A method for depositing, patterning and removing a layer of aluminum oxide as a masking material layer for performing a deep, high-aspect ratio etches into a substrate. The method comprising deposing a photoresist onto the substrate, performing lithography processing on the photoresist, developing the photoresist to pattern the photoresist into a mask design, depositing a thin-film layer of aluminum oxide; immersing the substrate into a solution to lift-off the aluminum oxide in regions where the aluminum oxide is deposited on top of the photoresist thereby leaving the patterned aluminum oxide layer on the substrate where no photoresist was present, performing deep reactive ion etching on the substrate wherein the hard masking material layer composed of aluminum oxide functions as a protective masking layer on the substrate to prevent etching from occurring where the aluminum oxide is present, and removing the aluminum oxide masking layer by immersion in a solution.