Leakage modeling of AlHfO3.5 semi-insulating dielectrics for power devices

Electrical characterization of hafnium aluminates gate dielectrics, using capacitance-voltage (C-V) measurements, was carried out for different frequencies. The dielectric film was deposited with equal molar concentrations of aluminum and hafnium (AlHfO_3.5) in order to analyze the influence of aluminum in the AlHfO_y system at high concentrations. In addition, the AlHfO_3.5 film was annealed at 1000°C for 60s to simulate the thermal budget during a conventional CMOS processing. C-V measurements were performed in darkness and under illumination, having as a result a high-frequency behavior of the minority carriers already from 1kHz under illumination. Also, flat band voltage (V_FB) was greater than or equal to zero for all conditions measured. On the other hand, the leakage phenomena occurring at the accumulation region, was modeled with a simplified electrical model using a leakage admittance Y_C whose influence was predominant at high frequencies (1MHz) in the accumulation region. Using a low frequency to obtain the accumulation capacitance without the influence of Y_C and knowing the physical thickness from X-ray reflectometry (XRR), the average permittivity obtained was 6.7±1.6, which is lower than the one reported for alumina (~10) and its achievement is possibly affected by the leakage process.