Technology of Thin Film Fabrication on Porous Metal Oxide Substrates

One of the main issues of the device technology on metal-dielectric (MD) substrates is poor adhesion of thin metallic films, which are used for interconnections in electrical circuits. Films are formed by vacuum deposition on a porous dielectric layer of substrates. The presence of pores sufficiently complicates the cleaning of the substrate surface, which significantly decreases the adhesion of the film deposited on it. Technology of metal films with high adhesion, fabricated by ion-plasma method is proposed in this work. Films were deposited on MD substrates produced by electrochemical oxidation of aluminum alloys. The main operations of the technology are the following. Removal of residual electrolyte after the oxidation is carried out by rinsing of substrates initially under running hot water, and then in deionized water, followed by drying in a flow of heated nitrogen. Annealing of substrates under the pressure of $10^{-3}$ Pa and temperature of 550-570 K for 20 min is carried on in the vacuum chamber before the deposition of metal films. Copper is used as the main material of the interconnection films. Adhesion sublayer is fabricated on the basis of chromium or vanadium, which have high enthalpy of the oxide formation. Measurements showed that the copper films with the thickness of 1.5 μm, deposited on the vanadium sublayer with the thickness of 0.12 μm, which is comparable with the roughness of oxide layer, have adhesion of $25 N//mm^{2}$ at the temperature of 520 K. Investigation of adhesion was carried on by the method of direct tear off with the error of up to 10%.