Thermal stability of HfON, HfSiON and HfTaON gate dielectrics

The thermal stability of HfON, HfSiON and HfTaON films on Si substrate prepared by physical vapor deposition were investigated using high resolution transmission electronic microscope and x-ray photoelectron spectroscopy. HfO₂ film has lower crystallization temperature. N, Si or Ta incorporation into HfO₂ film can improve its crystallization temperature. But HfON film-s crystallization temperature is still low and crystallizes partially under 700°C. HfSiON and HfTaON have higher crystallization temperature. And HfSiON can sustain amorphous under 1000°C, while partial crystallization of HfTaON is observed at the same temperature. Si or Ta incorporation has different influence on the gate dielectric¿s thermal stability. HfSiON film has good thermal stability and don¿t react with Si substrate under higher temperature. While, HfTaON film easily reacts with Si substrate, forming the low k interfacial layer.