Structural Changes of Y2O3and La2O3Films by Heat Treatment

Structural changes of Y2O3 films and La2O3 films deposited on some oxidized silicon substrates were studied using X-ray photoelectron spectroscopy (XPS), Secondary ion mass spectrometry (SIMS), and Fourier transform infrared spectroscopy attenuated total reflection method (FT-IR ATR). Y2O3 and La2O3 films on chemical oxide and NH3 annealed oxy-nitride were prepared by the Low-pressure chemical vapor deposition (LPCVD) method using an lanthanide–dipivaloyl-methanate (Ln–DPM) complex. The Y2O3 film and the La2O3 film on the both kinds of substrate already contained a partly silicate structure at the interface side as a result of an interface reaction during the deposition process. During post deposition annealing, the whole film structure of the Y2O3 and the La2O3 on the chemical oxide changed to a silicate structure due to silicon diffusion with interface reaction. In the case of the Y2O3 film, this interface reaction can be suppressed using thermal oxy-nitride as the interfacial layer. In the case of the La2O3 film, the suppression effect using oxy-nitride was smaller than the case with the Y2O3 film. Also, it was found that there was a strong correlation between the structural change of the films and the change of flat-band-voltage of both Y2O3 and La2O3 MIS diodes during post-deposition-annealing.