Modification of electrical properties and carrier transportation mechanism of ALD-derived HfO2/Si gate stacks by Al2O3 incorporation

• ALD-derived HfAlO gate dielectric has been deposited on Si substrate.
• Al2O3 incorporation into HfO2 leads to reduced leakage current.
• Poole-Frenkle emission is main conduction mechanism at low field.
• Direct tunneling dominates the conduction mechanism at high field.

Effect of Al2O3 incorporation on the electrical properties and carrier transportation of atomic-layer-deposited (ALD) HfAlO high-k gate dielectrics on Si substrates have been investigated. Electrical analyses indicate that interfacial properties of HfAlO/Si gate stack have been improved and leakage current is reduced after Al2O3 incorporation into HfO2. Additionally, the HfAlO sample with precursor ratio (TEMAH: TMA) of 4:2 exhibits the lowest interface state density (Dit) of 3.6 × 1011 cm−2 eV−1, the lowest border trapped oxide charge density (Nbt) of 2.4 × 1011 cm−2, the lower density of oxide charge (Qox) of 0.9 × 1012 cm−2, and the lowest frequency dispersion of 0.15%. In addition, the carrier transportation mechanism for both HfO2 and HfAlO has been investigated systematically. Based on the analysis, it can be concluded that Poole-Frenkle (P–F) emission is main conduction mechanism at the low electric field, and direct tunneling (D-T) dominates the conduction mechanism at the high field, respectively.

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