Properties of ALD HfTaxOy high-k layers deposited on chemical silicon oxide

HfTa_xO_y high-k dielectric layers with different compositions were deposited using ALD on 1 nm SiO₂ generated by ozone based cleaning of 200 mm Si(1 0 0) surface. Physical characterization of blanket layers and C-V mapping demonstrates that the ALD layers have excellent uniformity and controllable compositions. The layers with a composition of HfTaO_5.5 remain amorphous after annealing at 900 °C. The C-V measurements of MOS capacitors show no hysteresis, negligible frequency dispersion and interfacial state density smaller than 3 × 10¹¹ (cm⁻² eV⁻¹). k-value of the amorphous layers varies in the range from 20 to 25, depending on layer composition. The flat band voltage does not shift with the increase of EOT, implying that the effect of fixed charge densities in the layers is negligible. The I-V measurements show a leakage reduction comparable to that of the ALD HfO₂ layers.