Atomic Layer Deposition of Nickel Nitride Thin Films using NiCl₂(TMPDA) and Tert‐Butylhydrazine as Precursors

Abstract

This article describes the atomic layer deposition (ALD) of nickel nitride and nickel thin films using a diamine adduct of Ni(II) chloride, NiCl 2 (TMPDA) (TMPDA ¼ N,N,N 0 ,N 0 ,-tetramethyl-1,3-propanediamine), as the metal precursor. Owing to the high reducing power of tert-butylhydrazine (TBH), the films are grown at low temperatures of 190-250 C. This is one of the few lowtemperature ALD processes that can be used to grow Ni 3 N and Ni metal on both insulating and conductive substrates. The films are characterized in terms of crystallinity, morphology, composition, resistivity, and coercivity. Xray diffraction shows reflections compatible with either hexagonal Ni or Ni 3 N. Composition analyses suggest that the films are close to stoichiometric Ni 3 N. Despite the nitride component, the films exhibit low resistivity values and at the lowest, a resistivity of 37 μΩ cm is achieved. The result is lower than what is typically observed for Ni x N films and not much higher than the best results concerning ALD Ni metal. The nitrogen content of the films is lowered down to 1.2 at% by postdeposition reduction at 150 C in 10% forming gas. After the reduction, the nonmagnetic nitride films are converted to ferromagnetic Ni metal.

Structure, Thermal Stability, and Magnetism of Ni4N Thin Films

“…Here, it is worth mentioning that those Ni 4 N films were either deposited at a high (about 625 K) or some impurity of Ni phase was present. [ 30–32 ] In addition, the crystal structure of Ni 4 N seems to be unclear hitherto. Two different possible structures for Ni 4 N have been observed namely Ni 4 N‐I and Ni 4 N‐II.…”

Nickel Germanide Thin Films by Atomic Layer Deposition

“…This may indicate the decomposition of TBGH, as we have previously shown that NiCl 2 (tmpda) starts to decompose only at temperatures above 250 °C. 21 Another possibility is that the film is etched by the by-product HCl and the free tmpda ligands or that these start to block the surface sites from the precursor molecules. It is also possible that the precursor doses were insufficient for the highest growth rate so that the precursors were consumed before reaching the outlet edge of the substrate.…”

“…The precursor decomposes at temperatures above 250 °C. 21 NiCl 2 (tmpda) can be prepared from inexpensive starting materials with a high yield and is thus a good ALD precursor also from an industrial point of view. The compound is synthesized simply by mixing NiCl 2 solution with a threefold excess of the amine and refluxing for 3 h. A more detailed description of the synthesis can be found in the literature.…”

“…NiCl 2 (tmpda) has been used to deposit Ni 3 Sn 2 and Ni 3 N thin films by ALD. 20,21 A cobalt analogue with a slightly different amine ligand resulted in being useful for the ALD of CoO and Co 3 Sn 2 films. 20,22 What is common to all these processes is that the films are essentially free from impurities, indicating efficient ligand removal and complete reactions.…”

Thermal Chemistry of Nickel Diketonate Atomic Layer Deposition (ALD) Precursors on Tantalum and Silicon Oxide Surfaces

“…Being a chemistry-based technique, ALD requires the use of appropriate chemicals. − For the deposition of nickel, many metal organic compounds have been tested, including nickel tetracarbonyl (Ni­(CO) 4 ), nickel cyclopentadienyls such as bis­(cyclopentadienyl)nickel (NiCp 2 ), − bis­(methylcyclopentadienyl)­nickel (Ni­(MeCp) 2 ]), − bis­(ethylcyclopentadienyl)­nickel (Ni­(EtCp) 2 ), , and (η 3 -cyclohexenyl)­(η 5 -cyclopentadienyl)nickel (Ni­(Chex)­(Cp)]), nickel diamines such as NiCl 2 ( N , N , N ′, N ′,-tetramethyl-1,3-propanediamine) (NiCl 2 (TMPDA)), , diazadienyls such as bis­(1,4-diisopropyl-1,3-diazabutadienyl)­nickel (Ni­( i Pr-DAD) 2 ) and bis­(1,4-di- tert -butyl-1,3-diazabutadienyl)nickel (Ni­( t But-DAD) 2 ), − nickel acetamidinates such as bis­( N , N ′-diisopropylacetamidinato)nickel (Ni­( i Pr-amd) 2 ) and bis­( N , N ′-di- tert -butylacetamidinato)­nickel (Ni­( t But-amd) 2 ), − β-diketonates such as bis­(acetylacetonate)nickel (Ni­(acac) 2 ) − and bis­(2,2,6,6-tetramethyl-3,5-heptanedionate)nickel (Ni­(TMHD) 2 , or Ni­(thd) 2 ), − mixed nickel diamine-diketonates such as ( N , N , N ′, N ′-tetramethylethylenediamine)­(bis­(2,4-pentanedionato)­nickel (Ni­(acac) 2 (tmeda)), , and nickel amino-alkoxides such as bis­(1-dimethylamino-2-methyl-2-butoxide)nickel (Ni­(dmamb) 2 ). − …”