Adhesion enhancement of Ni films on polyimide using ion processing. II. 84Kr+ implantation

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Abstract
The influence of 84 Kr+ ion implantation on the interfacial chemistry and adhesion of 30 nm Ni films on poly[N,N-(p,p’-oxydiphenylene) pyromellitimide] polyimide (PI) substrates was examined. The Ni/PI specimens were held at temperatures below 100°C and implanted with 170 keV 84 Kr+ at doses of either 5×1015 , 1×1016 , or 5×1016 Kr/cm2 . At low doses, the topography of the specimens remained smooth. However, after implantation with 5×1016 Kr/cm2 , the Ni films were largely destroyed by island formation. The as-deposited films formed sharp interfaces with the PI substrates. After implantation, the interfaces remain sharp, but large quantities of C had been transferred from the PI substrates into the Ni films. An average film stoichiometry of approximately nickel carbide (Ni3 C) resulted after both the 5×1015 and the 1×1016 Kr/cm2 implants. X-ray photoelectron spectroscopy analyses showed (Ni3 C) formation at the interfaces of both the as-deposited and ion implanted Ni/Pl specimens. Although the Ni3C formation extended more deeply into the ion implanted Ni films, the chemical bonding at the Ni/PI interfaces was not greatly affected by the ion implantation. Adhesion evaluations, performed using a scratch test in conjunction with scanning electron microscopy and Auger electron spectroscopy analysis, showed an adhesion enhancement of greater than a factor of 3 for the specimens implanted with either 5×1015 or 1×1016 Kr/cm2 . This adhesion enhancement was attributed primarily to the mechanical interlocking (interfacial mixing) of the Ni films and the PI substrates. While this adhesion enhancement is significant, it is much less than the factor of 20 enhancement previously observed after 28 Si+ implantation.

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