Comparative passivation effect of ALD-driven HfO2 and Al2O3 buffer layers on the interface chemistry and electrical characteristics of Dy-based gate dielectrics

Abstract

Herein, a comparative study of the effects of atomic-layer-deposited (ALD) HfO₂ and Al₂O₃ interfacial passivation layers (IPL) on the sputtering-derived HfDyO_x (HDO)/Si gate stack has been systematically investigated. X-ray photoemission spectroscopy (XPS) measurements have confirmed that the ALD-driven IPL can effectively eliminate unstable native oxides on the substrates, and the inhibition effect on the formation of a low-k layer by the ALD HfO₂ IPL is superior to that of the ALD Al₂O₃ IPL. Electrical observations have demonstrated that the HDO/HfO₂/Si gate stack has improved performance, including a larger permittivity (22.1), negligible hysteresis (0.09 V), a small oxide charge density (∼10¹¹ cm⁻²) and the smallest gate leakage current density (1.85 × 10⁻⁶ A cm⁻²). Detailed analyses on the leakage current conduction mechanisms (CCMs) for HDO/Si MOS capacitors with different IPLs, measured at room and low temperatures, have been carried out. All the experimental results indicate the potential application of the HDO/HfO₂ gate stack as a promising passivation candidate for the future microelectronics devices.