Cobalt hydride tris(trialkylphosphites) CoH[(R1O)P(OR2)2]3(R1 = Me, Et, i-Pr, n-Pr, n-Bu, i-Bu, Ph, or benzyl; R2 = Me or Et) are volatile liquid or solid compounds, and were proposed as potential precursors for the growth of metallic Co films. The cobalt complexes were liquids for R1 lengthened from ethyl to longer chains. The thermal stability of the complex was lower in case of bulky R1, thus, HCo[n-PrOP(OMe)2]4 and HCo[n-BuOP(OMe)2]4 were distillable, but HCo[i-BuOP(OMe)2]4 was not.
The distillable CoH[nPrOP(OMe)2]4 and CoH[nBuOP(OMe)2]4 were successfully applied as CVD precursors for the deposition of pure Co films on Si at substrate temperatures as low as 270 °C under reduced pressure without use of H2. No C or O impurities were detected in the deposited Co films by XPS, the films had smooth and dense morphology as determined by AFM [[i]]
[i] H. Choi, S. Park, Chem. Mater., 2003, 15, 3121–3124.