The influence of target composition and thermal treatment on sputtered Al thin films on Si and SiO2 substrates

Al thin films deposited by DC magnetron sputtering from two different target compositions Al–1%Si and Al–1%Si–0.5%Cu on n-type Si (1 0 0) and on SiO2 substrates were investigated. Surface morphology was studied as a function of deposition temperature and thermal annealing of deposited Al thin films by optical microscopy, SEM and AFM analyses. Hillock formation in the Al layer was found to be strongly dependent on the deposition temperature in the range of 373–573 K and less on the annealing temperature in the range of 573–773 K. Hillock size and density were significantly increased when Al was sputtered on SiO2 substrate compared to Si substrates. Al grain size was increased when sputtered from Al–Si target composition compared to Al–Si–Cu and was not influenced significantly by the annealing process. Deposition of Al films from Al–Si–Cu target composition resulted in lower hillock density and orthogonally packed fine grain structure when deposited on (1 0 0) Si substrate. Strong (1 1 1) texture of Al films on SiO2 substrate for both target composition and (1 0 1) texture when deposited on Si substrate were determined by EBSD method.

Microstructural properties of A1 thin film are strongly influenced by the substrate type.Figure optionsDownload as PowerPoint slideHighlights
► Al hillock density and size in sputtered thin films are reduced by sputtering from Al–Si–Cu target instead from Al–Si target.
► Decreasing the substrate preheat temperature.
► Increasing the annealing temperature.
► Sputtering on Si instead on SiO2.
► Reducing the Al grain size.