Enhancement of Adhesion Between Cu Thin Film and Polyimide Modified by Ion Assisted Reaction

Abstract

Polyimide films are modified by ion assisted reaction method using various ion beams in various gases environments. Amount of ion and blown gases rate were changed from 5 × 10¹⁴ to 1 × 10¹⁷ and from 0 to 8 sccm, respectively. Wetting angles between water and polyimide films modified by Ar⁺ ion without oxygen blowing decrease from 67r. to 400r. and surface free energies increase from 46 to 64 dyne/cm². Wetting angle of polyimide films modified by Ar⁺ ion in an oxygen environment decreases to 12r. and surface free energy increases to 72 dyne/cm². The lowest wetting angle was obtained by oxygen ion irradiation in the oxygen gas environment and its value was 7r.. In the case of polyimide film modified by Ar⁺ ions in an oxygen environment, the wetting angle increases up to 65r. when it kept in air and that increases up to 46r. when it kept in water after 5 day. In the case of polyimide film modified by O₂⁺ ion in oxygen environment, however, the wetting angle of polyimide film dose not increase. X-ray photoelectron analysis shows that the chemical bonds between polyimide components are severed by ion irradiation and hydrophilic groups such as CO and C=O are formed by the reaction between newly formed radicals and blown oxygen. It was found that adhesion between Cu and polyimide modified by ion assisted reaction was improved. The main reason of the enhanced adhesion is due to the reaction between Cu and C-O or C=O groups formed by ion assisted reaction on the polyimide surface.