The diffusion of silicon atoms in stack structures of La2O3 and Al2O3

The interfacial reactions and electrical characteristics of stack structures of La2O3 and Al2O3 were investigated as a function of the annealing temperature. In the case of Al2O3/La2O3/Si (ALO structure), the La2O3 in contact with the Si substrate was readily transformed into La-silicate by the diffusion of Si atoms, while in the case of La2O3/Al2O3/Si (LAO structure), interfacial reactions between the Al2O3 layer and the Si substrate were suppressed. After an annealing treatment at 700 °C, the Al2O3 in the ALO structure can play an effective role in blocking the hydration of La2O3, resulting in an unchanged interfacial layer. However, the Al2O3 layer in the LAO structure was unable to suppress the diffusion of Si atoms into the La2O3 film. When the annealing temperature reached 900 °C, both structures showed a similar depth distribution with a high content of Si atoms diffused into the films. The change in the elemental distributions via the diffusion and reaction of Si atoms affected the electrical characteristics at the interface between ALO/LAO structure and Si substrate, specifically the trap charge density (Dit) and band gap (Eg) values.

► The alternative stack structure of La2O3 and Al2O3 are formed using ALD process.
► After post-annealing in N2 gas, the change of elemental distribution by diffusion and reaction of Si atoms affected electrical characteristics at the interface.
► In particular the trap charge density (Dit) and bandgap (Eg) values were affected.