A detailed study on the frequency-dependent electrical characteristics of Al/HfSiO₄/p-Si MOS capacitors

The detailed electrical characterizations of Al/HfSiO₄/p-Si (MOS) capacitors were investigated. HfSiO₄ thin films were fabricated by RF sputtering system with the power of 300 W onto p-type (100) Si substrate and then annealed at 750 °C in Nitrogen environment for 40 min. After fabrication of ohmic contacts, the electrical characteristics of the capacitors were determined by C–V and G/ω–V measurements for several frequencies from 50 kHz to 1 MHz. It is observed that the measured capacitance and conductance curves are quite sensitive to applied voltage frequency due to time dependent interface states (D_it), border traps (N_bt), and series resistance (R_s). We have observed that the series resistance may significantly deviate from the MOS capacitor characteristics and the relevant correction must be performed. In addition, the calculated interface state density was found to be in the order of 10¹⁰ eV⁻¹ cm⁻² which is in good agreement with reported convenient dielectric layers for MOS based technology. Moreover flat band voltage variation also observed under applied voltage frequencies and this behavior were attributed the basically border states. On the other hand, barrier potentials varied from 0.615 to 0.559 eV with increasing in frequencies depending on the charge accumulations due to time dependent trap sites. Consequently, D_it, N_bt, R_s are important factors that can affect electrical characteristics of the MOS capacitors. Although the reported values vary under different applied frequencies, the fabricated HfSiO₄ dielectric layer exhibits demanding electrical characteristics to be used in MOS-based technologies.