A method of ultrasonically bonding semiconductor elements includes the steps of: (a) aligning surfaces of a plurality of first conductive structures of a first semiconductor element to respective surfaces of a plurality of second conductive structures of a second semiconductor element, wherein the surfaces of each of the plurality of first conductive structures and the plurality of second conductive structures include aluminum; and (b) ultrasonically bonding ones of the first conductive structures to respective ones of the second conductive structures.