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

Abstract

Electrical properties and thermal stability of LaHfOx nano-laminate films deposited on Si substrates ty atomic layer deposition (ALD) have been investigated for future high-kappa gate dielectric applications. A novel La precursor, tris(N,N'-diisopropylformamidinato) lanthanum [La((i)PrfAMD)(3)], was employed in conjunction with conventional tetrakis-(ethylmethyl)amido Hf (TEMA HO and water (H2O). The capacitance-voltage curves of the metal oxide semiconductor capacitors (MOSCAPs) showed negigible hyste:esis 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 La2O3 to HfO2 content in the films. The EOTs obtained were in the rang of similar to 1.23-1.5 nm with leakage current densities of 1.3 x 10(-8) A/cm(2) to 1.3 x 10(-8) A/cm(2) at V-fb - 1 V. In addition, the films with a higher content of La2O3 remained amorphous up to 950 degrees C indicating very gocd thermal stability, whereas the HfO2 rich films crystallized at lower temperatures. (C) 2011 Elsevier B.V. All rights reserved.