Tungsten Nitrido Complexes as Precursors for Low Temperature Chemical Vapor Deposition of WNxCy Films as Diffusion Barriers for Cu Metallization

Abstract

Tungsten nitrido complexes of the form WN(NR2)3 [R = combinations of Me, Et, (i)Pr, (n)Pr] have been synthesized as precursors for the chemical vapor deposition of WN(x)C(y), 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(x)C(y) 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.