Silicon diffusion control in atomic-layer-deposited Al2O3/La2O3/Al2O3 gate stacks using an Al2O3 barrier layer

In this study, the physical and electrical characteristics of Al2O3/La2O3/Al2O3/Si stack structures affected by the thickness of an Al2O3 barrier layer between Si substrate and La2O3 layer are investigated after a rapid thermal annealing (RTA) treatment. Time of flight secondary ion mass spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS) tests indicate that an Al2O3 barrier layer (15 atomic layer deposition (ALD) cycles, approximately 1.5 nm) plays an important role in suppressing the diffusion of silicon atoms from Si substrate into the La2O3 layer during the annealing process. As a result, some properties of La2O3 dielectric degenerated by the diffusion of Si atoms are improved. Electrical measurements (C-V, J-V) show that the thickness of Al2O3 barrier layer can affect the shift of flat band voltage (V FB) and the magnitude of gate leakage current density.