We have investigated the local oxidation of an aluminum film to fabricate aluminum and aluminum oxide masks on Si and SiGe substrates. The local oxidation is made by negatively biasing the probe of an atomic force microscope operating in contact mode. The masks are defined by removing the unwanted material using highly selective etching solutions at room temperature. The produced aluminum-based masks can withstand reactive ion etching processes using fluorinated gases mixtures. We report examples of sub-100 nm pattern transfer on the substrate using the AFM fabricated masks. Preliminary observations suggest to use the sputtered aluminum films for which the anodization is found more efficient than for e-beam evaporated aluminum.