Thermal stability of hafnium–silicate and plasma-nitrided hafnium silicate films studied by Fourier transform infrared spectroscopy

Structure and bonding changes in ultrathin hafnium–silicate (HfSiO) and plasma-nitrided HfSiO (HfSiON) films as a result of thermal annealing are presented. To track these changes, attenuated total reflection Fourier transform infrared spectroscopy (FTIR) and high-resolution transmission electron microscopy were used. It is shown that for films with a given Si content, HfSiON films have superior thermal stability compared to the corresponding HfSiO films. It is also demonstrated that besides giving chemical state changes for the thin-film constituents, FTIR can also be used to track interfacial SiO2 growth as well as phase separation in ultrathin high-κ films resulting from thermal annealing.