A method of interconnecting metallic structures in the manufacture of a three-dimensional semiconductor is provided, the method comprising providing a first upper surface of a first substrate and a second upper surface of a second substrate with a bonding layer; bonding the first upper surface to the second upper surface to provide a bond; etching a via through a lower surface of the first substrate, through the first substrate, around a first metallic structure embedded in the first substrate, through the bond and to a second metallic structure embedded in the second substrate; and filling the via with a conductive material to provide a via structure, thereby electrically connecting the metallic structures.