Leakage modeling of AlHfO<inf>3.5</inf> semi-insulating dielectrics for power devices

Abstract

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 (AlHf03.5) in order to analyze the influence of aluminum in the AlHfOy system at high concentrations. In addition, the AIHf03.5 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 1 kHz under illumination. Also, flat band voltage (VFB) was greater than or equal to zero for all conditions measured. On the other hand, the leakage phenomenaoccurring at the accumulation region, was modeled with a simplified electrical model using a leakage admittance Yc whose influence was predominant at high frequencies (lMHz) 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 (-to) and its achievement is possibly affected by the leakage process.