Deposition of Pr- and Nd-aluminate by Liquid Injection MOCVD and ALD Using Single-Source Heterometallic Alkoxide Precursors

Abstract

Thin films of praseodymium aluminate (PrAlOx) and neodymium aluminate (NdAlOx) have been deposited by liquid injection metalorganic chemical vapor deposition (MOCVD) and atomic layer deposition (ALD) using the bimetallic alkoxide precursors [PrAl(OPri)6(PriOH)]2 and [NdAl(OPri)6(PriOH)]2. Auger electron spectroscopy showed that all the films were high purity, with no carbon detectable (est. detection limit ≈ 0.5 at %). X-ray diffraction showed that the PrAlOx and NdAlOx films remained amorphous up to temperatures of 900 °C. Films grown by ALD were all Pr- or Nd-deficient (Pr/Al = 0.54−0.71; Nd/Al = 0.30−0.42), but near-stoichiometric films of PrAlOx (Pr/Al = 0.76) and NdAlOx (Nd/Al = 0.87) were obtained by MOCVD at deposition temperatures of 500 and 450 °C, respectively. The electrical properties of the films were assessed using C−V and I−V on MOS capacitors. Post-metalization annealing (PMA) in forming gas was effective in reducing charge levels in all films. Following PMA, the dielectric properties of NdAlOx were superior to those of PrAlOx, MOSCs fabricated with NdAlxOy (Nd/Al = 0.87) and PrAlOx (Pr/Al = 0.76) showed leakage current densities below 7.5 × 10-10 A cm-2 (κ ∼ 14) and 1 × 10-6 A cm-2 (κ ≈ 12), respectively.