Polyimide Metallization Using Nickel Nano-Film as both Catalyst and Barrier Layer of Copper Electroless Deposition

Abstract

Polyimide (PI) metallization using Ni-nanofilm (Ni-nF) as the copper barrier layer and catalyst layer of electroless copper deposition was carried out. The surface of the PI film was hydrolyzed by KOH to form a layer of poly-amic acid (PAA) and subsequently performed ion-exchange of K+ ions with Ni2+ ions. The doped Ni2+ ions can be rapidly chemically reduced to the dense and continuous Ni-nF, if the reducing solution [i.e., dimethylamine borane (DMAB)] contained a trace amount of Ag+, Cu2+ or Pd2+ ions. To characterize the materials and propose a mechanism of Ni-nF formation, Fourier transform infrared spectrometer (FTIR), X-ray photoelectron spectrometer (XPS), field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), and secondary ion mass spectrometer (SIMS) were employed in this work. The main reason of Ni-nF formation is caused by a high concentration gradient of doped Ni2+ ions in the PAA that results from the addition of those metallic ions in the DMAB solution.