Interface chemistry modulation and dielectric optimization of TMA-passivated HfDyOx/Ge gate stacks using doping concentration and thermal treatment

Abstract

In this work, the effects of different Dy-doping concentrations and annealing temperatures on the interfacial chemistry and electrical properties of TMA-passivated HfDyO_x/Ge gate stacks have been investigated systematically. The microstructural, optical, interfacial chemistry, and electrical characteristics of sputtering-driven HfDyO_x gate dielectrics have been characterized by means of X-ray diffraction (XRD), UV-Vis transmission spectroscopy, X-ray photoelectron spectroscopy (XPS), and electrical measurements. This work reveals that the interfacial chemistry evolution takes place via two competing processes, including oxide growth and oxide desorption. XPS analyses have confirmed that the 10 W-deposited targeted gate dielectrics display optimized interface characteristics, which can be attributed to the suppressed unstable Ge oxides and inhibition effects on inter-diffusion at the interface. Electrical observations show that the 10 W-driven HfDyO_x/Ge MOS device without annealing treatment exhibits optimized electrical performance, including a larger permittivity of 22.4, a smaller flat band voltage of 0.07 V, vanishing hysteresis, a lowest oxide charge density of ∼10¹¹ cm⁻², and a lowest leakage current density of 2.31 × 10⁻⁸ A cm⁻². Furthermore, the influences of doping and annealing conditions on the leakage current conduction mechanisms (CCMs) of HfDyO_x/Ge MOS capacitors have also been investigated systematically. All of the experimental results indicate that TMA-passivated HfDyO_x/Ge gate stacks with appropriate doping concentrations demonstrate potential application prospects for Ge-based MOSFET devices.