Tungsten Nitrido Complexes as Precursors for Low Temperature Chemical Vapor Deposition of WN_<i>x</i>C_<i>y</i> Films as Diffusion Barriers for Cu Metallization

Tungsten nitrido complexes of the form WN­(NR₂)₃ [R = combinations of Me, Et, ^<i>i</i>Pr, ^<i>n</i>Pr] have been synthesized as precursors for the chemical vapor deposition of WN_<i>x</i>C_<i>y</i>, 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 (WN) 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(NMe₂)₃ indicated the lowest gas phase energy pathway for loss of HNMe₂ to be β-H transfer following formation of a nitrido bridged dimer. Amorphous films of WN_<i>x</i>C_<i>y</i> were grown from WN­(NMe₂)₃ 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 W₂NC 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_<i>x</i>C_<i>y</i> Thin Films from Tungsten Nitrido Complexes of the Type WN(NR₂)₃

Tungsten nitrido complexes of the type WN­(NR₂)₃ [NR₂ = combinations of NMe₂, NEt₂, N^<i>i</i>Pr₂, N^<i>n</i>Pr₂, N^<i>i</i>Bu₂, piperidine, and azepane] were synthesized as precursors for aerosol-assisted chemical vapor deposition of WN_<i>x</i>C_<i>y</i> thin films. The effects of the amido substituents on precursor volatility and decomposition were evaluated experimentally and computationally. Films deposited using WN­(NMe₂)­(N^<i>i</i>Pr₂)₂ 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_<i>x</i>C_<i>y</i> (∼5 nm)/Si samples prepared from WN­(NMe₂)­(N^<i>i</i>Pr₂)₂ 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