Chemical and energy deposition effects of keV ions on the adhesion of Cu films onto polymers

Abstract

The adhesion of copper films evaporated onto polyethersulfone, polyetherimide and polyimide was studied after ion beam mixing using a wide range of ions between 4 and 40 amu (He to Ar) as a function of the ion mass and energy, 60 and 120 keV ions were deposited in the Cu/polymer interface, and the bulk of the polymer, respectively. The adhesion of the modified polymers was measured using a peel test, and related to the energy deposition mechanisms characteristic for the different ions and energies. A comparison between the chemical, electronic and ballistic (nuclear) contributions of the projectiles to the adhesion changes shows a correlation between the electronic term of energy deposition and the adhesion for lower ion masses (up to 20 amu). When the collisional transfer mechanism becomes predominant, a substantial decrease of adhesion strength is observed. In addition to energy transfer effects, deposition of chemically active ions in the Cu/polymer interface may cause an additional increase of adhesion. The consequences of these findings for practical applications are discussed.