ALD of LaHfOx nano-laminates for high-κ gate dielectric applications

Electrical properties and thermal stability of LaHfOx nano-laminate films deposited on Si substrates by atomic layer deposition (ALD) have been investigated for future high-κ gate dielectric applications. A novel La precursor, tris(N,N′-diisopropylformamidinato) lanthanum [La(iPrfAMD)3], was employed in conjunction with conventional tetrakis-(ethylmethyl)amido Hf (TEMA Hf) and water (H2O). The capacitance–voltage curves of the metal oxide semiconductor capacitors (MOSCAPs) showed negligible hysteresis and frequency dispersion, indicating minimal deterioration of the interface and bulk properties. A systematic shift in the flat-band voltage (Vfb) was observed with respect to the change in structure of nano-laminate stacks as well as La2O3 to HfO2 content in the films. The EOTs obtained were in the range of ∼1.23–1.5 nm with leakage current densities of ∼1.3 × 10−8 A/cm2 to 1.3 × 10−5 A/cm2 at Vfb − 1 V. In addition, the films with a higher content of La2O3 remained amorphous up to 950 °C indicating very good thermal stability, whereas the HfO2 rich films crystallized at lower temperatures.

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