CHARACTERIZATION OF ALUMINUM FILMS DEPOSITED BY ION-BEAM-ASSISTED ULTRAHIGH-VACUUM EVAPORATION

Ion bombardment during deposition enables the microstructure and properties of thin films to be manipulated in a controlled manner. Aluminium films approximately 5-mu-m thick were deposited on oxidized silicon wafers at T almost-equal-to 250-degrees-C by ultrahigh vacuum electron beam evaporation. For normalized energies E(n) in the range 0-200 eV (Al atom)-1 the influence of krypton and xenon ion bombardment during evaporation was investigated by X-ray diffraction, transmission electron microscopy, small angle X-ray scattering, scanning electron microscopy and thermal desorption spectroscopy. The results are discussed in terms of the change in texture, stress, grain size and content of gas bubbles. For 5 eV < E(n) < 40 eV a characteristic tilt of the <111> fibre axis by approximately 20-degrees away from the surface normal is observed. This tilt is attributed to an ion-assisted interface reaction during the beginning of the deposition process. For E(n) almost-equal-to 100-200 eV, a (111) "single crystal" texture develops with the crystal aligned to the ion beam direction. For E(n) > 40 eV the average rare gas content saturates at about 1 at.% and 3 at.% for xenon and krypton respectively. The gas precipitates within smaller bubbles as high-density f.c.c. solid epitaxially oriented with the aluminium. The distribution of bubbles is rather inhomogeneous even within individual grains.