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
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Abstract
Tungsten
nitrido complexes of the form WN(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 (WN) 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 WN(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 WN(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