Adhesion of Reactive Ion Implanted Copper Films on Al2O3 and SiO2

Abstract

ABSTRACTImplantation of reactive ions at the Cu-Al2O3 or Cu-SiO2 interface has been explored as a means of producing adhesion of thin copper films on these otherwise inert substrates. The process may promote complex chemical bonding at the interface due to the presence of a reactive implanted species; it may also enhance adhesion by interface layer mixing. Thin copper films (400–800Å) were deposited on fused quartz or sapphire substrates. After implantation and, in some cases, heat treatment thick Cu stripes were added to enable peel testing of adhesion strength. The reactive ion species implanted were oxygen (100 keV), or titanium (120 keV) or chromium (80 or 160 keV), to doses ranging from 1015 to 1017 ions/cm2. In each case, the energy was chosen to place the reactive implant at the interface region. For comparison with simple ion beam mixing, a similar set of samples was implanted with krypton ions at 2 MeV to doses of 1 or 3.6 × 1016 ion/cm2. The peel strength was found to be about 0.5 gm/mm for the unimplanted Cu-sapphire samples; 1.3 gm/mm for those implanted with oxygen; 18 gm/mm for those implanted with krypton; 90 gm/mm for those implanted with chromium; and more than 200 gm/mm for the titanium implanted samples. No significant increase in adhesion was achieved for the implanted Cu-quartz samples, except for the titanium implant, which gave an average peel strength of 66 gm/mm after anneal for the dose of 5 × 1016 Ti+/cm2. Studies of the interfaces and of the peeled surfaces were made, using RBS. Changes in both chemical bonding and interface morphology appear to contribute to the phenomena of enhanced adhesion.