The microstructure of Al films deposited on SiO2 using the partially ionized beam (PIB) deposition technique is studied. It is shown that by employing less than 1% ions (ion-to-atom ratio) derived from the evaporated material and about 1–2 kV bias voltage at the substrate during deposition, one can grow highly (111) oriented Al films at room temperature. For a fixed bias potential, the value of the ion-to-atom ratio to achieve the optimum orientation effect is determined. At the optimum condition for the (111) preferred orientation growth, no significant enhancement in the grain size is observed. It is also found that a drastic reduction in the degree of the preferred orientation occurs when the films are deposited at a substrate temperature greater than 150 °C.