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

Abstract

In this study, the physical and electrical characteristics of Al 2 O 3 /La 2 O 3 /Al 2 O 3 /Si stack structures affected by the thickness of an Al 2 O 3 barrier layer between Si substrate and La 2 O 3 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 Al 2 O 3 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 La 2 O 3 layer during the annealing process. As a result, some properties of La 2 O 3 dielectric degenerated by the diffusion of Si atoms are improved. Electrical measurements (C-V, J-V) show that the thickness of Al 2 O 3 barrier layer can affect the shift of flat band voltage (V FB ) and the magnitude of gate leakage current density.