Liquid Cobalt (I) Hydride Complexes as Precursors for Chemical Vapor Deposition

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Volatile cobalt (I) hydride complexes HCo[R1OP(OR2)2]4 were synthesized, where R1 = Me, Et, i-Pr, n-Pr, n-Bu, i-Bu, Ph, and benzyl, and R2 = Me and Et. The cobalt complexes were obtained as liquids as R1 was lengthened from ethyl to longer chains. The thermal stability of the complex was lowered with 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. Pure cobalt films of smooth and dense surface morphology were deposited on Si at temperatures as low as 270 °C using the cobalt hydrides as precursors under reduced pressure without employing H2.