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

摘要

Electrical properties and thermal stability of LaHfO_x nano-laminate films deposited on Si substrates by atomic layer deposition (ALD) have been investigated for future high-K 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 (H_2O). 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 (V_(fb)) was observed with respect to the change in structure of nano-laminate stacks as well as La_2O_3 to HfO_2 content in the films. The EOTs obtained were in the range of～l.23-1.5nm with leakage current densities of ～1.3 × 10~(-8) A/cm~2 to 1.3 × 10~(-5) A/cm~2 at V_(fb) - 1 V. In addition, the films with a higher content of La_2O_3 remained amorphous up to 950 ℃ indicating very good thermal stability, whereas the HfO_2 rich films crystallized at lower temperatures.