Hf-aluminate films with and without an interfacial layer during growth and postannealing structural and electrical characteristics

The structural and electrical characteristics resulting from an interfacial layer of Hf-aluminate films grown by atomic layer deposition were investigated using medium energy ion scattering spectroscopy and electrical measurements. The Hf-aluminate films with an interfacial layer of SiO₂ grew with higher Hf contents and lower interdiffusion of Si than the film without an interfacial SiO₂ layer. In Hf-aluminate films with an interfacial layer of SiO₂, the thickness of HfO₂ decreased slightly after postannealing as a result of crystallization. In films without an interfacial layer of SiO₂, the structural rearrangement was observed due to the interdiffusion of Si with no change in thickness. The structural changes affected electrical properties such as the oxide trap charge and the interfacial trap charge. Moreover, reoxidation of the Hf-aluminate films without an interfacial layer of SiO₂ caused a dramatic increase in the thickness of the interfacial region. This resulted in a positive shift of flatband voltage.