Aerosol-Assisted Chemical Vapor Deposition of Tungsten Oxide Films and Nanorods from Oxo Tungsten(VI) Fluoroalkoxide Precursors

Aerosol-assisted chemical vapor deposition (AACVD) of WO_<i>x</i> was demonstrated using the oxo tungsten­(VI) fluoroalkoxide single-source precursors, WO­[OCCH₃(CF₃)₂]₄ and WO­[OC­(CH₃)₂CF₃]₄. Substoichiometric amorphous tungsten oxide thin films were grown on indium tin oxide (ITO) substrates in nitrogen at low deposition temperature (100–250 °C). At growth temperatures above 300 °C, the W₁₈O₄₉ monoclinic crystalline phase was observed. The surface morphology and roughness, visible light transmittance, electrical conductivity, and work function of the tungsten oxide materials are reported. The solvent and carrier gas minimally affected surface morphology and composition at low deposition temperature; however, material crystallinity varied with solvent choice at higher temperatures. The work function of the tungsten oxide thin films grown between 150 and 250 °C was determined to be in the range 5.0 to 5.7 eV, according to ultraviolet photoelectron spectroscopy (UPS)

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