering of the HfO2 film in O2 atmosphere was observed by infrared spectroscopy. Optical diagnosis of the plasma demonstrated a high density of O radicals in the system when working with O2. The small radius and high reactivity of these O radicals are the source of the SiN oxidation. However, the structure of the SiN film is preserved during Ar sputtering