Growth of Tantalum(V) Oxide Films by Atomic Layer Deposition Using the Highly Thermally Stable Precursor Ta(NtBu)(iPrNC(Me)NiPr)₂(NMe₂)

Abstract

The atomic layer deposition (ALD) growth of Ta 2 O 5 films was demonstrated using Ta(NtBu)-(iPrNC(Me)NiPr) 2 (NMe 2 ) and water with substrate temperatures between 225 and 400 °C. At 325 °C, self-limited growth was demonstrated with Ta(NtBu)(iPrNC(Me)NiPr) 2 (NMe 2 ) and water pulse lengths of g0.5 s. An ALD window was observed between 275 and 350 °C, with a growth rate of 0.28 A ˚/cycle. The growth rates were 0.33 and 0.37 A ˚/cycle at 250 and 225 °C, respectively. At 375 and 400 °C the growth rate increased slightly to 0.31 A ˚/cycle, and precursor thermal decomposition may contribute to growth at these temperatures. In a series of films deposited at 325 °C, the film thickness increased linearly with the number of deposition cycles. X-ray photoelectron spectroscopy of films deposited at 300 and 350 °C revealed stoichiometric Ta 2 O 5 with carbon and nitrogen levels below the detection limits. The films were amorphous as deposited, but annealing at 700 °C in dry air resulted in crystallization of hexagonal δ-Ta 2 O 5 . Atomic force microscopy found root-mean-square surface roughnesses of 0.6-0.7 nm for 45 nm thick films deposited at 300 and 350 °C. The index of refraction of films grown at 325 °C was determined to be 2.12-2.16 at 633 nm using ellipsometry.

Preparation of Lithium Containing Oxides by the Solid State Reaction of Atomic Layer Deposited Thin Films

“…Interestingly, the phase was also absent when the 50 nm Ta 2 O 5 film was annealed at 750 °C (Supporting Information, Figure S2). No crystalline Ta 2 O 5 was observed in any of our annealing experiments, although the material has been reported to crystallize at 700 °C and above. , …”

“…No crystalline Ta 2 O 5 was observed in any of our annealing experiments, although the material has been reported to crystallize at 700 °C and above. 23,24 Our first experiments revealed that annealing temperatures higher than 750 °C can lead to lithium silicate formation since the stacks are deposited onto single crystalline silicon (Supporting Information Figure S1). In most of the later experiments, temperatures below 700 °C were used for annealing.…”

Atomic Layer Deposition of Groups 4 and 5 Transition Metal Oxide Thin Films: Focus on Heteroleptic Precursors

“…An alkylamide‐imide‐amidinate compound, t BuN = Ta(N i PrC(Me) i PrN) 2 (NMe 2 ) was investigated for the ALD of Ta 2 O 5 , together with water as the oxygen source. Self‐limiting growth was confirmed at 325°C with a rather low GPC of 0.28 Å per cycle.…”

Evaluation of Volatility and Thermal Stability in Monomeric and Dimeric Lanthanide(III) Complexes Containing Enaminolate Ligands

“…The decomposition temperature of a precursor is often close to the upper temperature limit of the ALD window in an ALD process. 69,70 This similarity can be used to perform an initial comparison of previous precursors with 10− 15.…”

“…It is difficult to compare the precursor properties of the compounds in the present work with those of precursors that have been previously used in the ALD of lanthanide-containing thin films, however, since precursor decomposition temperatures are rarely given. The decomposition temperature of a precursor is often close to the upper temperature limit of the ALD window in an ALD process. , This similarity can be used to perform an initial comparison of previous precursors with 10 – 15 .…”