FT IR spectroscopy of nitric acid oxidation of silicon with hafnium oxide very thin layer

Hafnium oxide is promising for future CMOS devices owing to wide band gap, good thermal stability on silicon, high permittivity and high refractive index. Infrared spectroscopy was used to study of the structural properties of 5 nm HfO2 films after nitric acid oxidation (NAOS) of n-doped Si (1 0 0) substrates. Samples were annealed in N2 atmosphere at different temperatures 200-400 °C for 10 min. For NAOS passivation 100% vapor of HNO3 and 98% aqueous solution was used. The measurements revealed the formation of Hf-Si-O bonds depending on annealing temperature. The samples passivated in 98% aqueous HNO3 solution showed spectra with more developed Hf-Si-O structures. Obtained FTIR spectra indicate the presence of monoclinic HfO2 in amorphous layer in samples of A set and formation of cubic HfO2 phase in amorphous layer with increasing of temperature. Infrared spectroscopy reveals the stable solid silicon oxide layer. The structural properties of HfO2 are crucial for application in the future.