ION-BEAM INDUCED ADHESION OF COPPER-FILMS ON MOLYBDENUM

Ion beam induced adhesion of 500 nm copper films on molybdenum substrates has been studied using a variety of Mev ion beams, including 2 Mev helium, 2 Mev oxygen, 3 Mev silicon, 3 Mev nickel and 5 Mev gold. The trend is for the critical dose for adhesion to be dependent on the nuclear energy loss at the film substrate interface. As in earlier work, no gross mixing of the films has been detected and the conclusion is that only a thin layer (1-10 nm) has been affected at the film substrate interface wherein the free energy has been reduced by an increase in entropy caused by ion beam mixing. Also established during the course of this work is that blisters which develop in some irradiated films are caused by stress in those films at doses much less than the critical dose for adhesion.