Improved Structural and Electric Characterstics of Al/ALD-HfO2/Ge MOS Capacitor by Germanium Dioxide and Germanium Oxynitride as Interfacial Layer

In this work HfO₂ thin films has been deposited on Ge substrate by ALD with thickness of 9.77 nm. Thickness evaluation of film was done by Spectroscopic Ellipsometer (SE) and Filmetrics Reflectometer whereas chemical compositions and the states of the elements of the films were investigated by X-ray Photoelectron Spectroscopy (XPS). High-frequency Capacitance-Voltage (C-V), Conductance-Voltage (G-V) techniques and Current-Voltage (I-V) measurement were used to obtain the electrical properties of the high-k MOS capacitor. Different Ge surface cleaning methods preceding high-k ALD have been used for reducing oxide traps. Rapid Thermal Oxidation (RTO) and Rapid Thermal Nitridation (RTN) have been used to form the gate interlayer (IL) of GeO₂ and GeON for the gate stack of P-MOS capacitor. By assimilating a thin GeON interlayer, excellent MOS capacitors with very small capacitance–voltage hysteresis and low gate leakage have been demonstrated. Physical and Electrical characterization investigates the quality of the oxynitride interlayer and low interface trap density (D_it ≈ 0.63×10¹²eV^-1cm^-2) in case of GeON/Ge which is improved as compared to the GeO₂/Ge interface (D_it ≈ 2.53×10¹³ eV^-1cm^-2). Further electrical characterizations of HfO₂ gate dielectric MOS capacitors deposited by the ALD using RTO & RTN as IL were investigated for the measurement of EOT and Q_eff. The calculated EOT and Q_eff values for GeON/Ge are 3.23 nm and 16.92×10¹² cm^-2 respectively which is better in comparison with GeO₂ and as deposited samples.