Compositional control and electrical performance of atomic layer deposited Al2O3/TiO2 nanolaminates

Abstract

Nanolaminate Al₂O₃/TiO₂ (ATO) dielectric films were fabricated using atomic layer deposition (ALD) and evaluated as insulating layers in metal-oxide-semiconductor (MOS) capacitors. The TiO₂ content within the nanolaminates was systematically varied to modulating both optical and electrical properties. Precise thickness control and stable growth per cycle (GPC) for each sublayer were achieved at a deposition temperature of 200 °C. Spectroscopic ellipsometry revealed that increasing TiO₂ content led to a higher refractive index and optical dielectric constant, accompanied by a reduction in bandgap (E_g). Microstructural analysis demonstrated that the laminated structure suppressed surface roughness and enhanced interfacial quality. Electrical measurements showed that increasing the TiO₂ fraction enhanced the accumulation capacitance due to its high dielectric constant, but also resulted in higher leakage current, attributed to trap-assisted and Poole-Frenkel (P-F) conduction mechanisms. Notably, the introduction of Al₂O₃ sublayers as insulating barriers effectively suppressed leakage pathways and stabilized charge transport. These findings suggest that the ATO nanolaminate structure is a promising candidate for high-k gate dielectrics in advanced semiconductor applications.