Atomic layer deposition of hafnium oxide from tert-butoxytris(ethylmethylamido)hafnium and ozone: rapid growth, high density and thermal stability

Abstract

HfO 2 thin films were grown by atomic layer deposition (ALD) using a novel heteroleptic precursor, tert-butoxytris(ethylmethylamido)hafnium [HfO t Bu(NEtMe) 3 ; BTEMAH] and ozone. The structure of BTEMAH is similar to that of tetrakis(ethylmethylamido)hafnium [Hf(NEtMe) 4 ; TEMAH] except that one of its four amido ligands is replaced with a tert-butoxy ligand. This heteroleptic structure largely improves the ALD growth rate (0.16 nm cycle À1 ) and Hf density (Hf mass per unit volume of HfO 2 film, 7.6 g cm À3 ) of the HfO 2 films. The self-regulated ALD growth behavior was confirmed at a growth temperature of 300 C. Higher Hf density induces anti-crystallization properties in the as-grown film. Consequently, the amorphous phase of a HfO 2 film is retained up to $15 nm during deposition at 300 C. The more amorphous-like nature and the higher Hf density of the HfO 2 film also retard crystallization during post-deposition annealing (PDA), which strongly enhances the thermal stability of the electrical performance. The capacitance equivalent thickness of the films with thicknesses ranging from 4 to 13 nm is relatively constant up to a PDA temperature of 1000 C.

NiO Thin Films Synthesized by Atomic Layer Deposition using Ni(dmamb)2 and Ozone as Precursors

“…Moreover, the deposition temperature requirements of ALD processes are generally low compared to their CVD counterparts, rendering ALD compatible with the technological trend towards lower processing temperatures. [22][23][24] Despite these advantages that ALD offers, reports on its application for the synthesis of NiO are still comparatively rare. Over the past years, several Ni precursors have been examined for the ALD of NiO, such as Ni(acac) 2 (acac ¼ acetylacetonate), [25] Ni(apo) 2 (apo ¼ 2-aminopent-2-en-4-onato), [25] Ni(dmg) 2 (dmg ¼ dimethyl-glyoximato), [25] Ni(Cp) 2 (Cp ¼ cyclopentadienyl), [26] Ni(EtCp) 2 (EtCp ¼ ethylcyclopentadienyl), [27] Ni(thd) 2 (thd ¼ tetramethyl heptanedionato), [28] and Ni(dmamp) 2 (dmamp ¼ 1-dimethylamino-2-methyl-2-propanolate), [29] in combination with various oxygen sources.…”

The mechanism for the suppression of leakage current in high dielectric TiO2 thin films by adopting ultra-thin HfO2 films for memory application

“…,12 and number of deposition cycles. X ray fluorescence was also used to double check the deposition amount a)Author to whom correspondence should be addressed.…”

Initial surface reactions of atomic layer deposition

“…This unwanted silicon oxidation at the interface leaves an SiO 2 interlayer which degrades the average capacitance per unit thickness, and thus compromises the excellent scalability high-k dielectrics are known for. The presence of the interlayer is noted by the frequently observed surface-enhanced initial growth, 11 as was the case in M. Cho et al's experiment with HfO 2 film and silicon substrate. The thickness and composition of the interlayer, presumably formed by H 2 O and HfCl 4, 12 was governed by the deposition temperature and the thickness of the resulting HfO 2 film, reaching its peak with 100 cycles at 300C.…”