UC Santa Barbara

The influence of thick (~10 nm) AlN overlayers on the interface structure and reactions in Si gate stacks with HfO2 dielectrics was investigated. Annealing caused a reduction of the interfacial SiO2 at the Si interface. At high temperatures (~1000 °C) a silicide reaction was observed at the HfO2/Si interface. No reactions were observed for stacks processed similarly but with WN or TiN overlayers instead of AlN. The reaction mechanisms, in particular, the role of oxygen deficiency of the HfO2, and the consequences for the electrical properties are discussed.