Diffusion of metals deposited on a polyimide film (Kapton) under and out of irradiation

Copper and titanium layers deposited on a polyimide film (Kapton) have been studied under two adverse conditions: annealing and irradiation. Metals were deposited by sputtering at room or elevated temperatures (from 251 to 410 degrees C). Rutherford backscattering spectrometry and cross-sectional transmission electron microscopy studies have shown copper layer unwetting for annealing temperatures below the Kapton glass transition temperature (T-g approximate to 360 degrees C). We have observed copper cluster formation on the polyimide surface by surface diffusion that impedes the diffusion in depth. When the annealing temperature is above T-g, copper clusters formation occurs together with immersion under polyimide surface until 80 nm depth. The microscopy study of a copper layer deposited at room temperature shows the evolution of copper/Kapton interface after an irradiation by 300 keV krypton ions at a fluence of 3 x 10(16) ions/cm(2). We observe a large modification of the polymer surface up to 500 nm in depth, as compared with the nonirradiated surface, with a succession of more contrasting blocks at the surface. RES, EDS and ERD analyses indicate the modified polymer layer is impoverished in oxygen, nitrogen and hydrogen, which seems to confirm the formation of new carbonaceous materials. Electron microscopy shows clearly the presence of spherical copper clusters inside the modified film with an average size (10 nm radius) that agrees with the known existence of voids in Kapton. The copper distribution observed by microanalysis is in agreement with the quantitative results that we obtain by RES. Our studies of oxidized titanium layers have shown that, contrarily to copper layers, the oxidized titanium/Kapton systems do not experience changes after irradiation and annealing neither above T-g nor below T-g.