Significant Enhancement of the Dielectric Constant through the Doping of <scp> <scp>CeO</scp> </scp> ₂ into <scp> <scp>HfO</scp> </scp> ₂ by Atomic Layer Deposition

Abstract

Films of CeO 2 were deposited by atomic layer deposition ( ALD ) using a Ce (mmp) 4 [mmp = 1‐methoxy‐2‐methyl‐2‐propanolate] precursor and H 2 O reactant. The growth characteristics and film properties of ALD CeO 2 were investigated. The ALD CeO 2 process produced highly pure, stoichiometric films with polycrystalline cubic phases. Using the ALD CeO 2 process, the effects of Ce doping into an HfO 2 gate dielectric were systematically investigated. Regardless of Ce /( Ce + Hf ) composition, all ALD Ce x Hf 1− x O 2 films exhibited constant growth rates of approximately 1.3 Å/cycle, which is essentially identical to the ALD HfO 2 growth rates. After high‐temperature vacuum annealing at 900°C, it was verified, based on X ‐ray diffraction and high‐resolution cross‐sectional transmission electron microscopy results, that all samples with various Ce /( Ce + Hf ) compositions were transformed from nanocrystalline to stabilized cubic or tetragonal HfO 2 phases. In addition, the dielectric constant of the Ce x Hf 1− x O 2 films significantly increased, depending on the Ce doping content. The maximum dielectric constant value was found to be nearly 39 for the Ce /( Ce + Hf ) concentration of ~11%.