Si Surface Passivation by Atomic Layer Deposited Al₂O₃ with In-Situ H₂O Prepulse Treatment

We explored the electrical properties of Au/Al₂O₃/p-Si diodes subjected to in situ atomic layer deposition (ALD) preceded by H₂O pulsing, and derived capacitance–voltage (C–V) curves. Prepulsed samples exhibited lower frequency dispersion in the accumulation region, and negligible frequency dispersion in the inversion region, compared to control samples. The test samples also showed less marked flatband voltage shifts in terms of C–V hysteresis (about 60% reduction at 1 MHz). Analysis of frequency-dependent parallel conductance revealed that H₂O prepulsing reduced the interface trap density. The exponential dependence of the time constant of applied voltage deviated from linearity for samples not subjected to H₂O prepulsing, attributable to non-uniformity of the oxide charges. Border traps evident in the accumulation region at ~ 0.32 eV above the Si valence band with the time constant about 1 μs were passivated by H₂O prepulsing. These results suggest that H₂O prepulsing is a promising surface treatment for Si prior to ALD deposition.