3 research outputs found
Tungsten Nitrido Complexes as Precursors for Low Temperature Chemical Vapor Deposition of WN<sub><i>x</i></sub>C<sub><i>y</i></sub> Films as Diffusion Barriers for Cu Metallization
Tungsten
nitrido complexes of the form WNÂ(NR<sub>2</sub>)<sub>3</sub> [R =
combinations of Me, Et, <sup><i>i</i></sup>Pr, <sup><i>n</i></sup>Pr] have been synthesized as precursors for the chemical
vapor deposition of WN<sub><i>x</i></sub>C<sub><i>y</i></sub>, a material of interest for diffusion barriers in Cu-metallized
integrated circuits. These precursors bear a fully nitrogen coordinated
ligand environment and a nitrido moiety (Wî—¼N) designed to minimize
the temperature required for film deposition. Mass spectrometry and
solid state thermolysis of the precursors generated common fragments
by loss of free dialkylamines from monomeric and dimeric tungsten
species. DFT calculations on WNÂ(NMe<sub>2</sub>)<sub>3</sub> indicated
the lowest gas phase energy pathway for loss of HNMe<sub>2</sub> to
be β-H transfer following formation of a nitrido bridged dimer.
Amorphous films of WN<sub><i>x</i></sub>C<sub><i>y</i></sub> were grown from WNÂ(NMe<sub>2</sub>)<sub>3</sub> as a single
source precursor at temperatures ranging from 125 to 650 °C using
aerosol-assisted chemical vapor deposition (AACVD) with pyridine as
the solvent. Films with stoichiometry approaching W<sub>2</sub>NC
were grown between 150 and 450 °C, and films grown at 150 °C
were highly smooth, with a RMS roughness of 0.5 nm. In diffusion barrier
tests, 30 nm of film withstood Cu penetration when annealed at 500
°C for 30 min
Effect of the Ligand Structure on Chemical Vapor Deposition of WN<sub><i>x</i></sub>C<sub><i>y</i></sub> Thin Films from Tungsten Nitrido Complexes of the Type WN(NR<sub>2</sub>)<sub>3</sub>
Tungsten nitrido complexes of the
type WNÂ(NR<sub>2</sub>)<sub>3</sub> [NR<sub>2</sub> = combinations
of NMe<sub>2</sub>, NEt<sub>2</sub>, N<sup><i>i</i></sup>Pr<sub>2</sub>, N<sup><i>n</i></sup>Pr<sub>2</sub>, N<sup><i>i</i></sup>Bu<sub>2</sub>, piperidine, and azepane]
were synthesized as precursors for aerosol-assisted
chemical vapor deposition of WN<sub><i>x</i></sub>C<sub><i>y</i></sub> thin films. The effects of the amido substituents
on precursor volatility and decomposition were evaluated experimentally
and computationally. Films deposited using WNÂ(NMe<sub>2</sub>)Â(N<sup><i>i</i></sup>Pr<sub>2</sub>)<sub>2</sub> as a single-source precursor were assessed as diffusion barrier
materials for Cu metallized integrated circuits in terms of growth
rate, surface roughness, composition, and density. In diffusion barrier
tests, Cu (∼100 nm)/WN<sub><i>x</i></sub>C<sub><i>y</i></sub> (∼5 nm)/Si samples prepared from WNÂ(NMe<sub>2</sub>)Â(N<sup><i>i</i></sup>Pr<sub>2</sub>)<sub>2</sub> were annealed for 30 min at 500 °C and successfully
blocked Cu penetration according to four-point probe, X-ray diffraction,
scanning electron microscopy etch-pit test, and high-resolution transmission
electron microscopy measurements
A Trinuclear Gadolinium Cluster with a Three-Center One-Electron Bond and an <i>S</i> = 11 Ground State
The recent discovery
of metal–metal bonding and valence
delocalization in the dilanthanide complexes (CpiPr5)2Ln2I3 (CpiPr5 = pentaisopropylcyclopentadienyl;
Ln = Y, Gd, Tb, Dy) opened up the prospect of harnessing the 4fn5dz21 electron
configurations of non-traditional divalent lanthanide ions to access
molecules with novel bonding motifs and magnetism. Here, we report
the trinuclear mixed-valence clusters (CpiPr5)3Ln3H3I2 (1-Ln, Ln =
Y, Gd), which were synthesized via potassium graphite reduction of
the trivalent clusters (CpiPr5)3Ln3H3I3. Structural, computational, and spectroscopic
analyses support valence delocalization in 1-Ln resulting
from a three-center, one-electron σ bond formed from the 4dz2 and 5dz2 orbitals on Y
and Gd, respectively. Dc magnetic susceptibility data obtained for 1-Gd reveal that valence delocalization engenders strong parallel
alignment of the σ-bonding electron and the 4f electrons of
each gadolinium center to afford a high-spin ground state of S = 11. Notably, this represents the first clear instance
of metal–metal bonding in a molecular trilanthanide complex,
and the large spin–spin exchange constant of J = 168(1) cm–1 determined for 1-Gd is only the second largest coupling constant characterized to date
for a molecular lanthanide compound